• 한국건설순환자원학회논문집
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• 제2권1호
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• pp.46-51
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• 2014

본 연구에서는 단위수량 저감에 따른 하이볼륨 플라이애시 콘크리트의 강도 발현 특성을 평가하였으며, 목표강도 3수준 (40, 30 및 20MPa) 및 단위수량 변화에 따라 콘크리트를 제조하였다. 실험결과, 향상된 유동성은 50%이상의 플라이애시를 사용한 경우 플라이애시 구형 입자들의 볼베어링 효과, 플라이애시의 정전기적 반발력 및 플라이애시의 입도분포의 결과로 얻어졌으며, 이를 통하여 플라이애시 혼합이 콘크리트에 요구되는 물의 양을 감소시키는 것으로 나타났다. 또한 단위수량을 저감한 하이볼륨 플라이애시 콘크리트의 조기 강도는 일반적인 단위수량의 배합보다 약 66% 이상 향상되는 것으로 나타났다.

• Journal of Crop Science and Biotechnology
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• 제10권4호
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• pp.223-230
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• 2007

Vitellaria paradoxa commonly called shea is an important agro forestry and fruit-bearing species present in four agro-ecological zones of Cameroon. The goal of this work was the morphological characterization of certain populations of V. paradoxa which will serve as a necessary step for a subsequent genetic study of the species. Morphological observations related to 20 agronomic traits, studied on 8-13 trees selected from each of the eight shea populations across four different agro-ecological zones located in four provinces of Cameroon were studied. The study showed that there was a variation between the populations, related to the traits measured on the trunk, fruit, nut, and leaf. Three shapes of the tree(ball, broom, and trained), five shapes of the fruit(round, oblong, reversed pear, ovoid, and oblong), three colors of the nut(clear brown, dark brown, and blackish brown) were identified. The principal component analysis(PCA) carried out on the quantitative characters revealed 72% of the total variance expressed on the first and second main axis. This variation was essentially explained by the traits measured on the fruits and on the nuts. The analyses showed that only the traits of the fruits and the nuts were discriminative. The shea populations studied were structured into two distinct groups using these discriminative traits.

• 열처리공학회지
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• 제21권1호
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• pp.10-19
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• 2008

To investigate the effect of ultrasonic nano-crystalline surface modification (UNSM) treatment on rolling contact fatigue and residual stress properties of bearing steels, this paper carried out a rolling contact fatigue test, measured residual stress and retained austenite, performed a wear test, observed microstructure, measured micro hardness, and analyzed surface topology. After the UNSM treatment, it was found that the surface became minute by over $100{\mu}m$. The micro surface hardness was changed from Hv730~740 of base material to Hv850~880 with about 20% improvement, and hardening depth was about 1.3 mm. The compressive residual stress was measured as high as -700~-900 MPa, and the quantity of retained austenite was reduced to 27% from 34%. The polymet RCF-6 ball type rolling contact fatigue test showed over 4 times longer fatigue lifetime after the UNSM treatment under 551 kgf load and 8,000 rpm. In addition, this paper observed the samples, which went through the rolling contact fatigue test, with OM and SEM, and it was found that the samples had a spalling phenomenon (the race way is decentralized) after the UNSM treatment. However, before the treatment, the samples had excessive spalling and complete exploration. Comparison of the test samples before and after the UNSM treatment showed a big difference in the fatigue lifetime, which seems to result from the complicated effects of micro particles, compressive residual stress, retained austenite, and surface topology.

• 한국건축시공학회지
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• 제20권4호
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• pp.313-319
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• 2020

본 연구에서는 70MPa급 고강도 콘크리트에서 유공유리분말(HGP)의 적용성을 확인하기 위하여 HGP 사용량에 따라서 프레쉬 상태와 경화 상태의 물성을 검토하였고, 그 실험결과는 다음과 같다. 유동 특성은 HGP의 사용량이 증가할수록 슬럼프플로가 약간 증가하는 하는 것으로 나타났고 T₅₀₀은 HGP의 사용량이 증가할수록 약간 단축되었으며, 철근 통과성은 HGP의 볼베어링 효과로 인해 개선되는 것으로 나타났다. 특히 사용량 1.0kg/㎥에서 통과성 0등급으로 가장 양호한 철근통과성을 발휘하였다. 레올로지 특성으로는 HGP 1.0kg/㎥에서 소성점도가 Plain 대비 40% 정도 감소하여 HGP가 고강도 콘크리트의 소성점도를 낮추는 효과가 있는 것으로 확인되었다. 하지만 HGP 2.0kg/㎥에서는 1.0kg/㎥보다 오히려 소성점도가 크게 나타났다. 실험을 통하여 HGP가 고강도 콘크리트의 작업성 향상에 도움이 되는 것을 확인할 수 있었으며 사용량 1.0kg/㎥ 이 가장 적절한 것으로 판단된다. 또한 HGP가 콘크리트 압축강도에 영향을 미치지 않는 것으로 확인되었다.

• Physical Therapy Rehabilitation Science
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• 제6권2호
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• pp.96-104
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• 2017

Objective: The purpose of this study was to investigate the effect of the hip joint strengthening exercises using proprioceptive neuromuscular facilitation (PNF) on the clinical symptoms and the treatment effects in balance, sit to stand, and gait abilities in patients with TBI. Design: A single case study. Methods: A 13-year-old adolescent with quadriplegia and hip joint control impairment participated in this four-week training intervention. The patient, diagnosed with TBI, wastreated with hip joint strengthening exercises using PNF. In the first week, we focused on strengthening the body, relaxing the hip flexors and activating the hip extensor muscles in order to solve the patient's physical function and body structure. From the 2nd and 4th week, we improved the motivation through the task-oriented method, and then weight-bearing training of the right lower extremity was proceeded by kicking a soccor ball with the left lower extremity. The exercises were performed for 4 weeks, 5 days a week, for 60 minutes with the exercise intensity gradually increased according to the subject's physical abilities. Results: As a result of the study, the patient demonstrated improvements in the physical examination, which were evaluated before and after intervention and included the manual muscle test, modified Ashworth scale, sensory assessment, coordination assessment, Berg balance scale, 5-time sit to stand test, and the 10 meters walk test. Conclusions: The results of this case suggest that a hip joint strengthening exercise program using PNF may improve hip control ability, balance, sit to stand and gait ability in a patient with TBI.

• 한국해양공학회지
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• 제32권5호
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• pp.324-332
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• 2018

It is known that damages to the subsea cables used for electric power transmission between islands and countries, including renewable energy from offshore wind power, current, tides, etc., cost much to restore, which causes social and economic losses. Various types of fishing rigs and anchors have been reported to be the greatest hazards to subsea cables. It is possible to design and construct a suitable protection facility for a subsea cable by precisely estimating the underwater behavior of such hazardous apparatuses. In this study, numerical simulations of the underwater behaviors of various hazardous apparatuses were carried out using fluid-structure interaction (FSI) analysis as a basic study to simulate the actual behavior phenomena of hazardous apparatuses in relation to a subsea cable. In addition, the underwater drop characteristics according to the types of hazardous apparatuses were compared. In order to verify the accuracy of the FSI analysis method used in this study, we compared the test results for underwater drops of a steel ball bearing. Stock anchors, stockless anchors, and rocket piles, which were actually reported to be the cases of damage to subsea cables along the southwest coast of Korea, were considered as the hazardous apparatuses for the numerical simulations. Each hazardous apparatus was generated by a Lagrangian model and coupled with the fluid domain idealized by the Eulerian equation to construct the three-dimensional FSI analysis model. The accuracy of the numerical simulation results was verified by comparing them with the analytical solutions, and the underwater drop characteristics according to the types of hazard apparatuses were compared.

• The Journal of Korean Physical Therapy
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• 제28권1호
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• pp.27-32
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• 2016

Purpose: The purpose of this study is to examine the effects of sensorimotor training on knee joint stability after anterior cruciate ligament reconstruction. Methods: The subjects were sixteen 16 adults who received anterior cruciate reconstruction by arthroscopy, and underwent sensorimotor training for which was to have them maintenanceain of a standing position with a step Balance ball on the affected side over 30 degrees knee flexion with 100% weight bearing for 15-20 seconds. Before the genuine experiment commenced, the Lysholm scale was had been used to assess functional disorders on the affected knee joint. KT-2000 Arthrometer measurement equipment was used to measure anterior displacement of tibia against to femur before and after the sensorimotor training. Results: There was significant relaxation on the affected side in tibia anterior displacement of the affected and sound sides on in supine position before the sensorimotor training. There was little significant difference in tibia anterior displacement of the affected knee joints on in the supine position before and after the sensorimotor training. The results also showed that there was a reduction in the difference of tibia anterior displacement of the affected knee joints on in the standing position. These results suggest that the effects of sensorimotor training on knee joint stability after anterior cruciate ligament reconstruction is to induce the change of tibia anterior displacement against femur and the variation of muscles activation. Conclusion: The sensorimotor training may contribute to the improvement of joint functional stability in people who are in post-operation state and with orthopedic musculoskelectal injuries.

• Korean Journal of Acupuncture
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• 제26권2호
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• pp.75-89
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• 2009

Objectives: Warm needling combines simultaneously the effects of acupuncture and moxibustion. This study was to investigate whether warm needling could relieve acute knee arthritis induced by carrageenan in rats. Methods: To illuminate the underlying mechanisms of the warm needling-induced antinociception, weight bearing force (WBF) was observed on the acute knee arthritic rat model. Under general anesthesia, ST36, SP9, Hakjung extra point, LI4 were punctured and stimulated with 30 mg moxa ball combustion on top of the needle (${\emptyset}0.18{\times}8mm$). Results: In behavioral test, rats subsequently showed a reduced stepping force of the affected limb 3 hours after the induction of arthritis. Warm needling on the contralateral or ipsilateral ST36 failed to show antinociceptive effect on the acute knee arthritis. Warm needling on the contralateral SP9 or LI4 increased WBF values to normal level in the acute stage of the arthritis. Warm needling on the Hakjung extra-point resulted in the significant antinociceptive effects through acute stage. These effects of warm needling were suppressed by opioids receptor antagonist naltrexone (10 mg/kg, i.p.) and alpha adrenoceptor antagonist phentolamine (5 mg/kg, i.p.). Conclusion: The data suggest that warm needling-induced antinociception is differently mediated by acupoints and accomplished by activating the descending inhibitory systems including endogenous opioids and $\alpha$-adrenoceptors.

• Tribology and Lubricants
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• 제34권6호
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• pp.241-246
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• 2018

This research addresses the improvement of tribo-systems, specifically regarding the reduction of friction and wear through tribo-coupling between tetrahedral amorphous carbon (ta-C) with different types of counterpart materials, namely bearing steel (SUJ2), tungsten carbide (WC), stainless steel (SUS304), and alumina ($Al_2O_3$). A second variable in this project is the utilization of different values of duct bias voltage in the deposition of the ta-C coating - 0, 5, 10, 15, and 20 V. The results of this research are expected to determine the optimum duct bias and best counter materials associated with ta-C to produce the lowest friction and wear. Results obtained reveal that the tribo-couple between the ta-C coating and SUJ2 balls produces the lowest friction coefficient and wear rate. In terms of duct bias changes, deposition using 5 V produces the most optimum tribological behavior with lowest friction and wear on the tribo-system. In contrast, the tribo-couple between ta-C with a WC ball causes penetration through the coating surface layer and hence high surface delamination. This study demonstrates that the most effective ta-C coating duct bias is 5 V associated with SUJ2 counter material to produce the lowest friction and wear.

• Advances in concrete construction
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• 제8권1호
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• pp.65-76
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• 2019

This paper investigates the effect of recycled glass powder (RGP) on flowing properties of self-compacting mortars (SCMs) containing different ratios of fillers and superplasticizer dosages. Fly ash (FA), nano-silica (NS), micro-silica (MS), metakaolin (MK) and rice husk ash (RHA) are used as fillers and their synergistic effect with RFP is studied. The effects of fillers and high-range water reducer (HRWR) on flowing ability of mortars are primarily determined by slump flow and V-funnel flow time tests. The results showed that for composites with a higher RGP content, the mortar flowing ability increased but tended to decrease when the composites containing 10% MK or 5% RHA. However, the flowing ability of samples incorporating 5% RGP and 10% SF or 25% FA showed an opposite result that their slump flow spread decreased and then increased with increasing RGP content. For specimens with 3% NS, the influence of RGP content on flowing properties was not significant. Except RHA and MS, the fillers studied in this paper could reduce the dosage of HRWR required for achieving the same followability. Also, the mixture parameters were determined and indicated that the flowability of mixtures was also affected by the content of sand and specific surface area of cement materials. It is believed that excess fine particles provided ball-bearing effect, which could facilitate the movement of coarse particles and alleviate the interlocking action among particles. Also, it can be concluded that using fillers in conjunction with RGP as cementitious materials can reduce the material costs of SCM significantly.