• 한국정보전자통신기술학회논문지
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• 제11권4호
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• pp.408-413
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• 2018

본 논문은 천일염의 기계화 자동화 생산모델 설계에 필요한 입자크기, 산물밀도, 마찰계수 및 안식각 등 설계인자를 구명하기 위하여 천일염의 함수율 5수준(16.5, 13.2, 8.2, 4.9 및 3.7%,w.b.)에서 실험을 수행하였다. 입자크기는 함수율 3.7%에서 1.98mm이였으며, 함수율 8.2%까지는 감소하는 경향이었고, 이후는 다시 증가하는 경향이었다. 산물밀도는 함수율 3.7%에서 $643.5{\sim}675.3kg/m^3$이었으며, 이후 급격히 증가하여 함수율 4.9 및 8.2%에서 672.3~702.8 및 $705.4{\sim}723.1kg/m^3$으로 나타났다. 산물밀도는 함수율이 증가할수록 증가하는 경향이었으며, 입자의 크기보다는 함수율의 영향이 크게 나타났다. 정지마찰계수의 측정한 결과 재질에 따라 스테인레스에서 0.76~1.04로 가장 높게 나타났고, ABS수지, 아크릴 순으로 낮게 나타났다. 정안식각 측정은 함수율 8.2% 이하에서 거동이 발생하였으며, 함수율이 증가함에 따라 배출 안식각은 증가하고 퇴적 안식각은 감소하는 것으로 나타났다.

• Wind and Structures
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• 제39권3호
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• pp.207-222
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• 2024

This paper presents a numerical simulation method for snow drift that takes into account the cohesion effect of snow particles. The critical state of free collapse accumulation of idealized snow particles is used to indirectly infer the effect of interparticle interactions on snow transport and re-accumulation. With the help of the Hertz-Mindlin with JKR cohesion contact model, the particle angle of repose is calibrated with a number of contact parameters through numerical experiment. The surface energy for a given property of snow particles is determined using the observed snow angle of repose, and a continuous-discrete snow drift two-way coupled numerical model incorporating these optimized contact parameters is developed. The snow redistribution pattern on a stepped flat roof structure is simulated, and the results are found to be consistent with those of the field measured in terms of phenomena and general laws, verifying the achievability and effectiveness of the presented method. To eliminate the influence of environmental conditions, wind tunnel tests are also conducted, and it is found that the reconstructed depth and reaccumulated angle of snowdrift resulting from the numerical simulation are in closer agreement with the experimental results, further confirming the enhancement achieved by introducing the contact effect.

• 한국분말재료학회지
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• 제27권3호
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• pp.241-246
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• 2020

To develop Gastrodia elata (GE)-loaded particles for herbal extract dosage forms, various GE-loaded particles containing dextrin, isomalt, maltodextrin, and silicon dioxide as solidifying carriers in the GE water extract are prepared using the spray drying method. Their physical properties are evaluated using the repose angle, Hausner ratio, Carr's index, weight increase rate at 40℃/75% RH condition, and scanning electron microscopy (SEM). Particles made of dextrin improve the fluidity, compressibility, and water stability. In addition, 2% silicon dioxide increases the fluidity and moisture stability. The best flowability and compressibility of GE-loaded particles are observed with TP, dextrin, and silicon dioxide amounts in the ratio of 6/4/0.2 (34.29 ± 2.86°, 1.48 ± 0.03, and 38.29 ± 2.39%, repose angle, Hausner Ratio, and Carr's index, respectively) and moisture stability with a 2% weight increase rate for 14 h at 40℃/75% RH condition. Therefore, our results suggest that the particles prepared by the spray drying method with dextrin and 2% silicon dioxide can be used as powerful particles to improve the flowability, compressibility, and moisture stability of GE.

• 한국분말재료학회지
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• 제28권3호
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• pp.227-232
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• 2021

The purpose of this study is to optimize the powder formulation and manufacturing conditions for the solidification of an extract of the herb Bangpungtongseong-san (BPTS). To develop BPTS-loaded particles for the tablet dosage form, various BPTS-loaded particles composed of BPTS, dextrin, microcrystalline cellulose (MCC), silicon dioxide, ethanol, and water are prepared using spray-drying and high shear granulation (high-speed mixing). Their physical properties are evaluated using scanning electron microscopy and measurements of the angle of repose, Hausner ratio, Carr's index, hardness, and disintegration time. The optimal BPTS-loaded particles exhibit improved flowability and compressibility. In particular, the BPTS-loaded particles containing silicon dioxide show significantly improved flowability and compressibility (the angle of repose, Hausner ratio, and Carr's index are 35.27 ± 0.58°, 1.18 ± 0.06, and 15.67 ± 1.68%, respectively), hardness (18.97 ± 1.00 KP), and disintegration time (17.60 ± 1.50 min) compared to those without silicon dioxide. Therefore, this study suggests that particles prepared by high-speed mixing can be used to greatly improve the flowability and compressibility of BPTS using MCC and silicon dioxide.

• 터널과지하공간
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• 제22권6호
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• pp.403-411
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• 2012

최근 국내에서는 폐광산 지반보강공사를 실시함에 있어 수압식 충전법을 적용하는 사례가 증가하고 있으나 효율적인 충전법 적용을 위해 현장 특성을 고려한 다양한 연구가 미흡한 실정이다. 본 연구에서는 수압식 충전공법의 충전효율 개선을 위한 선단장치 개발을 위하여 수조 모형실험 및 현장실험을 실시하였다. 수조 모형 실험을 통해 동일조건 하에서 선단장치 노즐각도 및 노즐형태 변화에 따른 충전효율을 평가하고, 이로부터 고안된 선단장치 모델을 현장실험에 적용한 결과, 노즐각 $90^{\circ}$관을 사용한 경우 일반적인 수직관을 사용한 경우에 비해 충전량이 약 18% 증가하는 것을 확인할 수 있었다. 이때 안식각은 $30.82^{\circ}$였다. 현장에서는 일반적으로 안식각을 $40^{\circ}$로 가정하고 충전공 간격을 5m에서 최대 10m 이내로 설계하였지만, 본 연구 결과에 따라 안식각을 $30^{\circ}{\sim}35^{\circ}$로 적용하면 충전공 간격을 최소 10m에서 최대 15m까지 넓히는 것이 가능하여 경제적이고 효율적인 채굴적 충전이 가능할 것으로 기대된다.

• Archives of Pharmacal Research
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• 제2권1호
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• pp.1-8
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• 1979

The flow rate of various sand through circular orifice can be measured from a knowledge of a few easily measurable properties of the system. These are the orifice column and particle diameters, the angle of inclination of the orifice with the horizontal and an angle of repose of the granular sand material. Straight lines were obtained when the logarithm of the flow rate was plotted versus the logarithm of orfice diameter. No influence of excessive compaction and bed height was observed and the flow rate increased with decrease of particle diameter. The profile of flow developed the edge of the aperture in a way independent of its size. Linear relationship was observed between the angle of inclination of the orifice and the flow rate.

• 생태와환경
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• 제44권4호
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• pp.385-395
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• 2011

본 연구는 하천준설 및 골재채취로 인하여 2개의 웅덩이가 직렬로 발생하였을 때, 이동상 실내실험을 수행하여 웅덩이의 적응과정과 응답특성을 분석하였다. 웅덩이의 되메우기 과정은 웅덩이 상류에서 발달한 사주의 영향을 받지만, 웅덩이 하류에서는 웅덩이에서 유사가 포착되어 사주가 발달되지 않았으며, 하상이 지속적으로 저하되었다. 웅덩이의 되메우기가 진행될 때, 웅덩이의 이동속도는 거의 일정하며, 웅덩이의 수중 안식각은 일정하게 유지되었다. 그러나 웅덩이의 되메우기가 거의 완료되면서, 웅덩이의 이동속도는 증가하고, 웅덩이에서 수중 안식각은 작아졌다. 웅덩이와 웅덩이의 이격거리가 증가하면, 2차 웅덩이 하류에서 미부침식이 크게 발생하였다. 또한 웅덩이의 이격거리가 증가할수록 웅덩이의 이동속도는 감소하였다. 이것은 웅덩이가 되메워지는 데 시간이 증가하고, 웅덩이 하류하천에 미치는 영향이 크다는 것을 의미한다. 시간이 증가함에 따라, 무차원 웅덩이의 깊이는 지속적으로 감소하지만, 웅덩이의 이격 거리가 증가할수록, 무차원 웅덩이 깊이는 증가하였다. 그러나 무차원 웅덩이의 길이는 시간이 증가함에 따라서 전체적으로 감소하지만, 웅덩이와 웅덩이의 이격 거리가 증가할수록, 무차원 웅덩이의 길이가 증가하는 경향을 보여주었다.

• Journal of Biosystems Engineering
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• 제40권3호
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• pp.201-211
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• 2015

Purpose: Designing equipment for processing, sorting, and other post-harvest operations of agricultural products requires information about their physical properties. This study was conducted to investigate some of the mechanical and physical properties of Moringa oleifera L. pods and seeds. Methods: Properties such as the length, width, thickness, bulk density, porosity, mass, static coefficient of friction, and angle of repose were determined as a function of moisture content. Statistical data and force-deformation curves obtained at each loading orientation and moisture level were analyzed for bioyield point, bioyield strength, yield force, rupture point, and rupture strength using a testrometric machine. Result: The basic dimensions (length, width, and thickness) of moringa pods and seeds were found to increase linearly from 311.15 to 371.45 mm, 22.79 to 31.22 mm, and 22.24 to 29.88 mm, respectively, in the moisture range of 12 to 49.5% d.b. The coefficient of friction for both pods and seeds increased linearly with an increase in moisture content on all the surfaces used. The highest value was recorded on mild steel, with 0.581 for pods and 0.3533 for seeds, and the lowest on glass for pods, with a value of 0.501, and of 0.2933 for seeds on galvanized steel. The bioyield and rupture forces, bioyield and rupture energies, and deformation of the pods decreased with an increase in moisture content to a minimum value, then increased with further decrease within the moisture content range, while the yield force increased to a maximum value and then decreased as the moisture content increased. Conclusion: These results will help to determine the most suitable conditions for processing, transporting, and storing moringa pods, and to provide relevant data useful in designing handling and processing equipment for the crop.

• Journal of Pharmaceutical Investigation
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• 제33권1호
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• pp.7-14
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• 2003

The PVP-based solid dispersion systems (SDs) containing lovastatin (LOS) and solubilizers (sodium lauryl sulfate, tween 80 and oleic acid) were prepared to enhance dissolution rate of practically water insoluble LOS using solvent evaporation method. Two different organic cosolvents either acetone/ethanol or acetonitrile/ethanol were used for the preparation of SDs. The LOS contents were highly decreased when acetone/ethanol cosolvents were used. The decrease of LOS contents was not caused by acetonitrile or acetone, based on HPLC data. The surface morphology as investigated by scanning electron microscope (SEM) and angle of repose as an index of flowability of SDs were highly dependent on the type and amount of solubilizers used. Based on differential scanning calorimetry (DSC) and X-ray powder diffraction data, the SDs made crystalline LOS into amorphous structure or partially eutectic mixtures. The simultaneous use of the solubilizers in SDs was also useful to increase dissolution rate of LOS in gastric or intestinal fluid. The SDs containing solubilizers reached 76% and 60% in gastric and intestinal fluid, respectively but the commercial tablet gave only less than 4%. These solubilizers in SDs could be also applicable for enhancing dissolution and bioavailability of poorly water-soluble drugs.

• 대한의생명과학회지
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• 제25권2호
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• pp.170-176
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• 2019

The objective of this study was to evaluate the characteristics of the mixtures of choline alphoscerate (alpha-glycerylphosphorylcholine, alpha-GPC), in the liquid form, and sucrose ester, which formed a solid composite. The choline alphoscerate solid composites were prepared using different ratios of sucrose ester, and different preparation methods, such as air drying and rotary evaporation, were compared for their preparation efficacy. We examined the characteristics of the solid composites by using scanning electron microscopy (SEM), angle of repose, and moisture content. The ideal mixing ratio of choline alphoscerate and sucrose ester was determined as 1:3 and air drying was found to be more suitable for the preparation of solid composites than rotary evaporation. SEM measurements of the degree of dispersion and the size of particles indicated that a high-temperature air method was more suitable. These results demonstrated the successful preparation of choline alphoscerate solid composites that have potential for industrial use.