• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.154-160
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• 2005

Microwave Otters are essential device in modem wireless systems. A compact dimension BPF(Band-pass Filter) for IEEE 802.11a WLAN service is realized using LTCC multi-layer process. To extrude 2-stage band-pass equivalent circuit, band-pass and J-inverter transform applied to Chebyshev low-pass prototype filter. Because parallel L-C resonator is complicate and hard to control the inductor characteristics in high frequency, the shorted $\lambda/4$ stripline is selected for the resonator structure. The passive element is located in the different layers connected by conventional via structure and isolated by inner GND. The dimension of fabricated stacked band-pass filter which is composed of six layers, is $2.51\times2.27\times1.02\;mm^3$. The measured filter characteristics show the insertion loss of -2.25 dB, half-power bandwidth of 220 MHz, attenuation at 5.7 GHz of -32.25 dB and group delay of 0.9 ns at 5.25 GHz.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.1
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• pp.19-24
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• 2003

A very small size 2.4 GHz ISM band BPF(Band Pass Filter) is realized using LTCC Multi-layer technology. Proposed design method enables to achieve BPF size $2.0\times1.2\times0.8mm^3$. A $lambda/4$ resonator with shunt-to-ground loaded capacitor is used to shorten resonator length, achieving higher quality factor. Also this resonator enables BPF to improve out-of-band rejection. Coupling coefficients between coupled strip-line resonators and external quality factor (Qe) of a resonator are derived and applied to the filter design. The measured results show good agreement with simulated data.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.128-132
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• 2008

This paper presents a filter design technique with the embedded passive elements using the low temperature co-fired ceramic (LTCC) process. For the high performance and size reduction, the parasitic elements of the proposed multi-layer structure are positively considered by using the proposed circuit transformation procedures. As a result, the compact low ass filter (LPF) not only has at least 50% more compact thickness than other reported compact structures, but also provides ideal LPF response between 0.5GHz and 5GHz.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.18-21
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• 2007

Highly textured MgO template by ion-beam-assisted deposition(IBAD) was successfully fabricated using a continuous reel-to-reel(R2R) mode. To enlarge the deposition area, the previous IBAD system was modified into the system with 14-pass and five heating zone. Every processing step was carried out using this multi-turn IBAD system. The overall process consists of R2R electropolishing of a hastelloy C276 tape, deposition of $Al_2O_3$ diffusion barrier, $Y_2O_3$ seed layer, IBAD-MgO and homoepi-MgO layer. The IBAD-MgO templates were fabricated using the IBAD system with 216 cm-length deposition zone and 32 cm diameter ion source. The texture of MgO films developed during the IBAD process was monitored by in-situ reflection high energy electron diffraction(RHEED) to optimize the IBAD process. Recently, 100 m long IBAD-MgO tape with in-plane texture of $\Delta{\phi}<10^{\circ}$ was successfully fabricated using the modified IBAD system. In this report, the detailed deposition condition of getting a long length IBAD-MgO template with a good epitaxy is described.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.58-66
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• 2007

This paper introduces the new generic dynamic neuro-fuzzy local modeling system (DNFLMS) that is based on a dynamic Takagi-Sugeno (TS) type fuzzy inference system for complex dynamic hydrological modeling tasks. The proposed DNFLMS applies a local generalization principle and an one-pass training procedure by using the evolving clustering method to create and update fuzzy local models dynamically and the extended Kalman filtering learning algorithm to optimize the parameters of the consequence part of fuzzy local models. The proposed DNFLMS is applied to develop the inference model to forecast the flow of Waikoropupu Springs, located in the Takaka Valley, South Island, New Zealand, and the influence of the operation of the 32 Megawatts Cobb hydropower station on springs flow. It is demonstrated that the proposed DNFLMS is superior in terms of model accuracy, model complexity, and computational efficiency when compared with a multi-layer perceptron trained with the back propagation learning algorithm and well-known adaptive neural-fuzzy inference system, both of which adopt global generalization.

• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.961-966
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• 2003

A Multi-Layer Ceramic (MLC) chip type Band-Pass Filter (BPF) using BiNb$\_$0.975/Sb$\_$0.025/ $O_4$ LTCC (Low Temperature Co-fired Ceramics) and MLC processing is presented. The MLC chip BPF has the benefits of low cost and small size. The BPF consists of coupled stripline resonators and coupling capacitors. The BPF is designed to have an attenuation pole at below the passband for a receiver band of IMT-2000 handset. The computer-aided design technology is applied for analysis of the BPF frequency characteristics. The attenuation pole depends on the coupling between resonators and the coupling capacitance. An equivalent circuit and structure of MLC chip BPF are proposed. The frequency characteristics of the manufactured BPF is well acceptable for IMT-2000 application.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.403-408
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• 2012

A sample of ultra low carbon IF steel was processed by six-layer stack accumulative roll-bonding (ARB) and annealed. The ARB was conducted at ambient temperature after deforming the as-received material to a thickness of 0.5 mm by 50% cold rolling. The ARB was performed for a six-layer stacked, i.e. a 3 mm thick sheet, up to 3 cycles (an equivalent strain of ~7.0). In each ARB cycle, the stacked sheets were, first, deformed to 1.5 mm thickness by 50% rolling and then reduced to 0.5 mm thickness, as the starting thickness, by multi-pass rolling without lubrication. The specimen after 3 cycles was then annealed for 0.5 h at various temperatures ranging from 673 to 973 K. The microstructural evolution with the annealing temperature for the 3-cycle ARB processed IF steel was investigated in detail by transmission electron microscopy observation. The ARB processed IF steel exhibited mainly a dislocation cell lamella structure with relatively high dislocation density in which the subgrains were partially observed. The selected area diffraction (SAD) patterns suggested that the misorientation between neighboring cells or subgrains was very small. The thickness of the grains increased in a gradual way up to 873 K, but above 898 K it increased drastically. As a result, the grains came to have an equiaxed morphology at 898 K, in which the width and the thickness of the grains were almost identical. The grain growth occurred actively at temperatures above 923 K.

• Journal of the Korea Safety Management & Science
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• v.6 no.4
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• pp.155-170
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• 2004

Among the semiconductor If-chips, unlike memory chips, a majority of Application Specific IC(ASIC) products are produced by customer orders, and meeting the customer specified due date is a critical issue for the case. However, to the one who understands the nature of semiconductor manufacturing, it does not take much effort to realize the difficulty of meeting the given specific production due dates. Due to its multi-layered feature of products, to be completed, a semiconductor product(called device) enters into the fabrication manufacturing process(FAB) repeatedly as many times as the number of the product specified layers, and fabrication processes of individual layers are composed with similar but not identical unit processes. The unit process called photo-lithography is the only process where every layer must pass through. This re-entrant feature of FAB makes predicting and planning of due date of an ordered batch of devices difficult. Parallel machines problem in the photo process, which is bottleneck process, is solved with restricted roll out algorithm. Roll out algorithm is a method of solving the problem by embedding it within a dynamic programming framework. Restricted roll out algorithm Is roll out algorithm that restricted alternative states to decrease the solving time and improve the result. Results of simulation test in condition as same as real FAB facilities show the effectiveness of the developed algorithm.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.37-37
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• 2009

Due to their high corrosion resistance and improved mechanical properties super-duplex stainless steel (SDSS) are extensively used in petrochemical plants such as facilities in modern oil platform and off-shore process equipment. It is well known that the best mechanical and corrosion resistance properties of super-duplex stainless steel are obtained with a microstructure having approximately equal amounts of austenite and ferrite. And it is also known that sigma($\sigma$), chi($\chi$), secondary austenite(${\gamma}2$), chromium carbides and nitride affected adversely their properties. Therefore these phases must be avoided. However, effects of succeeding weld thermal cycle on the change of microstructure of weldment at multi-pass weld were not seldom experimentally researched. Therefore in the present work, the change of weldmetal microstructure and the effect of microstructure on pitting corrosion property at $40^{\circ}C$ by succeeding each weld thermal cycle were researched. The thermal history of root side was measured experimentally and the change of microstructure of root weld according to thermal cycle of each weld layer was evaluated. And the relationship between microstructure of root weld and pitting corrosion property at $40^{\circ}C$ was also investigated. Results of the present work are show as below. 1. The ferrite contents of root weld are gradually reduced by succeeding weld thermal cycle. 2. The 2nd phases such as sigma($\sigma$), chi($\chi$), secondary austenite(${\gamma}2$), chromium carbides and nitride are increased gradually by succeeding weld thermal cycle. 3. The pitting corrosion was detected in root weld part and weight loss by pitting corrosion is increased in proportional to the time exposed over $600^{\circ}C$ of the root weld. 4. The succeeding weld thermal cycles affect the microstructure of the former weldments and promote the formation of 2nd phases. That is, the more succeeding welds are added, the more 2nd phases are gradually increased. Consequently, it is thougth that this adversely affects pitting corrosion property.

• Journal of Welding and Joining
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• v.28 no.4
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• pp.18-25
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• 2010

Super-duplex stainless steels (SDSS) have a good balance of mechanical property and corrosion resistance when they consist of approximately equal amount of austenite and ferrite. The SDSS needs to avoid the detrimental phases such as sigma(${\sigma}$), chi(${\chi}$), secondary austenite(${\gamma}2$), chromium carbide & nitride and to maintain the ratio of ferrite & austenite phase as well known. However, the effects of the subsequent weld thermal cycle were seldom experimentally studied on the micro-structural variation of weldment & pitting corrosion property. Therefore, the present study investigated the effect of the subsequent thermal cycle on the change of weld microstructure and pitting corrosion property at $40^{\circ}C$. The thermal history of root side was measured experimentally and the change of microstructure of weld root & the weight loss by pitting corrosion test were observed as a function of the thermal cycle of each weld layer. The ferrite contents of root weld were reduced with the subsequent weld thermal cycles. The pitting corrosion was occurred in the weld root region in case of the all pitted specimen & in the middle weld layer in some cases. And the weight loss by pitting corrosion was increased in proportional to the time exposed at high temperature of the root weld and also by the decrease of ferrite content. The subsequent weld thermal cycles destroy the phase balance of ferrite & austenite at the root weld. Conclusively, It is thought that as the more subsequent welds were added, the more the phase balance of ferrite & austenite was deviated from equality, therefore the pitting corrosion property was deteriorated by galvanic effect of the two phases and the increase of 2nd phases & grain boundary energy.