Loop Channels Research Articles

Reliability and sensitivity analysis of loop-designed security and stability control system in interconnected power systems

Security and stability control system (SSCS) in power systems involves collecting information and sending the decision from/to control stations at different layers; the tree structure of the SSCS requires more levels. Failure of a station or channel can cause all the execution stations (EXs) to be out of control. The randomness of the controllable capacity of the EXs increases the difficulty of the reliability evaluation of the SSCS. In this study, the loop designed SSCS and reliability analysis are examined for the interconnected systems. The uncertainty analysis of the controllable capacity based on the evidence theory for the SSCS is proposed. The bidirectional and loop channels are introduced to reduce the layers and stations of the existing SSCS with tree configuration. The reliability evaluation and sensitivity analysis are proposed to quantify the controllability and vulnerable components for the SSCS in different configurations. By aiming at the randomness of the controllable capacity of the EXs, the uncertainty analysis of the controllable capacity of the SSCS based on the evidence theory is proposed to quantify the probability of the SSCS for balancing the active power deficiency of the grid.

Structural Plasticity of the Selectivity Filter in Cation Channels.

Ion channels allow for the passage of ions across biological membranes, which is essential for the functioning of a cell. In pore loop channels the selectivity filter (SF) is a conserved sequence that forms a constriction with multiple ion binding sites. It is becoming increasingly clear that there are several conformations and dynamic states of the SF in cation channels. Here we outline specific modes of structural plasticity observed in the SFs of various pore loop channels: disorder, asymmetry, and collapse. We summarize the multiple atomic structures with varying SF conformations as well as asymmetric and more dynamic states that were discovered recently using structural biology, spectroscopic, and computational methods. Overall, we discuss here that structural plasticity within the SF is a key molecular determinant of ion channel gating behavior.

Navigating a proximal loop in the radial artery and avoiding the recurrent radial artery

Several anatomical variations of the radial artery have been described in the literature. Common variations include radial artery loop, recurrent branch, and anastomotic channels connecting the radial and brachial arteries....

Hyperon production in Λc+→K−pπ+ and Λc+→KS0pπ0

We investigate $S=-1$ hyperon production from the $\Lambda_c^+\to K^-p\pi^+$ and $\Lambda_c^+\to K^0_Sp\pi^0$ decays within the effective Lagrangian approach. We consider the $\Sigma/\Lambda$ ground states, $\Lambda(1520)$, $\Lambda(1670)(J^p=1/2^-)$, $\Lambda(1890)(J^p=3/2^+)$; $\Lambda/\Sigma$-pole contributions from the combined resonances between 1800 MeV and 2100 MeV; and $N/\Delta$-pole and $K^\ast$-pole contributions, which include the proton, $\Delta(1232)$, and $K(892)$. We calculate the Dalitz plot density $(d^2\Gamma/dM_{K^-p}dM_{K^-\pi^+}$) for the $\Lambda_c^+\to K^-p\pi^+$ decay. The calculated result is in good agreement with experimental data from the Belle Collaboration. Using the parameters from the fit, we present the Dalitz plot density for the $\Lambda_c^+\to K^0_Sp\pi^0$ decay. In our calculation, a sharp peak-like structure near 1665 MeV is predicted in the $\Lambda_c^+\to K^-p\pi^+$ decay because of the interference effects between the $\Lambda(1670)$ resonance and $\eta$-$\Lambda$ loop channels. We also demonstrate that we can access direct information regarding the weak couplings of $\Lambda(1670)$ and $\Sigma(1670)$ from the $\Lambda_c^+\to K^0_Sp\pi^0$ decay. Finally, a possible interpretation for the 1665 MeV structure beyond our prediction is briefly discussed.

The Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels: from Biophysics to Pharmacology of a Unique Family of Ion Channels.

Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels are important members of the voltage-gated pore loop channels family. They show unique features: they open at hyperpolarizing potential, carry a mixed Na/K current, and are regulated by cyclic nucleotides. Four different isoforms have been cloned (HCN1-4) that can assemble to form homo- or heterotetramers, characterized by different biophysical properties. These proteins are widely distributed throughout the body and involved in different physiologic processes, the most important being the generation of spontaneous electrical activity in the heart and the regulation of synaptic transmission in the brain. Their role in heart rate, neuronal pacemaking, dendritic integration, learning and memory, and visual and pain perceptions has been extensively studied; these channels have been found also in some peripheral tissues, where their functions still need to be fully elucidated. Genetic defects and altered expression of HCN channels are linked to several pathologies, which makes these proteins attractive targets for translational research; at the moment only one drug (ivabradine), which specifically blocks the hyperpolarization-activated current, is clinically available. This review discusses current knowledge about HCN channels, starting from their biophysical properties, origin, and developmental features, to (patho)physiologic role in different tissues and pharmacological modulation, ending with their present and future relevance as drug targets.

Expression and cellular localization of HCN channels in rat cerebellar granule neurons

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels belong to the superfamily of voltage-gated pore loop channels. In mammals, this family consists of four different subunits (HCN1–4) and their ion channels activity have been proposed to play an essential role in regulating the membrane potential of excitable cells. Here, we describe the expression and relative abundances of HCN channels in cerebellum and primary cultures of cerebellar granule neurons (CGN). Quantitative determination of mRNA expression levels demonstrated the existence of an accumulation pattern of transcripts in cerebellum that encode HCN2 > HCN3 = HCN4 > HCN1 subunits. Immunolocalization analyses of HCN channels in cerebella revealed positive staining in Purkinje and granule cell layers. The presence of the HCN subunits in the cerebellar granule cell layer was then confirmed in primary cultures of CGN by quantitative real-time PCR (qPCR), as well as western blot and immunofluorescence analysis, demonstrating the presence of all four channel proteins.

On Feedback Architectures With Zero-Vibration Signal Shapers

The classical and recent feedback solutions for signal shapers are reviewed and critically analyzed in this paper. Based on this assessment, a new effective feedback control architecture is proposed, suitable for manipulation of weakly damped flexible structures. More specifically, we propose to include the inverse of a signal shaper's dynamics in the feedback path, and we justify this architecture by analysis of important feedback loop channels, namely the feedback responses from input disturbance to output and from reference to output. Both the classical ZV shaper with one lumped delay, and more recent shapers with distributed delays are considered and analyzed. The most appreciated features of suitable distributed-delay shapers are retarded characteristics—the closed-loop spectrum does not exhibit high-frequency roots close to the imaginary axis (in contrast to ZV shapers)—and at the same time reduced sensitivity of the closed loop interconnection to output disturbances. Feedback performance is demonstrated by two laboratory experiments.

Hybrid monopole/loop coil array for human head MR imaging at 7T.

The monopole coil and loop coil have orthogonal radiofrequency (RF) fields and thus are intrinsically decoupled electromagnetically if they are laid out appropriately. In this study, we proposed a hybrid monopole/loop technique which could combine the advantages of both loop arrays and monopole arrays. To investigate this technique, a hybrid RF coil array containing 4 monopole channels and 4 loop channels was developed for human head MR imaging at 7T. In vivo MR imaging and g-factor results using monopole-only channels, loop-only channels and all channels of the hybrid array were acquired and evaluated. Compared with the monopole-only and loop-only channels, the proposed hybrid array has higher SNR and better parallel imaging performance. Sufficient electromagnetic decoupling and diverse RF magnetic field (B1) distributions of monopole channels and loop channels may contribute to this performance improvement. From experimental results, the hybrid monopole/loop array has low g-factor and excellent SNR at both periphery and center of the brain, which is valuable for human head imaging at ultrahigh fields.

1027 発振流体素子を応用した壁面冷却性能の数値解析による検討

In this numerical study, the time-averaged and instantaneous heat transfer are assessed in terms of the self-oscillating fluidic device. This fluidic oscillator consists of one inlet, two outlets and two feedback loop channels. The fluid flows a feedback loop channel alternately and results in the impinging jet fluctuation. This self-fluctuating phenomena have successfully been simulated by numerical simulation. As a result, the linear relation between the input flow rate and oscillating frequency is indicated. Utilizing the self-oscillating fluidic device for wall cooling, lots of local maxima of the time-averaged and instantaneous Nusselt number were obtained at the hot target wall. This is because the quasi-steady impinging jet generated by the self-oscillating fluidic device produces the quasi-steady vortex.

Use of remote-controlled machinery to reduce worker radiation exposure

The results of using remote-controlled machinery in the disassembly of loop facilities of the MR research reactor, which was decommissioned at the National Research Center Kurchatov Institute, are presented. The results of an examination of the loop channels of the reactor and the handling of high-level wastes during extraction, fragmentation and packaging are presented. Methods of remote diagnostics for measuring the activity distribution along a channel are proposed. Means for cutting channels and methods of lowering worker dose loads are presented.

New Fluidic-Oscillator Concept for Flow-Separation Control

A novel fluidic oscillator, particularly suitable to serve as the key element in actuators for control of fluid flows, was proposed and experimentally investigated. Its core part, as in known oscillators, is a fluidic bistable jet-deflection diverter amplifier. The unique feature of the new layout is the absence of the closed feedback loop channels. Instead, there is a quarter-wave Helmholtz resonator tube connected to one of the amplifier control terminals. The acoustic waves traveling in it and reflected from its open end cause the phase-delayed switching of the amplifier. The main advantage is high achievable oscillation frequency and no dependence on the flow rate.

Digital tanlock loop architecture with no delay

This article proposes a new architecture for a digital tanlock loop which eliminates the time-delay block. The (rad) phase shift relationship between the two channels, which is generated by the delay block in the conventional time-delay digital tanlock loop (TDTL), is preserved using two quadrature sampling signals for the loop channels. The proposed system outperformed the original TDTL architecture, when both systems were tested with frequency shift keying input signal. The new system demonstrated better linearity and acquisition speed as well as improved noise performance compared with the original TDTL architecture. Furthermore, the removal of the time-delay block enables all processing to be digitally performed, which reduces the implementation complexity. Both the original TDTL and the new architecture without the delay block were modelled and simulated using MATLAB/Simulink. Implementation issues, including complexity and relation to simulation of both architectures, are also addressed.

Sampling from Nanoliter Plugs via Asymmetrical Splitting of Segmented Flow

A microfluidic device is developed to sample from oil-segmented fluid plugs of nanoliter volume by passive splitting. In the device, plugs are pumped into a loop where they split according to the flow resistance of each arm of the loop. The loop structure prevents changes in flow resistance over time, caused by accumulation of plugs in downstream collector capillaries, from interfering with the split ratio. To prevent plugs from recombining at the downstream junction of the loop, a series of posts is fabricated into the junction. This structure allows oil to cross, enabling pressure equalization, but not the aqueous plugs allowing them to be collected into separate capillaries or channels. The split ratio depended on both dimensions of the loop channels and frequency of plugs entering the loop. Split ratios from 1:1 to 34:1 were achieved for samples from 1.7 to 3.3 nL. Long-term stability was demonstrated by splitting over 7000 plugs with 6.3% relative standard deviation of the daughter plug size. The system will have application to high-throughput chemical analysis on a nanoliter scale by enabling several applications including performing multiple assays on a single sample, preserving sample while some is removed for analysis, and splitting reagents or test compounds for use in multiple assays.

HCN channels: structure, cellular regulation and physiological function.

Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels belong to the superfamily of voltage-gated pore loop channels. HCN channels are unique among vertebrate voltage-gated ion channels, in that they have a reverse voltage-dependence that leads to activation upon hyperpolarization. In addition, voltage-dependent opening of these channels is directly regulated by the binding of cAMP. HCN channels are encoded by four genes (HCN1-4) and are widely expressed throughout the heart and the central nervous system. The current flowing through HCN channels, designated I(h) or I(f), plays a key role in the control of cardiac and neuronal rhythmicity ("pacemaker current"). In addition, I(h) contributes to several other neuronal processes, including determination of resting membrane potential, dendritic integration and synaptic transmission. In this review we give an overview on structure, function and regulation of HCN channels. Particular emphasis will be laid on the complex roles of these channels for neuronal function and cardiac rhythmicity.

Oscillatory Flow in Loop Channel with Right Angle Branch and Reservoirs

Oscillatory flow in loop channels consisting of a T-branch, two reservoirs, and main and side branches was experimentally investigated. The following were found: (1) Oscillatory flow composed of oscillatory and steady components was induced in the loop channels. (2) The ratio of the flow rate of the steady component in the main and side branches to the maximum flow rate of oscillatory flow in the primary branch approached constant values in the Reynolds number range of 5 000 < Re p,max ≤ 10 000. (3) Time-averaged pressure differences were generated between the two exits of the T-branch and between the inside and outside of the reservoirs. These pressure differences induced the steady component in the oscillatory flow in the loop channel. (4) The ratio of the flow rate of the oscillatory component in the main branch to that in the side branch was nearly equal to the ratio of the reciprocal lengths of the main and side branches.

Equalization for discrete multitone transceivers to maximize bit rate

In a discrete multitone receiver, a time-domain equalizer (TEQ) reduces the intersymbol interference (ISI) by shortening the effective duration of the channel impulse response. Current TEQ design methods such as the minimum mean-squared error (MMSE), maximum shortening SNR (MSSNR), and maximum geometric SNR (MGSNR) do not directly maximize bit rate. We develop two TEQ design methods to maximize the bit rate. First, we partition an equalized multicarrier channel into its equivalent signal, noise, and ISI paths to develop a new subchannel SNR definition. Then, we derive a nonlinear function of TEQ taps that measures the bit rate, which the proposed maximum bit rate (MBR) method optimizes. We also propose a minimum-ISI method that generalizes the MSSNR method by weighting the ISI in the frequency domain to obtain higher performance. The minimum-ISI method is amenable to real-time implementation on a fixed-point digital signal processor. Based on simulations using eight different carrier-serving-area loop channels, (1) the proposed methods yield higher bit rates than MMSE, MGSNR, and MSSNR methods; (2) the proposed methods give three-tap TEQs with higher bit rates than 17-tap MMSE, MGSNR, and MSSNR TEQs; (3) the proposed MBR method achieves the channel capacity (as computed by the matched filter bound using the proposed subchannel SNR model) with a five-tap TEQ; and (4) the proposed minimum-ISI method achieves the bit rate of the optimal MBR method.

On the capacity of a twisted-wire pair: Gaussian model

The performance of a twisted-pair channel is assumed to be dominated by near-end crosstalk (NEXT) from other pairs in the same cable. Both intrabuilding local and central office loop channels can be modeled as NEXT-dominated channels. The capacity of this type of channel is found, using a Gaussian model. It is shown that the capacity is independent of the transmitted power spectral density. The results also indicate that present systems operate far below theoretical capacity. The capacity of a twisted-pair channel with both NEXT and white Gaussian noise present is also addressed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Calculation of energy liberation in the loop channels by the Monte Carlo method

Calculation of energy liberation in the loop channels by the Monte Carlo method

Local control of profile and magnitude of energy release of loop channels

Local control of profile and magnitude of energy release of loop channels