• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.1-7
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• 2018

The purpose of this study is to compare and analyze the response time of three mobile portal sites in Korea using distributions. The research subjects are the mobile portal site of Naver, Daum, and Nate. The experiment period is six years from April 18, 2012 when mobile portals started to activate, to April 17, 2018. The number of experiments is 4,060. Histograms and percentages were used for the distribution comparisons. For the theoretical comparison, Chi-Square test is adopted as a parametric method, and Kolmogorov-Smirnov test is as a nonparametric method. Naver was the fastest of all four methods, the next was Nate, the next was the slowest. The same result was obtained in terms of average response speed. These results are in contradiction to the results of the wired portal. Naver is a strategy to increase the response speed in accordance with the characteristics of media. Daum is a strategy to increase the contents at the cost of response speed. As for classification, we divide the response time into "Comfortable", "Tolerable", "Feedback", "Leave" according to response time. The ratio of more than 7 seconds that users leave called as "Leave" is 1.18% for Naver, 11.70% for Daum, and 1.5% for Nate. As Daum is overwhelmingly high, the response time is very much in need of improvement. In addition, we show the response time of three mobile portals needs to be reduced We hope that the results of this paper will facilitate technology competition to increase the response speed of mobile portals.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.433-436
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• 1998

The objective of this paper is to design a adaptive fuzzy controller for autonomous navigation of mobile robot. The adaptive fuzzy controller has an advantage in data processing time and convergence speed. The basic idea of control is to induct membership function and fuzzy inference rules and to scale inducted membership function to suitable robot state. The adaptive fuzzy control method is applied to mobile robot and the simulation results show the effectiveness of our controller.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.658-662
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• 1991

In this paper, a real-time obstacle avoidance for mobile robot based on the readings of the ultrasonic sensors is presented. The twenty eight ultrasonic sensors are arranged in ring and controlled by microprocessor. The readings of the ultrasonic sensor is converted into the virtual forces called repulsive forces, which are the elastic and damping forces. Then, the direction and speed of mobile robot in the cluttered environment are determined by the virtual forces. The effectiveness of the proposed method is verified from a series of simulation studies.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.592-595
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• 1986

This paper presents a mobile of robot (for the blind) commanded by written course route on MAP. Its locomotion module is composed of PWM motor driving unit, wheel's rotation measurement unit and display and keyboard unit. In algorithm, "COMMAND" and "NEXT PREDICTED POSITION" for locomotion are computed from the MAP and the next position is compared with the measured one. Also, locomotion method for the convenience of the blind is discussed and experimentally demonstrated. In the experiment, the average speed of robot is 0.4m/sec and the computation error of the map is negligible.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.6
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• pp.744-750
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• 2015

In this paper, development of mobile robot for the inspection of hull surface was mentioned. In the sea, it is difficult to proceed with the visual inspection of hull side and thus mobile robot for checking the status could be run with strap-on its surface. To do this, permanent magnet module to generate magnetic force between hull surface and mobile robot, and structure to minimize variance of the force under curvature circumstance were considered on the design. Based on the design, mobile robot with four NdFeB, four driving wheels and image aquisition module was applied. Load experiment to check the adhesive force, slip test during stop state and driving test to measure driving speed were executed. From the experiments 13 Kgf adhesive force was obtained and slip was not happened until 8 Kgf load on the inclined plate. Driving speed of mobile robot was measured at 0.82 m/s corresponding to 6.5 ampere. We confirmed the effectiveness of developed mobile robot by experiments to check its characteristics.

• Journal of Computing Science and Engineering
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• v.9 no.3
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• pp.155-162
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• 2015

The last decade has seen a rapid growth in the use of mobile devices all over the world. With an increasing use of mobile devices, mobile applications are becoming more diverse and complex, demanding more computational resources. However, mobile devices are typically resource-limited (i.e., a slower-speed CPU, a smaller memory) due to a variety of reasons. Mobile users will be capable of running applications with heavy computation if they can offload some of their computations to other places, such as a desktop or server machines. However, mobile users are typically subject to dynamically changing network environments, particularly, due to user mobility. This makes it hard to choose good offloading decisions in mobile environments. In general, users' mobility can provide some hints for upcoming changes to network environments. Motivated by this, we propose a mobility model of each individual user taking advantage of the regularity of his/her mobility pattern, and develop an offloading decision-making technique based on the mobility model. We evaluate our technique through trace-based simulation with real log data traces from 14 Android users. Our evaluation results show that the proposed technique can help boost the performance of mobile devices in terms of response time and energy consumption, when users are highly mobile.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.162-167
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• 2003

In this paper, a novel feasible real-time system was researched for a differential driven wheeled autonomous mobile robot so that the mobile robot can move in a smooth, safe and elegant way. Least Square Minimum Path Planning was well used for the system to generate a smooth executable path for the mobile robot, and the point-to-point tracking algorithm was presented as well as its application in arbitrary path tracking. In order to make sure the robot can run elegantly and safely, trapezoidal speed was integrated into the point-to-point path tracking algorithm. The application to guest following for the autonomous mobile robot shows its wide application of the algorithm. The novel design was successfully proved to be feasible by our experiments on our mobile robot Interactive Robot Usher (IRU) in National University of Singapore.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.1
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• pp.159-167
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• 2010

We research a competitive advantage of telecom bundling package of three mobile telecom company by figuring out utility that consumers perceived and focused on mobile telecom and high speed internet in one bundled package. As a method, conjoint analysis was applied. And in conclusion, consumers considered retaining mobile telecom company as the most important factor to them and branding as the following important one when one bundled package of telecom service is provided in total market. When the market is divided into two submarkets and the second largest submarket is analyzed personal bundled package was most important and three year agreement with a stipulated discount has the highest utility. As a result of this analysis, mobile telecom company managers need to organize bundled package after consideration of their current position and brand power in the market, and then devise proper market strategy

• Proceedings of the Technology Innovation Conference
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• 2002.06a
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• pp.257-268
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• 2002

Korean mobile communications industry has been a main locomotive of the drastic development of Korean IT industry and became one of core industries in national economy. To secure strong competitiveness of mobile communications industry, smooth cooperation should be reconsidered among government, universities, research institutions, and private companies. Future mobile communications technology will be evolved from IMT-2000 to system upgrade, 3.5G and 4G. And the goals of technology development are provision of mobile multimedia services based on better mobility and higher data speed rates. Therefore, Korea's technology development strategies of mobile communications should be focused on intensifying bondage of international cooperation, strengthening standardization activities, and enhancing core technology development capability to secure IPR.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.1113-1116
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• 1999

For mobile robot, the navigation effectiveness can be improved by providing autonomy, but this autonomy requires the mobile robot to detect unknown obstacles and avoid collisions while moving it toward the target. This paper presents an effective method for autonomous navigation of the mobile robot in structured environments. This method uses ultrasonic sensor array to detect obstacles and utilizes force relationship between the obstacles and the target for avoiding collisions. Accuracy of sensory data produced by ultrasonic sensors is improved by employing error eliminating rapid ultrasonic firing (EERUF) technique. Navigation algorithm controlling both the velocity and steering simultaneously is developed, implemented to the mobile robot and tested on the floor filled with the cluttered obstacles. It is verified that from the results of the field tests the mobile robot can move at a maximum speed of 0.66 m/sec without any collisions.