Effect of variations in thermophysical properties and design parameters on the performance of a V-shaped micro grooved heat pipe

The paper presents a detailed simulation of a V-shaped micro heat pipe. The effect of the substrate temperature on the model has been considered. A new method for calculating dry-out length has been proposed. The sensitivity of the model to variations in thermophysical properties and design parameters has been studied. The variations in the contact angle for the substrate-coolant liquid system, surface tension and viscosity of the coolant liquid, inclination, groove angle, length of adiabatic section and radius of ungrooved substrate have been considered. The effect of design and operating parameters on the performance of the heat pipe has been studied. The variations in contact angle have been found to significantly affect the performance of a micro heat pipe. The performance of a micro heat pipe is susceptible to ungrooved area of a V-shaped micro heat pipe. If the groove is not sharp enough i.e., the radius of ungrooved substrate is more; the micro heat pipe may cease to work even before it reaches its other operating limits. The various sensitivity studies made in this work gives better understanding of variations in thermophysical properties and design parameters of a micro heat pipe.     

Electrochemical and mechanical behavior of laser processed Ti–6Al–4V surface in Ringer’s physiological solution

Laser surface modification of Ti–6Al–4V with an existing calcium phosphate coating has been conducted to enhance the surface properties. The electrochemical and mechanical behaviors of calcium phosphate deposited on a Ti–6Al–4V surface and remelted using a Nd:YAG laser at varying laser power densities (25–50 W/mm²) have been studied and the results are presented. The electrochemical properties of the modified surfaces in Ringer’s physiological solution were evaluated by employing both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The potentiodynamic polarizations showed an increase in the passive current density of Ti–6Al–4V after laser modification at power densities up to 35 W/mm², after which it exhibited a decrease. A reduction in the passive current density (by more than an order) was observed with an increase in the laser power density from 25 to 50 W/mm². EIS studies at the open circuit potential (OCP) and in the passive region at 1.19 V showed that the polarization resistance increased from 8.274 × 10³ to 4.38 × 10⁵ Ω cm² with increasing laser power densities. However, the magnitudes remain lower than that of the untreated Ti–6Al–4V at OCP. The average hardness and modulus of the laser treated Ti–6Al–4V, evaluated by the nanoindentation method, were determined to be 5.4–6.5 GPa (with scatter <±0.976 GPa) and 124–155 GPa (with scatter <±13 GPa) respectively. The corresponding hardness and modulus of untreated Ti–6Al–4V were ~4.1 (±0.62) and ~148 (±7) GPa respectively. Laser processing at power densities >35 W/mm² enhanced the surface properties (as passive current density is reduced) so that the materials may be suitable for the biomedical applications.     

Scandium ion doped yttrium oxide transparent ceramic from nitrate alanine microwave combustion synthesized nanopowders

One atomic percent Neodymium ion doped Yttrium oxide, with 25 at% scandium ion (Nd_0.02Sc_0.5Y_1.48O₃), was synthesized by nitrate alanine microwave gel combustion followed by calcinations at 1000 °C for 2 h. Phase purity of nanopowder was characterized by X-Ray Diffraction (XRD). Neodymium and scandium ion doping was confirmed by cell parameter calculation and Scanning Electron Microscope-Electron Dispersive X-ray (SEM-EDX) analysis. Particles with size range 25–35 nm with close to spherical shape were obtained as observed by Transmission Electron Microscopy (TEM). Powder on compaction followed by vacuum sintering at 1765 °C for 40 min led to the formation of ceramic with 76% transmission at 2500 nm compared to translucent ceramic obtained without scandium ion doping. This indicates formation of highly sinterable neodymium doped yttrium oxide nanopowders by nitrate alanine microwave gel combustion route with scandium ion additive. Further the absorption and emission bands of Nd_0.02Sc_0.5Y_1.48O₃ are inhomogeneously broadened and fluorescence lifetime is longer than Nd_0.02Y_1.98O₃.     

Frozen storage stability of antioxidant-treated raw restructured beef steaks made from mature cows

Previous research has shown that beef quality decreased with the age of cattle. In this study, beef trimmings from nine mature cows (n = 9), equally representing three animal age groups (2–4, 6–8, and 10–12 yr), were restructured into steaks formulated with propyl gallate, alone or in combination with a beefy flavoring agent, to enhance palatability and stability during 6 months of frozen storage at −29 °C. Lipid oxidation, rancidity, and loss of beefy flavor in restructured steaks during extended storage were reduced by propyl gallate. The beefy flavoring agent inclusion masked mature, forage-fed beef off-flavors, intensified beefy flavor, and improved steak tenderness, juiciness and cooking yield. Thus, the combination of propyl gallate and beefy flavoring offers an effective means to enhance the palatability and storage stability of restructured beef prepared from mature cows.     

Antimicrobial properties of polypropylene films containing AgSiO<Subscript>2</Subscript>, AgZn and AgZ for returnable packaging in seafood distribution

Active antimicrobial films were prepared by incorporating AgSiO₂, AgZn and AgZ at 1, 3, 5 and 10 % (w/w) into a polypropylene (PP) matrix. Complete thermal, structural, mechanical and functional characterization as well as antimicrobial efficiency and returnable antimicrobial efficiency were determined according to the Japanese Industrial Standard method. The morphology of the films showed agglomerates of particles in the composites. The active formulation had decreased elongation compared to the pure PP sample. Thermal analyses indicated that the active formulation compositions had increased thermal stability. The films showed 50 % antimicrobial properties after the fifth wash against the tested microorganisms, presenting better activity against Gram negative organisms than Gram positive ones. These findings suggest that PP films with AgSiO₂, AgZn and AgZ particles can provide a significant contribution to the quality and safety of seafood in the distribution chain.     

A compact interband tunneling current model for Gate-on-Source/Channel SOI-TFETs

A tunneling probability-based drain current model for tunnel field-effect transistors (FETs) is presented. First, an analytical model for the surface potential and the potential at the channel–buried oxide interface is derived for a Gate-on-Source/Channel silicon on insulator (SOI)-tunnel FET (TFET), considering the effect of the back-gate voltage. Next, a drain current model is derived for the same device by using the tunneling probability at the source–channel junction. The proposed model includes physical parameters such as the gate oxide thickness, buried oxide thickness, channel thickness, and front-gate oxide dielectric constant. The proposed model is used to investigate the effects of variation of the front-gate voltage, drain voltage, back-gate voltage, and front-gate dielectric thickness. Moreover, a threshold voltage model is developed and the drain-induced barrier lowering (DIBL) is calculated for the proposed device. The effect of bandgap narrowing is considered in the model. The model is validated by comparison with Technology Computer-Aided Design (TCAD) simulation results.     

Aperiodic multilayers with enhanced reflectivity for extreme ultraviolet lithography

We have developed novel aperiodic multilayers, covered by capping layers resistant to environmental attack, that offer superior performance for extreme ultraviolet lithography. We have designed these coatings using an optimization procedure based on an algorithm able to acquire domain knowledge inside the space of possible solutions. An integrated intensity increase of up to 2.18 times that obtained using standard periodic multilayers has been estimated. The aperiodic structures have minimal absorption in the topmost layers, which makes them especially insensitive to both the choice of capping layer material and any subsequent capping layer degradation due to oxidation or contamination. This property allows for the use of the most resilient capping layer materials available, thereby leading to a significantly improved lifetime. We have produced prototype capped aperiodic coatings and have measured their performance.     

Robust Stationkeeping Control for Libration Point Quasi-Periodic Orbits

Libration orbit stationkeeping controls are designed based on selected reference quasi-periodic orbit trajectories. The baseline trajectory is designed to meet science requirements and in the same time achieve minimum fuel consumptions. The success of finding libration point reference orbits is based on accurate numerical computation, dynamics, and space environment modeling. The linear quadratic regulator controller has been developed widely for maintaining a spacecraft in such libration orbit reference trajectories as close as possible. However, any dynamics models, including the circular restricted three-body dynamics, space environment, sensor, and actuator, are only approximations of real physical systems. Any noise and uncertainties can cause spacecraft’ motion to diverge due to the high instability region around libration points. This study investigates the modeling and designing of a passive robust μ controller and an active adaptive linear quadratic regulator in libration point stationkeeping controls around L1. The adaptive law in the linear quadratic regulator is used to estimate unknown gains of spacecraft’ subsystems. The results are compared for a family of libration orbits with reasonable ΔV yearly budgets under the influence of perturbations, noise, and unmodeled dynamics. The comparison with a publicly accessible work indicates that the controller developed in this work can provide comparable annual cost by nearly even including the worst case of perturbations.     

Improving beef color stability: Practical strategies and underlying mechanisms

This paper overviewed the current literature on strategies to improve beef color and attempted to logically explain the fundamental mechanisms involved. Surface color and its stability are critical traits governing the marketability of fresh beef when sold, whereas internal cooked color is utilized as an indicator for doneness at the point of consumption. A multitude of exogenous and endogenous factors interact with the redox biochemistry of myoglobin in post-mortem skeletal muscles. The scientific principles of these biomolecular interactions are applied by the meat industry as interventions for pre-harvest (i.e. diet, animal management) and post-harvest (i.e. packaging, aging, antioxidants) strategies to improve color stability in fresh and cooked beef. Current research suggests that the effects of several of these strategies are specific to type of animal, feeding regimen, packaging system, and muscle source. Meat scientists should explore novel ways to manipulate these factors using a biosystems approach to achieve improved beef color stability, satisfy consumer perception, and increase market profitability.     

Primary structure of turkey myoglobin

Our objective was to determine the amino acid sequence of turkey myoglobin. Turkey myoglobin was isolated from cardiac muscles via ammonium sulphate precipitation and gel-filtration chromatography. Purified turkey myoglobin, separated as a 17 kDa band in SDS–PAGE, was subjected to digestion with trypsin or aspartic acid endopeptidase. The resulting peptides were separated by reverse-phase HPLC, and then subjected to Edman degradation to obtain the amino acid sequence. The complete amino acid sequence of turkey myoglobin was determined and compared with that of poultry and red meat myoglobins. Turkey myoglobin has 153 amino acids and nine histidine residues. Proximal (position 93) and distal (position 64) histidine residues, responsible for maintaining the stability of haeme, are conserved in turkey myoglobin. Turkey myoglobin shares 100% sequence similarity with chicken myoglobin, whereas it shares 92.5% homology with ostrich, 76.5% with pig, and less than 73% with ruminant myoglobins.