Methodology to Estimate Volume-Capacity Ratios at Traffic Signals Based on Upstream-Link Travel Times

So, Jaehyun (Jason),Stevanovic, Aleksandar,Ostojic, Marija American Society of Civil Engineers 2017 Journal of transportation engineering.Part A.Syste Vol.143 No.4

<P>This study utilizes travel time data from a well-equipped Intelligent Transportation System corridor to integrate travel time and traffic signal data with the goal of developing a volume-delay relationship between a signal's volume-capacity ratio and travel time. Specifically, the traffic signal timings were retrieved from an advanced transportation management system, individual travel time data were extracted from a WiFi-based travel time measurement system, and traffic volumes and queues were obtained by observing closed-circuit television video recordings. The collected data were then integrated on a cycle-by-cycle basis by using a C#-automated data postprocessing interface. Several traditional volume-delay functions were calibrated to fit the field data. Also, a new volume-delay function, named So-Stevanovic Volume-Delay Function, was developed to account for exponential behavior of travel time near and beyond the traffic saturation point. The So-Stevanovic Volume-Delay Function satisfied the seven Spiess's requirements for a well-behaved congestion function and produced slightly better results than the best traditional volume-delay function. All of the functions were then tested again on a different road segment in order to validate the results. These tests confirmed the previous findings that the So-Stevanovic Volume-Delay Function was the best predictor of relationship between volume-capacity ratio and link travel time. Further research should be conducted to validate this function in a variety of field traffic conditions. (C) 2017 American Society of Civil Engineers.</P>

Analysis of the Complex Mechanisms of Defect Generation in Construction Projects

Aljassmi, Hamad,Han, Sangwon,Davis, Steve American Society of Civil Engineers 2016 Journal of construction engineering and management Vol.142 No.2

<P>There have been numerous research efforts to minimize construction defects and a variety of suggestions have been provided. However, while all of these suggestions are valuable and have the potential to prevent defects, a construction company may have difficulty adopting them due to financial and practical constraints. Thus, this calls for the identification and characterization of the most influential causes of defects, in order to prioritize defect prevention strategies. To address this necessity, this paper aims to identify the most important causes of defects in terms of frequency, magnitude, and pathogenicity. For this goal, a questionnaire survey of 106 industry professionals was conducted to examine 30 causes of defects, collected through an extensive literature review. High frequency and high magnitude causes were identified and traced back to their initiating causes. Accordingly, the five most pathogenic causes were found to be (1)organizational culture, (2)time pressure and constraints, (3)workplace quality system, (4)financial constraints on operational expenses, and (5)inadequate employee training or learning opportunities. This paper is valuable to researchers in terms of developing a theoretical foundation to analyze and visualize the complex mechanisms of defect generation in construction. Further, this paper is of value to practitioners in terms of providing an effective tool to set defect prevention strategies and prioritize investment areas for quality improvements. (C) 2015 American Society of Civil Engineers.</P>

Artificial Neural Network-Based Slip-Trip Classifier Using Smart Sensor for Construction Workplace

Lim, Tae-Kyung,Park, Sang-Min,Lee, Hong-Chul,Lee, Dong-Eun American Society of Civil Engineers 2016 Journal of construction engineering and management Vol.142 No.2

<P>This paper presents a smart artificial neural network (ANN)-based slip-trip classification method, which integrates a smart sensor and an ANN. It was trained to identify the slip and trip events that occur while a worker walks in a workplace. It encourages preventive and collective actions to reduce construction accidents by identifying the type of near miss, i.e.,slip or trip, and the exact time that it occurs. The variation in the energy released by a worker is measured using a triaxial accelerometer embedded in a smart phone. This study is of value to researchers because the method measures a near miss quantitatively using acceleration. It is also of relevance to practitioners because it provides a computerized tool that records each and every moment of a near-miss event. A test was performed by collecting the three-axis acceleration streams generated by workers wearing a smart phone running the classifier as they walked around a simulated construction jobsite. It identified the type of near miss and the exact time of its occurrence. The test case verified the usability and validity of the computational methods. (C) 2015 American Society of Civil Engineers.</P>

Wave Transformation and Sand Transport on a Macrotidal Pocket Beach

Do, Kideok,Kobayashi, Nobuhisa,Suh, Kyung-Duck,Jin, Jae-Youll American Society of Civil Engineers 2016 Journal of waterway, port, coastal, and ocean engi Vol.142 No.1

<P>Available 17-day field data in Korea are analyzed to investigate the cross-shore wave transformation, currents and sand suspension in the intertidal zone, and beach profile changes of a macrotidal pocket beach with a gentle slope of 0.02 and tidal ranges of 4-7 m. The measured beach profile changes were less than 0.5 m despite the occurrence of two consecutive storms with significant wave heights exceeding 2 m. A cross-shore numerical model is shown to reproduce the gradual wave height decay in the migratory surf zone, the cross-shore current of the order of 0.1 m/s affected by flood and ebb tides, the suspended sand volume varying with the tidal cycle, and the small beach-profile changes. The computed cross-shore and longshore sand-transport volumes per unit width for the 17-day interval are relatively small, but extend the 400-m-wide cross-shore zone. The small volume and wide zone reduces the local erosion or accretion. (C) 2015 American Society of Civil Engineers.</P>

Effect of Bioethanol on Combustion and Exhaust Emissions in a Diesel-Bioethanol Dual-Fuel Combustion Engine

Park, Su Han,Lee, Chang Sik American Society of Civil Engineers 2016 Journal of energy engineering Vol.142 No.2

<P>The purpose of this study is to investigate the effect of the bioethanol port injection ratio and the in-cylinder diesel injection timing on combustion and exhaust emissions characteristics using a dual-fuel combustion strategy. Dual-fuel combustion was applied to a single-cylinder diesel engine with a displacement volume of 373.3 cm(3). In a diesel-bioethanol dual-fuel combustion system, there is no need for additives to solve any phase separation between diesel and bioethanol. The combustion and emissions characteristics were investigated through the study of the indicated mean effective pressure (IMEP), ignition delay, heat release rate, indicated specific nitrogen oxides (ISNOx), indicated specific soot (ISsoot), indicated hydrocarbon (ISHC), and indicated carbon monoxide (ISCO). It revealed that IMEP increased with increases to the bioethanol port injection ratio, and the effect of bioethanol on IMEP can be clearly observed in early injection timing. The rate of combustion pressure rise decreased with an increase of port injection ratio. The ignition delay increased with an increase of the bioethanol port injection ratio and with the advance of the in-cylinder injection timing. ISNOx and ISsoot emissions can be simultaneously reduced by a diesel-bioethanol dual-fuel combustion strategy because of the high latent heat and oxygen content of bioethanol. The ISHC and ISCO emissions in the dual-fuel combustion (DFC) generally increased with the port injection ratio. However, when the in-cylinder injection fuel flowed into the squish region, the ISCO emission decreased with an increase of port injection ratio due to the oxygen effect of bioethanol. (C) 2015 American Society of Civil Engineers.</P>

Broken-Line Model of Dam Storage and Evaluation of Water Supply Safety Using a Bivariate Frequency Analysis

Yoo, Chulsang,Jun, Changhyun American Society of Civil Engineers 2017 Journal of water resources planning and management Vol.143 No.10

<P>In this study, a new evaluation method for the water supply safety of a dam is proposed. This method considers both climatic conditions and storage characteristics of a dam. The annual variation of dam storage is represented by a broken-line model, the lines of which are determined by only three-factors: the monthly design water supply during the dry period; dam storage at the end of the dry period; and changes in dam storage during the wet period. From the results of bivariate frequency analysis, a unique broken-line model is derived under multiple scenarios with the given return periods for the evaluation of water supply. The proposed method is applied to a total of five major dams in Korea. It is shown that the water supply safety of a dam can be quantified by using the concept of the return period, and five major dams have water supply safety corresponding to return periods of 10-50 years. Among them, the Soyanggang Dam is found to be the most stable with respect to water supply safety in Korea. (c) 2017 American Society of Civil Engineers.</P>

Analysis of Constrained Optimization Problems by the SCE-UA with an Adaptive Penalty Function

Lee, Sangho,Kang, Taeuk American Society of Civil Engineers 2016 Journal of computing in civil engineering Vol.30 No.3

<P>Evolutionary algorithms are used to solve optimization problems in a wide range of fields and are considered to be global optimization algorithms. However, evolutionary algorithms are limited in that they cannot be used to solve optimization problems with constraints. Additional methods to implement constraints must be used with these algorithms when solving constrained optimization problems. The purpose of the study is to improve the Shuffled Complex Evolution-University of Arizona (SCE-UA) algorithm to include constraints. An adaptive penalty function that is easy to implement, free of parameter tuning, and guaranteed to find a solution for every problem at every run was used to impose constraints on the SCE-UA. The modified SCE-UA was validated by application to two constrained optimization problems. The algorithm was also applied to an automatic calibration of the storm water management model (SWMM), which is a hydrological model. An automatic calibration by unconstrained optimization (the original SCE-UA) was not able to properly simulate the observed data. On the other hand, the modified SCE-UA with the adaptive penalty function produced results superior to those obtained using unconstrained optimization. That is the reason why the calibration was advanced to improve the limitation of the unconstrained optimization by imposing constraints. The constrained optimization module modified by embedding the adaptive penalty function could help in solving various constrained optimization problems in the water resources engineering field. (C) 2015 American Society of Civil Engineers.</P>

Seismic Hazard Assessment Model for Urban Water Supply Networks

Yoo, Do Guen,Jung, Donghwi,Kang, Doosun,Kim, Joong Hoon,Lansey, Kevin American Society of Civil Engineers 2016 Journal of water resources planning and management Vol.142 No.2

<P>A new seismic reliability evaluation model is proposed that quantifies the impact of earthquakes on hydraulic behavior of water supply networks. Probabilistic seismic events are produced in the target areas, and the depth of earthquake failure is evaluated by seismic reliability indicators. The developed model was applied to several case studies and used for an intensive examination on how a water supply system hydraulically responds to a seismic event and what system characteristics influence the system's performance in the event of an earthquake. First, the system reliability of a real network in South Korea when subjected to earthquakes of various magnitudes and locations was quantified. Next, the reliabilities of full and simplified network models were evaluated to investigate how system layouts affect the reliability evaluation. Finally, networks with different configurations, pipe sizes, and system densities were compared with respect to the seismic reliability and various seismic damage indicators. (C) 2015 American Society of Civil Engineers.</P>

Mill Scale-Derived Magnetite Particles: Effective Adsorbent for the Removal of Phosphate in Aqueous Solutions

Doliente, Jonica Ella,Kim, Yunjung,Nam, Haewook,Choi, Younggyun American Society of Civil Engineers 2017 Journal of environmental engineering Vol.143 No.12

<P>Mill scale, an iron waste, was used to synthesize magnetite particles for the adsorption of phosphate from an aqueous solution. Several techniques were used to characterize the adsorbents. Mill scale-derived magnetite particles exhibited a strong uptake affinity to phosphate in a wide pH range of 3-7, with the maximum adsorptive removal of 100% at an adsorbent concentration of 1 g/L and pH 3-5. The Langmuir isotherm model well described the equilibrium data, exhibiting maximum adsorption capacities for phosphate up to 4.95 and 8.79 mg/g at 298 and 308 K, respectively. Kinetic data correlated well with the pseudo-second-order kinetic model, indicating that chemisorption is involved in the adsorption process. The phosphate adsorption was highly pH-dependent, and the presence of Cl-, SO42-, and CO32- ions had no effect on phosphate removal. X-ray photoelectron spectroscopy (XPS) results revealed that phosphate was bonded onto the surface of magnetite predominantly through bidentate complexation. Desorption was performed on mill scale-derived magnetite to check recyclability. Five successive adsorption/regeneration cycles were successfully applied with a slight decrease in the adsorbent adsorption capacity. (C) 2017 American Society of Civil Engineers.</P>

Mapping the Rescue Equipment Mobilization Potential: Decision Support Tool for Emergency Management

Kim, Daeho,Hong, Taehoon,Lee, Minhyun,Koo, Choongwan,Kim, Jimin,Jeong, Kwangbok American Society of Civil Engineers 2017 Journal of management in engineering Vol.33 No.6

<P>From a managerial perspective, prediagnosis of emergency response potential and decision support during rescue operations are essential for improving emergency response capability. Toward this end, this paper introduces a novel index to measure equipment availability at a certain location and time: rescue equipment mobilization potential within standard emergency response time (REMPSERT), which was estimated and visualized in a map based on the geographic information system (GIS). It is shown that the accuracy of the proposed map was in a highly acceptable range (i.e., 92.4%) compared with a commercialized navigation system. Using the validated map, two case studies are presented: (1) the prediagnosis of response potential (case: Seoul), and (2) the decision support for optimal dispatching of rescue equipment (case: Mauna Ocean Resort collapse), through which the utility and efficacy of the proposed map in emergency management were verified. (C) 2017 American Society of Civil Engineers.</P>