• 수산해양기술연구
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• 제21권1호
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• pp.7-11
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• 1985

1984년 7월 24일에서 동년 8월 2일까지 동해안과 울릉도를 항해중 정선하여 14개의 관측점에서 수심 5m~200m층을 관측한 해중소음의 음압레벨을 분석한 결과, 해중소음은 연안에서 멀리 떨어진 해역의 표층부근에서는 평균 1dB/16m의 비율로 수심이 깊어짐에 따라 낮아지는 경향을 나타내었으며, 정상적인 소음분포 형태를 이루고 있음을 알 수 있었다. 또한, 항구나 항만입구 부근에서는 육상소음의 영향을 받아, 단속적이고 지역적인 소음분포 형태를 이루고 있음과 해저지형과 해상에 따라서도 크게 변동됨을 알 수 있었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
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• pp.49-52
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• 2006

Epoxy resin has less reaction shrinkage, has better water proofing and thermal resistance than other repairing materials, to it has been applied broadly to repair and finish buildings and infrastructures. Although the ambient temperature constructed is varied with the seasons and epoxy resin has to mix with appropriate hardener due to the non self-hardening, as the real construction of it, the ambient temperature is ignored and the blending ration of epoxy resin and hardener is fixed. Also, because of the hardening time is aimed to temperature condition and the tolerance of blending ratio, we investigated the variation of viscosity according to ambient temperatures and hardener ratios. As a results of study, we can select the economical blending ratio of the epoxy resin and hardener according to site situation.

• 한국전기전자재료학회논문지
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• 제27권10호
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• pp.648-652
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• 2014

We have investigated the effect of electrical properties of amorphous InGaZnO thin film transistors (a-IGZO TFTs) by post thermal annealing in $O_2$ ambient. The post-annealed in $O_2$ ambient a-IGZOTFT is found to be more stable to be used for oxide-based TFT devices, and has better performance, such as the on/off current ratios, sub-threshold voltage gate swing, and, as well as reasonable threshold voltage, than others do. The interface trap density is controlled to achieve the optimum value of TFT transfer and output characteristics. The device performance is significantly affected by adjusting the annealing condition. This effect is closely related with the modulation annealing method by reducing the localized trapping carriers and defect centers at the interface or in the channel layer.

• Structural Engineering and Mechanics
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• 제22권1호
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• pp.53-70
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• 2006

The paper summarizes the dynamic-based assessment of a reinforced concrete arch bridge, dating back to the 50's. The outlined approach is based on ambient vibration testing, output-only modal identification and updating of the uncertain structural parameters of a finite element model. The Peak Picking and the Enhanced Frequency Domain Decomposition techniques were used to extract the modal parameters from ambient vibration data and a very good agreement in both identified frequencies and mode shapes has been found between the two techniques. In the theoretical study, vibration modes were determined using a 3D Finite Element model of the bridge and the information obtained from the field tests combined with a classic system identification technique provided a linear elastic updated model, accurately fitting the modal parameters of the bridge in its present condition. Hence, the use of output-only modal identification techniques and updating procedures provided a model that could be used to evaluate the overall safety of the tested bridge under the service loads.

• Computers and Concrete
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• 제20권6호
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• pp.683-688
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• 2017

This paper presents the experimental investigations on the compressive strength and permeation properties of geopolymer concrete prepared with low calcium fly ash as the primary binder activated with different percentage of Alccofine. The durability aspect was investigated by performing permeable voids and water absorption tests since permeability directly influences the durability properties. The test results show that Alccofine significantly improves the compressive strength and reduces the water permeability thus enhances the durability of geopolymer concrete at ambient curing regime which encourages the use of geopolymer concrete at ambient curing condition thus promising its use in general construction also.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.362-362
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• 2009

$MgB_2$ bulk samples were sintered at different ambient. In this work, high purity Ar gas was added with oxygen and hydrogen gas, which can be regarded as impurity in a sense, as a possible dopant in the $MgB_2$. It was found that oxygen in the sintering ambient leads to a decrease in the critical current density $J_c$ at self field and lower fields. However, we can obtained higher $J_c$ at higher fields. It was also noted that $MgB_2$ samples sintered with 5% hydrogen in Ar revealed the increased $J_c$ at all fields compared to those processed in pure Ar ambient. From the XRD and FESEM analysis, the impurity gas in Ar can refine the $MgB_2$ grain size and result in increased grain. boundary, which can act as a strong flux pinning sites in $MgB_2$ samples. Also discussed are the effects of sintering ambient on irreversibility field, $H_{irr}$ and the upper critical field, $H_{C2}$.

• 한국항공우주학회지
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• 제32권6호
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• pp.104-109
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• 2004

본 논문에서는 액체로켓 엔진에 많이 사용된 충돌형 분사기의 미립화 특성에 대해 연구하였다. 분사속도와 주위 기체압력은 분열과 미립화 과정에 결정적인 영향을 주는 변수로서 $3m/s{\sim}30m/s,\;0.1Mpa{\sim}4.0MPa$로 변화시키면서 실험을 수행하였다. 전체적으로 분사속도와 기체압력의 증가에 따라 측정된 분열길이, 분열파장, 액적크기 등이 감소하였다. 하지만 그 감소율은 이론에서 예측된 것과는 다른 값을 나타내었다.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.137-149
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• 2014

In this study, modal parameters such as natural frequencies, mode shapes and damping ratios of RC frames with low strength are determined for different construction stages using ambient vibration test. For this purpose full scaled, one bay and one story RC frames are produced and tested for plane, brick in-filled and brick in-filled with plaster conditions. Measurement time, frequency span and effective mode number are determined by considering similar studies and literature. To obtain experimental dynamic characteristics, Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification techniques are used together. It is shown that the ambient vibration measurements are enough to identify the most significant modes of RC frames. The results indicate that modal parameters change significantly depending on the construction stages. In addition, Infill walls increase stiffness and change the mode shapes of the RC frame. There is a good agreement between mode shapes obtained from brick in-filled and in-filled with plaster conditions. However, some differences are seen in plane frame, like expected. Dynamic characteristics should be verified using finite element analysis. Finally, inconsistency between experimental and analytical dynamic characteristics should be minimize by finite element model updating using some uncertain parameters such as material properties, boundary condition and section properties to reflect the current behavior of the RC frames.

• 한국분무공학회지
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• 제19권4호
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• pp.188-196
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• 2014

The spray and combustion characteristics of n-dodecane fuel were investigated in a CVCC (constant volume combustion chamber). The selection of ambient conditions for the spray followed ECN (engine combustion network) guidelines, which simulates the ambient condition of diesel engines at start of fuel injection. ECN is a collaboration network whose main objective is to establish an internet library of well-documented experiments that are appropriate for model validation and the advancement of scientific understanding of combustion at conditions specific to engines. Therefore repeatability of the experiments with high accuracy was important. The ambient temperature was varied from 750 to 930 K while the density was fixed at around $23kg/m^3$. The injection pressure of the fuel was varied from 500 to 1500 bar. The spray was injected in both non-reacting ($O_2$ concentration of 0%) and reacting conditions ($O_2$ concentration of 15%) to examine the spray and the combustion characteristics. Direct imaging with Mie Scattering was used to obtain the liquid penetration length. Shadowgraph was implemented to observe vapor length and lift-off length at non-reacting and reacting conditions, respectively. Pressure data was analyzed to determine the ignition delay with respect to the spray and ambient conditions.

• 한국전기전자재료학회논문지
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• 제29권4호
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• pp.215-217
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• 2016

For the improvement of the anti-pollution properties of porcelain electrical insulators, in this study, we have applied the functional film to the surface of insulator. The functional films were coated on the ceramic substrates which components were like the porcelain electrical insulator. The coating material was applied to ceramic substrate by spray coating method and then the film was cured at around $300^{\circ}C$ for 10 minutes with different gas ambient, such as $O_2$, $N_2$, and only vacuum. We have measured the contact angle of the coated surface, and obtained the lowest angle ($8.9^{\circ}$) and a strong hydrophilic property at vacuum condition. The anti-pollution properties were measured, revealing that as the contact angle decreased, the anti-pollution properties improved. The mechanical hardness and adhesion were both excellent regardless of the annealing ambient.