• Korean Journal of Applied Biomechanics
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• v.21 no.1
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• pp.25-29
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• 2011

The purpose of this study was to analyze quantitative and qualitative differences according to shoe type for the grand jete landing in ballet. The subjects for this study were 9 female ballet majors with an average of 12 years of experience. Subjects jumped, performing a front split, and landed on 1 foot, a movement called the grand jete. Analysis was performed on the students' landing. Independent variables were 3 shoe types: split sole, traditional out sole, and 5-toed forefoot shoes, with bare feet as a control group. Dependent variables were vertical passive ground reaction force and qualitative elements. Passive ground reaction force variables(maximum passive peak value, number of passive peaks, passive force-time integral, and center of pressure) were measured by the Kistler 9281B Force Platform. Qualitative elements were comfort, cushioning, pain, and fit. Statistical analysis included both 1-way ANOVA and Tukey's test for follow-up. Finalized data demonstrated that the 5-toed forefoot shoe allows the forefoot to expand and the toes to individually press down upon landing, increasing foot contact with the surface. Five-toed forefoot shoes minimize passive peaks and pain, while increasing comfort, cushioning, and fit. Most ballet movements are composed of jumping, balancing, landing, and spinning. Wearing 5-toed forefoot shoes allows for a natural range of movement in each toe, to improve both technique and balance. Pain and injuries from ballet can be minimized by wearing the correct shoe type. According to this analysis, it is possible to customized ballet shoes to increase the efficiency of techniques and movements.

• Journal of the Ergonomics Society of Korea
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• v.25 no.4
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• pp.115-119
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• 2006

To investigate the effects of independent suspension technology(IST) of hiking boot on the stability and load of foot, eight participants performed medial and lateral drop landing from 33.4cm height and 85cm distance to uneven surface while wearing normal & IST hiking boots. For the stability of foot during the drop landing, the balance angle & suspension angle and rearfoot angle was analyzed using high-speed video analysis. Also kinetic analysis using the force plate and insole pressure measurement was conducted to analyze vertical & breaking ground reaction force and pressure distribution. Not only the balance angle & suspension angle but also rearfoot angle was improved with IST boots for lateral drop landing. These results indicate the IST boots may have the suspension function which keeps the foot to be stable during landing. However the IST boots did not show any effect for medial landing. This might be related to the hardness of medial part of outsole. Therefore the softer outsole of medial part could be recommended. Furthermore the impact force & breaking force and insole pressure were reduced with IST boot. These results means that IST boot has not only cushioning effect but also good grip effect. Therefore the hiking boots applied the independent suspension function may help to reduce fatigue and prevent injury such as ankle sprain in hiking on uneven surface.

• Korean Journal of Applied Biomechanics
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• v.22 no.2
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• pp.237-242
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• 2012

The purpose of this study was (a) to develop carbon nanotube-based shock absorbers for reducing potentially harmful impact forces and excessive foot pronation, and (b) to briefly determine how the effects of carbon nanotube-based shock absorbers on biomechanical variance during drop landing. A university student(age: 24.0 yrs, height: 176.2 cm, weight: 679.5 N) who has no musculoskeletal disorder was recruited as the subject. Hardness, specific gravity, tensile strength, elongation, 100% modulus, tear strength, split tear strength, compression set, resilience, vertical GRF, and loading rate were determined for each material. For each dependent variable, a descriptive statistics was used for different conditions. The property test results showed that tensile strength, tear strength, split tear strength, compression set, and resilience in carbon nanotube-based shock absorbers were greater than general Ethylene Vinyl Acetate(EVA). These indicated that resistance against variable strength in developed carbon nanotube-based shock absorbers were greater than general EVA. In vertical GRF of CNTC was less than those of EVA during drop landing and loading rate of CNTC was greater than EVA. It seems that the use of CNT can be a effective way of reducing and controlling shock from impact.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.580-585
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• 2005

A QRT(Quad-Rotor Type) hovering robot system is developed for quick detection and observation of the circumstances under calamity environment such as indoor fire spots. The UAV(Unmanned Aerial Vehicle) is equipped with four propellers driven by each electric motor, an embedded controller using a DSP, INS(Inertial Navigation System) using 3-axis rate gyros, a CCD camera with wireless communication transmitter for observation, and an ultrasonic range sensor for height control. The developed hovering robot shows stable flying performances under the adoption of RIC(Robust Internal-loop Compensator) based disturbance compensation and the vision based localization method. The UAV can also avoid obstacles using eight IR and four ultrasonic range sensors. The VTOL(Vertical Take-Off and Landing) flying object flies into indoor fire spots and sends the images captured by the CCD camera to the operator. This kind of small-sized UAV can be widely used in various calamity observation fields without danger of human beings under harmful environment.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.459-459
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• 2000

The purpose of this paper is the application of the techniques for the new estimation of robustness for the aircraft systems having structured uncertainties. The basic ideas to analyze the system which is the originally nonlinear is Lyapunov direct theorems. The nonlinear systems have various forms of terms inside the system equations and this investigation is confined in the form of bounded uncertainties. The number of uncertainties will be the degree of freedoms in the calculation of the robust stability regions called the robustness bounds. This proposition adopts the theoretical analysis of the Lyapunov direct methods, that is, the sign properties of the Lyapunov function derivative integrated along finite intervals of time, in place of the original method of the sign properties of the time derivative of the Lyapunov function itself. This is the new sufficient criteria to relax the stability condition and is used to generate techniques for the robust design of control systems with structured perturbations. Using this relaxing stability conditions, in this paper, the quadratic form of Lyapunov function is utilized. In this paper, the practical system of vertical take-off and landing (VTOL) aircraft is analyzed with the proposed stability criteria based upon the Lyapunov direct method. The application of numerical procedures can prove the improvements in estimations of robustness with structured uncertainties. The applicable aircraft system is assumed to be linear with time-varying with nonlinear bounded perturbations.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.56-66
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• 2013

Weight reduction of the VTHL / TSTO type of the reusable launch vehicles using RBCC engines are investigated. To predict weight and thrust of the vehicles, equations of motion are analyzed. Analysis results are compared with specifications of existing launch vehicles for validations. For the mission of inserting 2.5 ton payload to 200 km circular orbit, the case A, which uses the RBCC engine in the 1st stage shows smaller weight than the case B, which uses the RBCC engine in the 2nd stage. The weight of the case A shows only 25.8% of a existing rocket launch vehicle's weight.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.17-25
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• 2017

Vertical reaction force between ground and tire is an important parameter determining the ground behavior characteristics of aircraft. This parameter can be used to calculate the lateral force and friction. However, it is hard to obtain this parameter in real-time when the aircraft is taxiing. Therefore, pre-analysis of ground behavior and vertical reaction force should be conducted using ground simulation results to prevent rollover or hazardous scenarios. In this paper, a Landing Gear and Full-Aircraft model was constructed using VI-Aircraft S/W. The roll behavior of aircraft was analyzed using steering simulation results compared with taxi-test data.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.3
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• pp.52-65
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• 2021

A large amount of time and cost is consumed due to congestions caused by an increasing number of cars which results in a lot of emissions. To overcome these problems, a new electric vertical takeoff and landing (eVTOL) aircraft is being considered. Since vertical take off and landing without a separate runway is realized and electricity is used as a power source, it could solve the saturated ground traffic congestions without emissions. In this paper, the initial sizing was performed based on the Nexus 6HX of Belltextron which is a tilt-ducted fan type. In this study, the electric propulsion system that only uses battery was implemented instead of current Nexus 6HX hybrid electric propulsion. Aerodynamic analyses were performed using OpenVSP and XFLR5. Power-to-weight ratio, wing loading, estimated weight were calculated with these analyses.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.1
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• pp.74-81
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• 2021

UAM(Urban Air Mobility) systems have evolved in the form of helicopters in the 1960~1970s, tiltrotors in the 1980s, small aircraft transportation systems in the 2000s, and electric-powered Vertical Take-Off and Landing (eVTOL) in the 2010s; accordingly, the early heliport has evolved to its current form of a Vertiport. Vertical Takeoff and Landing Sites, Vertiports, are important factors for the successful introduction of UAM, along with the resolution of air traffic control (ATC), air security, and noise problems. However, there are no domestic or international installation standards and guidelines yet. Therefore, in this study, installation standards were prepared by referring to domestic and international case studies, ICAO standards, and MIT research papers. The study proposes to establish standards for Final Approach and Takeoff Area (FATO) as 1.5D, 1D for Touchdown and Lift-Off Area (TLOF), and 1.5D for Safety Area (SA). It also proposes to add "UAM Vertiport Installation Standards" to the 「Act on the Promotion and Foundation of Drone Utilization, Drone Act」.

• International Journal of Internet, Broadcasting and Communication
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• v.14 no.1
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• pp.201-208
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• 2022

As around the world, ground and underground transportation capacity is reaching its limit, centering on urban areas. As urban traffic becomes congested, time and cost are astronomical, and environmental destruction caused by urban pollution is becoming increasingly serious. As a way to solve this problem, the means of flying over the air are in the spotlight as the next generation of future transportation, and the concept of urban air mobility (UAM, Urban Air Mobility) is defined as systematic planning. The development of an electric-powered vertical take-off (eVTOL) aircraft that obtains electric power through a battery using a personal aerial vehicle (PAV) as a means of transportation has accelerated. As the aircraft development of new technology aircraft in the evtol method is actively carried out, the need to prepare systems such as aircraft certification standards, pilot qualification systems, and qualification management is emerging. The Federal Aviation Administration (FAA) and the European Union Aviation Safety Agency (EASA), which lead international standards, announced new special technical conditions and temporary regulations SCVTOL-01, respectively. However, the pilot qualification system for operating the uam aircraft has not yet been clearly announced. Therefore, this paper analyzes the recently announced FAA regulations and EASA regulations to identify differences and directions in perspectives on UAMs and study the existing vertical take-off and landing aircraft (VTOL) pilot qualification system to present directions for qualification classification.