• 한국자동차공학회논문집
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• 제18권1호
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• pp.131-138
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• 2010

Because real flow of engine exhaust is very hot and highly transient, it may cause thermal and inertial loads on catalyzed filters in DPF. Transient and detailed flow and thermal simulations are necessary in this field. To assess the importance of time dependent phenomena, typical cone-type configuration such as an underbody DPF is selected for steady and transient analysis. User defined functions of FLUENT by sinusoidal inlet velocities are written and integrated with main solver for realistic simulation. Also, 4-cylinder and 6-cylinder engines for 3,000 L class are considered for the dynamic exhaust effect of engine type. Key parameters to understanding of catalyst performance and durability issues such as flow uniformity index and peak velocity are investigated. Also, pressure drop for engine power are considered. From the simulation results for three different cases, proper approach is recommended.

• 한국산림과학회지
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• 제38권1호
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• pp.33-45
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• 1978

본(本) 연구(硏究)는 소나무천연집단(天然集團)의 유전변이(遺傳變異)를 분석(分析)하는데 목적(目的)이 있다. 1974년도(年度)의 선발(選拔)에 이어서 1975년도(年度)에 3개(個)소나무천연집단(天然集團) 각각(各各)으로부터 20주(株)씩의 개체(個體)가 선발(選拔)되고 또 그들의 풍매종자(風媒種子)가 채취(採取)되었으며 그 집단(集團)들의 소재지역(所在地域)과 상태(狀態)는 표(表) 1, 2 및 그림 1에 기술(記述)되어 있다. 그 집단(集團)들의 몇몇 형태학적특징(形態學的特徵)들은 이미 보고(報告)된 논문(論文)(II)에 상술(詳述)되어 있으며 거기에서는 명주(溟洲) 및 울진집단(蔚珍集團)이 수원집단(水原集團)에 비(比)해 직관적(直觀的)으로 보아 우량(優良)한 것으로 판단 되었다. 본(本) 논문(論文)에서는 앞서 발표(發表)된 논문(論文)(III)의 방법(方法)에 따라서 구과(毬果), 종자(種子), 종자익(種子翼)의 형태학적(形態學的)인 특성(特性)과 아울러 묘목(苗木)의 성장(成長) 및 그 침엽(針葉)의 특성(特性)이 조사(調査)되었으며 얻어진 결과(結果)는 다음과 같이 요약(要約)된다. 1. 각집단(各集團)에서 가장 가까운 측후소(測候所)에서 측정(測定)된 30년(年) (1931~1960)간(間)의 기록(記錄)을 평균(平均)해서 얻어진 기상자료(氣象資料)는 그림 2, 3, 4에 보인다. 조사(調査)된 기후조건(氣候條件)은 대체로 지역간(地域間)에 유사(類似)하지만 수원지역(水原地域)의 여름철 강우량(降雨量)과 겨울철 기온(氣溫)이 타지역(他地域)과 크게 달랐다. 2. 구과(毬果)의 생중량(生重量), 길이, 직경(直徑), 형상비(形狀比)의 측정치(測定値)는 표(表) 7에 기재(記載)되어 있으며 구과직경(毬果直徑)을 제외(除外)한 다른 모든 조사(調査)된 특성(特性)은 집단간(集團間), 집단내가계간(集團內家系間)에 유의(有意)한 통계적차이(統計的差異)가 인정(認定)되었다. 3. 종자(種子)와 종자익(種子翼)의 형태학적특성(形態學的特性)은 표(表) 8, 9에 상술(詳述)되었으며 종자(種子)와 종자익(種子翼)의 길이 및 형상비(形狀比) 그리고 종자중량(種子重量)에서는 집단간(集團間), 집단내가계간(集團內家系間)에 유의차(有意差)가 인정(認定)되지만 다른 특성(特性)에서는 집단간(集團間)에 유의차(有意差)가 인정(認定)되지 않았다. 구과(毬果)와 종자(種子) 특성간(特性間)의 상관계수(相關係數)의 값은 표(表) 10에 주어져 있으며 비교(比較)된 특성(特性)의 대부분(大部分)에서 정(正)의 상관계수(相關係數)가 인정(認定)되었다. 4. 차대(次代)의 1-0묘(苗)와 1-1묘(苗)의 묘고성장(苗高成長)에서 집단간(集團間), 집단내가계간(集團內家系間) 통계적(統計的)인 유의차(有意差)가 인정(認定)되었지만 근원경(根元徑)에서는 집단내(集團內) 가계간(家系間)에만 그 차(差)가 인정(認定)되었다. 표(表)13에 보인바와 같이 묘목(苗木)의 성장(成長)과 종자(種子)의 특성간(特性間)에는 대부분 상관(相關)이 통계학적(統計學的)으로 인정(認定)되지 않았다. 5. 3개집단(個集團)의 각가계별(各家系別)로 묘목(苗木)에 있어서 침엽양면(針葉兩面)의 기공열수(氣孔列數)와 거치밀도(鋸齒密度)가 측정(測定)되었으며 표(表)14에 보이는 것처럼 거치밀도(鋸齒密度)에서는 집단간(集團間), 집단내가계간(集團內家系間)에 유의차(有意差)가 인정(認定)되었지만 기공별(氣孔別)에서는 집단간(集團間) 차이(差異)가 인정(認定)되지 않았다. 그 결과(結果)는 논문(論文)(III)의 것과 다르며 그 원인(原因)의 하나는 선발(選拔)된 집단(集團)의 다양성(多樣性) 때문인 것으로도 생각된다. 차대(次代)와 모수(母樹)와의 침엽형질(針葉形質)에서의 상관(相關)은 표(表)15에 보이는 바와 같이 대체로 인정(認定)되지 않았다.

• 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.