Experimental study of a technique for load measurement of powered supports

Despite the increasing popularity of mechanized coal mining, there are no convenient and accurate means available to measure the loads of powered supports. The measurement of such loads is important for monitoring mine pressure and ensuring production safety. The load-carrying features of a powered support were used to develop a method for load measurement using the mag-netoelastic principle. A cross bridge-type magnetoelastic stress sensor was designed for the support structures to measure the different parts of the supports. Tests on single-body hydraulic cylinders and simulated linkages showed that an approximately linear relationship between the values of the sensor output signal and the loads borne by the hydraulic cylinders or linkages. The results were used to analyze the load-carrying measurements of powered supports with the cross bridge-type magnetoelastic stress sensor.

No external load measurement strategy for micro thermoelectric generator based on high-performance Si_(1-x-y)Ge_(x)Sn_(y) film

In this study,a micro in-plane p-type thermoelectric generator(TEG),which consists of thin-film Si_(1-x-y)Ge_(x)Sn_(y) ternary alloy semiconductor on insulator,is developed to make efficient use of waste heat such as human body.A power factor value as high as 1095 mWm^(-1) K^(-2) had been achieved using Bion implanted and short-term rapid thermal annealing(RTA)process.In addition,a measuring scheme for micro TEG without external load resistance was designed.In one measuring session,multiple parameters can be measured.The micro single-arm TEG prepared by semiconductor process can output 0.29 nW power at a temperature difference of 15 K,and a cross-sectional power density has reached up to 0.58 mW/cm^(2),which is a superior value for wearable device.The findings of this study have important reference value for wearable device performance improvement and output power measuring of micro TEG.

Fatigue test loading methodfor wagon body basedon measured load

Purpose–In this paper,the C80 special coal gondola car was taken as the subject,and the load test data of the car body at the center plate,side bearing and coupler measured on the dedicated line were broken down to generate the random load component spectrums of the car body under five working conditions,namely expansion,bouncing,rolling,torsion and pitching according to the typical motion attitude of the car body.Design/methodology/approach–On the basis of processing the measured load data,the random load component spectrums were equivalently converted into sinusoidal load component spectrums for bench test based on the principle of pseudo-damage equivalence of load.Relying on the fatigue and vibration test bench of the whole railway wagon,by taking each sinusoidal load component spectrum as the simulation target,the time waveform replication(TWR)iteration technology was adopted to create the drive signal of each loading actuator required for the fatigue test of car body on the bench,and the drive signal was corrected based on the equivalence principle of measured stress fatigue damage to obtain the fatigue test loads of car body under various typical working conditions.Findings–The fatigue test results on the test bench were substantially close to the measured test results on the line.According to the results,the relative error between the fatigue damage of the car body on the test bench and the measured damage on the line was within the range of
16.03%–27.14%.Originality/value–The bench test results basically reproduced the fatigue damage of the key parts of the car body on the line.

Development of All-Weather and Real-Time Bottom-Mounted Monitor of Bed Load Quantity

Quantity of bed load is an important physical parameter in sediment transport research. Aiming at the difficulties in the bed load measurement, this paper develops a bottom-mounted monitor to measure the bed load transport rate by adopting the sedimentation pit method and resolving such key problems as weighing and desilting, which can achieve long-time, all-weather and real-time telemeasurement of the bed load transport rate of plain rivers, estuaries and coasts. Both laboratory and field tests show that this monitor is reasonable in design, stable in properties and convenient in measurement, and it can be used to monitor the bed load transport rate in practical projects.

Micro-scale behavior of granular materials during cyclic loading

This study presents the micro-scale behavior of granular materials under biaxial cyclic loading for differ- ent confining pressures using the two-dimensional （2D） discrete element method （DEM）. Initially, 8450 ovals were generated in a rectangular frame without any overlap. Four dense samples having confining pressures of 15, 25, 50, and 100 kPa were prepared from the initially generated sparse sample. Numeri- cal simulations were performed under biaxial cyclic loading using these isotropically compressed dense samples. The numerical results depict stress-strain-dilatancy behavior that was similar to that observed in experimental studies. The relationship between the stress ratio and dilatancy rate is almost indepen- dent of confining pressures during loading but significantly dependent on the confining pressures during unloading. The evolution of the coordination number, effective coordination number and slip coordina- tion number depends on both the confining pressures and cyclic loading. The cyclic loading significantly affects the microtopology of the granular assembly. The contact fabric and the fabric-related anisotropy are reported, as well. A strong correlation between the stress ratio and the fabric related to contact normals is observed during cyclic loading, irrespective of confining pressures.

Modelling the dynamics of population viral load measures under HIV treatment as prevention

In 2011 the Centers for Disease Control and Prevention(CDC)published guidelines for the use of population viral load(PVL),community viral load(CVL)and monitored viral load(MVL),defined as the average viral load(VL)of all HIV infected individuals in a population,of all diagnosed individuals,and of all individuals on antiretroviral treatment(ART),respectively.Since then,CVL has been used to assess the effectiveness of ART on HIV transmission and as a proxy for HIV incidence.The first objective of this study was to investigate how aggregate VL measures change with the HIV epidemic phase and the drivers behind these changes using a mathematical transmission model.Secondly,we aimed to give some insight into how well CVL correlates with HIV incidence during the course of the epidemic and roll out of ART.We developed a compartmental model for disease progression and HIV transmission with disease stages that differ in viral loads for epidemiological scenarios relevant to a concentrated epidemic in a population of men who have sex with men(MSM)in Western Europe(WE)and to a generalized epidemic in a heterosexual population in Sub-Saharan Africa(SSA).The model predicts that PVL and CVL change with the epidemic phase,while MVL stays constant.These dynamics are linked to the dynamics of infected subgroups(undiagnosed,diagnosed untreated and treated)in different disease stages(primary,chronic and AIDS).In particular,CVL decreases through all epidemic stages:before ART,since chronic population builds up faster than AIDS population and after ART,due to the build-up of treated population with low VL.The trends in CVL and incidence can be both opposing and coinciding depending on the epidemic phase.Before ART is scaled up to sufficiently high levels,incidence increases while CVL decreases.After this point,CVL is a useful indicator of changes in HIV incidence.The model predicts that during the ART scale-up HIV transmission is driven by undiagnosed and diagnosed untreated individuals,and that new infections decline due to the increase in the number of treated.Although CVL is not able to capture the contribution of undiagnosed population to HIV transmission,it declines due to the increase of people on ART too.In the scenarios described by our model,the present epidemic phase corresponds to declining trends in CVL and incidence.