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Passive Geometry Fluctuation in Minkowski Vacuum
Chun-Hsien Wu 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.1
The quantum uctuation of the stress tensor of a quantum field are discussed, as are the resulting spacetime metric uctuations. In the case of the Minkowski vacuum these were calculated explicitly and the operational signicance of metric uctuations are discussed using a test particle method. A test particle undergoes Brownian motion induced by an electromagnetic vacuum energy uctuation. The induced position uncertainty is considerable when measured in one unit of the Planck time and is supressed when the time scale is larger than a few units of the Planck time.
Performance Analysis of Permanent Magnet Brushless Motors for Mobility Scooters
Yu-Chuan Lu,Ming-Yang Cheng,Chun-Hsien Wu,Wei-Chih Chen,Cheng-Hu Chen 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Most modern commercial electric scooters are still equipped with the DC brush motor. This type of motor has mechanical structures such as permanent magnet, brush, and commutator. Therefore, it has attractive features, e.g., large start-up torque and easy to control. However, this kind of mechanical commutation often leads to drawbacks such as low power density, low reliability, and poor heat dissipation. In contrast, the Permanent Magnet Brushless Motors (PMBLMs) have advantages such as high efficiency and maintenance free, etc. Hence, the PMBLMs have great potential in becoming the actuators for electric scooters. In this paper, the performance of the PMBLMs with trapezoidal and sinusoidal back-emf waveforms driven by square wave commutation and sinusoidal commutation is investigated. To reduce the cost, low-resolution Hall sensors are used to implement sinusoidal commutation.
Nonequilibrium Backreaction on a Moving Charge and Mirror in Quantum Fields
Jen-Tsung Hsiang,Da-Shin Lee,Chun-Hsien Wu 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.2I
Backreaction on a nonrelativistic moving charge and mirror under the influence of quantum fields is studied. We employ the closed-time-path formalism to obtain the influence functional by tracing out quantum fields. The respective semiclassical Langevin equation is derived and can be used to describe the stochastic behavior on its mean trajectory with a self-consistent backreaction. In particular, when backreaction dissipation and fluctuations are taken into account, the corresponding fluctuation-dissipation theorem obtained from the first-principles derivation must be fulfilled. The implications of the results from solving the semiclassical Langevin equation are discussed.웗
The kinematic design of a planar-cam type pick-and-place device
Wen-Tung Chang,Long-Iong Wu,Chun-Hsien Liu 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.12
The planar-cam type pick-and-place device can clearly and effectively achieve the desired curvilinear motion of its end effector, and it can be designed and fabricated easily. By employing the concept of velocity instant center, the cam profiles, the paths of cutters, the pressure angles and the radii of curvature of the dual cams of the planar-cam type pickand- place device can be expressed parametrically. The cam profiles may have concave portions, and each minimum radius of curvature of the concave portion of the dual cam profiles is the upper bound of the grinding-wheel radius that may not cause undercutting.
Enhancing antimicrobial activity of mastoparan-B by amino acid substitutions
Mars J. Yang,Wen-Yuh Lin,Chun-Hsien Lin,Ching-Lin Shyu,Roger F. Hou,Wu-Chun Tu 한국응용곤충학회 2013 Journal of Asia-Pacific Entomology Vol.16 No.4
This study evaluated antimicrobial and hemolytic activities of mastoparan-B (MP-B) isolated fromthe venomof the hornet, Vespa basalis, and its analogs after substituting certain amino acid (aa) residues.MP-B exhibited significantly different antimicrobial activities against bacteria species/strains tested, especially two Escherichia coli strains, Staphylococcus xylosus and Citrobacter koseri at low dosages, and was non-specific against certain Gram-positive and -negative bacteria. Our results indicated that hydrophobicitymodification by single aa substitution may enhance their antimicrobial activities. An aa substituted MP-B, viz., MP-B-1, inwhich Trp substituted for Leu3, became more effective than the original peptide at inhibiting or killing the bacterial species tested, especially Klebsiella pneumonia, Salmonella typhimurium, and Salmonella Cholerasuis, and even up to 8 timesmore effective in some cases. However, MP-B-2 was virtually similar to MP-B against each bacterial species assayed,while MP-B-3 reduced its effectiveness greatly compared to others. On the other hand, MP-B and its analogs were not effective against the beneficial probiotics and they were not hemolytic to erythrocytes at the dosages tested. Our results suggested that MP-B becomes more potent against specific pathogenic bacteria and safe to the probiotics after undergoing appropriate amino acid substitutions.