我国与国外民间直升机救援的比较研究

本文通过对国外和我国民间直升机的救援现状进行分析,从救援装备、专业人才、基础设施、政策法规、运营模式等方面做了对比研究,发现我国在各方面都存在较大差距,提出了构建我国民间直升机救援体系的具体措施。     

2015年干季佛山一次重空气污染过程形成机理研究

2015年12月21-23日,广东珠三角佛山地区出现了一次PM_2.5重污染过程.利用佛山地区顺德、禅城、三水3个站点风廓线雷达、激光雷达和微波辐射计观测资料,结合地面气象观测数据和污染物浓度数据,分析研究了这次重污染过程的形成机理.结果表明：1形成这次污染过程的主要原因是近地层偏南风和偏北风对峙导致水平风速减小,大气水平输送能力变差;持续时间长且强度达到3℃·km^-1的强逆温抑制了污染物的垂直扩散;800 m以下超过90%的高相对湿度造成气溶胶粒子吸湿增长显著.2持续时间长且比较深厚的小风层是造成这次污染过程的直接原因,小风层厚度是预报空气质量变化的较好工具.与地面风速相比,PM_2.5浓度与小风层厚度的相关系数最多能提高0.36,且具有较长的预报时效.佛山地区小风层的风速阈值为3.8 m·s^-1.3这次污染过程存在两种不同的污染形成机制,污染前期（21-23日中午）主要以本地污染物累积为主,污染后期（23日下午）下风向地区（三水）的污染主要是受上风向地区（顺德和禅城）的污染输送影响.     

Shaping effects of rice,wheat, maize,and soybean seedlings on their rhizosphere microbial community

The rhizosphere microbiome plays critical roles in plant growth and is an important interface for resource exchange between plants and the soil environment. Crops at various growing stages, especially the seedling stage, have strong shaping effects on the rhizosphere microbial community, and such community reconstruction will positively feed back to the plant growth. In the present study, we analyzed the variations of bacterial and fungal communities in the rhizosphere of four crop species: rice, soybean, maize, and wheat during successive cultivations (three repeats for the seedling stages) using 16S rRNA gene and internal transcribed spacer (ITS) high-throughput sequencing. We found that the relative abundances of specific microorganisms decreased after different cultivation times, e.g., Sphingomonas, Pseudomonas, Rhodanobacter, and Caulobacter, which have been reported as plant-growth beneficial bacteria. The relative abundances of potential plant pathogenic fungi Myrothecium and Ascochyta increased with the successive cultivation times. The co-occurrence network analysis showed that the bacterial and fungal communities under maize were much more stable than those under rice, soybean, and wheat. The present study explored the characteristics of bacteria and fungi in crop seedling rhizosphere and indicated that the characteristics of indigenous soil flora might determine the plant growth status. Further study will focus on the use of the critical microorganisms to control the growth and yield of specific crops.

     

Crystallization and Mechanical Properties of Recycled Poly(ethylene terephthalate) Toughened by Styrene–Ethylene/Butylenes–Styrene Elastomer

Recycled poly(ethylene terephthalate) (R-PET) was blended with 15–30 wt% of styrene–ethylene/butylenes–styrene (SEBS) block copolymer and maleic anhydride grafted SEBS (SEBS-g-MA). Effects of nucleation and toughening of the elastomers were evaluated systematically by study of morphology, crystallization, thermal and mechanical properties of the blend. The addition of 30 wt% SEBS promoted the formation of co-continuous structure of the blend and caused the fracture mechanism to change from strain softening to strain hardening. Addition of SEBS-g-MA resulted in significant modification of phase morphology and obviously improved the impact strength. The compatibilization reaction of PET with SEBS-g-MA accelerated the crystallization of PET and increased the crystallinity. The shifts in glass transition temperature of PET towards that of SEBS-g-MA and the higher modulus for R-PET/SEBS-g-MA (70/30) blend found by DMA are also indications of better interactions under the conditions of compatibilization and interpenetrating structure.     

Application of response surface methodology to the treatment landfill leachate in a three-dimensional electrochemical reactor

The influence of different variables on the removal of ammonia nitrogen and COD from landfill leachate was investigated in a three-dimensional electrochemical reactor. Box–Behnken statistical experiment design and the response surface methodology were used to investigate operating condition effects, such as current density, activated carbon to water ratio and the reaction time, on ammonia nitrogen removal efficiency and COD removal efficiency. The positive and negative effects of variables and the interaction between variables on ammonia nitrogen removal and COD removal were determined. The response surface methodology models were derived based on the results and the response surface plots were developed accordingly.     

Effects of leachate accumulation on landfill stability in humid regions of China

Leachate levels are important to landfill stability and safety. High leachate or water levels often lead to landfill instability, which can cause accidents. Here a case study of a landfill located in a humid region of southern China is presented. Leachate distribution and quality were systematically analyzed, and the effect of leachate level on waste-mass stability was assessed. Boreholes were drilled in the field, samples were analyzed in the laboratory, and a simulation was performed. In addition, the safety and stability of the landfill was evaluated. The leachate level in the landfill was 9–19 m, which was higher than the top of the dam crest (8–20 m). Leachate accounted for more than 1/4 of the total landfill storage capacity. The contaminant concentration of the leachate samples collected directly from the waste body was very high, with large variation among the samples. The mean concentrations of NH₃–N, BOD, and COD from the waste body were 5404, 14,136, and 22,691 mg/L, nearly 2.7, 2.4, and 1.8 times the mean concentrations in the leachate pond, respectively. Three series of shear strength parameters were used in a slope stability analysis, and a limit equilibrium method was used to calculate the factor of safety (Fs). The analysis showed that Fs could be affected by potential anisotropy in the shear strength of the waste. The minimum values of Fs corresponding to series I were 1.84 and 1.17 for units ? and II, respectively. The Fs value of unit II was significantly lower than the safe design value (1.25). In addition, Fs decreased with increase in the normalized height of the leachate level, h/H, where h is the height of the leachate mound and H is the maximum thickness of the landfill. If the h/H values of units I and II are kept below 50% and 40%, respectively, a safe design value of 1.25 for Fs can be guaranteed. Therefore, some measures to prevent risk should be considered.     

Impact of carbon source on nitrous oxide emission from anoxic/oxic biological nitrogen removal process and identification of its emission sources

Wastewater treatment is an important source of nitrous oxide (N₂O), which is a strong greenhouse gas and dominate ozone-depleting substance. The purpose of this study was to evaluate the effect of carbon source on N₂O emission from anoxic/oxic biological nitrogen removal process. The mechanisms of N₂O emission were also studied. Long-term experiments were operated to evaluate the effect of three different carbon sources (i.e., glucose, sodium acetate, and soluble starch) on N₂O emission characteristics. And batch experiments, in the presence or absence of specific inhibitors, were carried out to identify the sources of N₂O emission. The ammonia-oxidizing bacteria (AOB) and denitrifiers community compositions under different circumstances were also analyzed based on which the underlying mechanisms of N₂O emission were elucidated. The conversion ratios of N₂O in reactors with glucose, sodium acetate, and soluble starch were 5.3 %, 8.8 %, and 2.8 %, respectively. The primary process responsible for N₂O emission was nitrifier denitrification by Nitrosomonas-like AOB, while denitrification by heterotrophic denitrifiers acted as the sink. Reactor with sodium acetate showed the highest N₂O emission, together with the highest nitrogen and phosphate removal ratios. Carbon source has a significant impact on N₂O emission quantity and relatively minor effect on its production mechanism.     

Fuzzy logic-based approach for identifying the risk importance of human error

In the system reliability and safety assessment, the focuses are not only the risks caused by hardware or software, but also the risks caused by “human error”. There are uncertainties in the traditional human error risk assessment (e.g. HECA) due to the uncertainties and imprecisions in Human Error Probability (HEP), Error-Effect Probability (EEP) and Error Consequence Severity (ECS). While fuzzy logic can deal with uncertainty and imprecision. It is an efficient tool for solving problems where knowledge uncertainty may occur. The purpose of this paper is to develop a new Fuzzy Human Error Risk Assessment Methodology (FHERAM) for determining Human Error Risk Importance (HERI) as a function of HEP, EEP and ECS. The modeling technique is based on the concept of fuzzy logic, which offers a convenient way of representing the relationships between the inputs (i.e. HEP, EEP, and ECS) and outputs (i.e. HERI) of a risk assessment system in the form of IF–THEN rules. It is implemented on fuzzy logic toolbox of MATLAB using Mamdani techniques. A case example is presented to demonstrate the proposed approach. Results show that the method is more realistic than the traditional ones, and it is practicable and valuable.