非正式自雇就业农民工的社会网络特征与差异——兼对波斯特“市场化悖论”的回应

以自雇就业为主的农民工非正式就业者的社会网络状况与正式就业的农民工不同,他们较少依赖社会网络的支持。综合考察他们的工作性质和制度环境,将地缘分布和行业聚集进行交互分类,可以发现其社会网络有四种类型:(1)同乡同业网络,主要表现为内部网络支持;(2)同乡异业网络,网络支持和互惠长期存在;(3)异乡同业网络,网络和市场规则并行;(4)异乡异业网络,市场契约部分取代关系网络。与波特斯的"市场化悖论"相反,中国农民工中的非正式自雇就业者逐步降低了关系网络的作用而进入到自发的市场规则之中。因而外来流动人口或移民的来源地与行业的"同质性"与"异质性"差异也许正是波特斯悖论的适用边界。

A simplified model for extreme-wave kinematics in deep sea

Based on the fifth-order Stokes regular wave theory, a simplified model for extreme-wave kinematics in deep sea was developed. In this model, from the wave records the average of two neighboring wave periods for the extreme crest or trough was defined as the period of the Stokes wave by the up and down zero-crossing methods. Then the input wave amplitude was deduced by substituting the wave period and extreme crest or trough into the expression for the fifth-order Stokes wave elevation. Thus the corresponding formula for the wave velocity can be used to describe kinematics beneath the extreme wave. By comparison with the published numerical models and experimental data, the proposed model is validated to be able to calculate the extreme wave velocity rather easily and accurately.

Effect of psychological stress on gastric motility assessed by electrical bio-impedance

AIM:To evaluate gastric motility using electrical bioimpedance(EBI) and gastric changes as a result of stress induced by psychological tests.METHODS:A group of 57 healthy women,aged 40-60 years,was recruited,and a clinical history and physical examination were performed.The women were free from severe anxiety,chronic or acute stress,severe depression,mental diseases and conditions that affect gastric activity.The women were evaluated under fasting conditions,and using a four-electrode configuration,the gastric signals were obtained through a BIOPAC MP-150 system.The volunteers were evaluated using the following paradigm:basal state,recording during the Stroop Test,intermediate resting period,recording during the Raven Test,and a final resting period.We analyzed the relative areas of the frequency spectrum:A1(1-2 cpm),A2(2-4 cpm),A3(4-8 cpm),and A4(8-12 cpm),as well as the median of area A2 + A3.The data were analyzed by an autoregressive method using a Butterworth filter with MatLab and Origin.Analysis of variance(ANOVA) and Friedman ANOVA(for nonparametric variables) were performed;in addition,pairs of groups were compared using the T dependent and Wilcoxon T tests.RESULTS:The results of the main values of area A2 were not significantly different comparing the five steps of the experimental paradigm.Nevertheless,there was a tendency of this A2 region to decrease during the stress tests,with recuperation at the final resting step.When an extended gastric region was considered(1-4 cpm),significant differences with the psychological stress tests were present(F = 3.85,P = 0.005).The A3 region also showed significant changes when the stress psychological tests were administered(F = 7.25,P < 0.001).These differences were influenced by the changes in the adjacent gastric region of A2.The parameter that we proposed in previous studies for the evaluation of gastric motility by electrical bio-impedance(EBI) was the median of the area under the region from 2 to 8 cpm(A2 + A3).The mean values of these frequencies(median of the A2 + A3 area) with the stress test showed significant changes(F = 5.5,P < 0.001).The results of the WilcoxonT test for the A4 area parameter,which is influenced by the breathing response,changed significantly during the Raven stress test(P < 0.05).CONCLUSION:We confirm that the gastric response to acute psychological stress can be evaluated by short-term EBI.

Analysis the First Arrival of P-Wave of Ina-TEWS and CTBT Stations to Support Earthquake Early Warning

The authors make the analysis of first arrivals of the P-wave from Ina-TEWS （Indonesian tsunami early warning system） and CTBT （comprehensive nuclear-test-band treaty） stations. These are used for earthquake early warning, magnitude determination and potential earthquake hazard mitigation based on seismogram acceleration. This research is focused on the study of energy duration of high frequency, and the maximum displacement of P-waves by observing broadband seismograms. The further analysis consists of deconvolution, integration or defferentiation, recursive filtering for data restitution, and applying a Butterworth filter of second order. The Butterworth filter uses high frequency 0.075 Hz to cut the effect of drift, and band-pass frequency 2-4 Hz for use in magnitude calculation. The authors choose potentially damaging earthquakes to be greater than Mw 〉 6.0. Based on the trigger on the three seconds the first arrival P-wave, the dominant period （Td） and amplitude displacement （Pd） was calculated by using data CISI （Indonesian CI Sompet） seismological station, Garut （west Java） and tested for data CTBT, LEM bang, Bandung （LEM station）. This research resulted determination of the P-wave arrival time accurately using integrated skewness and kurtosis. Performance data from the CTBT stations is very high. Signal to noise ratio 〉1,000 after passing through the filter. Such riset conducted to find out a rapid magnitude estimations from predominant frequency of displacement are： log Td = 0.2406 M- 1.3665 （R = 0.73） or M = 4.156 log Td ＋ 5.6797. Relationship of Pd, magnitude moment, Mw and hypocentre, R are log Pd = -4.684 ＋ 0.815 Mw - 1.36 log R. For relation of PGA （peak ground acceleration） and amplitude displacement are log PGA = 1.117 log Pd ＋ 0.728 （R = 0.91）. Furthermore, this formula can be used to support earthquake early warning in west of Java.

A Theoretical Dynamic Analysis of a Regenerative Heat Exchanger Assembly in a Fluctuating Flow Regime

A fluctuating flow was used to investigate the thermo-fluid characteristic of a regenerative heat exchanger assembly designed, modelled, built and constructed for the used in Stifling engines applications. Vibration of the regenerative heat exchanger assembly was a problem to deal with during the experimental investigation. Hence, a dynamic analysis of the regenerative heat exchanger assembly was undertaken. The main sources of excitation in vibrations of the regenerative heat exchanger assembly were investigated and calculated based initially on the empirical correlations provided in the literature. Thereafter, a mathematical model of the regenerative heat exchanger assembly was developed based on the energy equations for each moving part of the assembly. The kinetic and potential energy equations were formulated for each moving part of the regenerative heat exchanger assembly. From the kinetic and potential equations, the Lag, range operator was defined, and then the Lagrange formulations were used to derive the differential equations representing the dynamic behavior of each moving part of the assembly. The differential equations were integrated to determine the system natural frequencies. These were then compared to the frequency on excitation in vibrations in order to predict the regenerative heat exchanger working conditions despite the existence of vibration in the system.

New Weierstrass Semi-rational Expansion Method to Doubly Periodic Solutions of Soliton Equations

Based on the Weierstrass elliptic function equation, a new Weierstrass semi-rational expansion method and its algorithm are presented. The main idea of the method changes the problem solving soliton equations into another one solving the corresponding set of nonlinear algebraic equations. With the aid of Maple, we choose the modified KdV equation, (2+ 1)-dimensional KP equation, and (3+1)-dimensional Jimbo-Miwa equation to illustrate our algorithm. As a consequence, many types of new doubly periodic solutions are obtained in terms of the Weierstrass elliptic function.Moreover the corresponding new Jacobi elliptic function solutions and solitary wave solutions are also presented as simple limits of doubly periodic solutions.

Gaussian particle filter based pose and motion estimation

Determination of relative three-dimensional （3D） position, orientation, and relative motion between two reference frames is an important problem in robotic guidance, manipulation, and assembly as well as in other fields such as photogrammetry. A solution to pose and motion estimation problem that uses two-dimensional （2D） intensity images from a single camera is desirable for real-time applications. The difficulty in performing this measurement is that the process of projecting 3D object features to 2D images is a nonlinear transformation. In this paper, the 3D transformation is modeled as a nonlinear stochastic system with the state estimation providing six degrees-of-freedom motion and position values, using line features in image plane as measuring inputs and dual quaternion to represent both rotation and translation in a unified notation. A filtering method called the Gaussian particle filter （GPF） based on the panicle filtering concept is presented for 3D pose and motion estimation of a moving target from monocular image sequences. The method has been implemented with simulated data, and simulation results are provided along with comparisons to the extended Kalman filter （EKF） and the unscented Kalman filter （UKF） to show the relative advantages of the GPF. Simulation results showed that GPF is a superior alternative to EKF and UKF.

AN EFFICIENT SHAPE RETRIEVAL WAY

By using the generalized Gaussian density model, this letter puts forward a new shape retrieval way based on the wavelet coefficients. Experimental results show that the proposed shape feature description is superior to the traditional invariant moment algorithm. Moreover, this algorithm provides the important invariant trait to image's size and rotation, which can retrieve images based on shape with more similar results comparing with invariant moment method.

Study of Concurrence and D-Concurrence on Two-Qubits Resulted in Pair Coherent States in Language of SU(2) Coherent States

Pair coherent state, is a state of a two-mode radiation field that is known as a state with non-gaussian wave function. In this paper, study on the pair coherent state, we notice that with superposition of two first terms of this states, one two-qubits formed. Because of the importance of two-qubits in theory of quantum entanglement, with two different measures with the title of concurrence and D-concurrence, we have studied the amount of entanglement and discussed its details. At the end, we describe these measures for pair coherent states as a function of the amplitude of the SU（2） coherent states.

Gaussian fluctuation for linear eigenvalue statistics of large dilute Wigner matrices

This paper focuses on the dilute real symmetric Wigner matrix Mn=1/√n（aij）n×n, whose offdiagonal entries aij （1 ≤ em ≠ j ≤ n） have mean zero and unit variance, Eaij4 =θnα （θ 〉 0） and the fifth moments of aij satisfy a Lindeberg type condition. When the dilute parameter 0 〈 α ≤ 1/3 and the test function satisfies some regular conditions, it proves that the centered linear eigenvalue statistics of Mn obey the central limit theorem.