B&K4195人工耳等效电路模型修正

B&K 4195人工耳原有等效电路模型的仿真结果在3 k Hz以上频段与实测相差较大,无法满足精度要求。通过有限元仿真和声阻抗转移理论的对比,对突变截面结构提出了附加质量概念,从而完善了腔管结构在较大尺寸和较高频段下的等效电路模型。根据此方法修正了人工耳耳廓部分的等效电路模型,使仿真与实测在6 k Hz前的频段内吻合较好。     

Preparation and Thermoelectric Properties of Ag<Subscript>0.5</Subscript>In<Subscript>0.5−<Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript>5</Subscript>Sn<Subscript>4</Subscript>Te<Subscript>10</Subscript>

A series of compounds with composition Ag_0.5In_0.5−x Pb₅Sn₄Te₁₀ (x = 0.05 to 0.20) were prepared by slowly cooling the melts of the corresponding elements, and the effect of In content on the thermoelectric transport properties of these compounds has been investigated. Results indicate that the compounds’ electronic structure is sensitive to In content, and that the carrier concentration of these compounds at room temperature increases from 4.86 × 10¹⁸ cm⁻³ to 3.85 × 10²¹ cm⁻³ as x increases from 0.05 to 0.20. For these compounds, electrical conductivity decreases and Seebeck coefficient increases with increasing In content. Ag_0.05In_0.03Pb_0.5Sn_0.4Te₁₀ shows very low lattice thermal conductivity, and has a maximum dimensionless figure of merit ZT of 1.2 at 800 K.     

Photoluminescence and excitation features of Nd<Superscript>3+</Superscript> ions in (La<Subscript>0.97</Subscript>Nd<Subscript>0.03</Subscript>)<Subscript>2</Subscript>S<Subscript>3</Subscript> · 2Ga<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses

A combined study of the spectral photoluminescence distribution and excitation spectra of photoluminescence in La₂S₃ · 2Ga₂O₃ and (La_0.97Nd_0.03)₂S₃ · 2Ga₂O₃ glasses, along with the study of the transmission spectra of these glasses, was carried out. The radiative channel was ascertained to be the main channel for the energy transfer from the host matrix to the Nd³⁺ ions upon excitation of the glasses with light at a wavelength of the fundamental absorption band. Oxygen centers with the level E _c -2.0 eV act as sensitizing agents. The structural disordering of the glass host increases the variance in the magnitude of splitting of the multiplet levels from the 4f electronic states of the Nd³⁺ ion. This promotes nonradiative relaxation of the electrons from excited states to the laser ⁴F_3/2 level. The (La_0.97Nd_0.03)₂S₃ · 2Ga₂O₃ glasses can be considered as promising laser materials for obtaining the stimulated emission of radiation of Nd³⁺ ions under an optical pump in the range of the fundamental absorption band of the glass.     

The Power Factor of Bi<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Tl<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Se<Subscript>3</Subscript> Single Crystals

Single crystals of the ternary system Bi_2−x Tl _x Se₃ (nominally x = 0.0 to 0.1) were prepared using the Bridgman technique. Samples with varying content of Tl were characterized by measurement of lattice parameters, electrical conductivity σ _⊥c, Hall coefficient R _H(B║c), and Seebeck coefficient S(ΔT⊥c). The measurements indicate that incorporation of Tl into Bi₂Se₃ lowers the concentration of free electrons and enhances their mobility. This effect is explained within the framework of the point defects in the crystal lattice, with formation of substitutional defects of thallium in place of bismuth (Tl_Bi) and a decrease in the concentration of selenium vacancies (V_Se ^{+ 2} V_{\rm{Se}}^{ + 2} ). The temperature dependence of the power factor σS ² of the samples is also discussed. As a consequence of the thallium doping we observe a significant increase of the power factor compared with the parent Bi₂Se₃.     

High-Temperature Transport Properties of Yb<Subscript>4−<Emphasis Type="Italic">x</Emphasis></Subscript>Sm<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Sb<Subscript>3</Subscript>

Polycrystalline L₄Sb₃ (L = La, Ce, Sm, and Yb) and Yb_4−x Sm _x Sb₃, which crystallizes in the anti-Th₃P₄ structure type (I-43d no. 220), were synthesized via high-temperature reaction. Structural and chemical characterization were performed by x-ray diffraction and electronic microscopy with energy-dispersive x-ray analysis. Pucks were densified by spark plasma sintering. Transport property measurements showed that these compounds are n-type with low Seebeck coefficients, except for Yb₄Sb₃, which shows semimetallic behavior with hole conduction above 523 K. By partially substituting Yb by a trivalent rare earth we successfully improved the thermoelectric figure of merit of Yb₄Sb₃ up to 0.7 at 1273 K.     

Magnetic Properties of Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>In<Subscript>2</Subscript>S<Subscript>4</Subscript> Alloy Single Crystals

This study concerns the magnetic properties of single crystals of Fe _x Mn_{1 − x} In₂S₄ alloys. The basically antiferromagnetic character of indirect exchange interactions between Fe²⁺ and Mn²⁺ cations is established. As the concentration of Fe²⁺ cations is increased, the magnetic ordering temperature increases from ∼12 K (x = 0) to ∼22 K (x = 1). Short-range-order ferromagnetic correlations are observed. The basic magnetic phase state of the alloys is the spin glass state, with the freezing temperature increasing from ∼5 K (x = 0) to ∼12 K (x = 1). As the external magnetic field is increased, the magnetic ordering temperature slightly decreases. The most probable causes and mechanisms of formation of the magnetic state of the alloys are discussed.     

基于句柄分析的Windows Rootkit检测技术研究

作为网络入侵领域的一种新兴技术,Rootkit能隐藏入侵痕迹、阻止用户和检测软件发现恶意代码的存在,具有隐蔽性好、难以检测等特点。根据对Rootkit行为的分析,提出了一种基于句柄分析的Rootkit检测技术,该方法通过遍历内核句柄表,得到系统中运行的所有进程,再与调用API得到的进程列表对比,发现Rootkit隐藏的进程。实验证明,该方法对于Rootkit具有良好的检测效果。     

基于vmem文件的隐藏信息检测研究

针对采用Rootkit技术进行隐藏的恶意程序,文中提出了一种基于虚拟机内外视图交叉比对的恶意程序检测方案来提取其隐藏的信息。该方案通过将虚拟机内部获取的不可信系统信息和虚拟机外部通过vmem文件分析得到的可信系统信息进行交叉比对,发现系统中被Rootkit所隐藏的进程信息,使得Rootkit类型恶意代码检测的有效性得到了保障。     

应用专家系统开发Windows恶意代码检测系统的研究

传统的基于特征的恶意代码检测方法无法检测未知恶意代码以及一些采用加壳等规避技术的恶意代码。为克服这些缺点,文章提出了基于专家系统的启发式检测方法。该方法可以检测采用了底层技术的恶意代码,如rootkit,以及加过壳或加过密的恶意代码,而且其检测率比一些知名的反病毒工具的检测率要高。     

Windows服务隐藏技术研究与实现

恶意程序利用Windows服务可以实现自启动及部分隐藏功能,研究服务隐藏技术能够提高对此类恶意程序的检测能力.研究了Windows服务的启动过程及服务对象的内部数据结构,提出一种结合内存隐藏和注册表隐藏的多点联合隐藏方法,设计并实现了一个基于该方法的服务隐藏程序,在实验条件下测试了此方法的隐藏效果,分析了应对该类型服务隐藏技术的检测策略.实验证明该方法能够在不影响服务功能的前提下,有效隐藏服务,躲避各类检测工具.     

A Novel Game Theoretic Method for Efficient Downlink Resource Allocation in Dual Band 5G Heterogeneous Network

In this paper obfuscation techniques used by novel malwares presented and compared. IAT smashing, string encryption and dynamic programing are explained in static methods and hooking at user and kernel level of OS with DLL injection, modifying of SSDT and IDT table addresses, filter IRPs, and possessor emulation are techniques in dynamic methods. This paper suggest Approach for passing through malware obfuscation techniques. In order that it can analyze malware behaviors. Our methods in proposed approach are detection presence time of a malware at user and kernel level of OS, dumping of malware executable memory at correct time and precise hook installing. Main purpose of this paper is establishment of an efficient platform to analyze behavior and detect novel malwares that by use of metamorphic engine, packer and protector tools take action for obfuscation and metamorphosis of themself. At final, this paper use a dataset embeds different kind of obfuscated and metamorphic malwares in order to prove usefulness of its methods experiments. Show that proposed methods can confront most malware obfuscation techniques. It evaluated success rate to unpacking, obfuscated malwares and it shows 85% success rate to recognize kernel level malwares.     

基于权限频繁模式挖掘算法的Android恶意应用检测方法

Android应用所申请的各个权限可以有效反映出应用程序的行为模式,而一个恶意行为的产生需要多个权限的配合,所以通过挖掘权限之间的关联性可以有效检测未知的恶意应用。以往研究者大多关注单一权限的统计特性,很少研究权限之间关联性的统计特性。因此,为有效检测Android平台未知的恶意应用,提出了一种基于权限频繁模式挖掘算法的Android恶意应用检测方法,设计了能够挖掘权限之间关联性的权限频繁模式挖掘算法—PApriori。基于该算法对49个恶意应用家族进行权限频繁模式发现,得到极大频繁权限项集,从而构造出权限关系特征库来检测未知的恶意应用。最后,通过实验验证了该方法的有效性和正确性,实验结果表明所提出的方法与其他相关工作对比效果更优。     

基于对比权限模式的安卓恶意软件检测方法(英文)

As the risk of malware is sharply increasing in Android platform,Android malware detection has become an important research topic.Existing works have demonstrated that required permissions of Android applications are valuable for malware analysis,but how to exploit those permission patterns for malware detection remains an open issue.In this paper,we introduce the contrasting permission patterns to characterize the essential differences between malwares and clean applications from the permission aspect Then a framework based on contrasting permission patterns is presented for Android malware detection.According to the proposed framework,an ensemble classifier,Enclamald,is further developed to detect whether an application is potentially malicious.Every contrasting permission pattern is acting as a weak classifier in Enclamald,and the weighted predictions of involved weak classifiers are aggregated to the final result.Experiments on real-world applications validate that the proposed Enclamald classifier outperforms commonly used classifiers for Android Malware Detection.     

Using <Emphasis Type="Italic">G</Emphasis> Features to Improve the Efficiency of <Emphasis Type="Italic">Function Call Graph</Emphasis> Based Android Malware Detection

In this paper, we proposed a G features based Android malware detecting scheme with information of Function Call Graph. The experimental results showed that our G features based detecting scheme obtained a high detecting performance in up-to-date malware testing dataset. Besides, the collapsing issue induced by the high-dimension vectors of traditional Function Call Graph detection can also be avoided with our methods.     

一种有效的加密隐藏算法

以原始图像作为保护信息，利用迭代算法，求得作为加密结果函数和密钥函数的纯相位形式（相息图），然后将加密结果函数隐藏在一个普通图像（或者其它形式）中，完成图像的加密隐藏过程。纯相位形式的隐藏方法，不但将加密和隐藏两种技术结合起来，而且具有特别优良的特性：基于信息隐藏的特点，算法有效降低了外来的恶意攻击可能性；基于加密结果的噪声特性，提高了视觉容许的可隐藏信息量，同时能有效地抗击裁剪、噪声等的影响，具有很强的“鲁棒”性。计算机仿真结果验证了这一点。     

一种有效的加密隐藏算法

以原始图像作为保护信息,利用迭代算法,求得作为加密结果函数和密钥函数的纯相位形式(相息 图),然后将加密结果函数隐藏在一个普通图像(或者其它形式)中,完成图像的加密隐藏过程．纯相位形式的隐藏 方法,不但将加密和隐藏两种技术结合起来,而且具有特别优良的特性:基于信息隐藏的特点,算法有效降低了外 来的恶意攻击可能性;基于加密结果的噪声特性,提高了视觉容许的可隐藏信息量,同时能有效地抗击裁剪、噪声 等的影响,具有很强的“鲁棒”性。计算机仿真结果验证了这一点。