• Journal of the Korean Society of Combustion
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• v.12 no.2
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• pp.26-33
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• 2007

To reveal the newly found liftoff height behavior of hydrogen jet, we have experimentally studied the stabilization mechanism of turbulent, lifted jet flames in a non-premixed condition. The objectives of the present research are to report the phenomenon of a liftoff height decreasing as increasing fuel velocity, to analyse the flame structure and behavior of the lifted jet, and to explain the mechanisms of flame stability in hydrogen turbulent non-premixed jet flames. The velocity of hydrogen was varied from 100 to 300m/s and a coaxial air velocity was fixed at 16m/s with a coflow air less than 0.1m/s. For the simultaneous measurement of velocity field and reaction zone, PIV and OH PLIF technique was used with two Nd:Yag lasers and CCD cameras. As results, it has been found that the stabilization of lifted hydrogen diffusion flames is related with a turbulent intensity, which means that combustion occurs at the point where the local flow velocity is balanced with the turbulent flame propagation velocity.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.3
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• pp.266-273
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• 2012

In this paper, the new open fault detection and tolerant operation method for 3 phase PWM rectifier is proposed. When open fault occurred on the inverter switches of 3 Phase PWM rectifier, the DC link voltage ripple is increased because the input current of the faulty phase is distorted. In this case, the quality of electric power would decrease, and the life time of DC link capacitor is decreased. The open fault is detected by a simple MRAS(Model Reference Adaptive System) without additional hardware sensors, and the tolerant operation carried out by turning on the opposite switch of the faulty switch without any redundancy. By the proposed method, the faulty phase input current can be controlled, so that 3-phase input current is balanced relatively under the faulty condition and the voltage ripple of DC link output is reduced. The validity of the proposed technique is proved on the 6kW 3-phase PWM rectifier system by simulation and experiment.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.1
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• pp.33-41
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• 2002

In this paper, we present a frequency weighted model reduction using LMIs for minimizing the H$\infty$ weighted model error compared with the methods of frequency weighted balanced truncation and frequency weighted Hankel norm approximation. The proposed algorithm, its form is equal to the sufficient condition of performance preserving controller approximation, is based on an iterative two-step LMI scheme induced from bound real lemma. So, it can be applied to the problem of the performance preserving controller approximation. The controller reduction is useful in a practical control design and ensures its easy implementation and high reliability The validity of the proposed algorithm is shown through numerical examples. Additionaly, we extend the proposed algorithm to performance preserving controller approximation by applying to the HIMAT(highly maneuverable aircraft technology) system.

• Journal of Korean Home Economics Education Association
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• v.15 no.1
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• pp.15-32
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• 2003

This study examined teacher perception of the instructional method. activities and material in terms of class quality enhancement. Also this study established instructional method. activities and material application Per 7th Practical Arts Education Course guidance domain. and type identification of the instructional method and activities unique to the Practical arts curriculum. Conclusions : 1. Teachers consider the instructional method and material beneficial. However in the item relevant to application of diverse instructional methods Per specific teaching objective and educational content in the actual classroom. the highest percentage responding. ‘relatively yes’ (39.7%) . balanced out with those answering. ‘no’(37.7%) 2. In linking the instructional method and material to secondary school home economics education, teachers experienced difficulty in teaching only the clothing education domain . 3. In each guidance domain, lecture method, problem-solving learning. cooperative learning. home project learning and functional learning were surveyed for instructional method suitability. Notably, home project learning was identified as a significant instructional method. This result begs in-dept analysis as home project learning may be utilized as a tool to compensate for the absence of practical educational objective condition fulfillment and to substitute for teachers unable to Provide such functional guidance in class. 4. In each guidance domain. role-playing. debate/discussion. case study research, practical exercise and activity reporting were rated as essential teaching ㆍ learning activities. 5. In each guidance domain.‘VCR’, ‘CD-ROM’ and ‘Web media’ were identified as suitable instructional materials .

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.91-98
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• 2020

For form stability of membrane structures, membrane material is required to be in tension. Therefore, in planning and maintenance management, the engineer should consider enough about introduction of stress during construction and re-introduction of stress after completion. Clamping part is an important portion with the function for introducing tension into membrane materials, and the function to transmit stress to boundary structures, such as steel frames. Then, the purpose of this research is to clarify stress condition and stress transfer mechanism including clamping part of membrane structures, and to grasp the changing tendency of membrane structures with the passage of time. In this research, following previous one, we perform well-balanced evaluation by conducting tensile fractured tests of clamping part's specimens, and by measuring individually the amount of displacement of not only overall specimen's length but membrane material and clamping part. Thereby, we consider the influence the difference in the hardness of edge rope and the difference in the direction of thread affect modification and fracture load.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3215-3226
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• 1996

In this paper a K-band harmonic oscillator competitive to ordinary Push-Push type oscillators is introduced. This oscillator is composed of two-X-band dielectric resonance circuits. To favor its harmonic generation, the load effect and the bias effect are studied to allow the maximum harmonic distortion. As results, the dielectric resonated load and the class A bias are used for the 2nd harmonic generation. analytical study for modelling of voltage controlled dielectric resonator is carried out with theoretical background. The performance of the circuit is evaluated by simulation using harmonic balanced method. The novel structure has ont only a voltage tuning circuit but also an output port at fundamental frequency as the function of prescaler for phase lockede loop application on the just single oscillation structure. In experimentation, the output freqneyc of the 2nd harmonic signal is 20.5GHz and the maximum power level of output is +5.5dBm without additional post amplifiers. the harmonic oscillator exhibits -30dBc of high fundamental frequency rejection without added extra filters. The phase noise of -90dBc/Hz at 100kHz off-carrier has been achieved under free running condition, that satisfies phase noise requirement of IESS 308. The proposed oscillator may be utilized as the clean and stable fixed local oscillator in Transmit Block Upconvertor(TBU) or Low oise Block downconvertor(LNB) for K/Ka-band digital communications and satellite broadcastings.

• Journal of Environmental Science International
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• v.29 no.2
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• pp.167-175
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• 2020

The purpose of this study was to investigate the effect of shading on the growth and productivity of strawberries. Photosynthesis was normally achieved under natural light without shading treatment, and vegetative growth of under- and aboveground part of strawberry plants were excellent. Strawberry fruit productivity and quality were different depending on shading conditions. In natural light, they were improved possibly by balanced vegetative and reproductive growth. However, under light-shading conditions with insufficient sunshine, photosynthetic activity deteriorated and carbohydrate production was therfore inadequate; this adversely affected plant height and quality. The negative effects were more pronounced at 50% shading condition. Shading treatments resulting in insufficient sunshine had a detrimental impact on plant productivity and growth; this implies that proper shading conditions could heip improve yield and fruit quality.

• 한국해양학회지
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• v.16 no.1
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• pp.12-23
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• 1981

A numerical experiment is made in order to clarify the mechanism of the upwelling phenomenon along the coast near the poleward edge of the western boundary current. The possibility of the upwelling is suggested from the analysis of the observational data in the east of Honshu, Japan, and in the south eastern coast of Korean Peninsula. This upwelling phenomenon is very deep and can be traced to the bottom layer. The upwelling phenomenon seems to be a general oceanic feature which characterizes the region along the west coast near the poleward edge of the western boundary current. This experiment is simulating the oceanic condition of the transition region between Kuroshio front and the Oyashio front in the east of Honshu, Japan. The possible explanations of the causes of the upwelling are as follows;In the interior of the modeled ocean the cold heavy water supplied from the north and the warm light water from the south make the north-south gradient of the pressure field and accelerate the eastward current to produce the h-orizontal divergence feld near the west coast. The divergence is compensated by the upwelling near the separation region. Another one is that the upwell-ed cold water strengthen constantly the pressure gradient which is balanced by the northward current and is weakened by the horizontal diffusion.

• World Technopolis Review
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• v.6 no.1
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• pp.5.1-5.12
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• 2017

The Republic of Korea developed a national project to construct a new administrative capital, Sejong city and to relocate administrative organizations of the central government for improvement of overpopulated capital, Seoul and regional balanced development. By the way, to relocate the central administrative organizations was not a sufficient condition for the sustainable development of the city. An industrial infrastructure development has been tried to attract universities, enterprises and research institutions in the region as a demand for internal growth power of the city was increased. In addtion, a basis for regional endogenous growth through projects to establish innovation system based on industry-academia cooperation was prepared as well. This paper reviews the major contents of the development plans for Tech-Valley project and looks into major introductory functions, characterization plans, strategies for fostering strategic industry, cooperation system of the inside and outside the region, and a strategy for building innovation platform. This case can be regarded as a significance of constructing technology infrastructure for the sustainable growth by preparing foundation for establishing innovation system and a cluster based on this system in the process of building and developing new city which did not have any industrial platform in the region.

• The Research Journal of the Costume Culture
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• v.8 no.4
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• pp.611-622
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• 2000

The purposes of this study are as follows. First, it is to review the features of discount stores that are expected to grow rapidly and continuously due to their low price, low cost, bulk purchase, and multiple shops, and to pinpoint problems arising from the establishment and position of the stores. Second, it is to analyze relevant issues in regard to the present status of fashion good distribution in discount stores by studying the situation, structure and problems of domestic fashion distribution along with the present status of the distribution in discount stores, and to suggest directions for the development of fashion distribution and discount stores. A positive study was carried out on the buyers of big domestic discount stores through one-to-one interviews focusing on the distribution of fashion products within Seoul and the Metropolitan area. The following is the directions for the development of clothing distribution and discount stores ; 1. The relative importance of fashion goods in a discount store will be increased with the tendency of fashionable and differentiated shops ; 2. The GMS or category killers will be established from around 2003 when the market is expected to become saturated with a great deal of discount stores. 4. Discount stores will change and reform without being restricted to a certain existing industry or business condition, and distribution channels will diversify over the border. The demand and supply system will be balanced based on a global marketing which will be adjusted on the international level.