A new model for predicting surface mining subsidence: the improved lognormal function model

Weitao Yan,Junjie Chen,Yueguan Yan 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.1

Mining-induced problems in the coal field seriously threaten the normal operation of the mines and cause significant property losses and environmental disruption. Thus, high precision subsidence prediction is important on the processing of mining subsidence problems. In this paper, we analyzed the formation mechanism of skewed subsidence. The rock beam on the side of the gob and coal pillar presented different supporting reaction force, and the difference resulted in the asymmetric distribution of subsidence velocity, which further led to the formation of the surface skewed subsidence basin. The relationship between the wave curve and vibration curve was determined, and the skewed subsidence process of the surface point in the mining affected area was analyzed. The total duration of the initial and accelerated subsidence phases is smaller than that of the decelerated and end subsidence phases. Then, from the skewed subsidence characteristics, the skewed subsidence prediction model based on the lognormal function was built. An application example was selected to validate the feasibility and effectiveness of the proposed model. Results showed that the model has good prediction ability.

Comparison of Conventional DC-DC Converter and a Family of Diode-Assisted DC-DC Converter in Renewable Energy Applications

Yan Zhang,Jinjun Liu,Xiaolong Ma,Junjie Feng 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.2

In the conventional dc-dc converter, a pair of additional diode and the adjacent passive component capacitor/inductor can be added to the circuit with an X-shape connection, which generates a family of new topologies. The novel circuits, also called diode-assisted dc-dc converter, enhance the voltage boost/buck capability and have a great potential for high step-up/step-down power conversions. This paper mainly investigates and compares conventional dc-dc converter and diode-assisted dc-dc converter in wide range power conversion from the aspects of silicon devices, passive components requirements, electro-magnetic interference (EMI) and efficiency. Then, a comprehensive comparison example of a high step-up power conversion system was carried out. The two kinds of boost dc-dc converters operate under the same operation conditions. Mathematical analysis and experiment results verify that diode-assisted dc-dc converters are very promising for simultaneous high efficiency and high step-up/step-down power conversion in distributed power supply systems.

Comparison of Conventional DC-DC Converter and a Family of Diode-Assisted DC-DC Converter in Renewable Energy Applications

Zhang, Yan,Liu, Jinjun,Ma, Xiaolong,Feng, Junjie The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.2

In the conventional dc-dc converter, a pair of additional diode and the adjacent passive component capacitor/inductor can be added to the circuit with an X-shape connection, which generates a family of new topologies. The novel circuits, also called diode-assisted dc-dc converter, enhance the voltage boost/buck capability and have a great potential for high step-up/step-down power conversions. This paper mainly investigates and compares conventional dc-dc converter and diode-assisted dc-dc converter in wide range power conversion from the aspects of silicon devices, passive components requirements, electro-magnetic interference (EMI) and efficiency. Then, a comprehensive comparison example of a high step-up power conversion system was carried out. The two kinds of boost dc-dc converters operate under the same operation conditions. Mathematical analysis and experiment results verify that diode-assisted dc-dc converters are very promising for simultaneous high efficiency and high step-up/step-down power conversion in distributed power supply systems.

Surface crack and sand inrush disaster induced by high-strength mining: example from the Shendong coal field, China

Weitao Yan,Huayang Dai,Junjie Chen 한국지질과학협의회 2018 Geosciences Journal Vol.22 No.2

Sand inrush disaster and ground destruction induced by high-strength mining in the Shendong coal field seriously threaten the normal operation of the mine and cause significant property losses and environmental disruption. The physical simulation experiment demonstrate that the roof of high-strength mining working face can be regarded as a “step beam” structure and broken by sliding instability. The vertical damage state of overlying strata is summarized into three types: slightly, severely and very severely damage. On the basis of in situ data of the working face with the mining height greater than 3 m, the prediction formulas of the caved and fractured zone heights are given. The vertical damage types of working faces 22407 and 22402 are analyzed. Owing to the sliding instability of the roof and the thin bedrock, the surface stepped crack has become widely distributed above the highstrength mining working face. The sand inrush of working face 22402 can be interpreted by the very severely damaged of overburden and the thick aeolian sand aquifer. This work can be used to improve the understanding of mining-induced disaster and establish a disaster prediction model.

Comparison of leaf transcriptomes of cassava “Xinxuan 048” diploid and autotetraploid plants

Ling Yin,Junjie Qu,Huiwen Zhou,Xiaohong Shang,Hui Fang,Jiang Lu,Huabing Yan 한국유전학회 2018 Genes & Genomics Vol.40 No.9

Polyploidy breeding of cassava has been used to improve cassava traits over the past years. We previously reported in vitro induction of tetraploids in the cassava variety “Xinxuan 048” using colchicine. Significant differences in morphology and anatomy were found between the diploid and tetraploid plants. However, very little is known about the transcriptome difference between them. In this study, morphological and physiological characteristics including leaf thickness, plant height, internode length, chlorophyll content, and photosynthetic capacity were measured. Further, we investigated and validated the difference in gene expression patterns between cassava “Xinxuan 048” tetraploid genotype and its diploid plants using RNA sequencing (RNAseq) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Significant differences in morphology and physiology were observed during tetraploidization. A comparison revealed that tetraploidy induced very limited changes in the leaf transcriptomes of cassava “Xinxuan 048” diploid and autotetraploid plants. However, the differentially expressed genes (DEGs) between 2× and 4× plants, especially those upregulated in 4× plants, were strongly associated with hormonal and stress responses. Large changes in morphology and physiology between the diploid cassava “Xinxuan 048” and its autotetraploid were not associated with large changes in their leaf transcriptomes. Moreover, the differently expressed genes related to the regulation of gibberellin and brassinosteroids potentially explained why the plant height and internode length of 4× plants became shorter. Collectively, our results suggest that 4× cassava is potentially valuable for breeding strains with improved stress resistance.

Molecular dynamics simulation of tensile behavior of diffusion bonded Ni/Al nanowires

Zhenjiang Hu,Junjie Zhang,Yong Da Yan,Jiuchun Yan,Tao Sun,김동철,강성원 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.1

Interfaces play key roles in determining mechanical properties of materials. In current work we perform molecular dynamics simulations of diffusion bonding to evaluate the effect of temperature on the morphology of the Ni/Al interface and the strength of the diffusion bonded Ni/Al nanowires. The centro-symmetry parameter is adopted to identify defect atoms generated. Simulation results show that the thickness of the Ni/Al interface has strong dependence on the temperature of diffusion bonding. Following uniaxial tension tests indicate that the yield strength of Ni/Al nanowires is smaller than both the single crystalline Ni and Al nanowires, because of the Ni/Al interface acting as dislocation source and the mobilization of pre-existing dislocations at high temperature. It is shown that the mechanical properties of diffusion bonded Ni/Al nanowires strongly depend on the temperature.

An eight-degree-of-freedom upper extremity exoskeleton rehabilitation robot: design, optimization, and validation

Yuansheng Ning,Hongbo Wang,Junjie Tian,Hao Yan,Yu Tian,Congliang Yang,Jian Wei,Jianye Niu 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11

Upper extremity exoskeleton rehabilitation robots can be used for the training of patients with upper extremity motor dysfunction. In most cases, the design of such robots focuses on the configuration and the human-machine compatibility. For patients, the use of an exoskeleton rehabilitation robot mainly aims to improve their movement ability, which depends on the range of movement of the upper extremity joints. This paper proposes an eight-degreeof-freedom (DOF) upper extremity exoskeleton rehabilitation robot to improve the movement range of the patient’s upper extremity joints. The structural parameters of the shoulder joint are optimized and analyzed by the kinematic equations of the mechanism and the cyclic iteration algorithm such that the movement range of the patient joint can be maximized. The movement space of the robot is then simulated. Finally, the movement range of the rehabilitation robot joints and the movement space of the rehabilitation robot were measured. Experimental results show that the upper extremity exoskeleton rehabilitation robot can meet the patient’s shoulder, elbow, and wrist movement range, and the overlap with the human upper extremity movement space is 97.1 % and 95.7 % in the coronal and sagittal planes, respectively.

A Na-Rich Nanocomposite of Na1.83Ni0.12Mn0.88Fe (CN)6/RGO as Cathode for Superior Performance Sodium-Ion Batteries

Shimeng Yu,Danting Li,Yan Zhang,Hui Wang,Junjie Quan,Enze Xu,YANG JIANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.6

Prussian blue analogs are receiving intense attention due to their high theoretical energy density and low cost, but their real applications are still hampered by poor electronic conductivity and cycling stability. Here, Na1.83Ni0.12Mn0.88Fe(CN)6 wrapped with graphene was synthesized by a facile co-precipitation method. The existence of RGO not only significantly increases the conductivity of the cathode, but also makes the framework much more robust during long cycling process. As the cathode, the Na1.83Ni0.12Mn0.88Fe(CN)6/RGO is able to deliver a high initial discharge capacity of 120mAh g-1 at a current density of 20mA g-1 with superior capacity retention of 96.7% after 100 cycles. Even at a current density of 1000mA g-1, the cell still delivers a capacity of 86mAh g-1, indicating outstanding rate capability. The results and the facile synthesis method enable Na1.83Ni0.12Mn0.88Fe(CN)6/RGO to the competitive for a future energy storage system.

Experimental investigation on the propagation characteristics of pressure oscillation in direct contact condensation with low mass flux steam jet

Qiu, Binbin,Yang, Qingchuan,Yan, Junjie,li, Gen,Revankar, Shripad T. Elsevier 2017 Experimental thermal and fluid science Vol.88 No.-

<P><B>Abstract</B></P> <P>The propagation characteristics of pressure oscillation in direct contact condensation with low mass flux steam jet have been investigated experimentally. Steam is injected into subcooled water at one atmosphere pressure with steam mass flux and water temperature range of 186–272kg/(m<SUP>2</SUP> s) and 293–343K. The pressure oscillation propagates in the form of wave with stable dominant frequency, however the wave intensity attenuates with the increasing distance from the oscillation source. The root mean square of pressure wave <I>p</I> <SUB>rms</SUB> attenuates rapidly with the increasing dimensionless radial distance from the nozzle exit. At about dimensionless radial distance <I>R</I> =100, the <I>p</I> <SUB>rms</SUB> is attenuated by about 90%. Although the dominant frequency of the pressure oscillation is constant during the propagation, after <I>R</I> =100, there will be not enough energy for the pressure oscillation to resonate with relevant equipment. A correlation equation to calculate the root mean square of pressure oscillation along the radial distance is given. The prediction errors are within ±30% compared with the experimental data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The pressure oscillation propagates in the form of wave. </LI> <LI> In the propagation process, the frequency remains the same but the intensity attenuates. </LI> <LI> A correlation to calculate the <I>p</I> <SUB>rms</SUB> along the radial distance is given. </LI> <LI> At about R=100, the <I>p</I> <SUB>rms</SUB> is attenuated by about 90% and most of the energy is dissipated. </LI> </UL> </P>

Structure and Electrical Performance of Na₂C₆O₆ under High Pressure

Wang, Xuan,Zhang, Peijie,Tang, Xingyu,Guan, Junjie,Lin, Xiaohuan,Wang, Yajie,Dong, Xiao,Yue, Binbin,Yan, Jinyuan,Li, Kuo,Zheng, Haiyan,Mao, Ho-kwang American Chemical Society 2019 The Journal of Physical Chemistry Part C Vol. No.

<P>Sodium rhodizonate (Na<SUB>2</SUB>C<SUB>6</SUB>O<SUB>6</SUB>) has very high theoretical capacity as a positive electrode material of sodium-ion batteries, but it still has problems such as low actual capacity and poor electronic/ionic conductivity. In order to improve its conductivity, we investigated its structure and electrical properties under high pressure. By performing in situ X-ray diffraction, Raman, infrared absorption, and alternating current impedance spectroscopy in the range of 0-30 GPa at room temperature, we observed a phase transition at ∼11 GPa, with the conductivity increasing by an order of magnitude. Above ∼20 GPa, Na<SUB>2</SUB>C<SUB>6</SUB>O<SUB>6</SUB> gradually amorphized. During the decompression process, the pressure regulation of the structure and properties of the material are reversible. Our study shows that applying external pressure is an effective tool to improve the conductivity of molecular battery materials. The investigation will help to obtain next-generation electrode materials.</P> [FIG OMISSION]</BR>