Browsing by Author "Chang, SL"

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A general mathematical model for gears cut by CNC hobbing machines
(1997-03-01)
Chang, SL
;
Tsay, CB
;
Nagata, S
;
機械工程學系
;
Department of Mechanical Engineering
A hobbing machine's cutting mechanism is a mechanism with multi-degree of freedom during the cutting process. In this paper, we propose a general gear mathematical model simulating the generation process of a 6-axis CNC hobbing machine based on the cutting mechanism of CNC hobbing machine and worm-type hob cutter. The proposed gear mathematical model can be applied to simulate different types of gear cutting. Some examples are included to verify the mathematical model. Also, a novel type of gear named ''Helipoid'' which can be used in crossed axes transmission is proposed. The proposed general gear mathematical model can facilitate a more thorough understanding of generation processes and toward the development of novel types of gears.
A general mathematical model for gears cut by CNC hobbing machines
(1997-03-01)
Chang, SL
;
Tsay, CB
;
Nagata, S
;
機械工程學系
;
Department of Mechanical Engineering
A hobbing machine's cutting mechanism is a mechanism with multi-degree of freedom during the cutting process. In this paper, we propose a general gear mathematical model simulating the generation process of a 6-axis CNC hobbing machine based on the cutting mechanism of CNC hobbing machine and worm-type hob cutter. The proposed gear mathematical model can be applied to simulate different types of gear cutting. Some examples are included to verify the mathematical model. Also, a novel type of gear named ''Helipoid'' which can be used in crossed axes transmission is proposed. The proposed general gear mathematical model can facilitate a more thorough understanding of generation processes and toward the development of novel types of gears.
A possible nonpolar solvation mechanism at an intermediate time scale: the solvent-cage expansion
(2000-07-14)
Chang, SL
;
Wu, TM
;
物理研究所
;
Institute of Physics
Through studying the so-called 'epsilon' nonpolar solvation model, we propose that the expansion of the solvent cage, which is composed of the solvents at the vicinity of the first maximum of the solute-solvent radial distribution function, might be a possible solvation mechanism at a time scale between inertial motions and structural relaxation. The expansion is triggered by the strong repulsion between the solute and its neighboring solvents, originally inside the cage. This intermediate mechanism is found to be the cause for the bump following the ultrafast decay in the solvation time correlation functions of the 'epsilon' model at low densities. (C) 2000 Elsevier Science B.V. All rights reserved.
Characteristics of instantaneous resonant modes in simple dense fluids with short-ranged repulsive interactions
(2000-07-01)
Wu, TM
;
Ma, WJ
;
Chang, SL
;
物理研究所
;
Institute of Physics
We manifest the characteristics of the low-frequency, quasilocalized instantaneous normal modes, named as the instantaneous resonant modes (IRMs), in simple dense fluids with short-ranged repulsive interactions. The analyses include the potential energy profiles of the IRMs, and the local geometric structures and the number of the interacting neighbors of the particles at which the centers of the quasilocalization are located. We conclude that an IRM is created due to fluctuations in the local density, and has a barely-isolated center, which slightly interacts with one or two nearest neighbors, and the potential energy profile of an IRM is basically single-well with strong anharmonicity. The differences in character between the IRMs and the high-frequency localized instantaneous normal modes are also examined. Based on the barely isolated center picture, a necessary criterion for the occurrence of the IRMs is proposed. While only the imaginary-frequency IRMs are found in dense fluids with purely repulsive interactions satisfying the criterion, a tiny attractive well in the pair potential allows the occurrence of the real-frequency IRMs. The physical systems to detect the presence of the IRMs are discussed. (C) 2000 American Institute of Physics. [S0021-9606(00)50225-6].
Computerized tooth profile generation and undercut analysis of noncircular gears manufactured with shaper cutters
(1998-03-01)
Chang, SL
;
Tsay, CB
;
機械工程學系
;
Department of Mechanical Engineering
Pitch curves of a conjugate noncircular gear pair are derived based on kinematic considerations. A method for considering the inverse mechanism relationship and the equation of meshing, is proposed here to derive a complete mathematical model of noncircular gears manufactured with involute-shaped shaper-cutters. The proposed method is similar to the contact line method and the envelope method but is easier to apply to the determination of tooth profiles. A computer program is developed for generation the tooth profile with backlashes. Undercutting analysis is also investigated by considering the relative velocity and equation of meshing. Finally modified elliptical gears are presented to illustrate the tooth profile generation when the proposed mathematical model is applied and to investigate the phenomenon of tooth undercutting.
Dynamics of atomic pairs in a Lennard-Jones fluid: Mean relative displacement analysis
(1999-03-01)
Wu, TM
;
Chang, SL
;
物理研究所
;
Institute of Physics
We have analyzed the dynamics of atomic pairs in a simple fluid in terms of the mean relative displacement of two atoms with a given initial separation. The short-time expansion of the mean relative displacement has been derived exactly beyond the constant acceleration approximation (CAA) (up to the t(4) order). For a Lennard-Jones fluid, the mean relative displacements calculated by either the CAA or the t(4)-order approximation have been compared with the results obtained from a molecular-dynamics simulation. Through studying the relative motions of atomic pairs with different initial separations, we give a physical picture of the dynamics of neighboring atoms beyond the CAA. [S1063-651X(99)08603-1].
Improved electrical characteristics of CoSi2 using HF-vapor pretreatment
(1999-05-01)
Wu, YH
;
Chen, WJ
;
Chang, SL
;
Chin, A
;
Gwo, S
We have developed a simple process to form epitaxial CoSi2 for shallow junction. Prior to metal deposition, the patterned wafers were treated with HF-vapor passivation. As observed by scanning tunneling microscopy (STM), this HF, treatment drastically improves the native oxide-induced sur face roughness. The epitaxial behavior was confirmed by cross-sectional transmission electron microscopy (TEM), Decreased sheet resistance and leakage current, and improved thermal stability are displayed by the HF treated samples, which is consistent with STM and TEM results.
Improved electrical characteristics of CoSi2 using HF-vapor pretreatment
(1999-05-01)
Wu, YH
;
Chen, WJ
;
Chang, SL
;
Chin, A
;
Gwo, S
We have developed a simple process to form epitaxial CoSi2 for shallow junction. Prior to metal deposition, the patterned wafers were treated with HF-vapor passivation. As observed by scanning tunneling microscopy (STM), this HF, treatment drastically improves the native oxide-induced sur face roughness. The epitaxial behavior was confirmed by cross-sectional transmission electron microscopy (TEM), Decreased sheet resistance and leakage current, and improved thermal stability are displayed by the HF treated samples, which is consistent with STM and TEM results.
Improved electrical characteristics of CoSi2 using HF-vapor pretreatment
(1999-07-01)
Wu, YH
;
Chen, WJ
;
Chang, SL
;
Chin, A
;
Gwo, S
We have developed a simple process to form epitaxial CoSi2 for shallow junction. Prior to metal deposition, the patterned wafers were treated with HF-vapor passivation. As observed hy scanning tunneling microscopy (STM), this HF treatment drastically improves the native oxide-induced surface roughness. The epitaxial behavior was confirmed by cross-sectional transmission electron microscopy (TEM). Decreased sheet resistance and leakage current, and improved thermal stability are displayed by the HF treated samples, which is consistent with STM and TEM results.
Instantaneous normal mode analysis of orientational motions in liquid water: Local structural effects
(2004-08-22)
Chang, SL
;
Wu, TM
;
Mou, CY
;
物理研究所
;
Institute of Physics
We have investigated the effects of local structures on the orientational motions in liquid water in terms of the instantaneous normal mode (INM) analysis. The local structures of a molecule in liquid water are characterized by two different kinds of index: the asphericity parameter of its Voronoi polyhedron and the numbers of the H bonds donated and accepted by the molecule. According to the two kinds of index, the molecules in the simulated water are classified into subensembles, for which the rotational contributions to the INM spectrum are calculated. Our results indicate that by increasing the asphericity, the rotational contribution has a shift toward the high-frequency end in the real spectrum and a decrease in the fraction of the imaginary modes. Furthermore, we find that this shift essentially relies on the number of the donated H bonds of a molecule, but has almost nothing to do with that of the accepted H bonds. The local structural effects resulting from the geometry of water molecule are also discussed. (C) 2004 American Institute of Physics.
Instantaneous resonant modes in high-temperature gallium liquids
(2001-08-01)
Wu, TM
;
Tsay, SF
;
Chang, SL
;
Ma, WJ
;
物理研究所
We have studied the low-frequency, quasilocalized vibrational excitations in Ga liquids in terms of instantaneous-normal-mode analysis. We present strong numerical evidence for the existence of the instantaneous resonant modes (IRM's) in high-temperature Ga liquids. It is the exotic repulsive-core interaction between Ga particles that gives rise to the IRM's, which are associated with special local structures created by density fluctuation. In general, the IRM density of states is found to increase with temperature.
Kinematic optimization of a modified helical gear train
(1997-06-01)
Chang, SL
;
Tsay, CB
;
Tseng, CH
;
交大名義發表
;
機械工程學系
A mathematical model of a modified helical gear train (MHGT), manufactured with a practical hobbing machine using a curved-template guide, and which takes considerations of center-distance variation and axial misalignment into account, is developed. Tooth contact analysis (TCA) and kinematic errors of a MHGT due to mis-assembly are investigated. A multiple optimization method is applied to reduce the level of MHGT kinematic errors, and to investigate optimal gear tooth modifications. Computer simulation programs for TCA and optimization are also developed. Two numerical examples are presented to illustrate the kinematic optimization of the proposed helical gear train. The results of this study are most helpful in designing and analyzing a MHGT.
Kinematic optimization of a modified helical gear train
(1997-06-01)
Chang, SL
;
Tsay, CB
;
Tseng, CH
;
機械工程學系
;
Department of Mechanical Engineering
A mathematical model of a modified helical gear train (MHGT), manufactured with a practical hobbing machine using a curved-template guide, and which takes considerations of center-distance variation and axial misalignment into account, is developed. Tooth contact analysis (TCA) and kinematic errors of a MHGT due to mis-assembly are investigated. A multiple optimization method is applied to reduce the level of MHGT kinematic errors, and to investigate optimal gear tooth modifications. Computer simulation programs for TCA and optimization are also developed. Two numerical examples are presented to illustrate the kinematic optimization of the proposed helical gear train. The results of this study are most helpful in designing and analyzing a MHGT.
Level statistics of Hessian matrices: random matrices with conservation constraints
(2003-04-01)
Ma, WJ
;
Wu, TM
;
Hsieh, J
;
Chang, SL
;
物理研究所
We consider the Hessian matrices of simple liquid systems as a new type of random matrices. By numerically comparing the distribution of the nearest-neighbor level spacing of the eigenvalues with the Wigner's surmise, we round that the level statistics is akin to the generic Gaussian Orthogonal Ensemble (GOE), in spite of the constraints due to the summation rules and the presence of the correlation among the components inherited with the underlying spatial configuration. The distribution is in good agreement with the Wigner's prediction if only the extended eigenstates are considered. Indeed, our theoretical analysis shows that the ensemble of real symmetric matrices with full randomness. but constrained by the summation rules, is equivalent to the GOE with matrices of the rank lowered by the spatial dimension. (C) 2002 Published by Elsevier Science B.V.
Local geometric structures of instantaneous resonant modes in Ga liquids
(2002-05-01)
Wu, TM
;
Ma, WJ
;
Chang, SL
;
Tsay, SF
;
物理研究所
Recently, we have numerically found the instantaneous resonant modes (IRMs) in high-temperature Ga liquids. The occurrence of these IRMs is attributed to the cooperation of the exotic repulsive core of the Ga pseudopotential and the local volume expansion. In this paper, the local structures around the quasilocalized centers of these IRMs are analyzed. (C) 2002 Elsevier Science B.V. All rights reserved.
Mathematical model and undercutting analysis of elliptical gears generated by rack cutters
(1996-10-01)
Chang, SL
;
Tsay, CB
;
Wu, LI
;
機械工程學系
;
Department of Mechanical Engineering
The theory of gearing and geometry of the straight-sided rack cutter are employed to develop a mathematical model of elliptical gears that takes backlash into consideration. The mathematical model also includes the bottom land of the elliptical gear, which is equidistant from the pitch ellipse. A computer program is developed to generate the tooth profile of elliptical gears. The profile of elliptical gears obtained by applying the proposed method is compared with that obtained by the evolute method. Undercutting of elliptical gears is also investigated. The results of this research should be helpful in the design, manufacture, and measurement of elliptical gears. Copyright (C) 1996 Elsevier Science Ltd
Mechanism for singular behavior in vibrational spectra of topologically disordered systems: Short-range attractions
(2005-05-22)
Wu, TM
;
Chang, SL
;
Tsai, KH
;
物理研究所
;
Institute of Physics
At low-enough fluid densities, we have found some naive singular behavior, like the van Hove singularities in the phonon spectra of lattices, appearing in the instantaneous normal mode spectra of the Lennard-Jones (LJ) 2n-n fluids, which serve as a prototype of topologically disordered systems. The singular behavior cannot be predicted by the mean-field theory, but interpreted by the perturbed binary modes of some special pairs, called the mutual nearest neighbor pairs, at separations corresponding to the extreme binary frequencies, which are solely determined by the attractive part of the LJ 2n-n pair potential. By reducing the range of attraction in the pair potential under the conditions of the same particle diameter and well depth, the tendency for the appearance of the singular behavior shifts to higher fluid densities. From this study, we conclude that pair potential with a short-range attraction can be a mechanism to produce a counterpart of the van Hove singularity in the vibrational spectra of disordered systems without a reference lattice. 2005 American Institute of Physics.
Polyacetylenic compounds and butanol fraction from Bidens pilosa can modulate the differentiation of helper T cells and prevent autoimmune diabetes in non-obese diabetic mice
(2004-11-01)
Chang, SL
;
Chang, CLT
;
Chiang, YM
;
Hsieh, RH
;
Tzeng, CR
\Compelling evidence suggests that infiltrating CD4(+) type I helper T (Th1) cells in the pancreatic islets play a pivotal role in the progression of diabetes in non-obese diabetic (NOD) mice. We demonstrate in the present report that a butanol fraction of B. pilosa suppressed the development of diabetes, helped maintain levels of blood sugar and insulin in NOD mice in a dose-dependent manner and elevated the serum IgE levels regulated by Th2 cytokines in NOD mice. Moreover, the butanol fraction inhibited the differentiation of naive helper T (Th0) cells into Th1 cells but enhanced their transition into type II helper T (Th2) cells using an in vitro T cell differentiation assay. Two polyacetylenic compounds, 2-beta-D-glucopyranosyloxy-1-hydroxy-5(E)-tridecene-7,9,11-triyne and 3-beta-D-glucopyranosyloxy-1-hydroxy-6(E)-tetradecene-8,10,12-triyne, identified from the butanol fraction also prevented the onset of diabetes like the butanol fraction. The latter compound showed a stronger activity for T cell differentiation than the former. In summary, the butanol fraction of B. pilosa and its polyacetylenes can prevent diabetes plausibly via suppressing the differentiation of Th0 cells into Th1 cells and promoting that of Th0 cells into Th2 cells.
The distinct effects of a butanol fraction of Bidens pilosa plant extract on the development of Th1-mediated diabetes and Th2-mediated airway inflammation in mice
(2005)
Chang, CLT
;
Kuo, HK
;
Chang, SL
;
Chiang, YM
;
Lee, TH
Bidens pilosa is claimed to be useful for immune or anti-inflammatory disorders; however, little scientific evidence has been published concerning its function. In this paper., immune disease mouse models were used to study the function of a butanol fraction of B. pilosa. We demonstrated treatment with the butanol fraction of B. pilosa ameliorated Th1 cell-mediated autoimmune diabetes in nonobese diabetic (NOD) mice but caused deterioration of Th2 cell-mediated airway inflammation induced by ovalbumin (OVA) in BALB/c mice. We next showed that Th2 cytokines (IL-4 and/or IL-5) increased but Th1 cytokine (IFN-gamma) decreased following injections with the butanol fraction of B. pilosa in both mouse strains. Accordingly, Th2 cytokine-regulated IgE production in mouse serum increased following treatment with this fraction. Finally, we found that the butanol fraction of B. pilosa inhibited Th1 cell differentiation but promoted Th2 cell differentiation. Taken together, the butanol fraction of B. pilosa has a dichotomous effect on helper T cell-mediated immune disorders, plausibly via modulation of T cell differentiation.
The influence of serration on a shaving cutter with a pre-designed relief portion
(2006)
Chang, SL
;
Wu, UD
;
Hsieh, JK
;
Tseng, CH
;
Cheng, SD
In this paper, a shaving cutter with serration and a pre-designed relief portion manufactured by a hob cutter was designed. Due to the non-conventional manufacturing process, standard manufacturing problems were avoided and the production efficiency was enhanced as was the stiffness of the shaving cutter. Two solid models of the shaving cutter, one with the novel relief portion and the other a relief hole, were set up for stress analysis using the finite element method. The models confirmed that the shaving cutter with the novel relief portion had a higher stiffness compared to that with a relief hole in the presence of serration.