Evaluation of Rock Vibration Generated in Blasting Excavation of Deep-buried Tunnels

Jianhua Yang,Wenbo Lu,Peng Yan 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.7

The experimental tunnels of the China Jinping Underground Laboratory are constructed in a maximum overburden depth of 2375 mand subjected to extremely high in situ stress more than 50 MPa. When these deep-buried tunnels are excavated with the method ofdrill and blast, the surfaces created by blasting are generated almost instantaneously, and thus the initial stress on these surfaces is alsosuddenly released. This transient release of in situ stress causes elastic waves to propagate in rock masses and may have an importanteffect on the subsequent rock vibration. In this study, a three-dimensional FEM modeling in combination with site investigation isconducted to research the Peak Particle Velocity (PPV) attenuation and frequency characteristics for the rock vibration induced bytransient stress release and its combined actions with blast loading. The results indicate that the transient release of the high stressgenerates considerable vibration velocity that is comparable to that of blast loading. It is not a negligible excitation for the rockvibration generated in blasting excavation of deep-buried tunnels. Furthermore, the vibration induced by transient stress release hasmuch lower frequency than that caused by blast loading. This causes the unloading vibration to decay more slowly and become themajor vibration component at far distances. Also, the effect of transient stress release is found to enhance intensity of the totalvibration and furthermore cause an increase in its low-frequency content. On the basis of this, the allowable charge amount per delayand the minimum safety distance are finally discussed with a special emphasis on the contributions of the transient stress release tothe total vibration.

Theoretical Prediction of Heat Transport in Few-Layer Graphene/ Epoxy Composites

Jianhua Zeng,Jiao Li,Peng Yuan,Ping Zhang 한국고분자학회 2018 Macromolecular Research Vol.26 No.11

Graphene is widely employed to improve the overall thermal conductivity of polymer composites because of its remarkable thermal conductivity. However, the magnitude of its improvement of thermal conductivity is far below the values expected from the remarkably high thermal conductivity of graphene and is very much less than the production cost of graphene, greatly limiting its large-scale applications in the field of thermal management. Therefore, understanding heat transport behaviors within the polymer composites and studying the related influential factors are very important. Here, heat transport behaviors within few-layer graphene (FLG)/epoxy composites are studied using molecular dynamics (MD) simulations. The influences of interfacial thermal resistance, FLG volume fraction and FLG length on overall thermal conductivity of the composites are specifically analyzed, finding that there is a significant interfacial thermal resistance between FLG and epoxy because of the mismatch of the phonon vibration power spectrum (VPS). Furthermore, the interfacial thermal resistance, FLG volume fraction, and FLG length play important roles in improving the overall thermal conductivity of FLG/epoxy composites. Our findings provide a better understanding of the heat transport behaviors within polymer composites and should be useful for future development of various thermal management applications.

ENERGY-SAVING MODEL PREDICTIVE CRUISE CONTROL COMBINED WITH VEHICLE DRIVING CYCLES

SiLun Peng,ZhiHao Xu,JianHua Li,Feng Xiao,Xu Zhang,ShiXin Song,Da Wang,ChunYang Qi,JianFeng Wang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.2

This study analyzes the problem of adaptive cruise control of vehicles in different driving cycles and divides diverse weight coefficient intervals for the vehicles under the different driving cycles to improve the adaptability of the vehicles in various environments. This paper first describes the driving environment of the adaptive cruise vehicle, and a model prediction algorithm with fixed weight coefficients is established to control the vehicle state. Then, a neural network is established to identify the vehicle driving cycles, the weight intervals are divided in accordance with different driving cycles, and the weight value is dynamically adjusted through fuzzy control. Lastly, the variable weight coefficients of different driving cycles are combined with the model prediction controller. The software cosimulation shows that the method designed in this paper plays a positive role in the fuel economy of adaptive cruise.

Dynamic Metro Stations Importance Evaluation Based on Network Topology and Real-Time Passenger Flows

Peipei Peng,Zhao Liu,Jianhua Guo,Chao Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10

Identifying the importance of metro stations is crucial for enhancing the efficiency and safety of the urban rail transit system. This study proposes an integrated approach to evaluate the importance of metro stations based on jointly the static metro network topology and the dynamic real-time passenger flows. The static characteristics of metro stations are reflected through node degree and clustering coefficient of metro network topology based on the complex network theory. The dynamic characteristics of metro stations are assessed using the passenger flow time series, which were modeled using the autoregressive integrated moving average plus autoregressive conditional heteroscedasticity model (i.e., ARIMA+GARCH model). By combining the static and dynamic characteristics of metro stations, a comprehensive index is proposed to quantify the importance of metro stations. The integrated approach is tested using metro network and passenger flow data collected from Suzhou, China. The resultsindicate that compared with the topology analysis, the passenger flows could strengthen the importance of transfer stations and their neighboring stations. Especially for the loop lines that formed by the intersection of two or more lines within the network, the importance index of metro stations within these loop lines is inversely proportional to the number of stations in the loop. It indicates that as a metro network continues to expand with the addition of new lines and stations, this is a high likelihood of increased concentration of importance with the network. The concentration of importance in the metro network can be attributed to the emergence of highly connected loop lines that facilitate efficient movement of passengers.

Investigation of bipolar matrix based mixed host in highly efficient green delayed fluorescence organic light-emitting diodes

Zheng Yanqiong,Peng Junbiao,Tang Jie,Li Weiguang,Chen Juncong,Wang Chao,Zhang Jianhua,Wei Bin,Li Xifeng 한국물리학회 2021 Current Applied Physics Vol.22 No.-

The mixed cohosts of electron transport host (E-host): 4,40-bis(carbazol-9-yl)biphenyl (CBP) have been comparatively investigated for an efficient green fluorescent organic light emitting diode (OLED) doped with a thermally activated delayed fluorescence (TADF) emitter (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN). The E-host:CBP systems significantly enhance the electroluminescent (EL) properties. After doping Ehost, the lifetime of the emissive layer decreases and the surface becomes smoother, together with the impedance decreases for one magnitude and the hole-injection depresses. The charge balance and improved interface both contribute to the EL performance enhancement. Here we develop a universal mixed host system suitable to most of emitters.

Secrecy Spectrum and Secrecy Energy Efficiency in Massive MIMO Enabled HetNets

( Zhihao Zhong ),( Jianhua Peng ),( Kaizhi Huang ),( Lu Xia ),( Xiaohui Qi ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.2

Security and resource-saving are both demands of the fifth generation (5G) wireless networks. In this paper, we study the secrecy spectrum efficiency (SSE) and secrecy energy efficiency (SEE) of a K-tier massive multiple-input multiple-output (MIMO) enabled heterogeneous cellular network (HetNet), in which artificial noise (AN) are employed for secrecy enhancement. Assuming (i) independent Poisson point process model for the locations of base stations (BSs) of each tier as well as that of eavesdroppers, (ii) zero-forcing precoding at the macrocell BSs (MBSs), and (iii) maximum average received power-based cell selection, the tractable lower bound expressions for SSE and SEE of massive MIMO enabled HetNets are derived. Then, the influences on secrecy oriented spectrum and energy efficiency performance caused by the power allocation for AN, transmit antenna number, number of users served by each MBS, and eavesdropper density are analyzed respectively. Moreover, the analysis accuracy is verified by Monte Carlo simulations.

Mechanical Properties of Special-shaped Mo Fiber Reinforced Mineral-filled Polymer Composite

Xiuhua Ren,Chao Zhang,Jianhua Zhang,Peng Liu,Guangjiu Qin 한국섬유공학회 2021 Fibers and polymers Vol.22 No.2

With superior vibration alleviation property, mineral-filled polymer composite (MFPC) has attracted moreattention in the field of mechanical manufacturing. However, the application of MFPC is limited by its inferior mechanicalstrength. Straight-line and special-shaped Mo fibers were respectively added into MFPC to improve its mechanical propertiesin the paper. The influences of fiber shape and matrix performance on interface bonding property of fiber-matrix were studiedsystematically. And the effects of fiber shape and fiber content on compressive and flexural strength of MFPC wereseparately discussed. Finite element analysis was employed to further verify experimental results. Compared with straightlinefiber, both pulling ability and interfacial bonding strength of special-shaped Mo fiber are greatly improved when massratio r of resin and curing agent is identical. For the same fiber, interface bonding strength of r=4:1 is obviously greater thanthat of r=7:1. The maximum mechanical strength is achieved when mass fraction of fibers is 1.2 %. Mechanical properties ofMFPC reinforced by special-shaped fibers are much better than those reinforced by straight-line fibers. By contrast, thereinforcing effect of M-shaped fibers is optimal, followed by N-shaped, U-shaped the third, and V-shaped the minimum,which consists with the results of finite element simulation.

Synergistic effect of micro-textures and MoS2 on the tribological properties of PTFE film against GCr15 bearing steel

Xuan Xie,Xijun Hua,Jianhua Li,Xiaobin Cao,Zhixiang Tian,Rui Peng,Bifeng Yin,Peiyun Zhang 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.5

To enhance the friction and wear resistance of GCr15/PTFE sliding contact surfaces, the synergistic lubrication effect of micro-textures and solid lubricants were studied in this paper. Micro-textures were processed on GCr15 samples by Nd:YAG laser, which were filled with MoS 2 . Tribological performance tests were carried out on a Rtec-MFT 5000 tester. Tribological properties were optimal with the textures density of 20 % and depth of 9 μm. A continuous composite solid lubricating film was formed by PTFE and MoS 2 . As load increases, friction coefficient of the sample shows a rapid decline and then stabilizes. With the increase of reciprocating frequency, friction curve of the sample shows a trend of slight fluctuation. When frequency is 2.7 Hz, friction coefficient is the lowest. Tribological properties of PTFE/GCr15 contact surfaces could be significantly optimized by micro-textures and MoS 2 , which performs favorable prospect of engineering application such as guide rails, bearings, machinery seal, etc.

High-performance hybrid white organic light-emitting diodes employing p-type interlayers

Baiquan Liu,Hong Tao,Jianhua Zou,Miao Xu,Dongyu Gao,Linfeng Lan,Lei Wang,Honglong Ning,Junbiao Peng 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.27 No.-

A simplified hybrid white organic light-emitting diode (WOLED) employing a p-type interlayer isdesigned, simultaneously realizing high efficiency, high color rendering index (CRI), low efficiency roll-off, low voltage and stable color. The device exhibits maximum total efficiencies of 29.8 cd/A and20.9 lm/W, which slightly decrease to 28.6 cd/A and 16.5 lm/W even at a high luminance of 5000 cd/m2. Besides, a slight color-shift and a CRI of 85 at 100 cd/m2 (3.65 V) are obtained. Such superior resultssystematically demonstrate that the use of p-type interlayer is a new way to realize high-performancehybrid WOLEDs.

Efficient single-emitting layer hybrid white organic light-emitting diodes with low efficiency roll-off, stable color and extremely high luminance

Baiquan Liu,Honglong Ning,Lei Wang,Jianhua Zou,Zhongwei Zhou,Miao Xu,Hong Tao,Dongyu Gao,Linfeng Lan,Junbiao Peng 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.30 No.-

An efficient single-emitting layer hybrid white organic light-emitting diode (WOLED) was developed,simultaneously fulfilling low efficiency roll-off, stable color and extreme luminance. At the practicalluminance of 1000 cd/m2, a total current efficiency of 42.8 cd/A and power efficiency of 19.2 lm/W areachieved, maintaining as high as 40.5 cd/A and 15.5 lm/W even at 5000 cd/m2. Besides, a slight colorvariation [(0.025, 0.011)] and extreme luminance ( 106 cd/m2) are obtained. The working mechanism isunveiled and it is demonstrated that the triplet-exciton-confining ability of electron transport layersplays a more vital role in device performances, particularly for the lifetime.