• Smart Structures and Systems
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• 제30권2호
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• pp.209-219
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• 2022

The determination for bearing capacity of precast nodular piles is conventionally time-consuming and high-cost by using numerous experiments and empirical methods. This study proposes an intelligent method to evaluate the bearing capacity and shaft resistance of the nodular piles with high efficiency based on long short-term memory (LSTM) approach. A series of field tests are first designed to measure the axial force, shaft resistance and displacement of the combined nodular piles under different loadings, in comparison with the single pre-stressed high-strength concrete piles. The test results confirm that the combined nodular piles could provide larger ultimate bearing capacity (more than 100%) than the single pre-stressed high-strength concrete piles. Both the LSTM-based method and empirical methods are used to calculate the shift resistance of the combined nodular piles. The results show that the LSTM-based method has a high-precision estimation on shaft resistance, not only for the ultimate load but also for the working load.

• Restorative Dentistry and Endodontics
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• 제39권2호
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• pp.104-108
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• 2014

Objectives: To evaluate the effect of passive ultrasonic agitation on the cleaning capacity of a hybrid instrumentation technique. Materials and Methods: Twenty mandibular incisors with mesiodistal-flattened root shape had their crowns sectioned at 1 mm from the cementoenamel junction. Instrumentation was initiated by catheterization with K-type files (Denstply Maillefer) #10, #15, and #20 at 3 mm from the working length. Cervical preparation was performed with Largo bur #1 (Dentsply Maillefer) followed by apical instrumentation with K-type files #15, #20 and #25, and finishing with ProTaper F2 file (Denstply Maillefer). All files were used up to the working length under irrigation with 1 mL of 2.5% sodium hypochlorite (Biodyn$\hat{a}$mica) at each instrument change. At the end of instrumentation, the roots were randomly separated into 2 groups (n = 10). All specimens received final irrigation with 1 mL of 2.5% sodium hypochlorite. The solution remained in the root canals in Group 1 for one minute; and ultrasonic agitation was performed in Group 2 for one minute using a straight tip inserted at 1 mm from working length. The specimens were processed histologically and the sections were analyzed under optic microscope (x64) to quantify debris present in the root canal. Results: The samples submitted to ultrasonic agitation (Group 2) presented significant decrease in the amount of debris in comparison with those of Group 1 (p < 0.05). Conclusions: The hybrid instrumentation technique associated with passive ultrasonic agitation promoted greater debris removal in the apical third of the root canals.

• 설비공학논문집
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• 제18권4호
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• pp.320-327
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• 2006

Numerical analysis and experimental study are performed to investigate the effect of heat load and operating temperature on the thermal performance of several variable conductance heat pipe (VCHP) with screen meshed wick. The heat pipe is designed in 200 screen meshes, 500 mm length and 12.7 mm outer diameter tube of copper, water (4.8 g) is used as working fluid and nitrogen as non-condensible gas (NCG). Heat pipe used in this study has evaporator, condenser and adiabatic section, respectively. Analysis values and experimental data of wall temperature distribution along axial length are presented for heat transport capacity, condenser cooling water temperature change, degrees of an inclination angle and operating temperature. These analysis and experiment give the follow findings: For the same charging mass of working fluid, the operating temperature of heat pipe becomes to be high with the increasing of charging mass of NCG. When the heat flux at the evaporator section increases, the vapor pressure in the pipe rises and consequently compresses the NCG to the condenser end part and increases the active length of the condenser. From previous process, it is found out we can control the operating temperature effectively and also the analysis and experimental results are relatively coincided well.

• 한국항만학회지
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• 제3권1호
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• pp.35-55
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• 1989

Today, about 99% of total import and export cargo in Korea is being transported through the port. The general trends of cargo handling show increases in capacity and speed, In order to cope with these trends, it is not only required to raise the efficiencies of port operation and function but also necessary to decide the optimal amount of the skilled labor force for cargo handling in the port. Cargo handling in the port is basically relied on the cargo handling facilities. Therefore, it is very important to reserve the amount of labor force for cargo handling system has been developed up to a certain level but the personnel management system which is the superior structure has not been followed well. In this study, therefore, we show a method to determine the required amount of labor force for cargo handling considering the amount of cargo and type of cargo handling work per each cargo, and the optimal amount labor force in cope with the fluctuation of the basic cargo handling labor force with respect to the time of in and out cargo flow in the viewpoint of minimizing the expences due to reservation of extra labor force than needed and firing employment of labor force using the Dynamic Programming. The derived algorithm is introduced into the computer simulation for Pusan port with the analyzed real data such as amount of cargo handling in the port with respect to working hour, cargo capacity, working step, the ratio of cargo handling facility and actual number of workers and we estimated the required labor force. As a result of analysis the labor force of Pusan port showed the over-employment such as maximum 21.4%, minimum 8.2% when we assumed that the averages of actual working hours and days were 8 hours in a day and 20 day in a month.

• Steel and Composite Structures
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• 제31권1호
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• pp.13-25
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• 2019

Reactive powder concrete (RPC) is a type of ultra-high strength concrete that has a relatively high brittleness. However, its ductility can be improved by confinement, and the use of RPC in composite RPC filled steel tube columns has become an important subject of research in recent years. This paper aims to present an experimental study of axial capacity calculation of RPC filled circular steel tube columns. Twenty short columns under axial compression were tested and information on their failure patterns, deformation performance, confinement mechanism and load capacity were presented. The effects of load conditions, diameter-thickness ratio and compressive strength of RPC on the axial behavior were further discussed. The experimental results show that: (1) specimens display drum-shaped failure or shear failure respectively with different confinement coefficients, and the load capacity of most specimens increases after the peak load; (2) the steel tube only provides lateral confinement in the elastic-plastic stage for fully loaded specimens, while the confinement effect from steel tube initials at the set of loading for partially loaded specimens; (3) confinement increases the load capacity of specimens by 3% to 38%, and this increase is more pronounced as the confinement coefficient becomes larger; (4) the residual capacity-to-ultimate capacity ratio is larger than 0.75 for test specimens, thus identifying the composite columns have good ductility. The working mechanism and force model of the composite columns were analyzed, and based on the twin-shear unified strength theory, calculation methods of axial capacity for columns with two load conditions were established.

• 인지과학
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• 제22권2호
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• pp.193-215
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• 2011

본 연구에서는 읽기와 관련된 작업기억의 특징을 살펴보기 위해 초등학교 3, 4학년 읽기부진아들과 일반아동들을 비교하였으며, 성별 비교와 각 성분들 간의 상관분석도 실시하였다. 연구 결과 읽기부진아들은 일반아동들보다 작업기억의 모든 하위 검사에서 낮은 수행 수준을 나타내었다. 성별 비교에서 시공간 잡기장에서 성별차가 나타났으며, 그 중 미로이동 기억에서는 읽기능력과 성별 간의 상호작용도 있었다. 전체 집단에서 작업기억의 각 성분들 간의 모든 상관이 유의미하게 나타났으나, 읽기부진아와 일반아동을 분리해서 상관을 구했을 때는 하나의 상관을 제외하고 두 집단에 공통적으로 유의미한 상관이 나타나지 않았다. 중앙집행기의 영향을 제거했을 때 음운 작업기억과 시공간 작업기억 간의 상호관련성이 낮아짐을 확인할 수 있었다. 본 연구를 통해서 읽기부진아 지도에서는 수업자료를 간략하게 제시할 필요성이 있으며, 읽기부진 남학생에게는 가능한 한 시공간 정보를 활용할 필요가 있다는 시사점을 찾을 수 있었다.

• 청정기술
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• 제21권2호
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• pp.108-116
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• 2015

황화수소와 암모니아는 많은 하수처리장과 산업 플랜트로부터의 배출가스에서 발견되어질 수 있는 가장 흔한 악취성분이다. 이들 유해물질들은 인간에게 건강 문제를 일으키고 촉매에 악영향을 미치기 때문에 생활환경과 산업 현장에서의 제거는 매우 중요하다. 본 연구에서는 황화수소와 암모니아에 대한 우수한 흡착능력을 가지는 흡착제를 개발하기 위하여 폐타이어의 열분해 생성물인 카본블랙을 이용하였다. 카본블랙, 금속산화물과 산 또는 염기를 혼합하여 펠렛형 흡착제를 제조하였고, 상온상압에서 고정층 흡착탑의 파과곡선을 이용하여 황화수소와 암모니아에 대한 흡착성능을 평가하였다. 카본블랙, 산화철(III)과 수산화나트륨 혼합물로 제조된 흡착제가 황화수소에 대한 가장 우수한 작업능력을 나타내었다. 암모니아에 대해서는 카본블랙, 산화구리(II), 염산의 혼합물로 제조된 흡착제가 우수한 작업능력을 보였다.

• Journal of Biosystems Engineering
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• 제29권1호
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• pp.1-8
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• 2004

In order to solve the shortage of roughage supply for dairy farm in Korea, winter cereal forage production after harvesting of rice in the fallow paddy field was studied. Two parts are already reported at the previous paper - One was the model development of the mechanized production, and the other was the study of feasibility of the model and its desirable direction in Korea. In this study, the model system is applied for a winter cereal wrap silage production model to practice in Kyungbook National University farm on 3ha scale for 3 years. Results of the research are summarized as follows; It takes 2 or 3 working days to process the wrap silage in middle of May in Daegu region. Also, not much particular problem can be found during the application test of mechanized wrap silage production. Field capacity and field efficiency are estimated to be 0.6-0.85㏊/h and 50-70% in mowing, 1.1∼1.7㏊/h and 52∼80% in tedding and raking, 0.6∼1.1㏊/h and 25∼45％ in baling and 0.5∼0.57㏊/h and 75∼85% in wraping, respectively. Total production cost is estimated to be 1,257won/kg-TDN in oversowing and wrap-silage harvest in 1.6㏊ working area. As a result, large scale field is recommended to produce the wrap silage in order to maximize the field capacity.

• 벤처혁신연구
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• 제5권4호
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• pp.57-74
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• 2022

본 연구의 목적은 중소기업 구성원의 동기와 창의적 작업환경이 혁신행동에 미치는 영향을 검증하고, 개인적 흡수 역량에 따른 차이점을 보고자 한다. 이를 위한 연구 방법으로 중소기업에서 1년 이상 근무한 직원을 대상으로 전문리서치 회사에 설문조사를 의뢰하여 350부를 회수하였으며, SPSS 28과 Smart PLS 3으로 연구모형 및 가설을 검증하였다. 연구 결과, 접근동기와 창의적 작업환경은 개인의 혁신행동에 긍정적 영향을 미쳤고, 이는 개인의 흡수역량에 따라 유의한 차이점을 보였다. 본 연구의 시사점을 다음과 같이 요약하였다. 첫째, 인적 자원이 물적 자원보다 중요한 중소기업에서 혁신적 조직경영을 위해 중소기업은 창의적 작업환경을 제공하고, 구성원이 긍정적 혁신행동을 이끌어내기 위한 동기부여가 필요하다. 둘째, 개인적 흡수역량에 따라 혁신행동이 다르게 나타나며, 혁신행동은 기업 성장의 주체가 되므로 구성원에게 긍정적 동기 부여와 함께 개인적 흡수역량을 높이기 위한 다양한 관심과 지원이 필요함을 나타낸다.

• 한국환경보건학회지
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• 제37권1호
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• pp.50-56
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• 2011

The adsorption capacity of charcoal is a function of the airborne concentration of the target chemical. To evaluate the adsorption capacity of charcoal packed in the cartridges of air purifying respirators, breakthrough tests were conducted with carbon tetrachloride for three commercial cartridges (3M models #7251, #6000 and AX) at 25, 50, 100, 250 and 500 ppm. Adsorption capacities were calculated using a mass transfer balance equation derived from the curve fitting to the breakthrough curves obtained experimentally. Carbon micropore volumes were estimated by iteration to fit the Dubinin/Radushkevich (D/R) adsorption isotherm. They were 0.6566, 0.5727 and 0.3087 g/cc for #7251, #6000 and the AX cartridge, respectively. Above 100 ppm (at high challenge concentrations), #7251 and #6000 showed higher adsorption capacities. However, as the challenge concentration decreased, the adsorption capacities of #7251 and #6000 sharply dropped. On the other hand, the adsorption capacity of the AX cartridge showed little change with the decrease of the challenge concentration. Thus, the AX showed a higher adsorption capacity than #7251 and #6000 at the 5-50 ppm level. It is concluded that service-life tests of cartridges and adsorption capacity tests of charcoal should be conducted at challenge concentration levels reflecting actual working environmental conditions. Alternatively, it is recommended to use the D/R adsorption isotherm to extrapolate adsorption capacity at low concentration levels from the high concentration levels at which breakthrough tests are conducted, at a minimum of two different concentration levels.