• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.100-101
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• 2018

Environmental problems caused by air pollution have been considered as serious critical issues in global perspectives. Controlling greenhouse gases has become one of the major environmental problems in construction fields as well. However, similar studies were mainly focused on suggestion of various methodologies for measuring CO₂ emissions of construction equipment and calculating emissions. This study aims to analyze the correlation between the CO₂ emissions and RPMs of equipment by the construction process based on row data collected from construction equipment actually operated in job sites. This study allows site personnels to determine the amount of emitted CO₂ under particular construction equipment under specific conditions during the targeted construction operations. The research findings expect to be used as fundamental informations for establishing environment-friendly construction operation planning.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.4
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• pp.36-43
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• 2014

Recently, research has been conducted to develop the ORC (organic Rankine cycle), to recover waste heat from facilities such as industrial plants ultimately to create mechanical or electrical energy. The ORC system consists of a heat exchange, a condenser, a pump and a boiler. In this paper, 84 flow analyses were conducted with 21 cases and three variables, i.e., a number of large wings, a number of small wings, and RPMs. R245fa was used as a refrigerant. The flow cavitation phenomenon was investigated through a flow analysis, and a flow stream analysis was conducted.

• Geophysics and Geophysical Exploration
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• v.18 no.3
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• pp.143-153
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• 2015

Polymer flooding for enhancing hydrocarbon production injects into a reservoir polymer solution that is viscous. It is very important to monitor the behavior pattern of the polymer solution in order to evaluate the effectiveness of polymer flooding. To monitor the distribution of polymer solution and thus fluid substitution within the reservoir, we first construct seismic and resistivity rock physics models (RPMs), which are functions of reservoir parameters such as rocks and type of fluid, fluid saturation. For the seismic and resistivity RPMs, responses of seismic and electromagnetic (EM) tomography are numerically simulated as polymer injection, using two dimensional (2D) staggered-grid finite difference elastic modeling and 2.5D finite element EM modeling algorithms, respectively. In constructing RPM for EM tomography, three different reservoir rocks are considered: clean-sand, dispersed shale-sand, and sand-shale lamination rocks. The polymer solution is assumed to have 2 wt% of polymer as normally generated, while water is freshwater or saltwater. Further, neutron logging is also considered to check its sensitivity to polymer flooding. The techniques discussed in the paper are important in monitoring not only hydrocarbon but also geothermal reservoirs.

• Journal of Radiation Protection and Research
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• v.45 no.3
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• pp.117-129
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• 2020

Background: Radiation portal monitors (RPMs) involving plastic scintillators installed at the border inspection sites can detect illicit trafficking of radioactive sources in cargo containers within seconds. However, RPMs may generate false alarms because of the naturally occurring radioactive materials. To manage these false alarms, we previously suggested an energy-weighted algorithm that emphasizes the Compton-edge area as an outstanding peak. This study intends to evaluate the identification of radioactive sources using an improved energy-weighted algorithm. Materials and Methods: The algorithm was modified by increasing the energy weighting factor, and different peak combinations of the energy-weighted spectra were tested for source identification. A commercialized RPM system was used to measure the energy-weighted spectra. The RPM comprised two large plastic scintillators with dimensions of 174 × 29 × 7 ㎤ facing each other at a distance of 4.6 m. In addition, the in-house-fabricated signal processing boards were connected to collect the signal converted into a spectrum. Further, the spectra from eight radioactive sources, including special nuclear materials (SNMs), which were set in motion using a linear motion system (LMS) and a cargo truck, were estimated to identify the source identification rate. Results and Discussion: Each energy-weighted spectrum exhibited a specific peak location, although high statistical fluctuation errors could be observed in the spectrum with the increasing source speed. In particular, ¹³⁷Cs and ⁶⁰Co in motion were identified completely (100%) at speeds of 5 and 10 km/hr. Further, SNMs, which trigger the RPM alarm, were identified approximately 80% of the time at both the aforementioned speeds. Conclusion: Using the modified energy-weighted algorithm, several characteristics of the energy weighted spectra could be observed when the used sources were in motion and when the geometric efficiency was low. In particular, the discrimination between ⁶⁰Co and ⁴⁰K, which triggers false alarms at the primary inspection sites, can be improved using the proposed algorithm.

• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.46-54
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• 2021

In this paper, active noise control was performed to reduce radiated noise in the low frequency band of dishwashers. First, through an analysis of the noise environment of the dishwasher, it was confirmed that the pump noise contributed the most to the radiated noise in the low frequency band, From the result of the noise environment analysis, the reference signal was selected to be the vibration signal of the pump body. The reference signal was obtained by using the accelerometer on the pump body, which can prevent acoustic feedback. The error signal sensor was selected as a microphone located at 1 m in front of the dishwasher and 0.5 m in height. And to design the controller, the error signal and the reference signal were measured at the operational rpms of the dishwasher at 2,500 rpm, 2,600 rpm and 2,800 rpm, and the secondary path transfer function was measured. The designed controller was mounted on Digital Signal Processor (DSP) equipment, and the control performance was verified experimentally. As a result of the measurement at the 3 operational rpms, the 7th multiple component of pump operating frequency decreased by 1.93 dB, 4.43 dB, 5.15 dB per rpm, and the 12th multiple component decreased by 6.67 dB, 2.34 dB, 4.28 dB per rpm. And overall Sound Pressure Level (SPL) decreased by 0.84 dB, 2.58 dB, 1.48 dB by rpm.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.59-64
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• 2018

In general, tracked combat vehicles require excellent output performance of a power unit system to drive on special terrains and in extreme environmental conditions. However, high temperature and pressure are readily applied to the coolant hose in the power unit of the vehicles during high-speed driving under extreme road and weather conditions. These driving conditions can cause the separation phenomenon of the coolant hose in the power unit and consequentially engine overheating during driving. Therefore, a newly designed decompression device for the coolant hose has been proposed and manufactured to solve these problems in the present study. To validate of the newly proposed decompression device, the input and output pressures were measured under the before- and after-improvement conditions using experimental methods for different engine RPMs. In addition, the pre-heater temperature was measured under both conditions. From the experimental results, we expect that the current investigation can help to improve the driving performance of tracked combat vehicles.

• Journal of Radiation Protection and Research
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• v.35 no.4
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• pp.167-171
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• 2010

Fixed radiation portal monitors (RPMs) deployed at border, seaport, airport and key traffic checkpoints have played an important role in preventing the illicit trafficking and transport of nuclear and radioactive materials. However, the RPM is usually large and heavy and can't easily be moved to different locations. These reasons motivate us to develop a mobile radiation detection system. The objective of this paper is to report our experience on developing the mobile radiation detection system for search and detection of nuclear and radioactive materials during road transport. Field tests to characterize the developed detection system were performed at various speeds and distances between the radioactive isotope (RI) transporting car and the measurement car. Results of measurements and detection limits of our system are described in this paper. The mobile radiation detection system developed should contribute to defending public's health and safety and the environment against nuclear and radiological terrorism by detecting nuclear or radioactive material hidden illegally in a vehicle.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.837-844
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• 1986

Valve motion is one of the most important factors which affect on engine noise and efficiency. Since engine valve train is characterized as a spring-mass system, its dynamic response should be analyzed for varing operation RPM range. In this paper, a OHV type valve train motion was studied by dynamic model analysis. A five degrees of freedom model was set up and simulated for different operating conditions. Also in order to varify the usefulness of the model, the valve displacement and the pushrod force were directly measured for varying RPMs and compared with the simulation results. Then sensitivity analysis was done with the five degrees of freedom model in order to suggest for valve train design change.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.2
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• pp.99-106
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• 2014

Weather routing of a ship provides an optimal route to the destination by using minimal time or fuel in a given sea condition. These days, weather routing came into a spotlight with soaring fuel price and the environmental regulations of IMO and several countries. This study presents three scenarios of voyaging strategies for a ship and compared them in terms of the fuel consumption. The first strategy fixes the speed of a ship as a constant value for entire sailing course, the second fixes the RPM of the ship as constant for entire course, and the third determines the RPMs of the ship for each segment of the course. For each strategy, a ship route is optimized by using the $A^*$ search method. Wind, ocean current and wave are considered as ocean environment factors when seeking the optimal routes. Based on 7000 TEU container ship's sea trial records, simulation has been conducted for three scenarios, and the most efficient routing scenario is determined in the view of fuel consumption.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.734-737
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• 2012

인체 무선망이란 USN(Ubiquitous Sensor Network)을 통해 환자의 생체 정보를 실시간으로 수집하는 환경이다. 이를 기반으로 원격지에서 생체 정보를 전달 받는 시스템이 u-RPMS(USN Remote Patient Monitoring System)이다. u-RPMS에서 실시간으로 환자의 정보들이 발생하는데 이때 실시간으로 발생한 정보들은 공유가 불가피하다. 환자의 생체 정보는 생명과 연결되기 때문에 공유할 때 안전이 중요하다. 하지만 u-RPMS에서는 무선 통신으로 동작하기 때문에 보안에 취약하며, 이를 보안하기 위해서 서버와 DB(Data Base) 사이에 인증 서버를 통해서 해결 할 것을 제시한다. 본 연구에서는 인체 무선망을 기반으로 해서 모듈화 된 오픈 소스 원격진료 플랫폼인 OpenEMed의 개인 확인 서비스(PIDS, Personal Identification Service)를 이용해 네트워크를 기반으로 한 Kerberos 인증을 제안한다.