用精铁矿粉制备BaZnCoTi-W型微波吸收铁氧体材料

利用称重、磁性探测和XRD图谱相结合的方式,分析了精铁矿粉的氧化相变过程,发现在750℃时,精铁矿粉被氧化生成α-Fe2O3;采用氧化工艺,直接用精铁矿粉和BaCO3一次烧结制备W型钡铁氧体BaZn1-aMnaCo1+0.5xTi0.5xFe16-XO27,分别研究了Co2+Ti 4+含量(x值)和涂层厚度对磁性能的影响,结果表明:当厚度为2.1mm及x=1.25时,样品在x全波段内(8～12GHZ)吸收衰减大于10dB,吸收峰达到31dB。     

WSN中六边形集中式分簇多跳路由协议

针对节点随机分布的大规模无线传感器网络,提出了一种六边形集中式分簇多跳路由协议(HCCM)．基站根据能耗确定簇内平均节点数,并以合适的边长确定六边形完成初步分簇; 根据簇内的节点数进行分簇优化;依据节点剩余能量选择簇头及传输路径,分配合适的时隙以多跳形式完成信息的传输．仿真结果表明,与LEACH协议及其改进的协议(DE-LEACH)相比,在小规模网络中,协议HCCM延长了网络寿命,但接收的数据包数较少,性能略差; 在大规模网络中,协议HCCM提高了网络性能,比改进的协议(EECT)网络寿命延长了15%,接收的数据包增加了9.5%．     

A new type of anionic surfactant with four carboxylates for the preparation of mesoporous materials

In this paper, a new type of anionic surfactant containing four carboxylates was synthesized by a four-step synthetic reaction including bromination reaction and primary amide protective reaction. Intermediates and final products of each step in the whole synthetic process were characterized by ¹H NMR and MS. Purification of the anionic surfactant was accomplished through combination of recrystallization and silica gel column chromatography. The structure and the critical micelle concentration (CMC) of this surfactant at different temperatures were also investigated. Unlike traditional mono-carboxylate surfactant easy to form lamellar mesostructure, this surfactant has the hexagonal mesophase structure and comparatively low CMC, hopefully to be applied in the preparation of mesoporous metal oxides.     

毛坪铅锌矿水平矿柱形成与回采方法试验研究及应用

毛坪铅锌矿采用下向水平分层矩形进路式胶结充填采矿法,在多中段同时回采条件下,随着开挖深度的增加,将会出现760中段和720中段2个水平矿柱。水平矿柱何时形成与破坏,以及如何在保证开采安全的前提下最大限度地回收矿柱,是矿山目前遇到的难题。采用Flac3D数值模拟软件,分析了矩形进路采场结构条件下水平矿柱形成与破坏过程,得出当720中段未开挖矿体厚度为24 m时,水平矿柱形成;厚度减小为21 m时,水平矿柱完全被破坏。然后模拟分析采用六边形进路开采过程,最终提出毛坪铅锌矿应用下向水平分层六边形进路式胶结充填采矿法能够保证水平矿柱回采过程稳定,最大程度回收水平矿柱资源,为矿山生产提供指导。     

Application of BWR Simulator to Neutronics Calculation Tool in Fast Reactors

Scaling considerations have been made for liquid line small break simulation tests of a BWR affected by the stored heat released from loop structures. Necessary scaling parameters were given from lumped energy and mass balances equations. It was possible to compensate for excess stored heat released in the reduced-scale facility by increasing the coolant discharge flow area A_D . Although this compensation accelerated the blowdown process, actual pressure and coolant mass changes of the reactor system could be obtained by altering the time scale of the test results by the ratio of A_D/V (V: vessel volume) between the test loop and the reactor system. A semi-experimental evaluation of the stored heat release rate in the Two Bundle Loop (TBL) during blowdown after the operation of Automatic Depressurization System (ADS) was also presented on the basis of comparison of experimental diathermic and analytical adiabatic blowdown pressure changes. The obtained results were used in the determination of simulated ADS nozzle diameter for small break tests at the TBL.     

热态内高压成形工艺中粉末传压介质性能研究

为了研究硅微粉和六方氮化硼复合粉的传压性能,利用压力机对不同质量分数的复合粉在不同温度下施加压力,并利用耐高温压力传感器测量了筒壁上分布的压力。实验结果证实,加入的六方氮化硼的质量分数在2%时复合粉的传压效果最佳,同时发现温度对复合粉的传压性能影响不显著,高温下传压性能保持稳定。将该复合粉作为传压介质在500℃下进行了40Cr合金钢管件的热态内高压成形试验,获得了满意的内高压成形件。     

张力减径内六方成因分析及解决方法

分析了无缝钢管在张力减径时内六方产生的原因及影响因素,重点分析了温度不均匀对内六方的影响,并结合现有工艺条件提出多种减少直至消除内多边形的措施。     

Synthesis and characterization of polyimide/hexagonal boron nitride composite

Polyimide (PI)/hexagonal boron nitride (h‐BN) composites were produced via the thermal imidization procedure from solution mixtures of a polyamicacid, which is prepared from 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride and 3,3′‐diaminodiphenyl sulfone (DADPS) in N‐methyl‐2‐pyrrolidone (NMP), and alkoxysilane functionalized h‐BN. The structure, thermostability, thermal behavior, and surface properties of the resulting materials were characterized by means of Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM). The thermal characteristics of PI/h‐BN films were better than the pure PIs. The physical and mechanical properties of the films were evaluated by various techniques such as contact angle, chemical resistance, and tensile tests. The flame retardancy of the composite materials was also examined by the limiting oxygen index (LOI). The experiments showed that the LOI values of PIs increased from 32 to 43 for the materials containing hexagonal boron nitride. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Orthorhombic-hexagonal Phase Transition in High Density Polyethylene Crystals

Abstract

The crystal structure of drawn samples of high density polyethylene was investigated by using wide-angle X-ray scattering (WAXS) with CoKα and MoKa radiations. HDPE films with fiber-like morphology and constrained to a constant length on heating were studied in the range from room temperature to 158[ddot]C. Orthorhombic-hexagonal phase transition, which was previously reported only for UHMWPE fibers, was also proved to exist in moderate molecular weight HDPE drawn films. Differently from the orthorhombic phase, which melts at 129[ddot]C, the hexagonal phase formed melts at 158[ddot]C. A new hexagonal reflection with interplanar distance 2.139(7) Å, indexed as (101), is reported.