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Is p-Type Doping in SeO₂ Feasible?

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CHINESE PHYSICS LETTERS 2025年第2期42卷 72-77页

作者： Xiao, Zewen Huazhong univ Sci & Technol Wuhan Natl Lab Optoelect Wuhan 430074 Peoples R China

p-type transparent oxide semiconductors (TOSs) are significant in the semiconductor industry, driving advancements in optoelectronic technologies for transparent electronic devices with unique properties. The recent discovery of p-type behavior in SeO2 has stimulated interest and confusion in the scientific community. In this Letter, we employ density functional theory calculations to reveal the intrinsic intrinsic insulating characteristics of SeO2 and highlight the substantial challenges in carrier doping. Our electronic structure analyses indicate that the Se 5s2 states are energetically positioned too low to effectively interact with the O 2p orbitals, resulting in a valence band maximum (VBM) primarily dominated by the O 2p orbitals. The deep and localized nature of the VBM of SeO2 limits its potential as a high-mobility p-type TOS. Defect calculations demonstrate that all intrinsic defects in SeO2 exhibit deep transition levels within the bandgap. Regardless of the synthesis conditions, the Fermi level consistently resides in the mid-gap region. Furthermore, deep intrinsic acceptors and donors exhibit negative formation energies in the n-type and p-type regions, respectively, facilitating spontaneous formation and impeding external doping efforts. Thus, the reported p-type conductivity in SeO2 samples is unlikely to be intrinsic and is more plausibly attributable to reduced elemental Se, a well-known p-type semiconductor.

关键词： Semiconductor device manufacture

Comparing the Effectiveness of Coatings on Carbide andCermet Cutting Tool Inserts

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Journal of Materials Science & Technology 1995年第4期11卷 269-275页

作者： K.H. W.Seah M.Rahman and C.H.Lee (Dept. of Mech. & Prod. Eng., National university of singapore, 10 Kent Ridge Crescent, singapore 0511 T.N.Goh (Dept. of Ind. & Sys. Eng., National university of singapore, 10 Kent Ridge Crescent, singapore 0511) natl univ singapore DEPT IND & SYST ENGN SINGAPORE 0511 SINGAPORE

A series of metal cutting experiments was performed on a CNC lathe to evaluate the performance of various coatings on different tool substrates. The workpiece material was plain medium carbon steel and the cutting tool materials were carbide and cermet inserts coated with various single as well as multilayer coatings. Machining was done under various cutting conditions of speed and feed-rate, and for various durations of Cutting. The output parameters studied were the cutting forces (axial, radial and tangential), the surface roughness of the workpiece, as well as the tool wear (crater and flank wear). From these results, the performances of the various cutting inserts are evaluated and compared. Results show that cutting forces are significantly lower when using coated cermets than when using coated carbides although different coatings on the same substrate also result in different cutting forces. However, there is less difference in the surface roughness of the finished workpiece for the various coatings and substrates.

关键词： Tool Comparing the Effectiveness of Coatings on Carbide andCermet Cutting Tool Inserts

Insect seedling herbivory is influenced by multiple factors, but the plant apparency theory is more supported than other hypotheses - A case study in a subtropical forest

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FOREST ECOSYSTEMS 2025年第1期12卷 1-10页

作者： Yuan, Baozhu Wang, Bo Anhui univ Sch Resources & Environm Engn Hefei 230601 Peoples R China Anhui univ Anhui Prov Key Lab Wetland Ecosyst Protect & Resto Hefei 230601 Peoples R China Anhui Shengjin Lake Wetland Ecol natl Long term Sc Dongzhi 247230 Peoples R China

Insect herbivory is ubiquitous in various ecosystems, and directly influences the growth and survival of individual plants, especially during their vulnerable early life stages like the seedling phase. This, in turn, exerts a significant influence on forest community diversity and structure, as well as ecosystem function and stability. Notable variation in herbivory has been detected both among and within plant species. For decades, many hypotheses have been proposed to explain such variations, including both biotic and abiotic variables. However, most studies have considered only one or several of these hypotheses by focusing on a few potential variables, and their results were usually inconsistent;thus, the factors driving herbivory remain unclear. In this study, we examined leaf herbivory by insects of woody species seedlings in a subtropical forest in southwestern China over two seasons. In total, 24 potential variables that represented abiotic resource availability, characters of individual seedlings, conspecific and heterospecific species, and the whole seedling community were selected to test several commonly discussed alternative herbivory hypotheses. Overall, our findings showed that the plant apparency hypothesis was more supported than the other hypotheses in explaining insect seedling herbivory. Our results further indicated that the mechanisms and causes of insect herbivory are complex, multifactorial, species-specific and vary with seasons, indicating that there may be no uniform rules in explaining herbivory for all seedlings. Consequently, such complexity may play an important role in promoting species coexistence and biodiversity maintenance in seedling communities, which may further translate into the following generation of saplings or even adult communities. Changes in the community of insect herbivores and/or variables influencing insect herbivory, may disrupt stability of the original seedling community, thus affecting the regeneration and deve

关键词： Canopy openness Leaf size Plant animal interaction Plant apparency theory Seedling height Species richness

CONVERGENCE OF CASCADE ALGORITHMS AND SMOOTHNESS OF REFINABLE DISTRIBUTIONS

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Chinese Annals of Mathematics,Series B 2003年第3期24卷 367-386页

作者： SUN QIYU Department of Mathematics, university of Houston, Houston, TX 77204, USA. Department of Mathematics, National university of singapore, 10 Kent Ridge Crescent, 119260, singapore. univ Houston Dept Math Houston TX 77204 USA natl univ singapore Dept Math Singapore 119260 Singapore

In this paper, the author at first develops a method to study convergence of the cascadealgorithm in a Banach space without stable assumption on the initial (see Theorem 2.1), andthen applies the previous result on the convergence to characterizing compactly supportedrefinable distributions in fractional Sobolev spaces and Holder continuous spaces (see Theorems3.1, 3.3, and 3.4). Finally the author applies the above characterization to choosing appropriateinitial to guarantee the convergence of the cascade algorithm (see Theorem 4.2).

关键词： Cascade algorithm Cascade operator Refinable distribution Shift-invariant space Linear independent shifts Stable shifts Fractional Sobolev space

Quercus acutissima exhibits more adaptable water uptake patterns in response to seasonal changes compared to Pinus massoniana

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FOREST ECOSYSTEMS 2025年第1期12卷 29-37页

作者： Zhang, Suimeng Wang, Xiaodi Huang, Zhaowang Bao, Yitao Jiang, Jiang Liu, Ziqiang China Inst Water Resources & Hydropower Res Yinshanbeilu Grassland Ecohydrol Natl Observat & R Beijing 100038 Peoples R China Nanjing Forestry univ Co Innovat Ctr Sustainable Forestry Southern China Nanjing 210037 Peoples R China

Background: Seasonal precipitation variability significantly affects water use in forests;however, whether water uptake is adapted to changes in precipitation, particularly whether it could affect the coexistence of tree species, has rarely been quantified in forest systems. Method: In this study, dual stable isotopes and the Li-6400 portable photosynthesis system were used to determine the water sources of a mixed conifer ( Pinus massoniana) ) and broadleaf ( Quercus acutissima) ) forest and changes in hydraulic characteristics during the dry and wet seasons in a southern hilly region of China. Results: Although the hydraulic characteristics of P . massoniana were lower than those of Q . acutissima, , it maintained a stable water source from the deep soil layer and a higher stomatal conductance (Gs), leading to a higher transpiration rate (Tr) during the growing seasons. Q. acutissima mainly absorbed water from deeper soil layers in the dry season and took up from shallow soil layers in the wet season. Its Gs values exhibited sensitivity to precipitation, while it maintained a lower Tr value during the growing seasons. The excessive water-use strategy observed in P. massoniana may confer weak drought-tolerance during higher frequency and more intense extreme precipitation events, whereas Q. acutissima may exhibit better ecological adaption to precipitation changes. Conclusions: The overlap of water niches in mixed forests did not appear to affect the coexistence of tree species. The present study provides insights into reforestation and water management in the southern hilly regions of China.

关键词： Water use Transpiration Stable isotope Hydraulic characteristics

WAVE EQUATION MODEL FOR SHIP WAVES IN BOUNDED SHALLOW WATER

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Journal of Hydrodynamics 2000年第4期12卷 109-119页

作者： T.S.Lee Mechanical & Production Engineering Department, National university of singapore, singapore 119620 Wu Jian kang, Xiong Chuan guang Mechanics Department of Huazhong university of Science & Technology, Wuhan 430074, P.R.China C.Shu Mechani Mech. and Production Eng. Dep. Natl. Univ. of Singapore Singapore 119620 Singapore

Ships were modelled as moving pressure disturbances on the free surface of a shallow water basin in the present paper. The moving pressure generating waves were subjected to the reflection of land boundaries and the radiation of open boundaries. This paper proposed and examined a wave equation model (WEM) to solve the shallow water equations with moving surface pressures simulating ship waves in a bounded shallow water region. The Galerkin finite element method was used to solve a second order wave equation for the free surface elevations and the hydrodynamic pressure of the ship bottom simultaneously. Horizontal velocities were obtained from the momentum equations. Numerical solutions of Series 60 C B=0.6 ships moving with the depth Froude number of F h= 0.6, 1.0, 1.3 in a rectangular shallow water harbor were investigated. Three dimensional surface elevation profiles and the depth averaged horizontal velocities were analysed. The numerical results characterised very well the ship waves in shallow water. Strong boundary reflection waves were found in the case of high depth Froude number (F h=1.3). Waves generated by the interactions of two ships moving in the same directions and in the opposite directions were also numerically investigated in the present study.

关键词： ship waves shallow water equations FEH

ELASTICITY EFFECTS ON THE WATER IMPACT OF AN ELASTIC FLAT-BOTTOM BOX

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Journal of Hydrodynamics 2002年第2期14卷 64-70页

作者： Li, Wan-Ping Liu, Gui-Rong Chan, Eng-Song Huazhong univ. of Sci. and Technol. Wuhan 430074 China natl. univ. of singapore Singapore 119260 Singapore

To elucidate the effects of elasticity the hydrodynamic impact of a 2-D flat-bottom shell box onto a water surface was investigated in detail using the finite element code Dytran. An ALE coupling algorithm was employed to handle the interactions between the box and the fluids. In this study, both air and water were treated as compressible fluids and their properties were modeled through the equation of states. Calculated results show that the air cushion plays a very important role buffering the impinging. Under the deformed concave bottom an air cushion layer will be easier to form up. For high impact speed, the pressure for the elastic box is much lower than that for the rigid box. Excited by the impact, the impinging box oscillates with about its natural frequency.

关键词： Air cushioning Compressible flow Elasticity Finite element method Impact testing Water

NUMERICAL SOLUTIONS OF INCOMPRESSIBLE EULER AND NAVIER-STOKES EQUATIONS BY EFFICIENT DISCRETE SINGULAR CONVOLUTION METHOD

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Acta Mechanica Sinica 2000年第3期16卷 223-239页

作者： D.C.Wan G.W.Wei Shanghai univ Shanghai Inst Appl Math&MechShanghai 200072Peoples R China natl univ singapore Dept Computat SciSingapore 119260Singapore

An efficient discrete singular convolution (DSC) method is introduced to the numerical solutions of incompressible Euler and Navier-Stokes equations with periodic boundary conditions. Two numerical tests of two-dimensional Navier-Stokes equations with periodic boundary conditions and Euler equations for doubly periodic shear layer flows are carried out by using the DSC method for spatial derivatives and fourth-order Runge-Kutta method for time advancement, respectively. The computational results show that the DSC method is efficient and robust for solving tho problems of incompressible flows, and has the potential of being extended to numerically solve much broader problems in fluid dynamics.

关键词： incompressible flows periodic boundary DSC method fourth-order Runge-Kutta method

In honor of the 65th birthday of Professor Zhidong Bai

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Science China Mathematics 2009年第6期52卷 1233-1234页

作者： HU FeiFang & CHEN ZeHua univ Virginia Charlottesville VA 22903 USA natl univ singapore Singapore Singapore

We are thankful to Science in China Series A: Mathematics for the publication of this special issue in honor of Professor Zhidong Bai of his 65th birthday. Professor Bai is a leading statis-

关键词： Zhang