Merging Point Research Articles

Цифровая осциллография полимерных мембран с протонной проводимостью

Polyvinyl alcohol-based cast membranes have promising application in creating commonly available fuel cells and fuel synthesizers, as well as inexpensive water sources and microelectromechanical systems. In order to control the properties of such membranes a deep understanding of the charge transfer mechanisms and their relationship with the structure formed at a certain composition and manufacturing technology is required. A method for studying the structure of the proton-conductive polymer membranes using digital oscillography of ion currents excited by the low-frequency rectangular pulses with the amplitudes below the threshold voltage of the ionic conductivity in a dehydrated membrane, and for the analysis of the resulting ion current pulses (spikes) in the frames of the model of a proton pump acting in each layer of the membrane is proposed in this paper. Fast Fourier transform of these oscillograms reveals from 2 to 4 branches or spike sequences corresponding to the phases with different ionic conductivity and makes it possible to determine the thicknesses of both high-conductivity phase layers (7–30 µm) and low-conductivity phase interlayers (1–7 µm) formed in the process of polymerization. The reason of spike merging into bursts is described in terms of successively induced increase in the excited proton density over a threshold value in highly conductive layers. The resonance observed in dry proton membranes at the frequencies of about 2.2 to 3.0 kHz is interpreted as the burst merge point with the further increase in impedance due to proton lagging and respective decrease in the effective thickness of active layers. The effective charge carrier concentrations (as small as 1012 to 1013 cm−3) and the velocity (from 5 to 18 cm/s for the highly conductive phases which turned out to be much higher than those observed in solutions) are estimated. The asymmetry of the cast membranes, which becomes apparent at low frequencies and causes the generation of a direct ion current in response to excitation by a purely alternating current, is studied. It is found that the apparent conductivity determining contribution to the total ohmic resistance is made by a thin interlayer with a very low ion velocity, presumably surface layer, rather than the main layers. The conclusion on the optimization of the production technology and the composition of the proton membranes for various applications is made.

Comparison of RECAT-EU and ICAO wake turbulence category on the Point Merge System

AbstractThis study presents a mathematical model that schedules arrival aircraft regarding RECAT-EU that is new categorisation for applying separation minima and analyses its effect on the performance of the Point Merge System (PMS) at Sabiha Gökcen International Airport (LTFJ). There are two main scenarios: one of them uses RECAT-EU and the other employs the ICAO wake turbulence category. Both scenarios have ten different test problems to examine the mathematical model. The model applies RECAT-EU wake turbulence categories and compares the outcome with the ICAO wake turbulence categories. The model aims to minimise flight duration on the sequencing leg and ground delay in the departure queue using the RECAT-EU and ICAO wake turbulence categories individually. The results were analysed to reveal the PMS performance using the two different approaches to turbulence categories. Statistical analysis was also carried out to compare the means of the two groups in the model.

The effects of spacing to diameter ratio on mixing characteristics of circular and elliptical twin jets

Twin jets are encountered in many engineering and industrial applications, such as aircraft propulsion systems and combustors. Twin jets create a flow field that is more complex than a single jet due to its interaction with the individual jets. This paper investigates the effects of spacing to diameter ( S/ D e) ratio and orientation on the mixing properties of circular and elliptical twin jets at four different S/ D e ratios of 1.25, 1.50, 1.75, and 2.0, respectively. The numerical simulations of twin jets are carried out with a jet Mach number of 0.8 using the Shear Stress Transport ( SST) K- ω turbulence model. The results show that near the orifice exit, the twin jets are issuing into ambient conditions separately and resemble a free jet, leading to a potential core length independent of S/ D e. The merging and combined point locations change linearly from the exit with an increasing S/ D e ratio. The decay rate is higher for Twin Ellipse Minor than those in Twin Circle and Twin Ellipse Major, verified by a shorter converging region. In addition, near the jet exit, the spread rate is higher for Twin Ellipse Minor, which is consistent with the closer merging point location. The jet mixing is superior for twin minor elliptical configuration compared to twin circle and twin major elliptical jets at all S/ D e ratios.

Spatial and time scaling of coalescing multiple magnetic islands

Magnetic reconnection is a key fundamental process in collisionless plasmas, which converts magnetic energy to plasma kinetic energy. Past observation and simulation studies suggested that this process causes an efficient energy conversion through the formation and coalescence of multiple magnetic islands. In this study, based on a large-scale two-dimensional fully kinetic simulations of coalescing multiple islands with a moderate guide magnetic field, we first examined the spatial dimensions of the internal structures of the coalescing islands. The results show that the dimensions of the structures in the directions normal to and along the initial current sheet depend on the initial thickness of the current sheet and the number of coalescing islands. We then found that the horizontal dimension of the structures controls the evolution time scale of the island coalescence process. We further found that when the vertical dimension of the structures, which corresponds to the length of the reconnection X-line in the reconnection outflow direction at the merging point between the two coalescing islands, is sufficiently longer than the ion inertial length, reconnection in the merging current sheet can well mature and both ions and electrons can be effectively heated around the merging X-line. The obtained scaling predicts that such a strong heating by well-matured reconnection in the island coalescence process would be seen in various plasma environments, such as the Earth's magnetotail and solar flares.

Merged bound states in the continuum for giant superchiral field and chiral mode splitting

Enhanced circular dichroism (CD) signal is crucial for ultrasensitive detection of chiral species. This purpose strongly relies on the construction of superchiral field in achiral resonant nanostructures. Despite the progress, the research on superchiral fields and their related physics is fundamentally restricted. Here, we demonstrate an approach to construct superchiral field in achiral metasurfaces and explore its impact on chiral mode interaction. While the chiral field at individual bound states in the continuum (BIC) is small, all criteria for giant superchiral fields can be satisfied when two BICs with orthogonal polarizations are merged. Consequently, the typical photonic crystal slabs can produce superchiral fields with enhancement factors ($C\text{/}{C}_{\mathrm{CPL}}$) (where CPL is circular polarized light) orders of magnitude higher than state of the art in nanostructures. More interestingly, a type of chiral light-matter interaction has been revealed by introducing chiral active materials. The nearly orthogonal BICs couple one another at the merging point and result in chiral mode splitting.

Decentralized Time and Energy-Optimal Control of Connected and Automated Vehicles in a Roundabout With Safety and Comfort Guarantees

We consider the problem of controlling Connected and Automated Vehicles (CAVs) traveling through a roundabout so as to jointly minimize their travel time, energy consumption, and centrifugal discomfort while providing speed-dependent and lateral roll-over safety guarantees, as well as satisfying velocity and acceleration constraints. We first develop a systematic approach to determine the safety constraints for each CAV dynamically, as it moves through different merging points in the roundabout. We then derive the unconstrained optimal control solution which is subsequently optimally tracked by a real-time controller while guaranteeing that all constraints are always satisfied. Simulation experiments are performed to compare the controller we develop to a baseline of human-driven vehicles, showing its effectiveness under symmetric and asymmetric roundabout configurations, balanced and imbalanced traffic rates, and different sequencing rules for CAVs.

Merging of Dirac points through uniaxial modulation on an optical lattice

We analyze the scenario of modulating the potential strength of bound atoms in an optical honeycomb lattice patterned by an electric field to emulate uniaxial strain. This modulation can be achieved by a combination of the strength of the patterned electric field and gauge vector effects using the Floquet approach. We show that such a modulation allows one to follow through a topological transition between a semi-metal and a band insulator, when two non-equivalent K points merge as a function of the electric field strength. We explicitly compute the wavefunctions for the moving K points and the Chern numbers up to the transition. Anisotropic effective masses and the insulating gap are described close to the semimetal-insulator transition.

Constructing a “Four in One” fingerprint quality evaluation system of Cistanche Herba

Cistanche Herba, known as “Desert Ginseng”, is widely sought after as a medicine and food homology. Owing to the one-sided quality control of several markers, a comprehensive “Four in One” fingerprint quality evaluation system based on HPLC, UV, FTIR and DSC was developed to ensure safety and improve quality. Except for HPLC quantitative analysis of echinacoside (1.41–60.23 mg/g) and acteoside (0.13–14.71 mg/g), UV and FTIR spectral analyses, 12 characteristic parameters of the DSC curve were first developed. Particularly, HPLC fingerprints with UV, FTIR and DSC quantum fingerprints established by merging point method were integrated to evaluate the sample quality with systematically quantified fingerprint method. 45 samples (Cistanche deserticola: 26 batches, Cistanche tubulosa: 19 batches) were evaluated separately to retain their fingerprint characteristics, whose significant inter batch differences and grade differentiation were manifested. This study can provide a comprehensive, strict and objective evaluation strategy for Cistanche Herba and even other samples.

Optimal aircraft arrival scheduling with continuous descent operations in busy terminal maneuvering areas

Continuous Descent Operation (CDO), an aircraft arrival procedure in which an aircraft descends from an optimal position with minimum engine thrust, can significantly reduce aircraft noise, fuel burn and emissions. The implementation of CDOs, however, requires more separation buffers among flights than traditional stepwise descents, resulting in loss of airspace and runway capacity. It is therefore challenging to maximize the number of aircraft performing CDOs for an airport, especially in busy terminal maneuvering areas. In this paper, we tackle the difficulty by developing an aircraft arrival scheduling model to sequence arrival aircraft before their merge point and generate conflict-free trajectories by means of a lateral path stretching method. The contributions of our study to the research community are twofold: firstly, we investigate a new aircraft arrival scheduling problem that incorporates both the CDO trajectory optimization and aircraft scheduling, and develop the first model simultaneously considering these two procedures; secondly, we conduct extensive computational experiments based on historical data in Guangzhou Baiyun International Airport, which would provide an important reference for future research in the area. Our numerical results demonstrate the benefit of the proposed CDO-based aircraft arrival scheduling approach in terms of reducing total flight time and saving fuel consumption when applied in this congested airport.

Comparison of the mean flow and turbulence characteristics of a single offset jet and a dual offset jet

This study compares the mean flow characteristics of a dual offset jet, comprising two 2-dimensional or plane turbulent offset jets, to a single offset jet. An in-house computational model is used to solve the incompressible form of the governing equations which are based on the standard k−ϵ Reynolds Averaged Navier–Stokes turbulence model. The offset ratio, defined as the vertical distance from the solid wall to the jet centreline divided by the nozzle width, of the upper jet is varied from 7 to 13, while the same for the lower jet is equal to 3. The jets’ inlet Reynolds number is 10,000 with a turbulence intensity of 5%. The mean flow results reveal that the presence of the second offset jet greatly influences the flow patterns compared to those of the single offset jet, although at some distance downstream of the inlet, the flow fields of both jet configurations resemble that of a classical wall jet. A single recirculation zone is formed underneath the single offset jet, whereas the flow field of the dual offset jet comprises two recirculation zones, one below the lower jet and the other between the two jets. In the pre-impingement region, the dual offset jet experiences a more rapid decay of the jet half width as compared to the single offset jet; however, the rate of growth of the jet half width for the single offset jet is faster than the dual offset jet. The self-similar solutions confirm that the dual offset jet begins to preserve self-similar characteristics for the mean flow field at a downstream distance greater than that for the single offset jet. For a given offset ratio, the total momentum flux for the single offset jet is found to be greater than that for the dual offset jet. Furthermore, the turbulent Reynolds stresses in the neighbourhood of the merging point are greater for the dual offset jet, but near the reattachment point, they are greater for the single offset jet. No self-similar characteristic of turbulence Reynolds stresses is obtained for both the jets. The turbulent kinetic energy budget reveals the highest value of the production term in the outer shear layer of the lower offset jet for the dual offset jet, which is greater than that for the single offset jet.

Safety Analysis of Merging Vehicles Based on the Speed Difference between on-Ramp and Following Mainstream Vehicles Using NGSIM Data

Highway merging points are critical elements due to the interactions between merging vehicles and following vehicles on the outermost lane of the highway stream. Such interactions could have significant implications for safety and capacity at ramp locations. The aim of this study was to investigate the spacing adjustment behavior by the interacting drivers at merging locations. In this regard, we relied on the NGSIM trajectory dataset to investigate the impacts of the speed difference between the following and merging vehicles on a space headway, considering different geometric designs and vehicle classes. Nonlinear regression models were estimated to analyze the interactions. The results showed a significant and exponential tendency for headway reduction, particularly when the difference in speed was higher than 30 km/h. In addition, the findings revealed that the highway with an auxiliary lane performed better in terms of headway reduction. Furthermore, the space headway reduction trend was higher when the following vehicle was a truck rather than a car. Policymakers and practitioners aiming to improve road safety at merging locations could use this study’s findings. The resulting parameters can also be utilized in microsimulation models, e.g., for headway adjustment behavior in car-following models.

Coordinated regulation of the mitochondrial retrograde response by circadian clock regulators and ANAC017

Mitochondrial retrograde signaling (MRS) supports photosynthetic function under a variety of conditions. Induction of mitochondrial dysfunction with myxothiazol (a specific inhibitor of the mitochondrial bc1 complex) or antimycin A (an inhibitor of the mitochondrial bc1 complex and cyclic electron transport in the chloroplast under light conditions) in the light and dark revealed diurnal control of MRS. This was evidenced by (1) significantly enhanced binding of ANAC017 to promoters in the light compared with the dark in Arabidopsis plants treated with myxothiazol (but not antimycin A), (2) overlap in the experimentally determined binding sites for ANAC017 and circadian clock regulators in the promoters of ANAC013 and AOX1a, (3) a diurnal expression pattern for ANAC017 and transcription factors it regulates, (4) altered expression of ANAC017-regulated genes in circadian clock mutants with and without myxothiazol treatment, and (5) a decrease in the magnitude of LHY and CCA1 expression in an ANAC017-overexpressing line and protein–protein interaction between ANAC017 and PIF4. This study also shows a large difference in transcriptome responses to antimycin A and myxothiazol in the dark: these responses are ANAC017 independent, observed in shoots and roots, similar to biotic challenge and salicylic acid responses, and involve ERF and ZAT transcription factors. This suggests that antimycin A treatment stimulates a second MRS pathway that is mediated or converges with salicylic acid signaling and provides a merging point with chloroplast retrograde signaling.

국내 표준계기도착절차(STAR)의 활용도 및 연속강하접근 운항 비율 분석

In response to the recent surge in aviation demand, major airport and aviation authorities continue to make efforts to formulate arrival procedures that take into account efficient aircraft separation, noise and environmental issues related to carbon (CO₂) emissions. In order to ensure efficient traffic control and environmental issues, as a result, a new concept Trombone, Point Merge, etc. have been introduced and widely used. However, these new concept incisions are becoming a factor that hinders operational efficiency and stability due to the restricted domestic airspace such as military airspace and excessive constraints of altitude, speed, etc. which do not reflect the concept of continuous descent operation and eventually needs to be modified to make continuous descent operation as feasible as possible. We herewith analyze and propose the way of improving flight safety and efficiency in the arrival operation procedure by supplementary modification which consequently contribute to the aviation industry international competitiveness.

Mathematical Correlation Study of Nanofluid Flow Merging Points in Entrance Regions

Here, hydrodynamic features of laminar forced nanofluid flow between two parallel plates are numerically investigated, and the results are mathematically discussed. The conventional understanding of developing flow in the entrance region of internal flows is based on the idea that boundary layers start forming at the inlet and merge at some point just before the fully developed section. However, because of the consideration of mass and flow conservation, the entire conception is required to be detailed with appropriate criteria according to the numerical simulations. Hence, nanofluid flow between two parallel plates is solved by ANSYS Fluent 19.3 for laminar forced in an isothermal condition. Two major criteria are studied to find the location of the boundary layer merging points: vorticity and velocity gradient in a direction perpendicular to the flow. The former presents the influential area of wall shear stress, and the latter is the direct infusion of the boundary layer induced by the solid walls. Vorticity for an irrotational flow is obtained by calculating the curl of the velocity. It is found that the merging points for the hydrodynamic boundary layers are considered before the fully developed region. For the first time, in this study, the results of various Reynolds numbers are collected, and correlations are proposed to predict the length of the boundary layer merging location by using a regression analysis of the data.

Cyber Traffic Light: Safe Cooperation for Autonomous Vehicles at Dynamic Intersections

Autonomous driving systems are becoming increasingly feasible and highly expected to be the heart of intelligent transportation systems. To deploy the autonomous driving vehicles on public roads, one of the practical challenges might be safe cooperation and collaboration among multiple vehicles, in particular when conflicts arise on shared road segments, such as road intersections, merge points, construction zones, single-track lanes, and center turn lane. In the current traffic systems, human drivers navigate these regions using a combination of traffic rules, social norms, courtesy, hand signals, and common sense. In this paper, we identify and classify such Dynamic Intersections that might lead to vehicle accidents and/or deadlocks and that might appear almost anytime and anywhere on public roads. In addition, we present a cooperative dynamic intersection protocol that uses on-board perception systems and vehicular communications for peer-to-peer negotiation. Under our protocol, autonomous driving vehicles can create a vehicular communication-based traffic manager named Cyber Traffic Light when congestion arises. Cyber Traffic Light works as a self-organizing, self-planning, and self-optimizing traffic manager, and it allocates the green period for vehicles coming from the multiple directions. Finally, we showed that our decentralized protocol has much higher traffic throughput, compared to two simple protocols while guaranteeing road safety.

Numerical investigation into fuel–air mixing characteristics and cold flow field of single hydrogen-rich Micromix nozzle

As a promising gas turbine combustor for hydrogen-rich syngas, Micromix combustor may produce new design criteria due to its novel structure. Therefore, the mixing characteristics and flow field of single Micromix nozzle with multiple micro-mixing tubes were studied numerically. The results showed that, the Large-Eddy simulation model was more accurate in cold-state prediction of Micromix combustor than the Reynolds averaged equations model. For mixing characteristics, mass diffusion had greater effect on mixing process of hydrogen-rich syngas than momentum-driven diffusion. With the increase of premixing distance, the effect of fuel–air momentum ratio gradually disappeared. And the difference in mixing characteristics was mainly caused by the shear-layer instability at the initial stage of jet. By reducing the jet-direction diameter of micro-mixing tubes, the mixing uniformity improved, indicating that the jet-direction mixing ability was weak, but there was an upper limit of the mixing uniformity. In addition, fuel hole shapes had obvious effect on vortex structure and vorticity, but little impact on mixing characteristics. For the cold flow field, there was a recirculation region between jets near the nozzle outlet, which was helpful for flame stabilization. Compared with the multiple circular jets, the axial scale of recirculation region formed by multiple elliptical jets was larger, the jet merging point and the combined point moved to the burner outlet.

An integrated two‐dimensional merging trajectory optimization model for automated vehicles considering mixed traffic flow

Recently, automated vehicles have been recognized as a promising tool to address the problem of on-ramp merging. However, the complexity of the problem includes ignorance of the vehicle's lateral dynamics, the limitation of the fixed merging point, the mismatch problem caused by the sequential optimization scheme, and the fixed terminal states assumption. These factors make it intractable in practical driving scenarios. This paper proposed an integrated optimization model for on-ramp automated vehicles, which can guide the vehicle to complete the merging behaviour from the ramp lane to the main lane safely and efficiently. A merging path is first constructed in the two-dimensional plane with two critical parameters recommended by a neural network predictor, enabling it to incorporate both longitudinal and lateral dynamics. Then, an integrated Mixed Integer Quadratic Program (MIQP) model is built to determine the optimal velocity profiles and merging gap simultaneously while considering the safety and efficiency factors. Specifically, with the introduction of discretization and linearization techniques, linear collision avoidance constraints and smooth transition constraints can be built, which can address the challenging computational problem. The effectiveness of the proposed model is validated through the microscopic and macroscopic numerical results under different levels of mixed traffic.

Environmental Noise Assessment of Holding Approach Procedures Using a Multi-Level Simulation Framework

Computational models of sufficient quality are indispensable to quantitatively assess aircraft noise reduction measures. Within this study, a multi-level simulation framework is established in order to predict the environmental noise of holding approach procedures by coupling simulation models from three different domains: flight performance calculation employing the base of aircraft data (BADA), jet engine performance using the software Gasturb and aircraft noise simulations based on the software sonAIR. Two different concepts of holding approach procedures are investigated, namely, the vertical holding stack and the linear hold point merge. The study is conducted considering generic air traffic scenarios at a single-runway airport. Thereby, the investigated air traffic is based on a statistical analysis of traffic data at existing airports and thus assumed to be representative. As the aircraft’s noise emission depends on both the aircraft and the engine performance, reliable results can be expected only if all individual challenges and interdependencies are accounted for simultaneously. Addressing this challenge is the main contribution of the presented work. The presented results show the plausibility of the proposed multi-level simulation framework, thus supporting its use to investigate the environmental noise impact of air traffic scenarios.

Combined Safety and Coordination of Connected Automated Vehicles in Merging Area with Featuring Optimal Merging Positions

Freeway on-ramp merging area is deemed to be typical bottlenecks section, which leads to low traffic efficiency, congestions, and frequent accidents. Most existing studies on merging for the connected and automated vehicles focus on merging at a single fixed merging point. However, the problem of coordination between merging vehicle and arterial traffic flow in the acceleration lane is ignored in the existing studies. This study proposes a merging model, which combined safety and coordination of CAVs with featuring optimal merging positions. The proposed model has two stages: one is analysis of merging velocity of the insertable gap and the other one is determining constraint condition of cooperative merging. The outputs of first stage are interval of merging speed and the mergeable range. The outputs of second stage are optional insertable gap and the corresponding driving scheme. Then, a traffic simulation experiment is designed to evaluate the proposed model. The simulation results show that the proposed model can effectively guarantee driving safety and make the merging process smoother with 28.7% reduction in travel time for the CAV merging. Furthermore, the proposed model does not sacrifice the interests of surrounding traffic to assist in CAV merging. The results indicate the promising potential of using the proposed methods can approximately get a fair use of road resources for each CAV.

Anatomical Study of the Close Association between Latissimus Dorsi and Surrounding Muscles. How to Safely Harvest the Muscle?

sBackground We suggested an easy and effective harvesting technique to avoid injury to tissues adjacent to the latissimus dorsi (LD). Methods Between 2007 and 2017, breast reconstruction was performed with an LD flap using the “bottom-up” technique. Medical records were retrospectively reviewed. Data on postoperative complications, results, and follow-up were obtained. Nine cadaveric dissections were performed to assess positional relationships between LD and adjacent muscles based on the ribs where relevant muscles and LD attach. Overall, 78 LD flaps were harvested without complications. Results Average age was 45.4 years. The mean operation time was 260 minutes. There were no abnormalities or injuries in the adjacent fascia and muscles during the flap harvest. Drains were removed at an average of 21.9 days postoperatively. In all cadavers, there was conjoined fascia between the thoracolumbar and LD fasciae. The average level of the merging point between the LD and external oblique muscle (EOM) was 8.9 to 11.1 ribs. The average level of the overlapping point between the LD and serratus posterior inferior (SPI) was 9.5 to 11.1 ribs. Conclusions There are three dangerous zones during LD flap harvesting. The first zone is where the conjoined fascia encompasses the LD and thoracolumbar fasciae. The second zone is where the LD merges with the EOM and the serratus anterior. The third zone is the lower part where the LD merges with the SPI and EOM. The “bottom-up” technique enables a more meticulous and atraumatic operation by beginner flap surgeons.