Landing Speed Research Articles

Estimating PM2.5 Concentrations Using an Improved Land Use Regression Model in Zhejiang, China

Fine particulate matter (PM2.5) pollution affects the environment and poses threat to human health. The study of the influence of land use and other factors on PM2.5 is crucial for the rational development and utilization of territorial space. To explore the intrinsic mechanism between PM2.5 pollution and related factors, this study used the land use regression (LUR) model, and introduced geographically weighted regression (GWR), and random forest (RF) to optimize the basic LUR model. The basic LUR model was constructed to predict the annual average PM2.5 concentrations using three elements: artificial surfaces, forest land, and wind speed as explanatory variables, with adjusted R2 of 0.645. The improved LUR models based on GWR and RF, with an adjusted R2 of 0.767 and 0.821, respectively, show better fitting effects. The LUR simulation results show that the PM2.5 pollution in the northern Zhejiang is more serious and concentrated. The concentrations are also higher in regions such as the river valley plains in central Zhejiang and the coastal plains in southeastern Zhejiang. These findings show that pollution emissions should be further reduced and environmental protection should be strengthened.

China’s Transport Land: Spatiotemporal Expansion Characteristics and Driving Mechanism

The literature about changes in land use includes many studies of global sustainable development goals, while studies of transport land expansion have been relatively scarce. In this paper, we present an analysis of the spatiotemporal characteristics of transport land expansion in China’s 31 provinces from 2009 to 2017, applying the spatial Dubin model to identify the factors that influenced changes in per capita transport land area (PCTLA). The eastern and western regions have continued to lead the nation in terms of the total area dedicated to transport land. The expansion speed of transport land in the central and western regions, however, has been faster than in the eastern and northeast regions. As for PCTLA, the western region had the greatest amount and the central region the least. Further, PCTLA showed significant spatial autocorrelation. Economic development, government regulations, industrial structure, and the extent of opening up and urbanization had significant positive impacts on PCTLA, while the development of railway freight had a negative impact. This paper concludes with some policy suggestions for optimizing transport investment, accelerating the adjustment of industrial structure and transport structure, and implementing high-quality urbanization. The results should be of interest to those involved in the sustainable development of transport systems.

Bravo Segrave!

Abstract On March 29, 1927, Sir Henry Segrave hurtled down Florida's Daytona Beach to establish a new world land speed record of 203 mph. Two years later, Segrave returned to Daytona Beach to reclaim the land speed record for England, driving at over 231 mph. His achievements were hailed in every leading newspaper in England and the United States. This article interrogates the cultural significance of Segrave's feats and argues that Segrave personified an era intoxicated with the allure of speed and infatuated with the power of the machine. Segrave also straddled the cultural divide between the values and virtues of the Victorian era and the emergence of the new technologically sophisticated modern world. Even more significantly, Segrave stood astride a tectonic shift in the place and role of England in the postwar world.

Numerical Analysis of Standing Waves Phenomenon of Aircraft Tires.

In this paper, the generation mechanisms of standing waves on aircraft tires are discussed by comparing the time-domain model and FEA model. Unlike passenger car tires, aircraft tires accelerate to landing speed sharply when the airplane lands. According to the tire structure, the detailed finite element model of the aircraft tires is established in ABAQUS. The tire model runs on a 1.7 m spinning drum and accelerates to 300 km/h in 0.3 s. The proposed finite element model is verified by comparing the simulation results under inflation and static load with the experimental results. Similarly, by analyzing and comparing the calculated values of the time-domain model and FEA model, the variation of standing wave wavelength at different speeds is studied. In addition, the stress and strain field of the aircraft tires standing wave is analyzed. According to the definition of tire standing wave, a method for determining critical speed is proposed. Finally, the effects of tire inflation pressure and vertical load on the occurrence of standing waves were studied.

Fall arrest strategy training improves upper body response time compared to standard fall prevention exercise in older women: A randomized trial

Introduction Exercise can decrease fall risk in older adults but less is known about training to reduce injury risk in the event a fall is unavoidable. The purpose of this study was to compare standard fall prevention exercises to novel Fall Arrest Strategy Training (FAST); exercises designed to improve upper body capacity to reduce fall-injury risk in older women. Method Forty women (mean age 74.5 years) participated in either Standard (n = 19) or FAST (n = 21) twice per week for 12 weeks. Both interventions included lower body strength, balance, walking practice, agility and education. FAST added exercises designed to enhance forward landing and descent control such as upper body strengthening, speed and practice of landing and descent on outstretched hands. Results Both FAST and Standard significantly improved strength, mobility, balance, and fall risk factors from pre to post-intervention. There was a significant time by group interaction effect for upper body response time where FAST improved but Standard did not (p = 0.038). Discussion FAST resulted in similar gains in factors that reduce fall risk as a standard fall prevention program; with the additional benefit of improving speed of arm protective responses; a factor that may help enhance landing position and reduce injury risks such as head impact during a forward fall.

Investigation on the Horizontal Landing Velocity and Pitch Angle Impact on the Soft-Landing Dynamic Characteristics

The dynamic analysis of the soft landing of the lunar probe is very important to the design of the probe. The initial movement and attitude parameters of the probe during landing have a direct influence on the landing impact. In order to investigate the lunar probe soft-landing dynamic impact by different initial horizontal velocities, pitch angles, and inclinations of the lunar slope, an inertial force-based 7-DOF soft-landing dynamic model is applied under two conditions: the upward and downward slope landing surfaces. The impact on the dynamic characteristics of soft landing is analyzed in terms of body displacement, body overload, and the forces of the primary and secondary buffer struts due to the change of initial horizontal velocity and initial pitch angle of the probe. The result shows that, in 2-2 landing mode, the stress conditions on the primary and secondary struts are obviously impacted by initial horizontal velocity, and the initial pitch angle affects the body overload and the loading state of the secondary buffer strut. The body overload and landing impact could be significantly mitigated if the lunar probe’s horizontal landing speed is limited within 1 m/s, the pitch angle is limited within 12°, and the landing is along the uphill terrain with the inclination of the lunar slope less and equal to 9°. The analysis can directly determine the range of the horizontal speed and pitch attitude angle to ensure the safety of landing, and provide a reference for the reasonable control design of the lander’s horizontal speed and pitch attitude.

Electromagnetic damping asteroid landing cushioning mechanism and dynamic simulation analysis

In-situ scientific exploration is of great significance to asteroid exploration, and resource development and utilization. The asteroid surface landing cushioning is the basis of in-situ scientific exploration of asteroids. Therefore, a leg-type asteroid landing cushioning device is proposed based on the principle of electromagnetic damping. A dynamic simulation model is used to study the cushioning dynamics of the cushioning device in a microgravity environment. For the proposed landing cushioning device, the simulation investigates the influence of vertical landing speed and landing vertical tilt angle on the dynamic characteristics and landing stability. The dynamics simulation method is also adopted to investigate the influence of the landing horizontal tilt angle and the horizontal movement direction on the landing stability of the three-legged asteroid probe. The horizontal movement direction and the landing horizontal tilt angle have a coupling effect on the landing cushioning dynamics. Finally, based on the developed simulation device of asteroid microgravity environment, landing cushioning experiments are conducted to investigate the influence of soft and hard landing media on the cushioning process and verify the feasibility of the landing cushioning device. The comparison and analysis of the experimental results and the simulation results verify the accuracy of the landing cushioning dynamics simulation method.

Prediction method of construction land expansion speed of ecological city based on BP neural network

In order to solve the problems of low accuracy and poor convergence of traditional urban construction land expansion speed prediction, a new method based on BP neural network for ecological city construction land expansion speed prediction is proposed. On the basis of driving forces state responses (DSR) research framework model, this paper analyses the main components of the driving mechanism model of urban construction land expansion, finds out the driving factors, and verifies the unit root of its time series, as well as causality verification and screening, to establish the driving mechanism model of urban construction land expansion. After preprocessing the data in the model, the BP neural network is constructed to predict the expansion speed of urban construction land. The experimental results show that the proposed method has better convergence and higher prediction accuracy, which provides a reference for related research.

An experimental investigation of salt production improvement by spraying and heating

Several countries around the world currently use the conventional method to produce salt but this has been discovered to have some disadvantages such as dependence on rainfall, air humidity and temperature, land, sunlight, and wind speed. This, however, makes the production dependent on the season of a region such that a high rainfall leads to a decrease in production. Meanwhile, it is possible to produce salt by separating the particles from their water and creating a droplet forced by airflow and heat convection. Therefore, this research was conducted to examine a salt production process using the spraying and heating method which involves the application of a nozzle assisted by a blower and heater. The results showed the use of a nozzle and blower affected the salt production time and weight. The best yield and time were found at 0.1 mm nozzle with 1 h 50 min and 1067.67 g weight respectively while 4.9 m/s blower speed had 1026 g weight in 2 h 5 min. It is also important to note that the salt produced using this method is more white and smoother than using conventional methods.

Pengaruh Kecepatan Landing dan Pemilihan Material terhadap Faktor Keamanan Landing Skid Helikopter Tanpa Awak Menggunakan Ansys Workbench

Landing skids are an important component of uncrewed helicopters. The landing skid acts as a support when the helicopter lands or is parked. This paper examines the effect of landing speed and material selection on the safety factor of uncrewed helicopter landing skids using Ansys Workbench. The uncrewed helicopter weighs 100 kg and an impact time of 0.5 seconds. Landing speed variations are 2 m/s, 3 m/s, and 4 m/s. The materials used in the simulation are plastic types, namely ABS, HDPE, Polyamide (PA6), and Polycarbonate (PC). The simulation results show that the ABS and HDPE materials can only withstand impact loads up to a landing speed of 3 m/s because they have a safety factor of 3.57 and 3.69, respectively. Meanwhile, Polyamide (PA6) and Polycarbonate (PC) can withstand impact loads up to a landing speed of 4 m/s because they have a safety factor of 4.19 and 6.03, respectively

Determinant analysis and developing evaluation indicators of grade of execution score of double axel jump in figure skating

ABSTRACT A figure skating jump score is determined by the sum of the base value based on the difficulty and grade of execution (GOE) that indicates the performance quality. Therefore, performing a high-quality jump to obtain a high GOE is essential to win a competition. However, the relationship between the GOE and kinematic parameters remains unclear. We analysed the horizontal distance, vertical height, and landing speed of double axel jumps in the Ladies’ Short Program at the 2019 World Championships. The highest GOE group had significantly larger horizontal distances than the middle and lower groups, while the landing speed and vertical height were not significantly different. A principal component regression analysis was conducted to clarify the contrast between the three variables affecting the GOE. The results showed that greater horizontal distance and landing speed compared to vertical height (component 1) and greater horizontal distance compared to landing speed (component 3) contributed to higher GOE. We divided skaters into four clusters using these two components and provided general GOE acquisition strategies for each cluster. Finally, to apply our results to the industry, we proposed two new evaluation indicators which are highly correlated with the two components and easy to interpret.

On the subsonic and low transonic aerodynamic performance of the land speed record car, Bloodhound LSR

The land speed record vehicle, Bloodhound, undertook testing at subsonic and low transonic speeds (up to Mach 0.8) at Hakskeen Pan, South Africa, during October and November of 2019. A decade of CFD-led aerodynamic design had been undertaken to produce a vehicle with the aim of minimised Mach number aerodynamic dependencies and minimised overall drag. This paper sets out and explains the measured pressure distributions with a focus on the highest speed run of Bloodhound up to a peak speed of 628 mile/h. It compares the measured aerodynamic performance with the various CFD model predictions used throughout the design process showing that, whilst localised discrepancies between CFD model and real behaviour exist, overall the Reynolds-averaged Navier–Stokes (RANS)-based CFD tools used to design the car did result in sufficiently accurate aerodynamic data to predict the overall vehicle performance to a high degree of accuracy. The work outlined in this paper, and the conclusions and recommendations drawn, form the basis for a future record attempt and the understanding of what will be required in principle to extend the World Land Speed Record to 1000 mile/h. It also provides guidance on how to effectively make use of RANS-based CFD modelling predictions for other complex, ground-interacting high-speed applications.

Aerodynamic Analysis of a Supersonic Transport Aircraft at Landing Speed Conditions

Supersonic flight for commercial aviation is gaining a renewed interest, especially for business aviation, which demands the reduction of flight times for transcontinental routes. So far, the promise of civil supersonic flight has only been afforded by the Concorde and Tupolev T-144 aircraft. However, little or nothing can be found about the aerodynamics of these aeroshapes, the knowledge of which is extremely interesting to obtain before the development of the next-generation high-speed aircraft. Therefore, the present research effort aimed at filling in the lack of data on a Concorde-like aeroshape by focusing on evaluating the aerodynamics of a complete aircraft configuration under low-speed conditions, close to those of the approach and landing phase. In this framework, the present paper focuses on the CFD study of the longitudinal aerodynamics of a Concorde-like, tailless, delta-ogee wing seamlessly integrated onto a Sears–Haack body fuselage, suitable for civil transportation. The drag polar at a Mach number equal to 0.24 at a 30 m altitude was computed for a wide range of angles of attack (0∘,60∘), with a steady RANS simulation to provide the feedback of the aerodynamic behaviour post breakdown, useful for a preliminary design. The vortex-lift contribution to the aerodynamic coefficients was accounted for in the longitudinal flight condition. The results were in agreement with the analytical theory of the delta-wing. Flowfield sensitivity to the angle of attack at near-stall and post-stall flight attitudes confirmed the literature results. Furthermore, the longitudinal static stability was addressed. The CFD simulation also evidenced a static instability condition arising for 15∘≤α≤20∘ due to vortex breakdown, which was accounted for.

Simulation Optimization of Backrest Mechanism of Separable Bed Chair System

Research and design an intelligent bed and chair integration system for assisting inconvenient mobility and aging population. The system consists of a removable detached wheelchair and a c-shaped bed with a fixed structure. The user can switch freely between the mobile wheelchair and the bed to meet the user's requirements of free movement and repositioning.Through the simulation software to analyze the movement characteristics of the bed backboard, the angle of the take-off and landing of the backboard and the sudden change of the take-off and abrupt angular velocity will cause the user to have dizziness and discomfort. In the case of determining the speed of the driving push rod, the relationship between mechanism parameters and installation parameters is the key to affect the lifting rate of the rear plate. Modeling and analysis of each mechanism is performed to determine the relationship between the mechanism parameters and the take-off and landing speed of the backplane. After optimizing the mechanism, the simulation is compared again to obtain the optimal solution. Finally, the optimal solution parameter is the final solution to improve the overall comfort of the nursing bed.

Modified PDMS with inserted hydrophilic particles for water harvesting

Invisible water is viewed as a potential resource for plants grown in deserts. Amphiphilic surfaces with good flexibility and coalescence are desired for water harvesting applications, but they cannot be precisely controlled. Inspired by desert beetles, we present an amphiphilic surface array that can rapidly condense and slide water droplets. The surface consists of a hydrophilic particle array inserted on a hydrophobic substrate of PDMS mixed with graphene powder. SEM images showed that Fe-particles with different dimensions inserted on an amphiphilic surface enabled the formation of hydrophilic islands. The rapid dropping frequency and landing speed tiny drops were due to the presence of more hydrophobic spaces between single hydrophilic spots and the suitable size of hydrophilic spots. We further demonstrated that the Amphiphilic-15 surfaces, due to its suitable hydrophilic spots size matching with favorable hydrophobic space, outperforms hydrophobic, hydrophilic, and other surfaces during water harvesting.

Aerodynamics Characteristics of Compound Delta Wing at Sea Level

Compound delta-wing aircraft are in the top tier for great maneuverability and satisfactory take-off and landing speeds and low distance as delta wing have a property of vortex generation at different speeds, during flight the property of vortex generated depends on factors like the coefficient of lift, coefficient of drag and shock wave impact absorption upon varying speed from subsonic speed and supersonic speed with changing attack angle is studied by flow visualization of the wing in Ansys Fluent using ’k-ε 2nd equation model’ to simulate mean flow characteristics for turbulent flow conditions. Vortex generation is studied for flow physics at Subsonic speed and Supersonic speed at sea level over Pressure and Density based respectively. The flow velocity at Subsonic is 260m/s and 686m/s for Supersonic. During the experiment, we observed that the vortex flow generation of observable output starts forming at 5° angle of attack following a powerful vortex at 10° leading to a shortfall powerful vortex at 15° for both subsonic and supersonic speeds but as velocity is more in the supersonic state the vortex is denser and more stable and provides better shock absorption while transitioning on higher attack angle and lift force is very sensitive for the supersonic state as drag is substantially increased with speed.

Flow Distortion Into the Core Engine for an Installed Variable Pitch Fan in Reverse Thrust Mode

Abstract The flow distortion at core engine entry for a variable pitch fan (VPF) in reverse thrust mode is described from a realistic flow field obtained using an integrated airframe-engine model. The model includes the VPF, core entry splitter, complete bypass nozzle flow path wrapped in a nacelle, and installed to an airframe in landing configuration through a pylon. A moving ground plane to mimic the rolling runway is included. 3D Reynolds-averaged Navier–Stokes (RANS) solutions are generated at two combinations of VPF stagger angle and rotational speed settings for the entire aircraft landing run from 140 to 20 knots. The internal reverse thrust flow field is characterized by bypass nozzle lip separation, pylon wake, and recirculation of flow turned back from the VPF. A portion of the reverse stream flow turns 180 deg with separation at the splitter leading edge to feed the core engine. The core engine feed flow exhibits circumferential and radial nonuniformities that depend on the reverse flow development at different landing speeds. The temporal dependence of the distorted flow features is also explored by an unsteady Reynolds-averaged Navier–Stokes (URANS) analysis. Total pressure and swirl angle distortion descriptors, as defined by the Society of Automotive Engineers (SAE) S-16 committee, and, total pressure loss into the core engine are described for the core feed flow at different operating conditions and landing speeds. It is observed that the radial intensity of total pressure distortion is critical to core engine operation, while the circumferential intensity is within acceptable limits. Therefore, the baseline sharp splitter edge is replaced by two larger rounded splitter edges of radii, ∼0.1x and ∼0.2x times the core duct height. This was found to reduce the radial intensity of total pressure distortion to acceptable levels. The description of the installed core feed flow distortion, as described in this study, is necessary to ascertain stable core engine operation, which powers the VPF in reverse thrust mode.

The Expansion Mechanism of Rural Residential Land and Implications for Sustainable Regional Development: Evidence from the Baota District in China’s Loess Plateau

Rural residential land is the main space of a farmer’s life, rural culture, and social relations. Prior research of rural residential land has focused more on its evolvement in plain and traditional agricultural areas. Yet, there is no clear picture of rural residential land expansion, especially in ecologically fragile areas. This study analyzed the characteristics of rural residential land expansion based on 30 m spatial resolution land-use datasets of the Baota District of Yan’an City, Shannxi Province, and further explored the influencing factors and mechanisms of rural residential land expansion through binary logistic regression (BLR) modeling. Our findings indicated that the area of rural residential land in the Baota District increased by 116.16% during 1990–2015. More than 75% of the residential land expansion came from the occupation of cropland. Moreover, rural residential land expansion was heterogeneous in the rural regional system. The expansion scale, speed, and mode diversity of rural residential land decreased with the increased distance to urban built-up areas. Geographical conditions and resource endowments are the primary internal driving factors; urbanization and policy implementation are two major external driving forces. The authors suggest that the realization of regional sustainable development in ecologically fragile areas should strengthen urban–rural integration, focus on constructing central towns, and ensure ecological protection measures.

Low-Level Wind Shear Identification along the Glide Path at BCIA by the Pulsed Coherent Doppler Lidar

Low-level wind shear is usually to be a rapidly changing meteorological phenomenon that cannot be ignored in aviation security service by affecting the air speed of landing and take-off aircrafts. The lidar team in Ocean University of China (OUC) carried out the long term particular researches on the low-level wind shear identification and regional wind shear inducement search at Beijing Capital International Airport (BCIA) from 2015 to 2020 by operating several pulsed coherent Doppler lidar (PCDL) systems. On account of the improved glide path scanning strategy and virtual multiple wind anemometers based on the rang height indicator (RHI) modes, the small-scale meteorological phenomenon along the glide path and/or runway center line direction can be captured. In this paper, the device configuration, scanning strategies, and results of the observation data are proposed. The algorithms to identify the low-level wind shear based on the reconstructed headwind profiles data have been tested and proved based on the lidar data obtained from December 2018 to January 2019. High spatial resolution observation data at vertical direction are utilized to study the regional wind shear inducement at the 36L end of BCIA under strong northwest wind conditions.

A comparison of general aviation accidents involving airline pilots and instrument-rated private pilots

Introduction: The extremely low accident rate for U.S air carriers relative to that of general aviation (∼1 and ∼60/million flight hours respectively) partly reflects advanced airman certification, more demanding recurrency training and stringent operational regulations. However, whether such skillset/training/regulations translate into improved safety for airline pilots operating in the general aviation environment is unknown and the aim of this study. Methods: Accidents (1998–2017) involving airline pilots and instrument-rated private pilots (PPL-IFR) operating non-revenue light aircraft were identified from the NTSB accident database. An online survey informed general aviation flight exposure for both pilot cohorts. Statistics used proportion testing and Mann-Whitney U tests. Results: In degraded visibility, 0 and 40% (χ2p = 0.043) of fatal accidents involving airline and PPL-IFR airmen were due to in-flight loss-of-control, respectively. For landing accidents, airline pilots were under-represented for mishaps related to airspeed mismanagement (p = 0.036) relative to PPL-IFR but showed a dis-proportionate count (2X) of ground loss-of-directional control accidents (p = 0.009) the latter likely reflecting a preference for tail-wheel aircraft. The proportion of FAA rule violation-related mishaps by airline pilots was >2X (7 vs. 3%) that for PPL-IFR airmen. Moreover, airline pilots showed a disproportionate (χ2p = 0.021) count of flights below legal minimum altitudes. Not performing an official preflight weather briefing or intentionally operating in instrument conditions without an IFR flight plan represented 43% of airline pilot accidents involving FAA rule infractions. Conclusions: These findings inform safety deficiencies for: (a) airline pilots, landing/ground operations in tail-wheel aircraft and lack of 14CFR 91 familiarization regulations regarding minimum operating altitudes and (b) PPL-IFR airmen in-flight loss-of-control and poor landing speed management. Practical Applications: For PPL-IFR airmen, training/recurrency should focus on unusual attitude recovery and managing approach speeds. Airline pilots should seek additional instructional time regarding landing tail-wheel aircraft and become familiar with 14CFR 91 rules covering minimum altitudes.