• Geomechanics and Engineering
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• 제14권1호
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• pp.19-27
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• 2018

It follows from the basic principles of mechanics of deformable solids relating to the strength, stability and propagation of elastic waves that the Earth's inner core cannot exist in the form of a spherical structure in the assumed thermobaric conditions and calculation values of physico-mechanical parameters. Pressure level reaches a value that is significantly greater than the theoretical limit of medium strength in the model approximations at the surface of the sphere of the inner core. On the other hand, equilibrium state of the sphere is unstable on the geometric forming at much lower loads under the influence of the "dead" surface loads. In case of the action of "follower" loads, the assumed pressure value on the surface of the sphere is comparable with the value of the critical load of "internal" instability. In these cases, due to the instability of the equilibrium state, propagation of homogeneous deformations becomes uneven in the sphere. Moreover, the elastic waves with actual velocity cannot propagate in such conditions in solid medium. Violation of these fundamental conditions of mechanics required in determining the physical and mechanical properties of the medium should be taken into account in the integrated interpretations of seismic and laboratory (experimental) data. In this case, application of the linear theory of elasticity and elastic waves does not ensure the reliability of results on the structure and composition of the Earth's core despite compliance with the required integral conditions on the mass, moment of inertia and natural oscillations of the Earth.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.403-411
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• 2017

In this article, analytical solution for free vibration of micro composite laminated beam on elastic medium based on modified couple stress are presented. The surrounding elastic medium is modeled as the Winkler elastic foundation. The governing equations and boundary conditions are obtained by using the principle of minimum potential energy for EulerBernoulli beam. For investigating the effect of different parameters including material length scale, beam thickness, some numerical results on different cross ply laminated beams such as (90,0,90), (0,90,0), (90,90,90) and (0,0,0) are presented on elastic medium. Free vibration analysis of a simply supported beam is considered utilizing the Fourier series. Also, the fundamental frequency is obtained using the principle of Hamilton for four types of cross ply laminations with hinged-hinged boundary conditions and different beam theories. The fundamental frequency for different thin beam theories are investigated by increasing the slenderness ratio and various foundation coefficients. The results prove that the modified couple stress theory increases the natural frequency under the various foundation for free vibration of composite laminated micro beams.

• Asian-Australasian Journal of Animal Sciences
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• 제14권2호
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• pp.170-173
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• 2001

The objective of this study was to investigate the effect of selenium (Se) on in vitro development of bovine embryos. In CR1BSA, FBS-free medium, the bovine embryos could not proceed past the developmental block more efficiently to morula stage than in chemically undefined media. Addition of glutathione precursor, cysteine, with $\beta$-mercaptoethanol did not improve the development in chemically defined medium and neither did glutathione alone. Exogenous selenium improved the embryonic development to the morula and blastocyst stages at 6 days post-insemination (dpi) significantly (67.1% vs 57.5%, p<0.05), and blastocyst stage at 8 dpi (30.1% vs 20.5%, p>0.05). These improvements might be induced by elevated glutathione peroxidase activity due to addition of Se, and a possible mechanism of selenium to elevate the activity of glutathione peroxidase is discussed.

• Journal of Microbiology and Biotechnology
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• 제19권11호
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• pp.1421-1430
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• 2009

With an aim to evaluate dye decolorization by white rot fungus on natural living conditions, reproducing by solid-state fermentation, the process of triphenylmethane dyes decolorization using the white rot fungus P. ostreatus BP, cultivated on rice straw solid-state medium, has been demonstrated. Three typical dyes, including malachite green, bromophenol blue, and crystal violet, were almost completely decolorized by the fungus after 9 days of incubation. During the process of dye decolorization, the activities of enzyme secreted by the fungus, and the contents of soluble components, such as phenolic compounds, protein, and sugar, changed regularly. The fungus could produce ligninolytic, cellulolytic, and hemicellulolytic enzymes and laccase was the most dominant enzyme in solid-state medium. Laccase, laccase isoenzyme, and the laccase mediator could explain the decolorization of malachite green, bromophenol blue, and crystal violet by the fungus in solid-state medium, respectively. It is worth noting that the presence of the water-soluble phenolic compounds could stimulate the growth of fungus, enhance the production of laccase, and accelerate dye decolorization.

• 천문학회지
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• 제34권4호
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• pp.333-335
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• 2001

We study the properties of supernova (SN) driven interstellar turbulence with a numerical magnetohydrodynamic (MHD) model. Calculations were done using the RIEMANN framework for MHD, which is highly suited for astrophysical flows because it tracks shocks using a Riemann solver and ensures pressure positivity and a divergence-free magnetic field. We start our simulations with a uniform density threaded by a uniform magnetic field. A simplified radiative cooling curve and a constant heating rate are also included. In this radiatively-cooling magnetized medium, we explode SNe one at a time at randomly chosen positions with SN explosion rates equal to and 12 times higher than the Galactic value. The evolution of the system is basically determined by the input energy of SN explosions and the output energy of radiative cooling. We follow the simulations to the point where the total energy of the system, as well as thermal, kinetic, and magnetic energy individually, has reached a quasi-stationary value. From the numerical experiments, we find that: i) both thermal and dynamical processes are important in determining the phases of the interstellar medium, and ii) the power index n of the $B-p^n$ relation is consistent with observed values.

• 대한안전경영과학회지
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• 제11권3호
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• pp.1-9
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• 2009

The present management of the domestic and international advanced enterprises is transferring the systems and the regulations to the prevention system management. Expecially, KOSHA (Korea Occupational Safety & Health Agency) in Korea has supported to set up the OSHMS (Occupational Safety & Health Management System) by KOSHA 18001 since 1997. But small & medium enterprises (SMS) has many difficulties to set up the OSHMS system because of limited natural and human resources. In this study, the rating system as a judgment method of an OSHMS based on the certification standard of the OSHMS, which was suggested in previous study, was developed for SMS to adopt voluntarily the OSHMS, certify KOSHA 18001, and improve the safety and health level.

• Smart Structures and Systems
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• 제20권5호
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• pp.525-537
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• 2017

This paper explores different vibration control strategies for the cancellation of human-induced vibration on a structure with time-varying modal parameters. The main motivation of this study is a lively urban stress-ribbon footbridge (Pedro $G\acute{o}mez$ Bosque, Valladolid, Spain) that, after a whole-year monitoring, several natural frequencies within the band of interest (normal paring frequency range) have been tracked. The most perceptible vibration mode of the structure at approximately 1.8 Hz changes up to 20%. In order to find a solution for this real case, this paper takes the annual modal parameter estimates (approx. 14000 estimations) of this mode and designs three control strategies: a) a tuned mass damper (TMD) tuned to the most-repeated modal properties of the aforementioned mode, b) two semi-active TMD strategies, one with an on-off control law for the TMD damping, and other with frequency and damping tuned by updating the damper force. All strategies have been carefully compared considering two structure models: a) only the aforementioned mode and b) all the other tracked modes. The results have been compared considering human-induced vibrations and have helped the authors on making a decision of the most advisable strategy to be practically implemented.

• 한국미생물·생명공학회지
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• 제29권2호
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• pp.110-114
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• 2001

가축 사료첨가용 probiotics용 균주를 얻기 위해 특히 내열성이 높아 가공사료에 적합한 Bacillus sp.를 위주로 하여 가축에게 유용한 효소인 phytase를 비롯하여 protease, cellulase, xylanase, amylase의 활성을 모두 나타내는 4-3 균주를 얻어 동정한 결과 Bacillus subtilis로 밝혀졌으며, 이를 B. subtilis 4-3으로 명명하였다. 본 균주를 원료사료에 순수배양하여 사료의 항영양인자인 phytic acid 분해율을 검토한 결과 대두박 및 쌀겨에 있어서는 phytic acid 분해율이 낮았으나, 밀기울의 경우 80.63%로 상대적으로 높은 phytic acid 분해율을 나타내었다. 원료 사료를 이용한 균주의 생산 조건은 대두박 1%(w/v)와 당밀 2%(w/v)가 가장 적합한 균주 생산을 위한 배지조성으로 검토되었다.

• 한국약용작물학회지
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• 제17권3호
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• pp.192-197
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• 2009

Camptotheca acuminata, a native of South China is a well known natural source of monoterpene-indole alkaloid camptothecin(CPT), one of the most promising anti-tumoural compounds. This study was conducted to optimize plant growth regulators and culture conditions on plantlets regeneration through organogenesis from callus of Camptotheca acuminta. Callus were induced from various explants of in vitro germinated plantlets of C. acuminta using WPM medium containing 0.2 ㎎/L 2,4-D. Hypocotyl segments were exhibited higher embryogenic callus than the other explants. Shoot buds formation from embryogenic callus was affected by plant growth regulators, pre-treated dark condition and liquid culture. Organogenesis was optimal in WPM liquid medium containing 0.5 ㎎/L BA. The dark pre-treatment for 2 weeks before the solid culture was effective for organogenesis. The regenerated shoots were rooted in WPM medium with 0.2 ㎎/L NAA and successfully acclimated in green-house conditions.

• 천문학회보
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• 제44권1호
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• pp.73.4-73.4
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• 2019

The TXS0506+056 is a blazar and counterpart of the neutrino event IceCube-170922A. It is the first time that the neutrino event and flaring event in electromagnetic wave (EM) coincided. We observed TXS0506+056 with medium-bands in optical using 0.25m and 2.1m telescope at McDonald observatory about a month after the neutrino event. We tracked the variability of SED of the target for three weeks, and our observation showed no abrupt variability in optical range during this period. We concluded that a month after the neutrino event, the TXS0506+056 became less active and shows no feature of the energetic event. We also concluded that the medium-bands are well suited for tracking SEDs of objects. Our result demonstrates the potential of the wide-field 0.25m telescope (5.5 deg^2) for finding transient objects and track the variability of sources like AGNs.