Time series analysis of coal mine accident experience

This study investigates several forecasting techniques that can be useful to mine safety managers for studying mine accident rate behavior. Three time series models were studied for extrapolation of accident rates. These models are applied to historical accident incidence data from a coal mine. Further, a method is presented for evaluating the three models for the selection of an appropriate model. For this particular mine application, it is concluded that the more complex Box-Jenkins ARMA model as well as first order autoregressive model do not give better results than the simple exponential smoothing model. However, when the random variations or autocorrelations in the accident experience rates between periods are different, the models may predict differently. As such, specific models must be developed for each mine on the basis of statistical analysis of the mine accident experience data over time. Moreover, the importance of incorporating human judgement to interpret the results of statistical forecasting cannot be overemphasized. Integration of policy or operating changes, which may impact mine safety performance, with statistical forecasting techniques is essential to arrive at a realistic prediction of future performance.     

Managing Alberta's water: the decision-making process

Land and water are Canada's most valuable renewable natural resources. Canada possesses one-quarter of the world's known volume of fresh water. Fresh water covers 75369000 hectares of 7.1% of the country's surface. This area represents a very substantial number oflakes, rivers, streams, deltas and bays and is perhaps Canada's most vital and strategic resource. Canada has to have ab overall plan of management which provides direction, coordination, and assistance for the management of its water resources at the provincial and regional levels.     

The political economy of power generation in Zimbabwe since 1980

This article presents a historical analysis of the power generation choices in Zimbabwe since independence in 1980; their causes and consequences. In the early 1980s, the electricity supply choices of the country were dictated by a policy of self-sufficiency, and least-cost supply options (e.g. imports and hydropower) were rejected at a not negligible economic cost. At the end of the 1980s, a new political environment and pressures from the World Bank prompted substantial changes towards least-cost alternatives. In the early 1990s, security of supply motives still played an important role and financial constraints were severe. At present, however, there is little evidence that imported power is still as cheap a source of electricity as it was about 15 years ago. This situation together with the ongoing trend towards higher discount rates imply that thermal power, in particular coal-fired power, will dominate future electricity supply investments in Zimbabwe.     

Prospects for Exhaust Control by Engine Modification

In order to assist in assessing potential odor problems arising from chemical manufacturing operations, the odor thresholds of 53 commercially important odorant chemicals have been determined using a standardized and defined procedure. The odor threshold data previously available have shown wide variation reflecting the diversity of procedures and techniques used. Factors that may affect the odor threshold measurement include the mode of presentation of the stimulus to the observer, the influence of extraneous odorants in the presentation system, the type of observer used, the definition of the odor response, the treatment of the data obtained, and the chemical purity of the odorant. The experimental approach used has minimized these variations. The odorants were presented to a trained odor panel in a static air system utilizing a low odor background air as the dilution medium. The odor threshold is defined as the first concentration at which all panel members can recognize the odor. The effect of chemical purity has been determined by measuring the odor threshold of materials representing different modes of manufacture or after purification by gas chromatographic procedures. The threshold concentrations range over six orders of magnitude. Trimethylamine exhibited the lowest threshold (0.00021 ppm volume); methylene chloride was not recognizable below 214 ppm. Of the 53 chemicals, sulfur bearing compounds exhibit low threshold values on the order of parts per billion. Aside from the sulfides, it is not possible to anticipate the odor threshold of a material based on its chemical structure or functionality.     

双喷嘴三维洗罐器工作特性的研究

双喷嘴三维洗罐器是清洗容器内表面的清洗设备,其清洗参数的确定直接影响容器内表面的清洗质量及清洗效率。因此,对其工作特性的研究,可以确定其合理的使用参数,高效发挥其清洗能力。从研究其运动特性、动力特性入手, 分析了双喷嘴三维洗罐器喷注的运动规律及其覆盖容器内表面的清洗规律, 导出了合理确定双喷嘴三维洗罐器清洗时间或清洗速率的计算方法。实际上,在铁路罐车的高压水射流清洗系统中,用该法确定了清洗时间参数, 实践证明,这一选择取得了较好的效果     

广州流溪河河岸缓冲带生态治理的优良草种筛选试验

广州流溪河新筑的河堤完全裸露，河流两边的河岸缓冲带受到人类活动的破坏而成为裸露的砂石地或杂草丛生，二者都需要进行生态整治。为了对河流两岸进行生态改造，形成一种护坡效果好、景观效果佳的新流域景观，作者在一段河堤与两块不同性质的河岸缓冲带上进行了适宜草种的筛选试验。在河堤被测试的5个草种中，假俭草的综合表现最好，其次是百喜草，再次是钝叶草与森特钝叶草，野花生的表现最差。在砂石基质的河岸缓冲带样地I，丛生性的大雀稗、弯叶画眉草和香根草表现较好，而匍匐性的野花生、钝叶草和百喜草表现较差，这主要是后三者因根系浅，易遭洪水冲击。至于种植在土质的河岸缓冲带样地Ⅱ上的草种，由于土质状况好，淹水时间短，普遍表现良好。总的来看，弯叶画眉草、大雀稗在河岸缓冲带上的综合表现最好，但如果从耐淹角度来考虑，香根草也应是一个较理想的草种。     

A statistics-based system for treatment plant operation

This paper describes work toward development of a convenient computer system to improve everyday operation and control of the wastewater treatment process. The goal is to help the operator detect the problems in the process and to select appropriate control actions. The system comprises subsystems for a data base management, data analysis including several statistical methods, and an expert advisory system. The statistical methods investigated include construction of external reference distributions, computation of moving averages, graphical methods, discriminant functions for early detection of upsets, and several kinds of control charts. The latter two methods are still under development and are not built into the system. Reference distributions are used to help define the fuzzy terms such as high and low for the conditions of the variables involved in the expert system control rules. The system is written in dBase-III and Lotus-123 and has a user-friendly interface for the communication between the user and the system.