Partial Flows Research Articles

Modeling of hydrocarbon film deposition suppression in tokamak diagnostic ports

Because of the requirement of eliminating carbon deposition on mirrors that facilitate optical methods of plasma diagnostics in thermonuclear synthesis devices, the experimental study has been carried out of gasodynamic conditions and the relationship between the partial flows of hydrogen and methane, which are supplied to the direct current glow discharge. The formation of hydrocarbon deposits would be completely suppressed under these conditions. The processes of methane conversion in the discharge into heavier volatile hydrocarbons have been analyzed by mass spectroscopy and conversion into polymer-like a-C:H films have been analyzing by weighing and electron probe microanalysis. The degree of methane conversion was continuously decreasing upon the dilution of methane with hydrogen. The deposition was suppressed completely when methane concentration in the laminar flow of the mixture was approximately 1 mol %. The process of deposition of a-C:H films changed into the process of film erosion when methane content in the mixture was below 0.5 mol %, the Knudsen number Kn ≈ 0.1, and the Reynolds number Re ≈ 2. In order to provide the removal of plasmolysis products from the surface of the mirror located in a special diagnostic port of ITER, the specified gasodynamic conditions created by the carrier gas (hydrogen or deuterium) should be ensured, with the component of the velocity vector being directed at an angle to the surface under protection.

Estimation of Origin-Destination Matrix with Tolling Data

Prior matrix and surveyed link volumes were, in most cases, employed to estimate origin-destination matrix. With the development of BOT and of congestion pricing, charged links become an important component of road network, due to the fact that the tolling data: volumes and travel time on pricing entry-exit are traffic information, both cost-free and accurate. In this paper, we put forward a bi-level programming model, taking account of data on charging entry-exit to estimate OD matrix based upon the traditional model. Meanwhile, a heuristic method -the simulated annealing approach - is utilized to solve the OD estimation problem. Results of examples indicate that the accuracy of estimation will be improved while adding the tolling data, and that it is feasible to calculate OD matrix by combining the volumes and travel time on entry-exit with partial common link flows. In this light, this way can be applied to enhance accuracy, and also to reduce the cost spent on surveying the link flows in common OD matrix estimation.

Membrane technology for the future treatment of paper mill effluents: chances and challenges of further system closure

The pressure on the European paper industry to further close its water circuits has increased significantly during the past decade. Since the technologies of the past can no longer meet the requirements of the future, new water treatment methods have become necessary. A constant rise in the interest in membrane technology expressed by the European paper industry confirms that in the future this method will evolve into a key technology for continued water savings. The publication provides an overview of current and future applications of membrane plants in the European paper industry. A range of technologies is briefly presented together with their advantages and drawbacks, and the economic potential of membrane use is discussed. Among other topics, the authors take a look at the utilization of membrane filtration for treating internal circulation water, partial flows containing coating colours, and biologically treated effluents. The technologies addressed include ultrafiltration, nanofiltration and membrane bioreactor technology. Possible recovery and treatment routes for the concentrates produced by the nanofiltration of biologically treated effluents are examined and evaluated.

Self-consistent liquid-to-gas mass transfer calculations

This work develops an alternative gas transfer calculation method to the two methods currently used in anaerobic digestion modelling. The current calculation methods are problematic because one is computationally stiff, while the other introduces an artificial overpressure. The new approach began by noting that the gas partial pressures are the same as the partial flows at the liquid/gas interface, and then used the self-consistency requirement to develop gas pressure equations which were used by a search algorithm. The new approach took about three iterations to achieve a flow precision better than 2x10(-7) mol h(-1) l(-1), and was self-consistent and stable even when working with eight gases.

Application of the least-squares finite element method on the simulations of 3D incompressible free surface flows

This paper presents the simulation of 3D free surface flows by the two-phase least-squares finite element method (LSFEM). It is believed that this is the first time the LSFEM be extended from a 2D model to a 3D one and applied to investigate the 3D free surface flow phenomena. The dynamic and kinematic boundary conditions of free surface are described in an Eulerian coordinate system. The governing 3D Navier-Stokes equations in association with the color function are solved by the element-by-element scheme. In this simulation, the volume of fluid (VOF) method and continuous stress force (CSF) models are applied for the determination of the interface between the two phases of liquid and gas. The free surface position at each time step is determined by the distribution of the color function. The formation of the 3D model is carefully examined; and the quantitative comparisons of the 3D numerical simulations with experimental measurements and previous 2D numerical results are verified in good agreement. For the partial dam-break flows, it is shown that the two-phase LSFEM can effectively simulate the 3D flows. The unsteady water surface profiles of dam-break flow moving over an obstacle and the liquid drop are also simulated in this study. A 3D two-phase LSFEM has been established and carefully justified by some benchmark free surface flows. The method will be useful for the actual application to the two-phase flows with two immiscible fluids, such as liquid-gas flow, and metallurgic flow.

Patient flows as a key driver of university hospital modernisation: Lessons for other transitional countries from the Serbian case

AbstractThis paper describes the planning and implementation of patient flows as a key driver of university hospital modernisation in four large tertiary-care institutions in the Republic of Serbia. The project, supported by EU funding, aims to support the interrelated processes of health service delivery changes and major infrastructure investment. Together, the four clinical centres host over 2 million outpatients, 220,000 inpatients and 120,000 operations each year. All four have complete or partial pavilion (standalone) structure (from ten to more than 30 buildings) and fragmented patient flows (eg interrupted patient flow due to limitations of infrastructure and poor service organisation). A main project goal is to centralise facilities and to separate patient flows into four major patient groups (outpatients, day-patients, emergency patients and inpatients) and patients for surgery/intensive care. This paper will provide insights into the challenges and successes of a major hospital infrastructure i...

Simulation of molecular beam deposition during evaporation from the crucible

In the frame of molecular mass-transfer model during evaporation from horizontal molted metal surface and wall surface of a crucible vapor source, boundary conditions are analytically defined and analytical expression for distributions of partial vapor flows in the space of their propagation together with deposited films parameters are obtained taking into account effects of constructive crucible parameters and type of substrate moving

Whole effluent assessment of industrial wastewater for determination of BAT compliance. Part 2: metal surface treatment industry

Toxicity testing has become a suitable tool for wastewater evaluation included in several reference documents on best available techniques of the Integrated Pollution Prevention and Control (IPPC) Directive. The IPPC Directive requires that for direct dischargers as well as for indirect dischargers, the same best available techniques should be applied. Within the study, the whole effluent assessment approach of OSPAR has been applied for determining persistent toxicity of indirectly discharged wastewater from the metal surface treatment industry. Twenty wastewater samples from the printed circuit board and electroplating industries which indirectly discharged their wastewater to municipal wastewater treatment plants (WWTP) have been considered in the study. In all factories, the wastewater partial flows were separated in collecting tanks and physicochemically treated in-house. For assessing the behaviour of the wastewater samples in WWTPs, all samples were biologically pretreated for 7 days in the Zahn-Wellens test before ecotoxicity testing. Thus, persistent toxicity could be discriminated from non-persistent toxicity caused, e.g. by ammonium or readily biodegradable compounds. The fish egg test with Danio rerio, the Daphnia magna acute toxicity test, the algae test with Desmodesmus subspicatus, the Vibrio fischeri assay and the plant growth test with Lemna minor have been applied. All tests have been carried out according to well-established DIN or ISO standards and the lowest ineffective dilution (LID) concept. Additionally, genotoxicity was tested in the umu assay. The potential bioaccumulating substances (PBS) were determined by solid-phase micro-extraction and referred to the reference compound 2,3-dimethylnaphthalene. The chemical oxygen demand (COD) and total organic carbon (TOC) values of the effluents were in the range of 30-2,850 mg L(-1) (COD) and 2-614 mg L(-1) (TOC). With respect to the metal concentrations, all samples were not heavily polluted. The maximum conductivity of the samples was 43,700 microS cm(-1) and indicates that salts might contribute to the overall toxicity. Half of the wastewater samples proved to be biologically well treatable in the Zahn-Wellens test with COD elimination above 80%, whilst the others were insufficiently biodegraded (COD elimination 28-74%). After the pretreatment in the Zahn-Wellens test, wastewater samples from four (out of ten) companies were extremely ecotoxic especially to algae (maximum LID(A) = 16,384). Three wastewater samples were genotoxic in the umu test. Applying the rules for salt correction of test results as allowed in the German Wastewater Ordinance, only a small part of toxicity could be attributed to salts. Considering the PBS, wastewater from the metal surface treatment industry exhibited very low levels of PBS. In one factory, the origin of ecotoxicity has been attributed to the organosulphide dimethyldithiocarbamate (DMDTC) used as a water treatment chemical for metal precipitation. The assumption based on rough calculation of input of the organosulphide into the wastewater was confirmed in practice by testing its ecotoxicity at the corresponding dilution ratio after pretreatment in the Zahn-Wellens test. Whilst the COD elimination of DMDTC was only 32% in 7 days, the pretreated sample exhibited a high ecotoxicity to algae (LID(A) = 1,536) and luminescent bacteria (LID(lb) = 256). Comparative data from wastewater surveillance by authorities (data from 1993 to 2007) confirmed the range of ecotoxicity observed in the study. Whilst wastewater from the metal surface treatment industry usually did not exhibit ecotoxicity (median LID 1-2), the maximum LID values reported for the algae, daphnia and luminescent bacteria tests were very high (LID(A) up to 3,072, LID(D) up to 512 and LID(lb) up to 2,048). DMDTC was found to be one important source of ecotoxicity in galvanic wastewater. DMDTC is added in surplus, and according to the supplier, the amount in excess should be detoxified with ferric chloride or iron sulphate. The operator of one electroplating company had not envisaged a separate treatment of the organosulphide wastewater but was assuming that excess organosulphide would be bound by other heavy metals in the sewer. DMDTC degrades via hydrolysis to carbon disulfide (which is also toxic to animals and aquatic organisms), carbonyl sulphide, hydrogen sulphide and dimethylamine, but forms complexes with metals which stabilise the compound with respect to transformation. Although no impact on the WWTP is expected, the question arises whether the organosulphide is completely degraded during the passage of the WWTP. The results show that the organic load of wastewater from the electroplating industry has been underestimated by focussing on inorganic parameters such heavy metals, sulphide, cyanide, etc. Bioassays are a suitable tool for assessing the ecotoxicological relevance of these complex organic mixtures. The proof of biodegradability of the organic load (and its toxicity) can be provided by the Zahn-Wellens test. The environmental safety of water treatment chemicals should be better considered. The combination of the Zahn-Wellens test followed by the performance of ecotoxicity tests turned out to be a cost-efficient suitable instrument for the evaluation of indirect dischargers and considers the requirements of the IPPC Directive.

Friction Drag Reduction of External Flows with Bubble and Gas Injection

The lubrication of external liquid flow with a bubbly mixture or gas layer has been the goal of engineers for many years, and this article presents the underlying principles and recent advances of this technology. It reviews the use of partial and supercavities for drag reduction of axisymmetric objects moving within a liquid. Partial cavity flows can also be used to reduce the friction drag on the nominally two-dimensional portions of a horizontal surface, and the basic flow features of two-dimensional cavities are presented. Injection of gas can lead to the creation of a bubbly mixture near the flow surface that can significantly modify the flow within the turbulent boundary layer, and there have been significant advances in the understanding of the underlying physical process of drag reduction. Moreover, with sufficient gas flux, the bubbles flowing beneath a solid surface can coalesce to form a thin drag-reducing air layer. The current applications of these techniques to underwater vehicles and surface ships are discussed.

Two-dimensional distributed feedback lasers with excitation of TE waves in the active medium

Two-dimensional Bragg resonators with the coupling of TE- and TM-polarised waves are proposed. The selective properties of such resonators are analysed. Within the semiclassical approach, the nonlinear dynamics of laser radiation with a two-dimensional (in the xy plane) distributed feedback is studied, at which TE-polarised waves, propagating in the ±z directions, are amplified in the active medium (in particular, based on quantum wells). The latter, on a two-dimensional Bragg structure, are scattered into TM-polarised waves propagating in the ±x directions. These partial wave flows do not interact with the active medium but provide the spatial radiation synchronisation. The conditions of the solution self-similarity are obtained with increasing the dimensions of the active medium and the corresponding increase in the integral output power. It is shown that when an additional end mirror is mounted, almost unidirectional radiation coupling can be realised.

Effects of partial and total methane flows on the yield and structural characteristics of MWCNTs produced by CVD

Multi-walled carbon nanotubes (MWCNTs) were produced in a chemical vapor deposition (CVD) process employing methane and argon as hydrocarbon and carrier gas over supported sol–gel Co–Mo/MgO catalysts. A detailed study about the influence of the gas flow of both hydrocarbon and carrier gas on carbon yield, morphology, structure and graphitization degree is presented. Methane partial pressure, methane total flow rate, as well as the flow ratios of methane to argon and methane to hydrogen (reducing gas) were the parameters systematically varied. The results reveal that high MWCNT yields in the produced materials are strongly related to the methane partial pressure and the methane total flow, while a high degree of graphitization is more closely linked to the use of argon gas as inert atmosphere.

Green Pump Development Based on the Analysis of Unsteady Flow

Centrifugal pump is a kind of important industrial installation for fluid delivery. The research on the unsteady flow in centrifugal pump is very meaningful to reducing vibration. Particle image velocimetry (PIV) system and test pump designed for PIV measurement were introduced. The experimental scheme and the methods of numerical simulation were discussed. PIV technique was used to measure the unsteady velocity field near the volute tongue under the mode of external synchronization. The unsteady pressure field was simulated by using Sliding Mesh (SM) model provided by Fluent. The results show that the velocity and pressure fluctuate periodically with the rotation of impeller. Partial fluid flows back to the impeller passage and the velocity in the inlet of diffusion tube decreases significantly due to shunt effect of the volute tongue. On the section VIII, the magnitude and fluctuation range of velocity show a decreasing trend in radial direction. The fluctuation of circumferential velocity is related to the position of high-speed flow in impeller passage, and the fluctuation of radial velocity is influenced by blade interference and Coriolis force. The static pressure increases and the dynamic pressure decreases in the radial direction of volute. The velocity and the pressure on the section VIII and the outlet total pressure fluctuate intensively when the blade tail end passes the section VIII and the volute tongue. The vibration of pump can be reduced by increasing the volute tongue mounting angle and decreasing the blade outlet mounting angle properly.

A model of flight request collection and processing in the flight scheduling problem

A method of analysis of service systems with relative priority, where physical restrictions of request queue generating process are used to derive design formulas is considered. This approach allows one to formalize the interference of partial input flows with description of their dynamic equilibrium and, consequently, to avoid branching of a transition and system state graph by reducing the system model to an ordinary composition of Markov chains for each component of the complete request flow. An example of analysis of priority collection and processing of requests for airspace use in a centralized flight scheduling service established for the united system of Russian air traffic control is given.

Informational Valences of the Cash Flow Statement - Methodological and Interpretative Approaches

In latest decades, mainly with the advance of globalization and business expansion at worldwide level, with the diversification of the possible risks and with the uncertainty characterizing the business world, the demands on the type of information required by the ever-increasing competitive business milieu attained higher and higher values. The present investigation provides arguments in favor of the informational valences of the treasury flows in the process of an entity's financial communication, in reducing the informational asymmetry among the actors intervening on the capital market. To attain such an objective, a comparative study on the two methods of determination of the net treasury flows, the direct and the indirect methods, respectively, is first elaborated, permitting an estimation on which of them is capable of best evidencing the connection between the entity's aggregate strategy and its financial strategy. There follows the analysis of the cash-flow statement, through methodological and interpretative approaches of the partial treasury flows and through a system of indices expressed as ratios, which explains the movements influencing the monetary balance.

Pure spin currents induced by spin-dependent scattering processes in SiGe quantum well structures

We show that spin-dependent electron-phonon interaction in the energy relaxation of a two-dimensional electron gas results in equal and oppositely directed currents in the spin-up and spin-down subbands yielding a pure spin current. In our experiments on SiGe heterostructures the pure spin current is converted into an electric current applying a magnetic field that lifts the cancellation of the two partial charge flows. A microscopic theory of this effect, taking account of the asymmetry of the relaxation process, is developed being in a good agreement with the experimental data.

Free multiflows in bidirected and skew-symmetric graphs

A graph (digraph) G = ( V , E ) with a set T ⊆ V of terminals is called inner Eulerian if each nonterminal node v has even degree (resp. the numbers of edges entering and leaving v are equal). Cherkassky and Lovász, independently, showed that the maximum number of pairwise edge-disjoint T-paths in an inner Eulerian graph G is equal to 1 2 ∑ s ∈ T λ ( s ) , where λ ( s ) is the minimum number of edges whose removal disconnects s and T - { s } . A similar relation for inner Eulerian digraphs was established by Lomonosov. Considering undirected and directed networks with “inner Eulerian” edge capacities, Ibaraki, Karzanov, and Nagamochi showed that the problem of finding a maximum integer multiflow (where partial flows connect arbitrary pairs of distinct terminals) is reduced to O ( log T ) maximum flow computations and to a number of flow decompositions. In this paper we extend the above max–min relation to inner Eulerian bidirected graphs and inner Eulerian skew-symmetric graphs and develop an algorithm of complexity O ( VE log T log ( 2 + V 2 / E ) ) for the corresponding capacitated cases. In particular, this improves the best known bound for digraphs. Our algorithm uses a fast procedure for decomposing a flow with O ( 1 ) sources and sinks in a digraph into the sum of one-source-one-sink flows.

Series Solution for Unsteady Boundary-Layer Flows Due toImpulsively Stretching Plate

The third-order nonlinear partial differential equation modelling theunsteady boundary-layer flows caused by an impulsively stretchingflat plate is solved by using the Adomian decomposition method (ADM).The ADM yields analytic solution in the form of a rapidly convergentinfinite series with easily computable terms. The series solutionusing the ADM for the unsteady flows is presented for the first time.

Design and Manufacture of a Superconducting Fault Current Limiter With Bypass Reactor by Employing Two Different Types of HTS Wires

A resistive superconducting fault current limiter (SFCL) using Bi2223 wire and YBCO coated conductor has been developed. The SFCL has two coils; one is a bifilarly wound coil wound using coated conductor, and the other is typical inductive coil using Bi2223 wire. The bifilar coil plays the role of switching when a fault occurs, while it has a very small impedance in the normal operation. On the other hand, the inductive coil using Bi2223 wire has a very small resistance but a large inductance. The two coils were connected in parallel. Current flows mainly through the bifilar coil during normal operation. A partial fault current flows through Bi2223 coil because the resistance of the coated conductor bifilar coil rises. Two types of FCL were manufactured and tested; a conventional bifilar one, which has only one coil using a coated conductor, and the proposed one, which has two coils. The proposed one has a faster recovery than the conventional one.

Production integrated treatment of textile wastewater by closing raw material cycles

A method for the in-house treatment of partial wastewater flows and the recycling of treated process water into the textile finishing process was developed in order to recycle effluents from textile finishing industry and feed them back into the production process. The method is based on a two-stage biological anaerobic-aerobic process to split colouring wastewater agents and to degrade organic substances contained in the water as well as a chemical stage to remove the remaining color of the water with the help of ozone. In the framework of a research and development project a demonstration plant for a treatment capacity of 1440 m3 per working day was installed and started in a textile finishing company. At the plant, a wastewater flow and a recycling flow are treated separately in two different treatment lanes. Approximately 40% of the total wastewater flows, i.e. 576 m3/d are treated in the wastewater lane, and a maximum of 60% of total wastewater, i.e. 864 m3/d are treated in the recycling lane. Thanks to the preliminary treatment of wastewater flows, which are discharged into the municipal sewage works, a reduction of average COD levels in the sewage works effluents could be achieved.

The concept of "buffering" in systems and control theory: from metaphor to math.

The paradigm of "buffering" is used increasingly for the description of diverse "systemic" phenomena encountered in evolutionary genetics, ecology, integrative physiology, and other areas. However, in this new context, the paradigm has not yet matured into a truly quantitative concept inasmuch as it lacks a corresponding quantitative measure of "systems-level buffering strength". Here, I develop such measures on the basis of a formal and general approach to the quantitation of buffering action. "Systems-level buffering" is shown to be synonymous with "disturbance rejection" in feedback-control systems, and can be quantitated by means of dimensionless proportions between partial flows in two-partitioned systems. The units allow either the time-independent, "static" buffering properties or the time-dependent, "dynamic" ones to be measured. Analogous to this "resistance to change", one can define and measure the "conductance to change"; this quantity corresponds to "set-point tracking" in feedback-control systems. Together, these units provide a systematic framework for the quantitation of buffering action in systems biology, and reveal the common principle behind systems-level buffering, classical acid-base buffering, and multiple other manifestations of buffering.