A multi-sensor-based distributed real-time measurement system for glacier deformation

Glacier disasters occur frequently in alpine regions around the world,but the current conventional geological disaster measurement technology cannot be directly used for glacier disaster measurement.Hence,in this study,a distributed multi-sensor measurement system for glacier deformation was established by integrating piezoelectric sensing,coded sensing,attitude sensing technology and wireless communication technology.The traditional Modbus protocol was optimized to solve the problem of data identification confusion of different acquisition nodes.Through indoor wireless transmission,adaptive performance analysis,error measurement experiment and landslide simulation experiment,the performance of the measurement system was analyzed and evaluated.Using unmanned aerial vehicle technology,the reliability and effectiveness of the measurement system were verified on the site of Galongla glacier in southeastern Tibet,China.The results show that the mean absolute percentage errors were only 1.13%and 2.09%for the displacement and temperature,respectively.The distributed glacier deformation real-time measurement system provides a new means for the assessment of the development process of glacier disasters and disaster prevention and mitigation.

Resolving co- and early post-seismic slip variations of the 2021 MW 7.4 Madoi earthquake in east Bayan Har block with a block-wide distributed deformation mode from satellite synthetic aperture radar data

On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.

Adiabatic shear sensitivity of ductile metal based on gradient-dependent JOHNSON-COOK model

Based on the expression proposed by WANG for the local plastic shear deformation distribution in the adiabatic shear band（ASB） using gradient-dependent plasticity,the effects of 10 parameters on the adiabatic shear sensitivity were studied.The experimental data for a flow line in the ASB obtained by LIAO and DUFFY were fitted by use of the curve-fitting least squares method and the proposed expression.The critical plastic shear strains corresponding to the onset of the ASB for Ti-6Al-4V were assessed at different assigned ASB widths.It is found that the proposed expression describes well the non-linear deformation characteristics of the flow line in the ASB.Some parameters in the JOHNSON-COOK model are back-calculated using different critical plastic shear strains.The adiabatic shear sensitivity decreases as initial static yield stress,work to heat conversion factor and strain-rate parameter decrease,which is opposite to the effects of density,heat capacity,ambient temperature and strain-hardening exponent.The present model can predict the ASB width evolution process.The predicted ASB width decreases with straining until a stable value is reached.The famous model proposed by DODD and BAI only can predict a final stable value.

Numerical Analysis of Blade Stress of Marine Propellers

In this study,a series of numerical calculations are carried out in ANSYS Workbench based on the unidirectional fluid–solid coupling theory.Using the DTMB 4119 propeller as the research object,a numerical simulation is set up to analyze the open water performance of the propeller,and the equivalent stress distribution of the propeller acting in the flow field and the axial strain of the blade are analyzed.The results show that FLUENT calculations can provide accurate and reliable calculations of the hydrodynamic load for the propeller structure.The maximum equivalent stress was observed in the blade near the hub,and the tip position of the blade had the largest stress.With the increase in speed,the stress and deformation showed a decreasing trend.

Whole-process modeling of titanium disc forming for gradient distributions of temperature and deformation

Gradient distributions of temperature and deformation(GDTD)are crucial for achieving dual-performance discs of titanium alloys which is required by the service environment of aeroengine.However,heating,cooling and deforming sequence in the whole process of the titanium disc forming,which leads to difficulties for achieving GDTD due to a lot of parameters.To solve this problem,a whole-process model of the titanium disc forming for GDTD has been established.In the model,heating and cooling via heat radiation,conduction and convection,and deforming by local loading with mold chilling are all considered.Experiments on heating and cooling as well as deforming were carried out by using a furnace and the Gleeble-3500 machine.The experimental data are used to determine thermal parameters and constitutive relations of the IMI834 titanium alloy,and then to verify the reliability of the model.Then the model was used to simulate the evolution rules of temperature and deformation of the titanium disc.The results show that the heating surface,furnace temperature,billet profile and loading rate play the core role for the control of GDTD,and thus a set of parameters were determined.Therefore,this work provides a base for developing a new forming technology of the dual-performance titanium discs with the approach of local heating and local loading.

RELIABILITY OF TEST LANDS TARGETING IN BED-OF-NAILS STYLE TEST FIXTURE

A systematic, accurate and robust evaluating method for fine pitch printed circuit board （PCB） positioning assessment in testing fixture is developed. Targeting reliability of bed-of-nails tester is successfully evaluated by the 2D pattern transform. Probe offset vector with its Weibull and Gaussian distribution estimates are obtained for further investigation about the causes of misalignment on the basis of a batch tests for same kind of PCBs.