• The korean journal of orthodontics
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• v.54 no.6
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• pp.374-391
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• 2024

Objective: This meta-epidemiological study aimed to determine whether optimal sample size calculation was applied in orthodontic cluster randomized trials (CRTs). Methods: Orthodontic randomized clinical trials with a cluster design, published between January 1, 2017 to December 31, 2023, in leading orthodontic journals were sourced. Study selection was undertaken by two independent authors. The study characteristics and variables required for sample size calculation were also extracted by the authors. The design effect for each trial was calculated using an intra-cluster correlation coefficient of 0.1 and the number of teeth in each cluster to recalculate the sample size. Descriptive statistics for the study characteristics, summary values for the design effect, and sample sizes were provided. Results: One-hundred and five CRTs were deemed eligible for inclusion. Of these, 100 reported sample size calculation. Nine CRTs (9.0%) did not report any effect measures for the sample size calculation, and a few did not report any power assumptions or significance levels or thresholds. Regarding the specific variables for the cluster design, only one CRT reported a design effect and adjusted the sample size accordingly. Recalculations indicated that the sample size of orthodontic CRTs should be increased by a median of 50% to maintain the same statistical power and significance level. Conclusions: Sample size calculations in orthodontic cluster trials were suboptimal. Greater awareness of the cluster design and variables is required to calculate the sample size adequately, to reduce the practice of underpowered studies.

• Journal of the Ergonomics Society of Korea
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• v.35 no.5
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• pp.449-464
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• 2016

Objective: The objective of this study is to identify essential requirements of the instrument cluster's features and layout for elderly drivers through interview and paper prototyping. Background: Recent updates implemented in passenger vehicles require more complex information to be processed by drivers. Concurrently, a large portion of the US population, the baby boomer generation has aged, causing their physical and cognitive abilities to deter. Thus it is crucial that new methods be implemented into vehicle design in order to accommodate for the deterioration of mental and physical abilities. Method: Forty elderly drivers and twenty young drivers participated in this study. The test included three sessions including: 1) location value assessment to identify the priority of areas within the instrument cluster; 2) component value assessment to capture rankings of the degree of importance and frequency of use for possible instrument cluster components; and 3) paper prototyping to collect self-designed cluster with selection of designs for each component and location of features from each participant. Results: Results revealed differences in the area priority of the instrument cluster as well as the shape and location of component features for age and gender groups. Conclusion: The study provided insights on instrument cluster layout guidelines by proving elderly driver's mental model and preferred cluster design configurations to improve driving safety. Application: LCD-based vehicle instrument cluster design, with an adaptable feature configuration for cluster components and layouts.

• Journal of Veterinary Clinics
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• v.31 no.4
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• pp.288-292
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• 2014

A critical assumption of the standard sample size calculation is that the response (outcome) for an individual patient is completely independent to that for any other patient. However, this assumption no longer holds when there is a lack of statistical independence across subjects seen in cluster randomized designs. In this setting, patients within a cluster are more likely to respond in a similar manner; patient outcomes may correlate strongly within clusters. Thus, direct use of standard sample size formulae for cluster design, ignoring the clustering effect, may result in sample size that are too small, resulting in a study that is under-powered for detecting the desired level of difference between groups. This paper revisit worked examples for sample size calculation provided in a previous paper using nomogram to easy to access. Then we present the concept of cluster design illustrated with worked examples, and introduce design effect that is a factor to inflate the standard sample size estimates.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.939-950
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• 2003

Control charts are very useful tool for monitoring of process characteristics. This paper discusses the problem of design of control limits when the subgroups are composed by cluster sampling type. As an alternative method of design of control limits XbBar chart is proposed, which uses the control limits based on the variation between subgroups instead of using classical variation within subgroups. Two examples are presented for reasonable design of control limits and conditions of subgroups based on the cluster sampling. Through examples the guidelines for making proper control limits are proposed.

• Review of Culture and Economy
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• v.21 no.3
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• pp.89-124
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• 2018

Although design industry belongs to one of the creative industries and contributes significantly to urban cultural economy based on its cluster formation, researches on design industry are rarely made explicit from the perspective of creative industry cluster. After reviewing the life cycle of design industry clusters in Euljiro and Hongdae Area in Seoul, this study compares these two clusters with respect of diverse dimensions of creative industry cluster such as agglomeration economy, spin-off activities and institutional environments. Research methodology includes the analysis of ?Seoul Business Statistics? and the in-depth interviews with 14 professional designers. The result shows that design industry cluster in Euljiro is close to the traditional industry cluster mainly dependent on printing industry with very limited impact on urban economy, while Hongdae Area develops creative industry cluster by virtue of university spin-offs, art markets, hybrid cultural consumption spaces and the active participation of designers contributing to urban economy in diverse ways. This comparative analysis highlights the importance of various environmental components to encourage creative activities in developing the creative industry cluster.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.129-134
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• 2001

Linux cluster Server makes a high performance PC cluster system, and provides scalablity and availability as compared with an expensive single server. In this paper, we design and implement a VOD streaming service system to serve video and audio streaming services on the Linux cluster server. Our Streaming server supports the MS Window Media Format based on the RTSP streaming protocol.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.359-366
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• 2001

This paper overviews the design of SANique$^{TM}$ -a shred file system for Linux cluster based on SAN environment. SANique$^{TM}$ has the capability of transferring user data from network-attached SAN disks to client applcations directly without the control of centralized file server system. The paper also presents the characteristics of each SANique$^{TM}$ subsystem: CFM(Cluster File Manager), CVM(Cluster Volume Manager), CLM(Cluster Lock Manager), CBM(Cluster Buffer Manager) and CRM(Cluster Recovery Manager). Under the SANique$^{TM}$ design layout, then, the syndrome of '||'&'||'quot;split-brain'||'&'||'quot; in shared file system environments is described and defined. The work first generalizes and illustrates possible situations in each of which a shared file system environment may split into two or more pieces of separate brain. Finally, the work describes the SANique$^{TM}$ approach to the given "split-brain"problem using SAN disk named "split-brain" and develops the overall recovery procedure of shared file systems.

• International Journal of Contents
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• v.16 no.4
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• pp.39-49
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• 2020

The goal of this research was to understand the patterns of multidimensional engagement in MOOCs. An email with an online survey link was sent to enrollees in an MOOC course. The survey included 35 questions asking about engagement, teaching presence, and learning persistence. The items were validated in the literature, revised for the MOOC setting, reviewed by four professionals in the field of educational technology, and used in the study. A heterogeneous group of 170 individuals gathered through convenience sampling participated in the study. With cluster analysis of the engagement data, three groups were identified: Cluster1, 2, and 3. Cluster 1 scored high on behavioral, emotional, and cognitive engagement. Cluster 2 scored high on behavioral aspects but low on emotional and cognitive engagement. Cluster 3 scored low on behavioral and cognitive engagement but high on emotional aspects. The study addressed cluster-specific learner characteristics and differences in perceived teaching presence and learning persistence. Design strategies pertaining to each cluster were further discussed. These strategies may guide instructors and practitioners in the design and management of MOOCs and should be further validated through future studies.

• Proceedings of the Korea Society of Design Studies Conference
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• 2005.05a
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• pp.72-73
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• 2005

• Journal of Advanced Navigation Technology
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• v.22 no.6
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• pp.577-584
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• 2018

GNSS based transport infrastructure cluster is to broadcast satellite navigation correction information and integrity information capable of precise positioning for land transport users. This makes it possible to do lane-level positioning reliably. However, in order to provide the lane-level positioning and correction information service nationwide, new station sites selection and to build GNSS stations have a heavy cost and a burden for a considerable period of time. In this paper, we propose the cluster design criteria and national-wide network-based precise positioning for land transportation (NETPPI-LT) cluster design for a cluster-based precise positioning. Furthermore, it is analyzed the precise positioning pre-performance of this cluster design based on the spatial error and verified its suitability as the precise positioning pre-performance of the cluster design.