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针对一类系统—非线性环链系统,利用非线性反馈控制的方法,研究了该系统的混沌反控制问题.该方法不需计算Lyapunov函数,从而降低了混沌反控制的计算量.仿真结果表明了该系统可快速有效地跟踪给定的混沌系统,充分的显示了该系统的优势. 相似文献
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煤电生产是我国废弃物粉尘和酸性气体的排放最主要来源.以某2×600MW超临界燃煤发电机组为案例,按传统能值指标体系分别对简单发电系统、发电加除尘系统和发电加除尘脱硫系统进行能值分析.结果表明,投入废物循环利用系统后可持续性指标反而下降.因此,传统的能值指标已不适合废弃物产生较大的煤电生产系统的可持续性评价.针对这一特点,提出了能反映煤电生产系统的相应指标体系,即有效能值产出率(EEYR)、能值环境影响率(EEIR)、有效能值可持续指数(EESI),计算得出简单发电系统、发电加除尘系统和发电加除尘脱硫系统的EESI分别为2.249、2.628、2.642.随着废物处理程度的提高,系统的可持续性更好,显示出环保系统投入的积极意义. 相似文献
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基于能值的污水处理系统环境影响分析 总被引:1,自引:0,他引:1
污水处理厂及其“产物”(处理水和脱水污泥)的处理处置系统共同构成了污水处理综合系统,它从整体上涵盖了污水处理的全过程.污水处理综合系统在构建和运行的过程中主要包括两方面的环境影响:1)物质资源的消耗;2)排放污染物对环境的危害,而后者在既往有关的污水处理系统分析中往往被忽略.为了更全面地了解污水处理过程的环境影响状况,本文以能值分析理论为基础对污水处理综合系统进行分析,同时,结合生态足迹理论对系统的可持续性进行分析.结果表明:水体污染物的环境影响能值远大于大气污染物,且主要受氨氮排放量的影响;污水处理综合系统的能值消耗主要为废物流能值和本地可更新资源能值;“处理厂系统+填埋系统”的能值利用效率最高,“处理厂系统+中水回用系统+焚烧系统”的能值利用效率最低;“处理厂系统+中水回用系统+填埋系统”的环境可持续性最好,而“处理厂系统+焚烧系统”的可持续性最差. 相似文献
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本文研究了一类具有时滞的随机捕食-食饵系统,证明了系统全局正解的存在性和系统的解的随机最终有界性,确定了系统灭绝和平均持续生存的充分条件.最后,用数值模拟验证理论结果的正确性. 相似文献
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随着DNA重组技术的发展,外源基因的表达问题受到越来越多的关注.常用的外源基因表达系统有原核表达系统和真核表达系统,两种表达系统各有优缺点.本文主要对这两类表达系统的研究进展、存在问题等做一概述. 相似文献
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生物系统的科学与工程是整合系统论、实验、计算和工程方法的交叉学科研究与应用.系统生物学、系统医学,建立在系统科学和数学模型基础上,采用分子、组学生物技术和计算、生物信息技术,以及基因合成与转基因生物技术等研究生物系统原理和规律.系统遗传学与系统生物技术是研究天然与人工生物系统的基因系统与蛋白质系统构成细胞的软件信息与硬件运行系统的机理与方法.合成生物学、系统生物工程也是建立在系统科学和数学模型基础上,应用于生物系统原理设计虚拟计算机信息软件和仿生人工机器硬件、人造工程生物体和基因信息系统等. 相似文献
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研究了具有时滞的捕食与被捕食系统,分析了系统的正不变集、边界平衡点性质、全局渐近稳定性和持久生存性.当时滞(?)很小时,系统在正平衡点是局部渐近稳定的,当(?)从0增到(?)_0时,系统在正平衡点附近产生Hopf分支. 相似文献
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Lightner DV Riggs A Corbin JS Ostrowski AC 《Diseases of aquatic organisms》2007,74(1):77-9; discussion 81-3
It is the opinion of the authors of the Comment on Do et al. (2006), that those authors incorrectly interpreted their test results, which are more likely the result of mislabeling of samples or within-laboratory contamination, and that the TSV isolates found in Penaeus vannamei in Korea in 2004 and 2005 did not originate from Hawaii as claimed by the authors, but from a country (or countries) in southeast Asia. Finally, we believe that the authors did not follow proper international guidelines, extend a professional courtesy to the supplier of the disputed shrimp sample, nor take a critical approach in interpreting their own data. It is unfortunate that the authors did not follow through with additional testing, or seek a second opinion from an independent laboratory, before implicating shrimp imported from Hawaii as the source of TSV in Korea. 相似文献
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Background
Many journals now require authors share their data with other investigators, either by depositing the data in a public repository or making it freely available upon request. These policies are explicit, but remain largely untested. We sought to determine how well authors comply with such policies by requesting data from authors who had published in one of two journals with clear data sharing policies.Methods and Findings
We requested data from ten investigators who had published in either PLoS Medicine or PLoS Clinical Trials. All responses were carefully documented. In the event that we were refused data, we reminded authors of the journal''s data sharing guidelines. If we did not receive a response to our initial request, a second request was made. Following the ten requests for raw data, three investigators did not respond, four authors responded and refused to share their data, two email addresses were no longer valid, and one author requested further details. A reminder of PLoS''s explicit requirement that authors share data did not change the reply from the four authors who initially refused. Only one author sent an original data set.Conclusions
We received only one of ten raw data sets requested. This suggests that journal policies requiring data sharing do not lead to authors making their data sets available to independent investigators. 相似文献15.
一个竞争模型的一致持续生存 总被引:1,自引:0,他引:1
本文研究一个带有时滞的竞争模型的一致持续生存。首先证明了离散时滞不影响种群的一致持续生存,接着在种群增长率是周期的假设下讨论了正周期解的存在性,最后给出了连续时滞模型一致持续生存的充分条件。 相似文献
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本文讨论了一类主要由昆虫自食引起的非线性种群动态模型的稳定性.首先给出确定性模型,并着重讨论其一个特殊情形.通过在参数空间中辨识稳定域的边界,可以相对直观地分析种群动态.对于随机模型,是利用在确定性模型中加入对数尺度下的正态随机项形成的,该模型具有较好的统计性质,便于将现实的非线性时间序列数据引进系统中来. 相似文献
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Xin Li was inadvertently dropped from the list of authors for this article. The authors regret this error. 相似文献
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The authors report three cases of a new syndrome which characteristic anomalies are facial dysmorphism with anteverted nose, down slanting palpebral fissures, ptosis, severe microretrognatia, polydactyly. The authors insist on the particular severe genital anomalies, the failure to thrive and the constant lethal issue. The authors discuss the diagnosis of Smith-Lemli-Opitz syndrome and suggest the possibility of a new entity always confounded with others associations characterized by a polydactyly and a sexual reversion in male. 相似文献
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In June of 2000, the U.K. Medical Device Agency recommended the removal of Trilucent implants as a precautionary maneuver in response to reports of local inflammatory reactions. This decision allowed the authors to operate on 115 consecutive patients between June of 2000 and January of 2001. On the preoperative examination, the authors found a very high incidence of rippling (66 percent), whereas capsular contracture was seen in only three patients (2.6 percent). Rippling was significantly more common in patients with subglandular implants. Five implants were found ruptured during the operation. This figure, together with the relative ease of implant breakage at removal, shows a premature deterioration of the implant shell. The authors also comment on implant bleeding, which seems common in this type of breast implant. The authors think that this is a possible cause for the rippling phenomenon, resulting from a reduction of the implant content. On the basis of these findings, the authors conclude that Trilucent implants are associated with a poor cosmetic outcome and a high rate of complications. 相似文献