• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.171-176
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• 2008

As one way of design optimization of two-stage two-cylinder rotary compressor used for R410A heat pump application, displacement volume ratio, being defined by the ratio of the second stage cylinder volume to that of the first stage, has been varied and its effect on the compressor performance has been investigated by a computer simulation program. For simplicity, only the cylinder height of the second stage was varied to change the volume ratio. With increasing the volume ratio in the range of VR=$0.55{\sim}0.9$, volumetric efficiency increased monotonically, but adiabatic efficiency showed a maximum at around VR=0.6. Mechanical efficiency was little influenced by the volumetric ratio. As a consequence, maximum improvement of the compressor performance was found at around VR=0.7. Compared to a one-stage two-cylinder rotary compressor with about the same cooling capacity, COP improvement was about 6.96%.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.116-122
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• 2021

This study evaluated the effect of simulation training on cardiac arrest in hospitals for inactive nurses with 360 VR content, and attempted to prepare basic data for simulation training for inactiv nurses in the future. The design of this study is an experiment study before and after a single group. The study period was from October 13, 2020 to December 17, 2020. The subjects of the study were a total of 21 nurses who participated in the education program for inactive nurses. For simulation training for inactive nurses, Microsoft Powerpoint, hybrid simulation, high-fidelity simulation, and 360 VR content were applied for theories education and practical education. As a result of the study, the satisfaction level of the curriculum for the cardiac arrest situation in the hospital for inactive nurses was 4.78±0.36 points out of 5 points. Understanding of education was 4.71±0.46 points out of 5 points. Usefulness of education was 4.80±0.40 points out of 5 points. Confidence in airway maintenance before and after training, BLS review, manual defibrillator, emergency medication administration, airway maintenance, emergency situation simulation, and debriefing were all significant. According to the results of this study, simulation training of the situation of cardiac arrest in the hospitals for inactive nurses was effective. In future studies, it will be necessary to develope and verify specific teaching and learning methods by applying various cases of cardiac arrest situations in consideration of the type of hospitals.

• Korean Journal of Construction Engineering and Management
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• v.24 no.5
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• pp.63-72
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• 2023

This study investigates the virtual reality (VR) simulation to train construction workers for modular construction. Recently, the construction industry has been experiencing a growing demand for modular construction due to a shortage of labors and an increasing social need for safety. While the demand for modular construction has been increasing, construction labors suffer a basic knowledge regarding modular construction. The users of the simulation, developed by Unity program and Oculus Quest 2, experience the removal of hazardous elements at the location whether the modular unit suspended by a crane is lowered, the lowering and assembly of units through crane operation, and the fall from the roof which is the most frequent accidents in modular construction. The simulation was tested by 15 subjects. The effectiveness of the education was measured through a survey on self-efficacy, perceived usefulness, usability, and presence. It was found that the VR training is suitable for educating on the modular construction activities and safety issues related to them. This study also found that perceived usefulness is the factor that has the greatest impact on self-efficacy. This study can contribute to resolving the labor education issues for the deployment of modular construction.

• Journal of the Korean Chemical Society
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• v.66 no.4
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• pp.323-332
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• 2022

The purpose of this study is to investigate the effects of science classes using smart devices that combine augmented reality (AR) and virtual reality (VR) on the scientific attitude of middle school gifted students. In addition, it is intended to find out the perception of science classes using these smart devices. In addition to actual experiments, a science class program that allows students to experience science experiments virtually using AR and VR was applied to 15 middle school gifted students. Before and after the application of the program, the questionnaire is to investigate the interest in scientific classes, the attitude toward science exploration, and the professional interest in science, and the recognition of classes that combine AR and VR. In addition, through in-depth interviews, the perceptions of gifted students was accurately investigated. As a result of this study, the content of science classes and instructors showed high class satisfaction, but the smart devices and applications used during the science classes showed lower class satisfaction than others. As a result of comparing and analyzing the pre-post of gifted students, interest in science class, attitude toward science inquiry, and professional interest in science increased significantly among the sub-areas of the scientific attitude test. As a result of analyzing free responses and indepth interviews, gifted students responded with the advantage that classes using smart devices that combine AR and VR can be tested quickly and safely for a short time compared to actual experiments. On the other hand, they responded with low completeness of the application and dizziness when operating virtual reality. Based on this, implications for the development of applications and instructional programs using advanced technologies that can experience realistically limited scientific experiments such as experimental preparation, class time, and risk factors were obtained.

• Journal of the Korea Convergence Society
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• v.13 no.2
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• pp.55-65
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• 2022

The purpose of this paper was to investigate the relationship between cybersickness symptoms and visual function and to determine whether visual perception training is effective in reducing symptoms of cybersickness. The study subjects were healthy adult males who experienced the same virtual reality program for 15 minutes. Afterwards, the VR satisfaction score and cybersickness level were measured and classified into a comfortable virtual reality program viewer group (CVR group, 20 people) and an uncomfortable virtual reality program viewer group (UVR group, 20 people). Visual function test was performed on all subjects, and the vision therapy training program was applied to the UVR group once a week for 40 minutes 12 times, and then the visual function and SSQ questionnaire were re-evaluated. Subjects with diplopia were 55% in the UVR group and 5% in the CVR group, which was significantly higher in the UVR group, there were differences in stereopsis, exophoria, near point convergence(p<.01) and vergence function(p<.001) between the two groups. After vision therapy, changes in SSQ, stereopsis, near point convergence, and vergence function of UVR user group were positively changed(p<.01). Therefore, cybersickness symptoms are related to visual function, it seems that the vision therapy can be used as a way to alleviate the symptoms of cybersickness.

• Journal of the Korea Computer Graphics Society
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• v.26 no.3
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• pp.99-109
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• 2020

This study was conducted to improve the education method for improving perception awareness of the visually-impaired. 'Hear me later' was designed and implemented based on VR content that allows the visually-impaired experience in the eyes and environment. The main target is from middle and high school students to adolescents in their twenties. It is consisted of a student, the user's daily life with waking up at home in the morning, going to school, taking classes at school, and disembarking home late in the dark. In addition, 10 quests are placed on each map to induce users' participation and activity. These quests are a daily activity for non-disabled people, but it is an activity to experience uncomfortable activity for visually impaired people. In order to verify the effect of 'Hear me later', 8 participants in their early teens to early 20s' perception of visually impaired people was measured through pre and post evaluation of VR contents experience. In order to verify the effect of'Hear me later', 8 participants in their early teens to early 20s' perception of visually impaired people was measured through pre-post evaluation of VR experiences. As a result, it was found that in the post-evaluation of VR contents experience, the perception of the visually impaired was increased by 30% compared to the pre-evaluation. In particular, misunderstandings and changes in prejudice toward the visually impaired were remarkable. Through this study, the possibility of a VR-based disability experience education program that can freely construct space-time and maximize the experience was verified. In addition, it laid the foundation to expand it to various fields of improvement of the disabled.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.886-904
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• 2018

The 3D(dimension) vritual reality(VR) has already been used in various sports fields, especially in the training of elite athletes. It is mainly used to maximize the effectiveness of image training, and the use of VR-based image training has received special attention as evidence-based pratices for its feasibility, practicality, and appropriateness. However, in recent years, the use of VR is no longer used only for the training of elite athletes, but is widely used in social sports. This is because, the advantage of exercise in VR is that it is highly stable and has fewer restrictions from the external environment. Considering these advantages, it can be used for the elderly physical activity. This study identifies and reviews studies applying VR-based image training. Several recommendations for the future study on VR-based image training for the older such as interdisciplinary approach to VR-based image training, support needs regarding characteristics of the older, and generalization and maintenance of acquired technology were discussed.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.11 no.1
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• pp.7-12
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• 2013

Purpose : The purpose of this study was to identify effects of virtual reality-based closed kinetic chain (CKC) exercise on lower extremity muscle activity in chronic stroke patients Methods : Subjects were assigned randomly either to VR+CKC exercise group (n=15) or the CKC exercise group (n=15). When the study began, both groups received conventional physical therapy five times per week. The VR+CKC exercise group received virtual reality programs and the CKC exercise group received close kinetic chain exercises. Each exercise program was performed for six weeks (5 times per weeks; 20 minutes per time). Participants were measured on lower extremity muscle activity using EMG. Results : There was a significant increase of muscle activity (%RVC) in vastus lateralis and vastus medialis. Conclusion : In this study, the virtual reality-based closed kinetic chain exercise program was an effective exercise for improving lower extremity muscle activity in chronic stroke patients.

• Industrial Engineering and Management Systems
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• v.11 no.4
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• pp.371-384
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• 2012

This study proposes a multi-level data analysis approach to identify both superficial and latent relationships among variables in the data set obtained from a vocational rehabilitation (VR) services program of people with significant disabilities. At the first layer, data mining and statistical predictive models are used to extract the superficial relationships between dependent and independent variables. To supplement the findings and relationships from the analysis at the first layer, association rule mining algorithms at the second layer are employed to extract additional sets of interesting associative relationships among variables. Finally, nonlinear nonparametric canonical correlation analysis (NLCCA) along with clustering algorithm is employed to identify latent nonlinear relationships. Experimental outputs validate the usefulness of the proposed approach. In particular, the identified latent relationship indicates that disability types (i.e., physical and mental) and severity (i.e., severe, most severe, not severe) have a significant impact on the levels of self-esteem and self-confidence of people with disabilities. The identified superficial and latent relationships can be used to train education program designers and policy developers to maximize the outcomes of VR training programs.

• Nuclear Engineering and Technology
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• v.50 no.5
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• pp.745-750
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• 2018

New exercise technology such as the virtual reality (VR)-based exercise system is required to meet soaring demand for target participants in exercises and to alleviate the difficulties in personnel mobilization through an alternative approach to the exercise system. In a previous study, event tree methodologies were introduced in setting up an exercise scenario of a VR-based radiological exercise system. In the scenario, the locations at which major events occur are rephrased as nodes, routes as paths, and public response actions as protective actions or contents of an exercise at individual locations. In the study, a model for estimating effective doses to the participants is proposed to evaluate the exercise system, using the effective dose rates at particular times and locations derived from a computer program. The effective dose received by a student when she/he follows a successful route is about a half of the dose received when she/he does not follow the exercise guide directions. In addition, elapsed time to finish an exercise when following a successful route is less than one-third of the time spent to finish an exercise when following the guide's directions.