measurement

摘要： Radon is a radioactive gas that is naturally produced by the breakdown of uranium in soil,rock and water.Recent International Commission on Radiological Protection(ICRP)and World Health Organization(WHO)requirements include controlling indoor radon exposure and settings of a reference level for the annual average activity concentration of up to 300 Bq/m3 for dwellings and public buildings.Radon measurements in school buildings have long been carried out in many countries.Systematic measurements in schools in Bulgaria have started and are progressing.The study concerns the measurements of radon concentration(CRn)in all state school buildings in one of the Black Sea regions,Varna district,and the analysis of indoor variation.The survey of 1,185 premises of 107 schools was conducted from December 2019/January 2020 to March/May 2020 using a passive method.The AM(Arithmetic Mean)of CRn in the premises of the studied schools on the territory of Varna district is 130 Bq/m^(3),and the geometric mean is 97 Bq/m^(3).The number of premises exceeding the national reference level of 300 Bq/m^(3) is 72 located in 38 schools(about 36% of schools).A statistically significant difference(KW(Kruskal-Wallis),p<0.0001)was found between the radon data,grouped by municipalities.Furthermore,the radon data were classified into two groups based on municipality location:on the Black Sea coast and inland.Schools located near the sea have a higher value of CRn.In order to more accurately assess the exposure of pupils and teachers,the results are divided into four groups,depending on the type of use of the premises and the floor on which they are located.The highest CRn value was found in the study rooms used for specialized education such as physics,chemistry,music etc.(AM=155 Bq/m3),which can be explained by their smaller size and less frequent use.A statistically significant difference(KW,p<0.0001)was found,which means that the radon exposure in the examined rooms depends on the type of use.The key to reducing children’s exposure in schools is to measure CRn and then apply corrective action to the high levels of radon.

摘要： In the future smart transportation system, reliable vehicle-to-infrastructure(V2 I) communication is very important to ensure vehicle driving safety and to improve vehicle driving efficiency. In this paper, V2 I channel measurements at 5.92 GHz are conducted in typical urban and highway scenarios.The frequency and bandwidth of transmission, as well as the deployment of the RSU(roadside unit) and the OBU(on board unit), are selected by considering the recommendation proposed by 3 GPP TR 36.885. Then,based on the measured data, the key channel characteristic parameters of the V2 I channel are extracted,including path loss, root-mean-square delay spread,stationarity distance, and Doppler spread, etc. Also,the statistical characteristics of the parameters, including time-varying and Doppler characteristics, are investigated and characterized. The work in this paper helps researchers design technology and communication systems in similar scenarios.

摘要： This study investigates the measurement of social identification, interpersonal attraction, and cohesiveness in virtual groups. Different theoretical claims about relationships in computer-mediated groups rely on measurement strategies that are shown to reflect dramatically inconsistent semantic and administration features. A review of conceptual approaches and definitions for these constructs is presented. Data were collected from groups working asynchronously via the Internet under different geographic distributions, whose members completed a variety of measures related to these constructs. Analyses generated three likely dimensions of attraction. The research highlights the need for greater specificity in reports of the actual measures used in group research, and additional conceptual concerns regarding the contested relationships among these constructs.

摘要： Precise measurements of the cavity forward(Vf)and reflected signals(Vr)are essential for characterizing other key parameters such as the cavity detuning and forward power.In practice,it is challenging to measure V_(f) and V_(r) precisely because of cross talk between the forward and reflected channels(e.g.,coupling between the cavity reflected and forward signals in a directional coupler with limited directivity).For DESY,a method based on the cavity differential equation was proposed to precisely calibrate the actual V_(f) and V_(r).In this study,we verified the validity and practicability of this approach for the Chinese ADS front-end demo superconducting linac(CAFe)facility at the Institute of Modern Physics and a compact energy recovery linac(cERL)test machine at KEK.At the CAFe facility,we successfully calibrated the actual V_(f) signal using this method.The result demonstrated that the directivity of directional couplers might seriously affect the accuracy of V_(f) measurement.At the cERL facility,we calibrated the Lorentz force detuning(LFD)using the actual Vf.Our study confirmed that the precise calibration of V_(f) significantly improves the accuracy of the cavity LFD measurement.

摘要： The construction of a perfect evaluation index system of professional literacy of pre-science teachers is the basis of measuring the level of professional literacy of pre-science teachers in Xinjiang.It is of great practical significance to identify the advantages and disadvantages of education of pre-science teachers in Xinjiang.Based on“Professional Standards”and“Certification Standards”,this paper constructs an evaluation index system of Xinjiang pre-science teachers’professional literacy,including 3 first-level indicators and 18 second-level indicators.

摘要： Currently,the measurement methods for pneumatic system leakage include bubbling,ultrasonic,and pressure detection methods.These methods are sensitive to high-precision sensors,long detection times,and stable external environments.The traditional differential pressure method involves severe differential pressure fluctuations caused by environmental pressure fluctuations or electromagnetic noise interference of sensors,leading to inaccurate detection.In this paper,a differential pressure fitting method for an asymmetric differential pressure cylinder is proposed.It overcomes the limitation of the detection efficiency caused by the asynchronous temperature recovery of the two chambers in the asymmetric differential pressure method and uses the differential pressure substitution equation to replace the differential calculation of the differential pressure.The improved differential pressure method proposes an innovation based on the detection principle and calculation method.Additionally,the influence of the parameters in the differential pressure substitution equation on the leakage calculation results was simulated,and the specific physical significance of the parameters of the differential pressure substitution equation was explained.The experiments verified the fitting effect and proved the accuracy of this method.Compared with the traditional differential pressure method,the maximum leakage deviation of inhibition was 0.5 L/min.Therefore,this method can be used to detect leaks in air tanks.

摘要： To understand the research status of asphalt pavement texture,the related achievements and progress of pavement surface texture were systematically sorted out from three aspects:the characterization of pavement surface texture,the texture measurement and evaluation,and the relationship between texture and the skid resistance.Based on the statistical geometric characteristics,the spectral characteristics,the fractal characteristics and the multifractal characteristics,the characteristics of pavement texture were discussed.The test methods of pavement texture were divided into two categories:direct measurement methods and indirect measurement methods.The advantages and disadvantages of each measurement method were summarized.The effects of macro-texture and micro-texture on asphalt pavement were discussed,respectively.The relationship between texture and skid resistance was studied.This review shows that multifractal theory should be further studied from the aspect of road engineering.High-precision non-contact integrated detection technology should be further studied to meet the needs of complex testing environments.The method of finite element numerical simulation has potential for the analysis of pavement skid resistance.In addition,methods such as big data analysis,neural network,and deep learning should be studied to achieve the intelligent perception and management of the whole state of skid resistance prediction.

摘要： Deflection is the most direct indicator that reflects the bearing capacity of the bridge and the overall stiffness. There are many ways to measure the deflection of Bridges, and the inclination angle method is the most commonly used indirect method, but the existing theory of inclination angle method is relatively complicated. Based on the facts of the bridge small inclination, this article proposes the method of obtaining the bridge deflection by the inclination of the secant line constructed from the adjacent measurement points. Firstly, according to the bending deformation curve of general simply supported beam, the deflection calculation formula of each measuring point is derived based on the assumption of small deformation and the inclination Angle of measuring point. Secondly, a large commercial finite element software ANSYS 10.0 is used to carry out numerical simulation on the simply-supported beam under concentrated load in mid-span, and the deflection results of the numerical simulation are compared and verified with the theoretical results of the proposed method. Finally, the measured deflection results of the simply-supported beam model under mid-span load are compared with the theoretical results of the proposed method. The verification results show that if the actual model is consistent with the theoretical model, the proposed method has good accuracy.

摘要： The purpose of this article is to review recent PIV Studies from the basic to hybrid analysis, focusing on explaining epoch-making development of PIV. The overwhelming advantage of PIV over other velocity measurement methods is that it enables instantaneous and simultaneous velocity measurement of whole flow fields. We roughly classify PIV development and/or progress into the following five categories; A) Basics of PIV and post-processing. B) Simultaneous measurement of velocity and temperature, and 3D-PIV. C) Application to multiphase turbulent flows. D) Application to fluid machinery. E) Hybridization of PIV and CFD. This paper introduces the epoch-making research results from papers published in international journals as milestones related to (A) to (E), and concludes with additional forecast of future development of PIV research.

摘要： This article deals with the problem of calculating the comparative uncertainty of the main variable in the model of the studied physical phenomenon, which depends on a qualitative and quantitative set of variables. The choice of variables is determined by preliminary information available to the observer and dependent on his knowledge, experience and intuition. The finite value of the amount of information available to the researcher leads to the inevitable aberration of the observed object. This causes the existence of an unremovable and intractable processing by any statistical methods, a comparative (respectively, relative) uncertainty of the model. The goal is to present a theoretical justification for the existence of this uncertainty and proposes a procedure for its calculation. The practical application of the informational method for choosing the preferred model for the Einstein formula and for calculating the speed of sound is demonstrated.

摘要： Trace elements,especially heavy metals,are considered to be one of the main sources of pollution in the environment,Since they have a significant effect on i0ts ecological quailty.Human activities often mobilize and redistribute natural substances in the environment so much so that they can cause adverse effect environment so much so that they can causeintroduced into lake andadverse effect .a number of chemical,reservoir waters by riverine or atmosphericTrace heavy metalsinputs are involved inbiological and physical processes that control their concentrations inthe aqueous phase, and inspeciation of an element in environmentbioavailability , soil organic matter ingovernsenvironmentsites duereleasedill-defined substances, ediments. In general, the chemicalits biogeochemical behavior andpresents a large number of bindingbioorganisms. The largesubstances,.g，humic matter, or to different type of ligandsnumber of ionisable functional groups in humicsubstances,mainly carboxylic and phenolic groups, results in an appreciable ability to formstable complexes with heavy metal canons. In addition, different binding sites may presentdifferent degrees of lability, i.e., different dissociation rate constants. This depends notonly on the type of the metal ions and organic matter that are present in solution, but alsoon tnetr relative concentration .Due to the large number of complexmg sites withdifferent functional groups and different affinities for heavy metal canons (chemicalbydyheterogeneity), the complexation properties of humic substances are representedaverage stability parameters orequilibrium distribution functions. The complexation properties of humic andaim of this stuwas to study and compare theisolated from soils.fulvic substance.

摘要： A high-g beam-mass structure accelerometer was designed.In this structure, by means of KOH hack etching on the mass, V-groove structure was fabricated on the backside of the mass, so the weight of the mass and al-so the relative distance between the mass center and the neutral plane were all decreased.With the thin mass struc-tore, we can take advantage of both beam-mass structure and flat film structure; the fabrication process is also sim-ple.By means of Hopkinson shock test system, we did the accelerometer calibration.According to the test result,the sensitivity of the MEMS accelerometer is 0.71 μV/g, which keeps in accordance with the theoretical calculation.After a 200 000 g shocking test, the micro structure worked as usual, so this design can satisfy the requirements ofhigh shock, seriously vibration test environment.