• 대한방사선기술학회지:방사선기술과학
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• 제46권1호
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• pp.53-61
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• 2023

The aim of this study analyzed the important level (IL) and understanding level (UL) including the Borich's need for students preparing of the national examination for radiological technologists at online open chatting room. A total of 254 survey were collected from a total of 1,016 students who used open chatting room from December 13 to December 16, 2022. A general characteristics were the age, gender, curriculum (3 or 4 years), grade and area. The IL, UL, learning satisfaction (LS), learning achievement (LA) and intention to continue using (ICU) were analyzed by using the 5 point Likert scale. There was no significant difference the LS, LA, and ICU according to general characteristics (p>0.05). There was a statistically significant difference a total of sixteen subjects based on the t-test results of the response values from the IL and UL (p<0.05). The total of ten subjects with the highest priority in the Locus for Focus models were the Ultrasonography, Human anatomy, Magnetic resonance imaging, Radiation therapy, Cardiovascular and intervention, Computed tomography, Human physiology, Radiographic imaging, Fluroscopic radiography, and Nuclear medicine) that the Borich's need was also the same as the top 10 ranked subjects. The LS (4.23±0.72), LA (4.18±0.73), and ICU (4.15±0.78) for open chatting room were high. This study identified the subjects most needed by college students by the Borich's need analysis. First, it is necessary to provide intensive education on subjects with high scores that are most needed by college students. Second, it is necessary to improve the teaching method for subjects with low need and low level of understanding.

• 대한전기학회논문지:전력기술부문A
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• 제49권12호
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• pp.575-580
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• 2000

Switching of the transmission lines(T/L) is one of the ways for suppressing the short circuit capacity. This paper presents the extended optimal power flow(OPF) to the problem of selecting the T/Ls to be open. The constraints of the short circuit currents within limits are added to the inequalities of OPF. Also, the overload on the other lines due to switching of T/Ls is avoided by the linearized inequalities. The number of the open lines can be minimized by incorporating into the objective function of OPF in order to maintain reliability. The method of an effective calculation of the extended OPF is also proposed in this paper, which makes the two parts decoupled. The one concerning the generation dispatch is solved in the first place by the conventional method. Secondly, the other concerning the line-switching is optimized by the proposed formulation.

• Current Photovoltaic Research
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• 제9권4호
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• pp.145-159
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• 2021

Light soaking (LS) stability in polymer solar cells (PSCs) has always been a challenge to achieve due to unstable photoactive layer-electrode interface. Especially, the electron transport layer (ETL) and photoactive layer interface limits the LS stability of PSCs. Herein, we have modified the most commonly used and robust zinc oxide (ZnO) ETL-interface using an organic dye molecule and a co-adsorbent. Power conversion efficiencies have been slightly improved but when these PSCs were subjected to long term LS stability chamber, equipped with heat and humidity (45℃ and 85% relative humidity), an outstanding stability in the case of ZnO/dye+co-adsorbent ETL containing devices have been achieved. The enhanced LS stability occurred due to the suppressed interfacial defects and robust contact between the ZnO and photoactive layer. Current density as well as fill factors have been retained after LS with the modified ETL as compared to un-modified ETL, owing to their higher charge collection efficiencies which originated from higher electron mobilities. Moreover, the existence of less traps (as observed from light intensity-open circuit voltage measurements and dark currents at -2V) are also found to be one of the reasons for enhanced LS stability in the current study. We conclude that the mitigation ETL-surface traps using an organic dye with a co-adsorbent is an effective and robust approach to enhance the LS stability in PSCs.

• Geomechanics and Engineering
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• 제31권5호
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• pp.529-543
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• 2022

The lattice-spring-based synthetic rock mass model (LS-SRM) technique has been extensively employed in large open-pit mining and underground projects in the last decade. Since the LS-SRM requires a complex and time-consuming calibration process, a robust approach was developed using the Response Surface Methodology (RSM) to optimize the calibration procedure. For this purpose, numerical models were designed using the Box-Behnken Design technique, and numerical simulations were performed under uniaxial and triaxial stress states. The model input parameters represented the models' micro-mechanical (lattice) properties and the macro-scale properties, including uniaxial compressive strength (UCS), elastic modulus, cohesion, and friction angle constitute the output parameters of the model. The results from RSM models indicate that the lattice UCS and lattice friction angle are the most influential parameters on the macro-scale UCS of the specimen. Moreover, lattice UCS and elastic modulus mainly control macro-scale cohesion. Lattice friction angle (flat joint fiction angle) and lattice elastic modulus affect the macro-scale friction angle. Model validation was performed using physical laboratory experiment results, ranging from weak to hard rock. The results indicated that the RSM model could be employed to calibrate LS-SRM numerical models without a trial-and-error process.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.691-693
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• 2003

The development of an open LBS platform makes it easy to use of the location information between telecommunication companies which have different platforms and to develop various LBS solutions using position information. This paper proposes a mobile webservice solution providing public transportation services to the mobile subscribers.

• Journal of Electrical Engineering and Technology
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• 제2권4호
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• pp.441-444
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• 2007

The mechanical endurance is the critical characteristic of Magnetic contactors (MCs), which are widely used in such industrial equipments as elevators, cranes, and factory control rooms in order to close and open the control circuit. Testing time, however, is so long in most cases that some method of reducing the testing period is required. Therefore, the degradation test by the detected vibration of MCs is developed to reduce the testing time in this work. The degradation test data are analyzed and the prediction model is provided. Also, the possibility of this technology for Reliability Centered Maintenance (RCM) will be shown. This will reduce the period of the product development and raise the reliability of the equipment in power distribution.

• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.184-191
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• 2008

Electrical endurance is the critical characteristic of Magnetic contactors(MCs), which are widely used in such power equipment as elevators, cranes, and factory control rooms in order to close and open control circuits. Testing time, however, is not short in typical cases in which some method of reducing the testing period is required. This study shows the method of determining the stress level of electrical ALT(Accelerated Life Test) through optical temperature sensor and the relationship between 0.05 s and 0.1 s for on-time. The tool used for analyzing the test result is MINITAB. I will propose the method of determining the optimized stress level through optical temperature sensor, which will contribute to minimize the testing time and development period and also raise the product reliability.

• Journal of Electrical Engineering and Technology
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• 제2권2호
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• pp.188-193
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• 2007

Magnetic contactors (MCs) are widely used in industrial equipment such as elevators, cranes and factory control rooms in order to close and open the control circuits. The reliability of MCs mainly depend on mechanical durability and international standards such as IEC 60947-4-1, which stipulates the testing method for MCs. Testing time, however, is so long in usual cases that a method of reducing testing time is required. Therefore, a temperature and voltage-accelerated life testing (ALT) method has been developed to reduce the testing time in this work. The accelerated life test data are analyzed and acceleration factors (AFs) are provided.

• 환경생물
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• 제38권2호
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• pp.254-270
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• 2020

금강 하구해역 식물플랑크톤 군집의 시·공간적 변동 및 생물해양학적 환경특성을 파악하기 위해 2018년 2월, 5월, 8월 및 11월, 4계절에 거쳐 15개 정점을 대상으로 현장조사를 실시하였다. 조사기간 동안 출현한 식물플랑크톤 종은 58속 116종으로 겨울과 봄에 단순하였고, 여름과 가을에 상대적으로 다양하게 출현하였다. 현존량은 가을에 10 cells mL^-1에서 겨울에 2,904.0 cells mL^-1까지 큰 변동 폭으로 평균 577.2 cells mL^-1의 높은 현존량을 보였으며, 출현 종과는 달리 봄과 가을에 낮고, 여름과 겨울에 높은 현존량을 나타내었다. 우점종은 연중 규조류 점유율이 높았으며, 겨울은 Thalassiosira nordenskioeldii, Cerataulina bergonii, Skeletonema costatum-ls 및 Coscinodiscus angustelineata, 봄은 S. costatum-ls 및 C. bergonii, 여름은 Eucampia zodiacus 및 Th. nordenskioeldii, 그리고 가을 하구역은 Aulacoseira cf. granulata, 혼합해역은 S. costatum-ls 및 외해역은 Lingulodinium polyedra가 우점하였다. 그리고 주성분 분석에 의하면 금강 하구해역의 식물플랑크톤 군집은 연간 금강하굿둑을 통해 유입되는 높은 영양염을 포함하는 담수의 유입량과 확장 정도에 크게 영향을 받고 있었다. 그러나 하굿둑을 통한 직접적인 담수 영향은 금란도 주변까지의 영역에 한정되었고, 그 외 해역은 해수와 담수가 강하게 혼합되었다.

• Steel and Composite Structures
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• 제10권5호
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• pp.429-455
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• 2010

The current research presents a detailed methodology for generating air blast loading for use within a finite element context. Parameters describing blast overpressure loading on a structure are drawn from open literature sources and incorporated within a blast load generation computer code developed for this research. This open literature approach lends transparency to the details of the blast load modeling, as compared with many commonly used approaches to blast load generation, for which the details are not publicly available. As a demonstration, the load generation code is used with the finite element software LS-DYNA to simulate the response of a steel plate and girder subjected to explosions modeled using these parameters as well as blast parameters from other sources.