نتایج جستجو برای: coal mines
تعداد نتایج: 37421 فیلتر نتایج به سال:
The impact of discharges from abandoned metal and ironstone mines has been a much studied form of aquatic pollution in recent decades. Few attempts however, have been made to accurately determine the overall contaminant mass flux arising from abandoned mine sites at scales above catchment level. Such assessments are critical to determine the significance of former mining to national, regional a...
Introduction What can the canary in the coal mine tell us? Historically, canaries accompanied coal miners deep underground. Their small lung capacity and unidirectional lung ventilation system made them more vulnerable to small concentrations of carbon monoxide and methane gas than their human companions. As late as 1986, the acute sensitivity of these birds served as a biological indicator of ...
Modern underground coal mining requires certainty about geological faults and other structural features for safety reasons. Even a fault with a throw of a few metres can create safety issues and lead to costly delays in mine production. To ensure there are no unwelcome surprises concerning seam conditions during mining, seismic reflection surveys have been widely used by Australian coal mines, ...
To overcome the frequency-selective fading of ultra wide band (UWB) caused by the multi-path propagation in complicated environment of coal mines, an underground wireless communication system of UWB based on multi-band orthogonal frequency division multiplexing (MB-OFDM) for coal mine is presented. Independent angle impulse response is used to build up revised channel model for underground tunn...
— An average Transmitted-Reference (TR) receiver scheme based on orthogonal codes is proposed for improving the bit error rate (BER) performance and the transmitting rate of Ultra-wideband (UWB) TR receiver systems in coal mine. Orthogonal codes are used for modulating the reference pulses and the data pulses in each frame of every bit. Since the orthogonality of the two codes, the inter-pulse...
Coal is the major primary energy which fuels the economic growth in China. The Soviet-style institution of the coal sector was adopted after the People’s Republic was founded in 1949. But since the end of 1970s there have been major changes: the market mechanism was introduced to the coal sector and the Major State Coal mines were transferred from central to local governments. This paper explai...
The process of material cutting and fracture by high velocity water jets is a complex series of phenomena which may involve compression, tension, shear, erosion, wears, cracking, wave propagation, and cavitations damage. This makes the exact analysis of the jet cutting process to be very complicated. The problem of water jet coal cutting is a multiresponse problem. There are two output variable...
Plants that accumulate a small percentage of metals in constructed treatment wetlands can contribute to remediation of acidic, metal contaminated runoff waters from coal mines or processing areas. We examined root and shoot concentrations of elements in four perennial wetland species over two seasons in mesocosm wetland systems designed to remediate water from a coal pile runoff basin. Deep wet...
BACKGROUND In China, over 80% of all work-related deaths in the mining industry occur in coal mines and human factors constitute 85% of the direct causes of coal mine accidents, which indicates that significant shortcomings currently exist in the safety behavior management of Chinese coal mine workers. We aimed to verify the impact of human psychological behavior in coal mine accidents systemat...
BACKGROUND The Pearl River Origin area, Qujing District of Yunnan Province, has one of the highest female lung cancer mortality rates in China. Smoking was excluded as a cause of the lung cancer excess because almost all women were non-smokers. Crystalline silica embedded in the soot emissions from coal combustion was found to be associated with the lung cancer risk in a geographical correlatio...
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