TBAB hydrate formation and growth in a microdevice under static and dynamic conditions

The natural gas hydrate has become one of the most promising future green energy sources on the earth.The natural gas hydrates mostly exist in the sediments with porous structure, so a solid understanding of the hydrate formation and growth processes in the porous medium is of significance for the exploitation of natural gas hydrate. The micro-packed bed device is one of the efficient microfluidic devices in the engineering field, but it has been rarely used for the hydrate-based research. In this study, a transparent micro-packed bed device filled with glass beads was developed to mimic the porous condition of sediments, and used to in-situ visualize the hydrate formation and growth habits in the pore spaces under both static and dynamic conditions. For the static experiment, two types of hydrate growth patterns in porous medium were observed and identified in the micro-packed bed device, which were the graincoating growth and pore-filling growth. For the dynamic condition, the hydrate formation, growth,distribution habits and hydrate blockage phenomena in the pore spaces were in-situ visually captured.The impacts of flowrate and subcooling on the pressure variation of the micro-packed bed and the duration of the hydrate growth under dynamic flow condition in pores were in-situ monitored and analyzed. The higher flowrate could result in the faster hydrate growth and more severe blockage in pores, but the effect of subcooling condition might be less significant at the high flowrate.

In-situ 3D contour measurement for laser powder bed fusion based on phase guidance

In-situ layerwise imaging measurement of laser powder bed fusion(LPBF)provides a wealth of forming and defect data which enables monitoring of components quality and powder bed homogeneity.Using high-resolution camera layerwise imaging and image processing algorithms to monitor fusion area and powder bed geometric defects has been studied by many researchers,which successfully monitored the contours of components and evaluated their accuracy.However,research for the methods of in-situ 3D contour measurement or component edge warping identification is rare.In this study,a 3D contour mea-surement method combining gray intensity and phase difference is proposed,and its accuracy is verified by designed experiments.The results show that the high-precision of the 3D contours can be achieved by the constructed energy minimization function.This method can detect the deviations of common ge-ometric features as well as warpage at LPBF component edges,and provides fundamental data for in-situ quality monitoring tools.

A New Method for In-Situ Measurement of Internal Solitary Waves Based on the Stimulated Raman Scattering in Optical Fibers

In-situ measurement of internal solitary waves(ISWs)is complicated in the ocean due to their randomness.At present,the ISWs are mainly detected by the chain structure of conductivity-temperature-depth systems(CTDs)or temperature sensors.The high cost limits the spatial resolution,which ultimately affects the measuring accuracy of the ISW amplitude.In this paper,we developed an experimental measurement system for detecting ISWs based on the stimulated Raman scattering in distributed optical fibers.This system has the advantages of high precision,low cost,and easy operation.The experimental results show that the system is consistent with CTDs in the measurement of vertical ocean temperature variation.The spatial resolution of the system can reach 1.0 m and the measuring accuracy of temperature is 0.2℃.We successfully detected 3 ISWs by the system in the South China Sea and two optical remote sensing images collected on May 18,2021,the same day of two detected ISWs,verify the occurrence of the measured ISWs.We used the image pairs method to calculate the phase velocity of ISW and the result is 1.71 ms^(-1).By extracting the distances between wave packets,it can be found that the semi-diurnal tide generates the detected ISWs.The impact of the tidal current velocity on the ISW in amplitude is undeniable.Undoubtedly,the system has a great application prospect for detecting ISWs and other dynamic phenomena in the ocean.

Noise analysis and measurement of time delay and integration charge coupled device

Time delay and integration （TDI） charge coupled device （CCD） noise sets a fundamental limit on image sensor performance, especially under low illumination in remote sensing applications. After introducing the complete sources of CCD noise, we study the effects of TDI operation mode on noise, and the relationship between different types of noise and number of the TDI stage. Then we propose a new technique to identify and measure sources of TDI CCD noise employing mathematical statistics theory, where theoretical analysis shows that noise estimated formulation converges well. Finally, we establish a testing platform to carry out experiments, and a standard TDI CCD is calibrated by using the proposed method. The experimental results show that the noise analysis and measurement methods presented in this paper are useful for modeling TDI CCDs.

Device interchangeability on anterior chamber depth and white-to-white measurements: a thorough literature review

We have reviewed a set of recently published studies that compared the anterior chamber depth（ACD） and/or white-to-white（WTW） distance obtained by means of different measuring devices.Since some of those studies reached contradictory conclusions regarding device interchangeability,this review was carried out in attempting to clarify which clinical devices can or cannot be considered as interchangeable in clinical practice to measure ACD and/or WTW distance,among these devices：A-scan,ultrasound biomicroscopy,Orbscan and Orbscan Ⅱ（Bausch＆Lomb Surgical Inc.,San Dimas,California,USA）,Pentacam and Pentacam HR（Oculus,Wetzlar,Germany）,Galilei（Ziemer,Switzerland）,Visante optical coherence tomography（Visante OCT,Carl Zeiss Meditec Inc.,Dublin,California,USA）,lOLMaster（Carl Zeiss Meditec,Jena,Germany）,and Lenstar LS 900/Biograph（Haag-Streit AG,Koeniz,Switzerland/Alcon Laboratories Inc.,Ft Worth,Texas,USA）.

Free-space measurement-device-independent quantum-key-distribution protocol using decoy states with orbital angular momentum

In this paper, we propose a measurement-device-independent quantum-key-distribution（MDI-QKD） protocol using orbital angular momentum（OAM） in free space links, named the OAM-MDI-QKD protocol. In the proposed protocol,the OAM states of photons, instead of polarization states, are used as the information carriers to avoid the reference frame alignment, the decoy-state is adopted to overcome the security loophole caused by the weak coherent pulse source, and the high efficient OAM-sorter is adopted as the measurement tool for Charlie to obtain the output OAM state. Here, Charlie may be an untrusted third party. The results show that the authorized users, Alice and Bob, could distill a secret key with Charlie＇s successful measurements, and the key generation performance is slightly better than that of the polarization-based MDI-QKD protocol in the two-dimensional OAM cases. Simultaneously, Alice and Bob can reduce the number of flipping the bits in the secure key distillation. It is indicated that a higher key generation rate performance could be obtained by a high dimensional OAM-MDI-QKD protocol because of the unlimited degree of freedom on OAM states. Moreover,the results show that the key generation rate and the transmission distance will decrease as the growth of the strength of atmospheric turbulence（AT） and the link attenuation. In addition, the decoy states used in the proposed protocol can get a considerable good performance without the need for an ideal source.

Design and dynamic analysis of single-axis integrated inertia measurement device

The structure and measurement theory of a single-axis integrated inertia measurement device are discussed in this paper.The acceleration and angle velocity can be detected by the proposed sensor at the same time.The ki- netic model of the device is also established.In addition,the signal generation of the single-axis integrated inertia measurement device is analyzed and simulated.The results of the model are consistent with simulation result.

Development of a Measurement Software for the Characterization of WORM Devices for Novel Memory Storage Applications

We hereby propose a software solution to perform high quality electrical measurements for the characterization of WORM (write-once read many), a new generation memory device which is being intensively studied for non-volatile data storage. The as-proposed software is completely based on .NET framework and sample C# code. The paper performed a relevant measurement based on this software. Working WORM devices, based on a polymeric matrix embedded with gold and copper sulfide nanoparticles, have been used for test measurements. The aim of this paper is to show the main steps to develop a fully working measurement software without using any expensive dedicated software.

Comparison of Two Electronic Root Canal Length Measurement Devices: The Differences between Ratio Two Impedance Frequencies and Multi Frequencies

Accuracy electronic root canal length measurement devices were important for root canal treatment. Aim: To evaluate and compare accuracy of the two electronic root canal length measurement devices;two frequencies impedance ratio and multi frequencies. Methods: Forty anterior teeth were sectioned on their cervical area. All samples were measured root canal length by radiographic. On the second phase, all the samples were measured by two frequencies impedance ratio and multi frequencies electronic devices. In the final phase, the teeth were split vertically and actual lengths were measured. All measurement by radiographic and electronic method was subtracted with actual length. Statistical analysis was performed using Chi-square and the Kolmogorov-Smirnov test. Results: Accuracy of the two frequencies impedance ratio 50% and multi frequencies 47.5%. No statistical significance between two frequencies impedance ratio and multi frequencies. Conclusions: There is no difference between ratio two impedance frequencies and multi frequencies.

A Method of Insulator’s NSDD Measurement and Its Device Based on Laser Transmission Principle

Accuracy measurement of the Non-soluble Deposit Density (NSDD) on the insulator surface is very important for the transmission line anti-pollution flashover works. A method to measure the NSDD on double sheds porcelain insulator surface based on laser transmission principle is proposed in this paper. Laser unit and luminous intensity sensor are installed between the up and down surface of the double sheds porcelain insulators, two glass tablets are put between the double sheds. The contamination on the glass tablets will influence the luminous intensity that reaches the intensity sensor. The luminous signal is changed to electrical signal, and the insulator’s NSDD could be obtained based on the difference of luminous intensity. The device can be used in online monitoring of the insulator's NSDD condition on the insulator surface.

Measurement Device Independent Quantum Key Distribution Based on Orbital Angular Momentum under Parametric Light Source

On the one hand,existing measurement device independent quantum key distribution(MDI-QKD)protocols have usually adopted single photon source(SPS)and weak coherent photon(WCP),however,these protocols have suffered from multi-photon problem brought from photon splitter number attacks.On the other hand,the orbital angular momentum(OAM)-MDI-QKD protocol does not need to compare and adjust the reference frame,solving the dependency of the base in the MDI-QKD protocol.Given that,we propose the OAM-MDI-QKD protocol based on the parametric light sources which mainly include single-photon-added-coherent(SPACS)and heralded single-photon sources(HSPS).Due to the stability of OAM and the participation of parametric light sources,the performance of MDI-QKD protocol gradually approaches the ideal situation.Numerical simulation shows that compared with WCP scheme,HSPS and SPACS schemes have increased the maximum secure transmission distance by 30 km and 40 km respectively.

Performance Improvement of the LM Device and Its Application to Precise Measurement of Motion Trajectories within a Small Range with a Machining Centre

In order to apply the LM device previously developed to precisely measuring small motion trajectories located on the different motion planes, three major improvements are successfully performed under the condition of completely maintaining the advantages of the device. These improvements include 1) development of a novel connection mechanism to smoothly attach the device to the spindle of a machining centre;2) employment of a new data sampling method to achieve a high sampling frequency independent of the operating system of the control computer;and 3) proposal of a set-up method to conveniently install the device on the test machining centre with respect to different motion planes. Practical measurement experiment results with the improved device on a machining centre sufficiently demonstrate the effectiveness of the improvements and confirm several features including a very good response to small displacement close to the resolution of the device, high precision, repeatability and reliance. Moreover, based on the measurement results for a number of trajectories for a wide range of motion conditions, the error characteristics of small size motions are systematically discussed and the effect of the movement size and feed rate on the motion accuracy is verified for the machining centre tested.

Measurement-device-independent quantum cryptographic conferencing with an untrusted source

Measurement-device-independent quantum cryptographic conferencing（MDI-QCC） protocol puts MDI quantum key distribution（MDI-QKD） forwards to multi-party applications, and suggests a significant framework for practical multi-party quantum communication. In order to mitigate the experimental complexity of MDI-QCC and remove the key assumption（the sources are trusted） in MDI-QCC, we extend the framework of MDI-QKD with an untrusted source to MDI-QCC and give the rigorous security analysis of MDI-QCC with an untrusted source. What is more, in the security analysis we clearly provide a rigorous analytical method for parameters＇ estimation, which with simple modifications can be applied to not only MDI-QKD with an untrusted source but also arbitrary multi-party communication protocol with an untrusted source. The simulation results show that at reasonable distances the asymptotic key rates for the two cases（with trusted and untrusted sources） almost overlap, which indicates the feasibility of our protocol.

Performance analysis of continuous-variable measurement-device-independent quantum key distribution under diverse weather conditions

The effects of weather conditions are ubiquitous in practical wireless quantum communication links.Here in this work,the performances of atmospheric continuous-variable measurement-device-independent quantum key distribution(CV-MDI-QKD)under diverse weather conditions are analyzed quantitatively.According to the Mie scattering theory and atmospheric CV-MDI-QKD model,we numerically simulate the relationship between performance of CV-MDI-QKD and the rainy and foggy conditions,aiming to get close to the actual combat environment in the future.The results show that both rain and fog will degrade the performance of the CV-MDI-QKD protocol.Under the rainy condition,the larger the raindrop diameter,the more obvious the extinction effect is and the lower the secret key rate accordingly.In addition,we find that the secret key rate decreases with the increase of spot deflection distance and the fluctuation of deflection.Under the foggy condition,the results illustrate that the transmittance decreases with the increase of droplet radius or deflection distance,which eventually yields the decrease in the secret key rate.Besides,in both weather conditions,the increase of transmission distance also leads the secret key rate to deteriorate.Our work can provide a foundation for evaluating the performance evaluation and successfully implementing the atmospheric CV-MDI-QKD in the future field operation environment under different weather conditions.

In-situ measurement and distribution of flue gas mercury for a utility PC boiler system

The in-situ instrumentation technique for measuring mercury and itsspeciation downstream a utility 100 MW pulverized coal (PC) fired boiler system was developed andconducted by the use of the Ontario hydro method (OHM) consistent with American standard test methodtogether with the semi-continuous emissions monitoring (SCEM) system as well as a mobile laboratoryfor mercury monitoring. The mercury and its speciation concentrations including participate mercuryat three locations of before air preheater, before electrostatic precipitator (ESP) and after ESPwere measured using the OHM and SCEM methods under normal operation conditions of the boiler systemas a result of firing a bituminous coal. The vapor-phase total mercury Hg(VT) concentration declinedwith the decrease of flue gas temperature because of mercury species transformation from oxidizedmercury to particulate mercury as the flue gas moved downstream from the air preheater to the ESPand after the ESP. A good agreement for Hg°, Hg^(2+) and Hg( VT) was obtained between the twomethods in the ash-free area. But in the dense particle-laden flue gas area, there appeared to be abig bias for mercury speciation owing to dust cake formed in the filter of OHM sampling probe. Theparticulateaffinity to the flue gas mercury and the impacts of sampling condition to accuracy ofmeasure were discussed.

Preliminary Results of In-situ Stress Measurements along the Longmenshan Fault Zone after the Wenchuan M_s 8.0 Earthquake

Four months after the Wenchuan Ms 8 earthquake in western Sichuan, China, in situ stress measurements were carried out along the Longmenshan fault zone with the purpose of obtaining stress parameters for earthquake hazard assessment. In-situ stresses were measured in three new boreholes by using overcoring with the piezomagnetic stress gauges for shallow depths and hydraulic fracturing for lower depths. The maximum horizontal stress in shallow depths （-20 m） is about 4.3 MPa, oriented N19°E, in the epicenter area at Yingxiu Town, about 9.7 MPa, oriented N51°W, at Baoxing County in the southwestern Longmenshan range, and about 2.6 MPa, oriented N39°E, near Kangding in the southernmost zone of the Longmenshan range. Hydraulic fracturing at borehole depths from 100 to 400 m shows a tendency towards increasing stress with depth. A comparison with the results measured before the Wenchuan earthquake along the Longmenshan zone and in the Tibetan Plateau demonstrates that the stress level remains relatively high in the southwestern segment of the Longmenshan range, and is still moderate in the epicenter zone. These results provide a key appraisal for future assessment of earthquake hazards of the Longmenshan fault zone and the aftershock occurrences of the Wenchuan earthquake.

A distributed measurement method for in-situ soil moisture content by using carbon-fiber heated cable

Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content （SM-DTS） is introduced.The system is based on carbon-fiber heated cable （CFHC） technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue （Tt） can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas.

Advance of in-situ stress measurement in China

In-situ stress is an essential parameter for design and construction of most engineering projects that involve excavation in rocks. Progress in in-situ stress measurement from the 1950s in China is briefly introduced. Stress relief by overcoring technique and hydraulic fracturing： technique are the two main techniques for in-situ stress measurement in China at present. To make them suitable for application at great depth and to increase their measuring reliability and accuracy, a series of techniques have been developed. Applications and achievements of in-situ stress measurement in Chinese rock engineering, including mining, geotechnical and hydropower engineering, and earthquake prediction, are introduced. Suggestions for further development of in-situ stress measurement are also proposed.

Development of in-situ Marine Sediment Geo-Acoustic Measurement System with Real-Time and Multi Frequencies (the Second Generation)

Compared with the laboratory acoustic measurement of sediment samples, the in-situ acoustic measurement in marine sediment is considered more accurate and rehable, because it covers all of the surrounding environment factors and avoids the disturbance during the course of sampling and transporting of sediment samples. A new multi-frequency in-situ geoacoustic measurement system （MFIS^AMS） has been developed. The system can provide acoustic vdocity （compressional wave） and attenuation profiles of the uppermost 4 - 8 m sediment in the seafloor. It consists of 8 channels with 12 frequencies （multi-frequencies） and 0.5 - 2 MHz sampling rates. The data collected can be transmiuted in real-time. Associated with inclinometer and altimeter, it can provide the data for depth emendation. Acoustic velocity and attenuation data have been obtained from two in-situ experiments conducted in the Hangzhou Bay.

New development of hydraulic fracturing technique for in-situ stress measurement at great depth of mines

In-situ stress measurement using the hydraulic fracturing technique was made at Wanfu Coal Mine in Shandong Province, China. To solve problems caused by great measuring depth and extra thick overburden soil layers in the mine, a series of improved techniques were developed for the traditional hydraulic fracturing technique and equipment to increase their pressure-enduring ability and to ensure safe and flexible removal of the sealing packers with other experimental apparatus. Successful in-situ stress measurement at 37 points within 7 boreholes, which were mostly over 1000 m deep, was completed. Through the measurement, detailed information of in-situ stress state has been provided for mining design of the mine. The improved hydraulic fracturing technique and equipment also provide reliable tools for in-situ stress measurement at great depth of other mines.