Jung Hua Chou

Poisson Ratio Effect on Stress Behavior of Propellant Grains Under Ignition Loading

In this study, a transient finite element model, accompanied by the time-temperature shift principle, is used to simulate the transient response of a solid rocketmotor so that the response of the propellant grains under real ignition pressurization loading conditions is investigated. The results show that the transient effect is important for structural completeness of the solid propellant grains under the ignition loading conditions. There is an apparent difference among the stresses of different Poisson’s ratios.When changing the property of propellant grains from compressible into incompressible, the stress and strain of propellant grains under ignition pressurization loading decreased significantly. The stress variation versus Poisson’s ratio is nonlinear and cannot be neglected.

A friendly and intelligent human-robot interface system based on human face and hand gesture

A friendly and intelligent human-robot interface (HRI) system based on machine vision is established in this paper. A user uses his/her face and hand gestures to communicate with the robot. Three kinds of face detection, including shape, similarity and lip detections, are adopted to improve the recognition accuracy. The recognition of hand gestures is implemented through PCA, BPANN and their combined classifier. Successive dynamic commands are processed by dynamic programming. Experimental results show that the devised natural HRI works well and the system can process 8 image frames per second for practical real time applications.

Improved design of thermal-via structures and circuit parameters for advanced collector-up HBTs as miniature high-power amplifiers

An improved methodology, based on the genetic algorithm, is developed to design thermal-via structures and circuit parameters of advanced InGaP and InGaAs collector-up heterojunction bipolar transistors (C-up HBTs), which are promising miniature high-power amplifiers (HPAs) in cellular communication systems. Excellent simulated and measured results demonstrate the usefulness of this technique.

Effect of cooling load on the safety factor of propellant grains

The reliability of propellant grains of a solid-propellant rocket is crucial to the performance of a missile. The environment temperature changes greatly from the curing to the firing conditions of the missile. The propellant grains inside the missile experiences similar temperature variations as well. In this study, the time–temperature shift principle, cumulative damage theory, and finite element software are used to evaluate the time–temperature-dependent behavior of the structural integrity of the solid-propellant grains under cooling loads. The results show that the cooling load from the curing temperature to the storage temperature significantly influences the safety factor of the propellant grains; the larger the cooling rate, the smaller the safety factor. Thus, safety factors of the propellant grains can be tuned to a desired value within certain limits by adjusting the cooling load with a smaller cooling rate.

Advances in Selective Wet Etching for Nanoscale NiPt Salicide Fabrication

Currently, the two-step rapid thermal process (RTP) which includes a lower temperature RTP 1 and a larger amount of platinum (Pt) additive is the trend to form thinner nickel monosilicide (NiSi) for the NiPt silicide scaling together with complementary metal oxide semiconductor (CMOS) technology toward the 22 nm node. In this work, we re-investigate the piranha chemistry and match the Pt oxidation/dissolution behavior to develop a piranha chemistry base wet etching process. The result shows that higher temperature preheated sulfuric acid Piranha will boost the reaction rate drastically. Also, the two-time Pt additive will take three-time process time to clear the Pt residue. Compare to the traditional chloric acid base process, the new Piranha process has achieved the goal of effective Pt removal, lower material loss and no damage to nickel-rich silicide (Ni2Si/Ni3Si2). It results in a lower and more uniform silicide sheet resistance (RS) on both n/pMOS.

Design and implementation of a novel outdoor road-cleaning robot

In order to clean unknown outdoor environments, we devised a novel outdoor cleaning robot using mainly on-board vision-based auto-navigation in this paper. The track-driven and cleaning mechanisms of the robot are designed for cleaning tasks in outdoor rough terrain. A single image sensing module is exploited for clean-region detection and three ultrasonic ranging modules are used for obstacle avoidance. The cleaning task is performed autonomously after the boustrophedon path planning is completed in the grid-cell map. The map is obtained from transforming the two-dimensional images captured by the image sensor. The robot also self-localizes based on the deduced boundary lines at the end of each cleaning stage to continue its unfinished cleaning work. The experimental results prove that our outdoor cleaning robot performs well in general outdoor environments.

A low-cost filler-dissolved process for fabricating super-hydrophobic poly(dimethylsiloxane) surfaces with either lotus or petal effect

A low-cost filler (salt) water-dissolved method is developed to produce large-area and flexible super-hydrophobic surfaces by using poly(dimethylsiloxane) (PDMS) material. Five levels of salt grain sizes are used to examine the filler size effect on fabricating the super-hydrophobic surfaces and on the hydrophobic mechanism involved. The results show that the surfaces fabricated using grain sizes of 53–74 and 74–104 µm exhibit the lotus effect (cell adhesion (CA) > 150° and self-adhesion (SA) 150° and high adhesion even upside-down). The super-hydrophobic characteristic is achieved mainly by the large micro rib-like structures, small micro rock-like bumps, and textures on the bump due to the fillers.

Thermal Stability of High-Power LEDs Analyzed With Efficient Nondestructive Methodology

With the continuing advancement in light-emitting efficiency of high-power light-emitting diodes (LEDs), a nondestructive evaluation on thermal reliability, especially regarding the operating temperature and thermal resistance, which directly affect their lifetime and luminous characteristics, is needed. In this paper, we develop a methodology of using a 3-D numerical simulation for transient thermal-conduction analysis, which is combined with the electrical test method to evaluate the junction temperature of a variety of LEDs. As a result, the simulated temperature for LEDs was found to increase with time, whereas the slug temperature showed the same trend for the simulation and the experiment. The measured results indicate that the thermal resistance of AlGaInP-material-based red and amber LEDs reveals higher variability than that of InGaN-material-based white and green LEDs. Via the luminous flux experiment, we have found that the thermal resistance of the LEDs is not the major determination factor of their luminous flux decay. In contrast, the luminous flux decay of the LED is dependent on the chip material being used. Notably, the slug temperature, observed from the pulsed-driven experiment, of the LED appeared to be lower than that observed in the normal steady operation. It is demonstrated that the lifetime and reliability of high-power LEDs can be improved by decreasing the junction and slug temperatures of the devices. This is important as the slug temperature can be controlled by external cooling techniques. In practice, the developed methodology is not restricted to analyze particular LED packaging forms and can be used to investigate various kinds of multichip LED modules as well.

Experimental Study of Ablative Materials by Oxyacetylene Flame Flow System

A missile motor has precision design and complicated components, responsible to propel the missile forward to reach an expected range. The motor must be protected by the inhibitor, which limits the high temperature from the burning of propellant to the generator to ensure safety of shell. The solid rocket propellant grain burns in the parallel layer according to a certain rule. Recently, NBR (Nitrile Butadiene Rubber)、 EPDM(Ethylene-Propylene-Diene Monomer), Silicon Rubber and Polyisoprene are usually applied to the inhibitor matrix in solid propellant. The inhibitor can protect the external steel shell, and remains at a temperature of 300-400K under severe conditions of high temperatures of 2300-3700 K inside, free from any damage arising from internal high temperature. The oxyacetylene ablation performance test system is simple, economic and useful to estimate the thermal process of ablative materials. Based on this method, the relative thermal insulation effectiveness during the early stage of material research is determined.

Buoyancy Ventilation Efficiency Analysis of a Conference Hall

This study focuses on the efficiency of passive solar chimney in natural ventilation performance. A case study is conducted for the conference hall at the Magic School of Green Technology (MSGT) in Tainan, Taiwan. The efficiency of the passive solar chimney is evaluated using both computational fluid dynamics (CFD) and full-scale model tests. Simulation and experimental results demonstrate that without the thermal resources of people in the conference hall. The air exchange rates were 5.15ACH and 4.92ACH. With the thermal resources of 200 people in the conference hall, the air exchange rates were as high as 8.62ACH. When the external temperature is lower than 28°C, the internal temperature in conference hall is still in acceptable and comfortable scope. By using the passive solar chimney in the conference hall, the air-conditioning system can be shut off for 4 months and energy consumption can be reduced by roughly 27% annually in Taiwan.