• Journal of Korean Medicine Rehabilitation
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• v.21 no.2
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• pp.227-238
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• 2011

Objectives : This study was to investigate the effects on using Virtual reality exercise program($Wii-Fit^{TM}$) for dynamic balance and walking ability in patients with stroke. Methods : The 22 subjects were randomly selected from the patients of the S hospital who met the study conditions. They were divided into a $Wii-Fit^{TM}$ balance game group of 12 patients and a conventional physical therapy group of 10 patients. The $Wii-Fit^{TM}$ balance game group received $Wii-Fit^{TM}$ balance game group general physiotherapy for 5 days a weeks, 30 minutes a day, for a 4 weeks and the conventional physical therapy group received general physiotherapy for the same period. The subjects were measured and compared for Brunel balance assessment, functional gait assessment, 6 minute walk test, GAITRite system before and after the program. Results : The experimental group tend to improve more than control group in shifting the weight to the affected side(p=0.040) and tap test(p<0.001). The experimental group tend to improve more than control group in FGA(p=0.016). The experimental group improved significantly more than control group in 6MWT(p=0.008). The experimental group improved significantly more than control group in gait speed, cadence, stride length. Conclusions : Virtual Reality program($Wii-Fit^{TM}$) with conventional physical therapy shows the benefits on dynamic balance and gait parameters in patients with stroke.

• Journal of Radiation Protection and Research
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• v.29 no.4
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• pp.221-230
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• 2004

The probability of causation(PC) is the measure to ascertain the likelihood that a particular cancer may be attributed to a particular prior exposure to radiation. Since the PC is involved in several uncertainties, it is desirable to use the confidence limit for the PC, not a point estimate for determining whether to award compensation. We developed the program for estimating the PC to Korean radiation workers with cancer, the so-called RHRI-PEPC, which is based on the most reasonable model for radiation cancer risk and recent Korean baseline data. RHRI-PEPC gives us the upper confidence limit for the PC after adjusting several uncertainties and therefore we can assess more reasonably the causality of radiation exposure for cancer occurred in Korean radiation workers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1677-1688
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• 1998

In this paper, we analyze the performance of a DS-CDMA system employing adaptive adaptive array antenna technology at base-station. For the analysis the receiving architecture of a multiple team adaptive base-station array antenna is proposed as a major system omponent, and signal to interference and noise ratio(SINR) on the proposed architecture is developed. We show that the perfomance enhancement of the CDMA system is represented as great reduction of interfreence by employing an array antenna capable of resolving the angular distribution of the mobile users as seen at the ase-station. The energy associated with each mobile or a group of mobiles is thus confined within the addressed volume, greatly reducing the amount of co-channel interference experienced from and by neighboring co-channel cells. In order to ascertain the benefits of such an antenna, a theoretical approach, which eis based on the conventional and proposed antenna systems in a typical mobile radio environment, is adopted. Finally computer simulation results show the insight into how the adaptive array antenna operates when used in conjunction with DS-CDMA and illustrate the potential benefits in the SINR point of view.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1490-1500
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• 1996

One of the important issues for multimedia communications over ATM netowrks is efficient use of net-work resources since transmitting video at low cost requires high utilization of channel bandwidth. In this paper, we propose an effective bandwidth estimation scheme for MPEG sources in ATM networks. It has been known difficult to allocate effective transmission bandwidth to MPEG sources due to its bursty charactersitics. The MPEG traffic stream can bemodeled using five traffic parameters:service rate, burst load ratio, interburst load ratio, burst period, and interburst period. Using these parameters, a transmission bandwidth for each source can be estimated, and the estimated bandwidth is applied synchronously to reduce the queue size in a buffer. For a simple network modelof a high speed link that multiplexes a number of virtual-circuit connections, simulations on adaptive bandwidth allocation were performed, and the results show that the queueing delay is significantly reduced, when compared to a fixed bandwidth allocation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.1
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• pp.77-87
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• 2017

Even though current LTE/LTE-A mobile networks provide enough high data rate and low latency to support conventional wireless services, to support ultra-low delay services, such as virtual reality and remote control, in the next generation mobile communication network, it is required to provide very low delay about several ms. However, in the uplink transmission of the LTE/LTE-A system, the process of scheduling grant is required to obtain uplink resources for uplink transmission from the eNB. The process of granting uplink resources from eNB brings additional fixed latency, which is one of the critical obstacles to achieve low delay in uplink transmissions. Thus, in this paper, we propose a novel uplink transmission scheme called Cut-in uplink transmission, to reduce uplink latency. We provide the performance of the proposed uplink transmission scheme through simulations and show the proposed uplink transmission scheme provides lower uplink transmission delay than conventional uplink transmission scheme in LTE/LTE-A mobile networks.

• Journal of Korean Society for Quality Management
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• v.48 no.1
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• pp.13-27
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• 2020

Purpose: The purpose of this study is to present a recoil measurement and analysis of K2 rifle for the development of a virtual reality marksmanship training in the Republic of Korea Army. Methods: For the recoil measurement, a test-bed is built by a barrel that has exact dimensions of K2 rifle and three piezoelectric pressure sensors mounted on the barrel. Data of over 200 rounds of 5.56mm M193 and K100 bullets are collected and analyzed from live fire experiments. For the recoil analysis, both the free recoil method and the gas exhaust aftereffect method are used to calculate a recoil velocity, momentum and kinetic energy of K2 rifle by applying the law of conservation of momentum. In addition, a new method is proposed that uses the third law of motion and the chamber pressure model for the recoil measurement Results: The results show how different between the previous and proposed methods with respect to M193 and K100 bullets of K2 rifle. In M193, the free recoil method demonstrates 1.113, 4.197, and 2.335, the gas exhaust aftereffect method computes 1.698, 6.407, and 5.441, and the proposed method calculates 0.990, 3.734, and 1.848 in recoil velocity, momentum and kinetic energy, respectively. In K100, the free recoil method demonstrates 1.190, 4.487, and 2.669, the gas exhaust aftereffect method computes 1.776, 6.699, and 5.949, and the proposed method calculates 1.060, 3.998, and 2.119 in recoil velocity, momentum and kinetic energy, respectively. Conclusion: This study implements live fire experiments to provide recoil velocity, momentum, and kinetic energy of K2 rifle using both M193 and K100 bullets. For the development of the army virtual reality marksmanship, the results in this paper would be useful to design and produce a gun and/or a rifle of virtual reality.

• Journal of the Korea Society of Computer and Information
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• v.25 no.8
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• pp.73-79
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• 2020

Since the start of the 4th industrial revolution, technologies have been developed in the Internet of Things (IoT), artificial intelligence (AI), virtual reality (VR), and 5G. Compared to other technologies IoT is currently being commercialized more than other technologies where the numbers of connected things are increases every year. The IoT has a huge advantage to provide convenience and lots of information to users, but security cannot keep up with the speed of development. IoT services continue to provide services for related devices, but at present, more and more types of new services are being combined with other technologies by utilizing the services of devices. This paper reviews and analyzes research on security issues and services related to the Internet of Things to explore how security trends and service delivery will develop in the future.

• Journal of Digital Contents Society
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• v.16 no.1
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• pp.127-135
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• 2015

The development of stereoscopic display hardwares and 3D authoring softwares expands its application areas from particular virtual simulation applications to general movies, games, advertising applications. However, the binocular-based 3D stereoscopic images cause fatigue to viewers. Recent performed many research results about the binocular stereoscopy's depth perception and viewers' fatigue are derived from experimental users studies. In some results, watching and making guidelines for 3D stereoscopic imaging contents are introduced. The 3D stereoscopic-related contents have the contradictory aspects, which are audiences' pursuit of a tolerable minimum fatigue and producer's its of excessive depth changes for providing viewers' immersion. This paper provides user experiments and analysis data in aspects of 3D depth changes. For use of producers, a safety zone and translational velocity of 3D depth changes are introduced. Also, on the viewer side, we present the depth change adaptation time by using an EEG device.

• Journal of Platform Technology
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• v.6 no.2
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• pp.3-9
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• 2018

Recently VR environment is used in many areas including mobile learning, smart factory. However HMD(head-mounted display) is required to a dedicated and expensive system with high-end specification. When designing a VR system, it is needed to handle performance, mobility and usability. Many VR applications need to handle diverse sensors and user inputs continuously in a streaming manner. In this paper we design a VR mobile platform and implement a low-cost mobile VR HMD running on the platform. The VR HMD supports 3D contents delivery in a mobile manner. It is used to detect the motion detection based on angle value of a VR player from accelerator and gyro sensor. The MPU-6050, 6-axis sensor, is used to get a sensory value and the sensory value is taken as an input to a VR rendering server on a Unity game engine that is generated 3D images.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.45-52
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• 2006

In this study, a nonlinear control by feedback linearization method, one of nonlinear control schemes based on the nonlinear model, is proposed to suppress the flutter of a supersonic composite panel using piezoelectric materials. Most of the previous panel flutter controllers are the LQR(Linear Quadratic Regulator) which is based on the linear model. A nonlinear feedback linearizing controller proposed in this study considers the nonlinear characteristics of the system model. We use the actuator implemented by piezoceramic PZT. Using the principle of virtual displacements and a finite element discretization with the conforming four-node rectangular element, we first derive the discretized dynamic equations of motion, which are transformed into a nonlinear coupled-modal equations of motion of state space form. The effectiveness of the proposed method is also compared with the LQR based on the linear model through numerical simulations in the time domain using the Newmark method.