An error diffusion based method to generate functionally graded cellular structures

The spatial variation of cell size in a functionally graded cellular structure is achieved using error diffusion to convert a continuous tone image into binary form. Effects of two control parameters, greyscale value and resolution on the resulting cell size measures were investigated. Variation in cell edge length was greatest for the Voronoi connection scheme, particularly at certain parameter combinations. Relationships between these parameters and cell size were identified and applied to an example, where the target was to control the minimum and maximum cell size. In both cases there was an 8% underestimation of cell area for target regions

Comparison of power cycling reliability of flexible PCB interconnect smaller/thinner and larger/thicker power devices with topside Sn-3.5Ag solder joints

The power cycling reliability of flexible printed circuit board (PCB) interconnect smaller/thinner (ST) 9.5 mm × 5.5 mm × 0.07 mm and larger/thicker (LT) 13.5 mm × 13.5 mm × 0.5 mm single Si diode samples have been studied. With the assumption of creep strain accumulation-induced fatigue cracking as the failure mechanism of the Sn-3.5Ag solder joints, finite element (FE) simulations predicted a higher power cycling reliability of soldering the flexible PCB on a ST Si diode than on a LT Si diode under similar power cycling conditions. Then the power cycling test results of 10 samples for each type are reported and discussed. The samples were constructed with commercially available ST Si diodes with 3.2/0.5/0.3 μm thick AlSiCu/NiP/Pd topside metallization and LT Si diodes with 5/0.1/1/1 μm thick Al/Ti/Ni/Ag topside metallization. In contradiction with the FE prediction, most ST Si diode samples were less reliable than those LT Si diode samples. This can be attributed to the fact that the failure of the ST diode samples was associated with the weak bonding and hence the shear-induced local delamination of the topside solder joints from the AlSiCu metallization, while the failure of the LT diode samples was mainly caused by the creep strain accumulation-induced fatigue cracking within the solder joints. Such results can be used to not only provide better understanding of the different failure mechanisms, but also demonstrate the importance of employing an appropriate topside metallization on the power devices

Promoting a Culture of Care for College Students Experiencing Health Disparities Using an Embedded Prevention Navigation Model

Research indicates that college students are at increased risk for mental and physical health concerns such as depression, anxiety, substance use, HIV, and other sexually transmitted infections, creating greater demands for timely and responsive services. However, students experiencing health disparities often face greater challenges accessing physical and behavioral health services due to historic and systemic barriers. One unique and economical approach to helping students access care is to train peers to provide psychoeducation and timely and responsive linkages to behavioral and physical health resources and embed them in spaces where students naturally congregate. This approach has proven effective in reducing engagement in high-risk behaviors and encouraging resource utilization in community settings, but little research exists on using an embedded prevention navigator approach in college settings. The present study presents details concerning the development, implementation, and evaluation of such an approach piloted among 88 undergraduates, the majority of whom identified as students of color and first-generation college students. Findings support the feasibility of using a peer-delivered prevention navigation approach to provide students with mental health, substance use, and sexual health education and referrals to relevant resources. Lessons learned and recommendations for college mental health professionals are discussed

THERMAL APPLICATIONS OF OPEN CELL METAL FOAMS

Abstract: The key structural and thermo-physical properties of Reticulated Metal Foams (RMF) are reviewed. Analytical expressions relating such properties to basic structural parameters are developed through mathematical modeling and experimental studies. Conductive and convective aspects of thermal energy transfer through RMF based heat exchangers are reviewed. Mathematical model is developed which calculates maximum thermal performance for such heat exchangers .were estimated through a mathematical model. Results of experimental and Finite Element Analysis predicting thermal performance of test module using a thermal base plate, a power device and RMF heat exchanger and off the shelf external cold plate compared. The superior performance of RMF based heat exchangers are shown. 1) Introduction: It is being realized that the thermal aspects of many advancing technologies are in the critical path limiting the performance, size and the cost future products. The Reticulated Metal Foams (RMF), see The metal foam based thermal technology is generic, flexible and scaleable. It is generic in terms of its compatibility with the cooling media ranging from DI water, inert fluorocarbons, and jet fuel to air He or Ar. It is flexible it terms of its compatibility with various semiconductor devices and substrates such as Si, GaAs, and SiC, SiN not excluding many other ceramic metallic or composite materials. The metal foam based thermal technology is scaleable both in size and performance so that it could be applied to not only discrete devices but also to Hybrid Multi Chip Modules (HMCM) integrating photonic and electronic devices, and also to double sided Printed Wiring Boards (PWB) with constraining cores. The performance of the metal foam based advanced heat exchangers is also scalable along with its cost to address a wide range of both military and commercial applications. In a broader sense, it takes advantage of the materials and technologies developed under DoD contracts, and create synergism by increasing the value of R&D spending to the US economy. 2) Summary: The most significant benefits of the proposed technology include; elimination of as many thermal interfaces between the source of heat dissipation and the heat sink i.e. the ambient viewed as the circulating coolant in an open loop (air) or closed loop system (liquid or gas). The elimination of thermal interfaces will have a significant impact on the

Secure Initial Access and Beam Alignment Using Deep Learning in 5G and Beyond Systems

5G and beyond networks will require fast, energy efficient, and secure initial access. In this study, a deep learning-based secure initial beam selection method is proposed that ranks the beam pairs between a transmitter and a legitimate user aiming to maximize the signal strength the user receives, while keeping the signal strength that the eavesdropper sees below a threshold. Instead of an exhaustive search, the initial beam selection is performed over a limited number of the top beam pairs, leading to reduced communication overhead and energy consumption. The proposed scheme is evaluated using data obtained from a real-life mobile network topology as well as a synthetic data set based on the same geographical site but with statistical system-level environment variables. Utilizing a multi-layer perceptron model, the neural network takes receiver locations as input and produces a ranked list of beam pairs between transmitter and receiver based on the specified coverage criteria. Numerical results show that the signalling overhead can be reduced by 75% with 99.66% accuracy in terms of the best beam pair, and 99.89% of the achievable signal strength. In terms of security, the proposed method has been shown to improve secure coverage probability by 68.12% compared to the best-coverage beam selection scenario