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Construction safety climates can reflect organizational safety behavior and commitment, employees’ safety perceptions and attitudes, and the supervisory and support environments. Maintaining a healthy safety climate can help prevent workers from fatal accidents and illnesses. To enhance the safety climate and, consequently, improve safety performance at a construction site, it is very important to analyze the elements that affect the safety climate and are significant for different types of construction work organizations. Therefore, the main goal of this study was to develop a multi-spectra perception model to investigate which factors were considered critical from four key perspectives: managers, superintendents, skilled laborers, and general helpers. To achieve this goal, a survey questionnaire was conducted to collect empirical data from one commercial building construction project. Based on a stepwise regression analysis, it was revealed that the most significant factors enhancing the safety climate are: from the managers’ perspective, a combination of improvement in the support environment and reduction in work pressure; for superintendents and skilled laborers, increasing worker competence; and for general laborers, increasing worker involvement. This research contributes to a better understanding of the significant factors and provides a measure for each important role in enhancing the safety climate at a job site.

In microscale photogrammetry, the confocal microscopic imaging technique has been the dominant trend. Unlike the confocal imaging mostly for transparent objects, we propose a novel method to construct a 3D shape in microscale for various micro-sized solid objects in a broad spectr&micro, m of applications. Recently, the structure from motion (SfM) demonstrated reliable 3D reconstruction capability for macroscale objects. In this paper, we discuss the results of a novel micro-surface reconstruction method using the Structure from Motion in microscale. The proposed micro SfM technique utilizes the photometric stereovision via microscopic photogrammetry. The main challenges lie in the scanning methodology, ambient light control, and light conditioning for microscale object photography. Experimental results of the microscale SfM, as well as the modeling accuracy analysis of a reconstructed micro-object, are shared in the paper.

PURPOSES : This study aimed to develop a new highway capacity estimation method and provide comparative results among traditional capacity estimation methods and the recommended values in the latest version of KHCM. METHODS : The limitations of the existing methods, such as inconsistency and underestimation of the capacity value, are summarized through an extensive literature review. To overcome these limitations, a new method is introduced by adopting a definition of capacity and traffic flow characteristics at or near breakdown points. This method can produce the capacity value by searching a point corresponding to the maximum traffic flow through analysis of gradient changes (point of inflection) of the traffic flow and speed distribution. Comparative results of capacity values from each method are also presented to validate the new method by using data collected from detectors on freeways. RESULTS: From the analysis results, it is shown that a consistent capacity value can be estimated by applying the new method. In addition, the resulting capacity values are 3%-4% higher than those recommended in KHCM. CONCLUSIONS : The capacity values listed in the current KHCM tend to produce underestimated results. The new method presented in this paper may be included in the future edition of KHCM.

PURPOSES : This study evaluated the feasibility of implementing protected-permissive left-turn (PPLT) signals at three-leg signalized intersections. METHODS: A three-leg signalized intersection with permissive left-turn was first selected. A VISSIM simulation model was constructed using data collected from the test site. The VISSIM network was calibrated by adjusting related parameter values in order to minimize the difference between the simulated and surveyed critical gap. The calibrated network was validated by the number of waiting left-turning vehicles per cycle. Finally, the mobility and safety measures were extracted from simulation runs in which permissive, protected left turns as well as PPLTs were realized based on diverse traffic volume scenarios. RESULTS : The mobility-related measures of effectiveness (MOEs) of the case with PPLT outperformed the other two left-turn treatment scenarios. In particular, the average waiting time per cycle for the left-turn vehicles in the case with PPLT was reduced by 30 s. The safety-related MOEs of the case with PPLT were somewhat higher than those in the case with protected left-turns and much higher than those in the case with permissive left-turns. CONCLUSIONS : Based on the mobility- and safety-related MOEs generated from the VISSIM simulation runs, the use of PPLT seems to be feasible at three-leg signalized intersections where the left-turn is permissive and a pedestrian signal exists at the conflicting approach. However, in order to use the PPLT in earnest, it is necessary to revise the road traffic act, traffic signs, and related manuals.

PURPOSES : This study aims to investigate the direct and indirect influence areas from incidents on urban interrupted roadways and to develop traffic management strategies for each influence area. METHODS : Based on a literature review, various traffic management strategies for certain incidents were collected. In addition, the relationship between the measure of effectiveness and the characteristics of incidents was explored using an extensive simulation study. RESULTS : From the simulation studies, traffic delays increased as the number of lane closures increased, and the impact of lane closures was reduced to the direction upstream from the incident site. However, the magnitude of the delay change depended on the degree of saturation. Using these characteristics, the direct and indirect influence areas resulting from incidents were defined, and traffic management strategies were established for each direct and indirect influence area and for each level of incident. CONCLUSIONS: The results of this study will contribute to the improvement of national traffic safety by preventing secondary incidents and by effective adaptation to incident events.

A two-step annealing method with a low thermal budget is proposed for advanced surface-energy-driven secondary grain growth of Ge films without any agglomeration. In the first-step annealing, the normal grain growth from as-deposited poly-crystalline Ge films was induced to make the grain size equivalent to the film thickness at 800 °C. After the subsequent second-step annealing at 900 °C, the much larger secondary grains were obtained than those by single-step annealing at 900 °C. The possible explanation regarding the final microstructure of the two-step annealed film is proposed. The two-step annealing was able to form the microstructure of Ge thin film with very large-grained matrix without any agglomeration, resulting in higher carrier mobility. Therefore, the proposed two-step annealing is believed to be a promising process applicable for channel formation processes in the next-generation Ge thin film transistors for 3D integrated circuits and vertical NAND flash memories.

Korea Expressway Corporation has been utilizing vehicles equipped with dedicated short range communication (DSRC) based on-board equipment (OBE) for collecting path travel times. A path based method (PBM) estimates the path travel time using probe vehicles traveling whole links on the path, so it is not always possible to obtain sufficient samples for calculating path travel time in the DSRC system. Having this problem in utilizing DSRC for travel time information, this study attempted to estimate path travel time with the help of a link based method (LBM) and examined whether the LBM can be used for obtaining reliable path travel times. Some comparisons were made and identified that the MAPE difference between the LBM and the PBM estimates are less than 3%, signaling that LBM can be used as a proxy for PBM in case of sparse sample conditions. Some limitations and a future research agenda have also been proposed.

This paper proposes an improved stator flux estimator through ensuring conventional PLPF to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency and has the gain and phase compensators. The gain and phase compensators are determined on the assumption that the estimated synchronous angular speed is coincident with the real speed. Therefore, if the synchronous angular speed is not same as the real speed, the gain and phase compensation will not be appropriate. To overcome the problem of conventional PLPF, this paper analyzes the relationship between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, this paper proposes the synchronous speed error compensation scheme. To achieve a start-up without speed sensor, the current model is used as the stator flux estimator at the standstill. When the motor starts up, the current model should be switched into the voltage model. So a stable transition between the voltage model and the current model is required. This paper proposes the simple transition method which determines the initial values of the voltage model and the current model at the transition moment. The validity of the proposed schemes is proved through the simulation results and the experimental results.

We investigated the deep level photoluminescence and cathodoluminescence emissions from GaInP grown on Ge and Ge-on-Si substrates by metal-organic chemical vapor deposition. Considering the interface condition after the growth of GaInP on Ge, we speculated that the P vacancies and/or Ge atoms from the underlying layer due to interdiffusion were responsible for the deep level emissions. Moreover, the anti-phase boundaries in GaInP, incompletely suppressed even when grown on off-axis Ge substrates, were also responsible for the deep level emissions.

There has been a strong demand for providing diverse services to drivers utilizing existing ITS infrastructure. To this end, this study is aiming at improving the accuracy of a variable speed limit system by determining recommended speeds for the system utilizing the information from Urban Traffic Information System(UTIS) and Weather Information System(WIS). In order to determine appropriate speed limits under inclement weather conditions for the variable speed limit system, this study examined three methods: i) the method utilizing the information from WIS, ii) the method utilizing the information from UTIS, and iii) the method which combines the information from WIS and UTIS using different weights for diverse weather conditions. Finally, this study selected the third method which determines an appropriate speed limit using the relationship between the vehicle operating speed and the minimum stopping distance which is estimated using the existing speed limit, surface coefficient of friction and superelevation.

This study intended to improve traffic safety in work zones using fluorescent orange color traffic signs. For this end, the current problems of existing traffic signs and facilities in work zones were analyzed and some good examples of foreign countries were compared. More specifically, in order to identify current problems, the basic shape and color of traffic signs in use were examined through literature review, surveys and field studies. It was found that the fluorescent color worked more effectively than other colors in terms of visibility and conspicuity in work zone sign system. For evaluation, both Conspicuity surveys and in-door simulator experiments were conducted to effectively assess the merits and demerits of different types of traffic signs for work zones. The results of evaluations showed that black lettering on a fluorescent orange background outperformed more than 70% in terms of visibility and ability to call drivers` attention compared with those from black/red lettering on yellow/white backgrounds currently used at work zones on expressways and national highways. In addition, simulated driving experiment disclosed that drivers recognized the fluorescent orange background sign 15m ahead compared with the yellow background sign and 25m ahead compared with the white background sign, respectively. As for the diamond-shaped "Under Construction" sign, drivers recognized fluorescent orange background 11m ahead compared with the yellow background sign and 19m ahead compared with the white background sign, respectively.

This study intended to evaluate the operational performance change from the introduction of the bus signal priority system using the field data. To complete the objective, travel time and volume data were collected from the before and after study, then the distribution of individual vehicle's travel time and the difference of travel time and traffic volume were compared respectively.Analysis results showed that no significant volume change was observed from both passenger vehicle and bus for the major and cross streets. It was identified that the quality of travel time distributions of passenger vehicle and bus was improved after introducing the bus signal priority system. In terms of average speed, passenger car in a major direction increased by 6.5% and bus increased by 10.5% in general. Statistical tests showed that those speed differences were statistically significant at the 95% of confidence level. The results of this paper will be a good source for further research in the area of bus signal priority control.Key words : Bus signal priority, DSRC, travel time, traffic volume, distribution †이 논문은 2010년도 정부(교육과학기술부)의 재원으로 한국연구재단의 지원을 받아 수행된 연구임(NRF-2010-0029450) * 주저자 : 아주대학교 ITS대학원 박사과정 ** 교신저자 : 아주대학교 환경건설교통공학과 교수 *** 공저자 : 아주대학교 환경건설교통공학과 부교수**** 공저자 : 경찰대학 치안정책연구소 책임연구관 †논문접수일 : 2012년 3월 15일†논문심사일 : 2012년 4월 2일†게재확정일 : 2012년 4월 9일

An experiment-based, two-medium thermal model was developed to evaluate the thermal response and protective performance of permeable clothing systems under hot air jet impingement conditions. The clothing systems consisted of single- or double permeable fabric(s) and air volume between the fabrics and an enclosure wall (solid surface with an embedded heat sink of constant-temperature) to mimic human skin. Two types of permeable fabrics were considered for this study: (i) NOMEX IIIA as a thermal protective fabric and (ii) Cotton/Spandex as a commodity fabric. The predicted results from the model were well compared with the experimental results from a previous work. A parametric study was conducted using various jet impingement conditions and design variables of the protective clothing such as the number of fabric layers, air leakage rate, air gap thickness, and fabric type. It was concluded from the parametric study that the permeable clothing with multiple layers of fabric, less air leakage, and thicker air gap had better thermal protective performance under hot air jet impingement conditions.

A novel miniaturization technology for binary-fluid heat and mass exchange was developed and numerous components were fabricated for demonstration as different parts of an ammonia/water absorption heat pump. Short lengths of microchannel tubes are placed in an array, with several such arrays stacked vertically. The ammonia/water solution flows in falling film/droplet mode on the outside of the tubes while coupling fluid flows through the microchannels. Coupling fluid heat transfer coefficients are extremely high due to the use of microchannel tubes. Effective vapor–solution contact on the absorption side minimizes heat and mass transfer resistances. This concept addresses all the requirements for absorber design in an extremely compact geometry. The technology is suitable for almost all absorption heat pump components (absorbers, desorbers, condensers, rectifiers, and evaporators) and for a wide range of binary-fluid processes. The development of several components for absorption and desorption at different capacities using this technology is reported here.

The three major oil importing countries of Northeast Asia—China, Japan and South Korea—are concerned about future security of energy supplies to fuel their dynamic economic activity. Currently all three countries are highly dependent on imports of oil from the Middle East, a region with inherent political instability. Russia’s rich reserves of oil and gas in Eastern Siberia and the Russian Far East offer an obvious alternative. Given the geographical proximity of Russia and its desire to increase its energy exports to Northeast Asia, there is huge potential for cooperation. So far there has been no real intra-regional cooperation and no common external policy towards Russia. Despite obvious differences between Europe and North East Asia, the European model of energy cooperation, developed over the past 50 years, offers some useful lessons.

Actuated signal operations for congested conditions were evaluated with a simulation study at diamond interchanges. Both three-phase and four-phase with two-overlap phasing strategies were employed, with four ramp spacings and traffic patterns. The performance difference was discussed with throughput, average delay, and total stops. Results showed that four-phase control gave less or comparable average delay (or more throughput) for most traffic patterns at ramp spacings of 122 m or more. Three-phase control gave less delay (or more throughput) when an interchange had a balanced traffic pattern from all external approaches. In terms of stops, four-phase operation gave less stops than three-phase operation for all congested conditions investigated. Analysis results indicated that marginal operational benefits could be obtained when ramp spacing was designed between 122 and 183 m. In addition, several regression models were developed for use in performance estimation for congested traffic conditions. The test results showed that the models could provide good performance estimation of congested signal operation at diamond interchanges.

Two 3-phase actuated control strategies at diamond interchanges were investigated for different ramp spacings and traffic patterns. An advanced experimental design, hardware-in-the-loop control, was employed for the simulation study. Operational performance was identified in terms of cycle length, average delay, and total stops. Experimental results showed that the 2 phasing strategies gave similar performance in terms of cycle length and average delay, but not stops. The cycle length of 3-phase operation increased slightly as the ramp spacing became wider. The delay of each strategy was dependent on the traffic pattern, but there was a distinct movement preference for each strategy. The total stops decreased as the spacing increased, and it was the most sensitive variable for the studied traffic demand level. It was also shown that the concept of the hardware-in-the-loop control provides an effective way to evaluate the signal phasing and control strategies.

In this paper, the improved stator flux estimator has been proposed to ensure a Programmable Low Pass Filter (PLPF) to act as a pure integrator for sensorless control of induction motors. In a conventional PLPF, the estimated synchronous angular speed is used as a cutoff frequency of a PLPF whose gain and phase compensator is determined on the assumption of the estimated synchronous angular speed being coincident with the actual one. However, if the synchronous angular speed is not exactly estimated, the gain and phase compensation will not be appropriate. To overcome the mentioned problem, this paper analyzes the relation between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, the synchronous speed error compensation scheme is proposed. For a sensorless start-up, the current model is used as the stator flux estimator at the standstill. Therefore, a stable transition between the voltage model and the current model is required. This paper proposes the simple transition method which determines the initial values of the voltage model and the current model at the transition moment. The validity of the proposed schemes is proved through simulation results and experimental results.

In this paper, a sensorless control of an interior permanent magnet synchronous motors (IPMSMs) is proposed using an Extended Kalman Filter (EKF) based on the extended rotor flux concept. Also, simple parameter estimation method is proposed to improve the performance of sensorless drive method. The IPMSM sensorless drive system has nonlinearity characteristics and parameters variation. To overcome two main drawbacks, the estimation of Extended rotor flux using the EKF is suitable for high performance because of its ability to perform state estimation for nonlinear systems that involve random noise environment. The simple parameter estimation method is also adopted to reduce deterioration of estimation of variables. The experimental results illustrate the validity of the analytical approach and the efficiency of the proposed method.

In this paper, the improved stator flux estimator has been proposed to ensure A Programmable Low Pass Filter (PLPF) to act as a pure integrator for sensorless control of induction motors. Conventional PLPF uses the estimated synchronous speed as a cut-off frequency, with the magnitude and phase compensator determined on the assumption of the estimated synchronous speed being coincident with the actual one. However, if the synchronous speed is not exactly estimated, the magnitude and phase compensation will not be appropriate. Therefore, this paper has analyzed the relation between the synchronous speed error and the phase lag error of the stator flux. Based on this analysis, the synchronous speed error compensation scheme is proposed. In addition, this paper proposes the flux error compensation scheme because there still remain errors in spite of the speed error compensation. The validity of the proposed estimator has been proven using the simulation results.

In this paper, a sensorless control of an interior permanent magnet synchronous motors (IPMSMs) is proposed using an Extended Kalman Filter (EKF) based on the extended rotor flux concept. Also, simple parameter estimation method is proposed to improve the performance of sensorless drive method. The IPMSM sensorless drive system has nonlinearity charac-teristics and parameters variation. To overcome two main drawbacks, the estimation of Extended rotor flux using the EKF is suitable for high performance because of its ability to perform state estimation for nonlinear systems that involve random noise environment. The simple parameter estimation method is also adopted to reduce deterioration of estimation of variables. The experimental results illustrate the validity of the analytical approach and the efficiency of the proposed method.

In this paper, the improved stator flux estimator is proposed to ensure a programmable low pass filter (PLPF) to act as a pure integrator for sensorless control of induction motor. The estimated synchronous angular speed is used as a pole of a PLPF whose gain and phase compensator is determined on the assumption of the estimated synchronous angular speed being coincident with the actual one. However, if the synchronous angular speed is not exactly estimated, the gain and phase compensation will not be appropriate. To overcome the mentioned problem, this paper analyzes the relation between the synchronous speed error and the phase lag error of the stator flux. Based on the analysis, the synchronous speed error compensation scheme is proposed. For a sensorless start-up, this paper utilizes the current model as a flux estimator at the standstill. When the current model is switched to the voltage model, large fluctuations in the stator flux and the motor speed can be caused. Therefore, the simple method for a smooth transition between two models is proposed. Validity of the proposed schemes is verified through both simulation results and experimental results.

There are many trials to provide an optimal route for minimum energy consumption in a wireless sensor network. Currently, however, the mechanisms to find minimum energy property graph (MEPG) do not properly take into account the efficiency in time and storage, the optimality in results, and the feasibility in real systems. In this paper, we propose an efficient and first optimal algorithm to find the MEPG, in which all minimum energy paths are included, not only significantly reducing its total number of edges, but also obtaining an optimal result in O(VlogV+E). We also develop power aware data-centric routing protocol characterized by minimum energy consumption and longer lifetime.

We propose PPVR, a power-aware position vector routing protocol for wireless sensor networks. PPVR is an energy efficient geographical routing protocol that improves existing geographic routing protocols in two ways. First, in the forwarding phase, PPVR reduces the transmission energy by passing packets through a relay node called a power-aware node. Second, PPVR provides an efficient void node avoidance scheme that mitigates the cases forwarding packets to a wrong path so that higher route discovery success rate is achieved. The simulation results shows that the PPVR outperforms existing geographic routing protocols including GPSR and GEAR, in terms of the energy consumption and the successful delivery rate.