排序方式: 共有51条查询结果,搜索用时 500 毫秒
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针对流星余迹通信原理及信道特点,建立了适用于流星余迹通信系统的智能天线系统模型。在热区跟踪上,使用波束切换技术;而对于可用流星余迹使用自适应数字波束形成技术。针对流星余迹持续时间短的特点,为了获得最佳接收性能,缩短等待时间,对自适应算法提出了收敛速度快、计算复杂度小的要求,这里采用变步长LMS算法与判决导向算法相结合的半盲自适应算法,并对半算法进行了仿真分析。 相似文献
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Feifei Zhou Rong Huang Jun Jiang Fang Wang Wenzhuo He Guifang Guo Liangping Xia 《Canadian Metallurgical Quarterly》2011,10(6)
Objective: Male breast cancer (MBC) is a rare disease, and studies to compare the prognosis between the MBC and female breast cancer (FBC) available now were case-control studies and population-based studies, however, with controversial outcomes. To further investigate whether sex affects the prognosis of breast cancer, we performed a meta-analysis based on all the peered papers. Methods: The PubMed database was screened. Subsequently, the hazard ratios (HRs) for overall survival (OS) and disease special survival (DSS), were pooled using the Review Manager 5.0 package. Results: This study comprised of 254 MBC and 733 FBC patients enrolled in six case-control studies. There was no statistically significant heterogeneity among the trials for either outcome variable. The pooled HR showed that there was no significant difference in 5-year or 10-year DSS (HR: 1.25, 95% CI: 0.76-2.08; HR: 1.04, 95% CI: 0.66-1.59) and 5-year or 10-year OS (HR: 0.76, 95%CI: 0.51-1.14; HR: 0.74, 95% CI: 0.54-1.02) between MBCs and FBCs. Conclusion: MBC and FBC with similar prognosis are found in this meta-analysis based on only case-control studies which matched main potential prognostic factors such as age, clinical stage, and time at diagnosis. 相似文献
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本文研究了铜对低硼、低铬镍基钎料工艺性能的影响。试验结果表明,在降低镍基钎料中硼、硅元素的同时加入适量的铜可以使钎料的熔点基本不变。由于铜的加入,增大了钎缝中固溶体比例、减少了钎缝组织中的化合物,接头的MBC值明显增大,使钎焊接头对钎焊间隙的敏感性降低。随着钎料中铜含量的增加,钎料及其钎焊接头的耐蚀性相应增强。但是,铜的加入对接头的热强性有不利的影响。 相似文献
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Silvia Gonzlez-Martínez Beln Prez-Mies David Pizarro Tamara Caniego-Casas Javier Corts Jos Palacios 《International journal of molecular sciences》2021,22(14)
Metaplastic breast carcinoma (MBC) is a heterogeneous group of infrequent triple negative (TN) invasive carcinomas with poor prognosis. MBCs have a different clinical behavior from other types of triple negative breast cancer (TNBC), being more resistant to standard chemotherapy. MBCs are an example of tumors with activation of epithelial–mesenchymal transition (EMT). The mechanisms involved in EMT could be responsible for the increase in the infiltrative and metastatic capacity of MBCs and resistance to treatments. In addition, a relationship between EMT and the immune response has been seen in these tumors. In this sense, MBC differ from other TN tumors showing a lower number of tumor-infiltrating lymphocytes (TILS) and a higher percentage of tumor cells expressing programmed death-ligand 1 (PD-L1). A better understanding of the relationship between the immune system and EMT could provide new therapeutic approaches in MBC. 相似文献
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汽车发动机用粉末冶金主轴承盖 总被引:1,自引:0,他引:1
粉末冶金主轴承盖(MBC)于1993年第一次用于GM的3100与3800V6发动机.该零件一年消耗粉末5 000多t,是北美粉末冶金零件中应用量最大者.选择粉末冶金材料替代传统的铸铁,是因为其有利于零件的功能,而且因为粉末冶金工艺能成形为最终形状,从而使GM可节省下对主轴承盖的切削加工生产线的大部分投资.由于灰铸铁强度不够高,球墨铸铁的价格高又难切削加工,因此,为这种零件开发了一种强度高、成本低的粉末冶金合金钢.这篇论文说明了主轴承盖的功能要求,比较了铸铁与粉末冶金的材料和生产工艺,说明了粉末冶金的设计利益;此外,还讨论了粉末冶金主轴承盖要求的强度、一致性、完善性(无缺陷)及切削性,其中包括试验与试验验证. 相似文献
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一种RF发射电路中的LNA设计 总被引:2,自引:2,他引:0
针对射频发射电路前端的噪声系数过大的问题,设计了一种采用芯片设计的低噪声放大电路;首先结合目前几种常用的LNA的设计结构,文中选择了一种最可靠、性能最稳定的结构,该结构是采用了CMOS类芯片-MBC13720来设计的;并做出了具体的设计方案,包括输入匹配网络和输出匹配网络,以及供电模块的电路设计,给出了具体的参数;最后对所做的LNA电路进行了实物电路测试,结果表明本设计可以满足设计目的。其设计结构简单,外围电路容易搭配,容易调试,易于工程上的实现,因此具有极大的应用价值。 相似文献
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一、引言计算机仿真接口界面,随着计算机软硬件的不断提高也在快速地变化着。从其发展趋势中我们不难看出这一点:从早期的命令行提示编辑Command Line,到全屏幕菜单编辑(Menu based Editor),再到图形用户界面Graphic User In-terface(GUI),界面在不断追求如何更好地适应用户、与用户更直接地交互。其具体特点包括自然而又丰富的色彩、逼真而又完美的几何造型、柔和而又动听的环境声响、质感而又具有力反馈的实物等。这些人们所需要的真实感,一种技术是难以胜任的,它需要各种软、硬件技术的综合与集成。从目前的趋 相似文献
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丁香酚体外抑菌作用研究 总被引:6,自引:0,他引:6
应用微量稀释法对丁香酚体外抑菌活性进行了研究。结果表明,丁香酚对12种常见细菌具有较好的抑菌作用,其中对大肠杆菌ATCC25922(质控菌)的效果最好,其最低抑菌浓度(MIC)、最低杀菌浓度(MAC)分别为5μg/ml和10μg/ml;对蜡状芽孢杆菌作用较差,MIC和MBC分别为320μg/ml和64μg/ml其余菌株的MIC和MBC分别在20-80μg/ml和40-16μg/ml之间。而时间.杀菌曲线法实验结果表明,丁香酚抑菌作用特性表现为较强的浓度依赖性,其良好的抑菌活性可作为潜在的天然食品防腐剂进一步研究和开发。 相似文献