A Bridge to the World--Congratulations to the launch of China Standardization

After years of expedition in the journey of standardization, we've conquered milesand miles to be standing here.     

量传比变化对检定压力变送器的影响

本文说明了量传比变化对检定压力变送器的影响及实例评定.     

Response to Letter to the Editor

Sir, Response to ‘Are all photon radiations similar in largeabsorbers?—A comparison of electron spectra’ byA. M. Kellerer and H. Roos When the ICRP adopted a quality factor—and subsequentlya radiation weighting factor—that gives equal weight todifferent photon radiations, it did not, necessarily imply thatequal     

二次空气量对超细粉体分级机细料得率的影响分析

本文从理论上分析颗粒在分级机内运动分布,将分级空间划分为“分极内区”和“分级外区”,给出分级机细料得率定义,并指出影响分级得率的主要因素,着重提出在不影响细粒粒径的前提下,在分级机底部引入二次空气,并利用实验证实,当二次空气量补引入后,分级机分级得率可增大到７０％以上．     

浅谈仪器收发的重要性及要求

本文对计量仪器收发的重要性作了具体分析,对管理上存在的问题和收发人员的素质提出了更高要求.     

Aerosol formation due to a dental procedure: insights leading to the transmission of diseases to the environment

As a result of the outbreak and diffusion of SARS-CoV-2, there has been a directive to advance medical working conditions. In dentistry, airborne particles are produced through aerosolization facilitated by dental instruments. To develop methods for reducing the risks of infection in a confined environment, understanding the nature and dynamics of these droplets is imperative and timely. This study provides the first evidence of aerosol droplet formation from an ultrasonic scalar under simulated oral conditions. State-of-the-art optical flow tracking velocimetry and shadowgraphy measurements are employed to quantitatively measure the flow velocity, trajectories and size distribution of droplets produced during a dental scaling process. The droplet sizes are found to vary from 5 µm to 300 µm; these correspond to droplet nuclei that could carry viruses. The droplet velocities also vary between 1.3 m s⁻¹ and 2.6 m s⁻¹. These observations confirm the critical role of aerosols in the transmission of disease during dental procedures, and provide invaluable knowledge for developing protocols and procedures to ensure the safety of both dentists and patients.     

Experimental protocol to determine the ability of PET to crystallise

PET [poly(ethylene terephtalate)] is a semi-crystalline thermoplastic that is very suitable for forming processes and is widely used in various technologies. For specific applications, it is necessary to avoid the crystallization of the material by quenching from the melting state while for other applications this crystallization is required. It follows that the ability of PET to crystallize could be a crucial industrial problem, particularly because of the large range of PET proposed by plastic suppliers. This work deals with a calorimetric method able to discriminate this aptitude between various PET rapidly and to give a criterion of crystallizability.     

广州地铁四号线多联空调机组涡旋式压缩机故障分析与解决措施

通过对广州地铁四号线多联空调涡旋压缩机的故障分析,找出压缩机故障的主要原因,并提出了相关解决措施,得出多联空调安装质量的高低直接决定了系统能否长期稳定的运行。     

Application of the parameter of defect resistance to the evaluation of the susceptibility of structural steels to brittle fracture

We present the results of low-temperature tests for impact toughness and uniaxial tension of 10 KhSND and 12KhN3… shipbuilding steels. We demonstrate the applicability of the parameter of defect resistance D₂ (suggested earlier) to the comparative characterization and classification of steels according to their toughness. Translated from Problemy Prochnosti, No. 3, pp. 96–103, May–June, 1997.     

Assessment of doses to the offspring of the Techa River cohort due to intakes of radionuclides by the mother

The Techa River was contaminated as a result of radioactive releases by the Mayak plutonium production facility in 1949-1956. The residents of riverside communities were exposed to internal irradiation from radionuclides ingested mainly with river water, and also to external gamma irradiation resulting from shoreline and flood-plain contamination. The most important role in population exposure was played by (89,90)Sr and 137Cs. The persons born after the onset of the contamination have been identified as the 'Techa River Offspring Cohort' (TROC). The TROC has the potential to provide direct data on health effects in progeny that resulted from exposure of a general population to chronic radiation. This report describes the results of the calculation of fetal doses due to intakes of radionuclides by their mothers. Particular attention has been given to fetal dose from 90Sr because this nuclide is the most significant in terms of population dose for the Techa River. The comparison of the fetal bone marrow doses evaluated using different approaches proposed in the literature has shown a large dispersal in dose values. The main cause of this is the difference in model assumptions simplifying some developmental aspects of fetal haematopoiesis and bone formation. This paper presents an analysis of these basic assumptions that could be useful for further improvements in fetal dosimetry.     

Investigation of dynamic resistance to the shear of water-saturated sand according to the results of the inverse experiment technique

The results of an investigation of the shear resistance for compacted dry and water-saturated sand are presented on the basis of the experimental-calculation analysis of the drag force at the quasi-stationary penetration stage of a cylindrical impactor. We used a method proposed earlier based on the inverse experiment technique and using a measuring rod with a flat end. It is shown that with almost the complete water saturation of sand its shear properties decrease but remain significant in the practically important range of penetration rates.     

GPS在交通道路测量中的应用

1：500000量级的基础地理信息是我国最重要和最基本的基础空间数据集，对我国的各方面的发展都有着不可忽视的作用。交通道路的测量和数据采集是建立1：50000基础空间数据库的关键之一。将GSP应用于交通道路的测量，可以充分发挥GPS全球性、全天候、高精度、三维定位等优点；快速实现交通道路的测量和相关数据采集，通过研究和现场试验证明，采用差分GPS技术不仅可行，而且有着其它方法无法比拟的优点。     

标准信号产生和测量的智能化方法

本文研究了标准信号的产生和测量的智能化方法,以及采用该方法研制的校准仪。     

Corrections to the electronic heat capacity of metals due to finite lifetimes of the conduction electrons

The electron-phonon interaction is well known to enhance the low-temperature electronic heat capacity of metals, C _el. At high temperatures this enhancement vanishes, but the electron-phonon interaction gives the electrons a finite lifetime. That means a broadened density of states, which affects the high-temperature C _el. Starting from a many-body theory expression for the entropy, this paper presents an analytical calculation of the correction to C _el and a numerical calculation of C _el from a realistic density-of-states function, N(). The effect arising from the broadening of N() may have any sign and typically alters the heat capacity by 10% or less in transition metals.     

基于红外探测原理的多功能报警器

本文叙述了基于红外探测原理的多功能报警器的工作原理、仪器结构、主要性能指标等内容.该仪器可作为重要岗哨及值班人员的报警器材.     

浅谈电子汽车衡的安装要求

文章主要介绍了电子汽车衡安装的程序及应该注意的几个问题.