共查询到20条相似文献,搜索用时 315 毫秒
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目的:探索B超检查了解宫内节育器情况的应用价值。方法:选择2012年1月~2012年12月来我站检查IUD位置的育龄妇女82例,对其进行宫内节育器的B超诊断,并进行回顾分析所有妇女宫内节育器情况。结果:进行B超检查的82例妇女中,节育器位置正常者78例(95%),节育器异位者3例(3%),节育器嵌并发子宫内膜炎1例(1%),带环受孕1例(1%)。结论:B超对节育器异位诊断明确,暴露清楚,定位准确,分离钳取容易超声检查能较为准确的诊断宫内节育环异常情况,值得临床中推广应用。 相似文献
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复合材料在军事工业领域有着举足轻重的地位,目前军用复合材料正向高功能化、超高能化、复合轻量和智能化的方向发展.军用复合材料主要分为结构复合材料和功能复合材料两大类.列举了复合材料在军事领域的一些应用,并指出军用复合材料设计中的一些问题. 相似文献
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国家食品药品监督管理局对义齿基托聚合物、齿科水基水门汀、导管类产品、软性角膜接触镜、宫内节育器、橡胶避孕套、玻璃体温计、心电监护仪和高频手术设备等9类产品进行了国家质量监督抽验。其中玻璃体温计抽验合格率为87%,不合格产品的主要问题是“示值”、“自流”两个指标;此外,心电监护仪抽验合格率为66.7%,高频手术设备抽验项目合格率为20%。 相似文献
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热电偶测温的精度和可靠性很大程度上决定于热电偶材料的热电均匀性和稳定性。测温实践中为了获得最佳结果,不仅要注意热电偶的结构、安装和校准,更要注意密切结合测温现场和工况来选择材料,并注意热偶与环境介质间的相容性问题。文中介绍了近十几年来标准化热电偶材料、铠装热电偶材料、低温热电偶材料和高温热电偶材料的发展概况,以及在测温实践中的一些材料问题。 相似文献
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Vogel E 《Nature nanotechnology》2007,2(1):25-32
Scaling of the metal oxide semiconductor (MOS) field-effect transistor has been the basis of the semiconductor industry for nearly 30 years. Traditional materials have been pushed to their limits, which means that entirely new materials (such as high-kappa gate dielectrics and metal gate electrodes), and new device structures are required. These materials and structures will probably allow MOS devices to remain competitive for at least another ten years. Beyond this timeframe, entirely new device structures (such as nanowire or molecular devices) and computational paradigms will almost certainly be needed to improve performance. The development of new nanoscale electronic devices and materials places increasingly stringent requirements on metrology. 相似文献
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《Materials Today》2002,5(1):30-35
Intrinsically smart structural composites are multifunctional structural materials which can perform functions such as sensing strain, stress, damage or temperature; thermoelectric energy generation; EMI shielding; electric current rectification; and vibration reduction. These capabilities are rendered by the use of materials science concepts to enhance functionality without compromising structural properties. They are not achieved by the embedding of devices in the structure. Intrinsically smart structural composites have been attained in cement-matrix composites containing short electrically conducting fibers and in polymer-matrix composites with continuous carbon fibers. Cement-matrix composites are important for infrastructure, while polymer-matrix composites are useful for lightweight structures.Smart structures are important because of their relevance to hazard mitigation, structural vibration control, structural health monitoring, transportation engineering, thermal control, and energy saving. Research on smart structures has emphasized the incorporation of various devices in a structure for providing sensing, energy dissipation, actuation, control or other functions. Work on smart composites has focused on the incorporation of a functional material or device in a matrix material for enhancing the smartness or durability, while that on smart materials has studied materials (e.g. piezoelectric) used for making relevant devices. However, relatively little attention has been given to the development of structural materials (e.g. concrete and composites) that are inherently able to provide some of the smart functions, so that the need for embedded or attached devices is reduced or eliminated, thereby lowering cost, enhancing durability, increasing the smart volume, and minimizing mechanical property degradation (which usually occurs in the case of embedded devices). 相似文献
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Min-Ho Seo Jae-Young Yoo Min-Seung Jo Jun-Bo Yoon 《Advanced materials (Deerfield Beach, Fla.)》2020,32(35):1907082
Recently, geometrically structured nanomaterials have received great attention due to their unique physical and chemical properties, which originate from the geometric variation in such materials. Indeed, the use of various geometrically structured nanomaterials has been actively reported in enhanced-performance devices in a wide range of applications. Recent significant progress in the development of geometrically structured nanomaterials and associated devices is summarized. First, a brief introduction of advanced nanofabrication methods that enable the fabrication of various geometrically structured nanomaterials is given, and then the performance enhancements achieved in devices utilizing these nanomaterials, namely, i) physical and gas nanosensors, ii) nanoelectromechanical devices, and iii) nanosieves are described. For the device applications, a systematic summary of their structures, working mechanisms, fabrication methods, and output performance is provided. Particular focus is given to how device performance can be enhanced through the geometric structures of the nanomaterials. Finally, perspectives on the development of novel nanomaterial structures and associated devices are presented. 相似文献
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High‐energy storage devices are in demand for the rapid development of modern society. Until now, many kinds of energy storage devices, such as lithium‐ion batteries (LIBs), sodium‐ion batteries (NIBs), and so on, have been developed in the past 30 years. However, most of the commercially exploited and studied active electrode materials of these energy storage devices possess a single phase with low reversible capacity or unsatisfied cycle stability. Continuous and extensive research efforts are made to develop alternative materials with a higher specific energy density and long cycle life by element doping or surface modification. A novel strategy of forming composite‐structure electrode materials by introducing structure units has attracted great attention in recent years. Herein, based on previous publications on these composite‐structure materials, some important scientific points focusing on the design of composite‐structure materials for better electrochemical performances reveal the distinction of composite structures based on average and local structure analysis methods, and an understanding of the relationship between these interior composite structures and their electrochemical performances is discussed thoroughly. The lithiation/delithiation mechanism and the remaining challenges and perspectives for composite‐structure electrode materials are also elaborated. 相似文献
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A. Driessen H. J. W. M. Hoekstra F. C. Blom F. Horst G. J. M. Krijnen J. B. P. van Schoot P. V. Lambeck Th. J. A. Popma M. B. Diemeer 《Optical Materials》1998,9(1-4):329-333
Nonlinear polymers are promising materials for high speed active integrated optics devices. In this paper we evaluate the perspectives polymer based nonlinear optical devices can offer. Special attention is directed to the materials aspects. In our experimental work we applied mainly Akzo Nobel DANS side-chain polymer that exhibits large second and third order coefficients. This material has been characterized by third harmonic generation, z-scan and pump-probe measurements. In addition, various waveguiding structures have been used to measure the nonlinear absorption (two photon absorption) on a ps time-scale. Finally an integrated optics Mach Zehnder interferometer has been realized and evaluated. It is shown that the DANS side-chain polymer has many of the desired properties: the material is easily processable in high-quality optical waveguiding structures, has low linear absorption and its nonlinearity has a pure electronic origin. More materials research has to be done to arrive at materials with higher nonlinear coefficients to allow switching at moderate light intensity ( < 1 W peak power) and also with lower nonlinear absorption coefficients. 相似文献
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智能材料与结构的发展研究 总被引:1,自引:0,他引:1
智能材料与结构是由世界发达国家在80年代发展起来的一项高新技术,智能结构就是把传感器,致动器,光电器件和微型处理机等预先埋置在复合材料层压板内形成的。由于它奇特的功能和潜在的应用,目前已成为航空天部门专家和工程师们广为关心的课题。本文介绍了国外智能材料与结构的最新发展和应用,智能结构的组成和制造方法,最后讨论了目前存在的问题和我国开展智能结构发展研究的建议。 相似文献
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Redel E Huai C Renner M von Freymann G Ozin GA 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(24):3465-3471
To manipulate electrons in semiconductor electronic and optical devices, the usual approach is through materials composition, electronic bandgap, doping, and interface engineering. More advanced strategies for handling electrons in semiconductor devices include composition-controlled heterostructures and gradient structures. By analogy to the manipulation of electrons in semiconductor crystals by electronic bandgaps, photons in photonic crystals can be managed using photonic bandgaps. In this context, the simplest photonic crystal is the Bragg mirror, a periodic dielectric construct whose photonic bandgap is engineered through variations of the optical thickness of its constituent layers. Traditionally the materials comprising these periodic dielectric layers are nonporous, and they have mainly been used in the field of optical and photonic devices. More recently these Bragg mirrors have been made porous by building the layers from nanoparticles with functionality and utility that exploit their internal voids. These structures are emerging in the area of photonic color-coded chemical sensing and controlled chemical release. Herein, a strategy for enhancing the functionality and potential utility of nanoparticle Bragg mirrors by making the constituent dielectric layers aperiodic and porous is described. It is exemplified by prototypical tandem and gradient structures that are fully characterized with regards to their structure, porosity, and optical and photonic properties. 相似文献
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Danish Khan Xiaoyuan Liu Geping Qu Amit Ranjan Nath Pengfei Xie Zong-Xiang Xu 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(11):2205926
Perovskite solar cells (PSCs) have grabbed much attention of researchers owing to their quick rise in power conversion efficiency (PCE). However, long-term stability remains a hurdle in commercialization, partly due to the inclusion of necessary hygroscopic dopants in hole transporting materials, enhancing the complexity and total cost. Generally, the efforts in designing dopant-free hole transporting materials (HTMs) are devoted toward small molecule and polymeric HTMs, where small molecule based HTMs (SM-HTMs) are dominant due to their reproducibility, facile synthesis, and low cost. Still, the state-of-art dopant-free SM-HTM has not been achieved yet, mainly because of the knowledge gap between device engineering and molecular designs. From a molecular engineering perspective, this article reviews dopant-free SM-HTMs for PSCs, outlining analyses of chemical structures with promising properties toward achieving effective, low-cost, and scalable materials for devices with higher stability. Finally, an outlook of dopant-free SM-HTMs toward commercial application and insight into the development of long-term stability PSCs devices is provided. 相似文献
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Yueqi Zhu Hongbo Zhang Yiran Zhang Huayin Wu Liming Wei Gen Zhou Yuezhou Zhang Lianfu Deng Yingsheng Cheng Minghua Li Hlder A. Santos Wenguo Cui 《Advanced materials (Deerfield Beach, Fla.)》2019,31(8)
Cerebrovascular disease involves various medical disorders that obstruct brain blood vessels or deteriorate cerebral circulation, resulting in ischemic or hemorrhagic stroke. Nowadays, platinum coils with or without biological modification have become routine embolization devices to reduce the risk of cerebral aneurysm bleeding. Additionally, many intracranial stents, flow diverters, and stent retrievers have been invented with uniquely designed structures. To accelerate the translation of these devices into clinical usage, an in‐depth understanding of the mechanical and material performance of these metal‐based devices is critical. However, considering the more distal location and tortuous anatomic characteristics of cerebral arteries, present devices still risk failing to arrive at target lesions. Consequently, more flexible endovascular devices and novel designs are under urgent demand to overcome the deficiencies of existing devices. Herein, the pros and cons of the current structural designs are discussed when these devices are applied to the treatment of diseases ranging broadly from hemorrhages to ischemic strokes, in order to encourage further development of such kind of devices and investigation of their use in the clinic. Moreover, novel biodegradable materials and drug elution techniques, and the design, safety, and efficacy of personalized devices for further clinical applications in cerebral vasculature are discussed. 相似文献