Showing papers by "Sun Yat-sen University published in 1983"

Amorphous hydrogenated carbon from the plasma deposition of C2H2, C2H4 or CH4

Abstract: The growth of amorphous hydrogenated carbon (a-C : H) from the plasma deposition of C2H2, C2H4, or CH4 is reported. Measurements of the infrared absorption spectra, the optical gaps, and the photoluminescence spectra of these thin films are compared with each other, to those on a-C : H by previous workers, and to those on a-Si : C. The possibility of an a-C : H/a-Si : H hetero-junction solar cell is suggested.

Clinical observation on the uterotonic effect of I-mu Ts'ao (Leonurus artemisia).

Abstract: Normal fertile women gives an oral dose of I-mu Ts'ao decoction (30 g. dry weight equivalent) showed an increase in intra-uterine pressure in 41.3% of 121 cases. The increase ranged from 150% to over 300% of spontaneous activity before dosing. A slightly higher success rate was observed with 2 successive doses or with improved experimental skill in later cases. Ergonovine (0.2 mg i.m.) scored a success rate of 61%. Therefore, I-mu Ts'ao decoction appeared to have a relative potency of 91% compared with ergonovine when the highest success rate (55.5%) of the former is considered. Blank control with water yield a positive response rate of 2.7%. There are no observable side-effects apart from diuresis.

First-order strong variation algorithm for optimal control problems involving hyperbolic systems

Abstract: This paper considers an optimal control problem involving linear, hyperbolic partial differential equations. A first-order strong variational technique is used to obtain an algorithm for solving the optimal control problem iteratively. It is shown that the accumulation points of the sequence of controls generated by the algorithm (if they exist) satisfy a necessary condition for optimality.

A convex optimal control problem involving a class of linear hyperbolic systems

Abstract: In this paper, we consider a convex optimal control problem involving a class of linear hyperbolic partial differential systems. A computational algorithm which generates minimizing sequences of controls is devised. The convergence properties of the algorithm are investigated.

A comparison of various MO methods for predicting regioselectivity in Diels-Alder reactions

Abstract: Various semiempirical MO methods for predicting regioselectivity in Diels-Alder reactions are compared in order to examine their reliability. They are the frontier molecular orbital method using CNDO/2, HMO and MNDO molecular orbitals and the HMO approach on pericyclic reactions presented by Tang.

Effect of conjugation beyond multiple bonds on geometry and acidity

Abstract: A quantum chemical quantity referred to as the π-resonance integral contribution to energy is introduced as a measure of the quantum mechanical interaction between two atoms in the π-system of a molecule. The geometries of simple molecules related to gas-phase acidity as well as the protonated and the deprotonated species were calculated by the CNDO/2 method, which turns out to be fairly good in reproducing relative geometries. The resulting bond lengths are discussed in relation to π-bond order and π-resonance integral contribution to energy. Acidities are also discussed.

Violations of the noncrossing rule due to special symmetry and alternance

Abstract: This paper reports a study on which behavior of the Hamiltonian gives rise to violation of the noncrossing rule. In principle, the noncrossing rule may be violated when a special symmetry other than spatial and spin symmetries is present or there exists the so-called alternance, which corresponds to a Hamiltonian in a real vector space anticommuting with a Hermitian operator. In the HMO models for pericyclic reactions, violations due to special symmetry or alternance have been found. The [m,n] supra–antara cycloadditions have no symmetry in the traditional sense, but have special symmetry leading to the existence of crossings in the correlation diagram. Alternance results in one crossing in the middle of the correlation diagram of a forbidden pericyclic reaction with intermediate states in the form of even alternant hydrocarbon. For the reactions with intermediate states in the form of odd alternant hydrocarbon such as [2,4]-cycloaddition of an allyl cation or an allyl anion to butadiene, there should be no crossing in the correlation diagrams, and both the supra–supra and the supra–antara processes are predicted to be allowed. Such a prediction is beyond the Woodward–Hoffmann rule.

On an optimal control problem involving second order hyperbolic systems with boundary controls

Abstract: In this paper, we consider an optimal control problem involving second-order hyperbolic systems with boundary controls. Necessary and sufficient conditions are derived and a result on the existence of optimal controls is obtained. Also, a computational algorithm which generated minimizing sequences of controls is devised and the convergence properties of the algorithm are investigated.

Light-induced optical absorption changes in sputtered hydrogenated amorphous silicon

Abstract: In this paper, we report a new effect of prolonged illumination on hydrogenerated amorphous silicon (a-Si:H) -----the light-induced optical absorption changes in rf sputtered a-Si:H. After long and intensive illumination, a significant increase of optical absorption in the infrared spectrum has been observed and the intergrated strength of three vibrational modes of Si-H bond in IR absorption spectrum (at 2000, 850 and 600 cm−1) were enhanced significantly in a same proportion (about 34%). As in the case of other light-induced effects, these light-induced optical absorption changes could be reversed by thermal annealing (190°C, 30 min). The change of conductivity and ESR signal have been also measured after illumination. It is found that the change behavior of SiH bond integrated strength with illuminative time is similar to that of conductivity. A simple model is suggested to explain these effects.