The influence of liquid drop shape on crystalline structure of nanowires

The influence of liquid drop shape on the crystalline phase structure of growing nanowires (NWs) has been analyzed. It is established that, at the same concentration of substance in the catalyst, the crystalline phase of NWs can change depending on the contact angle of the liquid drop. Based on the established facts, some experimental data concerning changes in the crystalline phase of III–V nanowires, e.g., depending on the antimony concentration in the liquid drop, are explained.     

Effect of particle morphology on mechanical properties of liquid marbles

In order to better understand the influence of the shape of solid particles on the stability of liquid marbles, we investigated liquid marbles stabilized by hydrophobized calcium carbonate particles with spherical and rod-shaped morphologies. Static properties, such as the effective surface tension, and the dynamic behavior i.e. the compression-decompression features for several cycles of the liquid marbles were investigated. Liquid marbles stabilized with spherical CaCO₃ particles show an elastic response to mechanical deformation almost up to collapse. In contrast, liquid marbles prepared with rod-like particles exhibit a more plastic response to compression. It is concluded that the main differences in behavior of the prepared liquid marbles arise from how the solid particles can arrange/orient at the air/water interface.     

Particle accumulation structures in time-dependent thermocapillary flow in a liquid bridge under microgravity

The formation of a dynamic spiral string of particles with larger density than the fluid was investigated for time-dependent thermocapillary flow in liquid bridges under various gravity conditions including microgravity. The dynamic spiral string forms after approximately 20–60 oscillation periods from the homogeneous dilute particle suspension. It was found that the action of gravity is not decisive in the process of the particle accumulation structure (PAS) but gravity influences the flow field for PAS-formation. We could realize and observe PAS with modal structure m=3 under μ-g but modal structure m=2 occurred only during a transient of the operating parameters in an aspect ratio-range different from that under normal gravity. The correlation of the optically observed PAS structure with the temperature structure of the azimuthally rotating hydrothermal wave on the free surface is the same under microgravity as under normal gravity indicating that PAS is a pure Marangoni effect.     

The shape of jets during discharge of a superheated liquid (structure of wave formations and the reactive force)

Based on the boiling shock concept, a physical model of discharge from orifices and short nozzles of the flashing liquid with temperatures reaching the critical thermodynamic temperature has been constructed. The mechanism of formation of “daisy-shaped” jets that accompany the discharge modes with the radial jet expansion has been investigated. It has been shown that in the case under consideration the flow separates into two areas not connected with each other, viz., the central core in the vicinity of the flow axis and the peripheral liquid expansion region. The geometry of shock wave formations that occur during discharge of a high-temperature liquid has been studied. Comparison with experimental data shows a good agreement. The effect of a stepwise drop in the reactive force to zero upon onset of discharge modes with a jet radial expantion has been explained.     

Plasma Activated Sintering (PAS) of Tungsten Powders

Plasma Activated Sintering (PAS) is a short time, high temperature densification process based on three main contributions: resistance sintering, pressure application, and plasma generation. PAS was applied to the densification of untreated tungsten powder at temperatures between 2050 and 2685 K for 2 to 8 minutes in air or vacuum. The density values ranged between 80.2 and 91.5 % of theoretical density. The initial micron grain size was retained after consolidation at temperatures of 2350 and 2400 K. Net shape consolidation of a cutting tool was achieved by PAS densification of WC-Co powders.

The clean grain boundary observed by high resolution electron microscopy in some of the PAS consolidated specimens suggests that activation of the powder surfaces may take place to enhance the densification process. This physical surface activation may be responsible for enhanced sintering of tungsten particles with no need for additives. The major benefits from this new non-conventional technique include an unusual short densification time (minutes as compared to hours for conventional densification), retention of unique initial microstructures and properties, as well as sintering in one single step with no requirements for binders, prior cold compaction or controlled atmospheres.     

结构形状对密闭胞元抗射流侵彻性能的影响

针对液态复合装甲抗射流侵彻性能与胞元的结构形状密切相关性,研究了密闭胞元的结构形状对抗射流侵彻性能的影响。利用LS-DYNA有限元软件进行了数值仿真,分析了结构形状为四边形、圆形、六边形的3种密闭胞元对射流冲击波的反射能力和密闭胞元受到的压力、射流断裂时间及速度区间、剩余穿深、胞元内壁变形等参量,得出圆形密闭胞元反射冲击波的能力最优;圆形密闭胞元的抗射流侵彻能力最强,表现为剩余穿深最小,干扰射流头部速度区间最大;六边形密闭胞元的抗射流干扰能力稍小,干扰射流颈部速度区间最大,吸能最大,变形小且稳定性好;四边形密闭胞元的抗射流侵彻能力最差,内壁变形的振动幅度最大。为研究多胞结构液态复合装甲提供了结构上的设计依据。     

结构形状对密闭胞元抗射流侵彻性能的影响

针对液态复合装甲抗射流侵彻性能与胞元的结构形状密切相关性,研究了密闭胞元的结构形状对抗射流侵彻性能的影响。利用LS-DYNA有限元软件进行了数值仿真,分析了结构形状为四边形、圆形、六边形的3种密闭胞元对射流冲击波的反射能力和密闭胞元受到的压力、射流断裂时间及速度区间、剩余穿深、胞元内壁变形等参量,得出圆形密闭胞元反射冲击波的能力最优;圆形密闭胞元的抗射流侵彻能力最强,表现为剩余穿深最小,干扰射流头部速度区间最大;六边形密闭胞元的抗射流干扰能力稍小,干扰射流颈部速度区间最大,吸能最大,变形小且稳定性好;四边形密闭胞元的抗射流侵彻能力最差,内壁变形的振动幅度最大。为研究多胞结构液态复合装甲提供了结构上的设计依据。     

Discrete element model study into effects of particle shape on backfill response to cyclic loading behind an integral bridge abutment

The discrete element method, implemented in a modular GPU based framework that supports polyhedral shaped particles (Blaze-DEM), was used to investigate effects of particle shape on backfill response behind integral bridge abutments during temperature-induced displacement cycles. The rate and magnitude of horizontal stress build-up were found to be strongly related to particle sphericity. The stress build-up in particles of high sphericity was gradual and related to densification extending relatively far from the abutment. With increasing angularities, densification was localised near the abutment, but larger and more rapid stress build-up occurred, supported by particle reorientation and interlock developing further away.     

液氮温区固-液复合绝缘气体小桥对沿面放电的影响

采用IEC脉冲电流法(IEC60270标准)对液氮温区超导复合绝缘沿面放电现象及其影响因素进行了研究。在六面屏蔽的局部放电实验室内,研究了不同放电条件对放电起始电压、放电量、击穿电压等的影响,进而研究了其作用机理,并用有限元方法开展了相关计算。实验数据表明,不同放电条件明显影响放电重复率、平均放电量、最大放电量等,放电产生的气泡越容易逸出,放电越严重;液氮的流动使放电起始电压有一定的升高,但对最终击穿电压影响不大;在放电通道上施加阻挡之后可明显提高最终的闪络击穿电压。     

产品碳足迹核查主任核查员课程(5天)

培训机构BSI课程目标气候变化已被确定为未来几十年内各国家、政府、商业界和人类所面临的最大挑战之一。人们通常从全球、国家、社团或组织层次上看待温室气体(GHG)排放,这些排放可能源于企业内部的运作、企业之间和国家之间的各类供应链,而商品和服务以及商品和     

Effect of particle structure on mode I fracture process in concrete

Mode I fracture of concrete is normally regarded at the macro-level, and the effect of micro-structure is reduced to the use of several empirical constants in the fracture law. A key parameter is the softening diagram in tension. In a series of numerical analyses with a simple beam lattice model, the effect of material structure both on the pre-peak and softening regimes of the stress-deformation diagram in uniaxial tension has been established. The simulations are in good agreement with experimental observations that show the propagation of a large ‘crack-like’ feature in the steep part of the softening curve and substantial crack face bridging in the tail of the diagram. The simulations indicate that the density of stiff particles, which ranged between 35% and 83% in the analyses, has a significant effect on pre-peak micro-cracking. This part of the tensile stress-strain behaviour is usually ignored in macroscopic fracture models, but here it is shown that the material composition may have a significant effect in the pre-peak regime, but also on the peak stress. Furthermore the model analyses give output in terms of crack length distributions during the entire fracture process, which may be falsified in new experiments.     

Influence of particle shape on sheared dense granular media

We study by means of molecular dynamics simulations of periodic shear cells, the influence of particle shape on the global mechanical behavior of dense granular media. At large shear deformation samples with elongated particles, independent of their initial orientation, reach the same stationary value for both shear force and void ratio. At the micro-mechanical level the stress, the fabric and the inertia tensors of the particles are used to study the evolution of the media. In the case of isotropic particles the direction of the principal axis of the fabric tensor is aligned with the one of the principal stress, while for elongated particles the fabric orientation is strongly dependent on the orientation of the particles. The shear band width is shown to depend on the particle shape due to the tendency of elongated particles to preferential orientations and less rotation.     

Effect of particle shape on electrical conductivity and negative permittivity spectra of Cu granular composite materials

Journal of Materials Science: Materials in Electronics - Electromagnetic (EM) metamaterials with negative permittivity and permeability can be used to develop advanced EM devices such as perfect EM...     

Effect of the shape of imprinted alignment layer on the molecular orientation of liquid crystal

The molecular alignment of liquid crystals was studied with three different imprinted patterns. The three different shapes of molds (square-, V- and U-shaped) replicated the microstructures with electroplating process was fabricated. Surfaces with three different microgrooved patterns were used as the alignment layer of the liquid crystal cell. The effect of the shape of imprinted alignment layer on the molecular orientation of LC was investigated. Among these patterns, U-shaped groove pattern resulted in a high performance of liquid crystal orientation, pretilt angle and anchoring energy, which are quite comparable to the conventionally rubbed layer. It clearly shows that the molecular orientation of liquid crystals is influenced by the shape of microgrooved patterns.     

Effect of the pulsations of a liquid on the averaged motion of a suspended particle

It is shown that particles moving in a pulsating flow with relative velocities extending outside the normal Stokes range acquire average velocities differing from those normally associated with sedimentation.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 5, pp. 837–843, November, 1970.     

Effect of grafted polymer species on particle monolayer structure at the air-water interface

We have studied poly(methyl methacrylate)-grafted(PMMA) particle monolayer systems at the air-water interface. In previous papers, we reported that PMMA chains grafted from particles (silica particle and polystyrene latex) were extended on water surfaces. Through observing deposited particle monolayers on substrates using SEM, we have confirmed that PMMA of large molecular weights were either dispersed or arrayed in structure with long inter-particle distances approximately 500 nm. In contrast, low molecular weight PMMA were observed to aggregate upon deposition. We speculated that the difference in morphology in deposited particle monolayers would be attributed to the affinity between the grafted polymer and the substrate. To examine the effect of this affinity three new polymer-grafted silica particles were synthesized with a fairly high graft density of about 0.14 approximately 0.43 nm(-2). As well as PMMA-grafted silica particles (SiO2-PMMA), poly(2-hydroxyethyl methacrylate) and poly(t-butyl methacrylate)--grafted silica particles (SiO2-PHEMA and SiO2-PtBuMA) were also prepared and subjected to pi-A isotherm measurements and SEM observations. These pi-A isotherms indicated that polymer-grafted silica formed monolayer at the air-water interface, and the onset area of increasing surface pressure suggests that the polymer chains are extended on a water surface. However, the morphology of the deposited monolayer is highly dependent on polymer species: SiO2-PHEMA showed that the dispersed particle monolayer structure was independent of grafted molecular weight while SiO2-tBuMA showed an aggregated structure that was also independent of grafted moleculer weight. SiO2-PMMA showed intermediate tendencies: dispersed structure was observed with high grafted molecular weight and aggregated structure was observed with low grafted molecule weight. The morphology on glass substrate would be explaiened by hydrophilic interaction between grafted polymer and hydrophilic glass substrate.     

Influence of filler particle shape on elastic moduli of PP/CaCO3 and PP/Mg(OH)2 composites

The effects of filler particle shape on the Young's and shear moduli of PP/CaCO₃ and PP/Mg(OH)₂ composites were studied in the concentration interval up to 50 vol/vol % filler. Calcium carbonate had irregular, approximately spherical particles and magnesium hydroxide had particles either in the form of hexagonal plates or micro-needles. The analysis based on the classical models together with structural observations enabled explanation of the composition dependences of elastic moduli of the blends studied. It was found that immobilization of PP matrix on the filler surface prominently influenced the values ofG′ andE′ moduli of PP/CaCO₃ and PP/Mg(OH)₂ composites. The presence of the strongly immobilized PP with increasing geometrical anisotropy of the filler particles enabled a hyperstructure creation in the composites PP/Mg(OH)₂.