苏州古城区夜间光环境现状分析

为了解苏州古城区夜间光环境现状,对古城区夜间环境照度、亮度进行了测量,对夜间广告与标志灯数量进行了调查,并对统计结果进行分析,指出了古城区的主要光环境问题为照度、亮度不均与不足以及存在光污染现象,光环境建设需不断完善。     

紫外/亚硫酸钠还原降解三氯乙酰胺的效能

卤乙酰胺(HAc Ams)是一类具有高细胞毒性和高遗传毒性的饮用水含氮消毒副产物(N-DBPs),并在饮用水中被广泛检出,其中三氯乙酰胺(TCAc Am)的毒性显著高于传统DBPs.本实验以配置的TCAc Am溶液作为目标污染物,采用紫外(UV)活化亚硫酸钠(Na_2SO_3)体系降解水中的TCAc Am,并探究在该体系下光强、还原剂投加剂量(Na_2SO_3)和p H对还原降解TCAc Am效果的影响.结果表明,采用UV/Na_2SO_3体系可快速降解TCAc Am,其降解效果与光强、Na_2SO_3投加剂量和p H均呈正相关,且p H值对反应速率与降解率有显著影响,当p H值从6提高至9,TCAc Am的降解率在反应120 min时从12. 8%提高至99. 6%.在光强为450μW·cm~(-2),p H为9,Na_2SO_3投加剂量为1. 00 mmol·L~(-1),连续30 min光照条件下,TCAc Am降解率达到99. 4%.实验证明UV/Na_2SO_3体系是一种有效消减TCAc Am的高级还原技术,并且具备还原降解其他卤代DBPs的潜力,可用于饮用水中卤代DBPs的降解.     

The acceleration of flames in tube explosions with two obstacles as a function of the obstacle separation distance

The separation distance (or pitch) between two successive obstacles or rows of obstacles is an important parameter in the acceleration of flame propagation and increase in explosion severity. Whilst this is generally recognised, it has received little specific attention by investigators. In this work a vented cylindrical vessel 162 mm in diameter 4.5 m long was used to study the effect of separation distance of two low blockage (30%) obstacles. The set up was demonstrated to produce overpressure through the fast flame speeds generated (i.e. in a similar mechanism to vapour cloud explosions). A worst case separation distance was found to be 1.75 m which produced close to 3 bar overpressure and a flame speed of about 500 m/s. These values were of the order of twice the overpressure and flame speed with a double obstacle separated 2.75 m (83 characteristic obstacle length scales) apart. The profile of effects with separation distance was shown to agree with the cold flow turbulence profile determined in cold flows by other researchers. However, the present results showed that the maximum effect in explosions is experienced further downstream than the position of maximum turbulence determined in the cold flow studies. It is suggested that this may be due to the convection of the turbulence profile by the propagating flame. The present results would suggest that in many previous studies of repeated obstacles the separation distance investigated might not have included the worst case set up, and therefore existing explosion protection guidelines may not be derived from worst case scenarios.     

Land Degradation Evaluation in North Hebei Province Based on Remote Sensing and GIS

Land degradation is one of the serious environmental problems that can lead to poverty, and is especially prominent in eco-fragile areas in developing countries and increases the risk of environmental safety. North Hebei Province belongs to an ecologically fragile region in North China, which has great impact on the eco-safety of Beijing and Tianjin. Using Landsat TM data and GIS, this paper evaluates land degradation in North Hebei province of China from the the 1960＇s to 1987 and 2000. Land use/cover change pattern from 1987 to 2000, its regional difference and forest change characteristics will also be analyzed; soil erosion intensity and arable land suitability were also evaluated. Results revealed that land use/cover pattern in this study area did not change greatly from 1987 to 2000. The structure and function of regional land ecosystem was at a level of local improvement and integral deterioration. Land above medium soil erosion intensity reached 21 percent, which was also the area with a serious soil erosion and land degradation problem. Soil erosion and land degradation intensity of grassland was the biggest. For the present arable land, the proportion of high suitability was 13 percent.     

1556年关中大地震的震级

作者根据大量的历史地震资料和本人的研究成果对1556年发生在西关中华县大地震的震级提出了质疑,认为此次地震的震级应该定为8.5级。     

地震烈度及其评定

文章介绍了烈度概念的双重内涵和烈度评定的模糊性、综合性、平均性和主观性等特点,评述了烈度评定相关的国内外动态。建议区别地震动、房屋震害和地震地面破坏三类不同的物理现象以分别描述地震影响和地震灾害。     

竞争条件下光照对两种淡水藻生长的影响

研究了铜绿微囊藻与斜生栅藻在单种和三种配比(10:1、1:1、1:10)共同培养条件下,不同的光照强度对其生长的影响,计算了不同培养体系中两种藻的磷吸收半饱和常数。结果表明:单独培养时,铜绿微囊藻在3000lx获得最大增长率,而斜生栅藻在5000lx时增值最快;共同培养时,两种藻的生长速率相对单独培养条件下均有不同程度的下降,两种藻之间存在着互相的竞争抑制作用;在10:1共培养条件下,栅藻对微囊藻的抑制作用超过了微囊藻对栅藻的抑制作用;在1:1和1:10共培养条件下,光强低于6600lx时,微囊藻对栅藻的抑制作用相对于栅藻对微囊藻的抑制作用更大。从光吸收半饱和常数看,微囊藻的光吸收的半饱和常数总是小于栅藻,可见微囊藻对光更具亲和性。总体上看,较低光照下,微囊藻的竞争能力强于栅藻,微囊藻竞争成为优势种具有较高的概率;而光照强度较大时,栅藻竞争成为优势种具较高的概率。     

A comparison of general aviation accidents involving airline pilots and instrument-rated private pilots

Introduction: The extremely low accident rate for U.S air carriers relative to that of general aviation (∼1 and ∼60/million flight hours respectively) partly reflects advanced airman certification, more demanding recurrency training and stringent operational regulations. However, whether such skillset/training/regulations translate into improved safety for airline pilots operating in the general aviation environment is unknown and the aim of this study. Methods: Accidents (1998–2017) involving airline pilots and instrument-rated private pilots (PPL-IFR) operating non-revenue light aircraft were identified from the NTSB accident database. An online survey informed general aviation flight exposure for both pilot cohorts. Statistics used proportion testing and Mann-Whitney U tests. Results: In degraded visibility, 0 and 40% (χ² p = 0.043) of fatal accidents involving airline and PPL-IFR airmen were due to in-flight loss-of-control, respectively. For landing accidents, airline pilots were under-represented for mishaps related to airspeed mismanagement (p = 0.036) relative to PPL-IFR but showed a dis-proportionate count (2X) of ground loss-of-directional control accidents (p = 0.009) the latter likely reflecting a preference for tail-wheel aircraft. The proportion of FAA rule violation-related mishaps by airline pilots was >2X (7 vs. 3%) that for PPL-IFR airmen. Moreover, airline pilots showed a disproportionate (χ² p = 0.021) count of flights below legal minimum altitudes. Not performing an official preflight weather briefing or intentionally operating in instrument conditions without an IFR flight plan represented 43% of airline pilot accidents involving FAA rule infractions. Conclusions: These findings inform safety deficiencies for: (a) airline pilots, landing/ground operations in tail-wheel aircraft and lack of 14CFR 91 familiarization regulations regarding minimum operating altitudes and (b) PPL-IFR airmen in-flight loss-of-control and poor landing speed management. Practical Applications: For PPL-IFR airmen, training/recurrency should focus on unusual attitude recovery and managing approach speeds. Airline pilots should seek additional instructional time regarding landing tail-wheel aircraft and become familiar with 14CFR 91 rules covering minimum altitudes.     

PAM影响剩余污泥与酒精糟液高温共厌氧消化研究

为了使共厌氧消化技术在实际生产中得到应用,研究了广泛使用的絮凝剂阳离子聚丙烯酰胺(PAM)对剩余污泥与酒精糟液高温共厌氧消化的影响,并考察了不同搅拌强度消除PAM的影响.结果表明,阳离子PAM的含量越高,对共厌氧消化反应影响越明显,相对高的搅拌速度有利用消除高分子PAM对质子传输的束缚作用,增加厌氧微生物与污泥的接触机...     

喀斯特地区城市绿地土壤呼吸对降水变化的响应研究

降水是影响土壤呼吸一个重要的影响因子,研究降水对土壤呼吸的影响,对估计和预测陆地生态系统土壤呼吸变化有着重要的意义,但目前自然降水对喀斯特地区城市绿地土壤呼吸影响的研究目前还鲜有报道.本研究利用静态暗箱法,对降水后贵阳城市绿地土壤呼吸速率变化进行了24 h定位监测,对比研究了不同强度降水后土壤呼吸速率变化,并分析了水热...