Spaced Parallel Research Articles

Research on Safety Separation Distance in Paired Approach Based on Monte Carlo Simulation

Faced with the increasing number of flights, efficient and orderly operations have become a critical issue for busy airports. The closely spaced parallel runway paired approach technology has been proven to be an effective solution for increasing runway capacity and operational efficiency. This research focuses on determining the safety separation between paired aircraft, particularly the collision safety limit. This study refines the kinematic modeling process by constructing a three-dimensional kinematic model and advancing the starting point of paired approach, making the simulation process more aligned with reality. Subsequently, the Monte Carlo simulation method is applied, integrating the kinematic model and considering collision risks to simulate the entire paired approach process. Multiple scenarios are created, and simulation experiments are conducted to determine the safety separation between the two paired aircraft. Finally, by adjusting parameter settings and taking the example of the two closely spaced parallel runways at Chongqing Jiangbei International Airport, the correlation between various influencing factors and the safety separation is analyzed. Different scenarios are simulated 100,000 times each, and the results show that the speed difference between the two paired aircraft has the most significant impact on the safety separation, followed by the paired approach mode and runway centerline spacing. The wake turbulence category matching has a minimal effect on the safety separation. The results provide a theoretical basis for airports with closely spaced parallel runways to further reduce the separation between paired aircraft, thereby enhancing airport capacity and runway operational efficiency.

Revealing the phase transition scenario in antiferroelectric thin films by x-ray diffuse scattering

There is no consensus among researchers regarding how phase transitions occur in antiferroelectric (AFE) epitaxial heterostructures, in particular, in heterostructures based on model AFE lead zirconate. The questions about the number of phase transitions in such films and by what mechanism they occur remain controversial. This paper presents a look at the phase transition scenario in two types of epitaxial heterostructures: PbZrO3/Ba[La–Sn]O3/MgO (001) thin films with thicknesses from 25 to 1000 nm and PbZrO3/SrRuO3/SrTiO3 (001) thin film 100 nm thick using the diffuse x-ray scattering in the grazing incidence setup. We register the characteristic butterfly-shaped diffuse scattering (DS) intensity distribution in the HK pseudocubic planes, which corresponds to the anisotropic ferroelectric soft mode. No incommensurate soft mode was observed in the cuts of reciprocal space parallel to the film surface by diffuse scattering. We reproduce the shape of DS distribution at different temperatures by the model based on the dielectric stiffness and the electric polarization correlation tensor in the cubic approximation. Such modeling allows not only to characterize the DS parameters from the challengingly low signal-to-background data set, but also to extract experimentally the sensitivity of the materials with respect to inhomogeneous polarization. While the observed temperature evolution of DS is consistent with the dielectric measurements, the correlation between the DS and the phase transition sequence observed by superstructure reflections is yet to be understood better.

Reconstruction of High-Resolution 3D GPR Data from 2D Profiles: A Multiple-Point Statistical Approach

Ground-penetrating radar (GPR) is a popular geophysical tool for mapping the underground. High-resolution 3D GPR data carry a large amount of information and can greatly help to interpret complex subsurface geometries. However, such data require a dense collection along closely spaced parallel survey lines, which is time consuming and costly. In many cases, for the sake of efficiency, a choice is made during 3D acquisitions to use a larger spacing between the profile lines, resulting in a dense measurement spacing along the lines but a much coarser one in the across-line direction. Simple interpolation methods are then commonly used to increase the sampling before interpretation, which can work well when the subsurface structures are already well sampled in the across-line direction but can distort such structures when this is not the case. In this work, we address the latter problem using a novel multiple-point geostatistical (MPS) simulation methodology. For a considered 3D GPR dataset with reduced sampling in the across-line direction, we attempt to reconstruct a more densely spaced, high-resolution dataset using a series of 2D conditional stochastic simulations in both the along-line and across-line directions. For these simulations, the existing profile data serve as training images from which complex spatial patterns are quantified and reproduced. To reduce discontinuities in the generated 3D spatial structures caused by independent 2D simulations, the target profile being simulated is chosen randomly, and simulations in the along-line and across-line directions are performed alternately. We show the successful application of our approach to 100 MHz synthetic and 200 MHz field GPR data under multiple decimation scenarios where survey lines are regularly deleted from a dense 3D reference dataset, and the corresponding reconstructions are compared with the original data.

Visualisation of educational material in geometry using digital technologies on the Unity 3D platform

Relevance. Digital technologies are progressively being incorporated into the educational framework. Training with the use of digital technologies corresponds to the modern way of life, which is inextricably linked with access to, receipt, and use of information. This entails the modernization of not only the content of education, but also the forms, methods, and means of teaching. Purpose. This study aims to investigate the impact of augmented reality on the spatial abilities and academic performance of students. It involves the development and testing of an educational application for geometry classes to provide interactive material and improve learning efficiency. Methodology. The study used pedagogical experiments, observations, and assessments. The Geometria mobile application with augmented reality for visualizing spatial geometry problems was developed for a tenth-grade geometry textbook. Results. The study involved 40 tenth-graders studying the section "Parallelism in Space". Following the experiment, all participants except for four demonstrated improvements in their prior test outcomes, with ten out of nineteen participants achieving outstanding grades. According to the study results, teachers and students noted the originality of this product and the fact that its use increased the visibility and understanding of the geometric material. Conclusions. A positive experience of using augmented reality technology in the study of stereometry has been obtained. The study highlights the effectiveness of augmented reality in enhancing students' spatial abilities and academic performance in geometry. The results suggest that incorporating digital technologies like augmented reality can significantly improve learning outcomes and engagement in educational settings. Keywords: secondary education system; geometry; spatial thinking; stereometry

Plane and vertical design research on end-around taxiways at high plateau airports

The end-around taxiways have been proven to effectively reduce the risk of runway incursions caused by frequent aircraft crossings on closely spaced parallel runways, thus enhancing airport capacity. This practice has gained popularity in recent years, especially in large airports. However, there is currently limited experience in designing and operating end-around taxiways, particularly in high plateau airports facing challenging conditions such as a high water table and low obstacle clearance gradient. In this paper, we present a case study of the second runway project at a specific airport and propose various operational schemes for end-around taxiway construction, including straight, oblique, and controlled designs. We calculate aircraft payload under different obstacle clearance gradients using flight performance analysis. Taking into account both operational and groundwater levels, we determine the appropriate plane and vertical design of end-around taxiways. The findings of this research provide valuable references for the design of end-around taxiways.

Analysis and Simulation of Lateral Collision Risk under Paired Approach

The paired approach can improve the efficiency of closely spaced parallel runways. Calculating the probability and frequency of horizontal overlap is an indispensable step when evaluating the horizontal collision risk of the paired approach. As the generation of horizontal overlap probability is closely related to horizontal position error, we propose a calculation method of horizontal overlap probability based on position error from the perspective of pilot operation. First, according to the principle of flight mechanics, the attitude adjustment model is established for the horizontal direction of the approach process, and the pilot’s operation model for various position errors is based on the concept of the stochastic process. This attitude adjustment model can replicates the process of the pilot operating the steering column to change the aircraft’s attitude. When combined with the pilot’s operation model, it is possible to simulate the position errors generated during the approach process. Building on this, the horizontal overlapping conditions of two aircraft are analyzed to simulate the horizontal overlap process in the paired approach. The duration and instances of overlap counted and the ratio between these results and the total running time give the overlap probability and frequency. Multiple simulations in MATLAB reveal that higher pilot operating accuracy shortens the time for the aircraft to align with the course, whereas lower accuracy leads to unstable horizontal position errors. Furthermore, the horizontal overlap in paired approaches primarily occurs at the beginning of the procedure, and enhancing the pilot’s operating accuracy does not significantly affect the probability and frequency of horizontal overlap.

A numerical study on dynamic flows past three tandem inclined elliptic cylinders near moving wall

This numerical study focuses on the dynamic flows past three tandem inclined elliptic cylinders of equal spacing parallel to a moving wall using a lattice Boltzmann method. The gap ratio (G/D=0.6–2.5, where G and D are the gap between the wall surface and cylinder center and major axis, respectively), spacing ratio (L/D=1.5–10, where L is the distance of two adjacent cylinder centers), and inclination angle (α=±15°,±30°,±45°—the angle between normal vector and cylinder's major-axis) are explored at Reynolds number Re = 150 (based on D). The intended analysis links hydrodynamic coefficients, wake structures, and spectral analysis in parameter space of α−G/D−L/D to fluid mechanics. The flow is highly adjustable in this space, dividing into seven regimes: overshoot, continuous reattachment, alternative reattachment, wavy, meandering, quasi-coshedding, and coshedding, which are spatially classified into four modes due to flow interference: shear layer, primary, two-layered, and secondary vortex shedding modes. Transitions between adjacent modes determine three boundaries; and hydrodynamic coefficients differ substantially in parameter space. Due to shadowing, the upstream cylinder has a larger drag coefficient than the middle and downstream cylinders, reducing the drag coefficient of upstream cylinder and the lift coefficient of middle and downstream cylinders. α=±45° has the highest lift oscillation among the three cylinders and a small drag coefficient of the upstream cylinder. The moving wall's proximity effect increases the upstream cylinder's lift coefficient for α<0°, being negligible for high G/D across the full L/D range and stabilizing the lift oscillation of three cylinders.

Effects of different restoration stages on soil microbial community composition and diversity in Naolihe Wetland, China.

Soil microorganisms can be used as one of the important indicators of wetland ecosystem restoration. To study the effects of different restoration stages on soil microbial community composition and diversity in Naolihe Wetland, we employed a "time and space parallel" method. Four restoration stages, namely corn field (Corn), short-term restoration wetland (2 years, ST), long-term restoration wetland (8 years, LT) and natural wetland (>25 years, NW), were selected to represent the restoration time and geographical location in Naolihe Nature Wetland. We investigated the composition and diversity of soil microbial communities in different restoration wetland (from corn fields to natural wetlands) by using 16S rRNA and ITS rRNA gene sequencing. We also performed chemical experiments to measure soil enzyme activity and physicochemical properties at each sampling site. The results showed that soil physicochemical properties and enzyme activities significantly differed with the extension of wetland restoration years (p < 0.05). Proteobacteria, Acidobacteria, and Actinobacteria are the most dominant phyla in bacterial. The alpha diversity of soil bacteria was the highest in the corn field (Corn), and ST-LT-NW first decreased and then increased with the extension of wetland restoration years. There are two most dominant phyla (Ascomycota and Mucoromycota) in fungal. However, the alpha diversity of soil fungi was the lowest in the Corn and LT stage, and ST-LT-NW first decreased and then increased with the extension of wetland restoration years. The research findings indicated that the changes in soil physicochemical properties with the extension of wetland restoration years play a significant role in shaping the structure and diversity changes of soil microbial communities. Through the analyses of bacterial and fungal functions using the FUNGuild and FAPROTAX databases, the results showed that the abundance of aerobic bacteria in the soil increased more than that of anaerobic bacteria as the wetland restoration years prolonged, while the abundance of saprotrophic, symbiotic, and pathogenic fungi in the soil significantly decreased with the prolonged wetland restoration years. This study will help us better understand the process of restoration after farmland abandonment, providing valuable reference information for the implementation of a series of wetland ecological restoration projects in the future.

Evaluation and Analysis of the Joint Damming Effect of Small Spacing Parallel Bridges

Evaluation and Analysis of the Joint Damming Effect of Small Spacing Parallel Bridges

A silence meant to be heard: LIGNA’s radio ballet

This article analyzes the role of sound in the transformation of social space and organization of noncentered group action through a case study of the series of radio ballets programmed by the German artist collective LIGNA. Typically, LIGNA uses portable audio devices and wireless technology to disseminate instructions to the radio ballet participants, directing them to make synchronized body gestures but not giving them fixed movement paths or identities. This process creates a conceptualized acoustic space parallel to the physical space, challenges the regulations that come with the privatization of public spaces, and dismantles the dichotomies between inside and outside, public and private, and physical and mental. I argue that the radio ballet participants, who form a decentralized, temporary, and mobile community, can explore new possibilities for political intervention in the public sphere through silent collective performances in which sound not only serves the important function of sidestepping visual censorship and avoiding physical conflict but also provides a new methodology for reshaping the order of social space.

Phenology and radial growth of poplars in wide alley agroforestry systems and the effect on yield of annual intercrops in the first four years of tree age

Silvoarable agroforestry systems have the potential to combat the negative effects of climate change while also enhancing productivity per unit land. Although the growth rate of large-spaced trees remains poorly investigated and the yield of annual intercrops uncertain, silvoarable agroforestry systems with poplar are receiving an ever-growing interest. This study assessed the growth of the new HES (High Environmental Sustainability) poplar clone, Moncalvo, arranged in 40-m spaced parallel alleys with a density of 35 trees ha−1 (SA, silvoarable). Their growth was compared to those cultivated in a specialized poplar plantation (C, control) with 277 trees ha−1, and the agronomic impact on wheat and soybean as intercrops was explored. Measurements took place between 2018 and 2021 during the first 4 years, which represents the midpoint of the expected poplar rotation. Here it was demonstrated that at the end of the investigated period, diameter at breast height was significantly greater (23.8 vs. 20.5 cm, +16%) and the plant height lower (14.3 vs. 15.5 m, −8%) in poplar grown in SA as compared to those in C, likely due to reduced intraspecific competition for environmental resources. In SA, seasonal tree phenology was delayed by approximately two weeks in spring, possibly due to the high sensitivity of poplar to low soil water content and cooler night air temperatures in springtime. The grain yield of wheat was not impaired by tree shading but instead occasionally improved when neighboring the poplar alley (e.g., year 2021: +28% at 12 m from the tree row vs. full sun conditions), while soybean yield was generally reduced (maximum −38% at 6 m from the tree row). This study innovatively studied the growth response of HES poplar clones in silvoarable systems by providing valuable insights into the growth dynamics of trees grown in combination with field crops. It is concluded that poplars in wide spaced alleys of silvoarable systems in temperate climates grow faster than poplars in plantations of high population density due to enhanced access to resources, while future investigations will allow for the identification of clone-specific rotation durations. In the arable tree interrow, winter crops more readily benefit from such agroforestry system than summer crops due to reduced cycle overlap and light competition with the tree canopy.

Enhanced lipophilicity and wear resistance of 20CrMnTi induced by laser surface texturing

Gear transmission is crucial in mechanical engineering, extensively used in automobiles, ships, machine tools, and airplanes. However, as gear systems advance towards higher speeds, heavier loads, and smaller sizes, the tooth surface becomes more prone to pitting, wear, and other failures. The use of laser surface texturing technology has shown great promise in enhancing the hydrophobic and lipophilic properties of material surfaces. Thus, this paper presents a novel approach for machining equally spaced parallel and perpendicular microgrooves on the surface of gear steels (20CrMnTi) to facilitate lubricant storage and enhance the material’s surface lipophilicity. Laser power and scanning speed are optimized as parameters for laser processing to investigate the lipophilic properties, including the contact angle, diffusion velocity, and contact behavior of oil droplets. Comparative analysis of the processed and unprocessed specimens revealed that both static and dynamic contact behaviors are significantly changed. Compared with the unprocessed specimens, the static contact angle of the processed specimens decreases from 47° to 0° and is super lipophilic at different temperatures; the oil droplet diffusion distance increases by a maximum of 1.27 times; the vertical diffusion height increases by a maximum of 2.8 mm; and the wetting hysteresis coefficient increases by a maximum of 2.55 times. Additionally, the friction coefficient decreases during the stable wear phase, and the wear depth is reduced by 33.53 %. The research has demonstrated that the oil-attracting properties of 20CrMnTi can be greatly enhanced using laser micro-nano texture technology. This improves lubrication conditions and wear resistance, providing a novel approach to mitigating failure risks such as pitting and wear in various gear mechanisms. Furthermore, this method effectively extends the service life of gears, making it a valuable tool for gear engineering applications.

Based on point merge for paired approach sequencing on closely spaced parallel runways

Based on point merge for paired approach sequencing on closely spaced parallel runways

Fully Inkjet‐Printed, 2D Materials‐Based Field‐Effect Transistor for Water Sensing

AbstractDespite significant progress in solution‐processing of 2D materials, it remains challenging to reliably print high‐performance semiconducting channels that can be efficiently modulated in a field‐effect transistor (FET). Herein, electrochemically exfoliated MoS2 nanosheets are inkjet‐printed into ultrathin semiconducting channels, resulting in high on/off current ratios up to 103. The reported printing strategy is reliable and general for thin film channel fabrication even in the presence of the ubiquitous coffee‐ring effect. Statistical modeling analysis on the printed pattern profiles suggests that a spaced parallel printing approach can overcome the coffee‐ring effect during inkjet printing, resulting in uniform 2D flake percolation networks. The uniformity of the printed features allows the MoS2 channel to be hundreds of micrometers long, which easily accommodates the typical inkjet printing resolution of tens of micrometers, thereby enabling fully printed FETs. As a proof of concept, FET water sensors are demonstrated using printed MoS2 as the FET channel, and printed graphene as the electrodes and the sensing area. After functionalization of the sensing area, the printed water sensor shows a selective response to Pb2+ in water down to 2 ppb. This work paves the way for additive nanomanufacturing of FET‐based sensors and related devices using 2D nanomaterials.

Study of screwed bamboo connection loaded parallel to fibre

A method for connecting unfilled natural bamboo was proposed, comprising screws and metal plates. The method is commonly used in timber connections, yet in bamboo connections screws are rarely seen, mostly due to the perceived risk of splitting. This study aimed to assess the applicability of screws in bamboo through extensive testing of short-term laterally loaded connection parallel to fibre, including variation of several parameters. An existing timber model was found to be appropriate to estimate the connection yield capacity. In terms of the environmental benefits, connection capacity, stiffness and ductility, the method appears to be an attractive alternative to the common mortar-infilled bolted bamboo connection. The risk of splitting was found to be low provided appropriate spacing parallel and across fibre between screws is provided. The main outcome of the study is the design guidance for the proposed connection, including spacing rules and prediction of the connection capacity.

Time parallelism and Newton-adaptivity of the two-derivative deferred correction discontinuous Galerkin method

In this work, we consider a high-order discretization of compressible viscous flows allowing parallelization both in space and time.The discontinuous Galerkin spectral element method, which is well-suited for massively parallel simulations, is used for spatial discretization. The main novelty in this work is the additional demonstration of time-parallel capabilities within an implicit two-derivative timestepping procedure to further increase the parallel speedup. Temporal parallelism is made possible by a predictor-corrector-type time discretization that allows to split the associated workload onto multiple processors.We identify a homogeneous load balance with respect to the linear (GMRES) iterations on each processor as a key for parallel efficiency. To homogenize the load and to enable practical simulations, an adaptive strategy for Newton’s method is introduced. It is shown that the time-parallel method provides a parallel efficiency of approx. 60−70% on 4−7 computational partitions. Moreover, the capabilities of the novel method for the simulation of large-scale problems are illustrated with a mixed temporal and spatial parallelization on more than 1000 processors.

Accelerating the Assembly of Defect-Free Atomic Arrays with Maximum Parallelisms

Defect-free atomic arrays have been demonstrated as a scalable and fully-controllable platform for quantum simulations and quantum computations. To push the qubit size limit of this platform further, we design an integrated measurement and feedback system, based on field programmable gate array (FPGA), to quickly assemble two-dimensional defect-free atomic array using maximum parallelisms. The total time cost of the rearrangement is first reduced by processing atom detection, atomic occupation analysis, rearrangement strategy formulation, and acousto-optic deflectors (AOD) driving signal generation in parallel in time. Then, by simultaneously moving multiple atoms in the same row (column), we save rearrangement time by parallelism in space. To best utilize these parallelisms, we propose a new algorithm named Tetris algorithm to reassemble atoms to arbitrary target array geometry from two-dimensional stochastically loaded atomic arrays. For an $L \times L$ target array geometry, the number of moves scales as $L$, and the total rearrangement time scales at most as $L^2$. We present the overall performance for different target geometries, and demonstrate a significant reduction in rearrangement time and the potential to scale up defect-free atomic array system to thousands of qubits.

Nonlinear kinematics of space parallel robot with Bricard mechanism

The space parallel robot with Bricard mechanism (SPRBM) is a complex mechanical device used for capturing free-floating space debris. It consists of a 3-RRS (Revolute-Revolute-Spherical Joints) parallel mechanism and a Bricard mechanism. Space debris can be captured by the interior space of the SPRBM. Compared with the conventional manipulator system, the SPRBM can capture a target with an arbitrary shape and motion state if the target can be enwrapped by the mechanism. In addition, it does not impose any stringent requirement on the locations of the capture points on the debris. However, the SPRBM has complex configurations and therefore nonlinear kinematics. This paper presents a detailed kinematics analysis of the SPRBM. The analysis involves the degrees of freedom, singularity, forward and inverse kinematics, workspace, and the trajectory planning method. These analyses and the results provide the fundamentals for modeling and controlling the SPRBM.

Research on wake interval of paired departure at closely spaced parallel runways

AbstractTo assess and improve the operation system of paired takeoff separation and reduce the risk of wake turbulence encounters during paired takeoff, a computational fluid dynamics (CFD) method is used to study the operational conditions and wake turbulence safety intervals of paired takeoff separation mode. Firstly, the safe area of wake turbulence under the paired takeoff separation mode is analyzed, and a safety interval model is constructed. Secondly, the SST k‐ω turbulence model is selected, and a numerical simulation method for the wake flow of the leading aircraft before the pairing is established based on CFD. Finally, a calculation method for the safety interval of paired takeoff separation is established. Taking Hongqiao Airport as an example, A320‐200 and B737‐800 are selected as the leading and trailing aircraft, and the wake flow field is simulated at 0, −1, and −2 m/s crosswind conditions. The simulation results are then used to analyze the operational conditions and safety intervals of paired takeoff separation mode. The results provide data support for the implementation of the paired takeoff separation mode and demonstrate the applicability of the CFD method in studying aircraft wake turbulence.

Premixed Propane–Air Flame Propagation in a Narrow Channel with Obstacles

Flame interaction with obstacles can affect significantly its behavior due to flame front wrinkling, changes in the flame front surface area, and momentum and heat losses. Experimental and theoretical studies in this area are primarily connected with flame acceleration and deflagration to detonation transition. This work is devoted to studying laminar flames propagating in narrow gaps between closely spaced parallel plates (Hele–Shaw cell) in the presence of internal obstacles separating the rectangular channel in two parts (closed and open to the atmosphere) connected by a small hole. The focus of the research is on the penetration of flames through the hole to the adjacent channel part. Experiments are performed for fuel-rich propane–air mixtures; combustion is initiated by spark ignition near the far end of the closed volume. Additionally, numerical simulations are carried out to demonstrate the details of flame behavior prior to and after penetration into the adjacent space. The results obtained may be applicable to various microcombustors; they are also relevant to fire and explosion safety where flame propagation through leakages may promote fast fire spread.