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排序方式: 共有1520条查询结果,搜索用时 312 毫秒
141.
硬件演化原理及实现方法研究 总被引:7,自引:4,他引:3
文章对基于Virtex系列FPGA的硬件外部演化技术进行了研究,对演化算法的流程进行了分析,介绍了演化硬件的概念、原理、JBits API软件以及Virtex器件结构。基于JBits软件,采用外部演化的方式对电路进行演化,并通过仿真实例证明了这种方法的有效性。 相似文献
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河流生态修复的尺度格局和模型 总被引:14,自引:0,他引:14
通过分析水文过程与生态过程的耦合特征,论证了流域尺度是编制河流生态修复规划的适宜尺度。讨论了景观空间异质性与物种多样性的相关关系,提出了在流域和河流廊道两种尺度上改善景观格局配置的方法。特别指出了在河流廊道尺度下提高景观空间异质性的两个要点,一是增强地貌学意义上的空间异质性,二是改善生态水文学和生态水力学意义上的水文、水力学条件。本文还介绍了景观格局分析方法和景观格局-生态过程模型。 相似文献
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Split Plot Experiments: Taguchi's Ina Tile Experiment Reanalyzed 总被引:1,自引:0,他引:1
146.
Folding of coated papers is examined numerically using the finite element method. The analysis is focused on the influence from dynamic effects on the folding process. In particular, the behaviour of field variables relevant for cracking of the coating layers are studied in some detail. The results presented indicate that dynamic effects are of little importance as regards maximum strain levels in the coating but will influence the stress and strain distributions. Accordingly, a quasi-static analysis of the problem will be sufficient in order to describe many of the important features related to cracking. 相似文献
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1 INTRODUCTIONUltrafiltration(UF )isamembraneseparationprocesswhichhasfoundwideapplicationsinsuchfieldsaspetroleum ,textile ,bioseparation ,pharma cy ,food ,wastewatertreatment,preparationofdrinkingwater[13] .Manyresearchershavedevotedthemselvestoimprovingthe permeationfluxoftheUFmembraneunderthesamerejection ,andprevent ingtheformationofafoulinglayeronthesurfaceofUFmembrane .Manynovelmembranematerialsandvariousmodificationtechnologieshavebeendevel oped ,somemodificationmethods ,suchas… 相似文献
149.
BACKGROUND: An accurate pretherapeutic staging of laryngeal carcinoma is required for most treatment planning as well as for evaluation and comparison of the results of different treatment modalities. Neoplastic invasion of the laryngeal cartilage may have important therapeutic implications. To our knowledge, no data are available comparing the impact of endoscopic examination, computed tomography (CT), and magnetic resonance (MR) imaging on pretherapeutic staging accuracy. The purpose of our study was to determine which imaging should be used as an adjunct to other clinical examinations in the pretherapeutic staging of laryngeal carcinoma. METHODS: In this study, 40 consecutive patients with neoplasms of the larynx, who were treated surgically, were included in a prospective pretherapeutic staging protocol that included indirect laryngoscopy, direct microlaryngoscopy, contrast-enhanced CT, and gadolinium-diethylenetriamine pentaacetic acid-enhanced MR imaging at 1.5 Tesla. The surgical specimens were cut in whole-organ slices parallel to the plane of the axial CT and MR images. The histologic findings were compared with the clinical findings including the CT and MR images. The impact of each diagnostic method on pretherapeutic staging was analyzed. RESULTS: Clinical/endoscopic evaluation failed to correctly stage 17 tumors due to invasion of the paraglottic space (1 tumor), preepiglottic space (2 tumors), and extralaryngeal soft tissues (14 tumors), resulting in a pretherapeutic staging accuracy of 57.5%. Neoplastic invasion of cartilage was present in 28 patients and absent in 12 patients. Although MR imaging was more sensitive in detecting neoplastic invasion of cartilage than CT (94% vs. 67%; P = 0.001), MR imaging was less specific than CT (74% vs. 87%; P = 0.007). There was no difference between the overall accuracy of CT and MR imaging in detecting neoplastic invasion of cartilage (80% vs. 82%). The accuracy of combined clinical/endoscopic examination and CT staging was 80% and the accuracy of combined clinical/endoscopic examination and MR imaging staging was 87.5%; the difference was not statistically significant. CONCLUSIONS: Clinical/endoscopic examination alone failed to identify tumor invasion of the laryngeal cartilages and of the extralaryngeal soft tissues, resulting in a low staging accuracy (57.5%). Many pT4 (according to the International Union against Cancer TNM Staging System) tumors were clinically unrecognized. The combination of clinical/endoscopic evaluation and an additional radiologic examination, either CT or MR imaging, resulted in significantly improved staging accuracy (80% vs. 87.5%). MR imaging is significantly more sensitive but less specific than CT in detecting neoplastic cartilage invasion. Therefore, MR imaging tends to overestimate neoplastic cartilage invasion and may result in overtreatment, whereas CT tends to underestimate neoplastic cartilage invasion and may lead to inadequate therapy. 相似文献
150.
SBS浓溶液流动行为与粘度模型的研究 总被引:3,自引:0,他引:3
研究了诸因素对丁二烯-苯乙烯嵌段共聚物(SBS1401)的环已烷浓溶液和甲苯浓溶液粘度的影响,上述溶液的质量百分数范围为2%-25%,温度范围为25℃-50℃。结果表明,溶液的粘度随浓度的增大而增加,随剪切力和剪切速率的增大而减上;溶液的流动曲线符合幂律定律,并根据所测定的数据,利用回归方法对实验数据进行了处理,获得了在一定温度下,描述本体系溶液粘度特性的两变量的半经验关联式。 相似文献