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Liming Song,Jun Li,Kesong Wen 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1
Aerodynamic performance of partial admission dual row control stage at the rated and off-designed operating conditions was numericallyinvestigated using three-dimensional Reynolds-averaged Navier-Stokes (RANS) and k -e turbulence model. The full scale computationalmodel includes the four nozzle boxes, full first and second row rotor blade, as well as two admission guided vanes with considerationof the rotor tip clearance and stator diaphragm gland. The numerical results of the mass flow rate, power output and aerodynamicefficiency of the dual row control stage at the rated and off-designed conditions are well in agreement with the experimental data. The obtained results at rated condition show that the blocking segmental arc of guided vane increased the exit pressure of the upstreamnozzle, which reduced the mass flow rate and changed the aerodynamic performance of the nozzle. The circumferential non-uniformityof aerodynamic parameters and partial admission losses increases with the decrease in the admission degree for the computed three operatingconditions. The analysis of axial steam velocity shows that the trailing shedding vortex and the complex flow vortex in flow passageshave a significant impact on the magnitude and direction of the axial steam velocity. Furthermore, the partial admission degreechanged the proportions of the power output of two rotor blade rows. The lower partial admission degree leads to a larger proportion ofthe power output of the first rotating blade row. The detailed flow pattern in the partial admissions dual row control stage at differentoperating conditions is also illustrated.
Response of coal rock apparent resistivity to hydraulic fracturing process
Song, Dazhao,Wang, Enyuan,Qiu, Liming,Jia, Haishan,Chen, Peng,Wei, Menghan Techno-Press 2018 Geomechanics & engineering Vol.14 No.6
In order to explore the comprehensive evaluation means of the extent of hydraulic fracturing region in coal seams, we analyzed the feasibility of detecting the response of coal rock direct current (DC) apparent resistivity to hydraulic-fracturing using Archie's theory, and conducted experimental researches on the response of DC resistivity in the hydraulic fracturing process using small-scale coal rock samples. The results show that porosity and water saturation are the two factors affecting the apparent resistivity of coal rock while hydraulic fracturing. Water has a dominant effect on the apparent resistivity of coal rock samples. The apparent resistivity in the area where water flows through is reduced more than 50%, which can be considered as a core affect region of hydraulic fracturing. Stress indirectly impacts the apparent resistivity by changing porosity. Before hydraulic fracturing, the greater axial load applied, the more serious the rupture in the samples, resulting in the greater apparent resistivity. Apparent resistivity testing is a potential regional method to evaluate the influence range of hydraulic fracturing in coal seams.
EMR: An effective method for monitoring and warning of rock burst hazard
Song, Dazhao,Wang, Enyuan,Li, Zhonghui,Qiu, Liming,Xu, Zhaoyong Techno-Press 2017 Geomechanics & engineering Vol.12 No.1
Rock burst may cause serious casualties and property losses, and how to conduct effective monitoring and warning is the key to avoid this disaster. In this paper, we reviewed both the rock burst mechanism and the principle of using electromagnetic radiation (EMR) from coal rock to monitor and forewarn rock burst, and systematically studied EMR monitored data of 4 rock bursts of Qianqiu Coal Mine, Yima Coal Group, Co. Ltd. Results show that (1) Before rock burst occurrence, there is a breeding process for stress accumulation and energy concentration inside the coal rock mass subject to external stresses, which causes it to crack, emitting a large amount of EMR; when the EMR level reaches a certain intensity, which reveals that deformation and fracture inside the coal rock mass have become serious, rock burst may occur anytime and it's necessary to implement an early warning. (2) Monitored EMR indicators such as its intensity and pulses amount are well and positively correlated before rock bursts occurs, generally showing a rising trend for more than 5 continuous days either slowly or dramatically, and the disaster bursts generally occurs at the lower level within 48 h after reaching its peak intensity. (3) The rank of EMR signals sensitive to rock burst in a descending order is maximum EMR intensity > rate of change in EMR intensity > maximum amount of EMR pulses > rate of change in the amount of EMR pulses.
Song Jinling,Huang Liming,Gao Yan,Liu Aiyong,Liu Haibin 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.5
To ameliorate the limitations of traditional collaborative filtering technologies and enhance the recommendation quality of agricultural science and technology information, a collaborative filtering recommendation method based on synthetic strategy is proposed. Firstly, filter the user set and user-item rating matrix according to the location of target user, which can solve the regional problem. Then, predict ratings of items according to the similarity of users or item content, which can relax the impact of the sparse rating. In addition, add the rating time to the user-item rating matrix to distinguish the timeliness of the user preference, and add user preference shifting in the similarity formula as a factor which can express the similarity of users or item content better. Our method can not only guarantee the recommended information is local and suit to current season of agricultural production, but also ensure the recommending precision under sparse rating data.
Conformational Transitions of Polymer Brushes for Reversibly Switching Graphene Transistors
Liu, Song,Jamali, Safa,Liu, Qingfeng,Maia, Joao,Baek, Jong-Beom,Jiang, Naisheng,Xu, Ming,Dai, Liming American Chemical Society 2016 Macromolecules Vol.49 No.19
<P>We developed a facile, but efficient, approach to graphene field-effect transistors (FET) functionalized with polymer brushes, in which the conductance can be reversibly switched by solvent-induced polymer conformational changes. Our experimental and stimulation results demonstrated that the solvent-induced conformational transition of the polymer brush could affect the carrier concentration by changing the number of,scattering sites associated with the graphene-polymer contact areas, leading to reversible electrical switching for the graphene FET device. Both end-adsorbed diblock and triblock copolymers showed similar switching effect through the solvent-induced chain stretching-collapse and tail-to-loop conformational changes, respectively. This work provides new platform technologies for developing novel electronic devices with tunable electrical properties and for studying macromolecular conformations and conformational transitions.</P>
Study on Asymptotic Stability of Fractional Singular Systems with Time Delay
Dazi Li,Liming Wei,Tianheng Song,Qibing Jin 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.4
The stability of fractional singular systems with time delay is discussed. Considering the singularity of the system, a system is decomposed into two subsystems. Through fractional Laplacian transformation and inverse Laplacian transformation on the subsystems, the expression of the state variables in time domain is obtained. According to the characteristics of Mittag-Leffler function, some inequalities that have important influence on stability are derived. Finally, a new sufficient condition is found to make the fractional singular systems with time delay asymptotically stable when the fractional order belongs to1 < α < 2. Meanwhile, the sufficient condition is also obtained to make the system stable under the nonlinear disturbance. All processes are proved and numerical examples are provided to show the validity and feasibility of the proposed method.
Zhao Shuang,Song Gang,Chen Jian,Yao Man,Liu Liming 한국물리학회 2022 Current Applied Physics Vol.33 No.-
The interface between Mg alloy and the intermetallic compounds (IMCs) is the weak point during the welding of Mg alloy and steel. The models of AlNi surface under different number of absorbed magnesium atoms were established. The absorption energy and electronic properties of the Nth (N represents the number of Mg atoms, which may be 1, 2, 3, and 4 in this paper) Mg atom on the AlNi surface were calculated using first-principles calculations. The results show that the previously absorbed Mg atoms will promote the absorption of the latter Mg atom when the distance between them is equal or less than 2.89 Å. The absorption energy of the Mg atoms on the AlNi surface is related to the electronic exchange between different atoms. The results will provide a new perspective for understanding the atomic scale mechanism of the bonding between the Mg atom and AlNi IMCs.