Search

Film cooling is used to protect turbine components from the extreme temperatures by ejecting coolant through arrays of holes to create an air buffer from the hot combustion gases. Limitations in traditional machining meant film cooling holes universally have sharp inlets which create separation regions at the hole entrance. The present study uses experimental and computational data to show that these inlet separation are a major cause of performance variation in crossflow fed film cooling holes. Three hole designs were experimentally tested by independently varying the coolant velocity ratio (VR) and the coolant channel velocitty ratio (VRc) to isolate the effects of crossflow on hole performance. Leveraging additive manufacturing technologies, the addition of a 0.25D radius fillet to the inlet of a 7-7-7 shaped hole is shown to significantly improve diffuser usage and significantly reduce variation in performance with VRc. A second AM design used a very large radius of curvature inlet to reduce biasing caused by the inlet crossflow. Experiments showed that this “swept” hole design did minimize biasing of coolant flow to one side of the shaped hole and it significantly reduced variations due to varying VRc. RANS simulations at six VR and three VRc conditions were made for each geometry to better understand how the new geometries changed the velocity field within the hole. The sharp and rounded inlets were seen to have very similar tangential velocity fields and jet biasing. Both AM inlets created more uniform, slower velocity fields entering the diffuser. The results of this paper indicate large improvements in film cooling performance can be found by leveraging AM technology.

Among a variety of additive manufacturing technologies, constrained-surface image-projection-based stereolithography (SLA) technology has unique advantages in printing precision and commercial matu...

Road region and non-road region separation in the unstructured road intends to be an important task for safe navigation and collision avoidance for autonomous driving vehicles. The road that connects rural areas and cities to the national highways are considered as unstructured roads. Absence of clear lane marking on these unstructured roads makes them more prone to accidents in comparison to highways, which have clear lane marking for indication of road and non-road regions. However, the unstructured roads have different color information from its background that paves an easy way for design and development of an efficient road detection system for recognition and classification of road and non-road regions. Hence, in this paper, we propose an efficient road detection system for the classification of unstructured roads into road and non-road regions using multiple nearest neighbors (NN) classifier and soft voting aggregation approach. The proposed system utilized the chromatic information (i.e. *a,*b, and Hue) to train the NN classifiers and aggregated their output using soft voting (SV) approach for final output response. The output results of multiple classifiers were aggregated using SV approach based on the confidence score obtained by each individual classifier. The performance of the proposed system is evaluated in terms of precision, recall, accuracy, intersection over union (IOU), true positive rate (TPR), and processing time and compared with current state of art methods reported in the literature. The proposed system achieved precision, recall, accuracy, IOU, and TPR of 96.79%, 96.92%, 97.8%, 96.08% and 96%, respectively with the processing time three times smaller than those of the existing state of art methods. The experimental results demonstrate that the proposed system can provide an effective guidance to the autonomous vehicles through recognition and classification of road and non-road regions in rural, urban, and city areas, wherein single unstructured roads connect the national highways.

The mega elliptical roundabout is a new idea for intersections on rural multilane highways in the form of an elongated ellipse. Basically, there are no procedures or guidelines for designing the mega elliptical roundabout in the Highway Capacity Manual, Federal Highway Administration guides or the American Association of State Highway and Transportation Officials' ‘Green Book’. This research therefore presents the best geometric design scenarios of mega elliptical roundabout intersections at various traffic flows for all intersection entrances. The basis for selecting the best scenarios is to achieve minimum delay time, minimum emissions and minimum fuel consumption. This was studied at the intersection of a six-lane divided highway with a four-lane divided highway when the traffic enters from four approaches. Moreover, this research proposes the cases in which the mega elliptical roundabout is better than an interchange (full cloverleaf), and suggests the best time to make a decision to change from a mega elliptical roundabout to an interchange (full cloverleaf). The study was conducted by using Vissim software (version 10.00-02). In total, 1134 scenarios were analysed.

Magnetic nanoparticles (MNPs) have unique properties that have made them widely used in medicine and biology. They are easy to work with due to their responsiveness to external magnetic force. Functionalization of nanoparticles(NPs) effectively improves performance, increases stability in the body and acidic environment, and prevents the agglomeration of the particles. One of the important applications of these NPs is in the separation of materials as solid-phase extracting agents. On the other hand, functionalizing these NPs can increase the efficiency, stability, specificity, and sensitivity of the structure to separate the target. In this paper, various material separation studies were collected and classified into several main groups based on material types. Study groups included functional MNPs for separating pathogen, organic and inorganic substances of environmental resources, removal of heavy metal ions, separation of biomolecules, isolation of cells, especially tumor cells, and harvesting the microalgae. The results showed that this method has advantages such as high sensitivity and specificity, is easy to use without needing an operator, low costs, and is a time-saving technique for not requiring sample preparation and concentration.

A radial nonlinear multi-spring-damper tire (RNMST) model is proposed in this paper for dynamics behavior analysis of the cooperative bridge-vehicle (CBV) system by considering different road surface roughness and separation. First, both the finite element (FE) and force analysis of the RNMST model were analyzed and studied under different velocity and different class of road surfaces. The three types of tire models, nonlinear single-spring tire (NSST) model, nonlinear multi-spring tire model and RNMST model, were introduced as the vehicle tire devices for a quarter vehicle models into nonlinear cooperative bridge-vehicle system. The cooperative dynamics problem, alongside separation and the responses of road surface in terms of its uneven nature, is a typical dynamics problem with the nonlinearity of material which can be solved using the Newmark-β method. The comparison of the results demonstrated that the analysis of the dynamics of the cooperative bridge-vehicle system under the RNMST model and NMST model are generally similar. However, the radial nonlinear multi-spring-damper tire model is more accurate and closer to the stress state of the real tire model. Also, to further illustrate the comprehensive performance of the RNMST, the responses under different pavement excitations were analyzed by using the amplitude-frequency spectrum method. Finally, to research the influence dynamics of tire force on the CBV system, the horizontal component of tire force was analyzed. This is conducive to numerical research of the dynamic responses of both the bridge and the vehicle.

Sea-level projections depend sensitively on the parameterization used for basal slip in glacier flow models. During slip over rock-beds, ice-bed separation increases with slip velocity and basal water pressure. We present a method for using these variables and measured bed topography to estimate the average bed slope in contact with ice, ${\bar m}$. Three-dimensional numerical modeling of slip over small areas of former beds has shown that changes in ${\bar m}$ with increasing slip velocity and water pressure mimic changes in basal drag. Computed values of ${\bar m}$ can thus provide the form of the slip law that relates drag to velocity and water pressure, avoiding computationally expensive numerical modeling. The method is applied to 618 sections from four former glacier beds. Results generally show an increase in ${\bar m}$, and hence inferred basal drag, with slip velocity up to a limiting value, consistent with a regularized Coulomb slip law.

Impedance models of modular multilevel convers (MMC) are required to analyze the stability of the MMC-HVDC system. In practical engineering, the positive-negative sequence separation algorithm is the basis of positive- and negative-sequence current control of MMC. Therefore, the influence of sequence separation on the impedance models and stability of MMC system needs to be further studied. This paper develops complete impedance models of the MMC with consideration of all control loops and positive-negative sequence separation, and comprehensively analyzes the impact of sequence separation on impedances and stability of the MMC-HVDC. It is found that the positive-negative sequence separation results in periodic fluctuations in middle and high frequency regions of AC impedance, and distinct fluctuations in middle frequency region of the DC impedance. Meanwhile, the difference in the parameters of the positive- and negative-sequence current controllers will greatly aggravate the fluctuations of both AC and DC impedances, and increase negative damping of the system. Moreover, the analysis reveals that the sequence separation is a key factor weakening the stability of the MMC-HVDC. Finally, the correctness of the impedance models and the theoretical analysis are verified by experimental results.

Inherent uncertainties of the air transportation system (ATS) can induce unexpected anomalies in its operations such as deviations in flight schedules, sudden imbalances of demands and capacities, etc.. Current air traffic flow management (ATFM) models rarely consider both demand and capacity uncertainties in their algorithms, and generally focus on minimizing the flight delays under deterministic constraints. Thus, to bridge this gap, we propose a framework for en-route ATFM while scrutinizing uncertainties in en-route capacity and demand and their imbalance, via a chance constraint based probabilistic approach. The proposed framework plays a key role in ensuring the safety of the overall ATS in terms of maintaining the safety separation between flights and constraining the capacity of the sectors as well. Moreover, flight level assignments scheme is proposed based on the Base of Aircraft Data (BADA) of the European Organization for the Safety of Air Navigation (EUROCONTROL) with the objective of minimizing the fuel consumption. The model further minimizes the overall expected delay of the system using the control actions of ground holding, speed control, rerouting, and flight cancellations. At the implementation stage, two phases of ATFM as pre-tactical and tactical are considered, in which the former focuses on generating optimal trajectories and the latter focuses on real-time updates of flight plans. The computational complexity is reduced by shrinking the feasibility region and decomposing the problem into maximum weighted independent sets. The experimental results of realistic large-scale problems demonstrate the effectiveness and computational feasibility of our ATFM framework.

With unmanned aerial vehicle (UAV) technologies advanced rapidly, many applications have emerged in cities. However, those applications do not widely spread as the safety consideration hinders the UAV from integrating into civilian environment. This work focuses on investigating the UAV emergency landing problem which is a critical safety functionality of UAV. This work proposed a Graph Convolution Networkbased decision network to learn by imitating the human pilots' landing strategy. To alleviate the needs of a large amount of real-world data for model training, the proposed model allows to be trained in a simulated environment and then transferred to the real-world scenario due to the separation of domain-specific terrain classes and domain-independent topological structures among down-looking camera images. The Graph Convolution Network-based decision network can be coupled with a topological heuristic to improve the performance of action prediction in emergency situation. To evaluate the proposed method, this work implemented a simulation environment for collecting data and testing the UAV emergency landing. The empirical results in both simulated and real-world scenario show that the proposed methods can outperform the state-of-the-art counterparts in terms of predictive accuracy and success landing rate.

Background: In recent years, a kind of drilling method of solid-liquid separation combined with pulsating vacuum formed by vibrating screen and compressed air injection has emerged in oil drilling, which profoundly improves the gas, solid, and liquid separation ability of the drilling fluid vibration screen. Objective: Based on the above ideas, a kind of hydrocyclone used for gas-liquid separation with the pulsating feed boundary was proposed. The separation performance of gas-liquid hydrocyclone may change significantly due to the mixed pulsation of the gas-liquid fluid transported by the jet pump. Therefore, the flow characteristics of the pulsating feed hydrocyclone need to be analyzed and explored to provide basic data for further improvement of the structure. Methods: The development status of cyclone separators are summarized through related literature and patent investigation. The Computational Fluid Dynamics (CFD) software ANSYS Fluent 2019 R3 is used to analyze the flow field characteristics and optimize the parameters of the hydrocyclone with stable feed. Then, the programming by the User-Define-Function (UDF) of Fluent is used to simulate the flow field of the separator under the condition of pulsating feed. Meanwhile, the flow field analysis and parameter optimization are carried out accordingly. Results: The optimal parameters in a stable state and pulsed state are obtained from the analysis of the efficiency curve. The results show that the flow field can be stabilized in the pulsating feed state, and the sinusoidal pulsing with a frequency of 0.4 Hz is used to achieve the highest separation efficiency, i.e., 85.5%. Conclusion: The separators with pulsating feed and stable feed have similar flow field characteristics, and the optimal structural parameters under pulsating feed are obtained. Compared with the stable feed condition, the pulsating feed condition can connect multiple cyclone separators, which can separate more drilling fluid in unit time and improve the work efficiency. It has strong practicability, which provides a critical foundation for structure optimization in the future.

Column generation (CG) algorithms are well known to suffer from convergence issues due, mainly, to the degenerate structure of their master problem and the instability associated with the dual variables involved in the process. In the literature, several strategies have been proposed to overcome this issue. These techniques rely either on the modification of the standard CG algorithm or on some prior information about the set of dual optimal solutions. In this paper, we propose a new stabilization framework, which relies on the dynamic generation of aggregated rows from the CG master problem. To evaluate the performance of our method and its flexibility, we consider instances of three different problems, namely, vehicle routing with time windows (VRPTW), bin packing with conflicts (BPPC), and multiperson pose estimation (MPPEP). When solving the VRPTW, the proposed stabilized CG method yields significant improvements in terms of CPU time and number of iterations with respect to a standard CG algorithm. Huge reductions in CPU time are also achieved when solving the BPPC and the MPPEP. For the latter, our method has shown to be competitive when compared with a tailored method. Summary of Contribution: Column generation (CG) algorithms are among the most important and studied solution methods in operations research. CG algorithms are suitable to cope with large-scale problems arising from several real-life applications. The present paper proposes a generic stabilization framework to address two of the main issues found in a CG method: degeneracy in the master problem and massive instability of the dual variables. The newly devised method, called dynamic separation of aggregated rows (dyn-SAR), relies on an extended master problem that contains redundant constraints obtained by aggregating constraints from the original master problem formulation. This new formulation is solved in a column/row generation fashion. The efficacy of the proposed method is tested through an extensive experimental campaign, where we solve three different problems that differ considerably in terms of their constraints and objective function. Despite being a generic framework, dyn-SAR requires the embedded CG algorithm to be tailored to the application at hand.

The deviations of trajectory and attitude angle for internal store separation are evaluated by two wind tunnel test methods. One is the Freedrop Test (FDT), which is known as unsteady and time-dependent method of scaled model. The other is the Captive Trajectory System (CTS) test, which is usually regarded as a quasi-steady and time-averaged test technology. The result shows that there is a streamwise adverse pressure gradient on the cavity resulting in a nose-up pitching moment coefficient (>0) acting on the store model. When the initial pitch angular velocity is 0, the store exits the shear-layer with a nose-up pitch attitude causing the store to climb back towards and collide with the aircraft. However, the store passes through the shear-layer into the freestream with a nose-down pitch, which causes a successful separation event when the initial pitch angular velocity

The laminar boundary-layer separation phenomenon is an interesting and important aspect of boundary-layer flows. It occurs in various physical situations because of a decrease in wall shear stress caused by retarded flow velocity, among other things. Flow separation can be prevented or delayed by utilizing bodies of revolution because the surface transverse curvature produces a favorable pressure gradient, which in turn increases the wall shear stress that keeps the flow attached to the surface. Bodies of revolution, whose body contours follow a power-law form, also play a vital role in delaying flow separation. Bodies of revolution of varying cross sections and involving surface transverse curvature are utilized to examine their effects on flow separation. In particular, a convex transverse curvature has been considered owing to its effects on the nature of the favorable pressure gradient, which delays the flow separation. A Görtler-type retarded flow velocity was considered in this study to investigate the flow separation process. A detailed analysis is provided to understand the flow separation by calculating the separation points under various assumptions. It has been observed that the body contour exponent n and the convex transverse curvature parameter k play an assistive role in the delay of boundary-layer separation even under the influence of strong retardation. The results are presented through various tables and graphs to highlight the role of the power-law exponent of external velocity m, convex transverse curvature parameter k, and body contour exponent n on the separation points.

Suppression of shock-induced separation on all the walls of a rectangular duct using arrays of microvortex generators was experimentally investigated. The flowfield was analyzed using normal and in...

Computer-aided air traffic management has increasingly attracted the interest of the operations research community. This includes, among other tasks, the design of decision support tools for the detection and resolution of conflict situations during flight. Even if numerous optimization approaches have been proposed, there has been little debate toward homogenization. We synthesize the efforts made by the operations research community in the past few decades to provide mathematical models to aid conflict detection and resolution at a tactical level. Different mathematical representations of aircraft separation conditions are presented in a unifying analysis. The models, which hinge on these conditions, are then revisited, providing insight into their computational performance.

We demonstrate a sawtooth-based metasurface approach for flexibly orienting acoustic fields in a microfluidic device driven by surface acoustic waves (SAW), where sub-wavelength channel features can be used to arbitrarily steer acoustic fringes in a microchannel. Compared to other acoustofluidic methods, only a single travelling wave is used, the fluidic pressure field is decoupled from the fluid domain's shape, and steerable pressure fields are a function of a simply constructed polydimethylsiloxane (PDMS) metasurface shape. Our results are relevant to microfluidic applications including the patterning, concentration, focusing, and separation of microparticles and cells.

Modular Solar-Powered Aircraft (M-SPA) is a kind of High-Altitude Long-Endurance (HALE) aircraft which exploits the mission advantage of swarm UAV and the HALE advantage of large aspect-ratio SPA. M-SPA’s separated mode and combined mode give it the potential to maximize the mission efficiency with limited solar energy. In this paper, firstly, oriented by the mission of maximizing the cruise area, the overall design of the M-SPA is modeled, including the energy model, the aerodynamic model and the flight environment settings. Secondly, by analyzing the energy consumption of the flight modes, we design a multi-phase flight mission strategy. Then, a 24-hour three-dimensional (3D) flight profile of the M-SPA is optimized, including the sub-SPA cooperative path planning in the separation mode. Finally, inspired by the Traveling Salesman Problem (TSP), an improved Ant Colony Algorithm (ACA) is exploited to find the optimal path for each sub-SPA, which is further developed into a dynamic separation and combination scheme for the M-SPA. The simulation results show that the mission performance of the M-SPA outperforms that of the conventional SPA, and explicitly, the mission coverage of the M-SPA is slightly less than a linear increase under comparable simulation conditions.

When two trains travel along the same track in the same direction it is a common safety requirement that they should always be separated by at least two signals. If the signals are located at fixed positions that divide the track into sections, then safe separation means there must always be one clear section of track between the two trains. It is desirable to find optimal driving strategies that minimize total tractive energy consumption, but nevertheless allow the trains to reach their final destinations at the designated times, and remain safely separated everywhere. For each signal point there is a corresponding signal-point segment consisting of the two adjacent sections. The two trains can be safely separated on this segment, by specifying a signal-point segment clearance time and requiring that the leading train must leave before the specified time, and the following train must enter after the specified time. If feasible clearance times are specified for all signal points then the trains will be safely separated everywhere. Although the structure of the optimal strategies is well understood there is currently no efficient algorithm for calculating these strategies. In this paper we will show that on level track a Newton iteration can be used to determine the optimal strategies for each feasible set of signal-point clearance times. We also propose and justify a new greedy algorithm that can be used to find sets of optimal clearance times on level track. The theoretical results are illustrated with simple but realistic examples. Refereed/Peer-reviewed

Store separation of a generic, thin-finned, missile through a continuously oscillating shear layer into subsonic flow was conducted experimentally through 100 drop tests to identify potential group...

This study systematically investigates the aerodynamic interactions of a two-rotor system with a front rotor and an aft rotor aligned with the direction of flow. The rotors are 5.5 ftdiameter fixed-pitch rotors operating at approximately 12 lb/ft2 disk loading, representative of large eVTOL aircraft. Fluid flow is simulated using the commercial Navier–Stokes solver, AcuSolve, with a detached eddy simulation (DES) model. Simulations were performed nominally at 40 kt edgewise flight for nine cases corresponding to three values of longitudinal hub–hub separation (2.5R, 3R, 3.5R) and three values of vertical offset (0, 0.25 R, 0.5 R ). Aft rotor performance was compared to an isolated rotor operating in the same conditions in order to quantify the effects of rotor–rotor interaction. For the cases where the aft rotor is closest to the front rotor (2.5R longitudinal offset, zero vertical offset), the aft rotor produced 8.4% less thrust and required 13.4% higher torque than a rotor in isolation. When vertical rotor separation was increased, interactional aerodynamic effects decreased. For a 2.5R longitudinal offset, increasing the vertical offset to 0.5 R decreased the lift deficit to 4.6% and the torque penalty to 6.8%. Increasing the longitudinal offset to 3.5R (while keeping the vertical offset at zero) also reduced interactional aerodynamic effects, but reductions in lift deficit and torque penalty were smaller than those observed with 0.5R vertical offset. Reducing disk loading was found to strengthen interactional aerodynamic effects, with an 11.5% thrust deficit at 6 lb/ft2 compared to 9.0% at 12 lb/ft2. An increase in flight speed also increased interactional aerodynamic penalties from 5.4% thrust deficit at 20 kt to 12.2% at 60 kt. The increased interactional aerodynamic penalties with the reduction in disk loading and increase in flight speed were both attributed to an increase in wake skew angle and the resulting decrease in separation between the aft rotor disk and front rotor wake.

The performance of flighted rotary drums strongly depends on the distribution of the particles across the drum transverse and longitudinal sections. This work aims to determine the design and arrangement of flights that optimize the distribution of the particles in the active region. The prediction of the solids flow was investigated by DEM simulations. A multi-response optimization was performed, in which the obtained best configuration of three-segments flight presented the following internal angles: α1 = 95°, α2 = 130°, and α3 = 145°. The effect of the intercalated position of the flights on particles distribution in the active region was also evaluated. The configuration with the separation distance between flights of 15° promoted an increase of 24.6% in the area occupied by the particles in the active region, and a reduction of 38.5% in dispersion heterogeneity of solids when compared to that of the arrangement of aligned flights.

Satellite videos have recently served as a new data source for a wide range of applications in traffic management and military surveillance. Due to its wider coverage, satellite videos show more advantages in large-scale monitoring than ground surveillance videos. However, pseudomotion background and low-resolution targets pose new challenges to moving vehicle detection in satellite videos, resulting in poor performance of conventional target detection methods when applied to satellite videos. To overcome this difficulty, we propose a novel moving vehicle detection approach using adaptive motion separation and difference accumulated trajectory. Specifically, a new indicator is designed to assist adaptive separation of moving targets and background, considering the scale invariance of vehicles in satellite videos. Meanwhile, we offer a vehicle discrimination algorithm based on a differential accumulated trajectory to distinguish the moving vehicles from the pseudomotion background. Experimental results on two satellite video data sets demonstrate that the proposed approach achieves better detection performance over the state-of-the-art moving vehicle detection methods.

This chapter discusses current developments and latest applied solid–liquid separation technologies and equipment used for coal. It commences with a classification of the different solid–liquid separation technologies used and pre-treatment applied, such as thickening, coagulation and flocculation. It then describes all types of commonly used filters, including vacuum and pressure types, centrifuges such as vibrating basket, screen scroll, screen bowl and solid bowl types with their applications for different coal size fraction or coal tailings. An overview of non-mechanical technologies such as coal drying is given before the chapter closes with a discussion on the emerging and future trends in solid–liquid separation within the coal industry.

Diffracted waves provide an opportunity to detect small-scale subsurface structures because they give wide illumination direction of geologic discontinuities, such as faults, pinch outs, and collapsed columns. However, separating diffracted waves is challenging because diffracted waves have greater geometric amplitude losses and are generally weaker than reflections. To retain more diffracted waves, we have developed a prestack diffraction separation method based on the local slope pattern and plane-wave destruction (PWD) method. In general, it is difficult to distinguish between hyperbolic reflections and hyperbolic diffractions using data-driven local slope estimation in the shot domain. Therefore, we transfer slope estimation in the shot domain to velocity analysis in the common-midpoint domain and ray parameter calculation in the stack domain. The connection between local slope and the normal moveout velocity and the surface-ray parameter is known, which provides a novel approach for estimating the local slope of hyperbolic reflected waves in the shot domain. The estimated slope can provide an exact slope-based operator for the PWD method, thus allowing the PWD to separate diffracted waves from reflected waves in the shot domain. Synthetic and field data tests demonstrate the feasibility and effectiveness of our prestack diffraction separation method.

Synergistic effects of pool fires in fire-induced domino accidents can result in greater damage than single pool fire. Existing research mainly adopts a superposition method based on simplified assumptions to analyze the contribution of synergistic effect of pool fires for domino effects. Therefore, the synergistic effect of pool fires has not been well understood. In this study, a new CFD-based method is developed to model the synergistic effect of pool fires. Case studies were carried out taking double pool fires as an example. The influence of key factors, including wind speed, vertical fire location, fuel type, and separation distance has been investigated quantitatively. The results demonstrated that the proposed CFD based approach can model the consequences of pool fires more comprehensively and assess the domino effects under synergistic effect more precisely than the traditional superposition method. Compared with the single pool fire, the synergistic effect of double pool fires can increase the probability of domino accidents for the adjacent tanks at the downwind by six orders of magnitude. In addition, it is observed that the received maximum radiation heat flux and escalation probability of the target tank in the downwind direction rise with increased wind speed. While the maximum radiation heat flux received by target tanks and escalation probability reduced with increased separation distance and vertical fire location. Moreover, according to the minimum safety distance recommended by present design standards, the synergistic effect of double pool fires in diesel storage tank farms will lead to a higher escalation probability of near equipment than gasoline storage tank farms. This study can be used to predict accident consequences and assess the domino effect under the synergistic effect of pool fires, and guide the layout optimization of the chemical storage tank area.

Visible light communication (VLC) is a promising technology with a high data rate that can supplement radio frequency communication. Although VLC systems have a natural advantage of high security due to the line-of-sight light propagation characteristic, they are still vulnerable when facing an open environment. Device fingerprinting is a technique that is widely viewed to detect transmitter impersonation attack in radio frequency (RF) based wireless systems. In this paper, we introduce the fingerprinting technique to discriminate illegal transmitting devices in VLC systems. We first investigate the hardware imperfections of the VLC transmitter, which can provide a unique device ID. Then we implement a feature separation network for transmitter fingerprinting (TF-FSN) and design a two-stage training strategy to obtain a stable classifier. Finally, we experimentally demonstrate the feasibility and performance of the proposed method. The results show that the accuracy of identification and verification is 92.65% and 98%, respectively. Moreover, our method is robust over different distances and a wide range of signal-to-noise ratios.

In order to efficiently balance the current and future air traffic demands with the system capacity, a proper Air Traffic Flow Management (ATFM) approach is required. The current focus of ATFM is generally on optimally utilizing the available airspace and airport capacities, while maintaining the required safety separation between aircraft. Yet, only a minor focus is given to the inherent uncertainty in the Air Transportation System (ATS), especially to its adverse effect on safety and day-to-day operations. To this end, we propose an ATFM framework scrutinizing the stochastic nature of ATS through a chance-constraint-based probabilistic approach. Moreover, anticipating the high volumes in air traffic in the future, we propose to split the model into two stages, in which the first stage scrutinizes the behavior of a set of flights as a flow, while the second stage transforms them into individual flight plans, enhancing scalability. The two models are formulated as an Integer Linear Programming (ILP) problem, and a Mixed Integer Linear Programming (MILP) problem at stages I and II, respectively. The NP-hard nature of the overall problem is minimized by transforming the problem into a Maximum Weighted Independent Set (MWIS) finding problem.

With the increasing use of terrestrial laser scanning (TLS) technology in the field of forest ecology, a large number of studies have been carried out on the separation of wood and leaves based on TLS point cloud data. However, most wood–leaf separation methods adopt the point-wise classification strategy, which is not efficient for processing large-volume TLS datasets acquired at the forest plot level. In this study, we proposed a segment-wise classification strategy to improve the efficiency of the wood–leaf separation from large-volume TLS point cloud datasets collected at the forest plot. The proposed method first decomposes the point cloud into three parts based on the threshold values of its local curvature. Then, the first two parts with lower local curvatures were segmented respectively by a connected component labelling algorithm. Finally, the segmented point clouds were classified into wood or leaf segments according to the segment-wise geometric features of each segment. We tested our method on both needleleaf and broadleaf forest plots in temperate and tropical forests. We also compared our method with two other state-of-the-art wood–leaf separation methods, that is, the CANUPO and LeWoS. The results showed that our method was more than 10 times faster than the compared methods while maintaining comparable and even higher accuracy. Our study demonstrates that the segment-wise classification strategy applies to the large-volume TLS datasets and can greatly improve the efficiency of the classification. The proposed method is simple, fast and universally applicable to the TLS data from various tree species and forest types at the plot level, which may facilitate the adoption of TLS technology by forest ecologists in their studies.

As a principal reason for the deterioration of separation accuracy, the bypass effect in hydrocyclones has received widely concerned. This paper presents a numerical study about the effect of flat bottom structure width on the bypass effect with the respect of flow field characteristics, separation efficiency, and particle spatial distribution with a verified TFM model. Numerical results demonstrate that wide flat bottom structure increases the cut size and reduces the fine particles misplaced in the underflow. However, the excessive flat bottom structure width increases coarse particles misplaced in the overflow causing by the superior turbulence intensity and the entrapment of the internal swirling flow. A wide flat bottom structure width reduces the turbulence dissipation rate, while the split ratio first decreases and then increases, indicating that the bypass effect is controlled by the turbulence dissipation and does not comply with the trend of the split ratio.

In today’s world, owing to industrial expansion, urbanization, the rapid growth of the human population, and the high standard of living, the utilization of the most advanced technologies is unavoidable. The enhanced anthropogenic activities worldwide result in a continuous increase in global warming potential, thereby raising a global concern. The constant rise in global warming potential forces the world to mitigate greenhouse gases, particularly carbon dioxide. Carbon dioxide is considered as the primary contributor responsible for global warming and climatic changes. The global anthropogenic carbon dioxide emissions released into the atmosphere can eventually deteriorate the environment and endanger the ecosystem. Combating global warming is one of the main challenges in achieving sustainable development. Carbon capture and storage is a potential solution to mitigate carbon dioxide emissions. There are three main methods for carbon capture and storage: post-combustion, pre-combustion, and oxy-fuel combustion. Among them, post-combustion is used in thermal power plants and industrial sectors, all of which contribute a significant amount of carbon dioxide. Different techniques such as physical and chemical absorption, physical and chemical adsorption, membrane separation, and cryogenic distillation used for carbon capture are thoroughly discussed and presented. Currently, there are various materials including absorbents, adsorbents, and membranes used in carbon dioxide capture. Still, there is a search for new and novel materials and processes for separating and capturing carbon dioxide. This review article provides a comprehensive review of different methods, techniques, materials, and processes used for separating and capturing carbon dioxide from significant stationary point sources.

Sand sieving is now considered one of the essential needs in the construction industry. Where businesses collaborate to find the best and highest-quality methods for extracting pure sand suitable for construction. These businesses always require high-quality machines to complete the process flawlessly. This is also to prove its market power and guarantee its products. This research talks about the various mechanisms for designing and manufacturing sand sieving. The sand sieving process expresses the filtering of sand from the rest of the components such as stones or gravel. The literature department studied ten different studies in the design and manufacture of sand sieving machine in different ways. Where these methods vary between using the engine and electricity and using the primitive manual method. After performing these machines several tests and evaluation of the process, it was found that the engine speed affected the energy consumed to sift the sand. Also, the sieve holes are affected by the size of the sifted sand. Where sieves are manufactured in different sizes to suit the size of the sand to be purified. On the other hand, this article contains the future recommendation of the machine to avoid errors and give effective results as needed.

When the separation of the management and ownership right was implemented, famers were entitled to basic residential benefits and the stable development of rural society was maintained. With the rapid development of social urbanization, problems gradually arose concerning the use, management, and transfer of rural homesteads: a large number of idle homesteads, failure in large-scale planting as a result of scattered distribution, and the waste of homesteads, etc. In order to reuse the idle homesteads, increase farmers' income from property, and promote rural revitalization, the central government has proposed the "separation of three rights" system. Combined the policy background with rural development, the paper analyzed the significance of the policy on rural development, the potential risks and principles in implementation from the perspective of historical evolution, policy-making background and policy connotation.

In the paper a mathematical models of technological modes of filtration with automated removal of part of heat from interface surfaces (water purification from multicomponent impurities), backwashing, chemical regeneration and direct washing of rapid cone-shaped adsorption filters with chemical regeneration of piecewise homogeneous porous loads while maintaining constant velocities of the respective modes is formulated. The proposed models in the complex allow to conduct computer experiments to investigate the change in the concentrations of components of a multicomponent impurity in the filtration stream and on the surface of the loading adsorbent, retained by both physical and chemical adsorption, filtration flow temperature, filtration coefficient, active porosity and pressure along the filter height and on their basis to predict more optimal options for the use of adsorbents of each loading layer and increase the protective time of rapid cone-shaped adsorption filters with automated heat removal from the interface surfaces in filter mode.

During peak-hour busy airports have the challenge of turning aircraft around as quickly as possible, which includes sequencing their landings and take-offs with maximum efficiency, without sacrificing safety. This problem, termed aircraft sequencing problem (ASP) has traditionally been hard to solve optimally in real-time, even for flights over a one-hour planning window. In this article, we present a novel data-splitting algorithm to solve the ASP on a single runway with the objective to minimize the total delay in the system both under segregated and mixed mode of operation. The problem is formulated as a 0–1 mixed integer program, taking into account several realistic constraints, including safety separation standards, wide time-windows, and constrained position shifting. Following divide-and-conquer paradigm, the algorithm divides the given set of flights into several disjoint subsets, each of which is optimized using 0–1 MIP while ensuring the optimality of the entire set. One hour peak-traffic instances of this problem, which is NP-hard in general, are computationally difficult to solve with direct application of the commercial solver, as well as existing state-of-the-art dynamic programming method. Using our data-splitting algorithm, various randomly generated instances of the problem can be solved optimally in near real-time, with time savings of over 90%. Civil Aviation Authority of Singapore (CAAS) Nanyang Technological University This research has been partially supported under ATMRI (NTU-CAAS) Grant No. M4061216.

In this study, numerical simulations were carried out to investigate the separation of the helium-argon gas mixture by thermal diffusion column. This research determined the significant parameters and their effects on the process performance. Effects of feed flow rate, cut ratio, and hot wire temperature in a 950 mm height column with an inner tube of 9.5 mm radius were examined through the simulation of the thermal diffusion column. For minimizing the number of simulations and obtaining the optimum operating conditions, response surface methodology (RSM) was used. Analysis of separative work unit (SWU) values as a target function for helium-argon separation clearly showed that the maximum amount of SWU in thermal diffusion column was achieved, when hot wire temperature increased as large as technically possible, and the feed rate and cut ratio were equal to 55 Standard Cubic Centimeters per Minute (SCCM) and 0.44, respectively. Finally, the SWU value in optimum conditions was compared with the experimental data. Results illustrated that the experimental data were in good agreement with simulation data with an accuracy of about 90%.

Achieve high-efficiency dewatering and purification of emulsion is not always feasible using conventional single method. A centrifugal separator embedded in electric field can achieve efficient dem...

An effective approach to determining the parameters of the optimal schemes of the method of laser selective photoionization of atoms (elements and isotopes) with finite ionization due to collisions, ionization by a pulsed electric field, ionization through high (Rydberg) states and narrow autoionization resonances for the separation of heavy isotopes has been proposed. in gas separator devices. On the basis of the theory of optimal control and previously developed quantum models for calculating the characteristics of elementary atomic processes, optimization models of isotope separation are numerically implemented in the scheme of selective laser photoionization with ionization due to collisions in gas mixtures, ionization by a pulsed electric field, autoionization, etc. etc. The data obtained quantitatively confirm the promise of the method of laser photoionization with finite ionization due to collisions, ionization by a pulsed electric field, ionization through high-lying (Rydberg) states and narrow autoionization resonances and give a set of parameters for the desired optimal schemes, in particular, the laser pulse optimal shape for rubidium and uranium isotopes.

The production of plant terpenoids through biotransformation has undoubtedly become one of the research hotspots, and the continuous upgrading of the corresponding downstream technology is also particularly important. Downstream technology is the indispensable technical channel for the industrialization of plant terpenoids. How to efficiently separate high‐purity products from complex microbial fermentation broths or enzyme‐catalyzed reactions to achieve high separation rates, high returns and environmental friendliness has become the focus of research in recent years. This review mainly introduces the common separation methods of plant terpenoids based on biotransformation from the perspectives of engineering strain construction, unit separation technology, product properties and added value. Then, further attention was paid to the application prospects of intelligent cell factories and control in the separation of plant terpenoids. Finally, some current challenges and prospects are proposed, which provide possible directions and guidance for the separation and purification of terpenoids and even industrialization.

The article describes a project to use PLC technology in railway light signs. The proposal presents a solution for the separation of supplying circuits with the use of filters. The necessity of separation is a result of long distance data transmission between sign controllers and LED railway signs using PLC modems which work on the same frequency. Problems in the selection of filter parameters are presented due to the fact that there is no specification for the characteristic of the separation filter, there are only requirements for the reliability communication system. To meet these requirements, the circuits separation efficiency must be assessed. The paper presents a quick method to evaluate separation efficiency. Structure of the network, as well as the set of devices which realize this specific kind of wired sensor network for supervising railway LED sign network and maintenance parameters are also presented in this article.

Connected and autonomous vehicles (CAV) will open the future to vast possibilities in transportation, most of which have yet to be imagined. As these new technologies emerge, they also have the potential to render many of today’s most common transportation control methods irrelevant. In this paper, concepts of connected and autonomous are applied to coordinate and synchronize the arrival and departure of vehicles at intersections; effectively ending the need for traffic signals. Under a set of “autonomous rules of operation”, vehicles can be kept in near-continuous motion while also maintaining safe separation, creating a system of “virtual traffic signal” (VTS). Assessments of these rules shows that delay and stopping reductions of more than 50 to 97 percent will be possible over actuated control and fixed time signal control – and without the risk of collisions. Not will these rules reduce congestion, travel time, and prevent crashes; they will also lower fuel consumption and exhaust emissions.