Two-stream System Research Articles

Modelling a two-stream emergency department segregation and admission system from COVID-19 early rapid antigen testing: A pilot study.

Many factors influence patient flow through an ED, including streaming, treatment spaces and staff resources. This pilot study explored and compared real time patient flow using a single-stream system versus varying configurations of possible two-stream systems using computer simulation. Simulation modelling was used to assess the delay in treatment of a rapid-antigen-tested-based, two-stream model for patient flow through ED during the peak phase of the COVID pandemic. Modelling two-stream configuration for all patients (minimum time to be seen for both COVID-positive and COVID-negative patients) showed that in the case study ED, a two-stream system and linked changes in bed configuration for managing the risks of infection can impact delays in treatment. Data-driven modelling within specific clinical settings can inform the (in)efficiency of patient flow processes and help clinicians and managers make evidence-based decisions about patient transition through EDs. This can assist with reconfiguration of ED patient streaming particularly during periods of unique need, such as the recent COVID-19 pandemic.

Subcritical recuperative air-to-water heat pump with zeotropic mixtures: Comparative and performance assessment

For high temperature heating, traditional single-stage air-source heat pumps suffer severe challenges in low efficiency and poor operating conditions. Heat recuperation is a simple and effective method to expand the temperature lift. In this paper, two kinds of recuperative air-to-water heat pump (RAWHP) systems were investigated for heating water from 15 °C to 90 °C at an ambient temperature of 15 °C. The energy, exergy, and economy models were established to assess the performance of RAWHP systems and compare with that of transcritical CO2 heat pump (TCHP) system in detail. The results show that the three-stream RAWHP system is superior to the two-stream RAWHP system from the perspective of energy and exergetic performance. For the three-stream RAWHP system, the highest COP of 4.08 and exergy efficiency of 45.4% were obtained by propylene/n-hexane with the optimal mole fractions of 0.9/0.1. In this case, the overall temperature matching indicator is 2.87, indicating a smaller heat transfer irreversible loss. Compared with the TCHP system, RAWHP systems have more advantages in higher COP and lower payback period at the ambient temperature ranges from −25 °C to 25 °C. The three-stream RAWHP system by using propylene/n-hexane (0.9/0.1) is recommended due to its outstanding energetic and economic performance.

Investigation of mixing characteristics of coflow rectangular nozzle of aspect ratio 2 and 3

PurposeThe purpose of this study is to understand experimentally the mixing characteristics of a two-stream exhaust system with a supersonic Mach 1.5 primary jet that exits the rectangular C-D nozzle surrounded by a sonic secondary jet from a convergent rectangular nozzle by varying the aspect ratio (AR = 2 and 3) similar to those that can be available for future high-speed commercial aircraft.Design/methodology/approachThis paper focuses on the experimental results of effects of AR at various expansion levels of jets issued/delivered from a central rectangular convergent-divergent nozzle of AR 2 and 3 surrounded by a coflow from a convergent rectangular sonic nozzle. The lip thickness of the primary nozzle is 2.2 mm. various nozzle pressure ratios (NPRs) ranging from 2, 3, 3.69 and 4 were chosen for pressure measurements.FindingsFor all the NPRs, AR 3 had a shorter core than AR 2. Also, AR 3 was found to decay faster in the transition and fully developed zones. The lateral plots show that the AR has an influence on the jet spread.Originality/valueThe structure of waves existing in the potential core of the rectangular coflow jet along with the major and minor axis planes was visualized by the shadowgraph technique.

Numerical Scheme for Kinetic Transport Equation with Internal State

We investigate the numerical discretization of a two-stream kinetic system with an internal state, such system has been introduced to model the motion of cells by chemotaxis. This internal state models the intracellular methylation level. It adds a variable in the mathematical model, which makes it more challenging to simulate numerically. Moreover, it has been shown that the macroscopic or mesoscopic quantities computed from this system converge to the Keller-Segel system at diffusive scaling or to the velocity-jump kinetic system for chemotaxis at hyperbolic scaling. Then we pay attention to propose numerical schemes uniformly accurate with respect to the scaling parameter. We show that these schemes converge to some limiting schemes which are consistent with the limiting macroscopic or kinetic system. This study is illustrated with some numerical simulations and comparisons with Monte Carlo simulations.

The English/Urdu-Medium Divide in Pakistan: Consequences for Learner Identity and Future Life Chances

Both Urdu, the national language of Pakistan, and English the official language are widely used for spoken and written communication in different contexts in Pakistan. In education; however, a linguistic divide is evident in the two-stream system of education - mainly referred to as Urdu medium and English medium - according to the dominant language of instruction in an institutional setting. Urdu medium schools are normally the state schools providing free education to the poorer communities while the English medium schools are private fee-paying schools for the economically well-off sections of society. This disparity in the educational system has loaded the labels English medium and Urdu medium with a range of meanings that constitute self and other’s perceptions of identity, in addition to signaling linguistic capital, particularly in terms of proficiency in English. This paper reports findings of a small-scale qualitative study undertaken to understand how students at a higher education public-sector institution in Pakistan experience and construct their own and others’ identities in relation to their previous and current educational and social experiences of language learning and use. Insights gained from this study further our understanding of how linguistic inequalities can be sanctioned by the state’s language policy and related practices.

Analytical Predictions of Field and Plasma Dynamics during Nonlinear Weibel-Mediated Flow Collisions.

The formation of collisionless shocks mediated by the ion Weibel instability is addressed theoretically and numerically in the nonrelativistic limit. First, the model developed in C. Ruyer etal., Phys. Plasmas 22, 032102 (2015) for the weakly nonlinear ion Weibel instability in a symmetric two-stream system is shown to be consistent with recent experimental and simulation results. Large-scale kinetic simulations are then performed to clarify the spatiotemporal evolution of the magnetic-field and plasma properties in the subsequent strongly nonlinear phase leading to shock formation. A simple analytical model is proposed which captures the simulation results up to a point close to ion isotropization. Electron screening effects are found important in the instability dynamics, so that numerical simulations using a nonphysical electron mass should be considered with caution.

Complete Plasmon Spectrum of Two-stream System

The complete spectrum of plasmons of the two interpenetrating plasma streams is found in a closed analytic form. The orientation of the wave vector with respect to the stream direction is arbitrary and the plasmas, which are assumed to be collisionless and spatially homogeneous, can be nonrelativistic, relativistic or even ultrarelativistic. Our results apply to the electromagnetic plasma of electrons and passive ions and to the quark-gluon plasma governed by QCD.

Region-Based Artificial Visual Attention in Space and Time

Mobile robots have to deal with an enormous amount of visual data containing static and dynamic stimuli. Depending on the task, only small portions of a scene are relevant. Artificial attention systems filter information at early stages. Among the various methods proposed to implement such systems, the region-based approach has proven to be robust and especially suited for integrating top-down influences. This concept was recently transferred to the spatiotemporal domain to obtain motion saliency. A full-featured integration of the spatial and spatiotemporal systems is presented here. We propose a biologically inspired two-stream system, which allows to use different spatial and temporal resolutions and to pick off spatiotemporal saliency at early stages. We compare the output to classic models and demonstrate the flexibility of the integrated approach in different experiments. These include online processing of continuous input, a task similar to thumbnail extraction and a top-down task of selecting specific moving and non-moving objects.

Dynamical stability of infinite homogeneous self-gravitating systems and plasmas: application of the Nyquist method

We complete classical investigations concerning the dynamical stability of an infinite homogeneous gaseous medium described by the Euler-Poisson system or an infinite homogeneous stellar system described by the Vlasov-Poisson system (Jeans problem). To determine the stability of an infinite homogeneous stellar system with respect to a perturbation of wavenumber k, we apply the Nyquist method. We first consider the case of single-humped distributions and show that, for infinite homogeneous systems, the onset of instability is the same in a stellar system and in the corresponding barotropic gas, contrary to the case of inhomogeneous systems. We show that this result is true for any symmetric single-humped velocity distribution, not only for the Maxwellian. If we specialize on isothermal and polytropic distributions, analytical expressions for the growth rate, damping rate and pulsation period of the perturbation can be given. Then, we consider the Vlasov stability of symmetric and asymmetric double-humped distributions (two-stream stellar systems) and determine the stability diagrams depending on the degree of asymmetry. We compare these results with the Euler stability of two self-gravitating gaseous streams. Finally, we determine the corresponding stability diagrams in the case of plasmas and compare the results with self-gravitating systems.

Cell separation and transportation between two miscible fluid streams using ultrasound.

This paper presents a two-stream microfluidic system for transporting cells or micro-sized particles from one fluid stream to another by acoustophoresis. The two fluid streams, one being the original suspension and the other being the destination fluid, flow parallel to each other in a microchannel. Using a half-wave acoustic standing wave across the channel width, cells or particles with positive acoustic contrast factors are moved to the destination fluid where the pressure nodal line lies. By controlling the relative flow rate of the two fluid streams, the pressure nodal line can be maintained at a specific offset from the fluid interface within the destination fluid. Using this transportation method, particles or cells of different sizes and mechanical properties can be separated. The cells experiencing a larger acoustic radiation force are separated and transported from the original suspension to the destination fluid stream. The other particles or cells experiencing a smaller acoustic radiation force continue flowing in the original solution. Experiments were conducted to demonstrate the effective separation of polystyrene microbeads of different sizes (3 μm and 10 μm) and waterborne parasites (Giardia lamblia and Cryptosporidium parvum). Diffusion occurs between the two miscible fluids, but it was found to have little effects on the transport and separation process, even when the two fluids have different density and speed of sound.

Parton Energy Loss in Two-Stream Plasma System

The energy loss of a fast parton scattering elastically in a weakly coupled quark-gluon plasma is formulated as an initial value problem. The approach is designed to study an unstable plasma, but it also reproduces the well known result of energy loss in an equilibrium plasma. A two-stream system, which is unstable due to longitudinal chromoelectric modes, is discussed here some detail. In particular, a strong time and directional dependence of the energy loss is demonstrated.

Liquidity-Saving Mechanisms and Bank Behaviour

This paper investigates the effect of liquidity-saving mechanisms (LSMs) in interbank payment systems. We model a stylised two-stream payment system where banks choose (a) how much liquidity to post and (b) which payments to route into each of two ‘streams’: the RTGS stream, and an LSM stream. Looking at equilibrium choices we find that, when liquidity is expensive, the two-stream system is more efficient than the vanilla RTGS system without an LSM. This is because the LSM achieves better coordination of payments, without introducing settlement risk. However, the two-stream system still only achieves a second-best in terms of efficiency: in many cases, a central planner could further decrease system-wide costs by imposing higher liquidity holdings, and without using the LSM at all. Hence, the appeal of the LSM resides in its ability to ease (but not completely solve) strategic inefficiencies stemming from externalities and free-riding. Second, ‘bad’ equilibria too are theoretically possible in the two-stream system. In these equilibria banks post large amounts of liquidity and at the same time overuse the LSM. The existence of such equilibria suggests that some co-ordination device may be needed to reap the full benefits of an LSM. In all cases, these results are valid for this particular model of an RTGS payment system and the particular LSM.

Power Control Techniques for Two-Stream MIMO System With Maximum Likelihood Receiver

In this letter, simple power control techniques are proposed to minimize error probability of a two-stream multiple-input multiple-output (MIMO) system with two transmit antennas and a maximum likelihood (ML) receiver, which is known as an optimal receiver but has a high computational complexity problem. The proposed techniques using Euclidean distances of a few error vectors have the advantages of exactly same error performance and very low computational complexity, compared with an optimal power control technique.

Quasilinear transport approach to equilibration of quark-gluon plasmas

We derive the transport equations of quark-gluon plasma in the quasi-linear approximation. The equations are either of the Balescu-Lenard or Fokker-Planck form. The plasma's dynamics is assumed to be governed by longitudinal chromoelectric fields. The isotropic plasma, which is stable, and the two-stream system, which is unstable, are considered in detail. A process of equilibration is briefly discussed in both cases. The peaks of the two-stream distribution are shown to rapidly dissolve in time.

Chromohydrodynamic approach to the unstable quark-gluon plasma

We derive hydrodynamic-like equations that are applicable to short-time-scale color phenomena in the quark-gluon plasma. The equations are solved in the linear response approximation, and the gluon polarization tensor is derived. As an application, we study the collective modes in a two-stream system and find plasma instabilities when the fluid velocity is larger than the speed of sound in the plasma. The chromohydrodynamic approach, discussed here in detail, should be considered as simpler over other approaches and well-designed for numerical studies of the dynamics of an unstable quark-gluon plasma.

Incoherent Effects of Electron Clouds in Proton Storage Rings

Electron clouds in the beam pipe of high-energy proton or positron storage rings can give rise to significant incoherent emittance growth, at densities far below the coherent-instability threshold. We identify two responsible mechanisms: namely, (1) a beam particle periodically crosses a resonance and (2) a beam particle periodically crosses a region of the bunch where its motion is linearly unstable. Formation of halo or beam-core blow up, respectively, are the result. Key ingredients for both processes are synchrotron motion and electron-induced tune shift. The mechanisms considered provide a possible explanation for reduced beam lifetime and emittance growth observed at several operating accelerators. Similar phenomena are likely to occur in other two-stream systems.

Combined phenomena of beam-beam and beam-electron cloud interactionsin circulare+e−colliders

An electron cloud causes various effects in high intensity positron storage rings. The positron beam and the electron cloud can be considered a typical two-stream system with a certain plasma frequency. Beam-beam interaction is another important effect for high luminosity circular colliders. Colliding two beams can be considered as a two-stream system with another plasma frequency. We study the combined phenomena of the beam-electron cloud and beam-beam interactions from a viewpoint of two complex two-stream effects with two plasma frequencies.

Quasiquarks in two stream system

We study the collective quark excitations in an extremely anisotropic system of two interpenetrating streams of the quark-gluon plasma. In contrast with the gluon modes, all quark ones appear to be stable in such a system. Even more, the quark modes in the two-stream system are very similar to those in the isotropic plasma.

Wet–dry composting of organic municipal solid waste: current status in Canada

Source separation of municipal solid waste into wet and dry streams is proving to be an attractive alternative in dealing with solid waste, and in achieving provincial and national waste diversion objectives. The system provides important flexibility in the number of waste streams, collection methods, collection frequency, and waste processing. In the past few years, experience has been obtained with two-, three-, and four-stream source separation and collection, composting of the organic waste fraction, and recycling of the valuable dry waste. The systems used in Guelph, Ontario, Lunenburg, Nova Scotia, and Caledon, Ontario, are presented. Public interest and participation has been high, especially when a two-stream, mandatory system is used. Thus, the City of Guelph has reported a 98% participation rate in its two-stream system which means that the public accepted the two-stream approach. Experience has shown that, as the number of streams increase, there is a greater chance of putting waste in the wrong stream. There is a strong demand for compost at a bulk price of about $30/ t FOB at the plant. The processing cost of the three plants varied from $50/t to $80/t of waste received without allowing for credits derived from extended landfill life or reduction in environmental impact.Key words: municipal solid waste, organic, source-separation, composting.

Mode interaction in two-stream systems of hydrodynamic type

The nonlinear dynamics of nonequilibrium two-stream hydrodynamic systems is described within the framework of Hamiltonian formalism. A procedure is proposed for diagonalization of the quadratic part of the Hamiltonian based on diagonalization of the dynamic equations by going over to normal variables with subsequent construction of the Hamiltonian as a motion integral. Matrix mode interaction elements are found.