• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.677-684
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• 2013

A mixed refrigerant cycle (MRC) has been widely used in liquefaction of natural gas because it is simple and easily operable with reasonable equipment costs. One of the important techniques in MRC is selection of a refrigerant mixture and decision of its optimum mixing ratio. In this work, it is examined whether mixture components (refrigerants) and their mixing ratio influence performance of general MRC processes. In doing this, mixture design and response surface method, which are well-known statistical techniques, are used to find optimal mixture refrigerants and their optimal mixing ratio that minimize total energy consumption of the entire liquefaction process. A MRC process using several refrigerants and various mixing ratios is simulated by Aspen HYSYS and mixture design and response surface method are implemented using Minitab. According to the results, methane ($C_1$), ethane ($C_2$), propane ($C_3$) and nitrogen ($N_2$) are selected as best mixture refrigerants and the determined mixture ratio (mole ration) can reduce total energy consumption by up to 50%.

• Nuclear Engineering and Technology
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• v.56 no.11
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• pp.4716-4723
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• 2024

Metallic alloy fuels from fast reactors will be reprocessed by a non-aqueous electrochemical technique known as electrorefining. Electrorefining of spent metal fuel results in the accumulation of heat generating fission products especially ¹³⁷Cs in the electrolyte, which is a eutectic salt mixture of 44 wt% LiCl and 56 wt% KCl. The fission products need to be removed from the salt so as to reduce the decay heat load and contamination thereby facilitating reuse of the salt and minimizing waste generation. Melt crystallization technique is a simple separation process being pursued for separation of fission products. This is a single step process which utilizes the difference in solubility of fission products in the solid and liquid phase. Crystallization involves purification of a substance from a liquid mixture by solidification of the desired component. Numerical modeling of separation of CsCl from a LiCl-KCl eutectic mixture by solidification was carried out using ANSYS Fluent (19.2). The enrichment of CsCl during solidification, its distribution in molten salt and segregation time were evaluated. Further, solidification experiments were conducted using the molten salt mixture and the predicted numerical results were validated.

• Health Policy and Management
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• v.12 no.2
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• pp.1-22
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• 2002

Since the early 1980s scholars have applied latent structure and other type of finite mixture models from various academic fields. Although the merits of finite mixture model are well documented, the attempt to apply the mixture model to medical service has been relatively rare. The researchers aim to try to fill this gap by introducing finite mixture model and segmenting inpatients DB from one general hospital. In section 2 finite mixture models are compared with clustering, chi-square analysis, and discriminant analysis based on Wedel and Kamakura(2000)'s segmentation methodology schemata. The mixture model shows the optimal segments number and fuzzy classification for each observation by EM(expectation-maximization algorism). The finite mixture model is to unfix the sample, to Identify the groups, and to estimate the parameters of the density function underlying the observed data within each group. In section 3 and 4 we illustrate results of segmenting 4510 patients data including menial and ratio scales. And then, we show AHP can be identify the attractiveness of each segment, in which the decision maker can select the best target segment.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.1
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• pp.23-31
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• 2020

It is essential to estimate the vehicle localization for an autonomous safety driving. In particular, since LIDAR provides precise scan data, many studies carried out to estimate the vehicle localization using LIDAR and pre-generated map. The road marking always exists on the road because of provides driving information. Therefore, it is often used for map information. In this paper, we propose to generate the Gaussian mixture map based on road-marking information and localization method using this map. Generally, the probability distributions map stores the single Gaussian distribution for each grid. However, single resolution probability distributions map cannot express complex shapes when grid resolution is large. In addition, when grid resolution is small, map size is bigger and process time is longer. Therefore, it is difficult to apply the road marking. On the other hand, Gaussian mixture distribution can effectively express the road marking by several probability distributions. In this paper, we generate Gaussian mixture map and perform vehicle localization using Gaussian mixture map. Localization performance is analyzed through the experimental result.

• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.38-42
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• 2008

Miniature J-T cryocooler using nitrogen or argon has been widely adopted in cooling infrared sensor for space/military application and cryosurgery. Argon or nitrogen, however, has relatively low specific cooling power compared to nitrous oxide, but the ultimate operating temperature is much lower than nitrous oxide. On the other hand, nitrous oxide has large specific cooling power, but the operating temperature is limited to its boiling point (>183K). To compromise the different characteristics of these gases, the performance of miniature J-T cryocooler using argon and nitrous oxide mixture is investigated in this paper. Three different compositions of mixture (25/75, 50/50, and 75/25 molar fraction) are blended and tested. The results are compared with the experiments of pure argon and pure nitrous oxide. The experimental results show some encouraging potentiality of mixed refrigerant J-T cryocooler. The critical clogging problem, however, was observed with argon and nitrous oxide mixture, and the lowest achievable temperature with this mixture was limited to the freezing point of nitrous oxide. The paper discusses detailed clogging process of the mixture and suggests an alternative.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.55-60
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• 2017

The supercritical $CO_2$ (sc-$CO_2$) mixture and the sc-$CO_2$-based Photoresist(PR) stripping(SCPS) process were applied to the removal of the post etch/ash PR residue on aluminum patterned wafers and the results were observed by scanning of electron microscope(SEM). In the case of MDII wafers, the carbonized PR was able to be effectively removed without pre-stripping by oxygen plasma ashing by using sc-$CO_2$ mixture containing the optimum formulated additives at the proper pressure and temperature, and the same result was also able to be obtained in the case of HDII wafer. It was found that the efficiency of SCPS of ion implanted wafer improved as the temperature of SCPS was high, so a very large amount of MEA in the sc-$CO_2$ mixture could be reduced if the temperature could be increased at condition that a process permits, and the ion implanted photoresist(IIP) on the wafer was able to be removed completely without pre-treatment of plasma ashing by using the only 1 step SCPS process. By using SCPS process, PR polymers formed on sidewalls of metal conductive layers such as aluminum films, titanium and titanium nitride films by dry etching and ashing processes were removed effectively with the minimization of the corrosion of the metal conductive layers.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.1
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• pp.101-106
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• 1993

In order to separate the Freon-12 and air mixture$(CF_2Cl_2/Air=0.1/99.9 vol.%)$ by pressure swing adsorption (PSA), the breakthrough curve was experimentally observed in a fixed bed adsorption column. A single adsorber was packed with various adsorbents such as, the activated carbon(S-AC, W-AC) and the molecular sieve(MS-5A, MS-13X). The order of appearance of breakthrough curve is MS-5A > MS-13X > W-AC > S-AC. The activated carbon was found to be more effective adsorbent for separating Freon-12 from the mixture than the molecular sieve was. From the experimental data obtained by the separation of Freon-12 gas out of the air stream in the steady-state PSA process cycle, whose size is the same one of column used for the breakthrough curve observation, it has been confirmed that Freon-rich gas could be obtained from the purge step of PSA and Freon-free air could be obtained from the adsorption step of PSA cycle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.2
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• pp.111-121
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• 1993

Double-diffusive convection during solidification process of the binary mixture was studied numerically. Enthalpy method and finite element method were implemented in the analysis. Calculation carried out for $R{\alpha}_T=10^3-10^4$ and $R{\alpha}_T=0-10^5$. The results show that the variation of thermal Rayleigh number changes the fields of velocity, temperature and concentration, but the variation of solutal Rayleigh number gives little effects on those. In conclusion, concentration gradient can be negligible compared with temperature gradient in macroscopic point of view, although concentration gradient plays a role in forming dendrite.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.05a
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• pp.197-200
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• 2004

Compared to conventional flame combustion, catalytic combustion had the advantage of oxidation of V.O.C. gas which was high voluminous, low caloric mixture flow. However, the temperature of mixture gas should be over the one of catalytic reaction start and the control of reaction on the catalytic surface tends to be vulnerable. To overcome these obstacles, composition of both catalytic combustor and heat exchanger was devised and named the sequential catalytic combustion system. In this system, only trigger unit needed preheating process for transient starting time. Once trigger unit was ignited, the next unit w3s supplied heat to ignite from that and same process was performed to the last one sequentially. When it come to steady state, whole mixture gas was oxidated at each unit simultaneously and preheating for trigger unit was not needed any more. System of 100 kcalh/hr capacity was devised and operated successfully.

• International Journal of Automotive Technology
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• v.2 no.1
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• pp.25-31
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• 2001

It is necessary to understand the combustion process and cycle-by-cycle variation in combustion to improve the engine stability and consequently to improve the fuel economy and exhaust emissions. The pressure related parameters instead of mass fraction burned were compared for the effect of initial combustion pressures on the following combustion and the analysis of cycle-by-cycle variation in combustion for two pen injected SI engines. The correlation between IMEP and pressures at referenced crank angles showed almost the same trends for equivalence ratios, but the different mixture preparations indicated different tendency. The dependency of IMEP on pressure at the referenced crank angles increases as the mixture becomes leaner for both engines. The mixture distribution in the combustion chamber was varied with the coolant temperature and intake valve deactivation due to the evaporation of fuel and air motion. The correlation between pressure related parameters were also compared for the coolant temperatures and air motion.