• 상하수도학회지
• /
• 제26권2호
• /
• pp.177-189
• /
• 2012

Sediment load deposited in sewers and manholes reduces not only the capacity of pipes but also the efficiency of the whole sewer system. This causes the inundations of the low places and overflows at manholes, Moreover, sulfides and bad odor can occur due to deposited sediment with organic loads in manholes. Movements of sediment load in manholes are complicated depending on manhole size, location, inside structure, sediment load type, and time. Therefore, it is necessary to understand the movements of sediment load in manholes by experiments. In this study, experiments were implemented by a square manhole with straight path to measure deposited sedimentation quantity. The experimental apparatus was consisted of a high water tank, an upstream tank, test pipes, a sediment supplier, a manhole, and a downstream tank to measure the experimental discharge. The quantity of deposited sediment load was measured by different conditions, such as the inflow condition of sediment(continuous and certain period), the amount of inflow sediment, discharge, and the type of sediment. Jumoonjin sand(S=2.63, D50=0.55mm), general sand(GS, S=2.65, D50=1.83mm) and anthracite (S=1.45, D50=0.80mm) were employed for the experiment. The velocities in inflow pipe were 0.45 m/s, 0.67 m/s, and 0.9 m/s. Sediment load movement and sedimentation quantity in manhole were influenced by many factors such as velocity, shear stress, viscosity, amount of sediment, sediment size, and specific gravity. Suggested regression equations can estimated the quantity of deposited sediment in the straight path square manholes. The connoted equations that were evaluated through the experimental study have velocity range from 0.45 to 0.9m/sec. The study results illustrates that appropriation of design velocity ragne between 1.0 and 2.0m/sec could implement to maintain and manage manholes.

• 한국산학기술학회논문지
• /
• 제18권3호
• /
• pp.545-550
• /
• 2017

대동맥이나 협착된 경동맥에서는 심장수축기에 간헐적으로 난류현상이 발생하고 있으며, 혈액의 점성특성으로 인해 기존 난류모델로는 정확한 해석이 어려운 실정이다. 혈류는 점탄성 유체의 성질을 가지고 있어 유체의 전단 변형률 증가에 따라 점도가 감소하는 점탄성 유체이며, 이러한 점탄성 유체는 난류 유동시 저항 감소 현상이 발생한다. 기존의 난류해석 모델들은 점성변화가 없는 뉴턴 유체에 적합한 모델들이 대부분이기 때문에, 점탄성 유체의 저항 감소 현상을 고려한 비뉴턴 유체 해석에 적합한 난류 모델개발이 필요하다. 본 논문은 난류 모델 가운데 수렴성이 좋고 해석시간이 짧은 표준 $k-{\varepsilon}$ 모델을 기반으로 저항 완충 함수를 이용하여 비뉴턴 유체의 저항감소 현상을 해석할 수 있는 수정된 난류모델을 제시하였으며, 이를 기존 난류모델들과 비교하여 제시된 난류 모델을 검증하였다. 새로 제시된 수정된 난류모델은 벽함수 및 점성저층을 고려하지 않았기 때문에 해석시간이 대폭적으로 감소하였으며, 적은 격자수를 이용하여 효율적으로 비뉴턴 유체의 난류 현상을 해석할 수 있기 때문에 향후 혈류해석 및 점탄성유체 해석에 적용할 예정이다.

• 한국수산과학회지
• /
• 제53권5호
• /
• pp.681-687
• /
• 2020

Physicochemical properties of fucoidan and alginate extracted from Sargassium horneri were investigated. The alginates were extracted and purified via three different routes (CaCl₂, HCl and ethanol routes), and their rheological properties at various concentrations and temperatures were determined. The yield of fucoidan was 3.08%, and it was mainly composed of fucose and galactose. Fourier-transform infrared spectrum of fucoidan showed strong absorption band at 1,254 and 827 cm^-1 corresponding to the sulfate group. Flow behavior of the alginate solution was characterized using the power-law model. The consistency index increased with increasing concentrations. The sodium alginate solution (1.5%) exhibited Newtonian behavior when extracted via the CaCl₂ and HCl routes, while it exhibited pseudoplastic behavior when extracted via the ethanol route. The effect of temperature on the flow behavior was investigated in terms of the activation energy (E_a), which was obtained using the Arrhenius equation. The E_a value corresponding to the alginate solution decreased with increasing shear rates. The E_a values corresponding to the alginate solutions purified via the CaCl₂, HCl, and ethanol routes were 13.54-18.64 kJ/mol, 13.42-19.21 kJ/mol, and 9.51-10.67 kJ/mol, respectively. The low E_a values corresponding to the solutions extracted via the ethanol route suggest that the flow behavior does not depend significantly on temperature.

• 보존과학회지
• /
• 제26권2호
• /
• pp.183-190
• /
• 2010

무황변 가역성 도자기 복원 재료를 위하여 우레탄을 제조하여 이용하였다. 이 저점도형 우레탄은 사용자가 강도 조절이 가능하도록 제조하였다. 이 우레탄 복원재는 매우 강한 접착 강도와 전단 강도를 나타내고 있으며, 그간 일반적으로 사용되어온 에폭시 복원재와 같은 충진성, 수축성, 도색성을 갖도록 제조되었다. 특히, 현재 일반적으로 사용되는 에폭시계 복원재의 문제점인 황변 현상과 비가역성 문제를 해결함으로서, 도자기의 복원의 항구성과 지속적인 안정성을 부여할 수 있을 것으로 보인다. 또 본 우래탄 복원재를 이용하여 도자기를 직접 적용 복원하였으며 복원 후, 이를 재 용해하여 복원제를 완벽히 제거하는 과정을 통하여 복원의 가역성도 보이고자 하였다.

• 한국염색가공학회지
• /
• 제28권3호
• /
• pp.125-133
• /
• 2016

In this study, efforts were made to enhance the mechanical properties of the poly(vinyl alcohol) (PVA) fibers of medium molecular weight(number-average degree of polymerization=1735) varying the ratio in $DMSO/H_2O$ mixed solvent and spinning/drawing conditions. The gel fibers prepared from pure DMSO were opaquely frozen in the coagulating bath of $-20^{\circ}C$. However, transparent gel fibers were formed without freezing for the mixture to contain water less than 80wt%. As the amount of water in the mixture increased the residual solvent in the coagulated gel fibers decreased ranging from 85 to 42wt%. The complex viscosity increased with increasing PVA concentration in 80/20 $DMSO/H_2O$ exhibiting remarkable shear thinning at 18wt%. In the Cole-Cole plot, the 18wt% PVA solutions gave a deviated curve from 12 and 15wt% ones. Thus the optimum PVA concentration for the spinning processing of medium MW PVA solutions in 80/20 $DMSO/H_2O$ was determined to 18wt% with rheological concept. Low degree of drawing during hot drawing process in the dry state was available for high bath draft in the coagulation bath. The most improved mechanical properties were observed by applying the highest possible draw ratio attained by reducing bath draft over multi-step drawing process. In the given bath draft, linear relationship was observed between both tensile strength and modulus and draw ratio showing the inflection points at the draw ratio of 19.5 and 18.0 for tensile strength and modulus, respectively.

• Advanced Composite Materials
• /
• 제17권3호
• /
• pp.277-299
• /
• 2008

High quality and expedient processing repair methods are necessary to enhance the service life of bridge structures. Deterioration of concrete can occur as a result of structural cracks, corrosion of reinforcement, and freeze.thaw cycles. Cost effective methods with potential for field implementation are necessary to address the issue of the vulnerability of bridge structures and how to repair them. Most infrastructure related applications of fiber-reinforced plastics (FRPs) use traditional hand lay-up technology. The hand lay-up is tedious, labor-intensive and relies upon personnel skill level. An alternative to traditional hand lay-up of FRP for infrastructure applications is Vacuum Assisted Resin Transfer Molding (VARTM). VARTM uses single sided molding technology to infuse resin over fabrics wrapping large structures, such as bridge girders and columns. There is no work currently available in understanding the interface developed, when VARTM processing is adopted to wrap fibers such as carbon and/or glass over concrete structures. This paper investigates the interface formed by carbon fiber processed on to a concrete surface using the VARTM technique. Various surface treatments, including sandblasting, were performed to study the pull-off tensile test to find a potential prepared surface. A single-lap shear test was used to study the bond strength of CFRP fabric/epoxy composite adhered to concrete. Carbon fiber wraps incorporating Sikadur HEX 103C and low viscosity epoxy resin Sikadur 300 were considered in VARTM processing of concrete specimens.

• 한국재료학회지
• /
• 제31권9호
• /
• pp.532-538
• /
• 2021

In this study, a spray dryer is used to make granules of Y₂O₃ and YF₃, and then Y₅O₄F₇ is synthesized following heat treatment of them under Ar gas atmosphere at 600 ℃. Single and binary monomer mixtures are compared and analyzed to optimize photocurable monomer system for DLP 3D printing. The mixture of HEA and TMPTA at 8:2 ratio exhibits the highest photocuring properties and low viscosity with shear thinning behavior. The optimized photocurable monomer and synthesized Y₅O₄F₇ are therefore mixed and applied to printing process at variable solid contents (60, 70, 80, & 85 wt.%) and light exposure times. Under optimal light exposure conditions (initial exposure time: 1.2 s, basic exposure time: 5 s), YOF composites at 60, 70 & 80 wt.% solid contents are successfully printed. As a result of measuring the size of the printed samples compared to the dimensions of the designed bar type specimen, the deviation is found to increase as the YOF solid content increases. This shows that it is necessary to maximize the photocuring activity of the monomer system and to optimize the exposure time when printing using a high-solids ceramic slurry.

• 산업식품공학
• /
• 제13권4호
• /
• pp.341-347
• /
• 2009

다양한 식품군을 동결건조 또는 저온에서 건조하여 분말화한 생식은 물과 혼합 시 분산성이 저조하고 섭취방법이 불편하여 생식 소비 및 시장 확대에 제약이 있다. 생식의 섭취를 편의화하기 위하여 음료 타입의 생식을 개발하고자 생식 3종(BS, ES, SS)을 음료로 제조하여 품질을 비교하였다. 생식음료의 이화학적 특성과 관능적 특성을 조사한 결과 BS의 기호도가 가장 높았으며, 생식첨가량은 7.7%에서 기호도가 가장 우수하였다. 생식 BS를 사용한 음료의 경우 생식 함량이 증가함에 따라 점조도는 증가하였으며 함량 5.7% 이하의 음료는 팽창유체 양상을 보이다가 7.7%와 9.7%에서는 뉴튼유체와 유사한 특성을 나타내었고 11.7%에서는 뚜렷한 의가소성을 보였다. 생식음료 점조도의 시간의존성은 생식함량 5.7-9.7% 사이에서는 레오펙틱형 시간의존성이 관찰되었으나 3.7%와 11.7%에서는 시간독립적이었다.

• 한국조리학회지
• /
• 제9권4호
• /
• pp.123-135
• /
• 2003

본 연구는 도살한 후 식용 부위를 제거하고 폐기되는 닭발을 이용하고자 닭발껍질에서 식품 소재인 gelatin을 추출하였다. 샐러드 드레싱의 물성 및 기호성 증진을 위해 닭발껍질에서 추출한 gelatin을 첨가하여 가공적성실험을 하였다. 결과는 다음과 같다. \circled1Gelatin - 한천용액으로 제조한 드레싱의 관능평가 결과에서 gelatin용액에 대한 조림간장의 함량이 10%인 것이 관능적으로 우수한 결과를 나타냈다. 겨자 마요네즈 드레싱은 마요네즈 함량이 낮을수록(10% 이하) 선호도가 좋아 마요네즈 첨가량이 적은 것이 바람직한 것으로 판단되었다. 참깨 드레싱은 gelatin 용액에 대한 참깨의 함량이 15%일 때 기호도가 높은 것으로 나타났다. \circled245$^{\circ}C$에서 전단속도에 따른 전단 응력을 관찰한 결과, 간장 드레싱의 점도는 조림간장의 첨가량이 증가할수록 처리구간 유의적인 감소를 나타냈고, 겨자 마요네즈 드레싱의 경우는 마요네즈 첨가량이 증가할수록 점도도 증가하는 것으로 나타났다. 참깨 드레싱도 역시 첨가량이 증가할수록 점도의 증가를 나타냈다. \circled3Gelatin의 첨가량을 달리하여 제조한 드레싱의 점도는 gelatin의 첨가량이 증가할수록 모든 시험구에서 유의적인 증가를 나타냈다. 마요네즈드레싱과 참깨 드레싱에서 gelatin첨가에 의한 혼탁도의 감소가 관찰되었다. 색도 측정 결과 gelatin첨가량에 따른 모든 처리구에서 유의적인 차이를 나타내지 않았다. \circled4Gelatin의 함량을 달리한 드레싱의 관능평가 결과, 전반적인 기호도는 gelatin-한천 용액은 2%의 gelatin과 0.5%의 한천을 함유한 것이 가장 우수한 것으로 나타났다.(Table 5). 이상의 결과들을 종합해 볼 때 닭발껍질로부터 추출한gelatin의 첨가는 물성학적, 관능적으로 더 우수한 것으로 나타나 새로운 소재로서 닭발껍질의 이용 가능성이 매우 크다고 판단된다. 또한gelatin을 이용한 드레싱의 개발은 한층 더 산업화의 일조를 할 수 있을 것으로 기대가 된다.

• 한국도로학회논문집
• /
• 제20권1호
• /
• pp.47-58
• /
• 2018

PURPOSES : The purpose of this study is to evaluate the mechanical properties of a cold-recycling asphalt mixture used as a base layer and to determine the optimum emulsified-asphalt content for ensuring the mixture's performance. METHODS : The physical properties (storage stability, mixability, and workability) of three types of asphalt emulsion (CMS-1h, CSS-1h, and CSS-1hp) were evaluated using the rotational viscosity test. Asphalt emulsion residues, prepared according to the ASTM D 7497-09 standard, were evaluated for their rheological properties, including the $G*/sin{\delta}$and the dynamic shear modulus (${\mid}G*{\mid}$). In addition, the Marshall stability, indirect tensile strength, and tensile-strength ratio (TSR) were evaluated for the cold-recycling asphalt mixtures fabricated according to the type and contents of the emulsified asphalt. RESULTS : The CSS-1hp was found to be superior to the other two types in terms of storage stability, mixability, and workability, and its $G*/sin{\delta}$ value at high temperatures was higher than that of the other two types. From the dynamic shear modulus test, the CSS-1hp was also found to be superior to the other two types, with respect to low-temperature cracking and rutting resistance. The mixture test indicated that the indirect tensile strength and TSR increased with the increasing emulsified-asphalt content. However, the mixtures with one-percent emulsified-asphalt content did not meet the national specification in terms of the aggregate coverage (over 50%) and the indirect tensile strength (more than 0.4 MPa). CONCLUSIONS : The emulsified-asphalt performance varied greatly, depending on the type of base material and modifying additives; therefore, it is considered that this will have a great effect on the performance of the cold-recycling asphalt pavement. As the emulsified-asphalt content increased, the strength change was significant. Therefore, it is desirable to apply the strength properties as a factor for determining the optimum emulsified-asphalt content in the mix design. The 1% emulsified-asphalt content did not satisfy the strength and aggregate coverage criteria suggested by national standards. Therefore, the minimum emulsified-asphalt content should be specified to secure the performance.