Comparative performance of healthcare and transport PFI projects: Empirical study on the influence of key factors

Private Finance Initiative (PFI) has been used on many projects in the UK in the delivery of public services. Cost, time and risk performance in public projects was anticipated to be improved by the superior skills of the private sector. So far, there are limited empirical studies on the life cycle performance of PFI projects, especially performance comparison between different sectors. This study investigated and compared variations in costs, time, and client requirements tracking it through the strategic business case stage to the operational phase in healthcare and transport sectors. It explored the influence of sector-specific factors, project size and maturity of the PFI on these variations. It used documentary analysis of full business cases of five PFI projects and a questionnaire survey of 44 PFI projects in the UK. The findings reveal that there are still considerable cost and time overruns and requirement changes in PFI projects in both sectors over the development of the project and its early use. The health sector was better than the transport sector for time overruns but was worse on costs. Smaller-value projects outperformed larger projects on cost variations but underperformed on time.     

Variations in Physicochemical Properties of Chinese Fenjiu During Storage and High-Gravity Technology of Liquor Aging

Gas chromatography, gas chromatography/mass spectrometry, headspace/gas chromatography/mass spectrometry, and Dean's switch technology were used to identify the structure and investigate the transformation of aroma components of Chinese Fenjiu under different ages (from 0 to 30 years). Results showed that the variation in physicochemical properties of Fenjiu was due to the synergistic effects of volatilization of low boiling point matters, oxidation of dissolved oxygen, balance between esterification and hydrolysis, weak interaction among molecules, and involvement of metal elements extracted from storage vessels. By simulating the natural storage environment and utilizing high-gravity rotating packed bed technique, a multistage-spraying rotating packed bed was developed locally and successfully applied to liquor aging. The liquor treated by this method had qualities equivalent to the liquors aged naturally for more than two years. The present study reveals the traditional aging process of Chinese liquor and offers a perspective into the utilitization of high-gravity rotating packed bed technique as an alternative tool for liquor aging.     

A systematic approach to the evaluation of indirect costs of contract variations

A mechanism is proposed for the evaluation of compensation due in the event of a variation order under contracts for construction work. It demonstrates how the indirect costs of a variation can be derived by the use of influence curves. Commonly it is accepted that such costs are very difficult to evaluate systematically, and hence the parties to the contract have been left to argue over the cost and time effects of a variation and the compensation due. The technique suggested provides a simple solution to this problem.     

A Cylindrical Small Size Molten Carbonate Fuel Cell: Experimental Investigation on Materials and Improving Performance Solutions

An original cylindrical small size molten carbonate fuel cell is presented. The cell's main peculiarity is its unique architecture in terms of both elements geometry and gases arrangements. Experimental tests on materials and system solutions were carried out on a single cell preliminary facility. Results allowed to identify optimising solutions which were applied on a new single cell facility. Further experimental tests allowed to determine the final cell configuration where sealing is enhanced and compression strain is further kept uniform along the cell surface. Final tests were carried out on a 1 kW stack comprising 15 single cells. Results suggest that the proposed cell design is a promising solution for μCHP applications because of performances, durability and construction costs.     

Effect of the mix design on the robustness of fresh self-compacting concrete

Self-compacting concrete (SCC) has many advantages compared to vibrated concrete. A disadvantage is the lower robustness of fresh SCC. SCC is more sensitive to small changes in the mix design, material properties, and the applied production methods. In an experimental program, the influence of important mix design parameters on the robustness of SCC was studied. First, the influence of the paste volume and the water-to-powder volumetric ratio was investigated. Depending on the mechanisms providing stability in the mixture, different levels of impact were observed. When the yield stress is the main factor providing stability in the mixture, a change in the water content will mainly affect the yield stress, making the stability of the yield stress the most important factor determining the robustness of the mixture and can be improved by lowering the paste volume. Analogue, the sensitivity of the plastic viscosity is determining the robustness of mixtures in which mainly the plastic viscosity is providing stability. The robustness of such a mixture can be improved by increasing the water-to-powder volumetric ratio. The influence of two types of viscosity modifying agents (VMA's) on the robustness of fresh SCC was examined in a second stage. The two used VMA's (diutan gum and attapulgite clay) were especially effective in SCC mixtures having a high yield stress and a low plastic viscosity. In mixtures having a low yield stress and a high plastic viscosity, the inclusion of a VMA in the mix design resulted in a decrease of the robustness.     

EFFECTS OF VISCOSITY VARIATIONS IN STEADY AND OSCILLATORY COUETTE FLOW

A Newtonian fluid with small variations in the viscosity in the primary flow direction of steady and oscillatory Couette flow is studied. These variations in viscosity create a coupling of the components of the momentum equations between the flow-direction component and the gradient-direction component. The coupling leads to secondary flows even in planar Couette flow where a rectilinear flow may be expected for a purely viscous fluid under creeping flow conditions. A perturbation solution has been applied for small-amplitude oscillations in the viscosity in both steady and oscillatory Couette flow. Because many rheological measurements are made assuming rectilinear flow, these results may have important consequences and may allow error caused by heterogeneity to be estimated. Finally, the relation between the momentum and the assumption of a symmetric stress tensor is discussed by introducing an alternative constitutive equation that is linear in the velocity gradient tensor and objective, but gives an asymmetric stress tensor. By adjusting the degree of asymmetry for the stress tensor, the secondary flows can be altered or eliminated.     

电压瞬时跌落、短时中断和电压渐变的干扰试验

本文介绍了电磁兼容测量及试验中的电压瞬时跌落、短时中断和电压渐变的干扰的试验方法及试验结果的评估方法.     

A Robust Compile Time Method for Scheduling Task Parallelism on Distributed Memory Machines

The problem of compile time scheduling of tasks of a program represented as a directed acyclic graph (DAG) is NP-hard in its general form. A number of approaches have been proposed which attempt to solve the problem either sub-optimally for general cases or optimally for restrictive special cases. But all the compile time approaches suffer due to the inability to accurately model the computation and communication costs of the target architecture. A desirable property of a compile time scheduling algorithm is robustness against the variations in the computation and communication costs so that the run time performance is close to the compile time estimates; this aspect of scheduling has been left open in the literature.This paper first introduces a compile time scheduling algorithm for a variable number of available processors and then examines the impact of change of computation and communication costs on the generated schedule. The cost variations for all the nodes and all the edges are assumed to be uniform (in other words, all the node costs change by the same ratio and the edge costs change by the same ratio). This sort of variations could occur due to the inaccuracies in estimating the instruction execution times or the message passing delays. The ratio of the schedule length obtained by the new schedule based on the modified costs to the schedule length obtained by using the modified costs on the original schedule (obtained by initial costs) is used as a measure of the robustness of the algorithm. The essential conditions for robustness of the proposed algorithm are discussed and are demonstrated through an experimental study.     

多工位薄板装配偏差流传递的状态空间模型

借鉴控制理论中的状态空间方法,研究多工位薄板装配过程中偏差流传递、变换和累积关系的状态空间模型.以零件偏差为状态矢量,夹具偏差为控制矢量,研究夹具偏差和零件偏差之间的对应关系以及零件在工位间转换过程中的重定位偏差,建立多工位装配过程偏差流传递的状态方程;以零件测量偏差为输出矢量,建立表征测点位置和数量的输出方程.最后通过实际零件的装配过程说明该模型的应用方法.