Factors affecting user performance in haptic assembly

Current computer-aided assembly systems provide engineers with a variety of spatial snapping and alignment techniques for interactively defining the positions and attachments of components. With the advent of haptics and its integration into virtual assembly systems, users now have the potential advantage of tactile information. This paper reports research that aims to quantify how the provision of haptic feedback in an assembly system can affect user performance. To investigate human–computer interaction processes in assembly modeling, performance of a peg-in-hole manipulation was studied to determine the extent to which haptics and stereovision may impact on task completion time. The results support two important conclusions: first, it is apparent that small (i.e. visually insignificant) assembly features (e.g. chamfers) affect the overall task completion at times only when haptic feedback is provided; and second, that the difference is approximately similar to the values reported for equivalent real world peg-in-hole assembly tasks.     

Gastric and biliary excretion of meperidine in man

The role and importance of enterogastric secretion in the disposition and elimination of the weak base, meperidine (pKa 8.63), was studied after intravenous administration (50 mg) of the drug to 6 normal volunteers. Continuous collection of the gastric fluid over a 4-hr period demonstrated the establishment of high gastric fluid/plasma concentration ratios for meperidine (mean about 50, range, 10 to 200). However, the total amount of drug recovered, even after correction for incomplete collection, was only a small percentage of the administered dose. Under basal conditions a mean +/- SE of 1.9 +/- 0.3 mg, equivalent to 3.7% of the administered dose, was found in the total gastric aspirate. Stimulation of gastric secretion by subcutaneous injection of betazole (1.5 mg/kg) increased this recovery to 3.6 +/- 0.3 mg (7.2%) primarily due to the increase in gastric volumen output. Aspiration of the gastric fluid in either the basal or stimulated situation had no observable effect upon the plasma concentration/time profile of meperidine whether assessed by the terminal half-life, t 1/2 beta, or the plasma clearance; control values were 3.8 +/- hr and 1,190 +/- 130 ml/min, respectively. In 2 subjects "bile fluid" was also collected for 2.5 hr and found to contain less than 0.2% of the administered dose. Enterosystemic recycling is therefore of minor importance in the disposition and elimination of meperidine in man.     

Determination of glucose with glucoseoxidase-UV, using hexokinase as the reference method (author's transl)

Results obtained with the commercial test-set "GOD-UV" (Dr. Haury, München) are reported. This method permits the determination of serum-glucose within 3 minutes. The procedure is satisfactory in normal and hyperglycaemic patients. In the hypoglycaemic state, however, there is a danger of misinterpretation. The glucose oxidase-UV is compared with the hexokinase reaction.     

Exploitation versus Exploration in Market Competition

A general simulation model of market competition is developed to explore the effectiveness of and interactions between different types of product exploration and exploitation strategies, that is, innovation, imitation and process improvement. The model, like real markets, is highly non-linear such that analytical solutions are not possible. We use simulation experiments to examine firm survival and the effectiveness of different strategies under different market conditions including competitors' strategies, how long it takes for each strategy to bear fruit and how costly it is, and the timing, growth and duration of product life cycles. The model is implemented on the Internet and provides the basis for further experiments to examine the impact of different combinations of firm strategies on survival and performance.     

Comparison of Particle Size Distributions Measured Using Different Techniques

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

National and international university departmental Web site interlinking

Although many link patterns have been identified at the university level, departmental interlinking has been relatively ignored. Universities are multidisciplinary by nature and various disciplines may employ the Web differently, thus patterns identified at the university level may hide subject differences. Departments are typically subject-oriented, and departmental interlinking may therefore illustrate interesting disciplinary linking patterns, perhaps relating to informal scholarly communication. The aim of this paper is to identify whether and how link patterns differ along country and disciplinary lines between similar disciplines and similar countries. Physics, Chemistry and Biology departments in Australia, Canada and the UK have been chosen. In order to get a holistic picture of departments' Web use profiles and link patterns, five different perspectives are identified and compared for each set of departments. Differences in link patterns are identified along both national and disciplinary lines, and are found to reflect offline phenomena. Along national lines, a likely explanation for the difference is that countries with better research performances make more general use of the Web; and, with respect to international peer interlinking, countries that share more scholarly communication tend to interlink more with each other. Along disciplinary lines, it seems that departments from disciplines which are more willing to distribute their research outputs tend to make more general use of the Web, and also interlink more with their national and international peers.     

Vertical inertial sliding drive for coarse and fine approaches in scanning probe microscopy

Mechanisms for controlled approach of a probe tip toward the sample surface are essential in high resolution imaging by scanning probe microscopy (SPM). This work describes the development and performance of an inertial sliding drive capable of translating a relatively large mass (25 g) at up to 1 mms over 1 cm with step sizes of 10-250 nm in ambient conditions using various wave forms as measured by fiber optic interferometry. The drive functions independent of orientation with a threshold voltage of less than 15 V using a single drive signal. Use of piezotube actuators in a radially symmetric arrangement provides guided motion and minimizes differential thermal expansion between critical components. Controlled translation of the entire scanning component in both ambient and electrochemical scanning tunneling microscopy has been routinely achieved with no evidence of tip crash. This device has been specifically designed for use in in situ SPM applications where stability of the sample and that of the liquid environment are paramount.     

Use of kernel-based Bayesian models to predict late osteolysis after hip replacement

We studied the relationship between osteolysis and polyethylene wear, age at surgery, body mass index and height in 463 subjects (180 osteolysis and 283 controls) after cemented Charnley total hip arthroplasty (THA), in order to develop a kernel-based Bayesian model to quantitate risk of osteolysis. Such tools may be integrated into decision-making algorithms to help personalize clinical decision-making. A predictive model was constructed, and the estimated posterior probability of the implant failure calculated. Annual wear provided the greatest discriminatory information. Age at surgery provided additional predictive information and was added to the model. Body mass index and height did not contain valuable discriminatory information over the range in which observations were densely sampled. The robustness and misclassification rate of the predictive model was evaluated by a five-times cross-validation method. This yielded a 70% correct predictive classification of subjects into osteolysis versus non-osteolysis groups at a mean of 11 years after THA. Finally, the data were divided into male and female subsets to further explore the relationship between wear rate, age at surgery and incidence of osteolysis. The correct classification rate using age and wear rate in the model was approximately 66% for males and 74% for females.     

Development of an experimentally validated semi-empirical fully-coupled performance model of a PEM electrolysis cell with a 3-D structured porous transport layer

A semi-empirical non-isothermal model incorporating coupled momentum, heat and mass transport phenomena for predicting the performance of a proton exchange membrane (PEM) water electrolysis cell operating without flow channels is presented. Model input parameters such as electro-kinetics properties and mean pore size of the porous transport layer (PTL) were determined by rotating disc electrode and capillary flow porometry, respectively. This is the first report of a semi-empirical fully coupled model which allows one to quantify and investigate the effect of the gas phase and bubble coverage on PEM cell performance up to very high current densities of about 5 A/cm². The mass transport effects are discussed in terms of the operating conditions, design parameters and the microstructure of the PTL. The results show that, the operating temperature and pressure, and the inlet water flowrate and thickness of the PTL are the critical parameters for mitigating mass transport limitation at high current densities. The model presented here can serve as a tool for further development and scale-up effort in the area of PEM water electrolysis, and provide insight during the design stage.