bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic and metabolic aspects of Defluviicoccus vanus-related organisms as competitors in EBPR systems
Authors: Lanham A. B. , Reis M. A. M , Lemos P. C.
Published: November 2008

A reactor was successfully enriched (90% as shown by Fluorescence in situ Hybridization) in Defluviicoccus vanus-related organisms presenting a Glycogen Accumulating Organisms (GAO) phenotype. Initial batch tests were performed using anaerobic/aerobic conditions to assess the capacity of different carbon sources utilization frequently abundant in wastewater: acetate, propionate, butyrate, valerate and glucose. Acetate and propionate were totally consumed in the anaerobic phase as well as butyrate and valerate, though these last ones with a very low consumption rate. All substrates were converted to polyhydroxyalkanoates (PHA). Glucose had a very slight anaerobic consumption but failed to disclose a typical GAO phenotype. In aerobic conditions, again all carbon sources were readily consumed except for glucose, with acetate and propionate having the higher consumption rates. Therefore, glucose seems not be used by this type of organisms. Acetate and propionate consumption rates indicated that these GAOs could reveal good competition advantages in EBPR systems where these carbon sources are available, especially propionate. Volatile Fatty Acid (VFA) uptake in aerobic phase and consequential PHA production indicate these organisms as possible candidates for PHA production.
Focusing of an electromagnetic plane wave into a uniaxial crystal by a Wood lens
Authors: Ghaffar Abdul , Naqvi Qaisar
Published: November 2008

High frequency fields, refracted by a geometry containing a Wood lens placed at a certain distance from a planar uniaxial interface, are derived by using Maslov’s method. The geometrical optics approximation generally valid for high frequency fields fails in the vicinity of a caustic. Maslov’s method is a systematic procedure for predicting the field in the caustic region, combining the simplicity of the ray and the generality of the transform method. Numerical computations are made for the field pattern around the caustic by using Maslov’s method. The results are found to be in good agreement with those obtained using Kirchhoff’s approximation.
Distant 10 years results of laparoscopic operative treatment in patients with varicocele
Authors: Jabłonowski Zbigniew , Grzegorczyk Adam , Kȩdzierski Robert , Miȩkoś Eugeniusz , Sosnowski Marek
Published: November 2008

Varicocele has been regarded a curable cause of infertility for dozens of years. The impact of varicocele treatment in terms of increase in pregnancy rates is a debated issue. We evaluate data from a 10-year cohort of results from laparoscopic operative treatment of varicocele patients according to pregnancy rate, complication rate, and satisfaction with varicocele repair. Ninety seven patients were treated by means of laparoscopy between 1993 and 1996. Ten years after operation questionnaires were sent to all patients. Answers were obtained from 49/97 pts. (50,5%). Details connected with marital status, pregnancy rate, addictions and scrotal pain discomfort were collected. Statistical analysis was performed using chi-square independence test and Spearman’s rank correlation coefficient. After 10 years, 75.5% who answered the questionnaire were fully satisfied with the results of treatment, 12.3% pts of patients were partially satisfied; 63.3% of patients fathered 1 to 3 children. Married patients and those who fathered children were found to be the most satisfied with the operation. We also found the statistically significant negative dependency between smoking addiction and number of children. There were no major complications intra- or postoperatively. No harmful consequences of testicular artery ligation were found. In conclusion, long-time 10 years follow-up enables better estimation of the results of laparoscopic treatment in patients with varicocele. Pregnancy rate may depend not only on varicocele repair but on smoking addiction as well. There is still no evidence of harmful consequences due to testicular artery ligation after varicocele repair
Molecular theoretic study of Freedericksz transition. Symmetry breaking of oblique axial order
Authors: Kio M. , Torikai M. , Yamashita M.
Published: November 2008

Freedericksz transition, which is usually analyzed by an elastic theory, is studied on the basis of statistical mechanical ground, where nematics with positive dielectric anisotropy in homogeneous anchoring cell is exposed to an electric field in the direction of wall normal. In low temperature region, an oblique axial symmetry breaking occurs, which is nothing but the Freedericksz transition. In high temperature and high field region, biaxial nematic phase with principal axis parallel to the field direction at interior area of the system is proved to appear. A phase diagram on the field versus temperature plane is obtained and compared with the one at a bulk with common biaxial symmetry, where both of electric and magnetic fields are applied in directions perpendicular to each other. In the latter, no symmetry breaking occurs, in contrast with the former case above-mentioned, and the reason why this difference occurs is elucidated.
Compensating defect centres in semi-insulating 6H-SiC
Authors: Kamiński P. , Kozłowski R. , Miczuga M. , Pawłowski M. , Kozubal M. , Żelazko J.
Published: November 2008

Photoinduced transient spectroscopy (PITS) has been applied to study electronic properties of point defects associated with charge compensation in semi-insulating (SI) 6H-SiC substrates. The photocurrent relaxation waveforms were digitally recorded in a wide temperature range of 20–800 K and in order to extract the parameters of defect centres, a two-dimensional analysis of the waveforms as a function of time and temperature has been implemented. As a result, the processes of thermal emission of charge carriers from defect centres were seen on the spectral surface as the folds, whose ridgelines depicted the temperature dependences of emission rate for detected defect centres. The new approach was used to compare the defect levels in vanadium-doped and vanadium-free (undoped) SI 6H-SiC wafers.
Genetic and Non Genetic Aspects of Autism Spectrum Disorders
Authors: Avdjieva-Tzavella D
Published: November 2008

Genetic and Non Genetic Aspects of Autism Spectrum Disorders

Chromosome abnormalities have long been recognized as an important cause of learning disabilities and multiple malformation syndromes. About 0.8% of live born infants have numerical or structural chromosomal anomalies that result in an abnormal phenotype. Identification of such anomalies is important clinically and also for accurate genetic counseling. Recently, molecular cytogenetic and array-based techniques have enabled higher resolution screens for chromosome anomalies. This brief review of the etiology of autism spectrum disorders (ASD) focuses on the heritable and non heritable risk factors that underlie this major neuro-developmental disorder. Since all patients with a chromosomal imbalance are dysmorphic, the association of ASD with a facial dysmorphism seems to be a good indication for chromosomal anomaly screening.
Prenatal Diagnosis of Translocation 13;13 Patau Syndrome: Clinical Features of Two Cases
Authors: Pazarbaşi A , Demirhan O , Süleymanova-Karahan D , Taştemir D , Tunç E , Gümürdülü D
Published: November 2008

Prenatal Diagnosis of Translocation 13;13 Patau Syndrome: Clinical Features of Two Cases

Patau syndrome is associated with extra chromosome 13 material, either free as in the 47,++13 or in a Robertsonian translocation or another rearrangement. We report on two fetuses with trisomy 13 who were diagnosed prenatally via cord blood and amniocentesis, respectively. They showedde novoRobertsonian translocation between chromosome 13 and 13, and had normal parents. One was detected cytogeneticaly at 24 weeks of gestation with a karyotype of 46, XX, rob(13;13) and lived only 1 month after birth. Holoprosencephaly, proboscis, microphthalmia and heart septal defects were present. The other fetus was examined at 14 weeks gestation because of cystic hygroma, hydrothorax and hyperechogenic kidneys and had the karyotpe 46, XY, rob(13;13). After abortion the fetus was found to have a cleft lip and palate, postaxial polydactyly of the feet, micrognathia, omphalocele, low-set ears with abnormal helix and to be small for the gestational age. Due to the difference in chromosomal makeup seen in non disjunction, there may be differences in expression of several of the features often seen with trisomy 13, either classical type (as in the 47,++13) orde novoRobertsonian translocation type (as in the 46).
The Some of the Parts: Prosthesis and Function in Bertolt Brecht, Oskar Schlemmer, and Kurt Jooss
Authors: Elswit Kate
Published: November 2008

The period during and following World War I in Germany reconceptualized the physical function of bodies to emphasize activity over structure, as visible in the prosthetic appendages worn by amputees returning from war to be reintegrated into society. Such manipulation of the human form is critical to the dramaturgy of the drama and dance works explored here, which deconstructed bodies in order to reconstitute the identity of the performers. This article moves from the engineering of social function in Bertolt Brecht's A Man's a Man, in which a narrative of altered personality is primarily reflected in the dialogue's metaphors of physical damage and reconstitution, to a progressive reliance on the body as a medium of dramaturgy in the manipulation of physical identity in Oskar Schlemmer's Triadic Ballet and Kurt Jooss’ The Green Table. By considering the shift in medical approaches to prosthesis and the treatment of onstage bodies to reflect the same changing values from multiple vantage points, the culturally and historically specific medium of the body thus offers an opportunity to think of not only medicine and performance together, but also drama and dance in their engagement with the contemporary body.
Specific Directional Exercises for Patients with Low Back Pain: A Case Series
Authors: Long Audrey , May Stephen , Fung Tak
Published: November 2008

Purpose: To determine whether outcomes could be changed after poor response to non-specific exercise therapy when the prescription was changed to specific, directional-preference exercises (McKenzie method).

Methods: Patients who participated in a randomized clinical trial (RCT) and the alternative care phase immediately following formed the cohort for this case series. In an earlier RCT, patients with directional preference were randomized to exercises/advice matched to their individual directional preference or to one of two unmatched protocols. The primary inclusion criterion for our case series was patient reports of being unchanged or worse following 2 weeks’ treatment in the RCT. The secondary inclusion criterion was patient requests for “a change to one of the other stretching protocols to see if I can achieve better pain control.” Patients meeting either of these criteria were offered matched exercises/advice if they had not previously received this intervention. Two-way repeated-measures ANOVA and McNemar tests compared outcomes during two consecutive time intervals: baseline to 2 weeks and 2 weeks to discharge. Dropouts were included in the intention-to-treat analysis.

Results: Four patients from the matched group met the primary inclusion criterion of “unchanged” (none reported being worse); 10 additional patients requested alternative treatment for better pain control (secondary criterion). Eighty-five patients from the two unmatched treatment groups met all the inclusion criteria, and an additional 22 patients met only the secondary criterion. These patients were offered matched treatment, and 96 consented. Those reporting improvement or resolution of symptoms were 22 % in the first two weeks of unmatched care (during the RCT) compared to 84 % with matched care. Statistically significant and clinically meaningful changes occurred in all outcomes (p < 0.001) after receiving matched care, compared to clinically unimportant changes with previous unmatched care during the RCT.

Conclusions: Poor outcomes from non-specific/unmatched exercise protocols appeared to reverse when patients with directional preference were given sub-group-matched, direction-specific exercises. Because of the limitations of our study design, replication with a control group and longer-term follow-up are required to validate the findings.
Development of Traffic Delay Assessment Tool for Short-Term Closures on Urban Freeways
Authors: Lee Chanyoung , Noyce David A. , Qin Xiao
Published: November 2008

A certain amount of delay in work zones is typically assumed to be unavoidable and often considered a cost of doing business when roadway improvements are in progress. Therefore, developing a method to predict delay, such that appropriate countermeasures to minimize delay can be implemented, is critical to successful work zone management. Predicting work zone delay in an effective and efficient manner should not require extensive data collection or long, complex coding efforts. The procedure should be customizable for local data availability, easy to use, and, for practitioners, easy to interpret. To this end, the Work Zone Capacity Analysis Tool (WZCAT) analytical software program was developed to predict delays and queues for short-term (daily) work zone closures. WZCAT queue-length predictions are based on a simple input-output model, with capacity of the work zone controlling the throughput. The purpose of this study was to evaluate and enhance WZCAT with field data as well as summarize various aspects of traffic flow and queuing patterns during work zone operations on selected urban freeways. Findings from field observations were significant traffic volume changes on exit and entrance terminals upstream of work zones and the stabilization of vehicle queue after initial queue development. A demand-adjust factor was developed and applied to WZCAT-R for effectiveness and efficiency. WZCAT-R produces effective results for queue prediction. It can be an effective and reliable tool in predicting work zone delay and queue development. The tool can also help engineers proactively plan work phasing, lane restrictions, and potential detour routes to move traffic more efficiently.
Review and Development of Recommended Minimum Pavement Marking Retroreflectivity Levels
Authors: Debaillon Chris , Carlson Paul J. , Hawkins H. Gene , He Yefei , Schnell Tom , Aktan Fuat
Published: November 2008

Research was conducted to review and develop minimum levels for pavement marking retroreflectivity to meet nighttime driving needs. A previous study performed in the 1990s using a computer model called the Computer-Aided Road-Marking Visibility Evaluator resulted in a table of minimum levels of pavement marking retroreflectivity values that FHWA used to develop its initial set of minimum pavement marking retroreflectivity levels. Since then, additional research has been completed as well as development of a newer, more feature-intensive computer model called the Target Visibility Predictor (TarVIP). The research presented used TarVIP to study pavement marking retroreflectivity needs while using the most recently available information pertaining to driver, vehicle, and headlamp trends in the United States. In this research, previous pavement marking research efforts that included findings or recommendations related to minimum retroreflectivity are summarized. Next, a comprehensive survey on the factors that affect pavement marking visibility and minimum RL levels was performed, with key factors identified. They included pavement marking configuration, pavement surface type, vehicle speed, vehicle type, and presence of raised reflective pavement markers. From findings of the key factor reviews, the TarVIP model was used to generate preliminary results that could then be analyzed by sensitivity analysis. The research resulted in a set of recommended minimum pavement marking retroreflectivity levels for typical conditions on U.S. roadways. Limitations of the research were listed as well as concepts for future work.
Development of New Performance Measure for Winter Maintenance by Using Vehicle Speed Data
Authors: Lee Chanyoung , Loh Wei-Yin , Qin Xiao , Sproul Mike
Published: November 2008

The study investigated vehicle speed changes during winter weather events. A total of 954 winter maintenance logs in 24 counties over three winter seasons were analyzed. Several variables of interest were developed, such as storm duration, maintenance operation hour, crew delayed, maximum speed reduction, and the storm start and end times. Also, t1, which represents the start of vehicle speed reduction, and t3, the time at which vehicle speeds recover to normal winter driving speeds, were measured from automatic traffic recorder data. The study confirms that vehicle speed seems to be a good measure of representing driving conditions during winter weather events and winter maintenance performance alike. Speed recovery duration was found to be a dependent variable, defined as a possible evaluation of winter maintenance operations using vehicle speed data.
Recycling of Salt-Contaminated Storm Water Runoff for Brine Production at Virginia Department of Transportation Road-Salt Storage Facilities
Authors: Craver Vinka O. , Fitch G. Michael , Smith James A.
Published: November 2008

A large part of the Virginia Department of Transportation's (DOT) maintenance effort comprises the implementation of its anti-icing program. Earlier research confirmed that Virginia DOT captures a large volume of salt-laden storm water runoff at its 300-plus salt storage facilities throughout the state and that disposal options for this water are limited and costly. Although Virginia DOT is implementing recommended management options to reduce the quantity of salt water captured, this research was undertaken to determine the possibility of recycling salt-contaminated storm water runoff for brine production. Laboratory and field tests were conducted using bench-scale brine generation equipment. In the laboratory phase, brine was produced by using tap water, applying different hydraulic retention times and temperatures. Storm water runoff from a storage pond without any previous treatment was used in the field phase. Results show that the optimum conditions for brine production are low hydraulic retention time (high flow rates) and high temperatures. The total suspended solids present in the storm water runoff did not diminish the quality of brine in the field tests. Economic and environmental benefits can be obtained by applying this recycling strategy.
Application of Road Visibility Information System to Winter Maintenance
Authors: Nagata Yasuhiro , Hagiwara Toru , Araki Keiji , Kaneda Yasuhiro , Sasaki Hirokazu
Published: November 2008

A road visibility information system (RVIS) was developed that uses images transmitted by multiple closed-circuit television (CCTV) cameras as road visibility information. Feasibility studies in the daytime during the winters of 2005 to 2006 and 2006 to 2007 were performed on national routes 230 and 231. During those two winters, the RVIS calculated visibility scale and road visibility index (RVI) automatically, accurately, continuously, and in a timely manner from road images recorded by multiple CCTV cameras. The RVIS processed 90% of the images transmitted by 14 CCTV cameras. The RVIS provided areawide visibility information in many formats and through many kinds of media and devices. On the basis of stored road visibility data, the finding was a high correspondence between the RVI and the subjective visibility evaluation for the same road images. In addition, this study demonstrates that the RVI monitoring website and e-mail alerts can speedily and reliably inform road administrators of snowstorm-induced poor visibility. The RVIS has the potential to collect data on road visibility reliably during daytime using images transmitted by multiple CCTV cameras. However, it is necessary to improve data collection at night and to capture still images accurately and quickly.
Effects of Adverse Weather on Traffic Crashes
Authors: Qiu Lin , Nixon Wilfrid A.
Published: November 2008

Adverse weather obviously has an impact on vehicle crash rates on roads and highways. However, it would be valuable to quantify the extent to which weather conditions affect the crash rate. To do that, a meta-analysis has been conducted to generalize research findings on this subject and attempt to quantify the impact of weather on traffic crashes. Studies between 1967 and 2005 that examined the interaction of weather and traffic safety were reviewed. Thirty-four papers and 78 records that meet the predetermined criteria were included in the analysis. Crash rates from each study were normalized with respect to effect size for meta-analysis generalization. Results indicate that the crash rate usually increases during precipitation. Snow has a greater effect than rain does on crash occurrence: snow can increase the crash rate by 84% and the injury rate by 75%. Further results also suggest that variations in study results can be explained by study design, date of the study, and region or countries included in the study.
Effect of Windshield Veiling Glare on Driver Visibility
Authors: Bhise Vivek , Sethumadhavan Susheel
Published: November 2008

This paper presents results of a veiling glare prediction model that was developed by modeling veiling glare luminance measurements and by using Blackwell's visual contrast threshold data. A critical visibility condition for a driver approaching a tunnel with the sunlight falling on the windshield and attempting to detect a target inside the tunnel was modeled. The luminance of windshield reflections of 38 instrument panel samples was measured in a specially designed veiling glare simulator by varying the sun angle, the windshield angle, and the instrument panel angle. The measurements were used to develop a regression model to predict the veiling glare coefficient as a function of windshield angle, sun angle, instrument panel angle, and instrument panel material gloss value. The developed visibility–distance prediction model was exercised by varying eight factors: (a) windshield angle, (b) instrument panel angle, (c) sun angle, (d) sun illumination incident on the windshield, (e) gloss level of the instrument panel material, (f) driver's age, (g) target size, and (h) illumination incident on the target in the tunnel. For example, under a worst-case situation of 45,000-lux sunlight illumination incident on the windshield, a 65-year-old driver will not be able to see a 2-ft2 10% reflectance target while approaching a dark tunnel with 100 lux of tunnel lighting. In contrast, if the tunnel lighting is raised to 5,000 lux, the 65-year-old driver can see the target from 650 ft, and a 25-year-old can see it from 4,900 ft.
Safety Effectiveness of “Stop Ahead” Pavement Markings
Authors: Gross Frank , Jagannathan Ramanujan , Lyon Craig , Eccles Kimberly
Published: November 2008

There is a need for rigorous evaluation of low-cost safety strategies that states may implement as part of their strategic highway safety plans. Highway safety funds are limited, so it is important to identify cost-effective strategies. FHWA organized a pooled-fund study of 26 states to evaluate low-cost safety strategies; “Stop Ahead” pavement markings were one strategy selected for investigation. Geometric, traffic, and crash data were obtained for 175 intersections with “Stop Ahead” pavement markings in Arkansas, Maryland, and Minnesota. Similar data were obtained for reference sites within each state. An empirical Bayes approach was incorporated in a before–after study design to evaluate the safety effectiveness of the “Stop Ahead” pavement markings. An aggregate analysis indicated a significant reduction in total crashes for Arkansas, Maryland, and the two states combined. There was also a significant reduction in right-angle and rear-end crashes for Arkansas and a general reduction in injury crashes. A disaggregate analysis indicated that crash reductions are significantly greater at three-legged intersections than at four-legged intersections. The strategy was also more effective at intersections with all-way stop control. Given the low cost of this strategy, even with conservatively high cost estimates, only a modest reduction in crashes is needed to justify its use. On the basis of the estimated safety effectiveness, the necessary crash reduction is easily achievable.
Safety Effectiveness of Selected Treatments at Urban Signalized Intersections
Authors: Srinivasan Raghavan , Council Forrest , Lyon Craig , Gross Frank , Lefler Nancy , Persaud Bhagwant
Published: November 2008

This study conducted a before–after evaluation by means of the empirical Bayes methodology for four types of treatments at signalized intersections with data from Winston-Salem, North Carolina. The results indicated that changing to protected left-turn phasing from permissive or permissive–protected phasing could lead to a virtual elimination of left-turn crashes but other crashes, which were likely to be less severe, could increase. Conversion from nighttime flashback to regular phasing seemed effective in reducing nighttime crashes. Replacing 8-in. signal heads with 12-in. heads seemed effective in reducing right-angle crashes, but this measure could increase other, less-severe crashes. Adding another red-signal lens to an existing one or changing from permissive to permissive–protected left-turn phasing did not seem particularly effective in reducing crashes, but these results were not definitive because they were based on a limited number of sites. Further research using data from other jurisdictions is needed, so that more definitive conclusions can be made about the safety effectiveness of these treatments.
Effectiveness of Experimental Transverse-Bar Pavement Marking as Speed-Reduction Treatment on Freeway Curves
Authors: Gates Timothy J. , Qin Xiao , Noyce David A.
Published: November 2008

Researchers performed a before-and-after analysis of speeds to determine the short- and long-term effectiveness of an experimental transverse-bar pavement marking treatment at the Plainfield curve on I-43–I-94 in Milwaukee, Wisconsin. The experimental transverse pavement marking treatment was installed in all lanes for each of the northbound and southbound directions of the curve in early September 2006. Each section of the pavement marking treatment was 1,000 ft long. The treatment sections consisted of a series of white transverse-bar markings installed with continuously decreasing spacing between successive markings, giving drivers the perception of increasing speed, potentially causing them to slow down. Each individual marking was 18 in. in lateral width by 12 in. longitudinally. Speed data were collected for 2 weeks in late July 2006; again in September 2006, approximately 1 week after the markings had been installed; and again in March 2007, approximately 6 months after the markings had been installed (northbound only). The researchers used analysis of variance to analyze the mean speeds for more than 43,000 intervals of 5 min each measured at three locations in each lane of the northbound and the southbound directions. The results of the analysis suggest that the experimental transverse pavement marking treatment was effective at reducing curve speeds, especially shortly after installation. The marking treatment showed the greatest effects on speeds midway through the treatment section with approximately 1- to 4-mph reductions in mean speed observed between the before and the after periods. A lane-by-lane analysis showed that the marking treatment was most effective at reducing speeds in the shoulder and middle lanes, while speeds in the median lane were relatively unaffected.
Understanding Internal Structure Characteristics of Foamed Asphalt Mixes with Fracture Face Image Analyses
Authors: Fu Pengcheng , Harvey John T. , Jones David , Chao You-Chen
Published: November 2008

The rate of use of full-depth reclamation with foamed asphalt to rehabilitate cracked pavements is increasing worldwide. However, the state-of-the-art understanding of foamed asphalt mixes and the state-of-the-practice engineering application are largely empirical because of the lack of in-depth knowledge of this material's internal structure characteristics. A fracture face image analysis framework for quantification of the asphalt mastic phase distribution in foamed asphalt mixes, which is a key microscopic structure characteristic, is described. Fracture face asphalt coverage is a quantitative indicator of asphalt spot distribution on fractured faces and is primarily a function of the asphalt dispersion in the mix, the relative strengths of the asphalt mastic and mineral filler phases, and the boundary conditions of specimen compaction and testing. Fracture face image analyses combined with laboratory testing results are presented. It was found that (a) the strength of the asphalt mastic phase is much less susceptible to moisture conditioning than the strength of the mineral filler phase, (b) filler contents that are too low or too high both negatively influence the effectiveness of asphalt stabilization, and (c) the image analyses show that the impact of asphalt grade on the asphalt distribution in the mix dominates the effectiveness of asphalt stabilization but not the strength of the asphalt cement itself. Additionally, engineers can perform a qualitative fracture face asphalt distribution check at the project level of mix design to diagnose mix problems, for which an interim guideline is proposed.
Probabilistic Analysis of Fracture in Asphalt Mixtures Caused by Moisture Damage
Authors: Caro Silvia , Masad Eyad , Airey Gordon , Bhasin Amit , Little Dallas
Published: November 2008

Moisture damage in asphalt mixtures is a complex phenomenon involving thermodynamic, chemical, physical, and mechanical processes that contribute to pavement deterioration. The empirical nature of the majority of test methods and the inherent variability of the results are the two primary challenges impeding the reliable characterization and assessment of moisture damage. This paper addresses these two challenges by offering a framework that (a) is based on probabilistic analysis that accounts for the uncertainty of the deterioration process and the inherent variability associated with the experimental data, (b) is based on a fracture mechanics damage model for viscoelastic materials that has successfully been applied to the characterization of moisture damage in asphalt mixtures, and (c) combines the fundamental material properties of the asphalt mixture that can be obtained from reliable tests (e.g., surface energy measurements of the material components and dynamic shear test and relaxation modulus data from the dynamic mechanical analyzer). This framework was applied to analysis of the fine matrices of four asphalt mixtures containing different aggregate materials and fillers. The results are compared with the results obtained by assessment of moisture susceptibility for the full asphalt mixtures by the saturation aging tensile stiffness test.
Validity of Asphalt Binder Film Thickness Concept in Hot-Mix Asphalt
Authors: Elseifi Mostafa A. , Al-Qadi Imad L. , Yang Shih-Hsien , Carpenter Samuel H.
Published: November 2008

Despite the possible benefits of implementing asphalt binder film thickness into current specifications to address durability problems, most of the related research has been theoretical and only a few attempts have been made to measure this property experimentally. The objective of this study was to investigate the concept of asphalt binder film thickness experimentally on the basis of measurements obtained by image analysis techniques, reflective light microscopy, and scanning electron microscopy. The results of the experimental program were used to gain insight into the concept of asphalt binder film thickness and its validity. Experimental results indicated that asphalt binder films coating large aggregates do not actually exist in hot-mix asphalt. Instead, what are referred to as asphalt binder films surrounding large aggregates are actually asphalt mastic films. These films are highly irregular in shape and have a thickness greater than 100 μm in the mixture considered in this study. The asphalt binder films in the mastic were observed at a thickness of 2 μm in the mixtures considered. However, these entities do not represent asphalt binder coatings around aggregates; they are only part of a blend with fine aggregates and mineral fillers. Microscopic analysis showed that air voids usually appear near the boundary between large aggregates and asphalt mastic.
Interface Bonding between Hot-Mix Asphalt and Various Portland Cement Concrete Surfaces
Authors: Leng Zhen , Ozer Hasan , Al-Qadi Imad L. , Carpenter Samuel H.
Published: November 2008

Interface bonding between hot-mix asphalt (HMA) overlays and portland cement concrete (PCC) pavements can be one of the most significant factors affecting overlay service life. In this study, a direct shear test device was built and used to investigate the characteristics of the HMA–PCC interface and to determine the interface shear strength. Several parameters affecting the interface performance were included in this study, such as HMA type, tack coat type, tack coat application rate, PCC surface texture, and temperature. The test results showed that the use of SS-1hP emulsion resulted in a greater interface bonding strength than the use of RC-70 cutback. Surface mix SM-9.5 was found to have a better interface strength than binder mix IM-19.0. Among the four residual application rates considered in this study, 0.05 gal/yd2 was found to be the optimum rate, independent of test parameters. The direction of tining in the PCC surface was found to have no effect on interface shear strength at 20°C. At the optimum tack coat application rate, the PCC smooth surface showed a higher interface shear strength than tined surfaces. When tests were performed at the intermediate temperature range, as the temperature increased, the interface bonding strength decreased.
Verification of Superpave Number of Design Gyration Compaction Levels for Georgia
Authors: Watson Donald E. , Moore Jason , Heartsill Justin , Jared David , Wu Peter
Published: November 2008

The objective of this project was to evaluate the performance of Georgia's mixes designed by using the Superpave® gyratory compactor. Mixes designed with numbers of design gyrations that are too high would be rut resistant but may be difficult to compact adequately in the field and may lack sufficient durability because of reduced asphalt binder content. The following conclusions were made on the basis of an evaluation of field projects and from laboratory volumetric and performance testing with various aggregate sources and gyration levels: (a) It is unlikely that Superpave mixtures will reach the design air voids of 4.0% during the life of the pavement. After nearly 5 years, the average air voids measured in the wheelpaths were 5.7% for Superpave projects and 3.8% for Marshall projects. On the basis of volumetric comparisons, 66 gyrations with the laboratory-produced mix gave approximately the same density achieved on the Superpave projects in the field. (b) The difference between 4-in.-diameter Marshall samples and 6-in.-diameter gyratory samples for moisture susceptibility was not statistically significant enough to assign a relationship between the tensile strength ratio (TSR) for samples with a diameter of 4 in. and the TSR for samples with a diameter of 6 in. (c) Although the asphalt binder content was an important factor in extending fatigue life, aggregate source and strain level were the most significant variables affecting fatigue results.
Implementation of Quality Management of Hot-Mix Asphalt with Seismic Methods
Authors: Celaya Manuel , Nazarian Soheil
Published: November 2008

Existing practices for field quality management of hot-mix asphalt layers rely on the adequacy of parameters such as thickness, air voids, and density. Because mechanistic–empirical pavement design is primarily based on the modulus of the pavement layers, methods of measuring the asphalt modulus in the field shortly after construction may lead to the more reliable implementation of the design. Seismic methods of modulus-based quality management may be more beneficial than traditional techniques because they are nondestructive, they can be performed rapidly, results are obtained immediately, and the material is tested in its natural state. The approach presented here includes a six-step procedure that combines design, laboratory, and field quality management processes. To evaluate the proposed method, 10 new construction sites were investigated to corroborate its usefulness and convenience. On the basis of the information collected, transportation organizations can implement the method along with their traditional methods to develop quality control and acceptance criteria. Performance of the simplified seismic laboratory and field tests along with more traditional tests may result in a database that can be used to smoothly unify the design procedures with pavement evaluation.
Asphalt Material Characterization in Support of Mechanistic–Empirical Pavement Design Guide Implementation in Virginia
Authors: Flintsch Gerardo W. , Loulizi Amara , Diefenderfer Stacey D. , Diefenderfer Brian K. , Galal Khaled A.
Published: November 2008

The procedure proposed in the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures (referred to as MEPDG) heavily depends on the characterization of the fundamental engineering properties of paving materials. This paper presents the results of a project aimed at the characterization of hot-mix asphalt (HMA) in accordance with the procedure established by MEPDG to support its implementation in Virginia. The project examined the dynamic modulus, the main HMA material property required by MEPDG, as well as creep compliance and tensile strength, which are needed to predict thermal cracking. Loose samples of 11 mixes (four base, four intermediate, and three surface mixes) produced with PG 64-22 binder were collected from different plants across Virginia. Representative samples underwent testing for maximum theoretical specific gravity, asphalt content by the ignition oven method, and gradation of the reclaimed aggregate. Specimens for the various tests were then prepared by use of the Superpave® gyratory compactor. The test results showed that the dynamic modulus is sensitive to the mix constituent properties (aggregate type, asphalt content, percentage of recycled asphalt pavement, etc.) and that even mixes of the same type (SM-9.5A, IM-19.0A, and BM-25.0) had different measured dynamic modulus values. The Level 2 dynamic modulus prediction equation reasonably estimated the dynamic modulus measured; however, it did not capture some of the differences between the mixes found in the measured data.
Verification of Rutting Predictions from Mechanistic–Empirical Pavement Design Guide by Use of Accelerated Loading Facility Data
Authors: Azari Haleh , Mohseni Alaeddin , Gibson Nelson
Published: November 2008

As a part of FHWA's Accelerated Loading Facility (ALF) experiment, asphalt pavement lanes were built with six different asphalt binder types and two different thicknesses and were tested for rutting and fatigue cracking. Loose asphalt mixtures were taken from each lane at the time of construction and compacted in the laboratory. These plant-produced specimens compacted in the laboratory and other laboratory-produced specimens were subjected to dynamic modulus and flow number tests with a simple performance tester (SPT). Field rutting measurements of the ALF lanes were conducted during and after the loading. A good agreement between the permanent strains measured by the flow number test and the ALF rutting measurements was observed for the initial rutting. The rutting of asphalt mixture layers of the ALF lanes was also predicted by using Level 1 and Level 3 analyses with Mechanistic–Empirical Pavement Design Guide (MEPDG) software by using the detailed data that were available for the ALF lanes. Comparison of the predicted rutting with the rutting measured on the ALF indicated that the rutting predicted by Level 3 analysis with MEPDG software, based on the asphalt stiffness equation, agreed somewhat with the actual rutting on the ALF lanes. However, the rutting predicted by Level 1 analysis, based on the actual SPT-measured dynamic modulus, significantly over-predicted the amount of rutting. The NCHRP Project 1-37A permanent deformation prediction models used in MEPDG software were also used separately to predict the rutting of the ALF lanes by using the predicted and the measured stiffness values. Results similar to those obtained by Level 1 and Level 3 analyses with MEPDG software were obtained. The overprediction of rutting by Level 1 analysis with MEPDG software may be related to the calibration of the NCHRP Project 1-37A permanent deformation equation. The model seems to have been calibrated by using the stiffness predicted from the NCHRP Project 1-37A equation, which is proven to overpredict stiffness at high temperatures, rather than the tested SPT stiffness and, thus, can provide reasonable rutting estimates only for Level 3 analyses (by use of the predicted stiffness).
Link-Based Emission Factors for Heavy-Duty Diesel Trucks Based on Real-World Data
Authors: Frey H. Christopher , Rouphail Nagui M. , Zhai Haibo
Published: November 2008

Heavy-duty diesel vehicles contribute a substantial fraction of nitrogen oxides (NOx) and particulate matter (PM) to the on-road vehicle emission inventory. The objectives of this study are to estimate roadway link-based emission rates for heavy-duty trucks for use in emission inventory estimation and to quantify the impact of factors affecting truck emissions. A speed–acceleration modal emission approach is developed from a database gathered via a portable emission measurement system for single rear-axle and tandem-axle dump trucks. Second-by-second real-world truck speed profiles on links are analyzed on the basis of observed patterns of time distributions of speed–acceleration modes. Link-based emission rates are estimated as the product of the fraction of time spent in each mode and the corresponding modal average emission rate. The sensitivity of link-based emission rates to key factors including chassis type, vehicle load, and fuel type is discussed. Single rear-axle trucks have lower emission rates than do tandem-axle trucks for carbon dioxide, PM, nitric oxide (NO), and hydrocarbons (HC) but higher carbon monoxide (CO) emission rates. Loaded trucks have higher fuel use and emissions than unloaded trucks. Replacing diesel fuel with biodiesel fuel for heavy-duty trucks may reduce tailpipe NO exhaust emissions and will reduce emissions of PM, CO, and HC. However, both fuels generate similar CO2 emissions. Benchmark comparisons for link-based emission rates show that NO emission rates increase with mean speed. However, link-based CO and HC emission rates were not as sensitive to speed variation as NO emissions. The link-based emission rate approach is recommended to couple heavy-duty vehicle emission inventory estimation with transportation demand models.
Experimental Analysis of Vehicle Operation Parameters Affecting Emission Behavior of Public Transport Buses with Alternative Diesel Fuels
Authors: Vijayan Abhilash , Kumar Ashok , Abraham Martin
Published: November 2008

Key results are presented from an exhaust emission study conducted on more than 105 buses in idling condition and selected sample buses from seven fleets in real-world operating conditions in Toledo, Ohio, of the effects of varying vehicular operation parameters on public transport bus emissions. It was observed that for the same amount of time in operation, vehicles in idling mode produced higher average concentrations of carbon monoxide, nitric oxide, nitrogen dioxide, and sulfur dioxide than those in on-road operation. Operating the vehicles in normal engine idling mode and with higher engine temperatures was found to reduce vehicular emissions by up to 30% to 42% as compared with fast idling and lower or colder engine temperatures. Performing regular preventive maintenance reduced emission concentrations by 15% to 20%. The results also highlight that a combination of multiple influencing factors including engine technology, vehicle age, vehicular maintenance, fuel, and past and present operating conditions should be evaluated to better understand and predict vehicular emission behavior.
Environmental Impacts of Catalytic Converter Malfunctions
Authors: Ahn Kyoungho , Rakha Hesham , El-Shawarby Ihab
Published: November 2008

For effective reduction of total vehicle emissions, identifying and understanding the effects of high-emitting vehicles play an important role. Although several studies have documented the environmental impacts of high-emitting vehicles, these studies have not looked at the operational impacts of these vehicles on the environment. In this study, field-collected and simulated data are used to explain the operational effects associated with catalytic converter malfunctions on vehicle emissions. In addition, the study develops microscopic emission models for vehicles with catalytic converter malfunctions by using on-road emission measurement data. The study demonstrates that catalytic converter malfunctions produce significant increases in hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) emissions of 297%, 211%, and 378%, respectively, during cruising operations. Furthermore, increases of 63.4%, 26.9%, and 76.1% are observed during acceleration maneuvers. The study also found that under extremely aggressive driving conditions, both normal and high-emitting vehicles produce very high emission rates. The simulation results demonstrate that the highest impact of catalytic converter malfunction occurs in the 45- to 85-km/h speed range at mild acceleration levels for HC and CO emissions and between 20 and 55 km/h at high acceleration levels for NOx emissions. Simulation analysis of various driving cycles demonstrates that catalytic converter malfunctions produce overall increases in HC, CO, and NOx emissions in the range of 251%, 225%, and 336%, respectively. The study demonstrates that high-emitting vehicles can be significant contributors to air pollution, implying that eliminating high-emitting vehicles could significantly improve air quality in many metropolitan areas.
Emission Analysis at Toll Station Area in Beijing with Portable Emission Measurement System
Authors: Song Guohua , Yu Lei , Zhang Xiao
Published: November 2008

The primary objective of this paper is to analyze the emissions around a toll station area in Beijing by using a portable emission measurement system (PEMS). To this end, the real-world vehicle emission and activity data of a light-duty-gasoline vehicle, a 2000 Volkswagen Jetta, were collected at a freeway toll station in Beijing with the PEMS. The data on both electronic toll collection (ETC) lanes and manual toll collection (MTC) lanes were assembled for comparison. Then an analysis showed that all emissions were reduced by using ETC; however, the reduction in nitrogen oxide (NOx) emission was much less than that for hydrocarbons (HC) and carbon monoxide (CO) for the testing vehicle. Further, emission estimation approaches based on vehicle specific power (VSP) were studied with the collected data, and some errors in common were identified. For the toll station, the VSP interval [-2, 2] was found to be a critical interval in the driving modes as well as in the average emission rates. A finer binning approach was applied, and the accuracy of the emission estimation for the toll station was improved. Subsequently, a comprehensive analysis of speed, VSP, and the accumulated emissions around the tollbooths was conducted to explain why the percentage of NOx reduction was much less than those for HC and CO. Finally, a queue-based emission estimation model was studied for the MTC lanes by using the field data, and the model was found not suitable for the estimation of NOx emission.