• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.6
• /
• pp.875-882
• /
• 2021

To minimize occupational noise induced hearing loss, it is recommended that workers should not be exposed to noise levels exceeding 85 dBA for over 8 h. In the present study, noise exposure levels were measured for seven workers based on their tasks on a training ship. The A-weighted noise exposure level (L_ex,24h) was measured by taking into account the A-weighted equivalent continuous sound level (L_Aeq,i), duration (h) and noise contribution (L_ex,24h,i) from the workers' locations. Results are thus obtained for different job categories as follows: officer group L_ex,24h=56.1 dB, navigation crew L_ex,24h=58.9 dB, navigation cadet L_ex,24h=62.0 dB, ship's cook L_ex,24h=64.3 dB, engine cadet L_ex,24h=91.1 dB, engineer L_ex,24h=91.1 dB, and engine crew L_ex,24h=95.1 dB. It was determined that the engineers, engine crews, and engine cadets in charge of machinery must wear hearing protection devices. By wearing hearing protection devices when working in highly noisy engine rooms, it is estimated that the noise expose levels could be reduced by the following amounts: engineer L_ex,24h=23.1 dB, engine Crew L_ex,24h=24.4 dB, and engine cadet L_ex,24h=21.5 dB. Moreover, if the no. 2 lecture room and mess room bottom plates in the cadets accommodations were improved to the 64 mm A-60-class floating plates, then further reductions are possible as follows: navigation cadet L_ex,24h=4.3 dB and engine cadet L_ex,24h=1.8 dB.

• Journal of the Korean Society of Food Culture
• /
• v.22 no.4
• /
• pp.454-461
• /
• 2007

Antioxidative and antimicrobial activities were carried out on the Citrus Unshju peel solvent extracts in order to discover new functional activities. The amounts of polyphenol in 70% metanol extract (MtEx) was measured as 836.8 mg% in Citrus Unshju peel. The EDA (electron donating ability) of 0.01, 0.02 and 0.1% MtEx in Citrus Unshju peel were measured as levels of 81.3, 86.0 and 89.6%. The nitrite scavenging effects of Citrus peel were also determined as the levels of 34.4% (pH 1.2) and 19.5% (pH 7.0). The pH of react solution was more acidic, the nitrite scavenging effect was more increased. The order of antioxidatives was shown as TBHQ > BHT > TOC > ChEx > EaEx > EtEx > WaEx > Control in corn germ oil and TBHQ > ChEx > EaEx > BHT > EtEx > WaEx > TOC > Control in canola oil. A number of the extracts were certified to have antimicrobial activities for a small number of micro-organisms, similar gram negative and positive micro-organisms. According to the results above, it was summerized that Citrus Unshju peel had the higher total polyphenol, EDA, nitrite scavenging effects and antimicrobial activities. Also isolated extract from ChEx and EaEx had high antioxidative, these effects were very similar to that of ${alpha}$-tocopherol and BHT. It would be proposed that Citrus peel can become a new natural source for antioxidative agents in future food industry.

• Journal of the Korean Magnetics Society
• /
• v.7 no.5
• /
• pp.258-264
• /
• 1997

Exchange and interlayer couplings between a NiFe ferromagnetic layer and an antiferromagnetic NiO layer in NiO/NiFe/Cu/NiFe spin-valve films prepared by rf/dc magnetron sputtering were investigated. The interlayer coupling field ($H_{int}$ decreased with the Cu layer thickness, and the exchange coupling field $(H_{ex}$ saturated to 90 Oe. the magnetitudes of $H_{ex}$ and $H_{int}$ decreased with increasing thickness of the pinned NiFe layer. The increase of $H_{int}$ with the free NiFe layer may be due to the increased magnetization.

• Journal of the Korean Magnetics Society
• /
• v.12 no.2
• /
• pp.64-67
• /
• 2002

IrMn pinned spin valve (SV) films with stacks of Ta/NiFe/IrMn/CoFe/Cu/CoFe/NiFe/Ta were prepared by dc sputtering onto thermally oxidized Si (111) substrates at room temperature under a magnetic field of about 100 Oe. The annealing cycle number and temperature dependence of exchange coupling field (H$_{ex}$), magnetoresistance (MR) ratio, and coercivity (H$_{c}$) were investigated. By optimizing the process of deposition and post thermal annealing condition, we obtained the IrMn based SV films with MR ratio of 3.6%, H$_{ex}$ of 1180 Oe for the pinned layer. The H$_{ex}$ is stabilized after the second annealing cycle and it is thought that this SV reveals high thermal stability. The H$_{ex}$ maintained its strength of 600 Oe in operation up to 24$0^{\circ}C$ and decreased monotonically to zero at 27$0^{\circ}C$.

• Journal of Life Science
• /
• v.28 no.9
• /
• pp.1042-1047
• /
• 2018

The red algae Gracilaria vermiculophylla is widespread on seashores worldwide and has been used as food in Asian countries. Previous studies have reported that extracts of Gracilaria red algae have beneficial anti-oxidant and anti-inflammatory effects. The present study examined the anti-senescence effects of Gracilaria vermiculophylla extracts (GV-Ex) in replicatively senescent human bone marrow mesenchymal stem cells (hBM-MSCs). GV-Ex pretreatment improved the cellular viability of hBM-MSCs that had been injured by oxidative stress. These effects of GV-Ex were confirmed by MTT assay and immunoblot analysis using the apoptotic proteins p53 and cleaved caspase-3. The reactive oxygen species (ROS) levels were examined in long-term cultured Passages 17 (P-17) mesenchymal stem cells (MSC) and compared to P-7 MSC. The ROS accumulation was greater in the P-17 than in the P-7. However, these increased ROS levels in the P-17 were decreased significantly after treatment with GV-Ex, and restoration of the levels of the anti-oxidant enzymes SOD1, SOD2, and CAT was also observed under these conditions. In addition, P-17 hBM-MSC treated with GV-Ex had decreased levels of the senescence proteins p53, p21, and p16. The results show that the ability of P-17 hBM-MSC to differentiate into osteocytes and adipocytes was improved by GV-Ex treatment, suggesting that GV-Ex ameliorates the functional decline of senescent stem cells.

• Journal of the Korean Magnetics Society
• /
• v.27 no.1
• /
• pp.30-34
• /
• 2017

In this report, we calculated the angular dependence of exchange bias ($H_{ex}$) by using single domain model in exchange coupled ferromagnetic (F)/antiferromagnetic (AF) bilayers, which results with AF thickness ($t_{AF}$) were used for the analysis of measured ones in NiFe/MnIr bilayers. Angular dependence of $H_{ex}$ calculated at $t_{AF}$ > $t_c$ showed typical unidirectional behaviors, however, calculated one at $0.5t_c$ < $t_{AF}$ < $t_c$ showed peculiar angular behaviors by fixed AF spins at specified angle near ${\theta}_H=90^{\circ}$. Angular dependence of $H_{ex}$ measured in NiFe/MnIr (20 nm) bilayers showed typical unidirectional behaviors. However, measured one in NiFe/MnIr (4 nm) bilayers showed mixed behaviors including both of unidirectional and peculiar angular behaviors, which was explained by the grain size distribution of polycrystalline MnIr.

• Journal of the Korean Magnetics Society
• /
• v.11 no.4
• /
• pp.146-150
• /
• 2001

The effect of H$_2$ content in Ar sputtering gas on exchange coupling field(H$_{ex}$) for NiFe/FeMn interface was studied. When NiFe layer of Si(100)/Ta(50 $\AA$)/NiFe(60 $\AA$)/FeMn(250 $\AA$)Ta(50 $\AA$) was deposited at 8% H$_2$ in sputtering gas, the maximum exchange coupling field(H$_{ex}$) and minimum coercivity(H$_{c}$) were obtained. When Si(100)/Ta(50 $\AA$)/NiFe(60 $\AA$)/FeMn(250 $\AA$)/NiFe(70 $\AA$)/Ta(50 $\AA$) was deposited at 5% H$_2$ in sputtering gas, the maximum exchange coupling field(H$_{ex}$) of 148 Oe was obtained. The (111) preferred orientation and grain size of underlayer NiFe were increased and the internal stress was reduced by H$_2$ in sputtering gas. And the (111) preferred orientation and grain size of FeMn layer were also increased.d.ased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.265-268
• /
• 1999

In this study, we investigated the electromagnetic Properties of M $n_{Y}$Z $n_{1-x}$ F $e_{x}$ $O_4$(X=0.67~0.69, Y=0.13~0.19) doped with and without H $o_2$ $O_3$(each of 0.05~ 0.2wt%, step 0.05wt%). The greatest initial permeability of composition is M $n_{0.17}$Z $n_{0.16}$F $e_{0.67}$ $O_4$. As X and Y components, increased. generally resistivity slightly change by the various X and Y components. The initial permeability of M $n_{0.17}$Z $n_{0.16}$F $e_{0.67}$ $O_4$ doped with H $o_2$ $O_3$ showed the about 2.5 times higher than that of M $n_{0.17}$Z $n_{0.16}$F $e_{0.67}$ $O_4$ doped without H $o_2$ $O_3$EX>EX>EX>X>>EX>EX>EX>X>

• Journal of the Korean Magnetics Society
• /
• v.13 no.5
• /
• pp.187-192
• /
• 2003

The magnetic and thermal properties of NiFe/[IrMn-Mn]/CoFe with Mn additions have been studied. As-deposited CoFe pinned layers with [IrMn-Mn]layer had dominantly larger exchange biasing field ( $H_{ex}$) and blocking temperature ( $T_{b}$) than those with pure I $r_{22}$M $n_{78}$ used. The $H_{ex}$ and $T_{b}$ improved with 76.8-78.1 vol% Mn, but those of the NiFe/IrMn/CoFe dropped considerably with more addition of 0.6 vol % Mn. The average x-ray diffraction peak ratios of fcc [(111)CoFe, NiFe]/(111)IrM $n_3$ textures for the Mn inserted total vol of 75.5, 77.5, and 79.3% were about 1.4, 0.8, and 0.6, respectively. For the sample without Mn inserted layer, the $H_{ex}$ between IrMn and CoFe layers was almost zero, but it increased to 100 Oe after annealing of 250 $^{\circ}C$. For as-grown two multilayers samples with ultra-thin Mn layers of 77.5 and 78.7 vol %, the $H_{ex}$s were 259 and 150 Oe, respectively. In case of IrMn with 77.5 vol% Mn, the $H_{ex}$ was increased up to 475 Oe at 350 $^{\circ}C$ but decreased to 200 Oe at 450 $^{\circ}C$, respectively. The magnetic properties and thermal stabilities of NiFe/[IrMn-Mn]/CoFe multilayer were enhanced with Mn additions. In applications where higher $H_{ex}$ and $T_{b}$ are required, proper contents of Mn can be used. be used. used.

• Journal of Magnetics
• /
• v.16 no.2
• /
• pp.97-100
• /
• 2011

Bilayers of soft NiFe (150 nm-420 nm) on hard Ni (150 nm) were prepared by electrodeposition. The process of magnetization reversal in the NiFe/Ni bilayers was then investigated. The hysteresis loop generated by a magnetization reversal of soft NiFe under a positive saturation state of a hard Ni layer shows a shift along the negative field axis, which is clear evidence for the exchange spring effect in the NiFe/Ni bilayers. The dependence of the coercive field $H_c$ and exchange bias field Hex on the thickness of the NiFe layer was also investigated. As the NiFe thickness increases from 150 nm to 420 nm, both $H_c$ and $H_{ex}$ decrease rapidly from $H_c$= 51.7 Oe and $H_{ex}$ = 12.2 Oe, and saturate to $H_c$ = 5.8 Oe and $H_{ex}$ = 3.5 Oe.