广西陆上风电场开发存在的环境问题及对策研究

广西从保证能源安全,减少污染物排放,保护环境,满足低碳经济社会发展对能源的需要,将风电项目作为新能源项目重点推进.广西陆上风电场大部分位于水源涵养和生物多样性保护生态功能区、水土流失重点防治区等敏感区,通过分析目前风电规划、建设在选址、生态环境破坏方面存在的问题,对广西陆上风电场开发建设、环境管理提出相关建议.建议对广西风能资源开发所取得环境经济效益进行全面评估,指导推进广西陆上风电场的开发建设.     

黄河下游历史泥沙灾害的宏观特征及其与流域因素及人类活动的关系(Ⅰ)──历史气候及植被因素的影响

以历史上黄河下游的决溢频率为泥沙灾害的代用指标；研究了黄河下游历史泥沙灾害的宏观特征．研 究表明，气候因素对黄河下游决溢频率有深远的影响．隋唐以前，天然植被尚未遭到显著破坏，当湿润指标 增大时，有利于植被的生长，故黄河下游决溢频率减小．１０世纪以后，二者的关系与此相反，当湿润指标增 大时，决溢频率也增大，反之亦然．每世纪大旱年颁次与每世纪决溢频次之间呈明显正相关，说明目前受到 各方面广泛关注的黄河下游“小水大灾”现象，在历史上已经存在．干旱时期中，河槽萎缩，一旦大水来 临，很容易发生决溢．以华山松树木年轮指数为气温的代用指标，研究了气温变化与决溢频率变化的关系， 结果表明，在５０ａ的尺度上，当气温降低时，决溢频率增大，反之亦然．人类活动是影响黄河下游泥沙灾害 的重要因素．     

薄膜结构的气弹动力失稳临界风速

笔者采用解析方法研究了三维薄膜结构的气弹失稳临界风速。首先应用薄壳的无矩理论建立了薄膜结构的动力平衡方程 ;随后假设来流为均匀的理想势流 ,考虑流固耦合作用 ,采用不考虑流动分离和考虑流动分离两种气弹模型应用流体力学中的势流理论 ,并参考空气动力学中的薄翼型理论 ,确定了作用于薄膜表面的气动力 ,得到了两种模型情况下薄膜结构的气弹动力耦合作用方程 ;进而利用Bubnov Galerkin方法将此耦合作用方程转化为一常系数二阶微分方程 ,并根据Routh Hurwitz稳定性准则确定了薄膜的失稳临界风速 ;最后通过对临界风速的影响因素进行分析并对两种模型得到的结果进行比较 ,得到了一些重要结论。     

Exploitation of renewable energy resources for environment‐friendly sustainable development in Saudi Arabia

The recent increase in energy costs, driven by a surge in oil prices, has increased world‐wide efforts on the exploitation of renewable/wind energy resources for environment‐friendly sustainable development and to mitigate future energy challenges. Moreover, experience in the wind energy industry has reached high levels in the field of manufacturing and application. This inevitably increases the merits of wind energy exploitation. In order to exploit wind resources, through the establishment of wind power plants, specific attention must be focused on the characteristics of wind and wind machines. The literature indicates that wind‐energy resources are relatively better along coastlines. In the present study, long‐term hourly mean wind speed data for the period 1986–2003, recorded at Dhahran (Eastern Coastal region, Saudi Arabia), has been analysed to examine the wind characteristics including (but not limited to): yearly/monthly/diurnal variations of wind speed, frequency distribution of wind speed, impact of hub‐height/machine‐size on energy production, etc. Data have been checked/validated for completeness. Data analysis indicated that long‐term monthly average wind speeds ranged from 3.8 to 5.8 m/s.

Concurrently, the study determined monthly average daily energy generation from different sizes of commercial wind machines (150, 250, 600 kW, etc.) to assess the impact of wind machine size on energy yield. The study also estimated annual energy production (MWh/year) from wind farms of different capacities (3, 6, 12, 24 MW, etc.) by utilising different commercial wind energy conversion systems (WECS). It was observed that, for a given 6 MW wind farm size, a cluster of 150 kW wind machines (at 50 m hub‐height) yielded about 32% more energy when compared to a cluster of 600 kW wind machines. The study also estimated the cost of wind‐based electricity (COE, US$/kWh) by using different capacities of commercial WECS. It was found that the COE per kWh is 0.045 US$/kWh for 150 kW wind machine (at 50 m hub‐height) whereas COE was 0.039 US$/kWh for 600 kW wind machine (at 50 m hub‐height). The study also dealt with wind turbine characteristics (such as capacity factor and availability factor). These characteristics are important indicators of wind turbine performance evaluation.     

软岩隧道自旋锚管抗拔力的计算理论

在软岩隧道支护中,大多数情况下需要向上钻孔打锚杆,目前应用较多的中空注浆锚杆和砂浆锚杆在向上打锚杆的情况下,均存在注浆不饱满及不能形成快速初锚力的问题,影响支护效果和工程安全。自旋注浆锚管能比较好的解决上述工程中存在的技术缺陷。在软岩隧道支护中,自旋注浆锚管的抗拔力是至关重要的技术参数,关系到锚固体系的安全。本文根据自旋注浆锚管的结构特点和作用机理,对其抗拔力的计算理论进行了探讨,对实际支护工程有一定的参考作用。     

Nouvelles informations relatives aux variations temporaires de l'activite nitrifiante d'un sol evaluee au laboratoire. incidences d'un apport de matieres organiques

Abstract

The results reported in this paper confirm the seasonal influence on soil nitrifying activity estimated in the laboratory. The variations of this activity depend on different factors: climatic conditions, soil nature, occurence of plants, characteristics of the organic matter added to the soil.

A fresh organic matter (straw, for example) leads to reduced nitrifying activity immediately after its incorporation; its depressive action disappears after a month under laboratory condi‐tions. A decomposed organic matter, as a manure, produces no effect.

This work also shows the seasonal variations of the mineral nitrogen immobilization after addition of a fresh organic matter.     

城市隧道机电系统模糊综合安全评价

本文对城市隧道机电系统安全指标进行了分析,应用模糊数学理论建立了模糊综合安全评价指标体系和模型,并以厦门云顶隧道为例,对该隧道机电系统进行了模糊综合安全评价,得出隧道机电系统安全运营状态,对提高城市隧道机电系统安全管理水平具有重要的意义.     

Pilot study on road traffic emissions (PAHs,heavy metals) measured by using mosses in a tunnel experiment in Vienna,Austria

BACKGROUND, AIMS AND SCOPE: Over the last few years there has been extensive research for new indicators providing information about deposition resulting from road traffic and tunnel experiments received special attention in emission research. Mosses have been used for the estimation of atmospheric heavy metal and PAH depositions for more than three decades, although they were used only a few times for estimating ambient air pollution caused by traffic. In the current study, the suitability of using a moss species for monitoring road traffic emissions inside a tunnel was evaluated. This was a first-time ever attempt to use plants (mosses) as bioindicators in a tunnel experiment. Specifically, two relevant questions were examined: 1) Do mosses accumulate toxic substances derived from road traffic emissions under the extremely adverse conditions which can be found in a tunnel, and 2) Which substances can mainly be attributed to road traffic emissions and therefore be taken as efficient and reliable indicators for motor vehicles? METHODS: For the first time a biomonitor (the moss species Hylocomium splendens (Hedwig) B.S.G.) was used in a road tunnel experiment to analyse emissions from road traffic. Moss samples were exposed for four weeks in wooden frames (size 10 cm x 10 cm), covered by a thin plastic net with a mesh size of 1 cm x 1 cm. 17 elements, mainly heavy metals, and the 16 EPA-PAHs together with coronene were analysed by ICP-AES, AAS and GC-MSD. RESULTS: Enrichment factors, calculated by comparing post-experiment concentrations to those of a background site, were high for most PAHs, especially benzo(g,h,i)perylene (150.7), coronene (134.7), benzo(a)anthracene (125.0), indeno(1,2,3-c,d)pyrene (79.8), chrysene (78.1), pyrene (69.6) and benzo(b)-fluoranthene (67.4), and among the other elements for Sb (73.1), Mo (59.6), Cr (33.9), As (24.1), Cu (19.6), and Zn (17.1). All these substances can thus be taken as indicators for road traffic pollution. Concentrations were also significantly higher in the tunnel mosses for all investigated substances than along busy roads outside tunnels. Cluster analysis revealed groups of substances which could sensibly be attributed to various sources (abrasion processes, Diesel combustion) and enrichment in the various particle size classes. DISCUSSION: The extreme high concentrations in the analysed moss samples from inside the tunnel were due to higher concentrations in the ambient tunnel air, and the fact that already deposited chemical substances are not lost by rain, as well as efficient uptake capacities even under the extremely adverse conditions in a tunnel. In accordance with previous studies our results suggest that PAHs are better indicators for emissions from the burning process than heavy metals. CONCLUSIONS: As in open fields, mosses are suitable indicators for monitoring traffic emissions in tunnels. In addition to biomonitoring in open fields, in tunnel experiments mosses are even better indicators, because the confounding effects of other sources of pollution and the 'noise' in the accumulation process (e.g. washout through wet deposition) are minimised. The results of our study demonstrate the usefulness of mosses for surveying heavy metals and PAH emissions and deposition arising from road traffic sources, even under the extremely adverse conditions of the tunnel environment. RECOMMENDATION: It can be considered that biomonitors like mosses are a suitable alternative to technical particle filters inside tunnels. They are easy to handle, low in costs and valuable information regarding traffic emissions can be obtained. PERSPECTIVE: The results of this pilot-study proved the feasibility of the method, however, should be corroborated by further investigations based on a sample set that allows for generalization of the findings and might even include other moss species. A comparison of technical measurements with the biomonitoring method could lead to a more general acceptance of the results.     

Solid-state controller for an IAG-based stand-alone wind energy conversion system

This paper deals with an implementation of voltage and frequency controller (VFC) for isolated asynchronous generator-based three-phase autonomous wind energy conversion system. The focus of the proposed work is to provide a feasible solution for rural communities to serve their electricity needs. The least mean square algorithm is used for the extraction of active and reactive power components of the load currents. A three-leg voltage-sourced converter with a battery energy storage system is used as a VFC. The control algorithm is implemented using a digital signal processor. The steady-state and dynamic performances of VFC are demonstrated through test results under static and dynamic loads.     

A review on transient stability of DFIG integrated power system

With the increasing penetration of doubly fed induction generators (DFIGs), the impact of the DFIG on transient stability attracts great attention. Transient stability is largely dominated by generator types in the power system, and the dynamic characteristics of DFIG wind turbines are different from that of the synchronous generators in the conventional power plants. The analysis of the transient stability on DFIG integrated power systems has become a very important issue. This paper reviews the current research on the issue from two aspects. One is to describe the methods to improve the fault ride through capability of DFIG wind turbines and the other is to analyse the impact of the DFIG wind farm on transient stability of power systems.