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ISSN 1000-0585
CN 11-1848/P
Started in 1982
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  • Table of Content
      , Volume 56 Issue 12 Previous Issue    Next Issue
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    HYDRAULIC ENGINEERING
    Mini-slump flow measurement tool based on self phase image processing
    NIE Ding, AN Xuehui
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1249-1254.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.034
    Abstract   PDF (2721KB) ( 870 )
    The workability of self-compacting concrete (SCC) is mainly affected by the SCC formulated paste rheological parameters. The paste rheological parameters are obtained from relative mini-slump flow tests. A mini-slump flow measurement tool was developed based on image processing for use on smart phones. First, a predefined mark is placed on the surface of the test plate. Then, the paste spread is imaged over time with the positions of the mark in the images recorded by the smart phone camera found by image processing. Every image of the tests is analyzed to calculate the relative mini-slump flow. The mini-slump flow rate is then calculated with the rheological parameters. The tool was evaluated using a series of mini-slump flow tests. The results show that the mini-slump flow times calculated by the tool are accurate and are nearly the same as those given by the standard method. Thus, this tool is a convenient, effective tool for mini-slump flow tests to obtain the rheological parameters of the paste.
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    Mathematical model for dowel bearing capacity considering the effect of concrete damage
    LI Pengfei, AN Xuehui, HE Shiqin, CHEN Chen
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1255-1263.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.035
    Abstract   PDF (1815KB) ( 824 )
    The measured bearing capacities of dowels embedded in concrete were compared with existing formula for various conditions. A total of 11 specimens were tested to failure to investigate the effect of the bar diameter, concrete strength and concrete cover on the dowel bearing capacity. The effect of localized crushing of the concrete found from the experiment and numerical results was used to improve the formula accuracy. Specimens with different concrete covers were simulated to study the key parameters affecters the failure mechanisms. Comparisons of the analytical results with experimental data showed that the model gives good predictions for both failure mechanisms.
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    Suitability of simulating flow in meandering channel by modified depth-averaged model
    QIN Cuicui, SHAO Xuejun, ZHOU Jianyin, ZHOU Gang, XIAO Yi
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1264-1270,1277.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.036
    Abstract   PDF (1602KB) ( 644 )
    Secondary flow plays an important role in bend flow simulations. There are numerous models in the literature that consider the secondary flow effects. However, these models have generally been verified through simulating flows in a single bend or meandering channels with weak curvature. These models may not be applicable to channels with strong curvature or natural meandering rivers. This paper presents a model which is applied to two laboratory channel bends, one with strong curvature and the other with curvature varying like a natural river. The results show that the modified model predicts a higher water surface and improves the velocity simulation results. The dispersion terms have the same order of magnitude as the viscous stress term and should not be neglected in flow simulations of meandering channels with strong curvature. In addition, the dispersion term plays an important role in improving the velocity simulation results near the wall. Thus, this model is applicable to flow simulations in meandering channels with similar configurations and is more suitable for simulating the lateral evolution of meandering rivers.
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    Impact of horizontal plug-in flow meterson the velocity field-An experimental study
    WANG Hao, CHEN Huai, LI Danxun, WANG Xingkui
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1271-1277.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.037
    Abstract   PDF (1723KB) ( 717 )
    Horizontal plug-in flow meters disturb the velocity fields when deployed to measure rates flow. The spatial extent of such disturbances has been experimentally studied here on a simplified flow meter model. The Pitot tube used as the flow model was placed horizontally in the water flow with instantaneous two-dimensional velocity fields also measured by particle image velocimetry (PIV). Analysis of the spatial variations of the velocity fields in front of the model shows that the streamwise velocity increases with the distance from the model nose and gradually approaches that of the incoming flow with the spanwise velocity, turbulent intensities, and Reynolds stresses decreasing with the distance. The streamwise velocity requires the longest distance to recover from the disturbance with the turbulent intensity requires the shortest distance. The spatial extent of the disturbance is proportional to the flow meter diameter.
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    PHYSICS AND ENGINEERING PHYSICS
    Disaster relief based on Pseudo Base Stations
    TANG Shiyang, SHU Xueming, SHEN Shifei, WANG Guodong
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1278-1283.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.038
    Abstract   PDF (2242KB) ( 811 )
    The time for searching and locating victims in disaster-relief work is a key factor for the rescue efficiency. A fast search and locating operation can significantly reduce casualties and property loss. A cellphone search and locating system based on Pseudo Base Stations (PBS) is described in this paper to alleviate the problems caused by lack of rescue resources and large rescue areas. The receive signal strength indicator (RSSI) data and cellphone signal transmission power data were collected in simulated disaster areas. Then, data was analyzed to evaluate the effectiveness of searches in large disaster areas. The data analyses show that the system can search and locate cellphones in large areas for use by rescue teams in widely damaged areas.
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    Dose equivalent of neutron and induced gamma rays near a medical accelerator
    CHEN Yizheng, LI Junli, QIU Rui, WU Zhen, KANG Xi
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1284-1289.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.020
    Abstract   PDF (1136KB) ( 965 )
    High energy accelerators are widely used in medicine, but the related radiation shielding calculations are difficult, especially for rapid assessments of the radiation dose in a maze. This study describes typical estimating methods for the dose equivalent of neutron and induced gamma rays in a maze, and calculates the dose equivalent in a multiple-bend maze. The results were compared with Monte Carlo simulations using the Monte Carlo N-particle transport code (MCNP). The methods can accurately estimate the dose equivalent of the neutron and induced gamma rays in the maze, within an order of magnitude of the Monte Carlo simulation results, with underestimates in some cases. Therefore, a safety factor is suggested for practical applications.
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    Development of lymphatic nodes in the Chinese reference adult male voxel model (CRAM) with applications to radionuclide therapy
    LIU Huan, QIU Rui, PAN Yuxi, LI Junli
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1290-1296.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.039
    Abstract   PDF (1922KB) ( 619 )
    The dosages to lymphatic nodes are critical to evaluating the dose in lymphoma patients treated with radionuclide therapy in studies using human computational phantoms. Furthermore, the International Commission on Radiological Protection (ICRP) now considers the lymphatic nodes to be a radiosensitive tissue in ICRP Publication 103. Since lymphatic nodes are widely distribute the human body and are quite small, they are difficult to model in human computational models. This paper introduces a method that automatically develops lymphatic nodes in the Chinese reference adult male voxel model (CRAM). The S-values for 131I are calculated with the lymphatic nodes as the source organs and the other organs and tissues in the human body treated as the target regions. The CRAM model has a total of 17 lymphatic node sites. Both the number and mass of the lymphatic nodes accord with the Chinese reference values. The S-value calculation illustrates the dose assessment for radionuclide therapy and its value is related to the position of the lymphatic nodes and other organs and tissues in the human body.
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    Smoke bay design in buildings
    WANG Wandi, ZHANG Hui
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1297-1301,1311.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.040
    Abstract   PDF (2062KB) ( 775 )
    Smoke bays in buildings are an important measure of fire smoke control. One fire compartment can be divided into various smoke bays. To figure out the rational division way with high safety, the influence of the smoke bay design on the fire safety was studied by using field model simulations to find the best method that ensures safety. The results show that smoke bays should be divided to match the evacuation exit distribution. The safety is seriously compromised if too many evacuation exits are connected to one smoke bay. The number of smoke bays should match the number of exits to improve fire safety.
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    AUTOMOTIVE ENGINEERING
    Protection performance simulation and anchoring optimization of seat safety belts of vehicle under vertical intensive shock
    SUN Jingxuan, LÜ Zhenhua
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1302-1311.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.041
    Abstract   PDF (1810KB) ( 663 )
    The passenger protection performance of seat belts in special-purpose vehicles subjected to vertical shocks has rarely been studied. This paper describes numerical simulations of the vertical shock response of seat-passenger systems equipped with 5 different types of safety belts. Anchoring systems of 5 or 6 anchor-point belts are optimized to improve the protection under strong performance vertical shocks, and the influences of the anchoring configuration changes for the two types of safety belts also numerically analyzed for frontal and lateral collisions. The results show the remarkable influence of the configuration of multi-anchor-point safety belts on the passenger protection performance and the optimized anchoring systems of safety belts significantly improve the passenger's vertical shock protection. The study gives a comprehensive optimal design method for safety belt systems of special-purpose vehicles.
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    CIVIL ENGINEERING
    Particle flow simulations of the compaction of filling materials in highly filled foundation with analyses of the transverse isotropy
    ZHOU Mengjia, SONG Erxiang
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1312-1319.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.042
    Abstract   PDF (1599KB) ( 1030 )
    Compaction is widely used in the construction of highly filled foundations with the filling material composed of a mixture of broken rock and soil. The rockfill usually comes from explosion and, thus, has irregular shapes. In addition, with the soil, the response of the broken rock-soil mixture during compaction differs from that of pure rockfill. This study simulates the compaction of highly filled foundations filled with broken rock-soil mixtures using the particle flow software PFC3D with the particles assumed to be elongated. Two other with pure rockfill with and without elongated rockfill particles were used to investigate the influence of particle shape and fine soil grains. The tamper response and the dynamic stress distribution in the soil were carefully studied and verified by field tests. The void ratio and the settling ratio predictions by the three models and the void ratio reduction are used to evaluate the models. Then, samples taken from foundations and triaxial tests are simulated with different orientation angles of the major principal stress to compare the soil properties before and after compaction. Finally, a static model is used to analyze the three-dimensional mesoscopic fabric to study the transverse isotropy of the soils after compaction. The results indicate that the broken rock-soil mixture with elongated rockfill particles is the best among the three models and that the soil behavior with elongated rockfill particles is cross-anisotropic after compaction with a larger modulus and higher peak strength in the vertical direction than in the horizontal direction. The soil simulations with spherical particles show that soil remains isotropic after compaction.
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    Driving styles during rapid urbanization
    QI Geqi, WU Jianping, DU Yiman, JIA Yuhan
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1320-1326.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.019
    Abstract   PDF (1614KB) ( 652 )
    Traffic congestion, traffic safety, and traffic related environmental problems caused by rapid urbanization have become increasingly important with "human-centered" intelligent transportation systems (ITS) needed that are based on individual driving characteristics. Thus, common driving styles were analyzed to more effectively utilize the existing road transport resources. However, driving styles are difficult to identify and quantify, which leads to difficulties modelling the individual driving characteristics. In this paper, the driving characteristics of 16 drivers on actual roads were analyzed using a topical model. The hidden driving characteristics were extracted and used to convert the data from "driving style-driving behaviour data" into "driving style-driving state-driving behaviour data". The discovered driving style structural information provides theoretical support for more efficient intelligent transportation systems. The reconstructed model data is shown to correlate well with the original data which verifies the model for analyzing driving style diversity.
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    Operating subsidies for urban rail transit PPP projects
    ZHANG Zhihui, ZHANG Jianhan
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1327-1332.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.046
    Abstract   PDF (991KB) ( 1520 )
    The basic features of urban rail transit (URT) such as the shared operational responsibilities and the partial public ownership determine the public-private partnership (PPP) mode for developing URT projects. In this paper, the use of the PPP mode to develop URT projects is analyzed to study the relationship between the external benefits and government subsidies on the URT. Government regulations were used to develop a model for URT annual operating subsidies that was used to predict the government operating subsidies for Beijing subway line 4 in 2012. Then, the "with and without methods" were used to analyze Beijing subway line 4 in 2012 to determine the external benefits of this project. The results show that the government operating subsidies for Beijing subway line 4 in 2012 were significantly lower than the external benefits and that the government operating subsidies for this project are reasonable.
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    AUTO MATION
    Short-term traffic breakdown prediction using a hidden Markov model
    ZHOU Hao, HU Jianming, ZHANG Yi, SHEN Yingzhen
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1333-1340.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.043
    Abstract   PDF (2389KB) ( 739 )
    Traffic breakdown reduces road capacity as one of the main factors causing congestion on urban expressways. Accurate short-term traffic breakdown predictions on urban expressways are becoming more and more important because of their vital role in traffic management and control. Traffic flow data was obtained from the Caltrans performance measurement system (PeMS) with traffic breakdown states classified by a lane-based method. A Hidden Markov model (HMM) is then established with the traffic breakdown state as the hidden state and the road occupancy as the observed state with the Viterbi algorithm to solve the problem. The traffic breakdowns were successfully predicted to show that the HHM accurately predicts short-term traffic breakdowns.
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    CHEMISTRY AND CHEMICAL ENGINEERING
    Resource productivity estimates at the municipal and intra-county levels in China
    ZHU Bing, CHEN Zengbo, ZHANG Yupeng, CHEN Dingjiang, JIANG Meng
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1341-1345.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.044
    Abstract   PDF (1014KB) ( 563 )
    Resource productivity is a comprehensive indicator used to evaluate economic development that has been used at the national level in China. However, there source productivity is more difficult to define at various regional levels, especially for the municipal and intra-county levels. The effectiveness of the accounting method has not been verified for local economics. This study focuses on issues related to establishing a resource productivity indicator for municipal and intra-county levels based on a economic-wide material flow analysis. This study presents a simple estimation method for the municipal and intra-county resource productivity using local statistical data. As typical and extreme examples, 32 cities and counties from 4 provinces in China were selected to calculate the resource productivity using this estimation method. The results indicate that the accounting frame is suitable for most of the selected cities and counties and can be used to evaluate development economic. This estimation method provides a basis for further resource productivity estimates at the municipal and intra-county levels.
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    NUCLEAR AND NEW ENERGY ENGINEERING
    Improved linear interpolation algorithm for multi-slice helical CT
    WAN Xin, LIU Ximing, MIAO Jichen, WU Zhifang
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1346-1351.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.045
    Abstract   PDF (2440KB) ( 822 )
    Linear interpolation (LI) is one of the basic reconstruction algorithms for multi-slice helical CT (MSCT) which searches for the upper and lower projection data sets adjacent to the reconstructed slice for interpolation. However, the searching for the data and computing the weighting function significantly reduces the reconstruction efficiency. An improved LI method was developed for a range of helical pitches with a 4-slice helical CT as an example. The algorithm defines the projection data weighting function from different detector rows, which can be used directly for interpolation to increase the reconstruction efficiency. The 3D projection data for the Shepp-Logan head phantom was simulated to verify the reconstruction capability and the applicable range of this method. The results show that this method does well for moderate and small helical pitches. The image restoration capacity is very good and the volume coverage is quite fast with good image quality. This method can be used in situations requiring fast reconstruction.
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    PRECISION INSTRUMENT
    Full-profile fit pendent drop method for surface tension measurements
    ZHOU Bin, LI Siwei, CHEN Zhiyong, ZHANG Rong
    Journal of Tsinghua University(Science and Technology). 2016, 56 (12): 1352-1356.   DOI: 10.16511/j.cnki.qhdxxb.2016.25.047
    Abstract   PDF (1230KB) ( 1407 )
    The accuracy and stability of surface tension measurements are improved fitting the entire surface profile in the pendent drop method with an algorithm to determine the initial value for two-dimensional optimization. Moreover, the error function was modified by a weighting factor which reduced the influence of the droplet profile deviation point on the surface tension measurement. The full-profile fitting method was used to calculate the surface tension of water and ethanol at 25℃ and atmosphere. The final results show the standard deviation was reduced by 40% compared with the previous method, which verifies the stability and repeatability of this full-profile fitting pendent drop method.
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