Windows堆保护机制及绕过的可能性分析

Windows堆管理器是一个用于动态分配内存的子系统。堆溢出是指在动态分配堆内存过程中堆块块首中的前向指针和后向指针被上一堆块中的溢出数据修改,这样在被溢出堆块被分配时可转去执行恶意代码。微软针对这种堆溢出提出了一系列安全机制,先简要叙述这一系列安全机制的工作原理,然后分析了这些安全机制存在的弱点,并对利用这些弱点绕过安全机制的可能性做了简要的分析。     

粗颗粒煤水混合物的稠度和流变特性的研究

燃煤增压流化床的燃料制备与输送系统往往需采用气力输送方法送入加压罐后再送入炉内，系统复杂．采用煤水混合燃料泵送技术则可解决上述困难．提出了用塌落度测定方法判断０～６ｍｍ粗颗粒煤水混合物的可泵性，并选择适于泵送的较佳颗粒级配．建立了泵送与管道输送试验台进行粗颗粒徐州煤水混合物的流变特性试验，所得的泵送流变试验数据处理后的模型，可用于商用粗颗粒煤水混合物输送系统的设计计算．     

High Performance Piezoelectric Microspeakers and Thin Speaker Array System

This paper reports on an improved piezoelectric microspeaker with a high sound pressure level of 90 dB, a total harmonic distortion of less than 15%, and coherence higher than 0.9. The fabricated Pb(Zr,Ti)O₃ (PZT) microspeakers have a thickness of only 1 mm including the speaker frame and an active area of 18 mm×20 mm. To achieve higher sound pressure and lower distortion, the PZT piezoelectric microspeaker has a well‐designed speaker frame and a piezoelectric diaphragm consisting of a tilted PZT membrane and silicone buffer layer. From the simulation and measurement results, we confirmed that the silicon buffer layer can lower the first resonant frequency, which enhances the microspeaker's sound pressure at a low frequency range and can also reduce useless distortion generated by the harmonics. The fabricated PZT piezoelectric microspeakers are implemented on a multichannel speaker array system for personal acoustical space generation. The output sound pressure at a 30 cm distance away from the center of the speaker line array is 15 dB higher than the sound pressure at the neighboring region 30 degrees from the vertical axis.     

2μs低损耗声体波微波延迟线

通过优化换能器拓扑结构,探索长延时传声介质的双面光刻及探针提取S参数进行网络匹配等技术,改进了声体波微波延迟线换能器设计及制作工艺.研制出中心频率为4.3 GHz,带宽为200 MHz,延迟时间为1.999 7μs,插入损耗仅26 dB,直通抑制45 dB,3次渡越抑制42 dB的声体波微波延迟线.     

熔石英亚表面微缺陷原位表征及损伤阈值研究

通过对熔石英表面和亚表面划痕的原位测量,研究划痕的表面均方根(RMS)粗糙度、宽度和深度在HF溶液中刻蚀不同时间后的变化规律,测试了不同刻蚀时间下熔石英的损伤阈值。实验结果表明:随刻蚀时间的增加,表面RMS、划痕深度及宽度的总体变化趋势是增加的;熔石英的损伤阈值随刻蚀时间的增加,在1～10min时间段呈增加趋势,在20～40 min时间段呈下降趋势,而在60～120 min时间段先增加后降低。综合熔石英划痕的微观形貌损伤阈值的测量结果认为,刻蚀10 min时效果最佳。     

Large-Scale Synthesis of Graphene Films by Joule-Heating-Induced Chemical Vapor Deposition

We report large-area synthesis of few-layer graphene films by chemical vapor deposition (CVD) in a cold-wall reactor. The key feature of this method is that the catalytic metal layers on the SiO₂/Si substrates are self-heated to high growth temperature (900°C to 1000°C) by high-current Joule heating. Synthesis of high-quality graphene films, whose structural and electrical characteristics are comparable to those grown by hot-wall CVD systems, was confirmed by transmission electron microscopy images, Raman spectra, and current–voltage analysis. Optical transmittance spectra of the graphene films allowed us to estimate the number of graphene layers, which revealed that high-temperature exposure of Ni thin layers to a carbon precursor (CH₄) was critical in determining the number of graphene layers. In particular, exposure to CH₄ for 20 s produces very thin graphene films with an optical transmittance of 93%, corresponding to an average layer number of three and a sheet resistance of ~600 Ω/square.     

“传感技术与测控电路”实验教学改革

本文从目前学生普遍缺少动手能力的现状出发,对实践教学课程设计环节进行了教学改革研究。根据不同学生的学习要求,将＂传感器技术与测控电路＂实验课程结合起来,并设定不同的设计任务,从而保证能通过实验教学最大程度的提高学生们的认知与动手能力。     

JOB-9003炸药热冲击损伤的超声波检测

观察了JOB-9003炸药在水浴法热冲击试验中发生的损伤及变化过程,研究了超声特性参数(增益)与炸药热冲击损伤因子的关系,曲线关系预示出炸药存在预损伤。研究结果表明超声波检测技术及装置适合于JOB-9003炸药热冲击损伤及其演变的实验测试,可为研究炸药在外载条件下的动态响应提供一项新的实验技术。     

浅谈声发射技术在含能材料研究中的应用

综述了国内外声发射技术的发展及其在含能材料研究中应用进展。从含能材料的声发射特性研究和多项性能试验等方面对含能材料的声发射检测技术和应用途径进行分析和比较，结果表明声发射检测技术作为一种动态无损检测技术，在含能材料的产品质量控制、性能研究、内部损伤的监测与评估以及加工安全监测等方面都有其独特的可靠性和优越性。     

Modulation of Mechanical Interactions by Local Piezoelectric Effects

Piezoelectricity is a well‐established property of biological materials, yet its functional role has remained unclear. Here, a mechanical effect of piezoelectric domains resulting from collagen fibril organisation is demonstrated, and its role in tissue function and application to material design is described. Using a combination of scanning probe and nonlinear optical microscopy, a hierarchical structuring of piezoelectric domains in collagen‐rich tissues is observed, and their mechanical effects are explored in silico. Local electrostatic attraction and repulsion due to shear piezoelectricity in these domains modulate fibril interactions from the tens of nanometre (single fibril interactions) to the tens of micron (fibre interactions) level, analogous to modulated friction effects. The manipulation of domain size and organisation thus provides a capacity to tune energy storage, dissipation, stiffness, and damage resistance.