Effects of the initiation position on the damage and fracture characteristics of linear-charge blasting in rock

To study the effects of the initiation position on the damage and fracture characteristics of linear-charge blasting, blasting model experiments were conducted in this study using computed tomography scanning and three-dimensional reconstruction methods. The fractal damage theory was used to quantify the crack distribution and damage degree of sandstone specimens after blasting. The results showed that regardless of an inverse or top initiation, due to compression deformation and sliding frictional resistance, the plugging medium of the borehole is effective. The energy of the explosive gas near the top of the borehole is consumed. This affects the effective crushing of rocks near the top of the borehole, where the extent of damage to Sections Ⅰ and Ⅱ is less than that of Sections Ⅲ and Ⅳ. In addition, the analysis revealed that under conditions of top initiation, the reflected tensile damage of the rock at the free face of the top of the borehole and the compression deformation of the plug and friction consume more blasting energy, resulting in lower blasting energy efficiency for top initiation. As a result, the overall damage degree of the specimens in the top-initiation group was significantly smaller than that in the inverse-initiation group. Under conditions of inverse initiation, the blasting energy efficiency is greater, causing the specimen to experience greater damage. Therefore, in the engineering practice of rock tunnel cut blasting, to utilize blasting energy effectively and enhance the effects of rock fragmentation, using the inverse-initiation method is recommended. In addition, in three-dimensional(3D) rock blasting, the bottom of the borehole has obvious end effects under the conditions of inverse initiation, and the crack distribution at the bottom of the borehole is trumpet-shaped. The occurrence of an end effect in the 3D linear-charge blasting model experiment is related to the initiation position and the blocking condition.

Three-dimensional positions of scattering centers reconstruction from multiple SAR images based on radargrammetry

A method and procedure is presented to reconstruct three-dimensional(3D) positions of scattering centers from multiple synthetic aperture radar(SAR) images. Firstly, two-dimensional(2D) attribute scattering centers of targets are extracted from 2D SAR images. Secondly, similarity measure is developed based on 2D attributed scatter centers' location, type, and radargrammetry principle between multiple SAR images. By this similarity, we can associate 2D scatter centers and then obtain candidate 3D scattering centers. Thirdly, these candidate scattering centers are clustered in 3D space to reconstruct final 3D positions. Compared with presented methods, the proposed method has a capability of describing distributed scattering center, reduces false and missing 3D scattering centers, and has fewer restrictionson modeling data. Finally, results of experiments have demonstrated the effectiveness of the proposed method.

New Three-Dimensional Assessment Model and Optimization of Acoustic Positioning System

This paper addresses the problem of assessing and optimizing the acoustic positioning system for underwater target localization with range measurement.We present a new three-dimensional assessment model to evaluate the optimal geometric beacon formation whether meets user requirements.For mathematical tractability,it is assumed that the measurements of the range between the target and beacons are corrupted with white Gaussian noise with variance,which is distance-dependent.Then,the relationship between DOP parameters and positioning accuracy can be derived by adopting dilution of precision(DOP)parameters in the assessment model.In addition,the optimal geometric beacon formation yielding the best performance can be achieved via minimizing the values of geometric dilution of precision(GDOP)in the case where the target position is known and fixed.Next,in order to ensure that the estimated positioning accuracy on the region of interest satisfies the precision required by the user,geometric positioning accuracy(GPA),horizontal positioning accuracy(HPA)and vertical positioning accuracy(VPA)are utilized to assess the optimal geometric beacon formation.Simulation examples are designed to illustrate the exactness of the conclusion.Unlike other work that only uses GDOP to optimize the formation and cannot assess the performance of the specified size,this new three-dimensional assessment model can evaluate the optimal geometric beacon formation for each dimension of any point in three-dimensional space,which can provide guidance to optimize the performance of each specified dimension.

Hydrogel-supported poly(L-lactic acid) and polystyrene microsphere-based three-dimensional culture systems for in vitro cell expansion

The in vitro expansion of stem cells is important for their application in different life science fields such as cellular tissue and organ repair.An objective of this paper was to achieve static cell culture in vitro through peptide hydrogel-supported microspheres(MSs).The peptides,with their gel-forming properties,microstructures,and mechanical strengths characterized,were found to have good support for the MSs and to be injectable.The internal structures of poly(L-lactic acid)microspheres(PLLA-MSs)and polystyrene microspheres(PS-MSs)made in thelaboratory were observed and statistically analyzed in terms of particle size and pore size,following which the co-cultured MSs with cells were found to have good cell adhesion.In addition,three-dimensional(3D)culturing of cells was performed on the peptide and microcarrier composite scaffolds to measure cell viability and cell proliferation.The results showed that the peptides could be stimulated by the culture medium to self-assembly form a 3D fiber network structure.Under the peptide-Ms composite scaffold-based cell culture system,further enhancement of the cell culture effect was measured.The peptide-Ms composite scaffolds have great potential for the application in 3D cell culture and in vitro cellexpansion.

Effects of lower body positive pressure treadmill on functional improvement in knee osteoarthritis:A randomized clinical trial study

BACKGROUND Knee joint pain and stiffness are the two main symptoms of knee osteoarthritis(OA)and thus restrict a patient’s activities,such as walking and walking up and downstairs.The lower body positive pressure(LBPP)treadmill as one of the emerging body weight support system devices brings new hope for exerciserelated rehabilitation for knee OA patients.AIM To investigate the biomechanical effects and the subjective clinical assessment of LBPP treadmill walking exercise when compared with conventional therapy in mild to moderate knee OA patients.METHODS Eighteen patients with mild-to-moderate knee OA were recruited in this randomized controlled trial(RCT)study.The eligible knee OA patients were randomly assigned to two groups:LBPP and control groups.The patients in the LBPP group performed an LBPP walking training program for 30 min/session per day,6 d per week for 2 wk whereas the patients in the control group performed walking on the ground for the same amount.All patients underwent clinical assessments and three-dimensional gait analysis at pre-and 2-wk post-treatment.RESULTS The Western Ontario and McMaster Universities Arthritis Index and visual analog scale scores in both the LBPP group and control group were found to decrease significantly at the post-treatment point than the pre-treatment point(LBPP:70.25±13.93 vs 40.50±11.86;3.88±0.99 vs 1.63±0.52;control:69.20±8.88 vs 48.10±8.67;3.80±0.79 vs 2.60±0.70,P<0.001).Moreover,compared with the control group,the LBPP group showed more improvements in walking speed(P=0.007),stride length(P=0.037),and knee range of motion(P=0.048)during walking,which represented more improvement in walking ability.CONCLUSION The results of our RCT study showed that the LBPP group has a greater effect on improving gait parameters than the conventional group,although there was no significant advantage in clinical assessment.This finding indicates that LBPP treadmill walking training might be an effective approach for alleviating pain symptoms and improving lower extremity locomotion in mild to moderate knee OA patients.

Local Scenario Perception and Web AR Navigation

This paper proposes a local point cloud map-based Web augmented reality(AR)indoor navigation system solution.By delivering the local point cloud map to the web front end for positioning,the real-time positioning can be implemented only with the help of the computing power of the web front end.In addition,with the characteristics of short time consumption and accurate positioning,an optimization solution to the local point cloud map is proposed,which includes specific measures such as descriptor de-duplicating and outlier removal,thus improving the quality of the point cloud.In this document,interpolation and smoothing effects are introduced for local map positioning,enhancing the anchoring effect and improving the smoothness and appearance of user experience.In small-scale indoor scenarios,the positioning frequency on an iPhone 13 can reach 30 fps,and the positioning precision is within 50 cm.Compared with an existing mainstream visual-based positioning manner for AR navigation,this specification does not rely on any additional sensor or cloud computing device,thereby greatly saving computing resources.It takes a very short time to meet the real-time requirements and provide users with a smooth positioning effect.

Synthesis of Hollow Three-Dimensional Channels LiNi_(0.5)Mn_(1.5)O_4 Microsphere by PEO Soft Template Assisted with Solvothermal Method

A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion.

超声脂质微泡与聚乳酸-聚乙醇酸共聚物纳米微球复合体在小鼠肝脏的定位释放

目的探讨新型超声微泡[荧光标记的聚乳酸-聚乙醇酸共聚物(PLGA)纳米微球与超声脂质微泡共价结合复合体]在一定声强的超声定位辐照下,PLGA纳米微球在小鼠体内肝脏组织的定位释放情况。方法用机械振荡法制备超声脂质微泡,双乳化法制备荧光标记的PLGA纳米微球,碳二亚胺法制备新型超声微泡。将实验小鼠分为3组:PLGA纳米微球组(NP组)、超声脂质微泡混合PLGA组(MB+NP组)、新型超声微泡组(MB-NP组),均用一定声强的超声经体表定点辐照小鼠肝脏。以激光共聚焦扫描荧光显微镜定性观察小鼠肝组织中PLGA纳米微球的分布。以DFY微泡测量软件对肝组织中荧光标记的PLGA纳米微球进行计数分析。结果 MB-NP组中的超声微泡周围布满数量不等的纳米微球,呈花环状,且PLGA纳米微球数量明显高于其他组(P均<0.01),MB+NP组的数量高于NP组(P<0.05)。结论新型超声微泡能够明显提高靶组织区内的PLGA纳米微球浓度,从而使PLGA携带的药物更多释放于靶组织中。

国产与进口注射用醋酸亮丙瑞林微球对绝经前激素受体阳性乳腺癌患者卵巢功能抑制的效果比较

目的比较国产与进口注射用醋酸亮丙瑞林微球对于绝经前激素受体阳性乳腺癌患者卵巢功能抑制(OFS)的效果。方法回顾性分析2018年6月至2019年6月于北京肿瘤医院接受注射用醋酸亮丙瑞林微球治疗的绝经前激素受体阳性乳腺癌患者54例,使用国产注射用醋酸亮丙瑞林微球患者作为观察组(27例),使用进口注射用醋酸亮丙瑞林微球患者作为对照组(27例)。比较2组患者治疗前及治疗后1、3、6、12个月雌二醇和卵泡刺激素(FSH)水平。结果2组患者在年龄、月经状态、体重指数、病理类型、治疗阶段及OFS合并药物方面差异均无统计学意义(均P>0.05)。治疗前,观察组雌二醇和FSH水平与对照组比较,差异均无统计学意义(均P>0.05)。所有患者均完成至少连续6个月的治疗,但部分患者未在全部时点进行性激素水平检测。治疗后1、3、6、12个月,观察组各时点激素检测患者为25、22、23、14例,雌二醇水平为(14±7)、(14±9)、(9±5)、(8±5)ng/L,FSH水平为(3.9±1.9)、(7.1±2.5)、(8.6±3.5)、(8.8±3.6)IU/L,对照组各时点激素检测患者为25、24、20、12例,雌二醇水平为(14±8)、(12±6)、(7±6)、(8±5)ng/L,FSH水平为(3.8±1.5)、(6.7±2.5)、(7.2±2.4)、(8.7±2.9)IU/L,2组治疗前及治疗后各时点雌二醇、FSH水平比较差异均无统计学意义(均P>0.05)。结论国产注射用醋酸亮丙瑞林微球对绝经前激素受体阳性乳腺癌患者的卵巢功能抑制作用与进口药相当,能有效降低患者性激素水平。

神经生长因子缓释微球移植对AD模型鼠基底前脑ChAT阳性神经元的保护作用

目的观察神经生长因子微球对AD模型鼠基底前脑ChAT阳性神经元的保护作用。方法采用双乳化技术制备神经生长因子缓释微球;切断SD大鼠左侧穹隆海马伞,基底前脑注射神经生长因子缓释微球;4周后,利用免疫组化法观察各组大鼠基底前脑ChAT阳性神经元变化。结果损伤组损伤侧的MS和VDB的ChAT阳性神经元大量减少,分别减少61.9%和51.4%;神经生长因子缓释微球治疗组损伤侧的ChAT阳性神经元得到明显的保护,MS和VDB细胞数分别下降20.60%和20.9%,明显高于损伤组损伤侧的ChAT阳性神经元存活数。结论神经生长因子缓释微球能够成功地将神经生长因子运载到脑内,神经生长因子缓释微球移植对AD模型鼠基底前脑ChAT阳性神经元有明显的保护作用。

用弯曲的纳米光纤定点输送和释放聚苯乙烯微球

提出了用弯曲的纳米光纤定点输送和释放聚苯乙烯微球的方法。纳米光纤是由标准单模光纤通过热熔法拉制而成,其直径为600 nm。由理论分析可知,激光在弯曲的纳米光纤中传输时,由于弯曲损耗的存在,当激光强度小于临界值,光力将不足以稳定地将微球捕获到光纤表面,并使之沿着光的传播方向运动时,微球将脱离光纤表面的束缚,被释放到水溶液中。该技术可用于沿光纤运动的微颗粒的定点输送和释放。

3D mesoporous rose-like nickel-iron selenide microspheres as advanced electrocatalysts for the oxygen evolution reaction

The development of efficient and stable non-noble metal-based electrocatalysts for the oxygen evolution reaction （OER） is one of the essential challenges for the upcoming hydrogen economy. Herein, three-dimensional （3D） mesoporous nickel iron selenide with rose-like microsphere architecture was directly grown on Ni foam via a successive two-step hydrotherrnal method. The unique 3D mesoporous rose-like morphology leads to a higher number of active sites as well as fast mass and electron transport through the entire electrode, and facilitates the release of 02 bubbles formed during the OER catalysis. As a result, the synthesized Ni0.76Fe0.24Se exhibits superior OER performances, with an ultralow overpotential of 197 mV needed to produce a current density of 10 mA.cm-2 in 1 M KOH, outperforming all transition metal selenide OER catalysts reported to date.

基于两台显微相机主动运动的微球孔姿态高精度测量方法

在一些微装配任务中,对微器件姿态的测量是至关重要的一步.带有微孔的球形微器件,特征较少,姿态测量困难.为此,本文提出一种基于双目显微视觉的微球孔姿态高精度测量方法.设计了微球/微孔边缘提取方法,实现了微球球心和微孔孔心的精确定位.通过对两路显微相机聚焦轴方向的标定,弥补了由相机聚焦轴运动引入的测量误差,提高了微球孔姿态的测量精度.通过两路倾斜正交的显微相机的主动运动,计算出微球孔姿态向量在相机运动坐标系中的分解角.根据相机运动坐标系与微球调整平台坐标系间的角度转换矩阵,将相机运动坐标系中的分解角转换为微球调整平台坐标系中的旋转角,从而计算出精确的微球孔姿态向量.实验结果表明,微球孔姿态测量的最大误差为0.08°,验证了本文方法的有效性.

去卷积数字全息重构的微球位置精确测量

微球三维位置的精确测量是单分子力谱测量技术中的关键。采用同轴数字全息技术对微球的三维位置进行测量。通过同轴数字全息显微系统采集一系列微球的全息图像,利用瑞利-索末菲传播原理对全息图进行三维重构,同时对重构光场进行去卷积运算,消除了散斑、离焦信号等噪音,并对微球球心纵向光场分布进行多项式拟合,提高了微球三维位置测量精度。实验表明,该方法不仅能够对全视场中的微球进行并行测量,而且能够对交叠微球进行测量,纵向分辨力达到2 nm,在生物单分子动力学、粒子图像测速技术等研究领域具有重要意义。

采用反义寡核苷酸聚乳酸可降解微球建立小鼠肾阳虚模型

目的:研究以反义寡核苷酸聚乳酸可降解微球建立小鼠肾阳虚模型的可行性。方法:取3周龄小鼠随机分为A、B、C、D、E组,每组6只,A组小鼠皮下注射0.2 ml生理盐水,其余组依次皮下注射反义寡核苷酸聚乳酸可降解微球0.1、0.2、0.4、0.8 mg/只。给药后,观察各组小鼠体质量和活动度,并于4周后采集其肝脏、肾上腺、脑等标本,采用实时定量聚合酶链反应(RT-PCR)法测定其中糖皮质激素受体(GR)表达情况。结果:除A组外,其余各组小鼠均见发育迟缓、体质量偏轻、活动减少、扎堆等肾阳虚证表现;与A组比较,其余组小鼠肝脏、肾上腺、脑中GR表达均降低,差异具有统计学意义(P<0.05)。结论:反义寡核苷酸聚乳酸可降解微球可抑制GR表达,GR表达被抑制的小鼠呈现肾阳虚证的临床表现。本方法可为小鼠肾阳虚模型的建立提供参考。

微球三维位置快速精密测量的新方法

为了实现对液态环境中微球三维位置的快速精密测量,尤其是轴向的测量分辨力和速度,基于离焦成像测量理论,结合并改进象限插值法和矢径投影算法,提出了一种新的方法,实现了对微球三维方向1nm测量分辨力的跟踪测量。该方法测量效率高,对单个粒子轴向位置的测量速率最快达到每秒上百帧甚至更高。进一步讨论了横向位置测量误差对轴向测量分辨力的影响,分析了轴向方向大范围的跟踪测量分辨力。通过和相同实验条件下的互相关方法对比,说明该方法在实际测量中具有可行性,在实现相同轴向测量分辨力的情况下测量效率更高。

离焦图像的互相关匹配法测量微球三维位置研究

为了提高在液态环境中对直径微米量级微球三维位置测量的空间分辨力,尤其是轴向的测量精度,将互相关算法对相似图像高精准的匹配特性与离焦成像法测量微球三维位置的思想相结合,讨论基于互相关匹配的离焦成像法测量微球三维位置的方法。实验表明,该方法对微球轴向位置4 min内连续定位的测量标准差约为0.64 nm,已实现对微球三维方向1 nm阶跃变化的分辨测量,这在生物单分子动力学、粒子图像测速技术等研究领域具有重要意义。相同实验条件下,与同轴数字全息显微术对微球三维位置的对比测量和分析也初步说明了该方法在实际测量应用中的可行性与高精度的特点。

Numerical Assessing Experiments on the Individual Component Impact of the Meteorological Observation Network on the "July 2000" Torrential Rain in Beijing

In an effort to assess the impact of the individual component of meteorological observations （ground-based CPS precipitable water vapor, automatic and conventional meteorological observations） on the torrential rain event in 4-5 July 2000 in Beijing （with the 24-h accumulated precipitation reaching 240 mm）, 24-h observation system experiments are conducted numerically by using the MM5/WRF 3DVAR system and the nonhydrostatic MM5 model. Results indicate that, because the non-conventional GPS observations are directly assimilated into the initial analyses by 3DVAR system, better initial fields and 24-h simulation for the severe precipitation event are achieved than those under the MM5/Litter_R objective analysis scheme. Further analysis also shows that the individual component of meteorological observation network plays their special positive role in the improvement of initial field analysis and forecasting skills. 3DVAR scheme with or without radiosonde and pilot observation has the most significant influence on numerical simulation, and automatic and conventional surface meteorological observations rank second. After acquiring the supplement information from the other meteorological observations, the ground-based GPS precipitable water vapor data can more obviously reflect initial field assimilation and precipitation forecast. By incorporating the groundbased CPS precipitable water vapor data into the 3DVAR analyses at the initial time, the threat scores （TS） with thresholds of 1, 5, 10, and 20 mm are increased by 1%-8% for 6- and 24-h accumulated precipitation observations, respectively. This work gives one helpful example that assesses the impact of individual component of the existing meteorological observation network on the high influence weather event using 3DVAR numerical system.

Real-time dynamic system to path tracking and collision avoidance for redundant robotic arms

An dynamic system for real-time obstacle avoidance path planning of redundant robots is constructed in this paper. Firstly, the inter-frame difference method is used to identify the moving target and to calculate the target area, then on the basis of color features and gradient features extracted from the target area, the feature fusion Cam-Shift mean shift algorithm is used to track target, improving the robustness of the tracking algorithm. Secondly, a parallel two-channel target identification and location method based on binocular vision is proposed, updating the target＇s three-dimensional information in real time. Then, a dynamic collision-free path planning method is implemented： the safety rods are removed through the intersection test, and the minimum distance is derived directly by using the coordinate values of the target in the local coordinate system of the rod. On this basis, the obstacle avoidance gain and escape velocity related to the minimum distance is established, and obstacle avoidance path planning is implemented by using the zero space mapping matrix of redundant robot. Experiments are performed to Study the efficiency of the proposed system.

多孔陶瓷微球在分枝杆菌快速培养中的应用

目的筛选对细菌生长具有促进作用的多孔陶瓷微球,并研究多孔陶瓷微球应用于分枝杆菌培养方面的价值,改变分枝杆菌特别是生长速度缓慢分枝杆菌的培养方式。方法制备平均孔径大小不同的陶瓷微球,进行细菌生长无害化处理,将处理后的的孔径不同的多孔陶瓷微球添加到分枝杆菌培养液中,比较不同培养状态下分枝杆菌的阳性报告时间;并用临床标本比较添加多孔陶瓷微球培养液与不添加多孔陶瓷微球培养液阳性报告时间的差异。结果添加多孔陶瓷微球对生长速度较快的分枝杆菌影响不明显,对生长速度缓慢的结核分枝杆菌有明显的促进作用,在临床标本考核中,可以提高临床标本的阳性平均报告时间。结论分枝杆菌培养液内添加多孔陶瓷微球可以加快分枝杆菌的阳性报告时间。