• Geomechanics and Engineering
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• 제13권5호
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• pp.715-742
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• 2017

Earth berms are often left in place to support retaining walls or piles in order to eliminate horizontal struts in excavations of soft soil areas. However, if the excavation depth is relatively large, an earth berm-supported retaining system may not be applicable and could be replaced by a multi-bench retaining system. However, studies on multi-bench retaining systems are limited. The goal of this investigation is to study the deformation characteristics, internal forces and interaction mechanisms of the retaining structures in a multi-bench retaining system and the failure modes of this retaining system. Therefore, a series of model tests of a two-bench retaining system was designed and conducted, and corresponding finite difference simulations were developed to back-analyze the model tests and for further analysis. The tests and numerical results show that the distance between the two rows of retaining piles (bench width) and their embedded lengths can significantly influence the relative movement between the piles; this relative movement determines the horizontal stress distribution in the soil between the two rows of piles (i.e., the bench zone) and thus determines the bending moments in the retaining piles. As the bench width increases, the deformations and bending moments in the retaining piles decrease, while the excavation stability increases. If the second retaining piles are longer than a certain length, they will experience a larger bending moment than the first retaining piles and become the primary retaining structure. In addition, for varying bench widths, the slip surface formation differs, and the failure modes of two-bench retained excavations can be divided into three types: integrated failure, interactive failure and disconnected failure.

• 지질공학
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• 제31권3호
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• pp.269-281
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• 2021

Land creeping is the imperceptibly slow, steady, downward movement o f slope-forming soil or rock. Because creep-related failures occur frequently on a large scale without notice, they can be hazardous to both property and human life. Korea Forest Service has operated the prevention and response system from land creeping which has been on the rise since 2018. We categorized and proposed three survey steps (e.g., preliminary, regional, detailed) for investigation of creeping susceptibility site with a focus on geophysical mapping of a selected test site, Yongheung-dong, Pohang, Korea. The combination of geophysical (dipole-dipole electrical resistivity tomography and reciprocal seismic refraction technique, well-logging), geotechnical studies (standard penetrating test, laboratory tests), field mapping (tension cracks, uplift, fault), and comprehensive interpretation of their results provided the reliable information of the subsurface structures including the failure surface. To further investigate the subsurface structure including the sliding zone, we performed high-resolution geophysical mapping in addition to the regional survey. High-resolution seismic velocity structures are employed for stability analysis because they provided more simplified layers of weathering rock, soft rock, and hard rock. Curved slip plane of the land creeping is effectively delineated with a shape of downslope sliding and upward pushing at the apex of high resistive bedrock in high-resolution electrical resistivity model with clay-mineral contents taken into account. Proposed survey steps and comprehensive interpretation schemes of the results from geological, geophysical, and geotechnical data should be effective for data sets collected in a similar environment to land-creeping susceptibility area.

• Physical Therapy Rehabilitation Science
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• 제10권4호
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• pp.503-511
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• 2021

Objective: This study compared pain, muscle power (MP), muscle thickness (MT), and normalized position of the scapula (POS) between general physical therapy and general physical therapy with strengthening exercises of the lower trapezius in patients with rounded shoulder and chronic neck pain. Design: Randomized controlled trial. Methods: The participants were 30 patients of W hospital in Gangnamgu, Seoul, with rounded shoulders who were diagnosed with chronic neck pain. Rounded shoulder was defined as a distance between the surface and acromion of >1 inch in the supine position. The participants were assigned to an experimental group (n=15) and a control group (n=15). The experimental group completed four types of strengthening exercises program for 15 minutes, twice weekly, for a total of 5 weeks. Soft tissue mobilization (STM), cervical extension flexion rotation (CEFR), and physical modality were also performed in both groups. Results: The degree of pain was assessed using the numerical rating scale (NRS), MP was measured a handheld dynamometer, MT was measured by ultrasound, and POS was measured using a tapeline. Significant between-group differences were observed in VAS, MP, MP, and POS. Significant changes were observed in the experimental group for VAS, MP, MT, and POS. Conclusions: Based on the results of this study, it was indicated that lower trapezius strengthening exercises performed together with general physical therapy was significantly improved in pain, MP, MT, and POS in patients with rounded shoulder and chronic neck pain compared to when general physical therapy was performed alone.

• 한국환경농학회지
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• 제37권3호
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• pp.221-228
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• 2018

BACKGROUND: Spoilage fungi can reduce the shelf life of fresh fruits and cause economic losses by lowering quality. Especially, mulberry fruits have high sensitivity to fungal attack due to their high water content (> 70%) and soft texture. In addition, the surface of these fruits is prone to damage during harvesting and postharvest handling. However, any study on postharvest spoilage fungi in mulberry fruit has not been reported in Korea. This study aimed to examine the spoilage fungi occurring in mulberry fruits during storage after harvest. METHODS AND RESULTS: In this study, we isolated postharvest spoilage fungi from mulberry fruits stored in refrigerator (fresh fruits) and deep-freezer (frozen fruits) and identified them. In the phylogenetic analysis based on comparisons of the ITS rDNA sequences, the 18 spoilage fungi isolated from mulberry fruits and the 25 reference sequences were largely divided into seven groups that were subsequently verified by high bootstrap analysis of 73 to 100. Alternaria spp. including A. alternate and A. tenuissima, were the most frequently isolated fungi among the spoilage isolates: its occurrence was the highest among the 18 isolates (38.9%). CONCLUSION: The findings of this study will be helpful for increasing the shelf life of mulberry fruits through the application of appropriate control measures against infection by spoilage fungi during storage.

• 한국응용과학기술학회지
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• 제36권1호
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• pp.305-311
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• 2019

높은 함수율을 갖는 소프트렌즈를 제조하기 위하여 아크릴계 공중합체를 설계, 제조하였다. 공중합체용 모노머로 2-hydroxyethyl methacrylate(HEMA)를 사용하였고 가교제로는 ethylene glycol dimethacrylate(EGDMA), glycerol dimethacrylate(GD) 혹은 glycerol 1,3-diglycerolate diacrylate(GDD)를 이용하여 렌즈를 제조하였다. 함수율 측정결과, 고함수율 렌즈는 기존의 36%에서 46%로 높게 나타났으며 접촉각도 38.6 에서 34.4 로 낮아져 표면 친수성이 높게 나타남을 확인하였다. 인장강도는 가교제의 친수성이 증가함에 따라 0.1MPa 에서 0.08 그리고 0.05 로 감소하였고 전자현미경으로 렌즈의 단면을 확인한 결과 상분리 현상은 나타나지 않았다. 광중합은 Real-time infrared(RTIR)로 측정하였는데 초기 중합 속도가 가교제에 따라 0.6 에서 0.9 로 나타났다.

• Geomechanics and Engineering
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• 제24권4호
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• pp.307-321
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• 2021

In an earlier publication (Serrano et al. 2014), the theoretical basis for evaluating the shear strength in rock joints was presented and used to derive an equation that governs the relationship between tangential and normal stresses on the joint during slippage between the joint faces. In this paper, the theoretical equation is applied to two non-linear failure criteria by using non-associated flow laws, including the modified Hoek and Brown and modified Mohr-Coulomb equations. The theoretical model considers the geometric dilatancy, the instantaneous friction angle, and a parameter that considers joint surface roughness as dependent variables. This model uses a similar equation structure to the empirical law that was proposed by Barton in 1973. However, a good correlation with the empirical values and, therefore, Barton's equation is necessary to incorporate a non-associated flow law that governs breakage processes in rock masses and becomes more significant in highly fractured media, which can be induced in a rock joint. A linear law of dilatancy is used to assess the importance of the non-associated flow to obtain very close values for different roughness states, so the best results are obtained for null material dilatancy, which considers significant changes that correspond to soft rock masses or altered zones of weakness.

• 대한통합의학회지
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• 제9권2호
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• pp.13-21
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• 2021

Purpose : Instrument-assisted soft tissue mobilization (IASTM) has been widely used to improve pain and range of motion. However, research on IASTM using vibration stimulation is lacking. Therefore, this study investigates how IASTM using vibration stimulation affects chronic pain on muscle activity and flexibility of the shoulders. Methods : A total of 20 patients with chronic shoulder pain were divided into the experimental group and the control group. The experimental group (n=10) used vibration stimulus for IASTM, while the control group (n=10) used general IASTM. For six weeks, this training lasted for 30 min a day, twice a week. Muscle activity was evaluated using the surface electromyograph. The back and reach test was used to assess flexibility, the visual analogue scale to measure pain, and the paired t-test to compare the groups before and after the experiment. An independent ANCOVA was conducted to assess differences in the degree of transition between the two groups before and after the experiment. Results : Significant differences in muscle activity, flexibility, and pain in both groups before and after the experiment (p<0.05) were observed, as well as in the muscle activity of the pectoralis major and associated pain (p<0.05). however, muscle activity and flexibility of the upper trapezius and infraspinatus were not significantly different between groups (p>0.05). Conclusion : This study confirms the importance of IASTM using vibration. Design and manufacture of IASTM using vibration based on our results would be useful in the management of shoulder pain, Further clinical evidence are needed.

• 한국지반신소재학회논문집
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• 제21권2호
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• pp.1-9
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• 2022

최근 환경적 문제로 공유수면 매립사업이 감소추세에 있으나 매립사업의 특성상 일률적인 지표로 환경성을 평가하는 데 한계가 있다. 이 연구에서는 공유수면 매립지의 토질역학적 침하거동 인자를 활용하여 폐석회 매립시설의 침하 안정성을 분석하였다. 1차 압밀특성 인자로부터 폐석회는 압밀이 진행중인 점토특성과 유사함을 확인하였다. 매립지 지층을 얇은 토목섬유 보강재로 보강된 층상구조로 가정하고, Westergaard 방법에 따른 응력증가량을 이용하여 침하량을 예측하였다. 압밀도에 따른 침하량을 예측한 결과 연약지반의 표층이 토목섬유로 보강된 경우 보강되지 않은 경우보다 응력증가량이 40% 감소하는 것으로 나타났다. 또한, 폐석회의 소성지수와 내부마찰각의 상관관계를 이용하여 점토와 폐석회의 압밀거동 특성을 비교하였다. 공유수면 매립지내 폐석회는 압밀이 진행중인 상태이므로 장기적으로 침하는 더 증가하는 경향을 보일 것으로 예측되었다.

• 한국지반공학회논문집
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• 제22권9호
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• pp.15-22
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• 2006

선박을 정착시키기 위하여 해저지반에 관입된 드래그 / 영구앵커와 앵커에 연결된 닻줄의 지지력 및 변형을 해석하여, 기존의 앵커와 닻줄의 분석 및 개발을 위하여 만들어진 해석프로그램을 calibration 하기 위하여 원심모형시험기를 사용한 시험을 하였다. 시험에 사용된 닻줄은 ball chain 및 wire cable로써, 일정한 단면을 가지고 있으며, 해성점토 지반 안에 다양한 깊이로 정착시킨 후 원심모형시험을 실시하였다. 현장응력조건을 모사하기 위하여, 미리 응력을 가한 시험용 닻줄에 단계별 가속을 하였다. 이 논문은 닻줄의 해석을 위한 중요한 두 가지 변수인 닻줄과 지반의 부착력 및 접착면적환산계수를 결정하기 위한 과정을 설명하고자 하였으며, 이로 인한 닻줄의 변형 및 지지력 변화를 규명하였다.

• 한국지반공학회논문집
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• 제25권11호
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• pp.117-130
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• 2009

본 논문에서는 순환골재 다공질 콘크리트말뚝(Recycled-Aggregate Porous Concrete Pile, RAPP)에 의한 지반개량효과를 파악하기 위하여 기존에 수행된 실내모형실험(유승경 등, 2008(a)) 결과를 분석하였다. 본 연구에서 얻어진 실험 결과를 동일한 조건에서 수행한 SCP 실험 결과와 비교하여 RAPP로 개량된 복합지반의 침하량과 과잉간극수압 및 연직응력증분의 시간에 따른 변화 특성과 복합지반의 거동 특성을 비교, 분석하였다. 또한, 수치해석을 통하여 실내모형실험 결과를 평가하였다. 그 결과, RAPP로 개량된 복합지반에서 하중재하시 응력분담이 뚜렷이 발생하여 침하저감 효과가 크게 얻어졌다. 또한, 복합지반의 압밀도를 산정하여 분석한 결과, RAPP는 배수재로서의 기능을 충분히 발휘하여 압밀촉진 효과가 있음을 확인할 수 있었다.