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Intensified Low-Temperature Fischer-Tropsch Synthesis Using Microchannel Reactor Block : A Computational Fluid Dynamics Simulation Study (마이크로채널 반응기를 이용한 강화된 저온 피셔-트롭쉬 합성반응의 전산유체역학적 해석)

  • Kshetrimatum, Krishnadash S.;Na, Jonggeol;Park, Seongho;Jung, Ikhwan;Lee, Yongkyu;Han, Chonghun
    • Journal of the Korean Institute of Gas
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    • v.21 no.4
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    • pp.92-102
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    • 2017
  • Fischer-Tropsch synthesis reaction converts syngas (mixture of CO and H2) to valuable hydrocarbon products. Simulation of low temperature Fischer -Tropsch Synthesis reaction and heat transfer at intensified process condition using catalyst filled single and multichannel microchannel reactor is considered. Single channel model simulation indicated potential for process intensification (higher GHSV of 30000hr1 in presence of theoretical Cobalt based super-active catalyst) while still achieving CO conversion greater than ~65% and C5+ selectivity greater than ~74%. Conjugate heat transfer simulation with multichannel reactor block models considering three different combinations of reactor configuration and coolant type predicted ΔTmax equal to 23 K for cross-flow configuration with wall boiling coolant, 15 K for co-current flow configuration with subcooled coolant, and 13 K for co-current flow configuration with wall boiling coolant. In the range of temperature maintained (498 - 521 K), chain growth probability calculated is desirable for low-temperature Fisher-Tropsch Synthesis.

RBM-based distributed representation of language (RBM을 이용한 언어의 분산 표상화)

  • You, Heejo;Nam, Kichun;Nam, Hosung
    • Korean Journal of Cognitive Science
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    • v.28 no.2
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    • pp.111-131
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    • 2017
  • The connectionist model is one approach to studying language processing from a computational perspective. And building a representation in the connectionist model study is just as important as making the structure of the model in that it determines the level of learning and performance of the model. The connectionist model has been constructed in two different ways: localist representation and distributed representation. However, the localist representation used in the previous studies had limitations in that the unit of the output layer having a rare target activation value is inactivated, and the past distributed representation has the limitation of difficulty in confirming the result by the opacity of the displayed information. This has been a limitation of the overall connection model study. In this paper, we present a new method to induce distributed representation with local representation using abstraction of information, which is a feature of restricted Boltzmann machine, with respect to the limitation of such representation of the past. As a result, our proposed method effectively solves the problem of conventional representation by using the method of information compression and inverse transformation of distributed representation into local representation.

MILP-Espresso-Based Automatic Searching Method for Differential Charactertistics (효율적인 MILP-Espresso 기반 차분 특성 자동 탐색 방법)

  • Park, YeonJi;Lee, HoChang;Hong, Deukjo;Hong, Seokhie
    • Journal of the Korea Institute of Information Security & Cryptology
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    • v.28 no.3
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    • pp.533-543
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    • 2018
  • In this paper, we propose an MILP-based method for Optimal Probability of Bit-based Differential Characteristic in SP(Substitution-permutation) ciphers based on Automatic Differential Characteristic Searching Method of Sasaki, et al. In [13], they used input/output variables and probability variables seperatably, but we simplify searching procedure by putting them(variables) together into linear inequalities. Also, In order to decrease the more linear inequalities, we choose Espresso algorithm among that used by Sasaki, et al(Quine-McCluskey algorithm & Espresso algorithm). Moreover, we apply our method to GIFT-64, GIFT-128, SKINNY-64, and we obtained results in the GIFT(Active S-boxs : 6, Probabilities : 211.415) compared with the existing one.(Active S-boxs : 5, Probabilities : unknown). In case of SKINNY-64, we can't find better result, but can find same result compared with the existing one.

Evaluation and Analysis of The Building Energy Saving Performance by Component of Wood Products Using EnergyPlus (EnergyPlus를 이용한 건물 부위별 목질제품 적용에 따른 건축물 에너지 절감 기여도 평가)

  • Seo, Jungki;Wi, Seunghwan;Kim, Sumin
    • Journal of the Korean Wood Science and Technology
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    • v.44 no.5
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    • pp.655-663
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    • 2016
  • Increasing green house gas and it consequent climate change problems are discussed as a global issue. Accordingly, future local green house gas emission will increase up to 40% of the entire local green house gas emission and therefore, efforts to reduce the emission in construction industry is urgently required. Therefore, in this study, heating energy demand was analyzed by using the EnergyPlus simulation according to wood material finishes configuration. EnergyPlus has the entry for a variety of buildings and heating, ventilation, air conditioning (HAVC) system components, in particular buildings, air conditioning systems, and performs simultaneous integrated calculated through the feedback between the heat source unit, a verification program according to the ASHRAE Standard 140-2007 to be. The climate data for the simulation we used the data IWEC in Incheon and Gwangju provided by EnergyPlus. The analysis of simulation model was farm and fishing house standard design drawings: 2012, presented at the Korea Rural Community Corporation. The results of simulation of central region and southern region were effected by wood products of simulation model into the interior finish, exterior finish, windows, wooden structure. Also, it was confirmed that the reduced heating energy demand.

Calculation of Motor Power with Convenience Equipment for Pepper and Fruit Vegetable Harvest (고추 및 노지채소 수확작업 편이장치의 구동모터 선정)

  • Kim, Yeongsu;Jang, SukGeun;Kim, JiMan;Choi, Hwon;Oh, Sungkil;Lim, HackKyu;Kim, TeaHan
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • 2017.04a
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    • pp.61-61
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    • 2017
  • 노지 고추 수확작업은 100% 인력에 의존하고 있으며 7~9월에 걸쳐 5~6회의 다수의 작업이 수행되어 노동 강도가 크다. 또한 농촌의 고령화와 노동력 감소로 인하여 수확인력의 부족이 발생하고 있음에도 불구하고 시중에 유통되고 있는 고추 및 노지채소 수확작업 편이기기는 동력이 아닌 인력으로 이랑사이를 이동하며 작물을 수확하는 구조로 되어있다. 이는 노동 강도를 줄여주는 효과가 미미하기 때문에 동력이 수반된 편이장치가 필요하며 또한 적절한 모터 및 제어장치가 요구된다. 적절한 모터를 선정함에 있어서 영향을 주는 인자는 주행저항(RR)이며, 구성요소로는 구름마찰저항(Rr), 공기저항(RА), 등판저항(Rg), 가속저항(Ra)이 있으며, 다음과 같은 식으로 정의된다. 주행저항(RR)=구름마찰저항(Rr)+공기저항(RA)+등판저항(Rg)+가속저항(Ra) 구름마찰저항(Rr)=구름마찰저항계수(μ)×차량총중량(W) 등판저항(Rg)=차량총중량(W)×Sinθ 공기저항(RА), 및 가속저항(Ra)은 1m/s 미만의 속도가 요구되기 때문에 무시할 수 있다. 동력원에서 최종 구동축으로 전달된 동력은 주행장치를 통하여 지면에 전달되고 이 동력에 의해 작업차의 주행장치에 추진력이 발생하며 주행장치의 추진력이 주행저항 이상이 될 때 작업차는 전진하게 된다. 따라서 작업차의 주행속도를 V(m/s), 전동기의 효율을 μm, 동력전달효율을 μTD라고 하면 다음과 같은 식이 산출된다. 전동기의 소요출력(P)=주행저항(RR)×속도(V)/전동기의 효율(μm)×동력전달효율(μTD) 구름마찰계수를 0.3이라고 할 때 포장의 경사도와 작업차의 주행속도 변화에 따른 주행소요 동력을 비교하였다. 주행소요동력은 포장의 경사각과 주행속도의 증가와 더불어 증가한다. 고추 및 노지채소 수확작업 편이장치의 작업시 요구되는 주행속도는 일반적으로 0.25m/s, 등반각은 5도이다. 이때 구동 전동기의 출력은 안전율을 고려하여 식에 의해 계산한 결과 1ps으로 산출 되었다. 선정한 구동모터의 감속비는 7.18 : 1, 에너지의 효율은 78 %, 기동토크는14 N/m 이며, 축전지의 경우 구동모터에 기반 하여 구입이 간편하고 상용화 되어있는 연축전지를 사용하여 교체 및 수리가 간단하도록 하였다. 축전지는 12V 18Ah의 축전지 2개를 사용한다.

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Safety Evaluation of Clearance of Radioactive Metal Waste After Decommissioning of NPP (원전해체후 규제해제 대상 금속폐기물에 대한 자체처분 안전성 평가)

  • Choi, Young-Hwan;Ko, Jae-Hun;Lee, Dong-Gyu;Hwang, Young-Hwan;Lee, Mi-Hyun;Lee, Ji-Hoon;Hong, Sang-Bum
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.18 no.2_spc
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    • pp.291-303
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    • 2020
  • The Kori-Unit 1 nuclear power plant, which is scheduled to be decommissioned after permanent shutdown, is expected to generate large amounts of various types of radioactive waste during the decommissioning process. Among these, nuclear reactors and internal structures have high levels of radioactivity and the dismantled structure must have the proper size and weight on the primary side. During decommissioning, it is important to prepare an appropriate and efficient disposal method through analysis of the disposal status and the legal restrictions on wastes generated from the reactors and internal structures. Nuclear reactors and internal structures generate radioactive wastes of various levels, such as medium, very low, and clearance. A radiation evaluation indicates that wastes in the clearance level are generated in the reactor head and upper head insulation. In this study, a clearance waste safety evaluation was conducted using the RESRAD-RECYCLE code, which is a safety evaluation code, based on the activation evaluation results for the clearance level wastes. The clearance scenario for the target radioactive waste was selected and the maximum individual and collective exposure doses at the time of clearance were calculated to determine whether the clearance criteria limit prescribed by the Nuclear Safety Act was satisfied. The evaluation results indicated that the doses were significantly low, and the clearance criteria were satisfied. Based on the safety assessment results, an appropriate metal recycle and disposal method were suggested for clearance, which are the subject of the deregulation of internal structures of nuclear power plant.

National Pension Income Redistribution: The Case of Early Insureds by Net Benefit Measure (생애 순혜택으로 측정한 국민연금 초기 수급자들의 소득재분배)

  • Choi, Ki-Hong;Shin, Seung-Hee
    • The Korean Journal of Applied Statistics
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    • v.28 no.4
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    • pp.721-739
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    • 2015
  • The importance of the old age income security will increase for an aging society due to the deepening income polarization. The National Pension(NP) is a representative Social Security scheme in charge of old age income security as well as income redistribution for the insured. Studies by Kim (2002), Kim et al. (2003), and Hong (2013) have reported the possibility of unsatisfactory income redistribution of the NP. Recently Choi (2015) attributed those results to an unnoticed defect in the benefit formula. This study is a test for the unsatisfactory income redistribution of the current National Pension using early participants who have now become pensioners. The method aggregates cohorts and combines individual history data before the year 2013 and the results of the actuarial projection model of the 2013 after the year 2014. The results are divided by measures taken. The redistribution is obviously progressive by the income replacement rate; however, it is significantly regressive when measured by the net benefit theoretically as more plausible. Considering the effect of differing lifetime contribution year among income classes, the regressive redistribution will prevail more in the future pensioners.

Hardware-Based High Performance XML Parsing Technique Using an FPGA (FPGA를 이용한 하드웨어 기반 고성능 XML 파싱 기법)

  • Lee, Kyu-hee;Seo, Byeong-seok
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.12
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    • pp.2469-2475
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    • 2015
  • A structured XML has been widely used to present services on various Web-services. The XML is also used for digital documents and digital signatures and for the representation of multimedia files in email systems. The XML document should be firstly parsed to access elements in the XML. The parsing is the most compute-instensive task in the use of XML documents. Most of the previous work has focused on hardware based XML parsers in order to improve parsing performance, while a little work has studied parsing techniques. We present the high performance parsing technique which can be used all of XML parsers and design hardware based XML parser using an FPGA. The proposed parsing technique uses element analyzers instead of the state machine and performs multibyte-based element matching. As a result, our parsing technique can reduce the number of clock cycles per byte(CPB) and does not need to require any preprocessing, such as loading XML data into memory. Compared to other parsers, our parser acheives 1.33~1.82 times improvement in the system performance. Therefore, the proposed parsing technique can process XML documents in real time and is suitable for applying to all of XML parsers.

Stress-Strain Responses of Concrete Confined by FRP Composites (FRP 합성재료에 의하여 구속된 콘크리트의 응력-변형률 응답 예측)

  • Cho, Soon-Ho
    • Journal of the Korea Concrete Institute
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    • v.19 no.6
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    • pp.803-810
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    • 2007
  • An analytical method capable of predicting various stress-strain responses in axially loaded concrete confined with FRP (fiber reinforced polymers) composites in a rational manner is presented. Its underlying idea is that the volumetric expansion due to progressive microcracking in mechanically loaded concrete is an important measure of the extent of damage in the material microstructure, and can be utilized to estimate the load-carrying capacity of concrete by considering the corresponding accumulated damage. Following from this, an elastic modulus expressed as a function of area strain and concrete porosity, the energy-balance equation relating the dilating concrete to the confining device interactively, the varying confining pressure, and an incremental calculation algorithm are included in the solution procedure. The proposed method enables the evaluation of lateral strains consecutively according to the related mechanical model and the energy-balance equation, rather than using an empirically derived equation for Poisson's ratio or dilation rate as in other analytical methods. Several existing analytical methods that can predict the overall response were also examined and discussed, particularly focusing on the way of considering the volumetric expansion. The results predicted by the proposed and Samaan's bilinear equation models correlated with observed results with a reasonable degree, however it can be judged that the latter is not capable of predicting the response of lateral strains correctly due to incorporating the initial Poisson's ratio and the final converged dilation rate only. Further, the proposed method seems to have greater benefits in other applications by the use of the fundamental principles of mechanics.

Reliability Analyses of Breakwater Armor Blocks of Harbors in Korea (국내 항만의 방파제 피복 블록의 신뢰성 해석)

  • Kim, Seung-Woo;Suh, Kyung-Duck;Lee, Cheol-Eung;Park, Dong-Heon
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.21 no.1
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    • pp.15-29
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    • 2009
  • Most breakwater armor blocks are designed by using Hudson's or van der Meer's formula. The minimum weight of armor blocks is calculated by equating the resistance to the load in each formula. The larger value is then chosen as the design weight. In this study, we have performed reliability analyses for thus designed breakwater armor blocks of 12 trade harbors and 8 coastal harbors in Korea. The probability of failure calculated by the reliability analysis provides a criterion for evaluating the stability of armor blocks. The calculated probability of failure was almost same for all the breakwaters so that we were able to quantitatively evaluate the safety level of armor blocks of existing breakwaters. We also found that the safety factor used in the deterministic design method and the probability of failure in the reliability design method show a linear relationship. Therefore the probability of failure of existing breakwaters can be quantitatively calculated from the safety factors. The calculated probability of failure could also be used for determining the target probability of failure in the future.