KUET Institutional Repository (Khulna University of Engineering & Technology)
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Disposable and Low-cost Free Chlorine Sensor Based on Pencil Drawn Paper Electrode
No full textThis thesis is submitted to the Department of Chemistry, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Chemistry, April 2017.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 99-108).This is the first alternative analysis of pencil drawn paper electrode for free available chlorine (FAC) detection. It is one of the new technologies for fabricating simple, low lost, portable and disposable analytical device for many application areas including clinical diagnosis, food quality control and environmental monitoring. In this work a complete analysis of physical and electrochemical properties of pencil graphite electrode (POE) and pencil drawn paper electrode (PDPE) has been performed to detect FAC in surface water. Cyclic voltammetry (CV) and amperometry were used to study the electro-catalytic properties. Excellent catalytic activity has been obtained for free chlorine detection using both POE and PDPE with a sensitivity of 121 ± 5.38 .iAmMcm 2 and 36 ± 3.65 pAmM4cm 2 respectively and a linearity range up to 12 mM and 7 mM for both platforms respectively. Also limit of detection POE and PDPE has been found to be 59.5 and 88.9 p.M respectively. There is no response obtained for common interfering ions in surface water such as NO3 , SO 2 , C0 32 , Cl'and HCO3 . Both the sensors were evaluated for their storage stability and response time and thereby can be applied as a low-cost electrochemical sensor for determining FAC in surface water. The unique properties of this sensor allow the passive liquid transport and compatibility with chemical/biochemical are the main advantage of using this sensing platform. In addition, this sensor could better meet the current objectives of a viable low cost and portable device in addition to offering high sensitivity, selectivity and multiple analyte discrimination.Apu Kumar DuttaMaster of Science in Chemistr
Efficient DBA Algorithms for Delay Reduction and Solving the Over-granting Problem of Long Reach PON
No full textThis thesis is submitted to the Department of Electronics and Communication Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Electronics and Communication Engineering, December, 2017.Cataloged from PDF Version of Thesis.Includes bibliographical references.The conventional open access optical network (OAN) with point to multipoint structure needs active components to cover large number of users in a wide area. Requirement of more active components significantly increase the network deployment costs. Cover large range congregation of point to multipoint networks is one of the effective solutions to reduce the network deployment costs. This idea offers the long-reach passive optical network (LR-PON) concept with 100 Km spanning the conventional OAN without any active components between sources to destination. However, the LR-PON involves larger propagation delay as well as end-to-end packet delay compared to the conventional PON system, i.e., spanning distance of 20 km. These delays significantly degrade the performances of the LR-PON with the existing centralized dynamic bandwidth allocation (DBA) algorithms. That is why advanced DBA schemes compatible to the LR-PON are required to reduce its longer propagation as well as end-to-end delays. Proper scheduling of the Report and Gate messages is one of the main challenges to design a new DBA algorithm for the LR-PON. Without proper scheduling of the Report and Gate messages, the LR-PON system suffers from over-granting problem. In this thesis, we propose two DBA schemes, i.e., scheme1 and scheme2, for the LR-PON system. The scheme1 is used to reduce the end-to-end packet delay while the scheme2 is used to mitigate the over-granting problem. In the scheme1, the maximum length of a time cycle is subdivided into multiple units called grant processing units and rapidly grants the window size to each optical network unit (ONU). In the scheme2, in the Report message, each ONU sends the frame information instead of total buffer occupancy to avoid the over-granting problem. The combined effect of the scheme1 and scheme2 effectively improves the overall quality of services (QoSs) of the LR-PON system. The performances of the proposed schemes have been evaluated by numerical simulations. The simulation results also have compared with the three existing DBA schemes, i.e., enhance interleaved polling with adaptive cycle time (E-IPACT), multi-thread polling (MTP), and conventional single thread poling (STP), in terms of end-to-end packet delay, bandwidth utilization, over-granting rate, computational
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complexity, and throughput. It shows that the proposed schemes can ensure the enlargement of the LR-PON system with better QoSs.Shuvashis SahaMaster of Science in Electronics and Communication Engineerin
Dynamic Hybrid-Slot-Size Bandwidth Allocation Algorithm for Improving Quality of Services of Real Time Traffic in Ethernet Passive Optical Network (EPON)
No full textThis thesis is submitted to the Department of Electronics and Communication Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Electronics and Communication Engineering, January, 2017.Cataloged from PDF Version of Thesis.Includes bibliographical references.In the modern data networks, users are communicating via real time traffic, i.e., high
priority (HP) traffic, very often. The demand is increasing for interruption free, high speed,
high efficiency, and best quality of services to perform successful communications. This thesis
emphasizes on the HP traffic like video conferencing, video chat, telemedicine,
teleconferencing, and interactive gaming for the real time communication. In contrast, the low
priority data is considered as the best effort (BE) traffic because the BE traffic do not require
delay sensitive applications.
To achieve better quality data communication for the HP traffic, Ethernet passive optical
network (EPON) is used to fulfill the bandwidth demand of such real time traffic. The
effectiveness of EPON mostly depends on dynamic bandwidth allocation (DBA) algorithm. In
this thesis, we propose a new DBA algorithm called dynamic hybrid-slot-size bandwidth
allocation (DHSSBA) algorithm. To ensure better performance, the proposed DHSSBA is also
incorporated with the new multi-point control protocol (MPCP). As the DHSSBA scheme uses
two Gate messages, one Gate message for the HP traffic and other one for the BE traffic, for
each optical network unit (ONU) in a time cycle, the proposed MPCP protocol eliminates the
synchronization problem between the two Gate messages. The performances of the proposed
scheme are also compared with the existing hybrid-slot-size/rate (HSSR) scheme and delay
variation guaranteed polling (DVGP) scheme. The performance of the proposed scheme has
been analyzed by using numerical simulation in terms of the end to end packet delay, jitter
variation and throughput for both the HP and BE traffic. From the comparison of the
simulation results it is clear that the proposed scheme provides lesser end to end packet delay
for the HP traffic and provides better performances than those of the HSSR and DVGP
schemes.Md. Selim MorshedMaster of Science in Electronics and Communication Engineerin
Crystallographic Orientation-Dependent Performance of InGaN Blue Laser
No full textThis thesis is submitted to the Department of Electrical and Electronic Engineering, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Science in Electrical and Electronic Engineering, December 2017.Cataloged from PDF Version of Thesis.Includes bibliographical references (pages 97-104).This thesis attempts to address a comprehensive in-depth study on the crystal orientation and
strain-dependent optoelectronic performance and frequency response of 445nm InGaN/GaN
single quantum well (QW) Blue Laser operating at 300K by solving a six-band k.p
Hamiltonian at the Brillouin zone center point using finite difference method. Here 8nm
In0.17Ga0.83N is used in the active layer and 10nm GaN is used in the guiding/barrier layer. The
well is compressively strained due to lattice mismatch between well and barrier layer. The
simulation is carried out in MATLAB/Simulink environment along (0001), (1010), (1012),
(1122) and (1011 ) crystal orientations. Tensor rotation scheme is applied to modify the wave
vector and Hamiltonian matrix from conventional (0001) crystal orientation. The compositions
of well materials are selected as In0.15Ga0.85 N, In0.17Ga0.83 N, In0.19Ga0.81 N and In0.21Ga0.79 N
for strain-dependent performance analysis along (1122 ), (1012) and (0001) crystal
orientation. In crystal orientation-dependent analysis for 17% Indium composition, it is found
that there is a substantial correlation of the energy band dispersion profile, momentum matrix,
piezoelectric (PZ) field, peak gain and peak emission wavelength with change of crystal
orientation. The PZ field is found to be zero in (1122) and (1010) crystal orientation (growth
angle of 58.4° and 90° w.r.t z-axis). The optical gains are inspected as 3845, 4460, 4880, 4750
and 4178 cm-1 corresponding to peak emission wavelength of 447, 455, 446, 441 and 438nm
at (0001), ( 1012), (1122), (1011) and (1010) orientations when the injection carrier density
is of 3.5×1019 cm-3. Moreover, the optical gain in (1122) orientation is always higher than
other orientation in any injection carrier density. During compressive strain-dependent
performance evaluation, significant amount of optical gain and emission wavelength variations
are found for the value of In composition from 15% to 21%. For example, in (1122)-oriented
QW; optical gain changes from 4730 to 5190 cm-1 with a corresponding emission wavelength
shifting from 452 to 430 nm for changing the indium composition from 15% to 21%. Output
optical power characteristics are analyzed by developing a Simulink model with the help of 2-
level rate equations and following the concept of signal-flow diagram. In (1122), (1012) and
(0001)-oriented structure, higher optical power is found when the indium composition is 21%
in the active region. Among arbitrary crystal orientated structure, maximum optical power of
4.35mW and minimum threshold current of 0.74mA is obtained in (1122) crystal orientation.
A state-space model is formed for each (hkil)-orientated crystal structure in order to observe
their frequency responses (Bode Plot) close to corner frequencies. The laser system for each
orientation and indium composition is found to be stable as positive gain and phase margin is
achieved. Highest magnitude (dB) response is obtained in semipolar (1122) crystal orientation
for 21% indium composition in well. This numerical result demonstrates that semipolar
(1122)crystal orientation is of special interest and can be incorporated into the active layer of
blue laser in order to have best performance for high-speed lightwave communication
technologies which can be used for medical & industrial purpose, precision measurement,
military defence & security, thermal imaging, DVD and Blu-ray players etc.Sourav RoyMaster of Science in Electrical and Electronic Engineerin