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| 1 | Space Debris Reentry Analysis Methods and Tools显示文摘The reentry of uncontrolled spacecraft may be broken into many pieces of debris at an altitude in the range of 75-85 km. The surviving fragments could pose great hazard and risk to ground and people. In recent years, methods and tools for predicting and analyzing debris reentry and ground risk assessment have been studied and developed in National Aeronautics and Space Ad-ministration (NASA), European Space Agency (ESA) and other organizations, including the group of the present authors. This paper reviews the current progress on this topic of debris reentry briefly. We outline the Monte Carlo method for uncertainty analysis, breakup prediction, and parameters affecting survivability of debris. The existing analysis tools can be classified into two categories, i.e. the object-oriented and the spacecraft-oriented methods, the latter being more accurate than the first one. The past object-oriented tools include objects of only simple shapes. For more realistic simulation, here we present an object-oriented tool debris reentry and ablation prediction system (DRAPS) developed by the present authors, which introduces new object shapes to 15 types, as well as 51 predefined motions and relevant aerodynamic and aerothermal models. The aerodynamic and aerothermal models in DRAPS are validated using direct simulation Monte Carlo (DSMC) method. | WU Ziniua HU Ruifeng QU Xi WANG Xiang WU Zhe | 2011 | Chinese Journal of Aeronautics2011，24，4： | 14 |
| 2 | Review of shock wave detection method in CFD post-processing显示文摘In the present computational fluid dynamics (CFD) community, post-processing is regarded as a procedure to view parameter distribution, detect characteristic structure and reveal physical mechanism of fluid flow based on computational or experimental results. Field plots by contours, iso-surfaces, streamlines, vectors and others are traditional post-processing techniques. While the shock wave, as one important and critical flow structure in many aerodynamic problems, can hardly be detected or distinguished in a direct way using these traditional methods, due to possible confusions with other similar discontinuous flow structures like slip line, contact discontinuity, etc. Therefore, method for automatic detection of shock wave in post-processing is of great importance for both academic research and engineering applications. In this paper, the current status of methodologies developed for shock wave detection and implementations in post-processing platform are reviewed, as well as discussions on advantages and limitations of the existing methods and proposals for further studies of shock wave detection method. We also develop an advanced post-processing software, with improved shock detection. | Wu Ziniu Xu Yizhe Wang Wenbin Hu Ruifeng | 2013 | Chinese Journal of Aeronautics2013，26，3： | 11 |
| 3 | Aerodynamic map for soft and hard hypersonic level flight in near space显示文摘In this note,we design a velocity-altitude map forhypersonic level flight in near space of altitude 20-100 km.This map displays aerodynamic-related parameters associ-ated with near space level flight,schematically or quantita-tively.Various physical conditions for the near-space levelflight are then characterized,including laminar or turbulentflow,rarefaction or continuous flow,aerodynamic heating,aswell as conditions for sustaining level flight with and withoutorbital effect.This map allows one to identify conditions tohave soft flight or hard flight,and this identification wouldbe helpful for making correct planning on detailed studies ofaerodynamics or making initial design of near space vehicles. | Ruifeng Hu Ziniu Wu Zhe Wu Xiaoxin Wang Zhongwei Tian School of Aerospace, Tsinghua University, 100084 Beijing, China | 2009 | Acta Mechanica Sinica2009，25，4： | 11 |
| 4 | An Ensemble Approach for Emotion Cause Detection with Event Extraction and Multi-Kernel SVMs显示文摘In this paper, we present a new challenging task for emotion analysis, namely emotion cause extraction.In this task, we focus on the detection of emotion cause a.k.a the reason or the stimulant of an emotion, rather than the regular emotion classification or emotion component extraction. Since there is no open dataset for this task available, we first designed and annotated an emotion cause dataset which follows the scheme of W3 C Emotion Markup Language. We then present an emotion cause detection method by using event extraction framework,where a tree structure-based representation method is used to represent the events. Since the distribution of events is imbalanced in the training data, we propose an under-sampling-based bagging algorithm to solve this problem. Even with a limited training set, the proposed approach may still extract sufficient features for analysis by a bagging of multi-kernel based SVMs method. Evaluations show that our approach achieves an F-measure 7.04%higher than the state-of-the-art methods. | Ruifeng Xu Jiannan Hu Qin Lu Dongyin Wu Lin Gui | 2017 | Tsinghua Science and Technology2017，22，6： | 6 |
| 5 | High-sensitivity self-powered temperature/pressure sensor based on flexible Bi-Te thermoelectric film and porous microconed elastomer显示文摘Electronic skins are artificial skin-type multifunctional sensors,which hold great potentials in intelligent robotics,limb prostheses and human health monitoring.However,it is a great challenge to independently and accurately read various physical signals without power supplies.Here,a self-powered flexible temperature-pressure bimodal sensor based on high-performance thermoelectric films and porous microconed conductive elastic materials is presented.Through introducing flexible heat-sink design and harvesting body heat energy,the thin-film thermoelectric device could not only precisely sense temperature signal but also drive the pressure sensor for detecting external tactile stimulus.The integration of Bi-Te based thermoelectric film with high stability in wide temperature range enables the sensor to sense the ambient temperature with high resolution(<0.1 K)as well as excellent sensitivity(3.77 mV K^(-1)).Meanwhile,the porous microconed elastomer responds to pressure variation with low-pressure detection(16 Pa)and a high sensitivity of 37 kPa^(-1).Furthermore,the bimodal sensor could accurately and simultaneously monitor human wrist pulse and body temperature in real time,which demonstrates promising applications in self-powered electronic skins for human health monitoring systems. | Yaling Wang Wei Zhu Yuan Deng Pengcheng Zhu Yuedong Yu Shaoxiong Hu Ruifeng Zhang | 2022 | Journal of Materials Science & Technology2022，，8： | 4 |
| 6 | Fabrication of sharp silicon hollow microneedles by deep-reactive ion etching towards minimally invasive diagnostics显示文摘Microneedle technologies have the potential for expanding the capabilities of wearable health monitoring from physiology to biochemistry.This paper presents the fabrication of silicon hollow microneedles by a deep-reactive ion etching(DRIE)process,with the aim of exploring the feasibility of microneedle-based in-vivo monitoring of biomarkers in skin fluid.Such devices shall have the ability to allow the sensing elements to be integrated either within the needle borehole or on the backside of the device,relying on capillary filling of the borehole with dermal interstitial fluid(ISF)for transporting clinically relevant biomarkers to the sensor sites.The modified DRIE process was utilized for the anisotropic etching of circular holes with diameters as small as 30μm to a depth of>300μm by enhancing ion bombardment to efficiently remove the fluorocarbon passivation polymer.Afterward,isotropic wet and/or dry etching was utilized to sharpen the needle due to faster etching at the pillar top,achieving tip radii as small as 5μm.Such sharp microneedles have been demonstrated to be sufficiently robust to penetrate porcine skin without needing any aids such as an impact-insertion applicator,with the needles remaining mechanically intact after repetitive penetrations.The capillary filling of DRIE-etched through-wafer holes with water has also been demonstrated,showing the feasibility of use to transport the analyte to the target sites. | Yan Li Hang Zhang Ruifeng Yang Yohan Laffitte Ulises Schmill Wenhan Hu Moufeed Kaddoura Eric J.M.Blondeel Bo Cui | 2019 | Microsystems & Nanoengineering2019，5，1： | 4 |
| 7 | Study on thermal wave based on the thermal mass theory显示文摘The conservation equations for heat conduction are established based on the concept of thermal mass.We obtain a general heat conduction law which takes into account the spatial and temporal inertia of thermal mass.The general law introduces a damped thermal wave equation.It reduces to the well-known CV model when the spatial inertia of heat flux and temperature and the temporal inertia of temperature are neglected,which indicates that the CV model only considers the temporal inertia of heat flux.Numerical simulations on the propagation and superposition of thermal waves show that for small thermal perturbation the CV model agrees with the thermal wave equation based on the thermal mass theory.For larger thermal perturbation,however,the physically impossible phenomenon pre-dicted by CV model,i.e.the negative temperature induced by the thermal wave superposition,is eliminated by the general heat conduction law,which demonstrates that the present heat conduction law based on the thermal mass theory is more reasonable. | HU RuiFeng CAO BingYang | 2009 | Science China(Technological Sciences)2009，52，6： | 3 |
| 8 | On proactive eavesdropping using anti-relay-selection jamming in multi-relay communication systems显示文摘This paper considers a multi-relay legitimate surveillance system, where a suspicious link may transmit illegal information with the help of relays and a legitimate monitor aims at intercepting the information. We assume that the relay selection method is adopted by the suspicious link to improve the efficiency of the information transmission. We propose anti-relay-selection(ARS) jamming strategies for two different information transmission scenarios, namely the event-based information and content-based information. Beamforming vector of jamming is optimized and the iterative algorithms are used to improve the jamming efficiency. We demonstrate the effectiveness and the superiority of the ARS jamming strategies through numerical results and simulations. | Yingdong HU Ruifeng GAO Ye LI Shibing ZHANG | 2019 | Science China(Information Sciences)2019，62，4： | 2 |
| 9 | Coupled GIMP and CPDI material point method in modelling blast-induced three-dimensional rock fracture显示文摘Three-dimensional rock fracture induced by blasting is a highly complex problem and has received considerable attention in geotechnical engineering.The material point method is firstly applied to treat this challenging task.Some inherent weaknesses can be overcome by coupling the generalized interpolation material point(GIMP)and the convected particle domain interpolation technique(CPDI).For the media in the borehole,unchanged GIMP-type particles are used to guarantee a homogenous blast pressure.CPDITetrahedron type particles are employed to avoid the fake numerical fracture near the borehole for the rock material.A blasting experiment using three-dimensional single-borehole rock was simulated to examine the applicability of the coupled model under realistic loading and boundary conditions.A good agreement was achieved between the simulation and experimental results.Moreover,the mechanism of three-dimensional rock fracture was analyzed.It was concluded that rock particle size and material parameters play an important role in rock damage.The reflected tensile waves cause severe damage in the lower part of the model.Rayleigh waves occur on the top face of the rock model to induce a hoop failure band. | Duanying Wan Meng Wang Zheming Zhu Fei Wang Lei Zhou Ruifeng Liu Weiting Gao Yun Shu Hu Xiao | 2022 | International Journal of Mining Science and Technology2022，32，5： | 2 |
| 10 | Diagnostic value of the soluble triggering receptor expressed on myeloid cells‐1 in lower respiratory tract infections: A meta‐analysis显示文摘 | Wu Ye Yanjie Hu Ruifeng Zhang Kejing Ying | 2014 | Respirology2014，，4： | 1 |
| 11 | Large eddy simulation of high-Reynolds-number atmospheric boundary layer flow with improved near-wall correction显示文摘It is highly attractive to develop an efficient and flexible large eddy simulation(LES)technique for high-Reynolds-number atmospheric boundary layer(ABL)simulation using the low-order numerical scheme on a relatively coarse grid,that could reproduce the logarithmic profile of the mean velocity and some key features of large-scale coherent structures in the outer layer.In this study,an improved near-wall correction scheme for the vertical gradient of the resolved streamwise velocity in the strain-rate tensor is proposed to calculate the eddy viscosity coefficient in the subgrid-scale(SGS)model.The LES code is realized with a second-order finite-difference scheme,the scale-dependent dynamic SGS stress model,the equilibrium wall stress model,and the proposed correction scheme.Very-high-Reynolds-number ABL flow simulation under the neutral stratification condition is conducted to assess the performance of the method in predicting the mean and fluctuating characteristics of the rough-wall turbulence.It is found that the logarithmic profile of the mean streamwise velocity and some key features of large-scale coherent structures can be reasonably predicted by adopting the proposed correction method and the low-order numerical scheme. | Shengjun FENG Xiaojing ZHENG Ruifeng HU Ping WANG | 2020 | Applied Mathematics and Mechanics(English Edition)2020，41，1： | 1 |
| 12 | Modelling the spreading rate of controlled communicable epidemics through an entropy-based thermodynamic model显示文摘A model based on a thermodynamic approach is proposed for predicting the dynamics of communicable epidemics assumed to be governed by controlling eforts of multiple scales so that an entropy is associated with the system.All the epidemic details are factored into a single and time-dependent coefcient,the functional form of this coefcient is found through four constraints,including notably the existence of an inflexion point and a maximum.The model is solved to give a log-normal distribution for the spread rate,for which a Shannon entropy can be defined.The only parameter,that characterizes the width of the distribution function,is uniquely determined through maximizing the rate of entropy production.This entropy-based thermodynamic(EBT)model predicts the number of hospitalized cases with a reasonable accuracy for SARS in the year 2003.This EBT model can be of use for potential epidemics such as avian influenza and H7N9 in China. | WANG WenBin WU ZiNiu WANG ChunFeng HU RuiFeng | 2013 | Science China(Physics,Mechanics & Astronomy)2013，56，11： | 1 |
| 13 | KLF4 facilitates chromatin accessibility remodeling in porcine early embryos显示文摘Chromatin accessibility remodeling driven by pioneer factors is critical for the development of early embryos.Current studies have illustrated several pioneer factors as being important for agricultural animals,but what are the pioneer factors and how the pioneer factors remodel the chromatin accessibility in porcine early embryos is not clear.By employing low-input DNase-seq(liDNase-seq),we profiled the landscapes of chromatin accessibility in porcine early embryos and uncovered a unique chromatin accessibility reprogramming pattern during porcine preimplantation development.Our data revealed that KLF4 played critical roles in remodeling chromatin accessibility in porcine early embryos.Knocking down of KLF4 led to the reduction of chromatin accessibility in early embryos,whereas KLF4 overexpression promoted the chromatin openness in porcine blastocysts.Furthermore,KLF4 deficiency resulted in mitochondrial dysfunction and developmental failure of porcine embryos.In addition,we found that overexpression of KLF4 in blastocysts promoted lipid droplet accumulation,whereas knockdown of KLF4 disrupted this process.Taken together,our study revealed the chromatin accessibility dynamics and identified KLF4 as a key regulator in chromatin accessibility and cellular metabolism during porcine preimplantation embryo development. | Wei Zhu Guowei Bu Ruifeng Hu Jixiang Zhang Lianyong Qiao Kai Zhou Tingting Wang Qiao Li Jingjing Zhang Linhui Wu Yali Xie Taotao Hu Shichun Yang Jiaqi Guan Xiaoyu Chu Juanjuan Shi Xia Zhang Falong Lu Xin Liu Yi-Liang Miao | 2024 | Science China(Life Sciences)2024，67，1： | 0 |
| 14 | Focal mechanism of Luding M 6.8 earthquake, September 2022 and analysis of the loading role of the tectonic stress on the seismogenic fault显示文摘To reveal the seismogenic mechanism of the Luding earthquake, we employed the 118 China Seismic Network stations to collect the P-wave polarity data from each station, which was then used in the P-wave first motion approach to calculate the focal mechanism solution of the M6.8 Luding earthquake that occurred on September 5,2022. We have also studied the loading effect of tectonic stress on the Luding earthquake fault based on the stress field data for the research area. The results indicate that this earthquake was a strike-slip type, the nodal plane I:strike 167°, dip angle 78°, slip angle 2°;Nodal plane II: strike 77°, dip angle 88°, slip angle 168°. The two fault planes’ instability coefficients of the Luding earthquake are examined considering the region’s background stress field’s condition. The nodal plane I in the Moho circle is discovered to practically coincide with the Coulomb failure line and the tangent point of the Moho circle, indicating that this nodal plane has a high instability coefficient compared to the nodal plane II. The conclusion is that the nodal plane I has a higher likelihood of being the seismogenic fault plane, which is congruent with the seismogenic fault plane suggested by the aftershock distribution, the earthquake radiation energy distribution of a single station, and seismic intensity distribution.The Luding earthquake’s focal mechanism is highly like the theoretical focal mechanism of the fault situated at the location where the Coulomb failure line intersects the Mohr circle, demonstrating that background stress is what caused the earthquake. The substantial fault instability and similarity between the solved and theoretical focal mechanisms make it easier to comprehend the loading effect of tectonic stress on the Luding earthquake fault. | Yansong Hu Zhenyue Li Ruifeng Liu Zibo Wang | 2023 | Earthquake Research Advances2023，3，3： | 0 |
| 15 | Palladium Nanoparticles/Graphdiyne Oxide Nanocomposite with Excellent Peroxidase-like Activity and Its Application for Glutathione Detection显示文摘In this study, palladium nanoparticles loaded graphdiyne oxide (Pd/GDYO) nanocomposite were fabricated by in-situ reduction of palladium chloride in the dispersion of GDYO, and characte-rized by Raman spectra, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The synthesized Pd/GDYO was first found to have catalytic activities similar to those of the peroxidase enzyme, which can catalyze the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine(TMB) in the presence of hydrogen peroxide(H2O2). Steady-state kinetic studies showed that the catalytic reaction of Pd/GDYO follows a ping-pong mechanism, and Pd/GDYO has a stronger activity to TMB with a Michaelis constant(Km) value of 5.32×10-4 mmol/L. Based on the shielding effect of glutathione(GSH) on the Pd/GDYO-H2O2-TMB reaction system, a colorimetric detection method for GSH was deve-loped with a wide linear range from 0.1 μmol/L to 40 μmol/L and a limit of detection of 0.1 μmol/L. The method was successfully applied for fast and accurate detection of GSH in injection powder drugs. It was expected that this peroxidase-like Pd/GDYO nano- composite would have wide applications in the fields of biomedicine and environmental chemistry. | LAN Weifei HU Ruifeng HUANG Danrong DONG Xu SHEN Gangyi CHANG Shan DAI Dongsheng | 2022 | Chemical Research in Chinese Universities2022，38，2： | 0 |
| 16 | The Distribution of Relative Light Intensity in a Peach Tree Canopy Affects Fruit Yield and Texture显示文摘Light is crucial to the uniform production of high-quality fruit since it is the driving force for leaf photosynthesis and hence overall plant nutrition.The objective of this study was to evaluate the relationship between the distribution of relative light intensity in the peach tree(Prunus persica)canopy and the yield and texture of peach fruits.The canopy of 7-year-old‘Qiuyan’was divided into cubical volumes and the relative light intensity distribution was measured for each cube,along with yield distribution and fruit textural properties at different growing times.The relative light intensity decreased gradually from outside to inside the canopy and from top to bottom.The yield distribution and the relative light intensity were clearly correlated.The percentage of the canopy receiving<30%relative light intensity was 49.07%in May,56.02%in June,and 58.95%in July,whereas the percentage receiving>80%relative light intensity was 32.72%,17.28%,and 10.96%,respectively.Consistent with this,peaches were found in the upper and middle portions of the canopy,within 1.5-3.0 m of the top.The regression equation showed that fruit texture index correlated significantly with relative light intensity.Relative light intensity is the main factor affecting peach yield and texture and must be above 41.83%for good peach quality.Orchardists should carefully plan summer pruning strategies to adjust the number and spatial distribution of branches accordingly. | Zhaoyuan WANG Qihang TIAN Yong GUO Ruifeng CHANG Guojian LIU Hu CHEN Yonghong LI | 2021 | Agricultural Biotechnology2021，10，3： | 0 |
| 17 | Direct observation of nodeless superconductivity and phonon modes in electron-doped copper oxide Sr_(1-X)Nd_(X)CuO_(2)显示文摘The microscopic understanding of high-temperature superconductivity in cuprates has been hindered by the apparent complexity of crystal structures in these materials.We used scanning tunneling microscopy and spectroscopy to study the electron-doped copper oxide compound Sr_(1-x)Nd_(x)CuO_(2),which has only bare cations separating the CuO_(2) planes and thus the simplest infinite-layer structure of all cuprate superconductors.Tunneling conductance spectra of the major CuO_(2) planes in the superconducting state reve aled direct evidence for a nodeless pairing gap,regardless of variation of its magnitude with the local doping of trivalent neodymium.Furthermore,three distinct bosonic modes are observed as multiple peak-dip-hump features outside the superconducting gaps and their respective energies depend little on the spatially varying gaps.As well as the bosonic modes,with energies identical to those of the external,bending and stretching phonons of copper oxides,our findings reveal the origin of the bosonic modes in lattice vibrations rather than spin excitations. | Jia-Qi Fan Xue-Qing Yu Fang-Jun Cheng Heng Wang Ruifeng Wang Xiaobing Ma Xiao-Peng Hu Ding Zhang Xu-Cun Ma Qi-Kun Xue Can-Li Song | 2022 | National Science Review2022，9，4： | 0 |
| 18 | Inner-outer decomposition of wall shear stress fluctuations in turbulent channels显示文摘Fluctuating wall shear stress in turbulent channel flows is decomposed into small-scale and large-scale components.The large-scale fluctuating wall shear stress is computed as the footprints of the outer turbulent motions,and the small-scale one is obtained by subtracting the large-scale one from the total,which fully remove the outer influences.We show that the statistics of the small-scale fluctuating wall shear stress is Reynolds number independent at the friction Reynolds number larger than 1000,while which is Reynolds number dependent or the low-Reynolds-number effect exists at the friction Reynolds number smaller than 1000.Therefore,a critical Reynolds number that defines the emergence of universal small-scale fluctuating wall shear stress is proposed to be 1000.The total and large-scale fluctuating wall shear stress intensities approximately follow logarithmic-linear relationships with Reynolds number,and empirical fitting expressions are given in this work. | Limin Wang Ruifeng Hu | 2022 | Theoretical & Applied Mechanics Letters2022，12，2： | 0 |
| 19 | RIS-Assisted Communications in Correlated Rayleigh Channels:Comparison of Training Overhead Reduction Schemes显示文摘Channel training in reconfigurable intelligent surface(RIS)-assisted communications is usually conducted in an on-off manner,resulting in unaffordable training time overhead when the number of RIS elements is large.In this paper,for correlated Rayleigh channels,we compare three typical training overhead reduction schemes,namely RIS element selection(Scheme 1),element grouping(Scheme 2),and statistical CSI-based phase shifts design(Scheme3).For Scheme 1 and Scheme 2,we propose two algorithms to select RIS elements(or form element groups) and determine the optimal number of activated elements(or formed groups),based on the channel correlation information only;for Scheme 3,we consider a semi-definite programming-based approach in the literature,and propose an alternative dominant eigenvector-based method for determining the RIS phase shifts vector.Via extensive simulations,we compare the achievable ergodic rates of these schemes versus the signal-to-noise ratio,the channel correlation level,and the element number-to-coherent time ratio,respectively,and discuss possible switching of the three schemes over these system parameters.At last,operation regions of the considered training overhead reduction schemes are shown in the plane characterized by the system parameters,which provides useful guidelines for practical scheme determination. | Jue Wang Shuaifeng Lu Jing Wang Zhenyu Jiang Rui Tang Ruifeng Gao Yingdong Hu Ye Li | 2022 | China Communications2022，19，12： | 0 |
| 20 | Petroleum geological features and hydrocarbon enrichment of Linhe Depression in Hetao Basin, NW China显示文摘Based on paleogeomorphology, drilling and seismic data, this paper systematically studies the structural and sedimentary evolution, source rock characteristics, reservoir characteristics and formation mechanism, hydrocarbon accumulation model and enrichment law in the Linhe Depression of the Hetao Basin, NW China. The Hetao Basin mainly experienced three stages of evolution, namely, weak extensional fault depression, strong extensional fault depression and strike-slip transformation, giving rise to four positive structural belts(Jilantai, Shabu, Nalinhu and Xinglong), which are favorable areas for oil and gas accumulation. The two main saline lacustrine source rocks, Lower Cretaceous Guyang Formation and Oligocene Linhe Formation, are characterized by high sulfur content, rich algae, early maturity, early expulsion, and wide oil generation window. The large structural transition belt in the intermountain area around the Hetao Basin controls the formation of large-scale braided river delta deposits, which are characterized by high quartz content(50%-76%), long-term shallow burial and weak compaction, low cement content, and good reservoir properties in delta front sandbody. The burial depth of the effective Paleogene reservoirs is predicted to reach 8000 m. Three hydrocarbon accumulation models, nose-uplift near sag, buried hill surrounding sag, fault nose near source rock, are constructed. The law of hydrocarbon accumulation in the Linhe Depression is finally clarified as follows: near-source around the depression is the foundation, high-quality thick reservoir is the premise, good tectonic setting and trap conditions are the key. | ZHANG Ruifeng HE Haiqing ZHU Qingzhong CHEN Shuguang LIU Xiheng DAN Weining HU Yanxu SHI Yulei ZHANG Yufei YU Haijun ZHANG Ximeng | 2023 | Petroleum Exploration and Development2023，50，4： | 0 |
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