Roll Angle Research Articles

Study on the effect of ocean rolling motion on the thermal–hydraulic performance of supercritical carbon dioxide in horizontal tube

The effect of ocean rolling motion on the flow and heat transfer characteristics of the S-CO2 has been numerically investigated in this article. The results showed that increasing the rolling period makes the influence of rolling motion tend to be gentle. Increasing the maximum rolling angle and the rolling radius will increase the centrifugal and tangential forces on the fluid inside the tube, further making the swing motion of the flow field become more intense. Thus, this directly results in the tube wall temperature oscillation of 10 K to 50 K as well as the total pressure drop fluctuation of about 6%. In addition, the effect of three spatial positions relative to the rolling axis is also investigated. This research work can provide a theoretical reference for the development of marine equipment.

A robust superhydrophobic-superoleophilic PDMS/Al2O3/CM composite ceramic membrane: Stability, efficient emulsified oil/water separation, and anti-pollution performance

To address the issue of membrane fouling and low separation efficiency of ceramic membrane (CM) commonly encountered in oil/water separation, the implementation of a robust superhydrophobic coating on the surface of CM represents a viable and efficacious strategy. This study presented a facile approach for the fabrication of a durable superhydrophobic-superoleophilic composite coating on the surface of CM by the in-situ growth of needle-shaped alumina (Al2O3) followed by the impregnation of a polydimethylsiloxane (PDMS) coating. Various characterization techniques, such as FESEM, XPS, CLSM, bubble point porometer, contact angle etc. were used to characterize the microstructure, surface composition, pore size distribution, and surface characteristics of the PDMS/Al2O3/CM. The mechanical, chemical, and thermal stability were evaluated by means of sandpaper abrasion, tape peeling, immersion tests including organic solvent, acid, and base solutions, and heat treatment. The separation performance, anti-pollution property, and reusability of the modified CM were evaluated by oil/water mixture and water-in-oil emulsion. And the oil/water separation model and anti-fouling mechanism was also elaborated. The results indicated that a homogeneous needle Al2O3 cluster with a micro/nano dual-scale hierarchical roughness was grown on the surface of the CM, and the further introduction of PDMS gave the modified CM excellent superhydrophobicity with a water contact angle (WCA) of ∼160° and a water rolling angle (WOA) of 7.6°. The PDMS/Al2O3/CM composite membrane exhibited remarkable capability in segregating oil/water mixtures, including emulsified water-in-oil. The separation efficiency remained above 99 %, even after 15 cycles of separation. This study presents a simple technique for fabricating a robust superhydrophobic coating onto the Al2O3-based CM surface, which exhibits the potential for application to other ceramic membrane substrates. And the anticipated outcome of this developing is a broad spectrum of industrial applications for emulsified oil/water purification.

Combination of HOSM and FORM for extreme wave-induced response prediction of a ship in nonlinear waves

This paper proposes a method for predicting the extreme values of linear and nonlinear wave-induced responses of a ship in nonlinear waves. The method is based on a combination of the Higher Order Spectrum Method (HOSM) and First Order Reliability Method (FORM), allowing the most-probable wave episodes for extreme values of interest to be efficiently calculated. The proposed HOSM + FORM approach is first applied to extreme wave crest prediction, and the results are validated through comparisons against Monte Carlo simulations. The HOSM + FORM approach is then used to predict the extreme wave-induced vertical bending moment (VBM) distribution in a container ship. The wave-induced VBM is assumed to be linear with respect to the incident wave profile by leveraging pre-computed VBM transfer functions. Finally, the extreme value distribution of nonlinear roll motion in beam seas is investigated. The proposed HOSM + FORM approach is shown to predict the extreme linear and nonlinear wave-induced responses efficiently and accurately. The effect of wave nonlinearity is found to be significant under circumstances where the VBM is sensitive to high-frequency waves or large roll angles are excited by the wave crests.

Biomimetic superhydrophobic matrix constructed on a buffer aluminum layer: A compositing coating for Mg-Li alloy corrosion inhibition

The magnesium-lithium (Mg-Li) alloy, highly valued for its low density and high strength, has been hampered by its susceptibility to corrosion caused by the presence of active Mg and Li elements. In order to enhance the corrosion inhibition performance of Mg-Li alloy, a double-layer coating is fabricated on its surface in this report. Initially, a sealing aluminum layer is deposited onto the alloy using the magnetron sputtering (MS) technique. Subsequently, an alkyl-ketone dimer (AKD) layer is coated onto aluminum by spray method, resulting in a facile formation of superhydrophobic surface (SHS) at room temperature. In-depth characterization of the microstructure, chemical composition, topology and wettability is conducted using scanning electron microscopy, X-ray photoelectron spectroscopy, and contact angle measurement. The resulting aluminum/AKD composite coating exhibits superhydrophobic properties, displaying a static contact angle of 156.3° and a rolling angle of approximately 1°. The low frequency impedance (|Z|0.01 Hz) of the aluminum /AKD coating is ca. 7.85 × 103 Ω cm2, which is around 100 times of magnitude larger than that of bare Mg-Li alloy. Additionally, immersion of the SHS in a 3.5 wt% NaCl solution for 72 h reveals no visible corrosion pitting, confirming the enhanced corrosion resistance of this superhydrophobic coating.

Dynamic Analysis and Numerical Simulation of Arresting Hook Engaging Cable in Carried-Based UAV Landing Process

Carrier-based unmanned aerial vehicles (UAVs) require precise evaluation methods for their landing and arresting safety due to their high autonomy and demanding reliability requirements. In this paper, an efficient and accurate simulation method is presented for studying the arresting hook engaging arresting cable process. The finite element method and multibody dynamics (FEM-MBD) approach is employed. By establishing a rigid–flexible coupling model encompassing the UAV and arresting gear system, the simulation model for the engagement process is obtained. The model incorporates multiple coordinate systems to effectively capture the relative motion between the rigid and flexible components. The model considers the material properties, arresting gear system characteristics, and UAV state during engagement. Verification is conducted by comparing simulation results with experimental data from a referenced arresting hook rebound. Finally, simulations are performed under different touchdown points and roll angles of the UAV to analyze the stress distribution of the hook, center of gravity variations, and the tire touch and rollover cable response. The proposed rigid–flexible coupling arresting dynamics model in this paper enables the effective analysis of the dynamic behavior during the arresting hook engaging arresting cable process.

LARGE-AREA FABRICATION OF A HARD AND WEAR-RESISTANT SUPERHYDROPHOBIC MATERIAl

Different types of superhydrophobic materials have been fabricated by constructing surfaces with low surface energy and micro-nanostructures, most of which are coatings. Due to the fragile rough structure of the coating, it is very easy to lose its superhydrophobic properties when exposed to friction, corrosion, high temperature, and other effects of the external environment. This has largely hindered the large-scale application of superhydrophobic materials. Here, a rigid superhydrophobic material with polyurethane foam as the substrate, polytetrafluoroethylene (PTFE) nanoparticles as the matrix phase, and carbon nanotubes as the reinforcing phase have been reported. The fabricated material showed excellent superhydrophobicity (157∘ ± 1∘) and robustness. The contact angle of the superhydrophobic material surface remained above 150∘ and the rolling angle below 10∘ after 1000 cycles (distance is 40[Formula: see text]m) of abrasion using 800 # sandpaper at pressure of 5[Formula: see text]kPa.

Model-Based Optimization Approach for PID Control of Pitch–Roll UAV Orientation

This study focuses on the modeling and control optimization of the pitch–roll angles orientation in a quad-rotor UAV (unmanned aerial vehicle) drone system. To address the control challenge, PID (proportional–integral–derivative) controllers are used, which have been tuned through a model-based optimization approach. A non-linear model of the system is obtained and further validated experimentally. The model is implemented in Simulink to conduct model-based optimization. The controller design uses an IMC (internal model control) model-based approach to establish the initial parameters for a PID controller. In the subsequent design phase, a multiobjective approach is taken, incorporating weighted cost functions that account for IAE (integral absolute error) and ITAE (integral of time-weighted absolute error) forms, along with battery usage. The outcomes of this design are showcased through simulations and real-world platform testing.

Real Time Estimate and Computational Model of Fighter Aircraft Fuel Gauge System

An onboard program for the fighter aircraft fuel gauge system is developed using a computational model resulting in to an optimal estimate of fuel gauge system. A fighter aircraft has several fuel tanks and the fuel quantity of the fuel tanks is required to be gauged reliably taking into account the various dynamic effects of flight maneuvers like aircraft pitch angle, roll angle and acceleration parameters for aircraft CG management. Real time estimation and computational modeling of fuel gauging system is realised by using the least square estimation numerical method with Microcontroller based Electronic unit. It was seen that the fluctuations in the fuel quantity estimation under the dynamic flight conditions are reduced and fuel gauging accuracy is improved.

Analysis of Roll Decay for Surface-Ship Model Experiments With Uncertainty Estimates

Abstract Roll decay of David Taylor model basin (DTMB) Model 5720, a 23rd-scale free-running model of the research vessel (R/V) Melville, is evaluated with uncertainty estimates. Experimental roll-decay time series was accurately modeled as an exponentially decaying cosine function, which is the solution of a second-order ordinary differential equation for damping coefficient of less than one (N < 1). The curve-fit provides damping coefficient (N), period (T), and offset. Roll period in calm water was dependent on Froude number (Fr) and initial roll angle (a). Roll decay data are from 76 runs for three nominal Froude numbers, Fr = 0, 0.15, and 0.22. The initial roll angle variation was 3 deg–25 deg. The natural roll period was 2.139 ± 0.041 s (±1.9%). The decay coefficient data were approximated by a plane in three dimensions with Fr and initial roll amplitudes (a) as the independent variables. Curve-fit results are compared to decay coefficient by log decrement and period from time between zero crossings. Examples demonstrate average values for a single roll decay event from log decrement are the same as values by the curve-fitting method within uncertainty estimates. The uncertainty estimate for the decay coefficient is significantly less by curve-fit method in comparison to log-decrement method. By log decrement, the relative uncertainty increases with decreasing roll amplitude peak; consequently, focus should be on the damping coefficient at the largest peaks, where the uncertainty is the smallest.

Anti-Icing Properties of a Polyurethane Superhydrophobic Coating on Asphalt Pavement

Snow and ice accumulation on asphalt pavement can increase the risk of traffic issues. The traditional method of removing snow and ice manually or mechanically from the road surface is time-consuming and labor-intensive. Another common method of spraying salt pollutes the surrounding environment. To overcome these issues, the objective of this study is to study a polyurethane superhydrophobic coating on asphalt pavement and characterize its anti-icing and road properties. A polyurethane superhydrophobic coating (PSC) using polyurethane and carbon nanotube particles (CNTPs) was developed in the lab. The contact angle and roll angle tests, surface roughness test, water droplet icing test, differential scanning calorimetry (DSC) test, ice adhesion test, pavement skid resistance test, water permeability test, and load wheel rolling test were conducted. The results show that the static contact angle and the rolling angle of the water droplet on the PSC surface are 161.176° and 6.6°, which satisfy the requirements to be superhydrophobic. The icing time of the water droplet on the asphalt mixture coated with PSC (AMC) is twice that of the surface of the ordinary asphalt mixture (OAM). In the differential scanning calorimetry test, the PSC released heat slower than polyurethane and asphalt binder during the cooling process. The ice adhesion strength of AMC is 82.78% smaller than that of the OAM. This means the PSC has great anti-icing and deicing properties. In addition, the pendulum value on the AMC surface is 45.7, satisfying the pavement skid resistance requirement. The results of the water seepage test show that the AMC is impermeable to water, thus reducing the risk of water damage to the pavement. Finally, the contact angle of the AMC after the indoor load wheel rolling is still greater than 150°, which proves that the PSC has good wear resistance. In summary, the PSC has good anti-icing properties and road performance.

Flight Test Investigation on Loss of Control Due to Flap and Landing Gear Configuration Change

Extension of flaps during landing and take-offs not only increases the lift produced by the wing due to change in camber of the aerofoil but also increases the wing downwash which reduces the angle of attack on the horizontal tail and reduces the tail efficiency resulted in to significant change in pitch attitude, aircraft altitude and airspeed. Lowering of landing gear increases the interference drag and lead to vortex shedding which reduces the pressure underneath the wing, as a result aircraft have pitching down moment. During this phase pilot is pre-occupied and might be distracted and if requisite control input is not provided by the pilot to maintain required aircraft attitude it can lead to uncontrollable flight condition and loss of control in flight. To investigate these effects, Flight tests were carried out on Hansa-3 and Cessna-206H aircraft at IIT Kanpur along with Pilot and on Cirrus Jet SF-50 in X-Plane 11 Flight Simulator. During flight test aircraft exhibited significant change in pitch attitude, roll angle, aircraft altitude and airspeed and aircraft even stalled. Extension of flaps with 30° bank along with extended landing gear has given more stability to the aircraft and increase in pitch attitude and altitude was less in comparison of retracted Landing Gear.

Airborne hydrocarbon induced multifunctional coating towards bouncing characteristics, icing delaying, hot-water repellency, and anti-corrosion on copper

Some studies have confirmed copper coating can realize superhydrophobicity after exposure to air. However, the comprehensive characteristics of the special wettable coating such as surface energy, bouncing behavior, hot water repellency, icing delaying, and corrosion resistance are still not well understood. Here, without further chemical processing, an electrodeposition technique creates a superhydrophobic layer on a copper substrate. The wettability versus different exposure routes is investigated. As a result, the slow oxidation of Cu and adsorption of airborne hydrocarbon contribute to a low rolling angle and enhanced water droplet bouncing ability. The coating displays strong 95 °C hot water repellency, icing delaying (∼78s), and great anti-corrosion ability, which also has a high protection efficiency (98.84%) and an improved coating resistance of 2.198 × 105 Ω cm2. The multifunctional properties are attributed to the airborne hydrocarbon and the constructed hierarchical structure. This preparation process avoids complex chemical modification and it can provide a new strategy for designing multifunctional coating for surface protection on metals.

Relative roll control of satellite docking using electromagnetic coils

An electromagnetic coil topology and its control strategy, which can be incorporated into the electromagnetic docking device, have been proposed for the relative roll control of two satellites in space. The target satellite and the chaser satellite are respectively embarked with four and six coils evenly arranged around the docking axis. All the coils on the target satellite are Direct Current (DC) energized, while the currents in the coils of the chaser satellite are regulated to achieve the relative roll control. The electromagnetic force/torque model is built by utilizing the frequently-used far field model. Based on the fundamental components extracted from that model, this paper proposes a real-time magnetic moment vector distribution formula that simply generates a constant roll torque. This paper not only presents an equation for calculating the relative roll angle through the Euler angles of two satellites, but also an equation that converts the roll torque setpoint to the setpoints of the coil currents. A 3-closed-loop positioning controller composed of angle, angular velocity, and current loop is developed. The proposed topology is verified by finite element simulation, and the control strategy is validated by dynamics simulation and ground-based tests.

Evaluation of Parametric Roll Mode Applying the IMO Second Generation Intact Stability Criteria for 13K Chemical Tanker

In this paper, the evaluation procedure for Level 1, Level 2A, and Level 2B for the parametric roll among the five modes of the IMO second generation stability criteria was explained in detail. Parametric roll mode evaluation was performed using the design data of a medium-sized 13K chemical tanker instead of a well-known container ship. As a result of the Level 1 evaluation, δGM1/GM was smaller than the standard value, thus satisfying the first criterion, but the second criterion value was smaller than 1, so it was found that the Level 1 criterion was not satisfied. Subsequently, in the Level 2A evaluation, the weighted sum value was larger than the standard value under the ship speed and given wave conditions, so it was also not satisfied. In particular, the process of numerical analysis in the time domain was described through the equation of motion when estimating the maximum roll angle of a ship in the Level 2B evaluation, which was not detailed in previous studies. The calculation result was larger than the standard value, so it was not satisfied, and consequently, the 13K chemical tanker did not satisfy Level 1, Level 2A, and 2B.

Three-dimensional low-order fixed-time integrated guidance and control for STT missile with strap-down seeker

Strap-down seeker is rigidly fixed onto the missile body, which results in detection information being coupled to the missile’s attitude and having a narrow field-of-view (FOV). During the terminal guidance flight, attitude adjustment of the missile may lose the target’s lock and reduce interception accuracy. Therefore, this paper investigates three-dimensional integrated guidance and control (IGC) under the constraints of the FOV and roll angle for skid-to-turn (STT) missile with strap-down seeker. A new low-order IGC model is constructed by establishing a second-order model of body line-of-sight (BLOS) angle based on strap-down decoupling theory and combining it with the second-order roll angle equation. Furthermore, a low-order fixed-time IGC scheme is developed using the integral barrier Lyapunov function (iBLF) to limit BLOS and roll angles. Fixed-time filter, which avoids the “complexity explosion” caused by conventional back-stepping technique, is utilized for obtaining virtual control command and its derivative. A fixed-time disturbance observer is introduced to compensate for the lumped disturbance. According to Lyapunov stability theory, it is proven that the proposed IGC scheme can make the closed-loop system converge within a fixed time. Finally, the effectiveness and robustness of the IGC scheme are verified by various numerical simulations.

Fabrication of periodic hierarchical structures with anti-icing performance by direct laser interference lithography and hydrothermal treatment

Ice accumulation could result in a massive economic burden as well as major life safety issues. Because of their immense potential to ease icing problems, superhydrophobic structures have captured the curiosity of many researchers. Herein, the periodic hierarchical porous structures that have outstanding anti-icing performance were created using two-beam direct laser interference lithography and hydrothermal treatment. The periodic hierarchical porous structures were composed of periodic micro ridge arrays covered with interlaced grown standing nanoflakes. The high-water repellency of the periodic hierarchical porous structures was characterized by the high contact angle and the low rolling angle of 163.7° ± 1.5° and 3.4° ± 0.8°, respectively. The high-water repellency of the periodic hierarchical porous structures exhibits a long-term stability in air and durability in contact with water. The experimental results indicated that the anti-icing performance of the periodic hierarchical porous structures was achieved through the long-term inhibition of ice nucleation and low ice adhesion strength. The ice nucleation inhibition time could reach up to 378 s, which was more than 11.8 times longer than the untreated surface. The ice adhesion strength could be reduced to 48.3 kPa, which was more than 6.3 times lower than the untreated surface. The proposed manufacturing strategy and designed structures could be useful for designing anti-icing structures.

An Experimental Study on the Influence of the Fractal Characteristics of X80 Steel Surface Morphology on Water Ring Stability

The surface morphology of X80 steel with hydrophilic underwater oleophobic characteristic is described greater comprehensively and quantitatively in this work by combining fractal dimension and multifractal. X80 steel with hydrophilic underwater oleophobic surface characteristics was constructed using a chemical etching method. Then, with the aid of three wettability parameters—contact angle, rolling angle, and adhesion work—this study investigated the relationship between the surface fractal dimension of X80 and the stability of the water ring in the core annular flow. The results showed that: (1) the fractal dimension of X80 steel specimens increased first and then decreased with the increase of reaction time. Besides that, the value of it was greater than 2, indicating that the surface had obvious fractal characteristics. The spectral difference, Δf(α), and the spectral width, Δα, supplemented the description of the X80 steel surface morphology, which was consistent with the scanning electron microscope results. (2) When the maximum fractal dimension was 2.0808, the minimum contact angle of distilled water on its surface was 50.2°, and the maximum contact angle of underwater oil droplets was 166.4°. The larger the fractal dimension of X80 steel with hydrophilic underwater oleophobic properties, the more hydrophilic and underwater oleophobic it is. This illustrated that there was a strong binding force between the water and the X80 steel pipe wall, and hence the quality and efficiency of the core annular flow was improved, which was more conducive to the promotion of this technology in the field of heavy oil transportation.

Gantry triggered x-ray verification during single-isocenter stereotactic radiosurgery: Increased certainty for a no-margin strategy

BackgroundSingle-isocenter linac-based stereotactic radiosurgery (SRS) has emerged as a dedicated treatment option for multiple brain metastases. Consequently, image-guidance for patient positioning and motion management has become very important. The purpose of this study was to analyze intra-fraction errors measured with stereoscopic x-rays and their impact on the dose distribution. Materials and methodsTreatments were planned with non– coplanar dynamic conformal arcs for 33 patients corresponding to 127 brain lesions and 356 arcs. Intra-arc positioning errors were measuredusing stereoscopic x-rays (ExacTrac Dynamic, Brainlab), triggered during arc delivery. Couch corrections above 0.7 mm and 0.5° were always applied. Intra-arc positioning data was analyzed. The dose impact was evaluated by applying the measured errors to the dose given in each arc. ResultsMedian residual errors were 0.10 mm, 0.13 mm and 0.08 mm for the lateral, longitudinal and vertical directions and 0.10°, 0.08° and 0.13° for the pitch, roll and yaw angles respectively. 90% of the treatment arcs showed shifts of less than 0.4 mm and 0.4°in all directions. Dosimetric impact of motion showed the largest losses in coverage on small targets. All targets achieved at least 95% of the prescription dose to 95% of their volume, even when planned without margins. ConclusionsIntra-fractional errors measured during beam delivery were found to be notably low with a dose impact that showed acceptable target coverage when applying these intra-arc errors to the dose distributions of the individual treatment arcs. Using an adequate immobilization and intra-fraction imaging prior to and during irradiation, no margins need to be added to compensate for intra-fraction motion.

Building element recognition with MTL-AINet considering view perspectives

Abstract The reconstruction and analysis of building models are crucial for the construction of smart cities. A refined building model can provide a reliable data support for data analysis and intelligent management of smart cities. The colors, textures, and geometric forms of building elements, such as building outlines, doors, windows, roof skylights, roof ridges, and advertisements, are diverse; therefore, it is challenging to accurately identify the various details of buildings. This article proposes the Multi-Task Learning AINet method that considers features such as color, texture, direction, and roll angle for building element recognition. The AINet is used as the basis function; the semantic projection map of color and texture, and direction and roll angle is used for multi-task learning, and the complex building facade is divided into similar semantic patches. Thereafter, the multi-semantic features are combined using hierarchical clustering with a region adjacency graph and the nearest neighbor graph to achieve an accurate recognition of building elements. The experimental results show that the proposed method has a higher accuracy for building detailed edges and can accurately extract detailed elements.

Sensory prediction error drives subconscious motor learning outside of the laboratory.

Sensorimotor adaptation is supported by at least two parallel learning systems: an intentionally controlled explicit strategy and an involuntary implicit learning system. Past work focused on constrained reaches or finger movements in laboratory environments has shown subconscious learning systems to be driven in part by sensory prediction error (SPE), i.e., the mismatch between the realized and expected outcome of an action. We designed a ball rolling task to explore whether SPEs can drive implicit motor adaptation during complex whole body movements that impart physical motion on external objects. After applying a visual shift, participants rapidly adapted their rolling angles to reduce the error between the ball and the target. We removed all visual feedback and told participants to aim their throw directly toward the primary target, revealing an unintentional 5.06° implicit adjustment to reach angles that decayed over time. To determine whether this implicit adaptation was driven by SPE, we gave participants a second aiming target that would "solve" the visual shift, as in the study by Mazzoni and Krakauer (Mazzoni P, Krakauer JW. J Neurosci 26: 3642-3645, 2006). Remarkably, after rapidly reducing ball-rolling error to zero (due to enhancements in strategic aiming), the additional aiming target caused rolling angles to deviate beyond the primary target by 3.15°. This involuntary overcompensation, which worsened task performance, is a hallmark of SPE-driven implicit learning. These results show that SPE-driven implicit processes, previously observed within simplified finger or planar reaching movements, actively contribute to motor adaptation in more complex naturalistic skill-based tasks.NEW & NOTEWORTHY Implicit and explicit learning systems have been detected using simple, constrained movements inside the laboratory. How these systems impact movements during complex whole body, skill-based tasks has not been established. Here, we demonstrate that sensory prediction errors significantly impact how a person updates their movements, replicating findings from the laboratory in an unconstrained ball-rolling task. This real-world validation is an important step toward explaining how subconscious learning helps humans execute common motor skills in dynamic environments.