Earticle

S-box mainly plays the role of confusion in the encryption process as an important component. For the new encryption algorithm PRESENT proposed in 2007, S-box impacts on the security of the encryption algorithm directly. This paper briefly describes the process of PRESENT algorithm and proposes an improved S-box to solve the problem that the original PRESENT S-box has anti-fixed point. Then a random PRESENT encryption algorithm based on dynamic S-box is proposed. The dynamic multiple S-boxes technology is used to implement random PRESENT algorithm, to enhance the security of the cryptographic algorithm. Finally, the security analysis is done, and it suggests that dynamic S-box has a superior ability to resist differential attack and linear attack. By comparison to the diffusion rate of original PRESENT S-box, our dynamic S-box has better avalanche effect.

Measuring occurrence times of random events, aimed to determine the statistical properties of the governing stochastic process, is a basic topic in science and engineering, and has been the subject of numerous mathematical modeling approaches. Often, true statistical properties deviate from measured properties due to the so called dead time phenomenon, where for a certain time period following detection, the detection system is not operational. Understanding the dead time effect is especially important in radiation measurements, often characterized by high count rates and a non-reducible detector dead time (originating in the physics of particle detection). The effect of dead time can be interpreted as a suitable rarefied sequence of the original time sequence. This paper provides a limit theorem for a high rate (diffusion-scale) counter with extendable (Type II) dead time, where the underlying counting process is a renewal process with finite second moment for the inter-event distribution. The results are very general, in the sense that they refer to a general inter arrival time and a random dead time with general distribution. Following the theoretical results, we will demonstrate the applicability of the results in three applications: serially connected components, multiplicity counting and measurements of aerosol spatial distribution.

The lithium ion diffusion coefficients of bare, carbon-coated and Cr-doped $LiFePO_4$ were obtained by fitting the discharge curves of each half cell with Li metal anode. Diffusion losses at discharge curves were acquired with experiment data and fitted to equations. Theoretically fitted equations showed good agreement with experimental results. Moreover, theoretical equations are able to predict lithium diffusion coefficient and discharge curves at various discharge rates. The obtained diffusion coefficients were similar to the true diffusion coefficient of phase transformation electrodes. Lithium ion diffusion is one of main factors that determine voltage drop in a half cell with $LiFePO_4$ cathode and Li metal anode. The high diffusion coefficient of carbon-coated and Cr-doped $LiFePO_4$ resulted in better performance at the discharge process. The performance at high discharge rate was improved much as diffusion coefficient increased.

In Part 1, the flame structure of the counterflow nonpremixed flames computed by using Fire Dynamics Simulator was compared with that of OPPDIF for different concentrations of methane in the fuel stream. In this study, comparisons were made for the global strain rate that is an important parameter for diffusion flames for further evaluation of FDS. At each of the three fuel concentrations, $20% CH_4＋ 80% N_2, 50% CH_4 ＋ 50% N_2, 90% CH_4 ＋ 10% N_2$ in the fuel stream, the temperature and axial velocity profiles were investigated for the global strain rate in the range from 20 to $100s^{-1}$. Changes in flame thickness and radius were also compared with OPPDIF. There was good agreement in the temperature and axial velocity profiles between the axisymmetric simulations and the one-dimensional computations except for the regions where the flame temperature reach its peak and the axial velocity rapidly changes. The simulations of the axisymmetric flames with FDS showed that the flame thickness decreases and the flame radius increases with increasing global strain rate.

증기-확산 단백질 결정화의 물-증발 속도를 조절하기 위해서, 간결한 모세관 내의 다중-단계 농도 장착법 (multistep-concentration setting in capillaries) 이 이용되었다. “조절 용액 (regulatory solution)”이라고 일컬어지는 2차 침전 용액이 이용되어, 이 방법으로 다양한 증발 속도 곡선들이 얻어졌다. 이때, 조절 용액은 단백질 용액에 직접적으로 노출되지 않는다. 모델 단백질인 lysozyme의 결정화에 이 그래프들이 적용되었다. 결정 성장은 증발속도에 달려있다는 것을 실험 결과들이 명백하게 보여주었다. 특히나. 단백질 용액의 침전 농도가 어떤 점까지 증가하다가 평형 농도로 줄어드는 decoupling 곡선이 가장 좋은 결정들을 만들어냈다.

A simple multistep-concentration setting in capillaries was used to control the water-evaporation rate in vapor-diffusion protein crystallization. In the method used, a variety of evaporation rate curves were obtained by using the secondary precipitant solution referred to as “regulatory solution”, which is not directly exposed to the protein solution. The curves were applied to the crystallization of lysozyme as a model protein. The results clearly showed that crystal growth is dependent on the evaporation rate. Especially, the decoupling curves in which precipitant concentration in protein solutions increases to a certain point and then decreases to the equilibrium concentration gave the best crystals.

In this note, we consider a system of two reaction-diffusion equations with absorption, under homogeneous Dirichlet boundary. Using scaling methods, we establish the blow-up rate estimates.

We will deal with an n locus model in which mutation and gene conversion are taken into consideration. Also random partitions of the number n determined by chromosomes with n loci should be investigated. The diffusion process describes the time evolution of distributions of the random partitions. In this paper, we find the probability of distribution of the diffusion process with special diffusion operator $L_1$ and we show that the average probability of genes at different loci on one chromosome can be described by the rate of gene frequency of mutation and gene conversion.

Generally, plasma nitriding process has composed with a nitriding layer within glow discharge region occurred by energy exchange. The dissociations of nitrogen molecules are very difficult to make neutral atoms or ionic nitrogen species via glow discharge area. However, the captured electrons in which a double-folded screen with same potential cathode can stimulate and come out some single atoms or activated ionic species. It was showed an important thing that is called "hat is a dominant component in this nitriding process?" in plasma nitriding process and it can take an effective species for without compound layer. During a plasma nitriding process, it was able to estimate with analyzing and identification by optical emission spectroscopy (OES) study. And then we can make comparative studies on the nitrogen transfer with plasma nitriding and ATONA process using plasma diagnosis and metallurgical observation. From these observations, we can understand role of active species of nitrogen, like N, $N^+$, ${N_2}^+$, ${N_2}^*$ and $NH_x$-radical, in bulk plasma of each process. And the same time, during DC plasma nitriding and other processes, the species of FeN atom or any ionic nitride species were not detected by OES analyzing.

본 연구는 고등학교 화학 Ⅱ 교과서에 제시되는 ‘기체의 확산속도 실험’에서 나타나는 문제점을 분석하고 그 원인을 실험과 이론적 고찰을 통해 이해함 과 더불어 개선된 실험을 제안하는 것을 목적으로 한다. 교과서에 제시된 확산속도 측정에 관한 전형적인 실험으로 유리관 양 끝에 염산과 암모니아수를 떨어뜨리고 여기서 발생한 염화수소 기체와 암모니아 기체가 확산하여 만나는 지점에서 나타나는 염화암모늄 흰 띠의 위치를 측정하였다. 생성된 흰 띠의 위치가 시간에 따라 일정하지 않고 이동하는 것이 관찰되었다. 이에 대한 원인을 찾기 위해서 순수한 기체 HCl과 NH_3를 사용하여 확산 실험을 수행하였고, 생성된 염화암모늄 흰 띠가 시간에 따라 이동하지 않는 것을 확인하였고 두 기체의 상대적 확산 거리는 Graham의 확산이론과 차이가 나고 Loschmidt의 확산이론과 일치하는 결과를 얻었다. 이 결과를 바탕으로 염산과 암모니아수의 농도를 다양하게 조절하여 두 용액에서 HCl과 NH_3 기체의 분압이 같아지는 조건을 찾을 수 있었고 이 조건에서 생성된 흰 띠의 위치가 변하지 않았고 그 위치는 이론으로 설명할 수 있었다. 본 연구를 통해 개선된 실험은 학습자의 실험에 대한 이해를 높이고 과학적 개념 도출에 도움을 줄 수 있을 것으로 기대된다.

This study is to analyze the problems observed in the experiment on ‘diffusion rate of gases’ in high school Chemistry Ⅱ text books and investigate the reason followed by suggestion of an improved experimental method. As typically introduced in textbooks, a few drops of HCl(aq) and NH_3(aq) were dropped at both ends of a glass tube, and then the position of ammonium chloride white ring created by the reaction with HCl(g) and NH_3(g) was measured. The position of the white ring changed with time. In order to investigate the reason of such change, the experiment was repeated using HCl and NH_3 gases, and the position of white ring did not changed with time. Meanwhile, the relative diffusion distance did not match with the theoretical expectation of the Graham's diffusion experiment but did with that of the Loschmidt's diffusion experiment. Based on this result experimental condition allowing equal partial pressure of HCl and NH_3 gases in hydrochloric acid and aqueous ammonia solution, respectively was found, and under the obtained condition the position of white ring did not change and was consistent with the theoretical expectation. This study is anticipated to help learners to understand the scientific concept of diffusion through the improved experiment.

메탄/질소-공기 저 신장율 대향류 확산화염에서 화염소화 거동과 에지화염의 진동불안정성에 대한 실험적 연구를 수행하였다. 특히, 저 신장율 화염에서 복사열손실 뿐만 아니라 측면전도 열손실이 현저해 진다. 각 전체 신장율에서 화염진동의 시작조건과 진동모드를 제안하였다. 화염길이는 측면 전도열손실과 밀접한 관계를 가지고 있으며 화염소화와 화염진동에 중대한 영향을 미친다. 저 신장율 에지화염의 진동모드는 성장모드, 감쇠모드 그리고 조화모드로 요약된다. 또한, 각 진동모드의 조건을 전체신장율과 희석제의 몰분율에 대한 안전화선도를 작성하였다.

Experiments in methane-air low strain rate counterflow diffusion flames diluted with nitrogen have been conducted to study the behavior of flame extinction and edge flame oscillation in which lateral conduction heat loss in addition to radiative heat loss could be remarkable at low global strain rates. Onset conditions of edge flame oscillation and flame oscillation modes are also provided with global strain rate. It is seen that flame length is closely relevant to lateral heat loss, and this affects flame extinction and edge flame oscillation. Edge flame oscillations in low strain rate flames are categorized into three: a growing oscillation mode, a decaying oscillation mode, and a harmonic oscillation mode. The regime of flame oscillation is also provided at low strain rate flames.

Experiments in methane-air low strain rate counterflow diffusion flames diluted with nitrogen have been conducted to study the behavior of flame extinction and edge flame oscillation in which flame length is less than the burner diameter and thus lateral conduction heat loss in addition to radiative heat loss could be remarkable at low global strain rates. Critical mole fraction at flame extinction is examined with velocity ratio and global strain rate. Onset conditions of edge flame oscillation and flame oscillation modes are also provided with global strain rate and added nitrogen mole fraction to fuel stream (fuel Lewis number). It is seen that flame length is closely relevant to lateral heat loss, and this affects flame extinction and edge flame oscillation considerably. Edge flame oscillations in low strain rate flames are experimentally described well and are categorized into three: a growing oscillation mode, a decaying oscillation mode, and a harmonic oscillation mode. The regime of flame oscillation is also provided at low strain rate flames. Important contribution of lateral heat loss even to edge flame oscillation is clarified.

Experiments have been conducted to clarify impacts of curtain flow and velocity ratio on low strain rate flame extinction, and to further display transition of shrinking flame disk to flame-hole. Critical mole fractions at flame extinction are examined in terms of velocity ratio, global strain rate, and nitrogen curtain flow rate. It is shown that multi-dimensional effects at low strain rate flames through global strain rate, velocity ratio, and curtain flowrate dominantly contribute to flame extinction and transition of shrinking flame disk to flame hole. Our concerns are particularly focused on the dynamic behavior of an edge flame in shrinking flame disk.

Reactivity of gasification defined by bouardard reaction is critical parameter in efficiency of the gasifier. In this study, char reactivity of the gasification was derived from the experiments using the intrinsic reaction kinetics model. Pressurized wire mesh heating reactor (PWMR) can produce high temperature and high pressure conditions up to 50 atm and 1750 K, respectively and PWMR was designed to evaluate the intrinsic reaction kinetics of $CO_2$ gasification. In this study, Kideco and KCH (sub-bituminous Indonesian coal) were pulverized and converted into char. Experiments used the PWMR were conducted and the conditions of the temperature and pressure were 1373~1673 K, 1~40 atm. To distinguish the pressure effect from high pressurized condition, internal and external effectiveness factors were considered. Finally, the intrinsic kinetics of the Kideco and KCH coal char were derived from $n^{th}$ order reaction rate equations.

급속 혼화공정에서 응집제의 동력학적 수화반응 특성을 고려하여 1초 이내의 순간혼합을 제시하고 있으며, 이러한 이론에 근거하여 설치된 Pump Diffusion Mixer(PDM)의 관내 응집제 확산 분포특성을 조사하였다. D=1,200mm 관경에서 압력수 유량비에 따라 응집제 주입지점으로부터 4.5D되는 지점에서 관 단면의 지점별 제타 전위를 측정하여 평가한 결과, 압력수의 유량비가 2%에서는 분사속도가 낮아 관 단면에 응집제가 골고루 분사되지 못하는 것으로 조사되었다. 그러나 압력수 유량비가 4% 이상이 되면 비교적 균등하게 혼합되며, 8%에서는 관 단면 전체에 균등하게 확산 분포되는 것으로 나타났다.

This study collected the latest 30-year (1976~2005) continuous rainfall data hourly recorded at 61 meterological observatories in Korea, and the continuous rainfall data was divided into individual rainfall events. In addition, distribution charts of average rainfall event-depth were created to facilitate the application to the overflow risk-based design of detention storage basin. This study shows that 4 hour is appropriate for SST (storm separation time) to separate individual rainfall events from the continuous rainfall data, and the one-parameter exponential distribution is suitable for the frequency distribution of rainfall event depths for the domestic rainfall data. The analysis of the domestic rainfall data using SST of 4 hour showed that the individual rainfall event was 1380 to 2031 times, the average rainfall event-depth was 19.1 to 32.4mm, and ranged between 0.877 and 0.926. Distribution charts of average rainfall event-depth were created for 4hour and 6 hour of SST, respectively. The inland Gyeongsangbuk-do, Western coastal area and inland of Jeollabuk-do had relatively lower average rainfall event-depth, whereas Southern coastal area, such as Namhae, Yeosu, and Jeju-do had relatively higher average rainfall event-depth.

본 연구에서는 S15C 및 S45C의 이온 질화에 있어서 확산층 및 합성층의 생성 속도를 계산하였고 이를 기초로 질소의 활성화 에너지를 구하였다.

This paper deals with nitrogen diffusion velocity and activation energy in diffusion layer and compound layer in ion-nitriding, and presents observations on the effect of deformation according to nitriding methods. During the experiment the activation energy and diffusion velocity of nitrogen have been examined in S45C steel samples. It is found that the results of an investigation correspond with the theoretical data and the ion-nitriding method offers less deformation than conventional salt-bath method of nitriding.

이 논문에서는 한국의 주별 익일물 콜금리를 사용해 국면전환 확산과정모형을 추정했다. 일반적인 비선형 추세 함수와 분산 탄력성이 상수인 변동성 함수를 갖는 확산과정모형에서 모수들이 경제상황에 따라 서로 다른 두 가지 값을 가질 수 있도록 모형을 설정한 후에 최우도추정법을 이용해 모형을 추정했다. 우도를 계산하기 위해 해밀턴의 알고리즘을 이용하고, 확산과정의 전이확률밀도 함수가 알려져 있지 않기 때문에 Aït-Sahalia (2008)의 축소가능하지 않은 방법을 이용해 근사적 로그-전이확률밀도 함수를 구체적인 식으로 구한 후에 Choi (2015a)의 방법으로 전이확률밀도 함수를 구했다. 서로 다른 두 국면 L과 H가 존재한다는 여러 가지 증거들을 확인할 수 있었으며 추세 함수보다는 변동성 함수가 두 국면 모두에서 이자율의 움직임을 설명하는 데 중요한 역할을 한다는 사실을 밝혔다. 또한 국면변수의 변화를 결정하는 전이 확률이 이자율에 의존해 시간에 따라 변하며 이자율이 늘어날수록 다음 기에도 같은 국면 L에 머무를 확률은 줄어들고 같은 국면 H에 머무를 확률은 증가함을 알 수 있었다. 각 데이터 시점에서 추정된 국면 H의 평활확률은 시계열 자료에서 대체로 변동성이 큰 부분은 1과 가깝고 작은 부분은 0과 가까워 뚜렷하게 다른 두 국면이 있다는 증거가 된다. 마지막으로 주요 모형과 이 모형에 포함된 기존의 연구들에서 사용됐던 다른 모형들을 비교했을 때 일반적인 모형이 더 선호됨을 알 수 있었다.

This paper estimates a regime-switching diffusion process model for Korean call rate. Parameters of the diffusion model with nonlinear general drift and volatility function vary depending on the economic states and are estimated using maximum likelihood method. In order to obtain the maximum likelihood estimates, we use the algorithm of Hamilton (1989) and calculate transition probability density function(TPDF) using Choi (2015a)’s method from the approximate log-TPDF obtained by Ait-Sahalia (2008)’s irreducible method. We find evidences that there exist two different regime and that the volatility term of the model explains the movements of the call rate better than the drift term. Also, the model shows that the transition probability varies depending on the level of interest rate. As interest rate increases, the probability of remaining at the same regime “L” next period decreases while the probability for the regime “H” increases. The estimated smoothed probability of regime “H,” which is close to 1 and 0 during the period with high and low volatility respectively, is a clear evidence of the existence of two different regimes. Lastly, comparison with existing models demonstrates that the generalized model in this paper is preferred in explaining the call rate behaviour.

본 연구의 목적은 국내 화력발전소에서 사용중인 인도네시아 석탄촤의 연소반응율을 연구하는 것이다. 석탄촤의 반응율은 External, Internal effectiveness factor를 고려하여 입자 내부 및 외부확산을 정량적으로 정리하였으며, Random pore model을 사용하여 탄소변환율에 따른 입자내부비표면적의 변화를 반영하였다. 가열 및 측정이 가능한 WHR(Wire Heating Reactor)를 활용하여 반응시간을 측정함으로써 석탄촤의 반응율을 도출하였고 BET(Brunauer-Emmett-Teller) 및 TGA(Thermo-Gravimetric Analysis) 장비를 활용하여 석탄촤의 물리적인 특성인 내부비표면적과 Random pore model의 구조변수(${\Psi}$)를 측정하였다. 석탄 종에 따른 활성화에너지 및 빈도인자를 도출하기 위해 아역청탄인 BARAMULTI, ENERGYMAN, AGM탄을 사용하였다. 본 연구 결과에서 External, Internal effectiveness factors를 통해 확산에 따른 kinetics를 비교한 결과 외부 확산 보다 내부 확산의 영향이 지배적임을 확인하였다. 최종적으로 내부 및 외부 확산에 대한 영향을 고려한 3종의 석탄촤 Intrinsic kinetics의 활성화에너지는 110~118 kJ/mol의 값을 보였다.

The experiment was designed to compare the char combustion kinetics of pulverized Indonesia coals commonly utilized in Korea power plants. The reaction rate of coal char has been formulated using the external and internal effectiveness factors to describe the diffusion effect quantitatively. The Random Pore Model (RPM) was used for applying internal specific surface area as a function of carbon conversion ratio. Reaction rate was obtained from reaction time using the Wire Heating Reactor (WHR) which can heat and measure the char particle temperature at the same time. BET and TGA were used to obtain physical properties such as internal specific surface area and structural parameter. Three kinds of Indonesia Sub-bituminous coals "BARAMULTI, ENERGYMAN, AGM" were used in order to derive the activation energy and pre-exponential factor. The results of this study showed that the effect of internal diffusion than that of external diffusion is the dominant as comparison of kinetics was reflected in external and internal effectiveness factors. For three kinds of coal char, finally, activation energy of intrinsic kinetics indicates 110~118 kJ/mol.