Thermal Analysis and Shape Optimization of an In-Space Radiator Using Genetic Algorithms

In this paper, the optimization for the reduction of copper loss, iron loss, and permanent magnet (PM) eddy current loss considering harmonics is carried out to improve thermal performance. The effect in terms of thermal performance is confirmed through thermal analysis using a lumped-parameter thermal network (LPTN). First, the optimal shape is determined using an automatic optimization method that combines the explorative particle swarm optimization algorithm and finite element analysis. Then, the iron loss and PM eddy current loss considering carrier harmonics are recalculated by inputting the actual pulsewidth modulation current. Finally, an LPTN-based thermal analysis is performed with the calculated loss as the input. In particular, the thermal parameter is confirmed through an experimental method to validate the accuracy of the thermal analysis. The advantages over the conventional motor are clarified.

Thermal analysis has long been essential for designing reliable, high-performance, cost-effective integrated circuits (ICs). Increasing power densities are making this problem more important. Characterizing the thermal profile of an IC quickly enough to allow feedback on the thermal effects of tentative design changes is a daunting problem, and its complexity is increasing. The move to nanoscale fabrication processes is increasing the importance of quantum thermal phenomena such as ballistic phonon transport. Accurate thermal analysis of nanoscale ICs containing hundreds of millions of devices requires characterization of thermal effects on length scales that vary by several orders of magnitude, from nanoscale quantum thermal effects to centimeter-scale cooling package impact. Existing chip.package thermal analysis methods based on classical Fourier heat transfer cannot capture nanoscale quantum thermal effects. However, accurate device-level modeling techniques, such as molecular dynamics methods, are far too slow for use in full-chip IC thermal analysis. In this work, we propose and develop ThermalScope, a multi-scale thermal analysis method for nanoscale IC design. It unifies microscopic and macroscopic thermal physics modeling methods, i.e., the Fourier and Boltzmann transport modeling methods. Moreover, it supports adaptive multi-resolution modeling. Together, these ideas enable efficient and accurate characterization of nanoscale quantum heat transport as well as chip.package level heat flow. ThermalScope is designed for full-chip thermal analysis of billion-transistor nanoscale IC designs, with accuracy at the scale of individual devices. ThermalScope enables accurate characterization of temperature-related effects, such as variation in leakage power and delay. ThermalScope has been implemented in software and used for full-chip thermal analysis and temperature-dependent leakage analysis of an IC design with more than 150 million transistors. It will be publicly released for free academic and personal use.

A thick Cu column based double-bump flip-chip structure is one of the promising alternatives for fine pitch flip-chip applications. In this study, the thermal cycling (T/C) reliability of Cu/SnAg double-bump flip-chip assemblies was firstly investigated and the failure mechanism was analyzed through correlation of T/C test and the finite element analysis (FEA) results. After 1000 thermal cycles, the T/C failure site was the Cu column/Si chip interface, where was identified via a FEA as the location of the maximum stress concentration during thermal cycling. During thermal cycling, the Al pad and Ti layer between the Si chip and Cu column bumps were displaced due to thermo-mechanical stress. Based on the low cycle fatigue model, the accumulation of equivalent plastic strain resulted in thermal fatigue deformation of the Cu column bumps, and ultimately reduced the thermal cycling lifetime. In addition, the normal plastic strain of the y-direction, ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</inf> , was determined to be compressive and was a dominant component in relation to the plastic deformation of Cu/SnAg double-bumps. As the number of thermal cycles increased, normal plastic strains in the perpendicular direction to the Si chip were accumulated on the Cu column bumps at the chip edge in the low temperature region. Thus it was found that displacement failure of the Al pad and Ti layer, the main T/C failure mode of the Cu/SnAg flip-chip assembly, occurred at the Si chip/Cu column interface by compressive normal deformation during thermal cycling. Next, the effect of Cu column height was investigated for the enhancement T/C reliability. As results of T/C test for 60 um and 85 um Cu column heights, flip chip assemblies with thicker Cu column height showed better T/C reliability. In the real time moiré interferometry, shear strain and normal strain of the x-direction was almost same regardless of Cu column height. On the other hand, the normal strain of y-direction (perpendicular direction to the Si chip) at Si chip/Cu column interface for 85 um-thick Cu samples shows significantly reduced value compared with 60 um-thick Cu samples. This relaxation of the normal plastic strain of the y-direction is the origin that thicker Cu column height guarantees better T/C reliability

Thermal design and thermal analysis of control cabinet for pattern sewing machine was researched to make components’ temperature meets the requirement. Basic flow sheet of research process was introduced. Then, preliminary thermal design and thermal analysis was performed, and the computed result indicated that temperature of some components was out of limit. Next, by optimizing the location of fan and components in cabinet, the temperature of servo driver 1 to 3 dropped 11.1 oC, 10.8 oC and 11.3 oC respectively. The data shows that cabinet’s heat dissipation is improved, and the thermal design of the cabinet is reasonable. Finally, Thermal test of the prototype was performed, which proves the thermal design is effective, and the numerical simulation result is correct.

Thermal cycling (TC) is an important method to evaluate the reliability of electronic products. During the TC process, the solder joints have the risk of cracking due to fatigue stress, but the internal interfaces in the package will also be affected by the fatigue loads, presenting delamination at several interface areas. Due to the difficulty in experimental monitoring of delamination and the lack of effective simulation methods, the research on evaluating the risks of interface delamination has outstanding deficiencies during the TC process. This paper uses finite element analysis (FEA) to evaluate the risk of interface delamination of the underfill (UF) during TC. The viscoelastic property of UF is introduced in FEA. The stress and strain at the interface are carefully analyzed during TC, and the accumulated strain energy (ASE) at the risk position of the interface is calculated as the characteristics reflecting the damage of UF at the interface during TC. In addition, the influence of the coefficient of thermal expansion (CTE) of UF, the dwell time, and the stress-free temperature on ASE are systematically analyzed. This study provides a method for the qualitative and quantitative assessment of the risk of delamination for UF during TC.

The paper presents an analysis of the use of optimization algorithms in parallel solutions and distributed computing systems. The primary goal is to use evolutionary algorithms and their implementation into parallel calculations. Parallelization of computational algorithms is suitable for the following cases - computational models with a large number of design variables or cases where the objective function evaluation is time consuming (FE analysis). As the software platform for application of distributed optimization algorithms is using MATLAB and BOINC software package.

The disc brakes are exposed to large thermal stresses and heat during routine braking. The extraordinary thermal stresses, tremendous heat occurred in the disc during hard braking. The aim of the project or research work is to design and analysis of disc. The modelling or design of the disc is done using solid works software. The Thermal analysis is to be done on the Non-vented disc brakes using ANSYS software with different materials. The thermal analysis is done to analyze the thermal properties e.g. Thermal deformation. Comparison can be done for temperature distribution between different materials. In this analysis, different materials to check which material are best. Solid works is a 3d modelling software widely used in the design process. The ANSYS software is general-purpose finite element analysis (FEA) software package. Finite Element Analysis is a numerical solution method of deconstructing the complex system into very small pieces called elements. Keywords – Rotor brake, solid works, structure and thermal analysis, ANSYS.

Copper has been used for high power semiconductor package to satisfy thermal radiation performance. However, copper easily deforms and warpage increases during thermal cycle. In this research, warpage increase mechanism of copper package during thermal cycle is clarified using experiment and finite element analysis (FEA). As a result, this phenomenon occurs as a interaction with plastic deformation of copper at low temperature and a stress relaxation due to solder creep at high temperature. Therefore, warpage increases with minimum temperature of thermal cycle increase or maximum temperature decrease. Minimum temperature conditions affect plastic deformation of copper and maximum temperature conditions affect solder creep. In addition, we found this phenomenon is sensitively controlled by the temperature condition. And the results of elasto-plastic FEA that includes plasticity of copper and solder creep deformation agree well with the experimental result under various thermal cycle conditions.

A crater detection and identification algorithm for autonomous lunar landing

Maintenance of human health on long-duration exploration missions is a primary challenge to mission designers. Indeed, human health risks are currently the largest risk contributors to the risks of evacuation or loss of the crew on long-duration International Space Station missions. We describe a quantitative assessment of the relative probabilities of occurrence of the individual risks to human safety and efficiency during space flight to augment qualitative assessments used in this field to date. Quantitative probabilistic risk assessments will allow program managers to focus resources on those human health risks most likely to occur with undesirable consequences. Truly quantitative assessments are common, even expected, in the engineering and actuarial spheres, but that capability is just emerging in some arenas of life sciences research, such as identifying and minimize the hazards to astronauts during future space exploration missions. Our expectation is that these results can be used to inform NASA mission design trade studies in the near future with the objective of preventing the higher among the human health risks. We identify and discuss statistical techniques to provide this risk quantification based on relevant sets of astronaut biomedical data from short and long duration space flights as well as relevant analog populations. We outline critical assumptions made in the calculations and discuss the rationale for these. Our efforts to date have focussed on quantifying the probabilities of medical risks that are qualitatively perceived as relatively high risks of radiation sickness, cardiac dysrhythmias, medically significant renal stone formation due to increased calcium mobilization, decompression sickness as a result of EVA (extravehicular activity), and bone fracture due to loss of bone mineral density. We present these quantitative probabilities in order-of-magnitude comparison format so that relative risk can be gauged. We address the effects of conservative and nonconservative assumptions on the probability results. We discuss the methods necessary to assess mission risks once exploration mission scenarios are characterized. Preliminary efforts have produced results that are commensurate with earlier qualitative estimates of risk probabilities in this and other operational contexts, indicating that our approach may be usefully applied in support of the development of human health and performance standards for long-duration space exploration missions. This approach will also enable mission-specific probabilistic risk assessments for space exploration missions.

The National Aeronautics and Space Administration (NASA) is continuously working in furthering its space and aero communications capabilities required for the successful accomplishment of its aerospace missions. With the ever present demand for higher communication data rates and larger bandwidth required by future space exploration missions, optimization of the communications systems supporting such missions is necessary to ensure that critical scientific data and high definition video and imagery of human and robotic exploration is properly transmitted back to Earth. In the aeronautics side, the envisioned increase in aircraft volumes under the Urban Air Mobility (UAM) and Advanced Air Mobility (AAM) ecosystems could benefit from communications capabilities impervious to interference and free from spectrum limitations constraints. This work discusses examples of GRC’s ongoing technology development and integration efforts relevant to the aforementioned scenarios. In particular, the ability to increase the versatility, affordability, and reliability of ground-based optical receivers for space-to-ground communications will be presented. Our current activities on the development of highly secure airborne laser communications links augmented with Quantum Key Distribution (QKD) will also be discussed, as well as scenarios in which optical communications could be beneficial to UAM/AAM. The status of efforts in quantum communications, high rate optical networks, and on the development of current efforts to demonstrate integrated Radio/optical communications (iROC) will also be addressed.

Future space exploration missions may be undertaken by flights of two or more large, manned vehicles launched in timed sequences along nearly common trajectories. Primary communications modes in such missions are those between the spacecraft and between any one spacecraft and an Earth station. In either mode, a duplex, real-time, video channel is an assumed mission requirement. Performance comparisons are presented for laser communication links and 5 band microwave links in the light of this mission requirement. Because of the difference in severity of the acquisition and tracking constraints in the two communication modes, system requirements and performance results are different. The wideband, duplex TV requirement can be provided for the interspacecraft link with ranges of about 10 miles between spacecraft by the use of lasers. For transmission to Earth, from ranges of about 10 miles, neither lasers nor microwaves will satisfy the TV requirement, but the relative performance of the two types of systems clearly favors microwave when judged on the bases of total ava lable bandwidth and available bandwidth per unit payload weight.

Spectroscopic investigations of fungal biomarkers after exposure to heavy ion irradiation

While there are multiple methods to ventilate protective clothing, there is still room for improvement. In our research, we are using ventilation elements that are positioned at the ventilation holes in the air space between the body and clothing. These ventilation elements allow air to flow freely while preventing sun radiation, rain drops, and insects from directly accessing the body. Therefore, the shape of the ventilation element is crucial. This led us to study the shape optimization of ventilation elements through the utilization of metamodels and numerical approaches. In order to accomplish the objective, it is crucial to thoroughly evaluate and choose suitable criteria for the optimization process. We know from prior research that the toroidal cut-out shape element provides better results. In a previous study, we optimized the shape of this element based on the minimum pressure difference as a criterion. In this study, we are using different criteria for the shape optimization of ventilation elements to determine which are most effective. This study involves a metamodeling strategy that utilizes local and global approximations with different order polynomials, as well as Kriging approximations, for the purpose of optimizing the geometry of ventilation elements. The goal was achieved by a sequential process. (1) Planning the position of control points of Non-Uniform Rational B-Splines (NURBS) in order to generate elements with a smooth shape. (2) Constructing geometric CAD models based on the design of experiments. (3) Compute detailed model solutions using SolidWorks Flow Simulation. (4) Developing metamodels for responses using computer experiments. (5) Optimization of element shape using metamodels. The procedure is repeated for six criteria, and subsequently, the results are compared to determine the most efficient criteria for optimizing the design of the ventilation element.

With the CHESS-U upgrade in 2018, the south arc region of Cornell Electron Storage Ring (CESR) has been replaced with new magnets and vacuum chambers, and CESR will operate with higher beam energy and beam current at lower beam emittance. A new crotch absorber has been designed for the upgrade, based on previous CHESS crotch absorbers. The main body of the crotch absorber is a water-cooled hollow cylinder made of oxygen-free high-conductivity copper, and it has a 5-mm thick beryllium band brazed on the outside in the middle section to reduce the power density it absorbs on the surface. In this paper, we describe the mechanical design, present finite element thermal and structural analysis results with a focus on the region with high temperature and high thermal stress, and discuss the fatigue lifetime of the absorber. For typical operation with 6 GeV beam energy and a 200 mA beam current, the highest temperature on the crotch is approximately 300 °C based on the thermal analysis. Correspondingly, the fatigue lifetime is conservatively estimated to be around 4 × 104 cycles. We also show some details in the fabrication of the crotch assembly, especially about the vacuum furnace brazing joint between the beryllium band and the copper main body, including X-ray fluorescence inspection of the brazing joint. In addition, in order to have a relevant comparison in an effort to estimate the fatigue lifetime, we carry out finite element analyses (FEA) for the low cycle fatigue experiment with beryllium tiles using electron-beam heating of Watson et al. [Fusion Eng. Des. 37, 553 (1997)] in 1990s and provide new understanding for some of their experimental observations. These analyses assure the effectiveness of the design.