• Bulletin of the Korean Mathematical Society
• /
• v.59 no.1
• /
• pp.213-226
• /
• 2022

Let R be a ring and M an R-module. Then M is said to be regular w-flat provided that the natural homomorphism I ⊗_R M → R ⊗_R M is a w-monomorphism for any regular ideal I. We distinguish regular w-flat modules from regular flat modules and w-flat modules by idealization constructions. Then we give some characterizations of total quotient rings and Prüfer v-multiplication rings (PvMRs for short) utilizing the homological properties of regular w-flat modules.

• Journal of the Korea Concrete Institute
• /
• v.12 no.4
• /
• pp.113-119
• /
• 2000

The R/C flat plate system provides architectural flexibility, clear space, reduced building height, simple formwork, which consequently enhance constructibility. One of the serious problems in the flat plate system is brittle punching shear failure due to transfer of shear force and unbalanced moments in column-slab joint. Recently, the flat plate system accompanied with shear walls to resist the lateral loads is applied to high-rise buidings. Although the flat plate system is not considered in design as part of the lateral load-resisting system, it is required that this system keeps the ductile behavior for the lateral displacement of the building. However, it is unclear whether the column-slab joint possesses ductility enough to survive the lateral deformation. The objective of this paper is to investigate the major parameters that influence the ductility of R/C flat plate system by examining the existing experiments on column-slab joint. The effects of gravity load and shear reinforcement on the ductility of the flat plate system are presented.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.65 no.2
• /
• pp.142-150
• /
• 2016

This paper developed new manufacture process technology of slim type flexible flat lighting product used lower power white LED. Flexible flat lighting is applied to letter sign lighting, traffic lighting, interior wall lighting, flat lighting, aquarium back lighting, wreath light etc. Main manufacture process technology were developed drawing software for electronics circuit, inkjet electronic circuit pattern and inkjet white ink coating. For pattern printing it was utilized for piezoelectonic inkjet head printing technology. Also high vacuum pressure laminating technology was waterproofing for LED flat lighting protection. Hence, form process technology we were manufactured for flexible flat lighting product of the power 12 W, input voltage 48 V and plane size $480{\times}480mm$. It acquired a these validity from experiment results.

• Journal of applied mathematics & informatics
• /
• v.29 no.1_2
• /
• pp.497-504
• /
• 2011

In 1973, B. Y. Chen and K. Yano introduced the special conformally flat space for the generalization of a subprojective space. The typical example is a canal hypersurface of a Euclidean space. In this paper, we study the conditions for the base space B to be special conformally flat in the conharmonically flat warped product space $B^n{\times}_fR^1$. Moreover, we study the special conformally flat warped product space $B^n{\times}_fF^p$ and characterize the geometric structure of $B^n{\times}_fF^p$.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.1415-1417
• /
• 2003

In this study, as the passing of a year, the changes of tidal flat area in Seohan Bay, North Korea was monitored through using Landsat ETM Data and the ancient topological map. The map to present tidal flat distribution characteristic based on the ancient topographical map (1918) was constructed as GIS DB. In addition, a tidal flat distribution map was estimated by using the satellite images with unsupervised classification method. Even though it is difficult to approach to study area, it was possible to gain the data and to monitor the change of the coast tidal flat by comparing to area change yielded.

• Korean Journal of Optics and Photonics
• /
• v.28 no.6
• /
• pp.339-345
• /
• 2017

The flatness of a reference flat plays an important role, from the calibration of an interferometer to the reference for a semiconductor or flat-panel display, etc. Especially if we order the flatness measurement outside Korea, we may spend more time and money. In this paper, we measured the flatness of a reference flat using a three-flat test, which is one of the absolute measurement methods, and calculated its measurement uncertainty. In the three-flat test we adopted, each flat is tested against another flat, with three unknown flats, using an interferometer. Among several three-flat tests, we adopted Griesmann's method which has a low measurement uncertainty and is less dependent on the experimental equipment. As a result, the measurement uncertainty was found to be less than 0.5 nm rms, which is very accurate for high-tech industrial applications.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.8
• /
• pp.978-986
• /
• 1999

In this study, the general thermal and flow characteristics of flat tube with micro-channels has been studied and the correlation of Nusselt number and friction factor is proposed. The optimal flat tube geometry is determined by optimal design process. It is assumed to be a three dimensional laminar flow in the analysis of thermal and flow characteristics. The periodic boundary condition is applied since the geometry of flat tube with micro-channels shows uniform cross-section in primary flow direction. Local Nusselt number is examined for thermal characteristics of each membrane, and module average Nusselt number and friction factor are calculated to determine the characteristics of the heat transfer and pressure drop in overall flat tube with microchannels. The correlations between Nusselt number and friction factor are given by Reynolds number, aspect ratio of membranes, and the width of flat tube. ALM (Augmented Lagrangian Multiplier) method is applied to the correlations to determine an optimal shape of flat tube. It is shown that the optimal aspect ratio of flat tube is approximately 1.0, irrespective of the width of flat tube and Reynolds number.

• Journal of the Korean Society of Radiology
• /
• v.7 no.3
• /
• pp.227-232
• /
• 2013

The pixels used in a digital X-ray detector have different sensitivities and offset values. A non-uniform image is consequently obtained. Flat-field correction was introduced to resolve this problem and carried out image preprocessing in a digital imaging system. Nevertheless, the non-uniform images caused by several reasons have been being occasionally acquired. In this study, the non-uniform images acquired in digital imaging systems were applied to flat-field correction, and NPSs were calculated and analyzed with those images before and after correction. It was confirmed that low frequency noise were effectively eliminated.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.4
• /
• pp.103-113
• /
• 2004

The flat dilatometer test(DMT) is a useful geotechnical tool for estimating in-situ properties of various types of ground materials and the application of flat DMT is increasing. The existing relationships which are used to estimate the design parameters of soft deposit depend on the regional geotechnical characteristics and then it is necessary to investigate the applicability of the flat dilatometer in Korea. In this paper, the flat DMT has been conducted in soft marine deposits. The results estimated by existing relationships and those obtained from laboratory tests were compared. Based on the results, some factors influencing the relationships were examined and adjustment of empirical expression was performed.

• Environmental Engineering Research
• /
• v.17 no.2
• /
• pp.77-82
• /
• 2012

The spatial variation of organic matter sources in tidal flat sediment of the Nanakita River estuary, involving Gamo lagoon on the north-east coast of Honshu Island, Japan, was examined using carbon stable isotopes and fatty acid biomarkers. The spatial variation of total organic carbon (TOC) contents and ${\delta}^{13}C$ values were highly variable in between the stations, such as sandy flat (1.3 mg/g, -21.0‰), sand-muddy flat (2.6 mg/g, -21.9‰), and muddy flat (24.9 mg/g, -25.9‰), respectively. Particularly, at the muddy flat, high TOC content and low ${\delta}^{13}C$ value of the sediments indicated that the surface sediment was composed largely of terrestrial organic matter. Whereas, at the sandy flat and sand-muddy flat, the high ratios of diatom and bacteria biomarkers indicated the high contribution of abundant microorganism along with marine organic matter in sediment composition. From these results, it considered that the amount and origin of transported sedimentary organic matter indicated different characteristics in this study stations.