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404 results on '"Yang, Z.J."'

101. Polarization modification in InGaN/GaN multiple quantum wells by symmetrical thin low temperature-GaN layers

Author

Tao, Y.B., Chen, Z.Z., Zhang, F.F., Jia, C.Y., Qi, S.L., Yu, T.J., Kang, X.N., Yang, Z.J., You, L.P., Yu, D.P., and Zhang, G.Y.

Subjects
Gallium -- Electric properties, Gallium -- Optical properties, Indium -- Electric properties, Indium -- Optical properties, Light-emitting diodes -- Electric properties, Polarization (Electricity) -- Analysis, Quantum wells -- Electric properties, Quantum wells -- Optical properties, Quantum wells -- Composition, Physics
Abstract

Metal-organic vapor phase epitaxy is used for growing light emitting diodes (LEDs) by using InGaN/GaN quantum wells (QWs) with thin low temperature GaN (LT-GaN) layers bounding each InGaN layer. The better performance of LEDs incorporating the LT-GaN layers is because of the suppressed polarization from piezoelectric fields.

Published
2010

102. Strain effects on [In.sub.x][Al.sub.1-x]N crystalline quality grown on GaN templates by metalorganic chemical vapor deposition

Author

Miao, Z.L., Yu, T.J., Xu, F.J., Song, J., Lu, L., Huang, C.C., Yang, Z.J., Wang, X.Q., Zhang, G.Y., Zhang, X.P., Yu, D.P., and Shen, B.

Subjects
Gallium nitrate -- Electric properties, Gallium nitrate -- Chemical properties, Gallium nitrate -- Structure, Chemical vapor deposition -- Usage, Thermal diffusivity -- Analysis, Physics
Abstract

The transmission electron microscopy technique is employed to explain the microstructures of the various [In.sub.x][Al.sub.1-x]N epilayers that are grown on the GaN templates by the metalorganic chemical vapor deposition technique. The various effects of different strains on the structures and properties of these compounds are also analyzed.

Published
2010

103. Different origins of the yellow luminescence in as-grown high-resistance GaN and unintentional-doped GaN films

Author

Xu, F.J., Shen, B., Lu, L., Miao, Z.L., Song, J., Yang, Z.J., Zhang, G.Y., Hao, X.P., Wang, B.Y., Shen, X.Q., and Okumura, H.

Subjects
Chemical vapor deposition -- Usage, Gallium compounds -- Electric properties, Gallium compounds -- Mechanical properties, Gallium compounds -- Optical properties, Luminescence -- Analysis, Semiconductor doping -- Analysis, Positrons -- Emission, Positrons -- Analysis, Physics
Abstract

Photoluminescence and monoenergetic positron annihilation spectroscopy are used for examining the yellow luminescence (YL) in as-grown high-resistance (HR) and unintentional-doped (UID) GaN films grown by metal organic chemical vapor deposition. The studies have shown that the increased wave function overlap of electrons and holes induced by the strong space localization effect of holes deduced from the short positron diffusion length is the vital factor to increase the YL efficiency in HR-GaN.

Published
2010

104. Structural, optical, and magnetic properties of Cu-implanted GaN films

Author

Yang, X.L., Chen, Z.T., Wang, C.D., Zhang, Y., Pei, X.D., Yang, Z.J., Zhang, G.Y., Ding, Z.B., Wang, K., and Yao, S.D.

Subjects
Copper -- Magnetic properties, Copper -- Optical properties, Gallium compounds -- Optical properties, Gallium compounds -- Magnetic properties, Magnetization -- Analysis, Spin coupling -- Analysis, Physics
Abstract

The structural, optical, and magnetic properties of Cu-implanted GaN films are examined. The results have shown that the vacancylike defects are considered for understanding the magnetic properties of the Cu-implanted GaN films.

Published
2009

105. Microstructure and origin of dislocation etch pits in GaN epilayers grown by metal organic chemical vapor deposition

Author

Lu, L., Gao, Z.Y., Shen, B., Xu, F.J., Huang, S., Miao, Z.L., Hao, Y., Yang, Z.J., Zhang, G.Y., Zhang, X.P., Xu, J., and Yu, D.P.

Subjects
Chemical vapor deposition -- Usage, Etching -- Usage, Gallium -- Electric properties, Gallium -- Structure, Physics
Abstract

A combination of spectroscopic and microscopic studies is conducted to examine the morphology and microstructure of dislocation etch pits in GaN epilayers etched by molten KOH. The results revealed that the chemical stabilization of Ga-polar surface plays a significant role in the formation of various types of dislocation etch pits.

Published
2008

107. Morphology and microstructure evolution of [Al.sub.x][Ga.sub.1-x]N epilayers grown on GaN/sapphire templates with AlN interlayers observed by transmission electron microscopy

Author

Lu, L., Shen, B., Xu, F.J., Gao, B., Huang, S., Miao, Z.L., Qin, Z.X., Yang, Z.J., Zhang, G.Y., Zhang, X.P., Xu, J., and Yu, D.P.

Subjects
Aluminum compounds -- Structure, Aluminum compounds -- Chemical properties, Gallium nitrate -- Structure, Gallium nitrate -- Chemical properties, Transmission electron microscopes -- Analysis, Physics
Abstract

The morphology and microstructure evolution of [Al.sub.0.3][Ga.sub.0.7]N epilayers grown on GaN/sapphire templates with low-temperature (LT) AlN interlayers (IL) by using metal organic chemical vapor deposition are examined by transmission electron microscopy and atomic force microscopy. The strain in [Al.sub.x][Ga.sub.1-x]N epilayers is modified by inserting the AlN IL because of the lattice mismatch between AlN, GaN, and [Al.sub.x][Ga.sub.1-x]N, which has further changed the formation of the edge-type threading dislocations.

Published
2008

113. The behavior of runaway current in massive gas injection fast shutdown plasmas in J-TEXT

Author

Chen, Z.Y., primary, Huang, D.W., additional, Luo, Y.H., additional, Tang, Y., additional, Dong, Y.B., additional, Zeng, L., additional, Tong, R.H., additional, Wang, S.Y., additional, Wei, Y.N., additional, Wang, X.H., additional, Jian, X., additional, Li, J.C., additional, Zhang, X.Q., additional, Rao, B., additional, Yan, W., additional, Ma, T.K., additional, Hu, Q.M., additional, Yang, Z.J., additional, Gao, L., additional, Ding, Y.H., additional, Wang, Z.J., additional, Zhang, M., additional, Zhuang, G., additional, Pan, Y., additional, and Jiang, Z.H., additional

Published
2016
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114. Enhancement of runaway production by resonant magnetic perturbation on J-TEXT

Author

Chen, Z.Y., primary, Huang, D.W., additional, Izzo, V.A., additional, Tong, R.H., additional, Jiang, Z.H., additional, Hu, Q.M., additional, Wei, Y.N., additional, Yan, W., additional, Rao, B., additional, Wang, S.Y., additional, Ma, T.K., additional, Li, S.C., additional, Yang, Z.J., additional, Ding, D.H., additional, Wang, Z.J., additional, Zhang, M., additional, Zhuang, G., additional, and Pan, Y., additional

Published
2016
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120. CHARACTERISATION OF 3D FRACTURE EVOLUTION IN CONCRETE USING IN-SITU X-RAY COMPUTED TOMOGRAPHY TESTING AND DIGITAL VOLUME CORRELATION

Author

Yang, Z.J., Ren W.Y., Mostafavi, M., McDonald, S.A., and Marrow, T.J.

Subjects
In-situ X-ray computed tomography, Concrete in compression, Three-dimensional fracture visualisation, Fracture process zone, Segmentation, Digital volume correlation
Abstract

X-ray Computed Tomography (XCT) is a powerful technology that can accurately image the internal structures of composite and heterogeneous materials in three-dimensions (3D). In this study, in-situ micro XCT tests of concrete specimens under progressive compressive loading are carried out. The aim of the observations is to gain a better understanding of 3D fracture and failure mechanisms at the meso-scale. To characterise the fracture evolution as the deformation increases, two methods are used. The first segments the reconstructed absorption contrast XCT images using AVIZO software into different phases, namely, aggregates, mortar, cracks and voids. The second uses the digital volume correlation (DVC) technique to map the relative deformations between consecutive XCT images with high precision; bulk mechanical properties can be measured and cracks visualised via their opening displacement. The 3D crack profiles obtained by these two methods are compared, and the contributions that they can make to image-based modelling and its validation are noted.

Published
2013

122. Elastic and electronic properties of fluorite RuO₂ from first principle

Author

Yang, Z.J., Guo, A.M., Guo, Y.D., Li, J., Wang, Z., Liu, Q., Linghu, R.F., and Yang, X.D.

Abstract

The elastic, thermodynamic, and electronic properties of fluorite RuO₂ under high pressure are investigated by plane-wave pseudopotential density functional theory. The optimized lattice parameters, elastic constants, bulk modulus, and shear modulus are consistent with other theoretical values. The phase transition from modified fluorite-type to fluorite is 88 GPa (by localized density approximation, LDA) or 115.5 GPa (by generalized gradient approximation, GGA). The Young's modulus and Lamé's coefficients are also studied under high pressure. The structure turned out to be stable for the pressure up to 120 GPa by calculating elastic constants. In addition, the thermodynamic properties, including the Debye temperature, heat capacity, thermal expansion coefficient, Grüneisen parameter, and Poisson's ratio, are investigated. A small band gap is found in the electronic structure of fluorite RuO₂ and the bandwidth increases with the pressure. Also, the present mechanical and electronic properties demonstrate that the bonding nature is a combination of covalent, ionic, and metallic contributions. Пружнi, термодинамiчнi та електричнi властивостi флюориту RuO₂ при високому тиску дослiджуються за допомогою теорiї функцiоналу густини з плоскохвильовим псевдопотенцiалом. Оптимiзованi параметри гратки, пружнi сталi, об’ємний модуль i модуль зсуву узгоджуються з iншими теоретичними значеннями. Фазовий перехiд з модифiкованого флюориту до флюориту є при 88 GPa (наближення локальної густини, LDA), чи при 115.5 GPa (узагальнене градiєнтне наближення, GGA). Також дослiджено модуль Юнга i коефiцiєнти Ламе при високих тисках. Структура є стабiльною для тискiв до 120 GPa, якщо обчислювати пружнi сталi. Крiм того, дослiджено термодинамiчнi властивостi, включаючи температуру Дебая, теплоємнiсть, коефiцiєнт теплового розширення, параметр Грюнайзена i коефiцiєнт Пуассона. В електроннiй структурi флюориту RuO₂ знайдено малу зонну щiлину i ширина зони зростає iз тиском. Також, представленi механiчнi та електроннi властивостi демонструють, що природа зв’язування є комбiнацiєю ковалентного, iонного i металiчного вкладiв.

Published
2012

127. A sensitivity study of the human crystalline lens using finite element analysis

Author

Yang, Z.J., Coldrick, Benjamin, Swadener, Gregory, Davies, Leon, Yang, Z.J., Coldrick, Benjamin, Swadener, Gregory, and Davies, Leon

Abstract

Finite element analysis is a useful tool in understanding how the accommodation system of the eye works. Further to simpler FEA models that have been used hitherto, this paper describes a sensitivity study which aims to understand which parameters of the crystalline lens are key to developing an accurate model of the accommodation system. A number of lens models were created, allowing the mechanical properties, internal structure and outer geometry to be varied. These models were then spun about their axes, and the deformations determined. The results showed the mechanical properties are the critical parameters, with the internal structure secondary. Further research is needed to fully understand how the internal structure and properties interact to affect lens deformation.

Published
2012

128. Genetic Variation in Potential Kernel Size Affects Kernel Growth and Yield of Sorghum

Author

Yang, Z.J., van Oosterom, E.J., Jordan, D.R., Doherty, A., Hammer, G.L., Yang, Z.J., van Oosterom, E.J., Jordan, D.R., Doherty, A., and Hammer, G.L.

Abstract

Large-seededness can increase grain yield in sorghum [Sorghum bicolor (L.) Moench] if larger kernel size more than compensates for the associated reduction in kernel number. The aim of this research was to investigate kernel filling characteristics associated with the high kernel weight of KS115 germplasm and consider implications for grain yield improvement. Germplasm with a twofold range in potential kernel size was grown in two field experiments. In both experiments, a large-seeded hybrid based on KS115 yielded significantly more grain than a normal-seeded hybrid with the same female parent. Genotypic differences in final kernel weight were associated with both an increased rate and extended duration of kernel filling. A high kernel filling rate was associated with a high rate of increase in kernel water content and kernel volume, which resulted in large maximum water content and volume per kernel. The long kernel filling duration of KS115-based germplasm was associated with an extended duration of the period of rapid water uptake into the kernel following the onset of rapid dry mass accumulation in the grains. For this particular germplasm, this was likely due to the presence of large ovaries before fertilization. Because of a trade-off between potential kernel weight and number, prolonged duration, rather than an increased rate of kernel filling, appeared to be the main mechanism through which large-seededness of KS115 could increase grain yield.

Published
2010

129. Pre-anthesis ovary development determines genotypic differences in potential kernel weight in sorghum

Author

Yang, Z.J., van Oosterom, E.J., Jordan, D.R., Hammer, G.L., Yang, Z.J., van Oosterom, E.J., Jordan, D.R., and Hammer, G.L.

Abstract

Kernel weight is an important factor determining grain yield and nutritional quality in sorghum, yet the developmental processes underlying the genotypic differences in potential kernel weight remain unclear. The aim of this study was to determine the stage in development at which genetic effects on potential kernel weight were realized, and to investigate the developmental mechanisms by which potential kernel weight is controlled in sorghum. Kernel development was studied in two field experiments with five genotypes known to differ in kernel weight at maturity. Pre-fertilization floret and ovary development was examined and post-fertilization kernel-filling characteristics were analysed. Large kernels had a higher rate of kernel filling and contained more endosperm cells and starch granules than normal-sized kernels. Genotypic differences in kernel development appeared before stamen primordia initiation in the developing florets, with sessile spikelets of large-seeded genotypes having larger floret apical meristems than normal-seeded genotypes. At anthesis, the ovaries for large-sized kernels were larger in volume, with more cells per layer and more vascular bundles in the ovary wall. Across experiments and genotypes, there was a significant positive correlation between kernel dry weight at maturity and ovary volume at anthesis. Genotypic effects on meristem size, ovary volume, and kernel weight were all consistent with additive genetic control, suggesting that they were causally related. The pre-fertilization genetic control of kernel weight probably operated through the developing pericarp, which is derived from the ovary wall and potentially constrains kernel expansion.

Published
2009

134. Clear-cutting and slash burning effects on soil CO2 efflux partitioning in Chinese fir and evergreen broadleaved forests in subtropical China.

Author

Guo, J.F., Chen, G.S., Xie, J.S., Yang, Z.J., and Goss, Michael

Subjects
SLASHBURNING, CLEARCUTTING, CARBON dioxide, SILVICULTURAL systems, CHINA fir
Abstract

Clear-cutting ( CC) and slash burning ( SB) are common silvicultural practices in subtropical China, yet the time-course response of soil CO2 efflux components to such disturbance is not well understood. This study examined the effects of CC and SB on soil CO2 efflux components in a Cunninghamia lanceolata ( Lamb.) Hook ( Chinese fir, CF) plantation and a secondary evergreen broadleaved forest ( BF) located in Fujian Province, southeastern China. Aboveground litter removal and root trenching were used to estimate CO2 fluxes from soil organic matter decomposition ( RSOM), litter decomposition ( RL), and autotrophic respiration by roots and mycorrhizae ( RR). These components were measured 5-7 times per month from 18 October 2001 to 25 December 2003 using soda lime absorption. We found that RR, RL and RSOM were initially higher in CC and SB plots than controls in both forests, but these three component fluxes in disturbed plots all fell below those of the control 5-20 months after the disturbance. Also, Q10 values of these components decreased following disturbance. The annual flux of each respiration component was greater under BF than CF. The contribution of RR to soil CO2 efflux in the control plots averaged 35% in CF and 46% in BF. RSOM was the dominant component of soil CO2 efflux in CC and SB plots, accounting for over 50%. Our results highlight the importance of temporal trends of the component fluxes following disturbance and contribute to a broader understanding of forest management effects on the soil C cycle. [ABSTRACT FROM AUTHOR]

Published
2016
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135. Magnetoresistance of the magnetically ordered icosahedral quasicrystals Al-Pd-Mn-

Author

Yewondwossen, M.H., Ritcey, S.P., Yang, Z.J., and Dunlap, R.A.

Subjects
Crystals -- Magnetic properties, Boron -- Analysis, Magnetic fields -- Analysis, Physics
Abstract

Analysis of the magnetoresistance of magnetically ordered icosahedral quasicrystals Al-Pd-Mn-B shows that magnetoresistance undergoes a systematic alteration with changes in boron concentration. The crystals have negative magnetoresistance for boron concentrations of 8 and 10 at low magnetic fields and at high magnetic fields, they have positive magnetoresistance. The strong and weak spin-orbit scatterings due to high and low boron concentration account for the positive and negative magnetoresistance, respectively.

Published
1994

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