Showing papers by "Rensselaer Polytechnic Institute published in 1994"
TL;DR: In this article, a review of microfiltration is presented, focusing on the formation of cakes, the behavior of suspension flows and particle transport in simple geometry ducts, and the formation and behavior of fouling layers including those resulting from macromolecules, colloids and particles.
1,317 citations
TL;DR: A case-mix classification system for nursing home residents is developed, based on a sample of 7,658 residents in seven states, which achieves 55.5% variance explanation of total (nursing and therapy) per diem cost and meets goals of clinical validity and payment incentives.
Abstract: A case-mix classification system for nursing home residents is developed, based on a sample of 7,658 residents in seven states. Data included a broad assessment of resident characteristics, corresponding to items of the Minimum Data Set, and detailed measurement of nursing staff care time over a 24-hour period and therapy staff time over a 1-week period. The Resource Utilization Groups, Version III (RUG-III) system, with 44 distinct groups, achieves 55.5% variance explanation of total (nursing and therapy) per diem cost and meets goals of clinical validity and payment incentives. The mean resource use (case-mix index) of groups spans a nine-fold range. The RUG-III system improves on an earlier version not only by increasing the variance explanation (from 43%), but, more importantly, by identifying residents with "high tech" procedures (e.g., ventilators, respirators, and parenteral feeding) and those with cognitive impairments; by using better multiple activities of daily living; and by providing explicit qualifications for the Medicare nursing home benefit. RUG-III is being implemented for nursing home payment in 11 states (six as part of a federal multistate demonstration) and can be used in management, staffing level determination, and quality assurance.
548 citations
TL;DR: In this article, a critical evaluation of the performance capabilities of various wide bandgap semiconductors for high power and high frequency unipolar electronic devices is presented, and seven different figures of merit have been analyzed.
Abstract: This paper presents a critical evaluation of the performance capabilities of various wide bandgap semiconductors for high power and high frequency unipolar electronic devices. Seven different figures of merit have been analyzed. Theoretical calculations show that besides diamond and SiC, compounds like AlN, GaN, InN, and ZnO, and the intermetallics (Ga/sub x/In/sub 1-x/N, Al/sub x/In/sub 1-x/N, Al/sub x/Ga/sub 1-x/N, and (AlN)/sub x/(SiC)/sub 1-x/) offer several orders of magnitude improvement in the on-resistance and in the potential for successful operation at higher temperatures. >
473 citations
01 Apr 1994
TL;DR: Petri net modeling combined with heuristic search provides a new scheduling method for flexible manufacturing systems that can handle features such as routing flexibility, shared resources, lot sizes and concurrency.
Abstract: Petri net modeling combined with heuristic search provides a new scheduling method for flexible manufacturing systems. The method formulates a scheduling problem with a Petri net model. Then, it generates and searches a partial reachability graph to find an optimal or near optimal feasible schedule in terms of the firing sequence of the transitions of the Petri net model. The method can handle features such as routing flexibility, shared resources, lot sizes and concurrency. By following the generated schedule, potential deadlocks in the Petri net model and the system can be avoided. Hence the analytical overhead to guarantee the liveness of the model and the system is eliminated. Some heuristic functions for efficient search are explored and the experimental results are presented. >
401 citations
01 Apr 1994
TL;DR: This book discusses information modelling combined with a description of the express information model specification language, EXPRESS, a new language that when used with information modelling abstracts away the implementation bias prevalent in current data modelling technology.
Abstract: This book discusses information modelling combined with a description of the express information model specification language. EXPRESS is a new language that when used with information modelling abstracts away the implementation bias prevalent in current data modelling technology. One of the main tenets of EXPRESS is that a clear separation exists between the information model and the information system environment - a piece of information is not tied to a single application that uses it. The book will be of interest to data and information modellers in both universities and businesses, especially those concerned with object-oriented systems as it illustrates the development and use of information models using EXPRESS.
395 citations
TL;DR: This work constructs parallel finite element methods for the solution of hyperbolic conservation laws in one and two dimensions and presents results using adaptive h- and p-refinement to reduce the computational cost of the method.
370 citations
TL;DR: In this paper, laser and infrared reflow soldering methods were used to make Sn-Ag eutectic solder joints for surface-mount components on printed wiring boards, and the microstructures of the joints were evaluated and related to process parameters.
Abstract: Laser and infrared reflow soldering methods were used to make Sn-Ag eutectic solder joints for surface-mount components on printed wiring boards. The microstructures of the joints were evaluated and related to process parameters. Aging tests were conducted on these joints for times up to 300 days and at temperature up to 190°C. The evolution of microstructure during aging was examined. The results showed that Sn-Ag solder microstructure is unstable at high temperature, and microstructural evolution can cause solder joint failure. Cu-Sn intermetallics in the solder and at copper-solder interfaces played an important role in both the microstructure evolution and failure of solder joints. Void and crack formation in the aged joints was also observed.
275 citations
TL;DR: It is demonstrated that poly(alpha-hydroxy esters) can provide a suitable substrate for osteoblast culture and hold promise in bone regeneration by osteoblasts transplantation and in tissue culture polystyrene controls.
Abstract: Rat osteoblasts were cultured on films of biodegradable poly(L-lactic acid) (PLLA), 75:25 poly(DL-lactic-co-glycolic acid) (PLGA), 50:50 PLGA, and poly(glycolic acid) (PGA) for up to 14 days. Osteoblasts attached equally well to all the polymer substrates after 8 h in culture. By day 4 in culture, osteoblasts had exceeded confluency numbers, and their proliferation leveled off by day 7. An increase in alkaline phosphatase (ALP) activity from 1.92 (±0.47) × 10−7 for day 7 to 5.75 (±0.12) × 10−7 μmol/cell per min for day 14 was reported for osteoblasts cultured on 75:25 PLGA, which was comparable to that observed for tissue culture polystyrene (TCPS) controls. The ALP activities expressed by osteoblasts cultured on PLLA, 50:50 PLGA, and PGA films did not significantly increase over time. Collagen synthesis for osteoblasts cultured on all polymer substrates was similar to that of TCPS and did not vary with time. The morphology of cultured osteoblasts was not affected by the continuous degradation of the polymer substrates. These results demonstrate that poly(α-hydroxy esters) can provide a suitable substrate for osteoblast culture and hold promise in bone regeneration by osteoblast transplantation. © 1994 John Wiley & Sons, Inc.
258 citations
253 citations
TL;DR: An improved branch and bound code for zero-one mixed integer nonlinear programs with convex objective functions and constraints with Lagrangian duality is described.
TL;DR: In this article, the authors compared the performance of Croston's method and exponential smoothing with real-world data from industrial sources and concluded that Croston is robustly superior to exponential smoothed and could provide tangible benefits to manufacturers forecasting intermittent demand.
Journal Article•
TL;DR: In this article, the authors computed the photonic band structure for tree-pile structures having the periodicity of the simple tetragonal lattice and bandgaps have been found.
Abstract: Photonic band structure has been computed for ‘woodpile’ structures having the periodicity of the simple tetragonal lattice. Bandgaps have been found. Further research directions are explored.
Patent•
01 Mar 1994TL;DR: In this paper, an eye-tracking system was proposed to determine the position of a user's pupil and map this position into a point of regard of the user on an interface device, such as a display screen, or other real-world object by a system comprising a camera for acquiring a video image of the pupil; a frame grabber coupled to the camera for accepting and converting analog video data from the camera to digital pixel data; a computer coupled with the framegrabber for processing the digital pixels data to substantially determine the user's position.
Abstract: An eye-tracking system determines the position of a user's pupil and maps this position into a point of regard of the user on an interface device, such as a display screen, or other real-world object by a system comprising a camera for acquiring a video image of the pupil; a frame grabber coupled to the camera for accepting and converting analog video data from the camera to digital pixel data; a computer coupled to the frame grabber for processing the digital pixel data to substantially determine the position of the pupil; a display screen coupled to the computer; and a support connected to the camera and display screen for fixing the relative physical positions thereof relative to the user's pupil. The processing performed by the computer may include the selection of a first pixel intensity threshold for the segmentation of the digital pixel data into first and second groups, where the total pixel area of the first group is selected to be substantially equal to a pre-determined value expected to correspond to the area of a user's pupil. The system may be calibrated by the user's following a cursor on the display screen while the system measures the pupil position for known locations of the cursor.
TL;DR: Microgravity observations show that buoyancy-induced convection alters the growth kinetics of SCN dendrites at supercoolings as high as 1.3 K.
Abstract: We measured dendritic tip velocities in pure succinonitrile (SCN) in microgravity, using a sequence of telemetered binary images sent to Earth from the space shuttle Columbia (STS-62). Growth velocities were measured as a function of the supercooling over the range 0.05-1.5 K. Microgravity observations show that buoyancy-induced convection alters the growth kinetics of SCN dendrites at supercoolings as high as 1.3 K. Also, the dendrite velocity data measured under microgravity agree well with the Ivantsov paraboloidal diffusion solution when coupled to a scaling constant of ${\ensuremath{\sigma}}^{*}=0.0157$.
TL;DR: In this paper, the lateral phase distribution in bubbly flows in vertical ducts was analyzed using a three-dimensional two-fluid model based on analytic and experimental information on the behavior of a single bubble, and on the assumption of linear superposition of shear-induced and bubble-induced turbulence.
TL;DR: The purpose of this paper is to provide a thorough survey of papers on group technology and cellular manufacturing system design and to state some important design factors that cannot be ignored.
Abstract: A number of survey papers on group technology and cellular manufacturing system design have been published. Many of them focus primarily on clustering techniques that manipulate rows and columns of the part-machine processing indicator matrix to form a block diagonal structure. Since the last survey paper was published, there have been some developments in cellular manufacturing system design. A number of papers that consider practical design constraints while designing cellular manufacturing systems have been published. The purpose of this paper is to provide a thorough survey of papers on group technology and cellular manufacturing system design. Its purpose is also to state some important design factors that cannot be ignored. >
TL;DR: In this article, an extension of the k-epsilon model for bubble-like two-phase flow is proposed and tested against experimental data. The model not only agrees with the data trends, but also predicts the turbulence suppression which has been measured for high Reynolds number bubbly air/water flows in pipes.
Abstract: An extension of the k-[epsilon] model for bubbly two-phase flow is proposed and tested against experimental data. The basic assumption made is that the shear-induced turbulence and bubble-induced turbulence may be linearly superposed. This assumption results in a model with two time constants that matches both homogeneous two-phase turbulence data (Lance and Bataille, 1991) and pipe data (Serizawa, 1986). The coefficients of the single-phase k-[epsilon] model have not been modified and only one additional coefficient is required: the virtual volume coefficient of the bubbles, which may be determined from first principles. This model not only agrees with the data trends, but it also predicts the turbulence suppression which has been measured for high Reynolds number bubbly air/water flows in pipes.
TL;DR: In this paper, the authors evaluated the extent and source of variation of clinopyroxene-silicate melt partition coefficients (D) on natural basalts (picrite, alkaline basalt, nephelinite, high-alumina basalt; 1235-1300°C; 1.8 GPa).
TL;DR: The effects of gaseous and liquid environments on the fracture behavior of Fe3Al and FeAl are reviewed in this article, where the influence of variables such as composition, microstructure, loading rate and temperature are described.
02 Oct 1994
TL;DR: In this article, the authors present an active power filter for three-phase power systems, which is composed of a six-switch threephase inverter, a DC bus capacitor, and an isolation transformer.
Abstract: This paper presents an active power filter for three-phase power systems. The work is motivated by the need for active filtration in a current-source excitation system for a variable-reluctance generator. The active filter is comprised of a six-switch three-phase inverter, a DC bus capacitor, and an isolation transformer. The isolation transformer is required by the application. The leakage inductance associated with each phase of the isolation transformer is used as the series impedance with each phase, by which the inverter is able to actively shape the phase currents in order to compensate for the nonlinearities of all loads within the point of common coupling. The active filter is controlled through two control loops. The inner current regulation loop uses sliding-mode control by virtue of its ease of implementation. The outer voltage loop regulates the average voltage on the DC bus capacitor. The outer voltage loop is responsible for correctly setting the commanded magnitude of the phase currents. This paper presents the analysis, design, and operation of the active filter. Experimental results are provided for the active filter compensating a phase-controlled rectifier which is drawing 10.4 kW. >
TL;DR: Strontium chemical diffusion has been measured in plagioclase of three intermediate compositions (between An23 and An67) under anhydrous, 1-atmosphere conditions.
TL;DR: In this paper, a uniqueness theorem for the potential of the derived Sturm Liouville problem is proved when the data are the given spectra and partial knowledge of the potential is given.
TL;DR: Changes in the unaccommodated human crystalline lens were characterized as a function of subject age for 100 normal emmetropes over the age range 18-70 yr by Scheimpflug slit-lamp photography and the relationships to accommodation and presbyopia are discussed.
TL;DR: In this article, the authors describe how residential energy consumers measure and analyze their own energy consumption and energy costs using in-depth interviews and find more extensive data collection and analysis by residential consumers than has been previously documented in the energy literature, but the conclusions consumers can draw from their analytical efforts are restricted by the form in which they receive price and consumption data and their limited analytic capabilities.
TL;DR: The stochastic frontier cost function is fit to the data utilizing the composed error model, wherein statistical noise and allocative and technical inefficiency are jointly estimated.
Abstract: Convergence across the Java Trench has been estimated for the first time, from annual Global Positioning System (GPS) measurements commencing in 1989 The directions of motion of Christmas and Cocos Island are within 1 deg of that predicted by the No-Net Rotation (NNR) NUVEL-1 plate motion model for the Australian plate although their rates are 25% and 37% less than predcited, respectively The motion of West Java differs significantly from the NNR NUVEL-1 prediction for the Eurasian plate with a 1 deg difference in direction and a 40% increase in rate We infer that either West Java moves with a distinct Southeast Asian plate or this region experiences plate margin deformation The convergence of Christmas Island with respect to West Java is 67 +/- mm/yr in a direction N11 deg E +/- 4 deg which is orthogonal to the trench The magnitude of convergence agrees well with rescaled NUVEL-1 relative plate model which predicts a value of 71 mm/yr between Australia and Eurasia The direction of motion matches the direction inferred from earthquake slip vectors at the trench but may be more northerly than the N20 deg E +/- 3 deg predicted by NUVEL-1 On June 2, 1994, almost a year after the last GPS survey, an M(sub W) = 75 earthquake with slip vector direction N5 deg occurred south of central Java
TL;DR: This short communication examines the different forms that have been presented in the literature for the log-normal distribution, properly interprets the parameters that appear in these functions, and provides the appropriate equations required to transform between these different distributions and properly evaluate the appropriate statistical parameters.