• Journal of Korean Ophthalmic Optics Society
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• v.21 no.3
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• pp.265-274
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• 2016

Purpose: The aim of this study was to evaluate relationship between worker's ophthalmoxerosis symptom and IAQ (Indoor Air Quality) variation after planting indoor plants at newly-built office building. Methods: We selected a new office building located in Sejong-si and occupants who work in the Office for study. The indoor air pollutant was investigated according to applying indoor plants. The indoor air quality of the new building was evaluated by measuring volatile organic compounds (VOCs), aldehydes, temperature and humidity. The level of dry eye symptoms was classified into normal, mild, moderate and severe by using the Ocular Surface Disease Index (OSDI). Results: There was VOCs' reduction effect according to placing indoor plants because the concentration of VOCs in newly-built government office (Sejong-si) was highly decreased when the indoor plants was placed at the office. The occupants' SBS (Sick Building Syndrome) symptoms score was gradually decreased in accordance with applying indoor plants. However, SBS symptoms score was increased when the office was not applied indoor plants. There was not statistical significance in workers' dry eye questionnaire results. Conclusions: There was reduction effect of indoor air pollutant in applied indoor plants office. Also, in case of questionnaire results of ophthalmoxerosis and SBS (Sick Building Syndrome) symptoms score were showed positive effect. This study is needed longer-term study because of complements of difference of individual sensitivity and there are some limitations due to field survey research.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.4
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• pp.405-414
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• 2015

Purpose: We analyse characteristics of optical shop customer's segmented market by using clustering analysis, and we expect it would be a useful indicator of marketing strategy for optical shops. Methods: Survey was conducted from March 10 to March 31, 2015. The survey asked customers who have visited optical shops in Seoul and Northern Gyeonggi-do regions, and analyzed by utilizing SPSS v.10.0 statistical package program. The analysing methods are frequency analysis, factor analysis about variable of values, clustering analysis for market segmentation, and crosstabs. Results: The market is segmented based on values. In the process of establishing marketing strategy, it is useful to establish strategy by classifying customers into 3 types of cluster; "middle level value oriented cluster", "high level value oriented cluster", "high level value oriented and non-religious cluster". In marketing strategy of progressive lenses, it turned out that the most important strategy is to target self-employed person in "middle level value oriented cluster". Conclusions: As a result of market segmentation by using clustering analysis, it was classified into 3 types of cluster, and we found that most important customer for progressive lenses is self-employed person in "middle level value oriented cluster" who is more than 41 years old.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.2
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• pp.83-92
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• 2015

Purpose: This study was performed to offer some more effective marketing strategies for optical shops on a basis of analyses of what lifestyles influence most on 'store selection' and 'recommendation intention' and of what properties of 'store selection' influence most on 'recommendation intention'. Methods: Questionnaire surveys were conducted from the customers who visited the optical shops in Seoul and northern Gyeonggi-do region from January 1 to June 30, 2014. It was analyzed via utilizing SPSS v.20.0 statistical package program. Results: The results in lifestyle-factors which influence on store selection were arranged in order as follows: 'stability oriented', 'goal oriented', 'cultural activity oriented'. And the results in value-factors which influence on 'recommendation intention' were arranged in order as follows: 'stability oriented', 'health oriented'. The most positive factor for 'recommendation intention' was revealed as 'dealing with customers' among several factors of 'store selection'. Conclusions: Today's marketing activities for customers should be suited for different lifestyles of customers. Customers who have 'stability oriented', 'goal oriented', and 'cultural activity oriented' lifestyles tend to select optical shops in consideration of 21 items when selecting an optical shop. Customers who have 'stability oriented', and 'health oriented' lifestyles have positive influences related to 'recommendation intention'. Also, it is likely for customers to recommend optical shops to others when the factor 'dealing with customers' meets their expectations.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.4
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• pp.419-427
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• 2014

Purpose: We propose an effective marketing strategy for eyeglasses stores on the basis of surveys about the relationships between customers' social values, customer satisfaction and selecting glasses store. Methods: All 245 surveys were conducted about customers had visited the eyeglasses store located in Seoul and Northern Gyeonggi-do regions from January 1 to June 30, 2014, and it were analyzed by SPSS v.20.0 statistical package program. Results: The order of customers' social values factors which have an influence on 'Selecting Store' is "Society oriented", "Ability oriented", "Freedom oriented" and "Happiness oriented". Also, the order of customers' social values factors which have an influence on satisfaction is "Society oriented", "Ability oriented". In addition, Customer Satisfaction is affected by Service, one of the factor of 'Selecting Store' factors. Conclusions: Each type of marketing activities should be conducted for customers by their various values. The best plan to elicit good reactions from customers is meeting them through "Society-oriented" factors. Meeting with customers through the "Ability-oriented" factors is second only to the best option. It is shown that the method to increase the satisfaction for customers' return visit is to manage 'Service factors' well.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.385-390
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• 2015

Purpose: This study evaluated the static stereoacuity by Distance Randot Stereotest (STEREO OPTICAL. Co., Inc. USA) and the dynamic stereoacuity by three-rods test (iNT, Korea). Criterion and correlation of stereoacuity between both tests and usefulness of two stereotest methods were also evaluated. Methods: For normal adults of 109 (male 61, female 48), mean age of 20.88 (19-32 years) years old, static stereoacuity by using Distance Randot Stereotest at 3 m distance, dynamic stereoacuity by using three-rods test at 2.5 m distance were measured. Results: The mean of distance static stereoacuity was $155.77{\pm}133.11sec$ of arc and the mean of error distance dynamic stereoacuity $11.13{\pm}9.69mm$. With equivalent-conversion stereoacuity of $23.44{\pm}20.96sec$ of arc, there was statistically significant differences (p=0.00) between two dynamic stereoacuity, but correlation was relatively low (${\rho}=0.226$). In the case of dynamic stereoacuity, separated to normal range by criterion of the error distance 20 mm, it showed the error distance of less than 20 mm in 97 subjects(89%) whose average of error distance and conversion mean dynamic stereoacuity were $8.43{\pm}5.10mm$ and $17.68{\pm}10.67sec$ of arc. repectively. The error distance of was equivalent-conversion dynamic stereoacuity 40.99 sec of arc (PD 62 mm basis) was 20 mm. Conclusions: The results of lower correlation between static and dynamic stereoacuity suggest that seterotest should be applied separately to different functions. The results of this study also suggest that Distance Randot Stereotest can be applied to static stereoacuity excluding monocular cues. Three-rods test can be applied to dynamic stereoacuity containing the response of the eye-hand coordination in the daily life of natural vision condition, including the monocular cues. These different approaches canprovide a criterion of the two stereoacuity and parallel use of the two tests would be useful. For dynamic stereoacuity by three-rods test, error distance 20 mm in a normal range of adults can be used as a criteria to get statistical meaning of the results.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.110-117
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• 2013

PURPOSE. Polymethyl methacrylate (PMMA) is the most commonly used denture base material despite typically low in strength. The purpose of this study was to improve the physical properties of the PMMA based denture base resins (QC-20, Dentsply Ltd., Addlestone, UK; Stellon, AD International Ltd, Dentsply, Switzerland; Acron MC; GC Lab Technologies Inc., Alsip, Japan) by copolymerization mechanism. MATERIALS AND METHODS. Control group specimens were prepared according to the manufacturer recommendations. In the copolymer groups; resins were prepared with 5%, 10%, 15% and 20% acrylamide (AAm) (Merck, Hohenbrunn, Germany) content according to the moleculer weight ratio, respectively. Chemical structure was characterized by a Bruker Vertex-70 Fourier transform infrared spectroscopy (FTIR) (Bruker Optics Inc., Ettlingen, Germany). Hardness was determined using an universal hardness tester (Struers Duramin, Struers A/S, Ballerup, Denmark) equipped with a Vickers diamond penetrator. The glass transition temperature ($T_g$) of control and copolymers were evaluated by Perkin Elmer Diamond DSC (Perkin Elmer, Massachusetts,USA). Statistical analyses were carried out using the statistical package SPSS for Windows, version 15.0 (SPSS, Chicago, IL, USA). The results were tested regarding the normality of distribution with the Shapiro Wilk test. Data were analyzed using ANOVA with post-hoc Tukey test (P<.01). RESULTS. The copolymer synthesis was confirmed by FTIR spectroscopy. Glass transition temperature of the copolymer groups were higher than the control groups of the resins. The 10%, 15% and 20% copolymer groups of Stellon presented significantly higher than the control group in terms of hardness. 15% and 20% copolymer groups of Acron MC showed significantly higher hardness values when compared to the control group of the resin. Acrylamide addition did not affect the hardness of the QC-20 resin significantly. CONCLUSION. Within the limitation of this study, it can be concluded that copolymerization of PMMA with AAm increased the hardness value and glass transition temperature of PMMA denture base resins.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.6
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• pp.819-828
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• 2001

The operating point of a small-sized axial fan is strongly dependent upon the system resistance. Therefore, the turbulent flow characteristics around a small-sized axial fan may change significantly according to the operating point. This study represents three-dimensional turbulent flow characteristics around a small-sized axial fan measured at the ideal design point $\phi$=0.25, which is equivalent to the maximum total efficiency point, by using three dimensional fiber-optic type LDA system. This LDA system is composed of a 5 W Argon-ion laser, two optics in back-scatter mode, three BSAs, a PC, and a three-dimensional automatic traversing system. A kind of paraffin fluid is used to supply particles by means of fog generator. Mean velocity profiles downstream of a small-sized axial fan along the radial distance show that the streamwise and the tangential components exist in a predominant manner, while the radial component has a small scale distribution and shows the inflection which its flow direction is inward or outward. Moreover, the turbulent intensity profiles show that the radial component exists the most greatly among turbulent energies.

• Current Optics and Photonics
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• v.2 no.4
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• pp.368-377
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• 2018

In this paper, we evaluate cryptographic properties of a double random phase encoding (DRPE) scheme in the discrete Gyrator domain with avalanche and bit independence criterions. DRPE in the discrete Gyrator domain is reported to have higher security than traditional DRPE in the Fourier domain because the rotation angle involved in the Gyrator transform is viewed as additional secret keys. However, our numerical experimental results demonstrate that the DRPE in the discrete Gyrator domain has an excellent bit independence feature but does not possess a good avalanche effect property and hence needs to be improved to satisfy with acceptable avalanche effect that would be robust against statistical-based cryptanalysis. We compare our results with the avalanche and bit independence criterion (BIC) performances of the conventional DRPE scheme, and improve the avalanche effect of DRPE in the discrete Gyrator domain by integrating a photon counting imaging technique. Although the Gyrator transform-based image cryptosystem has been studied, to the best of our knowledge, this is the first report on a cryptographic evaluation of discrete Gyrator transform with avalanche and bit independence criterions.

• Journal of Korean Clinical Health Science
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• v.4 no.4
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• pp.671-679
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• 2016

Purpose. This research study is to understand the effects of field (clinical) Practice on employment choice and decision. Method. The research study conducts a questionnaire survey of trainees who received field (clinical) Training during the period of 2016 summer vacation to analyze the data, utilizing Likert 5 rating scales and conduct a statistical analysis with the tool of SPSS 18.0. Results.. As for the satisfaction of the participation of Practice, girl students account for the high rate (75.1%) compared with boy students (61.7%). Regarding the satisfaction of each Practice spot, ophthalmic clinic reaches the high rate (77.8%) compared with optical shop (65.7%). Practice about practice courses (53.2%) of regular subjects have somewhat close correlations compared with theory courses (46.8%). 75.2% of respondents in the group that shows the high satisfaction of the participation of Practice replied that they would decide employment as an academic major after Practice. And the figure is proved to assume a high ratio. Conclusion. The analytic research outcome indicates that those trainees who received Practice in an ophthalmic clinic have higher satisfaction than those who received Practice in an optical shop. There is the high accomplishment of employment in relation to academic major area instead of other area, after Practice.

• Current Optics and Photonics
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• v.2 no.6
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• pp.540-546
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• 2018

We propose an implementation scheme for an optical encryption system with hybrid-pattern random keys. In the encryption process, a pair of random phase keys composed of a white-noise phase key and a structured phase key are positioned in the input plane and Fourier-spectrum plane respectively. The output image is recoverable by digital reconstruction, using the conjugate of the encryption key in the Fourier-spectrum plane. We discuss the system encryption performance when different combinations of phase-key pairs are used. To measure the effectiveness of the proposed method, we calculate the statistical indicators between original and encrypted images. The results are compared to those generated from a classical double random phase encoding. Computer simulations are presented to show the validity of the method.