• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.517-521
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• 2001

Measurement techniques for the in-duct source characteristics of fluid machines can be classified into direct method and load method, according to whether the technique employs an external acoustic source or not. It has been known that the two methods yield different results and the load method used to come up with a negative source resistance, in spite of the fact that a very accurate prediction of radiated noise can be obtained by using any result. This paper is focused to the effect of time-varying nature of fluid machines on the output result. For this purpose, a simplified fluid machine consisting of a reservoir, a valve and a pipe is considered as representing a typical linear, periodic, time-varying system and the measurement techniques are simulated by utilizing the Hill equation and its steady-state forced response. In the load method, the source impedance turns out being dependent on the valve impedance at the calculation frequency and the valve and load impedances at other frequencies as well.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.1
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• pp.13-20
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• 2008

Sensor network consists of a large number of sensor node distributed in the environment being sensed and controlled. The resource-constrained sensor nodes tend to have various and heterogeneous architecture. Thus, it is important to make its software environment platform-independent and reprogrammable. In this paper, we present BeeVM, a Java operating system designed for sensor networks. BeeVM offers a platform-independent Java programming environment with its efficiently executable file format and a set of class APIs for basic operating functions, sensing and wireless networking. BeeVM's high-level native interface and layered network subsystem allow complex program for sensor network to be short and readable. Our platform has been ported on two currently popular hardware platforms and we show its effectiveness through the evaluation of a simple application.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.66-72
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• 2000

Commercial eddy current dynamometers control the torque of ratating body (poer supply machine) with the field coil current being operated as a braking force. In this paper, we studied about the relation between the field coil current and the torque load of eddy current dynamometer. By the torque measuring analysis of eddy current dynamometer, it is linear relation between the brake force measured from the torque meter (e.g. load cell, strain gage or spring balance etc.) which is installed at the case of dynamometer and the multiply of shaft rpm by the square of field coil current (N$\times$Ia2). To prove the relation, it was experimented and showed that the torque operated by the rotating body can be measured with the shaft rpm and the field coil current of eddy current dynamometer. This result shows a possibility that eddy current dynamometer can measures the torque of rotating body without special torque measuring devices.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.729-737
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• 2009

This paper introduces the machine tools feed system, which can be optimized the control's performance through simulation and the adjustment of the mechanical components. One method simulates the frequency response of the speed-loop with the design value using the MATLAB application, so that all of the interpolation axis can be equal to the response bandwidth, resulting in a high accuracy rate. The other method sees the mechanical component being adjusted by analyzing the results of various experiments. Lastly, this client's program is able to change the parameters that are related to the FFD, as well as the parameters in the friction compensation of the OPEN-CNC.

• Journal of Information Technology Services
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• v.13 no.3
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• pp.299-308
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• 2014

Due to indiscriminately received spam messages on information society, spam messages cause damages not only to person but also to our community. Nowadays a lot of spam filtering techniques, such as blocking characters, are studied actively. Most of these studies are content-based spam filtering technologies through machine learning.. Because of a spam message transmission techniques are being developed, spammers have to send spam messages using term spamming techniques. Spam messages tend to include number of nouns, using repeated words and inserting special characters between words in a sentence. In this paper, considering three features, SPSS statistical program were used in parameterization and we derive the equation. And then, based on this equation we measured the performance of classification of spam messages. The study compared with previous studies FP-rate in terms of further minimizing the cost of product was confirmed to show an excellent performance.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.68-70
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• 2002

Important category of brushless ac machine design is emerging in which the fundamental component of the stator MMF has fewer poles than the rotor. the torque being developed by a higher order MMF harmonic. The fundamental and lower order MMF harmonics can then give rise to significant rotor eddy currents. An analytical model is developed to predict rotor-induced eddy currents in such machines, and to quantify the effectiveness of circumferentially segmenting the permanent magnets in reducing the rotor loss.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.875-878
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• 2002

Braiding machines of maypole type have complex guide tracks. It is not easy to speed up drivers while carriers are moving with being at high speed. This paper presents a new design approach using dynamic analysis for moving carriers on the guide tracks. The proposed approach will be shown to be effective by using the simulation tool, WORKING MODEL 2D(equation omitted), for the high speed drivers on new models of braiding machines of maypole type.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.126-127
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• 2015

New technologies using a CNC machine to reduce the production cost of free-form buildings are being developed. To produce free-form members with such technologies, a vast free form building should be first divided into multiple panels that can be produced. Considering the curved surface of free-form buildings, the shape and size of divided freeform panels vary, which will lead to a great deal of errors. Currently, the engineers and designers complete the panelizing work through trials and errors even in large-scale projects, which results in increased construction duration and cost. Thus, it is necessary to develop a freeform panelizing technology to maximize the economic effects of free-form concrete member production technology. The purpose of the study is to analyze influence factors on panelizing of free-form buildings, which is a preceding research for development of a panelizing technology. The influence factors drawn will provide a core basis for development of panelizing technologies for free-form buildings.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.456-461
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• 2002

Nowadays, there are required more speed and accurate machining in order to improve the productivity through the reduction of cutting and non-cutting time. In this study, the high-speed HMC is specially designed to do remote control and high-speed mechanism with 30000rpm, 50000rpm, 40m/min, 100m/min and bridge type structure. Every structural deformation and vibration that is generated from all of factor is analyzed being based on the virtual manufacturing technologies: thermal characteristic analysis, machine-ability, tool wear measuring system, driving characteristic of linear motor and so on. As the application of these results had been consisted of three axes to move slight and rigid finally. Therefore, table errors that are resulted in change of work weight can be removed.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.140-145
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• 2008

Recently more complex geometric shapes, including freeform surfaces, are adopted for the design of products to emphasize style or beauty. Modeling of these products is extremely difficult or often impossible. Reverse engineering is the latest technology that can solve the problem by generating CAD models from the physical mockups or prototype models. Reverse engineering uses the coordinate measuring machine(CMM) to get the shape data of products. CMM is limited by the size of the product; therefore it must need the feature to solve it. The tooling-ball which is generally used for feature has difficulty in being used for soft products. Besides, the higher the accuracy of the tooling-ball is, the more expensive its cost is. This study will develop the feature of high accuracy without additional tools and compare the difference of accuracy by it.