A Hybrid Multilevel Inverter Topology for an Open-End Winding Induction-Motor Drive Using Two-Level Inverters in Series With a Capacitor-Fed H-Bridge Cell

In this paper, a new five-level inverter topology for open-end winding induction-motor (IM) drive is proposed. The open-end winding IM is fed from one end with a two-level inverter in series with a capacitor-fed H-bridge cell, while the other end is connected to a conventional two-level inverter. The combined inverter system produces voltage space-vector locations identical to that of a conventional five-level inverter. A total of 2744 space-vector combinations are distributed over 61 space-vector locations in the proposed scheme. With such a high number of switching state redundancies, it is possible to balance the H-bridge capacitor voltages under all operating conditions including overmodulation region. In addition to that, the proposed topology eliminates 18 clamping diodes having different voltage ratings compared with the neutral point clamped inverter. On the other hand, it requires only one capacitor bank per phase, whereas the flying-capacitor scheme for a five-level topology requires more than one capacitor bank per phase. The proposed inverter topology can be operated as a three-level inverter for full modulation range, in case of any switch failure in the capacitor-fed H-bridge cell. This will increase the reliability of the system. The proposed scheme is experimentally verified on a four-pole 5-hp IM drive.

Field-dependent changeover from current-to voltage-limiting characteristics by non-linear n-type BaTiO3 ceramics

Non-linear resistors having current-limiting capabilities at lower field strengths, and voltage-limiting characteristics (varistors) at higher field strengths, were prepared from sintered polycrystalline ceramics of (Ba0.6Sr0.4)(Ti0.97Zr0.03)O3+0.3 at % La, and reannealed after painting with low-melting mixtures of Bi2O3 + PbO +B2O3. These types of non-linear characteristics were found to depend upon the non-uniform diffusion of lead and the consequent distribution of Curie points (T c) in these perovskites, resulting in diffuse phase transitions. Tunnelling of electrons across the asymmetric barrier at tetragonak-cubic interfaces changes to tunnelling across the symmetric barrier as the cubic phase is fully stabilized through Joule heating at high field strengths. Therefore the current-limiting characteristics switch over to voltage-limiting behaviour because tunnelling to acceptor-type mid-bandgap states gives way to band-to-band tunnelling.

Adaptive Keeper Design for Dynamic Logic Circuits Using Rate Sensing Technique

The increasing variability in device leakage has made the design of keepers for wide OR structures a challenging task. The conventional feedback keepers (CONV) can no longer improve the performance of wide dynamic gates for the future technologies. In this paper, we propose an adaptive keeper technique called rate sensing keeper (RSK) that enables faster switching and tracks the variation across different process corners. It can switch upto 1.9x faster (for 20 legs) than CONV and can scale upto 32 legs as against 20 legs for CONV in a 130-nm 1.2-V process. The delay tracking is within 8% across the different process corners. We demonstrate the circuit operation of RSK using a 32 x 8 register file implemented in an industrial 130-nm 1.2-V CMOS process. The performance of individual dynamic logic gates are also evaluated on chip for various keeper techniques. We show that the RSK technique gives superior performance compared to the other alternatives such as Conditional Keeper (CKP) and current mirror-based keeper (LCR).

Resistivity imaging of a reconfigurable phantom with circular inhomogeneities in 2D-electrical impedance tomography

Resistivity imaging of a reconfigurable phantom with circular inhomogeneities is studied with a simple instrumentation and data acquisition system for Electrical Impedance Tomography. The reconfigurable phantom is developed with stainless steel electrodes and a sinusoidal current of constant amplitude is injected to the phantom boundary using opposite current injection protocol. Nylon and polypropylene cylinders with different cross sectional areas are kept inside the phantom and the boundary potential data are collected. The instrumentation and the data acquisition system with a DIP switch-based multiplexer board are used to inject a constant current of desired amplitude and frequency. Voltage data for the first eight current patterns (128 voltage data) are found to be sufficient to reconstruct the inhomogeneities and hence the acquisition time is reduced. Resistivity images are reconstructed from the boundary data for different inhomogeneity positions using EIDORS-2D. The results show that the shape and resistivity of the inhomogeneity as well as the background resistivity are successfully reconstructed from the potential data for single or double inhomogeneity phantoms. The resistivity images obtained from the single and double inhomogeneity phantom clearly indicate the inhomogeneity as the high resistive material. Contrast to noise ratio (CNR) and contrast recovery (CR) of the reconstructed images are found high for the inhomogeneities near all the electrodes arbitrarily chosen for the entire study. (C) 2010 Elsevier Ltd. All rights reserved.

Training-Symbol Embedded, High-Rate Complex Orthogonal Designs for Relay Networks

Distributed Space-Time Block Codes (DSTBCs) from Complex Orthogonal Designs (CODs) (both square and non-square CODs other than the Alamouti design) are known to lose their single-symbol ML decodable (SSD) property when used in two-hop wireless relay networks using the amplify and forward protocol. For such a network, a new class of high rate, training-symbol embedded (TSE) SSD DSTBCs are proposed from TSE-CODs. The constructed codes include the training symbols within the structure of the code which is shown to be the key point to obtain high rate along with the SSD property. TSE-CODs are shown to offer full-diversity for arbitrary complex constellations. Non-square TSE-CODs are shown to provide better rates (in symbols per channel use) compared to the known SSD DSTBCs for relay networks when the number of relays is less than 10. Importantly, the proposed DSTBCs do not contain zeros in their codewords and as a result, antennas of the relay nodes do not undergo a sequence of switch on and off transitions within every codeword use. Hence, the proposed DSTBCs eliminate the antenna switching problem.

Calcium/Calmodulin Dependent Protein Kinase II Bound to NMDA Receptor 2B Subunit Exhibits Increased ATP Affinity and Attenuated Dephosphorylation

Calcium/calmodulin dependent protein kinase II (CaMKII) is implicated to play a key role in learning and memory. NR2B subunit of N-methyl-D-aspartate receptor (NMDAR) is a high affinity binding partner of CaMKII at the postsynaptic membrane. NR2B binds to the T-site of CaMKII and modulates its catalysis. By direct measurement using isothermal titration calorimetry (ITC), we show that NR2B binding causes about 11 fold increase in the affinity of CaMKII for ATP gamma S, an analogue of ATP. ITC data is also consistent with an ordered binding mechanism for CaMKII with ATP binding the catalytic site first followed by peptide substrate. We also show that dephosphorylation of phospho-Thr(286)-alpha-CaMKII is attenuated when NR2B is bound to CaMKII. This favors the persistence of Thr(286) autophosphorylated state of CaMKII in a CaMKII/phosphatase conjugate system in vitro. Overall our data indicate that the NR2B- bound state of CaMKII attains unique biochemical properties which could help in the efficient functioning of the proposed molecular switch supporting synaptic memory.

Cardiac remodeling in Drosophila arises from changes in actin gene expression and from a contribution of lymph gland-like cells to the heart musculature

Understanding the basis of normal heart remodeling can provide insight into the plasticity of the cardiac state, and into the potential for treating diseased tissue. In Drosophila, the adult heart arises during metamorphosis from a series of events, that include the remodeling of an existing cardiac tube, the elaboration of new inflow tracts, and the addition of a layer of longitudinal muscle fibers. We have identified genes active in all these three processes, and studied their expression in order to characterize in greater detail normal cardiac remodeling. Using a Transglutaminase-lacZ transgenic line, that is expressed in the inflow tracts of the larval and adult heart, we confirm the existence of five inflow tracts in the adult structure. In addition, expression of the Actin87E actin gene is initiated in the remodeling cardiac tube, but not in the longitudinal fibers, and we have identified an Act87E promoter fragment that recapitulates this switch in expression. We also establish that the longitudinal fibers are multinucleated, characterizing these cells as specialized skeletal muscles. Furthermore, we have defined the origin of the longitudinal fibers, as a subset of lymph gland cells associated with the larval dorsal vessel. These studies underline the myriad contributors to the formation of the adult Drosophila heart, and provide new molecular insights into the development of this complex organ. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Synthesis of Trilaurin by Developing Pisa Seeds (Actinodaphne hookeri)

The developing seeds of Actinodaphne hookeri were investigated to delineate their ability to synthesize large amounts of trilaurin. Until 88 days after flowering the embryos contained 71% neutral lipids (NL) and 29% phospholipids (PL) and both these components contained C-16:0, C-18:0, C-18:2, and C-18:3 as the major fatty acids (FA). At 102 days after flowering the seeds began to accumulate triacylglycerols (TAG) and to synthesize lauric acid (C-12:0). By 165 days after flowering, when the seeds were mature, they contained about 99% NL and 1% FL. At this stage the TAG contained exclusively C-12:0, while the PL consisted of long-chain fatty acids (LCFA) only. Leaf lipids in contrast did not contain any C-12:0. Experiments on [1-C-14]acetate incorporation into developing seed slices showed that at 88 days after flowering only 4% of the label was in TAG, 1% in diacylglycerols (DAG), and 87% in FL. One hundred two days after flowering seeds incorporated only 2% of the label into TAG, 30% into DAG, and 64% into FL. In contrast at 114 days after flowering 71% of the label was incorporated into TAG, 25% into DAG, and only 2% into FL. Analysis of labeled FA revealed that up to 102 days after flowering it was incorporated only into LCFA, whereas at 114 days after flowering it was incorporated exclusively into C-12:0. Furthermore, 67% of the label in PL at 114 days after flowering was found to be dilaurylglycerophosphate. Analysis of the label in DAG at this stage showed that it was essentially in dilaurin species. These observations indicate the induction of enzymes of Kennedy pathway for the specific synthesis of trilaurin at about 114 days after flowering, Homogenates of seeds (114 days after flowering) incubated with labeled FA in the presence of glycerol-3-phosphate and coenzymes A and ATP incorporated 84% of C-12:0 and 61% of C-14:0, but not C-16:0, C-18:2, and C-18:3, into TAG. In contrast the LCFA were incorporated preferentially into FL. It is concluded that, between 102 and 114 days after flowering, a switch occurs in A. hookeri for the synthesis of C-12:0 and trilaurin which is tissue specific. Since the seed synthesizes exclusively C-12:0 at 114 days after flowering onwards and incorporates specifically into TAG, this system appears to be ideal for identifying the enzymes responsible for medium-chain fatty acid as well as trilaurin synthesis and for exploiting them for genetic engineering. (C) 1994 Academic Press, Inc.

Conformational preferences of α-functionalised keten-S,N-acetals: Potential role of SO and SS interactions in solution

PMR spectra of carbonyl compounds 2a-k reveal significant variations in the population of E and Z isomers on changing the solvent from CDCl3 to DMSO-d6. In non-polar media, the intramolecular N-H…. O hydrogen bonded form is exclusively observed. In DMSO-d6, the alternative Z form is also populated. A similar conformational switch is also noted in the corresponding thiones. Different interpretations are critically analysed. The most consistent explanation is suggested to involvean interplay of N-H….X hydrogen bonding and S…X attractive interaction (X = O,S) in these systems. Ab initio calculations support this interpretation.

Time-Resolved Photoluminescence and Microwave Conductivity at Semiconductor Electrodes: Depletion Layer Effects

Analytical expressions which include depletion layer effects on low-injection carrier relaxation are being presented for the first time here. Starting from the continuity equation for the minority carriers, we derive expressions for the output signal pertinent to time-resolved microwave and luminescence experiments. These are valid for the time domain that usually overlaps with the time scales of surface processes, such as charge transfer and trapping. Apart from the usual pulse form of illumination, theoretical expressions pertaining to other forms of illumination such as switch-on and switch-off transient modes, a periodic mode, and a steady state and their various inter-relationships are derived here. The expressions obtained are seen to be generalizations of existing flat-band low-injection results in the Limit of early or initial band bendings. The importance of the depletion layer as an experimental parameter is clearly seen in the limit of larger band bendings wherein it is shown, unlike the flat-band case, to exhibit pure exponential forms of carrier relaxation. Our results are consistent with the main conclusions of the numerical and experimental work published recently. Furthermore, this work provides the actual functional relationships between the applied potential and observed carrier decay. This should enable one to extract the surface kinetic parameters, after deciding on the dominant mode of carrier relaxation at the interface, whether charge transfer or trapping, by studying the potential dependence of the fate of relaxation.

NMR in liquid crystals spinning at and near magic angle

NMR spectra of liquid crystalline phases and the molecules dissolved therein, spinning at and near the magic angle provide information on the director dynamics and the order parameter. The studies on the dynamics of the liquid crystal director for sample spinning near magic angle in mesophases with positive and negative diamagnetic susceptibility anisotropies (Delta chi) and their mixtures with near-zero macroscopic diamagnetic susceptibility anisotropies have been reported. In systems with weakly positive Delta chi, the director has been observed to switch from an orientation parallel to the spinning axis at low rotational speeds to one perpendicular to the spinning axis at high rotational speeds, when the angle theta, the axis of rotation makes with the magnetic field is smaller than the magic angle theta(m). For systems with a small negative Delta chi, similar director behaviour has been observed for theta greater than theta(m). At magic angle, the spectra under slow spinning speeds exhibit a centre band and side bands at integral values of the spinning speeds. The intensities of the spinning side bands have been shown to contain information on the sign and the magnitude of the order parameter(s). The results are discussed with illustrative examples. Results on the orientation of the chemical shielding tensor obtained from a combination of the NMR studies in the solid and the liquid crystalline states, have been described.

OPSM - Opportunistic Power Save mode for Infrastructure IEEE 802.11 WLAN

We focus on the energy spent in radio communication by the stations (STAs) in an IEEE 802.11 infrastructure WLAN. All the STAs are engaged in web browsing, which is characterized by a short file downloads over TCP, with short duration of inactivity or think time in between two file downloads. Under this traffic, Static PSM (SPSM) performs better than CAM, since the STAs in SPSM can switch to low power state (sleep) during think times while in CAM they have to be in the active state all the time. In spite of this gain, performance of SPSM degrades due to congestion, as the number of STAs associated with the access point (AP) increases. To address this problem, we propose an algorithm, which we call opportunistic PSM (OPSM). We show through simulations that OPSM performs better than SPSM under the aforementioned TCP traffic. The performance gain achieved by OPSM over SPSM increases as the mean file size requested by the STAs or the number of STAs associated with the AP increases. We implemented OPSM in NS-2.33, and to compare the performance of OPSM and SPSM, we evaluate the number of file downloads that can be completed with a given battery capacity and the average time taken to download a file.

Throughput performance of distributed applications in switched networks in presence of end-system bottlenecks

The steady state throughput performance of distributed applications deployed in switched networks in presence of end-system bottlenecks is studied in this paper. The effect of various limitations at an end-system is modelled as an equivalent transmission capacity limitation. A class of distributed applications is characterised by a static traffic distribution matrix that determines the communication between various components of the application. It is found that uniqueness of steady state throughputs depends only on the traffic distribution matrix and that some applications (e.g., broadcast applications) can yield non-unique values for the steady state component throughputs. For a given switch capacity, with traffic distribution that yield fair unique throughputs, the trade-off between the end-system capacity and the number of application components is brought out. With a proposed distributed rate control, it has been illustrated that it is possible to have unique solution for certain traffic distributions which is otherwise impossible. Also, by proper selection of rate control parameters, various throughput performance objectives can be realised.

Application of an evolutionary fuzzy system for the estimation of workforce deployment and cross-training in an assembly environment

Owing to the increased customer demands for make-to-order products and smaller product life-cycles, today assembly lines are designed to ensure a quick switch-over from one product model to another for companies' survival in market place. The complexity associated with the decisions pertaining to the type of training and number of workers and their exposition to the different tasks especially in the current era of customized production is a serious problem that the managers and the HRD gurus are facing in industry. This paper aims to determine the amount of cross-training and dynamic deployment policy caused by workforce flexibility for a make-to-order assembly. The aforementioned issues have been dealt with by adopting the concept of evolutionary fuzzy system because of the linguistic nature of the attributes associated with product variety and task complexity. A fuzzy system-based methodology is proposed to determine the amount of cross-training and dynamic deployment policy. The proposed methodology is tested on 10 sample products of varying complexities and the results obtained are in line with the conclusions drawn by previous researchers.

Hyper-activation of the TCP4 transcription factor in Arabidopsis thaliana accelerates multiple aspects of plant maturation

Plant organs are initiated as primordial outgrowths, and require controlled cell division and differentiation to achieve their final size and shape. Superimposed on this is another developmental program that orchestrates the switch from vegetative to reproductive to senescence stages in the life cycle. These require sequential function of heterochronic regulators. Little is known regarding the coordination between organ and organismal growth in plants. The TCP gene family encodes transcription factors that control diverse developmental traits, and a subgroup of class II TCP genes regulate leaf morphogenesis. Absence of these genes results in large, crinkly leaves due to excess division, mainly at margins. It has been suggested that these class II TCPs modulate the spatio-temporal control of differentiation in a growing leaf, rather than regulating cell proliferation per se. However, the link between class II TCP action and cell growth has not been established. As loss-of-function mutants of individual TCP genes in Arabidopsis are not very informative due to gene redundancy, we generated a transgenic line that expressed a hyper-activated form of TCP4 in its endogenous expression domain. This resulted in premature onset of maturation and decreased cell proliferation, leading to much smaller leaves, with cup-shaped lamina in extreme cases. Further, the transgenic line initiated leaves faster than wild-type and underwent precocious reproductive maturation due to a shortened adult vegetative phase. Early senescence and severe fertility defects were also observed. Thus, hyper-activation of TCP4 revealed its role in determining the timing of crucial developmental events, both at the organ and organism level.