This article proposes a new space vector pulse width modulation (SVPWM) switching technique for three phase three level Z source inverter (3L-ZSI). The main feature of the proposed maximum boost control technique is that it eliminates the sixth frequency inductor current ripple, which is normally present in the conventional maximum boost control technique. Additionally, the proposed technique facilitates to reduce the switching frequency of the impedance network and common mode voltage, resulting in reduced size of the passive components. The vectors, “- - -” and “+ + +” of three level switching vectors have been implemented after proper modification for the concept of 3L- ZSI. The proposed technique is analyzed with respect to neutral point clamped (NPC), T-type NPC, and controlled diode bridge clamped 3L-ZSI. The efficacy of the proposed technique has been verified by both simulation and experimental results.

In a 3L-VSI, to realize reference vector, maximum of six switching per sub-cycle are permitted. A similar condition is looked for in 3L-ZSI (z source inverter). The current continuous SVPWM methods of 3L-ZSI have adopted two approaches to meet the desired condition. These are a selection of sub-cycles generating six and eight switching employing correct volt-second balance. The sub-cycles generating eight switching has the demerit of increased losses. Here a new switching pattern has been proposed to optimize the number of switching. The dependency of the modulation index and sub-cycle duration on the switching frequency has also been discussed. With the increase in carrier frequency, the proposed PWM technique offers a decrease in switching losses compared to the existing ones. This leads to the improved efficiency of 3L-ZSI.To verify the efficacy of the proposed technique, simulation and prototype results are presented.

In this work, the performance of closed-loop dual phase Interleaved Buck-Boost converter (IBBC) controlled by Dragonfly Algorithm (DA) optimized Type-III compensator has been investigated. The dual phase IBBC is constructed by connecting parallel of two identical conventional Buck-Boost converter (BBC) cells, which operate in 180° phase shifting operation (i.e., interleaving technique) between them in a switching period. The closed-loop IBBC with DA optimized Type-III controller demonstrates better performance than conventional Buck-Boost (BBC) converter & IBBC with classical Type-III controller in terms of dynamic performance, efficiency, ripple in source current and in output voltage. The efficacy of the proposed control scheme is verified by both simulation & experimental results.

One of the immune evasion strategies manifested by malignant cells is the downregulation of the Human Leukocyte Antigen (HLA). HLA Class I (HLA- A, -B, -C) present endogenous peptides including viral and tumor antigens to cytotoxic T lymphocytes for immune mediated destruction. We have found the Epstein Barr Virus (EBV) Latent Membrane Protein 2A (LMP2A) to be responsible for this HLA downregulation in gastric cancer cells. Our results further indicate the Sonic Hedgehog pathway; primarily Gli1 to bring about the LMP2A mediated decrease in HLA expression.

Electromagnetic levitation system (EMLS) is inherently unstable and strongly non-linear in nature. Controllers based on linear model and designed by classical approach for any EMLS have restricted zone of operation. For a small variation of operating air-gap there is sharp degradation of controller performance. But it is essential to design an optimized controller that will stabilize unstable EMLS and will provide satisfactory performance for a wide range of operating air-gap. In this paper a Genetic Algorithm (GA) based optimisation technique for controllers of two actuator based levitation system has been discussed. GA has a highly proven track record of optimisation of parameters for different types of control schemes. Here the work focuses mainly on an optimal control of a proposed two actuator based EMLS scheme, which is composed of a stochastic technique based on Genetic Algorithm (GA).

Magnetic levitation system is inherently unstable and strongly nonlinear in nature. Fixed optimal gain controllers designed at some nominal operating conditions fail to provide the best control performance over a wide range of off-nominal operating conditions. In this paper, an adaptive fuzzy parameter scheduling scheme for Gravitational Search Algorithm (GSA) based optimal Proportional Integral Derivative (PID) and Lag-Lead controllers has been proposed to control a single actuator based DC Attraction type Levitation System (DCALS). A Takagi-Sugeno (T-S) fuzzy inference system is used in the proposed controllers. The inference system is extremely well suited to the task of smoothly interpolating linear gains across the input space when a strongly non-linear DCALS moves around in its operating space. Simulation results show that both proposed adaptive fuzzy PID and Lag-Lead controllers offer better performance than fixed gain controllers at different operating conditions.

In this paper, design and implementation of an optimized controller for a single magnet-based electromagnetic levitation system (EMLS) where an electromagnet of 2.6-kg mass is levitated over a large gap under a fixed ferromagnetic guide-way has been discussed. EMLS is inherently unstable and strongly nonlinear in nature. A single position controller (lead type) along with an outer proportional-integral (PI) controller has been designed that will stabilize the EMLS represented mathematically by three different plants corresponding to three different operating points. An optimization technique utilizing the random search method with interval reduction, proposed by Luus and Jaakola, has been used for designing the controller. A "model matching control" design procedure has been utilized for the design of outer PI controller. The inner controller stabilizes the three unstable plants, whereas the outer PI control action is used to modify the three position outputs as per the desired model response. The combined control action provides good stability and satisfactory performance (like fast response, less overshoot, and zero steady-state error) for the different operating zones of EMLS. Stability has been confirmed by Kharitonov-Nyquist enclosure diagrams. The simulated controllers have been successfully implemented, thus validating the modeling and controller design procedure.

Power amplifier is one of the important elements of any attraction type levitation system. Due to the advancement in power electronics and control technology it is now possible to develop power amplifier which will have the properties like fast dynamics, large bandwidth, ability to carry large payload, energy efficient, high reliability and cost effective. Both linear and switching mode power amplifiers have been used in the field of DC electromagnetic suspension system. In this paper, different possible switched mode power circuits for both single as well as multi-magnet based electromagnetic levitation system have been discussed and a comparative study has been made of the different topologies of power amplifiers based on their structure, working principle and experimental results. In the actual work design, fabrication and testing of both single and multi-magnet based electromagnetic levitation scheme has been made as a complete project. But in this paper the main focus is on the power amplifier.

This paper describes the design and implementation of a single axis DC attraction type suspension system, where a platform (vehicle structure) of around 14 kg mass is made to remain suspended at the desired operating gap under a ferromagnetic guide-way. The prototype has four electromagnetic actuators of attraction type and four inductive gap sensors, all located at the corners of the platform. The four actuators are controlled independently through four identical controllers, and the stable levitation of the platform is achieved through the single input and single output (SISO) control of each air-gap. The emphasis of this work is on the design and development of the switched mode power amplifier cum controller unit for the four actuators. The proposed single switch-based power circuit simplifies the overall hardware, and it can be extended to any number of magnet-coils. A cascade lead compensation control scheme utilizing an inner current loop and outer position loop has been designed and implemented for the stabilization of such a highly unstable and strongly nonlinear system. The prototype has been successfully tested, and stable levitation was demonstrated with the desired operating gap.

This paper describes design and implementation of a control philosophy for simultaneous stabilization and performance improvement of an electromagnetic levitation system. An electromagnetic levitation system is an inherently unstable and strongly nonlinear system. To determine the overall closed loop stability for such a system, cascade lead-lag compensation has mostly been reported [1,2]. However, a single lead controller can not satisfy both stability and performance for such unstable systems [3]. Performance enhancement to satisfy the conflicting requirements of fast response with almost zero overshoot and zero steady state error has been successfully achieved by using a two loop controller configuration. The lead controller in the inner loop is designed to ensure stability while the outer loop PI controller is designed for performance enhancement. This approach decouples the twin requirements of stabilization (by the inner loop) and performance achievement (by the outer PI loop). The outermost PI controller has been designed using the 'Approximate Model Matching' technique [4]. The proposed control strategy has been implemented and the experimentation has been demonstrated successfully. Different experimental results have been included for verification.

This paper describes design and implementation of a single axis dc attraction type electromagnetic suspension system where an electromagnet of 2.6 kg mass is levitated over a large gap under a fixed ferromagnetic guide-way. The electromagnet exhibits nonlinear force-current-distance characteristics, and if controllers are to be designed by using linear analysis, the air-gap is restricted to a small region around the chosen nominal operating point. In this work, an attempt has been made to increase the operating range of an electromagnetic suspension system by using the concept of piecewise linear control where the nonlinear force-current-airgap relationships of the magnetic suspension system have been successively linearized at several operating points with a suitable controller designed for each operating point. A novel analog switching scheme has been designed and implemented to automatically switch to the relevant controller depending on the actual air-gap.

BACKGROUND. To understand whether the association between Epstein-Barr Virus (EBV) and gastric cancer (GC) has any role in loss of surface expression of human lymphocyte antigen (HLA) class 1, the authors analyzed locus-specific transcriptional expression of HLA-A, HLA-B, HLA-C, and HLA-E along with other HLA-associated molecules (beta 2-microglobulin [0,M], cellular latent membrane protein [LMP], and transporter associated with antigen presentation [TAP]) in EBV-associated, primary GC (EBVaGC) and EBV-negative GC (EBVnGC) tissues.METHODS. Approximately 20 EBVaGC tissues and 40 EBVnGC tissues and their corresponding normal tissues were used in the Study. The presence of EBV in GC was established by EBV-encoded small RNA in Situ hybridization analysis and BamHI W polymerase chain reaction (PCR) analysis. Transcriptional expression of viral LMP2A and several HLA class I genes were analyzed by reverse transcriptase (RT)-PCR. Surface expression levels of HLA class I proteins in cancer samples along with their normal counterparts also were quantified by flow cytometry.RESULTS. The RT-PCR data Suggested selective down-regulation of the HLA-A/HLA-B locus along with over-expression of HLA-E-transcripts in EBVaGC (P < .05). This was confirmed further by the flow-cytometric studies using antibodies to HLA-ABC and FILA-E. Among the accessory molecules, LMP7 transcript was down-regulated in a number of EBVaGC tissues compared with EBVnGC.CONCLUSIONS. The current results suggested that the establishment of EBV latent infection in gastric tissues allows malignant cells to avoid the immune surveillance of both cytotoxic T-lymphocytes and natural killer cells by regulating the differential expression of HLA class I molecules.

Malignant cells have been reported to escape immune surveillance by modulation of human lymphocyte antigen (HLA) class Ia molecule and/or other accessory molecules like TAP (transporter associated with antigen processing) and beta2-M expression. Most of these reports, however, are based on immunohistochemistry techniques with polymorphic- or isotype-specific antibodies. In the present study, we have instead used a locus-specific reverse transcriptase-polymerase chain reaction-based approach to detect the transcriptional expression of HLA class Ia as well as accessory molecules in gastric cancer. Our results indicate that HLA class Ia transcript is totally absent in only approximately 9% of cancer cases. Locus-specific expression of HLA-A and -B could, however, be detected in approximately 54% cases, whereas HLA-C was expressed in most of the cancer tissues. Interestingly, in some cases where HLA class Ia expression was observed, TAP1 expression could not be detected. Furthermore, we also investigated the frequency of nonclassical or HLA class Ib expression for molecules such as HLA-E and -G. HLA-G transcript was absent in gastric tissues both in cancerous and autologous normal region, whereas HLA-E was observed in a number of gastric cancers. Altogether these selective locus-specific losses of HLA class I along with impaired expression of accessory molecules may explain the complex phenomena by which gastric tumors escape both cytotoxic T-lymphocyte- as well as natural killer cell-mediated immune defense.

Haemoglobin (Hb) Sun Prairie (alpha2-globin cd130, GCT-->CCT, Ala-->Pro) is detected in three unrelated chromosomes, in association with a C-->T transition in the 5'-untranslated region (UTR), two bases upstream from the translation start site. Reported inversion of alpha/beta-mRNA ratio observed in Hb Sun Prairie mutants might stem from the second mutation and should be investigated. Molecular modelling studies indicate that the 130th residue of alpha-globin faces primarily the central cavity of the molecule and is not in contact with any beta-chain residue; further, no significant disruption of the Hb structure because of the Sun Prairie mutation is discernible. Depression of translation because of the second mutation of a conserved base in the 5'-UTR might explain the observed clinical severity.

We have detected, in three unrelated eastern Indian individuals, a hitherto unreported alpha zero deletion, - -KOL, in the heterozygous state, encompassing the embryonic zeta2-globin and the duplicated alpha-globin genes extending from c. 1150 bp upstream of the zeta2 globin gene to c. 960 bp downstream of the theta1 gene. Other deletions present in 120 unrelated, eastern Indian, putative alpha-thalassaemia patients are -3.7 kb (16.25%), -4.2 kb (5%) and - -SEA (3.33%).

This paper describe the design principle of a DC attraction type electromagnetic suspension system where a hollow steel cylinder of 658 gm mass is levitated under a fixed I core (solenoid type) electromagnet with a single degree of freedom. Electromagnet exhibits non-linear force versus distance characteristics and hence this controller has been designed by using linear small perturbation model of the magnet at the desired operating point. In all previously reported papers [1-4 ] the system design has been done by considering a suitable voltage source as the exciting input to the magnet coil. In the current work, over all system order reduction has been tried by taking a controlled current source as the excitation for the magnet coil. The resulting system is simpler and has second order transfer function. The current source is realized by using a two-switch asymmetrical bridge type switched mode dc to dc converter. The prototype has been successfully tested and levitation demonstrated.

Several government- and industry-funded prototyping and development activities in WDM optical networks are being conducted at various R&D centers. Optical networks can be deployed on top of an existing physical fiber plant that can provide a transparent all-optical signal path to its upper layer, thereby providing broadband services. For instance, an all-optical layer between the physical and ATM layers in a B-ISDN network will significantly improve both efficiency and flexibility for the provision of broadband services. One attractive feature of optical networks is the ease of its logical reconfigurability, i.e., any desired logical network topology can be embedded on top of any given physical fiber plant, subject to the limitations on the number of available wavelengths and transceivers. The logical topologies can be broadly classified into two categories: arbitrary and regular. Nodal connectivity patterns in regular topologies are very systematic and well defined, which simplifies routing and management operations. However, it is difficult to add an arbitrary number of nodes to a regular topology and still maintain its well-defined structure. Over the past few years, several regular logical topologies have been proposed for optical networks. In this article we provide brief descriptions of these regular logical network topologies and a comparative study of their various performance metrics, e.g., average hop distance (viz. network utilization), routing, fault tolerance, and scalability.

We consider the problem of designing logical optical network topology for a given physical topology (or fiber layout) and a given traffic demand matrix between the end-users. Traffic between the end-users is carried in a packet-switched form and the objective of our logical topology design is to minimize the maximum congestion on the logical links in the logical topology. The logical links are realized by wavelength continuous paths or between end-users and they are routed via wavelength-selective routers. Note that a topology with lower maximum link congestion will allow its traffic demand matrix to be scaled up by a larger factor. In the logical topology, each node is equipped with a limited number of optical transceivers, hence logical connections cannot be set-up between every pair of nodes. In this paper we present an analytical model for obtaining the maximum and average logical link loads for a given logical network and traffic demand matrix. The model is confirmed via simulation. A heuristic algorithm for constructing a logical topology that reduces maximum logical link congestion is also presented.

Wide area all-optical networks are emerging as practical and future-proof solution to the enormous bandwidth requirements of today's end-users. Over the past few years, the field of all-optical networks has experienced tremendous amount of research, development, and prototyping activities. Control and management issues of all-optical networks, which are getting increasing attention in the research and development communities, are considered in this paper.We present a new approach for modeling call blocking probability in wavelength-routed wide-area all-optical networks. When an optical connection (lightpath) request arrives at a node, first a route and a wavelength along that route is selected to establish the requested connection. If an available route or wavelength doesn't exist then the connection is blocked at the source node. If a route and an available wavelength along that route are found then the wavelength along the different links of the route are reserved as soon as possible. However, reserving the selected wavelength on all the links of the route takes finite amount of time which is dependent on the propagation delays of the links and processing speeds of the nodes along the route. Hence, the selected wavelength on one or more of the links along the route might be reserved by another lightpath request while the set-up procedure of the previous one is in progress. One of the primary goal of this work is to study blocking of lightpath requests at intermediate nodes. Note that, although several researchers have studied blocking at source node in optical networks [1,2,3], to our knowledge blocking characteristic at intermediate nodes has not been studied earlier.A new lightpath set-up approach is also proposed. Simulation results show that the proposed approach can reduce blocking at intermediate nodes. Numerical results from analytical as well as simulation models are presented for various network configurations.