bluuebunny/crossref_metadata_2025 huggingface dataset:
Oral versus intravenous tranexamic acid in enhanced-recovery primary total hip and knee replacement
Authors: Irwin A. , Khan S. K. , Jameson S. S. , Tate R. C. , Copeland C. , Reed M. R.
Published: October 2013

In our department we use an enhanced recovery protocol for joint replacement of the lower limb. This incorporates the use of intravenous tranexamic acid (IVTA; 15 mg/kg) at the induction of anaesthesia. Recently there was a national shortage of IVTA for 18 weeks; during this period all patients received an oral preparation of tranexamic acid (OTA; 25 mg/kg). This retrospective study compares the safety (surgical and medical complications) and efficacy (reduction of transfusion requirements) of OTA and IVTA. During the study period a total of 2698 patients received IVTA and 302 received OTA. After adjusting for a range of patient and surgical factors, the odds ratio (OR) of receiving a blood transfusion was significantly higher with IVTA than with OTA (OR 0.48 (95% confidence interval 0.26 to 0.89), p = 0.019), whereas the safety profile was similar, based on length of stay, rate of readmission, return to theatre, deep infection, stroke, gastrointestinal bleeding, myocardial infarction, pneumonia, deep-vein thrombosis and pulmonary embolism. The financial benefit of OTA is £2.04 for a 70 kg patient; this is amplified when the cost saving associated with significantly fewer blood transfusions is considered.

Although the number of patients in the study is modest, this work supports the use of OTA, and we recommend that a randomised trial be undertaken to compare the different methods of administering tranexamic acid.

Cite this article: Bone Joint J 2013;95-B:1556–61.
Modeling and Simulation of 5 and 11 DOF Ball Bearing System with Localized Defect
Authors: Marín J. M. , Rubio H. , García-Prada J. C. , Reinoso O.
Published: October 2013

This paper proposes a model of concentrated parameters for a rolling bearing operating in dynamic conditions with and without localized defect. The rolling bearing is modeled as a Z + 2 df degree of freedom (DOF) system, where Z is the number of rolling elements. The radial displacement of these rolling elements is considered in this model. In the analytical formulation, the contact force between the balls and races is considered as non-linear spring-dampers, whose stiffnesses are obtained applying Hertzian elastic contact deformation theory. The equations of motion are formulated using Lagrange's equation, considering the characteristics of the individual components of a rolling bearing, such as rotor, rolling elements, and inner and outer race. The Runge-Kutta method is used to solve the non-linear differential equations of motion. The simulation is accomplished by MATLAB and SIMULINK. To validate the simulated model, we have designed a testbed to carry out. The frequency components of the signal generated by the model in simulation and the experimentally obtained signal are compared. The results achieved experimentally demonstrate the validity of the mathematical model presented here. The model provides a powerful tool to predict the satisfactory behavior of this system.
Evaluating the Operational Efficiency of the Banking Sector in Taiwan: A Two-Stage Data Envelopment Analysis Approach
Authors: Wang Mu-Shun , Lu Shih-Tong
Published: October 2013

In this study we adopted two-stage data envelopment analysis (DEA) methods, including the Charnes–Cooper–Rhodes and Banker–Charnes–Cooper methods, to evaluate the performance of marketing-orientation and profit-orientation activities on the cost efficiency of Taiwan's banks. The conventional DEA model was modified to take into account the series relationship for dividing two sub-processes in order to identify the causes of inefficiency. Information was obtained from 37 Taiwanese banks for the period from 2008 to 2011. The Malmquist total factor productivity index was employed to measure the effect of productivity changes on the panel data. The empirical results from the two-stage approach indicate the following: (1) the mean efficiency score of profitability stage banks is higher than that of the marketability stage banks; (2) the technical efficiency is significantly different from ranking according to the operating scale and pure technical efficiency, and the scale efficiencies are significantly different from ranking according to fixed assets; and (3) economies of scale and scope exist at small and medium-sized banks.
Az adhaesioképződés mechanizmusa és modellezésének lehetőségei – Előkísérleti modellek
Authors: Szabó Györgyi , Gamal Eldin Mohamed , Sándor József , Ferencz Andrea , Lévay Bernadett , Csukás Domokos , Dankó Titanilla , Wéber György
Published: October 2013

Absztrakt

A hasüregi sebészeti beavatkozásokat követő adhaesio kialakulását számos műtéti körülmény segíti elő – pl. vérzés, idegen anyag bejutása, szövetsérülés, -roncsolódás, ischaemia, hypoxia. Képződése műtéti típustól függően akár 95%-os is lehet. Az adhaesio sok esetben elősegíti további posztoperatív szövődmények kialakulását. Ez lehet krónikus hasi fájdalom, a szervek megfelelő motilitásának akadályozása, de nőknél akár infertilitást is okozhat. Éppen ezért fontos a képződés mechanizmusának pontos ismerete, illetve a megfelelő állatmodell kidolgozása, amely lehetővé teszi a különböző prevenciós módszerek vizsgálatait. Az adhaesioképződésben kulcsszerepet játszó molekulákat, működésük és egymásra hatásuk mechanizmusát szakirodalmi adatok összefoglalásával állítottuk össze. Az adhaesiós állatmodell kidolgozásához hím Wistar-patkányokat használtunk. Az adhaesio kialakításához a következő módszereket alkalmaztuk: pontszerű vérzés előidézése, különböző idegen anyagok beültetése, ischaemizált terület létrehozása, kisebb és jelentősebb szöveti roncsolás. Modelljeinkben a pontszerű vérzések és ischaemizált hasfali területek esetén nem látható adhaesio. Idegen anyagok használatánál a behelyezett anyag felületétől függő méretű adhaesio képződött. Kisebb sérülés esetén szintén jól működött az adhaesio képződését gátló mechanizmus. Az adhaesiós kísérleteink közül a durva szövetsérülést okozó típus a legmegbízhatóbb, az adhaesioképződés minden állatban megfigyelhető, ezért további vizsgálatainkhoz jól használható modell. A bonyolult mechanizmusban a kulcsszereplők megismerése és a megfelelő modell kialakítása elengedhetetlen feltétele a megfelelő prevenciós módszerek kidolgozásának.
Ocorrência de mosca-branca em Annona squamosa no estado de São Paulo
Authors: Garcia Maria José De Marchi , Fischer Ivan Herman , Lourenção André Luiz , Lima Aurino Florencio de , Bueno Regiane Cristina Oliveira de Freitas , Souza Efrain Santana
Published: October 2013

No Brasil, é restrito o conhecimento sobre distribuição geográfica e plantas hospedeiras de moscas-brancas (Hemiptera: Aleyrodidae), principalmente em plantas cultivadas. Nesta comunicação, é registrada a ocorrência de Aleurodicus mirabilis (Cockerell, 1898) em altas infestações em fruta-do-conde (Annona squamosa Linnaeus, 1753) no estado de São Paulo, Brasil.
Gill rakers in six teleost species: influence of feeding habit and body size
Authors: Almeida Ana Paula Gottlieb , Behr Everton Rodolfo , Baldisserotto Bernardo
Published: October 2013

This study analyzed the structure of the gill rakers of Parapimelodus valenciennis and Parapimelodus nigribarbis (planktivorous), Serrasalmus maculatus and Hoplias malabaricus (piscivorous), Iheringichthys labrosus (benthophagous) and Hypostomus commersonii (detritivorous) and related it with the body size and feeding habits of these species. The species of Parapimelodus and H. commersonii showed long, filiform and closely spaced gill rakers, similar to those of species that use the gill rakers as a filter to assist in the retention of small particles. The widely spaced gill rakers of I. labrosus probably allow the retention of insect larvae, but not particles of inorganic matter. In H. malabaricus and S. maculatus the gill rakers are most likely related to prey capture and swallowing, as observed in other piscivorous species. In general, gill raker length and the distance between gill rakers have a positive relationship with fish length. The gill rakers show adaptations related to the diet of the fish, but morphological variation may occur even between species whose feeding habits are the same.
Milton Friedman e a efetividade da política fiscal
Authors: Lopreato Francisco Luiz C.
Published: October 2013

O objetivo do artigo é discutir a visão de Milton Friedman sobre o papel da política fiscal. O trabalho estrutura-se a partir da discussão de quatro pontos. O primeiro relembra traços da trajetória do autor, desde a fase inicial em que dá relevância à política fiscal até o momento em que a renega. O segundo retoma questões apresentadas no tópico anterior e os argumentos usados para negar a efetividade da política fiscal. O terceiro volta-se à apresentação da hipótese da renda permanente e a sua posição contra o uso e as implicações da função consumo nos estudos de caráter keynesiano da velha síntese. O último ponto destaca a crítica contra as ações discricionárias, com ênfase na discussão dos lags existentes na política fiscal. O retorno ao autor justifica-se porque as suas ideias influenciaram o modo de a atual teoria macroeconômica dominante pensar tópicos relevantes da área fiscal.
Importance of surface layers in solid surface free energy determination
Authors: Jańczuk Bronisław , Zdziennicka Anna
Published: October 2013

The problem of the solid surface free energy determination by using direct, theoretical and indirect methods was considered. Among the indirect methods, measurements based on the contact angle in the solid–liquid drop–air, solid–hydrocarbon drop–water, solid–water drop–hydrocarbon and solid–air bubble–water systems were discussed. In the studies, the importance of surface layers in determination of the surface free energy of solids from the Young’s equation was taken into account. As follows, there are considerable differences between the surface free energy values of a given solid obtained by direct or theoretical methods and those from the contact angle measurements in proper three-phase systems. It is suggested that the difference between these values can result from the presence of the surface layer at the solid–air and/or solid–liquid interfaces, which is not commonly taken into account.
Housing Instability and Mental Distress among US Veterans
Authors: Bossarte Robert M. , Blosnich John R. , Piegari Rebecca I. , Hill Lindsay L. , Kane Vincent
Published: October 2013

Evidence has suggested increased risk for homelessness and suicide among US veterans, but little is known about the associations between housing instability and psychological distress (including suicidal ideation). We examined frequent mental distress (FMD) and suicidal ideation among a probability-based sample of 1767 Nebraska veterans who participated in the 2010 Behavioral Risk Factor Surveillance Survey who had and had not experienced housing instability in the past 12 months. Veterans experiencing housing instability had increased odds of FMD and suicidal ideation.
Health Care Utilization Patterns of Homeless Individuals in Boston: Preparing for Medicaid Expansion Under the Affordable Care Act
Authors: Bharel Monica , Lin Wen-Chieh , Zhang Jianying , O’Connell Elizabeth , Taube Robert , Clark Robin E.
Published: October 2013

Objectives. We studied 6494 Boston Health Care for the Homeless Program (BHCHP) patients to understand the disease burden and health care utilization patterns for a group of insured homeless individuals.

Methods. We studied merged BHCHP data and MassHealth eligibility, claims, and encounter data from 2010. MassHealth claims and encounter data provided a comprehensive history of health care utilization and expenditures, as well as associated diagnoses, in both general medical and behavioral health services sectors and across a broad range of health care settings.

Results. The burden of disease was high, with the majority of patients experiencing mental illness, substance use disorders, and a number of medical diseases. Hospitalization and emergency room use were frequent and total expenditures were 3.8 times the rate of an average Medicaid recipient.

Conclusions. The Affordable Care Act provides a framework for reforming the health care system to improve the coordination of care and outcomes for vulnerable populations. However, improved health care coverage alone may not be enough. Health care must be integrated with other resources to address the complex challenges presented by inadequate housing, hunger, and unsafe environments.
Risk Factors for Becoming Homeless Among a Cohort of Veterans Who Served in the Era of the Iraq and Afghanistan Conflicts
Authors: Metraux Stephen , Clegg Limin X. , Daigh John D. , Culhane Dennis P. , Kane Vincent
Published: October 2013

Objectives. In this population-based cohort study, we assessed baseline risk factors for homelessness, including the role of service in the Iraq or Afghanistan conflicts, among a large cohort of recent veterans.

Methods. Data for this study came from administrative records for 310 685 veterans who separated from active military duty from July 1, 2005, to September 30, 2006. We used survival analysis methods to determine incidence rates and risk factors for homelessness, based on baseline data for military factors, demographic characteristics, and diagnoses of behavioral health disorders and traumatic brain injury.

Results. Service in Iraq or Afghanistan and, more specifically, posttraumatic stress disorder among veterans deployed there, were significant risk factors of modest magnitude for homelessness, and socioeconomic and behavioral health factors provided stronger indicators of risk. Gender was not a significant indicator of differential risk.

Conclusions. Although service in Iraq and Afghanistan was significant, socioeconomic and behavioral health indicators show more promise in efforts to use administrative data to inform prevention efforts by identifying veterans who are at elevated risk for becoming homeless upon their return to civilian life.
Efficient Targeting of Homelessness Prevention Services for Families
Authors: Shinn Marybeth , Greer Andrew L. , Bainbridge Jay , Kwon Jonathan , Zuiderveen Sara
Published: October 2013

Objectives. We developed and evaluated a model to target homelessness prevention services to families more efficiently.

Methods. We followed 11 105 families who applied for community-based services to prevent homelessness in New York City from October 1, 2004, to June 30, 2008, through administrative records, using Cox regression to predict shelter entry.

Results. Over 3 years, 12.8% of applicants entered shelter. Both the complete Cox regression and a short screening model based on 15 risk factors derived from it were superior to worker judgments, with substantially higher hit rates at the same level of false alarms. We found no evidence that some families were too risky to be helped or that specific risk factors were particularly amenable to amelioration.

Conclusions. Despite some limitations, an empirical risk model can increase the efficiency of homelessness prevention services. Serving the same proportion of applicants but selecting those at highest risk according to the model would have increased correct targeting of families entering shelter by 26% and reduced misses by almost two thirds. Parallel models could be developed elsewhere.
Comparing Homeless Persons’ Care Experiences in Tailored Versus Nontailored Primary Care Programs
Authors: Kertesz Stefan G. , Holt Cheryl L. , Steward Jocelyn L. , Jones Richard N. , Roth David L. , Stringfellow Erin , Gordon Adam J. , Kim Theresa W. , Austin Erika L. , Henry Stephen Randal , Kay Johnson N. , Shanette Granstaff U. , O’Connell James J. , Golden Joya F. , Young Alexander S. , Davis Lori L. , Pollio David E.
Published: October 2013

Objectives. We compared homeless patients’ experiences of care in health care organizations that differed in their degree of primary care design service tailoring.

Methods. We surveyed homeless-experienced patients (either recently or currently homeless) at 3 Veterans Affairs (VA) mainstream primary care settings in Pennsylvania and Alabama, a homeless-tailored VA clinic in California, and a highly tailored non-VA Health Care for the Homeless Program in Massachusetts (January 2011-March 2012). We developed a survey, the “Primary Care Quality-Homeless Survey," to reflect the concerns and aspirations of homeless patients.

Results. Mean scores at the tailored non-VA site were superior to those from the 3 mainstream VA sites (P < .001). Adjusting for patient characteristics, these differences remained significant for subscales assessing the patient–clinician relationship (P < .001) and perceptions of cooperation among providers (P = .004). There were 1.5- to 3-fold increased odds of an unfavorable experience in the domains of the patient–clinician relationship, cooperation, and access or coordination for the mainstream VA sites compared with the tailored non-VA site; the tailored VA site attained intermediate results.

Conclusions. Tailored primary care service design was associated with a superior service experience for patients who experienced homelessness.
Challenges Associated With Screening for Traumatic Brain Injury Among US Veterans Seeking Homeless Services
Authors: Russell Leah M. , Devore Maria D. , Barnes Sean M. , Forster Jeri E. , Hostetter Trisha A. , Montgomery Ann Elizabeth , Casey Roger , Kane Vincent , Brenner Lisa A.
Published: October 2013

We identified the prevalence of traumatic brain injury (TBI) among homeless veterans and assessed the TBI–4, a screening tool created to identify TBI history. Between May 2010 and October 2011, 800 US veterans from two hospitals, one eastern (n = 122) and one western (n = 678) completed some or all measures. Findings suggested that 47% of veterans seeking homeless services had a probable history of TBI (data for prevalence obtained only at the western hospital). However, psychometric results from the screening measure suggested that this may be an underestimate and supported comprehensive assessment of TBI in this population.
Achieving Public Health Goals Through Medicaid Expansion: Opportunities in Criminal Justice, Homelessness, and Behavioral Health With the Patient Protection and Affordable Care Act
Authors: DiPietro Barbara , Klingenmaier Lisa
Published: October 2013

States are currently discussing how (or whether) to implement the Medicaid expansion to nondisabled adults earning less than 133% of the federal poverty level, a key aspect of the Patient Protection and Affordable Care Act.

Those experiencing homelessness and those involved with the criminal justice system—particularly when they struggle with behavioral health diagnoses—are subpopulations that are currently uninsured at high rates and have significant health care needs but will become Medicaid eligible starting in 2014.

We outline the connection between these groups, assert outcomes possible from greater collaboration between multiple systems, provide a summary of Medicaid eligibility and its ramifications for individuals in the criminal justice system, and explore opportunities to improve overall public health through Medicaid outreach, enrollment, and engagement in needed health care.
Opportunities for Engaging Low-Income, Vulnerable Populations in Health Care: A Systematic Review of Homeless Persons’ Access to and Use of Information Technologies
Authors: McInnes D. Keith , Li Alice E. , Hogan Timothy P.
Published: October 2013

We systematically reviewed the health and social science literature on access to and use of information technologies by homeless persons by searching 5 bibliographic databases. Articles were included if they were in English, represented original research, appeared in peer-reviewed publications, and addressed our research questions.

Sixteen articles met our inclusion criteria. We found that mobile phone ownership ranged from 44% to 62%; computer ownership, from 24% to 40%; computer access and use, from 47% to 55%; and Internet use, from 19% to 84%. Homeless persons used technologies for a range of purposes, some of which were health related.

Many homeless persons had access to information technologies, suggesting possible health benefits to developing programs that link homeless persons to health care through mobile phones and the Internet.
Synthesis, characterization, electrochemical behavior and antibacterial/antifungal activities of [Cd(l)X2] complexes with a Schiff base ligand
Authors: Montazerozohori Morteza , Yadegari Sahar , Naghiha Asghar
Published: October 2013

A new symmetrical bidentate Schiff base ligand (L) was applied for the
synthesis of some new cadmium coordination compounds with general formula of
[Cd(L)X2] in which X is halide and pseudo-halide. The ligand and all cadmium
complexes were characterized by some techniques such as elemental analysis,
FT-IR, 1H, 13C NMR, UV-Visible and molar conductance. Electrochemical
behavior of ligand and Cd(II) complexes were investigated by cyclic
voltammetry method. Morphology and shape of [Cd(L)Cl2] particles were
depicted by SEM. Antimicrobial properties such as antibacterial and
antifungal activities of the complexes as compared with ligand were checked
against three Gram-negative bacteria; Escherichia coli (ATCC 25922),
Pseudomunase aeroginosa (ATCC 9027) and Salmonella Spp. and two Gram-positive
bacteria; Staphylococcus aureus (ATCC 6538) and Corynebacterium renale and
three fungal strains including Aspergillus Niger, Penicillium chrysogenum and
Candida albicans. The results revealed appropriate antibacterial and
antifungal activities for all compounds, and it was also found that the
coordination of ligand to Cd (II) lead to an increase in the antimicrobial
activities in most of cases.
A Practice-Based Statement of Cash Flows Learning Experience: An Initial Public Offering for Contempri Homes?
Authors: Canace Thomas G. , Wilkerson Jack E.
Published: October 2013

This case presents intermediate-level accounting and finance students with the task of constructing a U.S. GAAP-based statement of cash flows and performing financial and non-financial analysis to inform a decision about whether a company—Contempri Homes—should undertake an IPO. Students use a rich data set of recent financial statements, financial disclosures, and financial and operating data to prepare the company's statement of cash flows, conduct analysis, and make written recommendations regarding the proposed IPO. Case learning objectives include (1) simulation of accounting practice in a realistic setting, (2) development of a holistic view of the financial statements, (3) practice in cash flows financial reporting and analysis, and (4) practice in analyzing financial and non-financial factors for decision making. The case is designed specifically for the second intermediate financial accounting course and is well suited for use in other intermediate- or advanced-level financial accounting or finance courses.
Nonlaboratory-Based Risk Assessment Algorithm for Undiagnosed Type 2 Diabetes Developed on a Nation-Wide Diabetes Survey
Authors: Zhou Xianghai , Qiao Qing , Ji Linong , Ning Feng , Yang Wenying , Weng Jianping , Shan Zhongyan , Tian Haoming , Ji Qiuhe , Lin Lixiang , Li Qiang , Xiao Jianzhong , Gao Weiguo , Pang Zengchang , Sun Jianping
Published: October 2013

OBJECTIVE

To develop a New Chinese Diabetes Risk Score for screening undiagnosed type 2 diabetes in China.

RESEARCH DESIGN AND METHODS

Data from the China National Diabetes and Metabolic Disorders Study conducted from June 2007 to May 2008 comprising 16,525 men and 25,284 women aged 20–74 years were analyzed. Undiagnosed type 2 diabetes was detected based on fasting plasma glucose ≥7.0 mmol/L or 2-h plasma glucose ≥11.1 mmol/L in people without a prior history of diabetes. β-Coefficients derived from a multiple logistic regression model predicting the presence of undiagnosed type 2 diabetes were used to calculate the New Chinese Diabetes Risk Score. The performance of the New Chinese Diabetes Risk Score was externally validated in two studies in Qingdao: one is prospective with follow-up from 2006 to 2009 (validation 1) and another cross-sectional conducted in 2009 (validation 2).

RESULTS

The New Chinese Diabetes Risk Score includes age, sex, waist circumference, BMI, systolic blood pressure, and family history of diabetes. The score ranges from 0 to 51. The area under the receiver operating curve of the score for undiagnosed type 2 diabetes was 0.748 (0.739–0.756) in the exploratory population, 0.725 (0.683–0.767) in validation 1, and 0.702 (0.680–0.724) in validation 2. At the optimal cutoff value of 25, the sensitivity and specificity of the score for predicting undiagnosed type 2 diabetes were 92.3 and 35.5%, respectively, in validation 1 and 86.8 and 38.8% in validation 2.

CONCLUSIONS

The New Chinese Diabetes Risk Score based on nonlaboratory data appears to be a reliable screening tool to detect undiagnosed type 2 diabetes in Chinese population.
Cardinal Raúl Silva Henríquez Bridge during the 2010 Chile Earthquake
Authors: Wang Zuocai , Chen Genda , Yen Phillip W. , Buckle Ian
Published: October 2013

This paper presents a case study of the Cardinal Raúl Silva Henríquez Bridge, which experienced significant damage during an earthquake that occurred in Chile on February 27, 2010. Supported by reinforced concrete and steel columns of varying heights, the superstructure of the bridge consisted of 22 steel-girder spans, with one intermediate expansion joint located at the middle of the bridge. At each end of the bridge, the bottom flanges of the girders were welded to their bearing steel plates, which were embedded and anchored into the bridge abutment. Two, three-dimensional, finite element models (global versus local) with beam and solid elements, respectively, were established for bridge response and damage process simulations. Field observations indicated, and finite element simulations verified, that the damage was caused mainly by the excessive seismic load of 11 continuous steel-girder spans under longitudinal earthquake loading and its eccentricity from the girder-to-abutment connection, which resulted in a significant bending effect. Parametric studies demonstrated that an effective retrofit strategy could be developed through a reduction in the number of continuous spans, modification of the girder-to-abutment connection detail, an increase in the capacity of girders with enlarged bearing seats, added stiffeners for girders, and thicker flanges and webs.
Behavior of Bell and Spigot Joints in Buried Thermoplastic Pipelines
Authors: García David Becerril , Moore Ian D.
Published: October 2013

Failures in joints are among the most common sources of problems in buried gravity flow pipelines. Poor performance of these elements can cause infiltration and exfiltration, which lead to soil erosion and eventually to serviceability or strength limit states for the system. To prevent poor performance, joints should be designed to adequately accommodate the demands generated under normal loading conditions. Such demands are not clearly understood, however, because joint behavior has received scant attention. The goal of this research was to examine the response of gasketed bell and spigot joints in two, common, thermoplastic pipelines employed in gravity flow applications when subjected to live loading. The specimens examined were a high-density polyethylene pipeline, 1,500 mm in diameter, and a polyvinyl chloride (PVC) pipeline, 900 mm in diameter. Two burial depths and three loading locations were examined for each pipeline buried according to AASHTO guidelines. Moreover, two installations not specified by AASHTO were examined for the PVC specimen, which featured voids in the bedding under the joint. Subsequently, each specimen was loaded directly over the joint up to and beyond fully factored loads under recommended burial conditions to observe the joint performance and the final failure mode of the pipelines. The test measurements provide guidance on the key demands that develop at the joints and how they are influenced by the burial and loading condition. Finally, recommendations are made on the development of structural design procedures.
Experiments on a Hybrid-Composite Beam for Bridge Applications
Authors: Van Nosdall Stephen , Moen Cristopher D. , Cousins Thomas E. , Roberts-Wollmann Carin L.
Published: October 2013

This paper details a study of the structural behavior of hybrid-composite beams (HCBs), which consist of a fiber-reinforced polymer (FRP) shell with a tied concrete arch. The HCB offers advantages in life-cycle costs through reduced transportation weight and increased corrosion resistance. Through a better understanding of system behavior, the proportion of load in each component can be determined, and each component can be designed for the appropriate forces. A long-term outcome of this research will be a general, structural analytical framework, which can be used by transportation departments to design HCBs as rapidly constructible bridge components. This study focused on the identification of the load paths and load sharing between the arch and FRP shell in an HCB and on the test of an HCB with a composite bridge deck. Tests were performed through the application of point loads on simple span beams (before the bridge deck was placed) and with a three-beam, skewed composite bridge system, which resulted in strain data for the arch and FRP shell. The test results showed that strain behavior was linear elastic at service loads, and the FRP shell had a linear strain profile. Curvature from strain data was used to find internal bending forces, and the proportion of load within the arch was found. A stress integration method was used to confirm the internal force contributions. The arch carried about 80% of the total load for the noncomposite case without a bridge deck. When composite with a bridge deck, the arch made a minimal contribution to the HCB stiffness and strength, because most of the arch was below the neutral axis and cracked under the maximum live load expected for the bridge. For this composite case, the FRP shell and prestressing strands resisted about 80% of the applied load, while the bridge deck carried the remaining 20% to the end diaphragms and bearings.
Experimental Evaluation of Connections in Hybrid Precast Concrete Bridge Truss Girders
Authors: Elbadry Mamdouh , Schonknecht Kyle , Abe Hiroyuki
Published: October 2013

An innovative, corrosion-free, precast, prestressed concrete truss girder has been developed for short- and medium-span, slab-on-girder bridges. The girder consists of top and bottom concrete flanges connected by precast vertical and diagonal members and made of fiber-reinforced polymer (FRP) tubes filled with concrete. The verticals and diagonals are connected, respectively, to the concrete flanges by means of glass FRP dowels and stud reinforcement made of corrosion-resistant steel or FRP material. The flanges are pretensioned with carbon FRP tendons. The deck slab is reinforced with corrosion-resistant steel bars in the bottom transverse layer and with glass FRP bars in the bottom longitudinal and the top layers. The girders may be posttensioned with external carbon FRP tendons to balance the slab weight and to provide continuity in multispan bridges. The new system has the advantages of light weight and enhanced durability. The light weight reduces the initial cost and allows for longer spans. The improved durability reduces the maintenance cost and extends the structure's life span. This paper describes the general details of the system and presents an experimental evaluation of its critical components, namely, the FRP tubes and the truss connections. Two types of FRP tubes and four types of connections were investigated. The results are presented of tests of eight connection specimens under static loading and four specimens under fatigue. The tests showed excellent performance of the connections when filament-wound tubes and continuous double-headed studs were used.
Revisiting the Cycle Length
Authors: Day Christopher M. , Sturdevant James R. , Li Howell , Stevens Amanda , Hainen Alexander M. , Remias Stephen M. , Bullock Darcy M.
Published: October 2013

During oversaturation, a popular objective in traffic signal operations is to maximize throughput to keep traffic moving. As cycle lengths are increased, the proportion of lost time used to transition between signal phases is reduced. This factor is often a rationale for programming long cycle lengths into signal timing plans. An investigation of the impact of cycle length revisited the concept of the use of critical lane analysis to calculate throughput and applied the technique to data collected at an oversaturated intersection in Indianapolis, Indiana. Traffic volumes were measured for 10 weeks while various cycle lengths, ranging from 80 to 135 s, were tested at the intersection. During saturated conditions, no clear increase in the sum of critical lane throughput was observed, even when the cycle length increased by more than 50%. At 135 s, there was a slight reduction in the total critical lane sum volume. These findings concur with a recent study by Denney et al. The decrease in throughput during the longer cycle lengths is attributed to the reduction of saturation flow during long green times. Possible results of use of a time-dependent saturation flow rate are discussed. Additionally, critical lane analysis may have applications to evaluation and ranking of intersections within corridors as under, near, or over saturation.
Traffic Signal Timing Optimization
Authors: Hajbabaie Ali , Benekohal Rahim F. (Ray)
Published: October 2013

Choosing an appropriate objective function in optimizing traffic signals in urban transportation networks is not a simple and straightforward task because the choice likely will affect the set of constraints, modeling variables, obtained outputs, and necessary computer and human resources. A methodology for selection of an appropriate objective function for the problem of signal timing optimization was developed. The methodology was applied to a realistic case study network under four demand patterns (symmetric, asymmetric, undersaturated, oversaturated). Selection is made from a pool of five candidates: minimizing the delay, minimizing the travel time, maximizing the throughput-minus-queue, maximizing the number of completed trips (or trip maximization), and maximizing the weighted number of completed trips (or weighted trip maximization). Findings indicate that for all demand patterns, weighted trip maximization improved network performance compared with the other objective functions. Weighted trip maximization reduced system total delay by 0.1% to 5.2% in symmetric undersaturated demand, by 1.0% to 2.4% in asymmetric undersaturated demand, by 1.2% to 16.6% in symmetric oversaturated demand, and by 11.7% to 27.4% in asymmetric partially oversaturated demand. These figures indicate that the weighted trip maximization objective function is the most suitable of the candidates in oversaturated conditions, especially when demand is not symmetric. Throughput-minus-queue and trip maximization were the second most suitable objective functions for oversaturated conditions, and trip maximization was slightly more suitable when demand was asymmetric.
Two-Step Optimization Model for Dynamic Lane Assignment at Isolated Signalized Intersections
Authors: Zhao Jing , Ma Wanjing , Zhang H. Michael , Yang Xiaoguang
Published: October 2013

At isolated signalized intersections, congestion problems are caused in part by an imbalance in supply and demand, which may be caused by the variability of turning-movement volumes. Although signal timing can be adjusted to handle varying demand, the effect of this adjustment alone is limited, especially when traffic demand fluctuates significantly. A two-step optimization model for dynamic lane assignment is presented: the model overcomes the shortcoming of static lane markings and fully utilizes the existing traffic facilities. The first step is to obtain the best lane assignment scheme by using an arm-group-based integer nonlinear program model. The second step is to identify a suitable implementation scheme by determining a binary-type threshold. The results of VISSIM simulation show that the proposed model can correctly choose the occasion to change the lane assignment by ignoring the small volume fluctuation and can improve traffic operations effectively when the traffic demand varies significantly.
Optimized Advance Detector Configuration for Option Zone Protection at High-Speed Signalized Intersections
Authors: Li Zhixia , Wei Heng , Yao Zhuo , Xiong Hui , Yan Xuedong
Published: October 2013

Advance detection and green extension schemes are widely applied in practice as a typical solution to the safety issues associated with the intersection dilemma zone problem. Most existing detector configurations either were based on the traditional Type I dilemma zone model, in which some critical contributing factors were assumed static, or were based on generic Type II dilemma zones. A comparison analysis based on field-observed trajectory data showed that the option zone model estimated the location of a dilemma zone most accurately of all available dilemma zone models. Recent research on the quantitative modeling of the contributing factors of the option zone made accurate identification of the option zone locations possible. Accurate identification lays a solid foundation for an option zone–based detection scheme for achieving the most effective and efficient dilemma zone protection. An alternative advance detector con-figuration is presented for option zone protection via optimization trials within a calibrated VISSIM simulation model. The optimization objective was to minimize the combined cost of dilemma hazard (safety) and delay (mobility). Dilemma conflict potential, a comprehensive dilemma hazard model, was used to measure the safety performance quantitatively and replaced the traditional measure of number of vehicles in the dilemma zone. The optimal configuration was evaluated and validated through its comparison with four widely applied detector configurations. The results revealed the superiority of the developed optimal detector configuration in terms of the best safety performance and the least combined cost of dilemma hazard and delay of all configurations.
Probability Model for Understanding the Effects of Detector Delays on Right-Turn-on-Red Traffic
Authors: Zeng Xiaosi , Zhang Yunlong , Songchitruksa Praprut
Published: October 2013

Detector delay as a useful detector timing feature is often recommended for minimizing disruptions on major movements caused by one or more minor movements. However, this benefit of detector delay is not always certain because the applicability of detector delay is subject to a combination of gap demand, gap availability, critical gap acceptance, follow-up headways, and other factors. The improper use of detector delay could be costly to traffic on minor streets. With little literature on the subject, the complex relationship between detector delays and different critical factors has not been fully understood. An analytical model that estimates the probability of clearing right-turn-on-red queues within the period of detector delay is presented. This probability is the first step toward an understanding of how this detector feature affects an intersection's operational efficiency. The gap-finding process of multiple right-turn-on-red vehicles is divided into several realistic cases and analyzed in detail. Insights about the process described in each case are applied to derivation of a probability model. Validation of the model is conducted with more than 4,000 simulation runs. A close fit is found between the computed probability and the simulated data with errors no larger than 5.7% of the targeted values. The method for deriving the probability model provides a stepping-stone toward deriving the delay distributions for right-turn-on-red traffic.
Coordinated Optimization of Signal Timings for Intersection Approach with Presignals
Authors: Ma Wanjing , Xie Hanzhou , Liu Yue , Head Larry , Luo Zhenke
Published: October 2013

Many congested intersections have heavy traffic volume on movements for which there is insufficient capacity because of geometric limitations. Installing presignals at midblock locations and reorganizing traffic upstream of the approach of an intersection combine to be a promising and cost-effective method for addressing these capacity limitations. A coordinated optimization model was developed for an isolated intersection approach with presignals to increase the protected left-turn phase capacity. The presignal model was based on two principles: (a) explicitly capture the interaction between the presignal and the main signal by modeling the queuing process and capacity constraints of temporal and spatial limitations of the intersection and (b) optimize the signal timings of both the presignal and the main signal as well as the offset between them to produce the best operational strategy for the approach. The minimum green time required and the delay-minimization problems are considered. Extensive experimental analysis has shown that the presignal model outperforms the conventional control method (without presignal). Sensitivity analysis of the signal timing method that will assist traffic engineers with selecting the appropriate length of the sorting area, phase sequence, and early starting time of presignals was conducted. The results from the study offer a basis for traffic practitioners, researchers, and authorities on which to design and utilize presignals in locations where there is a need to increase intersection capacity for congested movements.
Methodology to Evaluate Cost and Accuracy of Parking Patrol Surveys
Authors: Cao Jin , Menendez Monica
Published: October 2013

Patrol surveys are frequently used to estimate average parking duration. However, error in estimating is unavoidable and yet unpredictable. It is, therefore, hard for surveyors to decide on survey budgets; lower ones may generate unusable results and higher ones are costly. Therefore, a method to evaluate and improve survey accuracy without increasing (and possibly even lowering) cost could be highly beneficial. In this paper, an analytical model is built to determine the effects of survey budget on survey accuracy in a systematic and generalized way. The relationship between the survey budget, the estimated average parking duration (i.e., the survey result), and the survey error is illustrated through dimensional analysis. On the basis of this analysis, objective criteria are found to evaluate patrol surveys, a budget test is provided to find the optimal survey budget, and a correction method is proposed to improve survey accuracy. Moreover, simulations are run on the basis of more realistic assumptions, so that the conclusions from the analytical model can be extended to real life situations. The model is well validated with real parking data. An example application is also provided that illustrates how to use the proposed approaches to choose a survey budget and to improve survey accuracy. It is hoped that this study will help surveyors to better understand patrol surveys and obtain high-quality results, while keeping costs to a minimum.
Parking at Sporting Event Stadiums in Denver, Colorado
Authors: Henao Alejandro , Marshall Wesley E.
Published: October 2013

Millions of people in the United States travel by personal automobile to attend professional sports matches played at various stadiums. Engineering and planning publications lack information on parking provisions for major sporting events. The results from this paper on parking outcomes suggest that the current parking provisions are not efficient. This case study examines parking supply, parking utilization, event auto occupancy, and event auto modal share at four major professional sports venues in the Denver, Colorado, region. The percentage of parking supply per parking demand was calculated for several surveyed games in terms of the average attendance, and parking utilization was evaluated during nonevent periods. In general, the surveys of the games indicated that more parking was provided than was necessary, even when attendance was higher than typical. For an event with average attendance, parking utilization was as low as 65%, with 2.2 persons per vehicle. In contrast, when parking occupancy was high, auto occupancy increased to 3.0 persons per vehicle. With such different carpool rates, as well as evidence suggesting that spectators who travel to some facilities are willing to park and walk farther than a half-mile, the results suggest that parking supply and travel behavior are endogenous and should not be treated independently. This study also considered parking occupancy at nonevent times and found whole-scale underutilization, even in downtown locations with great opportunity costs.
Quick-Scan Appraisal Method to Determine Cost-Effectiveness of Traffic and Demand Management Measures
Authors: Meurs Henk , van Wee Bert , Perdok Jan , Hoogendoorn Serge
Published: October 2013

This paper presents a quick-scan approach to assess the cost-effectiveness of smaller and poorly demarcated transportation measures; the approach can be used as an initial scan while packages are established to solve specific transportation problems. This paper adds to the available evaluation literature and relies on a combination of expert opinions and simple models rather than on data-intensive, four-stage transportation models. The approach consists of five steps and yields an assessment of the cost-effectiveness of the measure that is being evaluated. As an illustration of this approach, the cost-effectiveness of a pricing measure within a large Dutch travel demand management program was determined to illustrate the approach itself and the plausibility of its results. It was concluded that the proposed method was suitable for an initial quick-scan assessment. This assessment would be valuable in the first selection of packages of measures and could support policy makers who must decide in which measures to invest, even when those measures have not yet been described or designed at a highly detailed level.
Optimization of Dynamic Ridesharing Systems
Authors: Di Febbraro A. , Gattorna E. , Sacco N.
Published: October 2013

Internet-enabled technologies are becoming more widespread; users are constantly connected to the network in every place and daily activity. Access to transportation-related features—mobile payment systems, Global Positioning System connections, real-time public transit timetables or traffic congestion information, and so on—is easy. This access results in new ways to plan mobility. In the innovative mobility systems implemented and developed with these technologies, the new real-time capabilities of dynamic ridesharing, an extended version of traditional ridesharing, can play a key role if the relevant performance is improved. In other words, although ridesharing is not a new idea, recent technological advances should increase its popularity. In this paper, a proposed ridesharing system considers the interactions between drivers or riders and the system manager and the interactions between drivers and riders. The positions and speeds of the shared vehicles and the traffic flows in which such vehicles travel are omitted. To optimize the performance of the ridesharing system, a discrete event, dynamic pickup and delivery model that represents the considered dynamics and an optimal matching problem that optimally allocates an empty seat in a vehicle to a rider are proposed. The dynamic model represents the behavior of the ridesharing system and computes the relevant performance; the optimization problem finds the best match and path in the considered transportation network to minimize the difference between the desired departure and arrival times. In this paper, after the introduction of the ridesharing model, the discussion of the solution to the optimal matching problem, a simulation model is described. A real world case study is then presented and discussed.