• Journal of Ocean Engineering and Technology
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• v.19 no.2 s.63
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• pp.19-28
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• 2005

The present paper outlines the numerical investigation of the incident wave interactions with fully submerged and floating dual double hull pontoon/vertical porous membrane breakwaters. Two dimensional five fluid-domains hydro-elastic formulation was carried out in the context of linear wave body interaction theory to study the wave interaction with the double hull of pontoon-membranes. The submerged circular pontoon is consisted of double hulls, which is filled with water in the void space between the outer structure and inner solid buoyant structure. Hydrodynamic characteristics of the proposed system with dual floating double-hull-pontoons filled with water have been studied numerically for the various incident waves. This study is a beginning stage research for the dual double hull porous pontoons/vertical porous membranes breakwaters which is ideally designed in order to suppress significantly the transmitted and reflected waves simultaneously.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.123-132
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• 2020

Due to the various restrictions and problems related to the construction of new roads in urban areas, underground road construction has been receiving a great deal of attention in the field of tunnel engineering. In this study, a double-deck road tunnel with a diverging section was analyzed for the evaluation of its stability. Both numerical analysis and scale model tests were performed, the results were used to develop a stability evaluation method for double-deck tunnels with diverging sections constructed in rocks by NATM. From regression analyses conducted on the results of the numerical analysis, an equation and a chart were derived, these tools allow us to obtain the strength/stress ratio (SSR) for double-deck road tunnels with a diverging tunnel in various diverging conditions quickly and accurately. These tools have great potential to help engineers evaluate the stability of double-deck tunnels in the preliminary design stage.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.3
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• pp.447-453
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• 2007

The purpose of this study was to investigate the relationship between morphology and number of deciduous teeth and the occurrence of other dental anomalies in their successors, and to evaluate the necessity of early diagnosis of dental anomalies in the primary dentition. Prevalence of double teeth and congenital missing teeth was investigated in 254(134 boys, 120 girls) panoramic radiographic films, taken by 2 to 7-year-old children in Chonnam National University Hospital from 2000 to 2005. And then it was examined that relationship of anomalies of the primary dentition and their successors. Among them 11 children(6 boys, 5 girls) had double teeth or missing teeth. And prevalence of the double teeth was 1.6% and missing teeth was 3.1%. One subject had double teeth in in the mandible and missing teeth in the maxilla. Of the 11 cases of dental anomalies in primary dentition, 7 cases had congenital missing tooth in their successors. This study suggests that the dental anomalies in the primary dentition induced high prevalence of the congenital missing of permanent successors in the permanent dentition.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.37 no.3
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• pp.44-54
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• 2000

In this paper, a design methodology for the frequency-adaptive negative-delay circuit which can be implemented in standard CMOS memory process is proposed. The proposed negative-delay circuit which is a basic type of the analog SMD (synchronous mirror delay) measures the time difference between the input clock period and the target negative delay by utilizing analog behavior and repeats it in the next coming cycle. A new technology that compensates the auxiliary delay related with the output clock in the measure stage differentiates the Proposed method from the conventional method that compensates it in the delay-model stage which comes before the measure stage. A wider negative-delay range especially prominent in the high frequency performance than that in the conventional method can be realized through the proposed technology. In order to implement the wide locking range, a new frequency detector and the method for optimizing the bias condition of the analog circuit are suggested. An application example to the clocking circuits of a DDR SDRAM is simulated and demonstrated in a 0.6 ${\mu}{\textrm}{m}$ n-well double-poly double-metal CMOS technology.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1999.12a
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• pp.428-435
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• 1999

• Journal of computational fluids engineering
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• v.20 no.4
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• pp.1-6
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• 2015

Centrifugal pumps consume considerable amount of energy in various industrial applications. Therefore, improvement of the efficiency of these machines has become a major challenge. Cavitation is a phenomenon which decreases the pump efficiency and even causes structural demage. Hence, the goal of this paper is to investigate the cavitation problem in the single-stage and double-stage centrifugal pumps. The Volume of Fraction (VOF) method has been used for the numerical simulations together with Rayliegh-Plesset model for the gas-liquid two-phase flow inside the pump. In order to capture the turbulent phenomena, the standard k-${\varepsilon}$ turbulence model has been adopted, and the simulations have been done as unsteady cases. In addition, the motion of the rotating parts has been simulated using Multi Reference Frame(MRF) method. The results are presented and compared in terms of hydraulic head and NPSH for both the single-stage and double-stage pumps. The H-Q curves show the effects of cavitation on decreasing the pumps performances.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.3
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• pp.422-430
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• 1999

This paper concerns the study of a two-stage absorption heat pump cycle to utilize treated sewage. This two-stage cycle consists of coupling double-effect with parallel or series flow type and single effect cycle so that the first stage absorber and condenser produces hot water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as absorber temperature on the coefficient of performance have been studied for two-stage absorption heat pump cycle. The working fluid is lithium bromide and water solution. The efficiency of the two-stage absorption heat pump cycle has been studied and simulation results show that higher coefficient of performance could be obtained for the first stage with parallel flow type. The optimum ratio of solution distribution can be shown by considering the COP, the crystallization of solution and the generator temperature.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.719-724
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• 2006

In this paper, we designed the double conversion down mixer by using Half-LO frequency in 2.3 GHz band. The IF frequency is obtained by supplying two LO frequencies to HEMT in both gate type and resistive type. The proposed mixer uses Half-LO frequency the same way as conventional sub-harmonic mixers. However the proposed one uses fundamental component of Half-LO frequency in first stage instead of using second harmonic components of Half-LO frequency, and the IF frequency is obtained by resistive type mixer in second stage, thereby the proposed mixer can improve linearity in comparison with conventional active mixer. We can verify that the proposed mixer has an conversion loss of 5dBm and IIP3 of 16.25dBm by using 10 dBm Power.

• Clinics in Orthopedic Surgery
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• v.10 no.4
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• pp.413-419
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• 2018

Background: We aimed to examine the factors that influence synovialization of the grafted tendon after double-bundle anterior cruciate ligament (ACL) reconstruction based on second-look arthroscopic findings. Methods: Out of 205 knees that were treated between August 2008 and May 2016 with double-bundle ACL reconstruction using bio-absorbable cross-pins and Endobuttons for femoral tunnel fixation, we enrolled 65 knees (64 patients) that underwent second-look arthroscopy with hardware removal at 1 year postoperatively. Measured clinical outcomes included the Lysholm score and Tegner activity score that were evaluated preoperatively and during the final follow-up. We analyzed the relationship between synovial coverage and patient age, length of the preserved remnant tissue on the tibial side, type of bundle (anteromedial or posterolateral), type of graft (autograft or allograft), and time from injury to surgery. Results: The area of synovial coverage showed a significant statistical correlation with patient age and the length of the preserved remnant tissue on the tibial side. The average synovial coverage was significantly better for the anteromedial bundle than for the posterolateral bundle, better for the autograft than for the allograft reconstruction, and better when treated in the acute stage than in the chronic stage. However, synovialization of grafted tendon did not correlate to clinical outcomes. Conclusions: While we were able to identify several factors influencing synovialization of the grafted tendon after double-bundle ACL reconstruction, including patient age, length of preserved remnant tissue of the torn ACL, type of bundle, type of graft, and time from injury to surgery, we found no evidence that increased synovialization improves clinical outcomes at 1 year postoperatively.

• Journal of Korean Neurosurgical Society
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• v.62 no.1
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• pp.123-129
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• 2019

Objective : Ventriculoperitoneal (VP) shunt surgery is a common and effective treatment for hydrocephalus and cerebrospinal fluid disorders. Infection remains a major cause of morbidity and mortality after a VP shunt. There is evidence that a deep skin flora microbiome may have a role to play in post-operative infections. In this technical note, we present a skin preparation technique that addresses the issue of the skin flora beyond the initial incision. Methods : The patient is initially prepped, as standard, with. a single layer of 2% CHG+70% isopropyl alcohol. The novel stage is the 'double incision' whereby an initial superficial incision receives a further application of povidone-iodine prior to completing the full depth incision. Results : Of the 84 shunts inserted using the double-incision method (September 2015 to September 2016), only one developed a shunt infection. Conclusion : The double incision approach to skin preparation is a unique operative stage in VP shunt surgery that may have a role to play in reducing acute shunt infection.