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        검색결과 61

        41.
        1986.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        4,300원
        42.
        1983.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        4,600원
        43.
        2022.09 KCI 등재 서비스 종료(열람 제한)
        In this study, we improved the water-based condensation particle counter in Atmospheric Research Aircraft NARA and investigated the condensation particle number concentration over the Korean peninsula. Pump and set point information were changed to improve the instrument used by aircraft for observation. Ground-based observational result showed that the error between two instruments, which are water-based condensation particle counter and butanol-based condensation particle counter, was 4.7%. Aerial observational result revealed that the number concentration before improvement indicate large variation with unstable condition, whereas the number concentration after improvement indicate a reasonable variation. After improvement, the number concentration was 706±499 particle/㎤ in the West Sea and 257±80 particle/㎤ in Gangwon-do, and these are similar to the concentration range reported in previous studies. Notably, this is the first attempt to use aerial observation with water-based condensation particle counter to investigate condensation particle number concentration.
        44.
        2020.09 KCI 등재 서비스 종료(열람 제한)
        본 연구의 목적은 선상에서 열수광물 내 Au를 효과적으로 용출하기 위한 마이크로웨이브-차아염소 산 용출의 적용 가능성을 파악하는 것이다. 비교용출실험은 마이크로웨이브 질산용출의 유(T1)/무(T2)에 따른 Au 용출율의 영향을 확인하였다. 또한, 기계적 교반에 의한 전통적인 용출(T3)과 마이크로웨이브 용출에 따른 Au 용출율을 비교하였다. 마이크로웨이브 질산용출결과(고액비; 10%, 용출온도; 90oC, 용출시간; 20분), 금속의 용출율은 As>Pb>Cu>Fe>Zn 순으로 높게 나타났으며, 용출잔사 내 Au의 함량은 33.77 g/ton에서 60.02 g/ ton으로 증가하였다. 염화물 용매제를 이용한 비교용출실험 결과, Au의 용출율은 T1(61.10%)>T3(53.30%) >T2(17.30%)순으로 높게 나타났다. 따라서, 해수를 이용하여 제조 가능하고 용출과정에서 발생되는 염소 가스를 포집하여 재이용 가능한 염화물은 Au용출을 위한 최적의 용매제로 예상된다. 또한 마이크로웨이브를 적용함으로써 시간, 효율 및 에너지 측면에서 효과적일 것으로 판단되어진다.
        45.
        2020.06 KCI 등재 서비스 종료(열람 제한)
        Over the last years, a number of different path following methods for the autonomous parking system have been proposed for tracking planned paths. However, it is difficult to find a study comparing path following methods for a short path length with large curvature such as a parking path. In this paper, we conduct a comparative study of the path following methods for perpendicular parking. By using Monte-Carlo simulation, we determine the optimal parameters of each controller and analyze the performance of the path following. In addition, we consider the path following error occurred at the switching point where forward and reverse paths are switched. To address this error, we conduct the comparative study of the path following methods with the one thousand switching points generated by the Monte-Carlo method. The performance of each controller is analyzed using the V-rep simulator. With the simulation results, this paper provides a deep discussion about the effectiveness and limitations of each algorithm.
        46.
        2019.09 KCI 등재 서비스 종료(열람 제한)
        This paper proposes a parking space detection method for autonomous parking by using the Around View Monitor (AVM) image and Light Detection and Ranging (LIDAR) sensor fusion. This method consists of removing obstacles except for the parking line, detecting the parking line, and template matching method to detect the parking space location information in the parking lot. In order to remove the obstacles, we correct and converge LIDAR information considering the distortion phenomenon in AVM image. Based on the assumption that the obstacles are removed, the line filter that reflects the thickness of the parking line and the improved radon transformation are applied to detect the parking line clearly. The parking space location information is detected by applying template matching with the modified parking space template and the detected parking lines are used to return location information of parking space. Finally, we propose a novel parking space detection system that returns relative distance and relative angle from the current vehicle to the parking space.
        47.
        2017.07 KCI 등재 서비스 종료(열람 제한)
        본 연구는 학교현장실습 전 구성주의 교수학습이론에 기반하여 모의수업을 실행하고 평가해 본 기회를 가진 예비 생물교사들이 학교현장실습에 참여하면서 겪은 수업참관과 수업운영의 경험을 통해 교수-학습에 대한 신념이 어떻게 변화되고 재구성되었는지 살펴보았다. 학교현장실습 후 반구 조화된 개인별 면담 질문을 통해 예비교사들의 교과목적에 대한 신념, 교수학습에 대한 신념, 좋은 수업에 대한 신념, 그리고 앞으로 현장교사가 된다면 어떠한 교수학습방법을 활용할 것인지에 대한 질적 자료를 수집하였다. 본 연구에 참여한 예비 생물교사들은 학교현장실습 전 대학에서의 교육을 통해 과학적 소양의 함양을 위한 과학적 사고력과 탐구를 중요시 생각하였다. 학교현장실습 기간 동안 예비교사들은 실험이나 탐구활동이 이루어지지 않고 내용 전달식의 입시위주의 교육이 주로 이루어지고 있는 현장을 경험 하였으며, 한편으로는 교사 중심이지만 소통이 되는 수업, 학생 하나하 나 이끌어가는 수업, 교사의 노력에 반응해 주는 학생들의 모습을 경험하기도 하였다. 예비교사들은 학교현장실습 후 ‘구성주의’ 수업이 구현되기 힘들다는 점을 토로하면서도 학생들의 사고를 자극하 고 능동적인 참여를 이끌어내는 현장에 부합하는 교수학습방법을 찾고자 노력하였다. 또한, 수업에 대한 필요성과 흥미, 소통하는 수업, 교사의 노력과 열정의 중요성을 언급하는 등 대학에서 배운 이론을 현장에 맞게 실천하고자 하였다. 예비교사들은 현장의 긍정적 측면과 부정적 측면을 동시에 경험하면서도 교사교육 프로그램에서 학습한 구성주의 교수-학습이론의 실현 가능성에 대해 고민 하는 모습을 보였다. 본 연구는 학교현장실습 전 교사교육 프로그램, 현장실습 경험, 그리고 현장실습 후 예비교사들이 교수학습 신념을 어떻게 재구성하였는지 점검해 봄으로써 예비 교사 교육에서의 시사점을 제안하고자 하였다.
        48.
        2016.09 KCI 등재 서비스 종료(열람 제한)
        A minimum threshold for the signal to noise ratio (SNRmin) has to be set in the data processing system of wind profiler radar (WPR). The data collection rate and the accuracy of the WPR wind vector depend on the SNRmin. The WPR at Uljin is operated with an SNRmin of 1 dB which is a relatively large threshold. We found that the accuracy and the continuity of the WPR wind vector with height were directly related to the variability of the SNR and vertical gradient of the squared refractive index. We investigated a quantitative method for determining a new SNRmin for the WPR at Uljin and it was evaluated with radiosonde data. The accuracy and continuity of the wind vector from an SNR of less than 1 dB, began to decrease at an altitude of 3.5 km. Most of the SNR values were less than –3.5 dB in altitudes higher than 3.5 km. We retrieved high-accuracy wind vectors at altitudes over 3 km where measurements were deficient with an SNRmin of 1 dB.
        49.
        2016.02 KCI 등재 서비스 종료(열람 제한)
        Ground echo is radar return from stationary targets such as buildings and trees. Wind vectors from the wind profile radar in Gangneung are affected by ground echoes due to the complex mountainous terrain located to the west and the south. These ground echoes make a spurious peak close to the direct current (DC) line signal in Doppler spectra. Wind vectors polluted by ground clutters were determined from spectra of oblique beams. After eliminated the terrain echoes, the accuracy of wind vector compared with radiosonde was improved about 68.4% and its relative coefficient was increased from 0.58 to 0.97.
        50.
        2016.01 KCI 등재 서비스 종료(열람 제한)
        본 연구는 고강도 섬유보강 시멘트 복합체(UHSCC) 접착성능을 평가하는 것이 목적이다. Direct shear test를 통해 압축전단접착강 도를 측정한 결과 NC(보통강도콘크리트)+ NC 실험체(150×150×150)에서는 모든 수준에서 유사한 압축전당접착강도를 나타내었고, 반 면 UHSCC+UHSCC에서는 지연타설 30분 후부터 0분에 비해 압축전단접착강도가 낮아지는 것을 확인할 수 있었다. 이를 통한 접착면의 파괴 모드를 분석한 결과 NC+NC 에서는 모든 수준에서 비계면 파괴를 보였고 UHSCC+UHSCC에서는 30분, 60분, 90분 시험체에서 계면파괴가 일 어났다. NC 및 UHSCC의 타설면을 XRD 시험을 통해 분석한 결과 NC 시험체에 비해 UHSCC의 시험체 에서 많은량의 SiO2의 성분이 검출되 는 것을 알 수 있었고 UHSCC에서 나타난 코팅막의 주성분의 대부분은 SiO2로 사료된다. 따라서 본 연구에서 사용된 UHSCC는 지연타설 30분 후 부터는 접착성능의 저하로 구조체로서의 사용이 어렵다고 판단된다. 금후 연구에서는 콜드조인트 발생 부위의 면처리 방법을 통한 접착성 능 향상이 필요하다고 사료된다.
        51.
        2015.10 서비스 종료(열람 제한)
        This study is, when we pour the concrete, doing bonding shear performance evaluation to search the influence about an adhesive interface by a generated cold joint with a retardation time. In conclusion, this experiment shows that the higher a compressive strength of the concrete is, the higher a reduction ratio of the bonding shear strength is, and the instance of a none agitation and a compaction with 15 minutes of a retardation time are the lowest influence in a whole of the results; each of the reduction ratio of the bonding shear strength is approximately 4.5%.
        52.
        2015.04 KCI 등재 서비스 종료(열람 제한)
        Spatial distribution of precipitation has been estimated based on the local gauge correction (LGC) with a fixed inverse distance weighting (IDW), which is not optimized in taking effective radius into account depending on the radar error. We developed an algorithm, improved local gauge correction (ILGC) which eliminates outlier in radar rainrate errors and optimize distance power for IDW. ILGC was statistically examined the hourly cumulated precipitation from weather for the heavy rain events. Adjusted radar rainfall from ILGC is improved to 50% compared with unadjusted radar rainfall. The accuracy of ILGC is higher to 7% than that of LGC, which resulted from a positive effect of the optimal algorithm on the adjustment of quantitative precipitation estimation from weather radar.
        53.
        2015.01 KCI 등재 서비스 종료(열람 제한)
        Wind profiler provides vertical profiles of three-dimensional wind vectors with high spatiotemporal resolution. The wind vectors is useful to analyze severe weather phenomena and to validate the various products from numerical weather prediction model. However, the wind measurements are not immune to ground clutter, bird, insect, and aircraft. Therefore, quality of wind vectors from wind profiler must be quantitatively evaluated prior to its application. In this study, wind vectors from UHF wind profiler at Ganwon Regional Meteorological Administration was quantitatively evaluated using 27 radiosonde measurements that were launched every two or three hours according to rainfall intensity during Intensive Observation Period (IOP) from June to July 2013. In comparison between two measurements, wind vectors from wind profiler was relatively underestimated. In addition, the accuracy and quality of wind vectors from wind profiler decrease with increasing beam height. The accuracy and quality of the wind vectors for rainy periods during IOP were higher than for the clear-air measurements. The moderate rainfall intensity lead to multi-peaks in Doppler spectrum. It results in overestimation of vertical air motion, whereas wind vectors from wind profilers shows good agreement with those from radiosonde measurements for light rainfall intensity.
        54.
        2014.10 서비스 종료(열람 제한)
        Traditional methods for demolition of rocks may not adequate specially for urban areas and historical places. Accordingly, an use of soundless demolition chemical agent (SCDA) increases in those areas. In this study, required expansive pressure of SCDA for initiating cracks in maritime bedrock was study. It was found that shape of hole and distance between holes reduced required expansive pressure up to 59%.
        55.
        2014.10 서비스 종료(열람 제한)
        This study was conducted for investigating effect of retardation time of secondary placement on shear bonding strength. Evaluation experiment on the shear bonding performance of UHPC(180MPa level concrete) was conducted according to retardation time and size of specimen. As a result, the smaller the size of specimen, the weaker the measured bonding performance of specimen. Also, comparing specimen which is o minute occurrence time of cold joint with specimen which is after 15 minutes, it showd 70% lesser shear bonding strength.
        56.
        2014.06 KCI 등재 서비스 종료(열람 제한)
        The momentum flux and the sensible heat flux were measured with the scintillometers and ultrasonic anemometers at 6 sites of which surface characteristics like roughness length and zero-displacement are different each other. We estimated the momentum flux and the sensible heat flux based on the bulk transfer method with the drag coefficient and the heat transfer coefficient calculated from the temperature and wind speed at two heights. The variation of bulk transfer coefficients showed a remarkable difference depending on the atmospheric stability which is less influenced by the zero-displacement than the roughness length. The estimated sensible heat fluxes were in good agreement with those measured at 3 m, showing 23.7 Wm-2 of the root mean square error that is less than 10% of its maximum. Since the estimated momentum flux is not only effected by drag coefficient but also by wind speed square, the determination of wind speed in the bulk transfer method is critical.
        57.
        2014.04 서비스 종료(열람 제한)
        Traditional methods for demolition of concrete structures and rocks are jackhammer and explosives methods. However, these traditional methods may not adequate specially for urban areas and historical places. Accordingly, an use of soundless chemical demolition agent (SCDA) increases in those areas. SCDA is similar to portland cement and lime is a key ingredient. In this study, expansive pressure from the selected SCDA were measured using outer pipe measuring technique and crack length due to the SCDA were simulated using obtained test data.
        58.
        2013.09 서비스 종료(열람 제한)
        Capecitabine is a prodrug of a 5-fluorouracil (5-FU) that is converted to 5-FU inside the tumor cells. Here, we report a case of 5-FU induced encephalopathy which was subsequently treated with capecitabine without any neurologic complication. A 76-year-old man with rectal adenocarcinoma received chemotherapy, which consisted of 5-FU, leucovorin and oxaliplatin after resection of the primary and metastatic masses. Confusion and agitation were observed during the 2nd cycle of chemotherapy and reappeared during 4th cycle. Both events were completely disappeared within a few days. Capecitabine was administered for 4 cycles without any neurologic toxicity. Capecitabine could be an alternative in patients experiencing 5-FU induced encephalopathy.
        59.
        2013.04 서비스 종료(열람 제한)
        in this study, modulus of deflection and elasticity ware obtained by accomplishing field experiments to subgrade and subbase through LFWD equipment. Based on the interpretation of that results, we want to lay the foundation to utilize for compaction management of under construction and preventive maintenance management of after construction
        60.
        2008.12 KCI 등재 서비스 종료(열람 제한)
        이 논문은 차량용 사이드 미러에 적합한 광대역 RFID 태그안테나를 설계하고, 차체에 의한 지향성의 특성을 제시한다. 제안된 태그 안테나는 인식거리와 광대역 특성을 향상시키기 위해 대칭 구조로 설계되었다 제안된 태그 안테나(30 mm×24 mm×1 mm)는 910 MHz에서 공진하며 대역폭은 780 MHz(540 MHz~1320 MHz)를 가진다. 칩 임피던스는 16 - j131 Ω이고, 상용 칩의 복소 공액 임피던스가 태그 안테나의 설계에 사용되었다. 제안된 태그 안테나는 차량의 사이드 미러의 내부에 위치한다. 사이드 미러의 유전율뿐만 아니라 차체(도체)에 대한 태그 안테나의 효과를 평가하기 위해, 지향패턴 측정과 인식거리가 계산되고 측정되었다. 차량용 RFID 시스템을 위한 최적의 위치가 사이드 미러 내부에서 관측되었으며, 계산된 결과들은 측정된 결과들과 잘 일치하였다.
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