Investigation on the Dimensions and Shape of a Submerged Vane for Sediment Management in Alluvial Channels

A submerged vane is a flow-training facility mounted vertically on the channel bed to control the sediment movement in the channel cross section, and has been utilized in various applications, such as prevention of bank erosion, sediment exclusion at water intakes, and deepening channels for navigation. The performance of a submerged vane is related to its dimensions and shape. This study aims to investigate a vane’s sediment control effectiveness as a function of its size and shape, with the expectation of an optimal combination of dimensions and shape. A model for the calculation of the transverse bed profile in a cross section of a straight alluvial channel induced by a single submerged vane is developed. The model is utilized to investigate the performances for three types of vanes: (1) rectangular plates with various height and length; (2) tapered plates with linear decreasing in length from the base to the top; and (3) plates of parallelogram with the top of the plates swept forward or backward. Design guidelines and suggestions on the dimensions and shape of the vane are provided based on the results.     

Wave Diffraction by a Vertical Cylinder with a Porous Ring Plate

Linearized potential wave theory is applied to investigate the phenomenon of wave diffraction by a vertical circular cylinder with a thin ring plate in water of finite depth. By means of the eigenfunction expansion method, harmonic expressions for the velocity potential are obtained. The numerical results for the wave loads and the wave height surrounding the body are discussed. It is found that the presence of a thin ring plate causes the focusing of wave energy near the rear edge of the cylinder for small dimensionless porous-effect parameters. A porous ring plate behaves as a wave absorber, which leads to a decrease of the wave height until setdown occurs. The ring plate can decrease not only the horizontal wave force but also the moment on the cylinder. In general, the mechanism of decreasing the wave loads on the cylinder by a porous ring plate is different from that by an impermeable ring plate. An impermeable ring plate attached to the cylinder causes wave focusing near the rear edge of the cylinder so that the difference between wave heights at the front edge and at the rear edge of the cylinder becomes small; hence the wave loads on the cylinder are decreased. A porous ring plate behaves as a wave absorber, which decreases the wave height at the front edge of the cylinder, and thus leads to a decrease of wave loads on the cylinder.     

Indentation Plastometry for Study of Anisotropy and Inhomogeneity in Maraging Steel Produced by Laser Powder Bed Fusion

This work concerns the use of profilometry-based indentation plastometry (PIP) to obtain mechanical property information for maraging steel samples produced via an additive manufacturing route (laser powder bed fusion). Bars are produced in both “horizontal” (all material close to the build plate) and “vertical” (progressively increasing distance from the build plate) configurations. Samples are mechanically tested in both as-built and age-hardened conditions. Stress–strain curves from uniaxial testing (tensile and compressive) are compared with those from PIP testing. Tensile test data suggest significant anisotropy, with the horizontal direction harder than the vertical direction. However, systematic compressive tests, allowing curves to be obtained for both build and transverse directions in various locations, indicate that there is no anisotropy anywhere in these materials. This is consistent with electron backscattered diffraction results, indicating that there is no significant texture in these materials. It is also consistent with the outcomes of PIP testing, which can detect anisotropy with high sensitivity. Furthermore, both PIP testing and compression testing results indicate that the changing growth conditions at different distances from the build plate can lead to strength variations. It seems likely that what has previously been interpreted as anisotropy in the tensile response is in fact due to inhomogeneity of this type.     

Effect of the design of a supply nozzle on the ingot formation during semicontinuous casting of copper

The semicontinuous casting of copper using a T-joint submerged nozzle with various configurations of its internal contour and a various number of outlet holes is considered. The results of physical modeling and commercial tests are used to choose the design of the submerged nozzle that meets the conditions of copper casting under industrial conditions as much as possible.     

Dislocation transformations and the anomalies of deformation characteristics in TiAl—I. Models of dislocation blocking

An analysis is given of the models proposed to explain the temperature peak of yield point in TiAl. Results are provided of a theoretical investigation into the glissile dislocations of different types and of transmission electron microscopy (TEM) observations of nodes formed by these dislocations. Consideration is given to mechanisms of superdislocation blocking due to their resplitting into noncoplanar configurations such as “roof”-type barriers, barriers of the two-layer twin type, barriers similar to Kear-Wilsdorf locks and Lomer-Cottrell-Hirth barriers. A new blocking mechanism related to trapping of single dislocations in deep Peierls valleys is proposed.     

Influence of Sluice Gate Contraction Coefficient on Distinguishing Condition

Sluice gates are widely used for flow control in open channels. Flow through the gate may be free or submerged depending on tailwater depth. One may determine whether the flow will be free or submerged by determining the maximum tailwater level that permits free flow. This is called the distinguishing condition. This paper derives a theoretical equation for the distinguishing condition including the contraction coefficient as a parameter, based on the basic equations for free flow and the hydraulic jump. The equation is investigated using experimental data from two different gate types. The results show that the contraction coefficient varies with gate type and that this affects the distinguishing condition. The results also show that for a given upstream depth, tainter gates (radial gates) are less likely to become submerged than vertical gates due to larger contraction coefficients. The present study results are useful in the design and operation of sluice gates.     

Flow through Side Sluice Gate

The hydraulic characteristics of a side sluice gate were studied experimentally. It was found that the specific energy remains constant along the side sluice gate. The coefficient of discharge for the side sluice gate is related to the main channel Froude number and the ratio of upstream depth of flow to sluice gate opening for free flow. It also depends on an additional parameter: the ratio of tailwater depth to the gate opening for submerged flow. Suitable equations for discharge coefficient are obtained.     

Study of ionic currents across a model membrane channel using Brownian dynamics

Brownian dynamics simulations have been carried out to study ionic currents flowing across a model membrane channel under various conditions. The model channel we use has a cylindrical transmembrane segment that is joined to a catenary vestibule at each side. Two cylindrical reservoirs connected to the channel contain a fixed number of sodium and chloride ions. Under a driving force of 100 mV, the channel is virtually impermeable to sodium ions, owing to the repulsive dielectric force presented to ions by the vestibular wall. When two rings of dipoles, with their negative poles facing the pore lumen, are placed just above and below the constricted channel segment, sodium ions cross the channel. The conductance increases with increasing dipole strength and reaches its maximum rapidly; a further increase in dipole strength does not increase the channel conductance further. When only those ions that acquire a kinetic energy large enough to surmount a barrier are allowed to enter the narrow transmembrane segment, the channel conductance decreases monotonically with the barrier height. This barrier represents those interactions between an ion, water molecules, and the protein wall in the transmembrane segment that are not treated explicitly in the simulation. The conductance obtained from simulations closely matches that obtained from ACh channels when a step potential barrier of 2-3 kTr is placed at the channel neck. The current-voltage relationship obtained with symmetrical solutions is ohmic in the absence of a barrier. The current-voltage curve becomes nonlinear when the 3 kTr barrier is in place. With asymmetrical solutions, the relationship approximates the Goldman equation, with the reversal potential close to that predicted by the Nernst equation. The conductance first increases linearly with concentration and then begins to rise at a slower rate with higher ionic concentration. We discuss the implications of these findings for the transport of ions across the membrane and the structure of ion channels.     

Kramers' diffusion theory applied to gating kinetics of voltage-dependent ion channels

Kramers' diffusion theory of reaction rates in the condensed phase is considered as an alternative to the traditional discrete-state Markov (DSM) model in describing ion channel gating current kinetics. Diffusion theory can be expected to be particularly relevant in describing high-frequency (>100 kHz) events in channel activation. The generalized voltage sensor of a voltage-dependent ion channel is treated as a Brownian motion particle undergoing spatial diffusion along a one-dimensional energy landscape. Two classes of energy landscapes are considered. The first class contains large barriers, which give rise to gating currents with two distinct time scales: the usual low-frequency decay, which can modeled with a DSM scheme, and a high-frequency component arising from intrastate relaxation. Large depolarizations reduce potential barriers to such a degree that activation rates are diffusion limited, causing the two time scales to merge. Landscapes of the second class are either featureless or contain barriers that are small compared to kT; these are termed "drift landscapes." These landscapes require a larger friction coefficient to generate slow gating kinetics. The high-frequency component that appears with barrier models is not present in pure drift motion. The presence of a high-frequency component can be tested experimentally with large-bandwidth recordings of gating currents. Topics such as frequency domain analysis, spatial dependence of the friction coefficient, methods for determining the adequacy of a DSM model, and the development of physical models of gating are explored.     

X形浸入式水口对结晶器内钢水流动影响的数值模拟

应用粘性流体力学的基本原理,釆用专业流体力学软件FLUENT对160mmx160mm方坯连铸X 形浸入式水口对结晶器内钢水流动的影响进行数值模拟,验证了 X形浸入式水口浇注时,通过两块半椭圆形 导流板上、下平面与倒锥形圆筒内腔围成的螺旋形导流通道的导向作用,使钢水以涡流形式进入到结晶器,能 有效减轻钢水的冲击深度,有利于夹杂物、气泡聚集升浮和提高连铸效率。     

Full-Flowing Collection Conduits with Nonuniform Inflow

Collection conduits flowing full with nonuniform inflow (variable rate of increase in flow with distance along the conduit length) include well screens (vertical and directionally drilled); submerged effluent collectors; and certain types of inboard weir configurations for settling tanks. Certain subsurface drains used in environmental engineering applications and civil engineering more generally may be inadvertently designed for full-flowing conditions. Formulation of the problem for such collection conduits is presented in terms of the applicable differential equation, slope invariance, the frictionless solution for a general cross section, a uniform-inflow solution, and the difference formulation. The importance of checking inflow uniformity is discussed and exemplified. Dimensional analysis is then employed to demonstrate the relationship between variables, leading to a new generalized numerical solution. That solution is presented in a graphical form which provides further useful display of the relationships between variables and quantitative information for design and analysis. The detrimental effects of flowing-full conditions in subsurface drains is demonstrated, and it is noted that existing design methods may unintentionally cause such conditions to occur.     

Thermodynamic Framework for Analysis of Waste Containment Barrier Materials

In order to analyze the fate and estimate the transport rates of contaminants through a barrier system, textural parameters such as the specific surface, density, permeability, diffusion coefficient, and flow path tortuosity are usually measured or estimated. The magnitudes of transport parameters of barrier systems are expected to change in response to physicochemical reactions and other environmental stresses, the intensities of which may grow or wane over time. In essence, when discrete catastrophic events (for example, earthquakes) are discounted, the flaws that develop are macroscopic manifestations of microlevel processes. Processes such as crystallization and precipitation add solid material to pore spaces in barriers and can improve barrier performance. Conversely, processes that cause changes in state from solid to liquid (for example, material dissolution) degrade barriers through the creation of larger flow channels. An appreciation of the thermodynamics of contaminant/barrier interactions under various environmental (temperature, pressure, and moisture) conditions is a prerequisite for establishing the bounds for textural changes and estimating contaminant release rates from containment systems. Then, process kinetics can be used to estimate the rate at which such texture-controlling processes may occur. The alternative approach is to conduct numerous “test-and-see” factorial experiments of limited utility, in which one parameter is changed at a time. The latter approach consumes resources excessively, relative to an approach that involves the use of thermodynamics to minimize the number of tests. In this paper, long-term deterioration mechanisms are analyzed, and a framework for their assessment within the context of barrier system performance modeling is presented.     

School contact tracing for tuberculosis using two-step Mantoux testing

Using a 3-dimensional in vitro model, the stability of different types of osteosynthesis for the short sagittal osteotomy was tested. The following four groups of plate and screw configurations were evaluated: Group I: Fixation with miniplates using monocortical screws only, Group II: Fixation with miniplates, but with two of the screws engaging both fragments, Group III: Same as group II with an additional position screw, Group IV: Fixation with 3 position screws. The stability obtained with miniplate fixation using monocortical screws only (group I) was by a factor of 2.9 less than position screw fixation (group IV), which is considered to be an approved standard. In order to increase the stability of miniplate fixation, the screws in the area of overlapping bone should engage both fragments.     

Georadiological Barrier Gamma Attenuation Model for Waste Containment. II: Model Implementation

Herein, the Georadiological Barrier Gamma Attenuation Model that is developed in Part 1 of this paper, is utilized to estimate the attenuation of gamma (γ) rays by earthen barriers of various thicknesses and material composition. Activities of radioactive isotopes are calculated and coupled with an exponential absorption equation, to estimate γ exit intensities from these georad barriers. The results indicate that γ attenuation by georad barriers is more significantly affected by barrier thickness than by barrier density. A 33% increase in thickness from 15?to?20?cm produces a 50% reduction in emitted γ intensity, while a 33% increase in density from 1.5?to?2.0?g/cm3 produces a 19% reduction for a barrier comprising 45% sand, 25% clay, and 30% water (by weight). This model can be used to optimize barrier material mix composition, density, and thickness to increase γ attenuation in emergency response at existing radiologically contaminated sites and during response scenarios.     

Use of current-voltage diagrams in locating peak energy barriers in cell membranes

The current-voltage relations obtained by integrating the Nernst-Planck equations for a variety of energy profiles are obtained. A simple and approximate method for comparing these relations is described. The method is based on using a linearized transform of current-voltage relations for an Eyring single barrier model. A parameter, gamma, related to the location of the single barrier in the Eyring model, and to the shape of the barrier in other models, is readily obtained from the slopes of the linearized relations. It is then a simple matter to determine whether a given current-voltage relation allows discrimination between any particular energy profiles. The results show that the equivalent Eyring model does not always place the peak energy barrier in the same position as other models and that quite large errors in the assignment of position may be made if such a model is used. The results are also used to test the ability of some experimental current-voltage diagrams to discriminate between various energy profiles.     

矿热炉设计制造标准探讨

我国铁合金矿热炉设计与制造，至今未有统一的标准，相同容量（kVA）与相同产品的矿热炉参数结构差别较大，对其制作的质量评定，无统一标准。文章从矿热电炉设计原则、形式结构、质量评价与技术经济指标进行讨论，提出些个人看法、观点，以期达到认识的统一，确定基本的设计准则与质量评价，有利于铁合金行业矿热炉装备的发展与稳定。     

Cerebrospinal fluid proteins in the diagnosis of disorders of the blood-cerebrospinal fluid barrier in central nervous system diseases

BACKGROUND: Many neurological diseases are connected with the dysfunction of blood-CSF barrier. The quantitative determination of CSF proteins has already been used in the diagnosis of barrier impairments and inflammatory diseases of the central nervous system. PATIENTS: Serum and CSF, totaling 264 samples, were obtained from 15 controls and 117 patients with various diseases of the nervous system. Laurell's electroimmunoassay was used for estimation of albumin and IgG levels in serum and CSF. CSF-protein profile was evaluated according to Reiber's graph for the evaluation of the CSF-protein profile. RESULTS: The graph for the protein profile can be divided into 5 functionally different parts (1--normal range, 2, 3, 4--different types of barrier dysfunctions and 5--local humoral response in CNS without any barrier impairment). There was a good correlation of CSF-protein profiles and neurological diseases in our group of patients. CONCLUSIONS: According to our results, Reiber's graph was helpful for the diagnosis of blood-CSF-barrier dysfunctions. The graph has the following advantages: a) possibility of simultaneous assessment of the functional state of blood-CSF-barrier and the inflammatory response of the CNS, b)sensitivity for the determination of pathological local IgG-production in CNS and c) minimal number of protein assays necessary.     

Perforated Wall Breakwater with Internal Horizontal Plate

The hydrodynamic performance of a perforated wall breakwater with an internal horizontal plate is studied. It is suggested that a horizontally submerged plate be installed inside the wave chamber to enhance the stability of the structure. Based on the linear wave theory, the 2D problem is formulated to analyze the wave reflection with different porosity, physical dimensions, and wave conditions. The method of matched eigenfunction expansions is used to obtain the solution. Generally, the hydrodynamic performance of a wave chamber is similar with or without an internal horizontal plate. However, the minimum reflection occurs at some particular ratios of the length of the wave chamber to the wavelength, which are less than the corresponding ratios for a wave chamber without the plate, because the waves become shorter over the submerged plate. Thus, the size of the wave chamber can be reduced. It is also found that a moderate porosity is optimal to dissipate the wave energy. By investigating the wave-induced force and moment, such breakwaters with an internal horizontal plate can be designed and constructed with a higher degree of confidence and reliability.     

Effect of anode-cathode configuration on paresthesia coverage in spinal cord stimulation

OBJECTIVE: To provide a theoretical basis for the selection of the anode-cathode configuration in spinal cord stimulation for the management pain when one percutaneous epidural electrode or two electrodes in parallel are used. METHODS: A computer model of spinal cord stimulation at T8-T9 was used to calculate the dorsal column areas recruited in stimulation by various configurations used in clinical practice. RESULTS: Tripolar (or bipolar) stimulation by a single electrode, symmetrically placed over the dorsal columns, recruits the largest area and will give the widest paresthesia coverage. Stimulation by two symmetrically placed electrodes connected in parallel to a single channel pulse generator may give similar results, because of their generally smaller distance from the spinal cord, but a "summation effect" does not exist. A smaller dorsal column area is activated when two offset electrodes are used. An electrode placed laterally or transverse bipolar stimulation results in unilateral, usually segmentary, paresthesia. CONCLUSIONS: The relative positions of cathodes and anodes and their distance from the spinal cord are the major determinants of dorsal column/dorsal root activation and paresthesia distribution. The large interpatient variability of the intraspinal geometry is the main cause of differences in paresthesia coverage among patients having optimally placed electrode(s). Changes of paresthesia coverage over time are more probable when multiple electrodes are used.     

矿热炉电气参数的实时测量及对生产的指导作用

为了分析矿热炉生产中各项电气特性运行是否合理,本文应用美国施耐德公司生产的Power Logic2000电力参数线路监控仪-CM2250,对6.3 MVA矿热炉生产时的电气参数进行连续测量并记录,为合理调整矿热炉的运行参数,改善操作制度提供了理论依据.同时,它还对控制台上的仪表数据进行了校正.