<Emphasis Type="Italic">Bootstrap Confidence Interval of the Difference Between Two Process Capability Indices</Emphasis>

The process capability index, C_pk, is extensively used to assess process performance in manufacturing industry. Statistical hypothesis testing or an interval estimation of a single C_pk had been derived under a normally distributed process. However, the difference between two process capability indices, C_{pk 1} - C _{pk 2} , cannot be inferred statistically because of the complexity of the sampling probability theory. This study proposes a bootstrap resampling simulation method to construct the biased corrected percentile bootstrap (BCPB) confidence interval of (C _{pk 1} - C _{pk 2} ), which can be used to select the better of two suppliers. The various simulation results indicate that the bootstrap confidence interval of (C _{pk 1} - C _{pk 2} ) can be employed to evaluate effectively the difference between the performance of two suppliers. ID="A1"Correspondance and offprint requests to: Dr. J.-P. Chen, Department of Industrial Engineering and Management, National Chin-Yi Institute of Technology, 35 Lane 215 Section 1, Chung Shan Road, Taiping, Taichung 411, Taiwan. E-mail: chen504@chinyi.ncit.edu.tw     

<Emphasis Type="Italic">A Fuzzy TOPSIS Method for Robot Selection</Emphasis>

A fuzzy TOPSIS method for robot selection is proposed, where the ratings of various alternatives versus various subjective criteria and the weights of all criteria are assessed in linguistic terms represented by fuzzy numbers. The values of objective criteria are converted into dimensionless indices to ensure compatibility between the values of objective criteria and the linguistic ratings of subjective criteria. The membership function of each weighted rating is developed by interval arithmetic of fuzzy numbers. To avoid complicated aggregation of fuzzy numbers, these weighted ratings are defuzzified into crisp values by the ranking method of mean of removals. A closeness coefficient is defined to determine the ranking order of alternatives by calculating the distances to both the ideal and negative- ideal solutions. A numerical example demonstrates the computational process of the proposed method. ID="A1"Correspondance and offprint requests to: Dr T.-C. Chu, Department of Management and Information Technology, Southern Taiwan University of Technology, 1 Nan-Tai Street, Yung-Kang City, Tainan County 710, Taiwan. E-mail: mrchu@mail.stut.edu.tw     

<Emphasis Type="Italic">A Binary Morphology-Based Filtering Algorithm for Reverse Engineering</Emphasis>

A laser scanner is a common surface measurement tool in reverse engineering (RE). The point cloud obtained from a laser scanner usually has some noisy points. An algorithm based on a binary morphology technique is presented to identify the noisy points. After removing the noisy points, the filtered point cloud can be used to reconstruct the surface of a 3D object. The filtering algorithm described can remove both the points at a "far" distance from the scanned object and the "prods" on the surface of the object. ID="A1"Correspondance and offprint requests to: Dr C. L. Wang, Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. E-mail: wangcl@ust.hk     

<Emphasis Type="Bold">Monitoring of Ultraprecision Machining Processes</Emphasis>

New demands are being placed on monitoring systems in the manufacturing environment because of recent developments in machining technology and machine tool design. In-process sensors are used to generate control signals to improve both the control and productivity of manufacturing systems. Numerous different sensors are available for monitoring and controlling the machining environment including force, power, and acoustic emission (AE) sensors. This paper first discusses the requirements for sensor technology for precision manufacturing process monitoring in general. Details are also given about AE and its application for process characterisation and monitoring in ultraprecision machining.     

Two-Body Abrasive Wear of the Outside Shell Surfaces of Mollusc <Emphasis Type="Italic">Lamprotula fibrosa</Emphasis> Heude, <Emphasis Type="Italic">Rapana venosa</Emphasis> Valenciennes and <Emphasis Type="Italic">Dosinia anus</Emphasis> Philippi

Natural biological surfaces and biomaterials have some distinguishing properties for adapting themselves to natural surroundings. The outside shell surfaces of mollusc species often undergo the abrasive wear action from the sand particles in water sand slurry in natural conditions. The two-body abrasive wear behavior of the outside shell surfaces of three mollusc species Lamprotula fibrosa Heude, Rapana venosa Valenciennes and Dosinia anus Philippi was examined. Abrasive material used for tests were quartz sand (96.5 wt.%) with three different size ranges and powdered bentonite (3.5 wt.%). The two-body abrasive wear tests were run on a rotary disc type abrasive wear testing machine. The results showed that the abrasion resistance of the outside shell surfaces of the three mollusc species was higher when the corrugations on the shell surfaces were perpendicular to the sliding direction of the abrasive material than that when the corrugations on the shell surfaces were parallel to the sliding direction of the abrasive material. Basically, the shell of Lamprotula fibrosa Heude possessed the highest abrasion resistance among the three species of shell; the abrasion resistance of the shell of Rapana venosa Valenciennes was the lowest; and the abraded depth of the three species of shell increased with an increased abrasive particle size and relative sliding velocity. The abraded surfaces were observed with scanning electron microscope.     

<Emphasis Type="Italic">Continuous Secondary Ultrasonic Electropolishing of an SKD61 Cylindrical Part</Emphasis>

An effective ultrasonic-aided electropolishing system using low-cost electrodes for polishing cylindrical parts is developed. The process can be integrated with the primary processes of traditional turning, drawing, form rolling, or extrusion to achieve a good surface finish for moulds. Ultrasonic energy is applied to the electrolyte for residue discharge during electropolishing. Both continuous and pulsed direct current are tested in the study. The controlled factors include the chemical composition and concentration of the electrolyte, the electrolyte temperature, the flowrate of electrolyte, the initial gap width, and the rotational speed of the workpiece. The experimental parameters are the frequency and power of the ultrasonic vibration, electrical current density, pulse period, rotational speed of the electrode, the electrode feedrate, and the electrode geometry. The incorporation of ultrasonics is found to be more effective than the use of pulsed current, without sacrificing the polishing time. An average surface roughness of 0.3 μm can be obtained by this method. ID="A1"Correspondance and offprint requests to: Professor H. Hocheng, Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu, Taiwan. E-mail: hocheng@pme.nthu.edu.tw     

Silicon radiation detectors (<Emphasis Type="Italic">Review</Emphasis>)

The modern status of the field of development of silicon detectors of charged particles and x/γ rays is considered. The types and characteristics of spectrometric detectors are briefly described; the predominant attention is given to track devices. The results of studies of the radiation resistance of silicon detectors are presented.     

<Emphasis Type="Bold">A New Simulation Optimisation System for the Parameters of a Machine Cell Simulation Model</Emphasis>

Combinatorial scheduling rules optimisation has been a focus of most of the studies about flexible manufacturing systems (FMS), in the design and control of which, the performance optimisation of a machine cell is of great importance. To optimise the performance of a machine cell, the paper describes the design of a simulation optimisation system. It is constructed according to the principle of separating the models from the algorithms. The system consists of a simulation module and an optimisation module. The optimisation algorithms are the core of the paper, a new hybrid optimisation algorithm is proposed by combining the features of region-shrunk genetic algorithms with an enhanced continuous tabu search. The paper provides an example to demonstrate the validity of the system.     

End-grafted Sugar Chains as Aqueous Lubricant Additives: Synthesis and Macrotribological Tests of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)-<Emphasis Type="Italic">graft</Emphasis>-Dextran (PLL-<Emphasis Type="Italic">g</Emphasis>-dex) Copolymers

Comb-like graft copolymers with carbohydrate side chains have been developed as aqueous lubricant additives for oxide-based tribosystems, in an attempt to mimic biological lubrication systems, whose surfaces are known to be covered with sugar-rich layers. As adopted in the previous studies of the graft copolymer poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), which showed both excellent lubricating and antifouling properties, a similar approach was chosen to graft dextran chains onto the same backbone, thus generating PLL-g-dex. PLL-g-dex copolymers readily adsorb from aqueous solution onto negatively charged oxide surfaces. Tribological characterization at the macroscopic scale, either under pure sliding conditions or a mixed sliding/rolling contact regime, shows that PLL-g-dex is very effective for the lubrication of oxide-based tribosystems. The relative lubricating capabilities of PLL-g-dex copolymers compared with PLL-g-PEG copolymers were observed to be highly dependent on the molecular structure of the copolymers (in particular, side-chain density along the backbone) and the measurement conditions (in particular, time between tribocontacts); the PLL-g-dex copolymers with a low degree of grafted side chains (≤20% grafting of available protonated primary amine groups along the backbone) showed better lubricating performance than their PLL-g-PEG counterparts at high tribocontact frequency (≥ca. 0.32 Hz).     

<Emphasis Type="Italic">Joint Design of Continuous Sampling Plans and Specification Limits</Emphasis>

This paper explores the problem of integrating a Type I continuous sampling plan (CSP-1 plan) and the design of specification limits based on Taguchi’s quality loss function. By adopting the minimax-regret principle, we can obtain the economic specification limits and the optimal inspection policy. This study is an extension of Kapur and Wang’s work. ID="A1"Correspondance and offprint requests to: C.-H. Chen, Department of Industrial Management, Southern Taiwan University of Technology, 1 Nan-Tai Street, Yung-Kang City, Tainan 710, Taiwan, Republic of China. E-mail: chench@mail.stut.edu.tw     

<Emphasis Type="Italic">Modelling of Five-Axis Machine Tool Metrology Models Using the Matrix Summation Approach</Emphasis>

Five-axis machining has been used widely in manufacturing freeform surfaces. The traditional approach of using a homogeneous transformation matrix (HTM) relies on heavy symbolic manipulation of the matrix multiplication. In this work, a new approach – the matrix summation approach – is developed and implemented for modelling the geometric errors of five-axis machine tools. This approach breaks down the kinematic equation into six components, each of which has clear physical meaning. It reduces the computations substantially and makes the five-axis kinematic model manageable and understandable. ID="A1"Correspondance and offprint requests to: Yin-Lin Shen, Academic Center T727, MAE Department, George Washington University, 801 22nd Street, NW, Washington, DC 20052, USA. E-mail: shen@seas.gwu.edu     

Creep crack growth analysis using <Emphasis Type="Italic">C</Emphasis><Subscript><Emphasis Type="Italic">t</Emphasis></Subscript>-parameter for internal circumferential and external axial surface cracks in a pressurized cylinder

Creep crack growth at elevated temperatures is a critical consideration in estimating the remaining life of high temperature structural components and in deciding their inspection interval. In this study, creep crack growth analyses for external radial-axial and internal radial-circumferential surface cracks in a pressurized cylinder were conducted by an analytical method. The effect of crack depth and crack length on the variations in C _t and remaining life predictions were investigated for surface cracks with various initial aspect ratios. It was observed that the remaining life of an internal radial-circumferential surface crack was approximately 53 times longer than that of an external radial-axial surface crack for the same crack size and loading conditions with 316 stainless steel material. It was also observed that the variations in remaining life, crack propagations, and the C _t values were considerably sensitive to the crack location and crack depth. Convergence of crack aspect ratio was not observed when the crack depth ratio was increased. Since the method is independent of material properties and location of the crack geometries, it can be extended to various material properties and various locations of the surface crack geometries.     

<Emphasis Type="Bold">Reconfigurable Computing for Tool-Path Computation</Emphasis>

Tool-path generation is one of the most complex problems in computer-aided manufacturing. Although some efficient strategies have been developed to solve it, most of them are only useful for 3- and 5-axis standard machining. The algorithm called virtual digitising computes the tool path by means of a virtually digitised model of the surface and a geometry specification of the tool and its motion, so it can be used even in non-standard machining (retrofitting). This algorithm is simple, robust, and avoids the problem of tool-surface collision. However, its computing cost is high. Presented in the paper there is a virtual digitising optimisation that takes advantage of reconfigurable computing (using field programmable gates arrays) in order to improve the algorithm speed. A comparative study will show the gain and precision achieved.     

Macrotribological Studies of Poly(<Emphasis Type="Italic">L</Emphasis>-lysine)-<Emphasis Type="Italic">graft</Emphasis>-Poly(ethylene glycol) in Aqueous Glycerol Mixtures

We have investigated the tribological properties of surfaces with adsorbed poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) sliding in aqueous glycerol solutions under different lubrication regimes. Glycerol is a polar, biocompatible liquid with a significantly higher viscosity than that of water. Macrotribological performance was investigated by means of pin-on-disk and mini-traction-machine measurements in glycerol-PLL-g-PEG-aqueous buffer mixtures of varying compositions. Adsorption studies of PLL-g-PEG from these mixtures were conducted with the quartz-crystal-microbalance technique. The enhanced viscosity of the glycerol-containing lubricant reduces the coefficient of friction due to increased hydrodynamic forces, leading to a more effective separation of the sliding partners, while the presence of hydrated polymer brushes at the interface leads to an entropically driven repulsion, which also helps mitigate direct asperity–asperity contact between the solid surfaces under boundary-lubrication conditions. The combination of polymer layers on surfaces with aqueous phases of enhanced viscosity thus enables the friction to be reduced by several orders of magnitude, compared to the behavior of pure water, over a large range of sliding speeds. The individual contributions of the polymer and the aqueous glycerol solutions in reducing the friction have been studied across different lubrication regimes.     

<Emphasis Type="Italic">0.2BPM64-200</Emphasis> microfocus X-ray tube for projection radiography

The design of the first domestic microfocus X-ray tube with massive target and electrostatic 200-kV electron-beam focusing is presented. A monoblock X-ray device based on this tube and intended for projection radiography is described. The main characteristics of the X-ray unit, including its fluoroscopic parameters, are estimated.     

Water as an insulator in pulsed facilities (<Emphasis Type="Italic">Review</Emphasis>)

Transmission lines with distributed parameters are often used as electrical energy storage units and high-voltage (high-current) pulse shapers in electrophysical facilities. To increase the pulse power and reduce the dimensions of the equipment, deionized water, purified from mechanical impurities and gas, is used as an insulator in lines. Water has a high breakdown strength ((BS) 130 kV/cm) at pulses with a duration of 1 µs and electrode areas of up to tens of square meters, a large value of the relative permittivity (80), and a small loss tangent in the frequency range 0–1 GHz. Water also possesses a number of characteristics needed to achieve the above aims. We review here the data on the electrical properties of water and the studies of it published over the last three decades; the methods for increasing the water BS and the influence of numerous factors on the BS; the physical mechanism of water breakdown and the basic regularities of the BS in strong electric fields; the BS in the most frequently used electrode systems; formulas for calculating the water BS under different conditions and over the surfaces of solid dielectrics; the characteristics of mixtures of water and ethylene glycol or methanol; water purification systems for electrophysical facilities; the comparative parameters of coaxial energy storage units having various insulators, etc. The summary generalizes the brief and predominantly reference information on the electrical properties of water and its applications for researchers, engineers, and the users of the equipment having water insulation; it can help to solve related problems more quickly and reliably.__________Translated from Pribory i Tekhnika Eksperimenta, No. 2, 2005, pp. 9–38.Original Russian Text Copyright © 2005 by Gerasimov.     

A <Emphasis Type="Italic">Z</Emphasis>-pinch-based generator of focused rarefaction waves in liquid

The excitation of impulse acoustic waves in a liquid upon the deformation of a cable under the action of pondermotive forces is described. It is shown that rarefaction and compression waves of microsecond duration can be focused with the use of a ring transducer manufactured from a coaxial cable. Acoustic pulses, in which a rarefaction wave preceded a compression wave, were excited upon the passage of a current pulse through the cable shield. When the current was passed through the central conductor, a compression wave preceded a rarefaction wave. High-speed photography revealed the presence of cavitation bubbles at the focus of the radiator. This work shows the possibility of studying the dynamics of bubbles at the stage of their expansion from cavitation nuclei in a rarefaction wave and the dynamics of such processes as aspherical collapse, the formation of a cumulative jet, and bubble fragmentation in a compression wave.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 130–134.Original Russian Text Copyright © 2004 by Sankin.     

A novel MEMS nano-tribometer for dynamic testing <Emphasis Type="Italic">in-situ</Emphasis> in SEM and TEM

We present the design and fabrication of a micro-electro-mechanical (MEMS) tribometer with normal and lateral force resolutions of 100 and 1 nano-Newton, respectively and bandwidth of 50 kHz. The small size of the tribometer (2 × 2 × 0.3 mm) allows simultaneously quantitative and qualitative dynamic testing in electron microscopes.     

Investigating the 1/<Emphasis Type="Italic">z</Emphasis><Superscript>2</Superscript>-filtering in tomography algorithms

The filtering of projections in tomography algorithms, which is based on the regularization of distribution 1/z ², is investigated. Numerical simulations validate that changing the filter support will substantially improve the tomograms. Comparison of the results of reconstruction by the 1/z ²-filtering algorithm and the Shepp-Logan algorithm shows that the reconstruction accuracy of the latter is worse when the number of angles of observation is small or a high noise is present in the projection data.     

<Emphasis Type="Bold">An Integrated Machining Approach for a Centrifugal Impeller</Emphasis>

When a 3-axis CNC machining centre is used for producing an impeller, great difficulties, i.e. collisions between the cutting tool and the impeller, can occur. The blade of an impeller is usually designed with a ruled surface. As the surface is normally twisted in design to achieve the required performance, it can cause overcut and collision problems during machining. The hub of the impeller is usually designed with an irregular surface, and is machined within a narrow and deep groove. The issues – how to satisfy the quality requirements of the part, reduce the machining time, and avoid the occurrence of collision – become an integral problem. This work develops an integrated 5-axis machining module for a centrifugal impeller by combining related machining technologies. As a result, cutter location (CL) data based on the geometric model of blade and hub are generated. Finally, the CL data are confirmed through software simulation. The results of verification show that the machining methodology and procedure adopted are successful.