1,720,954 research outputs found
Quantification of moisture related damage in flexible and rigid pavements and incorporation of pavement preservation treatments in Aashtoware pavement-me design and analysis
No full textMoisture increase in pavement subsurface layers has a significant influence on granular material properties that affect the expected pavement performance. In-situ moisture variations in unbound base layer over time significantly depend on water infiltration after precipitation and pavement surface conditions. Consequently, base resilient modulus (MR) is decreased considerably, which leads to premature failure and reduced service life. This study presents Long-term Pavement Performance (LTPP) data analyses for quantifying the effect of moisture infiltration through surface discontinuities (cracks and joint openings) on flexible and rigid pavement performance. Subsurface moisture data obtained through Seasonal Monitoring Program (SMP) time domain reflectometry (TDR) are an excellent source to quantify the moisture-related damage in flexible and rigid pavements located in different climates. The artificial neural network (ANN) models were developed using SMP data for flexible and rigid pavement sections. The results show that higher levels of cracking and joint openings will lead to an increase moisture levels within base layer. Also, the moisture content increases with higher percentage passing # 200 sieve (P200), and higher precipitation levels, especially in wet climates. The MR of the base decreases significantly with an increase in moisture levels. For flexible pavements, the maximum reduction in base MR ranged between 40% to 175% for the pavement sections located in dry and wet regions, respectively. In rigid pavements, the maximum reduction in base MR may vary from 10% to 125% for the pavement sections located in dry and wet regions, respectively. The major reasons for higher base moisture variations in wet climates are higher levels of surface cracking and precipitation. The base moisture values do not vary significantly in dryer climates since the amount of precipitation and observed cracking levels were low in these regions. Due to increased moisture and a corresponding reduction in base MR values, the performance of pavement sections located in wet climates is adversely affected. The findings imply that an adequate and timely preservation treatment such as a crack sealing can enhance the pavements service life significantly, especially in wet climates. Therefore, cracks should be sealed when the extent of fatigue cracking is within 6% to 7% and between 10% to 11% for the flexible pavements sections located in wet and dry climates, respectively. In rigid pavements, the joints should be resealed when the damaged joint sealant length exceeds 50 to 75 meters.Thesis (M.S.)--Michigan State University. Civil Engineering, 2018Includes bibliographical references (pages 99-103
Wim sensors accuracy, guidelines for equipment selection and calibration, and traffic loading data applications
No full textWeigh-in-Motion (WIM) technology is one of the primary tools used for pavement management. It can provide essential and accurate truck traffic information, including vehicle class and speed, vehicle count, gross vehicle weight (GVW), single axle (SA) and tandem axle (TA) weights, axle spacing, and the date and time of the event. The State Departments of Transportation (DOTs) gather WIM data for various applications, including highway planning, pavement and bridge design, commercial vehicle weight enforcement, asset management, and freight planning and logistics. Overloaded trucks pose severe challenges to road transport operations. Overloaded trucks can cause more damage to the pavement systems than trucks loaded within legal weight limits. Truck overloading can also lead to severe consequences if involved in a traffic accident. Law enforcement agencies divert potentially overloaded trucks to static scales and issue tickets based on the information collected at a WIM station. Because of the wide range of applications, the data obtained at WIM stations must be accurate, consistent, and reflect actual field conditions.This study addressed four critical concerns related to WIM equipment performance, calibration needs, traffic loading data quality, and applications. Precisely, the current research advanced the state of the practice knowledge about (a) potential factors impacting WIM system accuracy, (b) accuracy and consistency of traffic loading data and calibration needs of WIM stations, (c) revised/modified guidelines for WIM equipment calibration, and (d) estimation of commercial freight tonnage from Gross Vehicle Weight (GVW) data. The research objectives were accomplished by synthesizing and analyzing the WIM performance and traffic loading data available in the Long Term Pavement Performance (LTPP) traffic database and data available through other state DOTs. The WIM sites analyzed in this study are from 30 states within the United States and 3 Canadian provinces. Several factors can affect the WIM system accuracy (i.e., measurement error). The potential site-related factors include road geometry, pavement stiffness, surface distresses, roughness, and climate. Decision tree models were developed in this study to illustrate a potential for estimating the expected WIM measurement error range using information about the WIM site and sensor-related factors. The results show that the sensor array and sensor types are the most important predictors, followed by WIM controller functionality (speed points). The data analysis and results also show that the climate can be important for some sensor types. One can integrate this information with equipment installation and life cycle costs to determine the most reliable and economical WIM equipment while also considering accuracy requirements by WIM data users.One way to evaluate WIM measurement errors is by using the data collected immediately before and after equipment calibration. The limitation of this approach is that the data represent a snapshot in time and may not represent a long-term WIM site performance. Consequently, an alternative approach was needed to characterize temporal variations in WIM data consistency. This study presents a method to estimate WIM system accuracy based on axle load spectra attributes [Normalized Axle Load Spectra (NALS) shape factors]. This analysis's main objective is to determine WIM system errors based on axle loading without physically performing equipment calibration. Using NALS to estimate WIM system accuracy can save a significant amount of time and resources, usually spent on equipment calibrations yearly.Successful WIM equipment calibration can eliminate systematic weight, speed, and axle spacing errors. The suggested changes in current WIM calibration procedures related to truck type (loaded truck), number of truck runs, and truck speed (multiple speed points) can significantly reduce the time and resources needed for successful equipment calibration. Accurate freight tonnage estimates and trends are essential due to their implications on economic, infrastructure development, and transportation policy decision-making. This study presents a practical application of WIM data to estimate freight tonnage and classify commodity types. The payloads computed for Class 9 trucks from GVW data strongly correlated with the average freight tonnage obtained from a commercial data source, i.e., Transearch from the IHS market. The user can independently verify the freight estimates from surveys at locations close to WIM sites.Thesis (Ph. D.)--Michigan State University. Civil Engineering, 2022Includes bibliographical references (pages 192-199
Influence of moisture infiltration on flexible pavement cracking and optimum timing for surface seals
Full text linkMoisture increase in pavement subsurface layers has a significant influence on granular material properties that affect the expected pavement performance. In situ moisture variations over time in an unbound base layer depend on water infiltration after precipitation and pavement surface conditions. Consequently, base resilient modulus (MR) is reduced, which leads to premature failure and reduced service life. This paper presents long-term pavement performance (LTPP) data analyses for quantifying the effect of moisture infiltration through surface cracking on flexible pavement performance. Subsurface moisture data obtained through the seasonal monitoring program (SMP) time domain reflectometry (TDR) are an excellent source for quantifying the moisture-related damage in flexible pavement located in different climates. An artificial neural network (ANN) model was developed based on the SMP data for flexible pavement sections. The results show that higher levels of cracking will lead to an increase in moisture levels within the base layer, which leads to a significant decrease in the base MR. For flexible pavement, the maximum reduction in base MR ranged from 18% to 41% and from 153% to 175% for the pavement sections located in dry and wet regions, respectively. Consequently, the performance of pavement sections located in wet climates is adversely affected. The findings imply that an adequate and timely preservation treatment for cracking sealing (e.g., surface seals) can enhance the pavement’s service life, especially in wet climates. The results suggest that cracks should be sealed when the extent of fatigue cracking is within 6% and 11% for the flexible pavement sections located in wet and dry climates, respectively.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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