Proposing a novel comprehensive evaluation model for the coal burst liability in underground coal mines considering uncertainty factors

Coal burst is a severe hazard that can result in fatalities and damage of facilities in underground coal mines.To address this issue,a robust unascertained combination model is proposed to study the coal burst hazard based on an updated database.Four assessment indexes are used in the model,which are the dynamic failure duration(DT),elastic energy index(WET),impact energy index(KE)and uniaxial compressive strength(RC).Four membership functions,including linear(L),parabolic(P),S and Weibull(W)functions,are proposed to measure the uncertainty level of individual index.The corresponding weights are determined through information entropy(EN),analysis hierarchy process(AHP)and synthetic weights(CW).Simultaneously,the classification criteria,including unascertained cluster(UC)and credible identification principle(CIP),are analyzed.The combination algorithm,consisting of P function,CW and CIP(P-CW-CIP),is selected as the optimal classification model in function of theory analysis and to train the samples.Ultimately,the established ensemble model is further validated through test samples with 100%accuracy.The results reveal that the hybrid model has a great potential in the coal burst hazard evaluation in underground coal mines.

Differences between physiological and pathological convulsive thresholds in patients with epilepsy

BACKGROUND： Physiological convulsive thresholds degrade when the brain is in some pathologic states; thus, a level of stimulus that cannot provoke a convulsion may evoke a seizure or epileptic seizure. OBJECTIVE： To investigate the changes that occur in the brain when the physiological convulsive threshold becomes pathological, and to determine what differences occur in pathological and physiological convulsive thresholds during the development of epilepsy. DESIGN： A randomized controlled animal experiment. SETTING： Research Institute of Epilepsy of Shanxi Medical University; Department of Neurology, The Third Hospital of Shanxi Medical University; Research Institute of Function of Shanxi Medical University. MATERIALS： Thirty-six female Wistar rats were selected for this study. The rats were obtained from the experimental animal center of Shanxi Medical University. All laboratory procedures complied with animal ethical standards. The animals were randomly divided into three groups： a strong current group, a weak current group and a control group, with 12 rats in each group. An automatic determinator of seizure threshold was made at Shanxi Medical University and Taiyuan University of Technology. Two bipolar stainless steel stimulating electrodes and an electrode connector （diameter 1.2 ram） were made at Taiyuan University of Technology. METHODS： This study was performed in the laboratory of Research Institute of the Epilepsy of Shanxi Medical University between December 2005 and August 2006. The threshold of localized seizures was measured by performing direct cortical stimulation in rats under anesthesia. After 1 week of post-operative recovery, electric stimulation was started with three different kinds of stimulation. Seizure activity was induced by a ramp-shaped single train of biphasic pulses （50 Hz, total pulse duration of 2 ms, increasing from 0 to 2 000μ A in 15 seconds）. The threshold of localized seizures （TLS） has been defined as the minimum current intensity necessary to provoke convulsion of the forelimbs and/or facial muscles. Up to the TLS, if stimulation continued, the current intensity necessary to provoke the generalized seizures is called the threshold of generalized seizures （TGS）. If stimulation is continued for about 2 seconds when the TGS is reached, rats still showed generalized clonic activity after stimulation ceased. When seizures stopped, a short period of immobility can be observed. The current intensity is called the threshold of prolonged seizures （TPS）. The rats in the strong current group were stimulated up to the current level required to reach the TPS. In the course of stimulation, first, the TLS was recorded, then the TGS, and finally the TPS. The stimulation interval in one session was 10 minutes, repeated twice daily. The rats in the weak current group were only stimulated up to the current levels required to reach the TGS; first, the TLS was recorded and then the TGS was measured at the same time as the strong current group. Control animals were also equipped with a full electrode set and placed in the same conditions, but no stimulation took place, only electroencephalogram （EEG） recording at the same times as the experimental groups. MAIN OUTCOME MEASURES： ① Stimulation of the two experimental groups lasted for 11 weeks and then observation of their behavior and electroencephalogram recording continued for 4 weeks. The control group was also observed over a total of 15 weeks. ② Observing neuronal damage/loss in the hippocampus with a light microscope using a 250x visual field. RESULTS： All 36 Wistar rats were included in the final analysis. At the beginning of the experiment, the convulsive thresholds were all above 1 100 μA, although there were significant individual variations among rats of the same group. Those thresholds quickly declined during the initial 4 weeks of repetitive electrical stimulation. The convulsive thresholds approached a constant level in the 10^th week after commencement of stimulation. There were no significant changes in thresholds when stimulations lasted longer; the convulsive thresholds and the variations in rats of the same group were significantly lower than at the beginning of the trial （P 〈 0.01）. An interictal discharge was also recorded in the 3^rd week in the strong current group, and in the 8th week in the weak current group; these discharges were concomitant with neuronal damage and loss in the hippocampus. There was no abnormality observed in the control group. CONCLUSION： These findings indicated that the convulsion threshold in the brain should be divided into two stages： a physiological convulsive threshold and a pathological convulsive threshold （epileptic threshold） The epileptic threshold is created by pathologically acquired factors, which give rise to brain damage. The increase in the intensity of these pathologically acquired factors led to aggravation of damage.

Industrialization Progress of Nanocellulose in China

Nanocellulose,a kind of cellulose with nanometer sizes,has drawn great interest in the pulp and paper industry due to its unique structure and excellent performance.It can be divided into five categories:nanocrystalline cellulose(NCC),nanofibrillated cellulose(NFC),bacterial cellulose(BC),electrospun cellulose nanofibers(ESC),and precipitation regenerated cellulose nanofibers(PRC).In this paper,we reviewed the industrialization progress of nanocellulose in China.Furthermore,we proposed that efficient and environmentally friendly preparation methods and high value utilization would be the focus of nanocellulose development.

同轴圆柱壳流固耦合附加质量研究

论文根据堆本体内窄间隙同轴设备支承筒的结构特征、边界条件和窄间隙环腔内流体流速,将结构简化为一端固定一端自由的同轴圆柱壳,将圆柱壳内外的流体简化为无旋、无黏、不可压缩流体.同轴圆柱壳通过流体压力场实现耦合,其径向位移模态决定了窄间隙流体域的压力场,故采用级数形式的圆柱壳径向正交位移模态构建既满足一端固定一端自由边界条件,又满足波动方程的压力场基函数,并由此基函数推导一端固定一端自由同轴圆柱壳由间隙流体耦合时自由振动且出现梁、壳复合振型的附加质量理论公式,基函数项数大于50时附加质量计算精度满足要求.为方便工程应用,参考俄罗斯标准以设计曲线形式给出论文推导的同轴圆柱壳流体附加质量结果.为验证以上理论公式,论文首先建立了不同高径比、不同间隙量和不同壁厚的同轴圆柱体流固耦合有限元模型,通过对比理论公式计算结果和包含窄间隙流体域的同轴圆柱壳有限元模型的模态结果可知,当圆柱壳高径比≤2.0时,主振型的频率误差在5%以内;同时笔者设计了双层同轴圆柱筒的流固耦合试验,通过对比模态试验的频率和振型结果进一步验证了论文推导理论公式的正确性.

OUTSOURCING DECISION AND ORDER POLICY WITH FORECAST UPDATING UNDER CAPACITY RESERVATION CONTRACT

This paper investigates an optimal decision problem in a single-period, two-stage supply chain with capacity reservation contract. At the beginning of the planning horizon, the retailer, who faces stochastic demand, reserves future capacity according to his forecasting of the demand. The supplier then constructs capacity. At the beginning of the selling season, the retailer updates the demand forecasting and places an order. When the retailer＇s demand is greater than the supplier＇s capacity, the supplier can meet the retailer＇s demand by outsourcing. We analyze the optimal decision of each player in both centralized and decentralized systems. Furthermore, under the case in which demand follows a uniform distribution, we obtain the closed-form optimal strategies of each player for both centralized and decentralized systems and conduct numerical studies to reveal additional conclusions. The numerical studies show that the optimal reservation capacity for the retailer and the optimal constructing capacity for the supplier in the decentralized system are both less than the optimal constructing capacity in the centralized system. Furthermore, we also find that the profit loss due to decentralization always exists and increases in indeterminacy.