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百年期刊
ISSN 1000-0585
CN 11-1848/P
Started in 1982
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Table of Content
, Volume 57 Issue 7
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COMPUTER SCIENCE AND TECHNOLOGY
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Unsteady aerodynamic identification of aircraft at high angles of attack
ZHANG Wanxin, ZHU Jihong
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 673-679. DOI: 10.16511/j.cnki.qhdxxb.2017.25.021
Abstract
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(1207KB) (
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Existing models cannot accurately identify aircraft at high angles of attack due to the unsteady aerodynamic characteristics high angle of attack flight. This paper presents a model using a dynamic block with a static block based on a general aerodynamic derivatives model, which was inspired by the modelling structure of the Wiener model. The model identification is then based on a squared correlation coefficient that estimates the contribution of each model term. The data processing procedure for the parameter estimations is given. Wind tunnel tests with a model similar to an F-22 are used to verify the method. The results show that the method is able to accurately identify the unsteady aerodynamic parameters with a relative error below 5%. The model can effectively describe the unsteady aerodynamic parameters.
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Fault tree method for DNS name resolution fault analyse
XU Haiyan, WANG Yingkang, DU Yuejin, YAN Jianen, ZHANG Zhaoxin
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 680-686. DOI: 10.16511/j.cnki.qhdxxb.2017.25.022
Abstract
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The domain name system (DNS) is an important part of the internet with core function being to resolve the domain name. The DNS servers must be stable to ensure the availability of the domain name resolution process and accurate resolution results. A domain name resolution fault analysis method is presented in this paper to resolve name resolution problems. Firstly, a name dependency graph is constructed according to the dependency relationship of the name resolution. Then a fault tree analysis is used to mine the DNS servers that give success for name resolution and the DNS servers that fail to give correct results. A single domain name and the Alex Top 50 000 domain names were analyzed using this method to show that there are unreasonable dependencies in the configurations of individual domain names which lead to some unnecessary resolution procedures and increase the DNS server load.
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Malicious node detection model for wireless Mesh networks
YANG Hongyu, LI Hang
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 687-694. DOI: 10.16511/j.cnki.qhdxxb.2017.25.023
Abstract
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Existing malicious node detection methods for wireless Mesh networks are not very efficient. This paper presents a malicious node detection method based on the mobile Ad-hoc networking (BATMAN) route protocol (MNDMB). The BATMAN route protocol is loaded into a wireless Mesh network in a source node message analysis module to generate the defection parameters and identify suspicious nodes depending on these parameters by comparisons to thresholds. Then, a multi-node voting mechanism is used to calculate the confidence value which is used as the criterion for judging the malicious node. Verification tests show that this protocol has higher detection rates and lower false positive rates in wireless Mesh networks than existing methods.
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Semi-formal method for security policies and design specifications
DENG Hui, SHI Hongsong, ZHANG Baofeng, YANG Yongsheng, LIU Hui
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 695-701. DOI: 10.16511/j.cnki.qhdxxb.2017.25.024
Abstract
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(1274KB) (
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Inadequacies in IT products can result from misunderstandings of the security requirements. Semi-formal methods can accurately describe the security requirements and implement reasonable requirements that avoid causing security flaws. Thus, semi-formal descriptions and verification methods are used in this study for security policies and design specifications represented by collections of the security requirements and module designs of security functionality interfaces. The system uses a loosely coupled partitioning method for the subsystem and module. Semi-formal methods are given to describe the security policy and design specification derived from existing semi-formal tools. The approach is applied to an IC card chip product to show that its security policies are adequate and the security design provides reasonable security. This approach can be used to evaluate all kinds of IT products.
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AUTO MATION
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Nonlinear compensation for optical vignetting in vision systems
DING Ying, FAN Jingtao, QUAN Wei, HAN Cheng
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 702-706. DOI: 10.16511/j.cnki.qhdxxb.2017.25.025
Abstract
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(1203KB) (
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Visual inspection systems are being more and more widely applied in industrial production, but optical vignetting directly affects the imaging quality, which affects the inspection accuracy. A nonlinear compensation method for optical vignetting is given which uses the vignetting principle, to define the relative exposure of the image with coupled sampling and decoupling reconstruction to determine the camera response curve. A vignetting compensation model is then developed to eliminate the vignetting effect of the lens to improve the image quality. Tests show that the method is effective and provides excellent vision inspection quality.
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COMPUTER SCIENCE AND TECHNOLOGY
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GSPAP based sub-band adaptive feedback cancellation algorithm
LIANG Weiqian, ZHENG Fang, CHEN Chaoyang, CHEN Gaojun
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 707-712. DOI: 10.16511/j.cnki.qhdxxb.2017.25.026
Abstract
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(1275KB) (
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Acoustic feedback cancellation needs robust and efficient adaptive filters. A Gauss-Seidel pseudo affine projection (GSPAP) sub-band adaptive filter based algorithm was developed using the auto-correlation matrix of the reference signal in the sub-band domain, instead of the power, to normalize the adaptation step size. A self-adjusting coefficient calculated from the maximum power of the input and output sub-band signals, was used to improve the robustness of the auto-correlation matrix. A two-order GSPAP algorithm was used to find the inverse of the auto-correlation matrix to balance the performance and complexity. Results from the added stable gain (ASG) experiment indicate that this algorithm gives 11 to 22 dB improved feedback cancellation for different types of hearing aids, which is 22% to 55% better than given by the time-domain normalized least mean square (NLMS) algorithm.
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HYDRAULIC ENGINEERING
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Simulation and parameter design of laser survey in underground energy storage caverns
LÜ Xiaoning, LIU Xiaoli, DUAN Yunling, TANG Zhili
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 713-719. DOI: 10.16511/j.cnki.qhdxxb.2017.25.027
Abstract
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(2924KB) (
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Laser survey parameters are difficult to select due to the effects of different factors on the laser measurements. The characteristics of laser survey parameters are used here to define a design criterion and a design model for the laser survey parameters. The storage cavern dimensions and application-dependent parameters were used on a laser survey simulation of an underground storage cavern based on the design model to identify the design parameters for an
in-situ
laser survey of an underground storage cavern. The results show that the laser survey simulation and parameter design are an efficient tool for studying the survey parameters to optimize the various tasks in the planning stage.
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Volume fraction allocation using characteristic points for coupled CFD-DEM calculations
LIU Detian, FU Xudong, WANG Guangqian
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 720-727. DOI: 10.16511/j.cnki.qhdxxb.2017.25.028
Abstract
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The coupled CFD-DEM method has been widely used for multiphase flows where the fluid volume fraction links the continuous medium (fluid) and the discrete medium (particles). This paper presents an improved volume fraction allocation algorithm based on the traditional SKM (statistical kernel method) model with subdividing of the characteristic points. Spatially distributed characteristic points within the region influenced by a particle mark all the CFD cells influenced by the particle so that the particle volume is correctly decomposed into each CFD cell. A traditional grid search algorithm then recognizes the characteristic points. After calibration of the model parameters, the algorithm reduces the truncation error at inner boundaries in parallel computing models. Numerical tests show that the algorithm is effective and efficient when the particle diameter size
D
and the CFD cell size
L
are of the same order of magnitude. The model reverts to the traditional unresolved particle model for
L
>>
D
and to the resolved particle model for
D
>>
L
. The algorithm improves coupled CFD-DEM calculations having a wide range of particle diameters to improve solid-liquid two-phase flow simulations.
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Centrifuge model test of geotextile-reinforced soil slopes during drawdown
ZHANG Ga, LUO Fangyue, LIU Yang, WANG Aixia
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 728-731,737. DOI: 10.16511/j.cnki.qhdxxb.2017.25.029
Abstract
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(1619KB) (
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Geotextiles are widely used to reinforce embankments and soil slopes. However, the geotextile reinforcement mechanism during drawdown is not well understood. Centrifuge model tests were conducted to observe the deformation and failure of geotextile-reinforced and unreinforced slopes during drawdown. The test shows that the geotextile significantly reduces the deformation and increases the slope stability. The slope deformation is restricted by the geotextile for water levels lower then a critical point and anchored by the geotextile at higher levels. The geotextile transmitted the interior restriction to the exterior of the slope via the soil-geotextile interaction. Thus, the deformation was more uniformly distributed. The geotextile delayed deformation localization, the precondition for slope failure.
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Benefit-sharing in hydropower projects: A mathematical model based on dynamic rate
CHEN Wenchao, QIANG Maoshan, XIA Bingqing, ZHENG Tengfei
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 732-737. DOI: 10.16511/j.cnki.qhdxxb.2017.25.030
Abstract
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(937KB) (
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Rebuilding the benefit-sharing mechanism is the key to solving problems related tore settling hydropower exploitation. A dynamic rate is used as the evaluation index in the mathematical model for the resettlement compensation and hydroelectricity price for different boundary conditions. The model is applied to the hydropower project in Southwest China as a case study. The results show that migrants get the lowest return among the various stakeholders, hydropower corporations and grid corporations get a moderate level of return, and local investment corporations get the best return. The large economic returns in large hydropower projects allow adjustments of the migrants' compensation as well as the hydroelectricity price so this model are useful in practical projects. This model can be used to improve migrant compensation with the conclusions providing guidance and hydropower resettlement policy.
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Relationships between organizational network coordination and capability: Evidence from Chinese hydropower firms
LEI Zhen, TANG Wenzhe, SUN Hongxin, YOU Richun
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 738-746. DOI: 10.16511/j.cnki.qhdxxb.2017.25.031
Abstract
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(1282KB) (
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The relationship between the organizational network coordination and the organization's capability is valuable for optimizing resource allocation and capability development. Existing studies, however, have only analyzed the relationship from a limited perspective with only a limited number of studies focusing on the construction industry. This study uses data from Chinese hydropower firms to study the interactions between organizational network coordination and capability. Mean value analyse provided holistic pictures of the firms' organizational coordination and capabilities. Cluster analyse revealed the resource-oriented nature of the construction firms' capabilities. A canonical correlation analysis and a regression analysis showed that internal coordination has a stronger effect on capability than external coordination and that the relationship between internal coordination and the dynamic capabilities of resource transformation and the relationship between external coordination and basic resource capability more strongly affect the interactions between coordination and capability. The relationships between network coordination and capability vary to some extent in different kinds of firms. The findings provide practical guidance to construction firms to optimize resource allocation and promote their sustainable development.
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AUTOMOTIVE ENGINEERING
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Torque characteristics of a controllable centrifugal clutch for electric vehicles
SONG Haijun, SONG Jian, FANG Shengnan, LI Fei, TAI Yuzuo, TRUONG Sinh Nguyen
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 747-752. DOI: 10.16511/j.cnki.qhdxxb.2017.25.032
Abstract
PDF
(1259KB) (
673
)
The adjustments of the engaged speed and torque is key for the control of centrifugal clutchs in electric vehicles automatic transmission. The factors affecting the clutch torque characteristics were analyzed to model the contact torque on the centrifugal shoe. The models for the uniform centrifugal force on the centrifugal shoe and the contact pressure between the shoe and drum are simplified to get an analytical expression for the clutch torque
β
. The regulation characteristics of the clutch engage speed and the torque about
β
are analyzed for speeds of 0° to 90° for automatic transmissions for electric vehicles. A virtual clutch prototype is used to verify the clutch torque regulation characteristics. The results show that the basic characteristics of the clutch torque regulation well are reflected by the
β
-model.
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Dynamic and static compression tests and FEA analyses of aluminum foam specimen with variable density in the loading direction
LÜ Zhenhua, SUN Jingxuan
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 753-762. DOI: 10.16511/j.cnki.qhdxxb.2017.25.033
Abstract
PDF
(3647KB) (
661
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Closed-cell aluminum foams with variable densities in the loading direction are widely used. A finite-element mode (FEM) is used to model the foam deformation and energy absorption characteristics with dynamic and quasi-static compression tests. The results show that large aluminum foam specimens with variable densities have density-dependent layered deformation characteristics, which differ from uniform-density aluminum foams. Predictions of an FEM model with a layered variable density and layered element sizes are compared with those of a conventional FEA model with uniform density and element size. The computation results show that the layered gradual deformation characteristics can be simulated by the layered models with quasi-static and dynamic compression simulation results agreeing well with experimental data. The uniform model cannot accurately predict the layered gradual deformation characteristics. The element size of the layered models influences the simulated layered gradual deformation characteristics with simulation results using the layered model with element sizes equal to the foam cell diameter agreeing best with the experimental data. These results will improve engineering designs using aluminum foam materials.
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PHYSICS AND ENGINEERING PHYSICS
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Heartbeat detection based on ballistocardiograms
ZHANG Xianwen, ZHANG Liyan, DING Lichao, WEI Rongrong, WANG Jie, TANG Jintian
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 763-767. DOI: 10.16511/j.cnki.qhdxxb.2017.25.034
Abstract
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2197
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A ballistocardiogram (BCG) unobtrusively records the weight variation caused by the reaction force of blood ejection and blood flow in the aorta. A BCG system was developed to record BCG signals and detect the heart beats in the BCG signal. Data from 24 healthy subjects was collected to investigate the system with simultaneous electrocardiograms (ECG) as a reference. The results show no significant difference between the heartbeats detected by the ECG and BCG system (
p
=0.95) with the BCG system having a sensitivity of 99.56% and an accuracy of 99.77%.
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Stability test and efficiency calibration of a gadolinium-loaded liquid scintillation detector
WANG Li, DU Qiang, KANG Kejun, YUE Qian
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 768-773. DOI: 10.16511/j.cnki.qhdxxb.2017.25.035
Abstract
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(2467KB) (
858
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The China dark matter experiment (CDEX) collaboration has developed a large gadolinium-loaded liquid scintillation detector for neutron background measurements in the China JinPing underground laboratory (CJPL). Coincidence measurements of the recoil proton and neutron capture signals are used to suppress the gamma background. This paper presents stability tests and monoenergetic neutron detection efficiency calibration of the detector. The tests show that the detector photon yield is stable. The detector has good neutron and gamma pulse shape discrimination and a highly detection efficiency. Thus, this system is suitable for low intensity fast neutron measurements in the underground laboratory.
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AEROSPACE AND ENGINEERING MECHANICS
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Effect of different species on physical properties for the surrogate of aviation fuel
PEI Xinyan, HOU Lingyun
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 774-779. DOI: 10.16511/j.cnki.qhdxxb.2017.25.036
Abstract
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(1535KB) (
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Thermo-physical properties for surrogate aviation kerosene RP-3 were developed in this study to lay a foundation of the further investigation of the heat transfer calculation and experiment. The specific heat calculated from different surrogate models of the RP-3 was compared with the experimental data. The effects of three kinds of species, i.e. paraffin, cycloalkanes, benzenes, on thermo-physical properties were analyzed. There are the big differences of thermal properties at pseudo-critical temperatures. Based on the previous research of surrogate models and the GC-MS analysis of RP-3, a four-species surrogate was proposed. The numerical results for thermo-physical properties were in good agreement with the experimental data, including the specific heat, density and viscosity.
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NUCLEAR ENERGY AND NEW ENERGY
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Crystal plasticity constitutive model for BCC based on the dislocation density
NIE Junfeng, TANG Zhenrui, ZHANG Haiquan, LI Hongke, WANG Xin
Journal of Tsinghua University(Science and Technology). 2017,
57
(7): 780-784. DOI: 10.16511/j.cnki.qhdxxb.2017.25.037
Abstract
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(1358KB) (
2166
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Crystal plasticity theory is a fundamental theory that combines the crystal microscopic slip mechanism with macroscopic plastic deformation to predict meso-scale plastic deformation. The dislocation density has an important influence on the hardening behavior of metal crystals. This paper presents a constitutive model based on crystal plasticity theory and dislocation motion theory for the BCC crystal structure. The model is used to study the mechanical behavior of a BCC lattice. Using the UMAT subroutine in ABAQUS for numerical simulations of a uniaxial tensile tests of single crystal and polycrystal iron. The results show that the constitutive model effectively simulates the mechanical behavior of the uniaxial tensile test for single crystal and polycrystal iron.
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