113 research outputs found
Reliability analysis of 3D CSP MEMS and IC under thermal cycle-impact coupled multi-physics loads
No full textIn this paper, reliability analysis of 3D CSP MEMS and IC under thermal cycle-impact coupled multi-physics loads was investigated. COMSOL Multiphysics, a finite element software, was used to analyze the mechanical behavior of our device under a -55 degrees C/125 degrees C thermal cycling and 1500G@1ms with half-sine pulse impact coupled load. MEMS chip was bonded on a silicon interposer by solder balls. An application specific integrated circuit (ASIC) for the signal processing was placed on the interposer beneath the MEMS. Combining the effects of thermal stress and impact loads, we hope to find out the failure modes of interconnect structures including solder joints and whole device. The deformation and stress distribution of the overall device will be carried out for layout optimization of interconnect structures
Brief Discussion on Significance of Rules for Children to Strengthen Occupational Cultivation of Secretary
No full textMeta optimization of stand management with population based methods
No full textThe amount of different products and services obtained from forests depends on several management decisions such as thinning years, thinning intensity, thinning type and rotation length. The relationships between management actions and the various outputs obtained from forests are complicated. This makes stand management optimization challenging, especially if the number of simultaneously maximized outputs and the number of optimized variables are high. The direct search method of Hooke and Jeeves (HJ) has been used much in stand management optimization. In recent years, population-based methods have been proposed as an alternative to the HJ method. The performance of a population-based method depends on its parameters such as number iterations and population size (number of solution vectors used in the population-based method). This study used two-level meta optimization to simultaneously optimize the parameters of a population-based method and the management schedule of a stand. Four population-based methods were analysed: differential evolution (DE), particle swarm optimization (PS), evolution strategy optimization (ES) and the method of Nelder and Mead (NM). With optimal parameter values, DE and PS found the best stand management schedules, followed by ES and NM. DE and PS performed better than HJ. Therefore, DE and PS should be used more in forest management and their search algorithms should be further developed.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Defect evolution in ZnO and its effect on radiation tolerance
No full textWe realized tuning the radiation tolerance of ZnO through engineering the type and concentration of intrinsic defect.</p
Spontaneous dewetting of a hydrophobic micro-structured surface
No full textInspired by recent experimental observations and natural phenomena that spontaneous dewetting transition occurs on a hydrophobic micro-structured surface, a thermodynamic model of a condensed water droplet on a micro-pillar arrayed surface is established in order to disclose the mechanical mechanism. Based on a general model of an arbitrary-shaped micro-structured surface, surfaces with conical, rectangular and parabolic micro-pillars are investigated. A critical water droplet volume is found, beyond which dewetting transition can be realized. The effect of the micro-pillar's size and intrinsic contact angle on the free energy difference and critical water droplet volume are further studied. The theoretical model may provide a possible explanation for the abnormal Wenzel wetting state of condensed water droplets on lotus leaves and the anti-fogging behavior of a mosquito's compound eyes. The present results should be very useful for the biomimetic design of functional dewetting surfaces in practical applications
Optimal management of larch (Larix olgensis A. Henry) plantations in Northeast China when timber production and carbon stock are considered
No full textInternational audienceAbstract• Key messageThe optimal management of larch (Larix olgensis) plantations in Northeast China consisted of 2 or 3 thinnings and a rotation length of 55–61 years when economic profitability, wood production, and carbon sequestration were simultaneously maximized. Wood production ranged from 5.4 to 11.7 m3 ha−1 a−1, depending on site quality.• ContextL. olgensis is an important tree species in the northeast forest region of China, playing a significant role in the establishment of fast-growing and high-yielding plantation forests in China. However, the management of these plantations has not been optimized in previous studies.• AimsThe objective of the study was to find the optimal combinations of thinning times, thinning types, and rotation length for L. olgensis stands when both timber production and carbon stock are considered.• MethodsFirst, a growth and yield model was developed to simulate the dynamics of larch plantations. Then, the models were linked with the Hooke and Jeeves optimization algorithm to optimize forest management for two commonly used planting densities and three site qualities.• ResultsTwo thinnings were found to be suitable for larch plantations when the stand density at 10 years was 2125 trees/ha (corresponding to a planting density of 2500 trees/ha) whereas three thinnings were recommended when the density at 10 years was 2800 trees/ha (planting density of 3300 trees/ha). When the stand density was 2800 trees/ha, the optimal rotation length was 61, 58, and 55 years for site indices (SI) 12, 16, and 20 m (dominant height at 30 years), respectively. The mean annual wood production was 5.4 m3 ha−1 for SI 12, 8.2 m3 ha−1 for SI 16, and 11.7 m3 ha−1 for SI 20. The results were nearly the same for the lower initial stand density. The better the site quality of the stand, the earlier the thinnings were conducted.• ConclusionIn multifunctional forestry, optimal rotation lengths of larch plantations were 10–20 years longer than advised in the current silvicultural recommendations for Northeast China
Evolution of Activation Energy of Interface Traps in LPNP Transistors Characterized by Deep-Level Transient Spectroscopy
No full textA Technique for Characterizing Ionization and Displacement Defects in NPN Transistors Induced by 1-MeV Electron Irradiation
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