• 한국정밀공학회지
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• 제22권8호
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• pp.92-99
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• 2005

Tungsten heavy metal is characterized by a high density and novel combination of strength and ductility. Among them, 90W-7Ni-3Fe is used for applications, where the high specific weight of the material plays an important role. They are used as counterweights, rotating inertia members, as well as fur defense purposes(kinetic energy Penetrators, etc.). Because of these applications, it is essential to detemine the dynamic characteristics of tungsten alloy. In this paper, Explicit FEM(finite element method) is employed to investigate the dynamic characteristics of tungsten heavy metal under base of stress wave propagation theory for SHPB, and the model of specimen is divided into two parts to understand the phenomenon that stress wave penetrates through each tungsten base and matrix. This simulation results were compared to experimental one and through this program, the dynamic stress-strain curve of tungsten heavy metal can be obtained using quasi static stress-strain curve of pure tungsten and matrix.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2000년도 7월 학술대회지
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• pp.364-364
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• 2000

It has been widely discussed in phonology that syllable structure of mother tongue influences one's acquisition of foreign language. However, the topic was hardly examined experimentally. So, we investigated effects of Korean syllable structure when Korean speakers pronounce English words, especially focusing on consonant strings that are not allowed in Korean. In the experiment, all the subjects are divided into 3 groups, that is, native, experienced, and inexperienced speakers. Native group consists of 1 male English native speaker. Experienced and inexperienced are each composed of 3 male Korean speakers. These 2 groups are divided by the length of residence in the country using English as a native language. 41 mono-syllable words are prepared considering the position (onset vs. coda), characteristic (stops, affricates, fricatives), and number of consonant. Then, the length of the consonant cluster is measured. To eliminate tempo effect, the measured length is normalized using the length of the word 'say' in the carrier sentence. Measurement of consonant cluster is the relative time period between the initiation of energy (onset I coda) which is acoustically representative of noise (consonant portion) and voicing. bar (vowel portion) in a syllable. Statistical method is used to estimate the differences among 3 groups. For each word, analysis of variance (ANDY A) and Post Hoc tests are carried out.

• 상하수도학회지
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• 제33권4호
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• pp.281-289
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• 2019

Desalination plants are generally studied with higher operating costs compared to water supply facilities. This study was conducted to reduce the cost of water production and to preserve existing water resources. Therefore, the purpose of this study was to utilize the control valves to increase maximum efficiency, thereby reducing the power of the pumps and operating costs. Specific energy consumption was shown to reduce the process operating power by up to 1.7 times from 6.17 to $3.55kWh/m^3$ based on seawater reverse osmosis 60 bar. In addition, the water intake process was divided into pre, inter, and post-according to the use method of blasting, and the water treatment process was divided into pre, inter, and post blending. In order to reduce power consumption, the blending process was combined to operate the facility, which resulted in the reduction of power consumption in the order post > pre-inter> inter blending.

• 한방재활의학과학회지
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• 제18권2호
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• pp.17-31
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• 2008

Objectives : This study was carried out to investigate the effects of Samgi-eum($S{\bar{a}}nq{\grave{i}}-y{\check{i}}n$) on the monosodium iodoacetate-induced osteoarthritis in rats. Methods : Osteoarthritis was induced by injection of monosodium iodoacetate intraarticularly in both knee joints. Arthritic rats were divided into control and treated group. Control group were taken distilled water for 20days. Treated group were taken extracts of Samgi-eum($S{\bar{a}}nq{\grave{i}}-y{\check{i}}n$) by orally for the same duration. Normal group were injected normal saline and taken distilled water. Body weights were measured at 0, 5th, 10th, 15th, 20th day after injection. At the end of the experiment, gross and histopathological examination on the articular cartilages of the knee joints were performed. Proteoglycan contents of articular cartilages were analyzed by safranine O staining method. The contents of $TNF-{\alpha}$, $IL-1{\beta}$ and IL-6 in synovial fluids were analyzed by ELISA method. Results : 1. Body weights of the treated group were significantly increased compared with control at 20days after injection. 2. Grossly, the severity of osteoarthritis in the treated group were alleviated compared with control. 3. Histopathologically, degenerative and necrotic lesion of articular cartilages in the treated group were alleviated compared with those of the control and histopathological scores of treated group were significantly decreased compared with control. 4. PG contents in articular cartilages of the treated group were significantly increased compared with control. 5. $TNF-{\alpha}$ contents in synovial fluids of the treated group were significantly decreased compared with control. Conclusions : According to above results, Samgi-eum($S{\bar{a}}nq{\grave{i}}-y{\check{i}}n$) has anti-arthritic effects on the monosodium iodoacetate-induced osteoarthritis in rats. And it is related with reduced secretion of $TNF-{\alpha}$ from osteoarthritic chondrocytes and synovial membranes.

• 콘크리트학회논문집
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• 제25권2호
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• pp.155-163
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• 2013

이 연구는 도넛형 이방향 중공슬래브에 매입된 이형철근의 부착특성 및 부착강도 산정을 위한 기초적인 연구이다. 도넛형 이방향 중공슬래브의 철근 부착특성 및 부착강도 산정을 위해 pull-out test를 수행하였다. 도넛형 중공형성체는 슬래브 내부에 배치되어 철근과 중공형성체 사이에 내부의 피복이 형성된다. 이러한 내부피복두께는 외부피복두께보다 상대적으로 작은 피복두께를 가지며 중공형상에 따라 $2.5d_b$보다 작은 내부피복두께가 형성되기 때문에 철근의 부착에 영향을 미치게 된다. 또한 중공형성체가 일정 간격으로 떨어져 배치되어 있으므로 인장철근을 감싸고 있는 피복두께의 조건이 철근의 길이방향으로 변하게 된다. 따라서 도넛형 이방향 중공슬래브의 부착특성을 알아보기 위해서 중공형성체 형상에 따라 부착구간을 구분하였다. 구간별로 내부피복두께에 따른 부착응력-슬립 관계를 확인하였으며, 중공형성체 전 구간에 걸친 부착응력분포를 확인하여 철근의 길이방향에 따른 부착응력의 발현정도를 확인하였다. 또한 구간별 부착응력-슬립 관계를 기반으로 하여 도넛형 중공슬래브의 부착강도를 산정할 수 있는 부착강도 산정 방법을 제안하였다.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제29권6호
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• pp.513-519
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• 2007

Typical surgical methods for the treatment of mandibular fractures include intermaxillary-fixation (IMF) for obtaining temporary intraoperative occlusion. Traditionally IMF has been achieved with arch-bars or interdental eyelet wiring. However, these techniques are time-consuming procedures, can produce periodontal damage, and are not well tolerated by the patient even under local anesthesia. Moreover, daily maintenance of oral hygiene is difficult for patients with an arch bar. Recently, intermaxillary fixation using intraoral skeletal anchorage screws (SAS) has been introduced for the treatment of mandibular fractures. This method solves the problems above, but they have the potential for tooth damage, screw fractures and intraoperative occlusal instability. In this study, patients with mandiblular fractures were divided into three groups. Group 1 was treated by IMF using archbars(both maxilla and mandible), Group 2 was treated with SAS(maxilla) and arch-bar (mandible), Group 3 was treated with SAS(both maxilla and mandible). The aim of this study was to evaluate the influence of the different IMF methods on periodontal tissue health and intraoperative occlusal rehabilitation about each groups, and to discuss the most favorable IMF method.

• 한국산업융합학회 논문집
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• 제18권3호
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• pp.167-172
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• 2015

In this paper, we propose a new approach to design and control a smart gripper of robot system. A control method for flexible grasping a object in partially unknown environment was proposed, where a proximate sensor detecting the distance between the fingertip and object was used. Based on the proximate sensor signal the finger motion controller could plan the grasping process divided in three phases. The first step is scanning process which two first joints were moved to mid-position of the detected range by a state-variable feedback position controller, after the scanning was finished. The contact force of fingertip was then controlled using the detection sensor of the servo controller for finger joint control. The proposed grasping planning was tested on rectangular bar.

• Steel and Composite Structures
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• 제35권4호
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• pp.475-494
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• 2020

Presented are experimental results from 24 full-scale push test specimens to study the behaviour of composite beams with trapezoidal profiled sheeting laid transverse to the beam axis. The tests use a single-sided horizontal push test setup and are divided into two series. First series contained shear loading only and the second had normal load besides shear load. Four parameters are studied: the effect of wire mesh position and number of its layers, placing a reinforcing bar at the bottom flange of the deck, normal load and its position, and shear stud layout. The results indicate that positioning mesh on top of the deck flange or 30 mm from top of the concrete slab does not affect the stud's strength and ductility. Thus, existing industry practice of locating the mesh at a nominal cover from top of the concrete slab and Eurocode 4 requirement of placing mesh 30 mm below the stud's head are both acceptable. Double mesh layer resulted in 17% increase in stud strength for push tests with single stud per rib. Placing a T16 bar at the bottom of the deck rib did not affect shear stud behaviour. The normal load resulted in 40% and 23% increase in stud strength for single and double studs per rib. Use of studs only in the middle three ribs out of five increased the strength by 23% compared to the layout with studs in first four ribs. Eurocode 4 and Johnson and Yuan equations predicted well the stud strength for single stud/rib tests without normal load, with estimations within 10% of the characteristic experimental load. These equations highly under-estimated the stud capacity, by about 40-50%, for tests with normal load. AISC 360-16 generally over-estimated the stud capacity, except for single stud/rib push tests with normal load. Nellinger equations precisely predicted the stud resistance for push tests with normal load, with ratio of experimental over predicted load as 0.99 and coefficient of variation of about 8%. But, Nellinger method over-estimated the stud capacity by about 20% in push tests with single studs without normal load.

• 한국지열·수열에너지학회논문집
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• 제17권1호
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• pp.14-22
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• 2021

Drilling equipment is an essential part used in various fields such as construction, mining, etc., and it has drawn increasing attention in recent years. The drilling method is generally divided into three types. There are a top hammer method that strikes on the ground, a DTH (Down-The-Hole) method that directly strikes a bit in an underground area, and a rotary method that drills by using rotational force. Among them, the DTH method is most commonly used because it enables efficient drilling compared to other drilling methods. In the conventional DTH hammer, the valve between the piston and the bit is opened and closed using a face to face method. In order to improve the power of the DTH hammer, a DTH hammer with foot valve which is capable of instantaneous opening and closing is used in the drilling field. In this study, we designed a lab-scale DTH hammer with the foot valve, and manufactured an evaluation device for the experiment of the DTH hammer. In addition, we analyzed the performance of the DTH hammer adopted with foot valve according to the pressure range of 3-10 bar. As a result, the internal pressure distribution in the DTH hammer was experimentally analyzed, and then, the movement of the piston according to the pressure was predicted. We believe that this study provides the useful results to explain the performance characteristics of the DTH hammer with the foot valve.

• 응용통계연구
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• 제30권2호
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• pp.301-309
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• 2017

일반적으로 각 N개의 모집단에서 2개 이상의 표본이 추출되었을 때, $H_0:{\mu}_1={\cdots}={\mu}_N$의 가설에 대하여 검정할 수 있지만 각 모집단으로부터 표본이 한 개씩 추출된다면 ${\bar{X}}$가 존재하지 않으므로 모평균의 차이 검정은 불가능하다. 하지만 하나씩 추출된 표본으로 구성된 집단을 두 집단으로 나누어 임의의 평균을 생성함으로써 평균의 차이를 비교한다면 표본들 사이에 존재할 수 있는 이질성을 파악할 수 있다. 따라서 우리는 두 집단으로 나눌 수 있는 조합의 수만큼 평균 차이를 검정할 수 있는 최소 조합 t-검정 방법을 제안하고자 한다. 최종적으로 본 논문에서는 한 개씩 추출된 표본들 사이의 이질성을 확인하기 위하여 평균 차이를 검정할 수 있는 방법을 제안하였고 모의실험 연구를 통해 성능을 확인하였고 실제 자료 분석을 통해 결과를 도출하였다.