• Transactions of the Korean Society of Mechanical Engineers A
• /
• 제25권7호
• /
• pp.1089-1096
• /
• 2001

This paper presents the fatigue behavior of composite materials with impact-induced damage under 2 level block loading. For this purpose, the 2 level block loading fatigue tests were performed on the impacted composite laminate. The fatigue life of the laminate under the block loading is greatly influenced by the impact damage; the effect of impact damage can be characterized by the present impact damage parameter. Based on this parameter, the model is developed to predict the fatigue life under block loading and the results by this model agree well with experimental results regardless of applied impact energy. Also, stochastic model is established to describe the variation of cumulative damage behavior and fatigue life due to the material nonhomogeneity.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제3권2호
• /
• pp.153-155
• /
• 2001

Eight new three-way cross heterozygotic hybrid genotypes of the mulberry silkworm Bombyx mori, resulted from hybridization of multivoltine as female and bivoltine Fl hybrid as male component, have been evaluated for the cumulative effect of nine traits of commercial economic importance with the objective of selecting out the most prospective ones for their exploitation as an intermediate technology during unfavorable season. Five of them namely, G(P5${\times}$NBl8) (E.I. =57.23); S(NB18${\times}$P5) (E.I. : 55.48); S(P5${\times}$NBl8) (E.I. = 52.44); S(KBN${\times}$B7) (E.I. = 50.42) and S(NB7${\times}$KB) (E.I. : 50.16) have scored higher values of the Evaluation Index (E.I.) and could be selected in the same order for exploitation during unfavorable seasons in tropical climates.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• 제16권12호
• /
• pp.1227-1233
• /
• 2004

Air handling unit (AHU)'s air filter pressure difference is important for energy consumption and indoor air quality. Both energy Performance data and air filter differential pressure of AHU in real office buildings were monitored and analyzed to investigate quantitatively energy impact as dust buildup level on air filter grows. We also modeled and simulated CAV system using HVACSIM＋ program to examine the energy effect of dust buildup on filters. Through analysis of time series pressure drop data, the filter pressure difference rate has been increased due to cumulative supply air flow rate increase. As filter pressure drop increased to 1 inch water column, it is found that the supply air flow rate was decreased by 10%, the chilled water flow rate was increased by 5.9% and the pump energy consumption was increased to 5.9%.

• Structural Engineering and Mechanics
• /
• 제27권3호
• /
• pp.263-276
• /
• 2007

This paper presents a fuzzy finite element model for the analysis of structures in the presence of multiple uncertainties. A new methodology to evaluate the cumulative effect of multiple uncertainties on structural response is developed in the present work. This is done by modifying Muhanna's approach for handling single uncertainty. Uncertainty in load and material properties is defined by triangular membership functions with equal spread about the crisp value. Structural response is obtained in terms of fuzzy interval displacements and rotations. The results are further post-processed to obtain interval values of bending moment, shear force and axial forces. Membership functions are constructed to depict the uncertainty in structural response. Sensitivity analysis is performed to evaluate the relative sensitivity of displacements and forces to uncertainty in structural parameters. The present work demonstrates the effectiveness of fuzzy finite element model in establishing sharp bounds to the uncertain structural response in the presence of multiple uncertainties.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 한국건축시공학회 2021년도 봄 학술논문 발표대회
• /
• pp.129-130
• /
• 2021

In order to solve the problem of low early-age compressive strength of high volume fly ash concrete. This paper studies the effect of 2% sodium sulfate (Na₂SO₄) as a chemical activator on the paste with 40% fly ash content and a water-binder ratio of 0.30. The results indicate that the addition of Na₂SO₄ can effectively improve the early-age compressive strength of the fly ash-cement system, and the strength improvement rate on the first day reached nearly 70%. In addition, calorimetric analysis reveals that the incorporation of Na₂SO₄ promotes the early hydration of cement and fly ash, increases the cumulative hydration heat and delays the heat peak of the aluminum phase.

• Journal of Chest Surgery
• /
• 제46권1호
• /
• pp.14-21
• /
• 2013

Background: Reactive oxygen species (ROS) are known to be related to cardiovascular diseases. Many studies have demonstrated that angiotensin-converting enzyme inhibitors have beneficial effects against ROS. We investigated the antioxidant effect of captopril and enalapril in nitric oxide mediated vascular endothelium-dependent relaxations. Materials and Methods: Isolated rabbit abdominal aorta ring segments were exposed to ROS by electrolysis of the organ bath medium (Krebs-Henseleit solution) after pretreatment with various concentrations (range, $10^{-5}$ to $3{\times}10^{-4}$ M) of captopril and enalapril. Before and after electrolysis, the endothelial function was measured by preconstricting the vessels with norepinephrine ($10^{-6}$ M) followed by the cumulative addition of acetylcholine (range, $3{\times}10^{-8}$ to $10^{-6}$ M). The relevance of the superoxide anion and hydrogen peroxide scavenging effect of captopril and enalapril was investigated using additional pretreatments of diethyldithiocarbamate (DETCA, 0.5 mM), an inhibitor of Cu/Zn superoxide dismutase, and 3-amino-1,2,4-triazole (3AT, 50 mM), an inhibitor of catalase. Results: Both captopril and enalapril preserved vascular endothelium-dependent relaxation after exposure to ROS in a dose-dependent manner (p<0.0001). Pretreatment with DETCA attenuated the antioxidant effect of captopril and enalapril (p<0.0001), but pretreatment with 3AT did not have an effect. Conclusion: Both captopril and enalapril protect endothelium against ROS in a dose-dependent fashion in isolated rabbit abdominal aortas. This protective effect is related to superoxide anion scavenging.

• Journal of Electrical Engineering and Technology
• /
• 제9권3호
• /
• pp.827-834
• /
• 2014

In order to meet the low voltage ride-through requirement in a grid code, a wind power plant (WPP) has to stay connected to a grid, supporting the voltage recovery for a grid fault. To do this, a plant-level controller as well as a wind generator (WG) controller is essential. The dynamic response of a WPP should be analyzed in order to design a plant-level controller. The dynamic response of a WPP for a grid fault is the collective response of all WGs, which depends on the wind speed approaching the WG. Thus, the dynamic response of a WPP should be analyzed by taking the wake effect into consideration, because different wind speeds at WGs will result in different responses of the WPP. This paper analyzes the response of a doubly fed induction generator (DFIG)-based offshore WPP with a grid fault taking into account the wake effect. To obtain the approaching wind speed of a WG in a WPP, we considered the cumulative impact of multiple shadowing and the effect of the wind direction. The voltage, reactive power, and active power at the point of common coupling of a 100 MW DFIG-based offshore WPP were analyzed during and after a grid fault under various wind and fault conditions using an EMTP-RV simulator. The results clearly demonstrate that not considering the wake effect leads to significantly different results, particularly for the reactive power and active power, which could potentially lead to incorrect conclusions and / or control schemes for a WPP.

• Journal of Korean Academy of Nursing
• /
• 제43권3호
• /
• pp.361-369
• /
• 2013

Purpose: The purpose of this study was to examine the effect of anorexia and neuropathic pain induced by cisplatin on hindlimb muscles of rats. Methods: Adult male Sprague-Dawley rats were divided into two groups, a cisplatin-treated group (n=10) and a control group (n=10). In the cisplatin-treated group, cisplatin at a dose of 2 mg/kg was injected intraperitoneally two times a week up to a cumulative dose of 20 mg/kg over 5 weeks, and in the control group saline (0.9% NaCl) was injected intraperitoneally at the same dose and duration as the cisplatin-treated group. At 34 days all rats were anesthetized, after which the soleus and plantaris muscles were dissected. Withdrawal threshold, body weight, food intake, activity, muscle weight, Type I and II fiber cross-sectional areas and myofibrillar protein content of the dissected muscles were determined. Results: Compared with the control group, the cisplatin-treated group showed significant decreases (p<.05) in withdrawal threshold, activity, food intake, body weight, Type I and II fiber cross-sectional areas, myofibrillar protein content and weight of the soleus and plantaris muscles. Conclusion: Muscular atrophy in hindlimb occurs due to anorexia and neuropathic pain induced by the cisplatin treatment.

• Corrosion Science and Technology
• /
• 제17권5호
• /
• pp.203-210
• /
• 2018

This paper compares the inhibition properties of aspartic and lactic acid salts with nitrite ions and their effect on critical chloride concentration. The tests were carried employing carbon steel specimens in saturated lime solution with varying pH in the range between13 to 13.6. The critical chloride concentration was estimated through multiple specimen potentiostatic tests at potentials in the usual range for passive rebar in the alkaline concrete of atmospheric structures. During tests, chloride salt was added every 48 h until all the specimens showed localized attacks. The cumulative distribution curves, i.e. the number of corroded specimens as a function of the chlorides concentration was obtained. Furthermore, IR spectra were recorded for the evaluation of the presence of the organic inhibitors on the passivity film. The results confirmed the inhibitory effect of 0.1M aspartate comparable with nitrite ions, at a similar concentration. Addition of calcium lactate did not result in an increase in the critical chloride concentration. However, the formation of a massive scale containing the substance that could reduce the corrosion propagation was observed.

• Journal of Information Technology Services
• /
• 제17권1호
• /
• pp.33-45
• /
• 2018

Recently, many South Korean firms have suffered financial losses and damaged corporate images from the data breaches. Accordingly, a firm should manage their IT assets securely through an information security investment. However, the difficulty of measuring the return on an information security investment is one of the critical obstacles for firms in making such investment decisions. There have been a number of studies on the effect of IT investment so far, but there are few researches on information security investment. In this paper, based on a sample of 76 investment announcements of firms whose stocks are publicly traded in the South Korea's stock market between 2001 and 2017, we examines the market reaction to information security investment by using event study methodology. The results of the main effects indicate that self-developed is significantly related to cumulative average abnormal returns (CAARs), while no significant effect was observed for discloser, investment characteristics and firm characteristics. In addition, we find that the market reacts more favorably to the news announced by the subject of investment than the vendor, in case of investments with commercial exploitation. One of main contributions in our study is that it has revealed the factors affecting the market reaction to announcement of information security investment. It is also expected that, in practice, corporate executives will be able to help make an information security investment decision.