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A Nonlinear Representation of Model Uncertainty in a Convective-Scale Ensemble Prediction System

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Advances in Atmospheric Sciences 2022年第9期39卷 1432-1450页

作者： Zhizhen XU Jing chen mu mu Guokun DAI Yanan MA Department of Atmospheric and Oceanic Sciences&Institute of Atmospheric Sciences Fudan UniversityShanghai 200438China Numerical Weather Prediction Center China Meteorological AdministrationBeijing 100081China Chinese Academy of Meteorological Sciences China Meteorological AdministrationBeijing 100081China

How to accurately address model uncertainties with consideration of the rapid nonlinear error growth characteristics in a convection-allowing system is a crucial issue for performing convection-scale ensemble *** this study,a new nonlinear model perturbation technique for convective-scale ensemble forecasts is developed to consider a nonlinear representation of model errors in the Global and Regional Assimilation and Prediction Enhanced System(GRAPES)Convection-Allowing Ensemble Prediction System(CAEPS).The nonlinear forcing singular vector(NFSV)approach,that is,conditional nonlinear optimal perturbation-forcing(CNOP-F),is applied in this study,to construct a nonlinear model perturbation method for *** experiments are performed:One of them is the CTL experiment,without adding any model perturbation;the other two are NFSV-perturbed experiments,which are perturbed by NFSV with two different groups of constraint radii to test the sensitivity of the perturbation magnitude *** results show that the NFSV-perturbed experiments achieve an overall improvement and produce more skillful forecasts compared to the CTL experiment,which indicates that the nonlinear NFSV-perturbed method can be used as an effective model perturbation method for convection-scale ensemble ***,the NFSV-L experiment with large perturbation constraints generally performs better than the NFSV-S experiment with small perturbation constraints in the verification for upper-air and surface weather *** for precipitation verification,the NFSV-S experiment performs better in forecasts for light precipitation,and the NFSV-L experiment performs better in forecasts for heavier precipitation,indicating that for different precipitation events,the perturbation magnitude constraint must be carefully *** the findings above lay a foundation for the design of nonlinear model perturbation methods for future CAEPSs.

关键词： Convection-Allowing Ensemble Prediction System model uncertainty nonlinear forcing singular vector

Ambient levels of atmospheric carbonyls in Beijing during the 2008 Olympic Games

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Journal of Environmental Sciences 2010年第9期22卷 1348-1356页

作者： Zhu Xu Junfeng Liu Yujie Zhang Peng liang Yujing mu Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China Graduate School of Chinese Academy of Sciences Beijing 100039 China

The measurements of atmospheric carbonyls concentrations in Beijing were conducted from 12 July to 8 October, 2008, covering the periods of the 2008 Olympic Games and Paralympic Games. Six carbonyls, including formaldehyde, acetaldehyde, acetone, butyraldehyde, valeraldehyde, and hexaldehyde, were identified in all air samples. The total average concentrations of these carbonyls before, during, and after traffic restriction were （48.1 ± 15.2）, （36.6 ± 14.5） and （23.4± 12.3） μg/m^3, respectively. Compared with the period after traffic restriction, the distinct high concentrations of the carbonyls before and during traffic restriction were primarily ascribed to the remarkable contribution of photochemical reactions. With respect to our previous investigation in the summer of 2005, the reductions of formaldehyde, acetaldehyde and acetone during traffic restriction period were about 64%, 47% and 27%, respectively, indicating that the air cleaning actions adopted by the Chinese government for the two games were efficient. The lowest levels of atmospheric carbonyls and the extremely high composition proportion of acetone after the traffic restriction were mainly attributed to the long-term effect of the control measures for the two games.

关键词： Olympic Games Paralympic Games carbonyl compounds traffic restriction photochemical reactions vehicular exhaust

An Improved Calculation of Nonlinear Stopping Power of an Electron Gas for Slow Hydrogen Ions

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Chinese Physics Letters 1996年第11期13卷 825-828页

作者： mu Yu-guang XIA Yue-yuan MEI liang-mo Department of Physics Shandong UniversityJinan 250100

The stopping power of an electron gas for hydrogen ions is calculated based on the full self-consistent nonlinear density-functional *** different configurations of hydrogen ions are considered and a criterion to test the validity of the self-consistent calculation is *** of calculation with available experimental data shows good agreement.

关键词： hydrogen Electron calculation

Revitalizing osmium-based catalysts for energy conversion

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Energy Reviews 2023年第4期2卷 81-88页

作者： Ding chen Shichun mu State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan430070China

Designing high cost-effective catalysts has been one of the core topics in energy conversion and *** to unique electronic structure and excellent comprehensive properties,Pt-group metal(PGM)based-materials occupy the top region of numerous volcanic curves and are currently difficult to be replaced by abundant tran-sition metal ***,we pay attention to the osmium(Os),as the cheapest and the least noticed PGM in the field of electrocatalysis,with promising application ***,the three main modification strategies(anion modulation,heterostructure construction,substrate engineering)of Os-based catalysts in hydrogen evolution reaction(HER),the structural advantages provided in oxygen evolution reaction(OER),and other energy-related electrocatalysis applications are discussed one by *** addition,we discuss the key problems and countermeasures faced in their further breakthroughs,and look forward to future development trends and ***,the insights in this work will promote the understanding and designation of Os-based catalysts.

关键词： Energy conversion Electrocatalysis Pt-group metals Os-based catalysts

Efficient and secure image authentication with robustness and versatility

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Science China(Information Sciences) 2020年第12期63卷 179-196页

作者： Haixia chen Xinyi HUANG Wei WU Yi mu Fujian Provincial Key Laboratory of Network Security and Cryptology Center for Applied Mathematics of Fujian ProvinceCollege of Mathematics and Informatics Fujian Normal University

Image authentication is the technology of verifying image origin, integrity and authenticity. A rich stream of research on image authentication has shown various trade-off among four favorable features,namely robustness, security, versatility and efficiency. Image data authentication has the highest level of security but provides no robustness/versatility. Image content authentication from robust hashing keeps robust to limited types of operations, and as a result its versatility is not satisfactory. Existing designs of image content authentication from advanced cryptographic primitives achieve robustness, security and versatility, at the cost of low efficiency. In this paper, we present a new design of image authentication with an improved trade-off among the aforementioned features. Our versatile design is robust to a number of predefined image processing operations. Its security can be reduced to q-strong Diffie-Hellman(q-SDH), a complexity problem used by existing cryptographic algorithms. From the aspect of efficiency, the new design has a constant-size authentication overhead( ≤2 kB) and a constant verification time(around 0.05 s). While the time of generating authentication overhead increases linearly with the number of permissible editing operations, it only takes around 0.33 s for 1000 types of permissible operations. We believe the new design will facilitate image applications where trustworthy image editing is required.

关键词： image authentication image processing cryptography bilinear maps

mutually Pumped Phase-Conjugate Mirror: Sickle Configuration

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Chinese Physics Letters 1996年第9期13卷 678-681页

作者： ZHANG liang-min ZHANG Jing-wen SHAO Zong-shu mu Xiao-dong chen Huan-chu JIANG Min-hua National Laboratory of Crystal Materials Shandong UniversityJinan 250100

A mutually pumped phase conjugator is demonstrated with a novel photorefractive crystal of copper-doped potassium sodium strontium barium niobate,in which the beams travel in a geometric path similar to the outline of a *** maximum reflectivity is up to 168%.Faster response times are measured and are also simulated as a function of incident beam power *** available input geometries are *** phase conjugation signals exist wide range of angular and positional *** apparent cross talk is *** faster build-up process of phase conjugation beams is tentatively explained.

关键词： pumped Configuration mutually

Mechanically strong,flexible,and multi-responsive phase change films with a nacre-mimetic structure for wearable thermal management

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Journal of Energy Chemistry 2022年第12期75卷 229-239,I0006页

作者： Jiankang Zhang Jiahui mu Sheng chen Feng Xu Beijing Key Laboratory of Lignocellulosic Chemistry Beijing Forestry UniversityBeijing 100083China

Phase change materials(PCMs)are a highly promising candidate for thermal energy storage owing to their large latent heat and chemical ***,their intrinsic brittle induces poor flexibility and low mechanical strength,which limits them use for wearable thermal ***,the electrical insulation and weak solar absorption make them lack multi-responsive ***,we report a facile strategy to synthesize mechanically strong and flexible multi-responsive phase change films by stirring an aqueous dispersion of cellulose nanofibrils(CNFs),MXene(Ti_(2)C_(3))nanosheets,and polyethylene glycol(PEG),followed by air-drying self-assembly and coating with hydrophobic *** hydrogen bonds and nacre-mimetic synergistic toughening networks formed by ternary CNFs,Ti_(2)C_(3)nanosheets,and PEG endow films with high mechanical strength(16.7 MPa)and strain(10.4%),which are 18.6 and 8.7 times higher than those of pure PEG film,*** films exhibit outstanding flexibility and do not crack or fracture even when bent,twisted,and folded into a complex small ***,the laminar structure formed by the self-assembly Ti_(3)C_(2)nanosheets enhances electrical conductivity(3.95 S/m)and solar absorption,affording excellent electro-thermal(68.3%–81.0%)and solarthermal(85.6%–90.6%)conversion efficiency,thus achieving multi-response to external stimuli(electron/solar radiation).In addition,the as-prepared films also deliver large latent heat(136.1 J/g),outstanding cyclic and shape stability,leak-free encapsulation even under compressed at above 5000 times its weight,excellent hydrophobicity(131.4°),and self-cleaning *** work paves the way for developing flexible,mechanically strong,and self-cleaning phase change film with multi-responsive function for wearable thermal management devices under high humidity condition.

关键词： Phase change materials Flexible Mechanically strong multi-responsive Wearable thermal management

Origin of Self-pumped Phase Conjugate Waves in KNSBN Crystals

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Chinese Physics Letters 1996年第7期13卷 523-526页

作者： ZHANG liang-min ZHANG Jing-wen SHAO Zong-shu mu Xiao-dong chen Huan-chu JIANG Min-hua National Laboratory of Crystal Materials Shandong UniversityJinan 250100

A multistage four-wave mixing interaction region model resulting in self-pumped phase conjugation output of the incident beam is suggested to explain the experimental *** competition between forward and backward two-wave mixing is demonstrated and used to explain the formation of the *** backscattering beams from random noise beams may be amplified by contradirectional two-wave mixing selectively and act as pumped beams from our experimental observations under a laser entering the negative c face of copper-doped potassium sodium strontium barium niobate *** phase conjugation reflectivity of as high as 33%is measured.

关键词： pumped mixing backward

A static-dynamic energy harvester for a self-powered ocean environment monitoring application

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Science China(Technological Sciences) 2022年第4期65卷 893-902页

作者： XUE Feng chen liang LI Chuncheng REN Jing YU JunBin HOU XiaoJuan GENG WenPing mu Jiliang HE Jian CHOU XiuJian Science and Technology on Electronic Test and Measurement Laboratory North University of ChinaTaiyuan 030051China

Ocean intelligent buoy is important for ocean environment *** the increase of requisite sensors and transportable data,a long power supply has become a problem to be solved *** this work,a hybrid nanogenerator integrating triboelectric,piezoelectric,electromagnetic,photovoltaic,and thermotropic units is proposed to maximize ocean ambient energy harvesting,which includes static energy(solar and thermal energy)and dynamic energy(wave energy).Compared with a device with a single energy conversion mechanism,this structural design breaks the limit of harvesting time and natural conditions during the energy harvesting process,thereby increasing the harvested *** energy harvesting is realized by the thermoelectric(TG)and photovoltaic(PV)units located inside the device and the PV unit attached to the device *** show that the maximum open-circuit voltage and short-circuit current are 5 V and 41 mA in the external PV and 1.33 V and 49 mA in the internal PV under 30000 Lux illumination,*** open-circuit voltage and short-circuit current of the TG unit are 5 V and 15 m A,*** core component of the dynamic generation unit is the gimbal used to harvest wave energy by the triboelectric nanogenerator(TENG),piezoelectric generator(PENG),and electromagnetic *** the frequency is 2.4 Hz,the maximum peak-to-peak power of the TENG,PENG,and EMG are 0.25,1.58,and 13.8 mW,***,an intelligent ocean buoy is fabricated by the integration of an energy harvester,a power management circuit,sensors,a microcontroller,and a wireless communication *** by static and dynamic energy,temperature signal,humidity signal,GPS signal,and sound signal are sent to the receiving terminal *** ocean energy harvester proposed in this work is of great significance for ocean energy harvesting and ocean wireless monitoring systems.

关键词： hybrid nanogenerator static energy dynamic energy energy harvester wireless monitoring system

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