• Computers and Concrete
• /
• 제16권5호
• /
• pp.759-774
• /
• 2015

This study simulates the flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) beams reinforced with steel and glass fiber-reinforced polymer (GFRP) rebars. For this, micromechanics-based modeling was first carried out on the basis of single fiber pullout models considering inclination angle. Two different tension-softening curves (TSCs) with the assumptions of 2-dimensional (2-D) and 3-dimensional (3-D) random fiber orientations were obtained from the micromechanics-based modeling, and linear elastic compressive and tensile models before the occurrence of cracks were obtained from the mechanical tests and rule of mixture. Finite element analysis incorporating smeared crack model was used due to the multiple cracking behaviors of structural UHPFRC beams, and the characteristic length of two times the element width (or two times the average crack spacing at the peak load) was suggested as a result of parametric study. Analytical results showed that the assumption of 2-D random fiber orientation is appropriate to a non-reinforced UHPFRC beam, whereas the assumption of 3-D random fiber orientation is suitable for UHPFRC beams reinforced with steel and GFRP rebars due to disorder of fiber alignment from the internal reinforcements. The micromechanics-based finite element analysis also well predicted the serviceability deflections of UHPFRC beams with GFRP rebars and hybrid reinforcements.

• 대한조선학회 특별논문집
• /
• 대한조선학회 2005년도 특별논문집
• /
• pp.216-221
• /
• 2005

Many tanks such as a fresh water tank, an aft peak tank and oil tanks are arranged in the engine room and aft part areas of the ship. By added mass effect of the fluid inside the tanks, the natural frequency will be changed according to filling height of the tank. For this reason, there is possibility of occurrence of excessive vibration by resonance between natural frequencies of local structure and excitation frequencies of the propeller or main engine. Therefore, calculation of natural frequencies is required for structure for many types of tank which are contacting with water or oil to consider added mass effect for anti-resonance design at design stage. In this study, a case of structure damage on the fresh water tank for 2600 TEU container vessel is introduced. In addition, natural frequency analysis and vibration measurement have been performed to investigate vibration characteristics for excessive vibration control.

• Food Science and Biotechnology
• /
• 제15권1호
• /
• pp.107-111
• /
• 2006

Kernel oils of Lindera erythrocarpa seeds had high level of unusual fatty acid. Picolinyl ester of this unknown fatty acid showed molecular ion at m/z = 317 with other diagnostic ions such as m/z = 151, 191 (40 amu between two peaks), 204, and 218 on GC-MS. Characteristic peak at $720\;cm^{-1}$ appeared in IR spectrum. In $^1H-NMR$ spectrum both methylene protons at C-3 and C-6 resonated at ${\delta}2.309$ and ${\delta}2.012$, and methine protons of double bond resonated in lower magnetic field centered at ${\delta}5.296$ (C-4) and ${\delta}5.387$ (C-5) as multiplet (J = 9.7Hz). In $^{13}C-NMR$, signals at ${\delta}22.669$ and ${\delta}27.048$ were due to C-3 and C-6 of ${\delta}^4$-monoenoic acid. Results obtained from spectroscopic measurements confirmed unknown fatty acid as cis-4-tetradecenoic acid (cis-4-$C_{14:1}$). Main fatty acid components of oils were cis-4-$C_{14:1}$ (44.5-45.1%), oleic acid ($C_{18:1}$), 20.4-21.3%), and lauric acid ($C_{12:0}$, 11.6-12.4%), along with trace amounts of cis-4-$C_{12:1}$ and cis-4-$C_{16:1}$.

• 한국응용곤충학회지
• /
• 제13권4호
• /
• pp.205-208
• /
• 1974

전북지방의 고랭지인 무주에서 진딧물의 밀도조사를 실시한 바 다음의 결과를 얻었다. 1. 진딧물의 종류는 감자바이러스 매개진딧물 4종을 포함하여 37종이었다. 2. 진딧물의 밀도는 평야부보다 훨씬 낮다. 3. 감자바이러스 매개진딧물은 복숭아혹진딧물(Myzus persicae), 싸리수염진딧물(Aulacorthum solami), 무테두리진딧물(Lipahis erysimi), 목화진딧물(Aphis gossypii)이다. 4. 본 조사지역의 우세종은 아카시아진딧물(Aphis craccivora), 누리장진딧물(Aphis clerodendri), 무테두리진딧물(Lipaphis erysimi)이다. 5. 진딧물의 발생소장은 평야부보다 늦게 출현하고 2순쯤 빠르게 동기주로 이동한다.

• 한국군사과학기술학회지
• /
• 제13권4호
• /
• pp.528-533
• /
• 2010

This paper describes a calculation method of source level of a ship transient noise, which is one of the important elements for the ship detection. Aim of transient noise measurements is to evaluate of acoustic energy due to singular occurrence, which is therefore defined as non-periodic and short termed events like an attack periscope, a rudder and a torpedo door. In generally, in the case of randomly spaced impulse, the spectrum becomes a broadband random noise with no distinctive pattern. Therefore, frequency analysis is not particularly revealing for type of signal. In the paper, it is performed in time domain to analyze a transient noise. However, a source level of transient noise is required an investigation for multiple frequency band. So, in order to calculate a source level of transient noise, a design of exponential weighting function, convolution, band pass filtering, peak detection, root mean square, and parameter compensation are applied. The effectiveness of this calculation scheme is studied through computer simulations and a sea test. Furthermore, an application of the method is applied in a real case.

• Nuclear Engineering and Technology
• /
• 제50권3호
• /
• pp.512-518
• /
• 2018

This article measured and analyzed the indoor radon concentrations at one university building in Gyeongju, Republic of Korea, to investigate if there is any relationship between earthquakes and indoor radon concentration. Since 12 September 2016, when two 5.1 and 5.8 magnitude earthquakes occurred, hundreds of aftershocks affected Gyeongju until January 2017. The measurements were made at the ground floor of the Energy Engineering Hall of Dongguk University in Gyeongju over a period between February 2016 and January 2017. The measurements were made with an RAD7 detector on the basis of the US Environmental Protection Agency measurement protocol. Each measurement was continuously made every 30 minutes over the measurement period every month. Among earthquakes with 2.0 or greater magnitude, the earthquakes whose occurrence timings fell into the measurement periods were screened for further analysis. We observed similar spike-like patterns between the indoor radon concentration distributions and earthquakes: a sudden increase in the peak indoor radon concentration 1-4 days before an earthquake, gradual decrease before the earthquake, and sudden drop on the day of the earthquake if the interval between successive earthquakes was moderately longer, for example, 3 days in this article.

• Geomechanics and Engineering
• /
• 제19권3호
• /
• pp.269-282
• /
• 2019

Due to top-coal and immediate roof as cushion layer connecting with support and overlying strata, it can make significant influence on strata behaviors in fully mechanical top-coal caving working face (TCCWF). Taking Qingdong 828 working face as engineering background, $FLAC^{3D}$ and $UDEC^{2D}$ were adopted to explore the influence of top-coal thickness (TCT), immediate roof thickness (IRT), top-coal elastic modulus (TCEM) and immediate roof elastic modulus (IREM) on the vertical stress and vertical subsidence of roof, caving distance, and support resistance. The results show that the maximum roof subsidence increases with the increase of TCT and IRT as well as the decrease of TCEM and IREM, which is totally opposite to vertical stress in roof-control distance. Moreover, although the increase of TCEM and IREM leading to the increase of peak value of abutment pressure, the position and distribution range have no significant change. Under the condition of initial weighting occurrence, support resistance has negative and positive relationship with physical parameters (e.g., TCT and IRT) and mechanical properties (e.g., TCEM and IREM), respectively.

• 한국해양공학회지
• /
• 제34권6호
• /
• pp.419-427
• /
• 2020

In this study, a particle image velocimetry (PIV)-based pressure estimation method was investigated, with application to the wave-in-deck loading phenomenon. An experimental study was performed in a two-dimensional wave tank using a fixed deck structure under a focused wave, obtaining local pressures by pressure sensors, global loads by load cells, and instantaneous velocity fields using the PIV measurement technique. The PIV-based pressure estimation method was applied using the Euler equation as the governing equation, and the proper time step for the wave impact pressure was studied using the normalized root-mean-square deviation. The pressure estimation method showed good agreement for the local impact pressure in comparison with the measured pressure by the pressure sensors. However, some differences were observed in the peak pressure due to the limitations of the Euler equation and the sampling rate of the measurement system. Using the estimation method, the pressure fields during wave-in-deck loading were determined in the study, with an analysis of the mechanism of impact and negative pressure occurrence.

• 대한중풍순환신경학회지
• /
• 제13권1호
• /
• pp.126-133
• /
• 2012

Object : The Purpose of this study is to report the clinical application of Korean traditional medicine on gait disturbance with arteriosclerosis of lower limbs. Methods : The patient in this case had been already treated by anticoagulation and varicose vein operation for subsiding and improving intermittent claduication and rest pain, but these methods didn't work on the patient. Although the patient was classified as TASC-II D, bypass operation couldn't be treated because of heart disease of the patient. We treated Korean traditional medicine such as acupuncture, moxibustion, Danggwisaeyeoktang. Results : After treatment, peak walking time was increased, rest pain occurrence was decreased and going up and down the stairs was improved. Conclusions : According to this study, Korean traditional medicine such as acupuncture, moxibustion, Danggwisaeyeoktang is effective for the cure of intermittent claudication and rest pain caused by arteriosclerosis of lower limbs.

• Journal of Ceramic Processing Research
• /
• 제23권4호
• /
• pp.436-442
• /
• 2022

Gallium nitride (GaN) substrates were ground in two different grinding wheel abrasive sizes of 270 and 800-mesh, and thechange in surface morphologies of the substrates and the depth of subsurface damage (SSD) were observed. With the 800-meshgrinding wheel, the surface roughness (SR) and the depth of SSD of the sample tended to decrease, which was not the casewith the 270-mesh grinding wheel. In the X-ray rocking curve, the sample exhibited some compressive stress with the 270-meshgrinding wheel, but with the 800-mesh grinding wheel, it demonstrated the occurrence of tensile stresses in the sample and adecrease in full width at half maximum (FWHM), which confirms an improvement in the crystallinity. In the Raman spectra,the compressive stress of the 270-mesh grinding wheel and the tensile stress of the 800-mesh grinding wheel were confirmedthrough peak shifts. Photoluminescence (PL) spectra confirmed that the intensity ratio of the yellow luminescence increasedat the 800-mesh grinding wheel, and a blue shift occurred further. These results indicate that the SR and the depth of SSDwere proportional to the abrasive grain size of the grinding wheel. At the same time, the increase in PL intensity at specificpeak positions indicates that the stress stemming from the grinding process was concentrated at the crystal surface. The abovemechanism is illustrated in a schematic diagram, which confirms the possibility of improving the grinding efficiency andsubsequent polishing processes in future applications.