Multi-parameter load sensing pump model simulation and flow rate characteristics research

Load sensing pumps have been widely used in diverse hydraulic systems.Studies show that structural parameters have undeniable impacts on the characteristics and efficiency of the load sensing pump.The main purpose of this article is to study the influence of load sensing pump structure parameters on flow characteristics.In the present study,a nonlinear multi-parameter model is proposed for this type of pump.In this model,different parameters,including spool clearance,spool covering amount,internal leakage are considered to reflect the displacement adjustment process of the load sensing pump.Moreover,a frequency sweep method is proposed to analyze the frequency domain of the nonlinear mathematical model.An experiment rig was built to study the influence of key structural parameters on the dynamic follow-up characteristics of the pump flow.The obtained results show that the diameter of the orifice d can significantly affect the working characteristics of the pump.It is found that a large diameter of the orifice d can improve the phase following ability of the system,while a small diameter of the orifice d can reduce the bypass flow rate and increase the amplitude following ability.This paper provides a new consideration to study the dynamic follow-up characteristics of the load sensing pump.

Numerical Simulation of the Scavenging Rates of Ice Crystals of Various Microphysical Characteristics

Numerical models of trajectories of small aerosol spheres relative to oblate spheroids were used to determine ice crystal scavenging efficiencies. The models included the effects of aerodynamic flow about the ice particle, gravity, aerosol particle inertia and drag and electrostatic effects. Two electric configurations of the ice particle were investigated in detail. The first applied a net charge to the ice particle, of magnitude equal to the mean thunderstorm charge distribution, while the second applied a charge distribution, with no net charge, to the ice particle to model the electric multipole charge distribution. The results show that growing ice crystals with electric multipoles are better scavengers than single ice crystals with net thunderstorm charges, especially in the Greenfield gap (0.1 to 1.0 um), and that larger single crystals are better scavengers than smaller single crystals. The results also show that the low density ice crystals are more effective scavengers with net charges than they are with charge distribution.

Employment and Wage Effects of RMB Exchange Rate for Manufacturing Sectors in China and the US

By creating a labor market dynamic general equilibrium model, this paper derives the pass-through mechanism of exchange rate's employment and wage effects,carries out an empirical study on the employment and wage effects of RMB exchange rate for manufacturing sectors in China and the United States based on ridge regression, and examines the role of industry characteristics in this process. Research findings suggest that: RMB depreciation will drive employment and wage growth for most of China's laborintensive manufacturing sectors, and RMB appreciation will increase employment for certain capital-and technology-intensive sectors; but RMB depreciation has insignificant employment and wage effects for most sectors in the US. Hence, in achieving the longterm stability of RMB exchange rate, China should take advantage of RMB appreciation's manufacturing upgrade effect and ensure the steady growth of manufacturing employment.The US should make breakthroughs in various links of its economic development in order to tackle unemployment, instead of blaming RMB exchange rate. In addition, the nature of business activities and trade union characteristic are both significant factors that lead to differences in inter-sector employment levels of Chinese and US manufacturing sectors.Technology characteristic and other monopolistic characteristics exert decisive effects on the difference of wage return for various sectors in China and the US.

On nonparametric change point estimator based on empirical characteristic functions

We propose a nonparametric change point estimator in the distributions of a sequence of independent observations in terms of the test statistics given by Huˇskov′a and Meintanis(2006) that are based on weighted empirical characteristic functions. The weight function ω(t; a) under consideration includes the two weight functions from Huˇskov′a and Meintanis(2006) plus the weight function used by Matteson and James(2014),where a is a tuning parameter. Under the local alternative hypothesis, we establish the consistency, convergence rate, and asymptotic distribution of this change point estimator which is the maxima of a two-side Brownian motion with a drift. Since the performance of the change point estimator depends on a in use, we thus propose an algorithm for choosing an appropriate value of a, denoted by a_s which is also justified. Our simulation study shows that the change point estimate obtained by using a_s has a satisfactory performance. We also apply our method to a real dataset.