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排序方式: 共有852条查询结果,搜索用时 31 毫秒
51.
Alan M. Allgeier Denise Andersen Michael D. Bartberger Emilio E. Bunel Robert D. Larsen Pingli Liu Thomas Storz Jason S. Tedrow 《Topics in Catalysis》2014,57(17-20):1335-1341
To overcome stability issues associated with the use of an aldehyde in a catalytic reductive amination reaction, a cyclic ketolactol (ω-hydroxylactone) was employed as an aldehyde surrogate to form a γ-aminoacid. The reaction proceeded most favorably over a Pt/C catalyst. The thermodynamics of each step were evaluated using density functional theory calculations, which correctly predicted the dominance of the ring-closed lactol reactant, yet suggested a preference for a ring-opened iminium intermediate upon the initial, slightly endoergic addition of amine substrate. Exoergic hydrogenation of this intermediate provided the thermodynamic driving force for the overall transformation. During development, the reaction was observed to depend significantly on the volumetric gas to liquid mass transfer coefficient (kLa) and this parameter was optimized to ensure successful scale up in a 400 L stirred tank reactor. 相似文献
52.
Solange Kazue Utimura Santiago Justo Arevalo Carlos Gonzalo Alvarez Rosario Mauro Quiones Aguilar Jorge Alberto Soares Tenrio Denise Crocce Romano Espinosa 《加拿大化工杂志》2019,97(11):2920-2927
In this study, the feasibility of using a biohydrometallurgical technique for selective metals recovery from electronic waste (e‐waste) by bacterial bioleaching was investigated. Acidithiobacillus was identified in coal mining acid mine drainage (AMD). The microorganism was studied using specific sequencing of a 16s rDNA fragment. The potential for the dissolution of copper from waste printed wire boards (PWBs) using the isolated Acidithiobacillus ferrooxidans (A. ferroxidans) was evaluated. The bioleaching experiments were performed in an orbital shaker at 30 °C and 170 rpm, with 10 % (v/v) inoculum and a pulp density of 30 g/L. The copper concentration was determined by energy dispersive x‐ray fluorescence (XRF). The result shows that copper recovery from PWBs using our A. ferrooxidans strain was 95 % after 8 days, which showed the feasibility of this process. 相似文献
53.
Study of the modulus of elasticity of polymer concrete compounds and comparative assessment of polymer concrete and portland cement concrete 总被引:1,自引:0,他引:1
The main aim of this study is to assess the modulus of elasticity of polymer concrete (PC) compounds produced using two types of binders: orthophtalic or isophtalic polyester. The compositions used were selected from a previous study that identified cost-effective PC compositions. Based on those data, the concentrations of polymer used were 12% of orthophtalic polyester and 13% of isophtalic polyester by weight of the dry materials. Fly ash was used as a filler and compositions with 8%, 12%, 16% and 20% of ash by weight of aggregate were studied. Results indicate that all compositions assessed in this study display high modulus of elasticity values. Statistical analysis of the data reveals that the type of resin and the concentration of fly ash, both in isolation and in combination, have a significant effect on the modulus of elasticity of these compounds. 相似文献
54.
55.
Denise Sato Yamashita Vinícius Amaral Armentano Manuel Laguna 《Journal of Scheduling》2007,10(1):67-76
We address a project scheduling problem with resource availability cost for which the activity durations are uncertain. The
problem is formulated within the robust optimization framework, where uncertainty is modeled via a set of scenarios. The proposed
solution method is based on the scatter search methodology and employs advanced strategies, such as dynamic updating of the
reference set, a frequency-based memory mechanism, and path relinking. A multistart heuristic was also developed and comparative
results are reported. The tradeoffs for risk-averse decision makers are discussed. 相似文献
56.
This paper presents a tabu search approach for scheduling jobs on identical parallel machines with the objective of minimizing the mean tardiness. Initially, we consider a basic tabu search that uses short term memory only. Local search is performed on a neighborhood defined by two types of moves. Insert moves consist of transferring each job from one machine to another and swap moves are those obtained by exchanging each pair of jobs between two machines. Next, we analyze the incorporation of two diversification strategies with the aim of exploring unvisited regions of the solution space. The first strategy uses long term memory to store the frequency of the moves executed throughout the search and the second makes use of influential moves. Computational tests are performed on problems with up to 10 machines and 150 jobs. The heuristic performance is evaluated through a lower bound given by Lagrangean relaxation. A comparison is also made with respect to the best constructive heuristic reported in the literature. 相似文献
57.
Definitions of business process given in much of the literature on Business Process Management are limited in depth and their related models of business processes are correspondingly constrained. After giving a brief history of the progress of business process modeling techniques from production systems to the office environment, this paper proposes that most definitions are based on machine metaphor type explorations of a process. While these techniques are often rich and illuminating it is suggested that they are too limited to express the true nature of business processes that need to develop and adapt to today's challenging environment. 相似文献
58.
This article presents information on the development and validation of the Facial Expression Coding System (FACES; A. M. Kring & D. Sloan, 1991). Grounded in a dimensional model of emotion, FACES provides information on the valence (positive, negative) of facial expressive behavior. In 5 studies, reliability and validity data from 13 diverse samples, including students, psychiatric patients, and community adults, are presented, and results indicate that raters can reliably agree on instances of positive and negative expressive behavior. Validity studies indicate that FACES ratings are related in predictable ways to another observational coding system, facial muscle activity, individual-difference measures of expressiveness and personality, skin conductance, heart rate, and reports of experienced emotion. FACES can be a useful tool for assessing expressive behavior in a variety of contexts. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
59.
Although libraries maintain collections of material on computer disks in climate controlled environments, a significant amount of digital heritage is in private collections. In this study we compared the outcomes of creating disk images of the State Library of South Australia’s born digital collections with those of a private collector to gauge the effect of long term storage conditions. The failure rates of both collections give cause for concern, and the results from the private collection are alarming. 相似文献
60.
We investigated the influences of odor exposure on performance and on breathing measures. The task was composed of tracking, short-term memory, and peripheral reaction parts. During rest or while performing the task, 12 participants were exposed to 4 different odors in 2 intensities. The higher intensity of the malodors induced a short-term decrement in mean inspiration flow (Vi/Ti) after stimulus onset and impaired performance in the short-term memory task, as compared with control trials; no effect was found for the positively judged odors. The study suggests that a distractor as simple as a bad smell may pull a person off task, however briefly, and may result in a detriment to performance. Actual or potential applications of this research involve designing or securing tasks in such a way that a brief withdrawal of attention does not have fatal consequences. 相似文献