Simulating convective die heating for forgings and pressure casting

A comparison is made of die temperature uniformity for two heating configurations: electric air heating and flame heating. The temperature uniformity with electric air heating is noted to be substantially superior to flame heating of large dies. The simulation results are compared with experimentally obtained numbers and found to be in agreement.     

The predictive value of intraoperative somatosensory evoked potential monitoring: review of 244 procedures

INTRODUCTION: There is some controversy regarding the value of intraoperative neurophysiological monitoring in predicting postoperative neurological deficits. We discuss our experience with the use of intraoperative somatosensory evoked potentials (SSEPs) during surgery of cranial base tumors. METHODS: We retrospectively reviewed all of the procedures that had been performed for the resection of cranial base tumors from July 29, 1993, through March 16, 1995. One hundred ninety-three consecutive patients had undergone a total of 244 procedures. SSEP waveforms were classified as follows: Type I, no change; Type II, change that reverts to baseline; Type III, change that does not revert to baseline; and Type IV, complete flattening of the SSEP waveform without improvement. Two patients had no waveforms from the beginning of the case (Type V) and were excluded from further analysis. New immediate postoperative neurological deficits were recorded. RESULTS: There were 64 male and 129 female patients, with a mean age of 46.6 years. One hundred seventy-seven patients had Type I SSEP waveforms, 13 of whom had postoperative deficits (7%). Fifty-six patients had Type II SSEPs, and nine (16%) of them had postoperative neurological deficits. Six patients had Type III SSEPs, and three had Type IV SSEPs, all of whom (100%) had postoperative deficits. There was a correlation between SSEP type and the results of the postoperative neurological examinations. The positive predictive value is 100%, and the negative predictive value is 90%. Although a change in the waveform that did not revert to baseline (Types III and IV) always predicted a postoperative deficit, a normal waveform did not always rule out postoperative deficits. Pathological abnormality, vessel encasement, vessel narrowing, degree of cavernous sinus involvement, brain stem edema, middle fossa location, final amount of resection, age, and tumor size correlated with a high predictive value of SSEP monitoring on univariate analysis (P < 0.05). None of these variables correlated significantly on multivariate analysis (P > 0.05), although brain stem edema was close (P = 0.0571). CONCLUSION: Intraoperative SSEPs have a high positive predictive value during surgery for cranial base tumors, but they do not detect all postoperative deficits.     

Dose control circuit for digital electrostatic electron-beam array lithography

This paper demonstrates a technique for controlling the electron emission of an array of field emitting vertically aligned carbon nanofibers (VACNFs). An array of carbon nanofibers (CNF) is to be used as the source of electron beams for lithography purposes. This tool is intended to replace the mask in the conventional photolithography process by controlling their charge emission using the “Dose Control Circuitry” (DCC). The large variation in the charge emitted between CNFs grown in identical conditions forced the controller design to be based on fixed dose rather than on fixed time. Compact digital control logic has been designed for controlling the operation of DCC. This system has been implemented in a 0.5 μm CMOS process. Chandra Sekhar A. Durisety received his B.E. (Hons.) Instrumentation from Birla Institute of Technology and Sciences, Pilani, India in 1997 and his M.S in Electrical Engineering from University of Tennessee, Knoxville in 2002. Since 2003, he has been working towards his Ph.D degree also in Electrical Engineering at Integrated Circuits and Systems Lab (ICASL), University of Tennessee, Knoxville. He joined Wipro Infotech Ltd, Global R & D, Bangalore, India in 1997, where he designed FPGA based IPs for network routers. Since 1999, he was involved in the PCI bridge implementation at CMOS chips Inc, Santa Clara, CA, and the test bench development for Sony’s MP3 player, while at Toshiba America Electronic Components Inc., San Jose, CA. His research interests include multi-stage amplifiers, data converters, circuits in SOI and Floating Gate Devices. Rajagopal Vijayaraghavan received the B.E degree in electronics and communication engineering from Madras University in 1998 and the M.S degree in electrical engineering from the University of Texas, Dallas in 2001.He is currently working towards the Ph.D degree in electrical engineering at the University of Tennessee. His research interest is in the area of CMOS Analog and RF IC design. His current research focuses on LNAs and VCOs using SOI based MESFET devices. Lakshmipriya Seshan was born in Trivandrum, India on April 30, 1979. She received her B.tech in Electronincs & Communication Engg from Kerala University, India in June 2000 and M.S in Electrical Engg from University of Tennessee in 2004. In 2004, she joined Intel Corporation as an Analog Engineer, where she is engaged in the design of low power, high speed analog circuits for various I/O interface topologies. Syed K. Islam received his B.Sc. in Electrical and Electronic Engineering from Bangladesh University of Engineering and Technology (BUET) and M.S. and Ph.D. in Electrical and Systems Engineering from the University of Connecticut. He is presently an Associate Professor in the Department of Electrical and Computer Engineering at the University of Tennessee, Knoxville. Dr. Islam is leading the research efforts of the Analog VLSI and Devices Laboratory at the University of Tennessee. His research interests are design, modeling and fabrication of microelectronic/optoelectronic devices, molecular scale electronics and nanotechnology, biomicroelectronics and monolithic sensors. Dr. Islam has numerous publications in technical journals and conference proceedings in the areas of semiconductors devices and circuits. Benjamin J. Blalock received his B.S. degree in electrical engineering from The University of Tennessee, Knoxville, in 1991 and the M.S. and Ph.D. degrees, also in electrical engineering, from the Georgia Institute of Technology, Atlanta, in 1993 and 1996 respectively. He is currently an Assistant Professor in the Department of Electrical and Computer Engineering at The University of Tennessee where he directs the Integrated Circuits and Systems Laboratory (ICASL). His research focus there includes analog IC design for extreme environments (both wide temperature and radiation immune), multi-gate transistors and circuits on SOI, body-driven circuit techniques for ultra low-voltage analog, mixed-signal/mixed-voltage circuit design for systems-on-a-chip, and bio-microelectronics. Dr. Blalock has co-authored over 60 published refereed papers. He has also worked as an analog IC design consultant for Cypress Semiconductor Corp. and Concorde Microsystems Inc.     

Oxynitride gate dielectric grown in nitric oxide (NO): the effectof reoxidation on dielectric reliability of the active edge

Reoxidation of an oxynitride gate dielectric grown by NO anneal of thermal oxide has been studied. This process has demonstrated ~3-5X improvement of Q_BD of active edge intensive capacitors in comparison to thermal oxide, N₂O and NO oxynitride. This improvement is believed to be due to the reduction of local thinning of the gate dielectric at the field oxide edge which also reduces local build-up of positive charge near the gate electrode at the isolation edges     

Surgical anatomy of the infratemporal fossa: the styloid diaphragm revisited

INTRODUCTION: The infratemporal fossa (ITF) gives passage to most major cerebral vessels and cranial nerves. Dissection of the ITF is essential in many of the lateral cranial base approaches and in exposure of the high cervical internal carotid artery (ICA). We reviewed the surgical anatomy of this region. METHODS: Direct foraminal measurements were made in seven dry skulls (14 sides), and the relationship of these foramina to each other and various landmarks were determined. Ten ITF dissections were performed using a preauricular subtemporal-infratemporal approach. Preliminary dissections of the extracranial great vessels and structures larger than 1 cm were performed using standard macroscopic surgical techniques. Dissection of all structures less than 1 cm was conducted using microsurgical techniques and instruments, including the operating microscope. The anatomic relationships of the muscles, nerves, arteries, and veins were carefully recorded, with special emphasis regarding the relationship of these structures to the styloid diaphragm. The dissection was purely extradural. RESULTS: The styloid diaphragm was identified in all specimens. It divides the ITF into the prestyloid region and the retrostyloid region. The prestyloid region contains the parotid gland and associated structures, including the facial nerve and external carotid artery. The retrostyloid region contains major vascular structures (ICA, internal jugular vein) and the initial exocranial portion of the lower Cranial Nerves IX through XII. Landmarks were identified for the different cranial nerves. The bifurcation of the main trunk of the facial nerve was an average of 21 mm medial to the cartilaginous pointer and an average of 31 mm medial to the tragus of the ear. The glossopharyngeal nerve was found posterior and lateral to stylopharyngeus muscle in nine cases and medial in only one. The vagus nerve was consistently found in the angle formed posteriorly by the ICA and the internal jugular vein. The spinal accessory nerve crossed anterior to the internal jugular vein in five cases and posterior in another five cases. It could be located as it entered the medial surface of the sternocleidomastoid muscle 28 mm (mean) below the mastoid tip. The hypoglossal nerve was most consistently identified as it crossed under the sternocleidomastoid branch of the occipital artery 25 mm posterior to the angle of the mandible and 52 mm anterior and inferior to the mastoid tip. CONCLUSION: The styloid diaphragm divides the ITF into prestyloid and retrostyloid regions and covers the high cervical ICA. Using landmarks for the exocranial portion of the lower cranial nerves is useful it identifying them and avoiding injury during approaches to the high cervical ICA, the upper cervical spine, and the ITF.     

On the extension of a crack due to rigid inclusions

Dislocation layers have been utilized to study the effect of rigid inclusion on the crack extension in an infinite body and thereby to derive the crack extension condition from Irwin's criterion. Some particular cases have also been considered.

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Résumé On a eu recours aux couches de dislocation pour étudier l'effet d'une inclusion rigide sur l'extension d'une fissure dans un corps infini et déterminer en conséquence les conditions d'extension d'une fissure en utilisant le critère d'Irwin. Certains cas particuliers ont également été considérés.

     

On the opening of two coplanar griffith cracks

The problem of opening two coplanar Griffith cracks in an infinite elastic medium has been considered in this note. The application of Somigliana's method to this mixed boundary value problem leads to a Föppl integral equation, whose solution has been derived in closed form with the help of a convolution theorem connected with finite Hilbert transforms.

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Résumé On a considéré, dans ce mémoire, le problème de l'ouverture de 2 fissures coplanaires de Griffith dans un milieu élastique infini. L'application de la méthode de Somigliana au problème de la valeur de la frontière indéfinie conduit à une équation intégrale de Föppl dont la solution a été dérivée sous une forme fermée en utilisant un théorème de convolution connecté à une transformée finie de Hilbert.

     

Fast ion conducting lithium glasses—Review

For the last few years fast ion conducting lithium glasses are being studied due to their potential use in advanced electrochemical devices. A number of glass systems containing oxides, sulphides and other lithium compounds prepared by both conventional cooling and rapid quenching techniques have been reported. In this paper we review the transport properties of lithium ion conducting glasses. The special features of the ionic conduction process have been highlighted and some experimental techniques to study transport properties have been described. Some of the common observations of the properties have been discussed and finally some important problems for future development have been pointed out.     

XYLANASE EFFECTS ON PULP DELIGNIFICATION

Xylanase effects on softwood pulp delignification were investigated experimentally and using mathematical models. The effect of xylanase molecular size on pulp delignification was investigated. As xylanase molecular weight decreased from 67 kDaltons to 20 kDaltons, lignin removal from pulp increased from 30 wt% to 48 wt%, respectively. The rate of xylanase-aided pulp delignification was studied using a batch system. The rate-data was fitted to a mathematical model of the batch system that enabled estimation of process parameters including xylanase and lignin effective diffusivities, lignin mass transport coefficient, and effective particle diameter for mass transport. Parameter values thus obtained were used to simulate the semi-batch delignification process, which predicted 84.6% of lignin available to UGA xylanase (MW=39,000 Daltons) would be removed in 2.5 h.