Absolute Polar Duty Cycle Division Multiplexing for High-Speed Fiber Optic Communication System

Multiplexing is one of the fundamental necessities in today’s digital communications. It allows multiple users to share the bandwidth of the transmission medium. In this dissertation a new design of the Duty cycle Division Multiplexing (DCDM) family, namely Absolute Polar Duty Cycle Division Multiplexing (APDCDM) which is based on the polar signaling and different return to zero (RZ) duty cycles is reported for high speed optical fiber communication systems. Unlike all the other techniques, in AP-DCDM different users share the communication medium to transmit in the same time period and at the same carrier wavelength, but with different duty cycles. The unique duty cycle for each channel helps to regenerate data at the receiver. Two different AP-DCDM designs, namely AP-DCDM with guard band (GB) and AP-DCDM without GB have been successfully demonstrated. This thesis is presented based on the alternative format which has been approved by University Putra Malaysia’s Senate, which is the manuscript-based format. The major difference between this alternative format and the conventional ones is that, this format uses published papers in place of the regular chapters on results and discussion. The first paper contains a novel concept of decision circuit and Bit-error-rate (BER) estimation method for AP-DCDM which is published in International Review of Electrical Engineering. This journal in indexed by ISI Thomson Scientific. The concepts have significant differences to those used in conventional microwave communication receivers. This is due to the unique characteristics of the multilevel signal produced in AP-DCDM system. The BER estimation method is validated by simulation and compared against bit-to-bit comparison method. The second paper contains the first design of AP-DCDM (AP-DCDM with guard band) which is published in Optical Fiber Technology journal (OFT) by Elsevier. This journal is indexed by ISI Thomson Scientific with 2008 impact factor of 1.253. It is demonstrated that AP-DCDM system has a clear advantage over conventional RZOOK. Complexity and performance comparison against other modulation formats namely Duobinary, Non-Return-to-Zero (NRZ)-OOK and RZ-Differential Quadrature Phase-Shift Keying (RZ-DQPSK) at aggregate speed of 40 Gb/s (2 x 20 Gb/s) are made. It is shown that AP-DCDM has less complexity and the best receiver sensitivity (-32 dBm) and better CD tolerance (±200 ps/nm). In reference to duobinary, AP-DCDM is less complex and has better receiver sensitivity but worse dispersion tolerance The third paper contains the second design of AP-DCDM (AP-DCDM without guard band) which is published in IET Journal of Optoelectronics by Institution of Engineering and Technology (IET), previously IEE. This journal is indexed by ISI Thomson Scientific with impact factor of 0.704. The system tolerance to signal impairments is investigated and it shows that the spectral width of the AP-DCDM can be furthered reduced which leads to better dispersion tolerance compared to other modulation techniques. The fourth paper presents the effect of self-phase-modulation on AP-DCDM system which is accepted for publication in IET Journal of Optoelectronics (with impact factor of 0.704) considering different number of channels, launched power and precompensation ratio. It was shown that SPM is a major factor that introduce penalty to the system. Nonetheless, our results indicate that transmission using AP-DCDM should be possible at the launched power of up to tens of dBm, which is consistent with the requirement of high-quality, long distance transmissions. Finally the fifth paper discusses the performance evaluation of AP-DCDM over Wave length Division Multiplexing (WDM), which is accepted for publication in Optics Communications by Elsevier, which is indexed by ISI Thomson Scientific with 2008 impact factor of 1.552. The narrow optical spectrum on AP-DCDM reduces the inter-channel coherent crosstalk. The possibility of setting channel spacing as narrow as 62.5 GHz for 40 Gbit/s AP-DCDM signal was confirmed. A capacity of 1.28 Tbit/s (32 x 40 Gbit/s) was packed into a 15.5 nm EDFA gain-band with 0.64 bit/s/Hz spectral efficiency by using 10 Gbit/s transmitter and receiver

Influence of Microstructure on Damage Behavior of Sound Absorbing Ceramics

Porous sound-absorbing ceramics contribute to the passive damping of thermo-acoustic instabilities and sound dissipation. As ceramic liners, they must satisfy all requirements respecting mechanical strength and thermal resistance. Design and development of such ceramics concern various aspects like thermal shock resistance, crack behavior, fatigue limit, creep and erosion resistance. The aim of this work is to investigate the mechanical behavior of highly porous sound absorbing ceramics and to predict the brittle damage behavior considering the material microstructure. It studies the applicability of such ceramics as insulation liners for the combustion chambers and gives a clue to further material improvement in terms of mechanical strength. Experiments were performed in this work to characterize the mechanical strengths of a new developed sound absorbing ceramic for the application as ceramic heat shields for the combustion chambers of premixed gas turbines. Compressive tests at both room and high temperature as well as four-point bending tests at room temperature have been carried out. Furthermore, the fits of fracture strengths of the material to the Normal, Weibull and Type I extreme value distributions are investigated. The characterization was then expanded to other physical properties such as porosity, density, thermal conduction coefficients and thermal expansion coefficients. A non-multi-physic but multi-scale approach is applied in this work which predicts the influence of the microstructure on the macroscopic properties. The scale transition method is known as mean-field homogenization method, based on assumed relations between average values of micro-strain and -stress fields in each phase. This homogenization model is based on the Eshelby model and assumes the pores (or rather inclusions) to be ellipsoidal. Influence of the pore density, pore form and pore orientation on the strength of these porous sound absorbing ceramic are studied here. Depending on the loading condition higher strength by higher porosity values is achievable by for example aligning the pores on a desired direction or changing their form from spherical to ellipsoid with high aspect ratios. Furthermore, direct finite element simulations of a representative-volume element (RVE) are also implemented in this work to investigate the pure brittle damage of this sound absorbing ceramic. An effective-stress degradation model has been implemented in a predefined user-subroutine of ABAQUS. It is based on the three dimensional rupture criterion and describes the pure brittle damage under mechanical, thermomechanical, static and quasi-static loadings. Different RVE s have been generated and investigated in terms of damage considering different structural parameters. The present results demonstrate the application potential of these sound absorbing ceramic as liner in terms of mechanical strengths, predict their brittle damage behavior considering the microstructure and provide a base for further material developments and numerical investigations. The applicability of these ceramic to line the combustion chambers in terms of sound absorption is investigated on an experimental set-up at the Faculty of Combustion of the Center of Applied Space Technology and Microgravity (ZARM). The validation of the results from this chapter will be performed on this set-up

The application of data envelopment analysis and queuing models to large scale computer networks

This paper considers a technique for evaluating the operational efficiency of large-scale computer networks via data envelopment analysis and queuing models. The technique consists of two stages. In the second stage, a target DEA model is used which yield the advantages of the proposed technique over the previous one. Numerical illustration is provided to show the improvement of our aspect

Emergency Response Planning for Providing Drinking Water in Urban Areas after Natural Disasters using Multi Criteria Decision Making Methods

9 p.International audienceThe impact of a natural disaster can cause contamination of water, breaking pipelines, structural damages, water shortages, and collapse of the entire system. In emergency or disaster situations water supply are imperative for the rapid return to normalcy. In this paper, water supply planning for emergency response after natural disasters has been studied. Multi Criteria Decision Making (MCDM) has been used as a tool for incorporating decision maker preferences for water supply planning in emergency conditions. Analytical Hierarchy Process (AHP) as a well-known MCDM method was utilized for prioritizing water resources alternatives. For this purpose, the quality and quantity of water for living in emergency conditions after natural disasters were reviewed. Different water resources alternatives which are possible to use for emergency response were identified. Water resources availability, water quality, cost, affected population and delay in service were used as criteria for ranking the water resources alternatives. The proposed methodology was used for Pardis City in the vicinity of Tehran metropolitan in Iran, which is highly vulnerable to earthquakes and floods. The developed methodology provides an opportunity for further incorporation of decision makers' preferences in preparing an Emergency Response Plan (ERP) to improve respond to provide necessary water in disaster situation

Setting targets with interval data envelopment analysis models via wang method

Data envelopment analysis (DEA) is a mathematical programming for evaluating the relative efficiency of decision making units (DMUs). The first DEA model (CCR model) assumed for exact data, later some authors introduced the applications of DEA which the data was imprecise. In imprecise data envelopment analysis (IDEA) the data can be ordinal, interval and fuzzy. Data envelopment analysis also can be used for the future programming of organizations and the response of the different policies, which is related to the target setting and resource allocation. The existing target model that conveys performance based targets in line with the policy making scenarios was defined for exact data. In this paper we improved the model for imprecise data such as fuzzy, ordinal and interval data. To deal with imprecise data we first established an interval DEA model. We used one of the methods to convert fuzzy and ordinal data into the interval data. A numerical experiment is used to illustrate the application to our interval model

Mechanism of deltamethrin resistance in field populations of Tuta absoluta (Lepidoptera: Gelechiidae)

The tomato leaf miner Tuta absoluta (Meyrick) may pose a threat to both greenhouse and open-field tomato production. The aims of this study were: 1) to assess the susceptibility to deltamethrin of seven field populations of T. absoluta in Hamedan province, in comparison with susceptible strain. 2) to investigate the effects of synergists for testing possible mechanisms involved in resistance. Bioassays were done by leaf dipping method to determine the resistance level. Resistance ratios calculated varied from 1.9- to 21.6-times (compared with the susceptible population). In synergism tests, PBO, DEF, and DEM were used to determine whether metabolism was involved in deltamethrin resistance. Tomato leaves treated with appropriate concentration of each synergist were fed to second instar larvae for 12 h. The concentrations of PBO, DEF, and DEM were 100, 100 and 120 mgL-1, respectively. These were the highest concentrations that caused no mortality in susceptible strain in preliminary tests. The cytochrome P450-dependent monooxygenase- inhibitor PBO significantly synergized the activity of deltamethrin in the three greenhouse field populations (with the highest synergism ratio of 5.4). No significant synergism of deltamethrin toxicity was observed when larvae were pretreated with the esterase-inhibitor DEF, and the glutathione depleter DEM, as indicated by the overlap in the 95% CL for treatment with deltamethrin alone or with deltamethrin +DEF/ DEM

Imprecise DEA for setting scale efficient targets.

This paper discusses the new aspects of setting scale efficient targets in DEA with imprecise data such as ordinal and interval. The achieved models are non-linear but it can be solved in linear Appa and Yue models with determining a set of exact data from imprecise input and output data. Numerical examples are provided to show the projection of DMUs to their most productive scale size under input minimization and output maximization criteria