A super-high resolution frequency standard measuring approach based on phase coincidence characteristics between signals

A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10^-13/s at 5 MHz, and the self-calibration resolution can achieve 10^-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10^-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.

Intrinsic background radiation of LaBr3(Ce)detector via coincidence measurements and simulations

The LaBr3(Ce)detector has attracted much attention in recent years because of its superior characteristics compared with other scintillating materials in terms of resolution and efficiency.However,it has a relatively high intrinsic background radiation because of the naturally occurring radioisotopes in lanthanum,actinium,and their daughter nuclei.This limits its applications in low-counting rate experiments.In this study,we identified the radioactive isotopes in theφ3"x 3"Saint-Gobain B380 detector by a coincidence measurement using a Clover detector in a low-background shielding system.Moreover,we carried out a Geant4 simulation of the experimental spectra to evaluate the activities of the main internal radiation components.The total activity of the background radiation of B380 is determined to be 1.523(34)Bq/cm^3.The main sources include 138La at 1.428(34)Bq/cm^3,207Tl at 0.0135(13)Bq/cm^3,211Bi at 0.0136(15)Bq/cm^3,215Po at 0.0135(3)Bq/cm^3,219Rn at 0.0125(12)Bq/cm^3,223Fr at 0.0019(11)Bq/cm^3,223Ra at 0.0127(10)Bq/cm^3,227Th at 0.0158(22)Bq/cm^3,and 227Ac at 0.0135(13)Bq/cm^3.Of these,the activities of 207Tl,211Po,215Po,223Fr,and 227Ac are deduced for the first time from the secular equilibrium established in the decay chain of 227Ac.

Measurements of non-equilibrium and equilibrium temperature behind a strong shock wave in simulated martian atmosphere

Non-equilibrium radiation measurements behind strong shock wave for simulated Martian atmosphere are presented in this paper. The shock wave is established in a hydrogen oxygen combustion driven shock tube. Time- resolved spectra of the Av = 0 sequence of the B^2∑^＋ → X^2∑^＋ electronic transition of CN have been observed through optical emission spectroscopy （OES）. A new method, which is based on fitting high resolution spectrum for rotational and vibrational temperatures measurement, is proposed to diag- nose temperature distribution behind the shock wave. It is estimated that the current scheme has the maximum deviation less than 8% （lσ） for vibrational temperature measurement through detailed analysis of the influence of the uncertainties of spectroscopic constants and spectral resolution. Radiation structure of the shock layer, including induction, relaxation and equilibrium process, and corresponding rotational and vibrational temperatures are obtained through time gating OES diagnostics with sub-microsecond temporal resolution. The present extensive results will strongly benefit the reaction rate estimation and computational fluid dynamics （CFD） code validation in high enthalpy Mars reentry chemistry.

MIMO Channel Measurement and Characterization at 6.0-6.4 GHz Under Typical Classroom Environment

An extensive 4 x 4 MIMO channel measurement is carried out at 6. 0-6. 4 GHz under a typical classroom environment with channel sounder based on vector network analyzer. Both LOS and NLOS scenarios are considered. The results on path loss, delay spread and spatial correlation are presented. The measurement shows that, for corridor coverage, 2x2 MIMO is more economical than 4x4 MIMO due to high correlation. In order to identify the unique characteristics at the high frequency band, the measured channel parameters at 6. 0-6.4 GHz are compared with those at 2. 45 GHz. The comparison shows that the shortened wavelength of this higher frequency band results in a great difference of channel characteristics. Therefore, our measurement results provide new gnidance for the design and development of the system working on 6. 0-6.4 GHz band.

Carrier fringe method of moire interferometry for tiny strain measurements in micro-field

In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the specimen surface, and the strain can be deduced from the changes in carrier fringes before and after the deformation of an object. Four coherent laser beams are used to obtain the carrier fringe patterns of field U and V. Both theoretical analysis and numerical simulation indicate that the ideal accuracy of strain can be controlled within a range of ±1με. Case study of a plane extension experiment shows that the measurement accuracy of strain can be controlled within the range of ±10με. The average strain values of every row of field U and every column of field V can be obtained by using this method, and approximated strain of every pixel in the whole-field can be further acquired, and thus it is possible to measure tiny strains occurred in a micro-field. The technology in this paper can provide comprehensive information for analyzing related mechanical content in the field of MEMS.

Measurement and simulation of the two-phase velocity correlation in sudden-expansion gas-particle flows

In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.

(d,pγ)-coincidence technique and its preliminary application

When there eaist many light elements in a sample or the sample is thick, a reliable (d,p) reaction analysis cannot be often obtained due to the interference of particle groupscorresponding to different elements and even different energy levels of an element. Therefore,(d,pγ) coincidence technique is tried. By measuring a charged particle(proton) group in coincidence with its accompanying gamma rays, the background can be greatly suppressed andthe interference can be effectively eliminated.

Disentanglement of a Singlet Spin State in a Coincidence Stern-Gerlach Device

We analyze the spin coincidence experiment considered by Bell in the derivation of Bells theorem. We solve the equation of motion for the spin system with a spin Hamiltonian, Hz, where the magnetic field is only in the z-direction. For the specific case of the coincidence experiment where the two magnets have the same orientation the Hamiltonian Hz commutes with the total spin Iz, which thus emerges as a constant of the motion. Bells argument is then that an observation of spin up at one magnet A necessarily implies spin down at the other B. For an isolated spin system A-B with classical translational degrees of freedom and an initial spin singlet state there is no force on the spin particles A and B. The spins are fully entangled but none of the spin particles A or B are deflected by the Stern-Gerlach magnets. This result is not compatible with Bells assumption that spin 1/2 particles are deected in a Stern-Gerlach device. Assuming a more realistic Hamiltonian Hz + Hx including a gradient in x direction the total Iz is not conserved and fully entanglement is not expected in this case. The conclusion is that Bells theorem is not applicable to spin coincidence measurement originally discussed by Bell.

3-Dimensional Body Measurement Technology

3 - dimensional body measurement technology, the basis of developing high technology in industry, accelerates digital development of aplparel industry. This paper briefly introduces the history of 3 - dimensional body measurement technology, and recounts the principle and primary structure of some types of 3 - dimensional automatic body measurement system. With this understanding, it discusses prospect of 3- dimensional CAD and virtual technology used in apparel industry.

Test of Normality of Waist Measurement Data of Young Male and Female Adults based on the Quantile - Quantile Plot

This paper investigates the normality of some real data set obtained from waist measurements of a group of 49 young adults. The quantile - quantile （Q-Q） plot and the analysis of correlation coefficients for the Q-Q plot is used to determine the normality or otherwise of the data set. In this regards, the probabilities of the quantiles were computed, modified and plotted. Thereafter the correlation coefficients for the quantile - quantile plots were obtained. Results indicate that at 0.1 level of significance, the data for young adult males of the sample were not normally distributed, and had a mean value that is within the range of low risk, healthwise, whereas the distribution of the data for young female adults showed reasonable normality, but also with a mean value that is within the range of low risk in terms of health condition.

A Steady-State Errors Correction Method for Eliminating Measurement Errors

This paper proposes a steady-state errors correction(SSEC)method for eliminating measurement errors.This method is based on the detections of error signal E(s)and output C(s)which generate an expected output R(s).In comparison with the conventional solutions which are based on detecting the expected output R(s)and output C(s)to obtain error signal E(s),the measurement errors are eliminated even the error might be at a significant level.Moreover,it is possible that the individual debugging by regulating the coefficient K for every member of the multiple objectives achieves the optimization of the open loop gain.Therefore,this simple method can be applied to the weak coupling and multiple objectives system,which is usually controlled by complex controller.The principle of eliminating measurement errors is derived analytically,and the advantages comparing with the conventional solutions are depicted.Based on the SSEC method analysis,an application of this method for an active power filter(APF)is investigated and the effectiveness and viability of the scheme are demonstrated through the simulation and experimental verifications.

Risk measurement of international oil and gas projects based on the Value at Risk method

International oil and gas projects feature high capital-intensity, high risks and contract diversity. Therefore, in order to help decision makers make more reasonable decisions under uncertainty, it is necessary to measure the risks of international oil and gas projects. For this purpose, this paper constructs a probabilistic model that is based on the traditional economic evaluation model, and introduces value at risk(VaR) which is a valuable risk measure tool in finance, and applies Va R to measure the risks of royalty contracts, production share contracts and service contracts of an international oil and gas project. Besides, this paper compares the influences of different risk factors on the net present value(NPV) of the project by using the simulation results. The results indicate:(1) risks have great impacts on the project's NPV, therefore, if risks are overlooked, the decision may be wrong.(2) A simulation method is applied to simulate the stochastic distribution of risk factors in the probabilistic model. Therefore, the probability is related to the project's NPV, overcoming the inherent limitation of the traditional economic evaluation method.(3) VaR is a straightforward risk measure tool, and can be applied to evaluate the risks of international oil and gas projects. It is helpful for decision making.

Spatial resolved temperature measurement based on absorption spectroscopy using a single tunable diode laser

A novel method based on wavelength-multiplexed line-of-sight absorption and profile fitting for nonuniform flow field measurement is reported. A wavelength scanning combing laser temperature and current modulation WMS scheme is used to implement the wavelength-multi- plexed-profile fitting method. Second harmonic （2f） signal of eight H20 transitions features near 7,170 cm^-1 are measured in one period using a single tunable diode laser. Spatial resolved temperature distribution upon a CH4/air premixed flat flame burner is obtained. The result validates the feasibility of strategy for non-uniform flow field diagnostics by means of WMS-2f TDLAS.

Overview and outlook on railway track stiffness measurement

Stiffness is one of the basic performance parameters for railway track. The efficient and accurate stiffness measurement has been considered as the foundation for further development of railway engineering, and therefore has great theoretical and practical significance. Based on a summary of the connotation and measurement of track stiffness, the state of the art of measurement methods for track stiffness was analyzed systematically. The standstill measurement of track stiffness can be performed with the traditional jack-loading method, impact hammer method, FWD （falling weight deflectometer） method, and track loading vehicle method. Although these methods can be adopted in stiffness measurement for a section of railway track, they are not desirable owning to small range and low efficiency. In the recent 20 years, researchers have proposed many methods like unbalancedloading laser displacement method, deflection basin deformation rate method, and eccentricity excitation method to continuously measure track stiffness; however, these methods have drawbacks like poor accuracy, low speed, and insufficient data analysis. In this work, the merits and demerits of these methods were summarized, and optimization suggestions were presented. Based on the wave transmission mechanism and principle of vibration energy harvesting, an overall conception on continuous measurement of stiffness and long-term stiffness monitoring for special sections was proposed.

Determination of gross α and β activities in Zouma River based on online HPGe gamma measurement system

This paper describes a low-cost and fast method to evaluate gross α and β^(-) radioactivities in natural water based on an online high-purity germanium detector gamma measurement system.The major gamma activities in natural water are provided by natural and artificial radionuclides such as ^(40) K,^(137)Cs,and radionuclides belonging to ^(238)U and ^(232)Th series.The main a emitters related to gamma emissions in natural water are ^(224)Ra(240.98 keV)and ^(226)Ra(186.21 keV),and the β^(-) emitters are ^(40) K(1460.85 keV),^(214)Bi(609.31 keV),^(208)Tl(583.19 keV),and ^(214)Pb(351.93 keV).The formula for gross α and β^(-) activity concentration is based on these radionuclides,and the short half-life decay products are considered in the calculation.The detection efficiency of the device across energy region(0–3 MeV)is obtained through Monte Carlo simulation,and a calibration experiment is conducted to verify the simulation results.Gamma radioactivity is measured continuously for 114 d in Pixian County and Dongfeng Canal located in the Zouma River,Chengdu,Sichuan Province,China.A comparison of the calculation results and monitoring data from the Sichuan Management and Monitoring Center Station of Radioactive Environment indicates that the percentage and absolute error of a activity concentration is lower than 53%and 0.02 Bq/L,respectively,and that of β-activity concentration is lower than 33.2%and 0.016 Bq/L,respectively.The method can rapidly determine gross α and β^(-) activity concentrations in natural water online.

Auto-measuring System of 3-Dimensional Human Body

To realize the automation of fashion industry measuring,designing and manufacturing, the auto-measurement of 3D size of human body is of great importance. The auto measurement system of 3D human body based on Charge Coupled Devices (CCD) and infrared sensors is presented in this paper. The system can measure the bare size of human body that excludes the effect of clothing quickly and accurately.

Fundamental Properties and Optimal Gains of a Steady-State Velocity Measured <i>α</i>-<i>β</i>Tracking Filter

This paper clarifies the steady-state properties and performance of an α-β filter for moving target tracking using both position and velocity measurements. We call this filter velocity measured α-β (VM-α-β) filter. We first derive the stability condition and steady-state predicted errors as fundamental properties of the VM-α-β filter. The optimal gains for representative motion models are then derived from the Kalman filter equations. Theoretical and numerical analyses verify that VM-α-β filters with these optimal gains realize more accurate tracking than conventional α-β filters when the filter gains are relatively large. Our study reveals the conditions under which the predicted errors of the VM-α-β filters are less than those of conventional α-β filters. Moreover, numerical simulations clarify that the variance of the tracking error of the VM-α-β filters is approximately 3/4 of that of the conventional α-β filters in realistic situations, even when the accuracy of the position/velocity measurements is the same.

Formation permeability evaluation and productivity prediction based on mobility from pressure measurement while drilling

Based on the measurement mechanism of mobility in pressure measurement while drilling, through analyzing a large number of mobility data, it is found that under the condition of water-based mud drilling, the product of mobility from pressure measurement while drilling and the viscosity of mud filtrate is infinitely close to the water phase permeability under the residual oil in relative permeability experiment. Based on this, a method converting the mobility from pressure measurement while drilling to core permeability is proposed, and the permeability based on Timur formula has been established. Application of this method in Penglai 19-9 oilfield of Bohai Sea shows:(1) Compared with the permeability calculated by the model of adjacent oilfields, the permeability calculated by this model is more consistent with the permeability calculated by core analysis.(2) Based on the new model, the correlation between the calculated mobility of well logging and the actual drilling specific productivity index bas been established. Compared with the relationship established by using the permeability model of an adjacent oilfield, the correlation of the new model is better.(3) Productivity of four directional wells was predicted, and the prediction results are in good agreement with the actual production after drilling.

基于Pixie-Net数字化仪的γ-γ符合测量实验

随着核物理技术的发展,传统的电子学插件已经无法满足日益增长的核物理实验要求.数字化仪凭借其集成度高、数据处理灵活的优势,获得了广泛的应用.本实验尝试将Pixie-Net数字化仪用于NaI和CeBr_(3)探测器构成的γ-γ符合测量实验,简化电子学,提升教学效果.测量结果表明:根据探测器的信号特点优化了数字化仪的参数,以及修正了探测器和放射源尺寸带来的角关联系数差异后,γ-γ符合测量法测量得到的放射源活度与理论值误差小于基于传统电子学的β-γ符合法.

Determination of the time resolution for neutron scintillation detectors by multi-coincidence measurement

Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors （BC501A） were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE （China Institute of Atomic Energy）.