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This paper aims to improve the bearing capacity of hydrostatic thrust bearing under working conditions of high speed and heavy load; a new wedge-shaped structure opened on an edge of oil seal is put forward, the loss and insufficiency for hydrostatic bearing capacity are made up by using dynamic pressure, and then, hydrostatic hydrodynamic lubrication is realized.

Oil film three-dimensional models of unidirectional and bi-directional hydrostatic hydrodynamic oil pad are established by using UG. The oil film pressure fields of two kinds of oil pad are simulated by using ANSYS ICEM CFD and ANSYS CFX; the pressure fields distribution characteristics are obtained, and the effects of workbench rotary speed and bearing weight on pressure field are analyzed. Also, the experimental verification is made.

The results demonstrate that with an increase in workbench rotary speed, the oil film pressure of two kinds of hybrid oil pad increases gradually, and the maximum pressure of the bi-directional one accounts for 95 per cent of the unidirectional one when the load is constant. With an increase in load, the oil film pressure of two kinds of hybrid oil pad increases gradually, the difference between them is 9.4 per cent under the condition of load of 25 t when the rotary speed is constant.

The paper can provide theoretical basis for a structure design of hybrid thrust bearing under different rotary speed and load conditions, and compensate the shortage of static pressure-bearing capacity by using dynamic pressure, improve the stability of vertical CNC machining equipment.

The purpose of this paper is to describe a simulation and experimental research concerning the effect of recess depth on the lubrication performance of a hydrostatic thrust bearing by constant rate flow.

The computational fluid dynamics and finite volume method have been used to compute the lubrication characteristics of an annular recess hydrostatic thrust bearing with different recess depths. The performances are oil recess pressure, oil recess temperature and oil film velocity. The recess depth has been optimized. A test rig is established for testing the pressure field of the structure of hydrostatic thrust bearing after recess depth optimization, and experimental results show that experimental data are basically identical with the simulation results, which demonstrates the validity of the proposed numerical simulation method.

The results demonstrate that the oil film temperature decreases and the oil film pressure first increases and then decreases with an increase in the recess depth, but oil film velocity is constant. To sum up comprehensive lubrication performance, the recess depth of 3.5 mm is its optimal value for the annular recess hydrostatic thrust bearing.

The computed results indicate that to get an improved performance from a constant flow hydrostatic thrust bearing, a proper selection of the recess depth is essential.

This study aims to address the issue of high-precision measurement of AC electric field. An electro-optical sensor with high sensitivity is proposed for this purpose.

The proposed sensor combines electromagnetic induction and fiber Bragg grating (FBG) sensing techniques. It is composed of a sensing probe, a piece or stack of piezoelectric ceramics (PZT) and an FBG. A signal processing circuit is designed to rectify and amplify the induced voltage. The processed signal is applied to the PZT and the deformation of PZT is detected by FBG. Theoretical calculation and simulation are conducted to verify the working principle of the probe. The sensor prototype is fabricated and its performance is tested.

The results of this study show that the sensor has good linearity and repeatability. The sensor sensitivity is 0.061 pm/Vm⁻¹ in the range from 250 to 17,500 V/m, enabling a measurement resolution of electric field strength of 16.3 V/m. The PZT stack is used to enhance the sensor sensitivity and the resolution can be improved up to 3.15 V/m.

A flexure hinge lever mechanism is used to amplify the deformation of PZT for further enhancement of sensitivity. The results show that the proposed sensor has high sensitivity and can be used for the accurate measurement of an electric field. The proposed sensor could have potential use for electric field measurement in the power industry.

The surging stock market in the late nineties lifted the funding level of most pension plans and led to plan management decisions that left them vulnerable to the stock market decline of 2000-2002. In this study, an analysis was conducted on the descriptive data of 51 state pension plans for the period 1998-2003 and it was found that overfunded plans were more likely to substantially increase benefits while simultaneously reduce contributions. This led to widespread underfunding and a need for sudden increase in contributions as market conditions grew worse and funding levels dropped sharply. This investment cycle emphasizes the need for more prudent surplus management strategies to protect pension plans from the consequences of stock market volatility.

There is significant variation in the way state-administered pension systems are structured in the United States. Some states, for example, consolidate their pension activity into a few larger systems while others sponsor several smaller ones. In this paper we (1) identify arguments in favor of and against system consolidation, (2) measure levels of consolidation in state-administered pension systems, and (3) use logistic regression to examine whether levels of consolidation are associated with indicators of the financial health of state pensions. Our results provide preliminary support for claims that the size and concentration of pension activity are positively associated with measures of the financial health of state pensions.

The Chief Financial Officers Act and subsequent legislation require federal agencies to produce corporate-style financial statements. Arguments for financial statements drew on private sector analogies and suggested policy makers and managers would use the information to make better public policy and management decisions and improve accountability for financial management and program performance. Nearly all major government agencies have unqualified audit opinions and improvements in financial management are claimed. But benefits for policy making and management are not yet well understood. This paper examines the question by comparison with the private sector and by examining what agencies say about the uses and users of financial statement information. The emerging challenge in the evolution of federal financial reporting is to develop better government-specific analytical tools and other financial information for policy makers and managers.

In mobile ad hoc networks, many routing protocols use broadcast mechanism to find route whereas one of the wireless network challenges is the bandwidth optimisation. This mechanism increases the control overhead and consumes bandwidth and energy. The overhead penalty increases with the density and the network size. Thus is important to reduce the number of participants in that mechanism. One of the used solutions consists of determining clusterheads nodes. In this paper, we propose an algorithm for choosing clusterheads (SRCAC). Each node in the network broadcasts its ID, status and election index. The election index is a combination of potentiality index and stability index. The potentiality index is a linear combination of the mobile resources like processor speed, RAM and ROM memories. The stability index shows the cluster life time. Then, we use SRCAC to build clusters. We suggest a backup clusterhead which could become the principal clusterhead when the first breaks down. To improve the reliability of interclusters communications, we build a mesh between gateway and distributed gateway. Moreover, we introduce Quality of Service (QoS) constraints in the ODMRP (On Demand Multicast Routing Protocol) mobility prediction version.We compare our algorithm with the WCA (Weighted Clustering Algorithm for Mobile Ad hoc Networks) algorithm in terms of clusterheads. The results show that our algorithm performs better than the WCA and, finally, the deterioration of the performances imposed by the constraints on this ODMRP version is unimportant.