• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.3
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• pp.1-10
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• 2012

In spite of high resistant to corrosion and its strength, over the last two decades, concerns still remain about the durability of FRP materials under severe environmental and thermal exposures. In this paper, authors experimentally examine the combined degradation by thermal and chemical attacks in heterogeneous FRP rebar be made up with various fibers and resins. Five types of Carbon, Glass and Hybrid FRP rebars had manufactured by different process and surface patterns are adopted for the experiments such as weight change, interlaminar shear strength, SEM and FT-IR analysis. FRP specimens were immersed in alkaline or distilled solution up to 150 days and then thermal exposed on 60, 100, 150 and $300^{\circ}C$ for 30 minutes. From the test results, the degradation of FRP bars are influnced by the resin type and manufacturing process as well as the fiber, and ILSS of exposed FRP bar in solutions is slightly increased in initial stage and then decresed with the passing of immersed time. But, in this test, it is observed that the discrepancy of ILSS between degraded by alkaline solution and distilled water is negligible value.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.385-391
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• 2018

The purpose of this study was to examine the lower-extremity muscle activation of flat-footed and normal-footed subjects descending stairs while wearing high-heels, thereby identifying any imbalance between the medial and lateral muscles.Thirty female students volunteered to participate in this study. The navicular drop test (NDT) was applied to the selection criteria for the flat-footed group and the normal-footed group. Surface electromyographic data was collected from the medial and lateral quadriceps, hamstrings, and gastrocnemius. Activation of MG and LG was significantly lower in the flat-footed group than in the normal-footed group. Both groups showed significant increases in MQMH and MHMG, but the co-activation in the medial and lateral muscles was lower in the flat-footed group. The co-activation ratios showed a significantly greater MQMH/LQLH in the flat-footed group. Flat-footed subjects who wear high-heels are more likely to experience impaired knee joint alignment than normal-footed subjects. Therefore, flat-footed subjects should use caution when descending stairs while wearing high-heels.

• Journal of Life Science
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• v.27 no.11
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• pp.1349-1356
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• 2017

Potassium channel openers (KCOs) produce physiological and pharmacological defense mechanisms against cell injuries caused by oxidative stress of diverse origins. Openings of mitochondrial and plasmalemmal $K^+$ channels are involved in the defense mechanisms. This study tested whether NS 1619, an opener of large-conductance BK channels, has a similar beneficial influence on the pigment epithelial cells of retinas. The human retinal pigment epithelial cell line ARPE-19 was exposed to $H_2O_2$-induced oxidative stress in the absence and presence of NS 1619. The degrees of the cells' injuries were assessed by analyzing the cells' trypan-blue exclusion abilities and TUNEL staining. NS 1619 produced remarkable protections against cell injuries caused by $H_2O_2$. It prevented apoptotic and necrotic cell deaths. The protective effect of NS 1619 was significantly diminished when the cells were treated with NS 1619 in combination with the BK channel-blocker paxilline. NS 1619 significantly ameliorated cellular ATP deprivations in $H_2O_2$-treated cells. It helped mitochondria preserve their functional integrity, which was estimated by their MTT reduction abilities and mitochondrial membrane potential. In conclusion, it was suggested that NS 1619 had a beneficial effect on mitochondria in regards to preserving their functional integrity under oxidative stress, and it produces defense mechanisms against oxidant-induced cell injuries in ARPE-19 cells.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.6 no.1
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• pp.1-9
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• 2013

Purpose: The purpose is to perform objective evaluation for rotator cuff using ultrasonography and validate factors influencing cuff integrity as well as efficacy of follow-up ultrasonography after unreamed antegrade intramedullary nailing for humerus fracture. Materials and Methods: Seventeen patients with an average age of $55.7{\pm}18.6$ years underwent antegrade intramedullary nailing for humerus fracture and follow-up ultrasonography of shoulder joint. Mean follow-up period was $43.5{\pm}32.2$ months. Intraoperative evaluation for preoperative cuff tear was performed, of which four cuffs were repaired by single row repair technique. Clinical evaluation included visual analogue scale (VAS), range of motion, Korean Shoulder Scoring System (KSS) and American Shoulder and Elbow Society (ASES) score. Ultrasonographic evaluation was performed on cuff integrity and protrusion of proximal nail tip as well. Radiographic evaluation included time to union, protrusion of proximal nail tip and migration of proximal interlocking screw which could affect shoulder joint function. Results: Mean VAS at last follow-up was $1.65{\pm}1.84$ points. Range of motion showed forward flexion of $137.0{\pm}33.5^{\circ}$, external rotation of $43.5{\pm}12.7^{\circ}$ and internal rotation of $16.4{\pm}2.0^{\circ}$ while KSS score and ASES score were $79.6{\pm}20.7$ and $83.7{\pm}17.0$ points, respectively. Bone union was demonstrated in all cases and average time to union was $3.4{\pm}1.3$ months. Migration of proximal interlocking screw was shown in 6 cases (35%). On ultrasonographic evaluation, there were normal in 8 (47%), weaving in 4 (24%), partial tear in 5 cases (29%), but no complete tear. Protrusion of proximal nail tip was demonstrated in 8 cases (47%) on plain radiographs whereas in 11 cases (65%) on ultrasonography and was associated with increasing age (p=0.038). Ultrasonographic weaving and partial tear was associated with protrusion of proximal nail tip (p=006), but not with repair of preoperative tear (p>0.05). Conclusion: Because weaving and partial tear on ultrasonography originated from protrusion of proximal nail tip, careful insertion of nail and meticulous repair of cuff during operation lead to stable fixation with satisfactory recovery of shoulder function follow-up ultrasonography can be a useful tool for evaluating protrusion of nail tip and rotator cuff tear, of which diagnosis is difficult on plain X-ray after antegrade intramedullary nailing for humerus fracture.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.442-445
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• 2009

지진에 대한 건축물의 확률적 성능평가에 대해서는 지진하중에 대한 건축물의 손상확률 또는 파괴확률을 나타내는 지진취약도 함수를 작성하여 대상 건축물에 대한 지진위험도를 평가하는 방법을 이용하고 있으며 이에 대한 많은 연구가 이루어지고 있다. 본 연구에서는 지진하중과 구조물 재료특성의 불확실성을 고려하고 대상 건축물의 지진취약도 해석을 통하여 비내력벽의 유무에 따른 건축물의 지진거동 및 내진성능을 평가하였다. 비내력벽을 보편화된 모형화 방법인 등가의 대각 압축 스트럿으로 고려하여 비내력벽의 유무에 따른 저층 철근콘크리트 건축물을 모형화하였으며 지진하중의 강도는 유효최대지반가속도를 이용하여 각 건축물에 대하여 지진취약도를 작성하였다. 취약도해석 결과로 연약층을 가지고 있는 건축물의 경우는 손상확률이 골조만 있는 경우보다 크며 동일한 해석모델의 경우에도 해석방법에 따라서 취약도 곡선의 형태가 다름을 알 수 있었다.

• Journal of Korean Academy of Nursing
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• v.39 no.3
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• pp.393-400
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• 2009

Purpose: The purpose of this study was to examine the effects of unilateral sciatic nerve injury on unaffected hindlimb muscles of rats. Methods: Adult male Sprague-Dawley rats were assigned to one of three groups: control(C) group(n=10) that had no procedures, sham(S) group(n=10) that underwent sham left sciatic nerve transection, and sciatic nerve transection(SNT) group(n=9) that underwent left sciatic nerve transection. At 15 days rats were anesthetized, and the soleus, plantaris and gastrocnemius muscles were dissected. Results: Muscle weight of the unaffected plantaris muscle in the SNT group was significantly lower than in the other two groups. Type II fiber cross-sectional areas of the unaffected plantaris and gastrocnemius muscles in the SNT group were significantly smaller than in the other two groups. The decrease of muscle weights and Type I, II fiber cross-sectional areas of the unaffected three muscles in the SNT group were significantly less than that of the affected three muscles. Conclusion: Hindlimb muscle atrophy occurs in the unaffected side after unilateral sciatic nerve injury, with changes in the plantaris and gastrocnemius muscle being more apparent than changes in the soleus muscle. These results have implications for nursing care, in the need to assess degree of muscle atrophy in unaffected muscles as well as affected muscles.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1684-1689
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• 2007

Fretting wear is one of the important degradation mechanisms of steam generator tubes in the nuclear power plants. Especially, impact fretting wear occurred between steam generator tubes and tube support plates or anti-vibration bar. Various tests have been carried out to investigate the wear mechanisms and to report the wear coefficients. Those are fruitful to get insight for the wear damage of steam generator tubes; however, most wear researches have concentrated on sliding wear of the steam generator tubes, which may not represent the wear loading modes in real plants. In the present work, impact fretting tests of steam generator tube were carried out. A wear progression model for impact-fretting wear has been investigated and proposed. The proposed wear progression model of impact-fretting wear is as follows; oxide film breaking step at the initial stage, and layer formation step, energy accumulation step and finally particle torn out step which is followed by layer formation in the stable impact-fretting progress. The wear coefficient according to the work-rate model has been also compared with one between tube and support.

• Journal of Korean Orthopaedic Sports Medicine
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• v.2 no.2
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• pp.119-126
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• 2003

The shoulder is a complex joint and, by virtue of having a large range of motion, is inherently unstable, relying on the surrounding soft tissue structures for stability. The bony joint consists of the glenoid, acromion, and humoral head, while the soft tissues include the glenoid labrum, the glenohumeral ligaments. and coracoacromial ligament as well as the muscles of the rotator cuff, the long head of the biceps, and the scapulothoracic muscles. Dysfunction in any one of these components can cause shoulder problems. The throwing motion involves a series of phases that stress to their limits the dynamic and static restraints of the glenohumeral and scapulothoracic joints. . Therefore, maintaining a balance of proper biomechanical forces is essential to avoiding shoulder injuries in throwing athletes. Over the last decade, signficant advances have been made in the study and understanding of the shoulder mechanics, and pathophysiology of injury. Additionally, advances in surgical techniques, particularly arthroscopy , have aided in the diagnosis of and the developement of less invasive surgical treatments for injuries that do not respond to nonoperative measures. In this article, we reviewed the pathophysiology of injuries , diagnostic techniques, and surgical management of shoulder injuries in throwing athletes .

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.10
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• pp.817-822
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• 2008

Fretting wear is one of the important degradation mechanisms of steam generator tubes in the nuclear power plants. Especially, impact fretting wear occurred between steam generator tubes and tube support plates or anti-vibration bar. Various tests have been carried out to investigate the wear mechanisms and to report the wear coefficients. Those are fruitful to get insight for the wear damage of steam generator tubes; however, most wear researches have concentrated on sliding wear of the steam generator tubes, which may not represent the wear loading modes in real plants. In the present work, impact fretting tests of steam generator tube were carried out. A wear progress model for impact-fretting wear has been investigated and proposed. The proposed wear progress model of impact-fretting wear is as follows; oxide film breaking step at the initial stage, and layer formation step, energy accumulation step and finally particle torn out step which is followed by layer formation in the stable impact-fretting progress. The wear coefficient according to the work-rate model has been also compared with one between tube and support.

• ETRI Journal
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• v.11 no.1
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• pp.89-96
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• 1989

$C_2F_6$/$CHF_6$ 플라즈마를 이용한 실리콘 산화막의 반응성이온 식각공정시 실리콘 표면에 형성되는 고분자 잔류막과 근표면 손상영역을 X-선 광전자분광법(x-ray photoelectron spectroscopy)과 러더포드 후방산란법(Rutherford backscattering)을 이용하여 연구하였다. 표면 잔류막은 CF, $CF_2$, $CF_3$, $C-CF_x$, 그리고 C-C/C-H 등의 결합을 가진 불화탄소 고분자로 구성되어 있으며, 또한 C 1s와 Si 2p X-선 광선자 스펙트럼으로부터 C-Si 결합이 존재함을 확인하였다. 반응성이온 식각을 거친 실리콘 표면 구조의 연구결과, 불소와 탄소로 구성된 고분자막($<20 \AA$)이 극표면에 존재하며, 식각 후 공기중에 노출됨에 따라 고분자 잔류층으로 산소가 통과하여 기판을 산화시킴으로써 실리콘 산화막( $~10\AA$)이 그 아래에 형성되었음을 알았다. 그리고 실리콘산화막 아래에 탄소-산소 결합영역이 관찰되었다. 플라즈마 가스의 조성에서 $CHF_3$의 량이 증가함에 따라 고분자 잔류막의 두께가 증가하였으며, 본 연구의 실험조건에서 2분간 overetching한 시편의 경우에도 실리콘 표면 영역의 손상정도가 매우 적음을 발견하였다.