Image denoising algorithm of refuge chamber by combining wavelet transform and bilateral filtering

In order to preferably identify infrared image of refuge chamber, reduce image noises of refuge chamber and retain more image details, we propose the method of combining two-dimensional discrete wavelet transform and bilateral denoising. First, the wavelet transform is adopted to decompose the image of refuge chamber, of which low frequency component remains unchanged. Then, three high-frequency components are treated by bilateral filtering, and the image is reconstructed. The result shows that the combination of bilateral filtering and wavelet transform for image denoising can better retain the details which are included in the image, while providing better visual effect. This is superior to using either bilateral filtering or wavelet transform alone. It is useful for perfecting emergency refuge system of coal mines.     

中小型磷矿井下安全避险系统建设方案

为了在中小型磷矿完成安全避险“六大系统”建设任务,本文对相关建设规范进行了研究,通过对中小型磷矿开采条件的分析及危险因素的识别,针对不同的矿山条件,分别形成了相应的“六大系统”建设方案.紧急避险系统由个体防护、避灾设施、避灾路线、应急预案等组成.有些矿山经论证可缓建或不建避灾设施,防透水型避灾硐室采用井巷内钢管供风供水、地表局扇抽出式排气方案.压风自救和供水施救系统从地表空压机或高位水池安装钢管至井下形成枝状管网.监测监控系统中选用较成熟的矿井井下环境监测系统,视频监控系统将地面及井下重要安全生产岗位的图像实时传送到矿井调度室.采空区地压监测采用包括岩体声发射、顶板变形、矿柱应力监测的综合监测方案.根据并下工作人员数量新建并下人员定位系统,或设置考勤系统.根据规范要求,对原有矿山有线通信系统进行升级改造.以上“六大系统”建设方案均已通过了省安监局组织的专家验收评审,并在矿山实施,目前已相继投入运行,使矿山安全保障能力得到显著提升.     

Loading characteristics of mechanical rib bolts determined through testing and numerical modeling

Underground coal mines use mechanical bolts in addition to other types of bolts to control the rib deformation and to stabilize the yielded coal ribs. Limited research has been conducted to understand the performance of the mechanical bolts in coal ribs. Researchers from the National Institute for Occupational Safety and Health(NIOSH) conducted this work to understand the loading characteristics of mechanical bolts(stiffness and capacity) installed in coal ribs at five underground coal mines. Standard pull-out tests were performed in this study to define the loading characteristics of mechanical rib bolts. Different installation torques were applied to the tested bolts based on the strength of the coal seam. A typical tri-linear load-deformation response for mechanical bolts was obtained from these tests. It was found that the anchorage capacity depended mainly on the coal strength. Guidelines for modeling mechanical bolts have been developed using the tri-linear load-deformation response. The outcome of this research provides essential data for rib support design.     

Air/CO2 cooling garment: Description and benefits of use for subjects exposed to a hot and humid climate during physical activities

The severity of the hot and humid conditions to which miners are exposed increases as the depth of the work site increases. This can cause heat stress that can greatly affect the health and safety of workers. To resolve this, a cooling garment has been developed that uses an atmospheric discharge of liquid CO₂ to create a cool microclimate with an average temperature of 12.5 (±0.4) °C beneath the garment. To evaluate the garment’s cooling efficiency, 19 male subjects participated in an experimental procedure. The two modes, cooling on and off, were compared. Significant physiological differences were found between the two modes after minute 27 (p < 0.05) until the end of the recovery phase for the heart rate (maximum difference of 10 beats per minute) and the internal body temperature (maximum difference of 0.33 °C). It was found that the modes also affected the subjects’ perceptions. The ON-mode was associated with better well-being and thermal comfort, and reduced humidity sensation. Perceptions of exertion were lower in the ON-mode condition from minute 2. The findings provide strong evidence of the ability of this cooling garment to reduce heat stress in hot and humid conditions similar to those encountered in deep mines.     

Analysis of ARMPS2010 database with La Model and an updated abutment angle equation

The Analysis of Retreat Mining Pillar Stability(ARMPS) program was developed by the National Institute for Occupational Safety and Health(NIOSH) to help the United States coal mining industry to design safe retreat room-and-pillar panels. ARMPS calculates the magnitude of the in-situ and mining-induced loads by using geometrical computations and empirical rules. In particular, the program uses the ‘‘abutment angle" concept in calculating the magnitude of the abutment load on pillars adjacent to a gob. In this paper, stress measurements from United States and Australian mines with different overburden geologies with varying hard rock percentages were back analyzed. The results of the analyses indicated that for depths less than 200 m, the ARMPS empirical derivation of a 21° abutment angle was supported by the case histories; however, at depths greater than 200 m, the abutment angle was found to be significantly less than 21°. In this paper, a new equation employing the panel width to overburden depth ratio is constructed for the calculation of accurate abutment angles for deeper mining cases. The new abutment angle equation was tested using both ARMPS2010 and La Model for the entire case history database of ARMPS2010. The new abutment angle equation to estimate the magnitude of the mining-induced loads used together with the La Model program was found to give good classification accuracies compared to ARMPS2010 for deep cover cases.     

Application of HEMS cooling technology in deep mine heat hazard control

This paper mainly deals with the present situation, characteristics, and countermeasures of cooling in deep mines. Given existing problems in coal mines, a HEMS cooling technology is proposed and has been successfully applied in some mines. Be-cause of long-term exploitation, shallow buried coal seams have become exhausted and most coal mines have had to exploit deep buried coal seams. With the increase in mining depth, the temperature of the surrounding rock also increases, resulting in ever increasing risks of heat hazard during mining operations. At present, coal mines in China can be divided into three groups, i.e., normal temperature mines, middle-to-high temperature mines and high temperature mines, based on our investigation into high temperature coal mines in four provinces and on in-situ studies of several typical mines. The principle of HEMS is to extract cold energy from mine water inrush. Based on the characteristics of strata temperature field and on differences in the amounts of mine water inrush in the Xuzhou mining area, we proposed three models for controlling heat hazard in deep mines: 1) the Jiahe model with a moderate source of cold energy; 2) the Sanhejian model with a shortage of source of cold energy and a geothermal anomaly and 3) the Zhangshuanglou model with plenty of source of cold energy. The cooling process of HEMS applied in deep coal mine are as follows: 1) extract cold energy from mine water inrush to cool working faces; 2) use the heat extracted by HEMS to supply heat to buildings and bath water to replace the use of a boiler, a useful energy saving and environmental protection measure. HEMS has been applied in the Jiahe and Sanhejian coal mines in Xuzhou, which enabled the temperature and humidity at the working faces to be well controlled.     

螺旋与弓形折流板换热器性能对比及螺旋角优化

对螺旋角为12、18、30、40°的螺旋折流板换热器进行传热和压降性能测试。应用英国传热协会的Tasc3软件对弓形折流板换热器的运行情况进行了模拟,得到了相应结构下的总传热系数和压降值。通过数据的计算整理,在相同流量下,进行了不同螺旋角的螺旋折流板换热器与弓形折流板换热器在单位压力降下总传热系数的对比,同时对12、18、30、40°螺旋角的螺旋折流板换热器的壳程膜传热系数及压降进行对比研究,优化螺旋角。实验结果表明,实验用12、18、30、40°螺旋角的螺旋折流板换热器的总传热系数要比相应结构下的弓形折流板换热器高59.48%以上,研究表明,实验条件下,18°螺旋角的螺旋折流板换热器的综合传热性能要优于12、30、40°螺旋角的螺旋折流板换热器。     

Cooling pathways for deep Australian longwall coal mines of the future

Cooling of coal mines in the Bowen Basin, characterized by steep geothermal gradient, is presently achieved mostly through rental surface bulk air cooling in summer months. This paper argues that future mines will be required to focus their cooling resources more intensively to manage a challenging thermal environment where virgin coal temperatures over 50 °C at a depth of 500 m are expected. Currently, mine cooling systems are employed to maintain the wet bulb temperatures(WBT) to below 27 °C at which point the risks of heat stroke or other heat related issues are manageable. The capacities of these systems are in the range of 6–10 MW refrigeration power. The relationship between high working temperature environment and injury frequency rates is well established. Therefore, provision of appropriate cooling strategies and understanding their optimum performance and suitability are important to Australian coal mines of the future. This paper evaluates the underground temperature profiles of deep, gassy coal mines with propensity for spontaneous combustion and proposes the long term cooling pathways to effectively manage the thermal hazards. Thermodynamic modeling is performed on a longwall face and includes air leakage effects from goaf streams at various locations along the longwall face. The strategy summarizes the application of underground bulk air cooling, chilled water sprays on the shearer and the resulting temperature profiles. Considering the new mining projects planned for the Bowen Basin region, a review of implementable cooling strategies such as mid-gate mobile bulk air coolers(BACs), spot coolers, underground bulk air cooling and the use of chilled water to enhance the positional efficiency of cooling plants,are discussed in this paper. Finally, the comparison of ‘rental' versus ‘ownership' of cooling plants is analysed as part of long-term cooling strategies.     

Estimation of deformed laser heat sources and thermal analysis on laser assisted turning of square member

Laser assisted machining (LAM) has difficulties in estimating temperature after applying a LAM process due to its very small heat input area, large energy and movement. In particular, in the case of laser assisted turning (LAT) process, it is more difficult to estimate the temperature after preheating because it has a shape of ellipse when a laser heat source is rotated. A prediction method and thermal analysis method for heat source shapes were proposed as a square shaped member was preheated. The temperature distribution was calculated according to the rotation of the member. Compared with the results of the former study, the maximum temperature of the calculation results, 1 407.1 °C, is 8.5 °C higher than that of the square member, which is 1 398.6 °C. In a LAT process for a square member, the maximum temperature is 1 850.8 °C. It is recognized that a laser power control process is required because square members show a maximum temperature that exceeds a melting temperature at around a vertex of the member according to the rotation.     

Design of a water curtain to reduce accumulations of float coal dust in longwall returns

Accumulation of float coal dust(FCD) in underground mines is an explosion hazard that affects all underground coal mine workers. While this hazard is addressed by the application of rock dust, inadequate rock dusting practices can leave miners exposed to an explosion risk. Researchers at the National Institute for Occupational Safety and Health(NIOSH) have focused on developing a water curtain that removes FCD from the airstream, thereby reducing the buildup of FCD in mine airways. In this study,the number and spacing of the active sprays in the water curtain were varied to determine the optimal configuration to obtain peak knockdown efficiency(KE) while minimizing water consumption.     

一种土壤湿度检测系统设计

本文设计了一种无线土壤湿度采集装置,该装置通过湿度传感器HS1101对土壤湿度进行采集,然后将采集到的数据通过无线模块PTR2000发送出去,接收方接收到数据后解包,计算出湿度值并在液晶屏上显示。系统发射部分以AT89S52为核心,包括湿度采集、无线发射。接收部分也以AT89S52为核心,将无线接收、液晶显示结合起来,通过适当的软、硬件抗干扰处理,该系统具有实用性、小型化等特点。     

Head-mounted display-based intuitive virtual reality training system for the mining industry

Virtual reality(VR) training technology in the mining industry is a new field of research and utilization.The successful application of VR training system is critical to mine safety and production. Through the statistics of the current research and applications of VR training systems in mining industry, all the input/output devices are classified. Based on the classifications of the input/output devices that are used in the VR system, the current VR training systems for the mining industry could be divided into three types: screen-based general type, projector-based customized type, and head-mounted display(HMD)-based intuitive type. By employing a VR headset, a smartphone and a leap motion device, an HMDbased intuitive type VR training system prototype for drilling in underground mines has been developed.Ten trainees tried both the HMD-based intuitive system and the screen-based general control system to compare the experiences and training effects. The results show that the HMD-based system can give a much better user experience and is easy to use. Three of the five components of a VR training system,namely, the user, the tasks, and software and database should be given more attention in future research.With more available technologies of input and output devices, VR engines, and system software, the VR training system will eventually yield much better training results, and will play a more important role in as a training tool for mine safety.     

Geological factors controlling deep geothermal anomalies in the Qianjiaying Mine,China

Here, the geological factors controlling deep geothermal anomalies in mines were studied based on the geotemperature, lithologic thermal conductivity, and related geological data collected from the Qianjiaying Mine, China. A simulation of the change in magma waste heat, conducted using the ANSYS Workbench, revealed the distribution characteristics of geothermal anomalies in this mine and the corresponding geological control factors. The results revealed the following points. (1) First-degree heat hazard level (temperature = 31–37 ℃) occurred in the central and southwestern parts of the mine at an ~600-m depth, while second-degree heat hazard level (temperature ≥ 37 ℃) occurred at an ~800-m depth. The geotemperature and geothermal gradient in the southwestern part of the mine were anomalously high. (2) The geotemperatures measured in the mine generally reflected a standard increase with depth, while the geothermal gradient remained unchanged with depth. The geothermal gradient and its average value in the study area were 0.70–4.23 and 2.12 °C·hm⁻¹, respectively. (3) A combination of stratum characteristics, geological structure, and groundwater characteristics led to geothermal anomalies in mines; additionally, the waste heat from magma had no significant effect on the geothermal field.     

Experimental and numerical study on a micro jet cooling solution for high power LEDs

An active cooling solution based on close-looped micro impinging jet is proposed for high power light emitting diodes (LEDs). In this system, a micro pump is utilized to enable the fluid circulation, impinging jet is used for heat exchange between LED chips and the present system. To check the feasibility of the present cooling system, the preliminary experiments are conducted without the intention of parameter opti-mization on micro jet device and other system components. The experiment results demonstrate that the present cooling system can achieve good cooling effect. For a 16.4 W input power, the surface temperature of 2 by 2 LED array is just 44.2℃ after 10 min operation, much lower than 112.2℃, which is measured without any active cool-ing techniques at the same input power. Experimental results also show that increase in the flow rate of micro pump will greatly enhance the heat transfer efficiency, how-ever, it will increase power consumption. Therefore, it should have a trade-off be-tween the flow rate and the power consumption. To find a suitable numerical model for next step parameter optimization, numerical simulation on the above experiment system is also conducted in this paper. The comparison between numerical and ex-periment results is presented. For two by two chip array, when the input power is 4 W, the surface average temperature achieved by a steady numerical simulation is 34℃, which is close to the value of 32.8℃ obtained by surface experiment test. The simu-lation results also demonstrate that the micro jet device in the present cooling sys-tem needs parameter optimization.     

基于FPGA的高速实时图像采集和自适应阈值算法

提出了基于FPGA的图像处理自适应阈值算法,实现了激光光斑中心的高速实时检测。采用3×3窗口模块和自适应阈值模块,先对CCD输入数据进行处理,判断光斑的范围,然后再运用光斑的质心算法对光斑所占的像元进行运算,得出光斑位置的脱靶量。本文达到了脱靶量帧速3000帧/s、精度2μrad的技术指标,实现了高速率、高精度的跟踪要求。     

A coal rib monitoring study in a room-and-pillar retreat mine

The National Institute for Occupational Safety and Health(NIOSH) conducted a comprehensive monitoring program in a room-and-pillar mine located in Southern Virginia. The deformation and the stress change in an instrumented pillar were monitored during the progress of pillar retreat mining at two sites of different geological conditions and depths of cover. The main objectives of the monitoring program were to better understand the stress transfer and load shedding on coal pillars and to quantify the rib deformation due to pillar retreat mining; and to examine the effect of rib geology and overburden depth on coal rib performance. The instrumentation at both sites included pull-out tests to measure the anchorage capacity of rib bolts, load cells mounted on rib bolts to monitor the induced loads in the bolts, borehole pressure cells(BPCs) installed at various depths in the study pillar to measure the change in vertical pressure within the pillar, and roof and rib extensometers installed to quantify the vertical displacement of the roof and the horizontal displacement of the rib that would occur during the retreat mining process.The outcome from the monitoring program provides insight into coal pillar rib support optimization at various depths and geological conditions. Also, this study contributes to the NIOSH rib support database in U.S coal mines and provides essential data for rib support design.     

Analysis of heat transfer of loop heat pipe used to cool high power LED

A novel loop heat pipe (LHP) cooling device for high power LED is developed. The thermal capabilities, including startup performance, temperature uniformity and thermal resistance of the loop heat pipe under different heat loads and incline angles have been investigated experimentally. The obtained results indicate that the thermal resistance of the heat pipe heat sink is in the range of 0.19–3.1 K/W, the temperature uniformity in the evaporator is controlled within 1.5°C, and the junction temperature of high power LED can be controlled steadily under 100°C for a heat load of 100 W.     

PTFE膜材料的偏轴拉伸性能及破坏机理

为深入把握PTFE膜材料的率相关力学性能及破坏机理,对3种常见的PTFE膜材料进行了偏轴拉伸试验,主要考虑了0°、5°、15°、25°、35°、45°、55°、65°、75°、85°、90°等11个偏轴角度和10、25、50、100、200、500 mm/min等6种拉伸速率,分析了主要力学参数的变化规律,研究了不同拉伸速率下的膜材破坏模式及破坏机理.结果表明:不同拉伸速率下膜材主要力学参数的变化规律比较一致,表现出明显的各向异性;材料的抗拉强度与破坏模式密切相关,随着拉伸速率的增加,抗拉强度逐渐升高,且与拉伸速率的对数呈近似线性关系,这主要与材料应变能及编织结构有关;材料的破坏模式和断裂延伸率受拉伸速率的变化影响不明显.     

Research methods and performance analysis for the moderately high temperature refrigerant

In China, directly dropping high temperature refrigerant into conventional compressor is considered as a dominant technical route for development of moderately high temperature heat pump. Based on this route, selection criteria for high temperature refrigerant were presented with consideration of several influencing factors. Moreover, a set of research methods were built including theoretical calculations and experimental tests. Four high temperature refrigerants from HTR01 to HTR04 were compared and analyzed. In results, firstly, HTR03 and HTR04 belonging to non-ozone depleting refrigerants could bring outstanding environmental benefits; secondly, the condenser outlet water efficiently generated by heat pump using high temperature refrigerants could cover 60°C–90°C;; finally, the feasibility of the technical route and the research methods were proved. Supported by Program for New Century Excellent Talents in University (Grand No. NCET-04-0078)     

Sintering and Electronic Conducting Properties of Lao.7Ca0.3CrO3 Perovskite Synthesized by a Glycine-nitrate Process

La0.7 Ca0.3 CrO3 powder consisting of superfine and uniform particles （ 100-200 nm ） were synthesized using a glycine-nitrate process （ GNP ）. The sintering and electronic conducting properties of La0.7 Ca0.3 CrO3 were invetigated in the sintering temperature range of 1 200-1 450 ℃. The desired morphology of the powder significantly improved its sinterability. La0.7 Ca0.3 CrO3 ceramics sintered at 1 250-1 450 ℃ show high relative densities above 95 % . The ceramics sintered at 1 250-1 400 ℃ have very similar electronic conduct- ing properties, providing electronic conductivities around 55 Ω^-1 cm^-1 at a measuring temperature of 800 ℃ . Further increasing the sintering temperature to 1450 ℃ led to an apparent degradation of electronic conducting properties. This research demonstrates the advantage of the GNP in producing La0.7 Ca0.3 CrO3 with respect to the enhanced sintering properties and superior electronic conducting properties.