• 한국안전학회지
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• 제38권3호
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• pp.20-26
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• 2023

Fiber-reinforced composite materials with carbon, glass, and aramid fibers are widely applied to industrial field structures due to their excellent properties. However, carbon fibers are vulnerable to external impacts, whereas aramid fibers degrade when exposed to water. This study evaluated carbon/aramid fiber composites degraded and damaged by high-temperature saline environments using acoustic emission (AE). The test specimen was molded using an autoclave and immersed in seawater at 70 ℃ for 224 days. In order to imitate the damage, a 3-mm-diameter hole was drilled using a diamond drill. Additionally, the specimen with the perforation was repaired by patch attachment processing. Three-point bending was used to conduct the flexural experiment, and an AE sensor with a 150-kHz resonance frequency was attached to evaluate the damage and the effect of patch attachment. AE accumulative counts obtained at the maximum load were 69.2, 67.1, and 91.2 for a high-temperature seawater deteriorated condition, a hole specimen, and a repaired patch specimen, respectively. Furthermore, the maximum amplitude of AE was detected at low values of 28 dB, 31.3 dB, and 30.3 dB.

• Strategy21
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• 통권30호
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• pp.200-235
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• 2012

Over the past few years, due to the climate change of the earth, the Arctic's sea ice cover is undergoing a historic transformation - thinning, extent reduction in all seasons, and mitigation in the area of multi-year ice in the central Arctic Ocean. These changes allow for increases in maritime access throughout the Arctic Ocean and for potential longer seasons of navigation and possibly transarctic voyage in the summer. These changes also allow more exploration for oil, gas, and other minerals. The Arctic is now an archetype of the complex, multi-dimensional global problems of the twenty-first century. Military security, environmental security, and economic security interact. The potentially enormous economic stakes, sufficient to change the strategic balance among the states of the region, set off competitive pressures for national advantage. Korea, which is heavily dependent upon the sea lane in terms of transportation of its exports and imports, is very much interested in the Arctic sea routes. Korea believes that the Artic sea route, particularly the Northern Sea Route (NSR), could serve as a new useful sea lane, which will enable shorter times between East Asia and Europe, thus resulting in substantial cost saving for ship operators. In addition to shipping, Korea is interested in other Arctic-related maritime industries. Korea, as a leading shipbuilder in the global market, is interested in building ice breakers, drill ships, and other vessels which can contribute to safe operation in Arctic resource development and exploration. Korea, as one of the future stakeholders in Arctic maritime activities, should be ready to foster international cooperation in the region.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2008년도 춘계학술발표대회
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• pp.73-75
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• 2008

현대는 시뮬레이션을 통하여 많은 모의 훈련을 대체하고 있다. 시뮬레이터는 고유의 훈련 임무를 수행하기 위하여 기획, 제작 되어진다. 하지만 현대와 같은 종합적인 입체훈련 체계는 고유의 훈련 임무 이외에 개개의 시뮬레이터의 임무가 가상의 종합 시뮬레이션 환경에 참가한 통합 훈련 체계의 필요성을 야기하게 되었다. 또한 각각의 시뮬레이터의 기능은 보다 세분화 되었으며 높은 성능을 요구하게 되었다. 현재 KA-32 헬기 시뮬레이터 영상 프로그램을 제작하고 있는 한국소프트스페이스(주)는 독립적인 시뮬레이터들에 HLA(High Level Architecture)를 적용하여 하나의 종합 훈련 시스템을 구축하였다. 고유의 임무를 지닌 시뮬레이테는 각각의 임무를 가상의 종합 훈련 환경에 참가하여 서로간의 훈련 효과를 극대화 시켜화 시켜준다. HLA 기반의 종합 훈련 시스템의 RTI(Run-Time Infrastructure)는 Pitch 사의 pRTI를 사용하였으며, 가상의 종합 시뮬레이션 환경의 핵심이 되는FOM(Federation Object Model)은 호환성을 및 모든 객체의 표현을 위하여 RPR FOM(Real-time Reference FOM)을 사용하였다. 본 종합 훈련 시스템에서는 각각의 시뮬레이션간에 최고의 성능을 내기 위하여, 기능 세부화 하여 구성하였다. Terrion 사의 FLAMES는 종합 훈련 시스템의 시뮬레이션 진행/설정 및 분석을 담당하며, Mantis는 훈련 상황을 사실감 있는 3 차원 영상으로 참가자에게 전달하여 준다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.15-16
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• 2023

In this paper, we aimed to develop a new method for diagnosing the depth of neutralization in architectural and civil engineering structures using the core drilling method, which combines the speed of drilling with the accuracy of core ringing. When compared to the drilling method, the core drilling method showed a lower measurement deviation of 1-2mm (7.6%) in confirming the depth of neutralization. This is believed to be a result of potential interference during the sample collection process in the drilling method, where the drill may pass through aggregates, leading to overestimation, as indicated in previous studies. The rapid evaluation of neutralization using the core drilling method serves as an alternative to address the issues associated with both drilling and core ringing methods in diagnosing the depth of neutralization. It offers a solution to the inaccuracy caused by coarse aggregates and the cumbersome post-processing steps required for neutralization diagnosis. Our proposed technique aims to provide an accurate and expedited diagnosis of neutralization depth without the need for additional processes.

• Journal of Biosystems Engineering
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• 제33권2호
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• pp.83-93
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• 2008

In order to save labor and cost, direct seeding has been considered as an important alternative to the machine transplanting in rice cultivation. Current direct seeding machines for rice in Korea drill irregularly under various operating conditions. This study was conducted to develope a precision seeder which enables the accurate, even-spaced in row placement of rice seeds at uniform depths of 3-4 cm on dry paddy. Design, construction and performance evaluation of the precision seeder were carried out. The tractor rear-mounted type 8-rows precision seeder which performs seeding in addition to fertilizing, ditching, and rotary tilling works on dry paddy was developed. Main components of the seeder were ditcher and leveller, rotary tiller, powered roller type furrow opener, seeding device, powered roller type furrow covering and firming device, hydraulic unit, seeding speed control system, power transmission system, hitch and frame. Ditching, furrow opening, and seed covering and firming performances were good and seeding depths of 2-4 cm could be maintained. Planting accuracies and planting precisions were within 13.6%, and 31.2%, respectively, for planting space of 15 cm, and seeding velocity of 0.5 m/s. These mean variations of average planting space were within 2.1 cm, and 90% of seeds in a hill were seeded within 4.7 cm of hill length, respectively. Error ratios between setting planting space and measured average planting space were shown within 6.7%. Therefore the seeder showed good planting performance up to seeding velocity of 0.5 m/s in field tests. And field capacity of the seeder was about 0.28 ha/hour.

• Journal of Oral Medicine and Pain
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• 제23권4호
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• pp.387-401
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• 1998

This study was performed to investigate the emotional state related to dental fear, hospital anxiety and depresison, and frequency of stress symproms of orofacial region. For this study, Dnetal Fear Surfey(DFS) scale, the Hospital ANxiety and Depression(HAD) scale, and Stress Symptom Questionnaire(SSQ) designed by the author were used in 549 dental outpatients. Dental Fear Survey scale is composed of avoidance of dentistry(AVOI), physiologic response scale(PRS) and dental stimulus response scale(DSRS). The Hospital anxiety and Depresiosn scale is composed of hospital anxiety(HA) and hospital depressoin (HD). Data were analyzed statistically with SPSS program and the results were as follows : 1. The item of the highest positive response rate in DFS scale was 'feeling drill'(82.0%), and in the HAD scale was ' feel as if I am slowed down'(84.1%). 2. Mean score of AVOI, PRS, DSRS and HD were higher in the older group(>25yr) than the yoiunger group(<25yr) and female patients showed higher score of DSRS, HA than male patients. 3. Mean number of items of stress symptoms in extraoral region were 3.4, and in intraoral region, were 4.7. Tongue wymptoms were increased in the older toup and female patients had more stress symptoms than male patients. 4. Correlation between DFS scale and HAD scale were significantly positive and these scales were also apositively correlated with tongue symptoms. 5. As for treatment types, the patients treated in the department of periodontics,conservative dentistry, and oral surgery showed higher score of DFS scale than the patients with temporomandibular disorders or treatedin the department of orthodontics.

• 터널과지하공간
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• 제19권6호
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• pp.479-489
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• 2009

터널 굴착시 굴진면 전방의 지반상태를 사전에 파악하는 것은 터널의 안정성을 증가시킴과 동시에 시공성을 향상시켜 경제적인 터널 시공을 할 수 있도록 한다. 이에 본 연구에서는 터널 천공시 획득되는 천공데이터를 이용하여 굴진면 전방의 암반강도를 예측하고자 하였다. 이는 암반강도가 현장에서 암반분류 및 지보패턴 설계 등의 핵심인자로 가장 보편적으로 활용될 뿐만 아니라, 암반강도의 변화를 통해 굴진면 전방의 지반상태 변화를 예측하는데도 활용할 수 있기 때문이다. 이를 위해 본 연구에서는 다양한 강도 특성을 보이는 균질한 암석시험편을 대상으로 착암기 종류를 변화시켜가며 천공실험을 수행하였다. 실험결과 천공속도는 다른 천공데이터들과 착암기의 종류 및 암석의 강도에 따라 고유한 값을 보이는 것으로 나타났다. 또한, 동일한 암석에 대해 천공시 타격압이 증가하면 천공속도는 선형적으로 비례하여 증가하는 것으로 나타났다. 이러한 결과를 바탕으로 본 연구에서는 터널 시공 현장에서 착암기의 제원, 현장 계측 데이터 및 천공속도와 암반강도의 상관관계를 이용하여 터널 굴진면 전방의 암반강도를 예측할 수 있는 방안을 제안하였다.

• 한국지반신소재학회논문집
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• 제11권4호
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• pp.45-53
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• 2012

지반굴착은 지반조사, 연약지반 개량, 선굴착 말뚝 시공 등 지반공학 분야에서 널리 사용되고 있다. 지반을 굴착하기 위해서는 오거의 상부에 설치된 구동모터를 회전시키는 전기에너지가 필요하게 된다. 본 논문에서는 지반굴착시 구동모터에 소요되는 전기에너지와 지반의 표준관입시험 N값의 상관관계를 분석하고자 하였다. 이를 위하여 지반굴착시 변화하는 전류값과 굴착깊이를 계측하기 위한 측정센서, 데이터 저장시스템, 굴착시스템 등의 실내실험 장치를 개발하였으며, 모형토조 실험을 수행하였다. 계측된 전류값과 굴착깊이는 표준관입시험 N값 추정에 이용되었으며 추정된 표준관입시험 N값은 실내실험으로부터 실측된 N값과 비교하였다. 비교결과 지반굴착에 소요되는 전기에너지를 이용하여 표준관입시험 N값을 추정할 수 있음을 확인하였다.

• 한국산림과학회지
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• 제31권1호
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• pp.37-42
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• 1976

본시험(本試驗)은 천보산지역(天寶山地域)의 황폐지(荒廢地)에서 효과적(效果的)인 지피식생(地被植生) 조성방법(造成方法) 구명(究明)코자 실시(實施)되었다. 이 지역(地域)은 심한 면상침식(面狀浸蝕)이 일어난 곳으로서 모재(母材)는 화강편마암(花崗片麻岩)으로 매우 침식위험(浸蝕危險)이 높다. 참싸리, 새, 아까시나무가 공시초목(供試草木)으로 사용 되었고 삽종방법(揷種方法)은 산파(散播)거적피복(被覆)과 산폐무피복(散廢無被覆), 조파(條播) 10cm와 조파(條播) 20cm, 점파(點播) 20cm와 점파(點播) 30cm 이상(以上) 3파종(播種) 6처리(處理)였다. 1. $30^{\circ}$이하(以下)의 경사지(傾斜地)에서는 산파(散播)거적피복방법(被覆方法)이 가장 효과적(效果的)이었다. 2. $30^{\circ}$이상(以上)의 급경사지(急傾斜地)에서는 조파(條播) 10cm가 효과적(效果的)이었다. 3. 토성(土性)은 토양수분(土壤水分)을 조절(調節)하여 식생조성(植生造成)에 영향을 준 것 같다. 피복도(被覆度)와 생중량(生重量)은 토양중(土壤中)의 세토량(細土量)과 함께 증가(增加)하였다. 4. 해가 지남에 따라 피복도(被覆度)는 생중량(生重量)과 함께 증가(增加)하였으나 생립본수(生立本數)는 감소(減少)하였다.

• 대한인간공학회지
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• 제19권2호
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• pp.75-86
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• 2000

In this study, the characteristics of transmitted vibration on HAS(hand-arm system) were identified to evaluate physical load due to the work surface orientation, tool weight and push force during powered drilling tasks. The characteristics of transmitted vibration on work surface orientation showed that the acceleration of transmitted vibration on horizontal work surface was higher than that on the vertical work surface. Regarding the characteristics of transmitted vibration on tool weight, the vibration acceleration level becomes lower as the tool weight becomes heavier. The amount of transmitted vibration on hand-arm system was decreased down to the tool weight of 2.4kg. However, as the tool weight becomes heavier than 2.8kg, the amount of transmitted vibration was increased and had peak value at 3.2kg of tool weight. Regarding the characteristics of transmitted vibration on push force, the vibration acceleration level goes higher, as the push force becomes larger. The characteristics of transmitted vibration on the axis of vibration showed that the direction of $Z_h$ had the highest acceleration compared to the direction of $X_h$, and $Y_h$. The direction of $X_h$, $Y_h$ and $Z_h$ had the highest acceleration of transmitted vibration on the hand, wrist and elbow, respectively. The results of this study showed that the condition which affect the lowest physical load to the subject on the powered drilling task would be working with the 2.4kg of tool weight on the vertical work surface.