• The Journal of the Acoustical Society of Korea
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• v.21 no.1E
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• pp.25-30
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• 2002

We report on the development of a fiber optic hydrophone consists of a sensing Michelson interferometer and a compensating Mach-Zehnder interferometer for optical path length compensation. The double interferometer configuration has the following advantages: the hydrophone can be made more small; a laser source with a relatively short coherence length can be used; and the compensating interferometer can be located near the signal processing electronics, far away from the sensing interferometer and noise introduced by reference arm can be greatly reduced. The performance of the hydrophone is evaluated experimentally by immersing the sensing interferometer in a water tank to detect underwater acoustic signals generated by an acoustic wave projector. Experimental results show that over the frequency range of 1 to 4 kHz, the hydrophone has an almost flat response with an average normalized sensitivity of -302 dB re 1/ μ Pa.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1036-1041
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• 2008

Double facade systems are often paid attention of as an effective energy saving measure for curtain wall buildings. However, it is not easy to install the system in existing buildings and requires substantial investment. An innovative double window system is proposed in this study which can be installed with exiting window systems in a cost effective way. the proposed system is connected to existing return ducts to make airflow between the existing window and the newly installed window. To ensure the best performance of the proposed system, simulation-based analysis was implemented in which airflow characteristics of inside double window were examined according to air pressures of return duct and window material by using computer simulation ESP-r. the overview of the proposed system and the results of the simulation-based analysis are presented in this paper.

• Korean Journal of Human Ecology
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• v.12 no.2
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• pp.253-263
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• 2003

The purposes of this study were to find out an evaluation scale that could predict wear comfort and to investigate the effect of the skin-contacting fiber type on the subjective sensation and microclimate. Sensorial evaluation was basically followed by the Human Perception Analysis (HPA) interviewing 144 consumers. Sixteen female subjects were participated in the sleeve wear test with and without wearing vapor permeable water repellent outerwear. Experimental sleeves were constructed using the same double knit by turning inside out to control other material effects except the skin-contacting fiber type, hence each different side of double knit, cotton side and the cotton/polypropylene blend side, was next to skin in each trial of the experiment. As results, it was noted that the term representing a combined feeling of thermal and wetness sensation, and muggy appeared to be a powerful language to measure perceptual responses of human subject among five dimensions of evaluation. although the ordinary users did not use the term very often. As for the comfort properties of double knits, it seemed that subjects slightly more preferred polypropylene/cotton blend to cotton as the skin-contacting fiber type when they wore outerwear and their skin were covered with sweat, although the result was rot statistically significant and need to be confirmed under higher work load.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.313-318
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• 1999

This study is aim to evaluate of the flexure toughness of fiber reinforced concrete with ring type steel fiber. The experiment proceeding ASTM C 78 is performed to make a comparision between the ring type flber and the double-hook type fiber which is recently come in to use. The size of the test specimen is 10$\times$10$\times$35mm and the flexture test is proceeded by third-point loading method. The test lasts until 2mm deflection and the loading speed is 0.01mm/min by deflection control. From the experimental results, the specimens with ring type fiber of 30kg/㎥ and 30mm diameter of ring circle show much higher toughness indices than those of the double-hook type fiber of 30kg/㎥ and 30mm long.

• Journal of Ocean Engineering and Technology
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• v.38 no.4
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• pp.164-173
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• 2024

In this study, a submerged breakwater with effective wave control and eco-friendly characteristics is developed and proposed. Hydraulic experiments are conducted to compare the hydraulic performance of a submerged breakwater and an eco-friendly double-row submerged breakwater. The hydraulic characteristics are analyzed based on wave reflections and the transmission-splitting method for each experimental cross-section. This splitting technique utilizes Goda's two-point method, which employs the spectra of two irregular superposed wave fields. In addition, the reliability of the results obtained from the hydraulic experiments is discussed by comparing the results with empirical formulas. The eco-friendly double-row submerged breakwater features approximately half the width of a typical submerged breakwater. Nevertheless, its transmission coefficient (K_T) is approximately 20% more effective, and the difference in the average reflection coefficient (K_R) values between the two is approximately 0.17. Moreover, the dissipation coefficient (K_D) shows a generally similar trend. Based on these experimental results, the hydraulic performance of the eco-friendly double-row submerged breakwater is more efficient regarding wave control, compared with a typical submerged breakwater. These hydraulic characteristics confirm that the numerical model developed for the eco-friendly double-row submerged breakwater accurately reproduces the K_T, K_R, and K_D values within ±5%.

• The Journal of Korean Philosophical History
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• no.36
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• pp.7-42
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• 2013

This article is on the introduction and origin of Korean Neo-Confucianism. In this article, it is verified and clarified that a scholar named Jeong, Sin-bo (鄭臣保) from Southern Song settled on today's Seosan Ganwoldo (看月島) in the year of 1237 (24th year of the king Gojong in Korean Dynasty) and he introduced the Neo-Confucianism both by Jeong, Myung-do (程明道) and Jeong, Yi-cheon (程伊川) who are also called Double Jeong to Korean scholars. Based on these facts, it overturns the history that Anhyang (安珦) first introduced Neo-Confucianism to Korean Dynasty in the year of 1290 even with 35 years ahead. When this gains official approval by the academia, the history of Neo-Confucianism seems to be rewritten. This article first examines changes in history of Korean Neo-Confucianism with three stages and then concentrates on the life of Jeong, Sin-bo. It presents that Jeong, Sin-bo was a descendant of a Southern Song's noble family named Pogang Jeong (浦江鄭氏) and he committed to Chunqiu thoughts (春秋思想) and spirit of loyalty (義理精神) naturally as the posterity of Pogang Jeong. Lastly, it also infers the transmission of Jeong, Sin-bo's scholastic mantle and his influence on the posterity.

• Tunnel and Underground Space
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• v.20 no.4
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• pp.233-240
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• 2010

Double Plug is constructed for preventing mixing of two different oils between two compartments in the underground oil storage cavern. And the gas and oil tightness of double plug is tested from the measurement of water leakage from double plug after the completion of double plug water filling. If water leakage is underestimated, it can increase construction cost and if water leakage is overestimated, it can increase operating cost. Therefore, optimum water leakage should be estimated to cut down the cost. In this study, hydraulic stability analysis was conducted to consider permeable properties of rock mass around double plugs and a water leak rate from double plug was estimated from the hydraulic stability analysis and case study. Finally, the reliability of estimation of water leak rate was proven by comparing estimated water leak rate with measured data.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.281-292
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• 2008

Prefabricated Board Drains (PBDs) recently become more widely used than conventional sand drains in improving soft ground because the PBD is more time and cost effective. The performance of PBDs is affected by disturbance in the adjacent soil formation during inserting mandrels, the intrusion of fine particles into filter fabric, and necking of the drain by excessive lateral pressure especially occurring in very deep clay formation such as the Busan New Port site. In this study, the PBD with double-core is introduced, which seems to overcome the shortcomings of usual single-core PBDs. An in-situ test program was established in the Busan New Port site, in which a set of the double-core PBDs and the single-core PBDs was installed to compare the efficiency of each of the drains. The discharge capacity of the double-core and the single-core PBDs was compared for various confining pressures in the modified Delft test and the chamber test. A series of CRS consolidation tests was performed in order to obtain profiles of void ratio-effective stress and void ratio-permeability relationships in the Busan New Port site that are used as input date in performing a numerical program ILLICON. The numerically simulated settlements of ground surface in the test site are in good agreement with those of in-situ measurements. In addition, the performance of the double-core and single-core PBDs has been experimentally and numerically compared in this paper.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.825-830
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• 2004

A numerical analysis based on two-dimensional and three-dimensional incompressible Navier-Stokes equations has been carried out for double-circular-arc (DCA) compressor cascades. Two types of double-circular-arc cascades were used in this analysis. The appropriate turbulence model for compressor analysis was selected among the conventional turbulence models such as Baldwin-Lomax, k-$\varepsilon$ and k-$\varepsilon$ models. The results of current study were compared with available experimental data at various incidence angles. The 2-D and 3-D computational codes based on SIMPLE/PWIM algorithm for collocated grid and hybrid scheme for the convective terms were the main features of numerical tools. As commonly known, turbulence modeling is very important for the prediction of cascade flows, which are extremely complex with separation and reattachment by adverse pressure gradient. For selection of turbulence model, 2-D analysis was performed. And then, k-$\varepsilon$ turbulence model with wall function chosen as the reasonable turbulence model for 3-D calculation was used to increase the efficiency of computation times. A reasonable result of 3-D flow pattern passing through the double-circular-arc cascade was obtained.

• Journal of Families and Better Life
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• v.32 no.4
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• pp.1-22
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• 2014

This study was focused on investigating the factors of the psychological adaptation of grandmothers raising their grandchildren. The Double ABCX family stress model provided the theoretical basis for this study, and the major factors examined in the study included a pile-up of stressors, family resources and social support, appraisal of situation(redefinition of nurturing), and adaptation(depressive mood and happiness). Data were collected by personal interview with 213 grandmothers raising their grandchildren utilizing the questionnaire survey method. Structural equation modeling analyses were performed and the results showed that a pile-up of stressors, the family resources(i.e., contact and emotional solidarity with grandchildren's parents), and the redefinition of nurturing had significant influences on the psychological adaptation of grandmothers raising their grandchildren. It was also found that social support had indirect influence on grandmothers' psychological adaptation. The redefinition of nurturing had the greatest effect on the participants' psychological adaptation, followed by a pile-up stressor, and then the family resources.