Assen Zlatarov University, Annual, Vol. XLVIIІ, BOOK 1, Technical and Natural Sciences, 2019

ANNUAL OF ASSEN ZLATAROV UNIVERSITY, BURGAS
BULGARIA, 2019, v. XLVIII (1)

MODERNIZATION OF THE STREET LIGHTING SYSTEM OF
A RESIDENTIAL DISTRICT

Mladen Proykov
E-mail: [email protected]

ABSTRACT

As a result of research data, measures are proposed to improve the energy efficiency of street light-
ing by introducing new LED lighting and a modern lighting management system.

Key words: street lighting, lighting classification, LED luminaires

INTRODUCTION system were mapped and marked on a digital
model of the cadastral plan of the residential
The improvement of lighting and energy per- district made with AutoCAD software.
formance of LED lighting creates conditions for
achieving high energy efficiency of street light- As a result of an energy audit of street light-
ing systems compared to conventional technolo- ing, it was found out that 100% of the existing
gies. The new BS EN13201: 2016 standard [1] high-pressure sodium lamps (HDLs) were in-
has been introduced and is in force in Bulgaria stalled over 20 years ago. The condition of the
for the classification of streets and normalization existing luminaires was relatively good, but they
of quantitative and qualitative lighting indicators. were at the end of their technical and operational
This paper presents the main results of a 2014 lifecycle (Fig. 1). This had led to deterioration of
analysis of the state of the street lighting system their light and electrical performance and to an
in Meden Rudnik residential district of Burgas. increased risk of damage to the luminaires.
The impact of its modernization with the intro-
duction of new energy-efficient lighting and a
control system to increase the energy perfor-
mance and characteristics of street lighting has
been evaluated. The assessment was made on the
basis of an analysis of the existing state of the
street lighting system.

ELECTRICAL ENERGY RESEARCH

The electric energy research of the existing Fig. 1. Existing lighting system
street lighting in Meden Rudnik residential dis-
trict was carried out in 2014 and includes the The existing light poles were in relatively
following steps and activities: good condition. They were of three types: trol-
ley, metal and concrete. The research found that
- research of the existing street lighting sys- there were places where the lighting fixtures
tem; were in areas with high vegetation, which im-
paired the lighting performance on the roadway.
- preparation of lighting classification of the
streets; A considerable part of the luminaires had a
wide boom angle, from 30° to 60°, which was
- analysis of the energy consumption of the unsuitable for the width of the roadways, reduced
street lighting system; the realized luminance of the roadway and at the
same time increased the dazzling effect. These
- digital mapping of the street lighting system. angles were unsuitable for modern LED street
lights with optimal boom angles from 0° to 10°.
A study was made of the current state, num-
ber and type of street poles and lighting powered On the basis of a summary of information on
by street panel boards (PB). The location of the existing street lighting in the residential district,
PB and the type of their control system were
examined. All elements of the street lighting

99

where a total of 1390 luminaires were installed, could not be achieved [1]. However, given the
Table 2 presents data on the type of lighting, the continued expansion of the district and the con-
type of light source, the number and the power of struction of new buildings on empty plots, a way
the lighting fixtures. The total installed capacity to increase the number of illuminators supplied
of the existing street lighting was 94 700W. by a PB can be found.

Table 1. Type, number and power of existing
street luminaires

Luminaires Power, W Number
Street luminaire 50 854
75 182
with HDLs 100 259
Street luminaire 150 83

with HDLs
Street luminaire

with HDLs
Street luminaire

with HDLs

The power supply came from 66 lighting PB, Fig. 2. Street lighting panel board
which are indicated in the cadastral plan.
On the basis of a detailed research of the con-
Most of these PB are in very poor technical dition of the lighting fixtures, the type of the
condition. There is no control system for the road lighting poles, the power lines and the power
lighting system. The control of the luminaires is supply PB, a graphical digital model of the exist-
carried out with individual clocks mounted in a ing state of the street lighting in the residential
PB (Fig. 2). district was developed (Table 2). Appropriate
graphic symbols indicate the different types of
A relatively large number of PB were estab- luminaires, the type of poles and the location of
lished, a total of 66. Practice shows that up to the PB.
200 luminaires can be controlled through one
PB, but due to the specifics of the layout of the
streets in the residential district, this number

Table 2. Condition of street lighting by averages

Road Poles ar- Roadway Sidewalk Pole Light Boom Power Luminaire
Category rangement
№ width width distance Centre high angle

m m m m °W

А Main two – sided 16 2,5 35 12 30 150 HDLs

А Regional two – sided 14 2,5 30 9 30 150 HDLs

B Regional one – sided 17,5 3 30 12 30 100 HDLs

А Assembly one – sided 14 3 30 9 30 100 HDLs

B Assembly one – sided 7 2,5 25 12 30 75 HDLs

C Assembly one – sided 7 2,5 25 9 30 75 HDLs

А Service one – sided 10 2,5 35 9 30 75 HDLs

B Service one – sided 6 2,5 30 9 30 50 HDLs

100

Fig. 3 shows part of the digital model with As a result of the analysis of the electric ener-
graphical and textual information. gy research of street lighting, measures are pro-
posed to improve energy efficiency. The first
Fig. 3. Part of a digital model with locations of step is to prepare a lighting technical classifica-
street lights and panel boards tion of the street network according to the new
standard BS EN13201: 2016 [5].

Traffic on the streets is mainly by motor ve-
hicles. Table 3 presents the light-technical cate-
gorization of streets. The classification of the
streets in the residential district divides them into
the following lighting classes: M3 - main streets
(1 pc); M4 - regional arteries (9 pcs); M5 - local
streets (16 pcs) and M6 - service streets (56 pcs).

Energy efficiency measures include the intro-
duction of LED lights to replace existing street
lamps with 150W, 100W, 70W and 50W LVLs,
or in places with existing pillars but missing
luminaires, new ones to be installed.

Table 3. Normal indicators for different road classes

Road Illuminance Lср, cd/m2 Indicators TI, % SR (min)
categorization 1 Uo (min) U1 (min) 15 0.3
Main streets class 15 0.3
Regional arteries 0. 75 0.4 0.6 15 0.3
Local streets M3 0.5 0.4 0.6 20 0.3
Service streets M4 0.3 0.35 0.4
М5 0.35 0.4
М6

RESULTS AND DISCUSSION

Lighting calculations were performed for the Fig. 4. LED street luminaire
different street categories, further divided by the
road width, poles arrangement, and pole distance
in view of the existing conditions.

The calculations were performed with street
LEDs with an asymmetric light distribution
curve (Fig. 4). Table 4 shows the parameters of
the LED luminaires.

Table 4. LED luminaires

Power, W Color temperature, K Luminous, Lm Ra (CRI) Curve, ° Voltage, V IP
19,6 3000/4000 3038 ≥70 67 160÷260 65
26,6 3000/4000 4123 ≥70 67 160÷260 65
39,6 3000/4000 6138 ≥70 67 160÷260 65
54 3000/4000 8370 ≥70 67 160÷260 65
80 3000/4000 12403 ≥70 67 160÷260 65

The calculation results are shown in Table 5, Table 6 shows the types of LED lights, their
in compliance with BS EN13201: 2016. parameters and how they are installed for the
different street classes.

101

Table 5. Indicators for different street classes implemented with new street LED luminaires

N Street Illuminance Indicators

category class Lср, cd/m2 Uo, (min) U1, TI, % SR, (min)
(min)
9 0.53
А Main streets М3 1.26 0.85 0.84 8 0.53
8 0.51
А Regional arteries М4 0.76 0.43 0.84 6 0.53
5 0.76
B Regional arteries М4 0.91 0.79 0.88 6 0.62
8 0.44
А Local streets М5 0.57 0.44 0.90 7 0.7

B Local streets М5 0.64 0.74 0.85

C Local streets М5 0.54 0.66 0.86

А Service streets М6 0.33 0.47 0.76

B Service streets М6 0.34 0.67 0.92

Table 6. LED street lighting by averages

Road Poles ar- Roadway Sidewalk Pole Light Boom Power, Luminaire
Category rangement angle
№ width width distance Centre high
two - sided
one – sided m mm m °W

А Main two - sided 16 2,5 35 12 0 80 LED
А Regional one – sided
one – sided 14 2,5 30 9 0 80 LED
B Regional one – sided
А Local one – sided 17,5 3 30 12 0 54 LED
one – sided
B Local 14 3 30 9 0 54 LED

C Local 7 2,5 25 12 0 39,6 LED
А Service
B Service 7 2,5 25 9 0 26,6 LED

10 2,5 35 9 0 26,6 LED

6 2,5 30 9 0 19,6 LED

Table 7. Type, number and power of new lumi- The summarized number, type and capacity
naires of the proposal for upgrading street lighting are
presented in Table 7.
Luminaires Power, Number
W On the basis of the cadastral plan of the exist-
LED road luminaire 19,6 530 ing lighting system, a new one was developed,
LED road luminaire 26,6 269 detailing the type of the grid, power lines and
LED road luminaire 39,6 96 feeders. Appropriate graphic symbols indicate
LED road luminaire 54 181 the different types of LED luminaires, the type of
LED road luminaire 80 314 poles and the location of street PB.

Fig. 4. Part of the new digital model with locations of street LEDs
102

The second major energy saving measure is The total power of the LED luminaires is
the introduction of an intelligent street lighting 51kW. For 4000 hours average annual usage this
control and management system. The construc- equals 204 000kWh of electricity consumed.
tion of such a system increases the quality and This is five times less power with LED lighting
reliability of street lighting and reduces the ongo- and five times less power consumption.
ing costs of electricity and maintenance. Widely
used in the city of Burgas is a system with au- The technical results correspond to the current
tonomous programmable controllers type AMC regulations in Bulgaria and represent an up-to
190 (G) with built-in GSM GPRS modem for date technical solution for the modernization of
communication and a server in a central control street lighting in order to improve the energy its
room for monitoring and control. One or more efficiency of street lighting.
“Matrix” meters are connected to each controller
to measure the parameters of the electrical net- ACKNOWLEDGMENTS:
work.
The author is grateful to the Scientific and
The controllers can autonomously control the Research Sector “Scientific and artistic-creative
street lighting according to a predetermined task activities” at University “Prof. Assen Zlatarov”-
taking into account environmental factors. They Burgas, for funding the research through contract
allow the MA to be controlled by: pre-schedule, No NIH - 427/2019.
sunrise and sunset at the current date, by illumi-
nation using an analog light sensor or an external REFERENCES
clock. They also allow for manual control of the
CDD system. The proven system has a relatively 1. Tzankov P., M. Jovchev, H. Ibrishimov, Tz.
low initial capital investment and is easy to Petkov, E. Stanev and L. Dimitrov, Electrical
maintain. energy research of street lighting in Gabrovo,
Proceedings of the National Lighting Confer-
For the implementation of the system in dif- ence for Young Scientists, Lighting 2016, 21 –
ferent variants of management, it is necessary to 23 October, Sofia, Bulgaria.
choose luminaires with the necessary functionali-
ty for control (dimming), which also depends on 2. Ashryatov A., Improving the efficiency of ex-
the initial investment for the reconstruction of all isting lighting systems, Proceedings of the Na-
MA cassettes in the residential district and con- tional Lighting Conference for Young Scien-
necting them to the already built such system in tists, Lighting 2016, 21 – 23 October, Sofia,
parts of Burgas. Bulgaria.

The presented energy efficiency research of 3. Van Tichelen P., T. Geerken, J. B. Vanden
the studied street lighting system is an example Bosch, M. Laborelec, V. Van Hoof, L.
of the transition from conventional lighting to Vanhooydonck, A. Vercalsteren, City of San
LED lighting. Josse Public Strreetlight Design Guide, USA,
2011,“Final Report Lot 9: Public street light-
The total installed power of the existing light- ing”, 2007/ETE/R/021.
ing system is 263kW. For an average annual
usage of 4000 hours, this equals 1055 417kWh 4. BS EN 13201:2016. Street lighting. Part 1-5.
of electricity consumed.

103

ANNUAL OF ASSEN ZLATAROV UNIVERSITY, BURGAS
BULGARIA, 2019, v. XLVIII (1)

LABORATORY MODEL FOR COMPENSATION OF REACTIVE POWER

Mladen Proykov
E-mail: [email protected]

ABSTRACT

А laboratory model for reactive power compensation was made. The benefits of reactive power
compensation were examined. The possible occurrence of resonance phenomena was investigated.

Key words: reactive power compensation, resonance.

INTRODUCTION Natural cosφ is the value of cosφ for a group
of consumers without considering the perfor-
Reactive power is used to generate electro- mance of the compensation devices:
magnetic fields in electrical machines. Its trans-
mission through the electricity network is associ- φ = ( ) = 2 (3)
ated with a number of negative consequences, √ 2 +
such as increased losses via the transmission
facilities. Reactive power is a reason for un- Actual cosφ is when the reactive power of the
derutilization of synchronous generators as it
overloads them. Its circulation through the ele- consumers and of the compensation systems
ments of the electricity system causes losses of
active power. The huge amounts of inductive (CS) are taken into account:
loads on the network have enormous jet power
that circulates between generators and consumers φД = ( − ) (4)
without doing any useful work.

Reactive power compensation (RPC) has a di- Rate of reactive power compensation [1]:
rect effect on the quality of electricity and the
improvement of the efficiency of the electricity = (5)
supply systems. This requires technical and or-
ganizational measures to be taken.
Power supply system (PSS) saturation with
Transformers, asynchronous motors (AM), compensating capacities takes into account the
induction furnaces and other devices, which may need for compensating power:
be called "inductive loads", are the main con-
sumers of reactive energy and degrade cosφ [1]. = К (6)
М

THEORETICAL Adverse situations of low cosφ are expressed

The following quantities are used to quantify in:
- The useful active power “P” of the genera-
the relationship between active and reactive
tors is reduced;
power [2, 3]:
Instantaneous value of cosφ: - The throughput of the transformers is re-

φ( ) = ( ) = ( ) (1) duced;
( ) √ 2( ) + 2( )
- Additional losses of active power and ener-
Average value of cosφ for time interval T:
gy occur in the power supply system;
φср. = 1 ; ср. = (2) - Reducing cosφ results in an increase in the

√1 + ( )2 current in the grids;
- Increased voltage losses at low cosφ;

This can be disadvantageous for many con-

sumers, such as asynchronous motors, light

sources, induction furnaces, welding units etc.

The aforementioned disadvantages of low
cosφ require measures to be taken regarding the

104

power supply system of the facilities to improve К = . СР. ( φЕ − φЖ) (7)
it. These activities are carried out in two direc-
tions: improvement of cosφ without compensat- Fig. 2. Vector diagram of active, reactive and
ing devices (natural modes) and use of CS (arti- total power
ficial modes).
Compensating power management is regulat-
The improvement of cosφ without compensat- ed in view of:
ing devices is accomplished in the following
ways: - improving the quality of the voltage;
- management of reactive loads in the elec-
- The right choice of electrical equipment tricity system and reduction of power and energy
during design; losses;
- optimized utilization of installed compensat-
- Arrangement of the technological process in ing powers;
order to improve the energy regime of the facili- - reducing the current load of power system
ties; elements of the facilities.
With the continuous increase in the capacity
- Using synchronous motors (SM) instead of of installed capacitors in industrial plants, it is
asynchronous motors of the same power when becoming more and more urgent and necessary
the technological process allows and is economi- to regulate their capacity. Compensation power
cally feasible; regulation can be manual, dispatcher or automat-
ic.
- Replacement of low load asynchronous mo- - Manual regulation is performed by the duty
tors with lower power engines; staff.
- Dispatching regulation is carried out by a
- Reducing the voltage; dispatching point.
- Limiting the idle time of electric motors; - Automatic regulation.
- Quality repair of electric motors; The reactive power compensation effect can
- Reduction of reactive power consumption of increase the efficiency of the transformer power,
transformers. reduce the losses in the power lines and improve
In most cases it is not possible to achieve the the quality of the voltage, which leads to in-
desired increase in cosφ by the "natural" methods creased economic and social benefits. A particu-
described above. It may then be technically and larly great effect is achieved through the imple-
economically feasible to use compensation de- mentation of an automatic reactive power com-
vices to improve cosφ, namely: pensation, which leads to optimization of the
- Static compensation devices: power capaci- compensating power control scheme, reduction
tors, reactors and thyristor-controlled capacitors of the time for switching the compensating pow-
and reactors; er on and off, precise control of the compensat-
- Dynamically compensating devices: syn- ing power and, accordingly, maintaining the
chronous motors, synchronized asynchronous desired cosφ more precisely [4].
motors, compensating converters, synchronous Controllers used for automatic power com-
(AC) and asynchronous (AC) compensators, etc.; pensation make a direct analysis of current and
- Modern solutions for reactive power com-
pensation based on flexible DC systems (Fig. 1).

Fig. 1. Active filter for reactive power
compensation

The determination of the required compensat-
ing power is carried out in accordance with the
vector diagram in Fig. 2. and formula (7):

105

voltage harmonics up to the 19th harmonic. The electrical parameters (current, voltage and cosφ)
maximum value is stored in their memory, the before and after compensation (Fig. 3).
total coefficients of harmonic current and voltage
distortions are calculated. If the distortion is
greater than the predetermined current, all stages
of the capacitor battery are disconnected from
the controller and an alarm is activated.

The use of a quality controller with good
software that also performs protective functions
can significantly extend the life of capacitors.
The controller effectively protects them from
rising and falling mains voltage, frequent starts
and even against resonance [5].

RESEARCH Fig. 3. Laboratory model

A laboratory model for automatic reactive Fig. 4 shows the circuit diagram of the labora-
power compensation based on transverse com- tory model.
pensation has been implemented. It can visually
simulate the benefits of implementing transverse
compensation in an electrical system and capture

Fig. 4. Circuit diagram of the laboratory model

Description of the laboratory model: - JKL is a controller for reactive power com-
pensation;
- L1; L2 and L3 are throttles for high pressure
sodium lamps with nominal data: Un = 220VAC; - HL1 and HL2 are light bulbs: Pn = 100W;
L = 230mH; f = 50Hz; In = 1А; Un = 220VAC;

- C1 is a capacitor with nominal data: Cn = The Reactive power compensation controller
0,4µF; Un = 220VAC; (Fig. 5) is a standalone device for automat-
ic/manual control of capacitor batteries in single-
- C2 and C3 are capacitors with nominal data: phase and three-phase networks. It has installed
Cn = 2,5µF; Un = 220VAC; filters for harmonic components of voltage and
current, which is why it is characterized by high
- C4 and C5 are capacitors with nominal data: precision and precision of reactive power con-
Cn = 2µF; Un = 450VAC; trol.

C6 and C7 are capacitors with nominal data:
Cn = 0,5µF; Un = 450VAC;

- Q is circuit breaker: number of poles = 2; Iн
= 6A;

106

Fig. 7. LCR meter HM8018

Fig. 5. Reactive power compensation controller Working with the layout involves defining the

Reactive power compensation controller pa- parameters of the laboratory model in modes

rameters: without and with reactive power compensation.
- Sensitivity: 100mA;
- Nominal frequency: 50Hz ± 5%; Defining the parameters of the laboratory
- Nominal current: (0 ÷ 5)A;
- Automatic or manual analysis function; model in the mode without reactive power com-
- Adjustment of desires cosφ: frоm 0,8 to
pensation includes several steps:
0,99, with step 0,01;
- Nominal voltage: 220VAC ± 10% / - The voltage and current flowing through the

380VAC ± 10%; circuit are recorded on the screen of the reactive
Fig. 6 shows the wiring diagram of a reactive
power compensation controller.
power compensation controller.
- The active, reactive and total power of the

system are determined by formulas 8, 9 and 10:

= . . ( 8)

= . . (9)

= √ 2 + ( )2 (10)

The required capacitive power of the compen-

sation system is determined according to formula

11:

К = . (tgφ − tgφЖ) (11),

Fig. 6. Wiring diagram of a reactive power where the desired tgφ (d) corresponds to desired
compensation controller cosφ (d).

The parameters of the throttles (L), the capac- - The required, total capacitance Ckb of the
itors (C) and the resistance of the light bulbs capacitors realizing the required Qkb. is deter-
were measured using HM8018 laboratory LCR
meter (Fig. 7) at a frequency of 1kHz before the mined according to formula 12:
laboratory model was switched on.
К = . К. 2 ( ) ; К = К (12)
. 2

Table 1. Parameters of the electrical circuit before reactive power compensation CКb, µF
5,57
I, А U, V P, W Q, VAr S, VA cos cos (d) tg sin К , VAr
0,66 235 82,2 131,5 155,1 0,53 0,92 1,6 0,85 96,5

- The following capacitors are installed to Defining the parameters of the laboratory

achieve the required reactive power: model in the mode with reactive power compen-
- one capacitor with capacity 0,4µF;
- two capacitors with capacity 0,5µF; sation includes several steps:
- two capacitors with capacity 2µF; - The voltage and current flowing through the
- two capacitors with capacity 2,5µF .
circuit and cosφ are recorded on the screen of

reactive power compensation controller;

107

- Cosφ must be equal to cosφ (d); ′ = . ′. φ (ж) (16),
- Determination of the capacitive power in-
cluded by the controller (formula 13): where sinφ (d) = 0,392 according to cosφ (d) =
0,92.
′ = . ′ . 2
(13) - The active “P” and full “S” powers in circuit
diagram after compensation are defined by for-
- Determination of the power supply system mulas 14 and 18:

saturation with compensating capacities (formula

13):

= ′ % (14) ′ = . ′. φ (ж) (17)

Determination of the rate оf reactive power ′ = √ 2 + ( ′)2 (18)

compensation:
′
= % (15) - The amount of compensated total power “S”
in the electrical circuit after the compensation is:

Determining the economic impact of reactive ∆ = − ′

power compensation: (19)

- Reported current in the circuit after the re- Table 2 shows the individual steps of the con-
active power compensation is I’ = 0,39mA;
troller work during compensation and Table 3

- Reactive power after compensation is de- shows the final results of the study.

fined by formula (16):

Table 2. Circuit parameters during automatic reactive power compensation

I′, A Ck′ b, µF Step number cosφ′ I′, A Ck′ b, µF Стъпки N cosφ′

0,66 0 1 0,53 0,37 6,5 8 0,96
9 0,78
0,64 0,4 2 0,55 0,45 4 10 0,82
11 0,86
0,51 2,9 3 0,69 0,43 4,5 12 0,89
13 0,99
0,4 5,4 4 0,88 0,41 5 14 0,92

0,35 7,4 5 0,98 0,4 5,4

0,37 7 6 0,97 0,36 7,9

0,43 4,5 7 0,82 0,39 5,9

Table 3. Circuit parameters after reactive power compensation

I′, A U, V Ck′ b, µF P′, W Qкб , VAr Q′, VAr S′, VA ∆S, VA cosφ′ H, % CK , %
65,4 0,92 124,5 77,8
0,39 235 5,9 82,2 102,3 35,9 89,7

In electrical circuits containing L and C ele- The equivalent inductance measured with the
ments, resonance phenomena can occur when LCR meter is = 1,34H. The value of the ca-
equalizing the inductive XL and capacitive XC
resistances in the circuit. For the circuit in Fig. 8, pacitance at which a resonance can occur are
there are conditions for a consistent resonance
between the equivalent inductance екв and determined by formula 20: 1
equivalent capacity екв . 2.
= ; . = . ; = (20)
Fig. 8. Resonance Lекв - Cекв circuit
= 1 = 7,6 µ
3142. 1,337

The test shows that values of Ceq = 7,6µF,
should be avoided due to conditions for the oc-
currence of consistent resonance and a sharp
increase of current in the electrical circuit.

108

The diagram in Fig. 9 shows alteration of: with fewer parameters, cables/wires with smaller
C ; I ; cosφ = f (N) sections, which is cost-effective. It also leads to a
decrease of active energy consumption due to a
reduction in active losses in wires and equip-
ment.

REFERENCES

RESULTS AND DISCUSSION 1. KarafeizovTz., Reactive power transmis-
sion in power lines, Energetika 2003;
The work of an automatic reactive power
compensator was investigated. 2. Kirov M., Reactive cargo compensation,
an effective way for saving electrical power,
After applying a transverse reactive power Energy forum, Proceedings, 2006;
compensation, cosφ increased from 0,53 to 0,92.
This measure leads to unloading the electrical 3. Kirov M., Optimization of reactive power
circuit from the transfer of reactive power “Q”. compensation, performance by synchronous
motors and capacitors in the power supplying
As cosφ increases to the value of 0,92, the to- systems of powerful industrial facilities,
tal current in the circuit decreases 1,7 times, the ELMA, 2011.
total power “S”decreases 2,37 times and the re-
active power “Q” decreases 3,66 times. 4. Baev D., A guide to enterprise energy
efficiency management, Sofia, 2015;
The reduction of the current in the circuit
makes it possible to choose electrical equipment 5. Gotman I., Criteria for evaluation of reac-
Fig. 9.C ; I ; cosφ = f (N) tive power compensation, Electricity, 2009;

109

ANNUAL OF ASSEN ZLATAROV UNIVERSITY, BURGAS
BULGARIA, 2019, v. XLVIII (1)

COMBINED ROAD AND RAILWAY TRANSPORT IN PRESENT-DAY BULGARIA

Vasil Bobev
E-mail: [email protected]

ABSTRACT

Combined transport is a highly-efficient technology aimed to optimally use different types of trans-
port. The peculiarity of combined transport is the combination of the advantages of the different kinds
of transport participating in haulage and their complementarities. The present paper describes the
process of Ro-La traffic. A model for the transportation of vehicles with railway transport from
Plovdiv intermodal terminal has been developed.

Key words: road transport; rail transport; combined transport.

INTRODUCTION trailers or only trailers) by trains. In practice they
As is known, combined goods transport is a are called Ro-La trains. In this case the major
highly-efficient technology aimed to optimally advantages of railway transport, such as ecology,
use different types of transport. The organization safety and big haulage capacity, are used.
of work at the terminals and vehicle-carrying
ferries is the major factor influencing the effi- This kind of combined transport to a great
ciency of the whole transport process [1]. degree combines the efficiency of railway trans-
port in haulage of the mass goods on a long dis-
Combined transport allows increasing the ef- tance with the indisputable priority of road trans-
ficiency of goods transportation. The peculiarity port on short distances and potentiality for direct
of combined transport is the combination of the delivery of goods to customers. The development
advantages of all kinds of transport participating of combined transport has and continues looking
in haulage and their complementarities. In this for new possibilities to solve transport problems,
way the infrastructure is used optimally and a such as traffic congestion, road accidents, pollu-
high quality of offering transport product is tion, etc.
achieved [2].
Regular connections with such trains exist be-
In [1] the process of the ferry traffic is pre- tween different countries in Europe. There are
sented. The evaluations corresponding to the such connections between Hungary and Austria,
ferry traffic make use of the theory of intuitionis- Romania and Austria, Slovenia and Austria, the
tic fuzzy sets. Ferry transport is the transport of Czech Republic and Germany, etc.
vehicles, persons and goods across a river, lake
or sea. This is a combined technology with hori- Nowadays, trains run on fixed schedules, e.g.
zontal transfer of transport. In this case the stan- fixed day of the week and departure time. The
dard combined unit is a vehicle. requirements for lorries are: to have a reservation
in advance, to arrive at the terminal by the speci-
The characteristics of this combined transport fied time before departure and to meet technical
result from the fact that the vehicles move in standards (weight and overall dimensions) [3].
shorter intervals. This is due to the fact that there
are a lot of means of transport. EXPERIMENTAL

In [2] the process of Ro-Ro traffic is de- In Bulgaria there are a lot of conditions for
scribed. Ro-Ro is a combined technology with a the development of combined road and railway
horizontal transfer of transport. In this case the transport. These are good transit car traffic and
standard combined unit is a vehicle: a lorry with good advanced combined transport. Unfortu-
a trailer or only trailers. The ships have two or nately, only this technology is being developed
more decks. Vehicles are driven on and off the in Bulgaria now, and only as the internal technol-
ship on their own wheels and cabins are available ogy transport of a private company.
for the drivers. Ro-Ro combined technology is
not being developed in Bulgaria these days. The Bulgarian government granted a 27-year-
long concession to the Terminali Company for
Combined road and railway transport is the the intermodal terminal in Plovdiv in the South
loading and railroading of vehicles (lorries with

110

Central Planning Region of Bulgaria. Terminali The number of vehicles in this case is shown
is solely owned by PIMK, the country’s largest in Fig. 3.
carrier company. The company, together with
DB Schenker, transports goods from Rousse.
Recently, it has invested in its own railway com-
pany, PIMK Rail and is licensed as a rail carrier.

Now the company transports trailers by train
between Plovdiv (BG) and Cherkezköy (TR).
The train has a capacity of 34 carriages. The
initial schedule is the following (Fig. 1):

BG (Friday) →→→→→TR(Saturday)
TR(Saturday)→→ →→→ BG(Sunday)

Fig. 1

The train will start every Friday from the in- Fig. 3
termodal terminal near Plovdiv. On Saturday, the
train will be unloaded in Turkey. On the same This allows for up to 68 vehicles/trailers (Op-
day the train will go back to Bulgaria and on tion II) or 102 vehicles/trailers (Option III) to be
Sunday it will be back at the terminal in Plovdiv. carried between Bulgaria and Turkey in every
direction every week.
There is a timetable for trains to move be-
tween Bulgaria and Turkey twice a week. In this In general, this means 204 trucks fewer on the
way, they will also carry trailers to other carriers, roads between Bulgaria and Turkey every week.
most often Turkish (Option II).
The future plans of the company envisage the
In [3] the model describing the process of Ro- launch of another train from the intermodal ter-
La floats is presented. The Generalized Net mod- minal in Plovdiv to Austria. The difference is
el described in [3] is a possible model for the that it can be up to 30 carriages long, because it
process of Ro-La traffic. In this case, the actual will pass through Serbia, where there are limita-
process is easier to describe. tions on the length of the train. The journey will
be about three days for each direction or about a
RESULTS AND DISCUSSION week to complete the entire turnover.

Based on these, a model about a specific This means 60 trucks fewer on the roads be-
timetable has been designed by the author. This tween Bulgaria and Austria and transit countries
model has a limit based on the number of car- every week and decreased costs for carriers in
riages in every train. The number of carriages is the future.
equal to the number of vehicles.
CONCLUSIONS
In this case it is possible to optimize the train
timetable. The aim is to ensure the transport of The presented results can be used to create a
more trailers. This improves the ability to trans- methodology for future plans of the company to
port trailers owned by other carriers (Option III). envisage the launch of another train from Plov-
In this case, the timetable is as shown in Fig. 2. div to Austria.

BG (Friday) →→→→→TR(Saturday) Thus, the major advantages of the railway
TR(Saturday)→→ →→→ BG(Sunday) transport, such as ecology, safety and big haul-
age capacity, appear in practice.
BG (Sunday) →→→→→TR(Monday)
TR(Monday)→→ →→→ BG(Thursday) Most of the model parameters can also be re-
garded as characteristics of tokens from an addi-
BG (Thursday) →→→→→TR(Wednesday) tional contour, thus achieving optimization with
TR(Wednesday)→→ →→→ BG(Thursday) respect to our given aim.

Fig. 2 Statistical information needs to be collected
in order to monitor the development of the proc-
ess.

111

REFERENCES Fuzzy Sets and Generalized nets, Warszawa,
2008, ISBN 978-83-60434-58-1, p.155-160;
1. Bobev V., S. Sotirov, Generalized net model 3. Bobev V., S. Sotirov, Generalized net model
of the auto ferry traffic, using intuitionistic of combined transport between road and rail-
fuzzy estimations, Notes on Intuitionistic Fuzzy way transport, Developments in Fuzzy Sets, In-
Sets, Sofia, 14-15 May 2008, ISSN 1310-4926, tuitionistic Fuzzy Sets, Generalized Nets and
p. 108-112; Related Topics. Volume II: Applications, Pol-
ish Academy of Sciences, Warszawa, 2010,
2. Sotirov S., Bobev V., Generalized net model ISBN 9788389475305, p. 25-30.
of the Ro-Ro traffic, Issue on Intuitionistic

112

ANNUAL OF ASSEN ZLATAROV UNIVERSITY, BURGAS
BULGARIA, 2019, v. XLVIII (I)

MODELING OF TRANSIENT PROCESSES IN A LINEAR ELECTRIC CIRCUIT OF THE
SECOND ORDER WITH A GENERALIZED NET

Yuliyan Petrov
E-mail: [email protected]

ABSTRACT

This article presents a method for modeling of transient processes in linear electrical circuits of the
second order with generalized nets. During the analysis we applied not only the Om and Kirchhoff’s
laws but also generalized methods. For modeling and describing the apparatus of generalized nets is
used, including the whole algorithm of the realization of every single step of the algorithm and there
are also foreseen possible exits and rules for making decisions. Generalized nets are one of the best-
known techniques for describing processes in a formal and abstract way.

Key words: linear electrical circuits, second order, generalized nets, algorithm, Om, Kirchhoff

INTRODUCTION The article examines the general structure for
describing the classical method for the analysis
When a circuit containing coils and capacitors of transitional processes through the generalized
passes from one mode to another, transitional network model for the following diagram (Fig.
processes occur (Fig.1). The event triggering this 2). The methodology for building generalized
process is called commutation, and the moment networks involves constructing the static struc-
when it happens is assumed to be 0. The transi- ture of the modeling process, reflecting the dy-
tion process does not take place instantly because namics of the model process, describing the
there is an electromagnetic energy stored in the functioning of the modeling process over time,
circuit. Theoretically, this process continues in- identifying the data that are of interest to the
definitely, but, practically, it happens very quick- modeling process.
ly. The analysis of these processes follows a cer-
tain algorithm that can be modeled using general-
ized networks.

Fig. 1. Electrical circuit

Generalized networks use a formal algorithm Fig. 2 Generalized network model
description and they are a technique for describ-
ing processes using a high degree of abstraction GENERALIZED NET MODEL
and intuitiveness [3 - 6]. Such an approach allows
to exclude the ambiguity in the semantics of the A generalized network model has been devel-
individual instances representing separate seman- oped with an entered multitude of transitions A
tic units in the presented model. The result of this which:
type of modeling is generating an abstract gener-
alized network, giving the opportunity for unim- A = {Z1, Z2 , Z3, Z4 , Z5} ,
peded implementation in program environments.
where the transitions describe the following proc-
esses:

113

Z1 ="Building a circuit"; transition, kernel l8 receives the feature "de-
Z2 ="Independent initial conditions (before
signed modeling scheme".
commutation)";
B) Transition Z2
Z3 ="Linear differential equation system (after Transition Z2 has the following description:

commutation)"; Z2 = {l8 , L2A},{l10 , L2A}, r2 , ∨ (l8, L2A )

Z4 ="System of equations with state variables"; where:
Z5 ="Determination of transition values".
l10 L2 A
А) Transition Z1 r2 = l8 false true
Transition Z1 has the following description:
L2 A W2 A,10 true
Z1 = {l1, l2 , l3, l4 , l5 , l6 , l7 , L1A},{l8 , L1A}, r1, ∨ (l1, l2 , l3, l4 , l5 , l6 , l7 , L1A )
where: W2A,10 = "there are independent initial condi-

l8 L1A tions before commutation"
r1 = l1 false true
The entrance kernel of position l8 receives a
l2 false true characteristic: "modeling pattern" in L2A , after
l3 false true the Z2 transition, kernel l10 receives a new char-
l4 false true
l5 false true acteristic "independent startup".
l6 false true
l7 false true C) Transition Z3
L1A W1A,8 true
Transition Z3 has the following description:
W1A,8 = "all entrance levels are available"
Transition Z1 consists of seven entrances Z3 = {l9 , L3A},{l11, L3A}, r3, ∨ (l9 , L3A )

l1, l2 , l3, l4 , l5, l6 , l7 and one exit l8 . Entranced where:
kernels from positions l1, l2 , l3, l4 , l5, l6 , l7 come
r3 = l9 l11 L3 A
with the following initial features [6]: L3 A false true

l1 = EC1, 1, 2, " DC voltage", U , W3 A,11 true

l2 = EC2, 2, 3, " Resistive", R1 , W3A,11 = "a system of differential equations is

l3 = EC3, 3, 4, " Inductive", L , available".

l4 = EC4, 4, 5, " Resistive", R , Transition Z3 consists of one entrance l9 and

l5 = EC5, 4, 5, "Switch", K , one exit l11 . The entrance kernel from position l9

l6 = EC6, 5, 1, "Capacitive", C , enters with the "initial data" characteristic in

l7 = EC7, 5, 1, " Resistive", R2 . L3A ; after the transition Z3 , kernel l11 receives a
After transition Z1 , the entered kernels from
l1, l2 , l3, l4 , l5, l6 , l7 are united into the exit kernel characteristic "a system of differential equations".
l8 to subsequently simulate the process. After the
D) Transition Z4
Transition Z4 has the following description:

{ } { } ( )Z4 = l10 , l11, L4A , l12 , L4A , r4 , ∨ l10 , l11, L2A

where:

114

r4 = l10 l12 L4 A
l11 false true
L4 A
false true
W4 A,12 true

W4A,12 = "a system of equations with state vari- a)

ables is available"

Transition Z4 consists of two entrances l10 , l11

and one exit l12 . Entered kernel of position

l10 , l11 enter with the characteristic "independent

initial conditions" and "systems of differential

equation" in L4A , after the transition kernel

l12 emerging from position L4A receives a charac-

teristic: "status equation system".

E) Transition Z5

Transition Z5 has the following description:

Z5 = {l12 , L5A},{l13, L5A}, r5, ∨ (l12 , L5A )

where:

r5 = l12 l13 L5 A b)
L5 A false true

W5 A,13 true

W5A,13 = "there are transitional variables that are

not variables of the state"

Transition Z5 consists of one entry l12 and

one exit l13 . The entry kernel from position l12 , is

provided with the characteristic "system of state

equation" in L5A , after the transition, the kernel

l13 emerging from position L5A receives the char-

acteristic "transitional magnitude".

SIMULATION RESULTS c)
Fig. 3 Simulations of transitional quantities
The Graphical User Interfaces (GUI) graphic
editor, which is part of the MATLAB base sys- (a)iL(t) – the current through the coil dur-
tem, is used to process the experimental data and
graphical interpretation of the obtained results [1, ing pseudo-periodic mode; (b)uc(t) – the
2]. The simulation is done using the following voltage of the condenser in the aperiodic
entrance data:
mode (c) ic (t) – the current through the
capacitor under aperiodic mode

115

CONCLUSIONS REFERENCES

The model allows to examine different stages 1. Mechkova V, L. Staneva, B. Mechkov, Math-
of the process of modeling transition processes, ematical models for examination of transients
as well as its simulation and behavior. The transi- processes in electric circuits of second order,
tion process study program includes monitoring Industrial technologies, vol.II (1), Burgas, сс
the change of transitional quantity over time, 17 – 20, 2015
examining the impact of chain parameters on the
character and speed of the transitional process, 2. Mechkova V, L. Staneva, B. Mechkov, „Raz-
and also the ability to determine some parameters rabotka cikla laboratornax rabot po kursu “Teo-
of the chain based on received images. reticheskaya electrotehnika“ v srede
MATLAB“, Sbornik nauchnax trudov ХІ meg-
The created mathematical model aims to show dunarodnoy nauchno – tehnicheskoy conferen-
a different approach for laboratory practice. The cii „Problema i perspektiva razvitiya otechest-
results obtained from the simulation can be com- venoy svetotechniki, electrotehniki I ener-
pared with the results obtained in a laboratory getiki“, Saransk, 2013, с. 392–396;
environment with actually connected chain. Their
implementation supports the development of 3. I. Vardeva, V. Gochev, Calculation of estima-
logical and algorithmic thinking, enables mastery tions of messages by generalized nets and in-
of the basic methods of research and analysis of tuitionistic fuzzy truth values, IEEE 6th Interna-
assigned tasks, and self-improvement of technical tional Conference “Intelligent Systems”, 2012
knowledge and finding rational solutions.
4. I. Vardeva Generalized net model for building
ACNOWLEDGMENT a virtual private dial-up network, Issues in IFSs
and GN, Vol.9 (2011), pp.70 - 76
This work was supported by the Bulgarian
Ministry of Education and Science under the 5. Gocheva P., N. Hinov, V. Gochev. Generalized
National Research Programme “Young scientists net based estimations on switching topologies in
and postdoctoral students”, approved with DCM electronic circuits, AIP Conference Proceedings
#577/17.08.2018. 2048, 060025 – pp.1-6 (2018)

6. P.Gocheva, N. Hinov, V. Gochev, Modeling of
Electronic Circuits with Generalized Nets, 2018
IX National Conference with International Par-
ticipation (ELECTRONICA), DOI:10.1109

116

ANNUAL OF ASSEN ZLATAROV UNIVERSITY, BURGAS
BULGARIA, 2019, v. XLVIII (I)

NOVEL MG-CONTAINING GLASS-CERAMICS IN THE SiO2-CaO SYSTEM AND THEIR
IN VITRO BIOACTIVITY: XRD, FTIR, SEM AND ICP-AES ANALYSIS

Lachezar Radev
E-mail: [email protected]

ABSTRACT

Novel Mg-containing glass ceramics in SiO2-CaO system were prepared via sol-gel method. The
obtained dried gels were thermally treated at different temperatures. The structure of the samples
obtained were characterized by XRD and FTIR, and the concentrations of Ca2+, Mg2+, Si4+ and P5+
after in vitro test in SBF were studied by ICP-AES technique. XRD of the thermally treated samples
proved the presence of the main phase of merwinite accompanied with akermanite or akermanite and
bredigite. FTIR of the thermal treated samples confirmed XRD results. FTIR of the samples after in
vitro test in SBF solution revealed that CO3HA was formed on the soaked samples in static conditions.
The obtained FTIR results are in a good agreement with XRD. ICP-AES showed that the precipitation
was similar for the two prepared glass ceramics. SEM revealed the presence of HA on the soaked
surface. Based on these results, it can be concluded that the Mg-containing glass ceramics in the SiO2-
CaO system are in vitro bioactive.

Key words: merwinite, akermanite, bredigite, glass ceramics, in vitro bioactivity

INTRODUCTION

Hydroxyapatite (Ca10(PO4)6(OH)2, HA) and In recent decades, pure and multiphase glass-
β-tricalciumphosphate (β-Ca3PO4, β-TCP) have ceramics in CaO-SiO2-MgO system have been of
been considered the most promising materials for particular interest for biomedical applications.
both dental and orthopaedic applications because Pure crystalline phases, such as akermanite
of their chemical similarity to that of human hard (Ca2MgSi2O7, Ak) [10-14], diopside (CaM-
tissue [1]. It is known that their applications are gSi2O6, Di) [15-19], merwinite (Ca3MgSi2O8,
limited due to some disadvantages. For example, Merw) [20], and bredigite (Ca7MgSi4O16, Bred)
HA shows a limited ability to stimulate the de- [15, 21-23] have been thoroughly investigated,
velopment of new bone tissue and does not sig- respectively, showing that they possess good
nificantly degrade over time [2]. biological properties. Furthermore, all authors
have reported that calcification temperature is an
On the other hand, biological HA structures important factor for obtaining glass-ceramics.
and their properties, such as bioactivity, biocom-
patibility, solubility, and absorption, can be im- A brief summary of previous studies of the
proved by modifying their composition by ionic polycrystalline Mg-containing glass-ceramics,
substitution processes, as described by W. including the composition of the gels, prepara-
Suchanek et al. [3]. Small quantities of cations tion methods, and crystalline phases observed,
(i.e. K+, Mg2+, Sr2+, Al3+) and/or anions (i.e. F−, are given in Table 1, where W is wollastonite,
SiO4−and CO32- ) in the HA- structure can play a PsW is pseudowollastonite, Cryst is crystoballite,
pivotal role in their overall biological perform- Lar is larnite (dicalcium silicate), and Per is peri-
ance, as can be seen in several studies [1, 2, 4-6]. clase.

Magnesium (Mg) is one of the most important The characteristics of the crystallization pro-
mineral elements in the human body. Some stud- cess in the CaO-MgO-SiO2 system provide the
ies have indicated that Mg2+ has a key role in synthesis of materials of an identical chemical
bone remodelling and skeletal development [7, but of a various phase composition and structure.
8]. A brilliant review on Mg-containing sol-gel The chemical composition corresponding to the
glasses and glass-ceramics was published by M. stoichiometry of merwinite 3CaO.MgO.2SiO2 is
Diba and co-workers [9]. chosen. Merwinite ceramics have recently drawn
attention, since they show not only mechanical

117

properties comparable to those of cortical bone, glass-ceramics studied have the same chemical
but also apatite forming ability in vitro and good composition but different phase composition due
in vivo biological properties [9]. to different synthetic conditions. The objective of
the present study is to determine the in vitro bio-
This study is a continuation of our studies activity of two glass ceramics of the CaO - MgO
[34, 35], which described bioactive ceramics - SiO2 system containing merwinite as the main
containing merwinite in the amount of 29% and crystal phase in the amount of 92% and 63%,
85%, respectively. It would be interesting to respectively, and different additional phases.
determine the effect of the phase composition on
the in vitro bioactivity of the glass-ceramics. The

Table 1. Summary of previous studies on the synthesis of Mg-containing glass-ceramics in CaO-SiO2-
MgO system with (or without) other components

Authors Composition of the gel Method Temperature,oC Phases Ref.
D-M.Liu 54.5CaO-32.8SiO2-6.1P2O5-6.0MgO- Melting 930-1150 Ak, W, HA [24]
R. Choud- 0.6CaF2 (mol.%) Sol-gel [25]
hary akermanite 900 Ak, Mer,Di
J. Ma Sol-gel 1000 Ak, Di [26]
J. Ma 28CaO-58SiO2-10MgO-4P2O5 Sol-gel 1200 Ak, Mer [27]
J. Ma (mol.%) Sol-gel 900 PsW, W, Ak [28]
E. Bernardo (38-x)CaO-xMgO-4P2O5-58SiO2, Oxidation decomposi- 1200 Ak, Cryst [29]
X. Chen where x=5,10,20 mol.% MgO tion of resins 1200 Ak, Cryst [30]
X. Chen (38-x)CaO-xMgO-4P2O5- Sol-gel, plasma spray- [31]
58SiO2,where x=5,10,20 mol.% MgO ing 1200 Ak, Cryst
M. Zhang Akermanite with micro- and nanofill- Sol-gel [32]
O.-M. Gou- ers of CaCO3, MgO and Mg(OH)2 Sol-gel 900 Ak [33]
douri Ak on Ti-6Al-4V alloy Sol-gel 1000 Ak, Mer, W
650-800 W, Lar, Ak
40.18CaO-46.43SiO2-13.39MgO Sol-gel
(mol.%) Sol-gel 1350 W, Ak, Lar
43.30CaO-45.98SiO2-10.72MgO 1320
(mol. %) Sol-gel 1300 Ak, W, Lar
45.98CaO-45.54SiO2-8.48MgO (mol.
%) Sol-gel 1300 amorphous
49.13CaO-49.13 SiO2-7.68MgO (wt. Di
%) Sol-gel 810 Di
70SiO2-20CaO-10MgO 850 amorphous
1050 Di
70SiO2-10CaO-20MgO 800 Di
840 amorphous
60SiO2-30CaO-10MgO 1050
810 Di, W, PsW
50SiO2-30CaO-20MgO 850 Lar
1050 Lar, Di
780 Di, Ak, Mer
820
1050

I.Michailova 51.2 CaO-12.3MgO-35.5SiO2 (wt. %) Sol-gel 1100 Lar, Mer. Ak, [34]
I.Michailova 50.0 CaO-16.7MgO-33.3SiO2 (mol. Sol-gel 1300 Per.
L. Radev %) Sol-gel 1200
51.2 CaO-12.3MgO-35.5SiO2 (wt. %) Mer, Ak [35]
50.0 CaO-16.7MgO-33.3SiO2 (mol.
%) Ak, HA [36]
46.7CaO-34.2SiO2-15.9P2O5-2.9MgO
(wt.%)

118

EXPERIMENTAL PART these solutions were determined by Inductively
Coupled Plasma Atomic Emission Spectroscopy
1. Synthesis of the glass-ceramics (ICP-AES), Iris 1000, Thermo Elemental, USA.
The two investigated sol-gel glass-ceramics
were synthesized by the sol-gel technique as RESULTS AND DISCUSSION
reported in [35].
Glass ceramics were prepared by the sol-gel X-ray diffraction analysis of the synthesized
method using tetraethyl orthosilicate samples is given in Fig. 1
((C2H5O)4Si, TEOS), magnesium nitrate hexahy-
drate (Mg(NO3)2.6H2O) and calcium nitrate tet- 
rahydrate (Ca(NO3)2.4H2O) as raw materials.
- Merwinite 
Nitric acid (HNO3, 2N) was used to catalyze
the hydrolysis of TEOS. The TEOS was mixed  - Akermanite 

with absolute ethanol, water and 2N HNO3 (mo- - Bredigite
lar ratio: TEOS/H2O/HNO3=1:8:0.16) and hydro-
lyzed for one hour under stirring. Then, the solu-  
tions of Ca(NO3)2.4H2O and Mg(NO3)2.6H2O
were added into the mixture (molar ratio: 
TEOS/Mg(NO3)2.6H2O/Ca(NO3)2.4H2O = 2:1:3),
and the reactants were stirred for 6 hours at room    
temperature. After mixing, the solution was dried 
at 100°C for 2 days to obtain the dry gel. The Intensity, a.u.   709
dried gel was calcined at 600°C for 2 hours. Fi-
nally, the powders were thermally treated. The     
sample obtained after thermal treatment at   
1250°C for 2 hours was denoted as 738. The 
other sample, obtained after thermal treatment at    
1350°C for 2 hours, was denoted as 709. 




         738

20 40 60 80

2θ, degree

Figure 1. XRD patterns of the 709 and 738 sam-
ples, after thermal treatment at 1350°C and
1250°C for 2 hours

2. Structural characterization The XRD diffractograms of prepared and
The crystal structure of the synthesized thermally treated samples are different. In sam-
glass-ceramic materials after heat treatment was ple 709, XRD detects the presence of merwinite
evaluated by Fourier Transform Infrared Spec- (PDF card35-0591) as the main crystalline phase
troscopy (FTIR) and X-Ray Diffraction (XRD). and akermanite (PDF card 35-0592). In the case
FTIR transmittance spectra were obtained using of sample 738, XRD proved the presence of
an FTIR spectrometer (Nicollet, USA) in the merwinite (PDF card 35-0591), akermanite (PDF
region 4000-400 cm-1 with a resolution of 4 cm- card 35-0592) and bredigite (PDF card 36-0399).
1 by the KBr pellet technique. The XRD meas- Similar results were published by R. Choudhary
urements were carried out using a D8 Brucker et al. [25], who prepared akermanite by the sol-
ADVANCE X-Ray diffractometer, equipped gel combustion method using eggshell waste as a
with a VANTEC-1 detector. The XRD spectra calcium source.
were recorded in the 2 Theta (2 θ) range using
CuKα radiation in the range 0-100o. The FTIR spectra of the prepared glass-
ceramics after annealing at 1350°C and 1250°C
3. In vitro apatite forming ability for 2 hours are shown in Fig. 2.
The apatite forming ability of the synthe-
sized glass-ceramics was assessed by immersion The peaks posited at 1023, 997, 970, 940,
of the pellets for 3, 9 and 15 days in Simulated 903 884, 863 (867), 587 (589), 535, 515 (513),
Body Fluid (SBF), prepared as described by Ko- 435 (437) and 407 (408) cm-1 confirmed the
kubo et al. [37]. When the samples were re- presence of merwinite [35, 38, 39].
moved from the SBF solution they were rinsed
with ethanol and distilled water, dried and stored The absorption bands centered at 970, 903,
in containers. After immersion in SBF, all spec- 847, 701, 684 (682), 638, 631, 587 (589), and
imens were characterized by FTIR and XRD. 407 (408) cm-1 could be related to akermanite
The ionic concentrations of Ca, P, Si, and Mg of [25, 38, 40, 41]. The bands at 610, 470, 460, 428,
and 417 cm-1 could be related to bredigite [23,
25, 40, 42]. The presented FTIR results are in
good agreement with the XRD results.

119

Fig. 3 shows the XRD patterns of the two CO32- are also detectable [44, 45]. It is well
glass-ceramics after soaking in SBF solution for known that carbonate containing HA structure
15 days in static conditions. (CO3HA) depends on its chemical composition.
There are two types of substitution in HA lattice:
709_after 15 days in SBF CO32- can replace PO43- ions (B-type) and CO32-
can replace OH- ions (A-type) [46-48].
 - Merwinite
 - Akermanite IR frequencies for the synthesized glass-
  - Carbonate-hydroxylapatite ceramics, after soaking in SBF solution for 3, 9
 - Calcite and 15 days are given in Table 2.

 ab

Intensity, a.u.  15 days
9 days


 

 
  

 

     
   
   
      

20 40 60 80 Intensity, a. u.
ν1PO4
2θ, degree ν2CO3
ν2PO4
738_after 15 days in SBF 3 days

  - Merwinite ν3CO3 ν3PO4 ν4PO4
 - Akermanite
- Hydroxylapatite 600
 - Calcite



Intensity, a.u. 1600 1400 1200 1000 800 400

 Wavenumbers, cm-1



 


  
 
  
  
  
   
  



20 40 60 80 Intensity, a.u. 15 days
ν1PO4
2θ, degree ν2CO3 9 days
ν2PO4
Figure 3. XRD patterns of the prepared and 3 days
thermally treated at different temperatures 709
and 738 glass-ceramics, after soaking in SBF

solution for 15 days in static conditions

From the data in Fig. 3 it is obvious that the ν3CO3 ν3PO4 800 ν4PO4 400
peaks of bredigite completely disappeared [15,
21, 22] and the characteristic peaks of CO3HA 1600 1400 1200 1000 600
(PDF card96-900-3553) appeared after soaking
for 15 days. On the other hand, the peak of cal- Wavenumbers, cm-1
cite (PDF card 5-0586) was also detected.
Figure 4. FTIR of the prepared glass-ceramics
FTIR spectra of the synthesized Mg- (sample 709, a, and sample 738, b), after immer-
containing glass-ceramics after soaking in SBF
solution for 3, 9, and 15 days are presented in sion in SBF solution in static conditions
Fig. 4.
On the basis of the results obtained, we can con-
Theoretically, four vibrational modes are clude that:
visible for the PO43- ions in HA structure: ν3 PO43
at 1190-980 cm-1, ν1 PO43 at 960-965 cm-1, ν4 • ν1 PO43 at 960 cm-1 shifts to lower wave
PO43 at 660-520 cm-1, and ν2 PO43 at 460 cm-1 numbers (963-967 cm-1) due to the CO32-
[43]. Furthermore, from the presented in Fig. 6 it substitution [49];
is visible that in the FTIR spectra ν3 CO32- and ν2
• B-type CO3HA is preferentially observed
on the surface of the soaking glass-
ceramics [4, 45, 51, 55-61];

120

• A-type CO3HA was also detected [46, 20 mg/l (for 738-15). From the data obtained, it
51, 55]. can be concluded that the silicon containing
CO3HA may be formed on the soaked surface of
Table 2. Vibration modes for the samples after the thermally treated samples. The concentration
of Mg2+ in SBF solutions shows the same trends.
soaking in SBF solution for 3, 9 and 15 days and For all studied samples, the concentration of
corresponding frequencies (cm−1), where A and Mg2+ in SBF solution (31 mg/l) increased to 99
mg/l (for 703-9) and to 83 mg/l (for 738-3 and
B are A-type CO3HA or B-type CO3HA, respec- then slightly decreased to 26 mg/l (for 709-15)
tively and to 20 mg/l (for 738-15). It is very likely that
Mg2+ is also included in CO3HA, which is
Vibra Sample 709 Sample 738 As- formed on the soaked surface. Finally, the P5+
tional signe concentration slightly decreased from 29 mg/l
mode (for the initial SBF solution) to 0 mg/l (for all
d samples) regardless of the soaking time
ν3 3 9 15 3 9 15 ac-
PO4 days days days days days days cord- Si4+ slightly decreased with increasing the
stretc 1022 1024 1026 ing to soaking times from 80 mg/l (for 709-3) to 26
hing 1044 1045 1040 1023 1024 1022 mg/l (for 709-15), and for 63 mg/l (for 738-3) to
1052 1044 1050 [44] 20 mg/l (for 738-15). From the data obtained, it
ν1 963, 965, 967, [44] can be concluded that the silicon containing
PO4 B B B 960, 964, 963, CO3HA may be formed on the soaked surface of
stretc BBB [49] the thermally treated samples. The concentration
hing 538 540 538 of Mg2+ in SBF solutions shows the same trends.
567 567 565 540 530 525 [20, For all studied samples, the concentration of
ν4 575 570 575 565 563 565 50] Mg2+ in SBF solution (31 mg/l) increased to 99
PO4 609 618 611 574 575 581 [31, mg/l (for 703-9) and to 83 mg/l (for 738-3 and
stretc 638 640 635 610 614 613 38, then slightly decreased to 26 mg/l (for 709-15)
hing 722 720 720 641 649 642 43] and to 20 mg/l (for 738-15). It is very likely that
765 765 719 720 720 [25] Mg2+ is also included in CO3HA, which is
[34] formed on the soaked surface. Finally, the P5+
763 763 [51] concentration slightly decreased from 29 mg/l
[51] (for the initial SBF solution) to 0 mg/l (for all
ν2 456 451 441 448 [52] samples) regardless of the soaking time.
PO4 454 456 458 458 [20,
stretc 1543, 1540, 49]
hing A A 1540, 1538, 1539, 1542, [53,
1521, 1521, A A A A 54]
ν3 A A 1521, 1517, 1518, 1522, [55]
CO3 1508 1504, A A A A [46]
stretc 1489, A 1509, 1503, 1504, 1505, [51]
hing B 1489, A A A A [51,
1473, B 1489, 1487, 1488, 1490, 56]
B 1473, B B B B [55,
1458, B 1473, 1473, 1470, 1474, 57]
B 1457, B B B B [45,
1434, B 1457, 1457, 1453, 1458, 58,
B 1436, B B B B 59]
1416, B 1436, 1440, 1433, 1436, [59,
B 1418, B B B B 60]
1396, B 1418, 1415, 1415, 1419, [61]
B 1397, B B B B [5]
B 1397, 1400, 1394, 1397,
B B B B

ν 2 867 866 864 865 867 867 [44]
CO3
bend-
ing

Ca- 710 710 712 710 712 714 [62]
CO3
cal-
cite

Briefly, we can summarize that the prepared Fig. 5. Changes in Ca, Si, Mg and P con-
glass-ceramics are in vitro bioactive. centrations for the SBF solutions (sample SBF)
and for samples 709 and 738, after in vitro test in
From the data presented in Fig. 5, it can be SBF solutions for 3, 9 and 15 days in static con-
seen that the Ca2+ concentration slightly in-
creased for all soaked samples, compared with ditions
the Ca2+ concentration (64 mg/l) in the initial
SBF solution. On the other hand, the concentra-
tion of Si4+ slightly decreased with increasing the
soaking times from 80 mg/l (for 709-3) to 26
mg/l (for 709-15), and for 63 mg/l (for 738-3) to

121

The obtained ICP-AES data indicate that the obtained results are in full agreement with XRD,
Si4+ and Mg2+ containing CO3HA may be formed FTIR and ICP-AES results.
on the soaked surface. Furthermore, the pres-
ences of the bands of PO43- in FTIR spectra in CONCLUSIONS
the in vitro test suggest that the prepared samples
are in vitro bioactive. The presented ICP-AES Novel Mg-containing glass ceramics were
data are in agreement with XRD and FTIR data synthesized via sol-gel method. The obtained
analysis for the soaked samples. dried gels were thermally treated at 1350oC and
1250oC. XRD of these samples proved that in the
SEM of the samples after soaking in SBF sample annealed at 1350oC merwinite crystal-
solution for 15 days in static conditions are pre- lized as a main phase accompanied with aker-
sented in Fig. 6. manite. When the sample was treated at 1250oC
merwinite was also present in the main phase,
a accompanied by the two additional crystalline
phases: akermanite and bredigite. FTIR of the
samples after in vitro tests in SBF solution for
different times in static conditions revealed that
B-type carbonate apatite (B-CO3HA) is preferen-
tially observed on the surface of the soaked sam-
ples. ICP-AES results showed that Mg2+ and Si4+
containing CO3HA may be formed on the surface
after immersion in SBF solutions for 3, 9 and 15
days of soaking.

ACKNOWLEDGEMENTS

I would like to thank Prof. Irena Michailova
b from the Department of Silicate Technology in

UCTM Sofia for her assistance with XRD data
and for comments that greatly improved the
manuscript

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Assen Zlatarov University
ANNUAL, VOL. XLVIII, BOOK 1, 2019
TECHNICAL AND NATURAL SCIENCES

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Iliana Ishmerieva

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