• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.216-219
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• 2000

The adhesive bonded single-lap joint is due to its intrinsic load eccentricity problem, severe peel stresses concentration occur at both end of the joint. In this paper, new lap-joint is designed to avoid the singular peel stress, and to compare the stresses of the middle adhesive layer between the single-lap joint and the wavy-lap joint. Two adherend lay-up, i.e., [90/0/90/0]$_{2s}$ and [0/90/0/90]$_{2s}$ were consider in the study.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.168-171
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• 2001

Due to intrinsic load eccentricity, severe peel stress concentration occurs at both ends of the single-lap joint. To avoid load eccentricity as well as the singular tensile peel stress in the joint interface, composite wavy-lap joint is proposed. In this paper, refined 3-D stress analysis of wavy-lap joint is performed by finite element method using parallel mutifrontal solver. Analysis results show that the singular tensile peel stress concentration is totally avoided in wavy-lap joint, and that loads are more evenly transferred over the length of the joint. Therefore, the strength of wavy-lap joint is significantly higher than that of conventional single-lap joint. And it is believed that even higher strengths can be obtained by optimizing the new design configuration.

• International Journal of Korean Welding Society
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• 제4권1호
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• pp.53-60
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• 2004

Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5mm/min. As a result, the load distribution showed a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.286-289
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• 2006

Headed bars have used to the anchoring of the tension or compression longitudinal bars and of the shear reinforcing bars. Recently, lap splices of headed bars are attempted to the joints of precast concrete members and to the connections between old and new concrete members. Previous Michael's experimental research showed that confinement details had an effect on the lap splice performances of headed bars. In this study, the lap splice performances of headed bars(D25) with lap length and confinement details are evaluated through the experimental works. Four specimens, of which variables were the lap length of headed bar and the type of confine details, were tested for the performance evaluation on lap splice. Test results show that the lap length confinement reinforcement improve the performance of lap splice.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.931-936
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• 2003

Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. Lap splicing is also permitted if hoops or spiral reinforcement are provided over the lap length in the current seismic design provision. But sudden brittle failure of lap splices may occur under inelastic cyclic loading. The purpose of this study is the analytical prediction of nonlinear hysteretic behavior and ductility capacity of reinforced concrete bridge piers with lap splices under cyclic loading. For this purpose, a nonlinear analysis program, RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. Lap spliced bar element is developed to predict behaviors of lap spliced bar. Maximum bar stress and slip of lap spliced bar is considered.

• 대한기계학회논문집
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• 제18권1호
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• pp.85-92
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• 1994

With the wide application of fiber-reinforced composite meterial in aircraft space structures and robot arms, the design and manufacture of composite joints have become a very important research area because they are often the weakest areas in composite structure. In this paper, the torque transmission capacities of the adhesive tubular single lap joint and double lap joint were studied. The stress and torque transmission capacity of the adhesive joints were analyzed by the finite element method and compared to the experimental results. The torque capacity of the double lap joint was increased 2.7 times over that of the single lap joint. Also, the fatigue limit of the double lap joint was increased 16 times over that of the single lap joint.

• 대한기계학회논문집A
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• 제28권6호
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• pp.783-790
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• 2004

Adhesive-bonded joints are widely used in the industry. Recently, applications of adhesive bonding joints have been increased extensively in automobile and aircraft industry. The strength of adhesive joints is influenced by the surface roughness, adhesive shape, stress distribution, and etc. However, the magnitude of the influence has not yet been clarified because of the complexity of the phenomena. In this study, as the fundamental research of adhesive bonding joints, the effects of adhesive shape and loading speed on bonding strength properties and durability of aluminum to polycarbonate single-lap joints were studied. To evaluate the effect of adhesive shape, several modified shapes were used, and loading speeds were varied from 0.05 to 5 mm/min. As a result, the load-displacement distribution was shown a brittle fracture tendency. The trigonal edged single lap and bevelled lap joints showed the higher strength than the plain single lap, trigonal single lap, joggle lap and double lap joints in same adhesive area. The fractures of trigonal single lap and trigonal edged single lap joints that had the higher strength level were shown as the mixture type of the cohesive and interfacial-failure, mostly joggle lap joints that had the lower strength level were shown as the adhesive-failure.

• 한국지진공학회논문집
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• 제20권6호
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• pp.351-360
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• 2016

In regions of low-to-moderate seismicity, various types of lap splices are used for longitudinal reinforcement of columns at the plastic hinge zones. The seismic performance of such lap spliced columns, such as strength, deformation capacity, and energy dissipation, is affected by material strengths, longitudinal re-bar size, confinement of hoops, lap splice location, and lap splice length. In the present study, cyclic loading tests were performed for columns using three types of lap splices (bottom offset bar splice, top offset bar splice, and splice without offset bend). Lap splice length($40d_b$ and $50d_b$) was also considered as test parameters. Ties with 90-degree end hooks were provided in the lap splice length. The test results showed that strength, deformation capacity, and energy dissipation of columns significantly differed depending on the details and the length of lap splices. The bottom offset bar splice showed high ductility and energy dissipation but low strength; on the other hand, the top offset bar splice and the splice without offset bend showed high strength but moderate ductility and energy dissipation.

• Radiation Oncology Journal
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• 제31권2호
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• pp.57-65
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• 2013

Beta-lapachone (${\beta}$-Lap; 3,4-dihydro-2, 2-dimethyl-2H-naphthol[1, 2-b]pyran-5,6-dione) is a novel anti-cancer drug under phase I/II clinical trials. ${\beta}$-Lap has been demonstrated to cause apoptotic and necrotic death in a variety of human cancer cells in vitro and in vivo. The mechanisms underlying the ${\beta}$-Lap toxicity against cancer cells has been controversial. The most recent view is that ${\beta}$-Lap, which is a quinone compound, undergoes two-electron reduction to hydroquinone form utilizing NAD(P)H or NADH as electron source. This two-electron reduction of ${\beta}$-Lap is mediated by NAD(P)H:quinone oxidoreductase (NQO1), which is known to mediate the reduction of many quinone compounds. The hydroquinone forms of ${\beta}$-Lap then spontaneously oxidizes back to the original oxidized ${\beta}$-Lap, creating futile cycling between the oxidized and reduced forms of ${\beta}$-Lap. It is proposed that the futile recycling between oxidized and reduced forms of ${\beta}$-Lap leads to two distinct cell death pathways. First one is that the two-electron reduced ${\beta}$-Lap is converted first to one-electron reduced ${\beta}$-Lap, i.e., semiquinone ${\beta}$-Lap $(SQ)^{{\cdot}-}$ causing production of reactive oxygen species (ROS), which then causes apoptotic cell death. The second mechanism is that severe depletion of NAD(P)H and NADH as a result of futile cycling between the quinone and hydroquinone forms of ${\beta}$-Lap causes severe disturbance in cellular metabolism leading to apoptosis and necrosis. The relative importance of the aforementioned two mechanisms, i.e., generation of ROS or depletion of NAD(P)H/NADH, may vary depending on cell type and environment. Importantly, the NQO1 level in cancer cells has been found to be higher than that in normal cells indicating that ${\beta}$-Lap may be preferentially toxic to cancer cells relative to non-cancer cells. The cellular level of NQO1 has been found to be significantly increased by divergent physical and chemical stresses including ionizing radiation. Recent reports clearly demonstrated that ${\beta}$-Lap and ionizing radiation kill cancer cells in a synergistic manner. Indications are that irradiation of cancer cells causes long-lasting elevation of NQO1, thereby sensitizing the cells to ${\beta}$-Lap. In addition, ${\beta}$-Lap has been shown to inhibit the repair of sublethal radiation damage. Treating experimental tumors growing in the legs of mice with irradiation and intraperitoneal injection of ${\beta}$-Lap suppressed the growth of the tumors in a manner more than additive. Collectively, ${\beta}$-Lap is a potentially useful anti-cancer drug, particularly in combination with radiotherapy.

• 대한임상검사과학회지
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• 제49권4호
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• pp.374-381
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• 2017

LAP 지수는 공복시 중성지방 농도와 허리둘레의 조합으로 과도한 지방축적을 평가하는 지표이다. 이 연구는 LAP 지수와 ALT간의 관련성과 LAP 지수가 ALT에 미치는 영향에 대해 알아 보고자 간질환의 병력이 없는 건강한 성인남성을 대상으로 횡단면 연구를 실시하였다. 2015년 1월부터 2017년 6월까지 경기지역 종합병원에서 건강검진을 시행한 20세 이상 70세 이하의 성인 남성 13,854명을 연구 대상자로 하였다. LAP 지수는 남성의 경우 [허리둘레(cm)-65]${\times}$[중성지방(mmol/L)]으로 산출하였으며, 혈청 ALT 농도의 이상치는 남성 40 IU/L 이상인 경우를 기준으로 설정하였다. 모든 대상자들은 인체측정학적 지표와 생리학적 검사를 실시하였다. LAP 분위수가 증가할수록 ALT는 통계적으로 유의한 증가를 보였다(p<0.001). LAP 지수는 ALT와 상관관계를 보였으며(r=0.238, p<0.001), 특히 인슐린(r=0.449, p<0.001) 및 HDL-콜레스테롤(r=-0.369, p<0.001)과 상관성이 높게 나타났다. 또한 LAP 지수는 ALT에 영향을 미치는 요인이었으며(p<0.001), LAP 지수가 높을수록 ALT가 상승할 위험이 높게 나타났다(p<0.001). 결론적으로 LAP 지수는 한국 성인남성에서 ALT 상승을 예측하는 지표로 나타났다.