• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.11
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• pp.727-736
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• 2016

In this study, a high-pressure multistage pump used in the combined cycle power plants is analyzed. The pump performance characteristics (differential head and efficiency) are numerically analyzed for different shapes of the radial diffuser. The design variables selected for the radial diffuser are, number of vanes, diameter ratio ($D_4/D_3$), return channel outlet angle(${\alpha}_6$), and pressure recovery factor ($C_p$). The numerical analysis results showed that the differential head and efficiency are the highest when the diameter ratio is the highest. Further, it was observed that the differential head was lower when the return channel outlet angle was $60^{\circ}$ than when it was $90^{\circ}$, because of pre-swirl at the diffuser outlet.

• Transactions of Materials Processing
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• v.28 no.6
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• pp.368-374
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• 2019

The past recent years have seen an increasing use of high-strength steel sheets in the automotive industry. However, the formability and damage prediction of these materials requires accurate acquisition of necking and fracture strains. Digital image correlation (DIC) is used to accurately capture the necking and fracture strains during testing. The fact that single time points of capturing vary with frame rate makes the need for an investigation necessary. For the high-strength steel DP980, the frame-rate dependences of the final necking and fracture strains values are analyzed here. To eliminate the influence of gauge length, the strains were measured locally by DIC. Results for three specimen shapes obtained with frame rates of 1 and 900 fps (frames per second) were considered and based on them, triaxiality failure diagrams (TFD) are established. It was observed that after diffuse necking, the deformation path departed from the initially linear one, and the stress triaxiality grew with ongoing deformation. It was further revealed that the frame rate-dependence of the necking strain was rather low (< 2%), whereas the fracture strain could be underestimated by up to 8% when the lower frame rate of 1 fps was used (compared with 900 fps). In this study, this issue is investigated while taking into consideration the three different triaxialities. These results demonstrate the importance of choosing an appropriate frame rate for the determination of necking and fracture strains in particular.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.04a
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• pp.7-13
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• 2003

Microlens arrays were fabricated using a novel fabrication technology based on the exposure of a PMMA (Polymethylmethacrylate) sheet to deep X-rays and subsequent thermal treatment. X-ray irradiation causes the decrease of molecular weight of PMMA, which in turn decreases the glass transition temperature and consequently causes a net volume increase during the thermal cycle resulting in a swollen microlens. A new physical modeling and analyses for micro lens formation were presented according to experimental procedure. A simple analysis based on the new model is found to be capable of predicting the shapes of micro lens which depend on the thermal treatment. For the replication of micro lens arrays having various diameters with different foci on the same surface, the hot embossing and the microinjection molding processes has been successfully utilized with a mold insert that is fabricated by Ni-electroplating based on a PMMA microstructure of micro lenses. Fabricated microlenses showed good surface roughness with the order of 1nm.

• The korean journal of orthodontics
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• v.25 no.6 s.53
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• pp.665-674
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• 1995

The purpose of this study is to investigate the cephalometric characteristics of the open-bite patients with DJD of TMJ. The DJD open-bite cases were compared with normal samples and Class II open-bite cases with normal TMJ respectively. Twenty three open-bite patients with bilateral DJD of TMJ($13.9\~35.3$ yens old, Group I) were selected from the Department of Orthodontics, SNUDH. Group ll consisted of thirteen Class II open-bite cases($13.2\~27.4$ years old) with no TMD signs/symtoms and good condylar shapes. Group III samples were the forty eight healthy dental students who have Class I molar relationships with no history of orthodontic treatment, good facial balance and no TMD symptoms($20.0\~26.8$ years old). First, sixty measurements in the lateral cephalometric radiographs and analysis of variance(P<0.05, Scheffe) were used to compare these three groups. The seven measurements showed significant difference(p<0.05) between Group I and Group II. After analysis of variance, six of them were used for the discriminant analysis(Wilks' stepwise analysis) and the discrminant function for Group I/Group II was obtained. The results and conclusions were as follows : In most of the measurments, Group I and Group II showed the same skeletal and dental characteristics. But seven of the sixty measurements(FH-PP angle, SNB, FH-ArGo angle, articulare angle, genial angle, upper gonial angle and Ar-Go length) were significantly different(p<0.05) between Group I and Group II. These differences may be explained by the fact that in DJD cases the mandible rotated backward due to the shortening of the ramus following the degenerative destruction of condylar head and its surrounding structures. The resulting discriminant function was : $D={-0.120X}_1+{0.066X}_2+{0.144X}_3-{0.058X}_4+2000,\;where\;X_1=ArGo\;length(mm),\;X_2=SArGo\;angle(degree),\;X_3=FH-PP\;angle(degree),\;X_4=Gonial\;angle(degree)$. Mean of the group centroids was -0.555 and percent of the 'grouped' cases correctly classified was $88.89\%$.

• Journal of the Korea Furniture Society
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• v.20 no.1
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• pp.21-30
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• 2009

This research is conducted on temporary street furniture, which is one of the significant factors that comprise the street landscape in modem cities. The primary purpose of this research is to present the guidance on direction of planning by examining the design and installation types of construction and screen fences usually established at construction sites for buildings, roads, parks and etc. The results are as follows: 1. The construction and screen fences at construction sites of urban areas used to be a mere tentative facility to prevent noise and safety accidents but have now incremented their roles to serve not only as a functional but also as an aesthetic element with a city view and harmonization with other elements taken into consideration. In particular, it is noticeable that, based on its unique feature of tentativeness, its role has developed to serve as street furniture that adds variability to the modem city. 2. There are two different types of screen fences: blackout type and transparent type. The transparent screen turns out to be used a lot at the construction site of building a skyscraper or differentiated building in downtown city area or in places where there are buildings of similar types and shapes located along the street in the vicinity of the construction site. 3. The actual cases of adopting the tentative construction and screen fences all at the same time as a single unit have been found in historically and culturally significant architectures with the screen design used to demonstrate the view after completion of construction or the characteristics of the architecture.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.1
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• pp.133-149
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• 1998

Clinical application of composite resin recently draw great concerns in dentistry. Especially due to advantages such as esthetics, adhesiveness, simple clinical procedures, various shapes and kinds of composite resins are widely being applied to prosthodontics, conservative dentistry, and orthodontics. But, clinical problems attributable to the polymerization shrinkage of composite resin have been proposed, and we have to regard clinical problems such as secondary caries, loss of restoration, fracture of the surrounding tooth structure, marginal discoloration, and tooth sensitivity, and many portions are remained to be overcome. Therefore, this study attempts to analyze stress distribution between resin and tooth structure which is generated during polymerization shrinkage of composite resin using three dimensional finite element method. Three dimensional finite element models with conventional box-shape cavity and erosion/abrasion type V-shape lesion cavity in upper central incisor were developed. These cavities were filled with four different types of placement techniques. (bulk filling, horizontal increment filling, oblique occlusal increment filling, oblique gingival increment filling) The stresses generated by polymerization shrinkage of composite resin were calculated. The results analyzed with three dimensional finite element method were as follows : 1. The increment filling technique showed the highest maximum normal stress in both conventional box-shape and V-shape cavities and showed a tendency to decrease after complete polymerization. 2. The bulk filling technique resulted in increased stresses during the curing process in both conventional box-shape and V-shape cavities and the highest maximum normal stress occurred after complete polymerization. 3. The bulk filling resulted in the lowest maximum normal stress in both box-shape and V-shape cavities 4. Regardless of placement method, in conventional box-shape cavity, the maximum normal stress increased in dentin floor, enamel, dentin sequence and in V-shape cavity, the maximum normal stress increased in enamel, dentin sequence.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.13-22
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• 2016

An optimized spudcan was designed for the Southwestern Sea, an area mostly comprised of sand and soft clay layers. The spudcan was designed using guidelines by SNAME, ISO, and InSafeJIP, as well as the yield surface for combined loads. The probe test method was applied to define a yield surface used in estimating spudcan stability. Numerical analyses that considered vertical, horizontal, and moment loads in Southwestern Sea resulted in a design of 8 m diameter spudcan. Additionally, the empirical equations suggested by previous studies can estimate a reasonable spudcan bearing capacity at shallow depth. Each yield surface calculated from Mohr Coulomb and Hardening soil model showed different shapes, however the yield surface also grew with increasing spudcan diameter. This yield surface is a useful reference, along with site investigation results and published guidelines, to estimate the stability of a spudcan in the Southwestern Sea.

• Journal of the Korean Geographical Society
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• v.35 no.5
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• pp.701-716
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• 2000

This study examines patterms of wage inequality across ownership types and its regional structure in post-reform China in order to understand an emerging process of inequality. Using industrial wage data, I explored historical changes of cross-ownership wage inequality and its spatial differentiation during the reform period. This stuy found that pattems of wage inequality need to be understood in the context of changing redistributive economy which shapes state-enterprise relation in china's industrial sector. This relationship in turn determines labor market outcomes during the reform period including wage inequality. Regional structure of cross-ownership wage inequality also needs to be understood in terms of the differentiated process in which reqional wage levels are related to different wage factors. The findings have significant implications for understanding new patterns of soical and spatial inequalities in post-reform China.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.461-468
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• 2008

The needs for visualizing interactive multimedia contents on portable devices with realistic three dimensional shapes are increasing as new ubiquitous services are coming into reality. Especially in digital fashion applications with virtual reality technologies for clothes of various forms on different avatars, it is required to provide very high quality visual models over mobile networks. Due to limited network bandwidths and memory spaces of portable devices, it is very difficult to transmit visual data effectively and render realistic appearance of three dimensional images. In this thesis, we propose a compression method to reduce three dimensional data for digital fashion applications. The three dimensional model includes animation of avatar which require very large amounts of data over time. Our proposed method utilizes temporal and spatial coherence of animation data, to reduce the amount. By grouping vertices from three dimensional models, the entire animation is represented by a movement path of a few representative vertices. The existing three dimensional model compression approaches can get benefits from the proposed method by reducing the compression sources through grouping. We expect that the proposed method to be applied not only to three dimensional garment animations but also to generic deformable objects.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.10
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• pp.1114-1120
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• 2009

The conductivity of various electro-threads is analyzed, and the washable electro-thread embroidery UHF RFID tag antennas using the character shape without T-matching structure are designed by adding a T-matching structure. The RFID tag antenna using the electro-thread is easy to be embedded on a cloth as a wearable antenna because it is flexible and different from general copper inlay shape and tape type tag. The embroidery tag antennas are designed with the English alphabet 'F' and the Korea alphabet 'ㄹ' character. Those are easy to be applied to general clothes. The parameters of antennas are optimized and fabricated. The characteristics and the reading range patterns of the tag antennas are measured. The reading ranges of wet tags(tap water, sea water and soapy water) are tested and compared.