Browsing by Author "Chang, CF"

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A new feature-based design system with dynamic editing
(1997-04-01)
Perng, DB
;
Chang, CF
;
交大名義發表
;
工業工程與管理學系
;
National Chiao Tung University
This paper proposes a feature-based design system for prismatic parts in which predefined 3D features, instead of low-level 2D lines and points, are used as entities for representation and manipulation. Two special sets of functions, a new construction function and a dynamic editing function, enable designers to freely construct and modify parts. The parts are saved as feature-based files in CSG form, while a B-rep form is also created. The feature-based file allows the proposed 3D part-design system to be easily integrated into CAPP/CAM systems without complex feature-recognition and -extraction processes. Object-oriented concepts are used in implementing the proposed system, and examples are given to show its feasibility and effectiveness. (C) 1997 Elsevier Science Ltd.
A new feature-based design system with dynamic editing
(1997-04-01)
Perng, DB
;
Chang, CF
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper proposes a feature-based design system for prismatic parts in which predefined 3D features, instead of low-level 2D lines and points, are used as entities for representation and manipulation. Two special sets of functions, a new construction function and a dynamic editing function, enable designers to freely construct and modify parts. The parts are saved as feature-based files in CSG form, while a B-rep form is also created. The feature-based file allows the proposed 3D part-design system to be easily integrated into CAPP/CAM systems without complex feature-recognition and -extraction processes. Object-oriented concepts are used in implementing the proposed system, and examples are given to show its feasibility and effectiveness. (C) 1997 Elsevier Science Ltd.
Absence of the paramagnetic contribution in the low-temperature specific heat of La1.9Sr0.1Cu0.98Zn0.02O4
(2000-11-01)
Lin, JY
;
Chang, CF
;
Yang, HD
;
物理研究所
;
Institute of Physics
The absence of the paramagnetic contribution in the low-temperature specific heat (C) of Zn-doped cuprates has attracted much attention recently. The phenomenon was usually explained as possible screening in the superconducting state. We have measured C of La1.9Sr0.1Cu0.98Zn0.02O4 which is not superconducting. Intriguingly, The upper limit of the magnetic contribution is found to be two orders of magnitude smaller than the expected value with no screening effect. This result puts the above explanation in a serious jeopardy.
Anisotropic impurity scattering effects on T-c and H-c2 in YBa2Cu3Ox
(1999-03-01)
Lin, JY
;
Chen, SJ
;
Chen, SY
;
Chang, CF
;
Yang, HD
We have studied the impurity effects on the superconducting transition temperature T-c and the upper critical field H-c2 in electron irradiated YBa2Cu3Oy with in-plane oxygen defects and YBa2(Cu1-xZnx)(3)O-y. It is found that the effects of the same type of defects or impurities on T-c are the same regardless of the oxygen contents of the samples. Furthermore, T-c decreases slower in irradiated YBa2Cu3Oy than in YBa2(Cu1-xZnx)(3)O-y. This may be well explained by the model that the scattering due to in-plane oxygen defects is more anisotropic than that due to Zn impurities. The different behavior of the reduced slopes (dH(c2)/dT)(Tc)/(dH(c2)/dT)(Tc0) these two types of samples can also be understood in this context. [S0163-1829(99)08309-5].
Anomalous spin polarization and dualistic electronic nature of CrO(2)
(2003-06-01)
Huang, DJ
;
Tjeng, LH
;
Chen, J
;
Chang, CF
;
Wu, WP
Spin-resolved O 1s x-ray absorption measurements on CrO(2) reveal that the spin polarization of the states at the Fermi level approaches 100%, providing direct evidence of the half-metallic nature of CrO(2). The measurements also show the existence of an atomiclike Cr 3d state not far away from the Fermi level with a spin polarization of only 50%, establishing its Mott-Hubbard character. We conclude that CrO(2) has a dualistic electronic nature, in which the states at the Fermi level are bandlike, while those at higher energies are strongly localized of completely different origin and symmetry. The finding of an exceptionally large number of O 2p holes suggests their important role in preventing the strongly correlated CrO(2) from being an insulator.
Anomalous spin polarization and dualistic electronic nature of CrO2
(2003-06-01)
Huang, DJ
;
Tjeng, LH
;
Chen, J
;
Chang, CF
;
Wu, WP
Spin-resolved O 1s x-ray absorption measurements on CrO2 reveal that the spin polarization of the states at the Fermi level approaches 100%, providing direct evidence of the half-metallic nature of CrO2. The measurements also show the existence of an atomiclike Cr 3d state not far away from the Fermi level with a spin polarization of only 50%, establishing its Mott-Hubbard character. We conclude that CrO2 has a dualistic electronic nature, in which the states at the Fermi level are bandlike, while those at higher energies are strongly localized of completely different origin and symmetry. The finding of an exceptionally large number of O 2p holes suggests their important role in preventing the strongly correlated CrO2 from being an insulator.
Assembly-part automatic positioning using high-level entities of mating features
(1997-07-01)
Chang, CF
;
Perng, DB
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We present a new and convenient method for automatically positioning parts in an assembly. High-level entities of mating features and mating relations are used to describe the composed state of parts in an assembly. The characteristics of volume, reference origin, and boundary face of mating features and parts are used to determine automatic part-positioning operations. Using the proposed approach, a hierarchical model of the assembly can be constructed more easily with fewer input data. This approach thus makes computer-aided assembly design systems more user-friendly and greatly reduces the amount of input data required, An example is presented to demonstrate the simplicity and effectiveness of the proposed approach. (C) 1998 Elsevier Science Ltd. All rights reserved.
Assembly-part automatic positioning using high-level entities of mating features
(1997-07-01)
Chang, CF
;
Perng, DB
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We present a new and convenient method for automatically positioning parts in an assembly. High-level entities of mating features and mating relations are used to describe the composed state of parts in an assembly. The characteristics of volume, reference origin, and boundary face of mating features and parts are used to determine automatic part-positioning operations. Using the proposed approach, a hierarchical model of the assembly can be constructed more easily with fewer input data. This approach thus makes computer-aided assembly design systems more user-friendly and greatly reduces the amount of input data required, An example is presented to demonstrate the simplicity and effectiveness of the proposed approach. (C) 1998 Elsevier Science Ltd. All rights reserved.
Bandpass filter of serial configuration with two finite transmission zeros using LTCC technology
(2005-07-01)
Chang, CF
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
This study proposes a second-order bandpass filter of serial configuration. The filter schema incorporates a grounding capacitor, connecting the two conventional parallel LC resonators with the ground, to provide two finite transmission zeros. The impedance matrix and graphical solutions describe proposed filter's operation principle. To demonstrate the proposed filter schema, two bandpass filters, with center frequencies of 2.44 and 4.8 GHz, were designed and implemented using low-temperature co-fired ceramic multilayer technology. The measured results were found to agree well with the simulation results. The 2.44-GHz fabricated bandpass filter was found to possess low in-band insertion loss and high out-band suppression, making it suitable in wireless local area networks, Bluetooth, and RF home links.
Contributions of CuO2 planes and CuO chains on the transport properties of YBa2Cu4O8
(1999-01-20)
Chatterjee, S
;
Weng, SS
;
Hong, IP
;
Chang, CF
;
Yang, HD
We have investigated the contributions of CuO2 planes and CuO chains on the transport properties of YBa2Cu4O8 by measuring the electrical resistivity and thermoelectric power (S) of Y1-xPrxBa2(Cu1-yZny)(4)O-8, Y1-xCaxBa2Cu4O8 and YBa2(Cu1-xGax)(4)O-8. Pr reduces the mobile carrier concentration in the CuO2 planes in YBa2Cu4O8, as a consequence, the superconducting transition temperature is progressively decreased with increasing Pr. The S(T) data suggest that the metallic behavior at lower temperature of the Pr and Zn doped compounds is contributed by the double CuO chains. On the other hand, the S(T) behavior of Ca doped samples is opposite to that of the Pr doped samples because the doping of Ca in Y-site introduces holes in the CuO2 planes. However, the substitution of Ga in Cu(1)-site suppresses the carrier concentration in CuO chains and increases the normal-state resistivity revealing the important contribution from CuO chains on the metallic behavior of YBa2Cu4O8 and PrBa2Cu4O8. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Decomposition of 2-mercaptothiazoline in aqueous solution by ozonation
(2004-07-01)
Chen, YH
;
Chang, CY
;
Chen, CC
;
Chiu, CY
;
Yu, YH
This study investigates the ozonation of 2-mercaptothiazoline (2-MT). The 2-MT is one of the important organic additives for the electroplating solution of the printed wiring board industry and has been widely used as a corrosion inhibitor in many industrial processes. It is of concern for the aquatic pollution control especially in the wastewaters. Semibatch ozonation experiments in the completely stirred tank reactor are performed under various concentrations of input ozone. The concentrations of 2-MT, sulfate, and ammonium are analyzed at specified time intervals to elucidate the decomposition of 2-MT during the ozonation. In addition, the time variation of the dissolved ozone concentration (C-ALb) is continuously monitored in the course of experiments. Total organic carbon (TOC) is chosen and measured as a mineralization index of the ozonation of 2-MT. The results indicate that the decomposition of 2-MT is efficient, while the mineralization of TOC is limited via the ozonation only. Simultaneously, the yield of sulfate with the maximum value of about 47% is characterized by the increases of TOC removal and ozone consumption. These results can provide some useful information for assessing the feasibility of the treatment of 2-MT in the aqueous solution by the ozonation. (C) 2004 Elsevier Ltd. All rights reserved.
Depression of quasiparticle density of states at zero energy in La1.9Sr0.1Cu1-xZnxO4
(2000-06-12)
Chang, CF
;
Lin, JY
;
Yang, HD
;
物理研究所
;
Institute of Physics
We have measured low-temperature specific hear C(T, H) of La1.9Sr0.1Cu1-xZnxO4 (x = 0, 0.01, and 0.02) in both zero and applied magnetic fields. A pronounced dip of C/T below 2 K was observed in Zn-doped samples, which is absent in the nominally clean one. If the origin of the dip in CIT is electronic, the quasiparticle density of states N(E) in Zn-doped samples may be depressed below a small energy scale Eo. The present data can be well described by the model N(E) = N(0) + alpha E-1/2, with a nonzero N(0) and positive alpha. Magnetic fields depress N(0) and lead to an increase in E-0, while leaving the energy dependence of N(E) unchanged. This novel depression of N(E) below Eo in impurity-doped cuprates cannot be reconciled with the semiclassical self-consistent approximation model. Discussions in the framework based on the nonlinear sigma model field theory and other possible explanations are presented.
Discovery of different types of inhibition between the human and Thermotoga maritima alpha-fucosidases by fuconojirimycin-based derivatives
(2006-05-09)
Ho, CW
;
Lin, YN
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Chang, CF
;
Li, ST
;
Wu, YT
An efficient method for examining the selectivity of inhibitors on two alpha-fucosidases, one from Thermotoga maritima and the other from human, was established. The X-ray crystal structure of the former enzyme makes possible the homology modeling of the human alpha-fucosidase, indicating the major difference between both enzymes in the periphery of the catalytic site. To investigate the difference at the molecular level, a variety of fuconojirimycin (FNJ) derivatives with substitution at Cl, C2, C6, or N were rapidly prepared in microplates and screened without purification for the inhibition activities of the two alpha-fucosidases. Among the molecules that were tested, only the substitution at Cl can significantly enhance the inhibitory potency, in contrast to the control (no substitution) and compounds with substitution at other positions. The majority of Cl-substituted FNJs were found to be slow tight-binding inhibitors of the Thermotoga enzyme, while acting as the reversible inhibitors of the human fucosidase. The best inhibitor exhibited 13700-fold difference in affinity between the two enzymes, which was attributed to the dissimilar aglycon binding site. Further investigations were carried out, including site-directed mutagenesis, the comparison of K-i values among the wild type and mutants, and the intrinsic fluorescence change upon inhibitor titration, all supporting the idea that Tyr64 and Tyr267 of the Thermotoga alpha-fucosidase are critically involved in closely interacting with the aglycon of inhibitors. The increased level of contact thus induced conformational change, leading to the observed slow tight-binding inhibition.
Dual-bandpass filters with serial configuration using LTCC technology
(2006-06-01)
Lin, KC
;
Chang, CF
;
Wu, MC
;
Chung, SJ
;
電信工程研究所
A dual-bandpass filter that utilizes a serial configuration of the inductive coupled-line (ICL) filter and the capacitive coupled-line (CCL) filter is investigated in this study. Numerical analysis is presented for the difference between the ICL and CCL filters. The dual-bandpass filter has a similar behavior to the individual single-band filter around the corresponding passband. An extra transmission zero can be generated between the two pass-bands of the dual-bandpass filter in that the ICL and CCL filters exhibit an out-of-phase response. Four architectures of dual-bandpass filters are proposed for the 2.4/5-GHz systems. Two of them are demonstrated by the low-temperature co-fired ceramic multilayer technology. Measurements results agree quite well with the simulation ones.
Impurity scattering effects on the low-temperature specific heat of d-wave superconductors
(2000-06-01)
Chang, CF
;
Lin, JY
;
Yang, HD
;
物理研究所
;
Institute of Physics
Recently, impurity scattering effects on quasiparticles in d-wave superconductors have attracted much attention. In particular, the thermodynamic properties in magnetic fields are of interest. We have measured the low-temperature specific heat C(T,H) of La1.78Sr0.22Cu1-xNixO4. The impurity scattering effects on C(T,H) of cuprate superconductors were clearly observed and are compared with the theory of d-wave superconductivity. It is found that impurity scattering leads to the relation gamma(H) = gamma(o)[1 + D(H/H-c2)ln(H-c2/H)] in small magnetic fields. Surprisingly, the sealing of C(T,H) is broken down by impurity scattering.
Magnetic circular dichroism in Fe 2p resonant photoemission of magnetite
(2004-02-01)
Chen, J
;
Huang, DJ
;
Tanaka, A
;
Chang, CF
;
Chung, SC
Measurements of magnetic circular dichroism in Fe 2p resonant photoemission and calculations based on a full-multiplet cluster model reveal the parameters of the electronic structure of Fe3O4. We obtained on-site Coulomb energy U-dd of 3d electrons, charge-transfer energy Delta which is defined as the energy required to transfer an electron from O 2p to Fe 3d, and the hybridization strength between Fe 3d and O 2p at different Fe ion sites of Fe3O4 by analyzing the data of magnetic circular dichroism. The charge-transfer energy of Fe3+ ions was found to be significantly smaller than that of Fe2+ ions. We determined the energy positions of the low-lying multiplets of each Fe ion site. These energy positions for Fe3+ ion sites are 1.5-2.5 eV higher than those obtained from band-structure calculations. Our calculations also show that the photoemission spectral weight in binding energy bigger than 10 eV is substantial, in contrast to the results of band-structure calculations. Our findings conclude that Fe3O4 is a system with strong electron-electron interactions.
Magnetic-field dependence of the low-temperature specific heat of La2-xSrxCuO4
(1998-12-01)
Chen, SJ
;
Chang, CF
;
Tsay, HL
;
Yang, HD
;
Lin, JY
Recently, possible evidence from the low-temperature specific heat (LTSH) for the lines of nodes in the superconducting order parameter of cuprate superconductors has attracted much attention and is still debated. To clarify this issue and to cover the studies in different carrier doping regimes, we have measured LTSH of La2-xSrxCuO4 (s = 0.10, 0.16, and 0.22) both in zero and applied magnetic fields. In all doping regimes, it is found that the increase in the Linear-T coefficient gamma is proportional to H-1/2, consistent with d-wave supercon ductivity. The data shows clear evidence for an alpha T-2 term at zero magnetic field in LTSH of La1.78Sr0.22CuO4. Furthermore, our results are compared with the recently proposed scaling theory.
Magnetic-field dependence of the low-temperature specific heat of La2-xSrxCuO4
(1998-12-01)
Chen, SJ
;
Chang, CF
;
Tsay, HL
;
Yang, HD
;
Lin, JY
Recently, possible evidence from the low-temperature specific heat (LTSH) for the lines of nodes in the superconducting order parameter of cuprate superconductors has attracted much attention and is still debated. To clarify this issue and to cover the studies in different carrier doping regimes, we have measured LTSH of La2-xSrxCuO4 (s = 0.10, 0.16, and 0.22) both in zero and applied magnetic fields. In all doping regimes, it is found that the increase in the Linear-T coefficient gamma is proportional to H-1/2, consistent with d-wave supercon ductivity. The data shows clear evidence for an alpha T-2 term at zero magnetic field in LTSH of La1.78Sr0.22CuO4. Furthermore, our results are compared with the recently proposed scaling theory.
Orbital magnetic moments of oxygen and chromium in CrO2
(2002-11-01)
Huang, DJ
;
Jeng, HT
;
Chang, CF
;
Guo, GY
;
Chen, J
With measurements of the magnetic circular dichroism and band-structure calculations in the local spin density approximation (LSDA+U) approach, we revealed that the orbital moment of O in CrO2 is ferromagnetically coupled to that of Cr, whereas the spin moment of O is antiferromagnetically coupled to that of Cr. Spin and orbital magnetic moments of Cr and O are enhanced as Coulomb interaction energy U increases. Comparing the magnetic circular diachromism data with the LSDA+U calculations, we conclude that it is essential to include the on-site Coulomb energy for adequately describing the orbital magnetic moments of CrO2.
Orbital moments of CrO2 and Fe3O4 studied by MCD in soft X-ray absorption
(2004-07-01)
Huang, DJ
;
Chang, CF
;
Chen, J
;
Lin, HJ
;
Chung, SC
We present studies of orbital magnetic moments of CrO2 and Fe3O4 by measuring magnetic circular dichroism (MCD) in soft X-ray absorption. The results show that Fe3O4 exhibits large orbital moments, as a consequence of the strong Coulomb interactions of Fe 3d electrons. In contrast, orbital moments of Cr in CrO2 are nearly quenched, revealing that Cr 3d electrons are strongly hybridized with O 2p electrons and more delocalized as compared with those of Fe in Fe3O4. Comparing the MCD data with the band structure calculations based on local spin density approximation with on-site Coulomb energy U taken into account, we conclude that to include the on-site Coulomb interactions of 3d electrons is essential for adequately describing the electronic structure of CrO2 and Fe3O4. (C) 2004 Elsevier B.V. All rights reserved.