• Journal of Electrochemical Science and Technology
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• 제2권3호
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• pp.157-162
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• 2011

We report a simple route for synthesizing multi-dimensional structured silicon anode materials from commercially available bulk silicon powders via metal-assisted chemical etching process. In the first step, silver catalyst was deposited onto the surface of bulk silicon via a galvanic displacement reaction. Next, the silver-decorated silicon particles were chemically etched in a mixture of hydrofluoric acid and hydrogen peroxide to make multi-dimensional silicon consisting of one-dimensional silicon nanowires and micro-scale silicon cores. As-synthesized silicon particles were coated with a carbon via thermal decomposition of acetylene gas. The carbon-coated multi-dimensional silicon anodes exhibited excellent electrochemical properties, including a high specific capacity (1800 mAh/g), a stable cycling retention (cycling retention of 89% after 20 cycles), and a high rate capability (71% at 3 C rate, compared to 0.1 C rate). This process is a simple and mass-productive (yield of 40-50%), thus opens up an effective route to make a high-performance silicon anode materials for lithiumion batteries.

• 소성∙가공
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• 제7권5호
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• pp.439-444
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• 1998

Recently many automotive parts have been made with stainless steels by deep drawing processes, But there are various problems occurred in deep drawing works of stainless steels compared with low carbon steels. For the severe deep drawing of complex cylindrical housing optimum process planning is required to eliminate intermediate annealing improve shape accuracy and maintain surface integrity without drawing defects such as tears wrinkles and scratches or galling. Therefore in this study a sample process planning of the severe of the severe deep drawing process is applied to a complex cylindrical housing needed for a 6 multi-stepped deep drawing of type STS 305 . A series of experiments are performed to investigate optimum process variables such as drawing rate radius and clearance. Through experiments the variations of the thickness strain distribution and hardness distribution in each drawing step are observed. Also the effects of other factors on formability such as drawing oil, blank holding force and die geometry are examined and discussed.

• 한국산업융합학회 논문집
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• 제24권5호
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• pp.641-644
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• 2021

Wearable devices and IoT are being utilized in various fields, where all systems are developing in the direction of multi-functionality, low power consumption, and high speed. In this paper, we propose a DC -DC Step-down C onverter for IoT smart devices. The proposed DC -DC Step-down converter is composed of a control block of the power supply stage. It also consists of an overheat protection circuit, under-voltage protection circuit, an overvoltage protection circuit, a soft start circuit, a reference voltage circuit, a lamp generator, an error amplifier, and a hysteresis comparator. The proposed DC-DC converter was designed and fabricated using a Magnachip / Hynix 180nm CMOS process, 1-poly 6-metal, the measured results showed a good match with the simulation results.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 자성 및 자성재료 국제학술대회
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• pp.29-30
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• 2011

We have demonstrated the fabrication of sub 30 nm MTJ pillars with PMA characteristics. The multi-step IBE process performed at $45^{\circ}$ and $30^{\circ}$, using NER resulted in almost vertical side profiles. There deposition on the sidewalls of the NER prevented lateral etching of the resist hard mask allowing vertical MTJ side profile formation without any reduction in the lithographically defined resist lateral dimensions. For the 28nm STT-MTJ pillars, the measured TMR ratio was 13 % with resistance of 1 $k{\Omega}$, which was due to remaining redeposition layers less than 0.1 nm thick. With further optimization in multi-step IBE conditions, it will be possible to fabricate fully operating sub 30 nm perpendicular STT-MTJ structures for application to future non-volatile memories.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권4호
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• pp.1579-1602
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• 2020

In the design of production system, buffer capacity allocation is a major step. Through polymorphism analysis of production capacity and production capability, this paper investigates a buffer allocation optimization problem aiming at the multi-stage production line including unreliable machines, which is concerned with maximizing the system theoretical production rate and minimizing the system state entropy for a certain amount of buffers simultaneously. Stochastic process analysis is employed to establish Markov models for repairable modular machines. Considering the complex structure, an improved vector UGF (Universal Generating Function) technique and composition operators are introduced to construct the system model. Then the measures to assess the system's multi-state reliability and structural complexity are given. Based on system theoretical production rate and system state entropy, mathematical model for buffer capacity optimization is built and optimized by a specific genetic algorithm. The feasibility and effectiveness of the proposed method is verified by an application of an engine head production line.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.19-20
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• 2006

Two methods that can reduce reflectance in solar cells are surface texturing and anti-reflection coating. Wet chemical etching is a typical method that surface texturing of multi-crystalline silicon. Wet chemical etching methods are the acid texturization of saw damage on the surface of multi-crystalline silicon or double-step chemical etching after KOH saw damage removal too. These methods of surface texturing are realized by chemical etching in acid solutions HF-$HNO_3$-$H_2O$. In this solutions we can reduce reflectance spectra by simple process etching of multi-crystalline silicon surface. We have obtained reflectance of 27.19% m 400~1100nm from acidic chemical etching after KOH saw damage removal. This result is about 7% less than just saw damage removal substrate. The surface morphology observed by microscope and scanning electron microscopy (SEM).

• 정보처리학회논문지B
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• 제8B권6호
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• pp.601-608
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• 2001

The automated assignment of multiple tasks to executing agents is a key problem in the area of multi-agent systems. In many domains, significant savings can be achieved by reallocating tasks among agents with different costs for handling tasks. The automation of task reallocation among self-interested agents requires that the individual agents use a common negotiation protocol that prescribes how they have to interact in order to come to an agreement on "who does what". In this paper, we introduce the multi-agent Traveling Salesman Problem(TSP) as an example of task reallocation problem, and suggest the Vickery auction as an interagent negotiation protocol for solving this problem. In general, auction-based protocols show several advantageous features: they are easily implementable, they enforce an efficient assignment process, and they guarantce an agreement even in scenarios in which the agents possess only very little domain-specific Knowledge. Furthermore Vickrey auctions have the additional advantage that each interested agent bids only once and that the dominant strategy is to bid one′s true valuation. In order to apply this market-based protocol into task reallocation among self-interested agents, we define the profit of each agent, the goal of negotiation, tasks to be traded out through auctions, the bidding strategy, and the sequence of auctions. Through several experiments with sample multi-agent TSPs, we show that the task allocation can improve monotonically at each step and then finally an optimal task allocation can be found with this protocol.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.1016-1020
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• 2001

The spinning is a very effective manufacturing technology for short production runs in a variety of sizes and shapes, because it can form the cross-section or tubular parts various shapes. However extensive experimental and analytical research has not been carried out. In this study, and fundamental experiment was conducted to improve productivity with process parameter such as tool path, angle of roller holder(a), feed rate(v) and corner radius of forming roller(Rr). These factors were selected as variables in the experiment because they were most likely expected to have and effect on spring back. The clearance was controlled in order to achieve the precision product which is comparable to deep drawing one. And also thickness and diameter distribution of a multistage cup obtained by shear spinning process were observed and compared with those of a commercial product produced by conventional deep drawing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.480-483
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• 2005

A roll forming process is developed for an automotive part of high strength steel. Forming rolls are designed through the plane strain elastic-plastic finite element analysis to estimate the springback. It is assumed that the process can be approximated as a series of multi-step bending processes. Then the 3D elastic-plastic finite element analysis with the solid element is carried out for the designed roll forming process. The prototype roll forming machine and the forming rolls are made and the experiments are carried out. The results of the analysis and the experiments are compared.

• 한국염색가공학회지
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• 제12권5호
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• pp.273-279
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• 2000

Interlace textured yarn was developed in order to increase weaving process efficiency. Today, interlace texturing is very useful method of manufacturing the high added value compound yarns for new synthetic fabrics. In this research, new silky type high added value compound yarns were. manufactured by interlace texturing technology and tested their properties. The object of this research is to investigate the relationship between interlace textured yarn properties and processing parameters that is air pressure, yarn tension and take-up speed. The original filament yarns used were TTD(Thick & Thin Semi-Dull) 110d/72f and SCD(Semi-Dull Cation Dyeable) 75d/36f. 27 specimens were manufactured and tested for their physical properties-nip density, tensile properties, multi-step shrinkage test and surface structure by SEM. The air pressure was main process condition to change properties of interlace textured yarns. And interlace textured process had influence on weaving preparation process, weaving, knitting and so on. It has some influence on shrinkage properties of dyeing and finishing processes.