Browsing by Issue Date, starting with "1997-02-07"

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Photochemistry of acetone in the presence of exocyclic olefins: An unexpected competition between the photo-Conia and Paterno-Buchi reactions
(1997-02-07)
Chung, WS
;
Ho, CC
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
When irradiated in the presence of several exocyclic olefins, acetone undergoes homoalkylation with the olefins to form a series of 4-cycloalkylbutan-2-ones (with quantum yields of 0.14 +/- 0.01) rather than exhibiting the expected Paterno-Buchi reaction; in contrast, the photolysis of perdeuteriated acetone gave both types of products.
Photochemistry of acetone in the presence of exocyclic olefins: An unexpected competition between the photo-Conia and Paterno-Buchi reactions
(1997-02-07)
Chung, WS
;
Ho, CC
;
應用化學系
;
Department of Applied Chemistry
When irradiated in the presence of several exocyclic olefins, acetone undergoes homoalkylation with the olefins to form a series of 4-cycloalkylbutan-2-ones (with quantum yields of 0.14 +/- 0.01) rather than exhibiting the expected Paterno-Buchi reaction; in contrast, the photolysis of perdeuteriated acetone gave both types of products.
Interaction between a cylindrical superconducting impurity and a vortex in a type-II superconductor
(1997-02-10)
Wei, JC
;
Chen, JL
;
Liu, RS
;
Yang, TJ
;
電子物理學系
We examined the effectiveness of an infinite cylindrical superconducting impurity of radius a in an infinite type-II superconductor as a pinning center. The impurity and the superconducting background have the penetration depth lambda(i) and lambda(s), respectively. With regard to a single-quantum vortex, the free energy of the system and the pinning potential for a vortex were calculated, based upon the London model of the vortex line. Here, the pinning potential U-pin is defined by the difference between the free energy of a vortex being at the center of the impurity and that being infinitely distant from the impurity. U-pin is negative for lambda(i) > lambda(s). On the other hand, U-pin is positive for lambda(i) < lambda(s). In the limit of a much greater than lambda(i) and lambda(s), the pinning potential is found to be U-pin = phi(0)(2)(1/lambda(i)(2) - 1/lambda(s)(2)) ln kappa/4 pi mu(0). In the limit of a much less than lambda(i) and lambda(s), the pinning potential is found to be U-pin = phi(0)(2)[(1/lambda(i)(2) - 1/lambda(ss)(2)) ln(lambda(s)/a) - (1/lambda(i)(2)) ln(lambda(i)/a)]/4 pi mu(0). There is a clear correlation between the intrinsic property of these two superconducting materials and the pinning potential.
文壇消息
(1997-02-13)
雪山
Separation of retinoids by micellar electrokinetic capillary chromatography
(1997-02-14)
Hsieh, YZ
;
Kuo, KL
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
In this study, we have developed a micellar electrokinetic capillary chromatography (MEKC) method with diode-array detection to separate five important retinoids, including retinol, retinal, retinoic acid, retinyl acetate and retinyl palmitate. These very hydrophobic retinoids are successfully separated with phosphate buffer containing sodium deoxycholate (SDC) and Brij 35 as the micellar pseudostationary phase. The effects of SDC and Brij 35 concentration on the migration behavior of the five retinoids are also discussed. The relative standard deviations of the migration times of the retinoids are less than 1.9% in the optimized separation condition. Moreover, a direct extraction method without saponification is employed to extract retinyl esters in pharmaceutical products. The ranges of recoveries are 95%-99% for retinyl esters with less than 2% relative standard deviations. Therefore, retinyl esters in pharmaceutical products can be determined by combining the direct extraction and the MEKC methods.
Analysis of prostaglandins by micellar electrokinetic capillary chromatography
(1997-02-14)
Hsieh, YZ
;
Kuo, KL
;
應用化學系
;
Department of Applied Chemistry
This paper presents a rapid and reliable micellar electrokinetic capillary chromatography (MEKC) method to separate major prostaglandins and thromboxane B-2. The running buffer was modified with sodium dodecyl sulfate (SDS). The effects of the SDS concentration on the migration behavior of analytes was also examined. Moreover, the influences of electrolyte concentration and capillary temperature on the separation were investigated. In optimum conditions, seven major prostaglandins and thromboxane B-2 could be separated within 8 min. The relative standard deviations of the migration times (reproducibility) of the analytes were less than 0.82%.
Analysis of prostaglandins by micellar electrokinetic capillary chromatography
(1997-02-14)
Hsieh, YZ
;
Kuo, KL
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
This paper presents a rapid and reliable micellar electrokinetic capillary chromatography (MEKC) method to separate major prostaglandins and thromboxane B-2. The running buffer was modified with sodium dodecyl sulfate (SDS). The effects of the SDS concentration on the migration behavior of analytes was also examined. Moreover, the influences of electrolyte concentration and capillary temperature on the separation were investigated. In optimum conditions, seven major prostaglandins and thromboxane B-2 could be separated within 8 min. The relative standard deviations of the migration times (reproducibility) of the analytes were less than 0.82%.
斜眼　
(1997-02-15)
管管
斜眼　
(1997-02-15)
管管
Local electric field effects in a SiGe quantum well investigated by photoluminescence
(1997-02-15)
Nilsson, S
;
Penner, U
;
Schmalz, K
;
Yassievich, IN
;
Chang, CY
We describe photoluminescence and admittance spectroscopy of p-type Si/Si0.25Ge0.25/Si quantum well structures with the SiGe quantum well surrounded by undoped Si spacer layers of various thickness. Holes confined in the SiGe quantum well create a local electric field, which induces potential barriers for holes in the surrounding Si: and a potential well for electrons in the vicinity of the Sice quantum-well region. Decreasing the thickness of one of the Si spacers from 30 nm to 5 nm increases the local electric field and shifts the SiGe-related near-band-edge photoluminescence spectrum to higher photon energies. This can be explained by a reduced exciton binding energy due to exciton polarization. The polarization is caused by the increasingly asymmetrical potential well for electrons and holes for the thinner Si spacer layers. In addition, admittance spectroscopy was carried out in order to measure the potential barriers for the confined holes for various thicknesses of the Si spacer layers. For thicker Si spacer layers, the results are in agreement with the photoluminescence data. For thinner Si spacer layers, thermally activated tunnelling of holes via the potential barrier was observed, Our interpretations are supported by theoretical calculations.
Ionization of the surface-state electron by half-cycle electric-field pulses
(1997-02-15)
Jiang, TF
;
物理研究所
;
Institute of Physics
The purpose of this research is to study the half-cycle pulse (HCP) ionization behavior of the surface-state electron (SSE). Motivated by the experimental progress in the HCP source, we propose to investigate the HCP excitation of the SSE system, which was confirmed to be one dimensional in nature. We examine the cases with a wide range of scaled electric-field amplitudes, which have different time scales and pulse shapes. Our results show some stabilization windows for the ionization probability with respect to these fields. The number of windows increases with the length of the pulse duration. The origin of the window is shown to be related to the energy gained from the driving electric fields.
斜眼　
(1997-02-15)
管管
Ozonolysis of 2-endo-7-anti-diacylnorbornenes. A new entry for the synthesis of 2,4,6,13-tetraoxapentacyclo[5.5.1.0(3,11).0(5,9).0(8,12)]tridecanes
(1997-02-17)
Wu, HJ
;
Chern, JH
;
Wu, CY
;
交大名義發表
;
應用化學系
A new route for the synthesis of the title compounds 4a, 4b, 10a, and 10b has been developed via ozonolysis of 2-endo-7-anti-diacylnorbornenes 3a, 3b, 9a, and 9b. The synthesis of the unsubstituted (parent) compound 4a of tetraacetal tetraoxa-cages has been accomplished for the first time by this new entry. Ozonolysis reactions of 3a, 3b, and 9a were also performed in CDCl3 for understanding the final ozonide structures and the ozonation chemistry. Ozonolysis of 3a, 3b, and 9a in CH2Cl2 at -78 degrees C followed by treatment with triethylamine provided an indirect support for the structures of the final ozonides 11a, 11b, and 14. (C) 1997, Elsevier Science Ltd.
Bifurcations and chaotic motions in a rate gyro with a sinusoidal velocity about the spin axis
(1997-02-20)
Ge, ZM
;
Chen, HH
;
機械工程學系
;
Department of Mechanical Engineering
An analysis is presented for a single-axis rate gyro mounted on a space vehicle undergoing sinusoidal motion and steady rotation about its spin and output axes. By varying the amplitude of sinusoidal motion, the periodic and chaotic responses of this parametrically excited non-linear system are investigated using the incremental harmonic balance (IHB) method and numerical integration. The multi-variable Floquet theory is applied to analyze the stability of periodic attractors and the behavior of bifurcations. Additionally, phase portraits, Poincare maps, average power spectra, bifurcation diagrams, parametric diagrams and Lyapunov exponents are presented to observe Hopf bifurcation, symmetry-breaking bifurcations, period-doubling bifurcations and chaotic motions. The cell mapping technique (MICM) is also used to study the basins of attraction of periodic attractors. (C) 1997 Academic Press Limited
Bifurcations and chaotic motions in a rate gyro with a sinusoidal velocity about the spin axis
(1997-02-20)
Ge, ZM
;
Chen, HH
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
An analysis is presented for a single-axis rate gyro mounted on a space vehicle undergoing sinusoidal motion and steady rotation about its spin and output axes. By varying the amplitude of sinusoidal motion, the periodic and chaotic responses of this parametrically excited non-linear system are investigated using the incremental harmonic balance (IHB) method and numerical integration. The multi-variable Floquet theory is applied to analyze the stability of periodic attractors and the behavior of bifurcations. Additionally, phase portraits, Poincare maps, average power spectra, bifurcation diagrams, parametric diagrams and Lyapunov exponents are presented to observe Hopf bifurcation, symmetry-breaking bifurcations, period-doubling bifurcations and chaotic motions. The cell mapping technique (MICM) is also used to study the basins of attraction of periodic attractors. (C) 1997 Academic Press Limited
A substrate-mode holographic collimating and beam shaping element for laser diodes
(1997-02-24)
Chang, JT
;
Su, DC
;
Huang, ZX
;
Huang, YT
;
電子物理學系
A new type of substrate-mode holographic collimating and beam shaping element for laser diodes is presented. Techniques and design considerations are described. A sample is fabricated and its function is demonstrated. It has many merits, such as easy fabrication, low cost, compactness of monolithic structure, and is easily used. (C) 1997 American Institute of Physics.
A substrate-mode holographic collimating and beam shaping element for laser diodes
(1997-02-24)
Chang, JT
;
Su, DC
;
Huang, ZX
;
Huang, YT
;
電機學院
A new type of substrate-mode holographic collimating and beam shaping element for laser diodes is presented. Techniques and design considerations are described. A sample is fabricated and its function is demonstrated. It has many merits, such as easy fabrication, low cost, compactness of monolithic structure, and is easily used. (C) 1997 American Institute of Physics.
Faithful 1-edge fault tolerant graphs
(1997-02-28)
Wang, SY
;
Hsu, LH
;
Sung, TY
;
資訊工程學系
;
Department of Computer Science
A graph G* is 1-edge fault tolerant with respect to a graph G, denoted by 1-EFT(G), if any graph obtained by removing an edge from G* contains G. A 1-EFT(G) graph is said to be optimal if it contains the minimum number of edges among all 1-EFT(G) graphs. Let G(i)* be 1-EFT(G(i)) for i = 1,2. It can be easily verified that the cartesian product graph G(1)* x G(2)* is 1-edge fault tolerant with respect to the cartesian product graph G(1) x G(2). However, G(1)* x G(2)* may contain too many edges; hence it may nor be optimal for many cases. In this paper, we introduce the concept of faithful graph with respect to a given graph, which is proved to be 1-edge fault tolerant. Based on this concept, we present a construction method of the 1-EFT graph for the cartesian product of several graphs. Applying this construction scheme, we can obtain optimal 1-edge fault tolerant graphs with respect to n-dimensional tori C(m(1), m(2),...,m(n)), where m(i) greater than or equal to 4 are even integers for all 1 less than or equal to i less than or equal to n. (C) 1997 Elsevier Science B.V.
Faithful 1-edge fault tolerant graphs
(1997-02-28)
Wang, SY
;
Hsu, LH
;
Sung, TY
;
資訊工程學系
;
Department of Computer Science
A graph G* is 1-edge fault tolerant with respect to a graph G, denoted by 1-EFT(G), if any graph obtained by removing an edge from G* contains G. A 1-EFT(G) graph is said to be optimal if it contains the minimum number of edges among all 1-EFT(G) graphs. Let G(i)* be 1-EFT(G(i)) for i = 1,2. It can be easily verified that the cartesian product graph G(1)* x G(2)* is 1-edge fault tolerant with respect to the cartesian product graph G(1) x G(2). However, G(1)* x G(2)* may contain too many edges; hence it may nor be optimal for many cases. In this paper, we introduce the concept of faithful graph with respect to a given graph, which is proved to be 1-edge fault tolerant. Based on this concept, we present a construction method of the 1-EFT graph for the cartesian product of several graphs. Applying this construction scheme, we can obtain optimal 1-edge fault tolerant graphs with respect to n-dimensional tori C(m(1), m(2),...,m(n)), where m(i) greater than or equal to 4 are even integers for all 1 less than or equal to i less than or equal to n. (C) 1997 Elsevier Science B.V.
A novel shallow trench isolation technique
(1997-03-01)
Cheng, JY
;
Lei, TF
;
Chao, TS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Shallow-trench isolation processes which involve refilling using deposition of oxide and polysilicon were investigated. Our results show that the oxide-filled shallow-trench isolation technology based on chemical-mechanical polishing (CMP) is difficult to control and results in poor uniformity. Use of this technology also involves in the dishing effect in wide field regions. However, shallow-trench isolation technology using a masking nitride layer, polysilicon refill, the CMP process with high etch selectivity, and local oxidation of polysilicon is easily implemented and absolutely field oxide encroachment (bird's beak) free. Although the CMP process results in the dishing effect in wide field regions, the local oxidation of polysilicon can reduce the amount of dishing. The polysilicon-filled shallow-trench isolation process can also achieve excellent uniformity across 6-inch diameter silicon wafers due to the high etching selectivity of polysilicon to chemical-vapor-deposited (CVD) oxide and SiN. Moreover, the n(+)/p junction leakage current of polysilicon-filled shallow trenches is comparable to that of oxide-filled shallow trenches. This simple and easily controllable process is a very promising candidate for shallow trench isolation.