资源类型

期刊论文 123

会议视频 1

年份

2024 1

2023 15

2022 11

2021 15

2020 5

2019 6

2018 6

2017 9

2016 4

2015 5

2014 7

2013 5

2012 6

2011 5

2010 3

2009 6

2008 4

2007 3

2006 1

2005 1

展开 ︾

关键词

中子通量密度 2

功率密度 2

功率谱密度 2

8英寸 1

Au/Ti双功能催化剂 1

BNCT医院中子照射器 1

GPU；密度峰值；聚类；并行计算 1

H2有效利用率 1

丙烯环氧化 1

中子和γ吸收剂量率 1

中子能谱 1

人群计数；密度估计；分割先验图；均匀函数 1

优快钻井 1

健康状态 1

公共行人舒适度 1

养殖密度 1

冲击波 1

分子动力学 1

初始干密度 1

展开 ︾

检索范围：

排序： 展示方式：

Presentation of regression analysis, GP and GMDH models to predict the pedestrian density in various

Iraj BARGEGOL; Seyed Mohsen HOSSEINIAN; Vahid NAJAFI MOGHADDAM GILANI; Mohammad NIKOOKAR; Alireza OROUEI

《结构与土木工程前沿（英文）》 2022年 第16卷 第2期   页码 250-265 doi: 10.1007/s11709-021-0785-x

摘要： In this study, the relationship between space mean speed (SMS), flow rate and density of pedestrians was investigated in different pedestrian facilities, including 1 walkway, 2 sidewalks, 2 signalized crosswalks and 2 mid-block crosswalks. First, statistical analysis was performed to investigate the normality of data and correlation of variables. Regression analysis was then applied to determine the relationship between SMS, flow rate, and density of pedestrians. Finally, two prediction models of density were obtained using genetic programming (GP) and group method of data handling (GMDH) models, and k-fold and holdout cross-validation methods were used to evaluate the models. By the use of regression analysis, the mathematical relationships between variables in all facilities were calculated and plotted, and the best relationships were observed in flow rate-density diagrams. Results also indicated that GP had a higher R2 than GMDH in the prediction of pedestrian density in terms of flow rate and SMS, suggesting that GP was better able to model SMS and pedestrian density. Moreover, the application of k-fold cross-validation method in the models led to better performances compared to the holdout cross-validation method, which shows that the prediction models using k-fold were more reliable. Finally, density relationships in all facilities were obtained in terms of SMS and flow rate.

关键词： pedestrian density     regression analysis     GP model     GMDH model    

HTML PDF 收藏

A Bayesian modeling approach to bi-directional pedestrian flows in carnival events

S. Q. XIE, S. C. WONG, William H. K. LAM

《工程管理前沿（英文）》 2017年 第4卷 第4期   页码 483-489 doi: 10.15302/J-FEM-2017023

摘要： Bi-directional pedestrian flows are common at crosswalks, footpaths, and shopping areas. However, the properties of pedestrian movement may vary in urban areas according to the type of walking facility. In recent years, crowd movements at carnival events have attracted the attention of researchers. In contrast to pedestrian behavior in other walking facilities, pedestrians whose attention is attracted by carnival displays or activities may slow down and even stop walking. The Lunar New Year Market is a traditional carnival event in Hong Kong held annually one week before the Lunar New Year. During the said event, crowd movements can be easily identified, particularly in Victoria Park, where the largest Lunar New Year Market in Hong Kong is hosted. In this study, we conducted a video-based observational survey to collect pedestrian flow and speed data at the Victoria Park Lunar New Year Market on the eve of the Lunar New Year. Using the collected data, an extant mathematical model was calibrated to capture the relationships between the relevant macroscopic quantities, thereby providing insight into pedestrian behavior at the carnival event. Bayesian inference was employed to calibrate the model by using prior data obtained from a previous controlled experiment. Results obtained enhance our understanding of crowd behavior under different conditions at carnival events, thus facilitating the improvement of the safety and efficiency of similar events in the future.

关键词： pedestrian flow model     bi-directional interactions     empirical studies     Bayesian inference    

HTML PDF 收藏

The Group Interaction Field for Learning and Explaining Pedestrian Anticipation

Xueyang Wang,Xuecheng Chen,Puhua Jiang,Haozhe Lin,Xiaoyun Yuan,Mengqi Ji,Yuchen Guo,Ruqi Huang,Lu Fang,

《工程（英文）》 doi: 10.1016/j.eng.2023.05.020

摘要： Anticipating others’ actions is innate and essential in order for humans to navigate and interact well with others in dense crowds. This ability is urgently required for unmanned systems such as service robots and self-driving cars. However, existing solutions struggle to predict pedestrian anticipation accurately, because the influence of group-related social behaviors has not been well considered. While group relationships and group interactions are ubiquitous and significantly influence pedestrian anticipation, their influence is diverse and subtle, making it difficult to explicitly quantify. Here, we propose the group interaction field (GIF), a novel group-aware representation that quantifies pedestrian anticipation into a probability field of pedestrians’ future locations and attention orientations. An end-to-end neural network, GIFNet, is tailored to estimate the GIF from explicit multidimensional observations. GIFNet quantifies the influence of group behaviors by formulating a group interaction graph with propagation and graph attention that is adaptive to the group size and dynamic interaction states. The experimental results show that the GIF effectively represents the change in pedestrians’ anticipation under the prominent impact of group behaviors and accurately predicts pedestrians’ future states. Moreover, the GIF contributes to explaining various predictions of pedestrians’ behavior in different social states. The proposed GIF will eventually be able to allow unmanned systems to work in a human-like manner and comply with social norms, thereby promoting harmonious human–machine relationships.

关键词： Human behavior modeling and prediction     Implicit representation of pedestrian anticipation     Group interaction     Graph neural network    

HTML PDF 收藏

Research on pedestrian escape route without visibility based on Markov chain model

Xiaoping ZHENG, Lijuan DU, Hongjiang WANG,

《化学科学与工程前沿（英文）》 2010年 第4卷 第3期   页码 283-289 doi: 10.1007/s11705-009-0272-8

摘要： It is a pioneering work to use a Markov chain model to study the pedestrian escape route without visibility. In this paper, based on the Markov chain probability transition matrix, the algorithms with random numbers and the spatial-grid, an escape route in a limited invisible space is obtained. Six pace states (standing, crawling, walking, leaping, jogging, and running) are applied to describe the characteristics of pedestrian behaviors. Besides, eight main direction changes are used to describe the transition characteristic of a pedestrian. At the same time, this paper analyzes the escape route from two views, i.e., pedestrian pace states and directions. The research results show that the Markov chain model is more realistic as a means of studying pedestrian escape routes.

关键词： pioneering     direction     spatial-grid     realistic     transition characteristic    

HTML PDF 收藏

基于混合强化学习的自动驾驶汽车行人避撞方法 Research Article

李惠乾1,黄晋1,曹重1,杨殿阁1,钟志华2

《信息与电子工程前沿（英文）》 2023年 第24卷 第1期   页码 131-140 doi: 10.1631/FITEE.2200128

摘要： 确保行人的安全对自动驾驶汽车而言至关重要，同时也具有一定挑战。经典的行人避撞策略无法应对不确定性，而基于学习的方法缺乏明确的性能保障。本文提出一种基于混合强化学习的行人避撞方法，以使自动驾驶车辆能够与具有行为不确定性的行人安全交互。该方法集成了规则策略和强化学习策略，并设计了一个激活函数选择具有更高置信度的作为最终策略，通过这种方式保证最终策略的表现不亚于规则策略。为说明所提方法的有效性，本文使用一种加速测试方法生成了行为随机的行人进行仿真验证。结果表明，该方法在测试场景中的成功率，相比基准方法的94.4%，提升至98.8%。

关键词： 行人；混合强化学习；自动驾驶汽车；决策    

HTML PDF 收藏

Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation

《环境科学与工程前沿（英文）》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1399-1

摘要：

• With the same charge, current density had little effect on As(III) removal in ACEC.

关键词： Electrocoagulation     Air cathode     Arsenic     Current density     Energy consumption    

HTML PDF 收藏

Effects of exercise therapy on bone mineral density in early postmenopausal women: a controlled trial

Shilin DENG MD ,

《医学前沿（英文）》 2009年 第3卷 第3期   页码 323-329 doi: 10.1007/s11684-009-0061-2

摘要： The purpose of this article is to determine the effect of a well-designed combined aerobic, resistance, and extension exercise program on bone mineral density (BMD) in postmenopausal women. The population comprised 45 postmenopausal women, who exercised over 12months (exercise group), and 36 women who served as a non-training control group. BMD of the hip, and lumbar spine was measured at the baseline and 12th month. Repeated measurement analysis of variance and nonparametric test were utilized to compare differences between the exercise group and controls. Thirty-six out of 45 persons in the exercise group and 36 controls completed the study. Average compliance was 82.2% for the whole exercise group at the 12th month. All the subjects had decreased BMD, but the rate of bone loss was lower in the exercise group than in the control group at the L4 and hip. Although the exercise program in this study may probably reduce the rate of bone loss in weight-bearing skeletal sites, we do not suggest the exercise by itself be viewed as prevention or treatment for osteoporosis. Further, the exact dose-response relationship of exercise and bone mass in early postmenopause is not clear.

关键词： early postmenopausal women     bone mineral density     exercise     effects    

HTML PDF 收藏

density measurement for plastic injection molding via ultrasonic technology

《机械工程前沿（英文）》 2022年 第17卷 第4期 doi: 10.1007/s11465-022-0714-2

摘要： Density variation during the injection molding process directly reflects the state of plastic melt and contains valuable information for process monitoring and optimization. Therefore, in-situ density measurement is of great interest and has significant application value. The existing methods, such as pressure−volume−temperature (PVT) method, have the shortages of time-delay and high cost of sensors. This study is the first to propose an in-situ density measurement method using ultrasonic technology. The analyses of the time-domain and frequency-domain signals are combined in the proposed method. The ultrasonic velocity is obtained from the time-domain signals, and the acoustic impedance is computed through a full-spectral analysis of the frequency-domain signals. Experiments with different process conditions are conducted, including different melt temperature, injection speed, material, and mold structure. Results show that the proposed method has good agreement with the PVT method. The proposed method has the advantages of in-situ measurement, non-destructive, high accuracy, low cost, and is of great application value for the injection molding industry.

关键词： ultrasonic measurement     melt density     in-situ measurement     injection molding    

HTML PDF 收藏

Testing development of different surface treatments on pervious concrete

Mina YEKKALAR,Liv HASELBACH,Quinn LANGFITT

《结构与土木工程前沿（英文）》 2016年 第10卷 第4期   页码 385-393 doi: 10.1007/s11709-016-0351-0

摘要： Pervious concrete systems are developing stormwater management technologies which also have wintertime benefits as melting snow may percolate into the system instead of refreezing on the surface. Enhancing the surface microtexture of pervious concrete may also be beneficial in preventing icing or slipping by pedestrians. This research explored different surface treatments on pervious concrete specimens both qualitatively from personal judgements, and quantitatively through static friction measurements with a spring balance with respect to “slipperiness”. The tests were performed on both dry and wet specimens. One aim was to determine whether the spring balance method may be a simple test for comparing surface treatments on pavement samples with little surface area such as laboratory specimens or sidewalk sections. The other purpose was to make a preliminary decision of which surface treatments to use for a sidewalk installation for future studies on wintertime performance. The reliability analysis of the spring balance results showed that there was high operator consistency. In addition, there was a high level of consistency on average results between the quantitative and qualitative methods. This implies that the spring balance test may be an acceptable methodology for comparative analyses with respect to static friction.

关键词： pervious concrete     static coefficient of friction     pedestrian    

HTML PDF 收藏

Relationship of adrenomedullin expression and microvessel density and prognosis in smooth muscle tumor

JIANG Yuan, TIAN Xuehong, YUAN Jie, JIN Yuemei, TAN Yusong

《医学前沿（英文）》 2007年 第1卷 第4期   页码 398-400 doi: 10.1007/s11684-007-0077-4

摘要： The aim of this paper was to investigate the relationship between the expression of adrenomedullin (ADM) and microvessel density (MVD) and prognosis in smooth muscle tumor of uterus. The expression of ADM was detected using immunohistochemical staining in specimens from 15 normal controls, 28 cases of uterine leiomyoma (LE) and 19 cases of uterine leiomyosarcoma (LES). The MVD was assayed by immunostainting with CD. There was a positive correlation between the ADM expression and MVD in LE and LES respectively ( = 0.823, <0.01; = 0.793, <0.01). The expression of ADM in LE was statistically lower than that in LES (<0.05). There was a positive correlation between the ADM expression and mitotic figures in LES (<0.05): the more mitotic figures, the higher levels of the ADM expression and poor prognosis. The ADM is an important angiogenic factor in smooth muscle tumor of uterus. The ADM can be used as an accessory marker in estimating the malignant potency of LE and judging the pro gnosis of LES, and as a novel molecular target of anti-angiogenic and anticarcinogenic strategies.

关键词： anticarcinogenic     microvessel density     malignant potency     muscle     uterine leiomyosarcoma    

HTML PDF 收藏

Single-electromagnet levitation for density measurement and defect detection

Yuhan JIA, Peng ZHAO, Jun XIE, Xuechun ZHANG, Hongwei ZHOU, Jianzhong FU

《机械工程前沿（英文）》 2021年 第16卷 第1期   页码 186-195 doi: 10.1007/s11465-020-0608-0

摘要： This paper presents a single-electromagnet levitation device to measure the densities and detect the internal defects of antimagnetic materials. The experimental device has an electromagnet in its lower part and a pure iron core in the upper part. When the electromagnet is activated, samples can be levitated stably in a paramagnetic solution. Compared with traditional magnetic levitation devices, the single-electromagnet levitation device is adjustable. Different currents, electromagnet shapes, and distances between the electromagnet and iron core are used in the experiment depending on the type of samples. The magnetic field formed by the electromagnet is strong. When the concentration of the MnCl aqueous solution is 3 mol/L, the measuring range of the single-electromagnet levitation device ranges from 1.301 to 2.308 g/cm . However, with the same concentration of MnCl aqueous solution (3 mol/L), the measuring range of a magnetic levitation device built with permanent magnets is only from 1.15 to 1.50 g/cm . The single-electromagnet levitation device has a large measuring range and can realize accurate density measurement and defect detection of high-density materials, such as glass and aluminum alloy.

关键词： single-electromagnet     electromagnetic levitation     density measurement     defect detection    

HTML PDF 收藏

Application of gamma-ray attenuation technology in density measurement of a slurry reactor

Jian XU, Weisheng WEI, Kai ZHANG

《化学科学与工程前沿（英文）》 2010年 第4卷 第4期   页码 486-490 doi: 10.1007/s11705-010-0509-6

摘要： Axial density profile of the gas-liquid-solid mixture in a slurry bubble column was measured by gamma-ray attenuation technology. Several measures for improving measurement precision were presented based on the discussion on attenuation law. It was found that the response frequency and the ray intensity should be as high as possible to improve the measurement precision. The mass absorption coefficient depended on not the object’s thickness but the location where the object was placed between the ray source and the detector. The results showed that the density in the column decreases with the increase of column height, which indicates that the measurement by gamma-ray attenuation is reasonable.

关键词： slurry reactor     axial density distribution     gamma-ray attenuation technology    

HTML PDF 收藏

frameworks as highly active electrocatalysts for oxygen reduction and oxygen evolution reaction: a density

《化学科学与工程前沿（英文）》 2023年 第17卷 第5期   页码 570-580 doi: 10.1007/s11705-022-2247-y

摘要： Recently, metal–organic frameworks are one of the potential catalytic materials for electrocatalytic applications. The oxygen reduction reaction and oxygen evolution reaction catalytic activities of heterometallic cluster-based organic frameworks are investigated using density functional theory. Firstly, the catalytic activities of heterometallic clusters are investigated. Among all heterometallic clusters, Fe2Mn–Mn has a minimum overpotential of 0.35 V for oxygen reduction reaction, and Fe2Co–Co possesses the smallest overpotential of 0.32 V for oxygen evolution reaction, respectively 100 and 50 mV lower than those of Pt(111) and RuO2(110) catalysts. The analysis of the potential gap of Fe2M clusters indicates that Fe2Mn, Fe2Co, and Fe2Ni clusters possess good bifunctional catalytic activity. Additionally, the catalytic activity of Fe2Mn and Fe2Co connected through 3,3′,5,5′-azobenzenetetracarboxylate linker to form Fe2M–PCN–Fe2M is explored. Compared with Fe2Mn–PCN–Fe2Mn, Fe2Co–PCN–Fe2Co, and isolated Fe2M clusters, the mixed-metal Fe2Co–PCN–Fe2Mn possesses excellent bifunctional catalytic activity, and the values of potential gap on the Mn and Co sites of Fe2Co–PCN–Fe2Mn are 0.69 and 0.70 V, respectively. Furthermore, the analysis of the electron structure indicates that constructing a mixed-metal cluster can efficiently enhance the electronic properties of the catalyst. In conclusion, the mixed-metal cluster strategy provides a new approach to further design and synthesize high-efficiency bifunctional electrocatalysts.

关键词： bimetallic metal–organic frameworks     bifunctional electrocatalyst     density functional theory     oxygen reduction reaction     oxygen evolution reaction    

HTML PDF 收藏

Influence of pressure and density on the rheological properties of rockfills

Erich BAUER, Zhongzhi FU, Sihong LIU

《结构与土木工程前沿（英文）》 2012年 第6卷 第1期   页码 25-34 doi: 10.1007/s11709-012-0143-0

摘要： Long-term deformations of rockfill dams can be related to the type of dam, the pre-compaction achieved during the construction of the dam, the history of loading events, the rheological properties of the rockfill material used, the seepage behavior caused by defects of the sealing, the interactions of the dam building with the foundation, and the hydrothermal phenomena of the stressed rockfill material. The present paper investigates the rheological properties of coarse grained rockfill materials using a hypoplastic constitutive model. Particular attention is paid to wetting deformation under different deviatoric loading states and pre-compactions. To quantify the state of weathering a so-called “solid hardness” is used in the sense of a continuum description. It is shown that an appropriate modeling of wetting deformations requires a unified description of the interaction at least between the state of weathering, the stress state, the density and the rate of deformation. The results obtained from the numerical simulations are compared with available experimental data for a rockfill material used in Xiaolangdi earth dam.

关键词： rockfills     solid hardness     wetting deformation     hypoplasticity     creep    

HTML PDF 收藏

Tripotassium citrate monohydrate derived carbon nanosheets as a competent assistant to manganese dioxide with remarkable performance in the supercapacitor

《化学科学与工程前沿（英文）》 2022年 第16卷 第3期   页码 420-432 doi: 10.1007/s11705-021-2065-7

摘要： Production cost, capacitance, and electrode materials safety are the key factors to be concerned about for supercapacitors. In this work, a type of carbon nanosheets was produced through the carbonization of tripotassium citrate monohydrate and nitric acidification. Subsequently, a well-designed manganese dioxide/carbon nanosheets composite was synthesized through hydrothermal treating. The carbon nanosheets served as the substrate for growing the manganese dioxide, regulating its distribution, and preventing it from inhomogeneous dimensions and severe agglomeration. Many manganese dioxide nanosheets grew vertically on the numerous functional groups generated on the surface of the carbon nanosheets during acidification. The synergistic combination of carbon nanosheets and manganese dioxide tailors the electrochemical performance of the composite, which benefits from the excellent conductivity and stability of carbon nanosheets. The carbon nanosheets derived from tripotassium citrate monohydrate are conducive to the remarkable performance of manganese dioxide/carbon nanosheets electrode. Finally, an asymmetric supercapacitor with active carbon as the cathode and manganese dioxide/carbon nanosheets as the anode was assembled, achieving an outstanding energy density of 54.68 Wh·kg–1 and remarkable power density of 6399.2 W·kg–1 superior to conventional lead-acid batteries. After 10000 charge-discharge cycles, the device retained 75.3% of the initial capacitance, showing good cycle stability. Two assembled asymmetric supercapacitors in series charged for 3 min could power a yellow light emitting diode with an operating voltage of 2 V for 2 min. This study may provide valuable insights for applying carbon materials and manganese dioxide in the energy storage field.

关键词： carbon nanosheets     manganese dioxide     asymmetric supercapacitors     energy density     power density    

HTML PDF 收藏

标题 作者 时间 类型 操作

Presentation of regression analysis, GP and GMDH models to predict the pedestrian density in various

Iraj BARGEGOL; Seyed Mohsen HOSSEINIAN; Vahid NAJAFI MOGHADDAM GILANI; Mohammad NIKOOKAR; Alireza OROUEI

期刊论文

A Bayesian modeling approach to bi-directional pedestrian flows in carnival events

S. Q. XIE, S. C. WONG, William H. K. LAM

期刊论文

The Group Interaction Field for Learning and Explaining Pedestrian Anticipation

Xueyang Wang,Xuecheng Chen,Puhua Jiang,Haozhe Lin,Xiaoyun Yuan,Mengqi Ji,Yuchen Guo,Ruqi Huang,Lu Fang,

期刊论文

Research on pedestrian escape route without visibility based on Markov chain model

Xiaoping ZHENG, Lijuan DU, Hongjiang WANG,

期刊论文

基于混合强化学习的自动驾驶汽车行人避撞方法

李惠乾1,黄晋1,曹重1,杨殿阁1,钟志华2

期刊论文

Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation

期刊论文

Effects of exercise therapy on bone mineral density in early postmenopausal women: a controlled trial

Shilin DENG MD ,

期刊论文

density measurement for plastic injection molding via ultrasonic technology

期刊论文

Testing development of different surface treatments on pervious concrete

Mina YEKKALAR,Liv HASELBACH,Quinn LANGFITT

期刊论文

Relationship of adrenomedullin expression and microvessel density and prognosis in smooth muscle tumor

JIANG Yuan, TIAN Xuehong, YUAN Jie, JIN Yuemei, TAN Yusong

期刊论文

Single-electromagnet levitation for density measurement and defect detection

Yuhan JIA, Peng ZHAO, Jun XIE, Xuechun ZHANG, Hongwei ZHOU, Jianzhong FU

期刊论文

Application of gamma-ray attenuation technology in density measurement of a slurry reactor

Jian XU, Weisheng WEI, Kai ZHANG

期刊论文

frameworks as highly active electrocatalysts for oxygen reduction and oxygen evolution reaction: a density

期刊论文

Influence of pressure and density on the rheological properties of rockfills

Erich BAUER, Zhongzhi FU, Sihong LIU

期刊论文

Tripotassium citrate monohydrate derived carbon nanosheets as a competent assistant to manganese dioxide with remarkable performance in the supercapacitor

期刊论文