• Journal of Intelligence and Information Systems
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• v.20 no.2
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• pp.73-92
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• 2014

An Adaptive Clustering-based Collaborative Filtering Technique was proposed to solve the fundamental problems of collaborative filtering, such as cold-start problems, scalability problems and data sparsity problems. Previous collaborative filtering techniques were carried out according to the recommendations based on the predicted preference of the user to a particular item using a similar item subset and a similar user subset composed based on the preference of users to items. For this reason, if the density of the user preference matrix is low, the reliability of the recommendation system will decrease rapidly. Therefore, the difficulty of creating a similar item subset and similar user subset will be increased. In addition, as the scale of service increases, the time needed to create a similar item subset and similar user subset increases geometrically, and the response time of the recommendation system is then increased. To solve these problems, this paper suggests a collaborative filtering technique that adapts a condition actively to the model and adopts the concepts of a context-based filtering technique. This technique consists of four major methodologies. First, items are made, the users are clustered according their feature vectors, and an inter-cluster preference between each item cluster and user cluster is then assumed. According to this method, the run-time for creating a similar item subset or user subset can be economized, the reliability of a recommendation system can be made higher than that using only the user preference information for creating a similar item subset or similar user subset, and the cold start problem can be partially solved. Second, recommendations are made using the prior composed item and user clusters and inter-cluster preference between each item cluster and user cluster. In this phase, a list of items is made for users by examining the item clusters in the order of the size of the inter-cluster preference of the user cluster, in which the user belongs, and selecting and ranking the items according to the predicted or recorded user preference information. Using this method, the creation of a recommendation model phase bears the highest load of the recommendation system, and it minimizes the load of the recommendation system in run-time. Therefore, the scalability problem and large scale recommendation system can be performed with collaborative filtering, which is highly reliable. Third, the missing user preference information is predicted using the item and user clusters. Using this method, the problem caused by the low density of the user preference matrix can be mitigated. Existing studies on this used an item-based prediction or user-based prediction. In this paper, Hao Ji's idea, which uses both an item-based prediction and user-based prediction, was improved. The reliability of the recommendation service can be improved by combining the predictive values of both techniques by applying the condition of the recommendation model. By predicting the user preference based on the item or user clusters, the time required to predict the user preference can be reduced, and missing user preference in run-time can be predicted. Fourth, the item and user feature vector can be made to learn the following input of the user feedback. This phase applied normalized user feedback to the item and user feature vector. This method can mitigate the problems caused by the use of the concepts of context-based filtering, such as the item and user feature vector based on the user profile and item properties. The problems with using the item and user feature vector are due to the limitation of quantifying the qualitative features of the items and users. Therefore, the elements of the user and item feature vectors are made to match one to one, and if user feedback to a particular item is obtained, it will be applied to the feature vector using the opposite one. Verification of this method was accomplished by comparing the performance with existing hybrid filtering techniques. Two methods were used for verification: MAE(Mean Absolute Error) and response time. Using MAE, this technique was confirmed to improve the reliability of the recommendation system. Using the response time, this technique was found to be suitable for a large scaled recommendation system. This paper suggested an Adaptive Clustering-based Collaborative Filtering Technique with high reliability and low time complexity, but it had some limitations. This technique focused on reducing the time complexity. Hence, an improvement in reliability was not expected. The next topic will be to improve this technique by rule-based filtering.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.2
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• pp.435-459
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• 1998

In order to achieve a successful endodontic treatment, root canals must be obturated three-dimensionally without causing any damage to apical tissues. Accurate length determination of the root canal is critical in this case. For this reason, I've used the conventional periapical radiography, Digora/sup (R)/(digital imaging system) and Root ZX/sup (R)/(the frequency dependent type apex locator) to measure the length of the canal and compare it with the true length obtained by cutting the tooth in half and measuring the length between the occlusal surface and the apical foramen. From the information obtained by these measurements, I was able to evaluate the accuracy and clinical usefulness of each systems. whether the thickness of files used in endodontic therapy has any effect on the measuring systems was also evaluated in an effort to simplify the treatment planning phase of endodontic treatment. 29 canals of 29 sound premolars were measured with #15, #20, #25 files by 3 different dentists each using the periapical radiography. Digora/sup (R)/ and Root ZX/sup (R)/. The measurements were then compared with the true length. The results were as follows: 1. In comparing mean discrepancies between measurements obtained by using periapical radiography(mean error: -0.449±0.444 mm), Digora/sup (R)/(mean error: -0.417±0.415 mm) and Root ZX/sup (R)/(mean error: 0.123±0.458 mm) with true length. periapical radiography and Digora/sup (R)/ system had statistically significant differences(p<0.05) in most cases while Root ZX/sup (R)/ showed none(p>0.05). 2. By subtracting values obtained by using periapical radiography, Digora/sup (R)/ and Root ZX/sup (R)/ from the true length and making a distribution table of their absolute values. the following analysis was possible. In the case of periapical film. 140 out of 261<53.6％) were clinically acceptable satisfying the margin of error of less than 0.5 mm. 151 out of 261 (53,6％) were acceptable in the Digora/sup (R)/ system while Root ZX/sup (R)/ had 197 out of 261(75.5％) within the limits of 0.5mm margin of error. 3. In determining whether the thickness of files has any effect on measuring methoths, no statistically significant differences were found(p>0.05). 4. In comparing data obtained from these methods in order to evaluate the difference among measuring methods, there was no statistically significant difference between periapical radiography and Digora/sup (R)/ system(p>0.05), but there was statistically significant difference between Root ZX/sup (R)/ and periapical radiography(p<0.05). Also there was statistically significant difference between Root ZX/sup (R)/ and Digora/sup (R)/ system(p<0.05). In conclusion, Root ZX/sup (R)/ was more accurate when compared with the Digora/sup (R)/ system and periapical radiography and seems to be more effective clinically in determining root canal length. But Root ZX/sup (R)/ has its limits in determining root morphology and number of roots and its accuracy becomes questionable when apical foramen is open due to unknown reasons. Therefore the combined use of Root ZX/sup (R)/ and the periapical radiography are mandatory. Digora/sup (R)/ system seems to be more effective when periapical radiographs are needed in a short period of time because of its short processing time and less exposure.

• Korean Journal of Poultry Science
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• v.32 no.2
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• pp.125-133
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• 2005

Morphometric changes in testicular Sertoli and Leydig cells from hatching to adulthood were studied using Korean native chickens of 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 21, 24, 28, 32, 44, 52 and 64 weeks (n=13 chickens per group) of age. The objective of this study was to understand the developmental phase of the Sertoli and Leydig cells with age. Testis of chickens was fixed by whole body perfusion using a fixative containing $2.5\%$ glutaraldehyde in cacodylate buffer, processed and embedded in Epon-araldite. Using 1 Um sections stained with methylene blue-azure II, qualitative and quantitative (stereological) morphological studies were performed. The average volume of a testis of 1 week old Korean native chickens was determined as $0.148\;cm^3$ and the parameter increased linearly from 1 week to 21 weeks days $(28.86\;cm^3)$, and did not change from 21 weeks to 64 weeks. The volume density of the seminiferous tubules increased with age from $32.6\%$ at week 1 to $92.89\%$ at week 64. The volume density of the interstitium represents $67.4\%$ of the testicular parenchyma at week 1. This proportion progressively diminished during development to reach a value of $7.11\%$ at week 64. The volume density of the Leydig cells decreased almost linearly from 1 week $(4.9\%)$ to 14 weeks $(1.7\%)$ and remained unchanged thereafter. In contrast, the Sertoli cells occupied a volume density of $3.4\%$ at week 1, increased progressively up to 18 weeks of age $(10.79\%)$ and remained unchanged thereafter. The absolute volume of the Leydig and Sertoli cells per testis increased significantly from week 1 to week 21 but did not change significantly from week 24 to week 64. The number of Leydig cells per testis increased almost linearly from 1 week to 21 weeks, remained high and unchanged with advancing age. The number of Sertoli cells per testis increased gradually with age from 1 week to 14 weeks and remained unchanged thereafter.

• Korean Journal of Poultry Science
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• v.19 no.4
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• pp.217-225
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• 1992

This research was carried out to determine the 25-Hydroxyvitamin $D_3$[25(OH)$D_3$] content in liver of broiler Hubbard chicks fed vitamin VD-deficient diet for 31 days in a subdued light room and exposed to UVB light (maximum intensity at 297nm) with dose of 0.204 or 0.408 mJ/$\textrm{cm}^2$(30 or 60 min irradiation) . The lipid in liver collected at 0~138 hr after irradiation was extracted by chloroform-methanol(2：1, v /v) and 25(OH)$D_3$ fraction was separated by Sep-Pak silica cartridge. The 25(OH)$D_3$ concentration was measured by normal phase HPLC. The negative control chicks Presented 25(OH)D$_3$17.5 ng/g liver. When 0.204mJ/$\textrm{cm}^2$ was treated to whole body of chicks, the 25(OH)$D_3$ level was increased to 37.8 ng/g at 12 hr after irradiation, the peak concentration, 40.5 ng /g was appeared at the time of 86 hr, and decreasing trend was shown thereafter until 138 hr, the final time in this study. When 0.408 mJ/$\textrm{cm}^2$ was applied, the 25(OH)$D_3$ content was 36.7 ng /g liver at 12 hr, 61.4 ng/g(maximum value ) was appeared at 42 hr, and 39.5 ng /g at 138 hr. The increased absolute amounts in liver 25(OH)$D_3$ were 23 and 43.9 ng/g as chicks were exposed to UVB light with dose of 0.204 and 0.408mJ/$\textrm{cm}^2$, respectively. Consequently, it was found that when double dose of UVB light was irradiated to the chicks, their liver samples produced nearly double 25(OH)$D_3$ at 42 hr after exposure, and the peak value was presented earlier by 24 hr than that in the low dose treatment.

• The Journal of Art Theory & Practice
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• no.13
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• pp.73-95
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• 2012

In terms of element and process, art today has already been fully systemized, yet tends to become even more systemized. All phases of creation and exhibition, appreciation and education, promotion and marketing are planned, adjusted, and decided within the order of a globalized, networked system. Each phase is executed, depending on the system of management and control and diverse means corresponding to the system. From the step of education, artists are guided to determine their styles and not be motivated by their desire to become star artists or running counter to mainstream tendency and fashion. In the process of planning an exhibition, the level of artist awareness is considered more significant than work quality. It is impossible to avoid such systems and institutions today. No one can escape or be freed from the influence of such system. This discussion addresses a serious distortion in the selection system as part of the system connotatively called "art museum system," especially to evaluate artistic achievement and aesthetic quality. Called "studio system" or "art star system," the system distinguishes successful minority from failed absolute majority and justifies the results, deciding discriminative compensations. The discussion begins from work by Hunter Jonakin and Dan Perjovschi. The key point of this discussion is not their art worlds but the shared truth referred by the two as the collusive "art market" and "art star system." Through works based on their experiences, the two artists refer to these systems which restrict and confine them. Jonakin's Jeff Koons Must Die! is avideo game conveying a critical comment on authoritative operation of the museum system and star system. In this work, participants, whether viewer or artist, are destined to lose: the game is unwinnable. Players take the role of a person locked in a museum where artist Jeff Koons' retrospective is held. The player can either look around and quietly observe the works, which causes a game-over, or he can blow the classical paintings to pieces and cause the artist Koons to come out and reprimand the player, also resulting in a game-over. Like Jonakin, Dan Perjovschi's some drawings also focuses on the status of the artist shrunken by the system. Most artists are ruined in a process of competition to survive within the museum system. As John Burger properly pointed out, out of the art systems today, public collections (art museums) and private collections have become "something unbearable." The system justifies the selection system of art stars and its frame of reference, disregarding the problem of producing numerable victims in its process. What should be underlined above all else is that the present selection system seriously shrinks art's creative function and its function of generating meaning. In this situation, art might fall to the level of entertainment, accessible to more people and compromising with popularity. This discussion is based on assumption and consciousness on the matter that this situation might cause catastrophic results for not only explicit victims of the system but also winners, or ones defined as winners. The system of art is probably possible only by desire or distortion stemmed from such desire. The system can be flourished only under the economic system of avarice: quantitatively expanding economy, abundant style, resort economy in Venice and Miami, and luxurious shopping malls with up-to-date facilities. The catastrophe here is ongoing, not a sudden emergence, and dynamic, leading the system itself to a devastating end.

• International Journal of Highway Engineering
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• v.8 no.2 s.28
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• pp.63-74
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• 2006

During the construction of circular underground pipe, the non-proper compaction along the pipe and the decrease of compaction efficiency have been the main problems to induce the failure of underground pipe or facility. The use of CLSM (controlled low strength materials) should be one of the possible applications to overcome those problems. In this research, the full-scaled field test and the numeric analysis using PENTAGON-3D FEM program were carried out for three different cases on the change of backfill materials, including the common sand, the soil from construction site, and the CLSM. From the full-scaled test in field, the use of in-situ CLSM as backfill materials reduced the vertical and lateral deformation of the pipe, as well as the deformation of the ground surface. The main reason for reducing the deformation would be the characteristics of the CLSM, especially self-leveling and self-hardening properties. The measured earth pressure at the surround of the corrugated pipe using the CLSM backfills was the smaller than the other cases, and the absolute value was almost zero. Judging from the full-scaled field test and FEM analysis, the use of CLSM as backfill materials should be one of the best choices reducing the failure of the underground pipes.

• Korea journal of population studies
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• v.20 no.1
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• pp.97-128
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• 1997

This paper was set out to study the structure of the career occupational mobility in the early and rapid phase of industrialization in Korea. By analyzing the individual life histories regarding occupational mobility and achievement, I propose a model of yearly career mobility of Korean men and Women during the period of 30 years between 1954 and 1983. With the occupational classification scheme of 5 groups - Upper Nonmanual, Lower Nonmanual, Self Employed, Manual, Farm - the mobility pattern in the person-year mobility table analyzed can be characterized primarily by the strong influence of immobility. The degree of immobility, however, is different by the occupational groups. The absolute amount of immobility can be summarized as being U-shaped. Overall, the pattern of mobility can be explained best by the concept of occupational distance. I then propose a model of relative career occupational mobility pattern that combines the conceptual and theoretical basis and the methodological rigor. The model is based on the notion of the reproduction of inequality, the labor market context, and the life history perspective. The model encompasses the 6 conceptual explanatory factors such as persistence effect, ceiling effect, traditional sector effect, nonmanual occupation effect, alternative mobility channel effect, and occupational distance effect, as well as the effects of both origin and destination occupations. The relative pattern of career mobiliity in Korea can be characterized by the following six findings. First, the persistence effect on the diagonal cells of the mobility table is dominant. Second, a clear evidence of the negative effect of occupational distance between nonmanual occupations and manual and farm occupations is found. Third, the out-mobility from farming took place regardless of the destination occupations. Fourth, the internal mobility within the nonmanual occupation block is high and bi-directional, and is exclusive against other occupations. Fifth, the 'self employed' occupation is serving a peculiar function in both inflow and outflow pattern. Last, the relative pattern of career occupation mobility is asymmetrical in terms of the upward and downward mobility.

• Korea journal of population studies
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• v.10 no.1
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• pp.28-38
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• 1987

This paper was set out to study the structure of the career occupational mobility in the early and rapid phase of industrialization in Korea. By analyzing the individual life histories regarding occupational mobility and achievement, I propose a model of yearly career mobility of Korean men and Women during the period of 30 years between 1954 and 1983. With the occupational classification scheme of 5 groups - Upper Nonmanual, Lower Nonmanual, Self Employed, Manual, Farm - the mobility pattern in the person-year mobility table analyzed can be characterized primarily by the strong influence of immobility. The degree of immobility, however, is different by the occupational groups. The absolute amount of immobility can be summarized as being U-shaped. Overall, the pattern of mobility can be explained best by the concept of occupational distance. I then propose a model of relative career occupational mobility pattern that combines the conceptual and theoretical basis and the methodological rigor. The model is based on the notion of the reproduction of inequality, the labor market context, and the life history perspective. The model encompasses the 6 conceptual explanatory factors such as persistence effect, ceiling effect, traditional sector effect, nonmanual occupation effect, alternative mobility channel effect, and occupational distance effect, as well as the effects of both origin and destination occupations. The relative pattern of career mobiliity in Korea can be characterized by the following six findings. First, the persistence effect on the diagonal cells of the mobility table is dominant. Second, a clear evidence of the negative effect of occupational distance between nonmanual occupations and manual and farm occupations is found. Third, the out-mobility from farming took place regardless of the destination occupations. Fourth, the internal mobility within the nonmanual occupation block is high and bi-directional, and is exclusive against other occupations. Fifth, the 'self employed' occupation is serving a peculiar function in both inflow and outflow pattern. Last, the relative pattern of career occupation mobility is asymmetrical in terms of the upward and downward mobility.

• Korean Journal of Remote Sensing
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• v.37 no.5_2
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• pp.1259-1268
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• 2021

The 2nd Geostationary Ocean Color Imager (GOCI-II) is the successor to the Geostationary Ocean Color Imager (GOCI), which employs one near-ultraviolet wavelength (380 nm) and eight visible wavelengths(412, 443, 490, 510, 555, 620, 660, 680 nm) and three near-infrared wavelengths(709, 745, 865 nm) to observe the marine environment in Northeast Asia, including the Korean Peninsula. However, the multispectral radiance image observed at satellite altitude includes both the water-leaving radiance and the atmospheric path radiance. Therefore, the atmospheric correction process to estimate the water-leaving radiance without the path radiance is essential for analyzing the ocean environment. This manuscript describes the GOCI-II standard atmospheric correction algorithm and its initial phase validation. The GOCI-II atmospheric correction method is theoretically based on the previous GOCI atmospheric correction, then partially improved for turbid water with the GOCI-II's two additional bands, i.e., 620 and 709 nm. The match-up showed an acceptable result, with the mean absolute percentage errors are fall within 5% in blue bands. It is supposed that part of the deviation over case-II waters arose from a lack of near-infrared vicarious calibration. We expect the GOCI-II atmospheric correction algorithm to be improved and updated regularly to the GOCI-II data processing system through continuous calibration and validation activities.

• Korea Science and Art Forum
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• v.37 no.2
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• pp.219-230
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• 2019

According to the National Statistical Office, the number of senior citizens aged 65 or over has exceeded 7 million as of 2017, and the number of senior citizens who live alone among them exceeded 1.3 million. Most of the senior citizens who live alone suffer from absolute poverty (68.5% of them has monthly income less than 500,000 won) and they have difficulties for basic living in the blind spot of our society. In particular, the heating is quite a serious issue for the senior citizens who live alone and belong to vulnerable social group in the winter, and to make it worse, they are exposed to frequent fire accidents due to the negligence in handling electric appliances such as electric heaters and electric pads. The main reason the indoor tent products are being used by senior citizens who live alone is that it saves energy, ensures warm sleep, and improves fire safety. Following the expansion of the indoor tent market, this study focused on the idea that there is a need for an in door tent suitable for senior citizens who live alone and belong to low income bracket and intended to improve its efficiency in relation to use, resting, and storage. For this, a basic survey was conducted on the products of existing brands to analyze advantages and disadvantages and it was possible to understand the demands that consumers have for existing products. Accordingly, a survey on consumer preference was conducted using a designed model and the Zabara typp, which demonstrated the best efficiency in terms of installation convenience, space usability, and appearance design was selected. Based on the results of selection, the product design and final prototype were completed. The results and details of the study are as follows; First, factors that were not recognized in product development phase could be identified through usability survey and interview with actual users. Second, for the effective aspect of the prototype, senior citizens could install and fold the tend more easily and quickly than expected. Based on these results of this study, it is expected that not only senior citizens who live alone but also various other users can use the tent to create another comfortable private space indoors.