Shahriar Jamasb

Bio: Shahriar Jamasb is an academic researcher from Bu-Ali Sina University. The author has contributed to research in topics: ISFET & Threshold voltage. The author has an hindex of 11, co-authored 25 publications receiving 1102 citations. Previous affiliations of Shahriar Jamasb include University of California, Davis & Conexant.

Classification and comparison of maximum power point tracking techniques for photovoltaic system: A review

Abstract: In recent years there has been a growing attention towards use of solar energy. The main advantages of photovoltaic (PV) systems employed for harnessing solar energy are lack of greenhouse gas emission, low maintenance costs, fewer limitations with regard to site of installation and absence of mechanical noise arising from moving parts. However, PV systems suffer from relatively low conversion efficiency. Therefore, maximum power point tracking (MPPT) for the solar array is essential in a PV system. The nonlinear behavior of PV systems as well as variations of the maximum power point with solar irradiance level and temperature complicates the tracking of the maximum power point. A variety of MPPT methods have been proposed and implemented. This review paper introduces a classification scheme for MPPT methods based on three categories: offline, online and hybrid methods. This classification, which can provide a convenient reference for future work in PV power generation, is based on the manner in which the control signal is generated and the PV power system behavior as it approaches steady state conditions. Some of the methods from each class are simulated in Matlab/Simulink environment in order to compare their performance. Furthermore, different MPPT methods are discussed in terms of the dynamic response of the PV system to variations in temperature and irradiance, attainable efficiency, and implementation considerations.

A physical model for drift in pH ISFETs

Abstract: A physical model is presented which quantitatively describes the threshold voltage instability, commonly known as drift, in n-channel Si3N4-gate and as well as Al2O3-gate pH ISFETs. The origin of the so-called drift is postulated to be associated with the relatively slow chemical modification of the gate insulator surface as a result of exposure to the electrolyte. The chemical modification of the surface is assumed to result from a transport-limited reaction whose rate is modeled by a hopping and/or trap-limited transport mechanism known as dispersive transport. The change in the chemical composition of the insulator surface leads to a decrease in the overall insulator capacitance with time, which gives rise to a monotonic temporal increase in the threshold voltage.

A physical model for threshold voltage instability in Si/sub 3/N/sub 4/-gate H/sup +/-sensitive FET's (pH ISFET's)

Abstract: A physical model is presented which quantitatively describes the threshold voltage instability, commonly known as drift, in n-channel Si/sub 3/N/sub 4/-gate pH ISFET's. The origin of the so-called drift is postulated to be associated with the relatively slow conversion of the silicon nitride surface to a hydrated SiO/sub 2/ or oxynitride layer. The rate of hydration is modeled by a hopping and/or trap-limited transport mechanism known as dispersive transport. Hydration leads to a decrease in the overall insulator capacitance with time, which gives rise to a monotonic temporal increase in the threshold voltage.

An analytical technique for counteracting drift in ion-selective field effect transistors (ISFETs)

Abstract: The instability of the dc operating point in pH-sensitive ion-selective field effect transistors (ISFETs) renders the continuous monitoring of physiological pH using these devices inaccurate. This instability, commonly known as drift, manifests itself as a relatively slow, monotonic change in the measuring output signal in the absence of variations in the pH. In this work, a method for correction of ISFET drift is presented. This method takes advantage of the relatively small instantaneous drift rate in ISFETs to compensate for the drift signal superimposed on the sensor output. The validity of this method is experimentally confirmed by continuous monitoring of pH under in vitro conditions approximating metabolic acidosis using a Si/sub 3/N/sub 4/-gate pH-sensitive ISFET.

Foundations and Challenges of Low-Inertia Systems (Invited Paper)

Abstract: The electric power system is currently undergoing a period of unprecedented changes. Environmental and sustainability concerns lead to replacement of a significant share of conventional fossil fuel-based power plants with renewable energy resources. This transition involves the major challenge of substituting synchronous machines and their well-known dynamics and controllers with power electronics-interfaced generation whose regulation and interaction with the rest of the system is yet to be fully understood. In this article, we review the challenges of such low-inertia power systems, and survey the solutions that have been put forward thus far. We strive to concisely summarize the laid-out scientific foundations as well as the practical experiences of industrial and academic demonstration projects. We touch upon the topics of power system stability, modeling, and control, and we particularly focus on the role of frequency, inertia, as well as control of power converters and from the demand-side.

Tackling Climate Change with Machine Learning

Abstract: Climate change is one of the greatest challenges facing humanity, and we, as machine learning experts, may wonder how we can help. Here we describe how machine learning can be a powerful tool in reducing greenhouse gas emissions and helping society adapt to a changing climate. From smart grids to disaster management, we identify high impact problems where existing gaps can be filled by machine learning, in collaboration with other fields. Our recommendations encompass exciting research questions as well as promising business opportunities. We call on the machine learning community to join the global effort against climate change.

Energy management strategies in hybrid renewable energy systems: A review

Abstract: Variability and intermittency are some of the main features that characterize renewable energy sources. Intermittency usually includes both predictable and unpredictable variations. The many drawbacks of intermittency of renewable sources can be overcome by considering some special design considerations. Integrating more than one renewable energy source and including backup sources and storage systems are among the few measures to overcome these drawbacks. These additional design considerations usually increase the overall cost of the renewable system. Furthermore, the presence of more than one energy supply/storage system requires the control of energy flow among the various sources. Therefore, optimizing the size of the components and adopting an energy management strategy (EMS) are essential to decreasing the cost of the system and limiting its negative effects. The energy management strategy is commonly integrated with optimization to ensure the continuity of load supply and to decrease the cost of energy production. Therefore, energy management is a term that collects all the systematic procedures to control and minimize the quantity and the cost of energy used to provide a certain application with its requirements. The energy management strategy usually depends on the type of energy system and its components. Various approaches and techniques have been used to develop a successful energy management strategy. In this paper, a comprehensive review of the approaches proposed and used by authors of many papers is conducted. These approaches include both the standalone hybrid renewable energy systems and the grid-connected hybrid renewable systems. More attention is focused on popularly used techniques to address the features of each system. The selected papers in this review cover the various configurations of the hybrid renewable energy systems for electric power generation only.

Nanopore Fabrication by Controlled Dielectric Breakdown

Abstract: Nanofabrication techniques for achieving dimensional control at the nanometer scale are generally equipment-intensive and time-consuming. The use of energetic beams of electrons or ions has placed the fabrication of nanopores in thin solid-state membranes within reach of some academic laboratories, yet these tools are not accessible to many researchers and are poorly suited for mass-production. Here we describe a fast and simple approach for fabricating a single nanopore down to 2-nm in size with sub-nm precision, directly in solution, by controlling dielectric breakdown at the nanoscale. The method relies on applying a voltage across an insulating membrane to generate a high electric field, while monitoring the induced leakage current. We show that nanopores fabricated by this method produce clear electrical signals from translocating DNA molecules. Considering the tremendous reduction in complexity and cost, we envision this fabrication strategy would not only benefit researchers from the physical and life sciences interested in gaining reliable access to solid-state nanopores, but may provide a path towards manufacturing of nanopore-based biotechnologies.