• Journal of Auto-vehicle Safety Association
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• v.4 no.2
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• pp.37-43
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• 2012

The purpose of this research is to obtain and analyze dynamic responses from human volunteers for the development of the human-like mechanical or mathematical model for Korean males in automotive rear collisions. This paper focused on the introduction to a low-speed rear impact sled test involving Korean male subjects, and the accumulation of the motion of head and neck. A total of 50 dynamic rear impact sled tests were performed with 50 human volunteers, who are 30-50 year-old males. Each subject can be involved in only one case to prevent any injury in which he was exposed to the impulse that was equivalent to a low-speed rear-end collision of cars at 5-8 km/h for change of velocity, so called, ${\Delta}V$. All subjects were examined by an orthopedist to qualify for the test through the medical check-up of their necks and low backs prior to the test. The impact device is the pendulum type, tuned to simulate the crash pulse of a real vehicle. All motions and impulses were captured and measured by motion capture systems and pressure sensors on the seat. Dynamic responses of head and T1 were analyzed in two cases(5 km/h, 8 km/h) to compare with the results in the previous studies. After the experiments, human subjects were examined to check up any change in the post medical analysis. As a result, there was no change in MRI and no injury reported. Six subjects experienced a minor stiffness on their back for no more than 2 days and got back to normal without any medical treatment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.68-75
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• 2017

This paper presents the experimental and theoretical results of the dynamic responses of a pendular energy extractor in a two-dimensional wave channel. By adopting a wave maker with varying wave height and period, the dynamic responses of the pendular buoy were experimentally obtained. Furthermore, with the aid of the co-simulation of moving particle analysis and rigid dynamic analysis, the dynamic responses of the pendular system were evaluated. In order to validate the feasibility of the proposed wave power generator, the force tuning of the pendular system with restoring energy was carried out. The results provide proof of concept data for the development and design of a commercial model for horizontal wave power generators in the shoreline area.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.29-37
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• 2015

Objective : The purpose of this study was to investigate the biomechanical properties of shock absorption strategy and postural stability during the drop landing for each types. Methods : The motions were captured with Vicon Motion Capture System, with the fourteen infra-red cameras (100Hz) and synchronized with GRF(ground reaction force) data(1000Hz). Ten male soccer players performed a drop landing with single-leg and bi-legs on the 30cm height box. Dependent variables were the CoM trajectory and the Joint Moment. Statistical computations were performed using the paired t-test and ANOVA with Turkey HSD as post-hoc. Results : The dominant leg was confirmed to show a significant difference between the left leg and right leg as the inverted pendulum model during Drop Landing(Phase 1 & Phase 2). One-leg drop landing type had the higher CoM displacement, the peak of joint moment with the shock absorption than Bi-leg landing type. As a lower extremity joint kinetics analysis, the knee joint showed a function of shock absorption in the anterior-posterior, and the hip joint showed a function of the stability and shock absorption in the medial-lateral directions. Conclusion : These findings indicate that the instant equilibrium of posture balance(phase 1) was assessed by the passive phase as Class 1 leverage on the effect of the stability of shock absorption(phase 2) assessed by the active phase on the effect of Class 2 leverage. Application : This study shows that the cause of musculo-skeletal injuries estimated to be focused on the passive phase of landing and this findings could help the prevention of lower damage from loads involving landing related to the game of sports.

• Journal of the Korea Computer Graphics Society
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• v.1 no.2
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• pp.201-212
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• 1995

This paper presents a new method of dynamics-based synthesis of bipedal, especially human, walking. The motion of the body at a time point is determined by ground reaction force and torque under the support foot and joint torques of the body at that time point. Motion synthesis involves specifying conditions that constrain ground reaction force and torque, and joint torques so that a given desired motion may be achieved. There are conditions on a desired motion which end-users can think of easily, e.g. the goal position and orientation of the swing foot for a single step and the time period of a single step. In this paper, we specify constraints on the motion of the support foot, which end-users would find difficult to specify. They are constraints which enforce non-sliding, non-falling, and non-spinning the support foot. They are specified in terms of joint torques and ground reaction force and torque. To satisfy them, both joint torques and ground reaction force and torque should be determined appropriately. The constraints on the support foot themselves do not give any good clues as to how to determine ground reaction force and torque. For that purpose, we specify desired trajectories of the application point of vertical ground reaction force (ground pressure) and the application point of horizontal ground reaction (friction) force. The application points of vertical pressure and friction force are good control variables, because they are indicators to kinds of walking motions to synthesize. The synthesis of a bipedal walking motion, then, consists of finding a trajectory of joint torques to achieve a given desired motion, so that the constraints are satisfied under the condition of the prescribed center of pressure and center of friction. Our approach is distinguished from many other approaches, e.g. the inverted-pendulum approach, in that it captures and formulates dynamics of the support foot and reasonable constraints on it.

• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.121-129
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• 2008

Environmental friendly UV-curable coatings, having excellent hardness, gloss, mar and chemical resistance, are commonly used for the wooden flooring coatings. Especially epoxy acrylate oligomers are chosen for the wooden flooring coatings, due to their thermal stability and fast curing. In this study, we investigated the effect of the acrylate functionality on the thermal stability and surface hardness. The thermal degradations of monomers, oligomer, photoinitiator and formulated coatings with different acrylate functionality were measured using a thermogravimetric analysis (TGA). And the surface hardness was also measured with a pendulum hardness tester to compare relationship between the thermal stability and the physical property. The cured coatings became thermally stable by crosslinking during UV-curing. Both the thermal stability and surface hardness of cured coatings were improved with increasing acrylate functionality.

• Journal of the Korean Institute of Intelligent Systems
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• v.7 no.4
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• pp.65-73
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• 1997

This paper proposes a new method of the structure pruning of dynamic recurrent neural networks (DRNN) using evolutionary computations. In general, evolutionary computations are population-based search methods, therefore it is very useful when several different properties of neural networks need to be optimized. In order to prune the structure of the DRNN in this paper, we used the evolutionary programming that searches the structure and weight of the DRNN and evolution strategies which train the weight of neuron and pruned the net structure. An addition or elimination of the hidden-layer's node of the DRNN is decided by mutation probability. Its strategy is as follows, the node which has mhnimum sum of input weights is eliminated and a node is added by predesignated probability function. In this case, the weight is connected to the other nodes according to the probability in all cases which can in- 11:ract to the other nodes. The proposed pruning scheme is exemplified on the stabilization and position control of the inverted-pendulum system and visual servoing of a robot manipulator and the effc: ctiveness of the proposed method is demonstrated by numerical simulations.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.133-141
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• 2015

The floor slipperiness is an essential property for the pedestrian safety. This study was conducted to develop the slip test apparatus to be well accorded with actual characteristics of human gait; and the correlation between RCOF (Required coefficient of friction), Rz (Surface roughness), and 3 coefficients of slip resistance (C.S.R (Coefficient of slip resistance), BPN (British pendulum number), and SCOF (Static coefficient of friction)) were analyzed. Result of the analysis revealed that the cadence, stride length, and step length were proportional to the walking speed, and the significant correlation between walking speed and RCOF was found. However, the correlation between RCOF and the other respective coefficients of slip resistance was almost unidentified thus it would be difficult to identify the actual property of floor slipperiness with the RCOF alone.

• Polymer(Korea)
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• v.27 no.3
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• pp.195-200
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• 2003

Alginate is a natural ionic polymer including numerous anionic groups and can be actuated by the ionic group under the electric field. The crosslinked alginate films were fabricated with CaCl$_2$. The thermal, mechanical and electroresponse properties of the films were investigated by thermogravimetric analysis, tensile and bending tests. The initial degradation and tensile strength increased according to the degree of crosslinking. Also, the swelling ratio of the films increased with decreasing degree of crosslinking and increasing pH due to free volume and electrostatic repulsion. The films actuated by an electric stimulus exhibited gentle and flexible action like a pendulum. In the electric field, the electric stimuli such as the applied voltage, ionic strength and kind of electrolyte solution had an effect on the electroresponse of the films. Alginate films with 5 wt% crosslinking agent showed the highest bending angle and reversible bending behavior. When the ionic strength of NaCl and KCl electrolyte solution was 0.1 M, the films showed the highest electroresponse. The bending behavior of the films increased with the applied voltage.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.57-62
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• 2014

Most analytical models of the human body have focused on conscious responses. A patellar tendon reflex, a representative example of spinal reflexes, occurs without a neural command. Muscle forces and activation of the quadriceps femoris muscles in healthy adults during patellar tendon reflex are identified in this study. The model is assumed to move in the sagittal plane, and the thigh and the trunk are assumed to be fixed in a sitting position so that the shank can move similar to a pendulum. The knee joint is modeled as a revolute joint, and the ankle joint is modeled as a fixed joint so that the shank and the foot can be regarded as one rigid body. Muscle forces are calculated following the inverse dynamic approach. Kinematic data obtained from an experiment (Mamizuka, 2007) are used as input data. Muscle activations are identified using a Hill-type muscle model. The obtained simulation results are compared with experimental results for validating the model and the underlying assumptions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.552-560
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• 2014

Pulse Detonation Engine(PDE) has been investigated as a next generation propulsion system with the advantages of the higher thermal efficiency by the compression effect and the wide operation ranges from zero speed at ground. In the present study, an efficient theoretical PDE performance prediction program was developed for realistic propellants based on the Endo's theory combining the Chapman-Jouguet detonation theory and expansion process of burnt gas in a constant area tube. The program was validated through the comparison with the experimental data obtained by a ballistic pendulum measurement. PDE performance analyses were carried out for various hydrocarbon fuels and oxidizer compositions by changing the mixture equivalence ratio and initial conditions. Theoretical PDE performance database could be established as a result of the analyses.