Channel Estimation and Throughput Evaluation for 5G Wireless Communication Systems in Various Scenarios on High Speed Railways

The fifth generation （5G） wireless communication is currently a hot research topic and wireless communication systems on high speed railways （HSR） are important applications of 5G technologies. Existing stud- ies about 5G wireless systems on high speed railways （HSR） often utilize ideal channel parameters and are usually based on simple scenarios. In this paper, we evaluate the down- link throughput of 5G HSR communication systems on three typical scenarios including urban, cutting and viaduct with three different channel estimators. The channel parameters of each scenario are generated with tapped delay line （TDL） models through ray-tracing sim- ulations, which can be considered as a good match to practical situations. The channel estimators including least square （LS）, linear minimum mean square error （LMMSE）, and our proposed historical information based ba- sis expansion model （HiBEM）. We analyze the performance of the HiBEM estimator in terms of mean square error （MSE） and evaluate the system throughputs with different channel estimates over each scenario. Simulation results are then provided to corroborate our proposed studies. It is shown that our HiBEM estimator outperforms other estimators and that the sys-tem throughput can reach the highest point in the viaduct scenario.

聚合物/镓基液态金属复合材料的研究及应用进展

液态金属(LM)是一种在常温下呈液态,由金属或其合金掺入改性剂复合而成的材料。由于兼具金属优秀的导电性、导热性和流体的流动性,近年来液态金属成为材料领域内的研究热点,尤其是在柔性电子应用领域备受关注。文中主要以镓基液态金属为描述对象,综述了液态金属主要特性,分析了液态金属复合材料聚合物基体的选择情况,介绍了液态金属柔性电子材料的制备方法以及主要应用背景。最后,总结了液态金属的研究现状并展望了未来的发展前景与面临的挑战。

A fluid flow model in the lacunar-canalicular system under the pressure gradient and electrical field driven loads

The lacunar-canalicular system(LCS)is acknowledged to directly participate in bone tissue remodeling.The fluid flow in the LCS is synergic driven by the pressure gradient and electric field loads due to the electro-mechanical properties of bone.In this paper,an idealized annulus Maxwell fluid flow model in bone canaliculus is established,and the analytical solutions of the fluid velocity,the fluid shear stress,and the fluid flow rate are obtained.The results of the fluid flow under pressure gradient driven(PGD),electric field driven(EFD),and pressure-electricity synergic driven(P-ESD)patterns are compared and discussed.The effects of the diameter of canaliculi and osteocyte processes are evaluated.The results show that the P-ESD pattern can combine the regulatory advantages of single PGD and EFD patterns,and the osteocyte process surface can feel a relatively uniform shear stress distribution.As the bone canalicular inner radius increases,the produced shear stress under the PGD or P-ESD pattern increases slightly but changes little under the EFD pattern.The increase in the viscosity makes the flow slow down but does not affect the fluid shear stress(FSS)on the canalicular inner wall and osteocyte process surface.The increase in the high-valent ions does not affect the flow velocity and the flow rate,but the FSS on the canalicular inner wall and osteocyte process surface increases linearly.In this study,the results show that the shear stress sensed by the osteocyte process under the P-ESD pattern can be regulated by changing the pressure gradient and the intensity of electric field,as well as the parameters of the annulus fluid and the canaliculus size,which is helpful for the osteocyte mechanical responses.The established model provides a basis for the study of the mechanisms of electro-mechanical signals stimulating bone tissue(cells)growth.

Depth determination of the Moho interface beneath the Tibetan plateau and other areas of China

We apply the adaptive moving window method of Sun et al. to the most recent catalog data and the data recorded by portable stations to construct the velocity structure of the crust and upper mantle, and to determine the depth of the Moho interface beneath the Tibetan plateau and other areas of China. We first select 2 600 locations in the study region with 1° intervals, then at each location invert for a five-layer 1-D P-wave velocity model from the surface down to the uppermost mantle by performing a Monte Carlo random search. The Moho depth at each location is then determined, and the Moho interface beneath the study region is obtained through proper interpolation with certain smoothing. Compared to depths obtained by previous studies, our results show more accurate Moho depths in the Tibetan plateau, Tianshan region and other areas of the study region.

Intelligent hydrogels for treating malignant melanoma

Malignant melanoma(MM)is an extremely aggressive and fatal form of skin cancer that primarily affects the bottom layer of the epidermis and is associated with poor clinical outcomes.Early-stage MM is typically treated through surgical removal,while chemotherapy and radiotherapy are common conventional treatment options that come with harmful side effects.Emerging therapies such as immunotherapy,photodynamic therapy,biologic therapy,and photothermal therapy present hopeful options for treatment due to their effective and secure drug delivery methods.To address the limitations of current treatment options,advanced methods of drug delivery for subcutaneous MM are being developed,with hydrogels emerging as a promising alternative.To date,significant advancements have been made in the treatment of MM through the use of hydrogels-based drug delivery systems through focal plastering,injection,implantation,and microneedles.Recent research on hydrogel-based drug delivery systems that integrate multiple therapies for the treatment of subcutaneous MM is discussed in this review.

水陆两栖飞机灭火飞行仿真系统构建与仿真

大型固定翼灭火飞机是应对森林火灾最有效的工具之一。首先针对中国缺少大型灭火飞机投水灭火飞行仿真系统的现状,基于水陆两栖灭火飞机投水灭火任务流程,对投汲水灭火仿真任务子系统、灭火飞机投汲水灭火仿真场景构建、投水数据处理与灭火效能评估方法进行了研究,设计和构建了一种水陆两栖飞机灭火飞行仿真系统,实现了大型灭火飞机投水灭火任务全流程飞行仿真。其次通过使用K-S检验方法对仿真飞行投水数据与真实飞行试验投水数据进行统计学检验,证实了本仿真系统具有较高的仿真真实度。最后还研究了在灭火飞行仿真中投水速度和投水高度对投水覆盖面积、投水均匀度和投水有效利用率3个灭火效能参数的影响,为灭火飞机指挥员进行投水方案的制订提供了支撑。本文成果对于提高灭火飞机飞行员培训效率,节省培训费用,节约灭火飞机飞行试验费用,缩短飞行试验的时间,加快中国森林航空消防力量建设具有参考意义。

四棱锥型钉头内固定系统用于治疗Pauwels Ⅲ型股骨颈骨折

目前治疗股骨颈骨折的临床选择包括传统的空心螺钉内固定、动力髋螺钉内固定、髋关节置换和最新的股骨颈系统(FNS).股骨颈系统因表现出优良的机械性能而受到关注和欢迎.在本研究中,采用三维有限元法对股骨颈系统进行了分析,并根据分析结果对四种不同螺钉头的新型内固定进行了优化设计.在对FNS的分析结果中,植入股骨头内的螺钉部分受力较小,移位较大,由于这里使用了两个螺钉,材料消耗增加.钢板和锁定螺钉的结构使内固定物和股骨上的内应力更加均匀.在四种类型的螺钉头内固定中,四棱锥型螺钉头内固定的机械性能更为均衡.在四棱锥型螺钉头内固定与股骨颈系统的比较中,四棱锥型螺钉头内固定的应力和位移数据都显示出其优越性.股骨颈系统的单一尺寸设计对股骨尺寸偏离平均值较大的人群没有起到最佳的治疗效果,可调节长度和角度的新型内固定可以得到更广泛的应用.