On-chip diamagnetic repulsion in continuous flow

We explore the potential of a microfluidic continuous flow particle separation system based on the repulsion of diamagnetic materials from a high magnetic field. Diamagnetic polystyrene particles in paramagnetic manganese (II) chloride solution were pumped into a microfluidic chamber and their deflection behaviour in a high magnetic field applied by a superconducting magnet was investigated. Two particle sizes (5 and 10 μm) were examined in two concentrations of MnCl₂ (6 and 10%). The larger particles were repelled to a greater extent than the smaller ones, and the effect was greatly enhanced when the particles were suspended in a higher concentration of MnCl₂. These findings indicate that the system could be viable for the separation of materials of differing size and/or diamagnetic susceptibility, and as such could be suitable for the separation and sorting of small biological species for subsequent studies.     

连续流动分析仪在石化水质分析中的应用

本文应用连续流动注射分析仪(FIA),成功地实现了一次进样同时完成水质中挥发酚和氰化物、硫化物和总氮的测定[1,2]。分析结果准确、可靠,大大缩短了分析时间,加标回收率在95%--105%之间,相关系数均大于0.9995。并与传统的分光光度法进行了比较,在保证分析方法准确度的前提下,FIA法能提高检测灵敏度和检测速率,此方法简单、快速,适合于批量分析。     

Recent progress of applied superconductivity in China

China has been involved for many years in the development of superconducting magnets for high energy physics, fusion research, magnetohydrodynamic power generation, magnetic separator, magnetic resonance imaging and other applications. The research activity in superconducting magnets has been intensified and diversified at the Institute of Electrical Engineering, Academia Sinica and other laboratories. This paper reviews the recent progress of applied superconductivity in China. A possible future programme is also outlined in this paper.     

Geometric method for global stability and repulsion in Kolmogorov systems

A class of autonomous Kolmogorov systems that are dissipative and competitive with the origin as a repellor are considered when each nullcline surface is either concave or convex. Geometric method is developed by using the relative positions of the upper and lower planes of the nullcline surfaces for global asymptotic stability of an interior or a boundary equilibrium point. Criteria are also established for global repulsion of an interior or a boundary equilibrium point on the carrying simplex. This method and the theorems can be viewed as a natural extension of those results for Lotka-Volterra systems in the literature.     

Device for orientation of crystals at low temperatures in a superconducting magnet for the production of single-domain horizontally-polarized specimens

A design is given for a device that can carry up to four single crystals mounted on individual three-way goniometers for mutual alignment of their crystallographic planes. The assembly, held at 4 K in the clear split of a superconducting magnet, may be rotated to a precise angle by simple external means. The rotation of the device permits the formation of horizontally-polarized, single-domain crystals of ferromagnetic materials when only a vertical magnetic field is available.     

连续流动法测定香料烟氯测量不确定度评定

为评定连续流动法香料烟氯的测量不确定度,对连续流动法测定氯的过程进行分析,得到简化的连续流动法香料烟氯的测定因果关系图,建立测量不确定度评定的数学模型,确定其测量不确定度的主要来源为样品的水分、连续流动分析仪测定的样品浓度和测量重复性。通过对测量不确定度进行评定,得出连续流动法香料烟氯测量结果的标准不确定度为0.04%,扩展不确定度为0.08%(α=0.05,k=2)。     

粗糙度对微流道内流体连续自搬运的影响

微流控芯片中各功能单元间样品的运输依赖于流体在微通道中的流动,尺度效应加剧表面作用效果,使得微流道内流体无需外部动力即可实现连续铺展搬运。为了深入研究微流道内流体的流动机制和动力学特性,分析影响微流道内流体自搬运效率的因素,基于近似Derjaguin法的同时充分考虑表面能和Casimir效应,利用数值计算和实验相结合的方法分析了微流道内壁粗糙度对流体流动特性和自搬运效率的影响,明确了微流道内流体的本构方程和流动控制方程,并设计搭建实验台验证所得结果的有效性和可靠性。结果表明：内壁粗糙度是影响微流道内流体流动特性和连续自搬运效率的重要因素;当粗糙度等效齿数、等效齿高和等效齿倾角变化时,微流道内近壁面齿隙间的主漩涡和伴生涡都相应改变,导致流体自搬运效率发生相应变化。研究结果对解决微流控润滑和微流控芯片减阻防粘等设计和使用问题具有重要理论指导意义,对微电子机械系统的小型化和集成化设计具有一定的参考价值。     

Localization effects on magnetic excitations, Coulomb repulsion, and critical temperature in a quasi-3D superconductor

Using the Eliashberg equations for superconductivity in a quasi-3D high-temperature super-conductor, taking into consideration the¯q-dependent phonon-mediated electron-electron interaction, the effect of the disordered magnetic correlations, and Coulomb repulsion affected by disorder, we calculated the expression for the critical temperature. The phonon and the magnetic kernels have a logarithmic divergence and the critical temperature differs from the McMillan form. The Coulomb repulsion in the presence of disorder has been estimated. The disordered magnetic correlations can decrease the critical temperature or can suppress the superconductivity. The effect of various parameters on the decrease of the critical temperature has been analyzed.     

用于环形正负电子对撞机探测器超导磁体的小型氦虹吸回路实验与数值模拟研究

在探测器超导磁体的低温系统预研中,搭建了小型的氦虹吸冷却回路实验系统,进行了气-液两相沸腾和传热特性实验研究,并利用VOF多相流模型模拟计算了氦的热虹吸自然冷却循环过程和过热烧干过程。在相同条件下,模拟计算结果与实验数据进行了比较,模拟计算得到的的温度分布、璧面过热度与实验测量数据符合度较好。     

连续挤压铜扁排的阻流角设计及物理场分布

基于Deform-3D平台,建立了Conform连续挤压生产大宽厚比铜扁排有限元模型,研究了连续挤压过程中阻流角变化对模具出口处金属流动及相应应力场分布的影响规律,并结合方差分析法获得了模具出口处的流速均方差,观察模具阻流角对扁排成型的影响.研究表明:模具阻流角从3°~15°变化时,随着阻流角的增加,金属流速均方差先增大后减小,其阻流角区域等效应力值以及模具入口处沿挤压方向应力也逐渐增加;在定径带长度一定以及模具载荷允许的情况下,选择3°、5°、15°的阻流角可使模具出口处金属流速相对稳定,扁排成形性较好;当模具容易损坏时,选择3°和5°阻流角既可降低模具载荷又可获得板形均匀的扁排.     

Continuous flow cryostats for experiments in the presence of appreciable heat influx to the specimen

The review describes several cryostat designs for spectral and magneto-optical studies representing continuous flow systems with sample cooling by preset temperature vapour blow-over. The characteristic features and advantages are discussed. It is shown that among present-day heat transfer methods, this one is the most efficient for studies involving appreciable heat influx to the cooled sample.     

Assessing the impact of alternative continuous improvement programmes in a flow shop using system dynamics

We use a system dynamics simulation model based on the Factory Physics perspective to study the cumulative effect of continuous improvement in arrival variability, process variability, defect rate, time to failure, repair time and set-up time on operating curves in a flow-shop environment. We find that small, simultaneous improvements at multiple locations in the line can provide reductions in cycle time comparable to, or sometimes superior to, those obtained by a major improvement at a single location. The reduction of process variability is often an excellent alternative to reducing the mean of a parameter, because process variability at a given station affects not only that station, but all downstream stations due to its impact on flow variability. Improvements at non-bottleneck stations also have significant benefits, again by reducing the variability of flow to the bottleneck station. These results suggest a broader interpretation of some aspects of the Theory of Constraints, and help explain the successful results of the Toyota Production System.     

连续流动分析法在烟草分析中的应用

连续流动分析法(CFA)作为一种快速、准确的批量检测方法已经广泛应用于国内外烟草行业。根据连续流动分析法的原理,详细介绍了该分析法在烟草中对烟碱、总糖及还原性糖、水溶性糖、总氮、蛋白质、氯以及钾等含量的测定方法及应用,并对连续流动分析法在烟草科学技术中的应用做了展望。     

Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet

Abstract

We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.     

An integrated,finite element‐based process model for the analysis of flow,heat transfer,and solidification in a continuous slab caster

An integrated, finite element‐based process model is presented for the prediction of full three‐dimensional flow, heat transfer, and solidification occurring in a continuous caster. Described in detail are the basic models for the analysis of turbulent flow and heat transfer in the liquid steel zone, in the zone of mixture of the liquid steel and solidified steel, and in the solidified zone. Then, the models are integrated to form a process model which can take into account the strong interdependence between the heat transfer behaviour and the flow behaviour. The capability of the process model to reveal the detailed aspects of turbulent flow, heat transfer, and solidification occurring in a continuous caster is demonstrated through a series of process simulations. Copyright © 2003 John Wiley & Sons, Ltd.     

Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet

We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.     

Perturbation analysis for continuous and discrete flow models: a study of the delivery time impact on the optimal buffer level

In this paper, a manufacturing system composed of a single-product machine, a buffer and a stochastic demand is considered. Two models are presented: continuous and discrete flow models including constant delivery times, machine failures and random demands. The objective is to determine the value of the optimal buffer level, for a hedging point policy which minimises the total average cost function. The cost function is the sum of inventory, transportation and lost sales costs. Infinitesimal perturbation analysis is used for optimisation of the failure-prone manufacturing system. The trajectories of buffer level are studied for the continuous and discrete cases and the infinitesimal perturbation analysis estimators are evaluated. These estimators are shown to be unbiased and then they are implemented in an optimisation algorithm which determines the optimal buffer level in the presence of constant delivery time. Numerical results are presented for continuous and discrete flow models and then compared in order to evaluate the application of the infinitesimal perturbation analysis on the discrete flow model.     

Flexible job shop with continuous material flow

A new scheduling problem, the continuous flow flexible job shop (CF-FJS) is proposed. The formulation combines the well-known flexible job shop (FJS) problem and a dedicated continuous material flow model (MFM). In the MFM, operations are represented by material flow functions derived by integration of arbitrarily defined speed patterns. Two main concepts of the MFM formalism, i.e. variable speed of processing and continuous material flow, lead to position-dependent processing times and overlapping in operations which extend standard FJS formulation. Properties of the CF-FJS are investigated. A tabu search sched uling algorithm utilising these properties is proposed. Effective neighbourhood functions are defined based on elimination approaches. Two auxiliary procedures: search intensification level switching and fast feasibility detection are added to improve algorithm efficiency. The algorithm is verified using dedicated benchmark instances which comprise non-trivial representations of the CF-FJS specific features, i.e. machine efficiency patterns and minimum inter-operation buffers. The research is motivated by task scheduling in a fastener factory, but the presented results can be useful in many domains, such as production of granular goods, steel details, glass and fluids. The solution can be used in real-world applications. The published results can be helpful in testing new CF-FJS scheduling algorithms.     

Blood flow in the rabbit aortic arch and descending thoracic aorta

The distribution of atherosclerotic lesions within the rabbit vasculature, particularly within the descending thoracic aorta, has been mapped in numerous studies. The patchy nature of such lesions has been attributed to local variation in the pattern of blood flow. However, there have been few attempts to model and characterize the flow. In this study, a high-order continuous Galerkin finite-element method was used to simulate blood flow within a realistic representation of the rabbit aortic arch and descending thoracic aorta. The geometry, which was obtained from computed tomography of a resin corrosion cast, included all vessels originating from the aortic arch (followed to at least their second generation) and five pairs of intercostal arteries originating from the proximal descending thoracic aorta. The simulations showed that small geometrical undulations associated with the ductus arteriosus scar cause significant deviations in wall shear stress (WSS). This finding highlights the importance of geometrical accuracy when analysing WSS or related metrics. It was also observed that two Dean-type vortices form in the aortic arch and propagate down the descending thoracic aorta (along with an associated skewed axial velocity profile). This leads to the occurrence of axial streaks in WSS, similar in nature to the axial streaks of lipid deposition found in the descending aorta of cholesterol-fed rabbits. Finally, it was observed that WSS patterns within the vicinity of intercostal branch ostia depend not only on local flow features caused by the branches themselves, but also on larger-scale flow features within the descending aorta, which vary between branches at different locations. This result implies that disease and WSS patterns in the vicinity of intercostal ostia are best compared on a branch-by-branch basis.     

Severe carbamazepine intoxication unresponsive to albumin‐enhanced continuous venovenous hemodiafiltration with low dialysate flow

Carbamazepine (CBZ) intoxication can be associated with severe toxicity, including neurological and cardio‐respiratory abnormalities. Highly protein‐bound, CBZ is not removed efficiently through conventional hemodialysis. Charcoal hemoperfusion is the most effective extracorporeal elimination therapy for CBZ intoxication. Recent reports have indicated that continuous venovenous hemodiafiltration (CVVHDF), albumin‐enhanced continuous venovenous hemodialysis, high‐flux hemodialysis and plasma exchange can be as effective as charcoal hemoperfusion. In contrast to recent reports, which demonstrated the effectiveness of CVVHDF with high dialysate flow in CBZ intoxication, we observed that serum CBZ level was decreased minimally by albumin‐enhanced CVVHDF with low dialysate flow. Therefore, albumin‐enhanced CVVHDF with high dialysate flow should be considered in severe CBZ intoxication, if hemoperfusion is unavailable because of the lack of facilities or if it cannot be performed.