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Robustness Analysis of a Simple and Augmented Proportional Plus Derivative Controller in Trajectory Following Robots Using the Floquet Theory
No full textThis paper deals with the issue of robustness in control of robots using the proportional plus derivative (PD) controller and the augmented PD controller. In the literature, a variety of PD and model-based controllers for multilink serial manipulator have been claimed to be asymptotically stable for trajectory tracking, in the sense of Lyapunov, as long as the controller gains are positive. In this paper, we first establish that for simple PD controllers, the criteria of positive controller gains are insufficient to establish asymptotic stability, and second that for the augmented PD controller the criteria of positive controller gains are valid only when there is no uncertainty in the model parameters. We show both these results for a simple planar two-degrees-of-freedom (2DOFs) robot with two rotary (R) joints, following a desired periodic trajectory, using the Floquet theory. We provide numerical simulation results which conclusively demonstrate the same
A FETI-DP based parallel hybrid stochastic finite element method for large stochastic systems
No full textThe computational cost of uncertainty propagation in a mechanics problem can become prohibitively large as the degrees of freedom (DOF) and the number of basic random variables - also referred to as stochastic dimensionality - increase. While a number of methods have been reported in the literature to address either large DOF or high stochastic dimensionality, there is no work addressing both. This work is aimed at filling this gap. Naturally, parallel computing becomes the only feasible option for these large problems. Accordingly, a parallel domain decomposition-based hybrid method combining stochastic Galerkin and Monte Carlo simulation is developed here. To achieve scalability, which is necessary for solving very large scale problems, first the dual-primal variant of the finite element tearing and interconnecting (FETI-DP) is chosen as the domain decomposition method. Then, three distinct approaches of parallel implementation are followed. Through a set of detailed numerical experiments, scalability and relative costs of computation and communication in these three approaches are studied. Finally, based on the observations in these experiments, the best approach is selected and used to solve a large three dimensional elasticity problem with high dimensional parametric uncertainty. (C) 2017 Elsevier Ltd. All rights reserved
A Reconfigurable and Scalable FPGA Architecture for Bilateral Filtering
No full textBilateral filter is an edge-preserving smoother that has applications in image processing, computer vision, and computational photography. In the past, field-programmable gate array (FPGA) implementations of the filter have been proposed that can achieve high throughput using parallelization and pipelining. An inherent limitation with direct implementations is that their complexity scales asO(omega(2)) with the filter width.. In this paper, we propose an FPGA implementation of a fast bilateral filter that requires just O(1) operations for any arbitrary omega. The attractive feature of the FPGA implementation is that it is both scalable and reconfigurable. To the best of our knowledge, this is the first scalable FPGA implementation of the bilateral filter. As an application, we use the FPGA implementation for image denoising
Part II: RF, ESD, HCI, SOA, and Self Heating Concerns in LDMOS Devices Versus Quasi-Saturation
No full textVarious LDMOS device design parameters to mitigate quasi-saturation (QS) have been identified. Based on this, a set of independent and mixed device designs to mitigate QS, while maximizing the device performance, are presented. The impact of QS on the analog/RF/switching performance of these independent and mixed designs is investigated thoroughly, while analogizing performance with QS for the first time. Furthermore, hot carrier induced (HCI) degradation in various independent and mixed LDMOS designs is studied using spherical harmonic expansion of Boltzmann transport equation. In addition to this self-heating behavior, safe operating area (SOA) boundaries and electrostatic discharge (ESD) behavior of independent and mixed LDMOS designs with and without QS are studied. For the first time, HCI degradation, self-heating behavior, SOA boundary, and ESD failure in LDMOS devices are correlated with the extent of QS in LDMOS devices, based on which device design guidelines to tackle all performance versus reliability challenges are derived
Hepatitis C virus: Enslavement of host factors
No full textHepatitis C virus (HCV) has infected over 170 million people world-wide. This infection causes severe liver damage that can progress to hepatocellular carcinoma leading to death of the infected patients. Development of a cell culture model system for the study of HCV infection in the recent past has helped the researchers world-wide to understand the biology of this virus. Studies over the past decade have revealed the tricks played by the virus to sustain itself, for as long as 40 years, in the host setup without being eliminated by the immune system. Today we understand that the host organelles and different cellular proteins are affected during HCV infection. This cytoplasmic virus has all the cellular organelles at its disposal to successfully replicate, from ribosomes and intracellular membranous structures to the nucleus. It modulates these organelles at both the structural and the functional levels. The vast knowledge about the viral genome and viral proteins has also helped in the development of drugs against the virus. Despite the achieved success rate to cure the infected patients, we struggle to eliminate the cases of recurrence and the non-responders. Such cases might emerge owing to the property of the viral genome to accumulate mutations during its succeeding replication cycles which favours its survival. The current situation calls an urgent need for alternate therapeutic strategies to counter this major problem of human health. (c) 2017 IUBMB Life, 70(1):41-49, 201
Relative role of pre-monsoon conditions and intraseasonal oscillations in determining early-vs-late indian monsoon intensity in a GCM
No full textThe aim of this paper is to identify relative roles of different land-atmospheric conditions, apart from sea surface temperature (SST), in determining early vs. late summer monsoon intensity over India in a high resolution general circulation model (GCM). We find that in its early phase (June-July; JJ), pre-monsoon land-atmospheric processes play major role to modulate the precipitation over Indian region. These effects of pre-monsoon conditions decrease substantially during its later phase (August-September; AS) for which the interannual variation is mainly governed by the low frequency northward propagating intraseasonal oscillations. This intraseasonal variability which is related to mean vertical wind shear has a significant role during the early phase of monsoon as well. Further, using multiple linear regression, we show that interannual variation of early and late monsoon rainfall over India is best explained when all these land-atmospheric parameters are taken together. Our study delineates the relative role of different processes affecting early versus later summer monsoon rainfall over India that can be used for determining its subseasonal predictability
Efficient Coding Architectures for Reed-Solomon and Low-Density Parity-Check Decoders for Magnetic and Other Data Storage Systems
No full textHigh-performance error correction codes are used in high-density data storage devices to overcome noise and channel impairments. In this paper, we develop novel and efficient decoding architectures for Reed-Solomon (RS) and low-density parity-check (LDPC) codes that are used in almost all data storage devices. First, we present a high-speed low-latency hard-decision-based pipelined RS decoder architecture that computes the error locator polynomial in exactly 2t clock cycles without parallelism. The RS decoder is a two-stage pipelined engine operating at the least latency possible, thereby, significantly reducing the size of the delay buffer. The RS decoder is implemented using Cadence tools and Kintex-7 field programmable gate array (FPGA). The technology-scaled normalized throughput of the pipelined RS decoder is almost two times compared with the existing decoders. The overall processing latency is reduced by almost 80% compared with the existing designs. Second, we design a high-throughput LDPC decoder using layered and non-layered min-sum algorithm based on non-uniform quantization (NUQ) on an FPGA kit. Unlike the standard state-of-the-art uniform quantization used in virtually all decoder circuits, our NUQ technique: 1) achieves a slight performance improvement of similar to 0.1 dB in the signal-to-noise ratio using equal number of bits and 2) yields 20% area savings (using 1 bit less) for the block RAMs used for storing intermediate check node and variable node messages
Emergence of cooperation and division of labor in the primitively eusocial wasp Ropalidia marginata
No full textIn most primitively eusocial wasps new nests are initiated by a single female or by small groups of females. To study the emergence of division of labor (DOL) among the nest foundresses and to determine its possible effect on nest productivity we maintained newly eclosed females of Ropalidia marginata in small boxes with one, two, or three nestmate wasps of the same age per box. Only one wasp developed her ovaries and laid eggs in each box, while the other wasp(s) built the nest, brought food, and fed larvae, demonstrating the spontaneous emergence of reproductive DOL in the presence of more than one wasp. In nests with three wasps there was also a strong negative correlation between intranidal and extranidal work performed by the two nonreproductive workers, suggesting the spontaneous emergence of nonreproductive DOL; such nonreproductive DOL was absent in nestswith two wasps. Both reproductive and nonreproductive DOL were modulated by dominance behavior (DB). In nests with two wasps the egg layer showed significantly more DB than the non-egg layer before nest initiation; in nests with three wasps queens showed significantly more DB than intranidal workers, which in turn showed significantly more DB than extranidal workers. Productivities of nests (as measured by total brood on the day of eclosion of the first adult) initiated by one or two wasps were not different from each other but were significantly lower than that of three wasps. Thus, nonreproductive DOL, and not merely reproductive DOL, is necessary for increase in productivity
Radical halogenation-mediated latent-active glycosylations of allyl glycosides
No full textRadical halogenation-mediated glycosylation using allyl glycosides as donors and as acceptors emerges to be an efficient and hither-to unknown glycosylation method, adhering to the concept of the latent-active methodology. Several di- and trisaccharides that possess the allyl moiety at their reducing end are prepared through this new glycosylation methodology
Possible origin of linear magnetoresistance: Observation of Dirac surface states in layered PtBi2
No full textThe nonmagnetic compounds showing extremely large magnetoresistance are attracting a great deal of research interest due to their potential applications in the field of spintronics. PtBi2 is one of such interesting compounds showing large linear magnetoresistance (MR) in both the hexagonal and pyrite crystal structure. We use angle-resolved photoelectron spectroscopy and density functional theory calculations to understand the mechanism of liner MR observed in the layered PtBi2. Our results uncover linear dispersive surface Dirac states at the (Gamma) over bar point, crossing the Fermi level with a node at a binding energy of approximate to 900 meV, in addition to the previously reported Dirac states at the (K) over bar point in the same compound. We further notice from our dichroic measurements that these surface states show an asymmetric spectral intensity when measured with left and right circularly polarized light, hinting at a substantial spin polarization of the bands. Following these observations, we suggest that the linear dispersive Dirac states at the (Gamma) over bar and (K) over bar points are likely to play a crucial role for the linear field dependent magnetoresistance recorded in this compound