Number Of Parallel Channels Research Articles

Quantitative Analysis of Acquisition Speed of High-Precision FLIM Technologies via Simulation and Modeling

In practical applications such as cancer diagnosis and industrial detection, there is a critical demand for fast fluorescence lifetime imaging (Fast-FLIM). The Fast-FLIM systems suitable for complex environments are typically achieved by enhancing the hardware performance of time-correlated single-photon counting (TCSPC), with an acquisition speed of about a few frames per second (fps). However, due to the limitation of single-photon acquisition, the imaging speed is still far from the demand of practical application. The synchroscan streak camera (SC) maps signals from the temporal dimension to the spatial dimension, effectively overcoming the long acquisition time caused by single-photon acquisition. This paper constructs a method to calculate the acquisition time for the TCSPC-FLIM and SC-FLIM systems, and it quantitatively compares the speed. The research demonstrates that the main factors limiting the acquisition speed of the FLIM systems are the photon emission rate, the photon counting rate, the required SNR, the dwell time, and the number of parallel channels. In high-quality and large-scale lifetime imaging, the acquisition speed of the SC-FLIM is at least 104 times faster than that of the TCSPC-FLIM. Therefore, the synchroscan streak camera has more significant potential to promote Fast-FLIM.

Density wave instability analysis in a parallel channel natural circulation loop of supercritical pressure fluid

To analyse the steady state behaviour and dynamic density wave instabilities (DWIs) of super-critical pressure fluid (SCF) inside a natural circulation loop (NCL) for a heated section with parallel channels, a numerical thermal-hydraulic (TH) model is developed. The capability of the TH model to simulate the above mentioned aspects for a two channel heated section is validated with the existing numerical results and experimental data points. Steady state analysis is performed mainly to find the loop mass flow rate at different operating conditions. It is also aimed to correlate the loop mass flow rate with the driving head, i.e., with the difference in pressure drops due to gravity and friction. Next, the transient model is integrated with that of the steady state to analyse DWI. The model accounts for compressible flow dynamics of SCF and can deal with any number of parallel channels in the heated section while analysing DWIs. With the transient simulations, it is aimed to bifurcate the operating regime into stable and unstable regions, and find the marginal stability boundary (MSB). Extensive simulations are, next, performed to determine the effect of different parameters on the MSB and the findings are reported accordingly.

Numerical Optimization of a Microchannel Geometry for Nanofluid Flow and Heat Dissipation Assessment

In this study, a numerical approach was carried out to analyze the effects of different geometries of microchannel heat sinks on the forced convective heat transfer in single-phase flow. The simulations were performed using the commercially available software COMSOLMultiphysics 5.6® (Burlington, MA, USA) and its results were compared with those obtained from experimental tests performed in microchannel heat sinks of polydimethylsiloxane (PDMS). Distilled water was used as the working fluid under the laminar fluid flow regime, with a maximum Reynolds number of 293. Three sets of geometries were investigated: rectangular, triangular and circular. The different configurations were characterized based on the flow orientation, type of collector and number of parallel channels. The main results show that the rectangular shaped collector was the one that led to a greater uniformity in the distribution of the heat transfer in the microchannels. Similar results were also obtained for the circular shape. For the triangular geometry, however, a disturbance in the jet impingement was observed, leading to the least uniformity. The increase in the number of channels also enhanced the uniformity of the flow distribution and, consequently, improved the heat transfer performance, which must be considered to optimize new microchannel heat sink designs. The achieved optimized design for a heat sink, with microchannels for nanofluid flow and a higher heat dissipation rate, comprised a rectangular collector with eight microchannels and vertical placement of the inlet and outlet.

Investigation on pressure fluctuation during parallel channel switching in fire-fighting

Many large-flow fires need sustained and stable water supplies, which are often challenging because of the complex fire ground. To analyze the causes and influencing factors of pressure fluctuation in the process of switching water sources, an experimental setup and a simulation model were established. The basic hydraulics principle is that pressure drop occurs during the switching between two channels. The pressure drop magnitude in the main pipe was studied for various resistance values of the main pipe, switching time of the control valve in the channel, the number of parallel channels, and the diameter of the clustered pipe. The results show that three key parameters affect the magnitude of the pressure drop: a longer switching time, less pipe resistance, and more parallel channels can minimize the pressure drop magnitude of the mine pipe. This study provides fire equipment designer with information about the influence of different variables on the pressure drop magnitude of the main pipe and basic design criteria to minimize these effects. Meanwhile, a simple scheme is proposed to minimize the large pressure fluctuation, and the pressure fluctuation can be decreased and even eliminated to some extent.

Constructive Bounds on the Capacity of Parallel Asynchronous Skew-Free Channels With Glitches

Transmission across a bus modelled as a parallel asynchronous communication channel is subject to fault injection attacks which cause glitches - pulses that are added to the transmitted signal at arbitrary times - and delays. We present self-synchronizing coding schemes with no latency at the receiver that do not require any acknowledgment to be sent and that can decode the received signal even when the signal suffers from random delays and distortion by random glitches. We make use of the codes to produce lower bounds on the information capacity of such channels when the number of parallel channels is large.

An experimental investigation of flow boiling heat transfer coefficient and pressure drop of R410A in various minichannel multiport tubes

The present work demonstrates the two-phase flow boiling heat transfer coefficient and pressure drop of R410A inside various minichannel multiport tubes. The experimental investigation was performed in four tube types with the hydraulic diameters of 1.16, 1.14, 1.07 and 0.96 mm and the number of parallel channels are 7, 11, 16 and 9, respectively. The data were conducted with the heat fluxes of 3 and 6 kW m−2, the mass flux ranging from 50 to 500 kg m−2 s−1, the saturation temperature of 6 °C and the vapor quality up to 1.0. The heat transfer coefficient of R410A was found to be affected by the heat flux, mass flux, vapor quality and the geometry of channel. The frictional pressure drop gradient was also affected by the mass flux and vapor quality but independent with the variation of heat flux. In addition, the present data were compared with various heat transfer coefficient correlations and pressure drop models in literature. Finally, new correlation of heat transfer coefficient was proposed based on the present experimental data.

Polymer electrolyte membrane fuel cell flow field design criteria – Application to parallel serpentine flow patterns

One key strategy for maximizing the performance of fuel cells is the choice of proper flow field pattern. In this paper, a procedure was developed for the proper design of parallel serpentine flow field for proton exchange membrane fuel cells. Several parameters including the channel width and height, the rib between two adjacent channels, and the numbers of parallel channels and serpentine turns were considered and all the possible flow field configurations within the range of these design parameters were defined. In the next step, six consecutive constraining filters were defined and enforced to all the possible flow field configurations. In the final step, a complete three dimensional simulations were conducted for the remaining cases. Based on the results of the simulations, these cases were ranked, with the best case corresponds to the flow field with the minimum pressure drop, the maximum oxygen content at the surface of catalyst layer, maximum uniformity of oxygen distribution within the catalyst layer and minimum content of the condensate produced within the catalyst layer.

One-Dimensional Nature of Superconductivity at the LaAlO_{3}/SrTiO_{3} Interface.

We examine superconductivity in LaAlO_{3}/SrTiO_{3} channels with widths that transition from the 1D to the 2D regime. The superconducting critical current is independent of the channel width and increases approximately linearly with the number of parallel channels. Signatures of electron pairing outside of the superconducting regime are also found to be independent of the channel width. Collectively, these results indicate that superconductivity exists at the boundary of these channels and is absent within the interior region of the channels. The intrinsic 1D nature of superconductivity at the LaAlO_{3}/SrTiO_{3} interface imposes strong physical constraints on possible electron pairing mechanisms.

A Sub-Nyquist Radar Electronic Surveillance System

The modulated wideband converter (MWC) is well-known for a sub-Nyquist wideband sampling capability based on compressed sensing (CS) theory. In this paper, our goal is to use the MWC as a base to design a sub-Nyquist radar electronic surveillance (ES) system. Our focus is then to extend the capabilities of the previous MWC system in order to meet the challenges, i.e., a very long acquisition time, a much larger simultaneous monitoring bandwidth, and a faster digital signal processing receiver. To this end, we present a new performance analysis framework and then a new digital domain receiver. The proposed performance analysis framework will be useful in comparing signal-acquisition performance of the proposed ES system with those of other sub-Nyquist receivers, including those of the classical Nyquist rate receivers, without resorting to extensive simulations. This framework can also be used to study the complex interplays of important system parameters of MWC, such as the sampling rate, the number of parallel channels, the period of Pseudo random sequence, and thus guides us in selecting the right system dimensions and parameters for desired performance. Radar surveillance application has its inherent needs for very long acquisition time and simultaneous monitoring of very large frequency range. To meet this challenge, a fast signal recovery system needs to be developed, so that radar signal logistics can be retained and recovered from compressed samples. We have proposed a split and synthesis process in which the radar signal recovery problem over a long signal acquisition time can be divided into many small CS signal recovery problems, and the solutions for small pieces are put together later on at the end. In addition, a sub-sampling method is proposed to have the multiple measurement vector problem complete signal recovery faster without noticeable performance loss.

Space division multiplexing optical communication using few-mode fibers

Abstract To realize ultra-high capacity long-haul transmission, space-division multiplexing (SDM) has emerged as a promising solution, in which each data channel is modulated into an individual spatial/polarization modes in few-mode fibers (FMF) to increase the overall number of parallel channels. In this paper, we review the latest advances in SDM technology on the FMF, component, digital signal processing (DSP), as well as transmission demonstrations. First, we introduce the FMF characteristics, fabrication and manufacturing issues including modal dispersion, mode coupling, and nonlinearities. We next discuss in detail several key SDM components such as spatial multiplexers/demultiplexers (MUX/DeMUX), optical amplifiers, mode converters and SDM reconfigurable optical add-drop multiplexer (ROADM). Accordingly, we explore the DSP algorithms for SDM systems, covering least mean squares (LMS), recursive least squares (RLS), hardware complexity analysis, and mode dependent effects. Besides, a number of recent experimental validations are evaluated enabling higher transmission capacity for short, medium and long distances.

Experimental Investigation on Characteristics of Boiling Two-Phase-Flow Instability in a Parallel-Multichannel Natural-Circulation System

Natural-circulation systems are gaining wide acceptance due to their inherent passive safety features, which makes them more reliable to use in nuclear power plants. In view of this, many Generation III and III+ nuclear reactors have been designed with natural circulation as a mode of core cooling. But, the major area of concern in these kinds of systems is still the complex phenomenon of boiling two-phase-flow instabilities, which is yet to be fully understood especially when power and pressure in the system are low (type I instability). A major factor in this regard is to know the sensitivity of the number of parallel channels to the characteristic behavior of these flow oscillations in systems like those of a boiling water reactor. Based on mathematical models, in the past, some authors reported that any number of channels behaves in the same way as a twin-channel system. There is no experimental study to validate this. This experimental investigation has been done to add insight. A parallel-multichannel closed loop filled with water and maintained at atmospheric pressure was used for the study. Power in the individual heated sections of the loop was increased from 0 to 2 kW in steps of 250 W. Each power level was maintained for ~30 min. After reaching 2 kW, power was decreased to 0 kW. Three cases of experiments were done by taking two, four, and six active channels at a time, respectively. Different flow oscillation parameters such as amplitude, frequency, phase difference, general characteristics, etc., were studied to see if they were affected when the number of parallel channels was changed. The present analysis showed that their behavior is sensitive toward changes in the number of parallel channels. We cannot extrapolate twin-channel data when there are more channels in a system. The present paper discusses the experiments performed and the detailed results in support of this argument.

Delay analysis of MSW-ARQ system based on wireless multimedia services

This paper firstly analyzes the transmission mechanism of the wireless broadband multi-media services in the MSW-ARQ(Multi-channel Stop-and-Wait ARQ) system. Considering the real-time multimedia service's four features (high requirement for delay but allows some loss rate, the constraints of the delay and jitter), in order to meet with professional standard, we model the real-time multimedia service packet transmission as an M[X]/G/1 queuing model for MSW-ARQ. The packet transition probability is derived by constructing steady state Markov Chain based on the method of selecting the reference packet. On the basis of equivalent service delay, we also solve the packet mean service delay. Then under the given condition, we analyze the influence of the channel number and channel environments on the mean delay through numerical simulating. The characteristics and superiorities of multi-channel transmission mechanism in wireless communication are checked enough by solving the M[X]/G/1 queuing model. So this paper provides useful thought and approach for optimizing system delay and throughput by checking the change of channel environments and the used number of parallel channels.

Calculating the spatial fluorescence distribution of a thick fluorophore layer in a multichannel confocal microscope

The propagation of rays in the optical system of a multichannel confocal microscope is numerically modelled in the Gaussian approximation, making it possible to estimate the shape of the image profile of a focused laser beam in a thick phosphor layer. The proposed method creates the possibility of calculating the signal-to-background-illumination-noise ratio of a confocal system in the case of a large number of parallel channels without using extensive computer resources. The results are compared with experimental measurements made by successively scanning a thick fluorophore layer in depth.

Polarized, phase-encoded and 2D angular multiplexed volume holographic correlator

The volume holographic correlator (VHC) is a highly parallel processor. For an angularly multiplexed VHC, the processing speed is limited by the ratio of the maximum angle range and the minimum angle interval of the reference beam. Limited by the angle scanning range of the reference beam, the pure angular multiplexing in the reference beam of the VHC can only establish thousands of parallel correlation channels, which is far from the high parallelism demand for real-time applications. In this paper, the maximum multiplexing number of the VHC system is increased. The polarized and phase-encoded multiplexing methods are introduced into the object beam, with the angular multiplexing method in the reference beam. The mutual orthogonality of the polarization multiplexing, phase-encoded multiplexing and angular multiplexing methods are verified with experiment. This shows that the number of parallel channels can be increased with the object beam both polarized and phase-encoded multiplexed and with the reference beam still angularly multiplexed in the VHC. The optical setup is established and the feasibility of the proposed hybrid multiplexing method is experimentally verified. The two multiplexing methods extended to the object beam make it possible to establish more parallel correlation channels in the VHC. Although millions of parallel correlation channels can be realized with the proposed multiplexing method in theory, the paper presents some principal experimental results.

Comparison of Possible Flow Distribution Systems for PbLi Self-Cooled Blankets With Respect to MHD, Fabrication, and Maintenance

Previous conceptual design studies for liquid-metal (LM) cooled blankets of a fusion power plant often omit details of the complete flow distribution network required to bring the coolant into and out of the blanket, and especially the manifolding required for the transition from a small number of feed pipes to sometimes a large number of parallel channels within the actively heated part of the power core. Manifolding can induce large 3-D magnetohydrodynamics (MHD) currents and therefore dominate the pressure and flow distributions within the entire blanket, which is especially problematic for designs with electrically insulated channels. Especially risky are those elements that require bends which redirect the flow from parallel to perpendicular to the magnetic field and vice versa, because in those cases a bulk of the liquid metal can act as a short circuit. A fully developed flow in insulated ducts normally retains well-balanced electric potentials, preventing large 3-D currents; internal flows parallel to the magnetic field can easily disrupt this delicate balance. Within the ARIES-ACT1 power plant study several design concepts for flow distribution networks have been analyzed. Each system provides pros and cons. MHD effects as well as fabrication and maintenance issues were considered. Using SiCf/SiC as a structural material for blanket and manifolding, and a complex structure for these parts with an inner and outer pipe separated by ribs required a more detailed consideration of manufacturing as well as joining and cutting possibilities. Available technologies have been considered for a possible solution. Tradeoffs associated with the vacuum vessel and structural ring penetrations as well as pipe connections required for maintenance are discussed for the preferred solution. A maintenance scenario and fabrication steps for the latest ARIES-ACT1 manifold design are shown.

Outage minimization for parallel fading channels with limited feedback

We address an optimal power allocation problem for minimizing the outage probability for M parallel block-Nakagami-fading channels under a long-term average sum transmit power constraint with finite rate feedback of channel state information (CSI). A simulation-based optimization technique called simultaneous perturbation stochastic approximation algorithm (SPSA) is employed first to numerically derive a locally optimal power codebook. Due to the high computational complexity and long convergence time of SPSA, we make an ordering assumption on the power codebook entries and derive effective hyperplane based approximations to the channel quantization regions and present a number of low-complexity suboptimal quantized power codebook design algorithms. Unlike existing work on outage minimization for multiple-input multiple-output (MIMO) channels with limited feedback, we do not assume that identical transmission power is used for all channels within each channel quantization region. We also do not resort to a Gaussian approximation for the instantaneous mutual information in general as used in many existing work. Based on our power ordering assumption and hyperplane based approximations, we show that allocating identical power to all channels within a given channel quantization region in the limited feedback scenario is asymptotically optimal only at high average power (or average signal-to-noise ratio (SNR)) for the Rayleigh fading case, whereas for the general Nakagami case, the transmit power allocation for an individual channel within each quantized region is asymptotically proportional to the corresponding Nakagami fading parameter (severity of fading). We also present a novel diversity order result for the outage probability for the Nakagami fading case. Finally, we derive a suitable Gaussian approximation based low-complexity power allocation scheme for a large number of parallel channels, which has important applications in wideband slow-fading orthogonal frequency-division multiplexing (OFDM) systems. Extensive numerical results illustrate that only a few bits of feedback close the gap substantially in outage performance between the limited feedback case and the full instantaneous CSI at the transmitter case.

Electrokinetic flow in parallel channels: Circuit modelling for microfluidics and membranes

The ‘ion current model’ (ICM), a one-dimensional electrokinetic circuit model that incorporates ion charge conservation at circuit nodes, is extended to describe channels connected in parallel. If the number of parallel channels is M, then the ICM has M−1 degrees of freedom, which means that the rates of fluid and ion transport within the parallel channels need not be distributed equally (even if the channels are identical). Using two-dimensional computational fluid dynamics (CFD) simulations of a simple network containing two parallel channels, we show that in a physical system the conductances (and hence, the flow behaviour) within each parallel channel are influenced by asymmetries within the system, including concentration polarisation. This observation suggests that by tuning channel arrangement, dimensions, and surface chemistry to achieve specific asymmetries, novel devices could be created for specific applications.

Packet Delay Statistics of the Multichannel Selective-Repeat Automatic-Repeat-Request

In this paper, we conduct stochastic modeling and analysis of the packet end-to-end delay in a multichannel selective-repeat automatic-repeat-request (MSR-ARQ) protocol. In this protocol, the transmitter continuously transmits packets over multiple parallel channels and retransmits erroneously received packets with either dynamic or static packet-to-channel scheduling policy. Under the assumption that packets are always supplied at the transmitter, denoted by the saturated traffic condition, we analyze the steady state probability distribution function of the delay of an arbitrary packet, which is measured by the duration between the instant at which the packet is transmitted for the first time and the time it departs from the resequencing queue at the receiver. Using the analysis result, we numerically compute the distribution function for chosen values of the number of channels and the error rates to demonstrate the computational effectiveness of the result. With numerical and simulation results, we then study the performance of MSR-ARQ in terms of the mean packet delay and compare the two scheduling policies. It is shown that the dynamic scheduling achieves a better packet delay performance than the static scheduling. With the dynamic scheduling and the presence of difference between the error rates of parallel channels, the mean packet delay decreases as the difference between channels’ error rates increases. Moreover, the number of parallel channels has an insignificant impact on the mean packet delay, which shows that the use of parallel channels is favorable for the wireless or mobile communications to increase the data transmission rate while keeping the mean packet delay at an acceptable level.

Collimated-hole structures as efficient differential pumping barrier, one-way valve and tool for aligning Penning traps

A collimated-hole structure consists of a very large number of parallel channels which have each a very small diameter and are closely packed together. Such devices, installed in vacuum systems allow one to separate regions of very different gas pressures. A collimated-hole structure has high transmission for a directed ion beam with low emittance but a very low conductance for rest gas atoms or molecules exhibiting random walk. Therefore it is proposed to use such a structure as one-way valve and/or efficient differential pumping barrier in set-ups using Penning traps. Furthermore, these devices might be very useful to align the axis of a Penning trap with the direction of the magnetic field lines which is essential to avoid systematic uncertainties in high-accuracy mass spectroscopy.

Design of thermal management subsystem for a 5 kW polymer electrolyte membrane fuel cell system

High-efficiency thermal management subsystem has a key role on the PEM fuel cell performance and durability. In this study, design of thermal management subsystem for a 5kW PEM fuel cell system is investigated. A numerical model is presented to study the cooling flow field performance. The number of parallel channels in parallel serpentine flow field is selected as the design parameter of the flow field and its optimum value is obtained by compromising between the minimum pressure drop of coolant across the flow field and maximum temperature uniformity within the bipolar plate criteria. The optimum coolant flow rate is also determined by compromising between different criteria. Test results of a 5-cells short stack are presented to verify the numerical simulation results.