• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.12
• /
• pp.2287-2297
• /
• 1992

The Formulation of a new Hermite straight beam element to eliminate the shear locking is presented. All the kinematic variables in Timoshenko beam are reinterpreted by the consideration of equilibrium equations together. It shows that when the modified transverse displacement field is used the Timoshenko beam looks apparently the same as the Euler beam. The element is formulated for the modified transverse displacement field to have the same interpolation scheme as that in the Hermite element. Transformation Matrix which relates a modified nodal vector with nonmodified one is also introduced to deal with general boundary conditions. Several examples are demonstrated and discussed for the purpose of verification of the concepts employed. The solutions obtained reveal that the element describes of the beam quite correctly, showing no locking and that it is also applicable to the analysis of both thin and thick beams.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.8 no.2
• /
• pp.10-17
• /
• 2004

The results of the combustion performance tests of gas generator which supplies hot gas into the turbine of turbo-pump for liquid rocket engine and uses LOx and kerosene as propellant are described. The gas generator consists of a injector head with F-O-F impinging injector, a water cooled combustion chamber, a gas torch igniter, a turbulence ring and an instrument ring. The effect of turbulence ring and combustion chamber length on performance of gas generator are investigated. The ignition and combustion at design point are stable and the pressure and gas temperature at gas generator exit meets the target. The turbulence ring installed at middle of chamber effectively mixes hot gas with cold gas and the effect of residence time of hot gas in gas generator on combustion efficiency is small. Test results show that the main parameter controlling the gas temperature at gas generator exit is overall O/F ratio.

• Geotechnical Engineering
• /
• v.13 no.4
• /
• pp.95-108
• /
• 1997

For normally consolidated clay, several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation However, depending on the assumptions and analytical techniques, it could considerably vary even for a specific degree of consolidation. In this paper, a method is proposed to determine a consistent coefficient of consolidation over all ranges of degree of consolidation by applying the concept of the Optimum Design Technique. The initial excess pore pressure distribution is assumed to be obtainable by the successive spherical cavity expansion theory. The dissipation of pore pressure is simulated by means of two dimensional linear-uncoupled axisymmetric consolidation analysis. The minimization of the differences between the measured and the predicted excess pore pressures was carried by BFGS unconstrained optimum design algorithm with one dimensional golden section search technique. By analyzing numerical and real field examples, it can be found that the adopted optimum technique gives a consistent and convergent results.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.2
• /
• pp.26-32
• /
• 2021

The photovoltaic properties and microstructure changes were observed while perovskite solar cells (PSCs) with a fabricated carbon electrode were formed using the following annealing processes: hot-plate, oven, and rapid thermal annealing (RTA). Perovskite solar cells with a glass/FTO/compact TiO2/meso TiO2/meso ZrO2/carbon structure were prepared. The photovoltaic properties and microstructure changes in the PSCs were analyzed using a solar simulator, optical microscopy, and field emission scanning electron microscopy. An analysis of the photovoltaic properties revealed outstanding properties when RTA was applied to the cells. Microstructure analysis showed that perovskite was formed locally on the carbon electrode surface when hot-plate and oven annealing were applied. On the other hand, PSC with RTA showed a flat surface without extra perovskite agglomeration. Denser perovskite formed on the porous carbon electrode layer with RTA showed superior photovoltaic properties. These results suggest that the RTA process might be appropriate for the massive production of carbon electrode PSCs considering the processing time.

• Clean Technology
• /
• v.26 no.3
• /
• pp.211-220
• /
• 2020

This experimental study investigates the design parameters to achieve ultra low NOx combustion of coal using a 80 kW capacity single-burner furnace. The influence of key design parameters such as SN, overall and burner-zone equivalence ratios, primary/secondary air ratio, overfire air (OFA) ratio were tested for a total of 81 cases. The results showed that weak swirl intensity of the burner leads to higher NOx emission whereas strong swirl intensity accompanies increased CO concentration desipte lower NOx emission. Therefore, finding an appropirate swirl intensity is essential for the burner design. Larger flow rate of secondary air increased NOx emission, whereas smaller flow rate stretches the flame and increased CO emission. The lowest NOx emission of 82 ppm (6% O₂) was achieved at the optimal condition of the present burner deisgn. It is expected to furrther lower the NOx emission by introducing splitting the burner secondary air into three or four streams.

• Korean Journal of Psychosomatic Medicine
• /
• v.13 no.2
• /
• pp.102-111
• /
• 2005

Objective : The purpose of this study was to investigate the quality of life and it's related factors in caregivers of attention deficit hyperactivity disorder patients. Methods : The subjects were 38 attention deficit hyperactivity disorder patients' caregivers(mean age : $37.5{\pm}6.5$, 38 women). Patients were diagnosed with DSM-IV-TR ADHD criteria. Korean version of WHOQOL-BREF(World Health Organization Quality of Life assessment instrument Abbreviated Version) was used for assessment. Results : 1) No significant differences were found in the score of WHOQOL-BREF, overall QOL, physical health domain, psychological domain, social relationships domain and environmental domain between caregiver and control group. 2) The score of Activity of daily living facet$(3.0{\pm}0.7\;vs.\;3.6{\pm}0.7)(p=0.008)$ and self-esteem facet $(2.8{\pm}0.7\;vs.\;3.3{\pm}0.7)(p=0.049)$ were significantly decreased in caregivers of ADHD. 3) Total score of WHOQOL-BREF(r=0.437, p=0.007) and physical health domain(r=0.370, p=0.024) were correlated with caregiver's educational age. 4) In the psychological domain, the score of self-esteem facet(r=-0.337, p=0.039) and thinking, learning, memory & concentration facet(r=-.341, p=0.036) were decreased with caregiver's age. 5) The score of environmental domain were significantly increased with caregiver's educational age (r=0.482, p=0.003), but decreased with patient's age(r=0.328, p=0.044). Conclusion : Although the quality of life in caregivers of ADHD patient had not significantly decreased than control, the quality of lift were positively correlated with educational age of caregives, and negatively correlated with chronological age of caregivers and children. Above results suggest that physicians should consider integrated approaches for caregiver's subjective quality of life in the management of ADHD.

• The Journal of Korean Academy of Sensory Integration
• /
• v.18 no.3
• /
• pp.1-13
• /
• 2020

Objective : The purpose of this study was to evaluate the differences in sensory processing and visual perception between school-age children with Attention Deficit Hyperactivity Disorder (ADHD) and typical children. Methods : The participants in this research were children in the first and second grade in elementary school in Kyoung-Nam Region; 25 children diagnosed with ADHD comprised the experimental group, and 51 typical children comprised the control group. To evaluate the sensory processing of the children, the Sensory Profile (SP) was used, and the Korean Developmental Test of Visual Perception-2 (K-DTVP-2) was used to assess visual perception skills. The data were analyzed using SPSS 20.0, and the Independent t-test was used to compare the sensory processing and visual perception skills of the two groups. Results : The study found differences in the Sensory Profile summary scores and factor summary scores between the two groups (p<.05). We also found differences in the visual perception index and subtest standard scores between the two groups (p<.05). Conclusion : The results of this study show that the experimental and the control groups had significant differences in sensory processing and visual perception skills. The result will contribute to the assessment and education of children with ADHD.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2015.10a
• /
• pp.1778-1781
• /
• 2015

본 논문에서는 최근 이슈가 되고 있는 마인드 컨트롤 기술을 이용하여 RC 카를 움직이는 기술에 대하여 설명한다. 사회적으로 주의력 결핍 과잉행동 장애(ADHD)를 갖는 사람이 늘어나고 있으며, ADHD는 여러 가지 치료 기술이 있지만 어릴수록 놀이 치료 등을 사용하는 것이 좋다. 본 논문에서 뇌파측정기를 이용하여 뇌파를 모은 뒤 K-평균 알고리즘과 재 클러스터링을 통하여 방향 뇌파를 데이터화하고, 그 이후에 데이터화 된 방향 뇌파들을 토대로 RC카를 움직이는 기술 제안하였다. 개발된 기술의 경우 성능이 높게 나타나지 않았지만, 앞으로 이 기술이 더 발전한다면, 아동의 놀이 등에 활용하여 ADHD도 효과적으로 치료할 수 있을 뿐만 아니라, 실제 자동차 시스템에 적용하는 등 다양한 응용이 가능할 것으로 생각된다.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.74-74
• /
• 2003

적외선 감지기는 냉장고, 에어컨, 자동차용 전자부품 등의 온도측정 및 제어, 과잉 전류의 억제를 위한 소자로 널리 사용되며, 또한 최근에는 온도보상형 수정발진기(TCXO) 또는 RF모듈, 액정 판넬의 온도보상회로 등 정보통신기기의 신뢰성 향상을 위해 그 수요가 날로 증가하고 있다. 현재 상용되는 적외선 감지기의 대부분은 벌크형 또는 후막형으로 제조되고 있으나, 최근 반도체공정 기술의 발달로 인하여 보다 향상된 특성이 요구됨에 따라 박막형 등 새로운 형태의 적외선 감지기 대해 활발한 연구가 이루어지고 있다. 본 연구에서는 열 질량과 전도에 의한 열손실을 최소화하여 소자의 감도 및 응답 특성을 향상시키기 위하여 SiO$_2$Si$_3$N$_4$/SiO$_2$ (ONO)다중층 위에 소자 감지부를 형성하고 bulk-micromachining기술을 이용하여 멤브레인 구조를 갖는 박막형 적외선 감지기를 제작하였다.

• Korea lubricating oil industries association bulletin
• /
• no.35
• /
• pp.18-22
• /
• 1989

윤활유는 전체 석유류 제품중에서 소비비중은 $2\~3$, 시장규모는 년간 약 3,500억원 수준이지만 산업기계의 보전기능과 함께 생산성 향상에 기여하고, 나아가 국가경제에 큰몫을 하게 되는 중요한 품목으로서 1일 약 8,800바렐을 사용하고 있다. 윤활유산업은 1960년대초에 태동하였으며, 우리의 토착기술이 아닌 외국의 제품상표(BRAND) 와 제휴한 생산형태로 성장하였다. 따라서 윤활유 핵심기술과는 무관한 기유와 첨가제의 배합이라는 단순공정의 업종형태이므로 대소업체가 쉽게 제조업에 참여 할 수 있어 시설과잉과 판매경쟁이 치열한 점이 특징이다. ''89. 하반기부터는 극동정유(주)가 윤활유공업협회에 가입하였고, 경인에너지(주)와 쌍용정유(주)가 제품시장에 참여하게 되므로서 윤활유업계는 정유 5사 모두가 동참하는 새로운 전기를 맞이하게 되었다. 여기에 윤활유산업의 발자취를 더듬어 보고 앞으로 업계가 나아갈 바 몇가지 과제를 알아보기로 하겠다.