弹射式无人机航摄系统的研究

随着科学、信息技术的进步,政策积极引导以及市场需求的不断增加,低空无人机航摄系统突破了众多技术瓶颈,整个行业都得到了快速发展,满足了众多领域的实际应用需要。现针对弹射式低空无人机航摄系统的发展现状、特点、实施过程以及存在的若干问题进行探讨,以此来指导低空无人机航摄实践,更好地满足我国经济社会迅猛发展的航摄测绘需求。     

Embryo implantation: A time for recalling and forwarding

The success of embryo implantation is a critical step towards further embryo development and pregnancy outcome. The observations and investigations on embryo implantation have been over a century. A huge body of knowledge has been accumulated in anatomy, histology, ultrastructure and hormonal regulation; as well as recently in depth information about molecular signaling pathways got from studies of genomic wide gene screening and specific gene deletion. The knowledge from basic research has also substantially helped to initiate and improve the Artificial Reproductive Technology （ART） in clinical applications. Now we＇ve known that the normal embryo implantation involves the embryo＇s development into an implantation-competent blastocyst and the synchronized transformation of uteri into a receptive stage. The interdependent relationship between the blastocyst and uterus involves complicated hormonal regulation and local paracrine, juxtacrine interactions. In this paper, we review some important historical findings regarding uterine receptivity and blastocyst activation, as well as some less discussed topics such as embryo spacing, embryo orientation. Further understandings on detailed mechanisms during the process of embryo implantation will help cure women infertility as well as develop new generation of non-steroids contraceptives.     

Expression, distribution and function of the focal adhesion kinase (pp125FAK) during murine ectoplacental cone outgrowthin vitro

Mouse embryo implantation is a complex process that includes trophoblast cells derived from ectoplacental cone (EPC) adhesion to and migration through the extracellular matrix (ECM) of uterine endometrium and invasion into the decidua. At the time of implantation, fibronectin (FN) is abundant in the decidua and is distributed pericellularly around each individual stromal cell, and its receptor (integrin α-5β-1) expression on trophoblast populations is up-regulated. The focal adhesion kinase, a 125 ku protein tyrosine kinase (pp125 FAK), is tyrosine phosphorylated upon integrin engagement with its ECM ligand, and its tyrosine phosphorylation sites then serve as the binding sites which couple it with cellular proteins that contain Src SH2 or SH3 domains. Through these linkages, pp125 FAK may integrate multiple signals triggered by integrins. The model of EPC culture %in vitro% was used to study the expression, distribution and function of pp125 FAK during EPC outgrowth on FN. Results indicated that, pp125 FAK primarily expressed and distributed in cellular focal adhesions of the front edge of trophoblast outgrowth from EPC, and was localized in the peripheral region of the individual migrating trophblast cell; antibody or antisense oligodeoxynucleotide to pp125 FAK inhibited EPC attachment and outgrowth, as well as trophoblast cells spreading and migration. This experiment demonstrated that pp125 FAK as an integrin-mediated signaling molecule was involved in EPC outgrowth %in vitro%, and played an important role during trophoblast cells interaction with FN.     

一语双关

作为一种最为常见的修辞方法，双关被广泛应用于广告、电影、谜语及日常生活中。人们用双关语来充实文章，使行文幽默且具有吸引力，所以说双关给人们带来好处，特别是广告语中的双关。因为使用了双关。广告才朗朗上口，才吸引了大量顾客。但同时有另外一个问题，就是怎样使不同国家的人都明白双关的奥妙呢？这就要求我们重视翻译技巧，搭好不同语言之间的桥梁，让不同国家的人们欣赏到双关的妙处。文章将从双关的定义、分类以及翻译技巧等方面对双关语进行探讨。     

Detecting network intrusions by data mining and variable-length sequence pattern matching

Anomaly detection has been an active research topic in the field of network intrusion detection for many years. A novel method is presented for anomaly detection based on system calls into the kernels of Unix or Linux systems. The method uses the data mining technique to model the normal behavior of a privileged program and uses a variable-length pattern matching algorithm to perform the comparison of the current behavior and historic normal behavior, which is more suitable for this problem than the fixed-length pattern matching algorithm proposed by Forrest et al. At the detection stage, the particularity of the audit data is taken into account, and two alternative schemes could be used to distinguish between normalities and intrusions. The method gives attention to both computational efficiency and detection accuracy and is especially applicable for on-line detection. The performance of the method is evaluated using the typical testing data set, and the results show that it is significantly better than the anomaly detection method based on hidden Markov models proposed by Yan et al. and the method based on fixed-length patterns proposed by Forrest and Hofmeyr. The novel method has been applied to practical hosted-based intrusion detection systems and achieved high detection performance.     

面向21世纪的物质科学

物质世界，从最最微小的基本粒子一直延伸到囊括一切的宇宙，构成了物质科学的研究对象。物质科学是以物理学与化学为主的学科群并向地球物理与化学、空间科学和天文学延拓。一、物质世界的层次化在本世纪初出现了两大理论的突破，即相对论与量子论。相对论可视为经典物理学的登峰造极之作，因为狭义相对论无非是经典电动力学的延伸，但同时带来了高速运动物体的力学和普遍的质能关系，并且改变了人们对于时—空的概念；而广义相对论实质上是引力的几何理论，对于现代天文学，特别是宇宙论，产生了深远的影响。量子论则开启了微观世界科学的…     

细胞凋亡与肿瘤治疗

细胞凋亡是机体维持自身稳定的一种生理机制,是由基因编码的控制细胞主动参与“自杀”的过程.细胞凋亡与肿瘤密切相关,已成为肿瘤治疗研究的新思路.本文主要阐述细胞凋亡及生理生化特征和肿瘤的形成与肿瘤的治疗.     

Two-step measurement update for extended Kalman filtering

1.INTRODUCTION TheextendedKalmanfilter(EKF)isthemost widelyusednonlinearfilterbecauseofitssimplicity despiteitsinconsistenceinsomeapplications.Thein consistenceoftheEKFmainlyarisesfromtheuseof linearization.Sincethereferencepointsforthelin earizationarearoundthepriorestimatesofthestate (filteredestimateforlinearizationofstatetransition equationandpredictiveestimateforlinearizationof measurementequation,respectively),agoodprior estimateisveryimportantfortheEKF.Inmanycas es,themeasur…     

1830—1856年中国“银荒”危机之传染路径探析

1830—1856年,货币供给严重不足及银贵钱贱的双重危机迅速导致中国经济严重萧条,政府税收因而大受影响,国家财政危机紧逼而至,社会危机重重。外国侵略者趁虚而入,中国日益陷入重重险境,民不聊生,纷纷起义。中国经济和社会危机进一步加深。     

傅里叶变换光谱仪动镜速度波动分析研究

在傅里叶变换光谱仪中,动镜速度的均匀性直接影响光谱图的质量。针对影响速度均匀性的多个因素展开研究,从运动机构自身特性、振动干扰、电路噪声等方面进行理论分析和实验测量,计算出各项因素导致的速度波动量;并讨论了降低外部干扰的方法。实验表明干扰造成的速度波动均在可接受的范围内,说明降低速度波动的工作主要在于优化控制算法。