联合布置采区与区内复式回采方式研究

本研究分析了乡镇煤矿在多煤层开采时,大多数煤矿仍采用单一煤层布置前进式回采方式存在的突出问题,提出了多煤层联合布置采区与区内复式回采方式,并对采用此方式时,煤层群分组、采区集中运巷的位置选择、采区巷道布置、各煤层回采顺序、采区通风、采区与回采工作面安全出口等问题进行了分析,为乡镇煤矿在选用采煤方法时提供参考。     

基于群力矿煤与瓦斯突出事故的数值模拟分析

本文通过对群力煤矿煤与瓦斯突出事故进行数值模拟,分析煤与瓦斯突出之后,瓦斯在整个通风系统的移动情况。突出的瓦斯会对矿井通风系统造成影响,造成瓦斯逆流,甚至巷道内风流发生紊乱。     

基于群力煤矿分析瓦斯自然风压对通风机影响

根据群力煤矿的基本情况,利用数值模拟煤与瓦斯突出事故,煤与瓦斯突出事故发生后,涌出的大量瓦斯在巷道内形成的压力差对整个矿井的通风系统造成影响,分析通风机工况点的变化情况。提高矿井的通风系统稳定性,以及突出事故发生后事故救援提供相应的依据。     

汞矿山环境汞污染研究进展

汞矿山开采对周边环境的汞污染一直受到关注,尽管全球多数汞矿山已经相继停产、闭坑,但这些废弃的汞矿山仍然通过采矿所遗留的尾矿等固体废弃物、坑道废水和污染的土壤等对当地的环境和居民健康产生着持续的影响和危害.本文总结了环境样品中各形态汞的分析方法,评述了全球范围内汞矿的分布以及汞矿山开采和冶炼过程所造成的环境影响,提出了对于污染治理和风险评价的展望.     

固定化微生物处理氨氮废水的研究进展

生物方法因其高效、持久及无二次污染已经成为治理水污染的重要方法,固定化微生物不仅加强微生物治理效果,更能保证微生物生存稳定,是现阶段生物方法治理水污染的主要组分.近年来学者们也做了很多固定化微生物处理各类废水的研究,并取得了大量优异成果.文章对固定化微生物技术进行剖析,分析各类固定化载体材料及各种固定化方法优缺点;解析...     

治理煤矿瓦斯爆炸的微生物技术

近年来,我国煤矿发生重大矿难事故多起(2004．2．15～2005．3．19),遇难总计逾千人,给国家、社会和家庭都造成了不可弥补的损失。为什么在我国频频发生重大矿难事故呢?除了安全管理层面上的问题,还与我国在治理煤矿瓦斯爆炸方面缺少先进技术的支撑、对这一领域的基础及应用开发研究较为薄弱有关。     

中国贵州喀斯特金矿区苔藓植物研究进展

金矿的开采, 无疑会带来巨大的财富, 但同时会造成大量的重金属污染, 给周围环境带来了不可估量的危害。近年来, 由于大量金矿的开采和冶炼活动, 导致了一系列生态环境问题的出现, 目前已受到广泛的关注。基于苔藓植物在喀斯特金矿区对重金属离子的敏感作用和特殊的生态适应机制, 认为苔藓植物可作为金矿区环境污染的指示植物, 并且具有潜在的应用价值。分析综述了苔藓植物在贵州喀斯特金矿区的生物地球化学作用、重金属污染监测、生态修复研究、石漠化治理等方面的研究工作。最后, 还指出了存在的问题及发展方向。因此, 对中国金矿区生态环境恢复治理的深入研究具有十分重要的意义。     

表面响应法优化黑曲霉过氧化氢酶的发酵工艺

采用表面响应法（response surface methodology)研究了黑曲霉发酵过氧化氢酶过程的搅拌与通风条件的优化,获得了1个二次模型用于描述搅拌与通风对产过氧化氢酶的影响,当搅拌与通风量分别为691r/min,1.3L.L^-1.min^-1时,黑曲霉产过氧化氢酶水平最高。     

绥宁河生物修复中浮游植物的生态特征研究

通过对上海市苏州河支流绥宁河治理段与非治理段水体浮游植物群落的分析,探讨了生物修复对浮游植物的影响.生物修复试验实施后治理点的浮游植物种类数比非治理点多;浮游植物细胞数、叶绿素a含量有明显下降,优势度由极度的高优势变为中度优势;Shannon-Wiener多样性指数有明显上升;治理点绿藻和硅藻种类百分比升高,并出现一些指示β中污和寡污的种类,水体浮游植物群落结构有所优化,表明水体质量有一定改善.     

陇东黄土高原石油开采对土壤线虫群落的影响

为研究陇东黄土高原石油开采对土壤线虫影响的强度与范围,选择长庆油田不同开采年限(1、10a和20a)油井共6口,按照距井基不同距离(3、6、10、20m和50m)采集土壤样品90个,共鉴定出土壤线虫22科43属;其中,食细菌线虫26属、食真菌线虫2属、植物寄生线虫9属、杂食/捕食线虫6属,优势类群为小杆属Rhabditis和孔咽属Aporcelaimus。土壤线虫生活史策略以c-p 2类群占优势,不同距离采样点,土壤线虫c-p 2和c-p 5差异极显著(P0.01)。随着距井基距离增加(3、6、10、20m和50m)线虫总数显著增加;其中,植食类、捕食杂食类和食真菌类线虫数量增加显著,且线虫群落多样性指数(H')显著增加(P0.05)。但不同距离之间优势度指数(λ),均匀度指数(J)和瓦斯乐斯卡指数(WI)差异不显著。不同开采年限油井,以10a土壤线虫群落多样性指数(H')、成熟度指数(MI)和瓦斯乐斯卡指数(WI)最低,而1a油井和20a油井较高,且与10a油井差异显著(P0.05)。油井作业改变周围土壤性质,导致土壤含水率降低、总石油烃(TPH)含量增高,但土壤线虫分布与土壤TPH无明显相关。研究结果表明,油田开采影响土壤线虫的组成与群落结构,但影响范围一般局限在作业区范围,指数H'和MI能较好的指示油田开采对线虫群落的影响。     

Stratified Pulmonary Blood Flow: Some Consequences in Emphysema and Pulmonary Embolism

Both ventilation and blood flow in the secondary lobule of the lung are stratified; each unit of lung tissue in the proximal portion of the lobule receives up to four times the blood flow of units in the peripheral portion. Questions of the limiting role of gas diffusion within the small airways become virtually irrelevant in the face of this stratification of function.The central portion of the lobule, with its high ventilation, blood flow, and gas exchange, is very vulnerable; small lesions at this site will produce disproportionately large disturbances of gas exchange and of pulmonary vascular resistance. This may well account for some of the phenomena of conditions such as centrilobular emphysema and pulmonary microembolism.     

Inspired CO(2) and O(2) in sleeping infants rebreathing from bedding: relevance for sudden infant death syndrome.

Some infants sleep facedown for long periods with no ill effects, whereas others become hypoxemic. Rebreathing of expired air has been determined by CO(2) measurement; however, O(2) levels under such conditions have not been determined. To evaluate this and other factors influencing inspired gas concentrations, we studied 21 healthy infants during natural sleep while facedown on soft bedding. We measured gas exchange with the environment and bedding, ventilatory response to rebreathing, and concentrations of inspired CO(2) and O(2). Two important factors influencing inspired gas concentrations were 1) a variable seal between bedding and infants' faces and 2) gas gradients in the bedding beneath the infants, with O(2)-poor and CO(2)-rich air nearest to the face, fresher air distal to the face, and larger tidal volumes being associated with fresher inspired air. Minute ventilation increased significantly while rebreathing because of an increase in tidal volume, not frequency. The measured drop in inspired O(2) was significantly greater than the accompanying rise in inspired CO(2). This appears to be due to effects of the respiratory exchange ratio and differential tissue solubilities of CO(2) and O(2) during unsteady conditions.     

A ventilation and odor test facility

The increased need for energy conservation in the built environment has heightened the interest in reducing the flow of outside air into buildings for ventilation and odor dilution purposes. The current criteria used to determine the amount of ventilation that a building will need is based on a limited amount of data from the past. This paper describes a new test facility to evaluate and improve for the United States Department of Energy the criteria for the ventilation of occupied spaces. The test space is 3 × 3.7 × 2.4 m with laminar air flow from floor to ceiling. Auxiliary test facilities consist of binary and force-choice dilution olfactometers and an external sniffing port from which the odor of the chamber can be observed without disturbing or seeing the chamber occupants. Subjective odor responses are compared to environmental parameters measured with a gas Chromatograph, CO and CO₂ instruments and particulate monitoring equipment.     

Ventilation distribution in rats: Part I - The effect of gas composition as measured with electrical impedance tomography

ABSTRACT: The measurement of ventilation distribution is currently performed using inhaled tracer gases for multiple breath inhalation studies or imaging techniques to quantify spatial gas distribution. Most tracer gases used for these studies have properties different from that of air. The effect of gas density on regional ventilation distribution has not been studied. This study aimed to measure the effect of gas density on regional ventilation distribution. METHODS: Ventilation distribution was measured in seven rats using electrical impedance tomography (EIT) in supine, prone, left and right lateral positions while being mechanically ventilated with either air, heliox (30% oxygen, 70% helium) or sulfur hexafluoride (20% SF6, 20% oxygen, 60% air). The effect of gas density on regional ventilation distribution was assessed. RESULTS: Gas density did not impact on regional ventilation distribution. The non-dependent lung was better ventilated in all four body positions. Gas density had no further impact on regional filling characteristics. The filling characteristics followed an anatomical pattern with the anterior and left lung showing a greater impedance change during the initial phase of the inspiration. CONCLUSION: It was shown that gas density did not impact on convection dependent ventilation distribution in rats measured with EIT.     

Physiological Responses Of Birds To Flight And Running

1. The energy required for sustained physical activity in flying and running birds is obtained from fatty acids mobilized from adipose stores under the influence of hormones. There is some evidence that glucagon, insulin and growth hormone may be involved in this process. 2. Energy expenditure can increase up to 14 times and 12 times resting values in flying and running birds, respectively. Energy expenditure varies only slightly over the normal range of flight speeds in individual species, but in running birds there is a linear correlation between oxygen consumption and speed. The slope of this relationship is an inverse function of body weight and indicates the energy cost of transport in ml O₂.kg^-1.m^-1. 3. Increased oxygen demands by the working muscles are met by increased ventilation and circulation. Increased oxygen delivery by the blood is achieved by rises in cardiac output and oxygen extraction. Cardiac stroke volume changes relatively little and the increased cardiac output results mainly from an increase in heart rate. Regional blood distribution during exercise may be determined not only by the demands of the locomotory muscles but also by the need to increase heat loss from the skin and respiratory tract. 4. Ventilatory movements during flight are frequently synchronized in a I:I fashion with wing movements. Increased ventilation during flight and running may be stimulated, not only by the need for increased gas exchange, but also in order to raise heat loss by respiratory evaporation. Thermal hyperventilation carries a risk of CO, washout from the lungs and consequent blood alkalosis. The risk is minimized in some species by appropriate alterations in the rate and depth of breathing, which help to confine excess ventilation to the respiratory dead space. 5. Metabolic heat produced during exercise is either lost from the respiratory linings and the skin, or stored by the body with a resultant rise in body temperature. Changes in peripheral blood perfusion and active regulation of the feathers may assist cutaneous heat loss. Respiratory evaporation usually accounts for less than 30% of the total heat loss, even at high air temperatures, and becomes progressively less efficient at higher exercise intensities. At high air temperatures and high exercise intensities, most of the metabolic heat is stored, and exercise duration is limited as the body temperature approaches the upper lethal limit.     

Effect of ventilation with soluble and diffusible gases on the size of air emboli

Pulmonary hypertension resulting from venous air embolism is known to increase after ventilation with highly soluble and diffusible gases. Exacerbation of the hypertension could be due to further blockage of the circulation if the bubbles enlarge as a result of ingress of gas by diffusion. This mechanism has been frequently cited but lacks direct proof. To determine directly whether intravascular air bubbles actually enlarge when highly soluble and diffusible gases are inspired, we used microscopy to measure the size of gas emboli in vivo. When air bubbles were injected into the right atrium, the bubbles that appeared in pulmonary arterioles were larger during ventilation with helium or nitrous oxide than with air. Air bubbles injected into the pulmonary artery enlarged when the inspired gas was changed to helium or nitrous oxide. The direction, magnitude, and timing of changes in bubble size were consistent with a net diffusion of gas into the bubbles. These data support the idea that venous air emboli enlarge during ventilation with soluble and diffusible gases and thereby cause further vascular obstruction.     

Investigating the shape and size distribution of dust in mechanized longwall method in Tabas coal mine

When the average size of coal dust particles is reduced, risk of explosion as well as probability of emergence of numerous diseases is increased. To find the rate of negative effects in mechanized longwall mining face, the amount of spread coal dust and the scattering manner of particles in each part of the face and tail gate are investigated. Accordingly, 19 samples were taken from the face and tail gate of Tabas mechanized coal mine. Then, using the Zetasizer device and TEM (Transmission electron microscopy), the samples were analyzed and their shapes were determined, respectively. Results showed that shape of the particles was almost spherical and their size followed Rosin–Rammler distribution in the tail gate and along the longwall. In the face, since there was no opportunity for the deposition of coarse particles, some disturbances were observed in their distribution. At the beginning of the tail gate and close to the face, as the height increased, coarser particles were observed, which deposited after passing through the tunnel and getting away from the face. Considering these results, the aggregation and sequestration regions of dust could be found and the ventilation system can be modified. Also, more suitable solutions can be adopted for dust control or more advanced equipment can be proposed for miners in terms of confronting these particles in their working environment.     

Simple contrivance "clamps" end-tidal PCO(2) and PO(2) despite rapid changes in ventilation.

The device described in this study uses functionally variable dead space to keep effective alveolar ventilation constant. It is capable of maintaining end-tidal PCO(2) and PO(2) within +/-1 Torr of the set value in the face of increases in breathing above the baseline level. The set level of end-tidal PCO(2) or PO(2) can be independently varied by altering the concentration in fresh gas flow. The device comprises a tee at the mouthpiece, with one inlet providing a limited supply of fresh gas flow and the other providing reinspired alveolar gas when ventilation exceeds fresh gas flow. Because the device does not depend on measurement and correction of end-tidal or arterial gas levels, the response of the device is essentially instantaneous, avoiding the instability of negative feedback systems having significant delay. This contrivance provides a simple means of holding arterial blood gases constant in the face of spontaneous changes in breathing (above a minimum alveolar ventilation), which is useful in respiratory experiments, as well as in functional brain imaging where blood gas changes can confound interpretation by influencing cerebral blood flow.     

A mathematical model of alveolar gas exchange in partial liquid ventilation

In partial liquid ventilation (PLV), perfluorocarbon (PFC) acts as a diffusion barrier to gas transport in the alveolar space since the diffusivities of oxygen and carbon dioxide in this medium are four orders of magnitude lower than in air. Therefore convection in the PFC layer resulting from the oscillatory motions of the alveolar sac during ventilation can significantly affect gas transport. For example, a typical value of the Péclet number in air ventilation is Pe approximately 0.01, whereas in PLV it is Pe approximately 20. To study the importance of convection, a single terminal alveolar sac is modeled as an oscillating spherical shell with gas, PFC, tissue and capillary blood compartments. Differential equations describing mass conservation within each compartment are derived and solved to obtain time periodic partial pressures. Significant partial pressure gradients in the PFC layer and partial pressure differences between the capillary and gas compartments (P(C)-Pg) are found to exist. Because Pe> 1, temporal phase differences are found to exist between P(C)-Pg and the ventilatory cycle that cannot be adequately described by existing non-convective models of gas exchange in PLV The mass transfer rate is nearly constant throughout the breath when Pe>1, but when Pe<1 nearly 100% of the transport occurs during inspiration. A range of respiratory rates (RR), including those relevant to high frequency oscillation (HFO) +PLV, tidal volumes (V(T)) and perfusion rates are studied to determine the effect of heterogeneous distributions of ventilation and perfusion on gas exchange. The largest changes in P(C)O2 and P(C)CO2 occur at normal and low perfusion rates respectively as RR and V(T) are varied. At a given ventilation rate, a low RR-high V(T) combination results in higher P(C)O2, lower P(C)CO2 and lower (P(C)-Pg) than a high RR-low V(T) one.     

Internal air current patterns depend on the ventilation method in a scaled-up culture vessel for micropropagation

Air current patterns were visualized inside a scaled-up culture vessel under natural or forced ventilation. Metaldehyde particles were used as tracers, and their patterns were recorded as video images by a high-resolution-and-contrast camera. Under natural conditions, the air currents were mainly influenced by natural convection that developed due to the lighting scheme, which caused differences in temperature among various articles in the chamber, including a sweet potato plantlet, supporting material, a multi-cell tray, and the culture vessel. Under forced ventilation, the air current pattern and air speed were affected by ventilation rates and by air-supply methods that were either parallel downward or circular upward. Uniformity of air movement could be achieved with air distribution pipes inside a modified vessel. Under forced ventilation, growth, photosynthetic rate, and transpiration of the micropropagated plantlets were enhanced around the air outlet as well as the inlet in the large-scale vessel. Those plant responses were probably induced by uniform spatial distribution of air current and gas concentrations.