477 research outputs found
Make a living: agriculture, industry and commerce in Eastern Hebei, 1870-1937
The existing scholarship on Chinese agricultural history and peasant economy always portrayed Chinese peasants as cultivators and equated agricultural commercialization as cash crop growing. Based on the field surveys made by the Chinese and Japanese investigators in the 1930s, this dissertation tries to correct the over-simplification of the Chinese peasant economy and describe how the peasants in Eastern Hebei made a living by a combination of agriculture, industry and commerce. By examining the ecosystem and calculating the grain production and consumption, it is found that the returns from farming were not even enough for the peasants own consumption. Eastern Hebei was a grain shortage area and the peasants there had to engage in non-farming activities to supplement their income and support their families.;Besides engaging in traditional sideline production, the peasants in Eastern Hebei took the opportunities provided by the development of domestic and international trade and produced on a large scale for outside markets. The bristle processing in Fengrun county, paper making in Qian-an county and handicraft weaving in Baodi county are selected to show the importance of rural industry in the peasant economy in Eastern Hebei. This study also finds that in the modern period, either forced by survival pressure or attracted by outside opportunity, more and more peasants in Eastern Hebei left their villages and found temporary or permanent jobs in the outside world. The causes and consequences of the large scale emigrating- going to Manchuria - are discussed in detail to show the importance of non-farming income in the peasant economy.;The 1930s witnessed increases in state taxation, the civil war, the Japanese invasion and the world economic depression. These developments are discussed in terms of impact upon the peasants of the villages under consideration. It is found that it was harder for the peasants to make a living in that period. In conclusion, this study supports Fei Xiaotong\u27s argument that it was impossible for Chinese peasants to make a living on farming alone and the final solution forChina\u27s agrarian problem was diffused rural industrialization
Dynamic Response of Flexible Foundations on Multilayered Medium
The dynamic response of flexible strip-foundations placed on a viscoelastic multi-layered medium under conditions of plane strain and subjected to harmonic excitation is studied in this paper. A semi-analytic model is developed to determine the dynamic flexibility matrix of the medium, and the spline finite element method is employed to treat the foundation. The two methods are appropriately combined through equilibrium and compatibility considerations at the soil-foundation interface. Numerical results describing the influence of the non-homogeneity of the soil medium on the compliance are presented, and the effects of the relative stiffness Kr on the foundation response are briefly discussed
The statistics of Wigner delay time in Anderson disordered systems
We numerically investigate the statistical properties of Wigner delay time in
Anderson disordered 1D, 2D and quantum dot (QD) systems. The distribution of
proper delay time for each conducting channel is found to be universal in 2D
and QD systems for all Dyson's symmetry classes and shows a piece-wise power
law behavior in the strong localized regime. Two power law behaviors were
identified with asymptotical scaling and ,
respectively that are independent of the number of conducting channels and
Dyson's symmetry class. Two power-law regimes are separated by the relevant
time scale where is the average level spacing.
It is found that the existence of necklace states is responsible for the second
power-law behavior , which has an extremely small distribution
probability.Comment: 7 page
Efficient spin-current injection in single-molecule magnet junctions
We study theoretically spin transport through a single-molecule magnet (SMM)
in the sequential and cotunneling regimes, where the SMM is weakly coupled to
one ferromagnetic and one normalmetallic leads. By a master-equation approach,
it is found that the spin polarization injected from the ferromagnetic lead is
amplified and highly polarized spin-current can be generated, due to the
exchange coupling between the transport electron and the anisotropic spin of
the SMM. Moreover, the spin-current polarization can be tuned by the gate or
bias voltage, and thus an efficient spin injection device based on the SMM is
proposed in molecular spintronics.Comment: 4 figure
Classification of spin Hall effect in two-dimensional systems
Physical properties such as the conductivity are usually classified according
to the symmetry of the underlying system using Neumann's principle, which gives
an upper bound for the number of independent components of the corresponding
property tensor. However, for a given Hamiltonian, this global approach usually
can not give a definite answer on whether a physical effect such as spin Hall
effect (SHE) exists or not. It is found that the parity and types of spin-orbit
interactions (SOIs) are good indicators that can further reduce the number of
independent components of the spin Hall conductivity for a specific system. In
terms of the parity as well as various Rashba-like and Dresselhaus-like SOIs,
we propose a local approach to classify SHE in two-dimensional (2D) two-band
models, where sufficient conditions for identifying the existence or absence of
SHE in all 2D magnetic point groups are presented
Systematic study on propulsive performance of tandem hydrofoils for a wave glider
This paper presents the propulsive performance optimization of tandem hydrofoils equipped in a wave glider in head sea conditions with the aid of computational fluid dynamic (CFD) method by using a commercial CFD code, STAR-CCM+. Firstly, this work performs a systematic study on a single 2D hydrofoil to study the effect of varying the pivot position and the torsional spring stiffness to seek for the optimum propulsive performance within a range of velocity. Secondly, parametric studies on the propulsive performance of 2D and 3D six tandem hydrofoils are conducted by varying the oscillation amplitude and the torsional spring stiffness. The result reports: The results show that the torsional springs play a critical role in propulsive performance, comparing to the pivot position. The propulsive performance of the middle hydrofoil is greater than the others in the fore and after positions. When 2D and 3D six tandem hydrofoils achieve the optimum propulsive performance, the frequency ratio is chosen to be around 25 (torsional spring stiffness (k S =0.8Nâ‹…m/rad)) and 17 (torsional spring stiffness (k S =11.8Nâ‹…m/rad)), respectively. Comparing to previous study, the propulsive performance of each hydrofoil in six tandem hydrofoil configuration is greatly improved and none of hydrofoil produce negative thrust
- …