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Improved MIMO-OFDM scheme for the next generation WLAN

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Journal of Systems Engineering and Electronics 2013年第1期24卷 52-59页

作者： Zhanji Wu xiang gao School of Information and Communication Engineering Beijing University of Posts and Telecommunications

The research and application of wireless local area networks （WLAN） technology are in a stage of rapid development. It has been one of research focuses of the wireless communications field. Through the use of enhanced single-user （SU）/multi-user （MU） multiple input multiple output （MIMO）-orthogonal frequency division multiplexing （OFDM） technology, the next generation WLAN IEEE 802.1 lac dramatically increases the throughput. An improved MIMO-OFDM scheme based on modulation diversity is proposed for the next generation WLAN. It uses two-dimensional modulation diversity to the current IEEE 802.11ac transmission scheme. Through the space-time-frequency component inter- leaver and the rotational modulation, the proposed scheme ex- hibits high spectral efficiency and low error rate in fading channels. The simulation results show that the proposed scheme significantly outperforms the SU/MU MIMO-OFDM scheme in the current IEEE 802.11 ac standard, which is up to 5 dB.

关键词： wireless local area networks (WLAN) I EEE 802.1 lac modulation diversity multiple input multiple output (MIMO) orthog- onal frequency division multiplexing (OFDM).

Acoustic Nonlinearity Parameters Due to Microstructural Defects

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Acta Mechanica Solida Sinica 2018年第5期31卷 525-534页

作者： xiang gao Jianmin Qu Department of Mechanical Engineering Tufts University Medford MA 02155 USA

This study presents a general approach to derive the acoustic nonlinearity parameters induced by various types of dislocation configurations including dislocation strings （monopoles）, dislocation dipoles, dislocation pileups and extended dislocations. It is found that expressions of the acoustic nonlinearity parameter induced by such a variety of dislocation con- figurations share a common mathematical form. They are all scaled with （Lch/b）n, where Lch is a characteristic length of the dislocation configuration, b is the magnitude of the Burgers vector, and n is either 3 or 4. Semiquantitative analysis is presented to compare the magnitudes of the acoustic nonlinearity parameters among different types of dislocation configurations.

关键词： Nonlinear ultrasound Nondestructive evaluation Acoustic nonlinearity parameter Microstructural defects Dislocations

P3HT STRIPE STRUCTURE WITH ORIENTED NANOFIBRILS ENABLED BY CONTROLLED INCLINING EVAPORATION

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Chinese Journal of Polymer Science 2013年第4期31卷 610-619页

作者： xiang gao 韩艳春 State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of Sciences Graduate School of the Chinese Academy of Sciences

The preparation of the poly（3-hexylthiophene）（P3HT） stripe structure with oriented nanofibrils prepared by controlled inclining evaporative technique is reported. The distance of the adjacent stripes could be controlled from 40 μm to 100 μm by decreasing the inclining angle. The oriented nanofibrils in the stripes can be obtained because the P3HT lamellae diffuse directionally and form 1D crystals at the three-phase contact line of the drop. In order to get the oriented P3HT stripes, the proper solvent evaporation rate which is controlled by the inclining angle and the wettability of the substrate must be carefully chosen to match the P3HT 1D crystallization rate. It is found that large inclining angle and the hydrophilic substrate （for example： glass and PEDOT） are beneficial to get P3HT stripe structure with oriented nanofibrils.

关键词： Inclining evaporative technique Orientation Stripe structure.

Comprehensive optimization design of aerodynamic and electromagnetic scattering characteristics of serpentine nozzle

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Chinese Journal of Aeronautics 2021年第3期34卷 118-128页

作者： Yubo HE Qingzhen YANG xiang gao School of Power and Energy Northwestern Polytechnical UniversityXi’an 710129China

Comprehensive optimization design of serpentine nozzle with trapezoidal outlet was studied to improve its aerodynamic and electromagnetic scattering *** nozzles with different center offsets and different ratios of the bases of the trapezoidal outlet were generated based on curvature control *** Fluid Dynamics(CFD)simulations have been conducted to obtain the flow field in the nozzle,and Forward-Backward Iterative Physical Optics(FBIPO)method was applied to study the electromagnetic scattering characteristics of the *** Convergence Particle Swarm Optimization(GCPSO)algorithm based on Radial Basis Function(RBF)neural network was used to optimize the geometry of the nozzle in consideration of its aerodynamic and electromagnetic scattering *** results show that the GCPSO method based on RBF can be used to optimize the aerodynamic characteristics of the internal flow and the scattering characteristics of the cavity of the serpentine nozzle with irregular *** optimized model has a higher center offset and a lower ratio of the bases of the trapezoidal outlet after optimization compared to the original *** optimized model leads to a slight change in aerodynamic performance,with a total pressure recovery coefficient increase of 0.31%and a discharge coefficient increase of 0.41%.In addition,the Radar Cross Section(RCS)decreases also by around 83.33%and the overall performance is significantly improved,with a decrease of the optimized objective function by around 38.74%.

关键词： Forward-Backward Iterative Physical Optics(FBIPO) Guarantee Convergence Particle Swarm Optimization(GCPSO) Nozzle design Optimization design Radar Cross Section(RCS) Serpentine nozzle

Experiment and Analysis of Compatibility between New Phase Change Mixed Molten Salt and 316L Stainless Steel

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Journal of Thermal Science 2024年第6期33卷 2259-2273页

作者： REN Chenxing ZHENG Chenghang gao xiang State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou 310027China Institute of Carbon Neutrality Zhejiang UniversityHangzhou 310027China Baima Lake Laboratory Zhejiang UniversityHangzhou 310051China

Molten salt is considered as a promising heat storage and heat transfer medium due to its efficient thermophysical *** order to study the compatibility of five new mixed molten salts obtained with KNO_(3),NaNO_(3),K,CO_(3),Ca(NO_(3))_(2)·4H_(2)O,ZnCl_(2),NaF,Na_(2)CO_(3),NaCl and MgO as materials and 316L stainless steel,corrosion weight loss,scanning electron microscopy,elemental analysis and XRD were used to analyze the compatibility of 316L stainless steel in the new mixed molten salt at different time and *** corrosion behavior under the conditions was studied and *** compatibility data was obtained,and the corrosion mechanism of 316L stainless steel in mixed molten salts was *** results show that the corrosion weight of 316L stainless steel increases,and the corrosion degree of grain,crystal crack depth and oxidation degree increase gradually with the increase of temperature and *** corrosion of molten salt on alloy is mainly caused by the selective diffusion loss and corrosion of Cr,Fe and other elements,and is accompanied by the formation of different metal *** formation of metal oxides can slow down metal corrosion and loss to a certain *** corrosion results under different working conditions show that 316L stainless steel has good compatibility with the new mixed molten salt,and has certain application value in the field of heat transfer and energy storage.

关键词： molten salt 316L stainless steel corrosion resistance heat treatment

The 2 ℃ Global Temperature Target and the Evolution of the Long-TermGoal of Addressing Climate Change-From the United Nations FrameworkConvention on Climate Change to the Paris Agreement

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Engineering 2017年第2期3卷 272-278页

作者： Yun gao xiang gao Xiaohua Zhang Department of Sdence & Technology and Climate Change China Meteorological Administration Beijing 100081 China Energy Research Institute National Development and Reform Commission Beijing 100038 China National Center for Climate Change Strategy and International Cooperation (NCSC) Beijing 100038 China

The Paris Agreement proposed to keep the increase in global average temperature to well below 2 ℃ abovepre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 ℃ above pre-industriallevels. It was thus the first international treaty to endow the 2 ℃ global temperature target with legal *** qualitative expression of the ultimate objective in Article 2 of the United Nations Framework Conventionon Climate Change （UNFCCC） has now evolved into the numerical temperature rise target in Article 2 of theParis Agreement. Starting with the Second Assessment Report （SAR） of the Intergovernmental Panel on Cli-mate Change （IPCC）, an important task for subsequent assessments has been to provide scientific informa-tion to help determine the quantified long-term goal for UNFCCC negotiation. However, due to involvementin the value judgment within the scope of non-scientific assessment, the IPCC has never scientifically af-firmed the unacceptable extent of global temperature rise. The setting of the long-term goal for addressingclimate change has been a long process, and the 2 ℃ global temperature target is the political consensuson the basis of scientific assessment. This article analyzes the evolution of the long-term global goal foraddressing climate change and its impact on scientific assessment, negotiation processes, and global low-carbon development, from aspects of the origin of the target, the series of assessments carried out by the 1PCCfocusing on Article 2 of the UNFCCC, and the promotion of the global temperature goal at the political level.

关键词： Climate change International negotiationln tergovernmental Panel on Climate Change United Nations Framework Convention on Climate ChangeLong-term goal Critical vulnerability Intuitive building

Reflection and operationalization of the common but differentiated responsibilities and respective capabilities principle in the transparency framework under the international climate change regime

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Advances in Climate Change Research 2018年第4期9卷 253-263页

作者： WANG Tian gao xiang National Center for Climate Change Strategy and International Cooperation Ministry of Ecology and Environment Beijing 100038 China Energy Research Institute National Development and Reform Commission Beijing 100038 China

“Common but differentiated responsibilities and respective capabilities”(CBDRRC) is the most significant guiding principle in the international climate change regime, created by the United Nations Framework Convention on Climate Change in 1992 and inherited by the Paris Agreement 24 years later. This paper examines the operationalization of the CBDRRC principle in one of the cornerstone rules of the regimedits transparency provisions, both in existing practice under the convention and possible evolvement in negotiations under the Paris Agreement, from the perspectives of both international rule-making and domestic implementation. The authors have found a continuous enhancement of the transparency framework since the 1990s, and gradual consolidation of a bifurcated system between developed and developing countries into a common one. The authors argue that the transparency framework, as part of the procedural rules, should be designed to facilitate transparent information sharing in accordance with substantive commitments under international climate change laws. Thus, it indirectly reflects historical responsibilities for climate change, while the framework should also be designed as feasible and reflective of the respective capabilities of nations. Finally, the evolution of the transparency framework will aim to enact common and enhanced provisions while differentiating between developed and developing countries in the near term, and greater transparency-related capacity-building for developing countries.

关键词： International climate change law UNFCCC Paris agreement Transparency Common but differentiated responsibilities and respective capabilities principle

Model animals and their applications

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Science China(Life Sciences) 2015年第4期58卷 319-320页

作者： gao xiang MOE Key Laboratory of Model Animal for Disease Study Model Animal Research Center Nanjing University

Looking back a decade ago when I decided to use ＂model animal＂ to name our newly established institute, my outrageous boldness can only be described by the old Chinese slang, ＂newborn calf could never sense the danger of tiger＂. Happily, my courageous belief, along with the hard work of my colleagues at Model Animal Research Center of Nanjing University, paid off eventually. We have witnessed the great progress in this research field in China in the past 10 years. This issue of Science China Life Sciences samplings some of these accomplishments.

关键词：模型动物应用生命科学旧中国初生牛犊模式动物南京大学研究所

Precision Calculations of Atomic Polarizabilities： A Relevant Physical Quantity in Modern Atomic Frequency Standard

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Chinese Physics Letters 2010年第6期27卷 78-81页

作者： gao xiang LI Jia-Ming Department of Physics Shanghai Jiao Tong University Shanghai 200240 Department of Physics and Key Laboratory of Atomic and Molecular Nanosciences of Ministry of Education Tsinghua University Beijing 100084

Electric dipole polarizabilities of atoms are very important in many different physical applications, such as the precision atomic frequency standard. Calculations of these properties are very important and challenging. We propose a calculation strategy to calculate the frequency dependent dipole polarizabilities with high precision variationally by using a set of high quality orbital bases where the electron correlations can be taken into account adequately. The static polarizabilitiez of the ground state of Na are calculated accurately by such a method and can be compared with precision experiment measurement directly. The calculation result is in excellent agreement with the available experimental measurements within about 0.1~, which demonstrates the validity of our strategy. Our calculation strategy has a wide usage, not only in polarizibilies, but also in other fields such as theoretical treatment of electron-atom scattering processes. Using the same orbital bases, we carry out precision calculation of Na- affinities. Our calculated affinity is in excellent agreement with precision laser spectroscopy measurements within 0. 1%.

关键词： PHYSICAL constants ATOMIC frequency standards DIPOLE moments POLARIZABILITY (Electricity) VARIATIONAL principles ATOMIC orbitals SCATTERING (Physics) LASER spectroscopy