226Ra, 232Th and 40K analysis in soil samples from some areas of Malwa region, Punjab, India using gamma ray spectrometry

The activity concentrations of soil samples collected from thirty different locations of Malwa region of Punjab were determined by using HPGe detector based on high-resolution gamma spectrometry system. The range of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the soil from the studied areas varies from 18.37 Bq kg⁻¹ (Sangrur) to 53.11 Bq kg⁻¹ (Sitoguno), 57.28 Bq kg⁻¹ (Dhanola) to 148.28 Bq kg⁻¹ (Sitoguno) and 211.13 Bq kg⁻¹ (Sunam) to 413.27 Bq kg⁻¹ (Virk Khera) with overall mean values of 35 Bq kg⁻¹, 80 Bq kg⁻¹and 317 Bq kg⁻¹ respectively. The absorbed dose rate calculated from activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K ranges between 8.47 and 24.48, 35.68 and 92.38, and 8.74 and 17.11 nGy h⁻¹, respectively. The total absorbed dose in the study area ranges from 58.08 nGy h⁻¹ to 130.85 nGy h⁻¹ with an average value of 79.11 nGy h⁻¹. The calculated values of external hazard index (H_ex) for the soil samples of the study area range from 0.35 to 0.79. Since these values are lower than unity, therefore, according to the Radiation Protection 112 (European Commission. Radiation Protection 112 1999) report, soil from these regions is safe and can be used as a construction material without posing any significant radiological threat to population.     

浙江省工业烟粉尘总量控制研究

通过对浙江省工业烟粉尘排放总量和排放源现状进行分析,提出工业烟粉尘减排治理对策,对工业烟粉尘4个重点行业(水泥制造行业、火力发电行业、钢铁行业(包括炼钢、钢压延加工和黑色金属铸造行业)、纺织染整行业(包括棉印染精加工、化纤织物染整精加工和棉织造加工行业)排放源的烟粉尘减排途径和潜力进行分析测算,研究提出工业烟粉尘总量控制措施和建议。     

空气及蚊香燃烧产生的亚微米气溶胶的粒径谱

蚊香烟雾是一类常见的影响人类健康的气溶胶。利用高分辨的静电扫描粒径谱仪,研究了实验室内外空气及室内蚊香燃烧产生的亚微米气溶胶(14～723nm)的粒径分布特征及衰减情况。实验表明,实验室内、外亚微米气溶胶的数浓度分别在1.09×104～4.45×104cm-3,1.15×104～3.56×104cm-3范围内。蚊香燃烧产生的亚微米气溶胶的数量中值粒径、表面积中值粒径及体积中值粒径分别为80nm、148nm和230nm。点燃蚊香15min产生的气溶胶恢复到背景水平需要1～2h。     

烟颗粒对太赫兹波衰减特性的影响研究

太赫兹成像系统相对于普通红外线成像系统而言,其受温度和烟雾密度的影响较小,将其引入火场环境侦测中能较好地解决火场环境能见度低的问题.但太赫兹波在火场烟气环境中传播时,会受到烟颗粒的吸收和散射作用影响,造成其传播特性发生变化,因此有必要开展烟颗粒对太赫兹波衰减特性的影响研究.采用离散偶极子近似法进行模拟运算,结合烟颗粒分...     

高效喷淋泡沫脱硫技术及装置的应用

SO2是产生酸雨的主要气体,其主要来源于工业燃煤锅炉.以沈阳一家电厂为例,该厂选用新型高效的喷淋泡沫脱硫除尘器对锅炉排放的SO2进行治理.进入喷淋泡沫塔前的SO2平均浓度为2780 mg/m3,经脱硫后出塔平均浓度为289.3 mg/m3,去除率为89.6%.结果表明,这种有别于传统湿法的新型高效的喷淋泡沫脱硫技术及装置具有脱硫效率高、装置占地少、运行稳定、沉淀物易于回收利用等特点,对锅炉排放的SO2进行治理是非常有效的.     

长大区间隧道抽出式串联通风机排烟能力实验研究

为实现有效通风以降低隧道火灾带来的损失和伤亡,依托青岛市地铁8号线大洋站至青岛北站区间隧道,建立线性比尺为1∶15的隧道通风排烟模型实验系统,针对通风机串联单抽,围绕3种通风机频率匹配组合,测定单机的变频频率值、电功消耗、排烟道与行车道的断面平均风速以及右侧行车道静压。研究结果表明：在相同功率消耗下,不同频率匹配的串联通风机排烟效果存在差异;针对此差异,利用气体挡烟墙性能及其计算欧拉数值比较发现,风井近端的通风机频率较大时,下游对污染气流的抵抗力更强,拥有更好的排烟效果。研究结果可为隧道火灾提供更有效率的防灾救灾数据支持,并从欧拉数方面为研究隧道临界风速提供新角度。     

横通道通风对隧道火灾烟气蔓延影响的数值模拟研究

为探究隧道横通道通风对隧道火灾烟气蔓延的影响规律,使用火灾动力学模拟软件FDS,对不同火源位置的横通道临界风速、主隧道温度分布以及烟气层高度进行研究。研究结果表明：在一定火源功率范围内,隧道横通道临界风速与火源功率的1/3次方成正比且火源距横通道越远,临界风速越小;当火源位于交叉口,横通道使用临界风速通风时,隧道内烟气温度明显降低,烟气迅速沉降到2 m以下;当火源距离交叉口10,20 m,横通道通风会加快火源下游烟气沉降,烟气沉降速度随横通道通风速率的增大而增大;当火源位于交叉口时,烟气沉降由横通道通风对烟气的降温作用和涡旋作用共同主导,当火源位于距离交叉口10,20 m时,烟气沉降主要由涡旋作用主导。     

Research based on double coverage rate and reliability of gas detector layout optimization

The gas detector layout should be highly attuned to combustible gas leakage and attain a good reliability in avoiding detector malfunction, which is an important guarantee for the normal production of the chemical industry and other related enterprises. Herein, a gas detector layout optimization method based on double coverage and reliability is proposed. The key gas leakage monitoring area is determined through layout scene field investigation. To improve the detection probability and detection system reliability, the dual coverage target and voting mechanism are set, and the gas detector layout is determined with the ray-casting algorithm according to the coverage target. Combined with FLACS software to simulate a variety of typical leakage conditions under different layout scenarios, the relationship between the leaked gas concentration detected by gas detectors in each layout scheme and time is obtained, and the gas leakage detection probability in each layout scheme, number of detectors that can trigger the alarm, shortest time to trigger the alarm and reliability are comprehensively evaluated. The decision-maker selects the final gas detector layout plan according to the evaluation results and actual site needs. The study shows that the detection probability of each layout scheme set according to the double coverage is high, and multiple detectors can trigger the alarm (up to 100%), which ensures that the alarm can be triggered within 10 s under all applicable conditions. According to the evaluation results, the decision-maker can obtain a layout scheme that not only agrees with the actual site conditions but also attains a high detection probability, short detection time and strong reliability.     

综合管廊内火灾自动报警探测器实验研究

为了能够有效提升综合管廊内火灾自动报警系统的准确性和可靠性,本文采用火灾实体试验的方法,通过对各类型火灾自动报警探测器响应时间的情况进行分析和比较,研究综合管廊电力舱内常用探测器的性能。研究结果表明:接触式缆式线型感温火灾探测器可以较早的探测到电缆温度异常变化的现象,可用于早期预警。点型感烟探测器对烟粒子浓度较为敏感,可用于综合管廊电力舱室的空间探测。分布式光纤型感温火灾探测器对明火温度的变化较为敏感,作为空间型的火灾探测器比较可靠。     

隧道与横通道交叉角对火灾烟气蔓延影响机制研究

为探索隧道与横通道交叉角对火灾烟气蔓延的影响机制,采用FDS数值模拟,研究横通道与隧道不同交叉角情况下火灾烟气温度、浓度、烟气层高度等的变化规律,建立开启火源下风向横通道时隧道内烟气最高温度修正公式,提出烟气纵向蔓延恢复长度的概念,并探讨其影响规律。 结果表明:隧道和横通道交叉角越小,隧道内同一位置烟气层高度越高,当交叉角由90°降低到30°时,烟气层高度最大增加32%;烟气纵向蔓延恢复长度与交叉角及通风速率呈正相关,而与火源功率几乎无关。研究结果对隧道通风排烟系统设计及相关标准的制定具有参考意义。