• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.843-871
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• 2015

Cloud computing evolve as a cost effective business model for IT companies to focus on their core business without perturbing on infrastructure related issues. Hence, major IT firms and Small & Medium Enterprises (SME) are adopting cloud services on rental basis from cloud providers. Cloud Service level agreements (SLA) act as a key liaison between consumers and providers on renting Anything as a Service (AaaS). Design of such an agreement must aim for greater profit to providers as well as assured availability of services to consumers. However in reality, cloud SLA is not satisfying the parties involved because of its inherent complex nature and issues. Also currently most of the agreements are unilateral to favour the provider. This study focuses on comprehensive, 360-degree survey on different aspects of the cloud service agreements. We detailed the life cycle of SLA based on negotiation, different types of SLA, current standards, languages & characteristics, metrics and issues involved in it. This study will help the cloud actors to understand and evaluate the agreements and to make firm decision on negotiation. The need for standardized, bilateral, semantic SLA has also been proposed.

• 대한치과보철학회지
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• 제52권3호
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• pp.211-221
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• 2014

목적: 기존의 SLA 표면을 높은 친수성을 가지는 표면으로 개질하고자 NaOH에 침적하는 방법이 SLA 표면 형상 및 특성에 어떤 영향을 미치는지 알아보고, 골모유사세포의 증식, 부착 및 분화에 어떤 영향을 미치는지 알아보고자 계획되었다. 재료 및 방법: Machined surface (대조군), SLA surface (SLA 군), SLA에 NaOH 처리한 표면(SLA/NaOH 군)의 각 시편을 제조하고 친수성을 극대화한 SLA/NaOH 군의 표면 특성을 평가하기 위해 표면성분(XPS), 표면 거칠기, 표면 접촉각 등을 평가하였다. 그 이후 MG-63 세포 배양 후 이번 실험에서 만든 표면들이 세포독성을 가지는지를 평가하고, WST assay를 통하여 세포 증식, F-actin 염색을 통하여 세포의 부착형태를 관찰하였다. 이 후 ALP assay를 통하여 세포 분화를 평가하였다. 각 군간 통계측정을 위해 ANOVA 후 다중비교를 하였다(P<.05). 결과: SLA/NaOH 군의 접촉각은 $5.59{\pm}1.13$도였다. 모든 군들은 MG-63 세포에 대해 세포독성을 가지지 않았다. 세포 부착 평가에서 SLA/NaOH 군에서 가장 높은 부착 정도를 보였고(P<.05), Machined 군과 SLA 군에서도 표면 거칠기가 높은 SLA군에서 더 높은 세포 부착정도를 확인할 수 있었다(P<.05). 배양 7일까지 모든 군에서 MG-63 세포의 증식이 점차 증가하였다. 모든 군에서 3일과 7일에 세포의 증식에서 유의할 만한 차이가 보였고, SLA/NaOH 군에서 가장 높은 세포증식을 보였다. ALP 활성도는 7일에서는 세 군 사이에 차이가 없었다. 하지만 14일에는 SLA/NaOH 군이 유의성 있는 증대를 보였다(P<.05). 결론: 본 연구를 통하여 NaOH를 처리하는 수화방식을 통해 SLA 표면을 변형시킴으로서 세포의 부착, 증식 및 분화를 촉진시켜 임플란트의 골유착을 증진시킬 수 있는 가능성을 확인하였다.

• 정보보호학회논문지
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• 제31권4호
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• pp.763-777
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• 2021

정보보안은 IT 운영프로세스로 시작하여 지금은 정보기술의 중요한 문제로 인식되면서 각 국제단체에서 개념을 새롭게 규정하고 있다. 정보보안 자체가 IT기술들의 새로운 조합으로 하나의 기술 집합이고 기술영역이다. 많은 공공부문에서 IT 아웃소싱이 일반화되면서 SLA(Service Level Agreement)를 도입하여 IT서비스 수준에 대해 평가를 한다. 정보보안 영역에서 SLA 성과지표 도출과 선정에 대한 많은 연구는 진행되었지만, 성과지표의 서비스 수준 평가, 성과체계에 대한 적용방안은 찾기 어렵다. 이 논문은 공공부문을 기반으로 하는 정보보안 성과지표의 서비스 평가 체계와 보상 규정이 포함된 성과체계 적용에 대한 연구를 수행하였다. 특정 공공부문의 환경과 특성을 고려한 성과지표의 기대치와 목표치를 정의하는 기준과 보상(인센티브·페널티) 규정을 제시하고 적절한 SLA 비용을 정의한다.

• 한국기계가공학회지
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• 제16권4호
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• pp.1-8
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• 2017

This paper concerns the possibility of 3D printing reverse idle gears for tractor transmission. For the purposes of this experiment, idle gears were manufactured using a SLA 3D printer, FDM 3D printer, and through machining. The accuracy of the idle gears produced in these three different ways were evaluated by the properties of their outer diameter, inner diameter, roundness, concentricity, parallelism, span, backlash, and gear grade. The tooth characteristics of the idle gears were evaluated by their profile, lead, and the pitch of the gears. The results of this experiment determined that the surface conditions created by the finishing process had a significant impact on the dimensional accuracy of the gears and the characteristics of their teeth.

• 정보과학회 논문지
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• 제42권5호
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• pp.591-600
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• 2015

SLA(Service Level Agreement)는 클라우드 컴퓨팅 서비스를 제공하는 사업자가 이용자에게 신뢰성 있고 일관된 품질을 제공하기 위해서 반드시 보장해야 하는 요소이며 특히 클라우드 서비스 브로커리지를 이용해서 서비스를 중개하는 환경에서는 SLA를 통한 서비스 사업자와 고객 간의 계약이 중요하다. 클라우드 컴퓨팅은 다양한 클라우드 서비스의 IT 자원에 따라 IaaS, PaaS, SaaS 등으로 구분되는데 기존의 SLA는 물리적인 네트워크 환경에 대한 요소만 고려하거나 명세에 대한 방법론적인 접근이 없어서 SaaS를 기반으로 제공되는 소프트웨어 서비스의 품질 요소를 반영하기 어렵다. 본 연구를 통해 SaaS 환경에 적합한 SLA 제공을 위해 소프트웨어적인 품질 특성을 명세할 수 있는 방법을 제시하고 SLA 명세를 서비스 제공자와 소비자 간에 교환할 수 있는 메커니즘과 구조를 제안하였다. SaaS 레벨에서의 SLA 명세를 위한 메타모델을 정의하였고 SaaS의 품질 요구사항은 제안한 명세 언어로 기술될 수 있으며, 사례연구를 통해 다양한 소프트웨어적인 품질 요소가 제안한 명세 언어로 표현됨을 검증하였다. SLA 명세는 이를 교환하기 위한 UDDI 기반의 중개 프로세스 및 아키텍처를 이용하여 품질 명세 저장소에 저장되며 교환 아키텍처를 기반으로 서비스 바인딩 시 교환된다.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.443-452
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• 2004

For stereo lithography process, accuracy of prototypes is related to laser power, scan speed, scan width, scan pattern, layer thickness, resin characteristics and etc. An accurate prototype is obtained by using appropriate process parameters. In order to determine these parameters, the stereolithography (SLA) machine using neural network was developed and efficiency of the developed SLA machine was compared with that of the traditional SLA. Optimum values for scan speed, hatching spacing and layer thickness improved the surface roughness and build time for the developed SLA.

• Journal of Periodontal and Implant Science
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• 제47권3호
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• pp.182-192
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• 2017

Purpose: Contact and distance osteogenesis occur around all endosseous dental implants. However, the mechanisms underlying these processes have not been fully elucidated. We hypothesized that these processes occur independently of each other. To test this, we used titanium (Ti) tubes to physically separate contact and distance osteogenesis, thus allowing contact osteogenesis to be measured in the absence of possible triggers from distance osteogenesis. Methods: Sandblasted and acid-etched (SLA) and modified SLA (modSLA) implants were used. Both types had been sandblasted with large grit and then etched with acid. The modSLA implants then underwent additional treatment to increase hydrophilicity. The implants were implanted into rabbit tibiae, and half were implanted within Ti tubes. The bone-to-implant contact (BIC) ratio was calculated for each implant. Immunohistochemical analyses of bone morphogenetic protein (BMP)-2 expression and new bone formation (Masson trichrome stain) were performed. Results: The implants outside of Ti tubes were associated with good bone formation along the implant surface. Implantation within a Ti tube significantly reduced the BIC ratio (P<0.001). Compared with the modSLA implants, the SLA implants were associated with significantly higher BIC ratios, regardless of the presence or absence of Ti tubes (P=0.043). In the absence of Ti tubes, the bone adjacent to the implant had areas of new bone formation that expressed BMP-2 at high levels. Conclusions: This study disproved the null hypothesis and suggested that contact osteogenesis is initiated by signals from the old bone that undergoes distance osteogenesis after drilling. This signal may be BMP-2.

• Journal of Periodontal and Implant Science
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• 제45권3호
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• pp.94-100
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• 2015

Purpose: The aim of this study was to investigate the combined effects of physical and chemical surface factors on in vivo bone responses by comparing chemically modified hydrophilic sandblasted, large-grit, acid-etched (modSLA) and anodically oxidized hydrophobic implant surfaces. Methods: Five modSLA implants and five anodized implants were inserted into the tibiae of five New Zealand white rabbits (one implant for each tibia). The characteristics of each surface were determined using field emission scanning electron microscopy, energy dispersive spectroscopy, and confocal laser scanning microscopy before the installation. The experimental animals were sacrificed after 1 week of healing and histologic slides were prepared from the implant-tibial bone blocks removed from the animals. Histomorphometric analyses were performed on the light microscopic images, and bone-to-implant contact (BIC) and bone area (BA) ratios were measured. Nonparametric comparison tests were applied to find any significant differences (P<0.05) between the modSLA and anodized surfaces. Results: The roughness of the anodized surface was $1.22{\pm}0.17{\mu}m$ in Sa, which was within the optimal range of $1.0-2.0{\mu}m$ for a bone response. The modSLA surface was significantly rougher at $2.53{\pm}0.07{\mu}m$ in Sa. However, the modSLA implant had significantly higher BIC than the anodized implant (P=0.02). Furthermore, BA ratios did not significantly differ between the two implants, although the anodized implant had a higher mean value of BA (P>0.05). Conclusions: Within the limitations of this study, the hydrophilicity of the modSLA surface may have a stronger effect on in vivo bone healing than optimal surface roughness and surface chemistry of the anodized surface.

• Tribology and Lubricants
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• 제37권1호
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• pp.1-6
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• 2021

This paper presents the experimental results of hydrophobic surfaces developed using a stereolithography-based additive-manufacturing technique. The additive manufacturing technique can be used to manufacture objects with complex geometries from computer-aided design data. Several additive manufacturing methods, such as selective laser sintering, fused deposition modeling, stereolithography apparatus (SLA), and inkjet-based system, have been developed. The SLA is a form of three-dimensional printing technology used to create prototypes, patterns, and production parts in successive layers through photochemical processes. Light causes chemical monomers and oligomers to cross-link together to form objects composed of polymers. Moreover, this method is economical for fabricating surfaces with high output resolution and quality. Here, we fabricate various surfaces using different shapes using an SLA. The surfaces with micro-patterns are fabricated for 10 cases, including the biomimetic surface. The fabricated surfaces with various micro-patterns are evaluated for hydrophobicity performance based on the static contact angle. The contact angle is measured three times for each case, and the averaged value is used. The results indicate that the arrangements in a staggered structure have a larger contact angle than those in a line when the same micro-pattern is applied. Moreover, the mimetic surfaces exhibit more hydrophobic characteristics than those of artificial micro-patterns.

• 한국기계가공학회지
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• 제21권9호
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• pp.56-62
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• 2022

This study analyzed the output precision of 3D printing methods. The inner impeller of the centrifugal compressor was printed in as a sheet with 100% packing density using two methods: field deposition modelling and stereolithography. Dimensional differences between the initial CAD and printed models were evaluated using a 3D scanner. To investigate the dimensional characteristics of the 3D printed impeller, 3D dimension analysis and point dimension analysis were performed. The point dimension analysis was divided into 3D and 2D for comparative analysis.