• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.11-18
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• 2013

Human spaceflight experience in extra-vehicular activity (EVA) is limited to two regimes: the micro-gravity environment of Earth orbit, and the lunar surface environment at one-sixth of Earth's gravity. Future human missions to low-gravity bodies, including asteroids, comets, and the moons of Mars, will require EVA techniques that are beyond the current experience base. In order to develop robust approaches for exploring these small bodies, the dynamics associated with human exploration on low-gravity surface must be characterized. This paper examines the translational and rotational motion of an astronaut on the surface of a small body, and it is shown that the low-gravity environment will pose challenges to the surface mobility of an astronaut, unless new tools and EVA techniques are developed. Possibilities for addressing these challenges are explored, and utilization of the International Space Station to test operational concepts and hardware in preparation for a low-gravity surface EVA is discussed.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.556-564
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• 2018

In this study, polyethylene oxide (PEO)/polyethylene-co-vinyl acetate (EVA)/multi-walled carbon nanotube (MWCNT)-COOH composite membranes were prepared by adding 1, 2, 3, and 5 wt% of MWCNT-COOH to PEO/EVA respectively. The gas permeation properties of $N_2$, $O_2$ and $CO_2$ at $30^{\circ}C$ and 4~8 bar pressure were investigated. In each PEO/EVA/MWCNT-COOH composite membranes, the permeability of $CO_2$ increased with increasing the pressure, but the permeability of $N_2$ and $O_2$ were independent of the feeding pressure. As the MWCNT-COOH content increased, the $CO_2$ permeability increased and then decreased above 2 wt% MWCNT-COOH content. The 2 wt% MWCNT-COOH composite membrane exhibited a $CO_2/N_2$ selectivity of 77.8 and a $CO_2$ permeability of 84 barrer at 8 bar. The high $CO_2/N_2$ selectivity and $CO_2$ permeability were due to the high affinity between the quadrupolar $CO_2$, polar ether groups of PEO, and the polar ester groups of EVA. Additionally, the strong affinity between $CO_2$ and the -COOH groups on the MWCNT surface contributed to the high permeability of $CO_2$.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.282-288
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• 2015

A new energetic thermoplastic elastomer based on the azidated polybutadiene(Az-PBD)/ethylene vinyl acetate copolymer (EVA) blends was prepared, and structure and properties of the blends were invetigated by SEM, DSC, DMA, tensile testing and combustion test. The Az-PBD was synthesized via a two-step process involving the addition reaction of commercially available 1,2-PBD with $Br_2$ and subsequent nucleophilic substitution reaction of the brominated PBD with $NaN_3$. EVA/Az-PBD with 90/10, 80/20, 70/30 (wt/wt) was prepared by a solution blending. SEM, DSC, and DMA results revealed that the blends are partially compatible and Az-PBD is dispersed in continuous EVA matrix. Tensile test showed that modulus and tension set increased while elongation-at-break of the blends decreased with increasing Az-PBD content in the blends, but all the blends showed a elongation at break as high as 700% and a tension set of less than 5%, indicating that the blends are typically elastomeric. Combustion test showed that, with increasing Az-PBD content in the blend, higher energy can be released.

• Biomolecules & Therapeutics
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• v.18 no.1
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• pp.106-110
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• 2010

The pharmacokinetics and bioavailability of ambroxol, an expectoration improver and mucolytic agent, were studied to determine the feasibility of enhanced transdermal delivery of ambroxol from the ethylene-vinyl acetate (EVA) matrix system containing polyoxyethylene-2-oleyl ether as an enhancer in rats. The ambroxol-010 matrix system (15 mg/kg) was applied to abdominal skin of rats. Blood samples were collected via the femoral artery for 28 hrs and the plasma concentrations of ambroxol were determined by HPLC. Pharmacokinetic parameters were calculated using Lagran method computer program. The area under the curve (AUC) was significantly higher in the enhancer group ($1,678{\pm}1,413.3\;ng/ml{\cdot}hr$) than that in the control group $1,112{\pm}279\;ng/ml{\cdot}hr$), that is treated transdermally without enhancer, showing about 151% increased bioavailability (p<0.05). The average $C_{max}$ was increased in the enhancer group ($86.0{\pm}21.5\;ng$/ml) compared with the control group ($59.0{\pm}14.8\;ng$/ml). The absolute bioavailability was 13.9% in the transdermal control group, 21.1% in the transdermal enhancer group and 18.1% in the oral administration group compared with the IV group. The $T_{max}$, $K_a$, MRT and $t_{1/2}$ of ambroxol in transdermal enhancer group were increased significantly (p<0.01) compared to those of oral administration. As the ambroxol-EVA matrix containing polyoxyethylene-2-oleyl ether and tributyl citrate was administered to rats via the transdermal routes, the relative bioavailability increased about 1.51-fold compared to the control group, showing a relatively constant, sustained blood concentration. The results of this study show that ambroxol-EVA matrix could be developed as a transdermal delivery system providing sustained plasma concentration.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.103-111
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• 2015

Objective : The purpose of this study was to evaluate the effect for running shoes with resilience of midsole on biomechanical properties. Methods : 10 healthy males who had no history of injury in the lower extremity with an average age of 26.5 year(SD=1.84), height of 172.22 cm(SD=4.44) and weight of 67.51 kg(SD=6.17) participated in this study. All subjects ran on the treadmill wearing three different running shoes. Foot pressure data was collected using Pedar-X system(Novel Gmbh, Germany) operating at 100 Hz. Surface EMG signals for biceps femoris, rectus femoris, vastus lateralis, medial lateralis, tibialis anterior, medial gastrocnemius, soleus and peroneus longus were acquired at 1000 Hz using Bignoli 8 System(Delsys Inc., USA). To normalize the difference of the magnitude of muscle contractions, it was expressed as a percentage relative to the maximum voluntary contraction (MVC). The impact resilience of the midsole data was collected using Fastcam SA5 system(Photron Inc., USA). Collected data was analyzed using One-way ANOVA in order to investigate the effects of each running shoes. Results : TPU midsole was significantly wider in contact area than EVA, TPE midsole in midfoot and higher in EMG activity than EVA midsole at biceps femoris. TPE midsole was significantly wider in contact area than EVA midsole in rearfoot and higher in peak pressure than EVA midsole in forefoot. EVA midsole was significantly higher in EMG activity than TPU midsole at tibia anterior. In medial resilience of midsoles, TPE midsole was significantly higher than EVA, TPU midsole. Conclusion : TPU midsole can reduce the load on the midfoot effectively and activate tibialis anterior, biceps femoris to give help to running.

• Electrical & Electronic Materials
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• v.2 no.1
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• pp.52-64
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• 1989

본 연구에서는 고분자-고분자 및 고분자-금속-고분자의 구조를 갖는 2층고분가물질에 관한 전도전류특성이 조사되었다. 그 결과 2층고분자시료의 전도전류는 인가전압의 극성에 따라 차이가 있었으며 폴리에틸렌과 산화폴리에틸렌으로 구성되는 2층시료 PE-OxPE의 경우 OxPE의 산화도가 증대될 수록 전도전류값이 증가하는 것으로 나타났다. 또한 2충시료 PE-EVA에 대한 전도전류의 극성효과는 (+)극으로부터의 전하주입성이 뛰어난 EVA의 특성에 기인한다. 2층 고분자시료의 중간에 금속(Al)이 삽입된 PE-Al-EVA계의 전도전류특성은 Maxell-Wagner모델에 의한 이론에 대체로 부합되지만 이때의 전도전류는 PE-EVA의 구조보다 낮게 관측되었다.

• Resources Recycling
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• v.18 no.1
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• pp.13-21
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• 2009

A research on material separation of EVA and PET mixture plastic waste using a triboelectrostatic separator has been carried out. It was found that PP was the best charging material to give the highest charge on the surface of EVA and PET mixture plastics with an opposite polarity. Therefore, a charger of pipe line type using PP material was manufactured for separation of EVA and PET mixture plastic waste. At optimum test conditions that used PP cyclone charger developed in this study, we could separate out PET with a glade of 98.7% and a recovery of 89.7%.

• Journal of Radiation Industry
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• v.3 no.1
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• pp.31-37
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• 2009

This paper describes the preparation of manufacturing a new nanocomposite material, which involves adding a multi walled carbon nanotube (MWCNT) to improve thermal characteristics of poly (ethylene-co-vinyl acetate) (EVA). We irradiated the prepared nanocomposites with doses of 50 kGy, 100 kGy and 200 kGy at a dose rate of $5kGy\;hr^{-1}$ and examined their thermal stability, activation energy and crosslink level by using a thermogravimetric analyzer (TGA) and gel fraction experiments. TGA results indicated that the samples with a MWCNT had higher Derivative Thermo Gravimetry (DTG) 2nd peak temperatures than those without a MWCNT. And activation energy of the samples reduced as the absorption dose and the MWCNT content increased. Finally, the gel fraction increased rapidly up to 100 kGy as total absorption dose increased, and then the growth rate of all samples was slowly increased from 100 kGy.

• Macromolecular Research
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• v.16 no.7
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• pp.620-625
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• 2008

A novel nitrogen-phosphorus compound, diphenyl piperazine-1,4-diylbis(methylphosphinate)(DPPMP) was synthesized via a two step reaction and its flame retarding efficiency as a single component additive was investigated. The success of synthesis was confirmed by FTIR and $^1H$ and $^{31}P$ NMR analysis. The product was mixed with polycarbonate (PC), poly(butylene terephtalate) (PBT), ethylene-vinyl-acetate copolymer (EVA), and acrylonitrile-butadiene-styrene copolymer (ABS). The flame-retarding efficiency was evaluated using the limiting oxygen index (LOI) and the UL-94 vertical test methods. The addition of DPPMP enhanced the flame retardancy of the polymers and the V-0 ratings were obtained for the polymers examined in this study at a loading of 7-30 wt%. The gas-phase flame retardancy mode of action was suggested for this material from the thermogrametry experiment results.

• Carbon letters
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• v.21
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• pp.23-32
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• 2017

A drop weight impact test was conducted in this study to analyze the mechanical and thermal properties caused by the changes in the ratio of carbon fiber reinforced plastic (CFRP) to ethylene vinyl acetate (EVA) laminations. The ratios of CFRP to EVA were changed from 10:0 (pure CFRP) to 9:1, 8:2, 6:4, and 5:5 by manufacturing five different types of samples, and at the same time, the mechanical/thermal properties were analyzed with thermo-graphic images. As the ratio of the CFRP lamination was increased, in which the energy absorbance is dispersed by the fibers, it was more likely for the brittle failure mode to occur. In the cases of Type 3 through Type 5, in which the role of the EVA sheet is more prominent because it absorbs the impact energy rather than dispersing it, a clear form of puncture failure mode was observed. Based on the above results, it was found that all the observation values decreased as the EVA lamination increased compared with the CFRP lamination. The EVA lamination was thus found to have a very important role in reducing the impact. However, the strain and temperature were inversely propositional.