• Journal of Pharmaceutical Investigation
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• 제36권1호
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• pp.31-38
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• 2006

Using a Rheometries Dynamic Analyzer (RDA II), the dynamic viscoelastic properties of a semi-solid ointment base (vaseline) in large amplitude oscillatory shear flow fields were measured over a temperature range of $25{\sim}45^{\circ}C$ and the linear viscoelastic behavior in small amplitude oscillatory shear flow fields was investigated over a wide range of angular frequencies. In this article, the nonlinear viscoelastic behavior was reported from the experimentally obtained data and the effect of temperature on this behavior was discussed in detail. In addition, the angular frequency and temperature dependencies of a linear viscoelastic behavior were explained. Finally, the applicability of a time-temperature superposition principle originally developed for polymeric materials was examined using a shift factor. Main results obtained from this study can be summarized as follows : (1) At very small strain amplitude region, vaseline shows a linear viscoelastic behavior independent of the imposed deformation magnitudes. Above a critical strain amplitude $({\gamma}_{0}=0.1{\sim}0.2%)$, however, vaseline exhibits a nonlinear viscoelastic behavior ; indicating that both the storage modulus and dynamic viscosity are sharply decreased with increasing deformation magnitude. (2) In large amplitude oscillatory shear flow fields, an elastic behavior (storage modulus) has a stronger strain amplitude dependence and begins to show a nonlinear behavior at a smaller strain amplitude region than does a viscous behavior (dynamic viscosity). (3) In small amplitude oscillatory shear flow fields, the storage modulus as well as the loss modulus are continuously increased as an increase in angular frequency and an elastic nature is always superior to a viscous behavior over a wide range of angular frequencies. (4) A time-temperature superposition principle can successfully be applicable to vaseline. This finding allows us to estimate the dynamic viscoelastic behavior of vaseline over an extraordinarily extended range (11 decades) of angular frequencies inaccessible from the experimentally measured range (4 decades).

• 대한기계학회논문집
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• 제17권6호
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• pp.1584-1595
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• 1993

본 연구에서는 Re수가 40이하의 정상 층류유동에서 온도가 실린더와 자유유동 사이의 열전달계수에 미치는 영향을 수치해석적으로 연구하였다. 유체의 온도 Ta를 200~900K, 실린더의 온도Tw를 300~900K의 범위에서 Tm/Ta를 0.67~2.75까지 변화시 키며 계산을 수행하였다. 수치계산 결과를 분석하여 실험적으로 관찰하기 어려운 불성치의 변화가 열전달에 미치는 영향을 검토하고, 아울러 실린더가 자유유동에 의해서 냉각되는 경우 뿐만 아니라 가열되는 경우의 연구도 병행하였고, 두가지 경우 에 모두 적용할 수 있는 열전달관계식을 구하였다. 본 연구에서는 Gr/$Re^2$=0 이고 복사에 의한 열전달량은 강제대류에 의한 열전달량의 1%이하이므로 자연대류 및 복사열 전달의 효과는 무시하였다.

• 한국진공학회지
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• 제16권4호
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• pp.298-304
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• 2007

rf 플라즈마 소스가 장착된 분자선 에피택시 장비를 이용하여 Si(111) 기판위에 GaN 나노로드를 성장할 때, N2의 흐름양을 조절하여 나노로드의 구조 및 광학적인 특성을 조사하였다. $N_2$의 양이 1.1sccm에서 2.0sccm으로 변할 때 육각형 모양의 나노로드가 성장되었으며, 평균 직경이 80nm에서 190nm 까지 변화 하였다. 그러나 나노로드와 compact한 영역의 길이 (두께)비는 $N_2$의 양이 1.7sccm 까지는 증가하지만 그 이상에서는 변화지 않았다. PL 측정으로부터, $N_2$의 양이 적은 나노로드에서 자유 엑시톤의 피이크가 더욱 뚜렷하게 관측되었고, 모든 PL 피이크의 위치는 직경이 적을수록 나노로드의 크기 효과에 의해서 고에너지 쪽으로 이동하였다. $N_2$의 양이 1.7sccm 인 시료에서는 온도에 따른 PL의 피이크의 위치가 온도가 증가함에 따라서 "S-형"의 거동을 나타내었다.

• 분석과학
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• 제30권1호
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• pp.1-9
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• 2017

Starch is a mixture of amylose (AMY) and amylopectin (AMP) which are different in physical properties such as molar mass (M), rms radius ($R_g$) and hydrodynamic diameter ($d_H$). The rheological and functional properties of starch are influenced by various factors including the molecular size, molar mass distribution (MD) and the concentration ratio of AMY and AMP. It is also important to analyze proteinaceous material in starch as they affect the flavor and texture of food to which starch is added. In this study, asymmetrical flow field-flow fractionation (AF4) was employed for separation and quantitation of AMY and AMP in starches (Amaranth, potato, taros and quinoa). AF4 was coupled with a multi-angle light scattering (MALS) and a refractive index (RI) detector for determination of the absolute M, MD and molecular structure. It was found that AMP has the M and $R_g$ ranging $3.7{\times}10^7{\sim}6.5{\times}10^8g/mol$ and 84 ~ 250 nm, respectively. Also the existence of branch was confirmed in higher M. In addition, proteinaceous material in starch was analyzed by AF4 coupled with a fluorescence detector (FS) after fluorescence-labeling. AF4-FS with fluorescence-labelling showed a potential for investigation on existence of proteinaceous material and the interaction between proteinaceous material and polysaccharide in starch.

• Elastomers and Composites
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• 제44권2호
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• pp.156-163
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• 2009

사출성형 시 흐름자국이 생기지 않는 흐름성이 향상된 PP(Polypropylene) 복합재료를 제조하기 위한 연구를 진행하였다. PP는 분자량 분포와 용융지수(MI)가 다른 4종류의 PP를 사용하였으며, PP, 탈크, 고무와 약간의 첨가제로 구성된 PP컴파운드의 유변학적 특성은 Spiral Flow(SF), MI, 전단점도를 측정함으로써 평가하였다. 분자량 분포가 넓은 PP를 사용한 경우 MI가 상대적으로 낮다 하더라도 SF는 MI가 높은 PP보다 높게 관찰되는 경우도 있었다. 사출성형시 표면에 흐름자국이 발생하지 않도록 하기 위해서는 분자량 분포가 넓은 PP를 사용하는 것이 바람직 함을 확인하였다.

• 한국세라믹학회지
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• 제38권11호
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• pp.1037-1041
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• 2001

저온(32$0^{\circ}C$)에서 SiH$_4$와 $N_2$O 가스의 혼합을 통해 플라즈마화학기상증착(PECVD)법을 이용하여 실리카 광도파로의 클래딩막으로 사용되는 SiO$_2$후막을 제조하였다. 증착변수가 SiO$_2$후막의 특성에 미치는 영향을 살펴보기 위해 $N_2$O/SiH$_4$flow ratio와 RF power에 변화를 주었다. $N_2$O/SiH$_4$ flow ratio가 감소함에 따라 증착속도는 2.9 $mu extrm{m}$/h), 굴절률은 thermal oxide의 굴절률(n=1.46)에 근접하였다.

• 한국건축시공학회지
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• 제12권1호
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• pp.22-30
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• 2012

Four types of foaming agents, including Alcohol Ethoxy Sulfate (AES), Alpha Olefin Sulfonate (AOS), Vegetable Soap (VS), and Fe-Protein (FP), are widely used in the construction field. These have different surface tensions and viscosities in water of the same concentration, affecting the flow speed of liquid, size and distribution of foam, and foam stability. However, there is a lack of data regarding the properties of foam concrete using various foam agents. The purpose of this study is to investigate influence of foaming agents on the properties of foamed concretes with various densities. We find that the foaming agent type has little effect on the density, compressive strength, and thermal conductivity of foam concrete, but considerably affects the unit weight of foam, flow and flexural strength of foamed concrete. While almost all properties of foam concrete are affected by density in fresh or hardened state, the potential energy changed by slurry density and the viscosity of foam are dominant factors in the flowability of foam slurry.

• Computers and Concrete
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• 제20권3호
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• pp.283-290
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• 2017

The aim of this study is to investigate the effect of the bond strength of self-compacting mortars (SCMS) produced from ground pumice powder (GPP) as a mineral additive. In this scope, six series of mortars including control mix were prepared that consist of 7%, 12%, 17%, 22% and 27% of ground pumice powder by weight of cement. A total of 54 specimens of $40{\times}40{\times}160mm$ were produced and cured at the age of 3, 28 and 90-day for compressive and tensile strength tests and 18 specimens of $150{\times}150{\times}150mm$ mortar were prepared and cured at 28 days for bond strength tests. Flexural tensile strength and compressive strength of $40{\times}40{\times}160mm$ specimens were measured at the curing age of 7, 28 and 90-day. Mini V-funnel flow time and mini slump flow diameter tests were also conducted to obtain rheological properties. As a result of the study, it was observed that the SCMs containing 12% of GPP has the highest bond strength as compared to control and GPP mortars. Compressive strength slightly increased up to 12% of GPP.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.260-261
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• 2008

In this study, we investigated the properties of Indium Zinc Oxide (IZO) films prepared in facing targets sputtering (FTS) system at room temperature as function of oxygen contents. As as-deposited films were rapidly thermal annealing on air atmosphere of $400^{\circ}C$ for 30s. As a result, the transmittance of IZO films increased with increasing oxygen flow in the visible range. After rapidly thermal annealing to films, the optical properties of films improved than films deposited at R.T, but the electrical properties decreased. Before RTA treatment, the lowest resistivity IZO is $5.4\times10^{-4}[\Omega{\cdot}cm]$ at oxygen gas flow. But, after RTA treatment, IZO films have the value of lowest resistivity at the lower oxygen gas ratio in compare with before RTA treatment. The resistivity of IZO films is $7.29\times10^{-4}[\Omega{\cdot}cm]$ at pure argon atmosphere.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.284-287
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• 2005

The flow of groundwater in fractured medium is related to the geometric characteristics of the fracture system. And a fracture aperture and a fracture density are considered as important factor concerning the permeability. Data acquisition of the properties of fracture such as aperture and density is so difficult and has uncertainty. We also cannot know the fracture characteristics through the in-situ tests. We usually obtain the fracture information from a ultrasonic scan logging or borehole television indirectly. Using the deduced results, we can make the fracture system and simulate the groundwater flow and solute transport in the crystalline rock. This study aimed to analyze the correlation between the properties of fracture and hydraulic conductivities obtained at the same interval. The properties of fracture are examined by acoustic televiwer and hydraulic conductivities are obtained by constant Pressure injection test. The distributioin of fracture width and fracture frequency shows the log-normal probability plot. And, Results of correlation analysis explain that opened type fractures have proper relation with hydraulic conductivity. But, as though there are semi-opened type fractures or closed type fractures, those have the permeable structure.