Towards Attacks and Defenses of Anonymous Communication Systems

Tianbo Lu,Puxin Yao1,Lingling Zhao,Yang Li,Feng Xie,Yamei Xia 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.1

Anonymous communication system has been hot topic in the field of information security, and attack techniques against anonymous systems are endless. This paper first classifies and summarizes the study of attacks against anonymous communication system in recent years, then analyzes the trend of the research on different attack technologies; secondly, it provides a comparative analysis of defense capability the mainstream anonymous communication system to the various attacks; Finally, combining the advantages and disadvantages of different systems, the authors propose an improved node selection and router forwarding algorithms for anonymous communication systems, and design an architecture of anonymous communications software based on the algorithm.

AAO-assisted synthesis of highly ordered, large-scale TiO ₂ nanowire arrays via sputtering and atomic layer deposition

Yao, Zhao,Wang, Cong,Li, Yang,Kim, Nam-Young Springer US 2015 NANOSCALE RESEARCH LETTERS Vol.10 No.1

<P>Highly ordered nanoporous anodic aluminum oxide (AAO) thin films were fabricated in oxalic acid under a constant voltage via a two-step anodization process. To investigate the high-aspect-ratio (7.5:1) filling process, both sputtering and atomic layer deposition (ALD) were used to form TiO<SUB>2</SUB> nanowires. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that mushroom-like TiO<SUB>2</SUB> structures were sputtered onto the AAO template surface, and the ALD-coated TiO<SUB>2</SUB> exhibited fine filling results and clear crystal grain boundaries. Large-scale and free-standing TiO<SUB>2</SUB> nanowire arrays were liberated by selectively removing the aluminum substrate and AAO template via a wet etching process with no collapsing or agglomeration after the drying process. ALD-deposited TiO<SUB>2</SUB> nanowire arrays that were 67 nm in diameter and 400 nm high were transferred from the AAO template. The ALD process enabled the rapid, simple synthesis of highly ordered TiO<SUB>2</SUB> nanowire arrays with desired parameters such as diameter, density, and thickness determined using diverse AAO templates.</P>

The Power of Simultaneous Multi-frequency Observations for mm-VLBI: Beyond Frequency Phase Transfer

Zhao, Guang-Yao,Algaba, Juan Carlos,Lee, Sang Sung,Jung, Taehyun,Dodson, Richard,Rioja, Marí,a,Byun, Do-Young,Hodgson, Jeffrey,Kang, Sincheol,Kim, Dae-Won,Kim, Jae-Young,Kim, Jeong-Sook,Kim, Soo American Institute of Physics 2018 The Astronomical journal Vol.155 No.1

<P>Atmospheric propagation effects at millimeter wavelengths can significantly alter the phases of radio signals and reduce the coherence time, putting tight constraints on high-frequency Very Long Baseline Interferometry (VLBI) observations. In previous works, it has been shown that non-dispersive (e.g., tropospheric) effects can be calibrated with the frequency phase transfer (FPT) technique. The coherence time can thus be significantly extended. Ionospheric effects, which can still be significant, remain however uncalibrated after FPT as well as the instrumental effects. In this work, we implement a further phase transfer between two FPT residuals (i.e., so-called FPT-square) to calibrate the ionospheric effects based on their frequency dependence. We show that after FPT-square, the coherence time at 3 mm can be further extended beyond 8 hr and the residual phase errors can be sufficiently canceled by applying the calibration of another source, which can have a large angular separation from the target (> 20 degrees) and significant temporal gaps. Calibrations for all-sky distributed sources with a few calibrators are also possible after FPT-square. One of the strengths and uniqueness of this calibration strategy is the suitability for high-frequency all-sky survey observations including very weak sources. We discuss the introduction of a pulse calibration system in the future to calibrate the remaining instrumental effects, allowing the possibility of imaging the source structure at high frequencies with FPT-square, where all phases are fully calibrated without involving any additional sources.</P>

An efficient Video Dehazing Algorithm Based on Spectral Clustering

Zhao, Fan,Yao, Zao,Song, Xiaofang,Yao, Yi Korean Society for Internet Information 2018 KSII Transactions on Internet and Information Syst Vol.12 No.7

Image and video dehazing is a popular topic in the field of computer vision and digital image processing. A fast, optimized dehazing algorithm was recently proposed that enhances contrast and reduces flickering artifacts in a dehazed video sequence by minimizing a cost function that makes transmission values spatially and temporally coherent. However, its fixed-size block partitioning leads to block effects. The temporal cost function also suffers from the temporal non-coherence of newly appearing objects in a scene. Further, the weak edges in a hazy image are not addressed. Hence, a video dehazing algorithm based on well designed spectral clustering is proposed. To avoid block artifacts, the spectral clustering is customized to segment static scenes to ensure the same target has the same transmission value. Assuming that edge images dehazed with optimized transmission values have richer detail than before restoration, an edge intensity function is added to the spatial consistency cost model. Atmospheric light is estimated using a modified quadtree search. Different temporal transmission models are established for newly appearing objects, static backgrounds, and moving objects. The experimental results demonstrate that the new method provides higher dehazing quality and lower time complexity than the previous technique.

Failure characteristics of combined coal-rock with different interfacial angles

Zhao, Tong-Bin,Guo, Wei-Yao,Lu, Cai-Ping,Zhao, Guang-Ming Techno-Press 2016 Geomechanics & engineering Vol.11 No.3

In order to investigate the influence of the interfacial angel on failure characteristics and mechanism of combined coal-rock mass, 35 uniaxial/biaxial compressive simulation tests with 5 different interfacial angels of combined coal-rock samples were conducted by PFC2D software. The following conclusions are drawn: (1) The compressive strength and cohesion decrease with the increase of interfacial angle, which is defined as the angle between structure plane and the exterior normal of maximum principal plane, while the changes of elastic modulus and internal friction angle are not obvious; (2) The impact energy index $K_E$ decreases with the increase of interfacial angle, and the slip failure of the interface can be predicted based on whether the number of acoustic emission (AE) hits has multiple peaks or not; (3) There are four typical failure patterns for combined coal-rock samples including I (V-shaped shear failure of coal), II (single-fracture shear failure of coal), III (shear failure of rock and coal), and IV (slip rupture of interface); and (4) A positive correlation between interfacial angle and interface effect is shown obviously, and the interfacial angle can be divided into weak-influencing scope ($0-15^{\circ}$), moderate-influencing scope ($15-45^{\circ}$), and strong-influencing scope (> $45^{\circ}$), respectively. However, the confining pressure has a certain constraint effect on the interface effect.

Effects of Submicron Metakaolin on Hydration and Compressive Strength of Portland Cement Slurry

Yao Yu Wang,Lihua Zhao,Jing Zhao 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7

Submicron metakaolin (SMK) is an ultrafine aluminosilicate material, which was used for improving properties of cement slurry in this paper. SMK was added to the slurry mix as a partial substitute for Portland cement in proportions of 1%, 3%, 5% and 7%. To explore the influence of SMK on hydration of cement slurry, the heat flow and pH measurement was used to indicate that SMK significantly increased the rate of heat release and total heat release,increase the rate of calcium hydroxide (CH) generation in the pore solution at initial stage of hydration. The hardened specimens at different ages (3 – 28 days) were measured by X–ray diffraction, Differential Thermal Analysis and Compressive strength. The results showed that:SMK displayed pozzolanic effect which reduced CH content and increased the generation of Calcium Silicate Hydrate (C-S-H) gel at later stages of hydration. The compressive strength tests showed that SMK highest increased compressive strength of the slurry by 67% and 19% at 3d and 28d over plain cement slurry. It was concluded that SMK could improve manyproperties of cement slurry and has the use potential on actual projects.

Advanced Diagnosis of Armature Winding Short-Circuit Faults in Variable Flux Reluctance Machines Using Information Fusion on Mechanical and Electrical Signals

Zhao Yao,Zhao Zhibo,Lin Shunfu,Yang Fan,Li Dongdong 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.4

Variable fl ux reluctance machines can be adopted in the fi eld of built-in starter generator for aero-engine. It is critical to achieve reliable protection of the power generation system in harsh environments. The single signal makes it diffi cult to identify the initial fault accurately due to the little impact by a small-turn short-circuit on the electromagnetic fi eld. Thus, this paper proposes a novel framework for multi-source information fusion fault diagnosis in VFRMs by extracted current signals manually and vibration signals automatically. Firstly, the armature winding short-circuit fault characteristics of the current and vibration signals in the VFRM are analyzed. Secondly, a multi-source fusion framework based on a kernel extreme learning machine combined with a multiscale convolutional neural network is presented according to the structural characteristics of the VFRM. Then, the Dempster-Shafer evidence theory is applied for achieving decision-level fusion. Finally, a four-phase 8/10-pole VFRM prototype with diff erent AWSC faults is used to validate the proposed method. The results indicate that the fault diagnosis rate of the proposed method is 97.28%, which is 10.37% and 3.7% higher than vibration and current signals, respectively. It is more reliable and eff ective to identify diff erent AWSC faults accurately in the early stages.

MULTI-EPOCH MULTI-FREQUENCY VLBI STUDY OF THE PARSEC-SCALE JET IN THE BLAZAR 3C 66A

Zhao, Guang-Yao,Chen, Yong-Jun,Shen, Zhi-Qiang,Sudou, Hiroshi,Iguchi, Satoru American Institute of Physics 2015 The Astronomical journal Vol.149 No.2

<P>We present observational results of the &ggr;-ray blazar 3C 66A at 2.3, 8.4, and 22 GHz at four epochs during 2004–2005 with the VLBA. The resulting images show an overall core-jet structure extending roughly to the south, with two intermediate breaks occurring in the region near the core. By model-fitting to the visibility data, the northmost component, which is also the brightest, is identified as the core according to its relatively flat spectrum and its compactness. Combining our results with previous results to investigate the proper motions of the jet components, we found the kinematics of 3C 66A to be quite complicated, with components of inward and outward, subluminal and superluminal motions all detected in the radio structure. The superluminal motions indicate strong Doppler boosting exists in the jet. The apparent inward motions of the innermost components last for at least 10 years and could not be caused by newborn components. A possible reason could be non-stationarity of the core due to opacity change.</P>

Effects of starting powder and thermal treatment on the aerosol deposited BaTiO ₃ thin films toward less leakage currents

Yao, Zhao,Wang, Cong,Li, Yang,Kim, Hong-Ki,Kim, Nam-Young Springer 2014 NANOSCALE RESEARCH LETTERS Vol.9 No.1

<P>To prepare high-density integrated capacitors with low leakage currents, 0.2-μm-thick BaTiO<SUB>3</SUB> thin films were successfully deposited on integrated semiconductor substrates at room temperature by the aerosol deposition (AD) method. In this study, the effects of starting powder size were considered in an effort to remove macroscopic defects. A surface morphology of 25.3 nm and an interface roughness of less than 50 nm were obtained using BT-03B starting powder. The nano-crystalline thin films achieved after deposition were annealed at various temperatures to promote crystallization and densification. Moreover, the influence of rapid thermal annealing process on the surface morphology and crystal growth was evaluated. As the annealing temperature increased from room temperature to 650°C, the root mean square (RMS) roughness decreased from 25.3 to 14.3 nm. However, the surface was transformed into rough performance at 750°C, which agreed well with the surface microstructure trend. Moreover, the crystal growth also reveals the changes in surface morphology via surface energy analysis.</P>

KVN SOURCE-FREQUENCY PHASE-REFERENCING OBSERVATION OF 3C 66A AND 3C 66B

ZHAO, GUANG-YAO,JUNG, TAEHYUN,DODSON, RICHARD,RIOJA, MARIA,SOHN, BONG WON The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2

In this proceedings, preliminary results of the KVN Source-Frequency Phase-Referencing (SFPR) observation of 3C 66A and 3C 66B are presented. The motivation of this work is to measure the core-shift of these 2 sources and study the temporal evolution of the jet opacity. Two more sources were observed as secondary reference calibrators and each source was observed at 22, 43, and 86 GHz simultaneously. Our preliminary results show that after using the observations at the lower frequency to calibrate those at the higher frequency of the same source, the residual visibility phases for each source at the higher frequencies became more aligned, and the coherence time became much longer; also, the residual phases for different sources, within 10 degrees angular separations, follow similar trends. After reference to the nearby calibrator, the SFPRed maps were obtained as well as the astrometric measurements, i.e. the combined coreshift. The measurements were found to be affected by structural blending effects because of the large beamsize of KVN, but this can be corrected with higher resolution maps (e.g. KAVA maps).