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Exhaustive review of acceleration strategies for Monte Carlo simulations in photon transit

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Journal of Innovative Optical Health Sciences 2024年第5期17卷 5-21页

作者： Louzhe Xu Zijie zhu Ting Li Institute of Biomedical Engineering Chinese Academy of Medical Sciences&Peking Union Medical College Tianjin 300192 P.R.China

Monte Carlo simulation techniques have become the quintessence and a pivotal nexus of inquiry in the realm of simulating photon movement within biological *** the stochastic sampling of tissue archetypes delineated by explicit optical characteristics,Monte Carlo simulations possess the theoretical capacity to render unparalleled accuracy in the depiction of exceedingly intricate ***,the quintessential challenge associated with Monte Carlo simulation methodologies resides in their extended computational duration,which significantly impedes the re¯nement of their ***,this discourse is speci¯cally dedicated to exploring innovations in strategies and technologies aimed at expediting Monte Carlo *** delves into the foundational concepts of various acceleration tactics,evaluates these strategies concerning their speed,accuracy,and practicality,and amalgamates a comprehensive overview and critique of acceleration methodologies for Monte Carlo ***,the discourse envisages prospective trajectories for the employment of Monte Carlo techniques within the domain of tissue optics.

关键词： Medical optics photon transport simulation Monte Carlo simulation acceleration

Effect of confining pressure on rock breaking by high-pressure waterjet-assisted TBM

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Underground Space 2024年第5期18卷 151-161页

作者： Chen Xu Yujie zhu Xiaoli Liu Fei Chen Min zhu Enzhi Wang Sijing Wang School of Resource and Environment Engineering Wuhan University of TechnologyWuhan 430070China Changjiang Institute of Survey PlanningDesign and ResearchWuhan 430010China State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China Key Laboratory of Geotechnical Mechanics and Engineering of Ministry of Water Resources Wuhan 430010China

High-pressure waterjet-assisted tunnel boring machine(WTBM)is an efficient method for improving the tunneling performance of a tunnel boring machine(TBM)and reducing the wear of its disc cutters in hard rock with high *** pressure directly affects the efficiency of rock breaking and the configuration of the disc *** this study,we evaluated the effect of confining pressure on WTBM rock breaking by developing a self-designed and manufactured experimental system,including confining pressure loading,TBM disc-cutter penetration,and high-pressure *** macro fracture,acoustic emission(AE),peak normal force drop,and specific energy(SE)were analyzed for four different confining pressures(10,20,30,and 35 MPa).The results showed that the cutting depth of the waterjet increased linearly as the waterjet pressure increased and decreased with the gradual increase in the nozzle moving *** expansion and development of cracks formed rock debris,and the size of the rock fragments decreased with an increase in confining *** the waterjet pressure was 280 MPa,the nozzle moving velocity was 800 mm/min and the kerf space was 75 mm,which indicated that the confining pressure,which was 23.16 MPa,minimized the cutting SE under this ***,regardless of the confining pressure,the maximum normal force of WTBM was less than that of a TBM,whereas the SE of WTBM was less than that of complete TBM cutting mode(CTCM).The average force drop and average drop rate of SE were approximately 25%,and 80%,*** results of this study can inspire the design and mechanism of a TBM assisted by a high-pressure waterjet.

关键词： Waterjet Tunnel boring machine(TBM) Confining pressure Specific energy Force drop

Chemoselective epoxidation of electron-deficient olefins with molecular oxygen via conjugated olefins epoxidation and BHT hydroxylation

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Science China Chemistry 2024年第9期67卷 3012-3018页

作者： Jia Nie Huanfeng Jiang Chuanle zhu School of Chemistry and Chemical Engineering Key Lab of Functional Molecular Engineering of Guangdong ProvinceSouth China University of TechnologyGuangzhou 510640China Guangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced Manufacturing South China University of TechnologyGuangzhou 510640China

The chemoselective epoxidation of electron-deficient olefins in the presence of electron-rich alkene moieties is *** chemoselective epoxidation strategy undergoes a conjugated olefin epoxidation and BHT hydroxylation process to give various useful oxiranes in high yields,especially for the 2-substituted ***,this protocol features mild conditions,is transition-metal free,operationally simple,and gram-scalable,and tolerates diverse functional *** candidate HSD-16 is synthesized smoothly by this *** studies indicate molecular oxygen is the terminal oxidant and the O-source of the oxiranes.

关键词： chemoselective epoxidation alkene fluorine molecular oxygen

Contribution of high-latitude permafrost regions in the Northern Hemisphere to global wildfire carbon emissions

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Science China Earth Sciences 2024年第10期67卷 3239-3251页

作者： Xingru zhu Xiyan XU Gensuo JIA Key Laboratory of Regional Climate-Environment for East Asia Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China

Wildfires are major disturbances in permafrost ecosystems, with increasing frequency and intensity in recent years. In permafrost regions, wildfires not only burn surface and subsurface organic matter but also accelerate permafrost thawing,releasing significant amounts of greenhouse gases such as carbon dioxide and methane into the atmosphere. However, the contribution of high-latitude permafrost regions in the Northern Hemisphere to global wildfire carbon emissions remains poorly understood. This study integrates remote sensing data and ground observations to analyze the contributions of aboveground and belowground fuel combustion in high-latitude permafrost regions to global wildfire carbon emissions from 2002 to 2020, as well as the spatiotemporal variations in these contributions. Our findings indicate that permafrost regions contribute approximately11.96% of global wildfire carbon emissions, with aboveground emissions accounting for approximately 3.94% of global aboveground emissions and belowground emissions contributing approximately 63.57% of global belowground emissions. The contribution of high-latitude permafrost regions to global emissions peaked in July and August, whereas the continuous permafrost zones(areas with more than 90% permafrost coverage) showed the most significant increase in June and July. The contributions of both aboveground and belowground emissions from high-latitude permafrost regions to global wildfire emissions have been increasing, primarily due to the reduction in global wildfire emissions, in contrast with the rising emissions from wildfires in high-latitude permafrost regions. This study highlights the significant role of wildfires, particularly the combustion of belowground biomass in high-latitude permafrost regions, in global carbon emissions. The decomposition and combustion of organic carbon in permafrost regions due to wildfires release more greenhouse gases into the atmosphere, potentially amplifying the positive feedback

关键词： Wildfire Permafrost Carbon emissions Climate change Belowground fuel consumption

Camera,LiDAR,and IMU Based Multi-Sensor Fusion SLAM:A Survey

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Tsinghua Science and Technology 2024年第2期29卷 415-429页

作者： Jun zhu Hongyi Li Tao Zhang Department of Automation Tsinghua UniversityBeijing 100084China

In recent years,Simultaneous Localization And Mapping(SLAM)technology has prevailed in a wide range of applications,such as autonomous driving,intelligent robots,Augmented Reality(AR),and Virtual Reality(VR).Multi-sensor fusion using the most popular three types of sensors(e.g.,visual sensor,LiDAR sensor,and IMU)is becoming ubiquitous in SLAM,in part because of the complementary sensing capabilities and the inevitable shortages(e.g.,low precision and long-term drift)of the stand-alone sensor in challenging *** this article,we survey thoroughly the research efforts taken in this field and strive to provide a concise but complete review of the related ***,a brief introduction of the state estimator formation in SLAM is ***,the state-of-the-art algorithms of different multi-sensor fusion algorithms are *** we analyze the deficiencies associated with the reviewed approaches and formulate some future research *** paper can be considered as a brief guide to newcomers and a comprehensive reference for experienced researchers and engineers to explore new interesting orientations.

关键词： multi-sensor fusion Simultaneous Localization And Mapping(SLAM) navigation localization

L^(*)—An index for evaluating long range performance of autonomous underwater vehicles(AUVs)

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Friction 2024年第10期12卷 2205-2221页

作者： Manfu zhu Liran MA Jianbin LUO State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

Autonomous underwater vehicles(AUVs)have various applications in both military and civilian fields.A wider operation area and more complex tasks require better overall range performance of ***,until recently,there have been few unified criteria for evaluating the range performance of *** the present work,a unified range index,i.e.,L^(*),considering the cruising speed,the sailing distance,and the volume of an AUV,is proposed for the first time,which can overcome the shortcomings of previous criteria using merely one single parameter,and provide a uniform criterion for the overall range performance of various *** constructing the expression of the L^(*)index,the relevant data of 49 AUVs from 12 countries worldwide have been collected,and the characteristics of the L^(*)range index in different countries and different categories were compared and ***,by analyzing the complex factors affecting the range index,methods to enhance the L^(*)range index value,such as efficiency enhancement and drag reduction,have been introduced and *** this condition,the work proposes a unified and scientific criterion for evaluating the range performance of AUVs for the first time,provides valuable theoretical insight for the development of AUVs with higher performance,and then arouses more attention to the application of the cutting-edge superlubricity technology to the field of underwater vehicles,which might greatly help to accelerate the coming of the era of the superlubricitive engineering.

关键词： autonomous underwater vehicles(AUVs) range performance range index superlubricity drag reduction

The Effect of Moisture in Different Altitude Layers on the Eastward Propagation of MJO

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Journal of Meteorological Research 2024年第3期38卷 437-452页

作者： Xiaoyu zhu Zhong ZHONG Yimin zhu Yunying LI Yijia HU Yao HA College of Meteorology and Oceanography National University of Defense TechnologyChangsha410000China Key Laboratory for Virtual Geographic Environment School of Geography ScienceNanjing Normal UniversityNanjing210023China Jiangsu Collaborative Innovation Center for Climate Change School of Atmospheric SciencesNanjing UniversityNanjing210000China

In this study,driven by ERA5 reanalysis data,the Weather Research and Forecasting(WRF)version 4.0 was used to investigate the eastward propagation of the Madden-Julian oscillation(MJO)in the tropical atmosphere during December-February(DJF)of 2007/*** experiment with 11 cumulus parameterization schemes respectively shows that the Grell 3D scheme is one of several worse ones in describing MJO *** addition,still by use of the Grell 3D scheme,four nudging assimilation experiments for water vapor in all model vertical layers(Ndg_all),lower layers(Ndg_low),middle layers(Ndg_mid),and upper layers(Ndg_upp)were *** is found that when the water vapor in the model approaches to the observed value,the model performance for MJO activities is improved *** the four nudging simulations,Ndg_all certainly performs *** Ndg_mid is important for the MJO-filtered profiles related to moisture,Ndg_low and Ndg_upp exhibit superiority to Ndg_mid in simulating MJO eastward ***_low has advantages when MJO features are represented by zonal wind at 850 hPa and precipitation because the lower-level MJO-filtered moisture is conducive to the existence of lower-level condensational heating to the east of the MJO convective ***_upp performs better when describing the MJO eastward propagation features by outgoing longwave radiation(OLR)since it can capture the moisture and cloud top temperature of deep convection associated with MJO,as well as front Walker *** results suggest that the lower-level moisture is more important in regulating the MJO eastward propagation,and the observed maximum MJO-filtered moisture in the middle troposphere might be a phenomenon accompanying the MJO deep convection,but not a factor controlling its eastward propagation.

关键词： Madden-Julian oscillation(MJO) nudging technique Weather Research and Forecasting(WRF)model vertical moisture structure

Isolation performances and optimization of triple quasi-zero stiffness isolators

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Science China(Physics,Mechanics & Astronomy) 2024年第7期67卷 124-141页

作者： Yuntian Zhang Guangnan zhu Qingjie Cao School of Astronautics Harbin Institute of TechnologyHarbin 150001China

In this paper,triple quasi-zero stiffness(QZS)passive vibration isolators whose restoring force curve has a three-stage softening effect are ***-coupled SD oscillators with three independent geometrical parameters are used as negative stiffness mechanisms to achieve QZS characteristics at the origin and symmetrical positions on both sides of the *** performances of different triple QZS isolators are analyzed to show influences of the selection of QZS regions away from the origin on the range of isolation *** optimizations of system parameters are carried out to get a larger range of small restoring force regions and small stiffness *** performances of two triple QZS isolators are discussed to show the influence of different Pareto optimization solutions through the comparisons with single and double QZS *** showed that triple QZS isolators have both the advantages of single and double QZS isolators which results in better isolation performances under both small and large excitation *** improvement in isolation performances for triple QZS isolators is found with the decrease in average stiffness due to the appearance of two symmetrical QZS regions away from the *** displacements of QZS regions away from the origin result in better isolation performances when excitation amplitude is large,and triple QZS characteristics are similar to double QZS isolators at this *** restoring forces of QZS regions away from the origin lead to better isolation performances when excitation amplitude is small,and triple QZS characteristics are similar to single QZS isolators at this *** with the decrease in average stiffness,the improvement of isolation performances shows a hysteresis phenomenon due to the difference between static and dynamic characteristics.

关键词： triple quasi-zero stiffness vibration isolation Pareto optimization force transmissibility geometrical nonlinear

Discovery of strong bulk Dzyaloshinskii-Moriya interaction in composition-uniform centrosymmetric magnetic single layers

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Science China(Physics,Mechanics & Astronomy) 2024年第2期67卷 174-180页

作者： Lijun zhu David Lujan Xiaoqin Li State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of SciencesBeijing 100083China College of Materials Science and Opto-Electronic Technology University of Chinese Academy of SciencesBeijing 100049China Department of Physics Center for Complex Quantum SystemsUniversity of Texas at AustinAustin 78712USA

Dzyaloshinskii-Moriya interaction(DMI)is the key ingredient of chiral spintronic phenomena and the emerging technologies based on such phenomena.A nonzero DMI usually occurs at magnetic interfaces or within non-centrosymmetric single ***,we report the observation of a strong unexpected DMI within a centrosymmetric polycrystalline ferromagnet that has neither a crystal inversion symmetry breaking nor a composition *** DMI is a bulk effect,increases with the thickness of the magnetic layer,and is insensitive to the symmetry of the interfaces or the neighboring *** observe a total DMI strength that is a factor of>2 greater than the highest interfacial DMI in the *** DMI most likely arises from the strong spin-orbit coupling,strong orbital hybrization,and a“hidden”long-range asymmetry in the *** discovery of the strong unconventional bulk DMI in centrosymmetric,composition-uniform magnetic single layers provides fundamental building blocks for the emerging field of spintronics and will stimulate the exploitation of unconventional spin-orbit phenomena in a wide range of materials.

关键词： Brillouin light scattering Dzyaloshinskii-Moriya interaction spin wave