• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.723-730
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• 1998

With the introduction of edge drop control system in Tandem Cold Rolling Mill, it is necessary to develop te numerical expression for the set-up and edge drop automatic control of cold rolled sheet. As a first step we developed a simulation program which predicts profile and the amounts of edge drop at the delivery side of each stand by using roll deformation anlysis with the slit roll model. And by using the program the effect of various rolling conditions on edge drop was investigated. As a result the relations were obtained between the amounts of edge drop and rolling conditions. Based on above relations, the numerical expression was developed for the set-up and automatic control of edge drop by multi-regression of simulation results for the variation of edge drop amount with each rolling condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1202-1215
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• 1996

In this study, in order to achieve the uniformity of mechanical properties and microstructures of a hot-rolled coil in the transversal direction, the edge mask device is newly device is newly developed and installed at the upper laminar-flow cooling head in the run out table, which controls the transversal temperature of strip with enco panel and bar edge heater. The device that is transversally movable prevents the temperature drop of strip edge by blocking the cooling water into the strip edge. So, the pattern of edge mask set-up condition of the device was derived by analyzing the characteristics of strip temperature and mechanical properties according to the on-line application of edge mask.

• Journal of the Korea Society for Simulation
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• v.18 no.3
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• pp.91-102
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• 2009

The average window size is most closely related to average throughput. In order to improve fairness, the proposed dropper tries to control the window size of each flow to equal level by intentional packet drop. Intentional packet drop is performed only to the flows that have been occupied bandwidth in a large amount. Because of intentional packet drop, this flow cut down its transmission rate to a half. Accordingly, somewhat capacity of core link comes into existence. And other flow can use this new capacity of this link. Hence other flows have more throughput than before. In this paper, we propose the TRC (Transmission Rate Control) Dropper improving the fairness between individual flows of aggregated sources on DiffServ network. It has the fairness improvement mechanism mentioned above paragraph.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4B
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• pp.255-269
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• 2006

The differentiated services(DiffServ) architecture provides packet level service differentiation through the simple and predefined Per-Hop Behaviors(PHBs). The Assured Forwarding(AF) PHB proposed as the assured services uses the RED-in/out(RIO) approach to ensusre the expected capacity specified by the service profile. However, the AF PHB fails to give good QoS and fairness to the TCP flows. This is because OUT(out- of-profile) packet droppings at the RIO buffer are unfair and sporadic during only network congestion while the TCP's congestion control algorithm works with a different round trip time(RTT). In this paper, we propose an Adaptive Regulating Drop(ARD) marker, as a novel dropping strategy at the ingressive edge router, to improve TCP fairness in assured services without a decrease in the link utilization. To drop packets pertinently, the ARD marker adaptively changes a Temporary Permitted Rate(TPR) for aggregate TCP flows. To reduce the excessive use of greedy TCP flows by notifying droppings of their IN packets constantly to them without a decrease in the link utilization, according to the TPR, the ARD marker performs random early fair remarking and dropping of their excessive IN packets at the aggregate flow level. Thus, the throughput of a TCP flow no more depends on only the sporadic and unfair OUT packet droppings at the RIO buffer in the core router. Then, the ARD marker regulates the packet transmission rate of each TCP flow to the contract rate by increasing TCP fairness, without a decrease in the link utilization.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.837-845
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• 1987

In the research of the rolling of strip, producing the strip with a close tolerance of thickness over the rolling direction was a principal object. But it was solved by the contribution of two-dimensional theory of rolling and the development of automatic gauge control system. And new requirements for the study of flatness, crown of rolled strip and edge drop grow up recently. These phenomena are closely related with the thickness distribution along the lateral direction of rolled strip. To analyse the thickness distribution of rolled strip along the lateral direction, elastic deformation of rolls and plastic deformation of work material must be discussed simultaneously. In this report, an approximate three-dimensional analysis based on Tozawa's three dimensional approach was applied to 12 cases of different rolling conditions and the numerical results were investigated. Especially stresses were laid upon the investigation of optimal boundary position between the three-dimensional analysis region and the plane strain analysis region.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.115-121
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• 2017

The efficiency of railway track cleaning vehicle for eliminating fine particulate matter (PM10 and PM2.5) in a subway tunnel depends strongly on the structure of the air blowing and suction system installed under the train. To increase the efficiency of underbody suction system, this paper proposes a novel method to use the Coanda effect for the air blower and dust suction module. In particular, through Computational Fluid Dynamics (CFD) analysis, the flow control device induced by the Coanda effect enables an increase in the overall flow velocity and to stabilize the flow distribution of the suction module at a control angle of $90^{\circ}$. In addition, the flow velocity drop at the edge of the air knife-type blower can be improved by placing small inserts at the edge of the blower. Those 4 modular designs of the dust suction system can help remove the dust accumulated on the track and tunnel by optimizing the blowing and suction flows.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.307-316
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• 2004

This study examined the cause of the wrinkle defect which is frequently encountered in wire rod rolling of low carbon steel$(C0.08\~0.13wt.\%)$. Even a small defect on the surface of rolled bars can easily develop into fatal cracks during cold heading process of low carbon steel, and it is therefore necessary to minimize inherent defects on the surface of hot rolled bars. Hot rolling process of low carbon steel was analyzed to identify the cause of the wrinkle defect in conjunction with FE analysis. The integrated analysis revealed that the wrinkle defect initiated in the first stage of rolling, and it was at the billet edge where severe deformation and drastic temperature drop were present. To elucidate the micro-mechanical mechanism of the wrinkle defect, hot compression tests were carried out at various temperatures and strain rates using Gleeble-3800. The surface profile of the each other compressed specimens was compared, and rough surface lines were observed at relatively low temperatures. Those surface defects can develop into wrinkles during multi-pass rolling. To control the wrinkle defect in rolling, it is necessary to design an adequate caliber which can minimize the loss of ductility, and thereby prevent flow localization. To use the result of this study fur other steels, the quantitative measure of the wrinkle defect and flow localization parameter should be proposed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.109-118
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• 2004

No.2 PCM (Pickling and tandem cold rolling mill) at Pohang works was revamped in 2003. The purpose of this project is to produce carbon and stainless steel using conventional carbon production process, rolling and annealing. This paper introduces the applied facilities and technologies of PCM which are used in production of carbon and stainless steel. To realize the main purpose of this project, POSCO have developed laser weld technology in normal carbon and special steel (stainless, high carbon and high silicon). And this report describes the method which is developed to get down the surface defect of stainless 400 series. After revamping, No.2 PCM can have competitive power in this field and can supply the special steel using carbon rolling process.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.482-487
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• 2005

In this paper, we propose the control method of output impedance of each cascode unit cell of distributed amplifier by connecting varactors in the gate-terminal of common gate. Compared to common source unit cell, cascode unit cell has many advantages such as high gain and high output impedance as well as negative resistance loading. But if the transistor model which is used in design is inaccurate and process parameter is changed, oscillation sometimes can occur at band edge in which the gain start to drop. Therefore, we need control circuit which can prevent oscillation, although the circuit has already fabricated, and varactor connected to gate-terminal of common gate of cascode gain cell can play that part. Measured result of fabricated distributed amplifier shows the capability of contol of gain characteristic by adjusting of value of varactors, this can guarantee the stability of the circuit. The gain is $8.92\pm0.82dB$ over 49 GHz, the group delay is $\pm9.3 psec$ over 41 GHz. All transistor which has $0.15{\mu}m$ gate length is GaAs based p-HEMT, and distributed amplifier is put together with 4 stages.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.3-3
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• 2001

Recently TiN, TiAlN, CrN hardcoatings have adapted many industrial application such as die, mold and cutting tools because of good wear resistant and thermal stability. However, in terms of high speed process, general hard coatings have been limited by oxidation and thermal hardness drop. Especially in the case of PCB drill, high speed cutting and without lubricant process condition have not adapted these coatings until now. Therefore more recently, superhard nanocomposite coating which have superhard and good thermal stability have developed. In previous works, WC-TiAlN new nanocomposite film was investigated by cathodic arc ion plating system. Control of AI concentration, WC-TiAlN multi layer composite coating with controlled microstructure was carried out and provides additional enhancement of mechanical properties as well as oxidation resistance at elevated temperature. It is noted that microhardness ofWC-TiA1N multi layer composite coating increased up to 50 Gpa and got thermal stability about $900^{\circ}C$. In this study WC-TiAlN nanocomposite coating was deposited on PCB drill for enhancement of life time. The parameter was A1 concentration and plasma cleaning time for edge sharpness maintaining. The characteristic of WC-TiAlN film formation and wear behaviors are discussed with data from AlES, XRD, EDS and SEM analysis. Through field test, enhancement of life time for PCB drill was measured.