Numerical Simulation of the Creep Behavior of Beishan Deep Granite Tunnel under the Coupling Thermal -Stress Field

Jiawei Wang,Ju Wang,Zhichao Zhou,Peng Wu,Haoran Sun,Jiale Dou,Nan Li,Xianzhe Duan 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.4

This study conducts a three-dimensional numerical simulation of the creep behavior of deep granite tunnels at 560 meters underground during the coupled thermal-stress process, with an aim to elucidate the effect of the temperature and stress fields on the creep behavior of these deep hard rock tunnels. A 100-h creep period was set, and the mechanical structure of the experimental chamber was accurately replicated at a 1:1 scale, considering the actual mechanical structure of the granite tunnels in the Beishan underground laboratory. The simulation results can demonstrate that: 1) The maximum stress at 90°C and 50°C are 2.86 and 1.91 times than that at 23°C, respectively, demonstrating significant strain accumulation in the deep granite tunnels at the surface. This phenomenon can primarily be attributed to the thermal stress resulted from the coupling between temperature and stress. 2) The maximum creep at 90°C and 50°C is 16 and 3.5 times than that at 23°C. Under the influence of thermal coupling, the creep increases significantly with increasing temperature, indicating that temperature is an important factor influencing creep in granite. 3) Compared with variations in the stress field, the temperature field emerges as the most critical factor influencing granite creep.

Role of span length in the adaptation of implant-supported cobalt chromium frameworks fabricated by three techniques

Zhou Ying,Li Yong,Ma Xiao,Huang Yiqing,Wang Jiawei 대한치과보철학회 2017 The Journal of Advanced Prosthodontics Vol.9 No.2

PURPOSE. This study evaluated the effect of span length on the adaptation of implant-supported cobalt chromium frameworks fabricated by three techniques. MATERIALS AND METHODS. Models with two solid abutment analogs at different inter-abutment distances were digitized using a laboratory scanner. Frameworks of two-, three-, and four-unit fixed prostheses were designed by a computer. Six dots with a diameter of 0.2 mm were preset on the surface of each framework. A total of 54 implant-supported cobalt chromium frameworks were fabricated by milling, selective laser melting (SLM), and cast techniques. The frameworks were scanned and exported as Stereolithography files. Distances between two dots in X, Y, and Z coordinates were measured in both the designed and fabricated frameworks. Marginal gaps between the framework and the abutments were also evaluated by impression replica method. RESULTS. In terms of distance measurement, significant differences were found between three- and four-unit frameworks, as well as between two- and four-unit frameworks prepared by milling technique (P<.05). Significant differences were also noted between two- and three-unit frameworks, as well as between two- and four-unit frameworks prepared by cast technique (P<.05). The milling technique presented smaller differences than the SLM technique, and the SLM technique showed smaller differences than the cast technique at any unit prostheses (P<.05). Evaluation with the impression replica method indicated significant differences among the span lengths for any fabrication method (P<.05), as well as among the fabrication methods at any unit prostheses (P<.05). CONCLUSION. The adaptation of implant-supported cobalt chromium frameworks was affected by the span length and fabrication method.

Experimental and numerical study on the dynamic behavior of a semi-active impact damper

Jiawei Zhang,Zheng Lu,Mengyao Zhou,Zhikuang Huang,Sami F. Masri 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.31 No.5

Impact damper is a passive damping system that controls undesirable vibration with mass block impacting with stops fixed to the excited structure, introducing momentum exchange and energy dissipation. However, harmful momentum exchange may occur in the random excitation increasing structural response. Based on the mechanism of impact damping system, a semi-active impact damper (SAID) with controllable impact timing as well as a semi-active control strategy is proposed to enhance the seismic performance of engineering structures in this paper. Comparative experimental studies were conducted to investigate the damping performances of the passive impact damper and SAID. The extreme working conditions for SAID were also discussed and approaches to enhance the damping effect under high-intensity excitations were proposed. A numerical simulation model of SAID attached to a frame structure was established to further explore the damping mechanism. The experimental and numerical results show that the SAID has better control effect than the traditional passive impact damper and can effectively broaden the damping frequency band. The parametric studies illustrate the mass ratio and impact damping ratio of SAID can significantly influence the vibration control effect by affecting the impact force.

Crack detection in concrete slabs by graph-based anomalies calculation

Yuqing Zhou,Weifang Sun,Jiawei Xiang,Binqiang Chen,Wei Feng 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.3

Concrete slab cracks monitoring of modern high-speed railway is important for safety and reliability of train operation, to prevent catastrophic failure, and to reduce maintenance costs. This paper proposes a curvature filtering improved crack detection method in concrete slabs of high-speed railway via graph-based anomalies calculation. Firstly, large curvature information contained in the images is extracted for the crack identification based on an improved curvature filtering method. Secondly, a graph-based model is developed for the image sub-blocks anomalies calculation where the baseline of the subblocks is acquired by crack-free samples. Once the anomaly is large than the acquired baseline, the sub-block is considered as crack-contained block. The experimental results indicate that the proposed method performs better than convolutional neural network method even under different curvature structures and illumination conditions. This work therefore provides a useful tool for concrete slabs crack detection and is broadly applicable to variety of infrastructure systems.

Size-Controlled Silver Nanoparticles Confined in Ordered Mesoporous Silica and Their Enhanced Catalytic Activities

Xiaofei Zhou,Jiawei Wan,Yefeng Liu,Di Liu,Hong Wang,Xiaoyong Lai,Yanzhao Zou,Guo Lin,Jian Chen 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.9

A cooperative assembly route has been developed, by which silver nanoparticles with controlled sizes are incorporated into the channels of ordered cubic mesoporous silica (KIT-6) with different pore sizes (4.3–6.4 nm). The samples were characterized by XRD, TEM, FT-IR, UV-Vis and N2 physisorption. The pore wall of mesoporous silica can efficiently confine the growth of silver nanoparticles within the channels and their average sizes decreased with the pore size reduction of KIT-6. Catalytic activities of the resultant Ag/KIT-6-x (x stands for hydrothermal temperature) composite for reducing harmful organic dye Rhodamine B (Rh B) by sodium borohydride (NaBH4) were investigated. All the Ag/KIT-6 composite samples show great catalytic activities, among which Ag/KIT-6-80 with higher loading and smaller size of Ag nanoparticles exhibits higher catalytic activity than those of Ag/KIT-6-60 and Ag/KIT-6-100.

Temperature field and demagnetization analysis of in‑wheel motors based on magneto‑thermal two‑way coupling

Xiuping Wang,Jiawei Zhang,Chunyu Qu,Chuqiao Zhou 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.2

Due to the narrow working space of an in-wheel motor, the heat generated by the motor loss is difficult to dissipate. This makes it easier for the in-wheel motor to demagnetize the permanent magnet due to the mega-temperature, which affects the output efficiency. To solve this problem, an external rotor hub motor is studied. First, in accordance with the theory of magnetic field modulation, the in-wheel motor to be studied is designed. By analyzing the electromagnetic characteristics of the motor, the correctness of the motor design is verified, and the losses of the motor under different working conditions are calculated. To acquire a more rigorous temperature increase record, the magnetic-thermal bidirectional coupling method is utilized to analyze the temperature field under different load conditions. The mechanism of the demagnetization of permanent magnets is analyzed, and demagnetization at different temperatures is obtained by magneto-thermal two-way coupling. Research shows that when the motor is overloaded for a long time, the temperature can reach a maximum of 220 °C. At this temperature, the permanent magnet undergoes irreversible demagnetization, which results in a 93.44% decrease in torque. Finally, temperature increase tests of a permanent magnet motor are carried out to verify the validity of the magneto-thermal two-way coupling analysis.

Microstructure and Magnetic Properties of Plasma-Sprayed Fe<SUB>73.5</SUB>Cu1Nb₃Si<SUB>13.5</SUB>B₉ Coatings

Xiaojun Ni,Xihui Bo,Jiawei Wu,Jinhua Guo,Zhichao Lu,Shaoxiong Zhou 한국자기학회 2010 한국자기학회 학술연구발표회 논문개요집 Vol.2010 No.12

Research on reliability of centrifugal compressor unit based on dynamic Bayesian network of fault tree mapping

Gao Yuan,Zhang Liang,Zhou Jiawei,Wei Bojia,Yan Zhongchao 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.5

For the first time, the fault tree mapping dynamic Bayesian network (DBN) method is applied to the reliability research study of centrifugal compressor units, and its usability and reliability are evaluated dynamically. First, the fault data using the K-means method eliminates abnormal data and builds a fault tree model. The structure is mapped to the DBN structure to complete the structure learning, and the logic gate is mapped to the conditional probability to achieve the parameter learning. Then the model is solved bidirectionally. The change rule of system node reliability with time is solved forward, and the posterior probability of the system node is solved reversely to complete fault diagnosis. Finally, Monte Carlo simulation analysis and the Markov process verify the dynamic reliability and steady-state availability. The results show that the Monte Carlo simulation method is almost consistent with the reliability prediction curve of the DBN model. Indicating that the accuracy of the DBN model is reliable and the computational efficiency is improved by about 81434 times. The steady-state availability calculated using the DBN model is approximately 0.99963, which is close to reality compared to the Markov process. This method can better describe centrifugal compressor units’ dynamic reliability and maintainability and provide decision support for regular maintenance of essential parts and enterprise procurement.

Structural Rationale for the Enhanced Catalysis of Nonenzymatic RNA Primer Extension by a Downstream Oligonucleotide

Zhang, Wen,Tam, Chun Pong,Zhou, Lijun,Oh, Seung Soo,Wang, Jiawei,Szostak, Jack W. American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.8

<P>Nonenzymatic RNA primer extension by activated mononucleotides has long served as a model for the study of prebiotic RNA copying. We have recently shown that the rate of primer extension is greatly enhanced by the formation of an imidazolium-bridged dinucleotide between the incoming monomer and a second, downstream activated monomer. However, the rate of primer extension is further enhanced if the downstream monomer is replaced by an activated oligonucleotide. Even an unactivated downstream oligonucleotide provides a modest enhancement in the rate of reaction of a primer with a single activated monomer. Here we study the mechanism of these effects through crystallographic studies of RNA complexes with the recently synthesized nonhydrolyzable substrate analog, guanosine 5′-(4-methylimidazolyl)-phosphonate (ICG). ICG mimics 2-methylimidazole activated guanosine-5′-phosphate (2-MeImpG), a commonly used substrate in nonenzymatic primer extension experiments. We present crystal structures of primer-template complexes with either one or two ICG residues bound downstream of a primer. In both cases, the aryl-phosphonate moiety of the ICG adjacent to the primer is disordered. To investigate the effect of a downstream oligonucleotide, we transcribed a short RNA oligonucleotide with either a 5′-ICG residue, a 5′-phosphate or a 5′-hydroxyl. We then determined crystal structures of primer-template complexes with a bound ICG monomer sandwiched between the primer and each of the three downstream oligonucleotides. Surprisingly, all three oligonucleotides rigidify the ICG monomer conformation and position it for attack by the primer 3′-hydroxyl. Furthermore, when GpppG, an analog of the imidazolium-bridged intermediate, is sandwiched between an upstream primer and a downstream helper oligonucleotide, or covalently linked to the 5′-end of the downstream oligonucleotide, the complex is better preorganized for primer extension than in the absence of a downstream oligonucleotide. Our results suggest that a downstream helper oligonucleotide contributes to the catalysis of primer extension by favoring a reactive conformation of the primer-template-intermediate complex.</P> [FIG OMISSION]</BR>

MSC p43 required for axonal development in motor neurons.

Zhu, Xiaodong,Liu, Yang,Yin, Yanqing,Shao, Aiyun,Zhang, Bo,Kim, Sunghoon,Zhou, Jiawei National Academy of Sciences 2009 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.106 No.37

<P>Neuron connectivity and correct neural function largely depend on axonal integrity. Neurofilaments (NFs) constitute the main cytoskeletal network maintaining the structural integrity of neurons and exhibit dynamic changes during axonal and dendritic growth. However, the mechanisms underlying axonal development and maintenance remain poorly understood. Here, we identify that multisynthetase complex p43 (MSC p43) is essential for NF assembly and axon maintenance. The MSC p43 protein was predominantly expressed in central neurons and interacted with NF light subunit in vivo. Mice lacking MSC p43 exhibited axon degeneration in motor neurons, defective neuromuscular junctions, muscular atrophy, and motor dysfunction. Furthermore, MSC p43 depletion in mice caused disorganization of the axonal NF network. Mechanistically, MSC p43 is required for maintaining normal phosphorylation levels of NFs. Thus, MSC p43 is indispensable in maintaining axonal integrity. Its dysfunction may underlie the NF disorganization and axon degeneration associated with motor neuron degenerative diseases.</P>