• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.299-300
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• 2010

This paper presents experimental results on frequency interference phenomena between WiFi and ZogBee communication systems which are used for wireless communication in a port. When communication systems use a frequency band in a region, it hurts communication reliability. Hence, understanding and analysis on frequency interference phenomena through experiments. With various experiments between WiFi and ZigBee, we find out that 26th channel of ZigBee collides with WiFi communication channels, which is unknown result yet.

• IE interfaces
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• v.22 no.1
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• pp.95-103
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• 2009

During the past few years, design of experiments (DOE) has been gaining acceptance in the telecommunications research community as a mean for designing and analyzing experiments economically and efficiently. In addition, the need for introducing a systematic robust design methodology (i.e., one of the most popular DOE methodologies) to network simulations has been increasing. In this paper, we present an architecture of voice over IP (VoIP) application and the E-Model for calculating the perceived quality of service (QoS). Then, we apply the Taguchi robust design methodology to optimize the perceived QoS of VoIP application, and describe the detailed step-by-step procedures. We have used ns-2 simulator to collect experimental data in which the SN ratio, a robustness measure, is analyzed to determine an optimal design condition. The analysis shows that "initial delay time in playout buffer" is a major control factor for ensuring robust behaviors of the perceived QoS of VoIP. Finally, we verify the proposed optimal design condition using a confirmation experiment.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.200-207
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• 2003

In this paper we present a new method of measuring the relative distance of two point objects in three-dimensional space by using phase-shifting digital holography. In our system the reference beam of a spherical wave is used instead of a plane wave. The system is computer simulated and built on an optical table for experiments. It is shown from computer simulations and experiments that the relative distance can be measured without the exact information on the reference beam used in the hologram record. It is shown from experiments that the relative distance between two point objects separated by 0.5 cm in the distance of about 300 cm from the CCD can be measured with an error less than 10％.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.70-76
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• 2011

This paper presents an optimization procedure for reducing warpage of injection molded part by using a volumetric shrinkage deviation as an objective function. A design of experiments based on orthogonal arrays was used in the optimization procedure, and the entire optimization was performed through a two stage process - a preliminary experimentation and a principal experimentation. Proposed optimization method was applied to the design of a CPU-base part in computer. With the moderate number of experiments, an optimal molding condition for uniform distribution of volumetric shrinkage was obtained, as a result, the warpage of the molded part was significantly reduced.

• Smart Media Journal
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• v.7 no.4
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• pp.79-89
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• 2018

In recent years, falls among elderly people have gained serious attention as a major cause of injuries. Falls often lead to fatal consequences due to lack of prompt response and rescue. Therefore, a more accurate fall detection system and an effective feature extraction technique are required to prevent and reduce the risk of such incidents. In this paper, we proposed an efficient feature extraction technique based on multiple sliding windows and validated it through a series of experiments using supervised learning algorithms. The experiments were conducted using the public datasets obtained from tri-axial accelerometers. The results depicted that extraction of the feature from adjacent sliding windows led to high accuracy in supervised machine learning-based fall detection. Also, the experiments conducted in this study suggested that the best accuracy can be achieved by keeping the window size as small as 2 seconds. With the kNN classifier and dataset from wearable sensors, the experiments achieved accuracy rates of 94%.

• Educational Technology International
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• v.14 no.2
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• pp.215-228
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• 2013

In engineering education practical experiments is very important for each student, but due to the limitation of time and available resources such as laboratory equipment, space and instructors enough hands-on real experiments could not be provided to all students enrolled in the program throughout the academic year. In this sense web-based remote experiments through internet become a solution for engineering education and an emerging new paradigm for students and teachers. This paper presents the development of the web-based remote vibration experiment system for mechatronics education. Students can access this experimental equipment through an internet and conduct vibration experiment remotely without any restriction on time and place. IP address for data communication and web-service are assigned in local computer and then students receive experimental results and the captured pictures using network. The developed system provides real-time feedback of the tested results. Ubiquitous access to the system gained popularity from students.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.5
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• pp.391-401
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• 2009

The hybrid approach for structural experiments decomposes a structure into independent substructures that can be tested or simulated. The results from the decomposed substructures are combined to predict the behaviors of the entires structure. The hybrid approach is especially useful for the hybrid pseudo-dynamic tests that overcome the limitations of size of a test structure present in a shaking table test. The development of a computer system for the hybrid experiment requires a data model that formally organizes the information involved in the hybrid experiments. This paper provides the data model for representing the information involved in the hybrid experiments, by modifying the classes and attributes for the hybrid experiments in the Lehigh Model that is one of the data models for structural experiments. The data model for the hybrid experiments includes the classes for the physical substructures being tested and the analytical substructures being analyzed, and the simulation coordinator managing the overall experiments. Some objects for classes are implemented as an example to show the links among the classes. The data model presented in this paper can be applied for developing a computer system that helps structural engineers and researchers store, share, and access the information for the hybrid experiments.

• Journal of Korea Foundry Society
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• v.14 no.6
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• pp.576-589
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• 1994

Water modeling experiments and computer simulation for the predictions of defects of die castings are very important to produce high quality castings with less cost. The relation between the variable air vent system and the characteristics of the fluid flow in the die cavity is studied by using water modeling tests, which give ideas on reasonable designing of die cavity, vent arrangement and gating system. In order to test the water modeling, injection is done by using water containing NaCl. Flow behaviors in cavities are visualized by high speed camera and video tape recorder, and local filling time is measured with electrode sensors. Special attention is paid to the configuration of die cavity. Simulated results by computer are examined and compared with the results of water modeling experiments. There are close correlations between the simulated results and water modeling ones.

• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.83-87
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• 2007

Correlation Propagation Neural Networks is proposed for On-line interpolation. The proposed neural network technique is the real time computation method through the inter-node diffusion. In the network, a node corresponds to a state in the quantized input space. Each node is composed of a processing unit and fixed weights from its neighbor nodes as well as its input terminal. Information propagates among neighbor nodes laterally and inter-node interpolation is achieved. Through several simulation experiments, real time reconstruction of the nonlinear image information is processed. 1-D CPNN hardware has been implemented with general purpose analog ICs to test the interpolation capability of the proposed neural networks. Experiments with static and dynamic signals have been done upon the CPNN hardware.

• The Journal of the Acoustical Society of Korea
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• v.22 no.2E
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• pp.62-68
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• 2003

This paper addresses a novel noise-compensation scheme to solve the mismatch problem between training and testing condition for the automatic speech recognition (ASR) system, specifically in car environment. The conventional spectral subtraction schemes rely on the signal-to-noise ratio (SNR) such that attenuation is imposed on that part of the spectrum that appears to have low SNR, and accentuation is made on that part of high SNR. However, these schemes are based on the postulation that the power spectrum of noise is in general at the lower level in magnitude than that of speech. Therefore, while such postulation is adequate for high SNR environment, it is grossly inadequate for low SNR scenarios such as that of car environment. This paper proposes an efficient spectral subtraction scheme focused specifically to low SNR noisy environment by extracting harmonics distinctively in speech spectrum. Representative experiments confirm the superior performance of the proposed method over conventional methods. The experiments are conducted using car noise-corrupted utterances of Aurora2 corpus.