1,721,004 research outputs found
Understanding Gas Adsorption in MOF-5/Graphene Oxide Composite Materials: A Computational Study
No full textAtomistic understandings of reduced graphene oxide as an ultrathin-film nanoporous membrane for separations
No full textThe intrinsic defects in reduced graphene oxide (rGO) formed during reduction processes can act as nanopores, making rGO a promising ultrathin-film membrane candidate for separations. To assess the potential of rGO for such applications, molecular dynamics techniques are employed to understand the defect formation in rGO and their separation performance in water desalination and natural gas purification. We establish the relationship between rGO synthesis parameters and defect sizes, resulting in a potential means to control the size of nanopores in rGO. Furthermore, our results show that rGO membranes obtained under properly chosen synthesis conditions can achieve effective separations and provide significantly higher permeate fluxes than currently available membranes.Deshpande Center for Technological Innovatio
Effects of Relative Volatility Ranking to the Design of Reactive Distillation: Excess-reactant Design
No full text多功程序在程序強化中是相當重要之一環，而多功程序中最主要例子為反應性蒸餾。過去10年的研究主要強調可行性分析、設計或控制方式探討，但針對相同或不同系統，在程序設計上，缺乏一系統化的整體概念性設計。在此研究中，礙於真實系統的複雜性，我們改而對一理想系統作探討，我們考慮一四成分的可逆放熱反應(A+B↔C+D)，並且忽略產物與反應物間個別的相對揮發度排列，最後歸列出6種可能的不同相對揮發度排列(4!/2!2!)。針對這些不同的相對揮發度排列，我們以年總成本(TAC)做為比較基準來找出最佳架構。在設計上，我們先以無回流反應性蒸餾系統(Neat)當作主軸，提出一系列的設計，並且針對其架構做更進一步設計，提出過量反應物(Excess-reactant)的設計步驟以及成果，此外，除了反應性蒸餾系統外，傳統反應/分離系統(Conventional)也將被探討，最後延伸其應用面，改變平衡常數(0.1~100)來涵蓋大部份反應系統的發生。結果顯示，相對揮發度排序不論在反應性蒸餾系統與傳統反應/分離系統設計與結果上皆扮演一個非常重要的角色，不同的相對揮發度排序表現出不同的設計架構，並且展現出不同的時機（平衡常數）採用過量反應物設計，同時也得到相差甚遠的年總成本，此外從結果也得知，針對所有可能之排序，反應性蒸餾系統的年總成本會較傳統反應/分離系統來的低廉，此結果也再次顯示出此種多功程序的重要性。Multifunctional process unit is an important element in process intensification and reactive distillation is one of the most common examples. For the recent ten years, the progress focus on understanding the feasibility, design, and, in some cases, control of reactive distillation. On the other side, for the design of same or different process, a systematic design procedure which is capable of covering a wide range of system parameters is lacking. The objective of this work is aimed to provide a systematic design procedure to determine the configuration of process. Instead of investigating real chemical systems, ideal chemical reaction systems with different relative volatility rankings will be studied. This provides a gradual transition as the reaction and separation properties change. The reaction considered is a reversible reaction A+B↔C+D, and this constitutes a quaternary system with 24 (4!) possible relative volatility arrangements. These 24 systems can further be grouped into six categories (4! /2! 2!) according to the ranking of relative volatilities of reactants and products. The likely process configurations will be explored and design will be optimized based on the total annual cost (TAC). First, in this work, proposing the configuration of neat design for those six categories, future more, excess design which is used to improve the performance of Neat design also be proposed. In addition to reactive distillation, the conventional reaction/separation system is also considered in order to do a basis of comparison. Finally, extending the application of this work, the equilibrium is changed (0.1~100) to cover almost all reaction, which is taken in real world. The results clearly indicate that the relative volatility rankings play a dominant role in the design and result of both reactive distillation and conventional reaction/separation process. Different relative volatilities ranking needs different configuration and has different timing (equilibrium constant) to use excess design, in the mean time, showing the different total annual cost (TAC). Besides, the result also indicates that the reactive distillation compares to conventional reaction/separation progress process has the lower TAC. The result tells us the important of multifunctional process unit, again.摘要 I
Abstract III
目錄 V
圖索引 VIII
表索引 XI
1. 緒論 1
1.1. 前言. 1
1.2. 文獻回顧. 4
1.3. 研究動機與目的. 9
1.4. 組織章節. 10
2. 程序架構分類與模式建立 12
2.1. 前言. 12
2.2. 程序架構分類. 12
2.2.1 Type I：One-Group 14
2.2.2 Type II：Two-Groups 15
2.2.3 Type III：Alternating 15
2.3. 理想反應蒸餾描述. 15
2.3.1動力學描述 15
2.3.2熱力學描述 16
2.3.3模式假設與規格 17
2.3.4建立程序模式 19
2.3.5模擬方法 22
3. 無回流反應性蒸餾系統之穩態設計(Neat)) 25
3.1. 前言. 25
3.2. 穩態設計之最適化步驟. 25
3.3. 最適化結果. 27
3.3.1 Type I：One-Group 27
3.3.1.1 Type Ip：LK+HK=LLK+HHK 27
3.3.1.2 Type Ir：LLK+HHK=LK+HK 30
3.3.2 Type II：Two-Groups 36
3.3.2.1 Type IIp：HK+HHK=LLK+LK 36
3.3.2.2 Type IIr：LLK+LK=HK+HHK 41
3.3.3 Type III：Alternating 45
3.3.3.1 Type IIIp：LK+HHK=LLK+HK 45
3.3.3.2 Type IIIr：LLK+HK=LK+HHK 48
3.4. 比較與討論. 51
4. 過量反應物之穩態設計(Excess-reactant)) 57
4.1. 前言. 57
4.2. 過量反應物之程序設計及其結果. 57
4.2.1 Type Ir：LLK+HHK=LK+HK. 59
4.2.2 Type IIr：LLK+LK=HK+HHK 68
4.2.2.1等劑量比進料之過量反應物設計 69
4.2.2.2非等劑量比進料之過量反應物設計 71
4.2.3 Type IIIr：LLK+HK=LK+HHK 74
4.2.4其他type 過量反應物設計架構之提出 78
4.3.4.1 Type Ip：LK+HK=LLK+HHK 79
4.3.4.2 Type IIp：HK+HHK=LLK+LK 82
4.3.4.3 Type IIIp：LK+HHK=LLK+HK 83
4.2.5設計結果 84
4.3. 平衡常數對反應性蒸餾系統設計的影響. 86
4.3.1 反應物最輕系統 87
4.3.1.1 Type Ir：LLK+HHK=LK+HK 87
4.3.1.2 Type IIr：LLK+LK=HK+HHK 88
4.3.1.3 Type IIIr：LLK+HK=LK+HHK 89
4.3.2產物最輕系統 90
4.3.2.1 Type Ip：LK+HK=LLK+HHK 90
4.3.2.2 Type IIp：HK+HHK=LLK+LK 91
4.3.2.3 Type IIIp：LK+HHK=LLK+HK 91
4.3.3 平衡常數與反應性蒸餾系統之架構轉變 92
4.4. 比較與討論. 96
5. 傳統反應分離程序之穩態設計(Conventional)) 99
5.1. 前言. 99
5.2. 最適化方法. 99
5.3. 最適化設計結果. 103
5.3.1 Type I：One-Group 103
5.3.1.1 Type Ip：LK+HK=LLK+HHK 103
5.3.1.2 Type Ir：LLK+HHK=LK+HK 107
5.3.2 Type II：Two-Groups 108
5.3.2.1 Type IIp：HK+HHK=LLK+LK 109
5.3.2.2 Type IIr：LLK+LK=HK+HHK 110
5.3.3 Type III：Alternating 111
5.3.3.1 Type IIIp：LK+HHK=LLK+HK 111
5.3.3.2 Type IIIr：LLK+HK=LK+HHK 113
5.3.3 設計結果之比較 114
5.4. 平衡常數與傳統反應分離系統. 115
6. 結論 121
參考文獻 123
附錄A年總成本計算公式 130
附錄B無回流反應性蒸餾系統之設計 132
附錄C Type Ir 無回流系統之新架構 142
附錄D傳統反應/分離系統設計 14
Evaluating mixture adsorption models using molecular simulation
Get PDFThe design of adsorption-based separation processes using novel adsorbents requires reliable data for the adsorption of fluid mixtures on candidate adsorbents. Due to the difficulty of generating sufficient data across possible operating conditions, process designs generally rely on interpolation of pure-component data using a model, most commonly ideal adsorbed solution theory (IAST), and related theories. There are many cases where IAST fails to provide an adequate description of mixture adsorption, usually due to the fact that practical adsorbents do not have uniform surfaces. We have evaluated the use of a segregated version of IAST, where competition is assumed to occur at isolated adsorption sites. This simple modification can provide the correct description of adsorption across a large range of pressures using ideal isotherm models. We also demonstrate the importance of identifying multiple sites even for weakly adsorbing components to provide the correct behavior at high pressure. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 3054-3064, 201
Two-dimensional covalent triazine framework as an ultrathin-film nanoporous membrane for desalination
Get PDFWe computationally demonstrate that two-dimensional covalent triazine frameworks (CTFs) provide opportunities in water desalination. By varying the chemical building blocks, the pore structure, chemistry, and membrane performance can be designed, leading to two orders of magnitude higher water permeability than polyamide membranes while maintaining excellent ability to reject salts.Netherlands Organization for Scientific ResearchUnited States. Dept. of Energy (Contract No. DE-AC02-05CH11231)Deshpande Center for Technological Innovatio
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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