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21.
In industrial systems, the formation of biofilms can cause many problems, such as an increase in the flow resistance of pipelines, energy losses in fluid transport and heat exchangers, product contamination, materials deterioration, and biocorrosion. As a result, biofilms contribute substantially to economic losses in the industry. Corrosion is particularly an issue in the petroleum industry and its implications range from down-hole completion through petroleum processing units. Much of this corrosion is attributed to microbial activities. This paper proposes a mathematical model for predicting substrate concentration for such microbial growth. Substrate concentrations in the system and near the biofilm surface are one of the parameters that has a great effect in determining the extent of the problems associated with biofilms. In this study, a convective-diffusion model under various flow conditions (stagnant, laminar, and turbulent) has been solved using the finite difference technique, employing the alternating direction implicit (ADI) method. The model assumes that a liquid containing substrate and bacteria is flowing in a pipeline with known concentrations at the inlet and then predicts the variation of the transient (as a function of time) substrate concentration along the pipeline and as a function of the pipe radius. The model is then used to predict and estimate the substrate concentration profiles on the biofilm surface under different environmental conditions. A parametric study was also conducted to study the effect of the different parameters influencing the substrate concentration profiles in the system and on the biofilm surface. 相似文献
22.
R.A. CARTER R. F. PLIMPTON H.W. OCKERMAN V.R. CAHILL N.A. PARRETT 《Journal of food science》1992,57(4):841-844
Total microbial count was not adversely affected by lowering the holding temperature of fabricated beef roast from 60°C to 54°C or by 12 hr holding time. If a reduction in holding temperature is anticipated, then initial roast contamination and sanitation of the food facility are of critical importance. A stabilizing period of 20 min at room temperature (~23°C) did not decrease yield, but caused a slight lowering of sensory scores. Tenderness was more acceptable in product held at 54°C compared to 60°C. In general, all sensory evaluation ratings were slightly lower with increased holding time. 相似文献
23.
本文通过住宅区总体规划与环境设计,居住户型的多样化,美观大方的住宅立面设计,方便安全的停车场所四个方面谈了自己对住宅设计的认识与体会. 相似文献
24.
无线信道中的电波传播 总被引:2,自引:0,他引:2
分析了信号在无线信道中传输时所经受的两种衰落,介绍了主要的无线传播模型,在此基础上提出了对抗衰落的措施。 相似文献
25.
26.
Kaslow Nadine J.; Rubin Nancy J.; Forrest Linda; Elman Nancy S.; Van Horne Barbara A.; Jacobs Sue C.; Huprich Steven K.; Benton Sherry A.; Pantesco Victor F.; Dollinger Stephen J.; Grus Catherine L.; Behnke Stephen H.; Miller David S. Shen; Shealy Craig N.; Mintz Laurie B.; Schwartz-Mette Rebecca; Van Sickle Kristi; Thorn Beverly E. 《Canadian Metallurgical Quarterly》2007,38(5):479
Working collaboratively, psychologist educators and trainers at the doctoral, internship, and postdoctoral levels; credentialers; practitioners; and students offer 8 proposals for psychologists to consider in recognizing, assessing, and intervening with problems of professional competence in students and practicing professionals. In the proposals, the authors address the following topics: definitions and categories; preparing the system; self-assessment; remediation; diversity; communication across various levels of the system; confidentiality; and ethical, regulatory, and legal underpinnings. They also propose future directions for the assessment of problems in professional competence in both students and practicing psychologists. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
27.
多版本软件通过设计相异性实现了软件容错。为了对这种方法进行研究,我们的课题实现了一个三版本软件系统,称之为SFTMP(SoftwareFault-TolerantMultiProcessor)。本文描述了SFTMP的硬件结构和软件执行支持环境,该环境包括同步、表决和监控功能、版本间的通讯及故障的恢复和重构。 相似文献
28.
This article identifies the key issues involved in the debate about affirmative action. The June 2003 Supreme Court decisions allowing consideration of race to ensure that there is a "critical mass" of African American, Latino/Latina, and Native American applicants to higher education are addressed. Social psychologists have identified key myths and provided clarifications about the need for and consequences of strategies used to promote equal opportunity for persons of color and women. A brief history of affirmative action and of the problems it was designed to solve is provided. The accomplishments, benefits, and compelling interest of diversity and affirmative action are described, as well as the concerns and counterpoints. The lack of a substantial applicant pool in psychology hinders progress toward diversity. Alternative strategies for remedying this lack beyond affirmative admissions policies in psychology are briefly discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
Alkylated ureas: mineralization and evaluation as N sources 总被引:2,自引:0,他引:2
An incubation experiment was conducted for 11 weeks to study the mineralization of ten alkylated ureas and urea in soil. Six of the alkylated ureas viz. methylurea(MU), 1,3-dimethylurea(1,3DMU), 1,1-dimethylurea(1,1DMU), ethylurea(EU), 1,3-diethylurea(1,3DEU) and butylurea(BU) and urea mineralized during the experiment. Urea mineralized immediately, while alkylated ureas mineralized after an incubation period ranging from less than a week to four weeks (delay period of mineralization). The delay period increased in the following sequence MU < 1,3DMU < EU < BU < 1,1DMU < 1,3DEU, but after the delay period was over the compounds mineralized almost as rapidly as urea. The delay period varied according to the number of carbon atoms in the alkyl group and their position with respect to each other on the molecule. It appeared to be specific for each compound and was apparently not influenced by the presence of urea or other alkylated ureas. This character can be used to develop mixture of various alkylated ureas to obtain N mineralization at the desired time. Rapid evolution of CO2 and N2O was observed during the mineralization of urea as well as alkylated ureas. Increase in soil pH was also observed during this period. The simultaneous ocurrence of these events suggested the formation of urea as an intermediate during the mieralization of alkylated ureas. None of the alkylated ureas showed adverse affect on emergence of wheat seedlings and except DEU and BU at high concentration no other alkylated urea showed any adverse effect on initial growth of wheat seedlings. 相似文献
30.
由于用户在各种不同场景下采用不同的MIMO模式可以达到不同的传输效果,为了使用户达到平均吞吐量和频谱效率的最佳要求,提高系统传输率,研究了TDD LTE系统下行MIMO模式切换技术。搭建TDD LTE下行业务控制信道PDSCH仿真平台,对MIMO传输模式进行仿真实验,通过比较不同模式下的误码率和吞吐量的仿真结果,确定切换门限,提出MIMO模式自适应切换算法。在实际应用中,根据这种算法自适应地配置适合的MIMO技术,可以最大限度的提高系统频谱利用率,此方法优于单独采用一种MIMO技术达到的传输效率。 相似文献