Showing papers by "National Tsing Hua University published in 1973"
TL;DR: In this article, the authors investigated the conditions marking the onset of longitudinal vortex rolls due to buoyant forces in the thermal entrance region of a horizontal parallel-plate channel, where the lower plate is heated isothermally and the upper plate is cooled is othermally.
Abstract: An investigation is carried out to determine the conditions marking the onset of longitudinal vortex rolls due to buoyant forces in the thermal entrance region of a horizontal parallel-plate channel where the lower plate is heated isothermally and the upper plate is cooled isothermally. Axial heat conduction is included in an analytical solution for the Graetz problem with fully developed laminar velocity profile. Linear-stability theory based on Boussinesq approximation is employed in the derivation of perturbation equations. An iterative procedure using high-order finite-difference approximation is applied to solve the perturbation equations and a comparison is made against the conventional second-order approximation. It is found that for Pr ≥ 0.7 the flow is more stable in the thermal entrance region than in the fully developed region, but the situation is just opposite for small Prandtl number, say Pr ≤ 0.2. Graphical results for the critical Rayleigh numbers and the corresponding disturbance wavenumbers are presented for the case of Pe → ∞ with Prandtl number as a parameter and the case of air (Pr = 0.7) with Peclet number as a parameter in the range of dimensionless axial distance from the entrance between x = 0.001 and 4 × 10−1 .
69 citations
TL;DR: In this article, high-temperature series expansions for spin-1 isotropic Hamiltonians with bilinear and biquadratic pair interactions were derived up to terms in the series.
Abstract: High-temperature series expansions are derived up to terms in ${T}^{\ensuremath{-}4}$ for the dipole and quadrupole susceptibilities for arbitrary lattices The expansions are evaluated for a spin-1 isotropic Hamiltonian with bilinear and biquadratic pair interactions We compare the dipole and quadrupole phase transition temperatures determined from these series to those obtained by the molecular-field and constant-coupling approximations There are large uncertainties in the estimates of the quadrupole transition temperatures because of the few terms in the series
46 citations
TL;DR: In this article, the central atoms model has been generalized to multicomponent interstitial solutions and the probabilities of various configurations in the nearest neighbor shell of an atom have been calculated and the thermodynamic properties of the mixture deduced.
41 citations
33 citations
TL;DR: In this article, the electronic energy bands of LiAu, RbAu and CsAu were calculated, and it was found that the semiconducting character decreases when the alkalo metal becomes lighter, and the transition occurs between RbBaaU and KAu.
15 citations
5 citations
TL;DR: Theoretical analysis on the asymmetrical effects of peripheral displacement of rods or unequal rod diameters on longitudinal laminar flow in a finite bundle of rods is presented in this article.
4 citations
TL;DR: The present dosimetric system by using radioactive /sup 60/Co as tracer and coupling with ion-exchange separation is found useful for routine radiation monitoring of medium level gamma -dose with relative simplicity and high reproducibility.
4 citations
TL;DR: In this paper, low-energy theorems for Compton scattering on targets of arbitrary spin are derived, but not C, P, and T invariance, and Lorentz invariance is assumed.
3 citations
TL;DR: The reaction of 2-methylindole with pyruvic acid was studied in this article, and two products were found to be depending on experimental conditions, including the 2:2 condensation adduct and 2:1 condensation adjacency.
Abstract: The reaction of 2-methylindole with pyruvic acid was studied. Two products are found to be depending on experimental conditions, including the 2:2 condensation adduct and the 2:1 condensation adduct. The reaction mechanism evidently involves a 1:1 adduct of 2-hydroxy-2-(2-methylindol-3-yl)-propionic acid as an intermediate.
3 citations
TL;DR: In this paper, the first eight terms of the high temperature series expansions for the mean-square fluctuations of the magnetization variables are derived for the spin − 1 2 anisotropic Heisenberg antiferromagnets.
TL;DR: In this article, the ion exchange behavior of Np(IV) in the presence of DTPA was investigated and the hydrogen ion activity of the solution was kept above 0·1 M. Thermodynamical data together with probable chemical species were estimated.
TL;DR: In this article, the absolute configuration of (S)-configuration was elucidated by chemical correlation to the known (R+)-β-methylterbic acid ((R)(+)-VII).
Abstract: (−)-Dimethyl 2-cyano-2-methylsuccinate ((−)-IIIa) was synthesized from menthyl cyanoacetate ((−)-I), and the absolute configuration of which was elucidated as (S)-configuration by chemical correlation to the known (R)(+)-β-methylterbic acid ((R)(+)-VII). (−)-Dimethyl 2-carbamoyl-2-methylsuccinate ((−)-IV) and (−)-methyl 3-methyl-2,5-dioxo-3-pyrrolidinecarboxylate ((−)-V) are also confirmed as belonging to (S)-configuration and (+)-3-(1-hydroxy-1-methylethyl)-3-methyl-2,5-pyrrolidinedione ((+)-VI) is belonging to (R)-configuration.
Preliminary experiments on racemic compounds are also described.
TL;DR: In this paper, an electron capture cross section by proton from carbon foil is calculated in Born approximation for the application in beam-foil spectroscopy, and the cross section in Oppenheimer-Brinkman-Kramer approximation is proportional to E −4, where E is the incident proton energy in high energy limit.
TL;DR: In this article, the classical averaging procedure of Roberts for the determination of the parameter Cn in the simple distortion potential, V0n(x) Cn exp(−αx), is examined further.
TL;DR: In this article, the diffusion of uranium in polyethylene was studied by counting induced fission tracks of the diffused uranium atoms irradiated in a thermal reactor with thermal neutrons, and the temperature dependence of the diffusion coefficient in this temperature range was obtained as D = 3.4 exp (−15000/ RT ).
TL;DR: In the photolysis of diazomethane-methanol mixture, the reaction of methylene with methanol gives dimethyl ether and ethanol as products as mentioned in this paper.
Abstract: In the photolysis of diazomethane-methanol. mixture, the reaction of methylene with methanol gives dimethyl ether and ethanol as products. The ratio of dimethyl ether to ethanol is found to be independent to pressure and to. the composition of diazomethane-methanol mixture. Methylene insertion into O—H bond is about 11 times faster than that into C—H bonds of methanol. The ratio decreases with increase of temperature.
In the diazomethane-ethanol system, ethylmethyl ether, propanol-1 and propanol-2 are found as the products of insertion reaction of methylene into ethanol. The ratios of ethylmethyl ether to propanol-1 and to propanol-2 are both found to be almost constant and independent to pressure and to the composition of diazomethane-ethanol mixture. A small temperature effect on the ratios are observed. The rate of insertion of methylene into O—H bond is about 7.3 and 14.2 times faster than those into primary and secondary C—H bonds of ethanol, respectively.
TL;DR: In this paper, the second-order terms of the e2 Compton scattering amplitudes were derived without assuming C, P and T invariances and the electric dipole moment was set to zero.
TL;DR: In this paper, the authors measured skin depth and related parameters of InSb using the damped-radiowave technique at room temperature and found that the latter can only give qualitative results.
Abstract: Skin depth and related parameters of InSb have been measured by using the damped-radiowave technique at room temperature. The results show that there is difference between the data obtained with a marginal oscillator-detector system and with a fixed-frequency signal detector system. We found that the latter is more reliable. The former can only give qualitative results. Moreover, the mobility μ and the carrier concentration η found with the traditional galvanomagnetic (Hall and conductivity) methods are substantially different from those by the fixed-frequency method. We show the comparison of the two.
TL;DR: In this paper, a trace amount of chromium was converted quantitatively to volatile chromium chelates such as chromium(III) acetylacetonate, Cr(acac)1, chromium-III trifluoracetyl acetonate and Cr(tfa)3, and the chelate solution was then analyzed by gas chromatography.
Abstract: Trace amount of chromium was first converted quantitatively to volatile chromium chelates such as chromium(III) acetylacetonate, Cr(acac)1, chromium(III) trifluoracetylacetonate, Cr(tfa)3, and chromium(III) hexafluoroacetylacetonate, Cr(hfa)3, and the chelate solution was then analyzed by gas chromatography. It was found that Cr(tfa)3 is the most suitable chemical form for this purpose. The method was profitably applied to the determination of chromium(III) incorporated in the six kinds of commerical products of potassium Chromate.