山西省耕地资源的开发与保护

文章从山西能源基地建设为出发点,分析了山西省耕地资源利用的现状特点,提出了耕地资源合理利用的途径以及保护性措施。     

几种碳氢燃料与空气混合物相对爆轰敏感度的测定

利用矩形激波管测定了几种碳氢燃料（丁烷，石脑油，ＪＣ５，戊烯，已烯）直接起爆时形成爆轰所需的临界起爆能，并以化学当量比的乙炔氧气混合物直接起爆形成爆轰的临界起爆能为基准，定义了一个无量纲常数Ｄｈ。再利用这个常数，比较了这几种燃料的相对爆轰敏感度。     

ESTIMATION OF ENERGY REQUIREMENTS OF MORNING DEW EVAPORATION FROM LEAF SURFACES1

ABSTRACT: Evapotranspiration from vegetation is generally computed without consideration for early morning energy loss involved in drying wet leaf surfaces. In humid areas where dew formation is frequent, estimation of energy requirements for evaporating dew should be of interest. In this study, sensible heat flux (H) was computed from wind and temperature profile measurements over the study site. A leaf wetness sensor was used to measure the duration of evaporation from an exposed leaf surface, and net radiation was measured with a radiometer. The energy flux during the period of wet leaf surface evaporation was integrated over time. A cattail lysimeter situated at the site indicated the time when evapotranspiration started after wet leaves were dry. The energy requirements to dry an exposed wet leaf surface was estimated using energy balance methods. The mean value based on 44 days of observations from mid February to early May of 1993 indicates that the energy required to evaporate dew from openly exposed wet leaves was 5 percent of the total daily evapotranspiration of cattails with a coefficient of variation of 0.72. The mean time required to evaporate dew from exposed leaf surfaces from the onset of positive net radiation was 78 minutes. The mean dew evaporation in a morning from an exposed leaf surface was 0.16 mm with a maximum value of 0.41 mm. The energy required to dry wet leaves is a factor that should be considered when modeling evapotranspiration at hourly or shorter time intervals. Also, physical evapotranspiration models need to account for energy requirements for drying dew and rainfall wetted leaves.     

Effects of increased wood energy consumption on carbon storage in forests of the United States

Large but feasible increases that have been projected for the production of wood energy in the United States can be expected to significantly alter the current carbon storage patterns in US forest vegetation. The 1976 net wood increment left after forest cutting equals about 136 × 10⁶ tons of carbon/year, with about 60% of the increment found in merchantable trees, and the remainder in nonmerchantable components.Achieving 5–10 quads of wood energy beyond 1976 levels by the year 2010 can significantly change current carbon storage patterns with the magnitude of change dependent on the extent of residue harvest to meet energy goals, and the rate of future forest growth. Complete loss of the apparent net wood increment is a possible outcome.Although the future growth and harvest situation cannot be known now, a range of possible scenarios suggests that US forests in the year 2010 will store much less carbon than today, thus significantly changing their role in the global carbon cycle.     

都西庙水库生物群落的牧食链结构与渔业利用

都西庙水库初级生产者只有浮游植物,它对太阳能年总辐射量的利用率为0.07%,生态学效率分别为10.5%、0.26%、6.40%,综合鱼产力为17.8g/m~2,各种经济鱼类对浮游植物的能量利用率为0.55%,表明牧食链中能量流动与分配不合理。本文对科学利用和保护该库饵料资源提出了建议。     

瓦勃氏呼吸仪测定乐果合成废水的可生化性

本文概述了瓦勃氏呼吸仪测定有机污染物的可生化性的基本原理和方法。通过测定用乐果合成废水驯化后的微生物的生化呼吸线和相对耗氧速度曲线,结果表明:乐果合成废水是有毒的,但是完全可以被特异驯化后的微生物所降解;其降解速度与时间和废水所含污染物的浓度有关。     

Economics and energetics of organic and conventional farming

The use of organic farming technologies has certain advantages in some situations and for certain crops such as maize; however, with other crops such as vegetables and fruits, yields under organic production may be substantially reduced compared with conventional production. In most cases, the use of organic technologies requires higher labor inputs than conventional technologies. Some major advantages of organic production are the conservation of soil and water resources and the effective recycling of livestock wastes when they are available.     

STABILITY AND REACH LENGTH IN WATER SURFACE PROFILE DETERMINATION1

ABSTRACT: Extension of basic step methods of backwater computation to reaches of finite length is examined. Accuracies of commonly accepted hydraulic loss equations under particular water surface profile conditions are compared. Simulation of energy lines within a reach by parabolic curves is found to minimize error provided orientation of the axis of the parabola is selected in accordance with prevailing hydraulic conditions. Theoretical basis for an index reach length beyond which single-step computation from end to end of the reach must be in error is developed. Reduction of this reach length by suitable factors tailored to hydraulic conditions yields a mathematically defined allowable reach length for backwater computation. When reach length does not exceed this allowable reach length, no significant error may be detected. Automatic insertion of synthetic cross sections interpolated between surveyed cross sections when these are inadvertently spaced too far apart enables computation to proceed. This device is error-free for prismatic channls but may introduce error for irregular natural channels. Preliminary trials indicate that results so obtained may be accepted provided the fall in the original reach does not exceed from one to two feet. When this is exceeded, additional cross sections should be surveyed.     

Will Limits of the Earth's Resources Control Human Numbers?

The current world population is 6 billion people. Even if we adopted a worldwide policy resulting in only 2.1 children born per couple, more than 60 years would pass before the world population stabilized at approximately 12 billion. The reason stabilization would take more than 60 years is the population momentum – the young age distribution – of the world population. Natural resources are already severely limited, and there is emerging evidence that natural forces already starting to control human population numbers through malnutrition and other severe diseases. At present, more than 3 billion people worldwide are malnourished; grain production per capita has been declining since 1983; irrigation per capita has declined 12% during the past decade; cropland per capita has declined 20% during the past decade; fish production per capita has declined 7% during the past decade; per capita fertilizer supplies essential for food production have declined 23% during the past decade; loss of food to pests has not decreased below 50% since 1990; and pollution of water, air, and land has increased, resulting in a rapid increase in the number of humans suffering from serious, pollution-related diseases. Clearly, human numbers cannot continue to increase.     

Policy conflicts in the siting of natural gas pipelines

ABSTRACT

Researchers often focus on the most intense conflicts, skewing our perception of the diversity and nature of policy conflicts. The paper examines the discourse engaged in the siting of three pipeline projects under construction, each with varying levels of conflict, and one rejected project of high conflict. We analyze over 700 newspaper articles that span the life of each proposed pipeline and supplement the news media data with interviews. Using these data, we compare differences in actor types, frames, and behaviors in natural gas pipeline siting processes characterized by high, medium, and low conflict. Comparing the characteristics of energy siting conflicts at varying intensities helps support corresponding portrayals of how people engage in the policy process. This paper offers theoretical and empirical guidance on understanding policy conflict intensity variation.