Stress intensity factors for an interfacial crack between an orthotropic half-plane bonded to a dissimilar orthotropic layer with a punch

The plane strain problem of determining Stress Intensity Factors (SIF) for a moving interfacial Griffith crack between an elastic orthotropic half-plane and a dissimilar orthotropic layer with a moving punch situated along the boundary of the layer have been considered. The problem is reduced to the solution of three simultaneous singular integral equations with Cauchy-type singularities. Expressions for SIF for the case of a general loading are obtained. Numerical results for some particular cases are also presented graphically.     

Job scheduling in mesh multicomputers

A new approach for dynamic job scheduling in mesh-connected multiprocessor systems, which supports a multiuser environment, is proposed in this paper. Our approach combines a submesh reservation policy with a priority-based scheduling policy to obtain high performance in terms of high throughput, high utilization, and low turn-around times for jobs. This high performance is achieved at the expense of scheduling jobs in a strictly fair, FCFS fashion; in fact, the algorithm is parameterized to allow trade-offs between performance and (short-term) POPS fairness. The proposed scheduler can be used with any submesh allocation policy. A fast and efficient implementation of the proposed scheduler has also been presented. The performance of the proposed scheme has been compared with the FCFS policy, the only existing scheduling strategy for meshes, to demonstrate the effectiveness of the proposed approach. Simulation results indicate that our scheduling strategy outperforms the FCFS policy significantly. Specifically, our strategy significantly reduces the average waiting delay of jobs over the FCFS policy. The fast implementation of the proposed scheduler results in low allocation and deallocation time overhead, as well as low space overhead     

The cut-groove technique to infer interfacial effects during hot rolling

This article presents a novel experimental technique to infer the coupled effects of friction and heat transfer during the hot rolling of steels. The technique, termed the “cut-groove” method, relates the behavior of the deforming grooves cut on the strip surface to the local effects of friction and heat transfer. Validation of the experimentally observed groove shapes involved developing two-dimensional (2-D) and three-dimensional (3-D) finite-element (FE) models that employed a probabilistic distribution diagram (PDD). The PDD framework modeled the roll-strip interface and accounted for the variations in the oxide scale as distinct states that affect both friction and heat transfer. The numerically predicted groove openings are in good agreement with the experimentally observed groove shapes, particularly for the 2-D case. For the 3-D model, deviations are observed at regions close to the strip edges that are affected by nonplanar strain arising from spread during laboratory rolling. S. DAS, formerly Student, Department of Engineering Materials, and later Research Associate, Institute of Microstructural and Mechanical Process Engineering, The University of Sheffield (IMMPETUS), Sheffield, SI 3JD, United Kingdom     

A Scalable Asynchronous Cache Consistency Scheme (SACCS) for mobile environments

In the literature, there exit two types of cache consistency maintenance algorithms for mobile computing environments: stateless and stateful. In a stateless approach, the server is unaware of the cache contents at a mobile user (MU). Even though stateless approaches employ simple database management schemes, they lack scalability and ability to support user disconnectedness and mobility. On the other hand, a stateful approach is scalable for large database systems at the cost of nontrivial overhead due to server database management. We propose a novel algorithm, called Scalable Asynchronous Cache Consistency Scheme (SACCS), which inherits the positive features of both stateless and stateful approaches. SACCS provides a weak cache consistency for unreliable communication (e.g., wireless mobile) environments with small stale cache hit probability. It is also a highly scalable algorithm with minimum database management overhead. The properties are accomplished through the use of flag bits at the server cache (SC) and MU cache (MUC), an identifier (ID) in MUC for each entry after its invalidation, and estimated time-to-live (TTL) for each cached entry, as well as rendering of all valid entries of MUC to uncertain state when an MU wakes up. The stale cache hit probability is analyzed and also simulated under the Rayleigh fading model of error-prone wireless channels. Comprehensive simulation results show that the performance of SACCS is superior to those of other existing stateful and stateless algorithms in both single and multicell mobile environments.     

Synthesis and characterization of TiC-reinforced iron-based composites Part II on mechanical characterization

The hardness, impact toughness and wear resistance properties of Fe-TiC composites, synthesized by aluminothermic reduction of an industrial waste, have been evaluated. The wear resistance property of the composites has been compared with some standard wear resistant materials. It has been found that the wear resistance property of the Fe-TiC composites with mostly pearlitic, fully pearlitic and pearlitic plus cementite type matrix with about 7 to 8 vol% TiC is better than that of a standard high chromium iron. The wear resistance property of ferritic and mostly ferritic type matrix with about 5 vol% TiC is better than that of a standard bearing steel.     

Synthesis of submicron size silver powder for passive components application

Submicron silver powder was prepared from AgNO₃ by a chemical reduction method in the presence of a mixture of caprylic acid and triethanolamine as a surfactant. Hydrazine hydrate (N₂H₄·H₂O) is preferred as a reducing agent. A spherical silver powder with an average particle size of about 150 nm was achieved. Effort was also made to correlate the crystal structure and microstructure evolution of the prepared powders with the resultant thick film characteristics.     

Note: Compact high voltage pulse transformer made using a capacitor bank assembled in the shape of primary

The experimental results of an air-core pulse transformer are presented, which is very compact (<10 Kg in weight) and is primed by a capacitor bank that is fabricated in such a way that the capacitor bank with its switch takes the shape of single-turn rectangular shaped primary of the transformer. A high voltage capacitor assembly (pulse-forming-line capacitor, PFL) of 5.1 nF is connected with the secondary of transformer. The transformer output voltage is 160 kV in its second peak appearing in less than 2 μS from the beginning of the capacitor discharge. The primary capacitor bank can be charged up to a maximum of 18 kV, with the voltage delivery of 360 kV in similar capacitive loads.     

Multi-Objective Approach for Reconfiguration of Distribution Systems with Distributed Generations

This paper presents a fuzzy multi-objective based heuristic algorithm for network reconfiguration of distribution systems considering distributed generations (DGs). The objectives of reduction of real power loss, branch current carrying capacity limit, maximum and minimum voltage constraints, and feeder load balancing are considered for performance enhancement of the distribution system. Since these objectives are non-commensurable and difficult to solve simultaneously using conventional approaches, they are converted into fuzzy domain and a fuzzy multi-objective function is formulated. A sensitivity analysis based on voltage profile improvement and real power loss reduction is used for obtaining optimal locations of DGs and genetic algorithm is used for optimal sizing of DGs. The proposed reconfiguration algorithm is implemented in two stages, initially in the first stage without incorporating DGs and in the second stage incorporating DGs for obtaining an optimal distribution system network reconfiguration. The advantage of the proposed method is demonstrated through a seventy node four feeders and a sixteen node three feeders distribution systems.     

Influence of temperature, voltage and hydrogen on the reversible transition of electrical conductivity in sol–gel grown nanocrystalline TiO2 thin film

Undoped nanocrystalline p-type TiO₂ thin film was deposited by sol–gel method on a thermally oxidized p-Si (2–5 Ω cm resistivity and $ \left\langle {100} \right\rangle $ orientation) substrate. The thin film was characterized by two-dimensional X-ray Diffraction (2D-XRD) and Field Emission Scanning Electron Microscopy (FESEM) to confirm the formation of stable nano crystalline anatase titania and to determine the grain size (~10 nm). Optical absorption spectroscopy was carried out to ascertain the band gap of the material. Two lateral Pd contacts were used as the metal electrodes to TiO₂ thin film to study the electrical conductivity. A clear p- to n-type transition was observed at 240 °C and a bias voltage of 0.83 V and the effect was enhanced on exposure to H₂ gas. The thin film showed fully n-type conductivity at 275 °C and 0.1 V. However, the reversal of the type of conductivity from n- to p-type was observed below 240 °C during lowering the temperature. The creation of oxygen vacancy and the diffusion of lattice oxygen to the surface of TiO₂ thin film might be the most possible mechanism of such transitions. Presence of hydrogen enhanced the process.