15 August 2016, Volume 56 Issue 8

    

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CIVIL ENGINEERING
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  Hurricane damage assessments for coastal areas based on a Poisson model

  LI Quanwang, WANG Cao, ZOU Aming, PANG Long, ZHANG Long

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 801-805. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.017

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  Previous hurricane damage assessments for coastal areas have ignored the intermittent nature of hurrucanes. This paper presents an hurricane damage assessment method that accounts for the intermittency. A Poisson model is used in this paper to describe the hurricane stochastic process with explicit formulas for the hurricane damage assessment. Hurricane data for Miami-Dade County, USA, from 1900 to 2010 were used to illustrate the method. The Poisson model provides a reasonable description of the hurricane stochastic characteristics. The mean and the variance of the hurricane damage are overestimated while the coefficient of variance is underestimated if the intermittency is ignored. For example, for a 50-year service period, the mean cumulative hurricane damage is overestimated by 41.4% while the variance is over estimated by 20.05% if the intermittency is ignored.
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  Accuracy of equivalent age method for predicting mass concrete properties

  ZHANG Zengqi, SHI Mengxiao, WANG Qiang, CUI Qiang

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 806-810. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.018

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  The accuracy of the equivalent age method on property prediction of mass concrete was evaluated for five mixture proportions and two kinds of curing conditions. The concrete specimens were cured using standard curing or matching curing based on adiabatic temperature rise test results. The results show that the calculated concrete properties predicted by the equivalent age method were much higher than the measured data for concrete prepared using matching curing. Thus, the equivalent age method cannot accurately predict the properties of mass concrete.
  
MECHANICAL ENGINEERING
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  System design and local optimization of a small humanoid soccer robot MOS-7

  ZHANG Jiwen, LIU Li, CHEN Ken

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 811-817. https://doi.org/10.16511/j.cnki.qhdxxb.2016.22.032

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  Small humanoid soccer robots can be used as inexpensive platforms to improve artificial intelligence and robotic systems. A new generation soccer robot, MOS-7, was developed with a modified structure, control system and software. The spatial arrangement of the lower limbs and trunk was optimized by changing the degree of freedom (DOF) configuration of its hip and improving the connections for the hip actuators to enhance the mechanical reliability. The decision-making and control tasks were arranged according to their real-time needs and running speed.The image capture system was optimized in 4 dimensions:resolution, accessible frame rate, reliablity and complexity. The artificial intelligence was improved by introducing novel particle decision-making abilities. The MOS-7 system is then a small humanoid platform that uses limited resources in an integrated and optimized mechanical-electronic system.
  
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  Stabilizing control of humanoids' walking based on AHRS feedback

  ZHANG Jiwen, LIU Li, CHEN Ken

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 818-823. https://doi.org/10.16511/j.cnki.qhdxxb.2016.23.018

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  An attitude and heading reference system (AHRS) feedback system was established using micro-electro-mechanical system (MEMS) sensors with low cost and the compensation algorithm described by the direction cosine matrix to realize the stabilizing control of humanoids' walking, being aimed to overcome the defect of incapability to compensate the large disturbance when using the zero moment point (ZMP) feedback control algorithm and the shortcoming of the current walking task interruption when using the reflex response control method. The walking stability criterion expressed by the linear composition of posture angles and angular velocities was also proposed, with a proportion-derivative controller for torso pose adjusting also implemented. Walking stabilization control was realized by the action style of tuning the next stride and walking frequency using the omni-directional walking gait planning method. Experimental results with a physical robot show that the robot can effectively avoid omni-directional walking task interruption and fall over even if disturbed by an impulse to reach the maximum inclination of 20° when marching on the spot and walking forward steadily.
ENGINEERING PHYSICS
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  CO₂ removal by zeolite molecular sieves

  LONG Bin, LI Junli, WANG Qunshu, FENG Shujuan, ZHOU Guoqing, FENG Tiancheng, ZHANG Yang, XU Ming, TIAN Yanjie, MA Huaicheng

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 824-829. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.021

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  Adsorption and separation by carbon molecular sieves is improves the detection sensitivity of radio xenon measurements. However, the adsorption capability including the adsorption column volume and the gas recovery are influenced by the CO₂ in the air. Therefore, the CO₂ must be removed before the xenon adsorption. This study analyzed CO₂ removal by zeolite molecular sieves for various operating conditions. The results show that the 13XHP zeolite molecular sieve more effectively removes CO₂ than the other adsorbents and that the CO₂ temperature and volume fraction are the most important of fact affecting the adsorption performances. The inlet pressure and flow rate have less effect on the adsorption of CO₂ by 13XHP for how rates of 564-2 015 mL/min and pressures of 103-353 kPa.
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  Cooperative scheduling model for multi-level emergency response teams

  KANG Kai, CHEN Tao, YUAN Hongyong

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 830-835,843. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.022

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  The increasing number of disasters and the increasing difficulties in dealing with these disasters cannot be easily handled by just the limited emergency rescue forces within one administrative area. Especially when the disaster happens at the edge of an administrative area, the emergency rescue teams within the stricken area can often be much slower than the rescue forces in the adjacent area. This paper describes a coordinated multi-level emergency rescue system with three forms of synergistic relationships in the disaster zone, the region and the grid. The analysis examines the principles of cooperative dispatch and gives models for effective cooperation. The cooperative dispatch of fire protection emergency rescue forces from different administrative regions is used to verify the regional cooperative dispatch model. This study can effectively shorten emergency rescue force arrivial times and optimize their dispatch.
CONSTRUCTION MANAGEMENT
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  Game analysis of reverse multiple attribute electronic bidding in construction markets for end users

  XUE Yanguang, DENG Xiaomei, FENG Ke

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 836-843. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.023

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  Electronic bidding platforms optimize resource allocation for the construction market and effectively prevent unfair competition. However, electronic bidding platforms for the construction market lack a response mechanism to the end users' demands, such as building quality, resulting in lower end-user satisfaction. The characteristics of the construction market, especially the demands of the end-users and the need for multi- attribute electronic bidding are incorporated into a two-stage auction model which includes an online multi-attribute reverse auction model and a bargaining game model with incomplete information and unlimited rounds. The solutions of the two stage model compared to the Bayesian Nash equilibrium strategy and the sub-game perfect Nash equilibrium. This model successfully responds to the end-user demands, reduces the total supply chain cost, and improves the construction industry supply chain competitiveness.
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  Organization-fit in project communication-A semantic labeling approach

  ZHU Enwei, LIAO Pinchao, ZHAO Yu

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 844-850. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.024

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  The actual communication relationships among construction project members are identified from data extracted from the e-mail base of an actual construction project with semantic labeling which excludes the impact of subjectivity in questionnaires used in existing studies. The data is used to build social network analysis models for different issues to analyse the relationships between the organization-fit and equipment procurement delays with the models verified by experts from the project. The results show that the decision power, experience and communication abilities of the members all affect equipment procurement delays. This communication network model developed using semantic labeling can identify communication network information missed in subjective evaluations.
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  Transaction prices of overseas mergers and acquisitions with a redemption provision

  LONG Dawei, HUANG Hongxuan, WANG Mengyue, YANG Yongsen

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 851-859. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.025

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  Chinese enterprises are competing in the global business through overseas mergers and acquisitions. This paper studies a mechanism for asset pricing and transaction price formation which includes fundamental concerns and key phases related to redemption provisions. The process assesses the target enterprise value by the real option method, determines the transaction price interval, computes the nominal values via the utility maximization or bargaining models, and updates the asset purchasing price for the transaction with repurchase clauses. The present value and utility equivalency strategies are used to predict the transaction price formation. The effect of the redemption provision is described by a probability which is related to the transaction price. A case study shows the feasibility of this method for evaluating overseas mergers and acquisitions for an A-share company purchasing an overseas bioenergy life science company with the redemption provision. This is a comprehensive, integrated approach for evaluating the value of a firm and determining the purchase price through the bargaining between the buyer and the seller.
ENVIRONMENTAL SCIENCE AND ENGINEERING
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  Material flow-related research using a Chinese multi-region input-output data approach

  CHEN Dingjiang, ZHANG Xiaoyang, ZHOU Wenji, ZHU Bing

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 860-864. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.028

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  The multi-region input-output (MRIO) approach can provide key information about the life cycle and the distribution of environmental resource. The regional and sectoral information in the MRIO table can be used to analyze the trade flow and the footprints of various environmental factors to identify inequalities in ecological services by demand-based analyses. This paper first reviews the research on international and subnational resource and environmental subjects using the MRIO approach. Chinese MRIO data has been rarely used to study resource-related topics. This study analyzes resource-related research using Chinese MRIO data. Analyses of interregional trade flows and regional material footprints are used to suggest policy initiatives to deal with the resource-related inequalities of ecological services, to improve regional resource use efficiency and to reduce the influence interregional transfers of ecological burdens.
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  Urban development suitability evaluations based on ecological assessments-A case study of Manasi County, Xinjiang Province

  YANG Ping, PENG Yu, LIU Xuehua, MENG Hongyan, WANG Bin

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 865-870. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.029

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  Ecological assessments are used to identify important areas for ecological protection and to provide scientific support for urban planning. This study took Manasi County, Xinjiang Province, as a case study and constructed an ecological sensitivity and ecological risk criteria system based on expert knowledge and an analytical hierarchy process (AHP) method. The ecological sensitivity and risk assessment was used to evaluate the urban development suitability and to divide the whole area into prohibited construction, restricted construction and appropriate building zones. The process shows that the integrated expert knowledge, AHP data, and GIS data provides an effective ecological assessment method. The Manasi County has 41.31% extremely sensitive areas, 16.17% highly sensitive areas, 16.44% moderately sensitive areas, 7.07% low sensitive areas, and 19.01% non-sensitive areas. The extremely high ecological risk areas are mainly in the southern part of Taxi River County, the middle and southern part of Qingshui River County, and the northern part of Guangdongdi County. The high risk areas are mainly in the upstream and midstream regions of the Manasi and Taxi Rivers. The areas suitable for development are mainly in the towns of Manasi, Lanzhouwan, the western part of the 147 Production and Construction Corps, the northern part of Beiwucha, the western part of Xinhu farm, and the 148, 149 and 150 Production and Construction Corps areas, the low suitability for development areas are mainly in the desert, mountains, and wetlands.
COMPUTER SCIENCE AND TECHNOLOGY
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  Distributed Top-k subgraph matching

  LAN Chao, ZHANG Yong, XING Chunxiao

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 871-877. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.026

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  Top-k subgraph matching is a key operation in graph queries which is widely used in all kinds of applications such as social networks and knowledge graphs. Top-k subgraph matching is more challenging in distributed environments since it involves data and task transfers. Thus, existing local Top-k subgraph matching methods do not work well in distributed environments. An algorithm was developed to address this issue by dividing the problem into query decomposition, query execution, and ranked join stages. The query decomposition avoids unnecessary data transfers during the querying stage. The ranked join technique avoids generating unnecessary temporal results that reduces the overall latency of the algorithm. The algorithm effectiveness and efficiency were tested using real data and the results indicate that the algorithm, especially the optimized version, effectively solves the distributed Top-k subgraph matching problem.
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  Reliability of interrupt services for embedded systems

  CUI Kai, WANG Jie, ZHOU Kuanjiu, LIANG Haoran, PAN Jie, LI Mingchu

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 878-884. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.027

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  In resource-constrained environments, the uses must evaluate whether the embedded software can meet the objectives. This paper presents an interrupt service reliability assessment method for embedded systems based on queuing theory that includes the effects of interrupt service randomness, real-time operations and concurrency. This queuing model includes the multilevel interrupt servicing preemptive priority and gives a performance evaluation index for interrupt servicing systems. The model gives a somewhat universal dynamic assessment of the reliability of embedded systems with a queuing interrupt servicing method.
THERMAL ENGINEERING
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  Simultaneous absorption of SO₂ and CO₂ from flue gas using aqueous ammonia

  QI Guojie, WANG Shujuan, GAO Jubao, LIU Jinzhao, ZHAO Bo, ZHUO Yuqun, CHEN Changhe

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 885-892. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.030

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  Coal-fired power plants emit large quantities of SO₂ and CO₂, so more research is needed on SO₂ and CO₂ capture. Experimental tests were conducted in a wetted wall column system to analyze the simultaneous absorption of SO₂ and CO₂ using aqueous ammonia (weight percent, 0.2%-7%). The Aspen Plus RateSep model was then used to analyze the CO₂ and SO₂ mass transfer in the packed column to comprise the design of the ammonia based CO₂ and SO₂ absorption system. The experiments show that the SO₂ selectivity absorption factor decreases as the CO₂ volume concentration increases. The CO₂ volume concentration (5%-20%) has little effect on the SO₂ mass transfer and the SO₂ absorption rate is always an order of magnitude higher than that of CO₂. Increasing the SO₂ mass concentration and reaction temperature has a negative effect on the CO₂ absorption and the ammonia tends to selectively absorb the SO₂. When the SO₂ loading (mole concentration ratio between SO₂ and NH₃ in the aqueous ammonia solvent) increases from 0.1 to 0.4, the CO₂ mass transfer rate significantly decreases. Increasing the ammonia mass concentration improves the absorption of both CO₂ and SO₂ and the predicted results are in good agreement with the experimental data. Thus, the packed column combined with an ammonia scrubber to reduce the ammonia slip and a resin exchange device used to control the SO₂ loading can achieve simultaneous removal of CO₂ and SO₂.
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  Vacuum and energy separation characteristics of tornado-like vortices

  QI Haiying, HUANG Xingliang, HU Yu, LI Ke, SUN Xinyu, WANG Zhipeng

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 893-900,907. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.031

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  A series of Ranque-Hilsch-effect-based vortex generators were designed for cold-state flow tests of tornado-like vortices. Flow visualizations and measurements show that the opposing effects of vacuum abstraction and centrifugal expansion are both derived from the intensive swirling which leads to small jet angles and less aerodynamic leaks than in a normal swirling jet. The vortex provides a slip and shielding effect to the environment, a high vacuum region in the center of the vortex and an inhomogeneous volcano-like velocity distribution with exponential attenuation of the vacuum in the axial direction. Energy separation accuses which is closely related to the local vacuum and flow direction. A high inlet pressure and vacuum are crucial to the vortex generation and the proportion of the energy conversion from pressure to swirling kinetic energy increases with increased pressure, which can be used to optimize the generator structure. The tornado-like vortex generation mechanism can be used to study the interaction between the vortex and combustion in the vortex.
BIOLOGICAL SCIENCE AND ENGINEERING
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  Estimation for the location of multiple moving sound sources in small-distance dual-microphone

  GONG Qin, LIU Yi

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 901-907. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.032

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  Angle measurements using traditional auditory analyse with dual-microphones have limited accuracy when the two microphones are close together and the sound sources are moving. This paper presents a method for multiple moving sound source localization with two closely spaced microphones. The method uses an improved gammatone filter bank for the time-frequency analysis of the mixed sound samples, extracts the zero-crossing time difference (ZCTD) that reflects the sound source location feature information and finally statistically analyzes the ZCTD with a Gaussian function to localize the sound source. Tests show that this method gives accurate angle estimates for various kinds of sound sources with various moving speeds along various trajection.
ELECTRICAL ENGINEERING
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  Scattering component consistency based parameter for polarimetric SAR image classification

  JIAO Zhihao, YANG Jian, YE Chunmao, SONG Jianshe

  Journal of Tsinghua University(Science and Technology). 2016, 56(8): 908-912. https://doi.org/10.16511/j.cnki.qhdxxb.2016.25.033

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  The scattering entropy accurately describes the randomness of a scattering medium, but analyses do not use the relationships between the three eigenvectors representing the different coherent scatterings. More polarization information is extracted by a parameter describing the consistency of the scattering components to classify of polarimetric SAR images. The parameter contains information on the eigenvalue distributions and similarities between the coherent scattering components and represents the closeness of the scattering to simplex coherent scattering. The AIRSAR L-band polarimetric image of San Francisco is segmented using this parameter instead of the scattering entropy and then adjusted by a Wishart classifier. Tests demonstrate the effectiveness of this parameter to improve the classification and object details.