• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.660-664
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• 2003

The optimal thickness distribution of an active damping layer is sought so that it satisfies a certain constraint on the dynamic performance of a system minimizing control efforts. To obtain a topologically optimized configuration, which includes size and shape optimization, thickness of the active damping layer is interpolated using linear functions. With the control energy as the objective function to be minimized, the state error energy is introduced as the dynamic performance criterion for the system and used lot a constraint. The optimal control gains are evaluated from LQR simultaneously as the optimization of the layer position proceeds. From numerical simulation, the topologically optimized distribution of the active damping layer shows the same dynamic performance and cost as the Idly covered counterpart, which is optimized only in terms of control gains, with less amount of the layer.

• Laser Solutions
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• v.3 no.3
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• pp.21-29
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• 2000

For the direct metal shape processing the powder feed device which is different from the widely used in rapid prototyping. is developed, The three dimensional object is shaped with the melting metal powder. The developed research has applied to rapid prototyping in ultraprecision for MEMS and medical science fields required of rapid manufacture of complex shape. The goal of this study make 3D model which has precision accuracy. Powder spreading apparatus has been more improved because that the control of powder spread is very important in layer manufacturing. It consists of the vibration motor, nozzle and tube which supplies various metal powder. This apparatus could control the spreading velocity that could control powder spreading thickness. Laser on/off switch was adapted because laser scanning velocity must be preserved constantly to prevent heat transformation of laser overheating. The error between sintered thickness md experimental one occurred by shrinkage in sintering melting process. The problem of heat transformation was solved by On/Off switching system.

• Journal of Biosystems Engineering
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• v.32 no.4
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• pp.207-214
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• 2007

Based on the profiles of cone index with depth, physical properties of hardpan in selected rice fields were measured and analyzed in the study. An error correction algorithm removing a random measurement error from raw CI profile data was introduced in the study. The properties of hardpan included the shape, the thickness and the rice root growing layer. The analysis of physical properties of hardpan in the rice fields showed that the type of hardpan could be classified into 6 categories. The thickness of hardpan ranged from 6 cm up to 41 cm and the average hardness of hardpan was analyzed to be from 1.1 MPa through 3.2 MPa in Cone index.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.12
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• pp.973-979
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• 2001

Sliding mode control guarantees robustness in the presence of modeling uncertainties and external disturbances. However, this can be obtained at the cost of high control activity that may lead to chattering As one way to alleviate this problem a boundary layer around sliding surface is typically used. In this case the selection of controller gain, control ban width and boundary layer thickness is a crucial problem for the trade-off between tracking error and chattering. The parameter tuning is usually done by trail-and-error in practice causing significant effort and time. An auto tuning method based on fuzzy rules is proposed in the paper in this method tracking error and chattering are monitored by performance indices and the controller tunes the design parameters intelligently in order to compromise both indices. To demonstrate the efficiency of the propose method a mass-spring translation system and a roboic control system are simulated and tested It is shown that the proposed algorithm is effective to facilitae the parameter tuning for sliding mode controllers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.39-47
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• 2022

In this paper, we proposed a thickness measurement method of concrete slab using GPR, and the verification of the suggested algorithm was carried out through real-scale experiment. The thickness measurement algorithm developed in this study is to set the relative dielectric constant based on the unique shape of parabola, and time series data can be converted to thickness information. GPR scanning were conducted in four types of slab structure for noise reduction, including finishing mortar, autoclaved lightweight concrete, and noise damping layer. The thickness obtained by GPR was compared with Boring data, and the average error was 1.95 mm. In order to investigate the effect of finishing materials on the slab, additional three types of finishing materials were placed, and the following average error was 1.70 mm. In addition, sampling interval from device, the effect of radius on the shape of parabola, and Boring error were comprehensively discussed. Based on the experimental verification, GPR scanning and the suggested algorithm have a great potential that they can be applied to the thickness measurement of finishing mortar from concrete slab with high accuracy.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.78-81
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• 2004

A technical performance of the coating depends greatly on the thickness of painting film or coating film. Therefore the confirmed report of the technique to measure accurately is essential to the coating film thickness for the assessment about a coating quality performance. In this paper, two gap sensors - eddy current gap sensor and capacitance gap sensor - which has a different operating principle were used to measure the thickness of a nonmagnetic substance coating film such as paint, enamel or ceramic that was coated on the metallic material. A capacitance gap sensor was used to measure the distance between the sensor head and a coating film and an eddy current gap sensor to measure the distance between the sensor head and a base metal. Then the thickness of a coating film was obtained by the difference of two measurement value. At this result, the suggested dual sensor can measure an arbitrary film thickness to be coated on a base metal as the measurement value of coating thickness exists accurately within the 2％ error.

• Nuclear Engineering and Technology
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• v.20 no.3
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• pp.179-188
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• 1988

A recently developed spatial differencing scheme, Linear Characteristic (LC) scheme is compared with some traditionally used schemes such as Step Difference (SD), Diamond Difference (DD), and Step Characteristic (SC) scheme by analyzing the truncation error calculated numerically in slab geometry. Those four candidate schemes are applied to one simple source sink problem and two criticality problems (one is calculation of multiplication factor and the other is slab critical half thickness). The calculated results are then examined by some equitable measures of error. It is concluded that the LC scheme is terribly more powerful than any other candidate scheme that has been prevalent up to the present time. Moreover, the LC scheme estimates integral parameter such as multiplication factor and critical half thickness much more efficiently than SD or SC scheme. This is due to the fact that the fortuitous error cancellation, which occurs when the deviations of cell average flux are summed over the whole gamut of spatial meshes, happens much more favorably to the LC scheme.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.9
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• pp.38-44
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• 2008

Light guide plate is one of most important components which are composed of back light unit, affecting the quality and performance of LCD. Average brightness and uniformity are especially key factors for designing the light guide unit. These qualities are affected and controlled by the pattern being attached to the back of light guide unit. In order to obtain high brightness and uniformity the optimized pattern design is adopted for LGP. In this study, optimized molding condition for LGP with 0.4 mm thickness was obtained by using the Moldflow simulation software and the optimized pattern for better brightness uniformity was designed for the thickness of the 0.4 mm by trial and error method. The brightness was measured for the different LGP thicknesses and the residual stress analysis was performed for 0.4 mmthickness by the photoelasticity and the results are compared with 0.5 mm, 0.6 mm thickness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.910-913
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• 2000

In this research we investigate geometric issues involved while using a particular rapid prototyping system, called Stereolithography(SLA). SLA create prototypes layer by layer, each layer being formed by scanning a laser beam across the x, y surface of a vat of liquid monomer mix. The performance of SLA is influenced by orientation and layer thickness of designed fabrication. The number of layer and the area needed support is influenced by the orientation and layer thickness of designed fabrication. The step influence and volume error is influenced by slice thickness. We minimize the support are, the number of layer and cusp height. These variables of fabrication is minimized using genetic algorithm. The time for genetic algorithm is as little as we can accept. So we calculate support area and cusp height simply.

• Journal of the Semiconductor & Display Technology
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• v.2 no.2
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• pp.9-15
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• 2003

This paper proposes a thickness measurement method of silicon-oxide and poly-silicon film deposited on 12" silicon wafer for spin etcher. Halogen lamp is used as a light source for generating a wide-band spectrum, which is guided and focused on the wafer surface through a optical fiber cable. Interference signal from the film is detected by optical sensor to determine the thickness of the film using spectrum analysis and several signal processing techniques including curve-fitting and adaptive filtering. Test wafers with three kinds of priori-known films, polysilicon(300 nm), silicon-oxide(500 nm) and silicon-oxide(600 nm), are measured while the wafer is spinning at 20 Hz and DI water flowing on the wafer surface. From experiment results the algorithm presented in the paper is proved to be effective with accuracy of maximum 0.8% error.rror.