An elementary theory of product-line variations

The primary aim of a software product-line is to maximise reuse of software components by managing the variability in component functionalities and product configurations. Feature oriented domain analysis (FODA) diagrams are a formalism for modelling the variability in a software product-line, and are used as a tool for managing a product-line and planning its evolution. This paper presents an elementary theory of variations in a product-line, leading up to a technique for extracting FODA diagrams from legacy product-lines. The theory is elementary in the sense that it is built using very simple mathematical structures, making minimal assumptions on the structure of product-lines. Examples drawn from the automotive domain are used to illustrate the theoretical developments.     

Ultrahigh Current Density Ion Implantation

A study of several engineering alloys implanted at ultrahigh current densities has revealed that the process induces no change in the bulk microsctructure of the materials. Even though temperatures induced during processing exceed the transformation (tempering and annealing) temperatures, there is insufficient time for nucleation and growth reactions to occur during the temperature excursion associated with typical implantation dose and energy conditions. Substantially lower costs should accompany the shorter duration ultrahigh current density implantation process. Auger electron spectrographs reveal a substantially extended nitrogen range over those observed at low current densities (four-fold increase). This enhanced range appears to be due to radiation enhanced diffusion effects. Deeper penetration could lead to more durable surface layers.     

Purification and identification of antioxidant peptide from black pomfret, <Emphasis Type=Italic>Parastromateus niger</Emphasis> (Bloch, 1975) viscera protein hydrolysate

To utilize fish waste, black pomfret, Parastromateus niger viscera was analysed for its proximate and amino acid composition followed by hydrolysis using various proteases to extract antioxidant peptide. Antioxidant activities of the crude hydrolysate was evaluated using DPPH (54%), metal chelating (78.6%) at a concentration of 1 mg/mL, whereas the reducing power assay was done with different concentration (0.5–2.5 mg/mL) and the activity also increased with increasing concentration (0.021–0.068). Furthermore, the hydrolysate was purified by diethylaminoethyl (DEAE) ion-exchange and Sephadex G-25 gel filtration chromatography. Finally, the purified peptide had a mass of 701.9 Da, and the amino acid sequence was identified as Ala-Met-Thr-Gly-Leu-Glu-Ala using electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Moreover, the protection ability of the peptide toward hydroxyl radical-induced oxidative DNA damage and inhibiting lipid peroxidation was evaluated and compared with natural antioxidant α-tocopherol.     

Linear precoding for space-time coded systems with known fadingcorrelations

We design an optimal linear precoder for a space-time coded system assuming knowledge of only the transmit antenna fading correlations. Assuming a flat fading channel and a maximum-likelihood receiver, we show that the linear precoder transmits power on the eigenmodes of the transmit antenna correlation matrix. The power allocation on the eigenmodes is a form of waterpouring policy. Simulation results are presented to show performance improvement on a space-time coded system     

Position-Based Adaptive Clustering Model (PACM) for Efficient Data Caching in Vehicular Named Data Networks (VNDN)

The seamless data delivery is essential in VANET for application such as autonomous vehicle, intelligent traffic management and for the road safety and emergency applications. The incorporation of named data networking (NDN) with VANET, intended to frame intelligent traffic flow and seamless data delivery. Such integration of vehicular ad hoc networks (VANET) with NDN is termed as vehicular named data networks (VNDN). Because of the continuous node/vehicle mobility, it is a tedious process to build constant and consistent communication between vehicles. With that concern, for enhancing the performance of VNDN and solving the issues such as frequent cluster formation on heavy loaded data transmissions, position-based adaptive clustering model (PACM) is developed. The major intention of PACM is to form clusters based on trajectory. Besides, PACM performs efficient data caching by collecting significant data from vehicles to establish consistent data communication with all nodes in the network. Efficient data caching is done with the elected cluster heads among the framed clusters based on its positions and mobility models. For handling the vehicles at higher mobility speed, mutual data caching process is also designed that makes vehicles to perform on-demand data gathering from cluster heads. Further, the model is simulated and the obtained results are compared with the existing models based on the metrics such as packet delivery ratio, mean delay, cache hit rate and mean hop distance. The comparative analysis shows that the proposed model outperforms the available techniques.

     

Performance analysis of linear precoding based on field trials results of MIMO-OFDM system

We use field trial results obtained from a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) wireless system with two transmitter and three receiver antennas (2/spl times/3), to first validate the properties of the transmit correlation matrix in a macro-cellular environment. We find that approximately 20% of the locations have well-defined transmit correlation matrices. Furthermore, the eigenvectors of the transmit correlation matrix vary slowly over distance with 60% of the locations having eigenvector variation of less than 1 dB over a distance of 20 m. Next, we quantify the performance of the optimal statistical linear precoding (OSLP) , and statistical one-dimensional (1-D) eigenbeamforming (SEB) based on transmit correlation matrices, and the 1-D eigenbeamforming (EB)-based on perfect channel knowledge at the transmitter. We find that the OSLP and SEB schemes obtain array gain over the Alamouti scheme at lower signal-to-noise ratio (SNR) with a median gain of 2.0 (1.5) dB at the 1.0-(3.5) km cell-radii. However, the SEB scheme (unlike the OSLP scheme) looses diversity order at higher SNR that leads to a performance loss. The EB scheme provides the best performance over the Alamouti scheme, at the expense of increased feedback requirements.     

Optimization of CdTe thin‐film solar cell efficiency using a sputtered,oxygenated CdS window layer

A major source of loss in cadmium sulfide/cadmium telluride (CdS/CdTe) solar cells results from light absorbed in the CdS window layer, which is not converted to electrical current. This film can be made more transparent by oxygen incorporation during sputter deposition at ambient temperature. Prior to this work, this material has not produced high‐efficiency devices on tin oxide‐coated soda‐lime‐glass substrates used industrially. Numerous devices were fabricated over a variety of process conditions to produce an optimized device. Although the material does not show a consistent increase in band gap with oxygenation, absorption in this layer can be virtually eliminated over the relevant spectrum, leading to an increase in short‐circuit current. Meanwhile, fill factor is maintained, and open‐circuit voltage increases relative to baseline devices with sublimated CdS. The trend of device parameters with oxygenation and thickness is consistent with an increasing conduction band offset at the window/CdTe interface. Optimization considering both initial efficiency and stability resulted in a National Renewable Energy Laboratory verified 15.2%‐efficient cell on 3.2‐mm soda‐lime glass. This window material was shown to be compatible with SnO₂‐based transparent conducting oxide and high resistance transparent coated substrates using in‐line compatible processes. Copyright © 2015 John Wiley & Sons, Ltd     

Integrated Study of APS YSZ Coatings with Different Spray Angle

Spray parameters play an important role on the microstructure and properties of plasma-sprayed coatings. Parameters such as spray distance, plasma gas flow and current, raster speed, and spray angle all can be varied. In this paper, an integrated study to investigate the effects and influences of spray angle on properties of yttria-stabilized zirconia coatings was carried out with spray angles of 60°, 75°, and 90° (to the substrate surface). In situ coating property sensor based on beam curvature measurements was used to measure the evolving stress and elastic moduli of the resultant coatings and combined with other characterization tools for thermo-physical property and microstructure analysis, such as laser flash and scanning electron microscopy. The results indicate that the coating with 60° spray angle had the lowest thermal conductivity and more compliant structure. This study seeks to understand the mechanism for this effect and will provide important insight into parametric sensitivities on complex spray parts.     

Comparison of TiAIN,AICrN, and AICrN/TiAIN coatings for cutting-tool applications

Monolayer and bilayer coatings of TiAlN, AlCrN, and AlCrN/TiAlN were deposited onto tungsten carbide inserts using the plasma enhanced physical vapor deposition process. The microstructures of the coatings were characterized using scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The SEM micrographs revealed that the AlrN and AlCrN/TiAlN coatings were uniform and highly dense and contained only a limited number of microvoids. The TiAIN coating was non-uniform and highly porous and contained more micro droplets. The hardness and scratch resistance of the specimens were measured using a nanoindentation tester and scratch tester, respectively. Different phases formed in the coatings were analyzed by X-ray diffraction （XRD）. The AlCrN/TiAlN coating exhibited a higher hardness （32.75 GPa）, a higher Young＇s modulus （561.97 GPa）, and superior scratch resistance （LcN = 46 N） compared to conventional coatings such as TiAlN, A1CrN, and TiN.     

Electrochemical oxidation of boron containing compounds on titanium carbide and its implications to direct fuel cells

Electrochemical oxidation of sodium borohydride (NaBH₄) and ammonia borane (NH₃BH₃) (AB) have been studied on titanium carbide electrode. The oxidation is followed by using cyclic voltammetry, chronoamperometry and polarization measurements. A fuel cell with TiC as anode and 40 wt% Pt/C as cathode is constructed and the polarization behaviour is studied with NaBH₄ as anodic fuel and hydrogen peroxide as catholyte. A maximum power density of 65 mW cm⁻² at a load current density of 83 mA cm⁻² is obtained at 343 K in the case of borhydride-based fuel cell and a value of 85 mW cm⁻² at 105 mA cm⁻² is obtained in the case of AB-based fuel cell at 353 K.