• 대한기계학회논문집A
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• 제24권2호
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• pp.496-505
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• 2000

A semi-infinite parallel crack propagated with constant velocity in two bonded anisotropic strip under anti-plane clamped displacement is analyzed. Using Fourier integral transform a Wiener-Hopf equation is derived. By solving this equation the asymptotic stress and displacement fields near the crack tip are determined, where the results give the more general expression applicable to the extent of the anisotropic material having one plane of elastic symmetry for the parallel crack. The dynamic stress intensity factor and energy release rate are also obtained as a closed form, which are the results applicable to the problem both of dynamic and static crack under the same geometry as this study. The stress intensity factor approaches zero at the critical crack velocity which is less than the shear wave velocity, but in typical case of isotropic or orthotropic material agrees with the velocity of shear wave. Also a circular shear stress around crack tip is considered, from which the stress is shown to be approximately symmetric about the horizontal axis. Referring to the maximum stress criteria, it could be shown that a brenched crack is formed by crack growth as crack velocity increases.

• 한국자동차공학회논문집
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• 제2권6호
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• pp.102-109
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• 1994

As a fundamental study to apply high pressure injection system to direct injection diesel engine, fuel injection system and constant volume combustion chamber were made and the behaviors of evaporating spray with the variation of injection pressure and the ambient gas temperature were observed by using high speed camera, and the combusion characteristics with the variation of injection pressure and A/F ratio were analyzed. As injection pressure increases, spray tip penetration and spray angle increase and, as a results spray volume increases. This helps an uniform mixing of fuel and air. Spray liquid core length decreases as ambient gas temperature increases, while it decreases as injection pressure increases but the effect of ambient gas temperature is dorminant. As injection pressure increases, ignition delay is shortened and combustion rate being raised, maximum heat release rate increases. It become clear that High injection pressure has high level of potential to improve the performance of DI-diesel engine.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.3-8
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• 2001

Dynamic stress intensity factors (DSIFs) are obtained when a crack propagates with constant velocity in rectangular functionally gradient materials (FGMs) under dynamic mode III load. To obtain the dynamic stress intensity factors, it is used the general stress and displacement fields of FGMs for propagating crack and the boundary collocation method (BCM). The stress intensity factors and energy release rates are the greatest in the increasing properties $(\xi>0)$, next constant properties $(\x=0)$ and decreasing properties $(\xi<0)$ under constant crack tip properties and crack tip speed.

• 수산해양기술연구
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• 제28권2호
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• pp.184-190
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• 1992

The combustion characteristics, ignition delay, p-t, dp/dt, Q-t of diesel oil and fish oil blended diesel oils was investigated according to pressure and temperature in a constant volume combustion bomb. The results are as follows: 1) The influence of temperature and pressure on the ignition delay was almost constant in high temperature, regardless of the blending rates, and the ignition delay was shortest in the 60% blend. 2) The maximum pressure was high in order of with pure diesel oil, with the 20% blend and the 60% blend. 3) The rate of pressure rise was high in order of with pure diesel oil, with the 20% blend and the 60% blend. The rate of maximum pressure rise was significantly higher with pure diesel oil than with two blends. 4) The amount of accumulative heat release was large in order of with pure diesel oil, with the 20% blend and the 60% blend.

• Journal of Ecology and Environment
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• 제38권3호
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• pp.319-326
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• 2015

This study investigates the behavioral characteristics and forms of phosphorus in the sediment according to the oxygen condition (aerobic/anaerobic). In the behavioral characteristics analysis, Al-P and Fe-P concentrations were the highest among the forms of inorganic phosphorus, and therefore had the strongest impact on sorption and release corresponding to environmental condition changes. In the experimental investigation of the inorganic forms of phosphorus in the sediment according to the oxygen condition, we determined that the forms of inorganic phosphorus did not greatly affect the sorption or release reaction because the distribution ratios of the inorganic forms remained constant corresponding to changes of dissolved oxygen (DO) conditions. In contrast, the forms of organic phosphorus in the sediments affected both sorption and release. Furthermore, labile-P and moderately labile-P forms were the major mechanisms of sorption in sediment. Moderately labile-P was the greatest contributor to phosphorus release action in sediment. As environmental changes are important for the behavioral characteristics of phosphorus in sediment, the forms of phosphorus should be considered to have a greater effect, especially in the organic phosphorus case. Therefore, based on the present study results, sediment evaluation aimed at controlling internal pollutants in reservoirs should include an examination of the forms of phosphorus present, as well as the release characteristics of environmental changes, which are influential factors of phosphorus control. Further research in this field is required.

• 폴리머
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• 제26권5호
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• pp.680-690
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• 2002

골 재흡수 치료를 목적으로 파미드로네이트를 지속적으로 방출하는 제형으로 제조하기 위하여 락타이드-글리콜라이드 공중합체 (PLGA, 락타이드 : 글리콜라이드 몰비 = 75 : 25, 분자량 20000 g/mole 및 90000 g/mole)를 이용하여 직접압축 성형방법으로 생분해성 웨이퍼를 제조하였다. 약물과 고분자의 함량비 웨이퍼의 두께, PLGA 분자량 등을 조절하여 PLGA 웨이퍼를 제조하였고 이들의 형태학적 특성과 방출거동 및 분해거동을 살펴보았다. 웨이퍼의 제조는 혼합된 분말을 웨이퍼 제작용 몰드에 넣은 후 프레스를 이용하여 일정 압력으로 일정시간 동안 상온에서 가압하여 제조하였다. 제조된 웨이퍼는 약물의 초기함량이 증가할수록 방출속도가 빠르게 나타났으며, 제형의 두께가 두꺼워질수록 시간이 경과함에 따라 약물의 방출속도가 증가하였다. 또한 고분자의 분자량이 큰 것이 작은 것에 비해 상대적으로 초기 약물 방출량이 적고 방출되는 속도 또한 느려져. 저분자보다 오랫동안 약물이 방출되었다. 이러한 약물전달 시스템은 압축성형방법에 의해 제조하므로 제조가 간단하고 약물방출속도를 정확하게 제어할 수 있으므로 이식을 위한 제형으로 제조시 유용하게 쓰일 것으로 예상되었다.

• 대한기계학회논문집
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• 제17권2호
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• pp.331-341
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• 1993

The propagating crack problems under dynamic antiplane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems by theoretical method or experimental method in orthotropic material, it is important to know the dynamic stress intensity factor in the vicinity of crack tip. Therefore the dynamic stress field and dynamic displacement field with dynamic stress intensity factor of orthotropic material in mode III were derived. When the crack propagation speed approachs to zero, the dynamic stress components and dynamic displacement components derived in this paper are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determined by using the concept of crack closure energy with the dynamic stresses and dynamic displacements derived in this paper. Finally, the characteristics of crack propagation are studied with the properties of orthotropic material and crack speed. The variation of angle .alpha. between fiber direction and crack propagating direction and crack propagation speed fairly effect on stress component and displacement component in crack tip. The influence of crack propagation speed on the speed on the stress and displacement is greater in the case of .alpha.=90.deg. than in the case of .alpha.=0.deg. and the faster the crack propagation speed, the greater the stress value and displacement value.

• 한국수산과학회지
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• 제44권3호
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• pp.290-297
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• 2011

The phenology of Campylaephora hypnaeoides J. Agardh and optimal conditions for carpospore release, growth and reproduction were examined in the field and in the laboratory from January to December 2007. In the field population of C. hypnaeoides, approximately 50% of the plants were vegetative during the study period. Additionally, the percentages of carposporophytes and tetrasporophytes were maximal in April (37%) and June (57%), respectively. Maximum growth in plant length, dry weight, and hook number coincided with the tetrasporophyte reproductive peak in the field. In culture, carpospore release, sporeling growth and reproduction were affected by environmental factors such as daylength, temperature, and salinity. The liberation of carpospores was maximum under continuous light and at a combination of $15^{\circ}C$ and $10\;{\mu}mol$ photons $m^{-2}\;s^{-1}$. Maximum growth of tetrasporophyte sporelings occurred at a combination of $20\;{\mu}mol$ photons $m^{-2}\;s^{-1}$ of constant light and $25^{\circ}C$. However, the growth of gametophyte sporelings was maximal under $40\;{\mu}mol$ photons $m^{-2}\;s^{-1}$ of constant light and in a combination of $20^{\circ}C$ and 35 psu. The tetrasporophyte sporelings were grew faster than gametophytes, indicating that gametophyte- and tetrasporophyte-sporelings have different physiological responses to irradiance and temperature. Tetrasporangial branches and cystocarps of C. hypnaeoides were produced from carpospores and tetraspores within 1 month, and they were stimulated at high temperature and irradiance levels. In conclusion, C. hypnaeoides should be seeded using carpospores during early winter (November-December) because cystocarps are easily identified by fishermen, and tetrasporophytes grow faster than gametophytes.

• 수산해양기술연구
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• 제55권4호
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• pp.411-418
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• 2019

In this study, to investigate the effect of physical and chemical properties of butanol on the engine performance and combustion characteristics, the coefficient of variations of IMEP (indicated mean effective pressure) and fuel conversion efficiency were obtained by measuring the combustion pressure and the fuel consumption quantity according to the engine load and the mixing ratio of diesel oil and butanol. In addition, the combustion pressure was analyzed to obtain the pressure increasing rate and heat release rate, and then the combustion temperature was calculated using a single zone combustion model. The experimental and analysis results of butanol blending oil were compared with the those of diesel oil under the similar operation conditions to determine the performance of the engine and combustion characteristics. As a result, the combustion stabilities of D.O. and butanol blending oil were good in this experimental range, and the indicated fuel conversion efficiency of butanol blending oil was slightly higher at low load but that of D.O. was higher above medium load. The premixed combustion period of D.O. was almost constant regardless of the load. As the load was lower and the butanol blending ratio was higher, the premixed combustion period of butanol blending oil was longer and the premixed combustion period was almost constant at high load regardless of butanol blending ratio. The average heat release rate was higher with increasing loads; especially as butanol blending ratio was increased at high load, the average heat release rate of butanol blending oil was higher than that of D.O. In addition, the calculated maximum. combustion temperature of butanol blending oil was higher than that of D.O. at all loads.

• Clinics in Shoulder and Elbow
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• 제20권3호
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• pp.117-125
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• 2017

Background: To compare the clinical outcomes of arthroscopic capsular release in patients with and without inferior capsular release for shoulder stiffness. Methods: Between January 2010 and December 2015, 39 patients who underwent arthroscopic capsular release for shoulder stiffness were enrolled and randomized into two groups. In group I, 19 patients underwent arthroscopic capsular release of the rotator interval and anterior capsule. In group II, 20 patients underwent arthroscopic capsular release of the anterior to inferior capsule, including the rotator interval. The American Shoulder and Elbow Surgeons score, Constant scoring system, Simple Shoulder Test, visual analogue scale for pain, and range of motion (ROM) were used for evaluation before surgery, at 3, 6, and 12 months after surgery and on the last follow-up. Results: Preoperative demographic data revealed no significant differences (p>0.05). The average follow-up was 16.07 months. Both groups showed significantly increased ROM at the last follow-up compared with preoperative (p<0.05). At the last follow-up, no statistical differences were found (p>0.05) between groups I and II in functional scores and ROM (forward flexion, p=0.91; side external rotation, p=0.17; abduction external rotation, p=0.72; internal rotation, p=0.61). But we found that group II gained more flexion compared to group I at 3 months and 6 months (p<0.05) after the surgery. Conclusions: Both techniques of capsular release are effective for stiffness shoulder. However, the extended inferior capsular release shows superiority in forward flexion over anterior capsular release alone during 6 months of follows-up (level of evidence: Level I, therapeutic randomized controlled trial).