• Advances in nano research
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• 제14권4호
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• pp.363-373
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• 2023

A novel type of steel fiber with a rounded-end shape is presented to improve the bonding behavior of fibers with Carbon Nanotubes (CNT)-reinforced Ultra-High Performance Concrete (UHPC) matrix. For this purpose, by performing a parametric study and using the nonlinear finite element method, the impact of geometric characteristics of the fiber end on its bonding behavior with UHPC has been studied. The cohesive zone model investigates the interface between the fibers and the cement matrix. The mechanical properties of the cohesive zone model are determined by calibrating the finite element results and the experimental fiber pull-out test. Also, the results are evaluated with the straight steel fibers outcomes. Using the novel presented fibers, the bond strength has significantly improved compared to the straight steel fibers. The new proposed fibers increase bond strength by 1.1 times for the same diameter of fibers. By creating fillet at the contact area between the rounded end and the fiber, bond strength is significantly improved, the maximum fiber capacity is reachable, and the pull-out occurs in the form of fracture and tearing of the fibers, which is the most desirable bonding mode for fibers. This also improves the energy absorbed by the fibers and is 4.4 times more than the corresponding straight fibers.

• Journal of Chest Surgery
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• 제24권7호
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• pp.663-668
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• 1991

To evaluate risks, complications and mortality of reoperations on heart valve prosthesis, we reviewed clinical records of 53 patients who underwent reoperation because of prosthetic valve failure[PVF], from Jan 1959 through Jun. 1991. They had undergone 48 mitral, 10 aortic valve rereplacement Primary tissue failure was the main cause of reoperation : it occurred in 51 valves at a mean postoperative interval of 58 months. Calcification and collagen disruption of prosthesis were main causes of primary tissue failure in macro and micropathology, In 3 failing mechanical prostheses, paravalvular leak was in 2 cases, another one case had the thrombi at the hinge portion. If conditions such as emergency operation with or without endocarditis, thromboembolism and advanced NYHA functional class are prevented, we think that reoperative valve replacement has similar morbidity and mortality to initial valve replacement surgery. But our sturdy represents higher mortality [22.6%] because of late surgical intervention failing the prevention of conditions leading to myocardial damage. In conclusion if the tearing, calcification, and a new murmur were detected the early reoperation should be considered to increase late survival.

• 대한수의학회지
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• 제63권3호
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• pp.24.1-24.6
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• 2023

This study compared the biomechanical properties of bone-stapling techniques with those of other fixation methods used for stabilizing tibial tuberosity fractures using 3-dimensionally (3D)-printed canine bone models. Twenty-eight 3D-printed bone models made from computed tomography scan files were used. Tibial tuberosity fractures were simulated using osteotomy. All samples were divided into 4 groups. Group 1 was stabilized with a pin and tension-band wire; group 2, with a pin and an 8 mm-wide bone staple; group 3, with 2 horizontally aligned pins and an 8 mm-wide bone staple; and group 4 with a 10 mm-wide bone staple. Tensile force was applied with vertical distraction until failure occurred. The load and displacement were recorded during the tests. The groups were compared based on the load required to cause displacements of 1, 2, and 3 mm. The maximum failure loads and modes were recorded. The loads at all displacements in group 4 were greater than those in groups 1, 2, and 3. The loads at 1, 2, and 3 mm displacements were similar in groups 1 and 3. There was no significant difference between groups 1 and 3. Groups 1 and 4 provided greater maximum failure loads than groups 2 and 3. Failure occurred because of tearing of the nylon rope, tibial fracture, wire breakage, pin bending, and fracture around the bone staple insertion. In conclusion, these results demonstrate that the bone-stapling technique is an acceptable alternative to tension-band wire fixation for the stabilization of tibial tuberosity fractures in canine bone models.

• 대한영상의학회지
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• 제82권5호
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• pp.1140-1162
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• 2021

비구순 파열은 만성 고관절 통증의 흔한 원인 중 하나이며, 고관절 자기공명관절조영술은 비구순의 평가를 위한 중요한 검사 방법이다. 비구순의 정상변이와 비정상 상태를 구별하여 정확한 진단을 하기 위해서는 고관절 자기공명관절조영술에서 보이는 다양한 영상 소견을 숙지하는 것이 필요하다. 본 글에서는 고관절 자기공명관절조영술 시행의 기술적인 방법 및 영상해석에 관해 종합적으로 검토하고자 한다. 고관절 자기공명관절조영술에서 비구순의 정상 및 비정상 소견을 살펴본다. 또한 비구순 파열과 유사하게 보여 감별이 필요한 고관절 주위틈, 비구순의 정상변이, 주름 등에 대해 알아보고, 고관절 자기공명관절조영술에서 볼 수 있는 골연골 및 연조직 병변 등의 소견에 관해 기술한다.

• Clinics in Shoulder and Elbow
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• 제27권1호
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• pp.26-31
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• 2024

Background: The coracoacromial ligament (CAL) is frequently observed to be damaged during arthroscopy and it is unclear how demographic, anatomic, and radiographic factors are related to CAL degeneration in full-thickness rotator cuff tears. Methods: A prospective study was conducted of patients at a single institution undergoing shoulder arthroscopy for first-time, full-thickness rotator cuff tears. We evaluated preoperative anteroposterior radiographs to obtain critical shoulder angle, glenoid inclination, acromial index, acromiohumeral distance, lateral acromial angle, and acromial morphology. We documented CAL quality, rotator cuff tear size and pattern during arthroscopy. Multiple logistic regression was used to identify predictive factors for encountering severe CAL fraying during arthroscopy. Results: Shoulders had mild CAL degeneration in 58.1% of cases, whereas severe CAL degeneration was present in 41.9% of shoulders. Patients with severe CAL attrition were significantly older (62.0 years vs. 58.0 years, P=0.042). Shoulders with severe CAL attrition had large rotator cuff tears in 54.1% of cases (P<0.001), and tears involving the infraspinatus (63.2% vs. 29.6%, P=0.003). The severe degeneration group was more likely to have a larger critical shoulder angle measurement on preoperative radiographs than those in the mild attrition group (36.1°±3.6° [range, 30°-45°] vs. 34.1°±3.8° [range, 26°-45°], P=0.037). Conclusions: While the clinical impact of CAL degeneration remains uncertain, increased severity of CAL degeneration is associated with older age, larger rotator cuff tear size, presence of infraspinatus tearing, and increased preoperative critical shoulder angle. Level of evidence: III.

• Journal of Ginseng Research
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• 제32권4호
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• pp.324-331
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• 2008

1. 1개월, 2개월, 3개월 투여 시 혈압은 세 군간에 유의한 차이가 나타났으며 한국 홍삼군 및 중국 홍삼군은 대조군에 비해 혈압 감소가 나타났다.(P<0.05) 각 군별로 보면 한국 홍삼군의 경우 0-1개월, 1-2개월 사이에 혈압이 유의하게 감소하였으며, 중국 홍삼 투여군의 경우 0-1개월에만 유의한 감소를 보였다.(P<0.05) 2. 1개월 투여 그룹의 경우, 혈관벽 두께는 세 군간에 유의한 차이를 보이는 것으로 나타났고, 각 군 간의 차이를 비교하였을 때 중국 홍삼군의 경우 다른 두 군에 비해 혈관벽두께 감소가 유의한 차이를 보였다.(P<0.05) 2개월 투여 그룹의 경우, 혈관벽 두께는 세 군간에 유의한 차이를 보이는 것으로 나타났고, 각 군 간의 차이를 비교하였을 때 중국 홍삼군의 경우 다른 두 군에 비해 혈관벽 두께 증가가 유의한 차이를 보였다.(P<0.05) 3개월 투여 그룹의 경우, 혈관벽 두께는 세 군간에 유의한 차이를 보이는 것으로 나타났고, 각군 간의 차이를 비교하였을 때 중국 홍삼군의 경우 한국 홍삼군에 비해 혈관벽 두께의 증가가 유의하였으며 대조군에 비해서는 혈관벽 두께 감소 경향을 나타내었으나 통계적 유의성은 없었다. 한국 홍삼군의 경우 두 군에 비해 혈관벽 두께의 감소가 유의하였다.(P<0.05) 3. 대동맥 조직 병리 검사 변화상 한국 홍삼군은 모두 대동맥 벽이 잘 유지되어 있고 단층 혈관 내피 세포가 잘 유지되어 있으나, 중국 홍삼의 경우 1개월, 2개월, 3개월 투여시 세포핵의 비후가 비교적 뚜렷하게 관찰되며 세포핵의 방향성(Orientation)과 극성(Polarity)의 소실이 특징적으로 관찰되었고 평활근 섬유가 갈라지거나 찢어진(Split or tearing) 양상을 관찰할 수 있었다. 이상으로, 홍삼 투여 시 혈압 강하 효과가 나타남을 알 수 있었고, 한국 홍삼이 중국 홍삼에 비해 혈압 하강 효과를 좀 더 지속시킬 가능성 및 대동맥 조직 병리 소견 상 혈관 보호 효과에 대한 추론을 할 수 있었다.

• Journal of Korean Biological Nursing Science
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• 제2권2호
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• pp.1-19
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• 2000

The purpose of this study was to identify the characteristics and physiological variables of chest pain induced by exercise test in angina suspected patients. The subjects of this study consisted of 28 inpatients and outpatients aged between 40 and 75 who underwent treadmill test at exercise testing laboratory of S-University from January 2000 to June 2000. Subjects were interviewed with questionnaire regarding sociodemography, the past health history and history related to chest pain before the exercise test. Subjects were interviewed with questionnaire concerning quality, intensity, duration of chest pain induced by walking on the treadmill(Marquette, U.S.A. 1992) according to Bruce protocol following exercise test. Systolic and diastolic blood pressure were measured before, during and after the test, heart rate was determined by ECG. The results of this study were as follows ; 1) Quality of chest pain induced by exercise test were feeling stiffness 19(67.9%), heavy 10(36.0%), exploded 9(32.1%), crushing, suffocating, tight 8(28.6%), stuffy, prickly 7(25.0%), burning 6(21.4%), clasp 5(17.9%), cleaved, tensed, piercing 3(10.7%), perfectly fitting, sore 2(7.1%), tearing, tingling, ticklish, heartburn 1(3.6%). 2) Mean score of VAS(intensity of pain) following exercise test was $5.79{\pm}2.27$ and mean duration of chest pain after the test was $7.83{\pm}5.31$ minutes. 3) Sites of chest-pain induced by exercise test were middle site 11(39.3%), left-chest 10(35.6%), right-chest 6(21.5%). Radiation site of chest-pain was neck(18.0%), right flank site 1(3.6%), left shoulder & arm 2(7.1%) and back 1(3.6%). 4) Symptoms other than chest-pain induced by exercise test were dyspnea 21(75.6%), perspiration 14(50.4%), fatigue 12(43.2%), leg-pain 11(39.6%), dizziness 7(25.2%) anxiety toward chest-pain 3(10.8%), thirst 2(7.1%), and palpation, headache and tingling sensation of hand and leg 1(3.6%). 5) Mean MET(intensity of exercise) during the exercise test was $7.64{\pm}2.57$ and mean RPE(rating of perceived exertion) was $15.89{\pm}2.36$. Mean duration of exercise was $6.79{\pm}2.88$. 6) correlation coefficients between RPE and VAS was 0.500(p=0.003), those between MET and VAS was 0.287(p=0.069) and those between either depression or elevation of ST segment and VAS was 0.236(p=0.114). 7) There was a significant difference in mean systolic pressure between before and after the test as $146.29{\pm}28.18mmHg$ and $177.96{\pm}28.82mmHg$(t=-5.640, p=0.000), a significant difference in mean diastolic blood pressure between before and after the test as $84.85{\pm}15.07mmHg$ and $88.89{\pm}13.72mmHg$(t=-2.082, p=0.047), and there was a significant difference in mean heart-rate between before and after the test as $81.89{\pm}12.22/min$ and $160.68{\pm}21.77/min$(t=-21.255, p=0.000).

• 대한기계학회논문집A
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• 제37권7호
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• pp.865-873
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• 2013

CNG 압력용기의 제조를 위하여 고성능 수평식 프레스를 이용한 딥드로잉과 아이어닝의 연속공정(D.D.I. 공정)이 도입되었다. 그러나, 몇몇 D.D.I. 공정 변수들은 현장 경험에 의존하여 결정되는 문제점이 있으며, 다이의 짧은 수명 역시 고성능, 저비용의 압력용기 제조를 위하여 필수적으로 개선되어야 한다. 본 연구에서는, 공정의 신뢰성 확보 및 다이 수명 향상을 위하여 기존 관련 연구 및 현장 경험을 바탕으로 드로잉비, 다이 간의 간격, 드로잉 다이의 라운딩 반경, 아이어닝 다이의 각도를 공정변수로 결정하였다. FEA 를 이용하여 각 성형 단계에서 찢어짐과 주름이 발생하지 않는 한계 드로잉비를 결정하였고, 다이 간의 간격, 드로잉 다이의 라운딩 반경, 아이어닝 다이의 각도에 대하여 실험계획법을 이용하여 최적 공정설계를 수행하였으며, 기존 공정에 의한 결과와 비교하여 효율성을 검증하였다.

• 한국주조공학회지
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• 제37권6호
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• pp.207-216
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• 2017

This study investigated the effects of the addition of Zn, Ca, and SiC on the microstructure and mechanical properties of Mg-Al alloys. The tensile properties of homogenized Mg-xAl (x = 6, 7, 8, and 9 wt.%) alloys increased with increasing Zn content by the solid-solution strengthening effect. However, when the added Zn content exceeded the solubility limit, the strength and ductility of the alloys decreased greatly owing to premature fracture caused by undissolved coarse particles or local melting. Among the Mg-xAl-yZn alloys tested in this study, the AZ74 alloy showed the best tensile properties. However, from the viewpoints of the thermal stability, castability, and tensile properties, the AZ92 alloy was deemed to be the most suitable cast alloy. Moreover, the addition of a small amount (0.17 wt.%) of SiC reduced the average grain size of the AZ91 alloy significantly, from $430{\mu}m$ to $73{\mu}m$. As a result, both the strength and the elongation of the AZ91 alloy increased considerably by the grain-boundary hardening effect and the suppression of twinning behavior, respectively. On the other hand, the addition of Ca (0.5-1.5 wt.%) and a combined addition of Ca (0.5-1.5 wt.%) and SiC (0.17 wt.%) increased the average grain size of the AZ91 alloy, which resulted in a decrease in its tensile properties. The SiC-added AZ92 alloy exhibited excellent tensile properties (YS 125 MPa, UTS 282 MPa, and EL 12.3%), which were much higher than those of commercial AZ91 alloy (YS 93 MPa, UTS 192 MPa, and EL 7.0%). The fluidity of the SiC-added AZ92 alloy was slightly lower than that of the AZ91 alloy because of the expansion of the solid-liquid coexistence region in the former. However, the SiC-added AZ92 alloy showed better hot-tearing resistance than the AZ91 alloy owing to its refined grain structure.

• Journal of Acupuncture Research
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• 제28권2호
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• pp.75-87
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• 2011

Objectives : The purpose of this study is research on facial palsy sequelae and evaluating scale that have studied insufficiently until now. Methods : We researched on the symptoms, epidemiology and evaluating scale of facial palsy sequelae. For this, we searched the research papers on facial palsy sequelae and the clinical papers that find out the effect of treatment by evaluating facial palsy sequelae. Results : The symptoms of facial palsy sequelae are synkinesis, contracture, spasm, crocodile tears syndrome, tearing decrease, gustation impairment, hearing impairment, tinnitus, hyperacusis, etc. Among these, synkinesis, contracture, spasm and crocodile tears syndrome are the most frequently observed broadly. The poor prognosis factor of facial palsy can be the risk factor of facial palsy sequelae. For example, severe degeneration of facial nerve can be the risk factor of facial palsy sequelae. Most of clinical papers on facial palsy sequelae have used NRS(numeric rating scale) as evaluating scale. But NRS is very subjective scale. The scales of Stennert, Peitersen, Murata et al. can evaluate facial palsy sequelae grossly. Sunnybrook scale, Sydney scale, SAQ(synkinesis assessment questionnaire), the scale of Kim, the scale of Scott, HFS-7(hemi facial spasm), HFS-36 and Schirmer's test can evaluate the respective symptoms of facial palsy sequelae. Conclusions : The symptoms of facial palsy sequelae are synkinesis, contracture, spasm, crocodile tears syndrome, etc. Most of clinical papers on facial palsy sequelae have used NRS as evaluating scale. There were some scales that can evaluate facial palsy sequelae grossly and respectively. In future, we will need more progressed study of facial palsy sequelae and evaluating scale.