薄煤层中垂直裂缝地震响应特征模拟分析

通过定义一个简单的薄煤层模型,在不断增加煤层中垂直裂缝数量的条件下,利用基于分裂节点的有限元数值方法模拟了含有不同条数裂隙煤层的地震反射波场;通过与不含裂缝、各向同性薄煤层反射的多波波场对比分析发现:裂缝的存在会对煤层的反射产生影响,但裂缝密度低时影响微弱,裂缝密度增加到一定程度后会出现类似调谐作用的反射能量干涉加强;裂缝密度进一步升高,对煤层反射的影响主要反映在高频成分的增加,对振幅影响较弱,说明煤层的反射强度主要受薄层的干涉作用影响较大;从理论地震波场分析的角度证明了薄煤层含裂缝的不可忽视性及反演的可能性。     

Decision support system of unplanned dilution and ore-loss in underground stoping operations using a neuro-fuzzy system

Unplanned dilution and ore-loss are the most critical challenges in underground stoping operations. These problems are the main cause behind a mine closure and directly influencing the productivity of the underground stope mining and the profitability of the entire operation. Despite being aware of the significance of unplanned dilution and ore-loss, prediction of these phenomena is still unexplained as they occur through complex mechanisms and causative factors. Current management practices primarily rely on similar stope reconciliation data and the intuition of expert mining engineers. In this study, an innovative unplanned dilution and ore-loss (uneven break: UB) management system is established using a neuro-fuzzy system. The aim of the proposed decision support system is to overcome the UB phenomenon in underground stope blasting which provides quantitative prediction of unplanned dilution and ore-loss with practical recommendations simultaneously. To achieve the method proposed, an uneven break (UB) prediction system was developed by an artificial neural network (ANN) considering 1076 datasets covering 10 major UB causative factors collected from three underground stoping mines in Western Australia. In succession, the UB consultation system was established via a fuzzy expert system (FES) in reference to surveyed results of fifteen underground-mining experts. The UB prediction and consultation system were combined as one concurrent neuro-fuzzy system that is named the ‘uneven break optimiser’. Because the current UB prediction systems in investigated mines were highly unsatisfactory with correlation coefficient (R) of 0.088 and limited to only unplanned dilution, the performance of the proposed UB prediction system (R of 0.719) is a remarkable achievement. The uneven break optimiser can be directly employed to improve underground stoping production, and this tool will be beneficial not only for underground stope planning and design but also for production management.     

Single- and multi-cycle high hydrostatic pressure treatment on microbiological quality of mud snail (Bullacta exarata) during refrigerated storage

High hydrostatic pressure (HHP) processing is an industrial technology used for preservation of a wide range of food products, and vacumm-packed mud snails (Bullacta exarata) were HHP processed to ensure food safety and shelf-life stability. The effects of single- and multi-cycle HHP treatment, especially the combination of different intensities, on the microbial behavior and shelf-life extension of B. exarata during subsequent storage were investigated. Total microbial count, psychrophilic microorganisms, Clostridium bacteria, total Enterobacteriaceae and H₂S-producing bacteria were enumerated during subsequent refrigerated storage, and Gompertz model was chosen to predict the shelf-life, growth rate, lag time and generation time. The results showed that the initial microbial load was obviously reduced as the pressure increased. Total Enterobacteriaceae and H₂S-producing bacteria were not detected in multi-cycle HHP processing during refrigerated storage. Moreover, multi-cycle HHP method (B + F) could improve the shelf-life of B. exarata for more than 38 days. The model indicated that the lag time for Clostridium bacteria processed with multi-cycle HHP (B + F) was extended to 24.65 days. Our findings will be of aid for the establishment of general process guidelines, and demonstrated that multi-cycle HHP technology has potential for application in mud snail preservation and processing.     

基于层次分析法的煤矿安全综合评价

为定量地综合评价煤矿安全状况,使矿山技术和管理部门及时了解矿山安全生产动态,制定有针对性的安全措施,根据影响煤矿安全的因素建立了安全性评价指标体系,利用层次分析法,建立煤矿安全综合评价模型。通过评价案例进行了验证,评价结果表明,该方法可以提高煤矿安全评价的有效性及精确度,更加符合客观实际。     

Characteristics and applications of interplanetary coronal mass ejection composition

Science China Technological Sciences - In situ measurements of interplanetary coronal mass ejection (ICME) composition, including elemental abundances and charge states of heavy ions, open a new...     

Increase in thermoelectric power factor of carbon-nanotube films after addition of polystyrene

We report the enhancement of the thermoelectric power factors of single-walled carbon-nanotube (SWCNT) films caused by the addition of polystyrene to the films as a binder. The Seebeck coefficient of the SWCNT films was increased by addition of polystyrene. On the other hand, the electrical conductivity gradually decreased with increasing amount of polystyrene. The power factor was maximum for a polystyrene concentration of 20 wt%; it was approximately 1.7 times higher than that of a pure SWCNT film. These results indicate that polystyrene is a superior binder polymer for synthesizing CNT/polymer thermoelectric composites.     

Distance estimation with mixed real and virtual targets in stereoscopic displays

In this paper we investigated the accuracy of center-to-center distance perception in near field augmented reality visual targets viewed by stereoscopic glasses. One real and one virtual targets were presented in four layout or target orientations (two horizontal and two vertical, by altering the relative positions of real and virtual targets) at three different parallax conditions (on screen, 5 cm from screen and 10 cm from screen) and four levels of scaled between targets’ distance (10–20 cm, 20–30 cm, 30–40 cm and 40–50 cm). The result revealed overall underestimation with an accuracy of about 84%. Interestingly, it was noticed that the main effects of layout, parallax and center-to-center distance were significant. Generally, accuracy improves when targets put vertical, close to observers’ position and smaller separation of targets. Significant interactions among the three main factors were also reported. The results are of great importance as it provides guide for the developers to decide where to present targets depending on the need for relative accuracy of judgment. Some engineering implications of the result are also discussed in this paper.     

A novel method for estimating the track-soil parameters based on Kalman and improved strong tracking filters

A tracked vehicle has been widely used in exploring unknown environments and military fields. In current methods for suiting soil conditions, soil parameters need to be given and the traction performance cannot always be satisfied on soft soil. To solve the problem, it is essential to estimate track-soil parameters in real-time. Therefore, a detailed mathematical model is proposed for the first time. Furthermore, a novel algorithm which is composed of Kalman filter (KF) and improved strong tracking filter (STF) is developed for online track-soil estimation and named as KF–ISTF. By this method, the KF is used to estimate slip parameters, and the ISTF is used to estimate motion states. Then the key soil parameters can be estimated by using a suitable soil model. The experimental results show that equipped with the estimation algorithm, the proposed model can be used to estimate the track-soil parameters, and make the traction performance satisfied with soil conditions.     

Quantification of roughness and spatial distribution of dislocations in MBE and MOVPE grown LED heterostructures

A combination of nanoscale imaging techniques such as atomic force microscopy and scanning electron microscopy are used to investigate the relationship between surface morphology and height statistics of GaN cap layers in InGaN/GaN light emitting diode heterostructures. The investigated samples were grown in two very different growth regimes which lead to distinct characteristic superficial landscapes. We also report here on the introduction of a new methodological approach that adapt the concept of height-height correlation function, a well known statistical tool in the field of studies on rough surfaces. We evaluate to which extent the geometrical properties of the constitutive ‘bricks’ (hillocks for ammonia assisted molecular beam epitaxial film) and structural defects (dislocation pits for metal organic vapor phase epitaxial film) affects the statistical properties of heights of these GaN surfaces. Finally, we have studied the spatial distribution of dislocation pits in both the samples to assess the quantitative differences between these heterostructures of very distinct surface morphology.