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131.
M. L. Li S. J. Zhu S. D. Xiao X. L. Che Y. N. U Y. J. Chen H. B. Ding L. H. Zhu G. S. Li S. X. Wen X. G. Wu 《The European Physical Journal A - Hadrons and Nuclei》2006,28(1):1-4
High-spin states of 137La have been investigated with the reaction 130Te(11B, 4n) at a beam energy of 50MeV. The level scheme of 137La has been expanded with spin up to 33/2ℏ. Several new bands have been found in this nucleus. A band crossing in the band
based on the 17/2- level has been observed at a rotational frequency of ℏω ∼ 0.48MeV. From systematic comparison, this band crossing probably
originates from the alignment of protons. One of the bands with strong M1 transitions is proposed as a collective oblate band ( γ ∼ -60°). 相似文献
132.
133.
Qingbao Song Xiaoxia An Fengfeng Che Tianhua Shen 《Journal of heterocyclic chemistry》2015,52(5):1496-1502
Di‐DACH‐pyridylamide ligands, symmetrical bridged bis‐Schiff base, and spiro pyrrolizines as catalysts in the synthesis of dihydropyrimidinethiones (DHPMs) using the Biginelli reaction is first reported. This new protocol has the advantages of environmental friendliness, short reaction time, excellent yields, and simple post‐treatment procedure. A series of DHPMs were obtained in high yields (up to 98%) in only 6 h. Moreover, based on the optimized condition, a novel Biginelli‐like reaction was first developed. 相似文献
134.
135.
本文基于计算结构力学概念提出了刚架结构连续变更定理,用数值分析与递推公式相结合的方法连续生成结构极限状态函数,给出了结构退化为机构的新判据。由于引用了计算结构力学方法,重分析不必重新形成结构刚度阵,不必反复求逆矩阵,大大提高了计算效率。 相似文献
136.
Foldamers 1–4 incorporating different terminal substituents have been designed and synthesized for binding halide anions.~1H NMR titration experiments carried out in DMSO-d_6/CDCl_3(15/85, v/v)demonstrated that the short oligo (aryltriazole)s backbone 1 could not bind halide anions unless that amide H-bond donors were incorporated at the termini of the oligomer. Terminal substituents on oligo(aryltriazoleamide)s foldamers 2–4 display a considerable influence on the binding affinities of the foldamers for halide anions. Large steric hindrance of the terminal substituents was found to be unfavorable for binding halide anions, but aromatic π-π interactions between two terminal substituents are capable of stabilizing the conformation of foldamers thus giving rise to an enhancement in the binding strengths. However, the terminal substituents were found to hardly affect the binding selectivity in the studied cases. 相似文献
137.
This paper is concerned with the following systems of Kirchhoff‐type equations: Under more relaxed assumptions on V(x) and F(x,u,v), we first prove the existence of at least two nontrivial solutions for the aforementioned system by using Morse theory in combination with local linking arguments. Then by using the Clark theorem, the existence results of at least 2k distinct pairs of solutions are obtained. Some recent results from the literature are extended. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
138.
The heat transfer process occurring in a condensing heat exchanger where noncondensible gases are dominant in volume is different from the condensation heat transfer of the water vapor containing small amount of noncondensible gases. In the process the mass transfer due to the vapor condensation contributes an important part to the total heat transfer. In this paper, the Colburn-Hougen method is introduced to analyze the heat and mass transfer process when the water vapor entrained in a gas stream condenses into water on the tube wall. The major influential factors of the convective-condensation heat transfer coefficient are found as follows: the partial pressure of the vapor p
v
, the temperature of the outer tube wall T
w
, the mixture temperature T
g
, Re and Pr. A new dimensionless number Ch, which is defined as condensation factor, has been proposed by dimensional analysis. In order to determine the relevant constants and investigate the convection-condensation heat and mass transfer characteristics of the condensing heat exchanger of a gas fired condensing boiler, a single row plain tube heat exchanger is designed, and experiments have been conducted with vapor-air mixture used to simulate flue gases. The experimental results show that the convection-condensation heat transfer coefficient is 1.52 times higher than that of the forced convection without condensation. Based on the experimental data, the normalized formula for convention-condensation heat transfer coefficient is obtained.
A
heat transfer area m2
-
Ch
condensation factor
-
c
p
specific heat at constant pressure, J/(kg·K)
-
G
mass flux Kg/(m2·s)
-
h
heat transfer coefficient W/(m2·K)
-
J
J-factor
-
Nu
Nusselt number
-
pa
pressure
- Pr
Prandtl number
-
Q
heat transfer rate
-
q
heat flux W/m2
-
r
latent heat, kJ/kg
- Re
Reynolds number
-
Sc
Schmidt number
-
T
temperature, C or K
-
heat conductivity m W/(m·K)
-
density, kg·m3
-
g
gas
-
h
moistened hot air
-
i
interface
-
v
vapor
-
w
water 相似文献
139.
The near-wall transport characteristics, inclusive of mass transfer coefficient and wall shear stress, which have a great
effect on gas–liquid two-phase flow induced internal corrosion of low alloy pipelines in vertical upward oil and gas mixing
transport, have been both mechanistically and experimentally investigated in this paper. Based on the analyses on the hydrodynamic
characteristics of an upward slug unit, the mass transfer in the near wall can be divided into four zones, Taylor bubble nose
zone, falling liquid film zone, Taylor bubble wake zone and the remaining liquid slug zone; the wall shear stress can be divided
into two zones, the positive wall shear stress zone associated with the falling liquid film and the negative wall shear stress
zone associated with the liquid slug. Based on the conventional mass transfer and wall shear stress characteristics formulas
of single phase liquid full-pipe turbulent flow, corrected normalized mass transfer coefficient formula and wall shear stress
formula are proposed. The
calculated results are in good agreement with the experimental data. The shear stress and the mass transfer coefficient in
the near wall zone are increased with the increase of superficial gas velocity and decreased with the increase of superficial
liquid velocity. The mass transfer coefficients in the falling liquid film zone and the wake zone of leading Taylor bubble
are lager than those in the Taylor bubble nose zone and the remaining liquid slug zone, and the wall shear stress associated
falling liquid film is larger than that associated the liquid slug. The mass transfer coefficient is within 10−3 m/s, and the wall shear stress below 103 Pa. It can be concluded that the alternate wall shear stress due to upward gas–liquid slug flow is considered to be the major
cause of the corrosion production film fatigue cracking. 相似文献
140.
The forced convection heat transfer with water vapor condensation is studied both theoretically and experimentally when wet
flue gas passes downwards through a bank of horizontal tubes. Extraordinarily, discussions are concentrated on the effect
of water vapor condensation on forced convection heat transfer. In the experiments, the air–steam mixture is used to simulate
the flue gas of a natural gas fired boiler, and the vapor mass fraction ranges from 3.2 to 12.8%. By theoretical analysis,
a new dimensionless number defined as augmentation factor is derived to account for the effect of condensation of relatively
small amount of water vapor on convection heat transfer, and a consequent correlation is proposed based on the experimental
data to describe the combined convection–condensation heat transfer. Good agreement can be found between the values of the
Nusselt number obtained from the experiments and calculated by the correlation. The maximum deviation is within ±6%. The experimental
results also shows that the convection–condensation heat transfer coefficient increases with Reynolds number and bulk vapor
mass fraction, and is 1∼3.5 times that of the forced convection without condensation. 相似文献