The study contains the methodology of finding the optimal time to start the operation of a desalting plant or any other non conventional source of water for agricultural use in Israel. The essence of the methodology is the moving equilibrium price and quantity of agricultural products. The market of agricultural products is represented by a single demand curve and a supply curve which is derived from the agricultural sector production function. Both the demand for and the supply of agricultural products functions are shifting over time. The marginal value product of water is the critical value that determines the optimal time of a desalting plant. The study is static in the sense that dynamic aspects per se are not dealt with-e.g. learning by doing of building and operating desalting plants. The empirical results although used for illustrative purposes can be used as reference points for other detailed and more ‘exact’ studies on water desalination. 相似文献
Differences between scientist and policy-maker response types and times, or the “how” and “when” of action, constrain effective
water resource management in suburbanizing watersheds. Policy-makers are often rushed to find a single policy that can be
applied across an entire, homogeneous, geopolitical region, whereas scientists undertake multiyear research projects to appreciate
the complex interactions occurring within heterogeneous catchments. As a result, watershed management is often practiced with
science and policy out of synch. Meanwhile, development pressures in suburban watersheds create changes in the social and
physical fabric and pose a moving target for science and policy. Recent and anticipated advances in the scientific understanding
of urbanized catchment hydrology and pollutant transport suggest that management should become increasingly sensitive to spatial
heterogeneities in watershed features, such as soil types, terrain slopes, and seasonal watertable profiles. Toward this end,
policy-makers should encourage funding scientific research that characterizes the impacts of these watershed heterogeneities
within a geopolitical zoning and development framework. 相似文献
Now in Russian Federation and other countries large-scale oil terminals (volume of one tank exceeds 100 000 m3, total volume of tanks exceeds 300 000 m3) are designed and constructed. Therefore fire safety of such objects becomes a very important task, solution of which is hardly possible without detail fire risk assessment. This study is aimed to a solution of this problem. Potential, individual and social risks were calculated. The potential risk was defined as a frequency of occurrence of hazardous factors of fires and explosions in a given point of space (the so-called risk contours). The individual risk was defined as a frequency of injuring a given person by hazardous factors of fires and explosions. Time of presence of this person in hazardous zones (near the hazardous installation) is taken into account during calculations of the individual risk. Social risk was defined as a dependence of frequency of injuring a given number of people by hazardous factors of fires and explosions on this number. In practice the social risk is usually determined on injuring not less than 10 people.
The oil terminal under consideration includes the following main parts: crude oil storage consisting of three tanks of volume 100 000 m3 each, input crude oil pipeline of diameter 0.6 m, crude oil pumps, output crude oil pipeline of diameter 0.8 m, auxiliary buildings and facilities. The following main scenarios of tank fires have been considered: rim seal fire, pool fire on a surface of a floating roof, pool fire on a total cross-section surface of the tank, pool fire in a dyke, explosions in closed or semiclosed volumes. Fires and explosions in other parts of the terminal are also taken into account. Effects of escalation of accidents are considered.
Risk contours have been calculated both for the territory of the terminal and for the neighbouring space. The potential risk for the storage zone is near 10−4–10−5 year−1, and at a distance 500 m from the terminal the potential risk values do not exceed 10−6 year−1. The values of the individual risk for various categories of workers are in the range of 10−5–10−6 year−1. Because of low number of the workers on the terminal and large distances to towns and villages the social risk value is negligible. These risk values are consistent with practice of the best oil companies, and fire hazard level of the terminal can be accepted as tolerable. 相似文献
The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRL Lake Lynn Experimental Mine (LLEM), and after laboratory explosions in the PRL 20-L chamber and the Fike 1 m3 chamber. The dusts studied included both high- and low-volatile bituminous coals. Low temperature ashing for 24 h at 515 °C was used to measure the incombustible content of the dust before and after the explosions. The data showed that the post-explosion incombustible content was always as high as, or higher than the initial incombustible content. The MSHA alcohol coking test was used to determine the amount of coked dust in the post-explosion samples. The results showed that almost all coal dust that was suspended within the explosion flame produced significant amounts of coke. Measurements of floor dust concentrations after LLEM explosions were compared with the initial dust loadings to determine the transport distance of dust during an explosion. All these data will be useful in future forensic investigations of accidental dust explosions in coal mines, or elsewhere. 相似文献
Rescue operations during mine fires or methane explosions are highly dangerous for rescue workers. The knowledge of the composition of the coal mine atmosphere and the calculations of its explosibility may help to increase the safety of the rescuers. In the Czech Republic, a system called “Mine Gas Laboratory” (DPL) has been used for these purposes. The DPL allows measurement of the composition of the mine atmosphere and transmits the data necessary for evaluation to the surface. Up to now the explosibility evaluation of the coal mine atmosphere has depended either on the rescuers’ experience or on software code calculation. The code called “Vybuchovy trojuhelnik” (explosion triangle) is a graphical computing system intended for fast assessment of explosibility of fuel–air mixture. This article introduces the code and describes two simple methods of explosibility evaluation. The first method is “explosion triangle analysis”—a graphical method based on empirical graphs transformed into equations. The second method uses thermodynamic calculation based on chemical balance dynamics and Gibbs and Helmholtz energy. According to the requirements of the Czech Bureau of Mining (CBU) and Central Mine Rescue Service (HBZS), the code solves the problems of explosion triangle for both standard and non-standard coal mine atmosphere compositions. Unfortunately, the atmosphere composition must be introduced manually due to the unknown format of the data transmitted from the old DPL model. On 1 September 2005, a project started to develop a new system for on-line monitoring and atmosphere explosibility evaluation. The system should be able to measure CO2, O2, CH4, H2 and CO concentrations as well as the wind speed, temperature and humidity. The “Vybuchovy trojuhelnik” code will be used as a basis for explosibility evaluation, and an on-line connection with the new model of DPL will be established. 相似文献
The authors investigated the ignitability of aluminium and magnesium dusts that are generated during the shredding of post-consumer waste. The relations between particle size and the minimum explosive concentration, the minimum ignition energy, the ignition temperature of the dust clouds, etc. the relation between of oxygen concentration and dust explosion, the effect of inert substances on dust explosion, etc. were studied experimentally.
The minimum explosive concentration increased exponentially with particle size. The minimum explosive concentrations of the sample dusts were about 170 g/m3 (aluminium: 0–8 μm) and 90 g/m3 (magnesium: 0–20 μm). The minimum ignition energy tended to increase with particle size. It was about 6 mJ for the aluminium samples and 4 mJ for the magnesium samples. The ignition temperature of dust clouds was about 750 °C for aluminium and about 520 °C for magnesium. The lowest concentrations of oxygen to produce a dust explosion were about 10% for aluminium and about 8% for magnesium. A large mixing ratio (more than about 50%) of calcium oxide or calcium carbonate was necessary to decrease the explosibility of magnesium dust. The experimental data obtained in the present investigation will be useful for evaluating the explosibility of aluminium and magnesium dusts generated in metal recycling operations and thus for enhancing the safety of recycling plants. 相似文献
A nonstationary time-series model is used to examine the changes occurring at sampling stations on the Chicago Sanitary and Ship Canal. Using data from upstream sampling sites, downstream levels of dissolved oxygen, total dissolved solids, nitrates and nitrites, and ammonia are accurately predicted. The method is simple, insensitive to extreme values, and responsive to changes in the system. 相似文献