Topological design of channels for squeeze flow optimization of thermal interface materials

Performance of thermal interface materials (TIMs) used between a microelectronic device and its associated heat spreader is largely dependent on the bulk thermal conductivity of the TIM, but the bond-line thickness (BLT) of the applied material as well as the interfacial contact resistances are also significant contributors to overall performance. Hierarchically Nested Channels (HNCs), created by modifying the surface topology of the chip or the heatsink with hierarchical arrangements of microchannels in order to improve flow, have been proposed to reduce both the required squeezing force and the final BLT at the interfaces. In the present work, a topological optimization framework that enables the design of channel arrangements is developed. The framework is based on a resistance network approximation to Newtonian squeeze flow. The approximation, validated against finite element (FE) solutions, allows efficient, design-oriented solutions for squeeze flow in complex geometries. A comprehensive design sensitivity analysis exploiting the resistance network approximation is also developed and implemented. The resistance approximation and the sensitivity analysis is used to build an automated optimal channel design framework. A Pareto optimal problem formulation for the design of channels is posed and the optimal solution is demonstrated using the framework.     

Performance investigation in modified and improved augmented power generation Kalina cycle using Python

In the generation of electricity and cogeneration, Kalina cycle is considered as one of the competitors to organic Rankine cycle. With the simplicity and identical components of the binary mixture, Kalina system makes it more prominent to get developed and implemented as well with its environmental friendly associate. This work proposes a new improved Kalina cycle system to convert the natural source from sun to useful work. The proposed system utilizes heat source suitable to medium temperature heat applications. The proposed cycle have 2 units of solar collector, favoring an additional heat recovery and higher performance. Solar hot source temperature and pressure are 190°C and 45 bar with additional flow to the turbine of 1.15 kg/s. Energy and second law analysis have considered in evaluating the performance of the proposed plant. The energy analysis shows minimum value of net power, energy efficiency and plant efficiency as 241 kW, 15.5% and 5.7. The exergy analysis defines that, to the proposed cycle, the exergy efficiency initializes at 77% with more exergy destruction at turbine with 31%. With the parametric analysis, the system is amended to have the maximum values of energy and exergy performances as 18.5%, 7.1% and 85%. The parametric study identifies the optimum value of the inlet temperature and pressure of the pump and turbine.     

Electrostatic spraying of food-grade organic and inorganic acids and plant extracts to decontaminate Escherichia coli O157:H7 on spinach and iceberg lettuce

The prevalence of foodborne illnesses is continually on rise. In the U.S.A., Escherichia coli O157:H7 (E. coli) has been associated with several outbreaks in minimally processed foods. Spinach and lettuce pose higher food safety risks and recurring food recalls suggest the insufficiency of current disinfection strategies. We aimed at offering a natural antimicrobial alternative using organic acids (malic, tartaric, and lactic acids [MA, TA, and LA, respectively]) and grape seed extract (GSE) and a novel application method using electrostatic spraying to evenly distribute the antimicrobials onto produce. Spinach and lettuce samples were washed, sanitized with sodium hypochlorite solution (6.25 mL/L), dip inoculated in water containing E. coli (7.0 log CFU/mL) for 24 h, and rewashed with sterile water to remove nonadhered pathogens. The samples were sprayed electrostatically with MA, LA, and GSE alone and in combinations and for comparison, with phosphoric acid (PA) and pH controls with deionized water adjusted to 1.5/2.3/3.6 and stored at 4 °C. When combined with LA (3%), MA (3%) showed 2.1 to 4.0 log CFU/g reduction of E. coli between the days 1 and 14 on spinach and 1.1 to 2.5 log CFU/g reduction on lettuce. Treatment with PA (1.5%) and PA (1.5%)-GSE (2%) exhibited 1.1 to 2.1 log CFU/g inhibition of E. coli on spinach during the 14-d storage. Our findings demonstrated the efficacy of electrostatic spraying of MA, LA, and GSE on fresh produce to improve the safety and lower the public health burden linked to produce contamination. PRACTICAL APPLICATION: Electrostatic spraying is an emerging technique that can be adopted to improve the distribution and application of antimicrobials during fresh produce sanitation. Relatively simple and quick, the process can access most/all parts of produce surface and offer protection from food pathogens. The use of malic and lactic acids with or without grape seed extract can serve as effective antimicrobials when sprayed electrostatically, lowering the risk from postcontamination issues with spinach and iceberg lettuce. This application technology can be extended to improve the commercial food safety of other produce, fruits, poultry, and meat.     

Impact properties of thermoplastic composites

The excellent properties exhibited by thermoplastic composites at much reduced weight have attracted attention in the development of products in different sectors. Thermoplastic (TP) composites, because of their distinctive properties as well as ease of manufacturing, have emerged as a competitor against the conventional thermoset resin-based composites. Depending on the application, these composites may undergo impact events at various velocities and often fail in many complex modes. Hence, the development of TP composites having high energy-dissipation at (the desired) much-reduced weight has become a challenging task, but it is a problem which may be alleviated through the appropriate selection of materials and fabrication processes. Furthermore, fibre surface modification has been shown to increase fibre-matrix interfacial adhesion, which can lead to improved impact resistance. Textile preforms are helpful in acting as a structural backbone in the composites since they offer a relatively free hand to the composite designer to tailor its properties to suit a specific application. Additionally, hybrid textile composite structures may help in achieving the desired properties at much lower weight.

Simulation software can play a significant role in the evaluation of composites without damaging physical samples. Once the simulation result has been validated with actual experimental results, it should be possible to predict the test outcomes for different composites, with different characteristics, at different energy levels without conducting further physical tests. Various numerical models have been developed which have to be incorporated into these software tools for better prediction of the result.

In the current issue of Textile Progress, the effects of various materials and test parameters on impact behaviour are critically analyzed. The effect of incorporating high-performance fibres and natural fibres or their hybrid combination on the impact properties of TP composites are also discussed and the essential properties of TP polymers are briefly explained. The effects of fibre and matrix hybridization, environmental factors, various textile preform structures and fibre surface modification treatments on the impact properties of thermoplastic composites are examined in detail. Various numerical models used for impact analysis are discussed and the potential applications of TP composites in automobile, aerospace and medical sectors are highlighted.     

Cystone,an ayurvedic herbal drug imparts protection to the mice against the lethal effects of γ‐radiation: A preliminary study

The effect of 5, 10, 20, 40, 60, 80, 100, 120, and 160 mg/kg body weight (b.wt.) of aqueous extract of cystone (an ayurvedic herbal medicine) administered intraperitoneally was studied on the radiation‐induced mortality in mice exposed to 10 Gy of γ‐radiation. Treatment of mice with different doses of cystone, consecutively for five days before irradiation, delayed the onset of mortality and reduced the symptoms of radiation sickness when compared with the non‐drug treated irradiated controls. The pretreatment of mice with different doses of cystone before exposure to 10 Gy of γ‐radiation resulted in a dose‐dependent elevation in the survival up to 40 mg/kg b. wt., where the highest number of survival (55.55%) was observed by 30 days post irradiation, when compared with the 10 Gy irradiated control (6.66%). Thereafter, the number of survivors declined and reached a nadir at 160 mg/kg, where no survivors could be observed. The optimum protection against irradiation was observed for 40 mg/kg cystone, where the highest number of survivors were reported by 30 days post irradiation and it was 8.34‐fold greater than that of the irradiated control group.     

Numerical appraisal of three low Mach number algorithms for radiative–convective flows in enclosures

The present study investigates three different algorithms for the numerical simulation of non-Boussinesq convection with thermal radiative heat transfer based on a low-Mach number formulation. The solution methodology employs a fractional step approach based on the finite-volume method on arbitrary polyhedral meshes. The three algorithms compute the coupled governing equations in a segregated manner using the conservative form of momentum equations in conjunction with a variable coefficient pressure Poisson equation. The first algorithm (Algorithm A) uses conservation of mass and energy equation to compute density and temperature. The other two algorithms (Algorithm B) and (Algorithm C) calculates temperature and density from the equation of state respectively and solves a conservative form of the continuity and energy equation to obtain density and temperature respectively. The energy and mass conservation errors arising due to the use of Algorithms B and C are derived concerning various non-dimensional parameters governing the flow and heat transfer. The significance of these errors is highlighted by performing investigations over a range of Rayleigh, Prandtl, and Planck numbers for various two and three-dimensional natural convection problems with radiative heat transfer. Finally, the role of balancing of the pressure and buoyancy terms is emphasized for robust calculations of large temperature difference thermo-buoyant convection with radiative heat transfer.     

Multi-item inventory model with variable backorder and price discount under trade credit policy in stochastic demand

In this paper, a two echelon supply chain with one manufacturer and one retailer is developed for multi products. The retailer faced with the uncertain demand for all products which follows a normal distribution. The production process is assumed to be imperfect, and the defectiveness is assumed to follow a beta distribution. The manufacturer produces and delivers the products in a number of equal-sized batches to the manufacturer's warehouse, and thereby it is delivers in a number of equal batches to the retailer's warehouse. Shortages are allowed to occur, at the retailer side, and it is backordered partially. The retailer offers a price discount for backordered items to his customers. Both the lead time crashing cost and the partial backorder ratio are considered as the inverse function of lead time. Under these assumptions, there are three inventory models proposed in this paper, one with non-integrated approach, the other with an integrated approach without trade credit and finally an integrated approach with trade credit. A new iterative algorithmic procedure has been developed to minimise the total cost. Finally, numerical examples are given to illustrate the models and the sensitivity analysis is conducted over various model parameters.     

Hikami-Larkin-Nagaoka (HLN) Treatment of the Magneto-Conductivity of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> Topological Insulator

We report the magneto-conductivity analysis at different temperatures under a magnetic field of up to 5 T of a well- characterized Bi₂Te₃ crystal. Details of crystal growth and various physical properties including high linear magneto-resistance are already reported by some of us. To elaborate upon the transport properties of Bi₂Te₃ crystal, the magneto-conductivity is fitted to the known Hikami-Larkin-Nagaoka (HLN) equation and it is found that the conduction mechanism is dominated by both surface-driven weak anti-localization (WAL) and the bulk weak localization (WL) states. The value of HLN equation coefficient (α) signifying the type of localization (WL, WAL or both WL and WAL) falls within the range of ??0.5 to ??1.5. In our case, the low-field (±?0.25 T) fitting of studied crystal exhibited a value of α close to ??0.86 for studied temperatures of up to 50 K, indicating both WAL and WL contributions. The phase coherence length (l_φ) is found to decrease from 98.266 to 40.314 nm with increasing temperature. Summarily, the short letter reports the fact that bulk Bi₂Te₃ follows the HLN equation and quantitative analysis of the same facilitates to know the quality of studied crystal in terms of WAL to WL contributions and thus the surface to bulk conduction ratio.     

Enhanced optoelectronic,thermal, mechanical and third order nonlinear optical properties of dichlorobis(thiourea)zinc(II) crystal: an effect of Phenol red dye

For the first time the growth of dichlorobis (thiourea) zinc(II) (ZTC) monocrystal in presence of Phenol red dye of considerably good size (~13 mm?×?5 mm) has been achieved from aqueous solution using slow evaporation solution technique at room temperature. The solubility was calculated at different temperatures. The crystal structure was confirmed through X-ray diffraction analysis. The crystallinity of the dyed crystals has been enhanced revealed by Powder X-ray diffraction study. The presence of dye was inveterate by FT-IR and FT-Raman spectroscopic studies. The scanning electron microscopy analyses show that the grown crystals with dye are better than pure. Diffused reflectance was measured and optical band gap was calculated found to be enhanced from 4.5 to 4.65 eV for dyed crystals. The enhancement in the PL intensity has been observed in the dyed crystals. DSC study shows that the thermal stability has been remarkably enhanced from 163?°C (pure) to 203?°C (dyed) and various other thermal parameters are calculated. The surface study shows that the grown crystals with dye possess less dislocation than pure. Mechanical strength of the dyed crystal is found to be remarkably enhanced. Third-order nonlinear optical susceptibility (χ3) of PRZTC was found to be 2 times higher than pure. All results suggest that the properties of ZTC crystals grown in presence of dye are enhanced and can be considered as better contender in various nonlinear devices.