Analysis on the Dynamic Characteristics of Cross-Tunnel Structures under Wheel-Rail Impact Forces

Zhigang Wang,Lianjin Tao,Jie Dong 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.9

The dynamic behaviour of cross-tunnel structures under the wheel-rail impact forces of heavyhaultrains is complicated. This paper establishes an impact force excitation input model tosimulate the wheel-rail vertical forces of rail welded joints. The calculated results of thecorrection formula of wheel-rail vertical forces for seamless rail joints are in good agreementwith the measured data and meet the accuracy requirements. The present paper describes a1/50 scale model experiment based on the case of the newly-built Jing-Zhang Railwayunderneath the existing Tang-Hu Heavy Haul Railway. Numerical simulation analysis usesFLAC3D to simulate the experiments and investigate the dynamic soil pressure characteristicsunder different factors. The test and numerical results showed that the dynamic responses ofthe upper tunnel monitoring points are stronger than the lower tunnel, but the maximumvertical settlement of the lower tunnel vault is bigger and prone to damage. As the depthincreases, the stress of the surrounding rock interlayer at each monitoring point graduallydecreases. In-depth, the surrounding rock stress decreased approximately non-linearly withincreasing surrounding rock grade and surrounding rock interlayer thickness.

Blockchain and central bank digital currency

Tao Zhang,Zhigang Huang 한국통신학회 2022 ICT Express Vol.8 No.2

With the development of blockchain and digital currencies, central banks all over the world are accelerating the process of CBDC development. However, it is still controversial on adoption of blockchain in CBDC design. In the paper, we analyze both functional and non-functional requirements of CBDC design, and make a literature review on blockchain based CBDC schemes. Analysis findings show that permissioned blockchain are more suitable for CBDC than permissionless blockchain. Besides, there are some challenges in blockchain based CBDC, such as performance, scalability, and cross-chain interoperability. Our analysis is timely and can provide guidelines for blockchain based CBDC design.

FPoR: Fair proof-of-reputation consensus for blockchain

Tao Zhang,Zhigang Huang 한국통신학회 2023 ICT Express Vol.9 No.1

Current consensus protocols for permissionless blockchain cannot balance security, performance and centralization issues. In the paper, we present a reputation based consensus, FPoR, which combines reputation, committee based consensus, PBFT, reward and penalization mechanisms. FPoR can balance scalability, security and decentralization, and promote fairness, increase participation and strengthen security. Experiment results show that FPoR is with high performance and scalability, which can be used for permissionless blockchain. FPoR can also be extended to permissioned blockchain applications.

Study of cable obstacle avoidance planning of a multi-robot collaborative towing system

Tao Li,Zhigang Zhao,Xiangtang Zhao,Mingtong Zhu,Ruina Chen 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.6

In order to solve the problem of ignoring the cable and only planning the trajectory of the lifted object and the robot ends, a planning scheme of a multi-robot collaborative towing system aiming at the cable obstacle avoidance motion planning was proposed. The univariate polynomial equation group of the cable was obtained by constructing the cable sweep equation and defining the implicit equation of the obstacle. Then, the point-to-point decomposition trajectory was planned for the initial trajectory of the lifted object in the variable cable length workspace. And the differential manifold and manifold tangent space theories were used to plan the predicted trajectory of the lifted object. Based on the system dynamics characteristics, the tangent vector selection of the predicted trajectory was determined. Finally, the three-level planning strategy with the lifted object as the planning object, the end of robot as the planning intermediate, and the cable obstacle avoidance as the planning purpose was finally realized.

Synthesis of g-C3N4/CQDs composite and its photocatalytic degradation property for Rhodamine B

Jin Tao,Liu Chengbao,Chen Feng,Qian Junchao,Qiu Yongbin,Meng Xianrong,Chen Zhigang 한국탄소학회 2022 Carbon Letters Vol.32 No.6

To solve the problem of water pollution, researchers have proposed a photocatalytic degradation technology, in which the key factor is the development of efficient photocatalytic materials. Graphitic carbon nitride (g-C3N4), an n-type semiconductor, has been widely studied due to its suitable band gap (2.7 eV), low cost, easy preparation, non-toxicity, and high photostability. However, the pure-phase g-C3N4 still has defects such as low specific surface area, insufficient visible light absorption, low charge mobility, few active sites for interfacial reaction, and easy recombination of photogenerated electron–hole pairs, which leads to the lower photocatalytic activity of g-C3N4. Aiming at the problems mentioned above, this paper focus on the synthesis of g-C3N4-based composites with high photocatalytic activity via lemon juice induction method. Thiourea and lemon juice were selected as precursors, and carbon quantum dots (CQDs) as electron mediators were introduced anchoring on the surface of g-C3N4 to build g-C3N4/CQDs with compact interface. The results showed that small-sized CQDs are uniformly distributed on the surface of g-C3N4, and the g-C3N4/CQDs composite has a 2D0D structure, which reduces the recombination of photogenerated electron–hole pairs. The photocatalytic degradation efficiency of 4% g-C3N4/CQDs for RhB reaches the highest data of 90.9%, and the photocatalytic degradation rate is 0.016 min−1, which is about 2.3 times that of g-C3N4. After four cycles of photocatalytic reaction, the photocatalytic degradation efficiency of the material remained at 81.7%. Therefore, the g-C3N4/CQDs synthesized via lemon juice induction has a more stable microstructure, and the charge separation efficiency is greatly improved, which is suitable for practical photocatalytic environmental protection.

Development and verification of PWR core transient coupling calculation software

Li, Zhigang,An, Ping,Zhao, Wenbo,Liu, Wei,He, Tao,Lu, Wei,Li, Qing Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.11

In PWR three-dimensional transient coupling calculation software CORCA-K, the nodal Green's function method and diagonal implicit Runge Kutta method are used to solve the spatiotemporal neutron dynamic diffusion equation, and the single-phase closed channel model and one-dimensional cylindrical heat conduction transient model are used to calculate the coolant temperature and fuel temperature. The LMW, NEACRP and PWR MOX/UO₂ benchmarks and FangJiaShan (FJS) nuclear power plant (NPP) transient control rod move cases are used to verify the CORCA-K. The effects of burnup, fuel effective temperature and ejection rate on the control rod ejection process of PWR are analyzed. The conclusions are as follows: (1) core relative power and fuel Doppler temperature are in good agreement with the results of benchmark and ADPRES, and the deviation between with the reference results is within 3.0% in LMW and NEACRP benchmarks; 2) the variation trend of FJS NPP core transient parameters is consistent with the results of SMART and ADPRES. And the core relative power is in better agreement with the SMART when weighting coefficient is 0.7. Compared with SMART, the maximum deviation is -5.08% in the rod ejection condition and while -5.09% in the control rod complex movement condition.

Feasibility Analysis on the Support of Rock Slopes Against Flexural Toppling Failure Using the DDA Method-A Case Study

Wen Jun Gong,Zhigang Tao,Man Chao He,Hui Jun Hou 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.9

As a typical and complex failure type of rock slopes, flexural toppling failure has increasingly received attention, mainly focused on its failure mechanism and introducing a proper numerical method to reproduce the failure phenomena. However, there are few studies related to the supporting mechanism against flexural toppling failure. This study attempted to make a preliminary analysis on the research gap. For this purpose, an anti-dip layered rock slope supported with anchor cables that failed owning to flexural toppling was taken as an example, and the numerical method discontinuous deformation analysis (DDA) was taken as the major analytical tool. Firstly, the rationality of DDA was verified by correctly simulating the failure state of the anti-layered rock slope and the underlying failure mechanism was studied. The results indicated that the lack of the support from slope toe is the crucial factor inducing the flexural toppling failure, which posed a great obstacle to the further excavation of the open-pit mine. Secondly, by introducing the anchor cable support to the slope toe in the DDA model, the interaction mechanism between the anchor cables and the rock slope was investigated. the results indicated that the supporting system of the ordinary anchor cables is very sensitive to the inhomogeneous flexural toppling deformation. The tension values of the anchor cables are very inhomogeneous, and once some of anchor cables beyond their tension limit, the anchor cables failed, which will greatly threaten the safety of the adjacent anchor cables and even the stability of the whole slope. Meanwhile, a novel anchor cable called constant-resistance-large-deformation (CRLD) anchor cable was introduced for a comparative study using DDA. just replacing the anchor cables of the original slope with the CRLD anchor cables, the slope can reach stable state eventually even without the slope toe being enhanced. In addition, the CRLD anchor cables were able to support the slope well against the inhomogeneous deformation, because they can provide high constant resistances and withstand large deformations. This study can provide a deeper insight into the support mechanism for the snit-layered rock slope against flexural toppling failure and introduce a novel supporting method for such slopes.

An Improved Discontinuous Deformation Analysis to Solve Both Shear and Tensile Failure Problems

Wenjun Gong,Jing Hu,Zhigang Tao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5

This paper is mainly aimed to present an improved DDA (discontinuous deformation analysis) that can deal well with both shear and tensile failure problems. Firstly, the shear mechanism of DDA is detailed investigated. The results show that when handling the frictional interface, the critical shear resistance can be accurately determined only if the penalty value is carefully selected, however, when handling the cohesive interface, the critical shear resistance is significantly underestimated. The inaccurate prediction is due to the inconsistent distribution of normal force and shear force between the two vertex-to-edge contacts in one edge-to-edge contact. Here an edge-to-edge treatment is introduced into DDA. Secondly, to moderately reflect the tensile failure process of rock masses, a two-phase constitutive model is introduced into the DDA with edge-to-edge treatment, and the improved DDA is obtained. Finally, the improved DDA is used to simulate the failure process of gypsum centrifuge model. The results show the improved DDA can deal well with rock failure problems by shear or tension failure.

Experimental Study on Key Parameters of Bidirectional Cumulative Tensile Blasting with Coal-Containing Composite Roof

Pengfei Guo,Kengkeng Ye,Zhigang Tao,Hongda Liang,Yadi Yuan 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.5

To improve the effectiveness of the directional-predetermined crack blasting in the weak and alternate composite roof, this paper took the coal-containing composite roof of the 12201 working face of Halagou Coal Mine as the engineering background, and based on the technical principles of roof cutting pressure releasing gob-side entry retaining, comprehensive used of theoretical analysis, field experiments and other means, carried out in-depth research on the shaped energy blasting method and parameter design of the coal-containing composite roof. The results show: Through theoretical analysis, in the process of shaped energy blasting, the air column in the hole can reduce the peak blast pressure, which can effectively prevent the weak surrounding rock in the hole from being damaged in the non-cumulative direction and enhance the pre-splitting effect. During detonation at the bottom, the instantaneous pressure in the blast hole is lower than that of detonation at the top, and the action time of blast pressure is longer than detonation at the top. When the buried depth of the explosive (near the blast hole) is less than the critical depth, a "V"-shaped blasting funnel will be formed after the rock blasting, and the critical depth is proportional to the charge. Through field tests on the charge quantity and the length of the sealing mud, when the blast hole depth is 6m, the charge parameters of "3+2+0+1" have a better effect of energy-concentrating blasting, and the crack rate reaches 87%. Besides, field tests have shown that when shaped energy blasting is carried out on soft and hard rock formations, the stemming separation in the shaped energy tube at the interlayer position can ensure the directional pre-cracking effect of hard rock, while effectively avoiding damage to the weak rock formation in the non-cumulative direction.

Neighbor Gradient-based Multicast Routing for Service-Oriented Applications

( Hui Wang ),( Jianbiao Mao ),( Tao Li ),( Zhigang Sun ),( Zhenghu Gong ),( Gaofeng Lv ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.9

With the prevalence of diverse services-oriented applications, such as IPTV systems and on-line games, the current underlying communication networks face more and more challenges on the aspects of flexibility and adaptability. Therefore, an effective and efficient multicast routing mechanism, which can fulfill different requirements of different personalized services, is critical and significant. In this paper, we first define the neighbor gradient, which is calculated based on the weighted sum of attributes such as residual link capacity, normalized hop count, etc. Then two distributed multicast routing algorithms which are neighbor Gradient-based Multicast Routing for Static multicast membership (GMR-S) and neighbor Gradient-based Multicast Routing for Dynamic multicast membership (GMR-D), are proposed. GMR-S is suitable for static membership situation, while GMR-D can be used for the dynamic membership network environment. Experimental results demonstrate the effectiveness and efficiency of our proposed methods.