• 한국연소학회지
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• 제5권2호
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• pp.51-62
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• 2000

The relationship among the flame radiation, NOx emissions, residence time, and global strain rate are examined for turbulent non-premixed jet flames with wide variations in coaxial air conditions. Measurements of NOx emission, flame geometry and flame radiation were made to explain the NOx emission scaling based on global parameters such as flame residence time, global strain rate, and radiant fraction. The overall 1/2-power scaling is observed in coaxial air flames, irrespective of coaxial air conditions, but the degree of deviation from the 1/2-slope curve in each case differs from one another. From the comparison between the results of pure hydrogen flames and those of helium diluted hydrogen flames, it is observed that flame radiation plays a significant role in pure hydrogen flames with coaxial air and the deviation from 1/2-power scaling may be explained in two reasons: the difference in the flame radiation and the difference in jet similarity in coaxial air flames. From the radiation measurements, more detailed explanations on these deviations were suggested.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.395-400
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• 2017

연소 중 고압의 환경에 노출되는 밸브의 구조적 강도를 평가하기 위해 수압시험을 수행하였다. 수압 시험에서의 보증압력은 MEOP의 1.05배를 적용하였다. 총 2조의 밸브로 수압시험을 수행하였으며, 시험 시 가압조건에 따른 밸브의 변형률 계측결과를 유한요소해석 결과와 비교 검증하였다. 유한요소해석과 수압시험 결과의 오차는 약 20%이내이며, 소성변형은 발생하지 않았다.

• 소성∙가공
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• 제13권6호
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• pp.497-502
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• 2004

The shape of cold rolled steel sheets is defined as the degree of flatness, and the flatter, the better. Because undesirable strip shapes of cold rolled steel sheets can affect not only visible problem but also automatic working process in customer's lines, the requirement of the customers is more and more stringent. So we usually used the tension leveler to make high quality of strip flatness. For the improvement of the quality of strip flatness, this report developed three- dimensional FEM (Finite Element Method) simulation model, and analysis about the strain and stress distribution of strip in the tension leveling process. The numerical study can be summarized as follows. (1) If we pass the edge wave material (steepness: $1.0\%$) that the stress-difference between the strip center and the edge is 5.2kgf through tension leveler. the stress-difference is decreased 0.45kgf and the steepness is improved to $0.29\%$. (2) If the Intermesh is increased from 6mm to 7mm, the steepness is improved from $0.294\%$ to $0.268\%$. (3) If the initial steepness is decreased form $1.0\%$ to $0.75\%$, the final steepness is improved from $0.294\%$ to $0.263\%$. We know that more increased intermesh and lower initial steepness make the final steepness improved.

• 한국초전도ㆍ저온공학회논문지
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• 제24권2호
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• pp.19-22
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• 2022

We studied the effect of substrate-induced strain state on the superconducting transition in GdBa₂Cu₃O_7-x(GdBCO)/La_0.7Sr_0.3MnO₃ (LSMO) bilayers deposited on a LaAlO₃ (LAO) substrate. The stain state of LSMO is controlled by increasing the thickness from 20 nm to 80 nm. Analyses on the extended X-ray absorption fine structure (EXAFS) measurements reveal difference in the direction of MnO₆ octahedral distortion depending on the LSMO thickness, which leads to a difference in anisotropy of magnetization of LSMO layer. The superconducting transitions of our system are strongly correlated with the magnetic anisotropy accompanied by the MnO₆ octahedron distortion in a specific direction. This result suggests the possibility of improving the superconducting transition in the GdBCO/LSMO bilayer system by controlling the degree of competition between superconductivity and ferromagnetism via adjusting strain state in the LSMO layer.

• Computers and Concrete
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• 제31권5호
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• pp.443-455
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• 2023

This is a research analyses on the bearing capacity at a pile tip embedded in rock. The aim is to propose a shape coefficient for an analytical solution and to investigate the influence of the plastic flow law on the problem. For this purpose, the finite difference method is used to analyze the bearing capacity of various types and states of rock masses, assuming the Hoek & Brown failure criterion, by considering both plane strain and an axisymmetric model. Different geometrical configurations were adopted for this analysis. First, the axisymmetric numerical results were compared with those obtained from the plane strain analytical solution. Then the pile shape influence on the bearing capacity was studied. A shape factor is now proposed. Furthermore, an evaluation was done on the influence of the plastic flow law on the pile tip bearing capacity. Associative flow and non-associative flow with null dilatancy were considered, resulting in a proposed correlation. A total of 324 cases were simulated, performing a sensitivity analysis on the results and using the graphic output of vertical displacement and maximum principal stress to understand how the failure mechanism occurs in the numerical model.

• 한국가금학회지
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• 제41권1호
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• pp.69-75
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• 2014

본 시험은 토종 실용오리를 생산하기 위한 토종 오리 A와 B 계통의 산란기 성적을 조사하기 위하여 수행하였다. 2계통의 토종 오리들은 계통 당 6반복, 반복당 14수씩 총 168수를 선별하여 산란기의 성적을 조사하였다. 사료는 산란오리 사료(CP 15%, ME 2,900 kcal/kg)를 20주령부터 80주령까지 급여하였다. 체중은 A와 B 계통 사이에서 유의적인 차이가 없었다. 주령별 체중을 보면 40주령부터 48주령까지의 체중이 가장 낮게 나타났으며, 24~32주령, 64~80주령에서는 체중이 유의적으로 높게 나타났다(P<0.05). 사료 섭취량은 체중과 마찬가지로 A와 B 계통 사이에서 유의적인 차이가 없었다. 주령별 사료 섭취량은 36~48주령, 68~72주령에 유의적으로 감소하였으며, 52~56주령에 사료 섭취량이 가장 높았다(P<0.05). 계통별 평균 난중은 A와 B 계통 사이에서 유의적인 차이를 보이지 않았다. 주령별 평균 난중은 32~40주령에서 낮게 나타났다. 산란율은 24~28주령, 60~64주령 및 20~80주령에 B 계통에서 A 계통에 비해 높게 나타났다(P<0.05). 주령별 산란율은 28주령에서 최고로 높아져 48주령까지 높은 산란율을 나타냈으며, 52주령부터 감소한 후 68주령에는 다시 산란율이 회복되기 시작하였다(P<0.05). 산란 수는 전반적으로 A 계통에 비해 B 계통이 높게 나타났으나, 산란율이 급상승하는 시기인 28주령부터 48주령까지는 A와 B 계통 사이에서 유의적인 차이가 없었다. 주령별 산란 수는 주령이 경과함에 따라 유의적으로 증가하였다. 전반적인 사료 요구율은 A 계통이 B 계통에 비해 높게 나타났다(P<0.05). 그러나 28~36주령에는 A와 B 계통의 사료 요구율은 유의적인 차이가 없었다. 이런 결과들은 토종 종오리의 산란기 성적에 대한 기초적인 자료로서 이용될 것이라 사료된다.

• 한국응용곤충학회지
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• 제35권4호
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• pp.297-301
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• 1996

온도가 살충제의 저항성과 감수성계통, 복숭아혹진덧물의 발육에 미치는 영향을 조사하기 위하여 핵형이 정상인 감수성 계통(URY-O)과 저항성 계통(ABURABI : 유일) 및 핵형이상(AI, 3 전좌)으로 저항성인 O-RY 계통을 사용하였다. $25{\circ}C$에서의 약충 기간은 저항성과 감수성 계통 간에 차이가 없었으나, $30{\circ}C$에서는 감수성 인 URY-O 계통은 8.3일간에 성층이 되었었음에 비하여 저항성인 O-RY 계통은 조사기간인 20일까지 약충상태로서 성충으로 발육하지 못하고 사망하였다. 감수성인 URY-O 계통과 저항성인 ABURABI 계통의 산자수는 $28^{\circ}C\;와\;25^{\circ}C$에서 서로 차이가 없었으나, 저항성인 O-RY 계통의 산자 수는 $28^{\circ}C\;에서\;25^{\circ}C$에서보다 1/10밖에 자충을 낳지 못하였다. 또한 충체중은 $28^{\circ}C$에서 URY-O와 유일은 각각 0.22와 0.27 mg/♀이었으나, O-RY는 0.16 mg/♀로서 차이가 컸다. 가수분해활성(n mol/IS min/female)이 19인 O-RY(-)9t 88인 O-RY(+)는 $28^{\circ}C에서\;G_1$, sub-strain의 산자수는 각각 3.4마리와 0.8마리로서 에스테라제 활성이 높은 O-RY(+)계통이 에스테라제 활성이 낮은 O-RY(-)계통보다 새끼수를 적게 낳았다.

• 대한치과교정학회지
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• 제48권6호
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• pp.384-394
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• 2018

Objective: This study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on time-dependent viscoelastic properties. Methods: Orthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated. Results: The degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length. Conclusions: Although prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.

• 한국직업건강간호학회지
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• 제17권2호
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• pp.216-223
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• 2008

Purpose: This study was performed to evaluate the worker's job stress status in the workplace of a local area. Method: Data were collected from October to December, 2007. The subjects were 208 workers at 2 work sites in Busan Metropolitan area, who were examined using Job-Strain-Model Questionnaire. Data were analyzed by SPSS 12.0 Win Program to get the percentage, mean, standard deviation, t-test, ${\chi}^2$-test, ANOVA. Results: The results of this study were as follows: In the mean sub-factors job stress level, the mean of job demand was $28.7{\pm}4.4$(median 29.0), the mean of job discretion was $54.7{\pm}8.2$(median 54.0), the mean of social support was $21.8{\pm}2.9$(range:8-32). This study's subjects were appeared as active group with relatively higher score of job demand and job discretion than the average value of those. There was no statistically significant difference of general characteristics among the different job strain groups. There was statistically significant difference with of social supports among the different job strain groups. Conclusion: In conclusion, the subjects of this study's were active group. Thus, it is suggested that it is be necessary to repeated the education of the job task work for active group with high score of job demand and job discretion.

• 대한핵의학회지
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• 제27권1호
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• pp.28-34
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• 1993

Using in vitro autoradiography with a digital autoradiography system and radioreceptor assay, the distribution and the binding characteristics of the muscarinic cholinergic receptors (mAChR) were studied in regions of rat brain. Radioreceptor assay revealed that mAChR could be measured with saturation binding assay in the brain and heart homogenates: No difference in Kd or Bmax of the brain or heart was found between the normal Wistar rats and SHR rats. Specific binding of $^3H$ quinuclidinyl benzilate (QNB) increased and saturation was reached by 2 hours after incubation with slide-mounted brain tissue. The distribution of mAChR was heterogeneous along the fields of brain. Affinity (Kd) of mAChR was not different significantly among cortex, hippocampus and caudate-putamen. No difference was found between normal rats and SHR strain. More receptors (Bmax) were found in the cortex and hippocampus than in the caudate-putamen in normal rats. More receptors were found in the cortex and caudate-putamen in SHR rats than in normal rats. Radioreceptor assay and digital autoradiographic analysis of affinity and number of mAChR gave the same results. With the above findings, we concluded that we could use digital autoradiographic system with $^3H$-QNB in the characterization of mAChR of rats and that the cortex and caudate-putamen of SHR strain rats have more receptors than those of normal rats.