• Journal of Mechanical Science and Technology
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• v.18 no.3
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• pp.379-387
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• 2004

A novel flatness sensing system which is called the Flatness Sensing Inter-stand Looper(FlatSIL) system is suggested and a self-tuning PI control system using the FlatSIL is designed for improving the flatness of hot strip in finishing mill processes. The FlatSIL system measures the tension along the direction of the strip width by using segmented rolls, and the tension profile is approximated through the tension of each segmented roll. The flatness control system is operated by using the tension profile. The proposed flatness control system as far as the tension profile-measuring device works for the full strip length during the strip rolling in finishing mills. The generalized minimum variance self-tuning (GMV S-T) PI control method is applied to control the flatness of hot strip which has a design parameter as weighting factor for updating the PI gains. Optimizing the design parameter in the GMV S-T PI controller, the Robbins-Monro algorithm is used. It is shown by the computer simulation and experiment that the proposed GMV S-T PI flatness control system has better performance than the fixed PI flatness control system.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.273-276
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• 2006

The focus of this study is on the enhancement of flatness for the shielded slot plate, one of main components of the MCFC stack. The shielded slot plate is to get curvature during manufacturing process since it is produced by forming operation from only one side of it. Therefore, a correction die is proposed to place just after the main die to apply unbending on the curved plate to get almost flat product. In the design for the correction die, four kinds of design factors are selected to study which factor is the most influencing one affecting the flatness of the plate. From the experimental results using Taguchi method, it has been revealed that the Young's modulus of urethane die is the most critical factor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.3
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• pp.23-28
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• 2006

The focus of this study is placed on the enhancement of flatness for the shielded slot plate, one of main components of the MCFC stack. The shielded slot plate is to get curvature during manufacturing process since it is produced by forming operation from only one side of it. Therefore, a correction die is proposed to place just after the main die to apply unbending on the curved plate to get almost flat product. In the design for the correction die, four kinds of design factors are selected to study which factor is the most influencing one affecting the flatness of the plate. From the experimental results using Taguchi method, it has been revealed that the Young's modulus of urethane die is the most critical factor.

• Transactions of Materials Processing
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• v.14 no.5 s.77
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• pp.477-481
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• 2005

Wafer scale micro mirror array with high surface quality for small form factor (SFF) optical pick-up was fabricated by micro UV-molding. To replicate micro mirror array for SFF optical pick-up, a high- precision mold was fabricated using micro-machining technology. Wafer scale micro mirror array was UV-molded using the mold and then the process was optimized experimentally. The surface flatness and roughness of UV-molded micro mirror array were measured by white light scanning interferomety system and analyzed the transcribing characteristics. Finally, the measured flatness of UV-molded micro mirror away for SFF optical pick-up, which was fabricated in the optimum processing condition, was less than 70nm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.762-768
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• 2003

This paper reports the effects of gain flatness for linearity improvement of feedforward power amplifier fur IMT-2000 band. To investigate the operational characteristics for gain flatness of each amplifier, WCDMA 4FA input signal was used and measured 10 W output power. Especially, linearity improvement for variation of gain flatness of each amplifier was investigated that have an effect on linearity improvement such as delay line, phase, and amplitude imbalances. Variation of gain flatness of main amplifier is 40 MHz and of error amplifier is 40 MHz and 80 MHz bandwidth, respectively. Measured results, gain flatness of main amplifier is less than 1.5 dB and of error amplifier is less than 0.5 dB for more than 20 dB improvement at 5 MHz offset. In addition to that results, the characteristics of feedforward amplifier are drastically varied by gain flatness of error amplifier and it is shown that gain flatness of error amplifier is more important factor for linearity improvement.

• Journal of Digital Contents Society
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• v.5 no.4
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• pp.251-256
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• 2004

The flatness of a silicon wafer concerned with ULSI chip is one of the most critical parameters ensuring high yield of wafers. That is necessary to constitute the circuit with high quality for he surface of silicon wafer, which comes to be base to make the direct circuit of the semiconductor, Flatness, therefore, is the most important factor to guarantee it wafer with high quality. The process of polishing is one of the most crucial production line among 10 processing stages to change the rough surface into the flatnees with best quality. Currently at this process, it is general for an engineer in charge to observe, judge and control the model of wafer from the monitor of measuring equipment with his/her own eyes to enhance the degree of flatness. This, however, is quite a troublesome job for someone has to check of process by one's physical experience. The purpose of this study is to approach the model of wafer with digital contents and to apply the result of the research for an algorithm which enables to control the polishing process by means of measuring the degree of flatness automatically, not by person, but by system. In addition, this paper shows that this algorithm proposed for the whole wafer flatness enables to draw an estimated algorithm which is for the thickness of sites to measure the degree of flatness for each site of wafer.

• Communications of the Korean Mathematical Society
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• v.35 no.3
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• pp.697-709
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• 2020

In this paper, the class of quasi-annihilator (homo)flat acts based on the notion of quasi-annihilator ideal is introduced. This class lies strictly between the classes of weakly (homo)flat and principally weakly (homo)flat acts. Some properties of such kinds of flatness are studied. We present some homological classifications for monoids by means of quasiannihilator (homo)flatness of their right Rees factor acts.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.92-92
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• 2008

The surface flatness of heteroepitaxially grown 3C-SiC thin films is a key factor affecting electronic and mechanical device applications. This paper describes the surface flatness of polycrystalline 3C-SiC thin films by the gas flow control according to the location change of geometric structure. The polycrystalline 3C-SiC thin film was deposited by APCVD(Atmospheric pressure chemical vapor deposition) at $1200^{\circ}C$ using HMDS(Hexamethyildisilane : $Si_2(CH_3)_6)$ as single precursor, and 5 slm Ar as the main flow gas. According to the location of geometric structure, surface fringes and flatness changed. It shows the distribution of thickness is formed uniformly in the specific location of the geometric structure.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.121-124
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• 2000

In mobile communication repeaters, very small size with sharp skirt response is needed as the BPF performances. The passband flatness of the proper BPF becomes very bad due to the low value of the resonator Q-factor used in the BPF. Which could girt serious level unbalance between channels. This flatness problem can he solved by a kind of compensated filler, which has 'reverse-curve'or 'concave shape'as the passband response. In this paper, the design method of the proposed 'concave bandpass filter'without matching and loss problems is presented. The designed and fabricated filter can properly and easily compensate the convex or bad flat passband response.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.58-63
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• 1998

There are lots of factors that are related to the geometric characteristics of machined surface. Among them, the tool path and milling mode (up cut milling or down cut milling) are the easiest controllable machining conditions. Thus, the first objective of this research is to study the effects of them on the milled surface that is generated by an end milling tool. To get precision parts, not only the machining process but also the measurement of geometric tolerance is important. But, this measurement requires a lot of time, because the infinite surface points must be measured in the ideal case. So, the second objective is to propose a simple flatness measurement method that can be available instead of the 3-D geometric tolerance measurement method, using a scale factor and characterized points. Finally, it is also shown that the possibility of flatness improvement by shifting the consecutive fine cutting tool path as compared with the last rough cutting tool path.