bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Fatty Acids in Ghee and Olive Oil and Their Probable Causal Effect in Lipoid Pneumonia
Authors: Mirghani Zein , Zein Tayseer , Annoble Samuel , Winter John , Mostafa Randa
Published: January 2011

Analysis of Fatty Acids in Ghee and Olive Oil and Their Probable Causal Effect in Lipoid Pneumonia

Lipoid pneumonia develops when lipids enter the bronchial tree. This form of pneumonia is common in some developing countries where it is a traditional practice to give infants oily products (ghee and olive oil) for various reasons. We have analyzed and identified the fatty acids found in homemade ghee and in olive oil and compared them to fatty acids found in bronchoalveolar lavage of children with lipoid pneumonia. The three fatty acids common to homemade ghee, olive oil and bronchoalveolar lavage are linoleic, oleic, and stearic. The rest of the fatty acids, namely, lauric, myristoleic, myristic, pentadecenoic, pentadecanoic, heptadecenoic and heptadecanoic are found either in homemade ghee and/or olive oil but not in bronchoalveolar lavage. Therefore the deleterious effects to the lung parenchyma found in lipoid pneumonia are probably caused by these three fatty acids. Further investigations are required to ascertain the effects of the individual fatty acids found in homemade ghee and olive oil.
Cardiovascular Disorders of Turner's Syndrome: A Review
Authors: Yuan S-M , Jing H
Published: January 2011

Cardiovascular Disorders of Turner's Syndrome: A Review

A series of cardiovascular abnormalities may be associated with Turner's Syndrome (TS). Over 50% of the reported cardiovascular malformations have been bicuspid aortic valve or coarctation of the aorta alone. or in a combination, which may lead to a higher risk for infective endocarditis. Isolated dilation of the ascending aorta was often seen in TS, while aortic dissection has been increasingly observed in recent years. The aortic root dilation was found more likely to be due to a mesenchymal defect rather than atherosclerotic changes. Women with TS are often hypertensive as a result of aortic abnormality or renal vascular disorder. They have an increased risk of developing neoplasms, such as gonadoblastoma and dysgerminoma, and therefore they may require regular monitoring while receiving hormone therapy. In patients with gonadal dysgenesis, exogenous estrogen treatment poses a problem of connective tissue disorders of the great vessels. To resolve the contradiction between exogenous estrogen therapies and the hold-up of the progression of the connective tissue abnormality is a topic to be coped with. Careful clinical assessment is mandatory in the evaluation of patients with TS with cardiovascular abnormalities.
Clinical and Molecular Data on Mental Retardation in Bulgaria
Authors: Todorov T , Todorova A , Avdjieva D , Dimova P , Angelova L , Tincheva R , Mitev V
Published: January 2011

Clinical and Molecular Data on Mental Retardation in Bulgaria

Mental retardation (MR) is clinically and genetically highly heterogeneous. We have done molecular genetic testing on 85 Bulgarian MR patients who were clinically classed as fragile X syndrome (FXS) (n = 32), Rett syndrome (RTT) (n = 36) and Prader-Willi/Angelman syndromes (PWS/AS) (n = 17). We tested for the fragile X MR 1 (FMR1), methyl-CpG binding protein 2 (MECP2), cyclin dependent kinase-like 5 (CDKL5), and Aristaless X (ARX) genes, and did methylation analyses of exon 1 of the small nuclear ribonucleoprotein polypeptide N (SNRPN), and multiplex ligation-dependent probe amplification (MLPA) analyses for large deletions/duplications, and for the methylation status of FMR1 and SNRPN genes. In the FXS group we only found four mutations in the FMR1 gene (12.5%). In the RTT group we found nine mutations in the MECP2 gene (25.0%) but no CDKL5 gene mutations. In the PWS/AS group we found nine mutations in the 15q11-q13 region (53%). Thus, we clarified the molecular basis in 26.0% of the patients. The proportion of genetically proved diagnoses in our RTT patients (25.0%) is relatively high and all these cases are due to MECP2 mutations. Despite the type of mutation, all these cases are very similar from the clinical point of view and well recognized in Bulgaria.
Clinical Manifestations of Partial Trisomy 4p
Authors: Demirhan O , Özgünen F , Taştemir D
Published: January 2011

Clinical Manifestations of Partial Trisomy 4p

We made the diagnosis prenatally from cytogenetic analysis of amniocytes cultured following amniocentesis performed at 20 weeks' gestation on a woman in whom ultrasound examination of the female fetus showed severe growth retardation, lung and kidney hypoplasia, and a congenital heart defect. Analysis revealed a de novo trisomy of the terminal short arm of chromosome 4 (4p16.1-pter). The parents opted to terminate the pregnancy. Fetopathological examination showed dysmorphic features and other abnormalities consistent with clinical manifestations of partial trisomy 4p.
Novel Mutation in the Apob Gene (Apo B-15.56): A Case Report
Authors: Bove M , Carnevali L , Cicero A , Tarugi P , Gaddi A
Published: January 2011

Novel Mutation in theApobGene (Apo B-15.56): A Case Report

Familial hypobetalipoproteinemia (FHBL) is a rare co-dominant genetic disorder characterized by decrease of plasma low density lipoprotein-cholesterol (LDL-c) or apolipoprotein B (Apo-B) equal to or less than the 5thpercentile for the population. We describe a 48-year-old male who presented with fatty liver disease (FLD), insulin resistance (IR), obesity and hypertension. Our patient thus met the latest diagnostic criteria of the metabolic syndrome (MS) proposed by the Adult Treatment Panel and the International Diabetes Federation. However, he had very low plasma concentration of LDL-c and Apo-B. DNA sequencing showed that he and two first-degree relatives affected by obesity and mild IR were heterozygous for a single nucleotide deletion on exon 15 of theAPOBgene, which was predicted to form a truncated Apo-B designated Apo B-15.56.
XYY Karyotype in a Mentally Retarded Man with Prognathism and Malformation of His Hands and Toe Nails
Authors: Mahjoubi F , Akbary M , Shafegatee Y
Published: January 2011

XYY Karyotype in a Mentally Retarded Man with Prognathism and Malformation of His Hands and Toe Nails

We report on a 25-year-old man who was referred for evaluation of possible Fragile X syndrome on the basis of mild mental retardation and malformation of his hands and toe nails. He was found not to have this syndrome but to have a 47, XYY karyotype. Only one other case of XYY syndrome with prognathism and malformation of hands has been reported.
Peat humification character in two ombrotrophic bogs depending on peat properties
Authors: Silamiķele Inese , Nikodemus Oļgerts , Kalniņa Laimdota , Purmalis Oskars , Kļaviņš Māris
Published: January 2011

Peat humification character in two ombrotrophic bogs depending on peat properties

Study of the living organic matter humification process is essential for understanding of the carbon biogeochemical cycle. The aim of this study is to determine the relations between peat properties and humification degree in two peat profiles in ombrotrophic bogs in Latvia, to identify the links between peat age, decomposition degree, peat properties, peat botanical composition and peat properties. The peat diagenesis process was described using multiproxy analysis of peat age, botanical composition, elemental composition, elemental ratios of the peat organic matter and peat alkaline extracts. This approach supports a better understanding of the peat properties and their relation both to peat decomposition processes, and also to original living organic matter. Multiproxy study of peat properties supports development of peat humification indicators.
Reuse in Software Development Organizations in Latvia
Authors: Kotov Vladimir
Published: January 2011

Reuse in Software Development Organizations in Latvia

The paper presents the results of a survey, which aims to investigate the field of software reuse in software development organizations in Latvia. The topic has a particular significance since reuse may provide some economic benefits by reducing software development and operating costs, and by efficient utilization of development knowledge and corporate expertise. The objective of the study is to identify the key factors to be considered by the companies interested in establishing a software reuse program, thus improving time-to-market, costs and quality of software products by ingraining reuse into the entire software development process. Twenty factors organized into four categories were considered important within the framework of the survey. The results were obtained through the questionnaire involving software organizations in Latvia, whose responses were analyzed and used to relate the characteristics of organizations with their reuse experience. As a result, the influence of the selected factors on the success of the reuse is evaluated using four different levels (strong, weak, none, no data). Additionally, the paper includes review of related researches and comparison of the results. In conclusion, the author provides suggestions for the improvement of the reuse in Latvian software development organizations on the basis of the survey.
Decision Tree Classifiers in Bioinformatics
Authors: Polaka Inese , Tom Igor , Borisov Arkady
Published: January 2011

Decision Tree Classifiers in Bioinformatics

This paper presents a literature review of articles related to the use of decision tree classifiers in gene microarray data analysis published in the last ten years. The main focus is on researches solving the cancer classification problem using single decision tree classifiers (algorithms C4.5 and CART) and decision tree forests (e.g. random forests) showing strengths and weaknesses of the proposed methodologies when compared to other popular classification methods. The article also touches the use of decision tree classifiers in gene selection.
Studies of New Multistory House Electrical Supply Load and Determination Methods Update
Authors: Budahs Martins , Vanzovichs Edvins , Zviedritis Mareks
Published: January 2011

Studies of New Multistory House Electrical Supply Load and Determination Methods Update

A large amount of work has devoted to electric supply system load determination. Most of the load calculation methods and values of the appropriate factors were found many years ago and are outdated, for example, electric supply system for new many dwelling houses. At this time, there is changed not only value of loads but also its character - thus leaving the impact on the calculation methodology and factors values.

Employers of Latvenergo Distribution Network are realized wide range of load inspection in more then 24 commercial buildings and dwelling houses over two years. The results are presented in the form of official instruction. This paper is continuing the ongoing theme and dedicating improving possibilities of the calculation methodology. Particular attention has paid to existing methods of load calculation, physical interpretation of factors and possible character changes in the range.

The method is designed for design engineers and engineering staff, working with the maintenance and control of apartment buildings.

The methodology is not applicable in buildings with electric heating and hot water.
Experimental Research of the Overvoltage in the Insulated Neutral Network
Authors: Gvozdas Vitalijus , Valatka Povilas
Published: January 2011

Experimental Research of the Overvoltage in the Insulated Neutral Network

The isolated neutral network isolation resistance is often affected by the lightning discharge surge to the line cables or towers. Several overvoltage waves are maid at the moment of the lightning discharge surge. It is dangerous for the devices because at the very short time period the isolation of the device is affected by the surge impact twice or even more. The analysis of the experimentally registered lightning discharge induced overvoltage transients effect from the lightning influence to the power line till the power line disconnection were analyzed in this work. Estimation of the overvoltage characteristics to the isolation resistance was made.
Determination of Equilibrium Points for Steady State Conservative Models
Authors: Panikovskaya Tatiana
Published: January 2011

Determination of Equilibrium Points for Steady State Conservative Models

The development and a more sophisticated structure of electric power systems, the transition towards deregulation and competition between the participants of the electric energy market cause the necessity of a complex steady state analysis, the evaluation of the electric power system stability, with its parameters being changed. The paper addresses the steady state analysis based on algebraic methods. Regular (trivial) and non-regular (additional) equilibrium points for the electric power system conservative model are determined. Changing regular and non-regular equilibrium points in a heavily loaded electric power system is studied.
L'effet des lois en matière de contrôle des armes à feu sur les homicides au Canada, 1974–2004
Authors: Blais Étienne , Gagné Marie-Pier , Linteau Isabelle
Published: January 2011

Bills C-51 (1977), C-17 (1991), and C-68 (1995) were enacted into law by the Government of Canada with a view to tightening controls on firearms in order to prevent homicides related to their use. The effectiveness of these laws has fuelled several debates on the political scene. Given the many limitations of assessments conducted to this day, the credibility of their results is often questioned. Using a multiple-time-series design, the purpose of this article is to assess the impact of the three most recent Canadian gun control laws, all the while overcoming the limitations identified in the scientific literature. Our results show that the enactment of Bills C-51 and C-68 was followed by a significant drop in the number of homicides committed with a firearm, a decrease of 5% to 10%, depending on the province. This reduction was most noticeable in the case of homicides committed with a shotgun or a hunting rifle. No tactical displacement was observed. Finally, results suggest that the effectiveness of these laws is due to the reduced access and availability of firearms rather than to the severity of sentences provided in the legislation.
Analysis of Cascading Incident Event Durations on Urban Freeways
Authors: Zhang Hongbing , Khattak Asad J.
Published: January 2011

Incident-induced traffic congestion is a major source of travel uncertainty. Sometimes multiple incidents occur sequentially because of queue backups, which substantially increase uncertainty. Such cascading incidents can be grouped into one event because of their spatial and temporal proximity. Events consisting of a primary and its secondary incidents are expected to have longer durations than single incidents and therefore to result in larger impacts on traffic. Though relatively rare, such cascading events are a major concern for transportation operations managers, and they are the focus of this paper. A unique event database, based on incident and road inventory data from Hampton Roads, Virginia, is created. Single-pair events (one primary and one secondary incident) and large-scale events (one primary and multiple secondary incidents) are identified and analyzed. “Event duration” is defined as the time elapsed from the notification of a primary incident to the departure of the last responder from the event scene after removal of the primary and associated secondary incidents. Events are further categorized as either contained or extended. If the primary incident is the last one being cleared during such an event, then it is a contained event; otherwise, it is an extended event. Correlates of contained and extended event durations are identified through a set of rigorous statistical models. The findings of this study provide knowledge that can aid in mitigating the impacts of cascading incidents.
Queue Management Techniques for Metered Freeway On-Ramps
Authors: Spiliopoulou Anastasia D. , Manolis Diamantis , Papamichail Ioannis , Papageorgiou Markos , Wu Jingcheng , Jin Xia
Published: January 2011

Ramp metering is beneficial for freeway throughput, but the ramp queues that are created should be prevented from extending to adjacent street junctions. A recently proposed ramp queue controller is investigated in conjunction with the local ramp-metering algorithm ALINEA. Microscopic simulation is used to compare the queue controller with a popular queue override scheme that is based on specifically designed scenarios and evaluation criteria. It is found that the queue controller outperforms the queue override and leads to fewer instances of ramp queue spillover. The concept is also demonstrated to work properly in an operational field environment.
Predicting Freeway Travel Time under Incident Conditions
Authors: Xia Jingxin , Chen Mei , Qian Zhendong
Published: January 2011

Prediction of corridor travel time is essential to achieving the promise of advanced traveler information systems. Although much research has been done on travel time prediction, procedures for practical prediction of travel time under incident conditions are lacking. This paper presents a framework for online prediction of freeway corridor travel time under incident conditions on the basis of inductive loop detector and incident data. The core component is a model for prediction of corridor travel time under incident conditions that produces estimated physical queue length at various time intervals. Testing shows that the method offers enhanced accuracy in prediction of corridor travel time compared with those methods that do not consider the impact of incidents.
Local Ramp Metering in Random-Location Bottlenecks Downstream of Metered On-Ramp
Authors: Wang Yibing , Papageorgiou Markos , Gaffney John , Papamichail Ioannis , Rose Geoffrey , Young William
Published: January 2011

This paper studies a control strategy applicable to local ramp metering in the presence of random-location bottlenecks (RLBs) downstream of a metered on-ramp. With the support of the Highway Department of Victoria State, Australia, local ramp metering in the RLB case has recently been investigated, with the aim of designing appropriate and practicable control approaches. A related control strategy has been developed and tested in macroscopic simulation. This paper presents some representative testing results. This strategy has been incorporated into the HERO (heuristic ramp-metering coordination) freeway ramp signal control system and will be applied in Melbourne in the frame of a large-scale freeway upgrade project.
Comparison of Algorithms for Systematic Tracking of Patterns of Traffic Congestion on Freeways in Portland, Oregon
Authors: Li Huan , Bertini Robert L.
Published: January 2011

Systems for automatically tracking traffic congestion that are integrated into freeway management systems as applications of an intelligent transportation system (ITS) have received a high level of attention in many cities in recent years. Some cities automatically provide traveler information on travel times, congestion activation times, and locations. However, different algorithms are used by professionals and decision makers. Some popular algorithms for automatically tracking congestion include parameter threshold–based algorithms such as those that use speed thresholds and the Automatische Staudynamikanalyse [automatic tracking of moving traffic jams–forecasting of traffic objects (ASDA-FOTO)] models. The rescaled cumulative curve tool has also been used for analyzing traffic features. The advantage of this tool is that it reveals traffic features in more detail, but one disadvantage is that it is a visual tool. When used to process data systematically in an operations environment, this tool can make analysis laborious. This paper proposes two algorithms for automatically tracking congestion by making use of the rescaled cumulative curve tool and compares them with the traditional speed threshold algorithm and the ASDA-FOTO algorithm. The results are represented graphically and numerically.
Spatial Analysis and Modeling of Traffic Incidents for Proactive Incident Management and Strategic Planning
Authors: Khattak Asad J. , Wang Xin , Zhang Hongbing
Published: January 2011

Traffic events involving secondary incidents can be particularly problematic for the public and for incident managers. This paper explores the associations of spatial characteristics, including geometric and land use factors, with secondary and nonsecondary incidents. The data used in this study are 2006 incident records from Hampton Roads in Virginia and roadway inventory data, enhanced through geographic information systems to include detailed spatial information. Secondary incidents in the same and opposite directions were identified by using a queue-based method. Such incidents represented nearly 2% of total recorded incidents but showed longer durations than other incidents. The study found statistically significant differences between the distributions of secondary and nonsecondary incidents, implying that higher risks of secondary incidents in certain roadway segments are not necessarily correlated with relatively high risk of nonsecondary incidents. Poisson, zero-inflated Poisson, and negative binomial regression models were estimated by combining traffic exposure, road segment characteristics, and spatial–land use information to explore factors associated with secondary incidents. The models provided helpful information for effective assignment of incident management resources and for support of regionally based strategic planning.
Exploration of Operational Concepts of Interoperability for Robust Interregional Transportation System Operations
Authors: Park Hyungjun , Smith Brian L. , Venkatanarayana Ramkumar , Song Houbing
Published: January 2011

Regional transportation operations centers (TOCs) are at the core of managing and operating a complex surface transportation system. To ensure reliable transportation services, particularly during emergency situations when transportation is vital, uninterrupted operations of TOCs should be guaranteed. Achieving TOC interoperability is of great importance. Interoperability of TOCs can be understood as the ability of one TOC to access and manage some set of the resources of another (remote) TOC. TOC interoperability can allow each metropolitan area or in some cases each state to achieve more robust and seamless interregional operations. In addition, interoperability may provide each region with a better understanding of each partner's practices and thus promote more consistent and coordinated transportation systems operations. Although these benefits are compelling, TOC interoperability cannot be easily established because of the complex technical and institutional situations of existing centers. Given this background, this study explored various operational concepts and developed a methodology to achieve interregional TOC interoperability. The methodology consists of four steps: (a) develop an emergency backup plan for each TOC, (b) establish relationships among TOCs, (c) develop a communications network, and (d) establish institutional interoperability between designated TOCs. In a case study, the proposed methodology was applied to the five regional TOCs in the Commonwealth of Virginia.
To What Extent Can High-Occupancy Vehicle Lanes Reduce Vehicle Trips and Congestion?
Authors: Plotz Joseph , Konduri Karthik C. , Pendyala Ram M.
Published: January 2011

Despite the increasing interest in and deployment of managed lanes on highways that involve pricing and tolling schemes, a considerable number of highway facilities still use high-occupancy vehicle (HOV) lanes with no other features to manage or price their use. These HOV lanes are often restricted to vehicles transporting two or more, or three or more, occupants and are viewed as mechanisms to reduce vehicular travel demand, motivate ridesharing among individuals, and curb greenhouse gas emissions. In this paper, an analysis of the 2001 National Household Travel Survey data set was conducted to determine the potential share of HOV trips that might be induced by the presence of an HOV lane. It was found that a vast majority of HOV trips were trips undertaken with family for discretionary activity purposes. Given that virtually all these HOV trips would have been undertaken regardless of the presence of an HOV lane, one could question the potential efficacy of implementing a pure HOV lane. This paper addresses this question by considering two extreme scenarios that provide a range of potential impacts of HOV lanes on vehicle trip reduction. In the specific hypothetical scenario considered in this paper, the range was found to lie between 1% and 37%, with a clear indication that true impacts in the real world were more likely to be closer to the lower bound than the upper bound. On the basis of these findings, it appears that pure HOV lanes provide modest benefits from the perspectives of vehicular trip reduction and congestion relief. The paper concludes that HOV lanes with additional managed use and pricing features are likely to yield substantially greater impacts from the perspectives of both vehicular trip reduction and revenue generation.
Can More Reclaimed Asphalt Pavement be Added?
Authors: Daniel Jo Sias , Pochily Jeffrey L. , Boisvert Denis M.
Published: January 2011

Results of a study conducted by the New Hampshire Department of Transportation (NHDOT) in cooperation with three local paving contractors are presented. Plant-produced hot-mix asphalt (HMA) mixtures containing reclaimed asphalt pavement (RAP) percentages from 0% to 25% were obtained from seven different batch plants. Twenty-eight mixtures were sampled and sent to the binder testing laboratories at NHDOT and Pike Industries, Inc. The virgin binders were also sampled and sent for binder testing. Binders were extracted and recovered from all of the mixtures and were tested to determine the performance grade (PG) binder grade and critical cracking temperature. The effect of the RAP at various percentages on binder properties was evaluated. High-end PGs were found to remain the same or increase only one grade for the mixtures tested. Low-end PGs also remained the same or bumped only one grade, and the critical cracking temperatures changed by only a few degrees for the mixtures examined in this study. Results of this study led to a change in the implementation of the new NHDOT specification in regard to the use of recycled asphalt binder in HMA.
Bulk Specific Gravity of Reclaimed Asphalt Pavement Aggregate
Authors: Kvasnak Andrea , West Randy , Michael Jenna , Loria Luis , Hajj Elie Y. , Tran Nam
Published: January 2011

Several methods are available for determining the bulk specific gravity (Gsb) of reclaimed asphalt pavement (RAP). However, a clear recommendation has not been had for determining this property. In this study, asphalt mixes with known aggregate properties were produced and aged in the laboratory to simulate RAP. The aggregates were recovered, and the aggregate properties, including Gsb, were reassessed. The aged mixtures were also tested to determine maximum theoretical specific gravity (Gmm), from which estimated Gsb values could be calculated. The Gsb values from both the extraction and Gmm methods were compared with the known or true Gsb values for these aggregates. The effects of the RAP Gsb errors on voids in mineral aggregate values from the various methods were also evaluated. On the basis of the results of this study, it is recommended that the Gmm method be used to determine the RAP Gsb when a regional absorption value is known.
Measuring Effects of Warm-Mix Additives
Authors: Hanz Andrew J. , Faheem Ahmed , Mahmoud Enad , Bahia Hussain U.
Published: January 2011

An emphasis on environmental stewardship has prompted the use of warm-mix technologies aimed at allowing for production of conventional asphalt mixtures at reduced temperatures. Successful use of warm-mix asphalt (WMA) in field demonstrations has created a need for development of mix design procedures. A major impediment in development of these procedures is the evaluation of the effect of WMA technologies on asphalt binder and mixture workability. The objective of this study was to introduce a new test methodology for estimating asphalt binder workability by measuring the lubricity effects of a surfactant-based additive as well as binder foaming processes through novel use of the dynamic shear rheometer with a new testing fixture. The new test allows measuring the coefficient of friction of binders at various temperatures, loading rates, and normal force. Asphalt binder lubricity measurements were correlated mixture to workability tests defined by the compactive effort required to densify a mixture to 8% air voids. Mixture testing was conducted at temperatures ranging from 90°C to 135°C. Results of asphalt binder workability testing demonstrated a significant reduction in coefficient of friction due to the use of a surfactant-based WMA additive and identified a need for revised procedures for evaluation of foamed asphalts. Both warm-mix processes demonstrated enhanced mixture workability relative to the hot-mix asphalt; however, significant differences were not realized until compaction temperatures were below those normally used in production.
Moisture Susceptibility of High and Low Compaction Dry Process Crumb Rubber–Modified Asphalt Mixtures
Authors: Rahman M. M. , Airey G. D. , Collop A. C.
Published: January 2011

The field performance of dry process crumb rubber–modified (CRM) asphalt mixtures has been reported to be inconsistent with stripping and premature cracking on the surfacing. One of the concerns is that, because achieving field compaction of CRM material is difficult due to the inherent resilient nature of the rubber particle, nonuniform field compaction may lead to a deficient bond between rubber and bitumen. To assess the influence of compaction, a series of CRM and control mixtures was produced and compacted at two levels: 4% (low, optimum laboratory compaction) and 8% (high, field experience) air void content. The long-term durability, in regard to moisture susceptibility of the mixtures, was assessed by conducting repeated moisture conditioning cycles. Mechanical properties (stiffness, fatigue, and resistance to permanent deformation) were determined in the Nottingham Asphalt Tester. Results indicated that compared with conventional mixtures, the CRM mixtures, regardless of compaction effort, are more susceptible to moisture with the degree of susceptibility primarily depending on the amount of rubber in the mixture, rather than the difference in compaction. This behavior is different from that of conventional mixtures in which, as expected, poorly compacted mixtures were found to be more susceptible to moisture than were well-compacted mixtures.
Local Calibration of Mechanistic–Empirical Pavement Design Guide Rutting Model
Authors: Hoegh Kyle , Khazanovich Lev , Jensen Maureen
Published: January 2011

The AASHTO interim Mechanistic–Empirical Pavement Design Guide (MEPDG) was recently introduced in the United States. Many state agencies have conducted validation and local calibration of the MEPDG performance prediction models. In this study, time history rutting performance data for pavement sections at the Minnesota Department of Transportation full-scale pavement research facility [Minnesota Road Research Project (MnROAD)] have been used for an evaluation and local calibration of the MEPDG rutting model. A detailed comparison of the predicted total rutting, asphalt layer rutting, and measured rutting is presented. The reason that a conventional MEPDG model calibration was not feasible is discussed. Also, a modification of the rutting model is recommended. It was found that the locally calibrated model greatly improved the MEPDG rutting prediction for various pavement designs in MnROAD conditions.
Effect of Surface Characteristics on Bonding Properties of Bituminous Tack Coat
Authors: Chen Jian-Shiuh , Huang Chien-Chung
Published: January 2011

The evaluation of the influence of surface characteristics on the bonding properties at the interlayer is important to understand better how multi-layered pavements behave under traffic conditions. Three double-layered systems were prepared with dense, porous asphalt concrete and stone mastic asphalt mixtures. The direct shear test was used to measure the bond properties provided by tack coat, whereas the surface characteristics were measured by traditional techniques. Variables included surface type, curing time, curing temperature, emulsion type, and residual application rate. For a given value of applied normal stress, the interface between the dense-graded asphalt mixtures resulted in higher peak shear strength than that between the open- and gap-graded mixtures. An increase in mean texture depth and film thickness led to a decrease in the peak shear strength and the reaction tangential modulus. The surface characteristics were shown to play a key role in interlayer bonding. Curing time was an important factor, indicating that paving could be performed right after the emulsion was broken. Increasing the residual application rate increased shear strength up to a point, then shear strength decreased gradually. The use of tack coat increased the interface bond strength, and an optimum residual application rate existed, at which the shear resistance reached a maximum value. The bonding properties at elevated temperatures were more associated with the surface characteristics than at lower temperatures.
Use of Mechanistic–Empirical Pavement Design Guide for Mix Performance Evaluation Using the Dynamic Modulus
Authors: Katicha Samer W. , Flintsch Gerardo W. , McGhee Kevin K. , Loulizi Amara
Published: January 2011

The Virginia Department of Transportation has worked toward end-result specifications (ERS) in hot-mix asphalt (HMA) since the mid-1960s. With the recent advances in HMA material characterization and the completion of the new Mechanistic–Empirical Pavement Design Guide (MEPDG) under NCHRP Project 1-37, the ultimate goal of true ERS that are performance related seems more feasible. The use of the HMA dynamic modulus as an HMA quality measure is investigated. An effective reduced frequency (temperature–frequency combination) at which the HMA dynamic modulus best correlates with the MEPDG-calculated HMA rutting is determined for eight climatic conditions. This effective reduced frequency did not coincide with the modified Witczak effective temperature–frequency equation. The effect of HMA layer thickness (51 to 254 mm) on effective reduced frequency was investigated for Roanoke, Virginia. It was found that layer thickness had a minor effect on effective reduced frequency, so that the latter can be assumed independent of layer thickness for all practical purposes. Finally, the HMA rutting calculated by using the effective reduced frequency was found comparable with the MEPDG-calculated HMA rutting with average and maximum differences of 6.5% and 23%, respectively. This difference is acceptable considering the variability in actual field rutting measurements (for the same conditions) as well as accuracy of the MEPDG in determining the average HMA field rutting. Use of the effective reduced frequency can result in considerable time and money savings, especially for quality assurance applications for which testing is regularly performed.
Fatigue Crack Propagation Model of Asphalt Concrete Based on Viscoelastic Fracture Mechanics
Authors: Kuai Hai Dong , Lee Hyun Jong , Lee Jung Hun , Mun Sungho
Published: January 2011

A fatigue crack propagation model of asphalt mixtures is developed on the basis of viscoelasticity and fracture mechanics. The fatigue model is extended from the generalized J-integral model proposed previously by the authors to consider the effects of temperature and air void. Laboratory fatigue crack propagation tests for three different asphalt mixtures are performed at various loading conditions, air voids, and temperatures. The test results indicate that the J-integral could take care of the loading magnitude and frequency dependence of the crack speed but could not consider temperature dependence completely. The air void and temperature effects on crack propagation in asphalt mixtures are investigated. Generally the crack propagation of the asphalt mixtures is developed more quickly at high temperatures and large air voids. Finally, the generalized J-integral model is extended by employing a regression function to take care of the temperature and air void effects. The resulting model could provide a reasonable prediction of fatigue crack propagation lives of the asphalt mixtures under various loading and temperature conditions.
Semiempirical, Analytical, and Computational Predictions of Dynamic Modulus of Asphalt Concrete Mixtures
Authors: Aragão Francisco T. S. , Kim Yongrak , Karki Pravat , Little Dallas N.
Published: January 2011

Dynamic modulus is the key property used to characterize stiffness of asphaltic mixtures in pavement performance evaluation programs such as the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures. This paper investigates various models for predicting the dynamic modulus of asphalt mixtures and compares model predictions with experimental test results. The predictions of two semi-empirical models (Witczak's model, modified Hirsch model), an analytical micromechanics model (Hashin's model), and the computational micromechanics model are compared with the dynamic modulus test results obtained from cylindrical asphalt concrete specimens. For the computational micromechanics approach, the finite element method was incorporated with laboratory tests that characterize the properties of individual mixture constituents and with a digital image analysis technique to represent detailed microstructure characteristics of asphalt concrete mixtures. All predicting models investigated in this paper are in fair agreement with the test results. Witczak's equation simulates dynamic moduli somewhat greater than laboratory test results, whereas the modified Hirsch model generally underpredicts moduli. The computational micromechanics model presents a relatively higher deviation at lower loading frequencies, but it shows better predictions because the loading frequency is higher. Hashin's analytical micromechanics model is limited to accurately predicting the dynamic modulus of the asphalt mixtures because of geometric simplifications and assumptions. With further improvements, the computational micromechanics method incorporated with the testing protocol seems attractive, because it can directly account for geometric complexity due to aggregates and inelastic mixture component properties with fewer of the required laboratory tests.
Fénix Test
Authors: Pérez-Jiménez Félix , Valdés Gonzalo , Miró Rodrigo , Martínez Adriana , Botella Ramón
Published: January 2011

This paper presents a new direct tensile test to evaluate cracking resistance of asphalt concrete mixtures: the Fénix test. First, the literature on cracking factors and mechanisms of bituminous mixtures, as well as current tests to measure cracking properties, is reviewed. Next, the Fénix test is described, and some initial experimental results of the influence of variables, such as binder type and content and test temperature, are provided. Additionally, test repeatability and sensitivity are statistically analyzed. Correlations between parameters obtained by the Fénix test and the three-point bending beam fatigue test are also shown. Finally, the main conclusions of this work are summarized. These conclusions confirm that the Fénix test is a practical and efficient method for characterizing cracking behavior of asphalt concrete mixtures as far as the studied variables are concerned.
Effect of Thermal Stresses on Pavement Performance under Mild Climate Conditions
Authors: Kim Jaeseung , West Randy C.
Published: January 2011

Thermal stress on the surfaces of pavements located in mild climates has been commonly considered to have a negligible effect on pavement performance. Current pavement design methodology focuses on maximum tensile stress rather than tensile stresses occurring over the design life of pavements. To identify the significance of thermal stress on pavement performance through structural stress analysis, this study investigated the predictive capability of the enhanced integrated climate model by comparing it with measured temperature data and introducing an analytical methodology of estimating thermal stress development using the dynamic modulus test. The identified thermal stresses were compared with the tensile stresses occurring at the bottom of an asphalt layer through the analysis method employed in the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures. Damage caused by the thermal and bottom stresses was evaluated on the basis of the damage ratio derived from the hot-mix asphalt fracture model. The conclusion drawn from the investigations was that the effect of thermal stress on pavement cracking performance, evaluated through the damage analysis considering the time-and temperature-dependent nature of asphalt mixtures, is much less significant than that of bottom stress under mild climate conditions. Under the nonaging condition, 1-year average damage occurring due to thermal stress at typical pavement structures would be slightly less than 0.5% of that which would be expected to occur at the bottom.
Use of Nonuniform Stress-State Tests to Determine Fracture Energy of Asphalt Mixtures Accurately
Authors: Koh Chulseung , Roque Reynaldo
Published: January 2011

Fracture energy of asphalt mixture is known to have a strong influence on the cracking performance of flexible pavement. Accurate determination of fracture energy of laboratory specimens requires accurate determination of strain through fracture, at the instant of fracture, on the plane where fracture occurs. Tests involving nonuniform stress states, such that the failure plane is known a priori, are suited for accurate and consistent determination of fracture energy because gauges from which strains can be determined can be placed directly on the failure plane. The Superpave®d; indirect tension (IDT) test and the recently developed dog-bone direct tension (DBDT) test fall into this category. They were used in this study to determine tensile failure limits and, more specifically, to test whether fracture energy determined from one of the tests agreed with that from the other test and thereby indicated that fracture energy can be accurately determined from these tests. Strength tests were performed at constant rate of load ram displacement on dense- and open-graded asphalt mixtures for a range of temperature and aging conditions. Results showed that although tensile strength and failure strain between Superpave IDT and DBDT tests were different, because of differences in loading rate on the failure plane, the resulting fracture energy from the two tests was the same. This supports earlier findings that fracture energy is a fundamental property that is independent of stress state or loading conditions and, perhaps more important, that either one of these tests can be used to determine fracture energy of asphalt mixture accurately.
Estimation of Stress Conditions for the Flow Number Simple Performance Test
Authors: Hajj Elie Y. , Ulloa Alvaro , Siddharthan Raj , Sebaaly Peter E.
Published: January 2011

The flow number simple performance test for asphalt mixtures was one of the final three tests selected for further evaluation from the 24 tests initially examined under the NCHRP 9-19 project. Currently, no standard triaxial testing conditions for the magnitude of the deviator and confining stresses have been specified. The objective of this research was to develop recommendations for the selection of the deviator and confining stresses that best simulate the stress conditions encountered in the pavement under traffic loads. Extensive mechanistic analyses of three different asphalt pavement structures subjected to moving traffic loads at various speeds and under braking and nonbraking conditions were conducted with the 3D-Move model. Prediction equations for estimating the anticipated deviator and confining stresses as a function of pavement temperature, vehicle speed, and asphalt mixture's stiffness have been developed. An increase of 40% was observed for the deviator stress when braking conditions were incorporated. A preliminary validation of the recommended magnitudes for the deviator and confining stresses on a field mixture from WesTrack showed consistent results between the flow number test results and field performance.
Development of a Flow Number Predictive Model
Authors: Rodezno Maria Carolina , Kaloush Kamil E. , Corrigan Matthew R.
Published: January 2011

The NCHRP 9-19 panel recommended the repeated load permanent deformation test as a laboratory procedure that could be used to evaluate the resistance of a hot-mix asphalt (HMA) to tertiary flow. No standard test protocol addresses the required laboratory stress to be applied. The test can take several hours until tertiary flow is reached and in many cases the sample may never fail. A model capable of predicting or providing general guidance on the flow number characteristics of a mix can be of great value. The model can be ideally used as a guideline to determine the stress–temperature combination that will yield tertiary flow within a reasonable testing time. In this study, an effort was undertaken to develop a flow number predictive model. The model uses HMA mixture volumetric properties and stress–temperature testing conditions as predictor variables. The laboratory test data used are a combination of two valuable databases. The first one included tests conducted at Arizona State University; the second one included tests conducted by the FHWA Mobile Asphalt Material Testing Laboratory. Ninety-four mixtures were evaluated, and 1,759 flow number test results were available. Various regression models were evaluated by combining several independent variables. The final model selected had fair statistical measures of accuracy, and it covered a wide range of mixtures, gradations, and binder properties, as well as laboratory-applied stress. As more testing data become available, the model could be refined and recalibrated for better accuracy.
Effects of Adaptive Lane Departure Warning System on Driver Response to a Surprise Event
Authors: Tijerina Louis , Blommer Mike , Curry Reates , Greenberg Jeff , Kochhar Dev , Simonds Craig , Watson David
Published: January 2011

A lane departure warning (LDW) system monitors the current lane position of a vehicle and presents a driver alert when one of the vehicle's front tires crosses a threshold, for example, the nearest lane line. The primary intent of such warning systems is to prevent or mitigate road departures and related crashes caused by driver distraction or drowsiness. The present evaluation compared adaptive and nonadaptive versions of an LDW system. The adaptive version adapted to the driver's state, whereas the nonadaptive version did not. The adaptive LDW system alerted the driver only if a driver state monitor (DSM) indicated that the driver was looking away from the road ahead for 2 s or longer at about the time when a lane line was crossed. Forty volunteers drove a high-fidelity, moving-base driving simulator in a study to compare driver responses to a surprise lane departure when they used a nonadaptive LDW system and then an adaptive LDW system or vice versa. The results indicated that in the adaptive LDW mode, 13 subjects (34%) either experienced delayed activation of the LDW alert or received no LDW alert at all when they should have, primarily because of both the 2-s rule in the adaptive LDW algorithm and DSM registration issues. The adaptive LDW resulted in significantly larger lane excursions at the onset of the LDW alert compared with those that occurred in the non-adaptive LDW mode. These results highlight the dependence of the performance effects of adaptive systems on system hardware, algorithms, and algorithm parameters.