• 대기
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• 제22권3호
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• pp.287-298
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• 2012

The predictability of heavy precipitation over the Korean Peninsula is studied using THORPEX Interactive Grand Global Ensemble (TIGGE) data. The performance of the six ensemble models is compared through the inconsistency (or jumpiness) and Root Mean Square Error (RMSE) for MSLP, T850 and H500. Grand Ensemble (GE) of the three best ensemble models (ECMWF, UKMO and CMA) with equal weight and without bias correction is consisted. The jumpiness calculated in this study indicates that the GE is more consistent than each single ensemble model. Brier Score (BS) of precipitation also shows that the GE outperforms. The GE is used for a case study of a heavy rainfall event in Korean Peninsula on 9 July 2009. The probability forecast of precipitation using 90 members of the GE and the percentage of 90 members exceeding 90 percentile in climatological Probability Density Function (PDF) of observed precipitation are calculated. As the GE is excellent in possibility of potential detection of heavy rainfall, GE is more skillful than the single ensemble model and can lead to a heavy rainfall warning in medium-range. If the performance of each single ensemble model is also improved, GE can provide better performance.

• 한국응용과학기술학회지
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• 제23권4호
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• pp.280-289
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• 2006

Multilayer adsorptions and BET adsorption are analyzed statistical-mechanically. Which ensemble is selected for the analysis is unimportant, because each ensemble yields the same results. However, the amount of mathematical manipulations and the matter of convenience vary from ensemble to ensemble. Hence, multilayer adsorptions and BET adsorption are examined using a canonical and a grand canonical ensembles, and an ensemble of subsystems. Also, the characteristics of multilayer and BET adsorptions are delineated.

• 대한화학회지
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• 제3권1호
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• pp.3-8
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• 1954

Fowler obtained thermodynamic quantities assuming the theory which could be derived by representing the system with microcanonical ensemble, in order to introduce the temperature T of the system proper, he considered the combined systems which are composed of the system proper and another arbitrary system that is in thermal contact with the former, and represented the combined system by a microcanonical ensemble, here, he used the steepest descent method in his calculation. This Fowler's treatment is not only unsatisfactory at the point of theoretical view but also he could not make the formulation of free energy of Helmholtz's so that this formular was forced to be assumed. From the point of Quantum Statistical Mechanical view, the materially closed system which is in an equilibrium state with the temperature T is best represented by canonical ensemble. At the actual derivation of the distribution law and thermodynamic quantities, however, in order to avoid the difficulty of calculation Tolman proceeded his calculation either representing the system proper by the grand-canonical ensemble or adding a certain limitation.

• 대기
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• 제24권1호
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• pp.1-15
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• 2014

This study compared ensemble mean and probability forecasts of snow depth amount associated with winter storm over South Korea on 28 December 2012 at five operational forecast centers (CMA, ECMWF, NCEP, KMA, and UMKO). And cause of difference in predicted snow depth at each Ensemble Prediction System (EPS) was investigated by using THe Observing system Research and Predictability EXperiment (THORPEX) Interactive Grand Global Ensemble (TIGGE) data. This snowfall event occurred due to low pressure passing through South Sea of Korea. Amount of 6 hr accumulated snow depth was more than 10 cm over southern region of South Korea In this case study, ECMWF showed best prediction skill for the spatio-temporal distribution of snow depth. At first, ECMWF EPS has been consistently enhancing the indications present in ensemble mean snow depth forecasts from 7-day lead time. Secondly, its ensemble probabilities in excess of 2~5 cm/6 hour have been coincided with observation frequencies. And this snowfall case could be predicted from 5-day lead time by using 10-day lag ensemble mean 6 hr accumulated snow depth distribution. In addition, the cause of good performances at ECMWF EPS in predicted snow depth amounts was due to outstanding prediction ability of forming inversion layer with below $0^{\circ}C$ temperature in low level (below 850 hPa) according to $35^{\circ}N$ at 1-day lead time.

• Bulletin of the Korean Chemical Society
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• 제18권3호
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• pp.291-295
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• 1997

The adsorption of methane in K+ ion exchanged zeolite L has been studied using grand canonical ensemble Monte Carlo simulation. Average number of molecules per unit cell, number density of molecules in zeolite, distribution of molecules per unit cell, average potential per sorbate molecule, and isosteric heats of adsorption were calculated, and these results were compared with experimental results. The simulation results agreed fairly well with experimental ones. All methane molecules were located in the main channel, and the average potential of sorbate molecule was almost constant regardless of average number of molecules per unit cell and the amounts sorbed in zeolite.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2553-2559
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• 2012

The adsorption properties of benzene, toluene, p-xylene in MCM-41 with heterogeneous and cylindrical pore were studied using grand canonical ensemble Monte Carlo simulation. The simulated isotherms were compared with experimental ones, and the different adsorption behaviors in MCM-41 with pore diameters of 2.2 and 3.2 nm were investigated. The simulated adsorption amounts above the capillary-condensation pressure agreed with the experimental ones. The simulation results showed that most molecular planes were nearly parallel to the pore axis. This orientation was not affected by the molecular position in the pore. The molecular planes were nearly parallel to the pore surface for the adsorbate molecules close to the pore wall, and the molecules in the MCM-41 with the pore diameter of 3.2 nm were ordered along the pore axis.

• 대한화학회지
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• 제15권6호
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• pp.285-293
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• 1971

The statistical thermodynamical properties of heavy water are calculated according to the transient state theory of significant liquid structure. The calculated values are shown to be in good agreement with the observed ones. The grand canonical ensemble partition function for the adsorbed phase of heavy water on graphite surface is derived using the theory. The adsorption isotherm, the surface pressure, the molar entropy and the molar internal energy for the adsorbed phase and then the molar heat of adsorption are calculated according to the derived partition function. The thermodynamic properties of the adsorbed water are also calculated and the results are compared with those of heavy water and discussed in view of the experimentally observed phenomena.

• 대한화학회지
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• 제42권1호
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• pp.16-21
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• 1998

칼륨이온이 교환된 제올라이트 L중 에탄과 프로판의 흡착 성질을 그랜드 카노니칼 앙상블 몬테칼로 시뮬레이션을 이용하여 연구하였다. 퍼텐셜 계산에서 흡착분자의 $CH_3\;와\; CH_2$그룹을 하나의 유사원자로 고려하였으며, 분자 내의 결합길이와 결합각도는 시뮬레이션 과정에서 고정시켰다. 단위세포당 평균 분자수, 단위세포당 분자들의 분포, 제올라이트 중 분자의 수밀도, 흡착 분자의 평균 퍼텐셜, 그리고 등량흡착열을 계산하였고, 이들을 실험 결과와 비교하였다. 에탄의 시뮬레이션 결과는 넓은 온도 범위에서 실험값과 상당히 잘 일치하였다. 에탄과 프로판 분자의 퍼텐셜은 흡착량의 증가에 따라 천천히 감소하였다.

• 대한화학회지
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• 제14권1호
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• pp.97-107
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• 1970

액체 구조의 천이상태 이론을 써서 고체 표면에 기체가 흡착된 계에 대한 상태합을 유도하였다. 이 상태합을 써서 아르곤, 질소, 벤젠 등이 여러 가지 흡착제에 흡착되었을 때의 흡착등온 곡선을 계산하였으며, 이 계산 값들은 측정치와의 좋은 일치를 보여 준다. 그리고 벤젠이 흑연 표면에 흡착되었을 때의 표면압, 물엔트로피, 물에너지, 몰흡착열 들을 계산하였다. 몰엔트로피는 표면이 단분자층으로 완전히 덮였을 때 최소값을 갖는다. 아울러 흡착에 관여된 여러 가지 물리적인 성질들의 계산 방법을 설명하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.113.2-113.2
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• 2010

We report that the novel covalent organic frameworks (COFs) are capable of reversibly providing an extremely high uptake capacity of carbon dioxide and hydrogen at room temperature. These COFs are designed based on the multiscale simulations approach via the combination of ab initio calculations and force-field calculations. For this goal, we explore the adsorption sites of carbon dioxide and hydrogen on COFs, their porosity, as well as carbon dioxide adsorption isotherms. We identify the binding sites and energies of $CO_2$ on COFs using ab initio calculations and obtain the carbon dioxide adsorption isotherms using grand canonical ensemble Monte Carlo calculations. Moreover, the calculated adsorption isotherms are compared with the experimental values in order to build the reference model in describing the interactions between the $CO_2/H_2$ and the COFs and in predicting the $CO_2$ and $H_2$ adsorption isotherms of COFs. Finally, we design three new COFs, 2D COF-05, 3D COF-05 (ctn), and 3D COF-05 (bor), for the high capacity $CO_2/H_2$ and $H_2$ storage.