• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.1
• /
• pp.53-61
• /
• 2011

Edge notched A16061-T6 aluminum was repaired with a GFRP composite patch as a function of the number of stacking, Damage progress of specimen for tension load has been monitored by acoustic emission(AE), AE energy rate, hit rate, amplitude, waveform and 1st peak frequency distribution were analyzed. Fracture processes were classified into Al cracking, Fiber breakage, Resin cracking and Delamination. Displacement of a specimen can be divided into Region I, II and ill according to acoustic emission characteristics. Region II where the patch itself was actually fractured was focused on to clarify the AE characteristics difference for the number of stacking.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.78-83
• /
• 1998

Alloy 600과 Alloy 690의 응력부식파괴(Stress corrosion cracking, SCC)에 미치는 TiO$_2$의 영향을 315$^{\circ}C$의 10%NaOH 수용액에서 RUB(reverse U-bend) 시편, C-Ring 시편과 CT(compact tension)시편을 사용하여 평가하였다. 시편은 alloy 600 MA(mill anneal), alloy 600 TT(thermal treatment) 그리고 alloy 690 TT로 제작하였다. SCC 시험은 탈산된 10%NaOH 수용액에 2 g/1 TiO$_2$를 첨가한 용액과 첨가하지 않은 용액에서 수행하였으며, 이 조건에서 분극곡선도 얻었다. SCC 시험시 시편을 부식전위로부터 +150 ㎷ 양극분극을 가하였다. 기준전극으로 external Ag/AgCl electrode를 사용하였다. Alloy 600 MA로 제작한 RUB 시편은 TiO$_2$가 없는 용액에서 5일 안에 벽 관통 균열을 보였으나 TiO$_2$가 첨가된 용액에서는 균열을 관찰할 수 없었다. TiO$_2$가 첨가됨에 따라 alloy 600과 alloy 690의 임계전류밀도는 크게 감소하였고 또한 부동태 전류밀도도 감소하였다. 부동테 영역에서 TiO$_2$가 있는 용액의 경우 여러 peak가 있는 반면에 TiO$_2$가 없는 용액은 peak가 뚜렷하지 않았다. 이런 결과는 TiO$_2$가 첨가점에 따라 active region에서도 안정한 부동태 피막이 존재한다는 것을 시사한다. 또한 TiO$_2$가 없는 경우 SCC가 잘 일어나는 영역에 존재하는 부동태 피막이 TiO$_2$ 첨가에 따라 repassivation kinetics 등의 성질이 변화한 것으로 판단된다.

• Journal of the Society of Naval Architects of Korea
• /
• v.53 no.5
• /
• pp.435-446
• /
• 2016

In this study, hydrodynamic and mooring analysis for LNG FSRU moored by an internal turret with 9 mooring lines are numerically performed using commercial softwares, Hydrostar and Ariane. Met-ocean combinations for screening method are taken from wave governed condition(BV Rule Note NR 493) with relative heading between wave and wind between −45° and +45° and relative heading between wind and current between −30° and +30°. Extreme mooring analysis and sensitivity analysis are performed for intact and damaged (=one line missing) conditions and the parameters for sensitivity analysis are wave peak period, peak enhancement factor and line pretension. In the viewpoint of the design tension in mooring line, chain diameter is designed to satisfy safety factor for each conditions. As the chain diameter is increased from 152mm to 171mm, the designtension is reduced while the minimum breaking load is increased.

• The Journal of Korean Physical Therapy
• /
• v.25 no.2
• /
• pp.71-75
• /
• 2013

Purpose: Although use of a tilt table is recommended in clinical practice, there are no published guidelines regarding pressure and inclination for tilt table use. The aim of the current study was to assess the changes of pressure on sacrum and buttock according to different inclination of the tilt table in healthy subjects. Methods: Thirty two healthy subjects participated in this study. Subjects were positioned supine on the tilt table and safety straps were secured across the chest, pelvic, and knee with sufficient tension to prevent the subjects from falling. Pressure and peak pressure of sacrum and buttock were measured using pressure mapping system with the tilt table standing at $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$, and $85^{\circ}$ inclination. Results: A significant decrease in the pressure of sacrum and buttock was achieved by increasing tilt table inclination (p<0.05): $0^{\circ}{\sim}15^{\circ}$ (8.16%), $15^{\circ}{\sim}30^{\circ}$ (8.02%), $30^{\circ}{\sim}45^{\circ}$ (11.61%), $45^{\circ}{\sim}60^{\circ}$ (16.18%), $60^{\circ}{\sim}75^{\circ}$ (16%), and $75^{\circ}{\sim}85^{\circ}$ (11.48%). A significant decrease in the peak pressure was achieved by increasing tilt table inclination (p<0.05): $30^{\circ}{\sim}45^{\circ}$ (9.91%), $45^{\circ}{\sim}60^{\circ}$ (19.24%), $60^{\circ}{\sim}75^{\circ}$ (19.93%), and $75^{\circ}{\sim}85^{\circ}$ (11.48%). No significant peak pressure change was observed in $0^{\circ}{\sim}15^{\circ}$, $15^{\circ}{\sim}30^{\circ}$ tilt table inclination (p>0.05). Conclusion: The results of this study showed that the pressure of sacrum and buttock were decreased according to increasing tilt table inclination in healthy subjects. Guidelines are needed in order to optimize patient safety and overall outcome for tilt table standing.

• The Korean Journal of Pharmacology
• /
• v.24 no.1
• /
• pp.103-109
• /
• 1988

Cyclobuxine D, extracted from Buxus microphylla var. koreana Nakai, is a steroidal alkaloid. Many pharmacological effects of cyclobuxine D were examined in our Lab. Cyclobuxine D showed a significant bradycardic effect in the rat heart and an inhibitory action on acetylcholine and $Ba^{++}-induced$ contraction of the longitudinal muscle isolated from the rabbit jejunum. In this study, we investigated the effect of cyclobuxine D on the contractile response-elicited by acetylcholine, oxytocin and $Ba^{++}$ in rat uterine. In order to analyse the inhibitory action of cyclobuxine D on the smooth muscle, we examined the inhibitory action of cyclobuxine D against the contractile response of the high potassium-depolarized rat ileum to calcium. Concentration-dependent decrease in the peak tension and duration of the acetylcholine, oxytocin and $Ba^{++}-induced$ contraction in the isolated rat uterus was observed when cyclobuxine D was added to the organ bath. The isolated longitudinal muscle from the rat ileum was immersed calcium-depleted potassium-depolarizing solution. Ten minutes after, 1.8 mM $CaCl_2$ was added to muscle bath and elicited a biphasic increase in muscle tension. Cyclobuxine D $(6.2{\times}10^{-5}\;M)$ produced an appreciable inhibition of both components of the mechanical response. In addition, $3.1{\times}10^{-4}\;M$ cyclobuxine D, introduced at a point when the tonic response had reached its maximum level, caused the muscle to exhibit a rapid lose of tension. Based on these experimental results, we propose the possibility that the inhibitory action of cyclobuxine D on the acetylcholine, oxytocin and $Ba^{++}-induced$ contraction in the isolated rat uterus may be due to blocking potassium-activated calcium channels, voltage-sensitive calcium channels.

• Journal of Chest Surgery
• /
• v.10 no.2
• /
• pp.205-213
• /
• 1977

In order to evaluate the therapeutic effect of thoracostomy on the patients with pathological changes in pleural cavity which were caused by various etiological factors, a clinical study was carried out during a period of 5 and half years from May 1972 to September 1977 in the department of thoracic surgery, Hanyang University Hospital, and the following results were obtained. Of a total of 264 patients, 205 cases were male, and 59 female, exhibiting the ratio of male to female being 3.5 to 1. The pathological changes in pleural cavity could occur at any age from 4 months after birth to 76 years old, the peak incidence being in the third decade in either male or female. The incidence decreased in the second, fifth and fourth decade in order. The type of pathological changes observed and their frequencies of occurrences were 93 cases [35.2%] in pneumothorax, 62 cases [23.5%] in hemothorax, 48 cases [18.2%] in pyothorax, 46 cases [17. 4%] in hemopneumothorax, 13 cases [4.9%] in hydropneumothorax, and one case each in hydrothorax and chylothorax. The incidence of the primary diseases which predisposed the pathological changes in pleural cavity were, 119 cases [45-1%] in trauma, 64 cases [24.2%]in lung tuberculosis, 38 cases [14.4%] in pneumonia or empyema, 14 cases [5.3%] in lung emphysema and blebs, 13 cases [4.9%] in process after thoracotomy, 3 cases [1.1%] each in lung malignant tumor and lung paragonimiasis, one case in mechanical ventilator and 9 cases [3.4%] in unknown origin. The pathological changes in pleural cavity were located in the right side of the cavity in 124 cases, in the left side in 133 cases and in both sides in 7 cases, indicating that the difference between the incidence of the left and rightside occurences was insignificant. Of 93 cases of pneumothorax studied, 63 cases were found to have been tension pneumothorax and 30 cases non-tension pneumothorax, showing greater prevalence of tension type over non-tension type. Of 119 cases of trauma observed, 82 cases were accompanied with rib fractures and 37 cases were without any fracture [non-bone fracture]. Patients with the rib fractures were characterized by multiple rib fractures and multiple double fractures of ribs, accompanying with or without fracture of bones other than ribs, and patients with non-bone fracture were characterized by penetrating stab wound and blunt trauma. Of 264 cases who received thoracostomy, 207 cases [78.4%] demonstrated that their pathological changes in pleural cavity were removed and subsided by a simple measure of thoracostomy. In 43 cases [16.3%], various surgical measures including radical operation and thoracotomy were required for complete healing, since their pathological changes were not abolished by thoracostomy alone. The rest 14 cases [5.3%] were expired following thoracostomy.

• Structural Engineering and Mechanics
• /
• v.22 no.3
• /
• pp.311-330
• /
• 2006

Standard compression tests of steel fiber reinforced concrete (SFRC) cylinders are conducted to formulate compressive stress versus compressive strain relationship of SFRC. Axial pullout tests of SFRC specimens are also conducted to explore its tensile stress strain relationship. Cover concrete spalling and reinforcement buckling models developed originally for normal reinforced concrete are modified to extend their application to SFRC. Thus obtained monotonic material models of concrete and reinforcing bars in SFRC members are combined with unloading/reloading loops used in the cyclic models of concrete and reinforcing bars in normal reinforced concrete. The resulting path-dependent cyclic material models are then incorporated in a finite-element based fiber analysis program. The applicability of these models at member level is verified by simulating cyclic lateral loading tests of SFRC columns under constant axial compression. The analysis using the proposed SFRC models yield results that are much closer to the experimental results than the analytical results obtained using the normal reinforced concrete models are.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2009.04a
• /
• pp.14-17
• /
• 2009

본 연구에서는 장대교량에서 케이블의 장력을 간편하게, 그리고 자동적으로 추정할 수 있는 저비용 무선장력계측시스템을 개발하였다. 개발된 시스템은 크게 비용이 저렴하고 설치 및 관리가 용이한 무선 기반 하드웨어와 케이블에서 계측된 가속도 데이터로부터 장력을 자동으로 추정하여 주는 내장 (Embedded) 자동화 소프트웨어로 구성된다. 저비용 무선 기반 하드웨어는 연산능력을 가진 무선계측유닛과, 계측 신호개선을 위한 신호처리보드, 그리고 상용 MEMS 가속도계로 구성되었으며, 내장 자동화 소프트웨어는 계측된 신호의 주파수 분석을 위한 FFT 모듈, 케이블의 푸리에 스펙트럼으로부터 고유진동수를 자동으로 추출하기 위한 자동 피크 추출(Peak-picking) 알고리즘 모듈, 그리고 추출된 고유진동수를 활용하여 케이블의 장력을 추정하는 진동법 모듈로 구성되었다. 개발된 시스템의 검증을 위하여, 사장교의 케이블 축소모델을 제작하고 케이블 모델에 다양한 장력과 새그를 주어 진동실험을 수행하였다. 실험 결과, 개발된 시스템은 케이블 모델의 주파수응답스펙트럼으로부터 고유진동수를 정확하게 추정하였으며, 장력과 새그의 크기에 상관없이 매우 정확한 장력을 추정하였다.

• Korea-Australia Rheology Journal
• /
• v.12 no.3_4
• /
• pp.181-186
• /
• 2000

Rheological Properties of polypropylenes having different molecular structures (linear polypropylene (PPL) and branched one (PPB)) were studied. Both the extensional flow and oscillatory shear flow properties were checked. Especially, the melt strength of polypropylenes having various shear history were investigated by using in-house-made Rheometer (called SMER). Compared to linear polypropylene, the branched polypropylene shows enhanced melt strength during extensional flow due to the retarded relaxation of molecules. When the slope of melt tension was plotted against take up speed of melt strand, the characteristic peak was observed in case of branched polypropylene, while the linear polypropylene shows only monotonously decreasing pattern. This entanglement was partially disrupted by physical forces such as shear during melt extrusion. However, the melt strength of PPB after multiple extrusion is still higher than PPL, implying the loss of elasticity during multiple extrusion is not so comprehensive. On dynamic experiments, PPB shows typical shear thinning behavior and the tangent delta of PPB is lower than PPL, reflecting high elasticity of PPB.

• Smart Structures and Systems
• /
• v.25 no.4
• /
• pp.393-399
• /
• 2020

In this paper, the design method and experimental validation for the two-degree-of-freedom (2DOF) electromagnetic energy harvester are presented. The harvester consists of the rigid body suspended by four tension springs and electromagnetic transducers. Once the two resonant frequencies and the mass properties are specified, both the constant and the positions for the springs can be determined in the closed form. The designed harvester can locate two resonant peaks close to each other and forms the extended frequency bandwidth for power harvesting. Halbach magnet array is also introduced to enhance the output power. In the experiment, two resonant frequencies are measured at 34.9 and 37.6 Hz and the frequency bandwidth improves to 5 Hz at the voltage level of 207.9 mV. The normalized peak power of 4.587 mW/G² is obtained at the optimal load resistor of 367 Ω.