• Journal of Mushroom
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• v.16 no.4
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• pp.304-310
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• 2018

Beta glucan was purified from Phellinus baumii and tested for its effect on the group performance of ants, a principal model of eusociality and of superorganisms. Japanese carpenter ants (Camponotus japonicus) were reared on diets containing beta glucans to characterize their effects on eusociality. Culturing structures for ants were assembled by implanting autoclaved soil into polyethylene terephthalate bottles. Three different eusocial strength indices were used to study the effect of beta glucan extract (BGE) on eusocial activities - the number of residence chambers, cooperative defense index (CDI), and group size and composition. Control, low- BGE, and high-BGE diets were prepared with the following three levels of BGE supplements in sucrose powder: 0, 20, and 50% (g/g). More residence chambers were observed in the BGE-fed groups than in the control. The CDI against a foreign queen ant was calculated according to the time taken to subdue the foreign queen. The high-BGE group took less time to complete their defense formation than the other groups. Differences were evident between control and BGE-fed groups in the total numbers of ants and eggs. The BGE-fed groups showed a significant increase in both the number of workers and the number of eggs. When fed with BGE, ants responded positively for all three eusocial strength indices. These results show that BGE exerts beneficial effects on the eusociality of ants as a superorganism.

• Korean Journal of Materials Research
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• v.32 no.1
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• pp.9-13
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• 2022

Bullets flying with a light from the back are called "tracers". Tracers are ignited by the combustion gas of the propellant and emit bright light that allows the shooter to visually trace the flight path. Therefore, tracers mark the firing point for allies to assist shooters to hit target quickly and accurately. Conventional tracers are constructed with a mixture of an oxidizing agent, raw metal, and organic fuel. Upon ignition, the inside of the gun can be easily contaminated by the by-products, which can lead to firearm failure during long-term shooting. Moreover, there is a fire risk such as forest fires due to residual flames at impact site. Therefore, it is necessary to develop non-combustion type luminous material; however, this material must still use the heat generated from the propellant, so-called "thermoluminescence (TL)". This study aims to compare the TL emission of Dy³⁺, La³⁺ and Ho³⁺ doped MgB₄O₇ phosphors prepared by solid state reaction. The crystal structures of samples were determined by X-ray diffraction and matched with the standard pattern of MgB₄O₇. Luminescence of various doses (200 ~ 15,000 Gy) of gamma irradiated Dy³⁺, La³⁺ and Ho³⁺ (at different concentrations of 5, 10, 15 and 20 %) doped MgB₄O₇ were recorded using a luminance/color meter. The intensity of TL yellowish (CIE x = 0.401 ~ 0.486, y = 0.410 ~ 0.488) emission became stronger as the temperature increased and the total gamma-ray dose increased.

• Journal of International Area Studies (JIAS)
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• v.14 no.4
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• pp.27-52
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• 2011

The regions of Central Asia have each acquired an elevated strategic importance in the new security paradigm of post-September 1lth. Comprised of five states, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan, Central Asia's newly enhanced strategic importance stems from several other factors, ranging from trans-national threats posed by Islamic extremism, drug production and trafficking, to the geopolitical threats inherent in the region's location as a crossroads between Russia, Southwest Asia and China. Although the U.S. military presence in the region began before September 11th, the region became an important platform for the projection of U.S. military power against the Taliban in neighboring Afghanistan. The analysis goes on to warn that 'with US troops already in place to varying extents in Central Asian states, it becomes particularly important to understand the faultlines, geography, and other challenges this part of the world presents'. The Kyrgyz military remains an embryonic force with a weak chain of command, the ground force built to Cold War standards, and an almost total lack of air capabilities. Training, discipline and desertion - at over 10 per cent, the highest among the Central Asian republics - continue to present major problems for the creation of combat-effective armed forces. Kyrgyzstan has a declared policy of national defence and independence without the use of non-conventional weapons. Kyrgyzstan participates in the regional security structures, such as the Collective Security Treaty Organisation (CSTO) and the Shanghai Co-operation Organisation (SCO) but, in security matters at least, it is dependent upon Russian support. The armed forces are poorly trained and ill-equipped to fulfil an effective counter-insurgency or counter-terrorist role. The task of rebuilding is much bigger, and so are the stakes - the integrity and sovereignty of the Kyrgyz state. Only democratization, the fight against corruption, reforms in the military and educational sectors and strategic initiatives promoting internal economic integration and national cohesion hold the key to Kyrgyzstan's lasting future

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.127-134
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• 2020

High supersonic aircraft are exposed to high temperature environments by aerodynamic heating during supersonic flight. Thermal protection system structures such as double-panel structures are used on the skin of the fuselage and wings to prevent the transfer of high heat into the interior of an aircraft. The thin-walled double-panel skin can be exposed to acoustic loads by supersonic aircraft's high power engine noise and jet flow noise, which can cause sonic fatigue damage. Therefore, it is necessary to examine the behavior of supersonic aircraft skin structure under thermal-acoustic load and to predict fatigue life. In this paper, we designed and fabricated thermal-acoustic test equipment to simulate thermal-acoustic load. Thermal-acoustic testing of the titanium specimen under thermal-acoustic load was performed. The analytical model was verified by comparing the thermal-acoustic test results with the finite element analysis results.

• Composites Research
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• v.29 no.4
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• pp.209-215
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• 2016

The failure of composite sandwich structures with thickness and material variation was studied. The main body of the structure is sandwich plate made of the carbon composite face and Aluminum honeycomb core. It is connected with composite laminated flange without core through transition region of tapered sandwich panel with foam core. Tension and compression tests were conducted for the total of 6 panels, 3 for each. Test results showed that the panels under compression are vulnerable to the face failure along the material discontinuity line between two different cores. However the failure load of which panel does not show such failure can carry 16% more load and fails in honeycomb core and face debonding. For the tensile load, the extensive delamination failure was observed at the corner radius which connects the panel and the flange. The average failure load for compression is about 7 times the tensile failure load. Accordingly, these sandwich structures should be applied to the components that endure the compressive loadings.

• Journal of the Korean Chemical Society
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• v.36 no.1
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• pp.3-15
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• 1992

Electronic structures and reactivities of the chromium, molybdenum, and tungsten carbene complexes, $(CO)_5Cr=CCHCH_2(XCH_3)\;,\;(CO)_5Mo=CCHCH_2(XCH_3)\;, and\;(CO)_5W=CCHCH_2(XCH_3)$, are studied by means of Extended Huckel calculations. The origin of the M=Ccarbene double bond is clarified from the diagram of the orbital correlation with the fragment orbitals. The ${\sigma}$ bond of the M=Ccarbene double bond is formed by the electron transfer interaction from the HOMO of the carbene to the LUMO of the $(CO)_5M$. The ${\pi}$ bond is formed through the back-transfer of electrons from one of the degenerated d${\pi}$ orbitals to the LUMO of the carbene. The polarization of charge of the M=Ccarbene bond is calculated to be M=Ccarbene for Mo, and W carbenes. The chemical and physical properties of these complexes are resulted from an appreciable positive charge on the carbene carbon. The electrophilic reactivity of the carbene carbon is not charge controlled, but is controlled by the frontier orbital, LUMO.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.959-965
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• 2017

In recent years, major airplane manufacturers have been using the laminate failure theory to estimate the strain of composite structures for airplanes. The laminate failure theory uses the failure strain of the laminate to analyze composite structures. This paper describes a procedure for the experimental assessment of laminate tensile failure characteristics. Regression analysis was used as the experimental assessment method. The regression analysis was performed with the response variable being the laminate failure strain and with the regressor variables being two-ply orientation ($0^{\circ}$ and ${\pm}45^{\circ}$) variables. The composite material in this study is a carbon/epoxy unidirectional (UD) tape that was cured as a pre-preg at $177^{\circ}C(350^{\circ}F)$. A total of 149 tension tests were conducted on specimens from 14 distinct laminates that were laid up at standard angle layers ($0^{\circ}$, $45^{\circ}$, $-45^{\circ}$, and $90^{\circ}$). The ASTM-D-3039 standard was used as the test method.

• Journal of Ocean Engineering and Technology
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• v.26 no.3
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• pp.13-19
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• 2012

Recently, as the importance of the interior noise in a ship cabin has risen, ship builders have becomeconcerned about the use of noise reduction panels to reduce cabin noise. The results of previous researches have been based on analytical and experimental methods using simple sandwich panels. However, panel structures are becoming more complex to improve the transmission loss. Thus, researches that analyze the transmission loss of a panel are reaching the limit of study. This paper reports on research that was performed to determine the sound transmission characteristics of multi-complex panels applicable to high value-added vessels. It presents comparisons between analytical methods and experimental results by using a mini-reverberant chamber with components of sound attenuation panels, including the core and surface materials. The sound transmission loss of multi-complex panels are also analyzed in terms of the influences of the inside perforate plates and air gap thickness on the attenuation. Finally, the multi-complex panel with the highest noise attenuation is proposed based on the analysis results and experimental results in mini-reverberant chamber, which wereverified using a real-size reverberant chamber.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.293-297
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• 2016

Ni-C composite films were prepared by co-deposition using a combined technique of plasma CVD and ion beam sputtering deposition. Depending on the deposition conditions, Ni-C thin films manifested three kinds of microstructure: (1) nanocrystallites of non-equilibrium carbide of nickel, (2) amorphous Ni-C film, and (3) granular Ni-C film. The electrical resistivity was also found to vary from about $10^2{\mu}{\Omega}cm$ for the carbide films to about $10^4{\mu}{\Omega}cm$ for the amorphous Ni-C films. The Ni-C films deposited at ambient temperatures showed very low TCR values compared with that of metallic nickel film, and all the films showed ohmic characterization, even those in the amorphous state with very high resistivity. The TCR value decreased slightly with increasing of the flow rate of $CH_4$. For the films deposited at $200^{\circ}C$, TCR decreased with increasing $CH_4$ flow rate; especially, it changed sign from positive to negative at a $CH_4$ flow rate of 0.35 sccm. By increasing the $CH_4$ flow rate, the amorphous component in the film increased; thus, the portion of $Ni_3C$ grains separated from each other became larger, and the contribution to electrical conductivity due to thermally activated tunneling became dominant. This also accounts for the sign change of TCR when the filme was deposited at higher flow rate of $CH_4$. The microstructures of the Ni-C films deposited in these ways range from amorphous Ni-C alloy to granular structures with $Ni_3C$ nanocrystallites. These films are characterized by high resistivity and low TCR values; the electrical properties can be adjusted over a wide range by controlling the microstructures and compositions of the films.

• Journal of Periodontal and Implant Science
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• v.43 no.5
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• pp.215-220
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• 2013

Purpose: Cigarette smoking is a major risk factor in periodontal diseases. The pathogenesis of periodontal diseases may be affected by alterations of the inflammatory response by smoke. Nitric oxide (NO) is a gaseous, colorless, highly reactive, short-lived free radical with a pivotal role in the regulation of various physiological and pathological mechanisms in the body. It is important in host defense and homeostasis, on the one hand, whereas, on the other hand, it modulates the inflammatory response in periodontitis, leading to harmful effects. The aim of this study was to assess the levels of NO in both the serum and saliva of smokers and nonsmokers having chronic periodontitis and to compare them with periodontally healthy controls. Methods: Sixty subjects participated in the study and were divided into three groups: group I, healthy nonsmoking subjects; group II, nonsmoking patients with chronic periodontitis; group III, smoking patients with chronic periodontitis. Each group consisted of twenty subjects. The biochemical estimation of NO in the collected serum and in the saliva was performed using the Griess colorimetric reaction. Results: The results showed that the mean value of the salivary and serum NO was greater in group II than in group I, and also greater in group III than in group II. Conclusions: NO appears to play an important and rather complex role in the immuno-inflammatory process and in the remodeling and maintenance of osseous structures. It is therefore logical that modulation of this mediator has potential for the treatment of a number of inflammatory conditions including periodontal disease.