Mining blackhole and volcano patterns in directed graphs: a general approach

Given a directed graph, the problem of blackhole mining is to identify groups of nodes, called blackhole patterns, in a way such that the average in-weight of this group is significantly larger than the average out-weight of the same group. The problem of finding volcano patterns is a dual problem of mining blackhole patterns. Therefore, we focus on discovering the blackhole patterns. Indeed, in this article, we develop a generalized blackhole mining framework. Specifically, we first design two pruning schemes for reducing the computational cost by reducing both the number of candidate patterns and the average computation cost for each candidate pattern. The first pruning scheme is to exploit the concept of combination dominance to reduce the exponential growth search space. Based on this pruning approach, we develop the gBlackhole algorithm. Instead, the second pruning scheme is an approximate approach, named approxBlackhole, which can strike a balance between the efficiency and the completeness of blackhole mining. Finally, experimental results on real-world data show that the performance of approxBlackhole can be several orders of magnitude faster than gBlackhole, and both of them have huge computational advantages over the brute-force approach. Also, we show that the blackhole mining algorithm can be used to capture some suspicious financial fraud patterns.     

提高定点精度的FPGA信号处理算法

为了满足速度、功耗等诸多限制的要求,数字信号处理算法常使用FPGA实现。而实现时由于硬件特点,通常将浮点运算转换成定点运算,但定点转换设计流程复杂、周期长,且存在数据范围和精度之间的矛盾。利用浮点数的优点,本文改进了基于FPGA的定点数的基本运算规则,有效解决了上述矛盾。本文详细论述了实现移位、加/减、乘、除基本运算模块的方法和步骤,最后以FIR数字滤波器为设计实例。仿真结果表明:改进的定点数算法比定点运算误差小、精度高、数据范围宽,能有效地防止溢出。     

稻壳基碳量子点对废水中Pb(Ⅱ)的检测

为了进一步实现生物质废弃资源的综合利用,以及对废水中污染物的检测,以稻壳粉为原料,在600℃和N2氛围下煅烧完成后使用一步水热法制备了钝化剂修饰的碳量子点,得到荧光为蓝绿光的二酸铵(ACA-CQDs)改性稻壳基碳量子点.采用SEM/EDS、HRTEM、FTIR等现代分析技术对碳量子点进行了理化特性表征,发现二酸铵(ACA-CQDs)量子点可以成功检测水中的Pb(Ⅱ).建立了一种有效的检测水体中Pb(Ⅱ)简便快速高效的方法.     

Enhanced Photoelectrochemical Performance of Hematite Photoanode by Decorating NiCoP Nanoparticles Through a Facile Spin Coating Method

Catalysis Letters - Hematite (α-Fe2O3) is a potential photoanode material for photoelectrochemical (PEC) water splitting, but its short hole diffusion length and low water oxidation kinetics...     

Effect of supports on the redox performance of pyrite cinder in chemical looping combustion

Chemical looping combustion (CLC) is a clean and efficient flame-free combustion technology,which combust the fuels by lattice oxygen from a solid oxygen carrier with inherent CO2 capture.The develop-ment of oxygen carriers with low cost and high redox performance is crucial to the whole efficiency of CLC process.As the solid by-product from the sulfuric acid production,pyrite cinder presented excellent redox performance as an oxygen carrier in CLC process.The main components in pyrite cinder are Fe2O3,CaSO4,Al2O3 and SiO2 in which Fe2O3 is the active component to provide lattice oxygen.In order to sys-tematic investigate the functions of supports (CaSO4,Al2O3 and SiO2) in pyrite cinder,three oxygen car-riers (Fe2O3-CaSO4,Fe2O3-Al2O3 and Fe2O3-SiO2) were prepared and evaluated in this study.The results showed that Fe2O3-CaSO4 displayed high redox activity and cycling stability in the multiple redox cycles.However,both Fe2O3-Al2O3 and Fe2O3-SiO2 experienced serious deactivation during redox reactions.It indicated that the inert Fe-Si solid solution (Fe2SiO4) was formed in the spent Fe2O3-SiO2 sample,which decreased the oxygen carrying capacity of this sample.The XPS results showed that the oxygen species on the surface of Fe2O3-CaSO4 could be fully recovered after the 20 redox cycles.It can be concluded that CaSO4 is the key to the high redox activity and cycling stability of pyrite cinder.     

CHARAC TERIZATION OF TiAl POWDER PRODUCED BY MECHANICAL ALLOYING

The microstructure,alloying reaction and sintering behavior of the powder produced by Mechanical Al-loying(MA)for 8 h from 64 wt.-% Ti powder and 36 wt.-% Al powder were studied by scanning electronmicroscopy,optical microscopy,X-ray diffractometry,differential scanning calorimetry(DSC)and dilatometry.The mechanically alloyed powder partictes are Ti-Al composite particles.Thus,titanium aluminides can formeasily in the powder through diffusion during heat treatment.It is shown that the sintering behavior of this pow-der,different from the behaviors of TiAl alloy powder and mixed powder of 64 wt.-% Ti powder and 36 wt.-%Al powder,changes from expansion at temperatures below 1000℃ to shrinkage at temperatures above 1000℃.Homogeneously alloyed TiAl material with a density over 96% of the theoretical density can be produced fromthe mechanically alloyed powder by compaction-sintering.     

含钼废渣冶炼钼铁的优化试验

利用含钼废料钼酸钙为原料,采用碳还原法冶炼钼铁,通过单因素分析试验及正交试验优化得出最佳的试验条件,钼酸钙加入量应低于10%,熔炼温度为1 525 ℃,保温时间为25 min,碱度为1.3。通过XRD、SEM、EDS分析得出用此方法生产得到的钼铁合金中,钼以Mo₂C、Fe₃Mo以及Fe₃Mo₃C的形式存在,渣系为二元玻璃渣系,具有与普通玻璃相似的成分系统。经测定合金中钼的回收率大于99%,钼资源回收效益可观。     

基于地质勘查技术的矿山环境地质灾害预防探析

中国矿产资源总量庞大,很多矿产资源开采难度较高,勘查和解决好矿山环境地质灾害,是从业人员面临的难题之一。简述了利用地质勘查技术勘查矿山环境地质灾害的重要性,分析了典型矿山环境地质灾害类型,介绍了先进地质勘查技术,并给出了相关技术支撑下的矿山环境地质灾害预防对策,以提升矿山资源开采安全性。     

冬季CO2水玻璃砂促硬防蠕变技术

介绍了使用一种专用改性荆加入普通水玻璃中，使CO2水玻璃砂在低温环境下也能速硬，可防止铸型（芯）蠕变的技术。