bluuebunny/crossref_metadata_2025 huggingface dataset:
CFD simulation of length to diameter ratio effects on the energy separation in a vortex tube
Authors: Bramo Reza , Pourmahmoud Nader
Published: January 2011

The objective of the present computational fluid dynamics analysis is an
attempt to investigate the effect of length to diameter ratio on the fluid
flow characteristics and energy separation phenomenon inside the
Ranque-Hilsch vortex tube. In this numerical study, performance of
Ranque-Hilsch vortex tubes (RHVT), with length to diameter ratios (L/D) of 8,
9.3, 10.5, 20.2, 30.7 and 35 with six straight nozzles was investigated. It
includes generating better understanding of the effects of the stagnation
point location on the performance of RHVT. It was found that the best
performance was obtained when the ratio of vortex tube length to the diameter
was 9.3 and also fort this case the stagnation point was found to be the
farthest from the inlet. The results show that the closer distance to the hot
end is produced the larger magnitude of the temperature difference. Computed
results show good agreement with published experimental results.
Thermal and stress analysis in Nd: YAG laser rod with different double end pumping methods
Authors: Shibib Khalid , Minshid Mohammed , Alattar Nebras
Published: January 2011

In this work, the finite element analysis has been used to predict the
temperature distribution in Nd: YAG laser rod; double end-pumped by two
methods Gaussian or top hat beam. The rod is cooled by water passing through
annular, which surrounds the active media. The temperature distribution has
been used to predict numerically, the nodal displacements, strain and stress
based on the principle of virtual work. The main task is to determine the
temperature distribution in Nd: YAG laser rod, the subsequent value and
location of maximum tensile hoop stress associated with the two types of the
double end pumping for different absorption power. Some conclusions are
obtained; as the radius pumping ratio increases the location of maximum hoop
stress will move toward the periphery and vice-versa. Small reduction is
observed in the location of maximum hoop stress when pumping method change
from the top-hat beam to Gaussian beam, especially at low radius pumping
ratio and high absorption power. Top hat beam end pumping will cause more
intense tension hoop stress at the facets of the rod than that of Gaussian
beam even the later may produce high center temperature. This work may be
important for designer while choosing the type of pumping, maximum produced
tensile hoop stress and its location, especially when hoop stress is
ultimate.
Expression of human melanocortin 4 receptor in Saccharomyces cerevisiae
Authors: Ignatovica Vita , Petrovska Ramona , Fridmanis Davids , Klovins Janis
Published: January 2011

The melanocortin 4 receptor (MC4R) is involved in the regulation of energy homeostasis and is known as one of the major hypothalamic regulators of food intake. Several studies have shown that replacement of aspartic acid at position 126 of the MC4R abolishes the ligand binding. We used the modified yeast Saccharomyces cerevisiae strain MMY28 to functionally express the MC4R and characterise the importance of this amino acid for ligand based activation of the receptor. The efficiency of the functional expression system was estimated by activation with αMSH, ACTH and THIQ and compared with cAMP response in mammalian cells. We generated the library of MC4R mutants randomised at the amino acid position 126. Recombinant MC4R clones were screened for the αMSH induced activity in yeast. From 9 different amino acids obtained only the natural aspartic acid displayed the ligand dependent activity of MC4R. The MC4R variants with glutamic acid and leucine at position 126, however, displayed higher background activity than other amino acid substitutions. The results suggest that the yeast expression system is suitable for screening of the MC4R receptor ligands and that the substitution of aspartic acid at position 126 of MC4R by different amino acids functionally inactivates the receptor.
Stieda process versus Haglund’s deformity: An uncommon presentation of posterior ankle impingement
Authors: Perdikakis Evangelos , Karantanas Apostolos
Published: January 2011

Posterior ankle impingement syndrome represents an important cause of chronic ankle pain and has been extensively described in the orthopaedic and radiology literature. A rare case of this painful hindfoot disorder that resulted from two concurrent developmental anomalies is presented herein.
RNA interference and its therapeutic potential
Authors: Ghosal Anubrata , Kabir Ahmad , Mandal Abul
Published: January 2011

RNA interference is a technique that has become popular in the past few years. This is a biological method to detect the activity of a specific gene within a cell. RNAi is the introduction of homologous double stranded RNA to specifically target a gene’s product resulting in null or hypomorphic phenotypes. This technique involves the degradation of specific mRNA by using small interfering RNA. Both microRNA (miRNA) and small interfering RNA (siRNA) are directly related to RNA interference. RNAi mechanism is being explored as a new technique for suppressing gene expression. It is an important issue in the treatment of various diseases. This review considers different aspects of RNAi technique including its history of discovery, molecular mechanism, gene expression study, advantages of this technique against previously used techniques, barrier associated with this technique, and its therapeutic application.
Modal operators on commutative residuated lattices
Authors: Kondo M.
Published: January 2011

We prove some fundamental properties of monotone modal operators on bounded commutative integral residuated lattices (CRL). Moreover we give a positive answer to the problem left open in [RACHŮNEK, J.—ŠALOUNOV Á, D.: Modal operators on bounded commutative residuated Rℓ-monoids, Math. Slovaca 57 (2007), 321–332].
A note on reidemeister torsion and period matrix of Riemann surfaces
Authors: Sözen Yaşar
Published: January 2011

We consider compact Riemann surfaces Σg with genus at least 2. We explain the relation between the Reidemeister torsion of Σg and its period matrix.
Asymptotic approximation of solutions of nonlinear third order difference equations
Authors: Parhi N. , Panda Anita
Published: January 2011

In this paper, we obtain asymptotic bounds, under appropriate conditions, of solutions of third order difference equations of the form $$
\Delta (p_{n - 1} \Delta (r_{n - 1} \Delta y_{n - 1} )) = f(n,y_n \Delta y_{n - 1} ) + g(n,y_n \Delta y_{n - 1} ),
$$ where {p
n} and {r
n} are sequences of positive real numbers, and f, g: ℕ×ℝ2 → ℝ. Different forms of discrete Gronwall inequality are used to obtain these results.
Lattice of retracts of monounary algebras
Authors: Jakubíková-Studenovská Danica , Pócs Jozef
Published: January 2011

We investigate lattices of retracts of monounary algebras. Semimodularity and concepts related to semimodularity (M-symmetry and Mac Lane’s condition) are dealt with. Further, we give a description of all connected monounary algebras with modular retract lattice.
Intron 2 Splice Mutation at CYP21 Gene in Patients with Congenital Adrenal Hyperplasia in the Republic of Macedonia
Authors: Anastasovska V , Kocova M
Published: January 2011

Intron 2 Splice Mutation at CYP21 Gene in Patients with Congenital Adrenal Hyperplasia in the Republic of Macedonia

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder. In 90-95% of cases it results from mutations in the gene for 21-hydroxylase (CYP21, also termed CYP21A2 and P450c21). The IVS-II-656 (C/A>G) mutation leaves ~2.0% enzyme activity, and comprises 25% of the classic CYP21 deficiency alleles and 51% of alleles in the salt-wasting form.

We performed direct molecular diagnosis of the IVS-II mutation in 41 Macedonian patients with different clinical forms of CAH and 55 of their healthy parents and siblings from 37 unrelated families, using the differential polymerase chain reaction/amplification created restriction site method (PCR/ACRS). The IVS-II mutation was detected in 41.5% patients (29.3% were homozygotes and 12.2% were heterozygotes). All homozygotes had a severe classical CAH phenotype (of which 91.7% were salt-wasting and 8.3% were simple virilizing). Three of the heterozygotes had a salt-wasting (SW) phenotype and were compound heterozygotes. The IVS-II mutation was also found in 30.9% of the family members (18.2% were homozygous and 12.7% were heterozygous) and none had any clinical manifestation. The frequency of the IVS-II mutation (41.5%) in these subjects was similar to that reported elsewhere.
Complement Factor H Y403H Polymorphism in the Turkish Population
Authors: Yunus Arikan , Türker Bilgen , Ibrahim Keser
Published: January 2011

Complement Factor H Y403H Polymorphism in the Turkish Population

Complement factor H (CFH) is an important regulator protein of the alternative pathway of the complement system. TheCFHmutations and polymorphisms in CFH have been associated with diseases of the kidney and eye. We investigated the allelic frequency of the most commonCFHpolymorphism, c.1277 T>C (Y402H), in 100 healthy Turkish volunteers from the Antalya Province by direct sequencing of the corresponding genomic region. We found a frequency of 0.65% for the T and 0.35% for the C alleles. The frequency of the TT, CT and CC genotypes was 0.40, 0.49 and 0.11% respectively. Thus, the disease-related C allele has a frequency in Turkey similar to that of Caucasian populations.
Value of the Combined Test in Prenatal Diagnostics
Authors: Lončar D
Published: January 2011

Value of the Combined Test in Prenatal Diagnostics

Congenital anomalies are the cause of 20.0-25.0% of cases of perinatal death, while 3.0% of children are born with malformations of varying size. We examined the predictive values and defined the credibility ratio of the combined test results. Of 317 examined pregnant women, 16 (5.05%) gave a pathological karyotype after amniocentesis: of these, nine (2.84%) had chromosomal number aberrations and seven (2.21%) had chromosomal structure aberrations. We determined the ultrasonographic parameters using the standards of the Fetal Medicine Foundation (location please). We measured free β-subunit of choriogronadotropin (β-HCG) and pregnancy associated plasma protein A (PAPP-A) in venous blood from pregnant women using a combined commercial assay. Sensitivity of the test is 94.0%, and specificity is 99.0%. The positive likelihood ratio [likelihood ratio test (LR+)] is 94.00, a negative likelihood ratio is [likelihood ratio test (LR-)] 0.06. The pretest probability that pregnant women carry a fetus with chromosomal abnormality is 1:250. Posttest odds after the combined test to discover this abnormality is 0.3760, and probability of the same case is 0.2732 if it happens that the test result is positive. The result of our study confirms the justification of combined test usage in routine clinical practice, since the posttest odds rate in the case of a positive screening increases several times over (almost 90 times); the probability of detecting a chromosomal abnormality was about 70 times. The combined screening test, if used methodologically correctly, has a high predictive value in detecting fetal congenital anomalies.
Multi-Agent Based Intelligent Tutoring System Source Code Generation Using MASITS Tool
Authors: Lavendelis Egons , Grundspenkis Janis
Published: January 2011

Multi-Agent Based Intelligent Tutoring System Source Code Generation Using MASITS Tool

Several agent development tools have been proposed. At the same time, specific tools for agent based Intelligent Tutoring System (ITS) development do not exist. However, ITSs have some specific characteristics that must be taken into consideration during the development. General purpose Agent Oriented Software Engineering (AOSE) methodologies and therefore development tools do not sufficiently correspond to the characteristics of ITSs. Additionally, the general purpose AOSE methodologies and tools do not allow plugging in domain specific rules and diagrams. Thus, usage of knowledge gained in ITS research during the development process is limited. In the absence of general tools that allow plugging in knowledge from ITS research, a specific tool named MASITS has been developed. The tool supports a specific agent based ITS development methodology named MASITS which takes into consideration specific characteristics of ITSs and integrates knowledge from ITS research. The tool supports all phases of ITS development, starting from requirements analysis and ending with deployment. Requirements analysis and design phases are supported by appropriate diagram creation tools. Implementation is supported by source code generation from diagrams created during the design phase. JADE platform is used for agent implementation. Thus, Java classes for ontology, agents and behaviours are generated from the design diagrams. The paper includes a brief overview of diagrams used in the source code generation and detailed algorithms for source code generation from the diagrams.
Testing and Traceability Aspects in the Context of the Model Driven Architecture (MDA)
Authors: Grave Andrejs
Published: January 2011

Testing and Traceability Aspects in the Context of the Model Driven Architecture (MDA)

With the growth of complexity of the software systems it becomes more complicated to ensure and evaluate quality of the software being built. This paper discusses quality of the software in the context of the Model Driven Architecture. Paper analyses factors that affect quality of the software in the software development projects that are developed using MDA. As one of the important factor that affects quality of the software, is traceability. This paper provides description of the traceability property and importance of it within development of the software. Within context of this paper traceability is considered as a property of a system description technique that allows changes in one of the system descriptions to be traced to the corresponding portions of the other descriptions. This paper is focused on such aspects of the software development as testing and traceability in the context of MDA. Paper contains in review of traceability, MDA and traceability within MDA. Also paper contains description of the method for formal definition of the problem domain - called Topological functioning modeling for model driven architecture (TFMfMDA). This paper introduces method of the application of the TFM as the traceability tool. TFM as the traceability tool can be used to analyze impact of the changes and select most important tests.
Tool Integration to Support SPEM Model Transformations in Eclipse
Authors: Nikulsins Vladimirs , Nikiforova Oksana
Published: January 2011

Tool Integration to Support SPEM Model Transformations in Eclipse

This paper propose the approach for integrating SPEM modeling tools with the Query/View/Transformation (QVT) tools using Eclipse Modeling Framework (EMF). The aim of tool integration is to support the adoption of Model Driven Architecture within the organizations, which currently use "traditional" software development approaches. The software development process lifecycle of organization is supposed to be expressed with the help of OMG SPEM language. The approach presented in the paper is based on the model-level integration using EMF based interfaces, which will help to link the MOF based Ecore models with the QVT transformation tools. The outcomes of the work are: (i) the design of EMF based tool integration, (ii) solution prototype for Eclipse environment (iii) QVT Relations transformation rules. Model transformations are performed using mediniQVT tool, which is able to operate with the models expressed as Ecore metamodels and provides debugging features and transformation rules tracing. The QVT Relations transformations are applied to the source model, which corresponds to the "traditional" software development lifecycle. The outcome of such unidirectional transformation is the new software development process, which corresponds to the model-driven software development process. The generated target model is SPEM compliant, and can be imported into the external tool supporting SPEM models in Ecore.
The Characteristics of the Map Merging Methods: A Survey
Authors: Andersone Ilze
Published: January 2011

The Characteristics of the Map Merging Methods: A Survey

The development of the autonomous mobile robots is a popular field of research in the artificial intelligence for more than twenty years. An important prerequisite for creation of autonomous robot is the ability to create a map of the environment. However there are several problems in the robotic mapping that are still not completely solved. The use of multiple robots for mapping solves some of these problems, but in this case several new problems, specific to multi-robot mapping, arise. One of the problems in multi-robot mapping is merging all of the local maps that robots have created into one global map. The application of the robot teams in the exploration is a relatively new research field and initially methods for multi-robot mapping were just extended single robot mapping methods. Consequently the map merging problem was simplified. The research of map merging has only recently evolved, thus existing papers on the map merging describe specific map merging methods and there are no comprehensive surveys on the state of the art in the field of map merging. Therefore the goal of this paper is to describe the situation in the field of the map merging and to identify the main characteristics of the map merging methods. The interrelations of these characteristics can then be identified and the corresponding map merging approaches of each characteristic set named.
Simulation of Pessimism Influence on Choice of Farming Strategy under Uncertainty
Authors: Merkuryev Yuri , Bardachenko Vladimir , Solomennikov Andrey
Published: January 2011

Simulation of Pessimism Influence on Choice of Farming Strategy under Uncertainty

Weather-related risks can substantially affect the crop volume depending on time and intensity of agricultural operations performed by the farmer. However, decisions under uncertainty are in some way also liable to another risk - that of excessively optimistic or pessimistic estimation of the decision maker. The paper presents results of optimistic and pessimistic farmer's agricultural operations efficiency based on the analysis of the developed discrete-event stochastic simulation model. The aim of the model is to obtain quantitative estimation of optimistic and pessimistic farmer's choice of agricultural operation strategy efficiency under fluctuation of weather conditions.
Improvement of Business-Activities in Telecommunication Enterprises by the eTOM Business-Process Structural Model Implementation
Authors: Korzachenko Olga , Getman Vadim
Published: January 2011

Improvement of Business-Activities in Telecommunication Enterprises by the eTOM Business-Process Structural Model Implementation

For now, in front of telecommunication branch enterprises of Ukraine, there is a problem of activity improvement with the purpose of granting high-quality services and maintenance of competitive position, both on internal, and on a foreign market. To solve this problem, telecommunication companies appropriate to use the mechanisms of business-oriented process management and improvement of end-to-end business-processes. The purpose of this article is a choice of effective business-process model that will allow telecommunications companies to provide modern, high quality and cost competitive services. During research, conditions of the telecommunication branch enterprises of Ukraine were investigated and key problems of their activity were revealed. Existing business-process models have been considered and analyzed and the optimal model was chosen, according to the put criteria. By results of the analysis a conclusion was drawn, that to the enterprises for business-process modeling is expedient for using eTOM - high-level system business-oriented model aimed for providing of any technological services, including IT. As advantages from introduction eTOM at the Ukrainian enterprises were analyzed.
An Overview of the Use of GML in Modern Spatial Data Infrastructures
Authors: Skoks Viktors , Steurer Christian
Published: January 2011

An Overview of the Use of GML in Modern Spatial Data Infrastructures

This paper introduces an overview of the use of Geography Markup Language in modern Spatial Data Infrastructures. The goal of the paper was to indicate some of the main consequences of the use of Geography Markup Language in the important geospatial data harmonisation processes, both search and access, which are in current use. In order to show a practical example of the use of Geography Markup Language, the system for Earth observation data processing and distribution at the Institute for Applied Remote Sensing at EURAC, Bolzano was studied. The results of the paper set out how Geography Markup Language is used in modern Spatial Data Infrastructures, and the degree to which the Geography Markup Language standard is helpful in achieving data harmonisation and interoperability.
IT Service Desk Implementation Solutions
Authors: Harcenko Maris , Dorogovs Pjotrs , Romanovs Andrejs
Published: January 2011

IT Service Desk Implementation Solutions

This paper analyzes main activities and issues regarding implementation and successful management of IT service desk. Paper not only defines how to determine whether company requires implementation of IT service desk but also describes auditing possibilities of operation of service desk if one already exists. Besides that paper outlines main phases of service desk implementation project as well as recommendations for prosperous realization of those phases. Also information about operation trends of service desks in Latvia and its' comparison with analogous research from Great Britain can be found below.
Research of Artificial Neural Networks Abilities in Printed Words Recognition
Authors: Bondarenko Andrey , Borisov Arkady
Published: January 2011

Research of Artificial Neural Networks Abilities in Printed Words Recognition

This paper provides a brief overview on document analysis and recognition area, highlighting main steps and modules that are used to build recognition systems of the mentioned type. We underline basic workflow of such system down to the problem of single character recognition problem and highlighting possibilities and ways for artificial neural networks usage. Further we are conducting a formal comparison of abilities of printed characters recognition between two well known types of second generation neural networks, namely feedforward back-propagation multilayer perceptron (MLP) and Kohonen self-organizing features map (SOM).
Analysis of Household Electricity Consumption Patterns and Economy of Water Heating Shifting and Saving Bulbs
Authors: Rosin Argo , Moller Taavi , Lehtla Madis , Hoimoja Hardi
Published: January 2011

Analysis of Household Electricity Consumption Patterns and Economy of Water Heating Shifting and Saving Bulbs

This article analyses household electricity consumption based on an object in Estonia. Energy consumption of workday and holiday by loads (including high and low tariff energy consumption) is discussed. The final part describes the evaluation of profitability of common investments of consumption shifting and replacing inefficient devices with more efficient ones. Additionally it describes shifting problems and shifting equipment profitability in real-time tariff system.
Customer Dissatisfaction Index and its Improvement Costs
Authors: Lvovs Aleksandrs , Mutule Anna
Published: January 2011

Customer Dissatisfaction Index and its Improvement Costs

The paper gives description of customer dissatisfaction index (CDI) that can be used as reliability level characterizing factor. The factor is directly joined with customer satisfaction of power supply and can be used for control of reliability level of power supply for residential customers. CDI relations with other reliability indices are shown. Paper also gives a brief overview of legislation of Latvia in power industry that is the base for CDI introduction. Calculations of CDI improvement costs are performed in the paper too.
Load Determination and Selection of Transformer Substations' Optimal Power for Tasks of Urban Networks' Development
Authors: Guseva Svetlana , Borscevskis Olegs , Skobeleva Nataly , Kozireva Lubov
Published: January 2011

Load Determination and Selection of Transformer Substations' Optimal Power for Tasks of Urban Networks' Development

In this paper an approach to solving the some problem of urban 110/10-20 kV network development until 2020 in Riga city in conditions of information uncertainty are considered. The following steps are considered in the paper: forecast of the total load of the Riga city until 2020, the definition of loads of existing and new substations until 2020, choice of 110/10-20 kV substations' the optimal power, determine the location of new substations.
Approach to Stochastic Modeling of Power Systems
Authors: Rubtsov Alexander
Published: January 2011

Approach to Stochastic Modeling of Power Systems

This paper presents an approach to modeling power system that contains sources of stochastic disturbance. It is based on frequency analysis of linearized model of power system. Power system dynamic properties are accounted by equivalent transfer functions of machines and their control equipment. This will allow more accurate calculations for different analysis tasks. Methodology of system linearization is proposed and results of linearized model test are delivered.

The research was made in frame of a project with funding participation of the European Commission.
Modeling Wind Turbines in the Simulation of Power System Dynamics
Authors: Erlich Istvan , Shewarega Fekadu , Scheufeld Oliver
Published: January 2011

Modeling Wind Turbines in the Simulation of Power System Dynamics

This paper deals with the modeling of variable speed wind turbines for stability studies. Using the space-phasor representation and the fundamental relationships governing the operation of the machine quasi stationary model, suitable control algorithms for the simulation of the doubly-fed induction machine (DFIM) as well as the permanent magnet synchronous machine (PMSM) operating on an interconnected system are developed. The control schemes include the pitch-angle/speed control and the decoupled control of the real and reactive power outputs. As an additional modeling option, the generic model for variable speed machine has been introduced. The models were then implemented on a representative test network, and simulations have been carried out to observe the response of the control system to typical abnormal situations such as three phase grid faults to compare the accuracy of the generic models with the detailed quasi-stationary (QSS) models.
Use of Pareto Principle in Power System Mode Analysis
Authors: Mahnitko Anatoly , Gavrilov Alexander
Published: January 2011

Use of Pareto Principle in Power System Mode Analysis

The optimal power dispatch problem in the power system is looked out in the given work. The mathematical model of power system optimal regime searching approach in the market conditions in accordance with Pareto principle is described. The theoretical layout is illustrated on a real power system model of the united power system, which consists of 17 nodes and 21 lines. The procedure is realized using the GAMS software.
Mathematical Modelling of Induction Motor Transient Processes During Stator Winding Interruption
Authors: Konuhova Marina , Orlovskis Guntis , Ketners Karlis
Published: January 2011

Mathematical Modelling of Induction Motor Transient Processes During Stator Winding Interruption

This research presents induction motor mathematical model in coordinate axis's α, β, which allows to learn transient processes in rotor and stator circuits in the conditions of stator windings opening. Such kind of researches is nowadays actual due to impossibility of main calculated values measuring directly, but only on the stator terminals. Induction motor mathematical model forms Park-Gorev equations in α, β coordinate axis. It is preferable to use this coordinate system because it allows comparing the results of mathematical modeling in one of the phases with experimental data without transformations.
Analysis of a Permanent-Magnet Brushless DC Motor with Fixed Dimensions
Authors: Brakanskis Uldis , Dirba Janis , Kukjane Ludmila , Drava Viesturs
Published: January 2011

Analysis of a Permanent-Magnet Brushless DC Motor with Fixed Dimensions

The purpose of this paper is to describe the analysis of a permanent-magnet brushless DC motor with fixed outer diameter and active zone length. The influence of air gap, material of permanent magnets and their size on the magnetic flux density of the machine and magnetic flux is analyzed. The work presents the calculations of two programs, the comparison of the results and the most suitable combination of factors that has been found.
Visible Minorities and Confidence in the Police
Authors: Cao Liqun
Published: January 2011

Few studies have been conducted about differential public perceptions of the police in Canada. Based on the 2004 General Social Survey of Canada, this article examines the impact of belonging to the category visible minorities on citizens' confidence in the police. Consistent with the theoretical prediction, results of multivariate analyses show that members of visible minorities had lower levels of confidence than non–members of visible minorities, even after the effects of perceptions, community contexts, and crime-related variables were controlled for. The small but persistent effect of visible minorities raises questions about race relations in Canada. Other interesting significant predictors of confidence in the police are community context, perceptions, and crime experiences. The findings indicate that equal racial confidence in the police is yet to be achieved and continued reform measures are needed if the police force is to win the hearts and minds of visible minorities in Canada.
Estimation of Freeway Traffic Density with Loop Detector and Probe Vehicle Data
Authors: Qiu Tony Z. , Lu Xiao-Yun , Chow Andy H. F. , Shladover Steven E.
Published: January 2011

Density, speed, and flow are the three critical parameters for traffic analysis. High-performance traffic management and control require the estimation–prediction of space mean speed and density for large spatial and temporal coverage. Speed, including spot mean speed and space mean speed, and flow estimation are relatively easy to measure and estimate, while less attention has been devoted to measuring and estimating density. Because IntelliDrive (previously known as vehicle infrastructure integration) is a promising technology for providing a new type of real-time traffic data, and loop detector systems have already been widely deployed, this paper proposes a method to estimate freeway traffic density with both loop detector data and IntelliDrive-based probe vehicle data. The proposed method has been validated with Berkeley Highway Laboratory loop detector data combined with field-collected probe vehicle data in the first validation study and next-generation simulation video trajectory data in the second validation test. The algorithm can be used offline and in real time.
Modeling Accident Duration and Its Mitigation Strategies on South Korean Freeway Systems
Authors: Chung Younshik , Walubita Lubinda F. , Choi Keechoo
Published: January 2011

Understanding the relationship between the characteristics of an accident and its duration is crucial for efficient response to and timely clearance of an accident, which can minimize traffic delays and congestion on the freeway. Although about 3,000 traffic accidents occur annually on South Korean freeways, only limited studies have been conducted that comprehensively model traffic accidents, including characteristic attributes such as accident duration. The objective of this study is to analyze the critical factors that affect accident duration by means of an accelerated failure time (AFT) metric model and to develop strategic plans and mitigation measures for reducing accident duration on South Korean freeway systems. In total, 2,940 accident data sets, spanning one year (2004), are used. On the basis of the log logistic AFT metric model and survival analysis, the paper suggests some strategic plans and mitigation measures to reduce accident duration on freeway systems in South Korea. In particular, it is hypothesized that, for accidents that occur at night or in a work zone area or are taxi related, the accident duration can be reduced by, among other measures, adding more roadside facilities, employing better freeway management strategies, changing taxi-related policies, or using any combination of those measures. Overall, analytical modeling of traffic accidents and their characteristic attributes, as demonstrated in this paper, should be used routinely as an aid in the strategic planning and formulation of mitigation measures for reducing accident duration on Korean freeway systems.
Freeway Sensor Spacing and Probe Vehicle Penetration
Authors: Feng Wei , Bigazzi Alexander Y. , Kothuri Sirisha , Bertini Robert L.
Published: January 2011

Accurate travel time prediction–estimation is important for advanced traveler information systems and advanced traffic management systems. Traffic managers and operators are interested in estimating optimal sensor density for new construction and retrofits. In addition, with the development of vehicle-tracking technologies, they may be interested in estimating optimal probe vehicle percentage. Unlike most studies focusing on data-driven models, this paper extends some limited previous work and describes a concept developed from first principles of traffic flow. The goal is to establish analytical relationships between travel time prediction–estimation accuracy and sensor spacing by means of two basic travel time prediction–estimation algorithms, as well as to probe vehicle penetration rate. The methods are based on computing the magnitude of under- and overprediction–estimation of total travel time (TTT) during shock passages in a time–space plane by using the midpoint method for online travel time prediction and the Coifman method for offline travel time estimation. Three shock wave configurations are assessed with each method so as to consider representative traffic dynamics situations. TTT prediction–estimation errors are calculated and expressed as a function of sensor spacing and probe vehicle percentage. Optimal sensor spacing is calculated with consideration of the tradeoff between TTT estimation error and sensor deployment cost. The results from this study can provide simple and effective support for detector placement and probe vehicle deployment, especially along a freeway corridor with existing detectors. Optimal sensor spacing results are analyzed and compared for various methods of travel time estimation during different types of shock waves.
Stochastic Characteristics of Freeway Traffic Speed during Breakdown and Recovery Periods
Authors: Ishak Sherif , Mamidala Chaitanya , Qi Yan
Published: January 2011

In recent years, major urban freeways have been experiencing frequent and prolonged congestion throughout the day. Freeways, which are the primary source of mobility, are now operating at conditions near or beyond capacity. Such conditions typically lead to cyclic breakdown and recovery periods during which traffic undergoes dynamic transitions between steady state conditions and unsteady state conditions. Such transitions are probabilistic in nature in that breakdown and recovery events are not necessarily observed under the same conditions all the time. This study examines the basic stochastic characteristics of freeway traffic behavior under a wide range of traffic conditions, with emphasis on transient periods of breakdown and recovery. The study used 30-s speed data as an indicative measure of traffic conditions. Transition probabilities were estimated from real-world speed observations and categorized into negative or positive transitions. On the functions of negative and positive transition probability, five critical points were identified by their probability values (minimum, maximum, and a value of .5). The comparison of critical states at different lanes and locations showed similar characteristics in relation to the speed values at which those states were observed. For each transition, the expected magnitude of change (negative or positive) in speed was also calculated, and three states were identified on the expected transition curves. The stochastic characteristics revealed in this study could help traffic agencies gain a better understanding of the behavior of freeway traffic during breakdown and recovery periods when they are applying appropriate freeway management strategies such as demand packaging, ramp metering, and short-term traffic prediction, among others.
Simulation Tool to Assess Impacts of Parameters of Service Patrol Operations
Authors: Hadi Mohammed , Shen Luou , Li Jianguo , Xiao Yan , Chen Dong
Published: January 2011

Freeway service patrol (FSP) programs constitute one of the most popular elements of intelligent transportation systems and have been increasingly implemented around the United States. Despite the successes and the benefits of these programs, however, recent budget cuts have increased the need to demonstrate the benefits of the programs, to show the differences in the benefits of different operation schedules, and to select the parameters of the operations to make the best use of available resources. This paper reports on an effort to develop a tool (a) to assess the performance of FSPs under different operation parameters and the impacts of FSP performance on transportation network measures and (b) to select operation parameters. The tool was developed by means of a general purpose simulation modeling environment. The output from the simulation is fed into a spreadsheet that allows assessment of changes in incident durations on transportation network performance in terms of delays, fuel consumption, emission, safety, and dollar values. The applications of the tool indicate that it can be used to assess FSP operation parameters and the systemwide and economic impacts of changing these parameters.
Empirical Method for Estimating Traffic Incident Recovery Time
Authors: Zeng Xiaosi , Songchitruksa Praprut
Published: January 2011

Incident duration and traffic recovery time are the two critical periods for any incident management process. Because incident durations are available in postevaluation analyses, the reliability of estimating incident-induced delay depends significantly on the accuracy of recovery time estimation. The dynamics of the traffic system under the combined impact of recurrent and nonrecurrent congestions are complex and thus make it difficult to quantify the incident impact from recurrent congestion. This paper extends the difference-in-travel-time method to estimate traffic recovery time by using both incident and travel time data. The proposed method uses percentile statistics to establish the background conditions that represent travelers' anticipation under incident-free conditions and then employs the concept of the difference in the travel time and the information from the incident database to estimate traffic recovery time. The variability of estimates of traffic recovery time was also obtained by using the proposed method. The case study conducted by using the proposed method revealed that the method is fairly straightforward and robust in that the “ground truth” representation of incident impacts can be captured without any model assumptions and calibrations. In addition, the method can be used to support the calculation of various measures to monitor the performance of freeway and incident management programs.
Violations Modeling in Studies of Concurrent-Flow Lanes
Authors: Chou Chih-Sheng (Jason) , Miller-Hooks Elise , Chen Xiaohan
Published: January 2011

State agencies have become increasingly interested in the construction of managed-lane facilities operating concurrently with general purpose lanes along existing roadways as a means of addressing the continued growth of traffic congestion on freeways. Nonbarrier separation techniques to restrict access to managed lanes are gaining in popularity. Such separation methods, however, permit nearly unlimited improper ingress to and egress from the managed lanes, affecting free-flow speeds, safety, and revenues. Even with significant enforcement, violation rates related to non-barrier-separated managed lanes in the United States are considerable. Despite this, such violation behavior has not been incorporated into any model developed to predict improvements in traffic performance metrics and the potential revenue that can be raised through the introduction of a new high-occupancy toll (HOT) lane facility within an existing roadway or to assess potential practicable operational strategies and facility designs. Nor has any prior study systematically considered the impact of violation on the performance of these facilities. This paper seeks to assess the importance of this omission. Results of this study indicate that vehicles whose drivers choose to violate restrictions on the studied non-barrier-separated, limited-access HOT lane facility significantly affect roadway facility performance estimates when violation rates reach 10% of roadway users or higher.
Dynamic Toll Concept to Assess Feasibility of High-Occupancy Vehicle Lane on Kyungbu Freeway, South Korea
Authors: Chung Younshik , Choi Keechoo
Published: January 2011

This paper presents a feasibility assessment and field survey for high-occupancy toll (HOT) lane implementation as an alternative improvement to the existing high-occupancy vehicle (HOV) facility on the Kyungbu Freeway in South Korea. Various factors such as traffic congestion, vehicle speed, traffic volume, safety issues, equity concerns, HOV–HOT enforcement issues, and toll pricing were evaluated, including carrying out motorist surveys. Eighty percent of motorist survey respondents confirmed the need for a HOT lane as a means to reduce travel time delays and traffic congestion on the Kyungbu Freeway. A dynamic toll concept based on the allowable traffic volume in the HOT lane and the vehicle speed difference between the HOT and general purpose (GP) lanes was then applied as the basis of dynamic control of traffic flow in the HOT lane. This means that toll fees vary dynamically in real time as a function of the traffic conditions in the HOT and GP lanes (i.e., changes in vehicle speed), subject to the traffic volume threshold for the HOT lane (i.e., ≤1,350 vehicles per hour per lane for Class C–level of service). For this study, the dynamic toll rate ranged from about $1.00 to $6.00, depending on the traffic conditions. Overall, the results of this analytical and field survey study have indicated that it is both feasible and practical to operate a HOT lane facility on the Kyungbu Freeway using a simple dynamic toll system.
Fracture Characteristics of Asphalt Mixtures Containing Incinerator Bottom Ash Aggregate
Authors: Hassan M. M. , Khalid H. A.
Published: January 2011

The documented results form part of a larger research program to study the mechanical and environmental properties of asphaltic mixtures containing incinerator bottom ash aggregate (IBAA). The fracture characteristics of four mixtures containing 0%, 30%, 60%, and 80% IBAA by weight were investigated under monotonic and cyclic semi-circular bending conditions. The linear elastic fracture mechanics (LEFM) approach was used to evaluate crack resistance of the tested mixtures with the aim of investigating the effect of IBAA content on these properties. LEFM led to the determination of the stress intensity factor, the J-integral, fracture energy, and Paris law parameters. Crack propagation was monitored with a digital camera, and a program developed in-house was adopted in interpreting crack growth. In addition, a new approach was presented to obtain asphalt fatigue damage parameters from fracture tests. Results showed a benefit to be gained in adding IBAA up to a certain amount, beyond which cracking properties become close to those of the control mix.
Temperature and Shear Susceptibility of a Nonpetroleum Binder as a Pavement Material
Authors: Raouf Mohamed Abdel , Williams R. Christopher
Published: January 2011

Most bituminous binders used for pavement materials are derived from fossil fuels, specifically crude petroleum. Nowadays, technical and economic prospects exist in using biorenewable resources to produce biobinders. Biobinders can be used in three ways to decrease the demand for crude petroleum–derived bituminous binders: direct alternative binder (100% replacement), bitumen extender (25% to 75% bitumen replacement), and bitumen modifier (<10% bitumen replacement). Applicability of developing biobinders from oakwood-based bio-oils to be used as a direct alternative has been investigated through studying the rheological properties. Temperature and shear rate (rate of loading) of biobinders and modified biobinders play major roles in changing the viscosity of bio-oils. The rheological properties of oakwood bio-oils have been investigated and compared with those of bitumen binders, to study the applicability of producing biobinders. Temperature and shear susceptibilities have been studied through measuring the viscosity of the bio-oils. Results reveal that the relationship between the viscosity of bio-oils and temperature and shear rates are log linear–like bitumen binders. In addition, temperature is the main contributor to the viscosity of the bio-oils in comparison with shear rate. Important is that the viscosity temperature susceptibility values for the bio-oils in comparison with bitumen blends indicate that bio-oils are more susceptible to temperature. Moreover, the addition of polymer modifiers leads to a change in temperature ranges of the bio-oils. In conclusion, the rheological properties of oakwood bio-oils are similar to and comparable with bitumen binders, and they represent a viable renewable alternative to petroleum-derived asphalt binders.
Assessment of Workability and Compactability of Warm-Mix Asphalt
Authors: Bennert Thomas , Reinke Gerald , Mogawer Walaa , Mooney Karissa
Published: January 2011

One of the main benefits advertised about the use of warm-mix asphalt is the increased workability at conventional and lower compaction temperatures. From a field perspective, “workability” is commonly defined as the asphalt mixture property that describes the ease with which the asphalt mixture can be placed, worked by hand, and compacted to the desired mat density. Unfortunately, a laboratory property and test condition have yet to be developed to quantify these field characteristics. A research effort to evaluate the workability and compactability of different warm-mix additives preblended in a polymer-modified asphalt binder at varying percentages is summarized. Different test procedures, both asphalt binder related and asphalt mixture related, were evaluated and compared. Test results indicated that conventional mixing and compaction temperature asphalt binder tests were insensitive to the different warm-mix additives and dosage rates. Compaction data obtained with the gyratory compactor also indicated the device was generally insensitive to workability and compactability. Meanwhile, the University of Massachusetts workability device and the Marshall compaction hammer were found to rank the general workability and compactability of the mixtures in a rational order and compared favorably with one another. Not only was a promising new asphalt binder test, the lubricity test, sensitive to dosage rate and warm-mix additive, but the ranking compared favorably with mixture tests. The hope is that the information in this research effort can help in the selection and validation of warm-mix additives as a compaction aid.