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71.
The superplastic deformation behavior of quasi-single phase Zn-0.3 wt. %Al was investigated. A series of load relaxation and
tensile tests was conducted at various temperatures ranging from RT (20 °C) to 200 °C. The recently proposed internal variable
theory of structural superplasticity was applied. The flow curves obtained from load relaxation tests were shown to consist
of contributions from interface sliding (IS) and accommodating plastic deformation. In the case of quasi-single phase Zn-0.3
wt.% Al alloy with an average agrain size of 1 μm, the IS behavior could be described as a viscous flow process characterized
by a power index of Mg=0.5. A large elongation of about 1400% was obtained at room temperature and the strain rate sensitivity parameter was about
0.4. Although relatively large-grained (10 μm) single phase alloy showed a high value of strain rate sensitivity comparable
to that of fine-grained alloy at very low strain rate range, IS was not expected from the analysis based on the internal variable
theory of structural superplasticity at room temperature. As the temperature increased above 100 °C, however, the contribution
from IS was observed at a very low strain rate range. A high elongation of ∼400% was obtained in a specimen of 10-μm-grain-size
at 200 °C under a strain rate of 2×10−4/sec.
Jointly appointed at Center for Advanced Aerospace Materials (CAAM) 相似文献
72.
73.
This paper presents dynamic performances of an adaptive tunable vibration absorber (TVA) designed to suppress the main harmonic disturbance of a miniature linear cryogenic cooler, which is being used in space applications such as an observation satellite. The adaptive TVA employs a magneto-rheological elastomer (MRE) for a variable stiffness element. This study first investigates the shear modulus change of MRE samples with respect to the magnetic flux density, which varies through the alignment of particle chains. The MRE with the maximal shear modulus change is mounted for the TVA on a prototype cooler, which emulates the characteristics of a miniature cryogenic cooler. Using the test setup, a series of vibration tests are performed to evaluate the performance and efficacy of the MRE TVA and its re-tuning ability. The experimental results show that the MRE TVA is able to robustly suppress the vibration of the cooler even when the frequency of resonant vibration is changed up to 87% from its initial frequency. 相似文献
74.
The problem of environmental sustainability has been growing in recent years with an interest from both researchers and practitioners. A major gap that exists is the absence of empirical studies that addressed business value of green IS (information systems). Thus, drawing on the resource-based view of the firm and IT (information technology) business value literature, this study aims to develop a comprehensive research model of green practice-IS alignment, the key cross-functional coordination of green practices with manufacturing and marketing functions, and firm performance. The study provides a better understanding of the relationship between green practice-manufacturing coordination and green practice-marketing coordination, and how both variables mediated the relationship between green practices-IS alignment and environmental performance. The data used in this study were collected from manufacturing firms. The results show that a firm’s green practices-IS alignment had a positive effect on both green practices-manufacturing coordination and green practices-marketing coordination. In turn, both green practices-manufacturing coordination and green practices-marketing coordination are the significant predictors of environmental performance. Meanwhile, green practices-IS alignment had an indirect effect on environmental performance via both green practices-manufacturing coordination and green practices-marketing coordination. Moreover, the findings of this study show that environmental performance is an important predictor of economic performance. 相似文献
75.
Dong-Hyuk Lee Hyungpil Moon Ja Choon Koo Hyouk Ryeol Choi 《International Journal of Control, Automation and Systems》2013,11(1):127-135
This paper presents a map building method for an in-pipe robot to navigate inside urban gas pipelines autonomously, whose configuration is unknown or partially known. In the first, we explain the reason why the navigation in the pipeline is difficult and then, present a method for obtaining a robot’s posture by using a pipeline’s unique geometrical features. The robot can obtain its heading direction by detecting the standardized geometries of pipe elements. Based on the method, we propose a robot controller consisting of discrete and continuous controllers. The discrete controller is activated by pre-defined events and generates appropriate paths for exploration. The continuous controller receives the desired path and physically moves the robot to the desired path. The method is implemented in an in-pipe robot, called MRINSPECT-V and its effectiveness is validated. 相似文献
76.
Development of a quadruped walking robot AiDIN-III using biologically inspired kinematic analysis 总被引:1,自引:0,他引:1
Ig Mo Koo Duc Trong Tran Yoon Haeng Lee Hyungpil Moon Ja Choon Koo Sangdeok Park Hyouk Ryeol Choi 《International Journal of Control, Automation and Systems》2013,11(6):1276-1289
This paper presents a bio-inspired mechanism design for a quadruped walking robot. The approach is derived from the observation on the behaviors of quadruped locomotion, skeletal structure, and the study on the stability of walking based on morphological analysis. In the first, we define the design parameters such as the dimensions of the body and limbs, the center of mass position, and locomotion mechanisms based on surveys on the literatures from biologists. Then, by using the parameters, we propose an useful framework for determining the design parameters of a quadruped walking robot. For implementations, we manufacture a dog-type self-contained quadruped walking robot, named AiDIN-III (Artificial Digitigrade for Natural Environment version III) and the effectiveness of the proposed idea is validated via experimental works. 相似文献
77.
Geun Bum Koo Jin Bae Park Young Hoon Joo 《International Journal of Control, Automation and Systems》2013,11(6):1075-1083
In this paper, a novel intelligent digital redesign (IDR) technique using the guaranteed cost control method is proposed for nonlinear systems which can be represented by a Takagi-Sugeno (T-S) fuzzy model. The IDR technique, which is one of the sampled-data fuzzy controller design methods, guarantees not only the stability condition of the sampled-data closed-loop system with the sampleddata fuzzy controller and the state-matching error is presented. By using the concept of the guaranteed cost control method, sufficient conditions are obtained for both minimization of the state-matching error and stabilization of the sampled-data closed-loop system and derived in terms of linear matrix inequalities (LMIs). Finally, a numerical example is provided to verify the effectiveness of the proposed technique. 相似文献
78.
Elhadi Shakshuki Hsiang-Hwa Koo Darcy Benoit Daniel Silver 《Journal of Computer and System Sciences》2008,74(2):279-296
Electronic calendars are important tools that are used by consumers on a daily basis. However, scheduling a meeting that involves persons with different commitments and preferences remains a difficult task. Meeting scheduling is difficult because current calendaring applications cannot handle the responsibility of automatically and autonomously managing time slots. This paper presents a distributed multi-agent system architecture in which each person is represented by an agent. These agents automatically and autonomously work together to assist different users to book meetings on their behalf. Each agent has the capability to manage, negotiate and schedule tasks, meetings, events, appointments for its assigned user. In this multi-agent system, the agents coordinate their activities and negotiate on behalf of their associated users to find a solution that satisfies the users' meeting requirements and preferences. A prototype of this system is implemented to demonstrate how the agents can automatically book meetings. 相似文献
79.
Hyun‐Sang Park Seon‐Beom Ji Min‐Koo Han Jae‐Sic Lee Chi‐Woo Kim Kwang‐Soo Choi 《Journal of the Society for Information Display》2009,17(8):681-686
Abstract— A new digital ambient‐light sensor system is presented which employs two linear light sensors with different sensitivities and automatically adjusts the sensitivity based on the illumination condition. The adaptation mechanism allows a very wide range of light intensity to be detected, and the input dynamic range of the system is substantially improved from 22.5 to 45.1 dB. The proposed method does not require any additional precision bits for output data. Due to the small number of the output bits and the simple conversion process, the system can be easily integrated on the display panel. 相似文献
80.
We investigate the relationship between superconductivity and spin glasses, which were observed to be coexistent in heavy fermion superconductors (HFSs). We begin by explaining the phase of spin glass using concepts of finite-sized block spin. We then introduce the phase of superconductivity in HFSs as collective Cooper pairing, that is, the pairing of block spins with net spin = 1/2, each of which is comprised of a large number of random spins that together produce a majority spin direction. The superconducting Bardeen-Cooper-Schrieffer (BCS)-type phonon-mediated electron-electron interaction is substituted for the BCS-type electron-electron interaction mediated by phonon-enhanced spin flips previously suggested by us. An effective charge of any value stemming from an electron attached to the flux of an electric field can be referred to as a composite charge. The distinguished difference between ours and the original BCS model is the following: (i) another BCS-type interaction, (ii) bare electrons that are substituted for block spins with net spin = 1/2 and net charge = e in the presence of electric fields, and (iii) Fermi-Dirac distributions that are replaced by a new distribution called as Brillouin distribution. 相似文献