• Geomechanics and Engineering
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• v.14 no.2
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• pp.203-209
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• 2018

Reliable estimation of compressive as well as tensile in-situ stresses is critical in the design and analysis of underground structures and openings in rocks. Kaiser effect technique, which uses acoustic emission from rock specimens under cyclic load, is well established for the estimation of in-situ compressive stresses. This paper investigates the Kaiser effect on marble specimens under cyclic uniaxial compressive as well as cyclic uniaxial tensile conditions. The tensile behavior was studied by means of Brazilian tests. Each specimen was tested by applying the load in four loading cycles having magnitudes of 40%, 60%, 80% and 100% of the peak stress. The experimental results confirm the presence of Kaiser effect in marble specimens under both compressive and tensile loading conditions. Kaiser effect was found to be more dominant in the first two loading cycles and started disappearing as the applied stress approached the peak stress, where felicity effect became dominant instead. This behavior was observed to be consistent under both compressive and tensile loading conditions and can be applied for the estimation of in-situ rock stresses as a function of peak rock stress. At a micromechanical level, Kaiser effect is evident when the pre-existing stress is smaller than the crack damage stress and ambiguous when pre-existing stress exceeds the crack damage stress. Upon reaching the crack damage stress, the cracks begin to propagate and coalesce in an unstable manner. Hence acoustic emission observations through Kaiser effect analysis can help to estimate the crack damage stresses reliably thereby improving the efficiency of design parameters.

• Earthquakes and Structures
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• v.15 no.5
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• pp.453-462
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• 2018

Damages to buildings affected by a near-fault strong ground motion are largely attributed to the vertical component of the earthquake resulting in column failures, which could lead to disproportionate building catastrophic collapse in a progressive fashion. Recently, considerable interests are awakening to study effects of earthquake vertical components on structural responses. In this study, detailed modeling and time-history analyses of a 12-story code-conforming reinforced concrete moment frame building carrying the gravity loads, and exposed to once only the horizontal component of, and second time simultaneously the horizontal and vertical components of an ensemble of far-field and near-field earthquakes are conducted. Structural responses inclusive of tension, compression and its fluctuations in columns, the ratio of shear demand to capacity in columns and peak mid-span moment demand in beams are compared with and without the presence of the vertical component of earthquake records. The influences of the existence of earthquake vertical component in both exterior and interior spans are separately studied. Thereafter, the correlation between the increase of demands induced by the vertical component of the earthquake and the ratio of a set of earthquake record characteristic parameters is investigated. It is shown that uplift initiation and the magnitude of tensile forces developed in corner columns are relatively more critical. Presence of vertical component of earthquake leads to a drop in minimum compressive force and initiation of tension in columns. The magnitude of this reduction in the most critical case is recorded on average 84% under near-fault ground motions. Besides, the presence of earthquake vertical components increases the shear capacity required in columns, which is at most 31%. In the best case, a direct correlation of 95% between the increase of the maximum compressive force and the ratio of vertical to horizontal 'effective peak acceleration (EPA)' is observed.

• Earthquakes and Structures
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• v.20 no.1
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• pp.71-86
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• 2021

This paper focuses on the development and assessment of the expected damage for the rocking response of rigid anchored blocks, with irregular geometry and non-uniform mass distribution, considering the site conditions and the seismicity of Mexico City. The non-linear behavior of the restrainers is incorporated to evaluate the pure tension and tension-shear failure mechanisms. A probabilistic framework is performed covering a wide range of block sizes, slenderness ratios and eccentricities using physics-based ground motion simulation. In order to incorporate the uncertainties related to the propagation of far-field earthquakes with a significant contribution to the seismic hazard at study sites, it was simulated a set of scenarios using a stochastic summation methods of small-earthquakes records, considered as Empirical Green's Function (EGFs). As Engineering Demand Parameter (EDP), the absolute value of the maximum block rotation normalized by the body slenderness, as a function of the peak ground acceleration (PGA) is adopted. The results show that anchorages are more efficient for blocks with slenderness ratio between two and three, while slenderness above four provide a better stability when they are not restrained. Besides, there is a range of peak intensities where anchored blocks located in soft soils are less vulnerable with respect to those located in firm soils. The procedure used in here allows to take decisions about risk, reliability and resilience assessment of different types of contents, and it is easily adaptable to other seismic environments.

• Journal of Biomedical Engineering Research
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• v.17 no.1
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• pp.43-48
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• 1996

We investigated the energistics of the physiological heart model by comparing predictive indexes of the myocardial oxygen consumption (MOC), such as tension-time index (R), tension-time or force-time inteual (FTI), rate-pressure product (RPP), pressure-work index, and systolic pressure-volume area (PVA) when using the electro-hydraulic left ventricular device (LVAD). We developed the model of LVAD incorporated the closed-loop cardiovascular system with a baroreceptor which can control heart rate and time-varying elastance of left and right ventricles. On considering the benefit of the LVAD, the effects of various operation modes, especially timing of assistance, were evaluated using this coupled computer model. Overall results of the computer simulation shows that our LVAD can unload the ischemic (less contractile) heart by decreasing the MU and increasing coronary flow. Because the pump ejection at the end diastolic phase of the natural heart may increase the afterload of the left ventricle, the control scheme of our LVAD must prohibit ejecting at this time. Since the increment of coronary flow is proportional to the peak aortic pressure after ventricle contraction, the LVAD must eject immediately following the closure of the aortic valve to increase oxygen availability.

• The Korean Journal of Pharmacology
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• v.12 no.1
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• pp.45-55
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• 1976

The effect of positive inotropic agents on the contractile properties of myocardial muscle were studied in the cat papillary muscle preparation. For the purpose, the effects of ouabain $(1{\times}10^{-6}g/ml)$, norepinephrine (0.05r/m1) and Aconiti tuber butanol fraction (AF(5), $1{\times}10^{-4}$, $5{\times}10^{-4}$, $1{\times}10^{-3}$, $2{\times}10^{-3}g/ml$) on the contractile dynamics of the papillary muscle preparation isolated from right ventricle of cat were observed in terms of the characteristics of isometric twitch and the lengh-tension relation, the force-velocity relation and the load-extension relation of the series elastic component of contractile model of A.V. Hill. All the studied inotropic drugs similary increased the rate and the intensity of the developed isometric tension, while shortened the time from onset of contraction to peak tension and the total duration of contraction. In the afterloaded simultaneous isotonic and isometric contraction, they also similary increased the maximal velocity of shortening accompanied with the increasing the maximum developed force. In the load-extension relation all the drugs, however, had no appreciable influence on the properties of the series elastic component. Increasing the concentration, Aconiti tuber butanol fraction produced more pronounced effect on all the studied parameters of isometric and isotonic contraction of cat papillary muscle preparation. From the aspect of contractile dynamics, it seemed that the positive inotropic effect of ouabain, norepinephrine and Aconiti tuber butanol fraction are similary achieved through an influence on the behavior of the contractile component only.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.3
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• pp.321-328
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• 1999

Pulmonary blood vessels with diameters of $200{\sim}400\;{\mu}m$ produce considerably more force in response to vasoconstrictor drugs than those which are either smaller or larger. We have therefore investigated whether or not hypoxic pulmonary vasoconstriction (HPV) is more powerful in vessels of these diameters. We have also looked at the possibility that vessels from different regions of the lung respond differently. To do this we have grouped vessels according to their location within the lung as well as by size. We used a small vessel myograph (Cambustion AM10, Cambridge, UK) to study 208 preconstricted $(1\;{\mu}M\;PGF_{2{\alpha}})$ small pulmonary arteries $(300{\sim}800\;{\mu}m$ diameter when stretched to a tension equivalent to 25 mmHg transmural pressure) from 39 rats anaesthetized with 2% inspired halothane. A biphasic contraction was observed in response to hypoxia (ca. 25 mmHg $Po_2).$ The magnitudes of both the first, transient, phase (PT, peak tension) and of the second, sustained, phase (SST, steady state tension) were measured. The latter was measured 40 min after the start of hypoxia. The first phase was most pronounced in vessels with an average diameter of 423 ${\mu}m$ while the second phase was most pronounced in larger vessels (mean diameter 505 ${\mu}m).$ These maximal responses were all seen in vessels somewhat larger than reported by others. The responses of smaller vessels $(400{\sim}500\;{\mu}m)$ did not depend upon their location within the lung, but those of larger vessels $(600{\sim}700\;{\mu}m)$ showed regional differences. Those from the right lobe and those from the base of the lung gave the largest responses. It was especially noticeable that large vessels (631 ${\mu}m$ diameter) from the base of the right lung gave the biggest responses. Thus HPV seems to occur not in a uniform manner, dependent solely to the size of vessels, but it also depends to some degree on the region of the lung from which vessels have been taken. Furthermore, our results suggest that larger vessels, as well as smaller ones, may contribute significantly to HPV.

• Journal of Chest Surgery
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• v.33 no.2
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• pp.125-131
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• 2000

Background: Hyperinflation during lung ischemia has been known to improve pulmonary functions after reperfusion which may be exerted through a pulmonary vasodilation and avoidance of atelectasis by an increased surfactant release and been known whether the improvement of pulmonary function was the effect of hyperinflation itself or the oxygen content in inflation gas. Therefore we attempted to clarify the effect of hyperinflation with oxygen in pulmonary inflation gas during warm ischemia on pulmonary function after reperfusion to solve the problem of ischemia-reperfusion injury after lung transplantation. Material and Method: sixteen mongrel dogs were randomly divided into two groups: the left lung was inflated to 30-35 cm H2O with 100% oxygen in oxygen group and 100% nitrogen in nitrogen group. The inflated left lung was maintained with warm ischemia for 100 minutes. Arterial and mixed venous blood gas analysis and hemodynamics were measured before ischemia and 30, 60, 120, 180 and 240 minutes afer reperfusion. Lung biopsy was taken for the measurement of lung water content after the end of reperfusion. Result: In oxygen group arterial oxygen tension the difference of arterial and mixed venous oxygen tension and the difference of alveolar-arterial oxygen tension at 30-minute after reperfusion were not significantly different from those before ischemia and were stable during the 40hour reperfusion. However in nitrogen group these values were significantly deteriorated at 30-minute after reperfusion. there was no significant difference between two groups in hemodynamic data peak airway pressure and lung water content. Conclusion : The results indicated that the oxygenation one of the most important pulmonary functions was improved by pulmonary inflation with 100% oxygen during warm ischemia but the hemodynamics were not. Oxygen as a metabolic substrate during warm ischenia was believed to make the pulmonary tissues to maintain aerobic metabolism and to prevent ischemic damage of alveoli and pulmonary capillary.

• KSTLE International Journal
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• v.2 no.1
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• pp.80-84
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• 2001

The purpose of this paper is to show the result from the study to improve the formability and appearance which is important in the cold rolled strip, the coated strip and prepainted strip. Furthermore, to give appropriate surface roughness, shape of work roll for temper mill is also important. The strip has a greater peak counts and homogeneous roughness. This makes the prepainted surface smooth and consistent in appearance with good image clarity. Therefore, the surface roughness of the work roll is very important. The reason that surface roughness of the work roll is transferred to the strip surface is the rolling farce and tension at the temper rolling or cold rolling. This study is classified in order to get an accurate and homogeneous roughness. There are few papers published in this field, because its importance is not known and the proper operation of the machine is not generally well known. This paper investigates the correlation between strip surface roughness and the surface of the work roll. After studying the surface roughness and shape according to the texturing method for roll surfaces at temper rolling, the findings were as follows. Irregular surface roughness can be compensated with several paint coatings, but this also makes the quality deteriorate and manufacturing costs go up.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.9
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• pp.931-942
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• 2013

In this study, we analyzed and compared the ultrasonic welding with the laser welding for the pure aluminium thin plates in a series of secondary lithium-ion batteries which are currently being produced by the ultrasonic welding; and performed the experiment for the purpose of the preceding study to replace the ultrasonic welding method with the laser welding method. As a result, the weld width of ultrasonic welding was 5mm, but that of laser welding was about 1~1.5 mm. As a result of tension test, the tensile strength was high when the pulse duration hour was short at the low peak power, while the high tensile strength was achieved when the pulse duration hour was long at the high peak power. The value of tensile strength was higher in the ultrasonic welding while the laser welding showed a maximum 45% better result as for the welding width.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.2
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• pp.79-85
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• 1996

Prediction of fatigue life and monitoring of fracture process for adhesively bonded CFRP composites joint have been investigated by analysis of acoustic emission signals during the fatigue and tension tests. During fatigue test, generated acoustic emission is related to stored elastic strain energy. By results of monitoring of AE event rate, fatigue process could be divided into two regions, and boundaries of two regions, fatigue cycles of the initiation of fast crack growth, were 70-80% of fatigue life even though the fatigue life were highly scattered from specimen to specimen. The result shows the possibility of predicting catastrophic failure by acoustic emission monitoring.