• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.385-388
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• 2008

Modern society is experiencing a high population density and a centralization of facilities. The clear trends in the construction field are aggrandizement, elevation and specialization of building structures. Such trends require improvements of skills in raising material performances, structuring, planning, designing, and increasing construction capacities. In order to procure high performance materials and construction techniques, a top-quality concrete should be used since it takes up a large part of the material. In recent years, active researches have been done on the ultra high strength concrete. Therefore, this experimental study is strength management to fixed quantity in the field of ultra-strong concrete.

• Journal of Ginseng Research
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• v.41 no.1
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• pp.10-22
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• 2017

Background: Asian ginseng and American ginseng are functional foods that share a close genetic relationship and are well-known worldwide. This article aims to investigate the correlation between morphological characteristics and the inherent quality of Asian and American ginsengs. Methods: In this study, an ultra-HPLC-quadrupole/time-of-flight MS (UHPLC-Q/TOF-MS) method was established for the quantitative analysis of 45 ginseng samples. The method developed for determination was precise and accurate. Results: The results showed that Asian ginseng samples with the same growing time (with the same or similar number of stem scars) that had a thinner main root, a longer rhizome and more branch roots contained greater amounts of ginsenosides. For American ginseng, two tendencies were observed in the relationship between the diameter of the main root and contents of ginsenosides. One tendency was that samples with thinner main roots tended to contain higher levels of ginsenosides, which was observed in the samples sold under the commercial name pao-shen. Another tendency was that samples with thicker main roots contained higher contents of ginsenosides, which was observed in the samples sold under the commercial name pao-mian, as well as in samples of American ginseng cultivated in Jilin, China. Conclusion: An approach using ultra-HPLC-quadrupole/time-of-flight MS was successfully established to link morphology and active components for evaluating the quality of Asian and American ginsengs. Clear correlation between visible morphological features and quality of Asian and American ginsengs was found. People can see the difference; this means consumers and vendors can evaluate ginseng by themselves.

• Journal of the Korea Furniture Society
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• v.10 no.1
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• pp.103-111
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• 1999

In the age of knowledge and information when every aspect of economy, education and culture in society is changing rapidly, the teacher is not just a provider of knowledge in classroom. Ultra-modern educational tools and materials have come into being with the latest developments in science and technology and we see classroom teaching in general tending towards more 'open' classroom and study. What the students need most for the coming century is the cultivation of higher faculties such as creative thinking, the power to solve problems, and the spirit of inquiry. The present-day teacher is required to make use of various teaching medial in order to provide the students with better educational environment for developing these faculties, not the teaching method of the past with the teacher at the center. One way to enhance classroom environment is in reintroducing the modernized teacher's desk to the center of teaching apparatus. This paper is about the better way of designing the teacher's multimedia desk equipped with a PC that will make it possible for the teacher to utilize the internet-based educational resources.

• Advances in Traditional Medicine
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• v.8 no.2
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• pp.103-110
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• 2008

Herbal medicine is the use of medicinal plants for prevention and treatment of diseases: it ranges from traditional and popular medicines of every country to the use of standardized and tritated herbal extracts. Generally cultural rootedness enduring and widespread use in a traditional medical system may indicate safety, but also efficacy of treatments, especially in herbal medicine where tradition is almost completely based on remedies containing active principles at very low and ultra low concentrations or relying on magical-energetic principles. The efficacy and safety assessments of medicines, whether modern or herbal, invariably encounter challenges or problems during the course of pre-clinical and clinical research. Some of the challenges in evidence-based herbal medicinal research are unique, and the researcher must be cognizant of them in order to safeguard the quality of the data obtained. Key challenges are: the quality of raw materials; appropriateness of biological/pharmacological activity assessment methodology, and data interpretation; standardization methodology; pharmacokinetics and bioavailability of active constituents and metabolites; clinical dosage formulation/production; and clinical study designs and outcome measures.

• Journal of the Korean Operations Research and Management Science Society
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• v.8 no.2
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• pp.57-65
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• 1983

Despite the recent phenomenal growth in computer installations in business and increasing interests in Management Information Systems in Korea, there are basic questions remained: how are the computers utilized, what is the current state of MIS, and what are the strategies which will enhance the current state of MIS in Korea？ The purpose of this paper is to answer these questions. To begin, the current state of MIS is investigated from the aspects of MIS budget, manpower, hardware, and various softwares based on the survey of 30 major industries. The results show that the overall MIS in Korea is still remained in the primitive stage despite its ultra modern computer hardwares. The obstacles that hinders the MIS evolution in Korea seems intractable for quite a long period of time. Some strategies are suggested which can partially remove two big obstacles-shortage in qualified manpower and lack of softwares that fit Korean industries.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.939-942
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• 2000

Single point diamond turning technique for optical crystals is reported in this paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle material.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.174-175
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• 2021

Currently, the construction structures become larger and more high-performance in modern society, demands for ultra-high strength and light weight construction materials are increasing rapidly. Therefore, this study aims to confirm the applicability of nanomixed cement supplemented with physical and mechanical properties using nanomaterials.Changes in compressive strength and properties were analyzed according to the ratio of cement paste and dispersant (PCE) made by ultrasonication of carbon nanotubes (CNT)

• Current Optics and Photonics
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• v.8 no.1
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• pp.16-29
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• 2024

This paper presents a comprehensive review of metasurface technology, focusing on its significant role in extraordinary flat optic functionalities. Traditional optical components, though optimized, are bulky and less congruent with modern integrated electromagnetic and photonic systems. Metasurfaces, recognized as the 2D counterparts of bulk metamaterials, offer solutions with their planar, ultra-thin, and lightweight structures. Their meta-atoms are adept at introducing abrupt shifts in optical properties, paving the way for high-precision light manipulation. By introducing the key design principles of these meta-atoms, such as the magnetic dipole and Pancharatnam-Berry phase, various applications in wavefront shaping and beam forming with simple amplitude/phase manipulation and advanced applications including retroreflectors, Janus metasurfaces, multiplexing of optical wavefronts, data encryption, and metasurfaces for quantum applications are reviewed.

• Current Optics and Photonics
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• v.6 no.6
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• pp.521-549
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• 2022

Fiber lasers have made remarkable progress over the past three decades, and they now serve far-reaching applications and have even become indispensable in many technology sectors. As there is an insatiable appetite for improved performance, whether relating to enhanced spatio-temporal stability, spectral and noise characteristics, or ever-higher power and brightness, thermal management in these systems becomes increasingly critical. Active convective cooling, such as through flowing water, while highly effective, has its own set of drawbacks and limitations. To overcome them, other synergistic approaches are being adopted that mitigate the sources of heating at their roots, including the quantum defect, concentration quenching, and impurity absorption. Here, these optical methods for thermal management are briefly reviewed and discussed. Their main philosophy is to carefully select both the lasing and pumping wavelengths to moderate, and sometimes reverse, the amount of heat that is generated inside the laser gain medium. First, the sources of heating in fiber lasers are discussed and placed in the context of modern fiber fabrication methods. Next, common methods to measure the temperature of active fibers during laser operation are outlined. Approaches to reduce the quantum defect, including tandem-pumped and short-wavelength lasers, are then reviewed. Finally, newer approaches that annihilate phonons and actually cool the fiber laser below ambient, including radiation-balanced and excitation-balanced fiber lasers, are examined. These solutions, and others yet undetermined, especially the latter, may prove to be a driving force behind a next generation of ultra-high-power and/or ultra-stable laser systems.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.107-119
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• 2021

The cross-flow turbine is one of the most famous and widely used hydraulic power systems for a long time. The cross-flow turbine is especially popular in many countries and remote regions where off-grided because of its many benefits such as low cost, high efficiency at low head, simple structure, and easy maintenance. However, most modern turbines, including the cross-flow turbine, are unsuitable for the ultra-low head situation, known as less than 3m water head or zero head with over 0.5m/s flow velocity. In this study, we demonstrated a 20kW class inverted-type cross-flow turbine's performance. First, we reevaluated our previous studies and introduced how to design the inverted-type cross-flow turbine. Secondly, we fabricated the 20kW class inverted-type cross-flow turbine for the performance test. And then, we designed a testbed and installed the turbine system in the demonstration facility. In the end, we compare the demonstration with its previous CFD results. The comparing result shows that both CFD and real model fitted on guide vane angle at 10 degrees. At the demonstration, we achieved 42% turbine efficiency at runner speed 125 RPM.