Vibrations induced by tunnel boring machine in urban areas: In situ measurements and methodology of analysis

Excavation with tunnel boring machine(TBM)can generate vibrations,causing damages to neighbouring buildings and disturbing the residents or the equipment.This problem is particularly challenging in urban areas,where TBMs are increasingly large in diameter and shallow in depth.In response to this problem,four experimental campaigns were carried out in different geotechnical contexts in France.The vibration measurements were acquired on the surface and inside the TBMs.These measurements are also complemented by few data in the literature.An original methodology of signal processing is pro-posed to characterize the amplitude of the particle velocities,as well as the frequency content of the signals to highlight the most energetic bands.The levels of vibrations are also compared with the thresholds existing in various European regulations concerning the impact on neighbouring structures and the disturbance to local residents.

Design and assembly of a nested imaging X-ray telescope for the Hot Universe Baryon Surveyor mission

The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conic-approximation type assembly to simplify the manufacturing process. The mirror substrate is made using the thermal glass slumping method, with mirrors characterized by a root-mean-square roughness of 0.3 nm, with expected high reflectivity and good thermal stability. We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror. The in situ measurement system program is developed to guide the telescope assembly process.

Rheo-optic in situ synchronous study on the gelation behaviour and mechanism of waxy crude oil emulsions

An improved rheo-optic in situ synchronous measurement system was employed to investigate the gelation behaviour and mechanism of waxy crude oil emulsions. By combining transmitted natural light and reflected polarized light microscopy, a multiangle composite light source was built to achieve the simultaneous observation of wax crystals and emulsified water droplets, as well as their dynamic aggregation process. Main outcomes on the microscopic mechanism were obtained by developed microscopic image processing method. It was found that the microstructure of W/O waxy crude oil emulsion has the evolution of “individual structure--homogeneous aggregate structure--heterogeneous coaggregate structure--floc structure” during the static cooling, which results in the four stages during gelation process. Different from previous studies, the aggregation of emulsified water droplets was found to be more significant and contributes to the formation and development of the wax crystals-emulsified water droplets coaggregate, which plays a decisive role in the further evolution of the gelled microstructure. Time series microscopic images show the dynamic aggregation of emulsified water droplets and wax crystals. Two different aggregation behaviours between wax crystals and water droplets were observed. That wax crystals can not only embed in gaps between adjacent water droplets and enhance the structure, but also surround the outside of the water droplets and continue to grow resulting in the interconnection of different coaggregates to form a larger floc structure. In addition, correlation between viscoelasticity and microstructure evolution of waxy crude oil emulsions of different water contents was discussed. With increasing water contents, the microstructure is changed from wax crystal flocculation structure as the main skeleton and the emulsified water droplets embedded in it, into the aggregation of emulsified water droplets occupying the main position. When the number of wax crystals and water droplets reaches a certain ratio, did wax crystals form coaggregates with emulsified water droplets, and the remaining wax crystals formed an overall flocculation structure, the viscoelasticity of the waxy crude oil emulsion is the highest.

A COMBINED MEASUREMENT SYSTEM FOR UV/V IN SITU SPECTROELECTROCHEMICAL STUDY

A microcomputer-based UV/V in situ spectroelectrochemical measurement system has been developed.This paper presents a description of the experimental details regarding the methods and equipment.

Development of Sb Microelectrode and In-situ pH Measurement of Electroless Nickel Reaction Interface

Sb microelectrodes were prepared by plating. The results of testing show that they have excellent stability, quick responding speed, high pH sensitivity (35～40 mV/pH) and long useful life in high temperature acidic electroless nickel (EN) bath. By using Sb microelectrode, the pH value in EN reaction interface was measured in situ . There exists the fluctuation of pH during EN plating, and the amplitude of fluctuation tends to decrease with plating time. The largest fluctuation amplitude can reach 1～2 pH value. The in situ pH measurement provides reliable experimental results for explaining the formation of layer structure of EN deposit.

New speckle pattern interferometry for precise in situ deformation measurements

A new electronic speckle pattern interferometry method is proposed to realize in situ deformation measurements.The feature of the method is the combination of a high-speed camera and multiple laser Doppler vibrometers(LDVs)for synchronous measurements.The high-speed camera is used to record and select effective interferograms,while the LDVs are used to measure the rigid body displacement caused by vibrations.A series of effective interferograms with known shifted phase values are obtained to calculate the deformation phase.The experimental results show that the method performs well in measuring static and dynamic deformations with high accuracy in vibrating environments.

In Situ Acquisition of Equivalent Circuit Parameters of Crystal Resonance during Copper Deposition and Dissolution in Acidic Solution by Electrochemical Quartz Crystal Impedance System

Electrochemical quartz crystal impedance system (EQCIS) which allows in situ dynamic quartz crystal impedance measurement in an electrochemical experiment was developed by combining an HP 4395A Network/Spectrum/Impedance analyzer with an EG&G M283 potentiostat. Equivalent circuit parameters of crystal resonance change significantly during electrodeposition and dissolution of copper in 0.1 mol/L H2SO4 aqueous solution in a cyclic potential sweep experiment, which is explained with an overall picture of mass loading, solution density and viscosity, etc..

Relationships between the sound speed ratio and physical properties of surface sediments in the South Yellow Sea

Building empirical equations is an effective way to link the acoustic and physical properties of sediments.These equations play an important role in the prediction of sediments sound speeds required in underwater acoustics.Although many empirical equations coupling acoustic and physical properties have been developed over the past few decades,further confirmation of their applicability by obtaining large amounts of data,especially for equations based on in situ acoustic measurement techniques,is required.A sediment acoustic survey in the South Yellow Sea from 2009 to 2010 revealed statistical relationships between the in situ sound speed and sediment physical properties.To improve the comparability of these relationships with existing empirical equations,the present study calculated the ratio of the in situ sediment sound speed to the bottom seawater sound speed,and established the relationships between the sound speed ratio and the mean grain size,density and porosity of the sediment.The sound speed of seawater at in situ measurement stations was calculated using a perennially averaged seawater sound speed map by an interpolation method.Moreover,empirical relations between the index of impedance and the sound speed and the physical properties were established.The results confirmed that the existing empirical equations between the in situ sound speed ratio and the density and porosity have general suitability for application.This study also considered that a multiple-parameter equation coupling the sound speed ratio to both the porosity and the mean grain size may be more useful for predicting the sound speed than an equation coupling the sound speed ratio to the mean grain size.

Safety of barricades in cemented paste-backfilled stopes

In underground mining,there has been an increasing use of"cemented paste"for the backfilling of stopes.As this cemented paste backfill(CPB)enters the stope as a fluid,shotcrete barricades are often used to retain the fill material during and after the filling operations.However,failures of barricades have been reported around the world in recent years.This paper presents an analytical solution based on the elastic thin plate theory for calibrating the design of shotcrete barricades in underground mines using CPB.This solution was used to determine the quantitative relationships between the lateral loading from the paste and the barricade response during the backfilling process.The results show that the proposed solution agrees well with in situ data.According to the actual barricade responses,the acceptable tensile stress and an analysis method of cracks development are proposed.The proposed solution has practical significance for underground mines.

Tectonic Stress State Changes Before and After the Wenchuan M_s 8.0 Earthquake in the Eastern Margin of the Tibetan Plateau

Crustal tectonic activities are essentially the consequences of the accumulation and release of in situ stress. Therefore, studying the stress state near active faults is important for understanding crustal dynamics and earthquake occurrences. In this paper, using in situ stress measurement results obtained by hydraulic fracturing in the vicinity of the Longmenshan fault zone before and after the Wenchuan Ms 8.0 earthquake and finite element modeling, the variation of stress state before and after the Wenchuan M. 8.0 earthquake is investigated. The results show that the shear stress, which is proportional to the difference between principal stresses, increases with depth and distance from the active fault in the calm period or after the earthquakes, and tends to approach to the regional stress level outside the zone influenced by the fault. This distribution appears to gradually reverse with time and the change of fault properties such as frictional strength. With an increase in friction coefficient, low stress areas are reduced and areas with increased stress accumulation are more obvious near the fault. In sections of the fault with high frictional strengths, in situ stress clearly increases in the fault. Stress accumulates more rapidly in the fault zone relative to the surrounding areas, eventually leading to a stress field that peaks at the fault zone. Such a reversal in the stress field between the fault zone and surrounding areas in the magnitude of the stress field is a potential indicator for the occurrence of strong earthquakes.

Numerical study of AE and DRA methods in sandstone and granite in orthogonal loading directions

The directional dependency of the acoustic emission （AE） and deformation rate analysis （DRA） methods was analyzed, based on the contact bond model in the two-dimensional particle flow code （PFC2D） in two types of rocks, the coarse-grained sandstone and Aue granite. Each type of rocks had two shapes, the Brazilian disk and a square shape. The mechanical behaviors of the numerical model had already been verified to be in agreement with those of the physical specimens in previous research. Three loading protocols with different loading cycles in two orthogonal directions were specially designed in the numerical tests. The results show that no memory effect is observed in the second loading in the orthogonal direction. However, both the cumulative crack number of the second loading and the differential strain value at the inflection point are influenced by the first loading in the orthogonal direction.

基于变形力监测数据的残余应力场推断和表征方法

残余应力是材料的基本属性之一,与零件的几何形状、尺寸稳定性和疲劳寿命直接相关。针对具有高精度要求的大型零件,其残余应力场的准确测量和预测一直是一个挑战。目前的残余应力场测量技术可以分为基于应变的破坏性方法和基于射线、声波等物理量的非破坏性方法,但均受限于测量效率和精度,且难以得到工件的整体残余应力场。针对以上问题,本文提出了一种基于加工过程中的变形力监测数据推断工件整体残余应力场的新方法。本方法通过能够反映去除材料后不平衡残余应力场整体效应的变形力推断零件的残余应力场。利用虚功原理建立了变形力与残余应力场之间的力学关系,并引入正则化方法求解整体残余应力场。理论验证和实际实验测试结果均表明,该方法对于大型结构件的残余应力场测量具有可靠的精度和灵活性。在数字化和智能制造的趋势下,该方法的基本原理为利用加工监测数据预测和补偿由残余应力引起的零件加工变形提供了重要参考。

First in situ UV profile across the UTLS accompanied by ozone measurement over the Tibetan Plateau

Ultraviolet radiation(UV) and ozone can greatly affect human health and the Earth's ecological environment. By deploying a UV radiometer aboard a stratospheric balloon released at Qaidam(QDM) during the Asian summer monsoon(ASM) period in 2019, we provided in situ measurement of the UV profiles from the surface to the upper troposphere and lower stratosphere over the Tibetan Plateau(TP), China, for the first time. Based on two in situ UV profiles accompanied by four ozonesonde measurements, this study exhibited detailed variations of downwelling UV and vertical ozone distributions over the TP during the ASM period. The UV differences between the surface and stratospheric balloon flight altitudes were 16.7, 15.8, 12.6 and 18.0 Wm^-2 during the four ozonesonde launches. Due to the diurnal variations in photochemical production and the stratosphere-troposphere exchange, the integrated ozone columns below 30 km ranged from 184.4 to 221.6 DU from four ozonesonde measurements. A positive correlation between UV attenuation and ozone column was exhibited under low cloud cover and clear sky conditions. The results of this study are expected to improve our understanding of UV and ozone properties, as well as their potential effects on terrestrial ecosystems and living environments over this significant plateau.

In situ method for stress measurements in film-substrate electrodes during electrochemical processes:key role of softening and stiffening

Electrode stress is one of the main driving forces of electrochemical degradation,which is directly related to battery cycle life,thus attracting great interest.Herein,we propose an in situ method to measure bilayer stresses in film-substrate electrodes during electrochemical processes.This method consists of two parts:stress models featuring Li-dependent material modulus and in situ deformation measurements,through which electrode bilayer stresses evolution accompanied by Li-dependent material modulus can be quantitatively characterized.As application of the method,typical silicon-composite and carbon-composite film-substrate electrodes are selected for in situ mechanical measurements and experimental analysis is performed.Results show that silicon material and carbon material exhibit significant,continuous softening and stiffening,respectively.In two film-substrate electrodes,electrode material films experience compressive stress and current collector substrates undergo a tensile-to-compressive conversion across the thickness.Besides,moduli and stresses in both electrodes vary nonlinearly with capacity,presenting non-overlapping paths between lithiation and delithiation.Based on experimental data,we further demonstrate the key role of Li-dependent modulus on electrode stresses,finding that silicon material softening decreases and carbon material stiffening increases electrode stresses.The deficiencies of current stress measurement method based on Stoney equation and the applicability of our method are discussed.

A Universal Blown Film Apparatus for in Situ X-ray Measurements

A setup of blown film machine combined with in situ synchrotron radiation X-ray diffraction measurements and infrared temperature testing is reported to study the structure evolution of polymers during film blowing. Two homemade auto-lifters are constructed and placed under the blown machine at each end of the beamline platform which move up and down with a speed of 0.05 mm/s bearing the 200 kg weight machine. Therefore, structure development and temperature changes as a function of position on the film bubble can be obtained. The blown film machine is customized to be conveniently installed with precise servo motors and can adjust the processing parameters in a wide range. Meanwhile, the air ring has been redesigned in order to track the structure information of the film bubble immediately after the melt being extruded out from the die exit. Polyethylene（PE） is selected as a model system to verify the feasibility of the apparatus and the in situ experimental techniques. Combining structure information provided by the WAXD and SAXS and the actual temperature obtained from the infrared probe, a full roadmap of structure development during film blowing is constructed and it is helpful to explore the molecular mechanism of structure evolution behind the film blowing processing, which is expected to lead to a better understanding of the physics in polymer processing.

Spatial and Temporal Stress Variations before and after the 2008 Wenchuan M_(w)7.9 Earthquake and its Implications:A Study based on Borehole Stress Data

In situ stress measurement data was analyzed to estimate the temporal and spatial stress variations at shallow depths in the Longmenshan fault zone(LMSF),prior to and following the 2008 Wenchuan earthquake(WCEQ).Analysis of the stress field related to fault strength and behavior is useful for understanding geodynamic processes and conducting hazard assessments.The shallow stress changes after the WCEQ show clear along-strike variations.Degrees of stress orientation rotations have a negative correlation with the horizontal principal stress ratios and the WCEQ apparently reduced the magnitude difference between horizontal principal stresses.Taking stress magnitudes and orientation distribution relative to the fault strike into account,we propose an intermediate-strength of LMSF,with a friction coefficient generally constrained between 0.35 and 0.6.In addition,high-pressure fluids in the fault zone reduce the effective normal stress and to a certain degree weaken the fault strength.The accumulated stress over a certain period following release of the WCEQ indicates the start of another earthquake cycle.The changing crustal stress field makes the LMSF stable or slipping optimally during geodynamic processes.The segmentation feature of the shallow crustal stress field in the LMSF may imply a different tectonic loading and seismic release processes along the fault.The southwestern section to the epicenter of the WCEQ favors the occurrence of future earthquakes,as highμm in a state of critical failure was present in this area,which indicates that the Wenchuan and Lushan earthquakes did not release the accumulated stress to a sufficient extent there.

A tunable diode laser absorption spectrometer for formaldehyde atmospheric measurements validated by simulation chamber instrumentation

A tunable diode laser absorption spectrometer （TDLAS） for formaldehyde atmospheric measurements has been set up and validated through comparison experiments with a Fourier transform infrared spectrometer （FT-IR） in a simulation chamber.Formaldehyde was generated in situ in the chamber from reaction of ethene with ozone.Three HCHO ro-vibrational line intensities （at 2909.71,2912.09 and 2914.46 cm-1） possibly used by TDLAS were calibrated by FT-IR spectra simultaneously recorded in the 1600–3200 cm-1 domain during ethene ozonolysis,enabling the on-line deduction of the varying concentration for HCHO in formation.The experimental line intensities values inferred confirmed the calculated ones from the updated HITRAN database.In addition,the feasibility of stratospheric in situ HCHO measurements using the 2912.09 cm-1 line was demonstrated.The TDLAS performances were also assessed,leading to a 2σ detection limit of 88 ppt in volume mixing ratio with a response time of 60 sec at 30 Torr and 294 K for 112 m optical path.As part of this work,the room-temperature rate constant of this reaction and the HCHO formation yield were found to be in excellent agreement with the compiled literature data.

Experimental Study on Molecular Arrangement of Nanoscale Lubricant Films——A Review

In order to understand lubrication mechanism at the nanoscale, researchers have used many physical experimental approaches, such as surface force apparatus, atomic force microscopy and ball-on-disk tribometer. The results show that the variation rules of the friction force, film thicknessand viscosity of the lubricant at the nanoscale are different from elastohydrodynamic lubrication （EHL）. It is speculated that these differences are attributed to the special arrangement of the molecules at the nanoscale. However, it is difficult to obtain the molecular orientation and distribution directly from the lubricant molecules in these experiments. In recent years, more and more attention has been paid to use new techniques to overcome the shortcomings of traditional experiments, including various spectral methods. The most representative achievements in the experimental research of molecular arrangement are reviewed in this paper： The change of film structure of a liquid crystal under confinement has been obtained using X-ray method. The molecular orientation change of lubricant films has been observed using absorption spectroscopy. Infrared spectroscopy has been used to measure the anisotropy of molecular orientation in the contact region when the lubricant film thickness is reduced to a few tens of nanometers. In situ Raman spectroscopy has been performed to measure the molecular orientation of the lubricant film semi-quantitatively. These results prove that confinement and shear in the contact region can change the arrangement of lubricant molecules. As a result, the lubrication characteristics are affected. The shortages of these works are also discussed based on practicable results. Further work is needed to separate the information of the solid-liquid interface from the bulk liquid film.

In situ observation of atomic movement in a ferroelectric film under an external electric field and stress

Atomic movement under application of external stimuli （i.e., electric field or mechanical stress） in oxide materials has not been observed due to a lack of experimental methods but has been well known to determine the electric polarization. Here, we investigated atomic movement arising from the ferroelectric response of BiFeO3 thin films under the effect of an electric field and stress in real time using a combination of switching spectroscop）6 time-resolved X-ray microdiffraction, and in situ stress engineering. Under an electric field applied to a BiFeO3 film, the hysteresis loop of the reflected X-ray intensity was found to result from the opposing directions of displaced atoms between the up and down polarization states. An additional shift of atoms arising from the linearly increased dielectric component of the polarization in BiFeO3 was confirmed through gradual reduction of the diffracted X-ray intensity. The electric-field- induced displacement of oxygen atoms was found to be larger than that of Fe atom for both ferroelectric switching and increase of the polarization. The effect of external stress on the BiFeO3 thin film, which was controlled by applying an electric field to the highly piezoelectric substrate, showed smaller atomic shifts than for the case of applying an electric field to the film, despite the similar tetragonality.

Function of large-volume high-pressure apparatus at SECUF

Pressure allows the precise tuning of a fundamental parameter, the interatomic distance, which controls the electronic structure and virtually all interatomic interactions that determine material properties. Hence, pressure tuning is an effective tool in the search for new materials with enhanced properties. To realize pressure tuning on matter, large-volume press （LVP） apparatuses have been widely used not only to synthesize novel materials but also to implement the in situ measurement of physical properties. Herein, we introduce the LVP apparatuses, including belt-type, cubic anvil, and 6-8 type multi-anvil, that will be constructed at the Synergetic Extreme Condition User Facility （SECUF） at Jilin University. Typically, cell volumes of 1000 mm3 can be obtained at 20 GPa in a belt-type apparatus that is significantly larger than that obtained in a 6-8 type multi-anvil apparatus at the same pressure. Furthermore, the in situ measurement of physical prop- erties, including thermological, electrical, and mechanical behaviors, is coupled to these LVP apparatuses. Some typical results of both synthetic experiments and in situ measurements obtained from the LVP apparatuses are also reviewed.