Browsing by Author "Lin, PH"

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BCS-like superconductivity in MgCNi3
(2003-02-01)
Lin, JY
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Ho, PL
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Huang, HL
;
Lin, PH
;
Zhang, YL
The low-temperature specific heat C(T,H) of the superconductor MgCNi3 has been measured in detail. DeltaC/gamma(n)T(c)=1.97 is estimated from the anomaly at T-c. At low temperatures, the electronic contribution in the superconducting state follows C-es/gamma(n)T(c)approximate to7.96 exp(-1.46T(c)/T). The magnetic-field dependence of gamma(H) is found to be linear with respect to H. T-c estimated from the McMillan formula agrees well with the observed value. All the specific-heat data appear to be consistent with each other within the moderate-coupling BCS context. It is amazing that such a superconductor unstable to ferromagnetism behaves so conventionally. The Debye temperature Theta(D)=287 K and the normal state gamma(n)=33.6 mJ/mol K-2 are determined for the present sample.
H-c2 of MgCNi3 determined from the specific heat and resistivity measurements
(2002-10-01)
Lin, JY
;
Lin, PH
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Ho, PL
;
Huang, HL
;
Zhang, YL
H-c2 of MgCNi3 has been determined from the specific heat C and resistivity rho measurements in the same sample. The results from rho are nearly identical with those determined from the anomaly in C. Furthermore, utilizing the relation gamma(H) proportional to H and the value of dgamma/dH, the obtained value of H-c2 is the same as that by the WHH model, if the spin paramagnetic effect and the spin-orbit interaction are taken into account. The results of this comparison have strong implications on the order parameter of MgCNi3.
Numerical analyses for downward flame spread over thin and thick fuels in a gravitational field
(1999-09-01)
Lin, PH
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Chen, CH
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機械工程學系
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Department of Mechanical Engineering
Numerical analyses for radiative autoignition and transition to flame spread over a vertically oriented solid fuel in a gravitational field
(2000)
Lin, PH
;
Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
This study numerically investigates the ignition behaviors of vertically oriented cellulosic materials subjected to a radiant heat flux in a normal gravitational field. The entire process is delineated into two distinct stages. In the heating up stage, the maximum temperature increases with time but at a decreasing rate because of the pyrolysis reaction. The flame development stage consists of ignition and transition processes. In the ignition process, the maximum temperature in gas phase increases dramatically within a short period of time because a large amount of heat is generated from chemical reaction of the accumulative, flammable mixture. The flame is in a transition from a premixed flame to a diffusion one, except for the small region around the flame front. For the effect of varying the heating duration on ignition behavior, prolonging the imposed radiative heat time leads the ignition from a transition one to a persisting ignition. The effect of varying the solid fuel thickness indicates that the ignition delay time increases with an increase of solid fuel thickness while delta(S)less than or equal to 1.802. For 1.802 less than or equal to delta(S)less than or equal to 3.244, the ignition delay times remain constant. Finally, if the external heating rate is the same order as the heat diffuse rate, the ignition delay time increases with an increase in solid fuel thickness.
Numerical analyses for radiative ignition and transition to flame spread over a horizontally oriented solid fuel in a gravitation field
(2001)
Lin, PH
;
Fan, WF
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Chen, CH
;
機械工程學系
;
Department of Mechanical Engineering
This study numerically investigates the ignition behaviors of horizontal-oriented cellulosic materials subjected to radiant heat flux under a natural convective environment. This process can be divided into two stages: (1) the heating-up stage, during which the maximum temperature increases with time and (2) the flame development stage, consisting of the ignition and transition processes, The ignition process is marked with a sharp increase in maximum temperature. Meanwhile, the flame is in a transition from a premixed flame into a diffused one. In the transition process, the flame propagates upstream, forming a so-called opposed flame spread. There is a time lag between solid fuel pyrolysis and the gas-phase chemical reaction. The pyrolysis front overtakes the flame front in the initial heating-up process. As soon as the flammable mixture ahead of the flame front is ignited, the flame moves forward quickly, moving ahead of the pyrolysis front. The ignition delay time is shorter for a horizontal solid fuel than for a vertical solid fuel under the same environment, because the resultant high-temperature region is not cooled and the flammable mixture is not diluted by the induced flow in a horizontal solid fuel. For the effect of changing gravity, the ignition delay time decreases with a decrease in gravity level, owing to the smaller induced flow velocity.
Peculiar hole doping by Ca substitution in cuprate superconductors
(2003-05-01)
Lin, JY
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Chung, PC
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Liu, SJ
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Hsiang, CC
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Lin, PH
The doping effect of Ca substitution in Y0.7Ca0.3Ba2Cu3Oy has been studied for y=6.9 and 6 by the x-ray absorption near edge spectroscopy (XANES). While Ca doping leads to an obvious increase in hole concentration in the CuO2 planes in Y0.7Ca0.3Ba2Cu3O6.9, XANES indicates absence of this doping effect in Y0.7Ca6.3Ba2Cu3O6. These two contradict results suggest that the doping effect by Ca substitution could be sensitive to the oxygen content when y similar to6.0. Comparisons with others' works are made.
Performance assessment for airport noise charge policies and airline network adjustment response
(2005-07-01)
Hsu, CI
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Lin, PH
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
Noise charges have been introduced at major airports to mitigate external noise. This research investigated airline network design, by considering aircraft noise charges, and analyzing the performance of airport noise charge policies, from multiple perspectives. We formulated an airline network design model for minimizing airline operating costs, to determine optimal air routes and flight frequencies, as well as types of aircraft, in response to airport noise charges. We further assessed the performance of different noise charge policies by evaluating changes in airport operating profits and the social cost to residents surrounding the airport. An empirical example, using the Chiang Kai-Shek International Airport, illustrates how airports should determine optimal noise charge policies, from different perspectives. The results show that airlines may adjust types of aircraft, flight frequencies and flight routes, in response to hub airport noise charge policies, which may lead to changes in social costs, airport revenues, and weekly aircraft schedules. Landing fees setting may, in addition, affect the control an airport has over social costs, due to noise surcharges. (c) 2005 Elsevier Ltd. All rights reserved.
Pinning effects induced by periodic arrays of structural corrugations in Nb thin films
(2003-05-01)
Horng, L
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Wu, JC
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Kang, PC
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Lin, PH
;
Wu, TC
Artificial vortex pinning arrays have been fabricated by electron-beam lithography in conjunction with reactive ion etching in Nb superconducting thin films in order to investigate flux pinning. Based on the structural corrugation in the Nb thin film, the square lattice of defects that act as pinning centers was created. A strong periodic pinning effect, as the vortex lattice matches the array of defects, can be observed in the evolution of resistivity and critical current with the applied magnetic fields in the mixed state of the Nb film, thus, revealing a synchronized pinning effect due to structural corrugation. This result is in agreement with the resistivity-temperature curves at matching fields and half-integer matching fields in which a crossover occurs for temperatures exceeding a certain threshold value. The phenomenon is related to the presence of the pinning structure at matching fields.
The electronic structure change induced by stripe phase formation in cuprates
(2004-08-01)
Lin, JY
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Huang, CW
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Lin, PH
;
Sun, CP
;
Lee, JM
It has been suggested that the stripe phase shows ID charge transport in the CuO2 planes instead of the 2D characteristics of the Zhang-Rice band. X-ray absorption near edge spectroscopy (XANES) has been used to study the electronic structure of the stripe phase compounds La2-xSrxCuO4, and La2-x-yNdySrxCuO4 for x around 1/8. The measurements were performed at both 300 and 28 K to examine the possible electronic structure change above and below the temperature of the stripe phase formation. (C) 2004 Elsevier B.V. All rights reserved.