• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.117-120
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• 2003

Electro-micromechanical techniques were applied using four-probe method for carbon nanotube (CNT) or nanofiber (CNF)/epoxy composites with their content. Carbon black (CB) was used to compare with CNT and CNF. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity for double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites, and in CB case they were the lowest compared with CNT and CNF. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

• Journal of Magnetics
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• v.7 no.4
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• pp.151-155
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• 2002

In situ stress changes at interfaces of ultrathin magnetic films were measured by means of a non-contact optical fiber bundle displacement detector. A bending of the substrate due to stress of a deposited film was detected in cantilever geometry. The highest sensitivity of 134 mV/$\mu$m for the displacement detector was realized with a help of computer simulation. The detector was applied to in situ stress measurements of Co/Pt and Ni/Pd magnetic multilayer films prepared on the glass substrates by dc magnetron sputtering. The detector turned out to have a submonolayer sensitivity that enables to observe coherent-to-incoherent transition in these mismatched multilayers and even detect the stress changes within the monoatomic coverage. This highly sensitive detector paves new way to probe the stress relaxation at an interface in ultrathin films.

• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.342-352
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• 2022

Purine catabolite screening enables reliable diagnosis of certain diseases. In this regard, the development of a facile detection strategy with high sensitivity and selectivity is demanded for point-of-care applications. In this work, the simultaneous detection of uric acid (UA), xanthine (XA), and hypoxanthine (HX) was carried out as model purine catabolites by surface-enhanced Raman Spectroscopy (SERS). The detection assay was conducted by employing high-aspect ratio Au nanopillar substrates coupled with in-situ Au electrodeposition on the substrates. The additional modification of the Au nanopillar substrates via electrodeposition was found to be an effective method to encapsulate molecules in solution into nanogaps of growing Au films that increase metal-molecule contact and improve substrate's sensitivity and selectivity. In complex solutions, the approach facilitated ternary identification of UA, XA, and HX down to concentration limits of 4.33 𝜇M, 0.71 𝜇M, and 0.22 𝜇M, respectively, which are comparable to their existing levels in normal human physiology. These results demonstrate that the proposed platform is reliable for practical point-of-care analysis of biofluids where solution matrix effects greatly reduce selectivity and sensitivity for rapid on-site disease diagnosis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.6
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• pp.365-370
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• 2023

This paper presents a particle-structure collision model for topology optimization, which requires sensitivity analysis. Therefore, a new model that incorporates sensitivity analysis is needed. The proposed particle-structure collision model conducts sensitivity analysis for topology optimization. To evaluate the accuracy of the proposed model, it was applied to a simplified one-dimensional collision problem. Optimization of the final positions of particles using topology optimization through this model confirmed the suitability of the proposed approach. These results demonstrate that it is possible to consider particle-structure collision in topology optimization.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.57-65
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• 2017

The electronic components in mobile device are composed of electronic chips and various other materials. These components become extremely thin and the constituent materials have different coefficient of thermal expansion, so that considerable warpages occurs easily due to temperature change or external load. Shadow $moir{\acute{e}}$ is non-contact, whole field technique for measuring out-of-plane displacement, but the measurement sensitivity is not less than $50{\mu}m/fringe$, which is not suitable for measuring the warpage of the electronic components. In this paper, we implemented a measurement method with enhanced sensitivity of $25{\mu}m/fringe$ by investigating and optimizing various experimental conditions of the shadow $moir{\acute{e}}$. In addition, four $moir{\acute{e}}$ fringe patterns recorded by the phase shift are processes to obtain a $moir{\acute{e}}$ fringe patterns with a sensitivity four times higher. The measurement technique is applied to small electronic components of a smart phone for measuring warpage with a high sensitivity of $5{\mu}m/fringe$ at room temperature and at the temperature of $100^{\circ}C$.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.51-60
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• 2011

Purpose: This study was to investigate visual performance and subjective satisfaction with multifocal soft contact lenses at near works in university students. Methods: In a cross-over study design, 26 students (6 male, 20 female) who did not have any ocular disorder with at least 20/20(1.0) binocular vision were fitted with singlevision lenses (SofLens$^{TM}59$, Bausch + Lomb Co. USA) or multifocal lenses (SofLens Multifocal, Bausch + Lomb Co. USA). After 2 weeks, visual performance assessments included visual acuity, stereoacuity and contrast sensitivity function at distance and near. Near point of accommodation, accommodative facility, near point of convergence, vergence facility and near range of clear vision at near were examined. Students' satisfaction and preference were measured using survey questionaries. Results: Subjects maintained at least 20/20 binocular vision with multifocal and single-vision lenses at distance and near. There was no difference between multifocal and single-vision lenses in stereoacuity, contrast sensitivity function and vergence facility at far and near. The near point of accommodation, accommodative facility, near point of convergence and the near range of clear vision with multifocal lenses were better than single-vision lenses. On the survey questionaries, subjects reported that they preferred and satisfied with multifocal lenses with near works, and single-vision lenses with distance works. Conclusions: The majority of university students preferred multifocal to single vision lenses because multifocal lenses provided better visual performance at near works. This study suggests that multifocal lens is helpful for young adult in prolonged near works.

• Journal of Photoscience
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• v.9 no.2
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• pp.236-239
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• 2002

Sunscreens have been advocated as an important means of preventing skin cancer. UV-induced immunosuppression is important for skin cancer development, yet the effectiveness of sunscreens in protecting the human immune system from UV radiation is unclear. The only currently accepted method of sunscreen rating is the Sun Protection Factor (SPF) based on prevention of erythema. We developed an in vivo non-invasive method for evaluating protection of the human immune system from UV radiation based on recall contact sensitivity to nickel, a common allergen. Using this system we showed that broad-spectrum sunscreens provide greater protection to the immune system than sunscreens which protect from UVB only. UVA was found to be immunosuppressive. We developed this technique to enable the study of solar simulated UV radiation dose responses and determined Immune Protection Factors (IPFs) for six commercially available sunscreens based on limits of protection from the dose response data. We found that the IPF did not correlate with the SPF and that protection from erythema therefore cannot be used to predict protection of the immune system. However, IPF was significantly correlated to the UVA protective capability of the sunscreens, indicating that sunscreen protection from UVA is important for prevention of immunosuppression. We recommend that sunscreens should be rated against their immune protective capability to provide a better indication of their ability to protect against skin cancer.

• Journal of Photoscience
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• v.9 no.2
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• pp.197-200
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• 2002

UVR-induced immunosuppression contributes to skin cancer. The aim was to construct accurate dose response curves for primary and secondary contact sensitivity for solar-simulated UVR (ssUVR; 290-400nm), UVA and UVB as the role of UVA in immunosuppression is controversial. We used a xenon arc source. The mice were immobilised, enabling accurate dosing. C57BL/6 mice were immunosuppressed at half the dose of ssUVR required to cause sunburn but not by higher doses (up to the sunburn dose). Thus, ssUVR causes systemic immunosuppression only over a narrow, low dose range. UVA caused suppression at low but not high doses whereas UVB induced immunosuppression at all doses tested. 8 weeks later the mice were resensitised to assess tolerance. Mice exposed to the minimum immunosuppressive dose of ssUVR prior to primary sensitisation were tolerant to re-sensitisation. However, at higher doses of ssUVR, these mice were protected from tolerance. Interestingly, while low doses of UV A caused immunosuppression, even lower doses enhanced the response to the second sensitisation. Higher doses of UVA had no affect. UVB induced tolerance in a dose related manner. Thus, ssUVR only induces immunosuppression and tolerance over a narrow dose range. Both UVA and UVB are immunosuppressive at this dose, while higher doses of UVA protect from the suppressive effects of UVB. Surprisingly very low doses of UVA enhanced memory development. Thus UVR has complex effects on the immune system depending on dose and spectrum.

• Restorative Dentistry and Endodontics
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• v.25 no.2
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• pp.254-261
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• 2000

본 연구에서는 35개의 구치부 2급 와동에 고밀도 구치부 복합레진(Surefil, Caulk, U.S.A.)을 수복하였다. 단일 충전군은 18개 치아의 인접면 와동을 한꺼번에 충전한 후 광중합하였고 분할 충전군은 17개 치아의 인접면 와동을 두 층으로 나누어 충전 및 광중합하였다. 6개월 후의 임상검사 결과 다음과 같은 결론을 얻었다. 1. 기초검사에서 단일 충전군과 분할 충전군 모두 색상조화도(Color match)를 제외한 다른 검사 항목들에서 Alfa로 나타났다. 2. 단일 충전군은 6개월 후 모든 검사(색상 조화도 제외)에서 인접면 접촉도(Proximal contact), 변연부 변색(Marginal discoloration), 술후 과민증(Postoperative sensitivity) 검사에서 소수의 치아가 Bravo, Charlie로 나타났으나 기초 검사와 3개월 후 검사 사이에 통계적으로 유의한 차이는 보이지 않았다. 3. 분할 충전군은 6개월 후 시행된 모든 검사(색상 조화도 제외)에서 인접면 접촉도(Proximal contact), 술후 과민증(Postoperative sensitivity) 검사에서 소수의 치아가 Bravo, Charlie로 나타났으나 기초 검사와 6개월후 검시 사이에 통계적으로 유의한 차이는 보이지 않았다. 4. 모든 검사항목에서 단일 충전군과 분할 충전군을 비교한 결과 통계적으로 유의한 차이는 보이지 않았다. 따라서 고밀도 구치부 복합레진(Surefil, Caulk, U.S.A)은 색상 재현의 어려움을 제외하고는 여러 평가에서 우수하게 나타났으므로 본 연구 결과를 기준으로 보면 이전 복합레진의 단점이 보완되어 구치부 2급 와동에 적절하게 사용될 수 있다고 사료되며 단일 충전군과 분할 충전군 사이에 통계적으로 유의한 차이를 보이지 않으므로 시술 시간을 좀 더 단축시킬 수 있을 것으로 사료된다.

• Imaging Science in Dentistry
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• v.53 no.3
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• pp.199-207
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• 2023

Purpose: The objective of this study was to evaluate the accuracy and effectiveness of an artificial intelligence (AI) program in identifying dental conditions using panoramic radiographs(PRs), as well as to assess the appropriateness of its treatment recommendations. Materials and Methods: PRs from 100 patients(representing 4497 teeth) with known clinical examination findings were randomly selected from a university database. Three dentomaxillofacial radiologists and the Diagnocat AI software evaluated these PRs. The evaluations were focused on various dental conditions and treatments, including canal filling, caries, cast post and core, dental calculus, fillings, furcation lesions, implants, lack of interproximal tooth contact, open margins, overhangs, periapical lesions, periodontal bone loss, short fillings, voids in root fillings, overfillings, pontics, root fragments, impacted teeth, artificial crowns, missing teeth, and healthy teeth. Results: The AI demonstrated almost perfect agreement (exceeding 0.81) in most of the assessments when compared to the ground truth. The sensitivity was very high (above 0.8) for the evaluation of healthy teeth, artificial crowns, dental calculus, missing teeth, fillings, lack of interproximal contact, periodontal bone loss, and implants. However, the sensitivity was low for the assessment of caries, periapical lesions, pontic voids in the root canal, and overhangs. Conclusion: Despite the limitations of this study, the synthesized data suggest that AI-based decision support systems can serve as a valuable tool in detecting dental conditions, when used with PR for clinical dental applications.