• Korea-Australia Rheology Journal
• /
• 제16권3호
• /
• pp.135-140
• /
• 2004

Morphological and rheological properties of the poly(methyl methacrylate) (PMMA) and polystyrene (PS) blends were studied by scanning electron microscopy (SEM) and advanced rheometric expansion system (ARES). From the SEM results, the PMMA-PS blends showed dispersed morphology and the particle size of the dispersed phase was quite small (0.1~0.6 $\mu\textrm{m}$ compared with other immiscible polymer blends. Values of the interfacial tension of the PMMA-PS blend were obtained from the Choi-Schowalter and the Palierne emulsion models using the storage modulus of the PMMA and PS, and found to be 1.0 and 2.0 mN/m, respectively. The interfacial tension between the PMMA and PS was also calculated from the Flory-Huggins polymer-polymer interaction parameter ($\chi$) and found to be from 0.98 to 1.86 mN/m depending on the molecular weight and composition. Comparing the values of the interfacial tension from the Flory-Huggins polymer-polymer interaction parameter and the values measured by oscillatory rheometer, it is suggested that the interfacial tension of the PMMA-PS blend obtained from the polymer-polymer interaction parameter are in good agreement with the values obtained by rheological measurements.

• Archives of Pharmacal Research
• /
• 제9권3호
• /
• pp.145-152
• /
• 1986

Magnetically reponsive gelatin microspheres for the targeting of drugs have been prepared using a water-in-oil emulsion technique with chemical cross-linking of the protein. The manufacturing variables affecting microsphere size, size distribution and surface characteristics have been examined as well as the magnetic responsiveness in vitro. Sesame oil was utilized for non-aqueous phase and magentic gelatin microspheres of different size from 1. 89 to 14.88 $\mu\textrm{m}$ in mean diameter could be obtained with variation of HLB values of non-ionic surfactants. The content of magnetite which uniformly distributed throughout the microspheres was 26.7% (w/w). It was possible to control the localization of magnetic gelatin microspheres at specific sites within capilary models by using external magnetic field of under 5K gauss.

• Membrane and Water Treatment
• /
• 제1권4호
• /
• pp.297-316
• /
• 2010

Membrane fouling is one of the major operational concerns of membrane processes which results in loss of productivity. This paper investigates the ultrafiltration (UF) results of synthetic oil-in-water (o/w) emulsion using flat sheets of polysulfone (PSf) membrane synthesized with four different compositions. The aim is to identify the mechanisms responsible for the observed permeate flux reduction with time for different PSf membranes. The experiments were carried out at four transmembrane pressures i.e., 68.9 kPa, 103.4 kPa, 137.9 kPa and 172.4 kPa. Three initial oil concentrations i.e., 75 $mgL^{-1}$, 100 $mgL^{-1}$ and 200 $mgL^{-1}$ were considered. The resistance-in-series (RIS) model was applied to interpret the data and on that basis, the individual resistances were evaluated. The significances of these resistances were studied in relation to parameters, namely, transmembrane pressure and initial oil concentration. The total resistance to permeate flow is found to increase with increase in both transmembrane pressure and initial oil concentration while for higher oil concentration, resistance due to concentration polarization is found to be the prevailing resistance. The applicability of the constant pressure filtration models to the experimental data was also tested to explain the blocking process. The study shows that intermediate pore blocking is the dominant mechanism at the initial period of UF while in the later period, the fouling process is found to approach cake filtration like mechanism. However, the duration of pore blocking mechanism is different for different membranes depending on their morphological and permeation properties.

• 터널과지하공간
• /
• 제31권6호
• /
• pp.508-519
• /
• 2021

본 연구에서는 발파 시 사람과 주변 환경에 영향을 끼치는 발파진동(peak particle velocity, PPV)을 예측하는 모델을 개발하였다. PPV를 예측하기 위해 kNN(k-nearest neighbors), CART(classification and regression tree), SVR(support vector regression), PSO(particle swarm optimization)-SVR 알고리즘을 이용한 4가지 머신러닝 모델을 개발하고 상호 비교하였다. 머신러닝 모델을 훈련하기 위해 경상남도 창원시에 있는 욕망산을 연구지역으로 선정하고 1048개의 발파 데이터를 획득하였다. 발파 데이터는 천공장, 저항선, 공간격, 최대지발장약량, 비장약량, 총공수, 에멀전비율, 이격거리, PPV로 구성되었다. 훈련된 모델들의 성능을 평가하기 위한 지표 값으로 MAE(mean absolute error), MSE(mean squared error), RMSE(root mean squared error)를 사용하였다. 평가결과 PSO-SVR 모델이 MAE, MSE, RMSE가 각각 0.0348, 0.0021, 0.0458으로 가장 우수한 예측 성능을 나타냈다. 마지막으로 개발된 머신러닝 모델을 이용하여 주변 환경에 영향을 끼치는 정도를 예측하는 방법을 제시하였다.

• 한국염색가공학회지
• /
• 제34권4호
• /
• pp.250-260
• /
• 2022

In this research, a high-elasticity acrylic emulsion binder with core-shell polymerization and self-crosslinking system is mixed with a flame-retardant water-dispersed polyurethane (PUD) binder. In addition, finite element analysis was conducted through virtual engineering software ANSYS by applying three representative nonlinear material models. The most suitable nonlinear material model was selected after the relative comparison between the actual experimental values and the predicted values of the properties derived from simulations. The selected nonlinear material model is intended to be used as a nonlinear material model for computational simulation analysis that simulates the experimental environment of the vibration test (ASTM E1399) and the actual fire safety test (ASTM E1966). When the mass fraction of thermally expandable graphite was 0.7%, the thermal and physical properties were the best. Among the nonlinear material models, the simulation result of the Ogden model showed the closest value to the actual result.

• 멤브레인
• /
• 제8권4호
• /
• pp.203-209
• /
• 1998

에멀젼형 절삭유(Caltex, Trusol) 수용액을 공칭 세공크기가 0.22 $\mu$m 인 Millipore사의 GVHP 막과 0.2$\mu$m인 SUS 관형막(Mott 사)이 설치된 dead-end 및 십자형흐름 정밀여과 시스템으로 각각 분리하였다. 오일입자의 분포는 0.07 내지 0.22$\mu$m의 분포이었다. 투과유속을 예측하기 위하여 cake 여과모델 (CFM)과 standard pore blocking 모델(SPBM)을 적용하였다. Dead-end 시스템에서 0.01 vol% 절삭유 수용액을 400 rpm으로 교반시켜 투과시킬 경우, 100 kPa 이하에서는 CFM 이 투과유곡을 잘 나타내었으나, 150 kPa 이상에서는 SPBM을 적용할 수 있었다. 운전압력을 60에서 200 kPa로 갑자기 증가시키면 분리막 표면에 형성된 오일층이 파괴되고, 다시 60 kPa로 감소시킬 때 반복하여 오일층이 형성됨을 알 수 있었다. 투과기구가 CFM에서 SPBM 으로 전환되는 이른바 임계압력을 추정하였으며, dead-end system에서는 약 100 kPa이었다. Reynolds 수가 7080인 십자형흐름 시스템에서 농도를 0.01에서 0.03 vol%로 증가시키면 입계압력이 약 100에서 150 kPa로 증가하였다.

• 화약ㆍ발파
• /
• 제34권4호
• /
• pp.10-18
• /
• 2016

화약 발파는 물질이 연소할 때 발생하는 에너지를 파괴 동력으로 이용한다. 화약은 흑색화약으로부터 강력한 위력을 가진 다이너마이트에 이어 취급의 안정성도 향상시킨 에멀션 폭약의 개발에까지 이르고 있으며, 또한 뇌관과 같은 화공품도 공업뇌관과 도화선으로부터 전기 뇌관, 비전기 뇌관에 이어 초정밀 시차를 제어할 수 있는 전자뇌관의 개발에까지 발전되어 왔다. 그러나 아무리 성능이 우수한 화약과 뇌관을 사용한다고 하더라도 좋은 발파 결과를 얻을 수 있는 것은 아니다. 실제 현장의 다양한 조건을 어떻게 고려하여 설계 및 시공에 활용할 것인가는 전적으로 발파기술자의 손에 달려 있다. 암반을 대상으로 하는 발파는 많은 미지의 영향 변수들 때문에 실제 현장에서의 경험에 기초한 접근 방법이 매우 중요하다. 또한 현장에서의 관찰 결과를 분석하고 실험을 통해 정량화된 경험적 모델을 도출하거나, 이론적 근거를 정립하여 이론적 모델로 발전시키는 것은 발파 설계에의 활용뿐만 아니라 새로운 기술개발에 대한 아이디어를 제공한다는 측면에서도 필요하다. 본 논문에서는 발파 분야에서 개발된 몇 가지 경험적 모델과 이론적 모델들을 통해 활용 시 주의해야 할 사항들이 고찰되었다.

• 한국조리학회지
• /
• 제23권7호
• /
• pp.20-30
• /
• 2017

This study was conducted for the optimization of ingredients in salad dressing using Hwangdo peach (Prunus persica L. Batsch). The experiment was designed according to the D-optimal design of mixture design, which included 14 experimental points with 4 replicates for three independent variables (olive oil 40~65%, peach puree 27~50%, vinegar 8~20%). The linear regression models for pH, viscosity and color value and the quadratic regression models for emulsion stability, all sensory evaluation of the products were proven to be valid by the F-test for the overall significance of the regression model at a 5% level. Viscosity and pH of the products increased as olive oil content. Color value, viscosity and pH of the products increased as peach puree content. pH, viscosity, redness, and yellowness of the products decreased as vinegar content. Sensory evaluation result of the products showed that general preference for the products were increasingly affected by the increases in contents then decreased as they exceeded the optimum levels. In consequence, according to result from the first stage of the experiment, the optimum ingredients ratios of the raw materials were set in olive oil 52.43%, peach puree 35.07%, and vinegar 13.91% for ingredients of apricot dressing. These results provided the possibility that peach can be applied to the preparation of a dressing, and thereby present baseline data for the development of new dressings. This is also presumed to meet demands of customers who are always in pursuit of new products.

• 한국축산식품학회지
• /
• 제42권3호
• /
• pp.536-555
• /
• 2022

The most abundant Orthoptera in Mexico is a small grasshopper (Sphenarium purpurascens) which is considered a food source with increased nutritional value due to its high protein content. Insect proteins have gained relevance because of their high potential as gelling, texturing, and extender agents in the food industry. The objective of this study was to evaluate the effect of substituting meat with a soluble protein extract from grasshopper obtained by alkalisation or alkalisation-piezoelectric ultrasound, on the techno-functional, physicochemical, and sensory characteristics of cooked meat models (sausages). The soluble protein was extracted in NaHCO₃ pH 8 and a piezoelectric ultrasound 5-mm sonotrode at 20 kHz with 99% amplitude. Different formulations with meat substitution: 0%, 5%, 10%, and 15% were prepared and characterised for their rheological behaviour, emulsion stability, weight loss by cooking, total protein content, colour, and texture. Sensory evaluation was conducted with consumers using a test involving check-all-that-apply and overall liking. The alkalisation-piezoelectric ultrasound method improved the solubility and the techno-functional properties of the soluble grasshopper protein when applied in sausages at maximum levels of 10% meat substitution. The sensory evaluation indicated that the formulation with 5% meat substitution exhibited the same acceptability as the control sample. Given these results, the soluble protein treated with alkalisation and piezoelectric ultrasound could be used as an extender in meat products.

• 접착 및 계면
• /
• 제5권2호
• /
• pp.31-42
• /
• 2004

Many animals possess on their legs adhesive pads, which have undergone evolutionary optimization to be able to attach to variable substrates and to control adhesive forces during locomotion. Insect adhesive pads are either relatively smooth or densely covered with specialized adhesive hairs. Theoretical models predict that adhesion can be increased by splitting the contact zone into many microscopic, elastic subunits, which provides a functional explanation for the widespread 'hairy' design. In many hairy and all smooth attachment systems, the adhesive contact is mediated by a thin film of liquid secretion between the cuticle and the substrate. By using interference reflection microscopy (IRM), the thickness and viscosity of the secretion film was estimated in Weaver ants (Oecophylla smaragdina). 'Footprint' droplets deposited on glass are hydrophobic and form low contact angles. IRM of insect pads in contact showed that the adhesive liquid is an emulsion consisting of hydrophilic, volatile droplets dispersed in a persistent, hydrophobic phase. I tested predictions derived from film thickness and viscosity by measuring friction forces of Weaver ants on a smooth substrate. The measured friction forces were much greater than expected assuming a homogenous film between the pad and the surface. The findings indicate that the rubbery pad cuticle directly interacts with the substrate. To achieve intimate contact between the cuticle and the surface, secretion must drain away, which may be facilitated by microfolds on the surface of smooth insect pads. I propose a combined wet adhesion/rubber friction model of insect surface attachment that explains both the presence of a significant static friction component and the velocity-dependence of sliding friction.