High-temperature lead-free solder alternatives

For lead-free solders in the high-temperature regime, unfortunately, a limited number of alloying systems are available. These are Bi based alloys, gold involving alloys and Zn-Al based alloys. Based on these systems, possible candidate alloys were designed to have a melting range between 270 °C and 350 °C. Each has its own superior characteristics as well as some drawbacks however none of them can fulfill all the requirements to replace the current high-lead content solders. Even the alternative technologies that are currently being developed cannot address several critical issues of high-temperature soldering. Therefore, further research and development of high-temperature lead-free soldering is obviously needed.     

Characterization and modeling of burr formation in micro-end milling

Mechanical micromachining is increasingly finding applications in fabrication of components in various fields, such as, biomedical devices, optics, electronics, medicine, communications and avionics. In order to ensure adequate functionality, there are stringent requirements for form and finish in case of biomedical devices like cochlear implants and metallic optics. This necessitates that the post machined surface must be burr free. To address these issues in micromachining, this paper presents results of an experimental study to investigate the influence of main process parameters i.e. speed, feed rate, depth of cut, tool diameter and number of flutes on the formation of the various types of burrs i.e. exit burrs and top burrs produced during micro-end milling operation. The experiments performed using Taguchi method shows that three types of burr formation mechanisms prevail during micro-end milling operations; these are: lateral deformation of material, bending and tearing of the chip. Also, three types of burrs were observed include: Poisson burr, rollover burr in down milling and tear burr in up milling. Further, it is observed that the depth of cut and the tool diameter are the main parameters, which influence the burr height and thickness significantly. However, the speed and the feed rate have small to negligible effect on the burr thickness and height. Besides the experimental analysis, the paper presents an analytical model to predict the burr height for exit burr. The model is built on the geometry of burr formation and the principle of continuity of work at the transition from chip formation to burr formation. Note that prediction of burr height in micro-end milling is extremely challenging due to the complex geometry of material removal and microstructural effects encountered during cutting at that length scales. The model fares well and the prediction errors range between 0.65 and 25%.     

Optimization of I-shape Microstrip patch antenna using PSO and curve fitting

This paper presents an optimization of Microstrip patch antenna, based on Particle Swarm Optimization (PSO) with curve fitting. An I shape antenna is used to demonstrate the optimization technique. An initial antenna is designed by cutting slots in rectangular patch to form shape I. By varying different parameters of the antenna, the data for developing PSO program in MATLAB is obtained. For Simulation, software IE3D and Graphmatica is used for Curve Fitting. Thus the optimized antenna is obtained, and finally the performance of the initial antenna is compared with the PSO optimized antenna. The result yields that obtained antenna have resonance near at 2.4 GHz and it also shows remarkable improvement over Fractional Bandwidth. For the Microstrip line feed I shape antenna, the Fractional Bandwidth is increased by 25 % as compared to the initial antenna.     

Empirical performance analysis of VCR engine fuelled with karanja oil and various additives using ANOVA technique

ABSTRACT

In this present paper, an experimental study is carried out on a single cylinder, four-stroke variable compression ratio (VCR), direct injection diesel engine to analyse the performance characteristics of 20% karanja oil (B20) with diethyl ether, methanol and ethanol as an additives by substituting 5% and 10%, respectively. The engine is operated at the speed of 1500 rpm with VCRs 17 and 18. Analysis of performance parameters such as brake power, indicated power, brake thermal efficiency, mechanical efficiency, specific fuel consumption and indicated thermal efficiency are arrived by the IC engine analysis software which has been coupled with the VCR engine. The outcome data of these blends are to be compared with the ordinary diesel. The results are optimised by using the design of experiments (DOE) method in MINITAB 17.0 software to find out the suitable blend for the engine.     

Catalytic effect of carbon nanostructures on the hydrogen storage properties of MgH2–NaAlH4 composite

The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH₂–NaAlH₄ composite. De/rehydrogenation study reveals that MgH₂–NaAlH₄ composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH₄ and MgH₂. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH₂–NaAlH₄ composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH₂–NaAlH₄ catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH₂–NaAlH₄ is diminished to 0.45 wt.%.     

Effect of Chemical Treatment on the Tensile Strength Behavior of Coir Geotextiles

ABSTRACT

The present study investigates the effects of chemical treatment on the tensile strength behavior of the two woven and two nonwoven coir geotextiles. The results reveal that tensile elongation at failure for the untreated and treated woven and nonwoven coir geotextiles was higher in the warp direction in comparison to the weft direction. The tensile elongation at failure for the untreated and treated woven coir geotextiles were influenced by the stiffness and the opening of kinks in the coir yarn whereas the tensile elongation at failure of the untreated/treated nonwoven coir geotextiles was influenced by the presence of the polyethylene (PE) yarn used in stitching along with PE netting and diameter of the yarn used in PE netting. The chemical treatment decreased and increased the tensile strength of both the woven and nonwoven coir geotextiles, respectively. The mass per unit area of woven coir geotextile decreased whereas it increased for both the nonwoven coir geotextiles after the chemical treatment. The chemical treatment modifies the surface characteristics of both the untreated woven and nonwoven coir geotextiles due the removal of impurities and filling up the voids present on the surface.     

A novel moment generating function based performance analysis over correlated Nakagami-m fading channels

The bit-error rate and channel capacity have been regarded as fundamental information theoretic performance measure to predict the maximum information rate of a communication system. In contrast, with the analysis of other important performance measures of the wireless communication systems, a novel and unified general approach for computing the bit-error-rate and channel capacity over the correlated Nakagam-m fading channels have been proposed. In this paper, we have analyzed and numerically simulated the bit-error-rate and channel capacity of the correlated Nakagami-m fading channel by using the moment generating function (MGF) based approach. The derived mathematical expression for the channel capacity is in terms of the Meijer G function which is valid for both integer and non-integer values of the fading parameters.     

Coronal mode ultrasound guided hemodialysis cannulation: A pilot randomized comparison with standard cannulation technique

Background: Infiltrations from cannulation result in significant morbidity including loss of hemodialysis (HD) vascular access (VA). Cannulation is dependent on personnel skill and VA characteristics. Surface marking of VA lacks real‐time information and traditional ultrasound (US) devices are large, expensive, requiring skilled operators. Sonic Window© (Analogic Ultrasound, Peabody, MA, USA) is a coronal mode ultrasound device (CMUD) approved for VA cannulation. Methods: Single center randomized, prospective pilot study comparing handheld US‐guided cannulation of new arteriovenous fistula (AVF) to standard cannulation practices. Patients with end stage renal disease (ESRD) on in‐center HD who had a new AVF cleared for cannulation and dialysis were enrolled. Patients with new AVF received either standard cannulation (control group) or image guidance using CMUD (study group) for 3 weeks. Ultrasound characteristics of VA, cannulation practices and complications end points were obtained. Results: An infiltration rate of 9.7% was noted during the study. Slightly lower odds ratio (OR) of infiltration was observed in the study group (OR 0.94, 95% CI: 0.26–3.41, P value = 0.93). Study group yielded longer time for assessment (101.8 ± 80.2 vs. 22.3 ± 22.5 seconds, P = < 0.001), increased cannulation time (41.1 ± 70.6 vs. 25.0 ± 27.9 seconds, P = 0.04), and increased patient satisfaction (94.6% vs. 82%, P = 0.04) compared to control group. Number of cannulation attempts, needle size, arterial or venous needle insertion, and tourniquet usage between groups were not statistically different. Conclusion: Handheld ultrasound is a safe and useful aid in cannulation of dialysis access.