bluuebunny/crossref_metadata_2025 huggingface dataset:
Producing Extra-Heavy Oil From the Orinoco Belt, Cerro Negro Area, Venezuela, Using Bottom-Drive Progressive Cavity Pumps
Authors: Ramos M. A. , Brown J. C. , Rojas M. , Kuyucu O. , Flores J. G.
Published: December 2007

The traditional means of artificial lift production for vertical and deviated wells in the Orinoco oil belt in eastern Venezuela used to be rod pumping and top-drive progressive cavity pumps (PCPs), particularly for wells with production rates ranging from 200 to 600 barrels of oil per day (BOPD) of extra-heavy oil (8°API gravity and viscosities of 2,000 cp at a reservoir temperature of 133°F). After 1995, with the implementation of horizontal drilling technologies for the construction of wells in unconsolidated sandstones, electrical submersible pumps (ESPs) became an alternative to handle higher production volumes (Ramos and Rojas 2001). More recently, top-drive PCPs have also been installed to produce extra-heavy oil at high rates.

Hybrid artificial lift technologies, such as bottom-drive progressive cavity pumping, which combine features of the ESP and the PCP systems, have recently been successfully evaluated in the Orinoco belt to exploit extra-heavy oil reserves economically. A typical completion assembly includes a multisensor gauge to obtain downhole pressures, temperatures, and vibration amplitudes of the system, and to detect power-cable current leaks; a four-pole motor; a protector; a 4:1-ratio gear box; and the PCP. The functional design of the bottom-drive PCP facilitates the handling of viscous and abrasive fluids, increases the flow rate, and diminishes the operational costs. Further advantages of this application include the complete elimination of tubing wear by eliminating the need for a rod string, greater torque capacity, lower surface maintenance cost, lower load and horsepower requirements, and lower frictional losses.

The application of bottom-drive PCPs in the Cerro Negro area has resulted in production rates of up to 1,000 BOPD of extra-heavy oil with 50% lower horsepower requirements in comparison to those of conventional top-drive PCP systems.
Challenging Convention in Sand Control: Southern North Sea Examples
Authors: McPhee Colin , Farrow Chris , McCurdy Phil
Published: December 2007

Sand production is a major issue facing many operators in the mature southern North Sea (SNS) gas fields. Historically, sand-control completion decisions have often been based on the assumption that sand control will occur and have been constrained by the restrictions imposed upon sand entering the gas transport pipeline. The inherent conservatism of this approach leads to significant increases in completion costs and misses potential productivity gains.

A holistic sand management strategy has been developed for the southern North Sea to challenge the conservative paradigm. This is based on a complete understanding of SNS reservoir rock properties and sand control completion performance in gas wells and has been tuned by learnings from SNS and analogous fields. It combines sand failure prediction, methodical and structured selection of sand control approach (including consideration of production performance, longevity, and risks), and novel solids lifting and erosion assessment models to achieve better quantification of the risk and consequences of sand production for wells and facilities. Key selection criteria are used instead of arbitrary decisions based on limited and often unaudited data. The role of an asset focal point with clear ownership of all relevant sand production data and issues is fundamental to the success of this integrated strategy.

Tools are available to predict when, where, and even how much sand will be produced, how much sand will be lifted to surface, and how much erosion it will cause. Methodologies are also available to evaluate and rank the available sand-control techniques in a consistent and systematic manner.

This systematic and integrated approach to sand management has enhanced well productivity and reduced completion costs without compromising sand management or exceeding sand production constraints. Challenging sand management convention in the demanding environment of the SNS compels operators to use these methodologies to much greater effect.
Development of a Correlation Between Performance of CO2 Flooding and the Past Performance of Waterflooding in Weyburn Oil Field
Authors: Asghari Koorosh , Dong Mingzhe , Shire Jessie , Coleridge Tom , Nagrampa Janelle , Grassick Jessie
Published: December 2007

Weyburn oil field, located in southeast Saskatchewan, has been the site of one of the largest carbon dioxide (CO2) flooding projects in the world since September 2000.

In this paper, data of the past performance of waterflooding in the Weyburn field was used to develop empirical correlations to predict the performance of CO2 flooding. Two different correlations were developed based on CO2-injection schemes in Wey-burn. The first correlation is based on a water-alternating-gas (WAG) process through vertical wells, and the second correlation is based on the cases in which CO2 is injected through horizontal wells and water is injected separately through vertical wells. The first step was to collect and analyze production data from 1958 to 2004. Oil-production rates for both waterflooding and CO2 flooding periods, water-injection rates, and CO2-injection rates were used in developing the correlations. The empirical model for injecting CO2 and water through vertical wells was verified using the Kinder Morgan CO2 flood-scoping model (this is not a trademark product) and actual field production data. The comparative analysis showed 12% error between our simple correlation and the Kinder Morgan model. For injecting CO2 in horizontal wells, the correlation could not be verified against the Kinder Morgan model, but the correlation followed the actual oil production in the field very closely.

This new model can be used effectively as a screening tool for predicting the performance of CO2 flooding in various locations in the Weyburn reservoir based on the data obtained from past waterflooding performance and the rate of CO2 injection. Therefore, it can contribute significant savings in time and expense to the operating oil company. Also, this approach can be used for other potential CO2-flooding processes in reservoirs with histories and properties similar to those of the Weyburn field.
Heavy metals speciation in soakaways sediment and evaluation of metal retention properties of surrounding soil
Authors: Hossain M.A. , Furumai H. , Nakajima F. , Aryal R.K.
Published: December 2007

Heavy metals speciation analysis was carried out on sediment samples accumulated within soakaways in an old stormwater infiltration facility in Tokyo, Japan and on a soil core sample collected near the facility. Heavy metals content in soakaways sediments were much elevated compared to nearby surface soil with the content for Zn, Pb and Cd reaching about 5 to 10 times the content in surface soil. Speciation results revealed that significant amount of the accumulated heavy metals were present in potential mobile fractions, posing threat of release to underlying soil with changing environmental conditions. Detail analyses of soil characteristics indicated significant heterogeneity with depth, especially between the surface soil and underlying soil at site. Decrease in potential adsorption sites with depth was observed in case of underlying soil. Reduced adsorption capacity for heavy metals was evidenced for underlying soil when compared with surface soil. Furthermore, less capability of the soil organic matter to bind heavy metals was evidenced through speciation analyses, which raises concern over the long-term pollution retention potential of the underlying soil receiving infiltrated runoff.
Postnatal Programming of Glucocorticoid Metabolism in Rats Modulates High-Fat Diet–Induced Regulation of Visceral Adipose Tissue Glucocorticoid Exposure and Sensitivity and Adiponectin and Proinflammatory Adipokines Gene Expression in Adulthood
Authors: Boullu-Ciocca Sandrine , Achard Vincent , Tassistro Virginie , Dutour Anne , Grino Michel
Published: December 2007

OBJECTIVE—Alterations of the perinatal environment, which lead to increased prevalence of the metabolic syndrome in adulthood, program an upregulation of systemic and/or adipose tissue glucocorticoid metabolism (11β-hydroxysteroid dehydrogenase type 1 [11β-HSD-1]-induced corticosterone reactivation). We hypothesized that postnatal programming could modulate high-fat diet–induced adipose tissue dysregulation in adulthood.

RESEARCH DESIGN AND METHODS—We compared the effects of chronic (since weaning) high- or low-fat diet in postnatally normofed (control) or overfed (programmed) rats.

RESULTS—Postnatal programming accentuated high-fat diet–induced overweight, insulin resistance, glucose intolerance, and decrease in circulating and epididymal adipose tissue adiponectin. Neither manipulation altered liver function. Postnatal programming or high-fat diet increased systemic corticosterone production, which was not further modified when both manipulations were associated. Postnatal programming suppressed high-fat diet–induced decrease in mesenteric adipose tissue (MAT) glucocorticoid sensitivity and triggered high-fat diet–induced increase in MAT glucocorticoid exposure, subsequent to enhanced MAT 11β-HSD-1 gene expression. MAT tumor necrosis factor (TNF)-α, TNF-receptor 1, interleukin (IL)-6, resistin, and plasminogen activator inhibitor-1 mRNAs were not changed by high-fat feeding in control rats and showed a large increase in programmed animals, with this effect further enhanced by high-fat diet for TNF-α and IL-6.

CONCLUSIONS—Our data show for the first time that postnatal manipulation programs high-fat diet–induced upregulation of MAT glucocorticoid exposure, sensitivity, and inflammatory status and therefore reveal the pivotal role of the environment during the perinatal period on the development of diet-induced adipose tissue dysregulation in adulthood. They also urge the need for clinical trials with specific 11β-HSD-1 inhibitors.
Comparison of Simple Performance Test |E*| of Accelerated Loading Facility Mixtures and Prediction |E*|
Authors: Azari Haleh , Al-Khateeb Ghazi , Shenoy Aroon , Gibson Nelson
Published: December 2007

The dynamic modulus, |E*|, of asphalt mixture has recently drawn much attention in the asphalt community. The |E*| test has been suggested by NCHRP Projects 9-19 and 9-29 as the simple performance test (SPT) to verify the performance characteristics of Superpave® mixture design. In addition, it has been recommended as the potential quality control-quality assurance parameter in the field. The dynamic modulus, |E*|, is an input to the Mechanistic-Empirical Pavement Design Guide (M-E PDG) and also supports the predictive performance models developed as part of NCHRP Project 1-37A. The importance of this parameter on one hand and its time-consuming determination on the other hand necessitated reliable prediction of dynamic moduli of asphalt mixtures at different temperatures and loading frequencies. In this respect, a number of predictive equations have been developed. The most widely used model is the NCHRP 1-37A, which is currently used for calculation of |E*| in Levels 2 and 3 of M-E PDG. The model has a reasonably good prediction capability of high modulus values; however, it tends to over-predict the moduli at the lower spectrum. This study shows that a recent modification to the NCHRP 1-37A model has improved the overall prediction of |E*| but has not significantly improved the overprediction of the lower moduli. While the replacement of the binder viscosity, η, with the binder shear modulus, |G*|, has increased the accuracy of the model, the inclusion of the binder phase angle, δ, in the revised equation was not found to have a significant effect.
Effects of Aggregate Surface and Water on Rheology of Asphalt Films
Authors: Cho Dong-Woo , Bahia Hussain U.
Published: December 2007

Most tests used to evaluate moisture damage require compacted asphalt mixtures. The tests generally simulate field material and conditions and provide a performance-related parameter of moisture effects. In mixtures, however, variable asphalt-aggregate-air void structure contributes to the difficulty of isolating the fundamental rheological properties of an asphalt-aggregate bond. To avoid the complications and obtain the properties of the asphalt-aggregate interface, a new experimental design was developed in this study. This test features a dynamic shear rheometer (DSR) as an improved tool for evaluating interface properties. One key feature of the experimental design is the use of rock disks to simulate an asphalt-aggregate interface. The simulated interface is easily wet-conditioned in a water cup installed on the DSR. From various testing protocols, a stress sweep test that defines a linear viscoelastic (LVE) region is adopted to evaluate the interaction and moisture effects of selected specimens. A viscoelastic characteristic produced from stress sweep tests is recommended as the fundamental property of the interaction and can be used to evaluate moisture effects onto the rheological behavior. One of the critical findings is that the LVE complex modulus, G*, measured at relatively small strains or stresses cannot evaluate the moisture effects on the bond of the asphalt-aggregate interface. The LVE G* measured at high shear stresses are instead much more effective at evaluating such moisture effects. Therefore, the results indicate that the role of moisture damage in pavement problems such as rutting or fatigue needs to be evaluated at design stresses covering a nonlinear viscoelastic range. This study focuses on understanding more the basic characteristics of asphalt-aggregate interface than the bulk properties of mixtures.
Investigation of Superpave Fine Aggregate Angularity Criterion for Asphalt Concrete
Authors: Johnson Ed , Li Xinjun , Zofka Adam , Marasteanu Mihai O. , Clyne Timothy R.
Published: December 2007

Fine aggregate angularity (FAA) requirement is one of the aggregate consensus properties recommended by SHRP. Many state highway departments include FAA as part of their Superpave® mixture design specifications. Recent concerns about pavement performance and aggregate shape have caused these agencies to reinvestigate whether standard FAA testing provides information indicative of performance. This paper presents the results from standard FAA tests and digital imaging to investigate the validity of FAA requirements. Testing was performed on four asphalt mixtures representing a range of FAA values. Dynamic modulus testing was performed at three temperatures and five frequencies, and master curves were obtained using nonlinear regression. Asphalt pavement analyzer data obtained at one temperature were analyzed with respect to the rutting curve and rate of rutting. The experimental results for aggregates and mixtures were analyzed together by using statistical methods to develop correlation coefficients and linear trends. It was found that dynamic modulus and rut resistance values were strongly related to aggregate blend FAA. Some additional parameters from digital imaging also predicted modulus and rut resistance very well and should be included in future research.
Influence of Reaction Times and Anticipation on Stability of Vehicular Traffic Flow
Authors: Treiber Martin , Kesting Arne , Helbing Dirk
Published: December 2007

Two causes for the instability of traffic flow are investigated: the time lag caused by finite accelerations of vehicles and the delay caused by finite reaction times of drivers. Furthermore, the degree to which drivers may compensate for these delays is simulated by looking several vehicles ahead and anticipating future traffic situations. Since vehicular traffic flow is an extended multiparticle system with many degrees of freedom, two concepts of linear stability have to be considered: (a) local stability of a car following a leader that drives at constant velocity and (b) string (chain) stability of a platoon of several vehicles following each other. Typically, string stability is a much more restrictive criterion than local stability. Both types of stability are simulated with the human driver model of M. Treiber et al. [Physica A, Vol. 360, No. 1, 2006, pp. 71-88], which includes all the foregoing features. Several interesting results were found: (a) with a suitable anticipation, string stability for reaction times exceeding the safety time gap was obtained (to the authors' knowledge, this result had not yet been achieved for any other car-following model); (b) parameter changes that destabilize the model variant with zero reaction time may stabilize the model with finite reaction times, and vice versa; and (c) distributed reaction times (every driver has a different reaction time) can stabilize the system compared with the case of drivers with identical reaction times that are equal to the mean.
Study of Freeway Speed Limit Control Based on Three-Phase Traffic Theory
Authors: Kerner Boris S.
Published: December 2007

Speed limit control at freeway bottlenecks is numerically studied on the basis of the Kerner-Klenov microscopic stochastic traffic flow model in the context of Kerner's three-phase traffic theory. It turns out that in some cases speed limit control, rather than preventing traffic breakdown, leads to induced congested pattern emergence at the bottleneck, whereas there is free flow at the bottleneck without speed limitation. In other cases, speed limit control can suppress moving jam emergence, which occurs without speed limitation. It is found that these effects are associated with the probabilistic character of traffic breakdown at a bottleneck as well as with complex spatiotemporal congested pattern features.
Relaxation Phenomenon after Lane Changing
Authors: Leclercq Ludovic , Chiabaut Nicolas , Laval Jorge , Buisson Christine
Published: December 2007

A calibration and an analysis of a recently proposed relaxation model that requires only one additional parameter ∊ are presented. The relaxation phenomenon takes place whenever a lane change occurs at a short spacing that falls outside the fundamental diagram. Such nonequilibrium spacing poses problems to car-following rules that can only handle equilibrium ones. The relaxation model has been already calibrated with macroscopic data. Trajectory data from NGSIM are used here to undertake a more rigorous calibration and validation. It is found that for a given driver there exists a value of ∊ that reproduces the relaxation process with uncanny accuracy and that the mean ∊-value does not worsen the fit significantly.
Calibration Procedure for Gipps Car-Following Model
Authors: Rakha Hesham , Pecker Caroline Cavagni , Cybis Helena Beatriz Bettella
Published: December 2007

A methodology is presented for calibrating the car-following model proposed by Gipps. This calibration procedure is concerned with steady-state conditions. A steady state occurs when the leader and follower vehicles travel at similar and near-constant speeds, maintaining similar space headways between each other. Steady-state calibration is important because it determines roadway capacity, speed at capacity, and jam density (spatial extent of queues when fully stopped). The calibration process allows the identification of adequate values for deceleration rates, b (maximum deceleration rate the driver is willing to use), b′ (the maximum deceleration rate estimated for the leader), and driver reaction time (T). Two different behavioral assumptions were developed concerning the deceleration rates: b equal to b′ and b different from b′. The first hypothesis assumes that the leader will be as aggressive as the follower. The second assumes that the driver considers the leader to have a different maximum deceleration rate. The results are presented in tables and graphs that correlate the car-following parameters to the fundamental traffic stream variables for the different behavioral assumptions. The procedures are then tested on sample field data to demonstrate the adequacy of the calibration procedures.
Estimation of Vehicle Trajectories with Locally Weighted Regression
Authors: Toledo Tomer , Koutsopoulos Haris N. , Ahmed Kazi I.
Published: December 2007

Vehicle trajectory data are important for calibrating driver behavior models (e.g., car following, acceleration, lane changing, and gap acceptance). The data are usually collected through imaging technologies, such as video. Processing these data may require substantial effort, and the resulting trajectories usually contain measurement and processing errors while also missing data points. An approach is presented to the processing of position data to develop vehicle trajectories and consequently speed and acceleration profiles. The approach uses local regression, a method well suited for mapping highly nonlinear functions. The proposed methodology is applied to a set of position data. The results demonstrate the value of the method to development of vehicle trajectories and speed and acceleration profiles. The conducted sensitivity analysis also shows that the method is rather robust regarding measurement errors and missing values.
Dynamic Choice Model of Urban Commercial Activity Patterns of Vehicles and People
Authors: Gliebe John , Cohen Ofir , Hunt John Douglas
Published: December 2007

Intraurban commercial vehicle travel is a relatively underdeveloped aspect of urban travel demand modeling despite the large share of the weekday traffic stream represented by commercial movements. One problem is the proprietary nature of these data and the corresponding lack of behavioral understanding of how establishments schedule their trips. Even when such data have been made available, such as through establishment travel surveys, the large variation in firm size, commodities and services, and logistics practices makes it difficult to create a generalized decision framework. This work uses establishment survey data collected by the Ohio Department of Transportation to create an intraurban commercial vehicle model to be run in a disaggregate microsimulation environment and focuses on commercial movement patterns. The model generates entire daily patterns for workers who regularly travel as part of their jobs and creates tours through a dynamic choice process that incrementally builds tours, taking into consideration elapsed time and time of day in next-stop purpose and location choices. Activity durations are embedded in the utility equations of “stay” alternatives and provide internal consistency between the dimensions of activity purpose, duration, time of day, and location. Model formulation and estimation results are presented for the dynamic activity choice model component. The model system can reproduce observed commercial travel patterns found in the survey data and provide intuitively plausible interpretations for commercial travel behavior in the absence of more detailed knowledge of individual and firm operations.
Tests of Dynamic Extensions to a Family of Trip Table Refinement Methods
Authors: Horowitz Alan J. , Dajani Layali
Published: December 2007

This paper addresses the problem of using traffic counts to ascertain dynamic origin-destination (O-D) tables when dynamic traffic assignments are performed within a traffic window. A family of dynamic O-D trip table estimation methods containing two previously unexplored members (single factor and biproportional) is proposed to solve this problem. The family is tested on a traffic network for the US-45 corridor in Milwaukee, Wisconsin. The tests show that dynamic traffic assignments can be made to match ground counts by a dynamic extension to a technique conceptually similar to Fratar factoring of both origins and destinations from a static O-D table. The two methods that directly solve for origin or destination factors have computational and statistical advantages over whole-table dynamic O-D trip table estimation procedures. Both methods have results that can be readily interpreted.
Offline Calibration of Dynamic Traffic Assignment
Authors: Balakrishna Ramachandran , Ben-Akiva Moshe , Koutsopoulos Haris N.
Published: December 2007

Advances in intelligent transportation systems have resulted in deployment of surveillance systems that automatically collect and store extensive networkwide traffic data. Dynamic traffic assignment (DTA) models have been developed for a variety of dynamic traffic management applications. They are designed to estimate and predict the evolution of congestion with detailed models and algorithms that capture travel demand and network supply and their complex interactions. The availability of rich time-varying traffic data spanning multiple days provides the opportunity to calibrate a DTA model's inputs and parameters offline so that its outputs reflect field conditions in future offline and online real-time applications. The state of the art of DTA model calibration is a sequential approach, with supply model calibration (assuming known demand inputs) followed by demand calibration with fixed supply parameters. An offline DTA model calibration methodology is presented for simultaneous estimation of all demand-and-supply inputs and parameters, with sensor data. A minimization formulation that can use any general traffic data and present scalable solution approaches for the complex, nonlinear, stochastic optimization problem is adopted. A case study with DynaMIT, a DTA model with traffic estimation and prediction capabilities, is used to demonstrate and validate the methodology. Archived sensor data and a network from Los Angeles, California, are used to demonstrate scalability. Results indicate that the simultaneous approach significantly outperforms the sequential state of the art in terms of modeling accuracy and computational efficiency.
Robust Approach to Modeling Choice of Locations in Daily Activity Sequences
Authors: Arentze Theo , Timmermans Harry
Published: December 2007

This paper supports the hypothesis that the spatial robustness of trip destination models depends on the extent to which activity sequences and the spatial configuration of activity locations are represented in the model. A destination-choice model is developed on the basis of the concept of detour time to take into account relative locations (i.e., distances between locations that may be combined in the same tour). The new model is incorporated in the activity-scheduling model of Albatross, an activity-based model of travel demand. The results indicate that using detour time instead of home-based travel distance substantially improves the prediction of spatial distributions of activities in a large sample of activity diaries.
Comprehensive, Unified Framework for Analyzing Spatial Location Choice
Authors: Sivakumar Aruna , Bhat Chandra R.
Published: December 2007

This paper develops a conceptual and econometric framework of non-work activity location choice that is comprehensive in its incorporation of spatial cognition, heterogeneity in preference behavior, and spatial interaction. The proposed framework subsumes a variety of restricted models, including the multinomial logit, first-order state-dependence logit, spatially correlated logit, and mixed spatially correlated logit models. The applicability of the framework is demonstrated through an empirical analysis with German Mobidrive data.
Multiclass Bid-Rent Network Equilibrium Model
Authors: Chang Justin S.
Published: December 2007

A two-way interaction between transport and land use is generally acknowledged, but conventional approaches in travel demand analyses and urban economics have not satisfactorily represented this mutual relationship. The bid-rent network equilibrium model adopted a bilevel program under game theory for addressing this reciprocal interaction. However, the transport component of the model assumed only one type of household. This structure resulted in difficulties in representing class-specific behavior and interclass interactions of transport. This problem can be mitigated by incorporating a multiclass framework, which establishes a multiclass bid-rent network equilibrium model. The single- and multiclass models are tested on an artificial network. The simulation intends to demonstrate the ability of the model to represent the relationship between transport and the location of activities. The result shows that the developed model successfully addresses the two-way interaction and a Nash equilibrium intended.
Component‐Based Software Engineering
Authors: Cao Fei , Gray Jeff , Bryant Barrett R.
Published: December 2007

Component‐based software engineering (CBSE) is becoming an accepted engineering discipline for promoting software reuse throughout the software engineering lifecycle. Beyond software reuse, CBSE also offers a promising way to manage the complexity and evolution of the development process through a unique means of encapsulation and separation of concerns at different abstraction levels.

This article begins with a description of the key characteristics of a software component and then provides a survey of the major component models based on those key characteristics. The latter part of this article discusses the existing engineering issues in CBSE and examines the major research projects that are addressing the challenges. Finally, this article explores recent software engineering technology toward automation in CBSE, which promises to offer yet another channel for boosting the productivity of software development.
Interconnection Networks for Parallel Computers
Authors: Jurczyk Michael , Siegel Howard Jay , Stunkel Craig
Published: December 2007

The interconnection network is responsible for fast and reliable communication among the processing nodes in any parallel computer. This article gives a brief introduction to some of the concepts involved in the design of interconnection networks for parallel machines.
Software Component Repositories
Authors: Luqi  , Zhang Lin
Published: December 2007

Component repositories are one element of a successful reuse program. This article introduces the concept of component repository, surveys the state‐of‐the‐art retrieval approaches and commerical software component repositories, and concludes that web‐based reuse and repositories in an integrated CASE environment are trends of component repositories.
Software Module Risk Analysis
Authors: Khoshgoftaar Taghi M. , Seliya Naeem
Published: December 2007

Estimating the quality of software modules provides a practical way to assess their potential risk. A software quality estimation can be used to provide a targeted software quality improvement initiative. The aim is to provide the management team with a practical quality assessment of software modules for a cost‐effective utilization of software quality improvement resources. In our previous and ongoing research, we have empirically investigated three different kinds of software quality models that are built using software measurement data—software quality classification, software fault prediction, and module‐order modeling. The classification model predicts the class membership of software modules into the fault‐prone and not fault‐prone classes. The fault prediction model estimates the number of faults expected in the modules. A module‐order model predicts the ranking of the modules with respect to their relative software quality. The preference among the three software quality models depends on the software quality improvement goals of the given software project team. We present the useful principles and a detailed overview of the three software quality estimation models, using a case study of a large‐scale telecommunications software system. The classification model is built using the logistic regression technique, whereas the fault prediction model is built using the multiple linear regression technique. The module‐order model is built using the estimations of the fault prediction model for ranking the software modules. We summarize our work with suggestions for software tools that can be used to build software quality estimation models.
Transaction Processing
Authors: Zhang Y. , Jia X. , Lee V. C. S.
Published: December 2007

A transaction processing (TP) is a computer system that processes transaction programs and is closcly associated with database systems. This article reviews traditronal transaction concepts and examines aduanced trasaction models. Then, mobile TP is presented. The article concludes with a discussion regarding future research directions.
Medical Image Processing
Authors: Kassim Asharf A. , Yan Pingkun
Published: December 2007

With the advent of more sophisticated and powerful imaging instruments using a variety of radiant energy forms, numerous improvements have been made to the basic tomographic techniques. These improvements enable greater specificity and sensitivity in clinical diagnostic and basic investigative imaging procedures. Modern medical imaging modalities, which includemagnetic resonance imaging(MRI),positron emission tomography(PET),single photon emission computed tomography(SPECT),ultrasound, and x‐ray CT, have revolutionized diagnostic capabilities. Medical professionals are now provided with significant capabilities for noninvasive and accurate examination of internal anatomy. These modern imaging modalities can capture not only anatomical information but also physiological, metabolic, and functional information.
Collaborative Virtual Environment: System Architectures
Authors: Lin Qingping , Zhang Liang
Published: December 2007

A collaborative virtual environment (CVE) is a shared synthetic space that provides users a shared sense of presence in a common context with natural interaction and communication. A CVE allows geographically dispersed users to interact with each other and virtual entities in a common synthetic environment via network connections. One of the challenging tasks for a CVE creator is to determine where the data of the virtual world should be stored and how the data changes (e.g., interaction with an object by a user) should be propagated to all the users who share the same virtual world. When a user navigates in a virtual world, the movement of the avatar representing the user as well as his/her interaction with virtual entities should be perceived by other users in the same CVE. These require data communication among CVE users over the network. The design of system architecture centers around the choice of data communication models, database distribution models, and world consistency maintenance methods, which will have a direct impact on the CVE system performance. It is the core of a CVE design.
Collaborative Virtual Environment: Web‐Based Issues
Authors: Lin Qingping , Zhang Liang
Published: December 2007

With the exponential growth of the Internent in the past decade, it has evolved from a repository of information to an interactive digital social world. Interactive multimedia contents can be embedded into Web pages to enrich the information presented in the cyberspace for enhanced social and business applications. Collaborative virtual environments (CVEs) function as a new type of interface that attempts to model the Internent into a real social world using the power of Internent communication and virtual reality. For Web‐based three‐dimensional (3‐D) interactive CVEs, due to the heterogeneous nature of the Internet, the most challenging issues of system scalability, virtual world database delivery, and consistent world states maintenance across all participants should be addressed with efficient protocol and data communication architecture incorporating with appropriate virtual world partition, content delivery, and world states synchronization methods if it is intended for use by a large number of concurrent users over the Internent. In this article, we discuss the existing standards, methods for constructing Web‐based CVEs, and popular solutions to the Web‐based CVE issues.
Markov Chain Monte Carlo Simulations
Authors: Berg Bernd A. , Billoire Alain
Published: December 2007

Markov Chain Monte Carlo (MCMC) simulations are widely used in many branches of science. We explain the basic method and illustrate it for a simple statistical physics system, the Ising ferromagnet in two dimensions An overview of MCMC updating scheme is subsequently given. The final section of this article focuses on so called generalized ensemble algorithms.
Synthesis and characterization of low relative molecular weight trans‐1,4‐poly(isoprene)
Authors: Shao Huafeng , Huang Baochen , Yao Wei , Li Haixia
Published: December 2007

Low relative molecular weight trans‐1,4‐polyisoprene oligomers were synthesized successfully by bulk precipitation and solution polymerization with supported titanium catalyst using hydrogen as relative molecular weight modifier. The effects of polymerization conditions on intrinsic viscosity ([η]), catalyst efficiency (CE) and structure of polymer were studied. Increasing the hydrogen pressure resulted in the decrease of [η] of the polymer. With the increasing of hydrogen pressure and reaction temperature, CE decreased but still maintained above 2500 g polymer/g Ti. The percentage composition of (trans‐1, 4‐unit) in the polymer was over 90% in all results. The crystallinity of polymer was about 50–60% with Tm being about 60°C. The relative molecular weight distribution index (MWD) was quite difference according to the polymerization method. While number average molecular weight (Mn) exceeded 860, polymer turned from viscous materials to fragile wax materials, and then to toughness materials at 1800. Dynamic property testing showed that the additional of this oligomer could increase the wet‐skid resistance of the rubber. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Water absorption properties of phosphate glass fiber‐reinforced poly‐ϵ‐caprolactone composites for craniofacial bone repair
Authors: Onal Levent , Cozien‐Cazuc Sophie , Jones I. Arthur , Rudd Christopher D.
Published: December 2007

The moisture uptake of polymers and composites has increasing significance where these materials are specified for invasive, long‐term medical applications. Here we analyze mass gain and the ensuing degradation mechanisms in phosphate glass fiber reinforced poly‐ϵ‐caprolactone laminates. Specimens were manufactured using in situ polymerization of ϵ‐caprolactone around a bed of phosphate glass fibers. The latter were sized with 3‐aminopropyltriethoxysilane to control the rate of modulus degradation. Fiber content was the main variable in the study, and it was found that the moisture diffusion coefficient increased significantly with increasing fiber volume fraction. Diffusion, plasticization, and leaching of constituents appear to be the dominant aspects of the process over these short‐term tests. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Effect of additives on release profile of leuprolide acetate in an in situ forming controlled‐release system: In vitro study
Authors: Zare M. , Mobedi H. , Barzin J. , Mivehchi H. , Jamshidi A. , Mashayekhi R.
Published: December 2007

In situ forming drug delivery system is prepared by phase inversion technique using poly (D,L‐lactic‐co‐glycolide) and leuprolide acetate dissolved in N‐methyl‐2‐pyrrolidone. The effects of ethyl heptanoate and glycerol additives are important determinant as rate modifying agents on the drug release kinetics in biodegradable in situ forming porous systems of poly(D,L‐lactide‐co‐glycolide) (PLGA) in N‐methyl‐2‐pyrrolidone (NMP). The release performance and porous structure morphology are investigated by scanning electron microscopy and UV–visible spectroscopy techniques to study the effect of additives. The experimental results exhibit the crucial role of ethyl heptanoate and glycerol at different loadings (1, 3, and 5% w/w) on release profile of leuprolide acetate loaded on poly(D,L‐lactide‐co‐glycolide)hydroxylated (PLGA‐H). Both additives at different concentrations reduce the burst effect, while increasing duration of drug release. Ethyl heptanoate, however, shows stronger effect than glycerol. The results of morphological studies show that ethyl heptanoate reduces the porosity of the polymer surface and interconnected tear‐like structures of the bulk disappear while the sponge‐like structures are observed. In this system glycerol reduces the surface porosity intensively, while the interconnected tears change into channel‐like structures. Therefore, morphological results confirm the effect of additives on leuprolide release profile. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Morphology and mechanical properties of polyamide‐6/K resin blends
Authors: Ding Qiong , Dai Wenli
Published: December 2007

Mechanical properties and morphological studies of compatibilized blends of polyamide‐6 (PA‐6)/K resin grafted with maleic anhydride (K‐g‐MAH) and PA‐6/K resin/K‐g‐MAH were investigated as functions of K resin/K‐g‐MAH and dispersed phase K resin concentrations, and all the blends were prepared using twin screw extruder followed by injection molding. Scanning electron microscopy (SEM) were used to assess the fracture surface morphology and the dispersion of the K resin in PA‐6 continuous phase, the results showing extensive deformation in presence of K‐g‐MAH, whereas, uncompatibilized PA‐6/K resin blends show dislodging of K resin domains from the PA‐6 matrix. Dynamic mechanical thermal analysis (DMTA) test reveals the partially miscibility of PA‐6 with K‐g‐MAH, and differential scanning calorimetry (DSC) results further identified that the introduction of K‐g‐MAH greatly improved the miscibility between PA‐6 and K resin. The mechanical properties of PA‐6/K resin blends and K‐g‐MAH were studied through bending, tensile, and impact properties. The Izod notch impact strength of PA‐6/K‐g‐MAH blends increase with the addition of K‐g‐MAH, when the K‐g‐MAH content adds up to 20 wt %, the impact strength is as more than 6.2 times as pure PA‐6, and accompanied with small decrease in the tensile and bending strength less than 12.9% and 17.5%, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and characterization of poly(ethylene glycol) crosslinked chitosan films
Authors: Kiuchi Hiroki , Kai Weihua , Inoue Yoshio
Published: December 2007

Poly(ethylene glycol) (PEG) crosslinked chitosan films with various PEG to chitosan ratio and PEG molecular weight were successfully prepared via the epoxy‐amine reaction between chitosan and PEG‐epoxy. The thermal and mechanical properties and swelling behavior were studied for the PEG crosslinked chitosan films. The mechanical strength of chitosan films were greatly enforced by the introduction of PEG‐epoxy, achieving an elongation of about 80%. It was found that the crosslinked chitosan films form hydrogel in water, achieving a swelling ratio higher than 20 times of original weight. The swelling behavior of chitosan films relied greatly on the molecular weight of the crosslinker PEG‐epoxy and the weight percent of PEG‐epoxy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Process analysis of macrotetrolide biosynthesis during fermentation by means of direct infusion LC‐MS
Authors: Jani Peter , Emmert Joachim , Wohlgemuth Roland
Published: December 2007

The optimization of the biosynthetic pathways is highly attractive for the large‐scale preparation of macrotetrolides, because overall yields in the chemical synthesis of compounds like nonactin have been very low. A key success factor determining the outcome of such optimizations is the adequate process analysis for the envisioned product. The analytical methods for process control involved in the past spectrophotometric and chromatographic measurements. LC‐MS offers a modern approach to obtain more detailed data than the spectrophotometric and chromatographic measurements used in the past. In this work, a fast and versatile analytical LC‐MS method has been set up, which has proven of much value for the in‐process analysis of macrotetrolides during fermentation and which has allowed rapid large‐scale bioprocess development.
Protoplast isolation and transient gene expression in switchgrass,Panicum virgatumL.
Authors: Mazarei Mitra , Al‐Ahmad Hani , Rudis Mary R. , Stewart C. Neal
Published: December 2007

Transient assay systems using protoplasts have been utilized in several plant species and are a powerful tool for rapid functional gene analysis and biochemical manipulations. A protoplast system has not been used in switchgrass (Panicum virgatumL.), even though it is a bioenergy crop that has received considerable attention. Here we report the first protocol to isolate large numbers of viable protoplasts from both leaves and roots of two switchgrass genotypes. Furthermore, we demonstrate transient expression of PEG‐mediated DNA uptake in the isolated protoplasts by measuring the activity of β‐glucuronidase (GUS) reporter gene driven by either theCauliflower mosaic virus(CaMV) 35S promoter or the maize ubiquitin 1 promoter. Protoplast transformation with either the 35S or the ubiquitin promoter resulted in an increase in GUS activity compared to the untransformed controls; however, the extent of GUS activity was considerably higher for the ubiquitin promoter than for the 35S promoter. Collectively, our results indicate an efficient protoplast isolation and transient assay system that can be used to facilitate gene expression studies in switchgrass.
The changing pattern of “smart” flow cytometry (S‐FC) to assist the cost‐effective diagnosis of HIV, tuberculosis, and leukemias in resource‐restricted conditions
Authors: Janossy George
Published: December 2007

There is a need to introduce cytometry into areas of the globe that have remained virtually untouched by modern laboratory medicine. With the demand to carry out tests on 100 000s of individuals requiring antiretroviral therapy (ART), flow cytometry must remain simple and cost‐effective – while being sustainable and industry supported as well as proven by quality assessment (QA). This outlook is referred to as “smart flow cytometry” (S‐FC). There are five main areas where the power of S‐FC is demonstrated. These are: (i) the use of CD45 to assist precise cell counting in blood and tissue samples; (ii) the primary CD4 gating to count CD4+ T cells in patients waiting for ART, including the combination (i) and (ii) in the panleucogating (PLG) protocol; (iii) monitoring of human immunodeficiency virus (HIV+) patients during ART by the decreasing levels of lymphocyte activation in a CD8/CD38 test – leading to economies of viral‐load assays; (iv) in tuberculosis and HIV–TB coinfections the use of TB‐antigen‐stimulated cytokine‐synthetic CD4+ Tcells to identify active disease; and (v) the utilization of “minimal residual disease (MRD)‐Lite” technology in patients 19 days after the start of antileukemic therapy to detect MRD. These methods of S‐FC have been successfully introduced in “resource‐restricted” countries with international and local QA.