浅析施工企业财务风险与化解

在建筑业竞争激烈的今天,施工企业面临的财务风险与日俱增,结合施工企业的特点及所面临的财务风险,对如何规避与化解财务风险进行探讨.     

数字信号处理中相位解卷绕问题分析——使用Matlab语言

对Matlab语言中能够保持复向量相位连续性的两个解卷绕命令unwrap和phase的使用方法进行比较,指出它们之间的不同之处。对其源文件进行深入解读,并举例说明同一信号在这两个命令的作用下所得结果不相符的原因。最后通过修改phase命令的M文件或改变unwrap命令的输入参数使二者的输出达到一致,从而扩大了这两个命令的适用范围。     

大坝安全监测研究的回顾与展望

中国水利水电科学研究院结构材料研究所是我国大坝安全监测领域的开创者和积极推动者。本文回顾了我国大坝监测领域的发展及结构材料研究所的开创性工作,介绍了1958年建院以来在大坝安全监测领域研究进展及取得的成果,主要包括大坝安全监测资料分析及安全评价和大坝安全监测数据分析软件和决策支持系统,并对今后大坝安全监测新技术、新理论、新方法研究和结构材料所在大坝监测领域的研究进行了展望。     

双锅筒无构架自撑式D型锅炉制造技术

<正>D型锅炉主要由汽鼓(上锅筒)、水鼓(下锅筒)和连接它们的对流受热面管束组成的锅炉本体,构成炉膛辐射受热面管束和围在本体部分外围炉墙所组成,为无构架的底部     

某补燃型余热锅炉的设计特点

<正>1联合循环对余热锅炉的要求燃-蒸联合循环发电机组与一般蒸汽轮机发电机组相比,具有其固有的特点,因此,余热锅炉设计也应与其特点相适应,以发挥联合循环机组的优势。     

活塞式混凝土湿喷机喷射脉动产生原因与消除方法探讨

国内开发的活塞式湿喷机虽然在结构上与国外产品并无多大不同,但却没有掌握泵送喷射过程消除"脉动"的方法.分析活塞式混凝土湿喷机喷射过程产生"脉动"现象的两个主要原因分别为:(1)由于活塞式湿喷机在进行活塞切换时的切换时间造成了混凝土喷射过程的"脉动";(2)活塞式湿喷机在吸料过程混凝土缸吸料不足,使混凝土不能完全填充混凝土缸,从而造成喷射时的"脉动"产生.针对这两个主要原因提出两种对应解决方案"筑峰填谷"法和"充浆单元"法."筑峰填谷法"核心思想就是让双活塞在交替往复推送混凝土时的速度可调,即在双柱塞刚刚完成切换时让活塞以较快的速度向前推送一小段行程,然后再以正常的速度向前推进.这样就在正常的输送中形成了混凝土的一个"堆积",这个"堆积"(比喻成波峰)在较长输送管路内被削弱正好可以填补刚刚由于双活塞切换而成的混凝土"断续"(比喻成波谷)使不连续现象得以改善."充浆单元"法就是强制填充两主混凝土缸以保证其100%填充,使输送管路的空气段(或称该气体间隔)最小,即输送泵缸的填充是靠外界高压来帮助完成的,而不是靠大气压.由于这种方式加快了填充速度,切换过程的有效时间重叠被充分利用从而保证了双缸在切换时间内都向输送管路推送混凝土.这种积极因素避免了混凝土柱状体变成静止,也就避免了输送管路中混凝土圆柱再重新加速以及输送高压使混凝土柱状体再次发生磨损和断裂,客观上降低了能耗.更重要的是由于活塞每次推送混凝土都被完全充满,因此提高了混凝土输出量,保证了一个比较均匀的输送流量速度,消除了"脉动"现象,也能使喷浆尾部的软管不再摆动.在研制成的"煤矿井下的湿喷作业系统"中应用了"筑峰填谷"法,并进行了试验验证.     

Nickel phosphonate MOF as efficient water splitting photocatalyst

A novel microporous two-dimensional(2D)Ni-based phosphonate metal-organic framework(MOF;denoted as IEF-13)has been successfully synthesized by a simple and green hydrothermal method and fully characterized using a combination of experimental and computational techniques.Structure resolution by single-crystal X-ray diffraction reveals that IEF-13 crystallizes in the triclinic space group Pi having bi-octahedra nickel nodes and a photo/electroactive tritopic phosphonate ligand.Remarkably,this material exhibits coordinatively unsaturated nickel(II)sites,free-P0₃H₂and-P0₃H acidic groups,a C0₂accessible microporosity,and an exceptional thermal and chemical stability.Further,its in-deep optoelectronic characterization evidences a photoresponse suitable for photocatalysis.In this sense,the photocatalytic activity for challenging H₂generation and overall water splitting in absence of any co-catalyst using UV-Vis irradiation and simulated sunlight has been evaluated,constituting the first report for a phosphonate-MOF photocatalyst.IEF-13 is able to produce up to 2,200 fimol of H₂per gram using methanol as sacrificial agent,exhibiting stability,maintaining its crystal structure and allowing its recycling.Even more,170μmol of H₂per gram were produced using IEF-13 as photocatalyst in the absence of any co-catalyst for the overall water splitting,being this reaction limited by the 0₂reduction.The present work opens new avenues for further optimization of the photocatalytic activity in this type of multifunctional materials.     

Controlling the particle size of nanobrookite TiO2 thin films

In this study, pure nanobrookite TiO₂ thin films were successfully deposited on glass substrates with the spin-coating method using titanium butoxide and acetic acid. The particle size of TiO₂ films was controlled by the water:AcAc volume ratio. This study shows that it is possible to obtain single oriented pure brookite films. The structural and optical properties of the nanobrookite TiO₂ thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet-visible spectroscopy (UV-vis), scanning electron microscopy (SEM), spectrophotometer (NKD), and Fourier transform infrared spectrometer (FTIR).     

Magnetic Properties of Zn1?x Ni x O (0.25≤x≤ 0.50) Prepared by Solid-State Reactions

In this study the origin of ferromagnetism in ZnO-based bulk systems has been investigated using Ni-doped ZnO samples, Zn_1−x Ni _x O with 0.25≤x≤0.50, prepared by solid-state reactions. The structural characterizations indicated that the Ni²⁺ ions almost uniformly distributed in all the samples, and the samples have hexagonal wurtzite structure; however, when x is increased toward 0.50, a new NiO phase is formed. A ferromagnetism (FM) has been observed for all the samples at and below the room temperature. In other words, the room temperature results of (M–H) curves show that the FM observed is intrinsic for all the Ni-doped ZnO samples. However, the saturated magnetizations decrease gradually with increasing Ni concentration. This indicates that, in addition to FM, the excessive doping of Ni in ZnO also causes an antiferromagnetic (AFM) contribution which increases with increasing Ni amount. This result is also supported by the magnetization against temperature measurements. Furthermore, the trend of the ac-susceptibility (χ) versus temperature curves, measured under an ac-magnetic field of 100 Oe, also support our conclusion about the antiferromagnetic contribution to ferromagnetism in our samples.