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허병기,목영일 한국화학공학회 1980 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.18 No.1
多成分系를 輕質 Key 成分과 重質 Key 成分으로 形成된 擬二成分系로 看做하고 系의 平均 比揮發度를 最上段과 最低段에서의 Key 成分의 幾何 平均으로 假定하는 등의 單純化 과정을 통하여 精密度는 多少犧牲하고 보다 신속한 그리고 지루한 試行錯誤法의 반복 계산을 迂回하는 새로운 精溜塔設計法을 提示하였다. 溜出液 및 塔低液의 組成, 最小 理論段數, 最小 還流比 計算法은 물론 하드웨어(Hardware)의 實際設計에 필요한 塔半徑, 높이, 段間隔, 熱負荷計算 등에 最適한 計算式을 提示하였다. 特히 全理論 段數를 求할 수 있는 圖解를 導出함으로서 복잡한 反復計算을 피하여 손쉽게 全 理論段數를 計算할 수 있게 하였다. 本 硏究에서 적용한 假定 및 單純化의 妥富性을 論證하기 위하여 Smith-Brinkly 簡易設計法(SB), Fenske-Underwood-Erbar-Maddox 簡易設計法(FUEM) 및 逐大段計算法(SBSM)에 의한 實際設計例를 本 硏究의 計算結果와 比較 檢討하여 상기 方法中 精密度가 가장 높은 SBSM과의 誤差는 約 10% 내외라는 것을 確認하였다. Use of iterative stepwise methods has been a common practice in designing multicomponent distillation columns, Sometimes, it is difficult to justify iterative calculations from the point of view of cost·effectiveness, particularly when the input information does not have precision or accuracy, or when one simply does not have sufficient information for the system under study. In this work a new method was proposed whereby quick and simple procedures give rise to values of 14 different parameters needed for the design of a column for a multicomponent distillation. Several simplifying assumptions are made in the course; the usual one of a quasi-binary in which the average relative volatility is represented by a geometric mean of relative volatilities of the light key referred to the heavy in the bottoms over the light key referred to the heavy in the distillate, Prater and Boyd's approximation for column efficiency, approximations for expedience that arise in the actual mechanical fabrications of columns according to the common industrial practice, and other simplifications in the heat exchanger calculations. In order to validate the proposed method, comparisons are made with other popular methods such as Smith-Brinkly Short-Cut Method(SB), Fenske-Underwood-Erbar-Maddox Short-Cut Method(FUEM) and Step-by-Step Method(SBSM) by means of an actual design example. Departure from the results by the Step-by-Step method was about l096, the latter being the method yielding the highest accuracy as well as precision. Also, in this work procedures are presented for calculations of several hardware parameters of a distillation column and of heat exchangers annexed to the column.
허병기,Periasamy Anbu,Dong-Uk Kim,Eun-Jin Jeh,Young-Su Jeong 한국생물공학회 2007 Biotechnology and Bioprocess Engineering Vol.12 No.6
Physiological properties of organism, such as the number of chromosomes, genome size, fatty acid profile and the activities of desaturases and elongases were investigated for four different Thraustochytrium species. The investigation revealed that Thraustochytrium aureum could synthesize a significant level of polyunsaturated fatty acids (PUFAs), particularly docosahexaenoic acid (DHA), when compared to the other three Thraustochytrium species tested. A higher level of saturated fatty acids was observed by T. striatum followed by Thraustochytrium sp. ATCC 26185. The PUFA accumulation rate was higher in the n-3 than in the n-6 pathway. A comparison of the activities for these desaturases and elongases of the four different species were also studied. Further, the electrophoretic karyotypes of Thraustochytrids were separated by pulsed-field gel electrophoresis (PFGE). The separation condition of PFGE was developed to obtain the different chromosomes from the various Thraustochytrium species. The number of chromosomes in T. aureum, T. striatum, Thraustochytrium sp. ATCC 20891 and Thraustochytrium sp. ATCC 26185 were 13, 17, 10, 8, and the whole genome size of those species were estimated to be 12.9, 11.7, 11.3, and 9.93 Mbp, respectively.
Eicosapentaenoic Acid (EPA) Biosynthetic Gene Cluster of Shewanella oneidensis MR-1
허병기,서정우,이수진,Young-Su Jeong,Dong-Uk Kim 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.6
The putative EPA synthesis gene cluster was mined from the entire genome sequence of Shewanella oneidensis MR-1. The gene cluster encodes a PKS-like pathway that consists of six open reading frames (ORFs): ORFSO1602 (multi-domain beta-ketoacyl synthase, KS-MAT-4ACPs-KR), ORFSO1600 (acyl transferase, AT), ORFSO1599 (multi-domain beta-ketoacyl synthase, KS-CLF-DH-DH), ORFSO1597 (enoyl reductase, ER), ORFSO1604 (phosphopentetheine transferase, PPT), and ORFSO1603 (transcriptional regulator). In order to prove involvement of the PKS-like machinery in EPA synthesis, a 20.195-kb DNA fragment containing the genes was amplified from S. oneidensis MR-1 by the long-PCR method. Its identity was confirmed by the methods of restriction enzyme site mapping and nested PCR of internal genes orf SO1597 and orf SO1604. The DNA fragment was cloned into Escherichia coli using cosmid vector SuperCos1 to form pCosEPA. Synthesis of EPA was observed in four E. coli clones harboring pCosEPA, of which the maximum yield was 0.689% of the total fatty acids in a clone designated 9704-23. The production yield of EPA in the E. coli clone was affected by cultivation temperature, showing maximum yield at 20℃ and no production at 30℃ or higher. In addition, production yield was inversely proportional to glucose concentration of the cultivation medium. From the above results, it was concluded that the PKS-like modules catalyze the synthesis of EPA. The synthetic process appears to be subject to regulatory mechanisms triggered by various environmental factors. This most likely occurs via the control of gene expression, protein stability, or enzyme activity.