Comparison of mixing layer heights determined using LiDAR,radiosonde, and numerical weather prediction model at a rural site in southern India

There is no agreed reference method for accurately determination of mixing layer height (MLH) in the existing literature. In part, this is due to different definitions of the atmospheric boundary layer exist, depending on the quantities and the physical processes invoked. In addition, MLH during late afternoon transition period is highly challenging to determine and perform model simulations because of the rapid variations in turbulent kinetic energy. For the first time, MLH has been determined at remote tropical site of Gadanki, India (13.45°N, 79.17°E, 360 masl) using ground-based elastic backscatter LiDAR (EBL). This article focuses on the late afternoon transition period and compares it with MLH obtained from the EBL to concurrent radiosonde (RS) observations [MLH (RS)] and numerical models. Five different techniques have been applied to the EBL backscatter profiles for the determination of MLH. The mean of the five methods agreed to within 15% with the RS-derived MLH under various synoptic conditions at the site. This indicates the potential capability of continuous monitoring of MLH by our EBL system. However, MLH determined by Weather Research and Forecasting model and European Center for Medium-Range Weather Forecasts Re Analaysis (ERA)-interim reanalysis systematically underestimated of the MLH (LiDAR) by about 62% and 48%, respectively. The mean growth rate of diurnal evolution of MLH was found to about 120 and 200 m h^?1 during winter and spring seasons, respectively.     

Characterization of proton exchange membranes based on SPSEBS/SPSU blends

Proton-conducting polymer membranes are used as an electrolytes in proton exchange membrane fuel cells (PEMFCs). The most widely used commercially available membrane electrolytes are perfluorosulfonic acid polymers, an expensive class of ionomers. In this study, the potential of polymer blends derived from sulfonated polystyrene ethylene butylene polystyrene (SPSEBS) and sulfonated polysulfone (SPSU) for use in electrolyte applications was examined. Although SPSEBS by itself exhibits good conductivity, flexibility, and chemical stability, it has poor mechanical stability. So, in an effort to improve the mechanical properties of SPSEBS while maintaining its good conductivity, it was blended with SPSU. SPSEBS/SPSU blends were therefore prepared by a solvent evaporation method, and the resulting blend membranes were characterized in terms of conductivity, ionic exchange capacity, and water uptake. Sulfonation was confirmed and the crystallinity of the blend membranes was studied by FTIR spectroscopy and X-ray diffraction. The morphologies of the membranes were studied by scanning electron microscope (SEM), and their thermal stabilities by TGA and DSC. Finally, the mechanical strength of SPSEBS was studied using a UTM (universal testing machine). This paper presents the results of recent investigations aimed at developing an optimized in-house membrane electrode assembly (MEA) preparation technique combining catalyst ink spraying and assembly hot pressing. Easy steps were chosen for this preparation technique in order to simplify the method, thus minimizing costs. The influence of MEA fabrication parameters like electrode pressing or annealing on the performance of the hydrogen fuel cell was studied by performing single cell measurements during H₂/O₂ operation. Carbon cloth was used as a gas diffusion layer (GDL), and the composition of the electrode ink was optimized to maximize fuel cell performance. A commercial E-TEK catalyst was used for the anode and cathode, with Pt loadings of 0.125 and 0.37 mg/cm², respectively. The MEA with the best performance delivered approximately 0.50 W/cm² at room temperature. The methanol permeability and the selectivity ratio strongly influenced DMFC performance. Both direct methanol fuel cells (DMFCs) and PEMFCs are discussed in this paper.     

Reduced complexity satellite broadcast receiver with interference mitigation in correlated noise

The recent commercial trends towards using smaller dish antennas for satellite receivers and the growing density of broadcasting satellites necessitate the application of robust adjacent satellite interference cancellation schemes. This orbital density growth along with the wider beamwidth of a smaller dish have imposed an overloaded scenario at the satellite receiver, where the number of transmitting satellites exceeds the number of receiving elements at the dish antenna. To ensure successful operation in this practical scenario, we propose a satellite receiver that enhances signal detection from the desired satellite by mitigating the interference from neighboring satellites. Towards this objective, we propose an enhanced list‐based group‐wise search detection (E‐LGSD) receiver under the assumption of spatially correlated additive noise. To further enhance detection performance, the proposed satellite receiver utilizes a newly designed whitening filter to remove the spatial correlation among the noise parameters, while also applying a preprocessor that maximizes the signal‐to‐interference‐plus‐noise ratio. We exploit the structure of this filter and propose a reduced complexity LGSD (RC‐LGSD) receiver. Extensive simulations under practical scenarios show that the proposed receiver enhances the performance of satellite broadcast systems in the presence of adjacent satellite interference compared with existing methods. Also, under pointing error, RC‐LGSD exhibits similar behavior to that of the optimum receiver.     

Design and simulation of RF MEMS shunt capacitive switch with non-uniform meanders for C-band applications

Microsystem Technologies - This paper presents, the design and simulation of RF MEMS shunt capacitive switch. The electromechanical and electromagnetic analysis of the switch has been done using...     

Adaptive Information Coding for Secure and Reliable Wireless Telesurgery Communications

Telesurgical Robot Systems (TRSs) have been the focus of research in academic, military, and commercial domains for many years. Contemporary TRSs address mission critical operations emerging in extreme fields such as battlefields, underwater, and disaster territories. The lack of wirelined communication infrastructure in such fields makes the use of wireless technologies including satellite and ad-hoc networks inevitable. TRSs over wireless environments pose unique challenges such as preserving a certain reliability threshold, adhering some maximum tolerable delay, and providing various security measures depending on the nature of the operation and communication environment. In this study, we present a novel approach that uses information coding to integrate both light-weight privacy and adaptive reliability in a single protocol called Secure and Statistically Reliable UDP (SSR-UDP). We prove that the offered security is equivalent to the existing AES-based long key crypto systems, yet, with significantly less computational overhead. Additionally, we demonstrate that the proposed scheme can meet high reliability and delay requirements of TRS applications in highly lossy environments while optimizing the bandwidth use. Our proposed SSR-UDP protocol can also be utilized in similar cyber-physical wireless application domains.     

A scalable multi-level feature extraction technique to detect malicious executables

We present a scalable and multi-level feature extraction technique to detect malicious executables. We propose a novel combination of three different kinds of features at different levels of abstraction. These are binary n-grams, assembly instruction sequences, and Dynamic Link Library (DLL) function calls; extracted from binary executables, disassembled executables, and executable headers, respectively. We also propose an efficient and scalable feature extraction technique, and apply this technique on a large corpus of real benign and malicious executables. The above mentioned features are extracted from the corpus data and a classifier is trained, which achieves high accuracy and low false positive rate in detecting malicious executables. Our approach is knowledge-based because of several reasons. First, we apply the knowledge obtained from the binary n-gram features to extract assembly instruction sequences using our Assembly Feature Retrieval algorithm. Second, we apply the statistical knowledge obtained during feature extraction to select the best features, and to build a classification model. Our model is compared against other feature-based approaches for malicious code detection, and found to be more efficient in terms of detection accuracy and false alarm rate.

Studies on structural,electrical and dielectric properties of nickel ion conducting polyvinyl alcohol based polymer electrolyte films

Polyvinyl alcohol (PVA) complexed with different weight percent ratios of Nickel Bromide (NiBr₂) salt were prepared by using solution cast technique. X-ray diffraction analysis confirmed the complexation of the salt with the polymer. Differential scanning calorimetry was used to determine the glass transition and melting temperatures of pure PVA and PVA:NiBr₂ complexed films. Electrical conductivity was measured using ac impedance analyzer in the frequency and temperature range 1 Hz–1 MHz and 303–373 K respectively. It was observed that the magnitude of electrical conductivity increases with NiBr₂ salt concentration as well as temperature. Frequency dependence electrical conductivity of the complexed polymer electrolyte films follows the Jonscher’s equation. The dielectric behavior was analyzed using dielectric permittivity\(\left( {{\varepsilon ^\prime}} \right)\) and loss tangent \(\left( {\tan \delta } \right)\) of the samples. Relaxation time was determined from the variation of loss tangent with frequency at different temperatures. The modulus spectra indicated the non-Debye nature of the material.     

Secure Data Objects Replication in Data Grid

Secret sharing and erasure coding-based approaches have been used in distributed storage systems to ensure the confidentiality, integrity, and availability of critical information. To achieve performance goals in data accesses, these data fragmentation approaches can be combined with dynamic replication. In this paper, we consider data partitioning (both secret sharing and erasure coding) and dynamic replication in data grids, in which security and data access performance are critical issues. More specifically, we investigate the problem of optimal allocation of sensitive data objects that are partitioned by using secret sharing scheme or erasure coding scheme and/or replicated. The grid topology we consider consists of two layers. In the upper layer, multiple clusters form a network topology that can be represented by a general graph. The topology within each cluster is represented by a tree graph. We decompose the share replica allocation problem into two subproblems: the Optimal Intercluster Resident Set Problem (OIRSP) that determines which clusters need share replicas and the Optimal Intracluster Share Allocation Problem (OISAP) that determines the number of share replicas needed in a cluster and their placements. We develop two heuristic algorithms for the two subproblems. Experimental studies show that the heuristic algorithms achieve good performance in reducing communication cost and are close to optimal solutions.     

Necessary and sufficient conditions for transaction-consistent global checkpoints in a distributed database system

Checkpointing and rollback recovery are well-known techniques for handling failures in distributed systems. The issues related to the design and implementation of efficient checkpointing and recovery techniques for distributed systems have been thoroughly understood. For example, the necessary and sufficient conditions for a set of checkpoints to be part of a consistent global checkpoint has been established for distributed computations. In this paper, we address the analogous question for distributed database systems. In distributed database systems, transaction-consistent global checkpoints are useful not only for recovery from failure but also for audit purposes. If each data item of a distributed database is checkpointed independently by a separate transaction, none of the checkpoints taken may be part of any transaction-consistent global checkpoint. However, allowing individual data items to be checkpointed independently results in non-intrusive checkpointing. In this paper, we establish the necessary and sufficient conditions for the checkpoints of a set of data items to be part of a transaction-consistent global checkpoint of the distributed database. Such conditions can also help in the design and implementation of non-intrusive checkpointing algorithms for distributed database systems.     

An intelligent simulation model for blind position control in daylighting schemes in buildings

The models for daylighting control are to contend with multi-variant, dynamic, nonlinear components impacted by geographical, environmental and occupancy factors amongst many other things. Conventional techniques for system analysis are not suitable for dealing with blind control systems whose positions are strongly influenced by occupant’s mood, emotions, and perception. This paper attempts to illustrate the effectiveness of using intelligent techniques in the visual environment control domain of the building systems. With the use of adaptive neuro fuzzy inference system (ANFIS), the paper models nonlinear blind position dynamics from the simulated data. The model thus obtained is then used for controller design and validation. Using MATLAB’s fuzzy logic toolbox, the paper also gives the procedure for creating such a model that is capable of maintaining a user-specified illuminance profile. When implemented in an adaptive control scheme, the model could be further tuned online for time-varying dynamics. The article’s ultimate objective is to accentuate the use of soft computing techniques towards significantly improving the effectiveness of control process and help address the problem of control search space reduction when used along with simulation.