共查询到19条相似文献,搜索用时 187 毫秒
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磷渣加气混凝土作为砌体材料已广泛应用于建筑物中,但在工程验收中对该材料砌筑后室内氡浓度的监测数据较少。为研究磷渣加气混凝土作为砌体材料后室内氡浓度的变化水平,根据国家现行规范,采用RAD7连续测氡仪对一栋用该材料砌筑后的建筑物,分不同时间段进行多次氡浓度的监测试验和数据采集。结果表明:磷渣加气混凝土作为砌体材料,氡气检测平均值均小于规范值。 相似文献
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结构有限元模型修正的频响函数方法 总被引:2,自引:0,他引:2
在将结构有限元模型的修正量表示为子结构的误差因子的线性函数的基础上,导出了一种利用试验频响函数修正有限元模型的质量、刚度和阻尼矩阵的方法。为减少大型复杂结构有限元模型修正的计算量,使用改进缩聚系统(IRS)方法缩减模型的自由度。该方法可以在结构振动试验的测量自由度小于模型自由度的情况下得到模型修正量,并使修正后的模型保持原有的自由度和稀疏特性。 相似文献
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本文介绍了常用的氡测量方法和测氡仪器,对氡测量技术进行了较详细分析,为选择适宜的方法进行氡浓度监测提供了参考。标准氡室的研制为各种测氡仪器的刻度和量值溯源性提供了技术支撑,保证了测量结果的准确可靠,文章简要介绍了国内外标准氡室的发展状况。 相似文献
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《纳米技术与精密工程》2015,(4)
本文设计了一套汽油挥发气远程监测系统,利用汽油挥发气在中红外波段的吸收光谱进行浓度检测,研究了现场测试条件下检测系统的性能参数对测量结果的影响.文中采用功率加权法计算吸收光谱的吸光度值,并通过仿真和实验分析了采样过程中影响气体浓度监测的相关因素.结果表明,气体流量对平衡时间和测量浓度的影响较小,在达到平衡后测量误差小于7%;而采样距离对结果影响较大,在15 m时,误差达到了18%,修正后误差可控制在4%以内;真空度与浓度之间呈现良好的线性度.通过实验和仿真数据分析,可以对实际测量的浓度进行修正,减小测量误差,为现场测试提供数据参考. 相似文献
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在彭州市丽春镇地区大约4km的区域内,利用IED3000R土壤测氡仪开展多剖面土壤氡浓度测量。根据测量结果绘制土壤氡测量剖面图及目标区土壤氡浓度分布的平面等值图,得出丽春镇地区隐伏断裂的位置、走向以及宽度等信息。将断裂信息与前人成果相比较,讨论汞污染与隐伏断裂的关系。 相似文献
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用工程级方法来测定真空泵噪声的声功率级,一般的室外场地、工厂的大车间和实验室可用作测试场地,用标准声源替代法确定的环境修正值k。必须小于或等于2dB,在矩形测量表面布置9个测点,泵的噪声与背景噪声的声压级之差在6—10分贝内,按规定修正测量值,真空泵按实际使用状况安装于测试场地,启动半小时后开始测量。 相似文献
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The aim of this work is to studying indoor radon distribution using the Finite Volume Method (FVM). This paper focuses on effects of exhalation from different sources (wall, floor and ceiling) and the ventilation profile on distribution the concentrations of radon indoor. The rate of radon exhalation and ventilation were measured and are used as input in FVM simulation. It has been found that the radon concentration is distributed in non homogeneous way in the room. The radon concentration is much larger near floor, and decreases in the middle of the room. The experimental validation was performed by measuring radon concentration at different locations in room using active and passive techniques. We notice that the results of simulation and experimental are in agreement. The annual effective dose of radon in the model room has been also investigated. 相似文献
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Bogacz J Mazur J Swakoń J Budzanowski M Olko P 《Radiation protection dosimetry》2002,101(1-4):267-270
A method of measurement of radon concentration in air was developed, based on high-sensitivity LiF:Mg,Cu,P (MCP-N, TLD Poland) thermoluminescent detectors installed in charcoal canisters. The canisters were exposed typically for 72 h in a calibration chamber with a radon concentration ranging from 100 Bq x m(-3) to 87 kBq x m(-3). It was found that in these conditions the signal registered by the TL detectors was proportional to the 222Rn concentration and the lowest limit of detection (LLD) was at a level of 100 Bq x m(-3). The proposed method can be used in large-scale, multi-site surveys aimed at screening for high levels of indoor radon concentration or for measuring ground radon exhalation rates. 相似文献
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The radon concentration and radon exhalation rates were studied in 39 soil samples collected from Hassan district of southern India. LR-115 Type II solid-state nuclear track detector was used to measure the radon exhalation rate using the sealed can technique. The radon exhalation rate increases with a decrease in the soil grain size. A strong positive correlation was observed between the radon exhalation rate and effective radium content. The α index and annual effective dose were also determined. 相似文献
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Simultaneous indoor radon, radon-thoron progeny and high-resolution in situ gamma spectrometry measurements, with portable high-purity Ge detector were performed in 26 dwellings of Thessaloniki, the second largest town of Greece, during March 2003-January 2005. The radon gas was measured with an AlphaGUARD ionisation chamber (in each of the 26 dwellings) every 10 min, for a time period between 7 and 10 d. Most of the values of radon gas concentration are between 20 and 30 Bq m(-3), with an arithmetic mean of 34 Bq m(-3). The maximum measured value of radon gas concentration is 516 Bq m(-3). The comparison between the radon gas measurements, performed with AlphaGUARD and short-term electret ionisation chamber, shows very good agreement, taking into account the relative short time period of the measurement and the relative low radon gas concentration. Radon and thoron progeny were measured with a SILENA (model 4s) instrument. From the radon and radon progeny measurements, the equilibrium factor F could be deduced. Most of the measurements of the equilibrium factor are within the range 0.4-0.5. The mean value of the equilibrium factor F is 0.49 +/- 0.10, i.e. close to the typical value of 0.4 adopted by UNSCEAR. The mean equilibrium equivalent thoron concentration measured in the 26 dwellings is EEC(thoron) = 1.38 +/- 0.79 Bq m(-3). The mean equilibrium equivalent thoron to radon ratio concentration, measured in the 26 dwellings, is 0.1 +/- 0.06. The mean total absorbed dose rate in air, owing to gamma radiation, is 58 +/- 12 nGy h(-1). The contribution of the different radionuclides to the total indoor gamma dose rate in air is 38% due to 40K, 36% due to thorium series and 26% due to uranium series. The annual effective dose, due to the different source terms (radon, thoron and external gamma radiation), is 1.05, 0.39 and 0.28 mSv, respectively. 相似文献
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Konstantin Kovler 《Materials and Structures》2007,40(4):419-430
The paper deals with one of the physical methods, which can be used for monitoring hydration of cementitious materials: the
radon exhalation method. Experiments with two types of hydrating cement paste (made with water to cement ratios of 0.25 and
0.33) are described. The kinetics of shrinkage and hydration heat development are discussed. Different mechanisms influencing
the radon exhalation rate E from cement and hydration products are considered. The initial E-values determined in the beginning of the tests were 0.01–0.02 mBq kg−1 s−1 for the cement pastes made at water/cement ratios of 0.25 and 0.33, respectively. In 3 days both pastes showed E = 0.04 mBq kg−1 s−1. However, the most important finding seems to be the dramatic increase of the radon exhalation rate up to the maximum observed
a few hours after mixing with water (0.66 and 0.58 mBq kg−1 s−1 for 0.25 and 0.33 pastes, respectively). This was registered in the radon chamber within the time period usually classified
as set. The test results showed a strong correlation between radon exhalation rate and liberation of hydration heat. Peaks
of the radon exhalation rate coincide with those of temperature measured on the surface of the cement paste. Analysis of the
literature data shows that heating of the materials weakens physical adsorption of radon gas atoms on newly formed solid surfaces
and can enhance the radon exhalation rate by several times. However, the performed experiment shows that the radon exhalation
rate drastically increases (by dozens of times), and then decreases again. Such a dramatic growth can be explained by a synergy
between temperature effect and two more phenomena: (a) intensive formation of microstructure with an extremely high specific
surface area, when cement sets and while porosity is still high and (b) intensive flow of water, which traps radon from the
newly formed solid surfaces of C-S-H and brings it to the sample surface, enhancing the radon flux. 相似文献
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Christer Samuelsson 《Journal of research of the National Institute of Standards and Technology》1990,95(2):167-169
Results from closed-can radon exhalation experiments must be interpreted bearing the time-dependent radon diffusion theory in mind. A rapid change from the free to final steady-state exhalation rate will take place for all samples that are thin compared with the radon diffusion length. The radon gas accumulating in a closed can corresponds to a free exhalation rate only if the outer volume of air is much larger than the pore volume of the enclosed sample, or the thickness of the sample is much larger than the radon diffusion length. 相似文献
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The sand samples have been collecting from the sea coast (Unniyal beach) of Tirur of Malappuram district of Kerala state (India) by the grab sampling method. Radon exhalation rates have measured by “Sealed Can Technique” using LR-115 type II plastic track detector to estimate the health risk level in the environment. The value of radon activity varies from 444.44 to 2204.44 becquerel meter?3 (Bq m?3) with a geometric mean (G.M.)/standard deviation (S.D.) value of 1017.21 Bq m?3/433.27. The value of mass exhalation rate for radon varies from 0.01 to 0.05 Bq kg?1 h?1 with a G.M./S.D. value of 0.024 Bq kg?1 h?1/0.010. The value of area exhalation rate for radon varies from 0.27 to 1.33 Bq m?2 h?1 with a G.M./S.D. value of 0.62 Bq m?2 h?1/0.26. The values of radon emanation ranged from 2.90?×?10?3 to 2.98?×?10?3 (%) with a G.M./S.D. value of 2.98?×?10?3(%)/0.05. The alpha dose equivalent of the studied area is found and it varies from 0.68 to 1.66 milli sievert year?1 (mSv yr?1) with a G.M./S.D. value of 1.03 mSv yr?1/0.24. Good positive correlation is observed between the effective radium content and area exhalation rate for sand samples. Therefore, the obtained result shows that this region is safe as for as the health risk effects of radium and radon exhalation rate are concerned. 相似文献
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The Authorized Metrological Centre (AMS) working by SUJCHBO (National Institute for Nuclear, Chemical and Biological Protection) ensures for the Czech Republic the metrological traceability for devices that measure the radon concentration and the energy equivalent radon concentration connected with the radon decay products (RnDP). The evaluation and the calibration of measuring devices for radon and RnDP require the stable conditions (first of all radon and the RnDP concentrations). The new AMS radon-aerosol chamber in Kamenná consists of the walk-in testing chamber with a volume of 10 m(3) and of the handling box with a volume of 0.3 m(3). The design of the chamber allows measurement and a control of environmental parameters such as the temperature, the pressure of air inside and outside of the chamber, the relative humidity of air, the concentration and the size distribution of aerosol particles and the air velocity. 相似文献