虚拟现实技术的研究现状、热点与趋势

近年来,在以科技创新等为大背景的新时代,国内对虚拟现实技术的研究已成为热点。文章选择用Citespace可视化分析软件对2015—2020年CNKI数据库中刊载的虚拟现实相关文献的数据来源进行统计分析。文章以定量研究的方法,基于软件提供的知识图谱系统对所选文献进行处理,综述虚拟现实技术在教育、医疗、军事等各大领域的研究现状、热点及趋势,并多角度分析虚拟现实的研究趋势,以期为相关研究人员提供一定的参考和借鉴。

Review of renal cell carcinoma and its common subtypes in radiology

Representing 2%-3% of adult cancers, renal cell carcinoma(RCC) accounts for 90% of renal malignancies and is the most lethal neoplasm of the urologic system. Over the last 65 years, the incidence of RCC has increased at a rate of 2% per year. The increased incidence is at least partly due to improved tumor detection secondary to greater availability of high-resolution cross-sectional imaging modalities over the last few decades. Most RCCs are asymptomatic at discovery and are detected as unexpected findings on imaging performed for unrelated clinical indications. The 2004 World Health Organization Classification of adult renal tumors stratifies RCC into several distinct histologic subtypes of which clear cell, papillary and chromophobe tumors account for 70%, 10%-15%, and 5%, respectively. Knowledge of the RCC subtype is important because the various subtypes are associated with different biologic behavior, prognosis and treatment options. Furthermore, the common RCC subtypes can often be discriminated non-invasively based on gross morphologic imaging appearances, signal intensity on T2-weighted magnetic resonance images, and the degree of tumor enhancement on dynamic contrast-enhanced computed tomography or magnetic resonance imaging examinations. In this article, we review the incidence and survival data, risk factors, clinical and biochemical findings, imaging findings, staging, differential diagnosis, management options and posttreatment follow-up of RCC, with attention focused on the common subtypes.

Accurate Shortwave Radiation Simulation with a Two-Layer Aerosol Model in Xinjiang Region

To harness the rich solar energy resources in Xinjiang Region of Northwest China,this study tries to address the issue of lack of downward surface shortwave radiation(DSSR)observations and the need to improve the accuracy of satellite retrieval and numerical simulation of DSSR under varied sky and meteorological conditions.(1)A two-layer aerosol model specific to Xinjiang was developed to capture the vertical distributions of aerosols based on multiple data sources including lidar,GPS sounding,ground meteorological observations,and profiles from the ECMWF reanalysis version 5(ERA5)data.The results show that the ERA5/PBLH(planetary boundary layer height)and ERA5/ALH(aerosol layer height)could be used to establish the two-layer aerosol model and characterize the vertical distribution of aerosols in Xinjiang Region.(2)Using the Santa Barbara Discrete Atmospheric Radiative Transfer(SBDART)model,a localized inverse model of clear-sky DSSR was established.After parameter adjustment and using the optimal combination of input parameters for DSSR simulation together with the two-layer aerosol model,the model-simulated DSSR(DSSRSBD)under clear-sky conditions improved significantly compared to the initial results,with all fitting indices greatly improved.(3)In addition,the study demonstrated that the impact of the two-layer aerosol model on DSSR was more pronounced under dust conditions than clear-sky conditions.(4)Using the localized clear-sky DSSR inversion model and its required parameters,simulations were also conducted to capture the spatiotemporal distribution of DSSR under clear-sky conditions in Xinjiang from 2017 to 2019.The annual average DSSR_(SBD)under clear-sky conditions in Xinjiang during 2017–2019 was 606.78 W m^(-2),while DSSR from CERES(DSSR_(CER))under the same conditions was generally higher(703.95 W m^(-2)).(5)It is found that satellite remote sensing products experienced data loss in high-altitude snow areas,where numerical simulation technology could serve as a valuable complement.

改革前后中国社保资金筹集和使用模式的比较分析

近年以来,中国社保资金运营的可持续性受到了来自学界和社会的广泛质疑。通过将本研究的观测对象分为改革前和改革后两个时期,对这两个时期的社保资金运营进行综述,并比较改革前后资金筹集、分配和循环等关键机制。本研究对严重动摇社保资金可持续性的'空账'(转制成本)的出现进行了详细的讨论和解析,并发现改革后'统账结合'的资金累加型社保资金累加模式的运作并未按照其设计的初衷运转,其实质上依旧延续了'统收统支'的运作模式。通过对改革前后的社保资金运营模式的可持续性同经济和社会发展间关系的综合检验,评估了两种模式的成效和资金使用效果,并对改革后社保资金走势向好的真正原因做了探究,还借此检验了发达国家普适理论对中国案例的解释力,在此基础上对中国社保资金运作模式的改进提出了相应的建议。

两岸公共养老保障制度的比较分析

公共养老保障在一国社会保障体系各组成部分中通常占最大权重,其制度设计和运转情况同该国的各项政治经济和社会指标的契合性及其运营的有效性一直是相关学界探讨的主题之一。近年来,虽然两岸在政治制度上还存在着很大差异,但是两岸在各个关键的经济和社会指标上却不断趋同。本研究对两岸公共养老保障体制的演化和现行制度进行了全面综述,并以两岸同样面临的人口老龄化加剧和经济增速放缓为前提,对两岸现行养老保障制度的有效性进行综合评估,并在此基础上,对作为本研究所要解决的核心问题的'两岸政治因素在养老保障制度设计和运营中的作用'进行了实证分析。最终,检验并证明了两岸政治制度差异对两岸养老保障发展演化的决定性影响。

Upconversion nanoparticles for super-resolution quantification of single small extracellular vesicles

Although small EVs(sEVs)have been used widely as biomarkers in disease diagnosis,their heterogeneity at single EV level has rarely been revealed.This is because high-resolution characterization of sEV presents a major challenge,as their sizes are below the optical diffraction limit.Here,we report that upconversion nanoparticles(UCNPs)can be used for super-resolution profiling the molecular heterogeneity of sEVs.We show that Er3+-doped UCNPs has better brightness and Tm3+-doped UCNPs resulting in better resolution beyond diffraction limit.Through an orthogonal experimental design,the specific targeting of UCNPs to the tumour epitope on single EV has been cross validated,resulting in the Pearson’s R-value of 0.83 for large EVs and~65%co-localization double-positive spots for sEVs.Furthermore,super-resolution nanoscopy can distinguish adjacent UCNPs on single sEV with a resolution of as high as 41.9 nm.When decreasing the size of UCNPs from 40 to 27 nm and 18 nm,we observed that the maximum UCNPs number on single sEV increased from 3 to 9 and 21,respectively.This work suggests the great potentials of UCNPs approach“digitally”quantify the surface antigens on single EVs,therefore providing a solution to monitor the EV heterogeneity changes along with the tumour progression progress.

Fatigue crack growth behavior of 2624-T39 aluminum alloy with different grain sizes

The microstructure of 2624-T39 aluminum alloy was analyzed by means of metallographic(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM). The effects of different microstructure characteristics on the tensile properties and fatigue crack growth rate of 2624-T39 aluminum alloy were studied.Results showed that the grain size of the alloy was a typical fiber structure along the rolling direction, and the main second phase was the A_(l2)CuMg phase. The grain size of the alloy had an obvious influence on the fatigue crack growth rate, and the alloy showed a lower fatigue crack growth rate due to the larger grain size. The crack initiation zone on the fracture surface of alloys with lower fatigue crack growth rate was relatively rough, the crack propagation zone had obvious fatigue striations, and the transient fracture zone had a large number of smaller dimples.

On the Integrability of Strictly Convex Billiard Tables with Boundaries Close to Ellipses with Small Eccentricities

In this paper,we introduce a new notion of integrability for billiard tables,namely,integrability away from the boundary.One key feature of our notion is that the integrable region could be disjoint from the boundary with a positive distance.We prove that if a strictly convex billiard table,whose boundary is a small perturbation of an ellipse with small eccentricity,is integrable in this sense,then its boundary must be itself an ellipse.

Optimizing hairy root production from explants of Phyllanthus hainanensis,a shrub used for traditional herbal medicine

Phyllanthus hainanensis is a shrub that has been used in traditional herbal medicine.It has great pharmaceutical potential for treating diseases such as cancer and diabetes.As a prerequisite for propagation of this species on a large scale,hairy roots in P.hainanensis were induced using Rhizobium rhizogenes and various factors affecting hairy root induction and growth evaluated.Seven factors were tested:(1)type of explant,(2)type of culture medium,(3)duration of pre-culture,(4)R.rhizogenes inoculum cell density,(5)duration of infection,(6)acetosyringone concentration in the culture medium,and(7)duration of incubation.The optimal protocol for hairy root induction and growth was:young shoots,pre-cultured in Y1 for 2 d,inoculated with R.rhizogenes broth with an OD600 of 0.6 for 20 min,and incubated for 3 d.Putative transgenic hairy roots were initially identified by morphology and then confirmed by polymerase chain reaction.Successful and optimal production of hairy roots is a critical prerequisite for industrial scale clonal propagation of P.hainanensis.Being able to cultivate the plant on a large scale will provide rapid and ready supply of the plant materials that can be used in herbal medicine and in scientific and industrial exploitation.