• 공업화학
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• 제34권2호
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• pp.144-152
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• 2023

연소성 물질의 화재위험성 평가를 하기 위해 Chung's equations-VII, Chung's equations-VIII, 그리고 Chung's equation-IX 을 새로 정립하였다. 화재위험성지수-IX (fire risk index-IX, FRI-IX)와 화재위험성등급(fire risk rating, FRR)을 산정하였다. 시험편은 은행나무, 메타세콰이어, 참죽나무, 피나무, 호두나무를 선택하였다. 콘칼로리미터(ISO 5660-1)를 사용하여 시험편에 대한 연소 특성을 시험하였다. 연소 종료 후 Chung's equations에 의해 산정된 화재성능지수-VII (fire performance index-VII, FPI-VII)는 15.15~182.53 s²/kW로 나타났고, 화재성장지수-VII (fire growth index-VII, FGI-VII)는 0.0023~0.0165 kW/s²로 나타났다. Polymethylmethacrylate (PMMA)를 기준으로 한 화재성능지수-VIII (FPI-VIII)는 0.29~3.45로 나타났고, 화재성장지수-VIII (FGI-VIII)는 2.88~20.63로 나타났다. 화재위험성 등급인 화재위험성지수-IX(FRI-IX)는 메타세콰이어가 71.14 (화재위험성등급: G)로 화재위험성이 매우 높은 목재로 나타났다. 그러므로 휘발성 유기 화합물을 다량 함유하고, 체적밀도가 낮은 목재는 FPI-VII와 FPI-VIII가 낮아지고, FGI-VII와 FGI-VIII가 높아짐에 의하여 FRI-IX가 높은 값을 나타내었다.

• Journal of Biosystems Engineering
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• 제13권4호
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• pp.1-8
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• 1988

A series of soil bin experiments was carried out on land to evaluate the soil physical properties whether they are pertinent to soil-wheel system and to investigate if true model theory u applicable to powered rigid wheel-soil system. Four different sized wheels having diameter of 45, 60, 75 and 90 em were wed for the experiment. The following conclusion was derived from the study. (1) True model theory can be sufficiently utilized to study the wheel traction and linkage on lands. (2) For both dry and wet sands, Cone Index(CI) and soil shear parameters (c, ${\phi}$) with bulk density (${\gamma}$) were found to be good measures of soil physical properties which are pertinent to predict the performance of the powered rigid wheel-soil system.

• 복식문화연구
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• 제8권2호
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• pp.282-292
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• 2000

The purpose of this study is to provide for some basic data useful to the development of the brassieres comfortable and more suitable for obese women. The results of this study can be summarized as follows ; 1. Obese women were categorized using Rohrer index into three groups, and thereupon, their breast forms were analyzed. As a result, it was found that group 1 and 2 had similar small breasts, while group 3 had the largest size of breasts. 2. The forms of obese women's breast split, protrusion and volume, factors related with breast area and drooping, factor affecting the breast protrusion and factor defining the lower form of breast. 3. The actual breast types of obese women could be classified into cone type, protrusion type, drooping type Ⅰ and Ⅱ. The more obese a woman was, her breast tended more to droop.

• Steel and Composite Structures
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• 제14권4호
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• pp.397-408
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• 2013

This paper deals with multiobjective optimization of symmetrically laminated composite truncated circular conical shells subjected to external uniform pressure load and thermal load. The design objective is the maximization of the weighted sum of the critical buckling load and fundamental frequency. The design variable is the fibre orientations in the layers. The performance index is formulated as the weighted sum of individual objectives in order to obtain optimal solutions of the design problem. The first-order shear deformation theory (FSDT) is used in the mathematical formulation of laminated truncated conical shells. Finally, the effect of different weighting factors, length-to-radius ratio, semi-cone angle and boundary conditions on the optimal design is investigated and the results are compared.

• 대한수학회논문집
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• 제21권4호
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• pp.701-717
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• 2006

The positive coexistence of a simple food chain model with ratio-dependent functional response and cross-diffusion is discussed. Especially, when a cross-diffusion is small enough, the existence of positive solutions of the system concerned can be expected. The extinction conditions for all three interacting species and for one or two of three species are studied. Moreover, when a cross-diffusion is sufficiently large, the extinction of prey species with cross-diffusion interaction to predator occurs. The method employed is the comparison argument for elliptic problem and fixed point theory in a positive cone on a Banach space.

• International Journal of Concrete Structures and Materials
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• 제6권1호
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• pp.59-64
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• 2012

Sand-concrete is being researched for potential usage in construction in Saharan regions of Algeria, because of shortage in coarse aggregate resources. This research work deals with the effect of dune sand, available in huge quantities in these regions, on the properties of flowing sand-concrete (FSC) prepared with different proportions of dune and river sands. Mini-cone slump test, v-funnel flow-time test and viscosity measurements were used to characterize the behaviour of FSC in fresh state. The 28-day compressive strength was also determined. Test results show that an optimal content of dune sand, which makes satisfied fresh and hardened properties of FSC, is obtained. Moreover, the obtained flow index (constant b) calculated by the help of power-law viscosity model is successfully correlated to the experimental results of v-funnel flow time.

• Journal of the Korean Wood Science and Technology
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• 제42권5호
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• pp.590-596
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• 2014

Wooden cultural heritages of Korea have been destroyed by fire in many cases. As a result, a number of methods to protect wooden cultural properties against fire were introduced. A way of protecting wooden cultural properties installations of fire equipments such as sprinkler, fire alarm system, or fire extinguisher. Another way of protecting wooden cultural properties is to treat them with flame retardants for their safety. Development of a very effective flame retardant with a good performance without affecting danchung and wood quality is required. At the same time, methods of evaluating flame retardant treated woods should be devised to assess their efficacy. In this study, combustion characteristics using cone-calorimeter, limit oxygen index, moisture absorption, iron corrosive and weathering were analyzed to evaluate the flame resistance efficacy and performance of flame retardants treated woods. The evaluation methods of flame retardants for wooden cultural heritage were suggested.

• Journal of Korean Vacuum Science & Technology
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• 제3권1호
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• pp.30-32
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• 1999

Electron beam trajectory simulation results on the high voltage FED with cone-type field emitters predict that the cross-talk phenomena would be seen due to the divergence of the electron beam. In this study, computer simulations with design of experiment technique and the SNU-FEAT program were carried out for five input parameters of the aperture focusing structure. The results tell that the focusing voltage is a dominant factor. And, the beam divergence index could be reduced to 10.7$\mu\textrm{m}$ with the aperture focusing structure, however, the operating voltage of the field emitter is predicted to increase by 40% maximum.

• 공업화학
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• 제21권4호
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• pp.469-474
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• 2010

목재는 연소성이 높은 본질적인 결함을 가지고 있다. 본 연구의 목적은 자연 건조된 굴참나무와 느티나무의 연소성질을 시험하였다. 열방출율과 CO/$CO_2$ 발생과 연기차폐와 같은 연기지수를 콘칼로리미터(ISO 5660-1)를 이용하여 측정하였다. $50kW/m^2$의 외부 열유속하에서 굴참나무의 총 방출열량, THR ($140.2MJ/m^2$)은 느티나무의 THR ($85.7MJ/m^2$) 과 비교하여 높게 나타났다. 그리고 굴참나무의 총 연기발생량, $TSP3.50m^2$는 느티나무의 $TSP0.65m^2$에 비하여 높게 나타났다. 이들 결과는 시험목의 체적밀도에 의존함을 보여준다. CO/$CO_2$ 발생비는 굴참나무와 느티나무가 각각 0.053, 0.043을 나타내었다. 또한 느티나무가 굴참나무에 비해 숯생성으로 인한 증대된 연소 억제성을 보여주었다.

• Imaging Science in Dentistry
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• 제50권2호
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• pp.117-124
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• 2020

Purpose: The purpose of this study was to evaluate possible differences in the location of the inferior alveolar canal in male and female Egyptians. Materials and Methods: This cross-sectional retrospective study involved the evaluation of 210 CBCT scans of Egyptian individuals (18-70 years old). The inferior alveolar canal was localized by measuring 8 linear dimensions: 2 for the vertical localization of the mental foramen (superior and inferior to the mental foramen), 4 at the first molar bifurcation for the vertical and horizontal localization of the inferior alveolar canal (superior, inferior, buccal, and lingual to the inferior alveolar canal), and 2 for the horizontal localization of the mandibular foramen (anterior and posterior to the mandibular foramen). The measurements were statistically analyzed via comparative analysis, stepwise logistic regression, and receiver operating characteristic (ROC) curve analysis. Results: Six of the 8 measured distances differed to a statistically significant extent between the sexes. Regression analysis suggested a logistic function with a concordance index of 84%. The diagnostic accuracy capabilities of the linear measurements as sex predictors were calculated using ROC analysis, and the 6 best predictors for sex determination were selected and ranked from highest to lowest predictive power. Moreover, combining these 6 predictors increased the predictive power to 84%. Conclusion: The location of the inferior alveolar canal in the Egyptian population varies significantly by sex; accordingly, this anatomic landmark could be used as a reliable indicator of sexual dimorphism.