• Earthquakes and Structures
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• v.6 no.4
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• pp.409-436
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• 2014

Although it is widely accepted that the interaction -between masonry infill and structural members significantly affects the seismic response of reinforced concrete (RC) frames, this interaction is generally neglected in current design-oriented seismic analyses of structures. Moreover, the role of masonry infill is expected to be even more relevant in the case of existing frames designed only for gravitational loads, as infill walls can significantly modify both lateral strength and stiffness. However, the additional contribution to both strength and stiffness is often coupled to a modification of the global collapse mechanisms possibly resulting in brittle failure modes, generally related to irregular distributions of masonry walls throughout the frame. As a matter of principle, accurate modelling of masonry infill should be at least carried out by adopting nonlinear 2D elements. However, several practice-oriented proposals are currently available for modelling masonry infill through equivalent (nonlinear) strut elements. The present paper firstly outlines some of the well-established models currently available in the scientific literature for modelling infill panels in seismic analyses of RC frames. Then, a parametric analysis is carried out in order to demonstrate the consequences of considering such models in nonlinear static and dynamic analyses of existing RC structures. Two bay-frames with two-, three- and four-storeys are considered for performing nonlinear analyses aimed at investigating some critical aspects of modelling masonry infill and their effects on the structural response. Particularly, sensitivity analyses about specific parameters involved in the definition of the equivalent strut models, such as the constitutive force-displacement law of the panel, are proposed.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.227-238
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• 2004

This paper is results of experimental and nunerical works on the behavior of the cut-and-cover tunnel. Centrifuge model tests were performed to simulate the behavior of the cut-and-cover tunnels having cross sections of national road and subway tunnels. Model experiments were carried out with changing the cut slope and the slope of filling ground surface. Displacements of tunnel lining resulted from artificially accelerated gravitational force up to 40g of covered material used in model tests, were measured during centrifuge model tests. In model tests, Jumunjin Standard Sand with the relative density of 80 % and the zinc plates were used for the covered material and the flexible tunnel lining, respectively. Basic soil property tests were performed to obtain it's the property of Jumumjin Standard Sand. Shear strength parameters of Jumunjin Standard Sand were obtained by performing the triaxial compression tests. Direct shear tests were also carried out to find the mechanical properties of the interface between the lining and the covered material. Numerical analysis with the commercially available program of FLAC were performed to compare with results of centrifuge model experiment In numerical modelling. Mohr-Coulomb elasto-plastic constitutive model was used to simulaye the behavoor of Jumunjin Standard Sand and the interface element between the lining and the covered material was implemented to simulate the interaction between them. Compared results between model tests and numerical estimation with respect to displacement of the lining showed in good agreements.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.43.3-43.3
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• 2017

NGC 6822 is a dwarf irregular galaxy in the Local Group and it is located in 500 kpc, further than the Large Magellanic Cloud and the Small Magellanic Cloud. Therefore, we can study star-forming processes by local condition in NGC 6822 instead of tidal force of the Galactic gravitational field. Hubble V is the brightest of several H II complexes in this galaxy. We observed Hubble V by using IGRINS attached on the 2.7 m telescope at the McDonald Observatory in Texas, US in May 2016. We performed a spectral mapping of $15^{{\prime}{\prime}}{\times} 7^{{\prime}{\prime}}$area on H and K bands, and detected emission lines of bright $Br{\gamma}\;{\lambda}2.1661{\mu}m$ and weak He I ${\lambda}2.0587{\mu}m$. Molecular hydrogen lines of 1-0S(1) ${\lambda}2.1218{\mu}m$, 2-1 S(1) ${\lambda}2.2477{\mu}m$, and 1-0 S(0) ${\lambda}2.2227{\mu}m$ was also detected. These emission lines show the structure of an ionized core and excited surface of clouds by far-ultraviolet photons, photodissociation region (PDR). We present three-dimensional maps of emission line distributions through multi slit scanning data and compare these results with the previous study. This presentation shows the physical structure of the star-forming regions and we discuss a PDR model and an evolution of Hubble V complex.

• Animal cells and systems
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• v.2 no.4
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• pp.477-481
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• 1998

Previous studies have postulated that isometric animals exert similar locomotory capacity (speed, distance) because the amount of energy available for the motion would be the same regardless of body mass (m). To test propriety of this theory, we examined body shape and take-off potential of two frog species, Rana nigromaculata (powerful jumpers) and Bombina orientalis (slow hoppers). Morphological measurements included thigh muscle mass (indicative of total muscle force), hindlimb length (L, determining acceleration distance), and interilial width (shaping take-off motion). To gauge locomotory capacity, take-off speed (v) and take-off angle ($\theta$) were measured from video analyses, and jump distance (R) and take-off Power ($P_{t}$ ) were calculated from equations $R=V^{2}sin2\theta/g$ and ($P_{t}$＝$㎷^{3}/2L$(where g is the gravitational constant). Scaling exponents of morphometric variables for both species were 0.96-1.11 for thigh muscle mass, 0.28-0.29 for hindlimb length, and 0.30-0.36 for interilial width. Scaling exponents of locomotory performance for the two species were -0.01-0.14 for take-off speed, 0.24-0.31 for jump distance, and 0.66-0.84 for take-off power. The results demonstrate that the frogs of this study showed isometric body shape within species, but that take-off response changed allometrically with body mass, indicating that these data did not fully support the previous proposition. An exception was found in take-off speed of B. orientalis, in which the speed changed little with body mass (slope＝-0.01). These findings suggest that the energy availability approach did not properly explain the apparent allometric relations of the take-off response in these animals and that an alternative model such as a power production approach may be worth addressing.

• Physical Therapy Korea
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• v.18 no.1
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• pp.9-17
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• 2011

The purpose of this study was to assess visual biofeedback's influence on trunk muscles' (EMG) activity and endurance holding time for correct position during whole-body tilt exercise. For the study, we recruited 14 volunteers who showed no symptom of lumbar disease during medical tests. We measured the EMG activity of their rectus abdominis, external abdominal oblique, internal abdominal oblique and erector spinae muscles, and their endurance holding time for correct position during $40^{\circ}$ anterior and posterior whole-body tilt under two conditions: whole-body tilt with and without visual biofeedback. Resistance with gravitational force on the trunk during whole-body tilt was applied by using a device that had a monitor on which the subjects could check their alignment and that sounded an alarm if a subject's alignment collapsed. The study showed an increase in the EMG activity of external abdominal oblique, internal abdominal oblique/rectus abdominis ratio and endurance holding time for correct position during both $40^{\circ}$ anterior and posterior whole-body tilt with visual biofeedback compared with without visual biofeedback (p<.05). We suggest that the whole-body tilt exercise with visual biofeedback could be a beneficial strategy for selectively strengthening the internal abdominal oblique muscle and minimizing the rectus abdominis muscle's activity while maintaining correct alignment during whole-body tilt exercise.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.66.2-66.2
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• 2014

We carried out photometric observations of Maria family asteroids during 134 nights spanning from July 2008 to May 2013, and derived synodic rotational periods for 51 objects including obtained periods of 34 asteroids for the first time. In this study, we found that there is a significant excess of fast and slow rotators. The one-sample Kolmogorov-Smirnov test confirms that the spin rate distribution is not consistent with the Maxwellian at a 92% confidence level. From the correlations between rotational period, amplitude of lightcurve, and size, we conclude that rotational properties of Maria family have been changed considerably by the non-gravitational force such as the Yarkovsky and the YORP effect. Using the lightcurve inversion method, we successfully determined the pole orientation for the 13 Maria members, and found the excess of prograde objects versus retrograde with a ratio ($N_p/N_r$) of 3. This implies that retrograde rotators could have been ejected by the 3:1 resonance to the inner Solar System since the generation of Maria family. We estimate that approximately 37 - 75 kilometer-sized Maria asteroids have entered to near-Earth space every 100 Myr.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.41-45
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• 2008

This paper deals with the estimation method on the initial pole position of a z-axis permanent magnet linear synchronous motor(PMLSM) without magnetic pole sensors such as Hall sensors. The proposed method takes account of the gravitational force at z-axis and also the load conditions. The algorithm consists of two steps. The first step is to approximately estimate the initial q-axis by monitoring the movements due to the test current at predefined different test q-axes. The second step is to estimate the real q-axis as accurately as possible by using the outputs corresponding to torques due to the test current at three different test q-axes in order to avoid the effect of load mass variations. Experimental results on the z-axis PMLSM show good estimation characteristics of the proposed method irrespective of load mass conditions.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.19 no.1
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• pp.51-56
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• 2013

From the time the product is manufactured until it is carried and ultimately used, the product is subjected to some form of handling and transportations. During this process, the product can be subjected to many potential hazards. One of them is the damage caused by shocks. In order to design a product-package system to protect the product, the peak acceleration or G force to the product that causes damage needs to be determined. When a corrugated fiberboard box loaded with products is dropped onto the ground, part of the energy acquired due to the action of the gravitational acceleration during the free fall is dissipated in the product and the package in various ways. The shock absorbing characteristics of the packaging cushion materials are presented as a family of cushion curves in which curves showing peak accelerations during impacts for a range of static loads are shown for several drop heights. The new method for determining the shock absorbing characteristics of cushioning materials for protective packaging has been described and demonstrated. It has been shown that cushion curves can be produced by combining the static compression and impact characteristics of the material. The dynamic factor was determined by the iterative least mean squares (ILMS) optimization technique in which the discrepancies between peak acceleration data predicted from the theoretical model and obtained from the impact tests are minimized. The approach enabled an efficient determination of cushion curves from a small number of experimental impact data.

• Imaging Science in Dentistry
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• v.53 no.1
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• pp.53-60
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• 2023

Purpose: This study evaluated maxillary sinus volume changes in military jet aircraft pilot candidates before and after the training program, in comparison with a control group, considering the effects of pressurization, altitude, and total flight hours, through multislice computed tomography. Materials and Methods: Fifteen fighter pilots were evaluated before initiating the training program and after the final approval. The control group consisted of 41 young adults who had not flown during their military career. The volumes of each maxillary sinus were measured individually before and at the end of the training program. Results: When comparing the initial and final volumes in the pilots, a statistically significant increase was observed both in the left and right maxillary sinuses. When evaluating the average total volume of the maxillary sinuses(i.e., the average volume of the right and left maxillary sinuses together), a significant increase in the volume of the maxillary sinuses was observed in the pilot group when compared to the control group. Conclusion: The maxillary sinus volumes in aircraft pilot candidates increased after the 8-month training program. This may be explained by changes in the gravitational force, the expansion of gas, and positive pressure from oxygen masks. This unprecedented investigation among pilots might lead to other investigations considering paranasal sinus alterations in this singular population.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.217-228
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• 2009

In case of application of electrophoresis method for leakage restoration of waste impoundment, main points of consideration were to evaluate the mobility of clay particles by electrophoretic force and capacity of leakage repair in leachate electrolyte system contained with various chemical species. However, the flocculation phenomena of clay particles induced by electrochemical interaction between various chemical species and clay particles would cause the big problems in electrophoresis method. Therefore, a series of laboratory tests such as one-dimensional electrophoresis and gravitational experiments were carried out in order to identify the specific chemical species affected flocculation of clay particles and the range of chemical concentration in leachate. In addition, the characteristics of clay particle behavior with chemical species and concentration range in leachate were analized using the concept of the settling velocity, zeta potential, and electrophoretic velocity.