• Wind and Structures
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• v.14 no.1
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• pp.55-70
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• 2011

This study investigates the design criteria required for wind barriers to protect vehicles running on an expressway under a high side wind. At the first stage of this study, the lateral deviations of vehicles in crosswinds were computed from the commercial software, CarSim and TruckSim, and the critical wind speeds for a car accident were then evaluated from a predefined car accident index. The critical wind speeds for driving stability were found to be 35 m/s for a small passenger car, yet 30 m/s for a truck and a bus. From the wind tunnel tests, the minimum height of a wind barrier required to reduce the wind speed by 50% was found to be 12.5% of the road width. In the case of parallel bridges, the placement of two edge wind barriers plus one wind barrier at center was recommended for a separation distance larger than 20 m (four lanes) and 10 m (six lanes) respectively, otherwise two wind barriers were recommended.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.54-59
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• 2001

The stability of a thin plate structure is very crucial problem which results buckling. Because the buckling strength of thin plates is lower than the yield strength of the material, reinforcement plate must be used to increase the buckling strength. And, in this case, spot welding is commonly used, however, the spot welded joints are practically designed by experimental decisions, so it is Inefficient and has the risks of buckling demolition. In this study, two parameters, such as the area ratio and the distance ratio of spot welding which have influence on the buckling strength, should be chosen. Under compressive and shearing load, the effect of two parameters on the critical stress is discussed.

• Journal of Korean Society of Transportation
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• v.21 no.5
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• pp.97-110
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• 2003

The sight distance at unsignalized intersections is the one of the fundamental geometric design elements, and can ensure safety and efficient operations. Despite its importance, little research attention has been directed in Korea compared to developed countries such as European countries, the United States, and Japan. AASHTO ISD policies have been applied to the intersection design in Korea without any revise, which can produce unrealistic and unadoptable design values. Those values are emerged from several reasons because the AASHTO ISD has been calibrated based on the local data. Therefore the ISD hardly takes into account the local characteristics of Korea such as driving behavior. vehicular movement and roadway conditions. The objective of this study is to calculate the appropriate ISD values for unsignalized intersections in the urban area in Korea. In this study, we employed the ISD model of AASHTO(2001), which is based on gap acceptance theory and can account for and take the driving and roadway conditions in Korea into consideration. The approach can also consider the complex driving maneuvers at the intersections in a proper and simple manner. The results in this study show that the ISD design criteria currently used in Korea are more conservative(safer) than those of the USA. In other words, the ISD using field data collected in this study has generally smaller values than those in USA.

• Journal of KIISE:Databases
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• v.35 no.6
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• pp.481-494
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• 2008

In this paper we propose Fourier magnitudes based privacy preserving clustering on time-series data. The previous privacy-preserving method, called DFT coefficient method, has a critical problem in privacy-preservation itself since the original time-series data may be reconstructed from privacy-preserved data. In contrast, the proposed DFT magnitude method has an excellent characteristic that reconstructing the original data is almost impossible since it uses only DFT magnitudes except DFT phases. In this paper, we first explain why the reconstruction is easy in the DFT coefficient method, and why it is difficult in the DFT magnitude method. We then propose a notion of distance-order preservation which can be used both in estimating clustering accuracy and in selecting DFT magnitudes. Degree of distance-order preservation means how many time-series preserve their relative distance orders before and after privacy-preserving. Using this degree of distance-order preservation we present greedy strategies for selecting magnitudes in the DFT magnitude method. That is, those greedy strategies select DFT magnitudes to maximize the degree of distance-order preservation, and eventually we can achieve the relatively high clustering accuracy in the DFT magnitude method. Finally, we empirically show that the degree of distance-order preservation is an excellent measure that well reflects the clustering accuracy. In addition, experimental results show that our greedy strategies of the DFT magnitude method are comparable with the DFT coefficient method in the clustering accuracy. These results indicate that, compared with the DFT coefficient method, our DFT magnitude method provides the excellent degree of privacy-preservation as well as the comparable clustering accuracy.

• Tuberculosis and Respiratory Diseases
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• v.87 no.2
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• pp.155-164
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• 2024

Background: Exercise capacity is associated with lung function decline in chronic obstructive pulmonary disease (COPD) patients, but a discrepancy between exercise capacity and airflow limitation exists. This study aimed to explore factors contributing to this discrepancy in COPD patients. Methods: Data for this prospective study were obtained from the Korean COPD Subgroup Study. The exercise capacity and airflow limitation were assessed using the 6-minute walk distance (6-MWD; m) and forced expiratory volume in 1 second (FEV₁). Participants were divided into four groups: FEV₁ >50%+6-MWD >350, FEV₁ >50%+6-MWD ≤350, FEV₁ ≤50%+6-MWD >350, and FEV₁ ≤50%+6-MWD ≤350 and their clinical characteristics were compared. Results: A total of 883 patients (male:female, 822:61; mean age, 68.3±7.97 years) were enrolled. Among 591 patients with FEV₁ >50%, 242 were in the 6-MWD ≤350 group, and among 292 patients with FEV₁ ≤50%, 185 were in the 6-MWD >350 group. The multiple regression analyses revealed that male sex (odds ratio [OR], 8.779; 95% confidence interval [CI], 1.539 to 50.087; p=0.014), current smoking status (OR, 0.355; 95% CI, 0.178 to 0.709; p=0.003), and hemoglobin levels (OR, 1.332; 95% CI, 1.077 to 1.648; p=0.008) were significantly associated with discrepancies in exercise capacity and airflow limitation in patients with FEV₁ >50%. Meanwhile, in patients with FEV₁ ≤50%, diffusion capacity of carbon monoxide (OR, 0.945; 95% CI, 0.912 to 0.979; p=0.002) was significantly associated with discrepancies between exercise capacity and airflow limitation. Conclusion: The exercise capacity of COPD patients may be influenced by factors other than airflow limitation, so these aspects should be considered when assessing and treating patients.

• The Journal of Art Theory & Practice
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• no.14
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• pp.187-215
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• 2012

In recent studies of art historical methodology, such as Critical Terms for Art History and The Art of Art History, subjectivity, identity, abjection, and other terms have been placed safely in the genealogy of contemporary art history. This paper questions the contemporaneity in the story of contemporary art in our time in relation to two other critical terms that have been regularly cited by contemporary critics, not only in Euro-American fields but also in Korea. The terms are postmedium and postproduction, respectively, as used by Rosalind Krauss and Nicolas Bourriaud. This paper stems from the critical condition in which art criticism and theory have their power in the rise of neo-liberalism. But this paper does not deal with the contemporary as a chronological term for art history but rather examines the three critical terms-contemporaneity, post-medium, and postproduction-that have garnered scholarly attention. I would like to put aside postmodernism for the moment; I don't disregard the postmodern condition although the death of postmodern critical terms has resulted in the loss of its polemical power in art worlds such as in exhibitions, etc. To look at "the postproduction in the age of post-medium age after postmodernism," I first explore Krauss's notion of post-medium because, unlike media artists like Lev Manovich and Peter Weibel, Krauss's post-medium condition is different and insists on medium specificity. In this sense, Krauss has turned out to be another Greenberg in disguise. For her, photography and video are expanded mediums after Greenberg, because Krauss has spent her life explicating those mediums. Under the Cup, her recent publication, came out in 2011, and discusses her desire to defend medium-specificity against the intermedia of installation art found ubiquitously in international exhibitions and biennales. Her usage of post-medium has been taken up by Weibel as postmedia in a broader sense. But whether the post-medium condition or the postmedia age, we nonetheless enter the new age of the contemporary. Consequently, this paper questions what constitutes contemporaneity in our times. It is said that there is nothing new on earth, yet I find original artistic strategies among the younger generation in the postmedia age. The contemporary justifies its place in art fields and criticism by keeping its distance from postmodernism although we still find the remnants of postmodern artistic practices and theoretical foundations. By looking at materials written by Terry Smith, I would like to examine contemporaneity as a rhetoric where artists, critics, and curators endeavor to set up a new spirit of criticism, distant from the past of modernism and postmodernism. In discussions, modernism and postmodernism act as catalysts interacting with each other while justifying their own place. In conclusion, my paper reaches to delineate where the contemporary finds its place among artists' responses and working methods. It explores the postproduction of the Internet and the World Wide Web generations, where images become data rather than representation (of modernism) and appropriation (of postmodernism). This paper analyzes Bourriaud's text, as well as relevant artists like Pierre Huyghe, Liam Gillick, and others. By examining the aforementioned critical terms, I would like to reconsider our own contemporary art in Korea, especially among young artists influenced by digital media and the World Wide Web in the 1990s.

• Radiation Oncology Journal
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• v.2 no.2
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• pp.271-280
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• 1984

The peripheral dose, defined as the dose outside therapeutic photon fields, which is responsible for the functional damage of the critical organs, fetus, and radiation. induced carcinogenesis, has been investigated for $^{60}Co\;\gamma$ ray and 10 MV Xray. It was measured by silicon diode controlled by semiautomated water phantom without any shielding or with lead plate of HVL thickness put horizontally or vertically to shield stray radiations. Authors could obtain following results. 1. The peripheral dose was larger than $0.7\%$ of central axis maximum dose even at 20cm distance from field margin. That is clinically significant, so it should be reduced. 2. Even for square fields of 10 MV Xray, radial peripheral dose distribution did not coincide with transverse distribution, because of the position of collimator jaws. 3. Between surface and $d_m$, the peripheral dose distributions show a pattern of the dose distribution of electron beams and the maximum doss was approximately proportional to the length of a side of square field. 4. The peripheral doses depended on radiation quality, field size, distance from field margin and depth in water. Distance from field margin was the most important factor. 5. Except for near surface, the peripheral dose from phantom was approximately equal to that from therapy unit. 6. To reduce the surface dose outside fields, therapist should shield stray radiations from therapy unit by lead plate of at least one HVL for 10 MV X-ray and by bolus equivalent to tissue of 0.5cm thickness for $^{60}Co$. 7. To reduce the dose at depth deeper than $d_m$, it is desirable to shield stray radiations from therapy unit by lead.

• Horticultural Science & Technology
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• v.18 no.6
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• pp.787-791
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• 2000

Lettuce seedlings used in this investigation of planting distance and labor-saving efficiency were first grown in 100-hole paper trays for 30 days. Seedling height for transplanting ranged from 3 cm to 6 cm and plants had 3 to 5 leaves. The beds prepared for transplanting were of the arched type and were 35-40 cm in width, 15-20 cm in bed height, and between-bed furrow width was 20 30 cm. Typical seedling planting depth with the transplanter was 4-5 cm, although depth was quite variable because of the irregularities of the ground. Total transplanting time with the transplanter varied from 2.6 to 2.7 hours per 10a, while it took 38.1 hours per 10a with conventional planting. It was critical that the condition of both the seedlings and the bed be adjusted to the transplanter before planting. Considering yield and inter-plant distance, optimal transplanter performance resulted with $60{\times}20cm$ or $60{\times}25cm$spacing, and the labor-saving efficiency using the transplanter was improved by over 93% of that of conventional planting by hand.

• The KIPS Transactions:PartA
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• v.14A no.3 s.107
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• pp.159-166
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• 2007

A arrival of u-teaming paradigm requires many u-teaming system and model that is varied and support to distance education, Accordingly, the distance education system in u-learning environment has attracted a fair amount of critical attention. However there remain many questions, as yet unresolved, such as it is difficult to maintain interaction between tutor and learner, the construction of system is a great expense to them, a tutor, who manages the system, lacks technologic background, in most current distance education system. To solve these problem, some preliminary observations have to be made first: to keep teaming process in situation that it is unconnected with tutor, to construct the system economically, and to make to be easy-to-use. Therefore, in this paper, we develop the 'Intelligent U-Learning System using Cyber Tutor', which includes the conception of u-learning such as mobility, immanency, supports to keep learning without real tutor by cyber tutor, and removes technological and economical costs, verify the validity.

• Journal of the Korean Society for Railway
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• v.12 no.1
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• pp.16-24
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• 2009

In this study, fatigue crack growth rate of a cracked railway bogie frame under variable amplitude loading is predicted by applying linear elastic fracture mechanics. For this purpose, we find the critical points by reference surveying on cracked railway bogie frames. And we make an effective load history by synthesizing the dynamic load measured from the critical points of railway bogie frame during commercial line operation and the static load calculated from structural analysis. Crack growth analyses are performed at the 3 critical points under the commercial operation loading condition by assuming an initial crack size as 40 mm. and the results are compared with the experimental results from Japanese railway bogie frame crack growth case. From the analysis results, we find that around 500,000 km operating distance is necessary to bring crack growth from the initial crack to unstable crack. And it takes around 3.8 normal operating years. We conclude that it is enough time to detect the crack between normal maintenance period.