The Promotion of Nano-SiO2 on the Compressive Strength of Alkali-Activated Materials

Nanomaterial which has high activity is widely used in the modification of cement-based materials due to its physical filling and chemical bonding. This paper mainly studied the influence of nano-SiO2 on the compressive strength of the alkali-activated materials, using XRD and SEM technology to analyze the mineral composition microstructure of alkali-activated materials, modification effect, etc. The results show that the doping of nano-SiO2 can enhance the compressive strength of alkali-activated materials. Under the condition of fixed water-binder ratio and alkali content, the optimum dosage of nano-SiO2 is 4%. When the content is 4%, the intensity of 28 days is increased by 26.81% compared with the blank sample, and compressive strength of 94.93 MPa is reached. By XRD and SEM, we can find a large number of CSH and a certain amount of CH in the sample. The promotion effect of nano-SiO2 on the alkali-activated materials provides a better support for the application of the alkaliactivated materials in reality

Design and control of a sit-to-stand assistive device based on analysis of kinematics and dynamics

Sit-to-stand is a common activity in daily life. It is difficult for the elderly and patients with lower limb disorders to complete this motion due to limb pain, muscle weakness, partial loss of motor control function, and physical defects in joints. An STS assistive device is a piece of automated medical equipment that can facilitate rehabilitation training for patients with lower limb disorders and improve their lower limb function. In this paper, we introduce a 3-DOF series type STS assistive device. First, we selected 26 healthy adults to carry out an STS transfer experiment, and we obtained the trajectory and velocity of each joint and the law of plantar pressure during STS motion. Second, based on the above kinematics and dynamics law, a 3-DOF series mechanism was designed. Through forward and inverse kinematics analysis, the relationship between the end-effector and the linear actuator was established. The trajectory planning of the end-effector was carried out according to the natural STS transfer trajectory, and the law of the linear actuator was obtained. The trajectory planning was verified by ADAMS. Finally, the Arduino controller was used to build the control system of the STS assistive device, and the prototype experiment was carried out

THE CHANGE OF LAND COVER/LAND USE IN EJINA OASIS OVER 20 YEARS

Abstract: Land use and land cover change have been of great concern in global change research in recent years. Base on comparison with the remote sensing data in1982 and 2000 and field investigation, the results of land cover and land use change were obtained by the method of landscape analysis. Ten types of land use were identified: riparian woods, riparian shrubbery, desert shrubbery, desert grassland, river-way and water area, salinised land, town, Gobi, shift sand dune, denudative upland. The results show that, (1) there were obvious Changes in land cover structure. The area of riparian woods decreased 0.97% and the number of patch decrease 376; The area of riparian shrubbery increased 0.92% and the number of patch decreased 1316. Meanwhile, the index of %LAND of desert shrubbery increased from 4.49% to 5.65%; Because of decrease of water quantity of discharge from middle reach. The patch of river-way and water area decreased from 40 to 6. The index of % LAND decreased 0.15%.At the same time, the index of % LAND of shift sand dune increased 0.42%. (2) the area of riparian woods dominated by Populus euphratica and desert grassland decreased to 45.02% and 14.55%. However, the areas of riparian shrubbery dominated by Tamarix SPP and desert shrubbery increase to 35.03% and 25.88%. The transition probability is 45.95% from riparian woods to riparian shrubbery. at the same time, they are 0.78% and 3.01% from riparian woods to desert shrubbery and desert grassland. The succession trend of ecosystem was obtained: riparian woods riparian shrubbery and grassland desert grassland. Meanwhile, the succession velocity becomes higher and higher

CellTradeMap: Delineating trade areas for urban commercial districts with cellular networks

Understanding customer mobility patterns to com-mercial districts is crucial for urban planning, facility manage-ment, and business strategies. Trade areas are a widely appliedmeasure to quantify where the visitors are from. Traditionaltrade area analysis is limited to small-scale or store-level studiesbecause information such as visits to competitor commercialentities and place of residence is collected by labour-intensivequestionnaires or heavily biased location-based social media data.In this paper, we propose CellTradeMap, a novel district-leveltrade area analysis framework using mobile flow records (MFRs),a type of fine-grained cellular network data. CellTradeMap ex-tracts robust location information from the irregularly sampled,noisy MFRs, adapts the generic trade area analysis frameworkto incorporate cellular data, and enhances the original trade areamodel with cellular-based features. We evaluate CellTradeMap ona large-scale cellular network dataset covering 3.5 million mobilephone users in a metropolis in China. Experimental results showthat the trade areas extracted by CellTradeMap are aligned withdomain knowledge and CellTradeMap can model trade areaswith a high predictive accuracy

A Realistic 3D Non-Stationary Channel Model for UAV-to-Vehicle Communications Incorporating Fuselage Posture

Considering the unmanned aerial vehicle (UAV) three-dimensional (3D) posture, a novel 3D non-stationary geometry-based stochastic model (GBSM) is proposed for multiple-input multiple-output (MIMO) UAV-to-vehicle (U2V) channels. It consists of a line-of-sight (LoS) and non-line-of-sight (NLoS) components. The factor of fuselage posture is considered by introducing a time-variant 3D posture matrix. Some important statistical properties, i.e. the temporal autocorrelation function (ACF) and spatial cross correlation function (CCF), are derived and investigated. Simulation results show that the fuselage posture has significant impact on the U2V channel characteristic and aggravate the non-stationarity. The agreements between analytical, simulated, and measured results verify the correctness of proposed model and derivations. Moreover, it is demonstrated that the proposed model is also compatible to the existing GBSM without considering fuselage posture.Comment: 12 pages, 8 figures, CNCO