• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.171-177
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• 2008

This work intends to investigate the effects of pedaling directions on the muscle actions during the bicycle's uphill propulsion. A test rig was developed that consists of a bicyle with a special planetary geartrain, a height-adjustable treadmill, a rear-wheel support and a magnetic brake. A three-dimensional motion analysis was performed for measuring kinematic characteristics of the forward backward pedaling and the electromygraphy(EMG) measurements were simultaneously performed for estimating the muscle actions of the leg. In this work, four muscles are considered including Gastrocnemius muscle(GM), Vastus lateralis(VL), Tibialis anterior(TA) and Soleus(SOL) while the uphill slope is varied from $0^{\circ}$ to $6^{\circ}$. Raw EMG signals were first processed through the root-mean-square(RMS) averaging and then ensemble curves were derived by averaging the EMG RMS envelopes over 50 consecutive cycles. Results show that both the kinemactic characteristics and the muscle actions are significantly affected by the pedaling direction. The crank speed of the forward pedaling is higher but the difference in speed is reduced as the slope is increased. The ensemble curves of the :ac signals clearly exhibit some differences in their patterns, peak values and the corresponding locations with respect to the crank angle. The peak values of most EMG signals are higher for the forward pedaling regardless of the slope magnitude. However, the averages of the EMG signals are not observed to have a similar relationship with the pedaling direction, which seems to be affected by several factors such as less experience of the participants' backward pedaling. inappropriate bicycle design for the backward pedaling. These limitations will be further considered in future work.

• Journal of the Ergonomics Society of Korea
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• v.35 no.1
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• pp.11-27
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• 2016

Objective: The purpose of this study was to develop and evaluate high technology adaptive driving controls, such as mini steering wheel-lever system and joystick system, for the people with physical disabilities in the driving simulator. Background: The drivers with severe physical disabilities have problems in operation of the motor vehicle because of reduced muscle strength and limited range of motion. Therefore, if the remote control system with driver-by-wire technology is used for adaptive driving controls for people with physical limitations, the disabled people can improve their quality of life by driving a motor vehicle. Method: We developed the remotely controlled driving simulator with drive-by-wire technology, e.g., mini steering wheel-lever system and joystick system, in order to evaluate driving performance in a safe environment for people with severe physical disabilities. STISim Drive 3 software was used for driving test and the customized Labview program was used in order to control the servomotors and the adaptive driving devices. Thirty subjects participated in the study to evaluate driving performance associated with three different driving controls: conventional driving control, mini steering wheel-lever controls and joystick controls. We analyzed the driving performance in three different courses: straight lane course for acceleration and braking performance, a curved course for steering performance, and intersections for coupled performance. Results: The mini steering wheel-lever system and joystick system developed in this study showed no significant statistical difference (p>0.05) compared to the conventional driving system in the acceleration performance (specified speed travel time, average speed when passing on the right), steering performance (lane departure at the slow curved road, high-speed curved road and the intersection), and braking performance (brake reaction time). However, conventional driving system showed significant statistical difference (p<0.05) compared to the mini steering wheel-lever system or joystick system in the heading angle of the vehicle at the completion point of intersection and the passing speed of the vehicle at left turning. Characteristics of the subjects were found to give a significant effect (p<0.05) on the driving performance, except for the braking reaction time (p>0.05). The subjects with physical disabilities showed a tendency of relatively slow acceleration (p<0.05) at the straight lane course and intersection. The steering performance and braking performance were confirmed that there was no statistically significant difference (p>0.05) according to the characteristics of the subjects. Conclusion: The driving performance with mini steering wheel-lever system and joystick control system showed no significant statistical difference compared to conventional system in the driving simulator. Application: This study can be used to design primary controls with driver-by-wire technology for adaptive vehicle and to improve their community mobility for people with severe physical disabilities.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.45-57
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• 2007

The mean shear wave velocity to the depth of 30 m (Vs30) derived from the western Vs is the current site classification criterion for determining the design seismic ground motion taking into account the site amplification potential. In order to evaluate the Vs30 at a site, a shear wave velocity (Vs) Profile extending to at least 30 m in depth must be acquired from in-situ seismic test. In many cases, however, the resultant depth of the Vs profile may not extend to 30 m, owing to the unfavorable field condition and the limitation of adopted testing techniques. In this study, the Vs30 and the mean shear wave velocity to a depth shallower, than 30 m (VsDs) were computed from the Vs profiles more than 30 m in depth obtained by performing various seismic tests at total 72 sites in Korea, and a correlation between Vs30 and VsDs was drawn based on the computed mean Vs data. In addition, a method for extrapolating the Vs profile from shallow depth to 30 m was developed by building a shape curve based on the average data of all Vs profiles. For evaluating the Vs30 from the shallow Vs profiles, both the methods using VsDs and shape curve result in less bias than the simplest method of extending the lowermost Vs equally to 30 m in depth, and are usefully applicable particularly in the cases of the Vs profiles extending to at least 10 m in depth.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.4
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• pp.247-254
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• 2013

In this paper, dynamic response analysis of a heave compensation system is performed for offshore drilling operations based on multibody dynamics. With this simulation, the efficiency of the heave compensation system can be virtually confirmed before it is applied to drilling operations. The heave compensation system installed on a semi-submersible platform consists of a passive and an active heave compensator. The passive and active heave compensator are composed of several bodies that are connected to each other with various types of joints. Therefore, to carry out the dynamic response analysis, the dynamics kernel was developed based on mutibody dynamics. To construct the equations of motion of the multibody system and to determine the unknown accelerations and constraint forces, the recursive Newton-Euler formulation was adapted. Functions of the developed dynamics kernel were verified by comparing them with other commercial dynamics kernels. The hydrostatic force with nonlinear effects, the linearized hydrodynamic force, and the pneumatic and hydraulic control forces were considered as the external forces that act on the platform of the semi-submersible rig and the heave compensation system. The dynamic simulation of the heave compensation system of the semi-submersible rig, which is available for drilling operations with a 3,600m water depth, was carried out. From the results of the simulation, the efficiency of the heave compensation system were evaluated before they were applied to the offshore drilling operations. Moreover, the calculated constraint forces could serve as reference data for the design of the mechanical system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.271-277
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• 2020

There are increasing cases of monitoring the structural response of structures using multiple sensors. However, owing to cost and management problems, limited sensors are installed in the structure. Thus, few structural responses are collected, which hinders analyzing the behavior of the structure. Therefore, a technique to predict responses at a location where sensors are not installed to a reliable level using limited sensors is necessary. In this study, a numerical study is conducted to predict the seismic response of low-rise buildings using limited information. It is assumed that the available response information is only the acceleration responses of the first and top floors. Using both information, the first natural frequency of the structure can be obtained. The acceleration information on the first floor is used as the ground motion information. To minimize the error on the acceleration history response of the top floor and the first natural frequency error of the target structure, the method for predicting the mass and stiffness information of a structure using the genetic algorithm is presented. However, the constraints are not considered. To determine the range of design variables that mean the search space, the parameter prediction method based on artificial neural networks is proposed. To verify the proposed method, a five-story structure is used as an example.

• Journal of the Korea Computer Graphics Society
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• v.23 no.3
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• pp.9-17
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• 2017

This study proposes a third-person virtual reality content production pipeline to provide users with a new experience and presence in a new virtual reality environment. For this purpose, we first create third-person virtual reality content, which includes a story, fun factors, and game characteristic. It consists of a tutorial scene in which a user can pre-learn the proposed interface suitable for a third person different from existing virtual reality content and a content scene that achieves its purpose by using game factors based on the background story. Next, we design an interface suitable for the third-person virtual reality content. This study proposes an interface in which users can interact with a virtual environment or object by using their hand. The proposed interface consists of three steps: character movement, virtual object selection with multiple selection, and 3D menu control using virtual space. Finally, through the survey experiment, third-person virtual reality content produced based on the proposed interface was confirmed to be easily controlled while ensuring high satisfaction.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.2
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• pp.247-258
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• 2003

In this paper, we present a pen-shaped input device equipped with accelerometers and gyroscopes that measure inertial movements when a user writes on 2 or 3 dimensional space with the pen. The measurements from gyroscope are integrated once to find the attitude of the system and are used to compensate gravitational effect in the accelerations. Further, the compensated accelerations are integrated twice to yield the position of the system, whose basic concept stems from the field of inertial navigation. However, the accuracy of the position measurement significantly deteriorates with time due to the integrations involved in recovering the handwriting trajectory This problem is common in the inertial navigation system and is usually solved by the periodic or aperiodic calibration of the system with external reference sources or other information in the filed of inertial navigation. In the presented paper, the calibration of the position or velocity is performed on-line and off-line. In the on-line calibration stage, the complementary filter technique is used, where a Kalman filter plays an important role. In the off-line calibration stage, the constant component of the resultant navigational error of the system is removed using the velocity information and motion detection algorithm. The effectiveness and feasibility of the presented system is shown through the experimental results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.810-817
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• 2018

In Korea, tuna purse seine fishery is the industry with the highest production volume in domestic deep-sea fishery. Research has been continuously carried out since the late 1980s, and research on modernization of technology has been actively conducted. However, while auxiliary works boats on the fishing vessels play an important role in the purse seine fishing, related research is not sufficient. In this study, we tried to rebuild the propulsion system of the Net-boat from the propeller to the waterjet type and to perform the hull form conversion to improve the resistance performance of the hull part and improve the motion performance. For this, we calculated the change of the fluid performance of the ship through computational numerical analysis. In addition, towing tank tests were carried out to verify the performance of the existing ship and the ship which changed the propulsion system. As a result, resistance performance of the waterjet type compared to the propeller type was improved by approximately 45 %. It was confirmed that this was due to reduction of the wetted surface area by removing net and improvements in hull form.

• Journal of Digital Convergence
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• v.15 no.8
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• pp.333-340
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• 2017

Timelapse is an imaging technique that captures motion at regular intervals and then projects it at normal speed. We looked at Timelapse advertising images of global brands and presented a model for analyzing components and expression methods of Timelapse, a new image technique. In previous research, literature research, Internet data survey, and YouTube data were investigated. Continuous photography has been developed as an imaging technique, and we have examined the current production status applied to domestic and foreign documentary, domestic and foreign drama, film, and advertisement. In 2015-2016, I will analyze the techniques of iPhones (2016), Ralph Lauren Polo Ads (2015), and Canon EOS (2013) videos that use Timelapse techniques in their recent advertisements. The results show that the Timelapse component is a static element, the static motif is mainly an artificial structure, the place is outdoor, the color is taken at a time showing the characteristics of the place, and the layout is all centered. The dynamic motif is a moving object. The dynamic line consists of a story based on the object. The time is about 11-15 seconds, the longest is about 1 minute and 30 seconds, and the editing is mainly focused on the product with the brand logo emphasized. In conclusion, it is the role of the image to pay attention to the advertisement and catch the eye. In order to motivate the buyer's mind, it is necessary to direct and edit such as Timelapse, which stimulates the emotions inherent in the mind and stimulates the non-verbal symbols. Future research is likely to reveal various attempts at temporal editing of images.

• Journal of Broadcast Engineering
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• v.25 no.4
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• pp.487-496
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• 2020

For the purpose of next generation technology for robot perfomances, a RAoRA (Robot Actor on Robot Arm) structure was proposed using a robot arm joined with a humanoid robot actor. Mechanical analysis, machine design and fabrication were performed for motions combined with the robot arm and the humanoid robot actor. Kinematical analysis for 3D model, spline interpolation of positions, motion control algorithm and control devices were developed for movements of the robot actor. Preliminary visualization, simulation tools and integrated operation of consoles were constructed for the non-professionals to produce intuitive and safe contents. Air walk was applied to test the developed platform. The air walk is a natural walk close to a floor or slow ascension to the air. The RAoRA also executed a performance with 5 minute-running time. Finally, the proposed platform of robot performance presented intensive and live motions which was impossible in conventional robot performances.