Energy minimization and design for testability

The problem of fault detection in general combinational circuits is NP-complete. The only previous result on identifying easily testable circuits is due to Fujiwara who gave a polynomial time algorithm for detecting any single stuck fault inK-bounded circuits. Such circuits may only contain logic blocks with no more thanK input lines and the blocks are so connected that there is no reconvergent fanout among them. We introduce a new class of combinational circuits called the (k, K)-circuits and present a polynomial time algorithm to detect any single or multiple stuck fault in such circuits. We represent the circuit as an undirected graphG with a vertex for each gate and an edge between a pair of vertices whenever the corresponding gates have a connection. For a (k, K)-circuit,G is a subgraph of ak-tree, which, by definition, cannot have a clique of size greater thank+1. Basically, this is a restriction on gate interconnections rather than on the function of gates comprising the circuit. The (k, K)-circuits are a generalization of Fujiwara'sK-bounded circuits. Using the bidirectional neural network model of the circuit and the energy function minimization formulation of the fault detection problem, we present a test generation algorithm for single and multiple faults in (k, K)-circuits. This polynomial time aggorithm minimizes the energy function by recursively eliminating the variables.     

Influence of cryogenic coolant on turning performance characteristics: A comparison with wet machining

Machining of 17-4 Precipitation Hardenable Stainless Steel (PH SS) is one of the difficult tasks because of its high cutting temperatures. Conventional cutting fluids are used to overcome the high cutting temperatures, but these are not acceptable from the health and environmental sustainable points of view. Cryogenic cooling is one of the potential techniques to overcome such problems. In the current work, comparison is made of cryogenic turning results, such as tool flank wear, cutting forces (feed force, main cutting force), cutting temperature, chip morphology and surface integrity characteristics with wet machining during machining of heat-treated 17-4 PH SS. The result showed that in cryogenic machining, a maximum of 53%, 78%, 35% and 16% reductions was observed in tool flank wear, cutting temperature, surface roughness and cutting force, respectively, when compared with wet machining. It was also evident from the experimental results that cryogenic machining significantly improved the machining performance and product quality even at high feed rates.     

Optical absorption and fluorescence properties of Er3+ in sodium borate glass

Spectroscopic properties of Er³⁺ ions in sodium borate glass have been studied. The indirect and direct optical band gaps (E_opt) and energy level parameters (RacahE ¹, E² and E³), spin-orbit (ξ_4f) and configurational interaction (α)) are evaluated. Spectral intensities for various absorption bands of Er₃₊ doped sodium borate glass are calculated. Using Judd-Ofelt intensity parametersΩ ₂, Ω₄, Ω₆, radiative transition probabilities (A), branching ratios (β) and integrated absorption cross sections (Σ) are reported for certain transitions. The radiative lifetimes (τ_R) for different excited states are estimated. From the fluorescence spectra, the emission cross section (σ_P) for the transition,⁴I_13/2 → ⁴I_15/2 is reported.     

Antimicrobial activity of a novel furan fatty acid, 7,10-epoxyoctadeca-7,9-dienoic acid against methicillin-resistant Staphylococcus aureus

Food Science and Biotechnology - We analyzed the antimicrobial potential of a novel furan fatty acid, 7,10-epoxyoctadeca-7,9-dienoic acid (7,10-EODA) against methicillin-resistant and -sensitive S....     

Effect of Wire Material on Productivity and Surface Integrity of WEDM-Processed Inconel 706 for Aircraft Application

Inconel 706 is a recently developed superalloy for aircraft application, particularly in turbine disk which is among the most critical components in the gas turbine engines. Recently, wire electrical discharge machining (WEDM) attained success in machining of gas turbine components which require complex shape profiles with high precision. To achieve the feasibility in machining of these components, the research work has been conducted on Inconel 706 superalloy using WEDM process. And, the effect of different wire materials (i.e., hard brass wire, diffused wire, and zinc-coated wire) on WEDM performance characteristics such as cutting speed, surface topography, surface roughness, recast layer formation, residual stresses, and microstructural and metallurgical alterations have been investigated. Even though, zinc-coated wire exhibits improved productivity, hard brass wire was found to be beneficial in terms of improved surface quality of the machined parts. Additionally, lower tensile residual stresses were obtained with hard brass wire. However, diffused wire has a moderate effect on productivity and surface quality. Under high discharge energy, higher elemental changes were observed and also the white layer was detected.     

Comparative evaluations of machining performance during turning of 17-4 PH stainless steel under cryogenic and wet machining conditions

Productivity in machining of 17-4 PH stainless steel is adversely affected by the premature failure of tool and poor surface finish as a consequence of high cutting temperatures. Conventional cutting fluids not only create environmental and health problems but also fail to overcome the high cutting temperatures during machining. Cryogenic cooling is an environmentally clean cooling technology for attractive management of machining zone temperatures. The present study investigates the effect of cryogenic liquid nitrogen (LN₂ at ?196°C) on cutting temperatures, cutting forces (main cutting force, feed force), surface roughness, tool flank wear and chip morphology in turning of 17-4 PH stainless steel with AlTiN PVD-coated tungsten-coated carbide inserts and results were compared to wet machining. In overall, cryogenic machining reduces the cutting temperature, cutting forces, surface roughness and tool flank wear to a maximum of 73.4, 17.62, 44.29 and 55.55%, respectively. Improved chip breakability was found in cryogenic machining.     

Design of testable sequential circuits by repositioning flip-flops

This paper presents a technique to enhance the testability of sequential circuits by repositioning flip-flops. A novel retiming for testability technique is proposed that reduces cycle lengths in the dependency graph, converts sequential redundancies into combinational redundancies, and yields retimed circuits that usually require fewer scan flip-flops to break all cycles (except self-loops) as compared to the original circuit. Our technique is based on a new minimum cost flow formulation that simultaneously considers the interactions among all strongly connected components (SCCs) of the circuit graph to minimize the number of flip-flops in the SCCs. A circuit graph has a vertex for every gate, primary input and primary output. If gatea has a fanout to gateb, then the circuit graph has an arc from vertexa to vertexb. Experimental results on several large sequential circuits demonstrate the effectiveness of the proposed retiming for testability technique in reducing the number of partial scan flip-flops.     

Prediction and analysis of process failures by ANN classification during wire-EDM of Inconel 718

Wire breakages and spark absence are two typical machining failures that occur during wire electric discharge machining (wire-EDM), if appropriate parameter settings are not maintained. Even after several attempts to optimize the process, machining failures cannot be eliminated completely. An offline classification model is presented herein to predict machining failures. The aim of the current study is to develop a multiclass classification model using an artificial neural network (ANN). The training dataset comprises 81 full factorial experiments with three levels of pulse-on time, pulse-off time, servo voltage, and wire feed rate as input parameters. The classes are labeled as normal machining, spark absence, and wire breakage. The model accuracy is tested by conducting 20 confirmation experiments, and the model is discovered to be 95% accurate in classifying the machining outcomes. The effects of process parameters on the process failures are discussed and analyzed. A microstructural analysis of the machined surface and worn wire surface is conducted. The developed model proved to be an easy and fast solution for verifying and eliminating process failures.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00327-w     

Raman and infrared study of 100 MeV swift Ag heavy ion irradiation effects in CaSO4·2H2O single crystals

The modifications of calcium sulphate (CaSO₄·2H₂O) single crystals are investigated by means of Raman and Fourier transform infrared spectroscopy (FT-IR) using 100 MeV Ag⁸⁺ ions in the fluence range 1 × 10¹¹ to 5 × 10¹³ ions/cm². It is observed that the intensities of the Raman modes decrease with increase in ion fluence. We determined damage cross-section (σ) for all the Raman active modes and found to be different for different Raman modes. Further, FT-IR studies have been carried out to confirm surface amorphisation for a fluence of 1 × 10¹³ ions/cm². It is observed that the absorption peaks at 1132–1156 cm⁻¹ corresponds to ν₃(SO₄²⁻) mode. The decrease in Raman peaks intensity with ion fluence is attributed to degradation of ν₃(SO₄²⁻) modes present on the surface of the sample.     

Test Set Compaction Using Relaxed Subsequence Removal

Recent work observed that a subset of states are frequently visited during the simulation of a test set for a sequential circuit. Re-visiting a state implies that a cycle has been traversed in the state diagram. Removal of subsequence responsible for the cycle can lead to static compaction. The size of a cycle is the number of vectors in its subsequence. In this work, we extend the subsequence removal technique to provide significantly higher static compaction for sequential circuits. We show that state relaxation techniques can be used to identify more or larger cycles in a test set. State relaxation creates more opportunities for subsequence removal and hence, results in better compaction. Relaxation of a state is possible since not all memory elements in a finite state machine have to be specified for a state transition. The proposed technique has several advantages: (1) test sets that could not be compacted by existing subsequence removal techniques can now be compacted, (2) the size of cycles in a test set can be significantly increased by state relaxation and removal of the larger sized cycles leads to better compaction, (3) only two fault simulation passes are required as compared to trial and re-trial methods that require multiple fault simulation passes, and (4) significantly higher compaction is achieved in short execution times as compared to known subsequence removal methods. Experiments on ISCAS89 sequential benchmark circuits and several synthesized circuits show that the proposed technique consistently results in significantly higher compaction in short execution times.