• Journal of the Korea Computer Graphics Society
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• v.27 no.3
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• pp.55-63
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• 2021

This study proposes an interface for providing mobile interaction suitable for mobile virtual reality (VR) and analyzes it through comparative experiments. The proposed interface is premised on not using additional equipment except for the mobile head-mounted display(HMD) in consideration of accessibility and usability. And the interface that controls the movement interaction using the user's gaze is designed in two phases. The key is to minimize the occurrence of negative factors such as VR sickness that can be caused by straight line movement in virtual reality. To this end, two phases are designed: an interface composed of forward/backward buttons to move the gaze toward the ground, and an interface composed of left and right buttons on the front in consideration of the gaze change in real walking motion. An application that can compare and analyze movement interactions through the proposed interface is produced, and a survey experiment is conducted to analyze the user's satisfaction with the interface experience and the negative impact on the movement process. It was confirmed that the proposed movement interaction reduced negative effects such as VR sickness along with a satisfactory interface experience for users.

• Advances in nano research
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• v.10 no.2
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• pp.115-128
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• 2021

In this article, free vibration behavior of electro-magneto-thermo sandwich Timoshenko beam made of porous core and Graphene Platelet Reinforced Composite (GPLRC) in a thermal environment is investigated. The governing equations of motion are derived by using the modified strain gradient theory for micro structures and Hamilton's principle. The magneto electro are under linear function along the thickness that contains magnetic and electric constant potentials and a cosine function. The effects of material length scale parameters, temperature change, various distributions of porous, different distributions of graphene platelets and thickness ratio on the natural frequency of Timoshenko beam are analyzed. The results show that an increase in aspect ratio, the temperature change, and the thickness of GPL leads to reduce the natural frequency; while vice versa for porous coefficient, volume fractions and length of GPL. Moreover, the effect of different size-dependent theories such as CT, MCST and MSGT on the natural frequency is investigated. It reveals that MSGT and CT have most and lowest values of natural frequency, respectively, because MSGT leads to increase the stiffness of micro Timoshenko sandwich beam by considering three material length scale parameters. It is seen that by increasing porosity coefficient, the natural frequency increases because both stiffness and mass matrices decreases, but the effect of reduction of mass matrix is more than stiffness matrix. Considering the piezo magneto-electric layers lead to enhance the stiffness of a micro beam, thus the natural frequency increases. It can be seen that with increasing of the value of WGPL, the stiffness of microbeam increases. As a result, the value of natural frequency enhances. It is shown that in hc/h = 0.7, the natural frequency for WGPL = 0.05 is 8% and 14% less than its for WGPL = 0.06 and WGPL = 0.07, respectively. The results show that with an increment in the length and width of GPLs, the natural frequency increases because the stiffness of micro structures enhances and vice versa for thickness of GPLs. It can be seen that the natural frequency for aGPL = 25 ㎛ and hc/h = 0.6 is 0.3% and 1% more than the one for aGPL = 5 ㎛ and aGPL = 1 ㎛, respectively.

• Physical Therapy Korea
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• v.28 no.1
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• pp.18-26
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• 2021

Previous studies have reported that deep neck flexor (DNF) exercise can improve neck problems, including neck pain, forward head posture, and headache, by targeting the deep and superficial muscles of the neck. Despite the prevailing opinion across studies, the benefits of DNF can vary according to the type of neck problems and the outcome measures adopted, ranging from positive outcomes to non-significant benefits. A meta-analysis was conducted in this study to assess conclusive evidence of the impact of DNF exercise on individuals with neck problems. We used PUBMED, MEDLINE, NDSL, EMBASE, and Web of Science to search for primary studies and the key terms used in these searches were "forward head posture (FHP)," "biofeedback," "pressure biofeedback unit," "stabilizer," "headache," and "neck pain." Twenty-four eligible studies were included in this meta-analysis and were coded according to the type of neck problems and outcome measures described, such as pain, endurance, involvement of neck muscle, craniovertebral angle (CVA), neck disability index (NDI), cervical range of motion (CROM), radiographs of the neck, posture, strength, endurance, and headache disability index. The overall effect size of the DNF exercise was 0.489. The effect sizes of the neck problems were 0.556 (neck pain), -1.278 (FHP), 0.176 (headache), and 1.850 (mix). The effect sizes of outcome measures were 1.045 (pain), 0.966 (endurance), 0.894 (deep neck flexor), 0.608 (superficial neck flexor), 0.487 (CVA), 0.409 (NDI), and 0.252 (CROM). According to the results of this study, DNF exercise can effectively reduce neck pain. Thus, DNF exercise is highly recommend as an effective exercise method for individuals suffering from neck pain.

• Journal of the Korean Applied Science and Technology
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• v.39 no.5
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• pp.701-709
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• 2022

The purpose of this study was to compare the differences according to the visual selection and rotation order during sequential rotational jump for female dancers of a Korean ballet company by classifying them into take-off and landing sections. 10 subjects (age: 26.0±2.9 yrs, height: 163.4±3.3 cm, weight: 46.8±3.6 kg, ballet career: 12.3±5.9 yrs) participated in the study. Using a 3D motion analyzer and a force platform, the height of the body center and the ground reaction force during take-off and landing were measured. According to the visual condition (using both eyes, using left eye, using right eye) and rotation order (first rotation, second rotation), it was analyzed through repeated measurement two-way analysis. Height of the CM was higher in the first jump. In take-off, Fx was lateral force of left foot and medial force of right foot were strong in second rotation, and Fy was forward force was strong in first rotation of right foot. Fz was no significant. In landing, Fy showed backward force was strong when landing the second time from the left foot, and the backward force was strong when using the left sight from the right foot. Fz was strong on the second landing on the left foot and the first landing on the right foot.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1244-1251
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• 2022

Marine accidents due to a loss of stability, have been gradually increasing over the last decade. Measures must be taken on the roll reduction of a ship. Amongst the measures, building an anti-roll tank in a ship is recognized as the most simple and effective way to reduce the roll motion. Therefore, this study aims to develop a computational model for a U-tube type anti-roll tank and to validate it by experiment. In particular, to validate the developed computational model, the height of the free surface in the tank was measured in the experiment. To develop a computational model, the mesh dependency test was carried out. Further, the effects of a turbulence model, time step size, and the number of iterations on the numerical solution were analyzed. In summary, a U-tube type anti-roll tank simulation had to be performed accurately with conditions of a realizable k-𝜖 turbulence model, 10^-2s time step size, and 15 iterations. In validation, the two cases of measured data from the experiment were compared with the numerical results. In the present study, STAR-CCM+ (ver. 17.02), a RANS-based commercial solver was used.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.113-120
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• 2008

One-dimensional site response analysis is widely used to simulate the seismic site effects. The equivalent linear analysis, which is the most widely used type of site response analysis, is essentially a linear method. The method applies constant shear modulus and damping throughout the frequency range of the input motion, ignoring the dependence of the soil response on the loading frequency. A new type of equivalent linear analysis method that can simulate the frequency dependence of the soil behavior via frequency-strain curve was developed. Various forms of frequency-strain curves were proposed, and all curves were asserted to increase the accuracy of the solution. However, its validity has not been extensively proven and the effect of the shape of the frequency-strain curve is not known. This paper used two previously proposed frequency-strain curves and three additional curves developed in this study to evaluate the accuracy of the frequency-dependent equivalent linear method and the influence of the shape of the frequency-strain curves. In the evaluation, six recordings from three case histories were used. The results of the case study indicated that the shape of the frequency-strain curve has a dominant influence on the calculated response, and that the frequency dependent analysis can enhance the accuracy of the solution. However, a curve that results in the best match for all case histories did not exist and the optimum curve varied for each case. Since the optimum frequency-strain curve can not be defined, it is recommended that a suite of curves be used in the analysis.

• Journal of the Korea Computer Graphics Society
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• v.29 no.3
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• pp.137-147
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• 2023

This paper presents a motion-capture-based projection VR system to explore the effectiveness of gamification in improving environmental awareness. We examine the key components of positive and negative VR game content and analyze the impact of individual and cooperative play methods on promoting sustainable behaviors. Our findings are as follows. Firstly, we discovered that the use of positive content in individual play mode was effective in improving awareness of the importance of recycling. Secondly, we confirmed that the use of positive content in cooperative play mode and the use of negative content in individual play mode were each effective in enhancing awareness of the seriousness of environmental pollution. Thirdly, we found that experiencing positive content first, followed by negative content, in individual play mode was effective in increasing interest in the environment. Based on these findings, we determined that adjusting the order of use of positive and negative content is more effective than simply using positive or negative content alone for improving environmental awareness. Moreover, considering the importance of recycling, the seriousness of environmental pollution, and the level of interest in the environment, we confirmed that individual play mode is effective and cooperative play mode can be more effective depending on the measure.

• 한국노년학
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• v.29 no.3
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• pp.987-1000
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• 2009

The purpose of the study was to examine the effect of resistance training on joint flexibility and muscle strength of upper extremities of institutionalized elderly with impaired cognition. The study design was pretest-posttest control group study and inclusion criteria were elderly aged 65-year older, MMSE score 23 or less, ones who had no serious physical and/or mental problem except impaired cognition, and were capable to carry out resistance training. After consents were obtained participants were randomly assigned. Pre-post evaluation was performed by staff nurses trained beforehand. Among those 4-week study period, experiment was carried out during 5 consecutive days a week for 3 weeks. ROM and extension range of shoulder joints and muscle strength of shoulders and hands for both sides were measured. Flexion, extension, abduction range of right shoulder joint was significantly improved. Flexion and extension muscle strength of left side shoulder and abduction muscle strength of both sides of shoulder were significantly improved. With the study result, it could be concluded that resistance training has therapeutic effects on joint flexibility and muscle strength. More studies adopted longer experimental period to evaluate timing of effect and extinction to refine the protocol are called for.

• Smart Media Journal
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• v.12 no.11
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• pp.48-56
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• 2023

The technology of Three-dimensional human posture estimation is used in sports, motion recognition, and special effects of video media. Among various methods for this, multi-view 3D human pose estimation is essential for precise estimation even in complex real-world environments. But Existing models for multi-view 3D human posture estimation have the disadvantage of high order of time complexity as they use 3D feature maps. This paper proposes a method to extend an existing monocular viewpoint multi-frame model based on Transformer with lower time complexity to 3D human posture estimation for multi-viewpoints. To expand to multi-viewpoints our proposed method first generates an 8-dimensional joint coordinate that connects 2-dimensional joint coordinates for 17 joints at 4-vieiwpoints acquired using the 2-dimensional human posture detector, CPN(Cascaded Pyramid Network). This paper then converts them into 17×32 data with patch embedding, and enters the data into a transformer model, finally. Consequently, the MLP(Multi-Layer Perceptron) block that outputs the 3D-human posture simultaneously updates the 3D human posture estimation for 4-viewpoints at every iteration. Compared to Zheng[5]'s method the number of model parameters of the proposed method was 48.9%, MPJPE(Mean Per Joint Position Error) was reduced by 20.6 mm (43.8%) and the average learning time per epoch was more than 20 times faster.

• Journal of the Korean Applied Science and Technology
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• v.40 no.4
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• pp.642-649
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• 2023

The purpose of this study was to analyze the effects of knee joint injury experiences of judo players on kinematic factors and center of pressure factors during uchimata. Among right-handed male college judo players specializing in uchimata, 13 people who had a knee joint injury experience(age, 20.69.1±0.75 years; height, 172.85±4.81 cm; body mass, 74.92±5.51 kg; and career, 8.92±0.95 years) and 13 people who did not have a knee joint injury experience(age, 21.08.1±0.76 years; height, 172.54±6.32 cm; body mass, 76.62±9.09 kg; and career, 9.46±0.94 years) within the last 2 years were divided into two groups and participated as subjects. The two groups were evaluated for differences in ankle, knee, and hip joint angle variables, COP range, and velocity components during uchimata. As a result of the study, the EIG group showed smaller values in the knee joint flexion angle at E3 and the hip joint extension angle at E4 during uchimata than the NIG group. In addition, the EIG group showed lower values in the range of motion of the COP and forward movement velocity of the COP in the one-leg support phase than the NIG group.