• 한국분말재료학회지
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• 제28권1호
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• pp.1-6
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• 2021

Accurate and effective powder compaction analyses are performed for brittle materials such as graphite, utilized as a solid lubricant, by using the discrete element method (DEM). The reliability of the DEM analysis is confirmed by comparing the results of graphite powder compaction analyses using the DEM particle bonding contact model and particle non-bonding contact model with those from the powder compaction experiment under the same conditions. To improve the characteristics, the parameters influencing the compaction properties of the metal-graphite mixtures are explored. The compressibility increases as the size distribution of the graphite powder increases, where the shape of the graphite particles is uniform. The improved compaction characteristics of the metal-graphite (bonding model) mixtures are further verified by the stress transmission and compressive force distribution between the top and bottom punches. It is confirmed that the application of graphite (bonding model) powders resulted in improved stress transmission and compressive force distribution of 24% and 85%, respectively.

• 대한수학회지
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• 제61권3호
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• pp.565-602
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• 2024

We study the collective behaviors of two second-order nonlinear consensus models with a bonding force, namely the Kuramoto model and the Cucker-Smale model with inter-particle bonding force. The proposed models contain feedback control terms which induce collision avoidance and emergent consensus dynamics in a suitable framework. Through the cooperative interplays between feedback controls, initial state configuration tends to an ordered configuration asymptotically under suitable frameworks which are formulated in terms of system parameters and initial configurations. For a two-particle system on the real line, we show that the relative state tends to the preassigned value asymptotically, and we also provide several numerical examples to analyze the possible nonlinear dynamics of the proposed models, and compare them with analytical results.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1997년도 한국재료학회 추계학술발표회
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• pp.25-25
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• 1997

• 한국구조물진단유지관리공학회 논문집
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• 제15권2호
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• pp.107-115
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• 2011

본 연구는 부착재료의 변화 및 동결융해에 따른 FRP-콘크리트구조물 경계면의 거동을 조사하였다. 실험 시 고려된 연구변수로는 부착경계면의 부착강도, 경계면 유효부착길이 등을 조사하였다. 경계면 부착재료에 따른 거동변화 실험체의 경우 FRP-구조물 부착경계면에 사용되는 에폭시의 종류를 각각 3가지로 분류하며 FRP-콘크리트간 다양한 부착길이를 고려하여 시편을 제작하였으며 동결융해에 따른 경계면 거동조사의 경우 0 cycle에서 300cycle까지 계속적으로 증가되는 주기에 대하여 실험체들을 제작, 장기거동 부착실험을 수행하였다. 본 실험결과, 적용 부착재료의 종류에 따라 최대 유효부착길이는 5~7% 차이가 있었으며 동결융해 주기증가에 따른 최대부착하중 및 유효부착길이의 경우 초기에 나타난 급격한 거동변화 이후 상대적으로 불규칙한 변화를 장기적으로 나타내었다.

• 대한전자공학회논문지SD
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• 제41권12호
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• pp.21-26
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• 2004

본 논문에서는 package된 BJT의 RF 등가회로 모델을 optimization과정 없이 직접 추출하는 방법을 개발하였다. 먼저, open 과 short package 구조를 사용하여 plastic package의 기생성분을 측정된 S-파라미터로부터 정확히 제거하였다. 이와 같이 package do-embedding된 S-파라미터로부터 package lead와 chip pad 사이의 bonding wire 인덕턴스와 chip pad 캐패시턴스를 직접 추출하는 간단한 방법을 구축하였다. 그 후에 내부 BJT소자의 소신호 모델변수들은 RF 등가회로로부터 유도된 Z나 Y-파라미터 방정식을 이용하여 결정하였다. 이 방법으로 모델화된 packaged BJT의 S-파라미터는 측정 데이터와 아주 잘 일치하였으며 이는 새로운 추출방법의 정확성을 증명한다.

• ETRI Journal
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• 제41권3호
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• pp.396-407
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• 2019

Laser-assisted bonding (LAB) is an advanced technology in which a homogenized laser beam is selectively applied to a chip. Previous researches have demonstrated the feasibility of using a single-tier LAB process for 3D through-silicon via (TSV) integration with nonconductive paste (NCP), where each TSV die is bonded one at a time. A collective LAB process, where several TSV dies can be stacked simultaneously, is developed to improve the productivity while maintaining the reliability of the solder joints. A single-tier LAB process for 3D TSV integration with NCP is introduced for two different values of laser power, namely 100 W and 150 W. For the 100 W case, a maximum of three dies can be collectively stacked, whereas for the 150 W case, a total of six tiers can be simultaneously bonded. For the 100 W case, the intermetallic compound microstructure is a typical Cu-Sn phase system, whereas for the 150 W case, it is asymmetrical owing to a thermogradient across the solder joint. The collective LAB process can be realized through proper design of the bonding parameters such as laser power, time, and number of stacked dies.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.613-614
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• 2010

• Journal of Periodontal and Implant Science
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• 제51권3호
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• pp.163-178
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• 2021

Purpose: The aim of this study was to evaluate clinical factors affecting the longevity of fixed retainers and the influence of fixed retainers on periodontal health in periodontitis patients. Methods: In total, 52 patients with at least 2 years of follow-up after periodontal and orthodontic treatment were included in this study. After scaling and root planing, orthodontic treatment with fixed appliances or clear aligners was performed. Fixed retainers with twist-flex stainless steel wires were bonded to the palatal or lingual sides of anterior teeth. Changes in clinical parameters, including the plaque index, gingival index, calculus index (CI), probing pocket depth, and radiographic bone levels, were evaluated before bonding of fixed retainers and at a 12-month follow-up. Cumulative survival rates (CSRs) for retainer failure were evaluated according to sex, site, CI, stage of periodontitis, and the severity of the irregularity with the log-rank test and hazard ratios (HRs). Results: Twelve months after bonding of fixed retainers, improvements were observed in all clinical parameters except CI and radiographic bone gain. The overall CSR of the retainers with a CI <1 at the 12-month follow-up after bonding of fixed retainers was significantly higher than that of the retainers with a CI ≥1 at the 12-month follow-up (log-rank test; P<0.001). Patients with stage III (grade B or C) periodontitis had a higher multivariate HR for retainer failure (5.4; 95% confidence interval, 1.22-23.91; P=0.026) than patients with stage I (grade A or B) periodontitis. Conclusions: Although fixed retainers were bonded in periodontitis patients, periodontal health was well maintained if supportive periodontal treatment with repeated oral hygiene education was provided. Nonetheless, fixed retainer failure occurred more frequently in patients who had stage III (grade B or C) periodontitis or a CI ≥1 at 12-month follow-up after bonding of fixed retainers.

• International Journal of Precision Engineering and Manufacturing
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• 제8권1호
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• pp.52-58
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• 2007

We propose a new contact detection algorithm for fine pitch wire bonding. Fast and stable contact detection of the z-axis in wire bonding is extremely important to maintain the quality of fine pitch gold wire bonding processes, which use a small pad less than $70{\mu}m$ in diameter. A small perturbation in the contact detection time causes a large difference in the size of the formed squashed ball. The new detection method is based on a statistical approach and designed for a discrete Kalman filter. It is faster and has smaller detection time variations than conventional detection methods. Experimental results are presented to demonstrate the advantages of the proposed algorithm.

• 소성∙가공
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• 제16권2호
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• pp.144-149
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• 2007

The superplastic forming/diffusion bonding(SPF/DB) is widely used in the automotive and aerospace industry because it has great advantage to produce complex, light and strong parts. But the superplastic forming process requires much forming time and generates excessive thinning in the thickness distribution of formed part. It is necessary to minimize trial and error for SPF/DB Process. Finite element analysis using $L_{18}$ orthogonal may table of Taguchi method for 3-Sheet D/B process is carried out. Through the study, effect of process parameters, such as DH region size, thickness and friction coefficient, is evaluated and the optimum condition is derived.