• Composites Research
• /
• v.19 no.4
• /
• pp.15-22
• /
• 2006

One of the primary factors limiting the application of composite-metal adhesively bonded joints in structural design is the lack of a good evaluation tool for the interfacial strength to predict the load bearing capacity of boned joints. In this paper composite-steel adhesion strength is evaluated in terms of stress intensity factor and fracture toughness of the interface corner. The load bearing capacity of double lap joints, fabricated by co-cured bonding of composite-steel adherends has been determined using fracture mechanical analysis. Bi-material interface comer stress singularity and its order are presented. Finally stress intensities and fracture toughness of the wedge shape bi-material interface corner are determined. Double lap joint failure locus and its mixed mode crack propagation criterion on $K_1-K_{11}$ plane have been developed by tension tests with different bond lengths.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.11
• /
• pp.57-65
• /
• 2016

This study was conducted to apply five dimensional education to help nursing students adjust to college life, decease study stress and to raise personal characters, and to check its effects on DQ, self-esteem, and self-efficacy. This study was designed with a single group and pre-and-post test. The program was designed to evenly improve the five dimensions of mental ability, physical ability, intellectual ability, self-management, and personal guide. The program was then run for a total of 28 sessions, twice a week. The program was applied from March to December 2014 and data were collected before the program and after its completion. The participants were 288 students who agreed to participate in the study among freshmen at a nursing college located in K city. The collected data were evaluated by frequency analysis, t-test, and ANOVA. The results revealed that self-esteem, self-efficacy and intellectual ability among DQ increased significantly. These findings suggest that the five dimensional education program enhances self-esteem and self-efficacy, thereby helping nursing students adjust to college life and to decrease study stress. To enhance the five dimensional education program to improve personal characteristics, it is necessary to increase sessions and supplement management inducing participation.

• Journal of Korean Society of Water and Wastewater
• /
• v.32 no.2
• /
• pp.183-192
• /
• 2018

Applicability of corrosion inhibitor was evaluated using pilot scale water distribution pipe simulator. Calcium hydroxide was used as corrosion inhibitor and the corrosion indices of the water were investigated. Corrosion indices, Langelier saturation index (LI) increased by 0.8 and calcium carbonate precipitation potential (CCPP) increased by 9.8 mg/L. This indicated that corrosivity of water decreased by corrosion inhibitor and the effects lasted for 18 days. Optimum calcium hydroxide dose was found to be 3~5 mg/L for corrosion inhibition. We suggest that monitoring of CCPP as well as LI need to be conducted to control corrosivity of water.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.2
• /
• pp.560-569
• /
• 2016

Purpose The purpose of this study was not only to explore the factors associated with the survival of OHCA(Out-of-hospital Cardiac Arrest), but to provide ideas for improving the operation of emergency medical system in Korea. Method 90,734 OHCAs(Out-of-hospital Cardiac Arrest) with a cardiac etiology, who had been transported by 119 EMS ambulances for seven years from 2006 to 2012 in Korea, were analyzed. The data had a multilevel structure in that patient's survival in the same region is interrelated, so two-level (patient-region) logistic regression analysis was applied to adjust this correlation. Results The adjusted OR in group who were given CPR(Cardiopulmonary Resuscitation) by a bystander were 1.40 for survival to discharge. In addition, the adjusted OR in the group with an implementation of AED (automated external defibrillator) before arriving in hospital was 2.98 for survival to discharge. we categorized some continuous variables (number of emergency physician, OHCAs volume fo hospital, area deprivation level) into five quintiles. The adjusted OR in the number of emergency physician compared with Q1(lowest) was 1.29(Q2), 2.89(Q3), 3.39(Q4), 4.07(Q5), respectively. the adjusted OR in OHCAs volume of each hospital compared with Q1(lowest) was 2.06(Q2), 3.06(Q3), 3.46(Q4), 4.36(Q5), respectively. Lastly, the adjusted OR in deprivation level compared with Q1(least deprived area) was 0.72(Q4), 0.64(Q5) so that the adjusted OR of survival to discharge tended to decrease in more deprived districts. Conclusion The survival to discharge was better significantly in group given CPR by a bystander and with the implementation of AED before arriving in hospital. The survival to discharge tended to be significantly better in hospitals with a larger number of emergency physicians and higher volume of OHCAs in less deprived districts.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.8 no.4
• /
• pp.363-372
• /
• 1997

We have developed the UHF CW/FM proximity sensor system. The UHF CW/FM Proximity Sensor is the system which recognizes the distance from the antenna to the target using the UHF band signal. To adjust sensing distance, we must change modulation frequency parameter or modulation index parameter. When we select the modulation frequency paramter for adjusting sensing distance, new modulation frequency generator and new band pass filter will be required. It is so inefficient that we choose modulation index parameters for adjusting sensing distance. In this paper, theoretical principles of the UHF CW/FM Proximity Sensor are analyzed and doppler signals for the distance from the antenna to the target are measured as the modulation index($\beta$) being changed. Three systems of which moduation indices are 38, 50, and 61 are made. We concluded that the sensing distance will decrease as the modulation index($\beta$) increases. It is in accord with the theory of this UHF CW/FM Proximity Sensor System.

• Electronics and Telecommunications Trends
• /
• v.19 no.3 s.87
• /
• pp.41-50
• /
• 2004

본 고에서는 이동통신 액세스 망의 기술 동향에 대하여 4세대 이동통신 액세스 망으로의 진화 관점에서 살펴 본다. 주요 표준화 기관인 3GPP2, 3GPP2, MWIF의 연구결과를 중심으로 3세대 이후의 기술에 대한 표준화 연구를 살펴 보며, 액세스 망이 추구하는 목표 및 요구사항에 따른 액세스 망의 구조를 예측해 본다. 핵심 망 및 단말을 포함하여 향후에는 액세스 망도 인터넷 프로토콜 기반의 패킷 망으로 발전될 것이며, 구조 및 인터페이스의 개방화, 기능의 분산화를 토대로 기존의 다양한 액세스 망을 수용하는 4세대의 액세스 망으로 발전될 것이다. 따라서 마지막으로 이러한 추세에 따른 3세대 이후, 즉 4세대를 지향하는 이동통신 액세스 망에 대하여 요구사항 및 기능, 구조 등에 대하여 분석해 본다.

• The Journal of Korean Physical Therapy
• /
• v.16 no.2
• /
• pp.128-139
• /
• 2004

말초신경은 외상이나 질병 등 여러 가지 원인으로 손상되기 쉬우며, 손상의 정도가 심하거나 치료가 지연되는 경우에는 심각한 기능 소실을 초래할 수 있다. 본 연구에서는 수영이 말초신경손상후 운동기능의 회복과 뇌유인성 신경영양인자 (brain-derived neurotrophic factor, BDNF) mRNA의 발현에 미치는 효과를 알아보기 위하여, 흰쥐 좌골신경에 압박 손상을 가하고 수영을 적용한 후 보행궤적분석 (walking track analysis)과 역전사연쇄반응 (reverse transcription-polymerase chain reaction, RT-PCR)을 실시하였다. 그 결과, 좌골신경 압박손상된 쥐는 특징적인 보행패턴을 나타내어 좌골신경기능지수 (sciatic function index, SFI)가 현저히 낮아졌으며, BDNF mRNA의 발현이 증가하였다. 좌골신경 압박 손상후 수영을 한 쥐에서는 SFI가 현저히 향상되었으며, BDNF mRNA의 발현은 억제되었다. 이러한 결과는 말초신경손상후 수영이 BDNF mRNA의 발현을 조절함으로써 기능 회복을 촉진시키는 효과적인 치료방법이 될 수 있음을 제안하고 있다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.05a
• /
• pp.262-262
• /
• 2004

오오스테나이트 스테인리스강은 강도, 연성, 인성, 내식성 등이 우수하여 광범위하게 사용되고 있지만 절삭 시 전단저항이 크므로 절삭날 결손이나 용융을 유발하여 가공면을 안정시키기 어려우며 난삭재로서 가공경화가 매우 큰 재료이다. 그리고 질소를 약 0.1wt.％ 첨가한 316LN강은 316L강에 비해 고온강도 특성이 우수하여 주목받고 있는 새로운 재료이이지만, 저탄소의 강도 약점을 보완하기 위하여 고용강화원소로 질소를 첨가하기 때문에 높은 강도로 인하여 절삭가공에 난점이 있으므로 이 재료를 응용하기 위해서는 절삭 시 재료 표층부에 발생하는 가공 변질층에 관한 연구가 필요하다.(중략)

• Journal of the Korean Geosynthetics Society
• /
• v.14 no.4
• /
• pp.105-115
• /
• 2015

In this study, to understand mechanical characteristic of hybrid reinforced concrete by PVA-fiber 6 mm and PP-fiber 50 mm, which are organic fiber replaced macro-fiber with PP-fiber, four mixed Hybrid Organic Fibers Reinforced Concrete (HFRC) is compared with one mixed plain concrete without fiber reinforcement. Volume portion of the fibers are limited under one percent. The result presents that hybrid reinforcement of the organic fibers cannot maximize stiffness and ductility behavior of the steel fiber reinforcement. however, in comparison to plain concrete, it is confirmed that meaningful relation between toughness index and equivalent flexural strength with advanced ductility behavior. Also, in the case of concrete hybrid reinforced by organic fiber, when the volume portion of the fiber increases, ductility also increases. PP-fiber, which is macro fiber, has more effect on the flexural behavior of concrete than PVA-fiber, which is micro fiber, does. The result also shows that it decrease chloride penetration in chloride penetration test.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.2
• /
• pp.167-173
• /
• 2016

This paper proposes ductile failure simulation under high strain rate conditions using finite element (FE) analyses. In order to simulate a cracked component under a high strain rate condition, this paper applies the stress-modified fracture strain model combined with the Johnson/Cook model. The stress-modified fracture strain model determines the incremental damage in terms of stress triaxiality (${\sigma}_m/{\sigma}_e$) and fracture strain (${\varepsilon}_f$) for a dimple fracture using the tensile test results. To validate the stress-modified fracture strain model under dynamic loading conditions, the parameters are calibrated using the tensile test results under various strain rates and the fracture toughness test results under quasi-static conditions. The calibrated damage model predicts the CT test results under a high strain rate. The simulated results were then compared with the experimental data.