SWIPT in energy constrained relay networks

Shah, Syed Tariq Sungkyunkwan University 2018 국내박사

Wireless energy harvesting is an efficient way to prolong the lifetime of energy constrained wireless networks. Since the radio frequency signals can simultaneously carry both energy and information, they can be utilized to transfer information and power-up the energy constrained nodes in the network. In this dissertation, we propose and study the performance of energy harvesting based relay networks, where the communicating nodes concurrently transmit their information signals to a relay node. The relay node is assumed to be an energy constrained node, and therefore it first harvests energy from the received signals. Then using the harvested energy, the relay node forwards the information signals to its corresponding destination. More specifically, the performance of three different network models, namely, point-to-point, multi-point-to-multi-point, and point-to-point cognitive networks are proposed and studied. For energy harvesting at a relay node, we analyze the performance of different energy harvesting protocols, i.e., the time switching based relaying protocol (TSR), power splitting protocol (PSR), and the hybrid power-time switching based relaying protocol (HPTSR). Once the energy is harvested using one of these protocols, the relay then forwards the received information signal towards its destination. For information processing at the relay node, we have proposed and analyzed the performance of three different relays, i.e., (i) amplify-and-forward (AF) relay, (ii) multiplicative relay, and (iii) decode-and-forward (DF) relay. For AF based relay networks, we derive the analytical expressions for the outage probability and achievable throughput for the aforementioned protocols. Our numerical results verify the analytical derivation and show the effect of different system parameters on achievable throughput at the destination. It is concluded, that for the considered two-way AF relay network, at high SNR and low transmission rate, HPTSR protocol outperforms TSR and PSR protocols. On the other hand, at low SNR and high transmission rates, TSR protocol outperforms the other two protocols. Furthermore, we have also proposed and studied a novel multiplicative relaying scheme for energy harvesting based two-way relay networks. With the help of numerical results, we show that in an energy constrained two-way relay network, the proposed multiplicative relay scheme can achieve higher throughputs than AF relay scheme. In addition to point-to-point relay network, we also study a multi-point-to-multi-point relay network, where multiple source nodes communicate with their respective destination nodes via an intermediate energy constrained DF relay. Based on PSR, the relay node first harvests the energy from all received source signals which is then optimally distributed among all possible destination nodes using a geometric water-filling technique. The decision on what portion of received signal power should be used for energy harvesting is dynamically decided based on two factors: (i) the power level of the received signal at relay node and (ii) the availability of transmit power for that particular signal, in order to forward it to its corresponding destination. Based on the proposed energy harvesting and power distribution mechanisms, four different relaying strategies are designed and studied. Our numerical results provide useful insights into different system parameters of an energy harvesting-based multi-pair DF-relay network. Our results also show that, compared to equal power distribution (EPD) schemes, our proposed optimal scheme can significantly improve the overall system sum-rate. To further enlarge the scope of this dissertation, an ambient backscatter-enabled DF cognitive relay network with wireless energy harvesting capabilities is also proposed. In the proposed scheme, a source node communicates with its destination node via a radio frequency-powered DF relay. The relay node is assumed to be equipped with two different interfaces and can concurrently harvest/decode and backscatter the received source signals. A power-splitting-based approach is adopted for information processing and energy harvesting at the relay. The analytical expressions for throughput and outage probability at all receiving nodes are derived. We show that our analytical results exactly match our simulation results. Our results also show that using the ambient backscatter for secondary communications can significantly improve the overall network performance in terms of achievable throughput and energy efficiency.

Energy Recycling Techniques for Ultra-Low Power Dynamic Voltage Scaler Circuits

Syed Asmat Ali Shah 충북대학교 전자공학전공 2020 국내박사

Spatio-temporal analysis of modes in lossy plasmonic waveguides

Ibrahim, Syed Muhammad Anas 세종대학교 대학원 2019 국내석사

A comprehensive case study on the modes evolving in dissipative plasmonic waveguide structures, including metal-insulator-metal (MIM) and insulator-metal-insulator (IMI), is presented. The dispersion and power-flow characteristics of the modes are analysed via two approaches: spatial and temporal. We show that two approaches result in not only different dispersion relations but also different power flow characteristics. There are six types of modes based upon the directions of their group velocity and associated power flow: forward, backward, negative power (NP), negative group velocity (NGV), non-propagating, and trapping modes. With the spatial loss approach, we can observe that metallic loss makes trapping and non-propagating modes disappear while NP and NGV modes survive in MIM and IMI structures, respectively. With the temporal loss approach, we can find that both MIM and IMI structures, under lossless and lossy conditions, do support forward, backward, NP, trapping, and non-propagating modes. A comprehensive case study on the modes evolving in dissipative plasmonic waveguide structures, including metal-insulator-metal (MIM) and insulator-metal-insulator (IMI), is presented. The dispersion and power-flow characteristics of the modes are analysed via two approaches: spatial and temporal. We show that two approaches result in not only different dispersion relations but also different power flow characteristics. There are six types of modes based upon the directions of their group velocity and associated power flow: forward, backward, negative power (NP), negative group velocity (NGV), non-propagating, and trapping modes. With the spatial loss approach, we can observe that metallic loss makes trapping and non-propagating modes disappear while NP and NGV modes survive in MIM and IMI structures, respectively. With the temporal loss approach, we can find that both MIM and IMI structures, under lossless and lossy conditions, do support forward, backward, NP, trapping, and non-propagating modes.

A Sensitivity Enhanced MWCNT/PDMS Tactile Sensor Using Micropillars and Low Energy Ar+ Ion Beam Treatment

SYED AZKAR-UL-HASAN University of Science and Technology 2016 국내박사

Flexible and wearable device of high sensitivity, which can detect delicate touch, has achieved a considerable attention of researchers for the various promising applications like bionic arms, touch screen panels. This PhD dissertation is aimed manipulating the conductivity associated with high aspect ratio multi-wall carbon nanotube (MWCNT) inside the inert, non-toxic and highly elastic polydimethylsiloxane (PDMS) for the realization of piezoresistive tactile sensor skin. The development of straight micropillars over the MWCNT/PDMS enhanced the sensitivity for piezoresistive tactile sensor skin especially pressures comparable to gentle touch. The low energy Ar+ ion beam treatment of micropilllars over MWCNT/PDMS substrate not only induced the enough stiffness to micropillars in order to withstand the pressures during the performance test but also generated curvature for the 20 μm micropillar. The low energy ion bombardment stabilizes the electrical property of MWCNT/PDMS surface and tunes the curvature of micropillars according to the treatment conditions. The straight micropillars which are treated by Ar+ ion with the angle of 0° enhances the sensitivity under normal pressure and the curved micropillars which are treated by Ar+ ion with the angle of 60° differentiates the direction of applied shear force. The ion beam treatment on micropillar structured MWCNT/PDMS tactile sensors can be applied on the reliable sensing under gentle touch with the directional discrimination.

Locally Distributed, Energy Efficient, Scalable and Adaptable Key Management Solution for Clustered Sensor Networks

Syed Muhammad Khaliq-ur-Rahman Raazi 경희대학교 2010 국내박사

Wireless Sensor Networks (WSN) have proved to be useful in applications that involve monitoring of real-time data. There is a wide variety of monitoring and tracking applications that can employ Wireless Sensor Network. Characteristics of WSN, such as topology and scale, depend upon the application, for which it is employed. Security requirements in WSN vary according to application dependent network characteristics and characteristics of an application itself. Key management plays an important role in preventing adversaries from listening, disrupting or blocking private communications. Also, Key management is the most important aspect of security as other security modules depend on it. However, key management should not incur too much overhead in resource constrained WSN. This thesis aims to propose an energy-efficient key management framework, which prevents a WSN from having a single point of failure and can adapt according to application characteristics, for clustered wireless sensor networks. Its primary contribution lies in the development of unified, energy-efficient framework, called scalable and energy efficient key management framework. WSN are susceptible to node capture and many network levels attacks. In order to provide protection against such threats, WSNs require lightweight and scalable key management scheme because the nodes are resource constrained and vary in number. Number of nodes in a WSN can be very high depending upon the application. Also, effect of node compromise should be minimized and node capture should not hamper the normal working of a network. Moreover, WSN should not have single point of failure, which means that compromise of a single node should not compromise other nodes or a large number of nodes. Therefore, I present an EBS-based Key Management scheme called MUQAMI+ for large scale clustered sensor networks. I have distributed the responsibility of key management to multiple nodes within cluster, avoiding single point of failure and getting rid of costly inter-cluster communication. MUQAMI+ is scalable because the ratio of nodes, used for key management decreases drastically as the number of nodes in a cluster of WSN increases. Also, it is highly efficient in terms of key refreshment and revocation of compromised nodes. Wireless body area networks (WBAN) consist of resource constrained sensing devices just like other wireless sensor networks (WSN). However, they differ from WSN in topology, scale and security requirements. WBAN have a small number of nodes tactically placed on a human body to support usability. When placed on a human body, many nodes fall in communication range of each other. Also, security requirements of WBAN differ from WSN because human intervention is possible or inevitable in many applications of WBAN. Moreover, WBAN are used to monitor biometrics, which can be used to generate key values. Due to these differences, key management schemes designed for WSN prove inefficient and unnecessarily complex when applied to WBAN. Also, monitoring of biometrics render key management of WBAN different from key management of WPAN. Therefore, I propose an energy-efficient and distributed key management scheme for WBAN called BARI+. BARI+ reduces key generation cost by using biometrics. Also, it has node revocation mechanism for applications, in which immediate human intervention can not be guaranteed.

Moisture movement in cement-stabilized base materials

Syed, Imran Majidali Texas A&M University 2000 해외박사(DDOD)

The aggregate base layer is the main load-bearing member in many pavement structures in Texas. If the locally available aggregates are viewed as marginal quality, they are frequently stabilized with cement to improve their properties. The amount of cement used with a base material is generally selected based on the unconfined compressive strength of the treated layer. When reduced levels of stabilization are used, there is a concern that the material property improvements may not be permanent and that the benefits of stabilization will “disappear” after a few years in service. It is well known that a primary factor influencing the long-term performance of cement-stabilized base materials is moisture. Joint research studies in Texas and Finland proposed the use of a new test procedure, the Tube Suction Test (TST), to evaluate the moisture susceptibility of untreated base materials (Saarenketo and Scullion, 1995). In this research the TST was evaluated on four commonly used base materials stabilized with low levels of cement in the state of Texas. The ultimate proposal is that this test can be used together with current strength tests to ensure that future base materials will have not only adequate initial strength but also be resistant to long term moisture damage. Concern with the TST is that the engineering significance of parameters measured, the surface dielectric constant, is not known. No fundamental studies have been conducted to relate this property to the factors influencing pavement performance. The primary goal of this research effort is to gain an understanding of the significance of TST results on the physical, chemical and engineering properties that influence long term pavement performance of both treated and untreated base materials. A controlled laboratory study was conducted in which different amounts of cement were used to stabilize a limited number of aggregate materials that are commonly stabilized with cement and used as base or subbase layers for road construction in the state of Texas. This study evaluated both the strength and moisture changes in these marginal materials. Advanced micro-analysis tools such as electron microscopy, X-ray diffraction, and other new advanced analytical techniques were evaluated to determine if they can show the changes in the amount of pore water before, during and after conducting the tube suction test. These tools were also used to study the chemical changes in cement-stabilized materials and to identify the precipitates that are observed on some samples after completion of TST.

Residues dissipation, safety assessment and correction of matrix effect for determination of selected pesticides in two minor crops

Sardar, Wasim Syed 강원대학교 대학원 2023 국내박사

Pesticides are extensively used in modern agriculture for eradicating pests and pathogenic diseases, to improve crop yields for the growing population. Although pesticides play a significant role in modern agricultural practices, the adverse impacts on human health cannot be avoided. To ensure the safety of crops and avoid the health hazard caused by pesticides, dissipation studies and safety assessments of pesticides are essential. This study was performed to determine the residues and dissipation of cyantraniliprole and indoxacarb in wild garlic and fenazaquin and metaflumizone in butterbur grown under greenhouse conditions. The pesticides were applied two times with 1-week intervals at 0, 3, 7, and 14 days before harvest. The analytes were extracted by QuEChERs method and analyzed by liquid chromatography coupled to tandem mass spectrometry. The residual data were obtained to investigate the dissipation pattern and residual characteristics of selected pesticides in both crops. The obtained results could provide a basis for the establishment of maximum residue limits (MRLs) and pre-harvest intervals (PHI) for the safe use of the investigated pesticides in the studied crops. The pesticide's acceptable daily intake (ADI) was used to estimate safety assessment, considering the crop's average consumption per person per day and the total pesticide consumed in the crop per person per day. The obtained data will be helpful to set pesticide safety use guidelines for crops and protect the environment as well as consumer health. Furthermore, in this study, the matrix effect for the determination of 8 compounds in wild garlic samples and 4 compounds in butterbur samples was evaluated, and for the elimination of the matrix effect, a new strategy called matrix correction factor (MCF) has been proposed. After the application of MCF, the matrix effect of the majority of compounds significantly decreased. Moreover, the recoveries obtained by using MCF applied solvent calibration curve were precise and in the acceptable range. The application of MCF in solvent calibration is economically advantageous and generally more robust than matrix-matched calibration. Hence, it is recommended to avoid the use of calibration curves prepared every time in matrix extracts for the quantification of these pesticides in real samples. 국민들의 소득향상과 식생활이 개선되면서 신선 채소류에 대한 수요가 지속적으로 증가하고 있다. 이에 맞춰 재배 기간 중 병해충으로 농산물을 보호하여 생산성 증대 및 품질향상을 위해 농약의 사용은 필수적이다. 한편, 농약은 살포된 이후 작물에 잔류하여 안전성 문제를 야기할 수 있으며, 이를 해소하기 위해 잔류농약의 반감기와 안전성평가에 관한 연구가 필요한 실정이다. 따라서 본 연구는 달래 중 cyantraniliprole, indoxacarb와 머위 중 fenazaquin, metaflumizone를 선정하여 작물 잔류성 시험을 통해 농약의 감소 경향을 파악하기 위해 수행되었다. 공시약제 4품목에 대한 약제처리는 두 작물 모두 수확 전 14, 7, 3 및 0일 전 7일 간격으로 2회 경엽처리 하였으며, 일시 수확하였다. 시료 분석은 QuEChERS 전처리법을 적용하였으며, 정량 및 정성 분석은 LC-MS/MS를 이용하였다. 작물 잔류성 시험의 결과로 산출된 잔류량을 바탕으로 잔류허용기준(maximum residue limit, MRL)과 안전사용기준(pre harvest interval, PHI)을 제안하였다. 또한, 본 연구에서 제안한 잔류허용기준을 바탕으로 안전성 평가를 수행하였으며, 해당 작물의 평균 섭취량과 일일섭취허용량(acceptable daily intake, ADI)을 고려하여 산출하였다. 또한 본 연구에서는 매질효과를 저감하기 위한 방법으로 매질보정계수(matrix correction factor, MCF)를 고안하였으며, 달래 중 8성분과 머위 중 4성분에 적용하였다. 매질보정계수를 적용한 결과에서 대부분의 농약에서 매질효과가 크게 개선되었으며, 이를 이용한 용매 검량선에서 회수율 산출 시 70~120%의 유효회수율 범위를 만족하였다. 따라서 매질보정계수를 이용한 방법은 기존의 매질보정법에 비해 간단하고 경제적인 방법으로 실제 분석 현장에 도입 시 보다 효과적으로 매질효과를 개선할 수 있을 것으로 사료된다.

Conditioned Seeing as Related to Bidirectional Naming for Unfamiliar Stimuli with Third through Fifth Grade Students Diagnosed with Autism

Syed, Noor Y Columbia University ProQuest Dissertations & These 2018 해외박사(DDOD)

Conditioned Seeing as Related to Bidirectional Naming for Unfamiliar Stimuli with Third through Fifth Grade Students Diagnosed with Autism In a series of three experiments, I investigated the emergence of conditioned seeing, defined as delayed drawing responses, as a potential component of bidirectional naming (BiN) for unfamiliar stimuli, which was defined in this study as the emergence of untaught listener and speaker responses following a naming experience with school-aged participants diagnosed with autism. Following exposure to incidental naming opportunities (stimulus-stimulus pairing), participants demonstrated BiN responses to non-contrived stimuli but did not demonstrate BiN responses to unfamiliar stimuli. In Experiment I, I assessed BiN and delayed drawing responses to unfamiliar stimuli following a naming experience in which attending to auditory stimuli, or names of the symbol, was paired with reinforcing stimuli for 6 participants. Participants were matched for level of verbal behavior and subsequently assigned to an experimental multiple exemplar instruction (MEI) or control group. A multiple probe design with a simultaneous treatment condition was utilized. Participants in the MEI group were exposed to listener, speaker, and drawing (transcription) responses with teaching sets of stimuli, while the control group experienced the school curriculum only, Direct Instruction. Participants in the control group were also exposed to a repeated probe condition during which they experienced a matched number of probe sessions with participants in the MEI-experimental group. Results of the first experiment indicated the presence of BiN with unfamiliar stimuli and conditioned seeing repertoires for participants in the MEI-experimental group following the intervention, however BiN and delayed drawing responses were not present for participants in the control group. Based on the results of Experiment I, I hypothesized that BiN and conditioned seeing behaviors may be evoked as a function of the establishment of a history for conditioned reinforcement for simultaneously observing a visual and auditory stimulus while engaging a drawing response. Two participants were selected for Experiment II as they demonstrated the presence of unidirectional naming for unfamiliar stimuli and delayed drawing responses during probe sessions; participants included in Experiment I did not demonstrate unidirectional naming for unfamiliar stimuli. Utilizing a multiple probe design, Experiment II tested whether the presence of unidirectional naming and drawing responses would evoke multiple stimulus control across speaker responses following exposure to a learn unit procedure. The learn unit procedure implemented in Experiment II required participants to emit an echoic for the name of the target stimuli while simultaneously attending to the visual and auditory stimuli, as well as drawing the stimuli. Results of the study indicated that BiN repertoires were present for unfamiliar stimuli following the intervention. In Experiment III, I again implemented the learn unit procedure but eliminated requirement of the echoic. Participants in Experiment III did not demonstrate unidirectional naming for unfamiliar stimuli or delayed drawing responses before the learn unit intervention. Three of these participants included in Experiment III had been assigned to the control group in Experiment I and a fourth participant was added. Results of Experiment III indicated that the learn unit procedure evoked BiN for unfamiliar stimuli and conditioned seeing for all four participants, indicating the presence of multiple stimulus control for verbal behavior. The source of this learning may be the establishment of conditioned reinforcement for observation of unfamiliar stimuli.

Titanium porous transport layers for high-current density operation of PEM water electrolysis

Syed Shabbar Hassan Shah University of Science & Technology, Korea 2021 국내석사

Polymer Electrolyte Membrane Water Electrolysis has received special attention as a source of hydrogen gas since last two decades owing to its high throughput, efficiency, dynamic response, and high purity of H2(g). However, in order to scale it up to commercial level, there is a need to reduce its capital (CAPEX) and operational expenditure (OPEX) significantly. Currently, the cell voltage is far above the thermoneutral voltage due to excess losses arising from interfacial contact resistances, limited kinetics of the anodic reaction, and impeding mass-transport at high-current densities (>3A/cm2). Titanium Porous transport layer acts as a medium for transport of reactant (H2O) and product (O2) to and from anode catalyst layer besides acting as a current collector. The pore profile (including pore-size, porosity, tortuosity) and surface characteristics (especially hydrophilicity, surface roughness, and surface oxidation) greatly influence the mass-transport and ohmic losses. The understanding and correlation of above mentioned features to each over-potential are the essentials of this thesis. For this purpose, a Tape-casted sintered powder PTL has been fabricated and characterized in-situ and ex-situ. Furthermore, it has been studied, along with the commercial PTLs, for the effects of porosity, roughness, contact angle, tortuosity, and electrical conductivities on the mass-transport and ohmic over-potential. Moreover, a CFD model reconstructed from µ-CT images of PTLs has been used to simulate the oxygen transport across the thickness/cross-section. The experimental and simulation results validate that in-plane tortuosity (along with MacMullin no.) and surface roughness of PTL has major influence on the mass-transport. Tape-casted TC-SP PTL having higher roughness, least porosity and pore size (43% and 8µm respectively) yields highest IV performance. This thesis provides a roadmap for the optimization of Ti PTLs henceforth encouraging commercialization of PEM water electrolysis. The 1st chapter of this thesis provides introduction to the PEM water electrolysis technology. It further states the research motivation and objectives of this thesis. The 2nd chapter provides a literature review of PEMWE, its components, particularly Porous Transport layers (PTLs). The 3rd chapter constitutes introduction, experimentation, and results with detailed discussion. Finally, the 4th and 5th sections give a conclusion and future recommendations respectively.

Dynamic Model for Electrode Force and Electrode Expansion in Resistance Spot Welding Machines

Syed Asad Ullah Shah 명지대학교 국제대학원 2009 국내석사

The complicated mechanical-thermal-electrical coupled processes occurring during welding and the complex mechanical structure of the machine bring difficulties in accurate and reliable monitoring and control of the process and the weld quality. Dynamic electrode force and displacement, both, being responses to nugget formation and growth, are two important parameters to monitor. The measure of electrical and mechanical parameters during welding can be used to monitor the welding process and weld quality. It has been realized that mechanical properties may be of even greater importance that electrical ones. However the complexity of the machine structure makes it very difficult to measure machine mechanical parameters such as moving mass, stiffness and damping. The electrode force is affected by thermal and metallurgical factors but the vibration due to these force changes is related with basic mechanical parameters. An analytical dynamic model for electrode force and displacement was designed; an experimental setup was developed to determine the mechanical characteristics (moving mass m, equivalent stiffness k and damping c) which govern the dynamic mechanical response of the resistance spot welding machine. During the test different levels of load were applied and measured using a load cell. The corresponding acceleration of the electrodes for each level of load was measured by accelerometer, filtered and numerically integrated to find the corresponding velocity and displacement. The machine dynamic parameters were determined by finding the unknowns of the proposed analytical model with experimentally calculated data. A lumped-mass damped vibratory unit was considering for weld head. A Simulink model, based on the proposed mathematical, was made to investigate the influence of these mechanical parameters on the welding process. The electrode response due to electrode force was simulated by changing the values of stiffness and damping. It was observed that the both of the machine characteristic parameters(c, k) have significant effect on the response of welding head movement. An equivalent heat input model has been developed in which the movement of electrode for different level of heat inputs is equivalent to the change in dynamic mechanical parameters values which can provide a base for predicting the change in dynamic mechanical parameters during welding time. Further, dynamic model of the weld head would allow an improved quantitative understanding of welding machine characteristics useful for subsequent design improvement and weld quality.