아스팔트는 점성이 높은 도로포장 재료로서 골재와 채움재를 결합시키는 역할을 하는 중요한 재료이다. 아스팔트 콘크 리트는 생산 및 시공 과정에서 혼합물이 장비에 부착되는 현상이 발생하여 생산 효율 및 성능 저하를 유발하기도 한다. 이와 같은 문제를 해결하기 위하여 석유류와 식물성 기름을 부착방지제(Asphalt Release Agent)로 사용하고 있다. 하지 만 석유류는 단시간에 아스팔트를 용해시켜 혼합물의 성능 저하를 유발할 수 있고, 발생하는 유증기로 인해 작업자를 위 험에 노출시킬 수 있다. 식물성 기름은 석유류에 비해 아스팔트에 대한 용해력은 다소 작지만 석유류와 동일한 문제를 야기하며 제품 단가로 인해 높은 비용을 발생시킨다. 이에 따라 아스팔트 혼합물 생산 및 시공현장에서 저독성이며 친환 경적인 부착방지제의 중요도가 상승하고 있다.

PURPOSES : In this study, high-viscosity grout for increasing ground stiffness is developed using industrial byproducts. METHODS : Based on literature review, the viscosity and viscosity expression time of domestic and foreign anti-washout admixture underwater were evaluated. In addition, grout was prepared by mixing 5% to 40% of fly ash (FA) in a standard mixture. Flow, setting time, and compressive strength tests were conducted to evaluate the quality of the grout. RESULTS : Experimental results show that the viscosity required is 35,000 to 40,000 cps, whereas the viscosity expression time required exceeds 300 min. As the amount of FA used for grouting increases, the physical and mechanical performances deteriorate. The strength of a test specimen manufactured underwater is lower than that of a test specimen manufactured under air, and the decrease on day 28 is lower than that on day 3. The FA applied to the grout should be less than 20%. CONCLUSIONS : Although industrial byproducts, which exhibit high viscosity, offer excellent mechanical performance and are thus suitable as a solidifying agent for strengthening grout, their application in the field must be evaluated.

PURPOSES : The objective of this study is to evaluate the feasibility of applying properties of asphalt binder other than absolute viscosity (AV) to evaluate the rejuvenation level of the binder from reclaimed asphalt pavement (RAP) in recycled asphalt mixtures (RAMs). METHODS : The G*/sin and critical temperature (CT) for determining high performance grade by DSR, and the large molecular size (LMS) using gel-permeation chromatography (GPC) were measured simultaneously with the AV of two virgin asphalt binders (58–22 for RAM and 64–22 for normal mix) and recovered binders from a RAP and four RAMs. Based on mix design, 20%, 30%, 40%, and 50% recycled RAMs were prepared, and the deformation strength (SD) of the RAMs were measured. The AV, LMS, G*/sin , and CT were measured from the recovered binders from each RAM of the SD-tested specimens. Regression analyses were performed between the LMS and AV, G*/ sin and AV, and CT and AV to determine the correlation of each property with the AV. The feasibility of evaluating the rejuvenation level of the RMA binder using the three properties (LMS, G*/sin , and CT) was evaluated. Regression analysis was performed between SD and AV, and the feasibility of using SD instead of AV ≤ 5,000 poise (p) was analyzed to evaluate the rejuvenation level of the RAM. RESULTS : The AV, LMS, G*/sin , and CT of RAM binders increased with the recycling ratio. Mixes with recycle ratios of 20% and 30% satisfied the AV ≤ 5,000 p criterion, unlike mixes with higher recycle ratios. The regression analysis results showed that the R2 values between the LMS and AV, G*/sin and AV, and CT and AV exceeded 0.96. Since these regressions showed extremely high R2 values, it can be inferred that the estimation of binder rejuvenation level using the LMS, G*/sin and CT, i.e., instead of the AV criterion, is applicable. Because SD exhibits high correlation with the binder stiffness, and the regression between SD and AV indicated R2 > 0.98, SD can be applied instead of the AV for binder rejuvenation level estimation. The main advantage of using the LMS and SD is to estimate the binder rejuvenation level without recovering the binder from the mix. CONCLUSIONS : For the binder rejuvenation level estimation of recycled mixes, it is concluded that the LMS by GPC and G*/sin and CT by DSR, and SD can be applied instead of the AV criterion. However, since this study was performed using limited materials, further studies involving many other materials may be performed to generalize the current conclusion.

Recently, air pollution from fossil fuels is at a serious level, and the IMO proposes to reduce greenhouse gas emissions by about 70% by 2050, and controls greenhouse gas emissions by applying the energy efficiency disign index(EEDI) to each ship type. In this study, the marine fuel oil viscosity of MGO, MDO, HFO and CGO according to the temperature change was compared and measured and the difference was analyzed. As a result, the viscosity of CGO was 3.32mPa·s, which was almost similar to MGO(3.40mPa·s) and MDO(3.51mPa·s) so it was judged that it could be used as a marine fuel, and it was found that there was a significant difference with HFO at P<0.01 there was.

이 연구는 최대근력형과 근지구력형 저항운동이 총운동량과 혈액점도 및 적혈구용적률에 미치는 영향을 조사하고자 하였다. 연구대상자는 저항운동 경력 12개월 이상의 20대 남성 15명으로 선정하였으며, 실험 전 벤치프레스 1RM을 측정하였으며, 조건 별 실험은 1주일간의 간격을 두고 교차배분하여 6세트 씩 최대반복수행 하였다. 그 결과 총운동량은 근지구력강도가 최대근력강도에 비해 높게 나타났으며 (p<.001), 혈액점도와 적혈구용적률은 총운동량에 관계없이 운동 전보다 운동 후에 높아졌다(p<.01). 종합 하면 혈액점도는 운동강도와 운동량에 영향을 받지 않으며, 일회성 저항운동으로 증가한다는 것을 알 수 있었다. 이는 저항운동 프로그램을 구성하는데 있어 임상적으로 의의가 있으며 혈관질환에 관련된 임상환 자들의 운동프로그램을 작성하는데 있어 참고자료가 될 수 있을 것으로 판단된다.

PURPOSES : This study evaluates the mechanical properties of high-viscosity polymer-modified asphalt binders using PG and MSCR tests. METHODS : Using the Superpave asphalt binder performance grade (PG) and multi-stress creep recovery (MSCR) test methods, the linear (dynamic shear modulus, stiffness, and viscosity) and non-linear properties — i.e., non-recoverable compliance (Jnr) and recoverable shear strain % recovery — of 16 different types (SBS, SIS, PE, PP) of polymer-modified asphalt binders were assessed. RESULTS : Based on the viscosity testing results. Most PG 82 binders did not meet the criterion of 3 Pa ·s. This indicates that they need to increase the mixing and compaction temperatures to reduce the high viscosity. The MSCR % Jnr results demonstrated that PG 76, PG 82–22, and PG 82-28/34 binders were below 1.0, 0.5, and 0.2, respectively. In addition, the MSCR % recovery results showed that PG 76, PG82-22, and PG82-28/34 were above 35 %, 55 %, and 80 %, respectively. CONCLUSIONS : It was found that the % Jnr decreased with an increase in the high-temperature PG of the asphalt binder, whereas the % recovery increased as the low-temperature PG of the binder increased.

In the manufacturing of bulk graphite, pores produced by vaporization and discharge of volatile materials in binders during carbonization reduce the density of bulk graphite, which adversely affects the electrical conductivity, strength and mechanical properties. Therefore, an impregnation process is introduced to fill the pores and increase the density of bulk graphite. In this study, bulk graphite is prepared by varying the viscosity of the impregnant. The microstructure of bulk graphite is observed. The flexural strength and electrical resistivity are measured. As the viscosity of the impregnants decreases and the number of impregnations increases, it is shown that the number of pores decreases. The density before impregnation is 1.62 g/cm3. The density increases to 1.67 g/cm3 and porosity decreases by 18.6 % after three impregnations using 5.1 cP impregnant, resulting in the best pore-filling effect. After three times of impregnation with a viscosity of 5.1 cP, the flexural strength increases by 55.2 % and the electrical resistivity decreases by 86.76 %. This shows that a slight increase in density due to the pore-filling effect improves the properties of bulk graphite.

Pores produced by carbonization in bulk graphite process degrade the mechanical and electrical properties of bulk graphite. Therefore, the pores of bulk graphite must be reduced and an impregnation process needs to be performed for this reason. In this study, bulk graphite is impregnated by varying the viscosity of the impregnant. The pore volume and pore size distribution, according to the viscosity of the impregnant, are analyzed using a porosimeter. The total pore volume of bulk graphite is analyzed from the cumulative amount of mercury penetrated. The volume for a specific pore size is interpreted as the amount of mercury penetrating into that pore size. This decreases the cumulative amount of mercury penetrating into the recarbonized bulk graphite after impregnation because the viscosity of the impregnant is lower. The cumulative amount of mercury penetrating into bulk graphite before impregnation and after three times of impregnation with 5.1cP are 0.144 mL/g and 0.125 mL/gm, respectively. Therefore, it is confirmed that the impregnant filled the pores of the bulk graphite well. In this study, the impregnant with 5.1 cP, which is the lowest viscosity, shows the best effect for reducing the total pore volume. In addition, it is confirmed by Raman analysis that the impregnant is filled inside the pores. It is confirmed that phenolic resin, the impregnant, exists inside the pores through micro-Raman analysis from the inside of the pore to the outside.

In this study, acoustic and viscosity data are collected in real time during the ball milling process and analyzed for correlation. After fast Fourier transformation (FFT) of the acoustic data, changes in the signals are observed as a function of the milling time. To analyze this quantitatively, the frequency band is divided into 1 kHz ranges to obtain an integral value. The integrated values in the 2–3 kHz range of the frequency band decrease linearly, confirming that they have a high correlation with changes in viscosity. The experiment is repeated four times to ensure the reproducibility of the data. The results of this study show that it is possible to estimate changes in slurry properties, such as viscosity and particle size, during the ball milling process using an acoustic signal.

Various electronic control parts and devices installed in electric vehicles have greatly improved the convenience of occupants, but electromagnetic waves emitted from electronic devices have greatly increased concerns about malfunctions, deterioration of performance, safety accidents, etc. There are two models of analysis. Case A is symmetrical about one axis of rotation. Case B has two axes of rotation. In this study, a flow analysis was conducted to find excellent flow conditions in the mixing process to develop a paint with excellent electromagnetic shielding and thermal insulation performance. The results of the flow analysis are reflected in manufacturing specifications and are intended to be used to develop high-quality systems.

Cross model correlates the dynamic complex viscosity of polymer systems to zero complex viscosity, relaxation time and power-law index. However, this model disregards the growth of complex viscosity in nanocomposites containing filler networks, especially at low frequencies. The current paper develops the Cross model for complex viscosity of nanocomposites by yield stress as a function of the strength and density of networks. The predictions of the developed model are compared to the experimental results of fabricated samples containing poly(lactic acid), poly(ethylene oxide) and carbon nanotubes. The model’s parameters are calculated for the prepared samples, and their variations are explained. Additionally, the significances of all parameters on the complex viscosity are justified to approve the developed model. The developed model successfully estimates the complex viscosity, and the model’s parameters reasonably change for the samples. The stress at transition region between Newtonian and power-law behavior and the power-law index directly affects the complex viscosity. Moreover, the strength and density of networks positively control the yield stress and the complex viscosity of nanocomposites. The developed model can help to optimize the parameters controlling the complex viscosity in polymer nanocomposites.

Tungsten heavy alloys (W–Ni–Fe) play an important role in various industries because of their excellent mechanical properties, such as the excellent hardness of tungsten, low thermal expansion, corrosion resistance of nickel, and ductility of iron. In tungsten heavy alloys, tungsten nanoparticles allow the relatively low-temperature molding of high-melting-point tungsten and can improve densification. In this study, to improve the densification of tungsten heavy alloy, nanoparticles are manufactured by ultrasonic milling of metal oxide. The physical properties of the metal oxide and the solvent viscosity are selected as the main parameters. When the density is low and the Mohs hardness is high, the particle size distribution is relatively high. When the density is high and the Mohs hardness is low, the particle size distribution is relatively low. Additionally, the average particle size tends to decrease with increasing viscosity. Metal oxides prepared by ultrasonic milling in high-viscosity solvent show an average particle size of less than 300 nm based on the dynamic light scattering and scanning electron microscopy analysis. The effects of the physical properties of the metal oxide and the solvent viscosity on the pulverization are analyzed experimentally.

The wakes behind a square cylinder were simulated using two-equation turbulence models, k-ε and RNG k-ε models. For comparisons between the model predictions and analytical solutions, we employed three skill assessments:, the correlation coefficient for the similarity of the wake shape, the error of maximum velocity difference (EMVD) of the accuracy of wake velocity, and the ratio of drag coefficient (RDC) for the flow patterns as in the authors’ previous study. On the basis of the calculated results, we discussed the feasibility of each model for wake simulation and suggested a suitable value for an eddy viscosity related constant in each turbulence model. The k-ε model underestimated the drag coefficient by over 40 %, and its performance was worse than that in the previous study with one-equation and mixing length models, resulting from the empirical constants in the ε-equation. In the RNG k-ε model experiments, when an eddy viscosity related constant was six times higher than the suggested value, the model results were yielded good predictions compared with the analytical solutions. Then, the values of EMVD and RDC were 3.8 % and 3.2 %, respectively. The results of the turbulence model simulations indicated that the RNG k-ε model results successfully represented wakes behind the square cylinder, and the mean error for all skill assessments was less than 4 %.

본 연구에서는 일반적으로 O/W 에멀젼에 비해 안정화가 어려운 W/O 에멀젼, 특히 유동성이 높은 저점도 W/O 에멀젼의 안정성 증진을 위하여 유화제, 전해질, 유화 안정화제, 겔화제 등을 적용한 다양한 실험을 수행하여 보았다. 그 결과 이번 실험에서는 Polyglyceryl-4 diisostearate/ polyhydroxystearate/sebacate를 주 유화제로 하면서 PEG-30 dipolyhydroxystearate와 Cetyl PEG/PPG-10/1 dimethicone을 보조 유화제로 하는 유화 체계에, 전해질로 Sodium chloride를 0.5 %, 유화 안정화제로 Distearyldimonium chloride를 1 %, 유상 겔화제로 Glyceryl behenate/eicosadioate를 0.5 % 적용한 유화 입자도 작고 조밀하며 점도도 2,000 cps 이하로 일정하게 유지되는 안정한 저점도 W/O 에멀젼을 제조할 수가 있었다. 또한 상기와 같은 에멀젼 베이스에 무기 자외선 차단성분의 적용 실험을 통하여 안정성이 우수한 저점도 플루이드형 자외선 차단제품의 개발 가능성도 긍정적으로 검토 할 수가 있었다.