기후변화 관점에서 수목의 이산화탄소 흡수·저장에 대한 관심이 높아지고 있으며, 도시 정주지 수목을 대상으로 한 탄소저장량 추정 모형의 개발에 대한 필요성도 증가하고 있다. 본 연구는 도시 지역에 조경수로 식재된 서양측백(Thuja occidentalis L.) 20본을 벌채한 후 수목 부위별 탄소 농도를 비교하고 탄소저장량 추정 상대생장식을 개발하였다. 수목 부위별 바이오매스는 흉고직경(DBH)의 증가와 강한 지수함수적 관계가 있었다. 수목 부위별 탄소 농도는 줄기 목질부가 51.7%로 가장 높은 값을 보였으며 뿌리는 42.9%로 가장 낮았다. 줄기 목질부 탄소 농도는 흉고직경과 양의 상관관계가 있었으나, 수피, 가지, 잎, 뿌리의 탄소 농도는 흉고직경과 상관관계가 나타나지 않았다. 흉고직경 또는 흉고직경 제곱과 수고(DBH2×H)를 독립변수로 하고 수목 부위별 탄소저장량을 종속변수로 하는 상대생장식의 결정계수(R2)는 잎(0.70~0.71)을 제외한 모든 부위에서 0.80~0.97로 나타났다. 본 연구 결과로부터 얻어진 수목 부위별 탄소저장량 추정 상대생장식은 도시 정주지에 식재된 서양측백의 탄소저장 량 및 흡수량의 추정에 활용이 가능할 것으로 사료된다.

For the sake of future generations, the management of radioactive waste is essential. The disposal of spent nuclear fuel (SNF) is considered an urgent challenge to ensure human safety by storing it until its radioactivity drops to a negligible level. Evaluating the safety of disposal facilities is crucial to guarantee their durability for more than 100,000 years, a period sufficient for SNF radioactivity to become ignored. Past studies have proposed various parameters for forecasting the safety of SNF disposal. Among these, radiochemistry and electrochemistry play pivotal roles in predicting the corrosion-related chemical reactions occurring within the SNF and the structural materials of disposal facilities. Our study considers an extreme scenario where the SNF canister becomes compromised, allowing underground water to infiltrate and contact the SNF. We aim to improve the corrosion mechanism and mass-balance equation compared with what Shoesmith et al. proved under the same circumstances. To enhance the comprehensibility of the chemical reactions occurring within the breached SNF canister, we have organized these reactions into eight categories: mass diffusion, alpha radiolysis, adsorption, hydrate formation, solidification, decomposition, ionization, and oxidation. After categorization, we define how each species interacts with others and calculate the rate of change in species’ concentrations resulting from these reactions. By summing up the concentration change rates of each species due to these reactions, we redefine the mass-balance equations for each species. These newly categorized equations, which have not been explained in detail previously, offer a detailed description of corrosion reactions. This comprehensive understanding allows us to evaluate the safety implications of a compromised SNF canister and the associated disposal facilities by numerically solving the mass-balance equations.

In this paper, the physical model and governing equations of a shallow arch with a moving boundary were studied. A model with a moving boundary can be easily found in a long span retractable roof, and it corresponds to a problem of a non-cylindrical domain in which the boundary moves with time. In particular, a motion equation of a shallow arch having a moving boundary is expressed in the form of an integral-differential equation. This is expressed by the time-varying integration interval of the integral coefficient term in the arch equation with an un-movable boundary. Also, the change in internal force due to the moving boundary is also considered. Therefore, in this study, the governing equation was derived by transforming the equation of the non-cylindrical domain into the cylindrical domain to solve this problem. A governing equation for vertical vibration was derived from the transformed equation, where a sinusoidal function was used as the orthonormal basis. Terms that consider the effect of the moving boundary over time in the original equation were added in the equation of the transformed cylindrical problem. In addition, a solution was obtained using a numerical analysis technique in a symmetric mode arch system, and the result effectively reflected the effect of the moving boundary.

PURPOSES : Steel deck bridges are the preferred structural type for reducing dead load, and the use of thin-layer asphalt concrete with excellent adhesion to the steel deck and excellent deformation followability is increasing for bridge pavements. However, because these materials are constructed at a high temperature of 240 °C or higher to maintain high fluidity during construction, excessive thermal deformation and stress may be temporarily induced in the steel deck. Therefore, the stability of the structure must be assessed by considering the environmental conditions of the site during pavement construction. Herein, a method is presented for estimating the heat source equation, in which conduction and convection effects are removed using temperature measurement data, for modeling U-rib using plate elements. The validity of the study is assessed by deriving the equivalent heat source equation using the temperature data measured from the underside of the steel deck while constructing a 40-mm-thick goose asphalt concrete pavement layer on a 12-mm-thick steel deck. In addition, the practicality is verified by performing heat transfer and thermal stress analyses. METHODS : By comparing the temperature data measured during the construction of high-fluidity asphalt concrete with the results of repeated heat transfer numerical analysis, heat source data without field conduction and convection conditions are obtained. Subsequently, a heat source equation suitable for the heat source data is derived using the least-squares method. RESULTS : The results of the heat transfer analysis using the equivalent heat source equation calculated using the presented method are almost consistent with the measured temperature data. In addition, the behavioral characteristics of the structure that matches the behavior of the actual structure can be derived through thermal stress analysis, which considers heat conduction and convection to adjacent members. CONCLUSIONS : Even when the steel deck and U-rib member are modeled as plate elements, thermal effect analysis can be performed reasonably while considering field conditions.

목적 : 수치 해석을 통해 Gullstrand 모형안에서 광학적 특성(초점거리, 구면수차 및 초점심도)를 분석했다. 방법 : 광학상수 값(방수)이 수정된 Gullstrand 모형안(각막 전·후면, 수정체 피질 전·후면 및 수정체 핵질 전·후면)을 사용하였다. 평행광선이 입사되었을 때 근축 근사 없는 Snell의 법칙에 따른 눈의 광학적 특성을 수치적으로 분석하였다. 결과 : 모형안으로 입사된 모든 평행광선은 입사 높이가 증가할수록 초점거리, 구면수차 및 초점심도에서 각각 비선형적으로 감소, 증가 및 감소한 것으로 나타났으며, 일반적으로 알려진 근축 근사가 적용된 Gullstrand 정식 모형안의 결과와 잘 일치되었다. 결론 : 생체적 분석이 제한될 수밖에 없는 눈의 광학적 특성을 근축 근사 없이 수치적으로 분석할 수 있었다. 이를 기반으로 다양한 눈의 광학적 현상을 이해할 수 있을 것으로 판단된다.

We present numerical simulations of decaying hydrodynamic turbulence initially driven by solenoidal (divergence-free) and compressive (curl-free) drivings. Most previous numerical studies for decaying turbulence assume an isothermal equation of state (EOS). Here we use a polytropic EOS, P ∝ ργ, with polytropic exponent γ ranging from 0.7 to 5/3. We mainly aim at determining the effects of γ and driving schemes on the decay law of turbulence energy, E ∝ t-α. We additionally study probability density function (PDF) of gas density and skewness of the distribution in polytropic turbulence driven by compressive driving. Our findings are as follows. First of all, we find that even if γ does not strongly change the decay law, the driving schemes weakly change the relation; in our all simulations, turbulence decays with α ≈ 1, but compressive driving yields smaller α than solenoidal driving at the same sonic Mach number. Second, we calculate compressive and solenoidal velocity components separately and compare their decay rates in turbulence initially driven by compressive driving. We find that the former decays much faster so that it ends up having a smaller fraction than the latter. Third, the density PDF of compressively driven turbulence with γ > 1 deviates from log-normal distribution: it has a power-law tail at low density as in the case of solenoidally driven turbulence. However, as it decays, the density PDF becomes approximately log-normal. We discuss why decay rates of compressive and solenoidal velocity components are different in compressively driven turbulence and astrophysical implication of our findings.

완도수목원내 백운로 상부의 붉가시나무림을 대상으로 난대 상록활엽수림 복원 시 붉가시나무의 성장 및 종실공급과 관련된 기초정보를 제공하는 목적으로 붉가시나무의 성장 및 결실특성을 조사하고 종실량 상대성장식을 구하였다. 성장특성은 평균흉 고직경급에 속하는 실생 임목 3주의 표본목을 선정 벌목하여 수간석해하였다. 표본목의 평균치의 수령(X)에 의한 흉고직경과 수고의 성장특성(Y)의 상대성장식(Y=aX+b)을 개발하였으며, 추정식에 의한 붉가시나무 수령에 따른 흉고직경 및 수고를 추정하였다. 결실특성은 성숙종실초기인 8월에 평균 흉고직경급에 속하는 임목을 대상으로 결실이 충실한 임목 3주의 표본목을 선정 벌목하여 조사하였다. 붉가시나무의 종실량 상대성장식을 개발하기 위하여 결실목 중 흉고직경이 고르게 10주의 표본목을 선정 벌목하였다. 벌목한 표본목은 흉고직경, 수고, 수관폭, 수관고 등의 성장특성(X)과 종실량(Y)을 조사 분석하여 종실량 상대성장식(Y=aXb)을 유도하였다. 표본목 평균치의 수령에 의한 상대성장식은 흉고직경 Y=0506X-2.064(R2=0.999), 수고 Y=0.321X+0689(R2=0.992)이었다. 개발된 상대성장식에 의하여 수령 10, 20, 30, 40년일 때 흉고직경은 각각 3.0㎝, 8.1㎝, 13.1㎝, 18.2㎝, 수고는 각각 3.9m, 7.1m, 10.3m, 13.5m가 되는 것으로 추정되었다. 결실특성 조사 결과 결과모지(結果母枝) 당 잎 수를 제외한 결과모지의 길이, 직경, 결과모지 당 결과지 수, 종실 수는 유의적인 차이를 보였으며, 수관 상, 중, 하부로 갈수록 감소하였다. 종실 총수의 경우 수관 상, 중, 하부 각각 1,312립, 115립, 5립이었다. 붉가시나무 표본목을 일괄하여 추정한 종실량 상대성장식의 흉고직경(D)를 독립변수로 하는 상대성장식은 Y=0.003X4.260, 결정계수(R2)은 0.896이었다. 흉고직경만을 독립변수로 하는 상대성장식은 흉고직경과 수고(D2H)를 독립변수로 하는 결정계수가 다소 낮으나, 측정오차를 고려하면, 흉고직경만을 독립변수로 하는 상대성장식을 적용하는 것이 실용적이라고 판단된다.

Many reinforced concrete (RC) buildings constructed prior to 1980's lack important features guaranteeing ductile response under earthquake excitation. Structural components in such buildings, especially columns, do not satisfy the reinforcement details demanded by current seismic design codes. Columns with deficient reinforcement details may suffer significant damage when subjected to cyclic lateral loads. They can also experience rapid lateral strength degradation induced by shear failure. The objective of this study is to accurately simulate the load-deformation response of RC columns experiencing shear failure. In order to do so, model parameters are calibrated to the load-deformation response of 40 RC column specimens failed in shear. Multivariate stepwise regression analyses are conducted to develop the relationship between the model parameters and physical parameters of RC column specimens. It is shown that the proposed predictive equations successfully estimated the model parameters of RC column specimens with great accuracy. The proposed equations also showed better accuracy than the existing ones.

곰솔의 줄기밀도, 현존량 확장계수, 상대생장식 및 임분 현존량을 파악하기 위하여 전라남도 여수지역에 위치하고 있는 15년생, 29년생, 45년생 등 3개 곰솔 천연임분을 대상으로 임분별 5주씩 총 15주의 표본목을 선정 벌목하여 조사하였다. 줄기밀도는 0.440-0.457g/cm³이었으며, 임분간 유의적인 차이는 없었다. 지상부와 뿌리를 포함한 임목 전체의 현존량 확장계수는 모두 임령이 증가할수록 감소하였으며, 임분 1은 지상부 현존량 확장계수에서 임분 2, 3과 유의적인 차이가 있었고, 임목 전체 현존량 확장계수에서 임분 3과 유의적인 차이가 있었다. 이것은 임령이 증가할수록 줄기의 건중량 구성비가 높아지기 때문이며, 임분 1의 경우 유령림의 생장특성을 보이기 때문으로 판단되었다. 흉고직경(D) 또는 흉고직경과 수고(D2H)를 독립변수로 하고 부위별 건중량(Wt)을 종속변수로 하는 2개 유형의 상대생장식(Wt=aDb, Wt=a(D2H)b)을 유도하고 적합도를 검정하였다. 임분 1, 2, 3의 지상부 현존량은 각각 50.72t/ha, 89.92t/ha, 194.07t/ha이었으며, 뿌리를 포함한 임목 전체 현존량은 각각 61.62t/ha, 113.12t/ha, 248.36t/ha이었다.

For evaluating equations of bursting force in different codes, comparative study of the formulas was conducted. Because the equations does not consider variables such as shape of anchorages, angle of tendons, and eccentricity, a relation between the bursting forces and the variables has to be analyzed. In this paper, therefore, a comparative analysis of bursting forces computed by equations in the codes and finite element analysis was performed. As a result, it could be figured out that bursting force equations in the local zone were determined by coefficient k.

Three bamboo stands(Phyllostachys pubescens(Mazel) Ohwi, P. bambusoides Sieb. et Zucc, P. nigra var. henonis Stapf ex. Rendle) were selected to determine suitable biomass equations and productivity of Gajwa and Wola National Experimental Forests, Jinju, Southern Korea. Different independent variables such as diameter at breast height(DBH) or the combination of DBH and height(H) were used to develop biomass equations(Allometric model : logY = a + blog DBH; Linear-quadratic model : Y=aDBH + bDBH2; Linear model with DBH and height : Y=a + bDBH2·H) for each bamboo component from two age-sequence(current-year, > 1-year-old) of three bamboo stands. Based on statistical indicators, the most suitable equation model to estimate biomass from bamboo stands was a linear-quadratic model. Aboveground biomass of three bamboo stands estimated by the model was 48.864 Mg ha-1 for the P. pubescens, followed by 36.632 Mg ha-1 for the P. bambusoides, and 36.504 Mg ha-1 for the P. nigra var. henonis stands, respectively. The highest biomass in the P. pubescens stand was attributed to the morphological growth characteristics such as DBH and height. Belowground biomass was also highest for P. pubescens(53.35 Mg ha-1), followed by the P. bambusoides(36.73 Mg ha-1) and the P. nigra var. henonis(29.75 Mg ha-1) stands. The results indicate that the morphological growth characteristics such as DBH and height among bamboo species were the most important factor to determine bamboo biomass productivity at a local level.

The cyclic behavior of braces is complex due to their asymmetric properties in tension and compression. For accurately simulating the cyclic curves of braces, it is important to predict the major parameters such as cyclic brace growth, cyclic buckling load, incidence local buckling and fracture with good precision. For a given brace, the most accurate values of these parameters can be estimated throughout experiments. However, it is almost impossible to conduct experiments whenever an analytical model has to be established for many braces in building structures due to enormous cost and time. For avoid such difficulties, empirical equations for predicting constituent parameters are proposed from regression analyses based on test results of various braces. This study focuses on rectangular hollow structural section(HSS) steel braces, which have been popularly used in construction practice owing to its sectional efficiency.

This study was conducted to evaluate the effect of site quality on allometric equations, stem density and biomass expansion factors(BEFs) in a 20-year-old Machilus thunbergii plantation. The study site was located in Jindo county, Chollanam-do, southern Korea. Total 14 trees were harvested from the good site(tree height: 6.7 m) or poor site(tree height: 4.6 m) assumed by tree height growth. Allometric equations, stem density and biomass expansion factors were calculated from the sampled trees. Site-specific allometric equations of tree components were significant(p<0.05) with diameter at breast height(DBH). Also, generalized allometric equations could be applied to estimate tree biomass regardless of the difference of site quality because of no significant effect on slope of site-specific allometric equations. Aboveground tree biomass was significantly higher in the good site(81.0 Mg ha-1) than in the poor site(46.3 Mg ha-1). Stem density was not significantly different between in the good site(0.65 g cm-3) than in the poor site(0.67 g cm-3), whereas aboveground tree and leaf BEFs were significantly higher(p<0.05) in the poor site(aboveground: 2.23; leaf: 0.42) than in the good site(aboveground: 1.82; leaf: 0.23). The results indicated that aboveground Biomass and Biomass expansion factors of a Machilus thunbergii plantation were affected by site quality.

In this study, the height of the flame required to estimate the heat flow path and flame spread in pool fire has been applied by the empirical formula, but it is calculated without applying the pressure and temperature parameters of the fire room. Until now, the height of the flame applied to pool fire was      in the Heskestad empirical formula, but accurate temperature calculation was not possible due to the temperature and pressure which are not influenced by the flame height. Therefore, applying the temperature and pressure around it can calculate the exact flame height, which can be applied to fire investigation and fire dynamics. The structure of the flame is divided into a continuous flame, an intermittent flame, and a buoyancy flame, but it is assumed that the flame height is calculated from the visual aspect to the intermittent flame region, and the temperature of the buoyancy flame is very low. The effect of heat of vaporization on the height of flame was investigated. The results showed that flame height was different according to the pressure and temperature around the fire room.

사용후핵연료 파이로 공정은 전기화학 이론들에 기초하여 개발되고 있다. 공정 모사는 공정 개발과 실험데이터 해석에 주 요한 방법 중 하나로 파이로 공정에서도 필요한 접근 방법 중 하나이다. 현재까지 파이로 공정의 공정 모사는 전해정련 공 정 위주로 진행되어 왔으며 전해환원 공정에 대한 연구는 많지 않았다. 전해환원 공정은 전해정련 공정과 달리 기체 발생과 다공성 전극의 특징을 지니고 있기 때문에 공정 모사를 위한 모델 개발을 위해서는 이를 고려한 수식들이 필요하게 된다. 본 연구에서는 전기화학 셀 해석에 필요한 열역학, 물질전달, 반응공학 이론 중 전해환원 공정 모델 개발에 필요한 개념과 수식 들을 정리하여 제시하였다. 전해환원 셀을 구분하여 각 부분에 적용해야하는 수식들을 나열했으며 각 부분들 연결에 사용되 는 경계조건들 역시 제시하였다. 이들 수식들은 추후 모델 개발에 기초로 사용될 수 있으며 실험데이터와 결합시켜 결정되 어야 하는 매개변수 파악에 활용될 수 있을 것으로 기대된다.

본 연구의 목적은 중부지방소나무와 굴참나무의 부위별 바이오매스 상대생장식 개발에 있다. 부위별 상 대생장식의 개발을 위하여 축적 및 임분의 구조를 고려하여 중부지방소나무에서 30개소 (70그루), 굴참나무에서 15개소 (32그루)를 선정하고 시료를 수집하였다. 바이오매스의 추정에 이용된 인자는 흉고직경, 흉고직경과 수고를 이용하는 두 가지이며, 지수식, 대수식, 2차방정식의 형태로 구분하였다. 최적의 상대 생장식을 도출하기 위하여 이용된 통계량은 적합도지수 (FI), 잔차의 평균 (Bias), 잔차의 표준오차 (SEE) 이다. 이를 통하여 추정된 수종별 바이오매스 상대생장식은 중부지방소나무에서 W=aDb, W=aDbHc 식이 적합하며 적합도는 0.937, 0.943이다. 반면, 굴참나무는 W=a＋bD＋cD2, W=aDbHc 식이 적합 하며 적합도는 0.865, 0.874이다. 또한, 중부지방소나무와 굴참나무의 부위별 바이오매스 상대생장식은 중부지방소나무 W=aDb이고, 굴참나무 W=a＋bD＋cD2으로 나타났다. 본 연구의 결과로 제시된 중부 지방소나무, 굴참나무의 바이오매스 상대생장식은 일부지역에 국한되어 개발되었던 상대생장식에 대한 단점을 보완할 수 있을 것이며 이들 수종에 대한 탄소량의 계정에 활용이 가능할 것이다.

한국형 포장 콘크리트에 있어 구조해석은 다양한 입력변수와 공용성 모형을 연결해주는 중간 매개체 역할을 하고 있어 그 중 요도가 매우 크다. 본 연구에서는 ABAQUS 구조해석 프로그램을 Shell 요소를 이용하여 콘크리트 포장의 거동을 분석할 수 있는 구조해석 기본 모형을 구축하였다. 이 모형을 Closed-Form Solution과 정확성이 검증된 Everfe 프로그램, 그리고 Solid 요소 모형과 비교하여 정확도를 검증하였다. 기본 Shell 모형을 이용하여 다양한 변수에 대한 구조해석을 수행하였으며 그 결과를 DB화하였다. SPSS 통계 프로그램과 해석 결과를 바탕으로 회귀식을 개발하였으며 온도 응력, 상향 응력, 하향 응력을 산정할 수 있는 응력식을 제안하였다.