• Coupled systems mechanics
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• 제12권6호
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• pp.539-555
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• 2023

Although some prediction models have successfully developed for ultra-high performance concrete (UHPC), they do not provide insights and explicit relations between all constituents and its consistency, and compressive strength. In the present study, based on the experimental results, several mathematical models have been evaluated to predict the consistency and the 28-day compressive strength of UHPC. The models used were Linear, Logarithmic, Inverse, Power, Compound, Quadratic, Cubic, Mixed, Sinusoidal and Cosine equations. The applicability and accuracy of these models were investigated using experimental data, which were collected from literature. The comparisons between the models and the experimental results confirm that the majority of models give acceptable prediction with a high accuracy and trivial error rates, except Linear, Mixed, Sinusoidal and Cosine equations. The assessment of the models using numerical methods revealed that the Quadratic and Inverse equations based models provide the highest predictability of the compressive strength at 28 days and consistency, respectively. Hence, they can be used as a reliable tool in mixture design of the UHPC.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.117-126
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• 2001

Tribological properties of high temperature fade were investigated by changing relative amounts of ingredients in the brake friction material. Based on a simple experimental formulation containing 10 ingredients, friction materials were tested using a pad-on-disk type friction tester. Twenty-five friction material specimens with different relative amounts of the ingredients were manufactured according to the constrained mixture design .The difference ($\Delta$${\mu}$=${\mu}$$\sub$max/. -${\mu}$$\sub$min/. ) of friction coefficients was measured to represent the high temperature fade. Results from elevated temperature tests showed that five ingredients including cashew, graphite, Sb$_2$S$_3$, ZrSiO$_4$, and Cu fibers played important roles on $\Delta$${\mu}$. In order to find relative importance on fade phenomena among these ingredients, ANOVA(analysis of variance) was performed in this investigation. Thirty-two friction material specimens by changing ${\pm}$50vol.％ of these five ingredients were tested to examine the relative importance. Results showed that cashew, graphite '||'&'||' Sb$_2$S$_3$, and cashew '||'&'||' graphite aggravated the fade behavior and Cu fibers improved on fade resistance.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.173-176
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• 2010

75톤급 가스발생기 기술검증시제에서 나타난 산화제 분사기 차압의 증가 원인을 파악하기 위하여 축소형 가스발생기를 설계, 제작하였다. 설계점 및 탈설계점 시험 조건을 포함한 총 6회의 연소시험을 성공적으로 수행하였다. 연소시험 결과 연소압을 고정한 후 혼합비를 증가시킨 경우 연료 및 산화제 유량계수는 일정한 것으로 나타났으며, 혼합비를 고정한 후 연소압을 증가시킨 경우에도 연료 및 산화제 유량계수는 변함이 없는 것으로 파악되었다.

• 한국식품영양과학회지
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• 제35권5호
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• pp.641-648
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• 2006

본 연구는 함초가루를 이용한 설기떡을 개발하기 위하여 재료의 최적 혼합비율을 찾는데 목적이 있다. 설기떡의 품질에 가장 영향을 미치는 수분, 함초가루, 설탕첨가율을 독립 변수로 설정하였고, 예비실험을 거쳐 수분 $13{\sim}18%$, 함초가루 $2{\sim}6%$, 설탕 $8{\sim}13%$의 범위에서 혼합물 실험계획법(mixture design) 중 D-optimal design을 이용하여 최적 재료 혼합비율을 찾고자 하였다. 각 설정된 범위를 입력하였을 때 10개의 실험점이 형성되었고, 4개의 반복점이 선택되어 실험점은 모두 14개가 설정되었다. 각 조건별 실험결과를 모델링화 하여 F-test를 통해 유의성을 검증한 결과 색도의 명도, 적색도, 황색도, 텍스쳐의 검성과 씹힘성, 관능검사 항목인 맛과 부드러운 정도는 linear 모델로 결정되었고, 텍스쳐의 경도, 관능검사의 색, 냄새, 촉촉한 정도, 전반적인 기호도는 quadratic 모델로 결정되었다. 모델의 적합성을 분석한 결과 모든 항목에서 probability가 모두 0.05% 이내에서 유의성을 보여 모델로서 적합함이 인정되었다. 반응표면과 trace plot의 결과 수분과 설탕첨가율이 높을수록, 함초가루 첨가량율이 낮을수록 명도는 높고, 적색도와 황색도는 낮았다. 텍스쳐의 경우 함초 첨가율이 증가할수록 경도, 검성, 씹힘성이 증가하여 함초가루의 첨가율이 높을 경우 설기떡의 부드러움을 저하하는 원인이 되었다. 관능검사 결과에서도 수분, 함초가루, 설탕을 많이 첨가할 경우에는 오히려 낮은 점수를 받았고, 특히 수분과 함초가루에 의하여 많은 영향을 받았다. 함초가루를 첨가한 설기떡의 최적 재료 혼합비율은 수치 최적화에서는 수분 15.2%, 함초가루 3.0%, 설탕 9.8%이었고, 모형적 최적화에서는 desirability가 0.620에 해당하는 수분 15.2%, 함초가루 3.1%, 설탕 9.7%로 수치 최적화점과 유사하게 나타났다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.250-253
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• 2003

This paper concerns about an experimental investigation about steering performance of tracked vehicle on extremely soft soil based on DOE(Design Of Experiment) using L8 orthogonal Array. A tracked vehicle model with principal dimensions of $0.9m{\times}0.8m{\times}0.4m$ and weight 167kg was constructed with a pair of driving chain links driven by two AC-servo motors. The tracks are configured with detachable grousers, the span of which can be varied. Deep seabed was simulated by means of bentonite-water mixture in a soil bin of $6.0m{\times}3.7m{\times}0.7m$. Turning radii of vehicle and torques of motors were measured with respect to experimental variables; steering ratio, driving speed, grouser chevron angle, grouser span, grouser height. The effects of experiment variables on steering performance are evaluated.

• Journal of Korean Biological Nursing Science
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• 제16권4호
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• pp.334-341
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• 2014

Purpose: The purpose of this study was to examine the effects of aroma-necklace application on perceived stress, symptoms of stress and changes in autonomic nervous system among nursing students in clinical training. Methods: A research design for this study was a non-equivalent control group, non-synchronized pre-post test. The experimental group (n=39) underwent aroma inhalation by necklace which contains an essential oil mixture of lavender and sweet orange mixture in ratio of 2:1 for 2 weeks while the control group (n=36) received placebo therapy. The data were collected using self-administered questionnaires and measurement of heart rate variability (HRV) and analyzed using the PASW 18.0 program. Results: The perceived stress scores and scores of peripheral manifestations in the experimental group were significantly lower than those of the control group. All indices of HRV were significantly different between the two groups. LF norm and LF/HF ratio in the experimental group were significantly lower than those of the control group, and HF norm in the experimental group was significantly higher than that in the control group. Conclusion: It can be suggested that aroma-necklace application was effective in decreasing perceived stress and peripheral manifestations of stress and in changing HRV indices among nursing students in clinical training.

• 대한기계학회논문집B
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• 제27권8호
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• pp.1051-1060
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• 2003

The heat and mass transfer on two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section, 3-tubes are horizontally installed, and steam-air mixture is vertically flowed from the top to the bottom. The pitch between tubes is 67mm, the out-diameter of tube is 25.4mm, and the thickness is 1.2mm ; blockage factor (cross sectional tube area over the cross sectional area of the test section) is about 0.38. All of sensors and measurement systems (RTD, pressure sensor, flow-meter, relative humidity sensor, etc.) are calibrated with certificated standard sensors and the uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 7%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. The degradation of overall heat transfer coefficient of Teflon coated tube comes from the additional heat transfer resistance due to Teflon coating. Its magnitude of heat transfer resistance is comparable to the in-tube heat transfer resistance. Nusselt and Sherwood numbers on Teflon (FEP) coated surface and bare stainless steel surface are discussed in detail with the contact angles of the condensate.

• 한국식품영양과학회지
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• 제37권4호
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• pp.505-511
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• 2008

고추장, 고춧가루, 과채열수추출액 첨가에 의한 돼지불고 기양념육의 항산화 증진 효과와 혼합물 실험설계법을 이용한 돼지불고기용 양념소스 재료의 최적 혼합 비율을 확립하고자 하였다. 냉동저장($-25^{\circ}C$, 5개월) 동안 간장양념을 사용한 대조구와 고추장양념첨가구(KG), 고추장양념.과채열수 추출액첨가구(KFVEG)의 TBA가는 저장기간 동안 원료육에 비해 모든 돼지불고기 양념육에서 낮게 유지되었다. 양념육 중에서는 대조구보다 고추장양념첨가구의 항산화력이 크게 우수하였으며, 고추장양념첨가구의 물 사용량을 과채 열수추출액으로 대체함으로써 항산화 상승작용이 유의적으로 나타났다. 따라서 양념소스에 고추장, 고춧가루, 과채열 수추출액 첨가로 돼지불고기양념육의 지방산화 안정성이 증진되었다. 양념육의 기호성은 고추장과 함께 사용된 고춧가루와 과채열수추출액 사용 비율이 증가함에 따라 향상되는 것으로 나타났다. 혼합물 실험 설계법에 의하여 추적된 돼지불고기용 고추장양념소스의 최적 혼합 비율은 고추장 0.04, 고춧가루 0.20, 과채열수추출액 0.39, 물 0.37로 나타났다.

• 한국게임학회 논문지
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• 제6권1호
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• pp.3-10
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• 2006

게임에서 레벨 디자인 (Level Design)과 캐릭터간의 밸런스는 게임의 흥미를 결정하는 매우 중요한 요소이며, 레벨 디자이너에 의해 결정 된다. 기존의 게임에서는 플레이어가 가장 큰 재미를 느낄 수 있는 캐릭터의 공격 패턴과 속성은 정적으로 정해졌으며 스크립트 형식으로 표현됐다. 이와 같이 정적으로 정해진 레벨에 따라 진행되면 플레이어가 쉽게 적응하게 되고, 플레이어의 학습능력에 따라 레벨 디자이너가 의도했던 밸런스가 깨질 수 있었다. 이런 문제점을 해결하기 위해 본 논문에서는 게임 도중에 플레이어의 대응 패턴을 GMM(Gaussian Mixture Model)으로 모델링하고 분석하여 레벨 디자이너가 의도했던 레벨과 재미를 느낄 수 있는 환경을 제공하는 방법을 제안한다. 제안한 방법을 실제 2D슈팅게임에 적용하여 플레이어의 패턴을 분석한 결과와 동적 레벨 디자인의 결과를 보인다.

• 한국기계가공학회지
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• 제21권8호
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• pp.79-86
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• 2022

With the recent increase in the demand for electric vehicles, it is necessary to identify the high current safety of automobile parts. Among the automobile parts, the EPDM parts required colored parts from the existing black; therefore, it was necessary to change the basic filler from carbon black to silica. The rubber used in automobile parts is flexible and exhibits basic characteristics of high strength and elongation. However, as the filler is changed to silica, its physical properties, such as tensile strength and elongation, are lower than those of the existing carbon black base. Therefore, it is necessary to evaluate the mechanical properties with the addition of the EPDM compound using silica as a base without degrading the physical properties of EPDM. In this study, an experiment based on the additive content was performed using the mixture experimental planning method to analyze the mechanical properties according to the additive type and mixing ratio of silica-based EPDM. The mixing ratio of the four additives was set using a simplex lattice design, and the tensile strength, elongation, modulus 300%, and permanent compression reduction rate were analyzed for mechanical characteristics, and rheometer experiments were performed for vulcanization characteristics. Through statistical analysis of the measured data, the main effects and interactions of the EPDM-blended rubber additives were analyzed. These results can be used to derive a mixing ratio of additives that satisfies the required characteristics of the EPDM compound.