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Search Results: 1 - 10 of 136079 matches for " Wei-Min Liu "
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Examining the Types of Mathematical Tasks Used to Explore the Mathematics Instruction by Elementary School Teachers  [PDF]
Wei-Min Hsu
Creative Education (CE) , 2013, DOI: 10.4236/ce.2013.46056

This study examined the different types of mathematical tasks used in the classroom to explore the nature of mathematics instruction of three sixth grade teachers in an elementary school. Case studies, instructional observations, and classroom artifacts were used to collect data. The results showed that the three teachers used different types of mathematical tasks and implementation methods. One teacher focused on high cognitive demand tasks, most of which involved substantial group discussion and students working cooperatively. Even though the other two also used many high cognitive demand tasks, these were mainly presented via teacher-student dialogue. By examining the types of mathematical tasks and their implementation, it was found that the group discussion tasks were generally all high cognitive demand tasks, in which the students fully explained the solution process. As for the tasks administered through teacher-student dialogue, due to the usage of large amounts of closed-ended dialogue, the students used low cognition to solve the mathematical tasks and did not have the opportunity to completely explain their thinking about the solutions. Thus, in order to fully understand the nature of mathematics instruction by teachers, there should be simultaneous consideration of the types of mathematical tasks used as well as how the tasks were implemented.

Research on the Performance of Sm0.2Ce0.8O1.9 (SDC) Prepared by Different Methods
DING Jiao,LIU Jiang,GUO Wei-Min
无机材料学报 , 2009, DOI: 10.3724/sp.j.1077.2009.00152
Abstract: Sm-doped CeO2-Sm0.2Ce0.8aaO1.9 (SDC) electrolyte powders were prepared by using glycine-nitrate process, solid-state process and citric-nitrate process, respectively. These three kinds of SDC powders were deposited onto the NiO-SDC anode substrates by colloidal spray coating technique. The single cell was completed after screen printing the BSCF cathode on the SDC electrolyte film. The performance of the single cell was tested by the CHI604B electrochemical work station. The granularity distribution of the SDC powders was analyzed by the HORIBA LA-920 and the microstructure of the cell was investigated by SEM. Results show that SDC electrolyte powders made by citric-nitrate process is content with the colloidal spray coating technique for SOFCS.
On the progenitors of millisecond pulsars by the recycling evolutionary channel
Wei-Min Liu,Wen-Cong Chen
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.19202.x
Abstract: The recycling model suggested that low-mass X-ray binaries (LMXBs) could evolve into binary millisecond pulsars (BMSPs). In this work, we attempt to investigate the progenitor properties of BMSPs formed by the recycling evolutionary channel, and if sub-millisecond pulsars can be produced by this channel. Using Eggleton's stellar evolution code, considering that the dead pulsars can be spun up to a short spin period by the accreting material and angular momentum from the donor star, we have calculated the evolution of close binaries consisting of a neutron star and a low-mass main-sequence donor star, and the spin evolution of NSs. In calculation, some physical process such as the thermal and viscous instability of a accretion disk, propeller effect, and magnetic braking are included. Our calculated results indicate that, all LMXBs with a low-mass donor star of 1.0 - 2.0 $M_\odot$ and a short orbital period ($\la 3-4 \rm d$) can form millisecond pulsars with a spin period less than 10 ms. However, it is difficult to produce sub-millisecond pulsars by this evolutionary channel. In addition, our evolutionary scenario cannot account for the existence of BMSPs with a long orbital period ($P_{\rm orb}\ga 70-80\rm d$).
Vertical convection in neutrino-dominated accretion flows
Tong Liu,Wei-Min Gu,Norita Kawanaka,Ang Li
Physics , 2015, DOI: 10.1088/0004-637X/805/1/37
Abstract: We present the effects of the vertical convection on the structure and luminosity of the neutrino-dominated accretion flow (NDAF) around a stellar-mass black hole in spherical coordinates. We found that the convective energy transfer can suppress the radial advection in the NDAF, and that the density, temperature and opening angle are slightly changed. As a result, the neutrino luminosity and annihilation luminosity are increased, which is conducive to achieve the energy requirement of gamma-ray bursts.
Magnetic braking of Ap/Bp stars: an alternative formation mechanism of compact intermediate-mass binary pulsars
Wei-Min Liu,Wen-Cong Chen
Physics , 2014, DOI: 10.1093/mnras/stu823
Abstract: It is difficult for the intermediate-mass X-ray binaries (IMXBs) evolutionary channel to form intermediate-mass binary pulsars (IMBPs) with a short orbital period (less than 3 d) via stable mass transfer. The main reason is that the magnetic braking mechanisms are generally thought not to work for donor stars with a mass of greater than 1.5 $\rm M_{\odot}$ in the canonical model. However, some intermediate-mass stars have anomalously strong magnetic fields (about 100 -- 10000 G), i. e. so-called Ap or Bp stars. With the coupling between the magnetic field and the irradiation-driven wind from the surface of Ap/Bp stars, a plausible magnetic braking mechanism should be expected. In this work, we attempt to investigate if IMXBs with Ap/Bp stars can produce IMBPs with a short orbital period (less than 3 d) by such an anomalous magnetic braking mechanism. Using a stellar evolution code, we have simulated the evolution of a large number of IMXBs consisting of a NS and an Ap/Bp star. For the spin evolution of the NS, we consider the accretion torque, the propeller torque, and the spin-down torque caused by the interaction between the magnetic field and the accretion disc. The calculated results show that, employing anomalous magnetic braking of Ap/Bp stars, IMXBs can evolve into compact IMBPs with short orbital periods of less than 3 d. However, there exists significant discrepancy between the spin periods of IMBPs in our simulated results and those observed.
Evolution of neutron star + He star binaries: an alternative evolutionary channel to intermediate-mass binary pulsars
Wen-Cong Chen,Wei-Min Liu
Physics , 2013, DOI: 10.1093/mnrasl/slt043
Abstract: It is difficult for intermediate-mass X-ray binaries to form compact intermediate-mass binary pulsars (IMBPs) with a short orbital-period ($\la 3 \rm d$), which have a heavy ($\ga 0.4 M_{\odot}$) CO or ONeMg white dwarf companions. Since neutron star + He star binaries may experience common-envelope evolution, they have some advantage to account for the formation of short orbital-period IMBPs. In this work, we explore the probability of IMBPs formed by this evolutionary channel. Using Eggleton's stellar evolution code, considering that the dead pulsars were spun up by the accreting material and angular momentum from the He star companions, we have calculated the evolution of a large number of neutron star + He star binaries. Our simulated results indicate that, the NS + He star evolutionary channel can produce IMBPs with a WD of $\sim0.5 - 1.1 M_{\odot}$ and an orbital period of $0.03 - 20$ d, in which pulsars have a spin-period of $1.4 - 200$ ms. Comparing the calculated results with the observational parameters (spin period and orbital period) of 9 compact IMBPs, the NS + He star evolutionary channel can account for the formation of 4 sources. Therefore, NS + He star binaries offer an alternative evolutionary channel to compact IMBPs.
Generalized Likelihood Ratio Tests for Varying-Coefficient Models with Censored Data  [PDF]
Rong Jiang, Wei-Min Qian
Open Journal of Statistics (OJS) , 2011, DOI: 10.4236/ojs.2011.11003
Abstract: In this paper, we extend the generalized likelihood ratio test to the varying-coefficient models with censored data. We investigate the asymptotic behavior of the proposed test and demonstrate that its limiting null distribution follows a distribution, with the scale constant and the number of degree of freedom being independent of nuisance parameters or functions, which is called the wilks phenomenon. Both simulated and real data examples are given to illustrate the performance of the testing approach.
Zhi-jian Wang,Wei-min Jia,Qing-lei Liu,Wei Wang
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811025803
Abstract: In the title molecule, C19H19ClN4OS, the 1,2,4-triazole ring forms dihedral angles of 86.0 (2) and 65.6 (2)° with the phenyl and chlorophenyl rings, respectively. In the crystal, intermolecular N—H...S and N—H...O hydrogen bonds link molecules into centrosymmetric dimers, which are further linked into chains in [001] via weak C—H...π interactions.
General analytical solution to exact fermion master equation
Matisse Wei-Yuan Tu,Jian-Heng Liu,Wei-Min Zhang
Physics , 2015,
Abstract: The exact fermion master equation previously obtained in [Phys. Rev. B \textbf{78}, 235311 (2008); New J. Phys. \textbf{12}, 083013 (2010)] describes the dynamics of quantum states of a principal system of fermionic particles under the influences of external fermion reservoirs (e.g. nanoelectronic systems). Here, we present the general solution to this exact fermion master equation. The solution is analytically expressed in the most intuitive particle number representation. It is applicable to an arbitrary number of orbitals in the principal system prepared at arbitrary initial states. We demonstrate the usefulness of such general solution with the transient dynamics of nanostructured artificial molecules. We show how various initial states can lead to distinct transient dynamics, manifesting a multitude of underlying transition pathways.
Field Surveys of Non-Residential Solar Water Heating Systems in Taiwan
Wei-Min Lin,Keh-Chin Chang,Yi-Mei Liu,Kung-Ming Chung
Energies , 2012, DOI: 10.3390/en5020258
Abstract: To develop indigenous alternative and renewable energy resources, long-term subsidy programs (1986–1991 and 2000–present) for solar water heaters have been enforced in Taiwan. By the end of 2010, the total installed area of solar collectors had exceeded 2 million square meters. However, over 98% of solar water heaters were used in residential systems for hot water production, with the areas of installed solar collector being less than 10 square meters. There were only 98 systems with area of solar collectors installed exceeding 100 square meters put into operation from 2001 to 2010. These systems were mainly installed for water heating in dormitories, swimming pools, restaurants, and manufacturing plants. In the present study, a comprehensive survey of these large-scale solar water heaters was conducted. The objectives of the survey were to assess the system performance and to collect feedback from individual users. It is found that lack of experience in system design and maintenance are the key factors affecting reliable operation of a system. Hourly, daily and long-term field measurements of a dormitory system were also examined to evaluate its thermal efficiencies. Results indicated that thermal efficiency of the system is associated with the daily solar radiation. Hot water use pattern and operation of auxiliary heater should be taken into account in system design.
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