bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Design of Process Variables in Multi-Pass Wire Drawing by Genetic Algorithms
Authors: Roy S. , Ghosh S. , Shivpuri R.
Published: February 2008

This paper describes a new method for design optimization of process variables in multi-pass wire drawing processes. An adaptive Micro Genetic Algorithm (μGA) has been implemented for minimizing the difference between maximum and minimum effective plastic strains in the end product and also for minimizing the total deformation energy in a multi-pass wire drawing process. The chosen design variables are die angles, area reduction ratios, and the total number of passes. Significant improvements in the simulated product quality and reduction in the number of passes have been observed as a result of the Genetic Algorithm based optimization process. The choice of annealing passes for further reduction of the total deformation energy and residual stresses has also been studied.
Laser Phased Array Measurement of Simulated Solidified Weld Penetration Depth
Authors: Yang J. , Sanderson T. , Graham G. , Ume C.
Published: February 2008

This paper presents an experimental investigation of the use of an optical fiber laser phased array to measure solidified weld pool penetration depth in butt and v-groove joints. The purpose was to determine the optimum distances between the ultrasound source (the array), receiver, and the weld joint, in order to measure weld penetration depth. The relationship between penetration depth and wave amplitude was approximately linear. A narrow range of distances between the ultrasound receiver and weld joint permitted the ultrasonic system to detect penetration depth over the entire thickness of the base metal. Maximum resolution in measuring penetration depth was achieved by keeping the distance between the array and the weld joint as small as possible.
Optimal Orthogonal Subdivision of Rectangular Sheets
Authors: Shpitalni M. , Manevich V.
Published: February 2008

The two-dimensional problem of optimal orthogonal subdivision of rectangular sheets (stock cutting) is of great interest to industry. In this paper, a new model is presented which formulates the problem in terms of integer linear programming (ILP). Using this new model, three objective functions dealing with important practical applications are formulated and demonstrated. They are: (i) selection and placement, including orientation, of rectangles on a given (single) sheet, while minimizing the unused (scrap) material; (ii) grouping the rectangles together in a predicted form, leaving a “good” and predetermined unused part of the sheet in cases where all the rectangles can be placed on a single sheet; and, (iii) optimal arrangement of rectangles on multiple sheets, including selection of the sheets to be used.
Integration of CAD and FEA for Concurrent Engineering Design of Sheet Stamping
Authors: Lu S. C. , Saran M. J. , Miller R. A.
Published: February 2008

The tedious process of building an input model and of manual communication between CAD and Finite Element Analysis (FEA) significantly restricts the designers from using FEA, particularly in preliminary design. Most of the previous works concentrate on expediting this process by interfacing CAD and FEA. This paper propose full integration of FEA simulation code within a CAD system, thus several problems are avoided. The section-based FEA is used as better suited to early design. It requires, comparing to the 3-D FEA, development of additional CAD functions to extract appropriate sections from the CAD model. The proposed integrated system allows for rapid use of the FEA and unifies the design environment to avoid inconsistency. It provides a mechanism to specify the part orientation relative to the punch traveling direction to support tipping. It also extracts the geometrical data of a specified section to automatically build and store a FEA input model. The numerical simulation of the process can be then performed without exiting the CAD system. Both existing as well as newly developed CAD functions, needed for the proposed integration system, are presented. The feasibility and advantages of such integration is demonstrated on the developed prototype system.
PMPS: A Prototype CAPP System for Parallel Machining
Authors: Levin J. B. , Dutta D.
Published: February 2008

Parallel N.C. machines, also referred to as mill-turns, are a new generation of machine tools aimed at increasing machining accuracy and reducing part cycle times. In addition to their capacity to do both milling and turning, these next generation machines tools can perform multiple machining operations simultaneously, involving one or more parts at a time, and can completely finish a part (front and back) in a single setup. Parallel machining raises issues with respect to computer aided process planning which have not been dealt with in the past. In this paper, a prototype CAPP system called PMPS, for parallel machining, is described. First, we briefly highlight the new issues to be dealt with in process planning for parallel machining. Next, the architecture and details of PMPS, a generative CAPP system, is described. Finally, the implementation and results are discussed.
The Effect of Workpiece Temperature on the Machinability of an Aluminum/SiC MMC
Authors: Barnes S. , Pashby I. R. , Mok D. K.
Published: February 2008

Metal matrix composites (MMCs) are becoming an increasingly important class of engineering material which are finding applications both in the automotive and aerospace industries. However, their machinability is regarded as poor due to the severe abrasive tool wear observed during machining. Prior to an investigation into the laser-assisted turning of an aluminium/silicon carbide MMC, the machining behaviour of the material after pre-heating to 200, 300, and 400°C was investigated. The results indicated that at cutting speeds from 20–90 m/min the wear rate increased with increasing workpiece temperature although the wear mechanism remained one of abrasion. The presence of a built-up edge (BUE) was noted and a strong correlation found between its presence and the amount of wear produced. The results of this work show that within the range of parameters investigated, the pre-heating of the MMC had a detrimental effect on its machinability.
Design of Forging Process Parameters With Deformation and Temperature Constraints
Authors: Grandhi R. V. , Cheng H. , Kumar S. S.
Published: February 2008

This paper presents a methodology for designing optimal process parameters for forging operations. The nonlinear rigid viscoplastic finite element (FE) method is used for deformation and thermal analyses. From the FE model a state space system is developed for representing the coupled deformation and thermal behavior of the metal forming system. Constraints are imposed on the strain rate and temperature of the deforming work-piece for obtaining the desired physical/microstructural properties in the final product. The linear quadratic regulator (LQR) theory for finite time control is used in designing the initial die temperature and optimal ram velocity schedules. The approach is demonstrated on a plane strain channel section forging under nonisothermal conditions.
Process and Technology Perspectives on Integrated Product Development
Authors: Izuchukwu J. I.
Published: February 2008

This paper discusses the role of automation in not only achieving faster product development and deployment, but also forging better collaboration between the functions responsible for product development and support. It presents how information should be shared, managed, and communicated throughout the product development process. The role of product data management system as an information technology for integrated product development is discussed.
Thermo-Viscoplastic Modeling of Machining Process Using a Mixed Finite Element Method
Authors: Wu Jung-Shu , Dillon O. W. , Lu Wei-Yang
Published: February 2008

This paper considers a thermo-viscoplastic model of the steady state orthogonal machining process by using a three-field mixed finite element method based on the Hu-Washizu variational principle. Assuming a trial chip geometry, work and tool material properties, and cutting conditions (cutting speed, feed rate and rake angle), detailed information on the state of the stresses, deformation, and temperature distributions in the workpiece and tool are obtained. This approach is shown to satisfy the nontrivial stress boundary condition better than the machining model that is based on the compatible displacement finite element method. The heat generated due to the plastic deformation, to the friction, and the heat conducted into the tool are calculated. The effects of the heat conduction and friction on the temperature field are studied. The isothermal machining case is also considered to study the thermal effect on the machining process. Numerical results are given for the aluminum 6061 alloy and pure titanium under several cutting conditions.
Study of Electrochemical Jet Machining Process
Authors: Kozak J. , Rajurkar K. P. , Balkrishna R.
Published: February 2008

Jet Electrochemical Machining (ECJM) employs a jet of electrolyte for anodic dissolution of workpiece material. ECJM is extensively used for drilling small cooling holes in aircraft turbine blades and for producing maskless patterns for microelectronics parts. ECJM process drills small diameter holes and complex shape holes without the use of a profile electrode. One of the most significant problems facing ECJM user industries is the precise control of the process. A theoretical analysis of the process and a corresponding model are required for the development of an appropriate control system. This paper presents a mathematical model for determining the relationship between the machining rate and working conditions (electrolyte jet flow velocity, jet length, electrolyte properties, and voltage) of ECJM. This model describes a distribution of electric field and the effect of change of conductivity of electrolyte (caused by heating) on the process performance. A maximum dissolution rate is determined from the allowable increase of electrolyte temperature. Experimental verification of theoretical results is also presented.
Active Thermal Preload Regulation for Machine Tool Spindles With Rolling Element Bearings
Authors: Tu J. F. , Stein J. L.
Published: February 2008

Modern machine tools are required to operate at wide speed ranges for higher productivity and quality. Because spindle bearings generate a large amount of heat at high speeds, the compensation for thermal effects in machine tools becomes exceedingly important. In this paper, a preload model is developed to describe how external cooling (or heating) affects the bearing preload. Based on the model, an active thermal preload regulation scheme is proposed and its feasibility is validated experimentally. The proposed preload regulation scheme is achieved by circulating a cooling (or heating) flow around the spindle housing to manipulate the housing and the outer ring temperatures. The results show that thermal preload is highly sensitive to the spindle outer ring and housing temperatures, and with proper preload level regulated by the cooling flow, the bearing runs steadier with less thermal preload fluctuations and is less disturbed by external loading. The results are significant for modern high performance spindle designs where different preload levels are required to cope with different machining conditions and where cooling is adopted to remove the large amount of heat produced at high speeds.
An Innovative Approach to Increase the Accuracy of Multi-Axis Machines for Process-Intermittent Inspection
Authors: Mou J. , Liu C. R.
Published: February 2008

A method for enhancing the effectiveness and robustness of process-intermittent inspection is presented. The method is developed first using mathematical models and measurements closely related to the real parts, thus reducing the uncertainty in both the error estimation and compensation for multi-axis machines. A predictive search algorithm is then developed to identify the minimum number of appropriate measuring points (with respect to the designated tolerance) for arbitrarily shaped manufacturing parts. The identified measuring points are robust in that they least sensitive to uncertainties in measurement and modeling. The search algorithm uses computer simulation with information obtained from previous measurements. Consequently, the measurement effort involved in error modeling has been greatly reduced. The error model derived from the method can be used to correct the process-intermittent probing data for a more accurate assessment of workpiece dimensions. Although the method is designed for general application in multi-axis machines (i.e., machine tools, robots, and coordinate measuring machines), this paper focuses on the specific application of a machining center. Experimental results demonstrate the effectiveness of the error modeling method for accuracy improvement of the machining center for process-intermittent inspection.
Thermal Evaluation of a Dry Nonrotating Thin Section Contact Bearing
Authors: Spence E. W. , Kaminski D. A.
Published: February 2008

The thermal resistance of an angular contact ball bearing as a function of the radial and axial load is investigated numerically. An elastic stress analysis, based on Hertzian contact theory, provides circumferentially-varying contact areas for input to the thermal model. A finite difference model of the combined conductive, convective and radiative transport from the inner to outer race is used to calculate the overall thermal resistance of the bearing.
Heating Effects in the Drawing of Wire and Strip Under Hydrodynamic Lubrication Conditions
Authors: Lucca D. A. , Wright R. N.
Published: February 2008

The use of high metal processing speeds to meet the demands for increased productivity has focused attention on the pronounced heating of tooling and workpiece which occurs under these conditions. In the present study, heating under hydrodynamic conditions in wire and strip drawing is addressed by considering a two-dimensional representation of the tool-lubricant-workpiece interface. An analytical formulation is presented for prediction of the resultant temperatures. The model considers deformation heating in the strip, lubricant viscosity to be a function of temperature and pressure, and matches the heat flux at the strip-lubricant boundary. Convection of heat in the lubricant film is considered. The model is constructed in terms of the governing non-dimensional parameters and solved by a Crank-Nicolson finite difference technique. By comparison with solutions which do not consider convection, it is found that convection only begins to play a role in the resulting temperatures when the Graetz number U0h02/αLl is greater than 0.4. For the high speed drawing of aluminum with mineral oil used as a lubricant, the model predicts a monotonic increase in mean lubricant temperatures from 366 K to 404 K over a range of initial strip velocities of 20.3 m/s to 50.8 m/s. The maximum strip surface temperature is predicted to monotonically decrease from 345 K to 335 K over this range of strip velocities. The ratio (kLρLcpL/ksρscpS)1/2 is shown to be important in determining the relative temperatures of lubricant and strip. Results are compared to those metalworking analyses which do not consider the role of the lubricant film.
Quantum Information Matters
Authors: Lloyd Seth
Published: February 2008

This Perspective discusses the role that quantum information plays in determining the quantum-mechanical aspects of matter. Beginning with the entwined concepts of information and entropy, the article discusses how quantum information theory can supply us with novel concepts and techniques for understanding how matter behaves at the most microscopic of levels.
Prevalence of Plasmid-Mediated AmpC β-Lactamases in a Chinese University Hospital from 2003 to 2005: First Report of CMY-2-Type AmpC β-Lactamase Resistance in China
Authors: Li Yi , Li Qing , Du Yuzhen , Jiang Xiaofei , Tang Jin , Wang Jianqiang , Li Guilan , Jiang Yanqun
Published: February 2008

The aim of this study was to investigate the prevalences of plasmid-mediated AmpC β-lactamases (PABLs) in isolates of
Escherichia coli
and
Klebsiella
spp. from a university hospital in China. A total of 1,935 consecutive nonrepeat clinical isolates of
Escherichia coli
,
Klebsiella pneumoniae
, and
Klebsiella oxytoca
were collected between January 2003 and July 2005. The isolates with cefoxitin zone diameters less than 18 mm (screen positive) were selected for PCR of the
bla
AmpC
genes and sequencing. Fifty-four (2.79%) isolates harbored PABLs, as demonstrated by PCR and isoelectric focusing. Sequence analysis revealed the presence of
bla
DHA-1
and
bla
CMY-2
genes. The Southern blot hybridization studies confirmed that
bla
CMY-2
and
bla
DHA-1
were located on plasmids. Based on species, PABLs were detected in 4.29% (29 isolates of DHA-1 and 1 isolate of CMY-2) of
K. pneumoniae
, 1.91% (11 isolates of DHA-1 and 12 isolates of CMY-2) of
E. coli
, and 3.03% (1 isolate of DHA-1) of
K. oxytoca
isolates. In contrast to our anticipation, the occurrence rate of DHA-1-producing
K. pneumonia
significantly decreased (
P
< 0.01), from 7.54% in 2003 to 2.72% in 2004. The results of random amplified polymorphic DNA analysis indicate that the prevalences of DHA-1-producing
K. pneumoniae
and CMY-2-producing
E. coli
strains were not due to epidemic strains. In conclusion, DHA-1 was the most prevalent acquired AmpC beta-lactamase in this collection of isolates from a medical center in China, and DHA-1-producing
K. pneumoniae
was the most prevalent bacterium harboring a PABL. To the best of our knowledge, this is the first report of CMY-2-type AmpC β-lactamases in the Chinese mainland.
Identifying Infections with Respiratory Syncytial Virus by Using Specific Immunoglobulin G (IgG) and IgA Enzyme-Linked Immunosorbent Assays with Oral-Fluid Samples
Authors: Okiro Emelda A. , Sande Charles , Mutunga Martin , Medley Graham F. , Cane Patricia A. , Nokes D. James
Published: February 2008

Currently, respiratory syncytial virus (RSV) infection is identified in epidemiological studies by virus antigen or nucleic acid detection in combination with serology. Oral-fluid specimens may provide a noninvasive alternative to blood, and oral fluid is more suitable for sampling outside of the clinic setting. We evaluated an indirect enzyme-linked immunosorbent assay for the detection of RSV-specific immunoglobulin G (IgG) and IgA by using oral-fluid samples collected from individuals with RSV infections confirmed by an immunofluorescent antibody test. For five children sampled repeatedly from birth, antibody profiles in oral fluid quite consistently tracked those in paired sera, and RSV infections were detected by rising titers of antibodies of at least one Ig class. Specific IgG responses were generally more reliable than IgA responses, except in early infancy, where the reverse was sometimes true. For a further five young children from whom oral fluid was collected weekly following RSV infection, boosted antibody responses, frequently of a transient nature, lasting a few weeks, were observed; specific IgG responses were of longer duration and more pronounced than specific IgA responses. Our data show significant promise for the use of oral fluid alone in RSV infection surveillance. The observed rapid dynamics of the antibody responses are informative in defining study sampling intervals.
Rapid PCR-Based Diagnosis of Septic Arthritis by Early Gram-Type Classification and Pathogen Identification
Authors: Yang Samuel , Ramachandran Padmini , Hardick Andrew , Hsieh Yu-Hsiang , Quianzon Celeste , Kuroki Marcos , Hardick Justin , Kecojevic Aleksandar , Abeygunawardena Avanthi , Zenilman Jonathan , Melendez Johan , Doshi Vishal , Gaydos Charlotte , Rothman Richard E.
Published: February 2008

Septic arthritis (SA) is a rheumatologic emergency associated with significant morbidity and mortality. Delayed or inadequate treatment of SA can lead to irreversible joint destruction and disability. Current methods of diagnosing SA rely on synovial fluid analysis and culture which are known to be imprecise and time-consuming. We report a novel adaptation of a probe-based real-time PCR assay targeting the 16S rRNA gene for early and accurate diagnosis of bacterial SA. The assay algorithm consists of initial broad-range eubacterial detection, followed by Gram typing and species characterization of the pathogen. The platform demonstrated a high analytical sensitivity with a limit of detection of 10
1
CFU/ml with a panel of SA-related organisms. Gram typing and pathogen-specific probes correctly identified their respective targets in a mock test panel of 36 common clinically relevant pathogens. One hundred twenty-one clinical synovial fluid samples from patients presenting with suspected acute SA were tested. The sensitivity and specificity of the assay were 95% and 97%, respectively, versus synovial fluid culture results. Gram-typing probes correctly identified 100% of eubacterial positive samples as to gram-positive or gram-negative status, and pathogen-specific probes correctly identified the etiologic agent in 16/20 eubacterial positive samples. The total assay time from sample collection to result is 3 h. We have demonstrated that a real-time broad-based PCR assay has high analytical and clinical performance with an improved time to detection versus culture for SA. This assay may be a useful diagnostic adjunct for clinicians, particularly those practicing in the acute care setting where rapid pathogen detection and identification would assist in disposition and treatment decisions.
Interaction between Simian Virus 40 Large T Antigen and Insulin Receptor Substrate 1 Is Disrupted by the K1 Mutation, Resulting in the Loss of Large T Antigen-Mediated Phosphorylation of Akt
Authors: Yu Yongjun , Alwine James C.
Published: February 2008

The cellular kinase Akt is a key controller of cellular metabolism, growth, and proliferation. Many viruses activate Akt due to its beneficial effects on viral replication. We previously showed that wild-type (WT) simian virus 40 (SV40) large T antigen (TAg) inhibits apoptosis via the activation of PI3K/Akt signaling. Here we show that WT TAg expressed from recombinant adenoviruses in U2OS cells induced the phosphorylation of Akt at both T308 and S473. In contrast, Akt phosphorylation was eliminated by the K1 mutation (E107K) within the retinoblastoma protein (Rb) binding motif of TAg. This suggested that Akt phosphorylation may depend on TAg binding to Rb or one of its family members. However, in Rb-negative SAOS2 cells depleted of p107 and p130 by using small hairpin RNAs (shRNAs), WT TAg still mediated Akt phosphorylation. These results suggested that the K1 mutation affects another TAg function. WT-TAg-mediated phosphorylation of Akt was inhibited by a PI3K inhibitor, suggesting that the effects of TAg originated upstream of PI3K; thus, we examined the requirement for insulin receptor substrate 1 (IRS1), which binds and activates PI3K. Depletion of IRS1 by shRNAs abolished the WT-TAg-mediated phosphorylation of Akt. Immunoprecipitation studies showed that the known interaction between TAg and IRS1 is significantly weakened by the K1 mutation. These data indicate that the K1 mutation disrupts not only Rb binding but also IRS1 binding, contributing to the loss of activation of PI3K/Akt signaling.
Identification and Characterization of the Product Encoded by ORF69 of Kaposi's Sarcoma-Associated Herpesvirus
Authors: Santarelli R. , Farina A. , Granato M. , Gonnella R. , Raffa S. , Leone L. , Bei R. , Modesti A. , Frati L. , Torrisi M. R. , Faggioni A.
Published: February 2008

We report the identification and characterization of p33, the product of Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame 69 (ORF69), a positional homolog of the conserved herpesvirus protein UL31. p33 is expressed upon induction of viral lytic cycle with early kinetics. Immunofluorescence analysis revealed that in infected cell lines, the protein is localized in the nucleus, both in dotted spots and along the nuclear membrane. Nuclear fractionation experiments showed that p33 partitions with the nuclear matrix, and both immunoblotting of purified virions and immunoelectron microscopy indicated that the novel protein is not a component of the mature virus. Following ectopic expression in KSHV-negative cells, the protein was never associated with the nuclear membrane, suggesting that p33 needs to interact with additional viral proteins to reach the nuclear rim. In fact, after cotransfection with the ORF67 gene, the KSHV positional homolog of UL34, the p33 intranuclear signal changed and the two proteins colocalized on the nuclear membrane. A similar result was obtained when ORF69 was cotransfected with BFRF1, the Epstein-Barr virus (EBV) positional homolog of UL34 and ORF67. Finally, upon cotransfection, ORF69 significantly increased nuclear membrane reduplications induced by BFRF1. The above results indicate that KSHV p33 shares many similarities with its EBV homolog BFLF2 and suggest that functional cross-complementation is possible between members of the gammaherpesvirus subfamily.
Conferral of Enhanced Natural Killer Cell Function by KIR3DS1 in Early Human Immunodeficiency Virus Type 1 Infection
Authors: Long Brian R. , Ndhlovu Lishomwa C. , Oksenberg Jorge R. , Lanier Lewis L. , Hecht Frederick M. , Nixon Douglas F. , Barbour Jason D.
Published: February 2008

A flurry of recent reports on the role of activating and inhibitory forms of the killer cell immunoglobulin-like receptors (KIR) in natural killer (NK) cell activity against human immunodeficiency virus type 1 (HIV-1) have yielded widely divergent results. The role of the activating NK receptor encoded by the
KIR3DS1
allele and its putative ligands, members of the HLA class I
Bw4Ile80
cluster, in early HIV-1 disease is controversial. We selected 60 treatment-naïve adults for study from the OPTIONS cohort of individuals with early HIV-1 infection in San Francisco. We performed NK cell functional assays measuring gamma interferon (IFN-γ) and CD107a expression by NK cells in the unstimulated state and after stimulation by the major histocompatibility complex class I-deficient 721.221 B-lymphoblastoid cell line. In addition, we measured CD38 expression (a T-cell activation marker) on T and NK cells. Persons who have at least one copy of the
KIR3DS1
gene had higher IFN-γ and CD107a expression in the unstimulated state compared to those who do not possess this gene. After stimulation, both groups experienced a large induction of IFN-γ and CD107a, with
KIR3DS1
carriers achieving a greater amount of IFN-γ expression. Differences in effector activity correlating with
KIR3DS1
were not attributable to joint carriage of HLA
Bw4Ile80
and
KIR3DS1
. We detected a partial but not complete dependence of KIR3DS1 on the members of B*58 supertype (B*57 and B*58) leading to higher NK cell function. Possessing
KIR3DS1
was associated with lower expression of CD38 on both CD8
+
T and NK cells and with a loss or weakening of the known strong associations between CD8
+
T-cell expression of CD38 mean fluorescence intensity and the HIV-1 viral load. We observed that possessing
KIR3DS1
was associated with higher NK cell effector functions in early HIV-1 disease, despite the absence of HLA
Bw4Ile80
, a putative ligand of KIR3DS1. Carriage of
KIR3DS1
was associated with diminished CD8
+
T-cell activation, as determined by expression of CD38, and a disruption of the traditional relationship between viral load and activation in HIV-1 disease, which may lead to better clinical outcomes for these individuals.
Seymouria sanjuanensis (Amphibia, Batrachosauria) from the Lower Permian Cutler Formation of north-central New Mexico and the occurrence of sexual dimorphism in that genus questioned
Authors: Berman David S , Reisz Robert R. , Eberth David A.
Published: February 2008

Six specimens of the amphibian Seymouria, preserved in a single block of matrix from the Lower Permian Cutler Formation of north-central New Mexico, are described and referred to Seymouria sanjuanensis Vaughn. They are the only Seymouria specimens known from New Mexico and provide a more extensive definition of the species. It is interpreted that the specimens from New Mexico were collected from an early to middle Wolfcampian horizon and therefore represent the earliest known members of the genus. Evidence is presented that challenges previous explanations for the variability of several features of the skull and axial skeleton in specimens of Seymouria baylorensis and S. sanjuanensis as an indication of sexual dimorphism. Differences in the number of maxillary teeth, depth of the maxilla, and development of the maxillary dentition, particularly in the "canine" region, are interpreted as closely related morphological trends in Seymouria. Although no satisfactory explanation is offered for differences in the serial position of the first haemal arch and in the interorbital breadth, sexual dimorphism is considered very unlikely.
Ordovician paleomagnetic results from the St. George and Table Head carbonates of western Newfoundland
Authors: Deutsch Ernst R. , Prasad Jagat N.
Published: February 2008

We have studied 85 limestone and dolostone samples from 21 sites of the St. George and Table Head groups (Lower and Middle Ordovician) on Port au Port Peninsula (Humber Zone). Their gentle (~15°) tilt is probably Devonian. A steep viscous component dominant in the natural remanence is removed by thermal and (less efficiently) alternating-field demagnetization. In about 60% of all samples, the thermal treatment yielded a southeasterly reverse component ("A"), which typically remained blocked to 450–500 °C and then decayed to noise. Mean A component directions calculated from Zijderveld plots and referred to bedding are D, I = 148.5°, +33.6 °for N = 9 St. George sites and D, I = 150.0°, I = +40.7 °for N = 5 Table Head sites. Corresponding antipoles are 17.5°N, 152.3°E, dp, dm = 2.8°, 4.9 °and 13.4°N, 149.2°E, dp, dm = 2.9°, 4.7°, respectively. We interpret these results as representative of the geomagnetic field in the Early and mid-Ordovician. In 14 samples, mainly from the older St. George strata, thermal treatment yielded a reverse ("B") component with mean direction D, I = 167.9°, −9.2°, corresponding to an antipole at 44.9°N, 138.2°E, dp, dm = 3.6°, 7.1°. We interpret this as a late Paleozoic overprint in diagenetic hematite. The 30° anticlockwise rotation of Newfoundland proposed by Wegener is not supported by our data.
Viscosité magnétique potentielle, aimantation détritique et viscosité réelle d'un sédiment lacustre quaternaire
Authors: Biquand Daniel , Sémah François
Published: February 2008

The magnetic viscosity of sediments, as indicated by thermal demagnetization of natural remanent magnetization (NRM), depends on two main parameters: (i) the specific magnetic viscosity of the material and (ii) the efficiency of the primary magnetization process. In an attempt to determine the relative importance of these two variables, we studied a Lower Pleistocene lacustrine sequence bearing a primary reversed detrital remanent magnetization (DRM).Using natural samples and small cores made of crushed sediment, our study is based on the thermodynamic theory of rock magnetism developed by L. Néel, who established an equivalence between time and temperature, that is, between viscous remanent (VRM) and thermoremanent (TRM) magnetization processes. The determination of the blocking temperature spectra from 20 to 152 °C allows us to calculate the maximum theoretical VRM acquired in situ at each horizon, while the detailed thermal study of the NRM permits an appraisal of the DRM quality. This leads us to define a geological viscosity index, which accounts, in a rather convincing manner, for the behaviour of the samples observed during the classical paleomagnetic study. For the section studied, it appears that the variations of this index are closely correlated with the efficiency of the DRM acquisition process.
THE MAXWELL LAGRANGIAN IN PURELY AFFINE GRAVITY
Authors: POPŁAWSKI NIKODEM J.
Published: February 2008

The purely affine Lagrangian for linear electrodynamics, that has the form of the Maxwell Lagrangian in which the metric tensor is replaced by the symmetrized Ricci tensor and the electromagnetic field tensor by the tensor of homothetic curvature, is dynamically equivalent to the Einstein–Maxwell equations in the metric–affine and metric formulation. We show that this equivalence is related to the invariance of the Maxwell Lagrangian under conformal transformations of the metric tensor. We also apply to a purely affine Lagrangian the Legendre transformation with respect to the tensor of homothetic curvature to show that the corresponding Legendre term and the new Hamiltonian density are related to the Maxwell–Palatini Lagrangian for the electromagnetic field. Therefore the purely affine picture, in addition to generating the gravitational Lagrangian that is linear in the curvature, justifies why the electromagnetic Lagrangian is quadratic in the electromagnetic field.
SCALING BEHAVIOR FOR RESISTANCE TRANSITION IN Hg-1223 SUPERCONDUCTOR UNDER PRESSURE
Authors: LIU S. L. , SHAO H. M. , HAN C. Y.
Published: February 2008

The effects of high pressure on the temperature dependence of the resistance transition of Hg -1223 superconductor are measured up to 7.8 GPa. At a pressure lower than 5.4 GPa, Tc increases from 130 K to a maximal value of 140 K with a rate of 1.85 K/GPa. At higher pressure, Tc begins to decrease. This pressure dependence of critical temperature can be explained with the sheet charge model, which introduces the inhomogeneous charge distribution in the inner and outer CuO 2 layer(s). The temperature dependence of the resistance under various pressure can be scaled onto a single curve with P=0ρ(T)=Pρ(aT), where the scaling parameter a is estimated to be smaller than 1. Further, the scaling parameter a reflects the relative change of the anisotropy factor γ.
LOCALIZED EXCITATIONS WITH AND WITHOUT PROPAGATING PROPERTIES IN (2+1)-DIMENSIONS VIA A REDUCTION APPROACH
Authors: QIANG JI-YE , MA SONG-HUA , ZHENG CHUN-LONG
Published: February 2008

In this paper, an objective reduction approach (a special conditional reduction approach) is presented. As a concrete application in nonlinear physical system, new types of variable separation solutions (including solitary wave solutions, periodic wave solutions, and rational function solutions) with arbitrary functions for the (2+1) -dimensional modified dispersive long-wave system are derived via the objective reduction approach. As special reduction cases based on the derived variable separation solutions, it is shown that some localized coherent structures like nonpropagating and propagating solitons with physical meaning exist in the (2+1) -dimensional modified dispersive long-wave system by prescribing different values of the arbitrary parameters in this short note.
Summary of progress in geomorphologic modelling of continental slope canyons
Authors: Mitchell Neil C.
Published: February 2008

Far less is known of the processes involved in erosion of submarine channels compared with channels eroded subaerially by water runoff, but geometrical properties derived for canyons of the USA Atlantic continental slope reveal some intriguing similarities. Slope-confined canyons are concave-upwards, displaying decreasing channel gradient with increasing contributing area, as observed in many bedrock-eroding rivers. Tributaries join principal channels at the same elevation (without intervening waterfalls), in effect obeying Playfair's law, as do many river networks. Gradient and contributing area data for channels at confluences also reveal a tendency for tributaries to have steeper gradients than their associated principal channels, reflecting their smaller drainage areas. The concavities of bedrock-eroding rivers are often explained by a balance between river discharge, which increases with increasing rainfall catchment area, and gradient, which declines to offset the erosive effect of the discharge. It is unclear, however, if such a balance can be invoked for submarine canyons because erosion is probably caused when sedimentary flows are active only in individual canyon branches, originating from isolated slope failures. Instead, the frequency of sedimentary flows experienced by canyon floors may increase downstream simply because the area of unstable canyon walls available to source sedimentary flows increases, and this effect becomes compensated by declining gradient. Knickpoints created by faults in tectonically active slopes provide a further way to infer the form of erosion by sedimentary flows. Such knickpoints typically lie upstream of the faults that probably generate them, implying that detachment-limited erosion is enhanced where sedimentary flows become more vigorous on steep gradients, leading to knickpoint migration.
Evaluating the perceptual realism of animated facial expressions
Authors: Wallraven Christian , Breidt Martin , Cunningham Douglas W. , Bülthoff Heinrich H.
Published: February 2008

The human face is capable of producing an astonishing variety of expressions—expressions for which sometimes the smallest difference changes the perceived meaning considerably. Producing realistic-looking facial animations that are able to transmit this degree of complexity continues to be a challenging research topic in computer graphics. One important question that remains to be answered is: When are facial animations good enough? Here we present an integrated framework in which psychophysical experiments are used in a first step to systematically evaluate theperceptualquality of several different computer-generated animations with respect to real-world video sequences. The first experiment provides an evaluation of several animation techniques, exposing specific animation parameters that are important to achieve perceptual fidelity. In a second experiment, we then use these benchmarked animation techniques in the context of perceptual research in order to systematically investigate the spatiotemporal characteristics of expressions. A third and final experiment uses the quality measures that were developed in the first two experiments to examine the perceptual impact of changing facial features to improve the animation techniques. Using such an integrated approach, we are able to provide important insights into facial expressions for both the perceptual and computer graphics community.
C-testable bit parallel multipliers over
GF
(2

m

)
Authors: Rahaman H. , Mathew J. , Pradhan D. K. , Jabir A. M.
Published: February 2008

We present a C-testable design of polynomial basis (PB) bit-parallel (BP) multipliers over GF(2

m

) for 100% coverage of stuck-at faults. Our design method also includes the method for test vector generation, which is simple and efficient. C-testability is achieved with three control inputs and approximately 6% additional hardware. Only 8 constant vectors are required irrespective of the sizes of the fields and primitive polynomial. We also present a Built-In Self-Test (BIST) architecture for generating the test vectors efficiently, which eliminates the need for the extra control inputs. Since these circuits have critical applications as parts of cryptography (e.g., Elliptic Curve Crypto (ECC) systems) hardware, the BIST architecture may provide with added level of security, as the tests would be done internally and without the requirement of probing by external testing equipment. Finally we present experimental results comprising the area, delay and power of the testable multipliers of various sizes with the help of the Synopsys® tools using
UMC 0.18
micron CMOS technology library.
A new efficient retiming algorithm derived by formal manipulation
Authors: Zhou Hai
Published: February 2008

A new efficient algorithm is derived for the minimal period retiming by formal manipulation. Contrary to all previous algorithms, which used fixed period feasibility checking to binary-search a candidate range, the derived algorithm checks the optimality of a feasible period directly. It is much simpler and more efficient than previous algorithms. Experimental results showed that it is even faster than ASTRA, an efficient heuristic algorithm. Since the derived algorithm is incremental by nature, it also opens the opportunity to be combined with other optimization techniques.
Interrupt modeling for efficient high-level scheduler design space exploration
Authors: Johnson F. Ryan , Paul Joann M.
Published: February 2008

Single Chip Heterogeneous Multiprocessors executing a wide variety of software are increasingly common in consumer electronics. Because of the mix of real-time and best effort software across the entire chip, a key design element of these systems is the choice of scheduling strategy. Without task migration, the benefits of single chip processing cannot be fully realized. Previously, high-level modeling environments have not been capable of modeling asynchronous events such as interrupts and preemptive scheduling while preserving the performance benefits of high level simulation. This paper shows how extensions to Modeling Environment for Software and Hardware (MESH) enable precise modeling of these asynchronous events while running more than 1000 faster than cycle-accurate simulation. We discuss how we achieved this and illustrate its use in modeling preemptive scheduling. We evaluate the potential of migrating running tasks between processors to improve performance in a multimedia cell phone example. We show that by allowing schedulers to rebalance processor loads as new tasks arrive significant performance gains can be achieved over statically partitioned and dynamic scheduling approaches. In our example, we show that system response time can be improved by as much as 1.96 times when a preemptive migratory scheduler is used, despite the overhead incurred by scheduling tasks across multiple processors and transferring state during the migration of running tasks. The contribution of this work is to provide a framework for evaluating preemptive scheduling policies and task migration in a high level simulator, by combining the new ability to model interrupts with dramatically increased efficiency in the high-level modeling of scheduling and commuincation MESH already provides.
Tailoring circuit-switched network-on-chip to application-specific system-on-chip by two optimization schemes
Authors: Chang Kuei-Chung , Shen Jih-Sheng , Chen Tien-Fu
Published: February 2008

As the number of cores on a chip increases, power consumed by the communication structures takes a significant portion of the overall power budget. In this article, we first propose a circuit-switched interconnection architecture which uses
crossroad switches
to construct dedicated channels dynamically between any pairs of cores for nonhuge application-specific SoCs. The structure of the crossroad switch is simple, which can be regarded as a NoC-lite router, and we can easily construct a low-power on-chip network with these switches by a system-level design methodology. We also present the design methodology to tailor the proposed interconnection architecture to low-power structures by two proposed optimization schemes with profiled communication characteristics. The first scheme is power-aware topology construction, which can build low-power application-specific interconnection topologies. To further reduce the power consumption, we propose the second optimization scheme to predetermine the operating mode of dual-mode switches in the NoC at runtime. We evaluate several interconnection techniques, and the results show that the proposed architecture is more low-power and high-performance than others under some constraints and scale boundaries. We take multimedia applications as case studies, and experimental results show the power savings of power-aware topology approximate to 49% of the interconnection architecture. The power consumption can be further reduced approximately 25% by applying partially dedicated path mechanism.
Wavelet-based dynamic power management for nonstationary service requests
Authors: Abbasian A. , Hatami S. , Afzali-Kusha A. , Pedram M.
Published: February 2008

In this article, a wavelet-based dynamic power management policy (WBDPM) is proposed. In this approach, the workload source (service requester) is modeled by a nonstationary time series which, in turn, represented by a nondecimated Haar wavelet as its basis. The proposed approach is robust and has the ability to minimize energy dissipation under different performance constraints. To assess the accuracy of the model, the algorithm was implemented for data extracted from the hard disks of computers. Prediction results of this approach for the case of a nonstationary service requester exhibit accuracies of more than 95%.
Synthesis of a novel timing-error detection architecture
Authors: Su Yu-Shih , Chang Po-Hsien , Chang Shih-Chieh , Hwang Tingting
Published: February 2008

Delay variation can cause a design to fail its timing specification. Ernst et al. [2003] observe that the worst delay of a design is least probable to occur. They propose a mechanism to detect and correct occasional errors while the design can be optimized for the common cases. Their experimental results show significant performance (or power) gain as compared with the worst-case design. However, the architecture in Ernst et al. [2003] suffers the short path problem, which is difficult to resolve. In this article, we propose a novel error-detecting architecture to solve the short path problem. Our experimental results show considerable performance gain can be achieved with reasonable area overhead.
Chip placement in a reticle for multiple-project wafer fabrication
Authors: Wu Meng-Chiou , Lin Rung-Bin , Tsai Shih-Cheng
Published: February 2008

Chip placement in a reticle is crucial to the cost of a multiproject wafer run. In this article we develop several chip placement methods based on the volume-driven compatibility optimization (VOCO) concept, which maximizes dicing compatibility among chips with large-volume requirements while minimizing reticle dimensions. Our mixed-integer linear programming models with VOCO are too complex to render good solutions for large test cases. Our B*-tree with VOCO and HQ with VOCO use 16%∼ 29% fewer wafers and 8%∼ 19% less reticle area than the hierarchical quadrisection (HQ) method proposed by Kahng et al. [2005]
Personalizing access to learning networks
Authors: Dolog Peter , Simon Bernd , Nejdl Wolfgang , Klobučar Tomaž
Published: February 2008

In this article, we describe a
Smart Space for Learning™
(SS4L) framework and infrastructure that enables personalized access to distributed heterogeneous knowledge repositories. Helping a learner to choose an appropriate learning resource or activity is a key problem which we address in this framework, enabling personalized access to federated learning repositories with a vast number of learning offers. Our infrastructure includes personalization strategies both at the query and the query results level. Query rewriting is based on learning and language preferences; rule-based and ranking-based personalization improves these results further. Rule-based reasoning techniques are supported by formal ontologies we have developed based on standard information models for learning domains; ranking-based recommendations are supported through ensuring minimal sets of predicates appearing in query results. Our evaluation studies show that the implemented solution enables learners to find relevant learning resources in a distributed environment and through goal-based personalization improves relevancy of results.