Balance Control and Energetics of Powered Exoskeleton-Assisted Sit-to-Stand Movement in Individuals With Paraplegic Spinal Cord Injury

Objective

To quantify the effects of initial hip angle and angular hip velocity settings of a lower-limb wearable robotic exoskeleton (WRE) on the balance control and mechanical energy requirements in patients with paraplegic spinal cord injuries (SCIs) during WRE-assisted sit-to-stand (STS).

Development of a positron-imaging detector with background rejection capability

Objective  Intra-operative probes have recently become important instruments in nuclear medicine. In such an application, the radiopharmaceutical F-18-fluorodeoxy glucose (FDG) is promising. For the FDG-guided surgery, we developed and tested a positron-imaging detector with background rejection capability. Methods  The detector consists of an array of phoswich scintillators, a multichannel position-sensitive photo-multiplier tube (PSPMT) and an electronic circuit. The scintillators and the PSPMT are encased in a tungsten shield and replaceable collimators are mounted on the top of the detector. Positrons are detected by the plastic scintillators while annihilation photons are detected by the BGOs. By employing a pulse-shape analysis, we can distinguish the true events (positrons) from background gamma events. The dimensions of each plastic scintillator are 2 mm x 2 mm x 3 mm and those of the BGO are 2 mm x 2 mm x 15 mm. These scintillators are optically coupled to each other and combined in an 8 x 8 array, which is optically coupled to a 1-inch square 8x8 multi-channel PSPMT via optical fibers. Position determination of the positrons is performed by 64-channel threshold circuits while the pulse shape analysis is applied for the summing signal. Results  The spatial resolution was measured by positioning an F-18 point source onto one pixel of the detector and found than the spillover to the neighbor pixel was less than 20%. The background count rate was less than 2 cps for a 20-cm diameter, 20-cm long cylinder phantom containing 3.7 MBq of F-18. Conclusion  These results indicated that the developed positron-imaging detector will be useful for FDG-guided surgery.     

Technical Challenges of Utilizing Ground Tire Rubber in Asphalt Pavements in the United States

At least 275 million scrap tires exist in stockpiles in the U.S. The practice of dumping scrap tires in landfills has been an environmental concern. To address this concern, many industries—and regional and national environmental protection agencies—have taken major initiatives to recycle scrap tires. One of the major uses of recycled scrap tires is in crumb rubber products, including rubberized asphalt. Rubberized asphalt is produced by blending ground tire rubber with asphalt to beneficially modify its properties for highway construction. The ground tire rubber (GTR) can be used either as part of the asphalt rubber binder (also known as asphalt rubber), seal coat, cap seal spray, joint and crack sealant or as substitute aggregate (rubber-modified asphalt concrete). Therefore, the largest single market for GTR is asphalt rubber, which consumes approximately 12 million tires, annually. Currently, several Departments of Transportation (DOTs) in the U.S. do not allow use of GTR in asphalt mixes. This is partly due to lack of information, laboratory test data and specifications or special provisions on the use of GTR in asphalt pavements. The current study was undertaken to summarize the available wealth of knowledge, identify research needs, and document the major findings of previous pertinent studies focused on GTR use in asphalt. Significant study findings—consisting of laboratory test results, field observations, and common practices—were documented, including: the use of GTR in asphalt mixes, wet and dry processes, characterization of hot mix asphalt (HMA) containing GTR and GTR performance when combined with virgin materials. In order to promote successful use of GTR, it is imperative to help DOTs develop specifications/special provisions for utilizing rubberized asphalt by collecting data, common practices and specifications utilized by other state DOTs. As a part of this effort, we conducted a survey of construction specifications used by different DOTs that currently allow the use of GTR in asphalt. Since some DOT practices are not readily available in the open literature, this survey proved to be an effective tool for gathering data on the current practices, methods and specifications associated with DOT use of GTR in asphalt pavement.     

Nordic Walking does not reduce the loading of the knee joint

The use of Nordic Walking (NW) as a rehabilitation modality has increased considerably. NW (walking with poles) is advocated as a healthy physical activity that reduces the load on the knees. Few studies using the techniques of NW exist, and the findings are contradictory. The aim of this study was to investigate whether NW reduces the loadings upon the knee joint compared with walking without poles (NP). Seven experienced female NW instructors volunteered. Three-dimensional gait analyses were performed. Internal flexor and extensor joint moments were calculated using an inverse dynamics approach and the knee joint compressive forces were calculated. No differences in compression or shear forces between NW and NP were found. The peak knee flexion angles were larger during NW (−32.5±6.0°) compared with NP (−28.2±4.2°). The hip range of motion (ROM) was significantly increased during NW (64.4±10.2°) compared with NP (57.8±9.7°); no differences in the knee and ankle joint ROM were observed. The changes in the joint angles were not followed by changes in the joint dynamics. The present study does not support the statement that NW reduces the load on the knees.     

Evaluation of Anthropogenic Substrate Variability Based on Non-Destructive Testing of Ground Anchors

The purpose of this paper is to describe the variability of soil rheological properties based on research carried out using load tests of ground anchors under complex geotechnical conditions. The heterogeneity of soil should always be considered when designing geotechnical constructions. In the present case, the earthwork created at the Warsaw Slope revealed an embankment of anthropogenic origin, located in a geologically and geomorphologically complex area of the Vistula valley slope. Excavation protection was anchored mainly in soils of anthropogenic origin. When the acceptance tests of the ground anchor were completed, the subsoil randomness was confirmed using nondirect, geostatistical methods. A standard solid rheological model with nonlinear fitting to the data was used. This model was established to describe the creeping activity of the ground anchor more accurately. The characteristics of man-made embankments were described using the parameters obtained with the rheological model of the subsoil.     

商河县生活垃圾无害化处理场库区杂填土地基处理

针对山东省商河县生活垃圾无害化处理场工程地质条件及垃圾堆载特点,介绍了地基处理方法的选用原则,根据地勘建议做水泥深层搅拌桩处理,与建筑常用的强夯法、换填法等处理方法进行综合分析比选,确定采用强夯法处理最为适合,并提出了具体的施工方法,对强夯后地基进行载荷试验检测,结果符合设计要求。     

不同产地、不同海拔地区的甘松地上部分无机元素的多维统计分析

目的:比较不同产地甘松药材地上部分的无机元素含量差异,分析其无机元素分布特征,为评价市场上流通的甘松全草统是否科学、合理提供试验依据。方法:采用湿法消解-ICP-OES法同时测定不同产地甘松药材地上部分的无机元素含量,通过相关性分析、主成分分析、聚类分析、偏最小二乘判别分析、正交偏最小二乘判别分析方法对测定结果进行分析。结果:元素间具有显著的相关性,多维统计分析确定甘松地上部分特征元素为Pb,Se,As,Si,Mo,Co,Ni,Cd,Cr,Tl,Na,Sn;对地上部分样品能够较好地聚类;海拔在3 400~3 500 m时,甘松地上部分各无机元素含量大都达到峰值(对植物生长有益元素)。结论:基于甘松地上部分无机元素的角度考虑,3 400~3 500 m为甘松最适宜生长海拔高度,同时土壤作为关键因素;对于甘松药材入药部位甘松根及根茎、甘松全草及甘松地上部分这三者是否可以互为替代、甘松资源的合理分配提供理论支撑和参考。     

人体足地接触模型的步速适用性

目的构建骨肌多体动力学足地接触模型,研究其适用速度范围。方法采集5名测试者的步态运动数据,以骨肌多体动力学仿真软件Any Body全身模型为基础,建立足地接触模型,分析慢走、正常行走、快走和慢跑不同步态速度下的地面反作用力(ground reaction force,GRF)和地面反作用力矩(ground reaction moment,GRM),并与测力板实验测量值进行对比,分析模型预测精度,获得足地接触模型的适用范围。结果在慢走、正常走和快走(步速0. 69~1. 68 m/s)时,足地接触模型预测能力较高,GRF预测值与实验值相关性大于0. 875,GRM预测值与实验值相关性大于0. 9。结论所开发的足地接触模型同时计算GRF和GRM,可以消除步态分析中对测力板的依赖,能够应用于老年人及病理性步态等低速步态的运动学分析。     

Electroactive High‐Temperature Shape Memory Polymers with High Recovery Stress Induced by Ground Carbon Fibers

Electroactive shape memory polymers (SMPs) are suitable for remote controllable actuators or applications where direct heat is inconvenient, and herein an electroactive shape memory polyimide (EASMPI) is reported for the first time. EASMPI is synthesized by incorporating ground carbon fibers (GCFs) into a polyimide matrix to form a compact conductive network, and percolation threshold of 0.312 S m^?1 meets the demands of both electroactive and shape memory effects. The glass transition temperature of 302 °C for EASMPI is much higher than that of other electroactive SMPs, and its shape recovery is activated effectively by a voltage of 15.87 V. Recovery stress is crucial for shape memory materials to output work, and EASMPI produces high recovery stress of 40.1 MPa. The possible mechanisms are discussed, and GCF mainly accounts for its electroactivity and recovery stress. EASMPI shows vast potential in practical applications with its electroactive shape memory effect and high recovery stress at high temperature.     

多原发肺癌病理结果与AI辅助CT诊断的相关性研究

目的 对比分析人工智能(Artificial Intelligence,AI)技术诊断多原发肺癌(Multiple Primary Lung Cancer,MPLC)与临床病理诊断结果 的一致性,进而探索AI在MPLC的诊断中的临床应用价值.方法 收集2017—2019年北京大学第三医院海淀院区收治的26例MPLC患者...