• Journal of Information Processing Systems
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• 제10권4호
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• pp.628-645
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• 2014

In past few years, distributed hash table (DHT)-based P2P systems have been proven to be a promising way to manage decentralized index information and provide efficient lookup services. However, the skewness of users' preferences regarding keywords contained in a multi-keyword query causes a query load imbalance that combines both routing and response load. This imbalance means long file retrieval latency that negatively influences the overall system performance. Although index replication has a great potential for alleviating this problem, existing schemes did not explicitly address it or incurred high cost. To overcome this issue, we propose, in this paper, an integrated solution that consists of three replication schemes to alleviate query load imbalance while minimizing the cost. The first scheme is an active index replication that is used in order to decrease routing load in the system and to distribute response load of an index among peers that store replicas of the index. The second scheme is a proactive pointer replication that places location information of each index to a predetermined number of peers for reducing maintenance cost between the index and its replicas. The third scheme is a passive index replication that guarantees the maximum query load of peers. The result of simulations indicates that the proposed schemes can help alleviate the query load imbalance of peers. Moreover, it was found by comparison that our schemes are more cost-effective on placing replicas than PCache and EAD.

• 박물관보존과학
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• 제25권
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• pp.63-84
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• 2021

본 연구는 전통도자기의 제작 전과 후, 소성 전과 후에 기물의 내부에서 일어나는 다양한 물리화학적 변화를 알아보고자 청자상감운학문매병의 재현품을 성형 → 조각 → 상감 → 초벌 → 유약 → 재벌 등의 6단계로 제작하여 과학적 조사 및 3차원의 정밀한 투과 이미지 촬영으로 획득한 이미지를 세부 영역별로 분석하였다. 재현편의 제작 재료는 각각의 재료가 가진 성분에 따라 다른 광물상이 존재하며, 산화철(Fe₂O₃)의 함량이 높은 흑상감은 어두운 색을 나타냈고, 알루미나(Al₂O₃)의 함량이 높은 백상감은 백색이 나타나는 것과 같이 색상에도 영향을 준다. 재현편의 색도와 전암대자율, 주요성분 등의 물리화학적 특성을 CT이미지를 통해 밀도의 차이로 확인할 수 있었으며, 미세조직과 흡수율, 겉보기기공률, 주요구성광물 등의 번조에 따른 특성 변화는 영상 분석에서 기물 내부의 기공 유무와 존재량, 균열의 발달과 확장으로 파악하였다.

• 한국조경학회지
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• 제19권2호
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• pp.32-40
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• 1991

Damage to natural resources from inappropriate visitor behavior is a problem faced by National Park management. Based on the data gathered by personal interview and mail questionnaire, this study examines the effects of communication strategies to reduce depreciative behavior in Carlsbad Caverns National Park. One-quarter of Carlsbad Caverns visitors indicates that they have noticed damage to cave formation during their tour. Almost 38% of visitors say that they have witnessed someone touch a formation inside the Caverns. This is a relatively high percentage compared with other depreciative behavior research to refrain from "tattling" on fellow visitors. Two-thirds of the respondents recalls touching formation replicas before entering the Cavern, while almost all visitors (97.9%) say that they have heard the ranger's talk about not touching formation or leaving the trail. Visitors feel that the ranger's talk is more effective in reducing depreciative behavior than the formation replicas, although at least three-fourths of all respondents believes both techniques are effective.

• 한국경영과학회지
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• 제21권1호
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• pp.31-50
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• 1996

In this paper we prescribe a replication server scheme with an algorithm DRF (Differential Refresh File) to refresh multiple materialized views and replicas in distributed environments. Before sending relevant tuples in server sites to client sites, an effective tuple reduction scheme is developed as a preprocessor to reduce the transmission cost. Because it utilizes differential files with out touching base relations, the DRF scheme can help to minimize the number of locks, which enhances the system's performance.

• ETRI Journal
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• 제42권3호
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• pp.388-398
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• 2020

We herein propose a heuristic redundancy selection algorithm that combines resubmission, replication, and checkpointing redundancies to reduce the resiliency overhead in fault-tolerant workflow scheduling. The appropriate combination of these redundancies for workflow tasks is obtained in two consecutive phases. First, to compute the replication vector (number of task replicas), we apportion the set of provisioned resources among concurrently executing tasks according to their needs. Subsequently, we obtain the optimal checkpointing interval for each task as a function of the number of replicas and characteristics of tasks and computational environment. We formulate the problem of obtaining the optimal checkpointing interval for replicated tasks in situations where checkpoint files can be exchanged among computational resources. The results of our simulation experiments, on both randomly generated workflow graphs and real-world applications, demonstrated that both the proposed replication vector computation algorithm and the proposed checkpointing scheme reduced the resiliency overhead.

• Applied Science and Convergence Technology
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• 제23권1호
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• pp.54-59
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• 2014

The roll-to-roll (R2R) fabrication method to make micro-scale pillar arrays for biomimetic functionalization of surfaces is presented. Inspired by the micro-structure of plants in nature, a surface with a synthetic micro-scale pillar array is fabricated via maskless photolithography. After the surface is SAM (self-assembled monolayer) coated with trichlorosilane in a vacuum desiccator, it displays a hydrophobic property even in R2R replicas of original substrate, whose properties are further characterized using various pitches and diameters. In order to perform a comparison between the original micro-pattern and its replicas, surface morphology was analyzed using scanning electron microscopy and wetting characteristics were measured via a contact angle measurement tool with a $10{\mu}L$ water droplet. Efficient roll-to-roll imprinting for a biomimetic functionalized surface has the potential for use in many fields ranging from water repelling and self-cleaning to microfluidic chips.

• 전자통신동향분석
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• 제36권1호
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• pp.99-108
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• 2021

Digital twins are digital replicas of objects and systems in the real world. These digital replicas in a virtual environment can be connected with smart sensors and a variety of analyses, and simulations of real-time data from these sensors enable effective the operation, rapid feedback, and future predictions of real world phenomena. Until now, digital twins have been adopted and used mainly in the field of manufacturing, especially for smart factories. As digital twins are expected to be useful not only for productivity improvement but also for social problem solving, it is predicted that they will be extended to other fields such as those of transportation and cities. Digital twins will especially help realize smart cities through real-time monitoring, operation, and predictions using virtual digital twin cities. This paper summarizes the trends in digital twins for smart cities, the concept of digital twins, their application to smart cities, the strategies of various countries, and the development status of companies.

• 컴퓨터교육학회논문지
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• 제12권4호
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• pp.65-75
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• 2009

결과 검증은 데스크톱 그리드 환경에서 불특정 자원들에 의해 수행된 작업 결과의 정확성을 보장하는데 필수적이다. 전형적으로 투표기반 기법과 믿음기반의 기법이 데스크톱 그리드 환경에서 사용되어 왔지만, 이들 기법은 작업의 잉여 중복에 의한 자원 낭비와 동적 환경의 비적응성에 의한 반환 시간의 증가 문제를 갖고 있다. 이러한 문제점을 해결하기 위해 본 논문에서는 자원의 믿음 정도와 결과 반환 확률을 이용하여 적응적으로 작업 복제 개수를 결정할 수 있는 퍼지 추론 기반의 복제 기법을 제안한다. 따라서, 제안 기법은 동적 연산 환경의 적절한 대처를 통해 작업 복제 개수를 결정함으로써 자원 낭비를 줄여주고 전체 작업의 반환 시간을 향상시킨다. 시뮬레이션 결과는 제안 기법이 반환 시간, 자원 낭비, 작업의 재복제 횟수의 관점에서 우수함을 보여준다.

• 대한치과기공학회지
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• 제42권4호
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• pp.321-325
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• 2020

Purpose: This study is to evaluate the accuracy of gypsum replica models made from various gypsum products. Methods: One main model was made of stainless steel by CNC milling process. Molds were formed from the main model, and the gypsum replica models were made using 8 types of type IV gypsum, 10 pieces each. The main model was digitized by a contact scanner (Incise; Renishaw) and the gypsum replicas were digitized by an optical scanner (E4; 3Shape A/S). The difference between the main model and the gypsum replicas were measured by inspection software (3D Systems). One-way ANOVA was performed to evaluate the statistical significance of differences between groups. In addition, the independent sample T test was performed to determine the difference between the conventional and scannable stone group (n=10, α=0.05). Results: The root mean square of the stone models were 7.24 ㎛ to 10.78 ㎛, and statistical significance was found between the two groups (SR, FR) and the other 6 groups (IS, SG, CA, CS, ER, EBG) (p<0.05). The accuracy of the gypsum replicas was 9.04 ㎛ and 7.62 ㎛ in the conventional and scannable stone group, respectively. There was statistical significance between the two groups (p<0.01). Conclusion: In the limited results of this study, the product with low setting expansion and the scannable showed high accuracy. Therefore, in order to obtain a stable and accurate scan model, it is more effective in terms of accuracy to use a scannable stone with a low setting expansion.

• Journal of Korean Society for Atmospheric Environment
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• 제22권E2호
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• pp.78-88
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• 2006

In order to study the characteristics of cloud, a real-scale experiment for cloud generation was carried out using an extinct vertical mine (430 m height) located in the northeastern Honshu, Japan. The dry particles generated from the three-step concentrations of NaCl solutions were used for cloud generation. The number size distributions of initial dry particles and cloud droplets were monitored by Scanning Mobility Particle Sizer (SMPS) and Forward Scattering Spectrometer Probe (FSSP) at bottom and upper sites of pit, respectively. The polymeric water absorbent film (PWAF) method was employed to measure liquid water content ($W_L$) as a function of droplet size. Moreover the chemical properties of individual droplet replicas were determined by micro-PIXE. The CCN number concentration shows the lognormal form in dependence of the particle size, while the number size distributions of droplets are bimodal showing the peaks around $9{\mu}m$ and $20{\mu}m$ for every case. In comparison to background mineral particles, right shifting of size distribution line for NaCl particles was occurred. When NaCl solutions with three-step different concentrations were neulized, $W_L$ shows the strong droplet size dependence. It varied from $10.0mg\;m^{-3}$ up to $13.6mg\;m^{-3}$ with average $11.6mg\;m^{-3}$. A good relationship between $W_L$ and cloud droplet number concentration was obtained. Both chemical inhomogeneities (mixed components with mineral and C1) and homogeneities (only mineral components or C1) in individual droplet replicas were obviously observed from micro-PIXE elemental images.