• Korean Journal of Applied Biomechanics
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• v.20 no.2
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• pp.167-174
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• 2010

This study aims to quantitatively compare and analyze kinetic variables in the motion of male and female professional golfers to suggest basic scientific materials for golf iron swing. Five male and five female professional golfers participated in this experiment. Ground reaction force and foot pressure were measured during performing 10 swings for each participants using an iron club. The result of the ground reaction force indicates that the force occurs at the left foot toward right(-) direction in the mid-downswing(E3) and impact(E4) events in X-axis, while it occurs at the right foot toward anterior(-) direction in Y-axis for both male and female, showing a big difference between them. Also, in Z-axis, large force occurs at the left foot in most events. The analyzed result on foot pressure indicates that men have the highest pressure and area at the left foot, and women have the highest ones at the right foot in the mid-downswing(E3) and impact(E4) events in the max foot pressure, ground contact area and average pressure. It is considered that there is difference of central movement methods between men and women. Thus, different education and training on golf swing should be necessary by gender due to their different patterns of golf iron swing.

• International Journal of Computer Science & Network Security
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• v.22 no.7
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• pp.252-258
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• 2022

Ukraine has a significant in quantity and unique in quality parameters, in particular, the level of education, a resource - the labor force, which, along with natural resources, can serve as the basis for economic growth and the achievement of sustainable development goals. The study is aimed at a thorough identification of the main factors influencing the formation and use of the labor force in Ukraine, including by comparing with the indicators of the EU countries, before the start of the active phase of military aggression by the Russian Federation. It was found that until February 24, 2022, there were negative trends in the change in the quantitative and qualitative indicators of the labor force due to the demographic crisis, the transformation of the national economy and shortcomings in state regulation of labor market development processes. The military actions not only exacerbated pre-existing problems, but also led to the emergence of new ones. A significant number of refugees and internally displaced persons, with the termination of the activities of half of the economic entities, provoked a sharp increase in real unemployment and a decrease in wages. The specific problem of the labor market of Ukraine - the "labor crisis", which has and will have a significant impact on the labor force, is carefully considered.

• Advances in materials Research
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• v.13 no.5
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• pp.391-416
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• 2024

Hybrid composite materials are widely used in various load-bearing structural components of micro - mini UAVs. However, the design of thin laminates for better impact resistance remains a challenge, despite the strong demand for lightweight structures. This work aims to assess the low-velocity impact (LVI) behaviour of thin quasi-isotropic woven carbon/ aramid epoxy hybrid laminates using experimental and numerical techniques. Drop tower impact test with 10 J and 15 J impact energies is performed on carbon/epoxy laminates having aramid layers at different sequences and locations. The impact behaviour is experimentally evaluated using force-time, force-deformation, and energy-time histories considering delamination threshold load, peak load, and laminate deflection. Ultrasonic C-scan is performed on the post-impact samples to analyse the insidious damage profile at different impact energies. The experimental data is further utilized to numerically simulate LVI behaviour by employing the representative volume element model. The numerical results are in good agreement with the experimental data. Numerical and experimental approach predicts that the hybrid laminates with aramid layers at both impact and non-impact sides of the laminate exhibits significant improvement in the overall impact behaviour by having a subcritical damage morphology compared to carbon/epoxy laminate. A combined numerical-experimental approach is proposed for evaluating the effective impact performance.

• Journal of KSNVE
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• v.5 no.4
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• pp.515-524
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• 1995

Tubes in heat exchanger of fuel rods in reactor core are supported at intemediate point by support p0lates or springs. Current practice is, in case of heat exchanger, to allow clearance between tube and support plate for design and manufacturing consideration. And in case of fuel rod the clearance in support point can be generated due to the support spring force relaxation. Flow-induced vibration of a tube can cause it to impact or rub against support plate or against adjacent tubes and can result in fretting-wear. The tube-to- support dynamic interaction is used to relate experimental wear data from single-span test rigs to real multi-span heat exchanger configurations. The dynamic interaction cna be measured during experimental wear tests. However, the dynamic interaction is difficult to measure in real heat exchangers and, therefore, analytical techniques are required to estimate this interaction. This paper describels the nonlinear impact model of DAGS(Dynamic Analysis of Gapped Structure) code which simulates the tube response to external sinusodial or step excitation and predicts tube motion and tube-to-support dynamic interaction. Three experimental measurements-two single span rods excited by sinusodial force and a two span rod impacted by a steel ball are compared from the simulation nonlinear model of DAGS code. The simulation results from DAGS code are in good agreement with measurements. Therefore, the developed model of DAGS code is good analytical tool for estimating tube-to-support dynamic interaction in real heat exchangers.

• Journal of Information Processing Systems
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• v.15 no.6
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• pp.1350-1364
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• 2019

The ice damage occurs frequently in cold and dry region of western China in winter ice period and spring thaw period. In the drift ice condition, it is easy to form different extrusion force or impact force to damage tunnel lining, causing project failure. The failure project could not arrive the original planning and construction goal, giving rise to the water allocation pressure which influences diversion irrigation and farming production in spring. This study conducts the theoretical study on contact-impact algorithm of drift ices crashing diversion tunnel based on the symmetric penalty function in finite element theory. ANSYS/LS-DYNA is adopted as the platform to establish tunnel model and drift ice model. LS-DYNA SOLVER is used as the solver and LS-PREPOST is used to do post-processing, analyzing the damage degrees of drift ices on tunnel. Constructing physical model in the experiment to verify and reveal the impact damage mechanism of drift ices on diversion tunnel. The software simulation results and the experiment results show that tunnel lining surface will form varying degree deformation and failure when drift ices crash tunnel lining on different velocity, different plan size and different thickness of drift ice. The researches also show that there are damages of drift ice impact force on tunnel lining in the thawing period in cold and dry region. By long time water scouring, the tunnel lining surfaces are broken and falling off which breaks the strength and stability of the structure.

• Journal of Korean Association for Spatial Structures
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• v.10 no.4
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• pp.75-83
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• 2010

Laminated composite plates have shown their superiority over metals in applications requiring high specific strength, high specific modulus, and so on. Therefore, they have used in various industry. However, they have poor resistance to impact compared to typical metal materials. So, many researchers have investigated about impact behavior of laminated composite plate. To investigate impact behavior of laminated composite plate, we have to calculate contact force between impactor and laminated composite plate at the first. Impactor's equation of motion, plate's equation of motion and correlations for indentation were solved to know the contact force at the same time. In this study, low velocity impact behavior of composite plate was investigated using the finite element program which is involved the classical Hertzian law, Sun's law and Sun & Yang's experimental law and Sun & Tan's experimental law considering the stacking method.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.311-325
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• 2003

A relation between the movement range of arms and arising moment has been studied to find out efficient movement range to minimize impact concerning arm landing in sports aerobics. Four male athletes who won top three in national-level sports aerobics competition were chosen for the experiment. They were allowed to jump in between two force platform so that the right hand and the right leg could land onto the front and rear force platform, respectively. The sampling frequency was 200 Hz. The main conclusions based on the analysis of the angle and joint moment parameters of wrist, elbow, and shoulder are as follows: 1. The wrist moment was small when its angle was small, indicating that the dorsi-flexion of the wrist joint offered a positive influence to reduce wrist moment. 2. The elbow angle increased as wrist angle decreased and vice versa. This means that the movement range of the wrist joint affects that of the elbow joint. The darsi-flexion of the wrist is the position to absorb the impact of the elbow effectively rather than to absorb the impact of the wrist itself. The impact is absorbed by the flexion of wrist joint rather than the wrist. 3. The degree of moment transfer of the shoulder joint, having absorbed the impact from the elbow and elbow joint, became dependent on the efficiency of the fore-joints impact absorption.

• Structural Engineering and Mechanics
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• v.78 no.1
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• pp.31-39
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• 2021

To investigate numerically the effect of all parameters on the outcome of an aircraft impact into robust engineering structures like nuclear power plant containments is a tedious task. In order to reduce the problem to a manageable size, we propose a single dimensionless parameter, the damage potential, to characterize the main features of the impact. The damage potential, which is the ratio of the initial kinetic energy of the aircraft to the work required to crush it, enables us to find the crucial parameter settings that need to be modelled numerically in detail. We show in this paper that the damage potential is indeed the most important parameter of the impact that determines the time-dependent reaction force when either finite element (FE) modelling or the Riera model is applied. We find that parameters that do not alter the damage potential, like elasticity of the target, are of secondary importance and if parameters are altered in a way that the damage potential remains the same then the course of the impact remains similar. We show, however, that the maximum value of the reaction force can be higher in case of elastic targets than in case of rigid targets due to the vibration of the target. The difference between the Riera and FE model results is also found to depend on the damage potential.

• Korean Journal of Applied Biomechanics
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• v.17 no.3
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• pp.189-195
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• 2007

The purpose of this study was to analyze the effects of shoes with curved out-sole on the pressure, reaction force(sum of pressure) on foot and relations between the rolling speeds and pronation of foot. The foot pressure, reaction force and pressure center on the foot surface of shoe were measured with NOVEL padar system, and 3 type shoes were used to compare the position and speed of pressure center and the foot reaction force, which were s(target) shoe with soft cushions in middle part of out-sole and curved out-sole, m shoes with two type- soft, hard, hardness out-sole and curved out-sole and n shoes with flat out-sole. The subjects were 13 female university students, had weared the 3 type shoes for 6 weeks on two-weeks shifts for adaptation before experiment and put on 3-type shoes repeatedly and randomly and walked on treadmill with 3.5km/h and 80 steps/min. The data were captured with 30Hz and readjusted with 5kgf threshold reaction force. The results can be summarized as follow. 1. There were no difference in maximum reaction force on initial contact period and total foot impact, but statistical difference in maximum reaction force on takeoff period : s, m, n in ascending order. 2. There were some difference in rolling speeds for support periods. At initial contact, the rolling speed of s shoes was fastest but at periods between first and second maximum reaction force, that of m shoes fastest. 3. There was a negative relation between rolling speeds and the length of lever arm on initial reaction force related to pronation. It seems shoes with various curved shapes and hardness could make effects on the rolling features and the rolling speed also have some relationships with walking efficiency, absortion of impact and pronation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.372.1-372
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• 2002

Although impact hammer is widely used as a convenient excitation tool in structural modal testing, little is known about the dynamic charateristics of its impulse mechanism. Transmission of the impulsive force to the structure depends on the dynamic properties of the impact hammer as well as the stiffness of the tip. An improved dynamic model of the impact hammer is proposed in this study with numerical simulations based on this model. (omitted)