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Liu, Zhiyuan,Wang, Jianhui,Zhang, Qinggen 서울대학교 교육연구소 2023 Asia Pacific Education Review Vol.24 No.1
This study provides empirical evidences on the differentiation of the academic community amid the latest classified reform of faculty evaluation, highlighted by up-or-out policy in the non-research university context in China. The systematic data analysis sketches out faculty’s segmentation and four characterizations including academic bureaucrats, academic elites, academic weight-bearers, and academic realists were taxonomized accordingly. By distinguishing the “powerful minority” and the “powerless majority” in the academic community, the paper indicated that there exist heterogeneous interpretations of faculty evaluation policies departure from faculty’s perception toward their academic identity and trajectory. The findings of this research contribute to extant studies and provide insights that social interactions take place not only between faculty policies and the academic community but also among heterogeneous academic professional groups, which can be profoundly utilized to enhance faculty’s sense making of evaluation policies and adopt more rational strategies. It also suggests that under the dual managerial structure of Chinese universities, the segmentation of the academic community may continue to be intensified along with the changing faculty evaluation policies.
ALMA Reveals Sequential High-mass Star Formation in the G9.62+0.19 Complex
Liu, Tie,Lacy, John,Li, Pak Shing,Wang, Ke,Qin, Sheng-Li,Zhang, Qizhou,Kim, Kee-Tae,Garay, Guido,Wu, Yuefang,Mardones, Diego,Zhu, Qingfeng,Tatematsu, Ken’ichi,Hirota, Tomoya,Ren, Zhiyuan,Liu, Sheng-Yu American Astronomical Society 2017 The Astrophysical journal Vol.849 No.1
<P>Stellar feedback from high-mass stars (e.g., H II regions) can strongly influence the surrounding interstellar medium and regulate star formation. Our new ALMA observations reveal sequential high-mass star formation taking place within one subvirial filamentary clump (the G9.62 clump) in the G9.62+0.19 complex. The 12 dense cores (MM1-MM12) detected by ALMA are at very different evolutionary stages, from the starless core phase to the UC H II region phase. Three dense cores (MM6, MM7/G, MM8/F) are associated with outflows. The mass-velocity diagrams of the outflows associated with MM7/G and MM8/F can be well-fit by broken power laws. The mass-velocity diagram of the SiO outflow associated with MM8/F breaks much earlier than other outflow tracers (e.g., CO, SO, CS, HCN), suggesting that SiO traces newly shocked gas, while the other molecular lines (e.g., CO, SO, CS, HCN) mainly trace the ambient gas continuously entrained by outflow jets. Five cores (MM1, MM3, MM5, MM9, MM10) are massive starless core candidates whose masses are estimated to be larger than 25 M-circle dot, assuming a dust temperature of <= 20 K. The shocks from the expanding H II regions ('B' and 'C') to the west may have a great impact on the G9.62 clump by compressing it into a filament and inducing core collapse successively, leading to sequential star formation. Our findings suggest that stellar feedback from H II regions may enhance the star formation efficiency and suppress low-mass star formation in adjacent pre-existing massive clumps.</P>
Zhiyuan Liu,Peng Wang,Ben Zhao 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.11
Flow instability attracts much attention for air compressors but little for a supercritical carbon dioxide (CO2) compressor that is a critical component in the supercritical CO2 Brayton cycle. This paper presents a numerical investigation of the rotating instability in a megawatt-scale (MWe-scale) supercritical CO2 centrifugal compressor from the Institute of Engineering Thermophysics. Unsteady full annulus simulations were carried out at different operating conditions and validated by the experimental data. According to the validated method, we analyzed the blade tip leakage flow, the rotating instability, and the propagation speed of the stalled flow cell. The findings are that (1) the blockage effects of leakage flow are responsible for rotating instability, and (2) the propagation speed of rotating cells is approximately 16.67% of the rotor speed. The novelty is that the figure is lower than that in air compressors, close to that found in water pumps.
A City-Level Boundary Nodes Identification Algorithm Based on Bidirectional Approaching
( Zhiyuan Tao ),( Fenlin Liu ),( Yan Liu ),( Xiangyang Luo ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.8
Existing city-level boundary nodes identification methods need to locate all IP addresses on the path to differentiate which IP is the boundary node. However, these methods are susceptible to time-delay, the accuracy of location information and other factors, and the resource consumption of locating all IPes is tremendous. To improve the recognition rate and reduce the locating cost, this paper proposes an algorithm for city-level boundary node identification based on bidirectional approaching. Different from the existing methods based on time-delay information and location results, the proposed algorithm uses topological analysis to construct a set of candidate boundary nodes and then identifies the boundary nodes. The proposed algorithm can identify the boundary of the target city network without high-precision location information and dramatically reduces resource consumption compared with the traditional algorithm. Meanwhile, it can label some errors in the existing IP address database. Based on 45,182,326 measurement results from Zhengzhou, Chengdu and Hangzhou in China and New York, Los Angeles and Dallas in the United States, the experimental results show that: The algorithm can accurately identify the city boundary nodes using only 20.33% location resources, and more than 80.29% of the boundary nodes can be mined with a precision of more than 70.73%.
Linya Liu,Zhiyuan Zuo,Qinyue Zhou,Jialiang Qin,Quanmin Liu 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.4
CA mortar layer disengagement will give rise to the overall structural changes of the track and variation in the vibration form of the ballastless track. By establishing a vehicle-track-viaduct coupling analysis and calculation model, it is possible to analyze the CRTS-I type track structure vibration response while the track slab is disengaging with the power flow evaluation method, to compare the two disengaging types, namely partial contact loss at one edge beneath track slab and partial contact loss at midpoint beneath track slab. It can also study how the length of disengaging influences the track structures vibration power. It is showed that when the partial contact loss beneath track slab, and the relative vibration energy level between the rail and the track slab increases significantly within [10, 200]Hz with the same disengaging length, the partial contact loss at one edge beneath track slab has more prominent influence on the vibration power than the partial contact loss at midpoint beneath track slab. With the increase of disengaging length, the relative vibration energy level of the track slab grows sharply, but it will change significantly when it reaches 1.56 m. Little effect will be caused by the relative vibration energy level of the viaduct. The partial contact loss beneath the track slab will cause more power distribution and transmission between the trail and track slab, and will then affect the service life of the rail and track slab.
Zhiyuan Yang,Junjie Wang,Lu Chen,Mengjun Liang,Yulin Xu,Chentao Zou,Xiaoxia Liu,Shuijin Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.5
In this work, we developed a simple hydrothermal method toward the fabrication of TiO2/ Bi3.64Mo0.36O6.55 heterostructure, which had superior photocatalytic performance for degrading of RhB under visible light irradiation. The as-prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM), UV-Vis diffuse reflectance spectroscopy (DRS) and photoelectrochemical measurements. The optimal composite with 15 wt.% TiO2/Bi3.64Mo0.36O6.55 (TBMO3) exhibits a much higher photocatalytic activity than that of Bi3.64Mo0.36O6.55 and P25 by degradation of RhB under visible light irradiation within 20 min. The enhanced performance of TBMO3 is predominantly attributed to the synergistic effect both in the higher surface area and the improved separation of photogenerated charge carriers between the two semiconductors. Recycling experiments indicated that TiO2/Bi3.64Mo0.36O6.55 photocatalysts had excellent cycle performance and stability. The photocatalytic mechanism of nanocomposite photocatalysts was proposed, which is confirmed by the active species trapping experiments and photoluminescence tests.
Yue Xue,Zhiyuan Zheng,Shuwei Shen,Guangli Liu,Ronald X. Xu 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.2
Electrospun nanofibrous mats (ENM) have been extensively used for removal of suspended particles, cells and bacteria in membrane filtration because of its high porosity and permeability. However, microfiltration process is driven by a certain transmembrane pressure, and the filtration performance of traditional ENM are thereby hindered by its limited mechanical property. In this study, we propose a new strategy that sandwich the ENM between two layers of electrospray-deposited microparticles to enhance the mechanical properties of ENM membrane. Through a suitable thermal treatment, the microparticles stick with each other forming firm networks, while the ENM is rarely influenced. The mechanical tests show that the tensile strength and elastic modulus of the sandwich-structure composite membrane are 5 times and 7 times higher than those of the fibrous membrane, respectively. Meanwhile, the filtration tests show that the rejection rate of the composite membrane is also higher than the fibrous membrane. Our study implies the composite membrane fabricated by layer-by-layer deposition via electrospray and electrospinning has a great potential in microfiltration applications.
Controller and Observer Design for a Class of Discrete-Time Nonlinear Switching Systems
Guowei Fan,Zhiyuan Liu,Hong Chen 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.6
The main contribution of this paper is to present some controller synthesis results for the discrete-time nonlinear (Lipschitz-like) switching systems. Under the assumption that the discrete state of switching systems is known, three related problems are considered, which are full-state feedback controller design, continuous state observer design, and observer-based output feedback controller design. The basic idea of the proposed approaches is to construct the different types of Hybrid Lyapunov function to guarantee the stability, and all of these methods are given in terms of linear matrix inequalities. The results obtained in this paper are only dependent on the Lipschitz-like constant matrices without regard to the specific nonlinear forms. Finally, a numerical example made up of two subsystems is given to show the applicability of theoretical results.