• 한국물환경학회지
• /
• 제20권4호
• /
• pp.313-320
• /
• 2004

In this study, variable characteristics of drinking water and the influences on underground water reservoirs, rooftop water tanks, and service water pipes in the building were assessed. The influence of underground water reservoir material and water capacity on water quality also were assessed. The results are the following as; First of all, the drinking water passing through underground water reservoirs or service water pipes in the building, averagely metal component concentration more increased from percent of 41.3 to percent of 74.2 totally than other items of water quality. On the other hand, both residual chlorine and total solid highly decreased 65.6 percent and 35.3 percent, respectively. Therefore, it was thought that water quality could be getting worse for microorganism re-growth by residual chlorine reduction, and total solid also could be a cause for extraneous matters accumulated in water reservoir. Secondly, the variations on water quality of each stage for water supply system in the building were higher in water service pipes connected from rooftop water tanks to the tap than in underground water reservoirs. In addition to, among of twelve items on water quality, ten items on water quality except dissolved oxygen and residual chlorine increased. Therefore, it was thought that the influence of water service pipes connected from rooftop water tanks to the tap on water quality were higher than other stages of water supply system in the building. Thirdly, in case of materials of underground water reservoir, it was likely that the variation on water quality by stainless steel and concrete materials got some similar. In case of water capacity, the variations on water quality of underground water reservoirs over $1,000m^3$ higher than those under $1,000m^3$. That reasons was likely that the retention time(49.72 hours averagely) of underground water reservoirs over $1,000m^3$ was two times longer than it of those under $1,000m^3$(23.37 hours). Therefore, it was thought that the influence on water quality by materials were some similar, but in case of water capacity, the influence of underground water reservoirs were higher.

• 한국식품조리과학회지
• /
• 제17권4호
• /
• pp.316-322
• /
• 2001

본 연구에서는 보교조생 딸기의 최적조건의 배합 비(딸기 중량의 설탕 50%와 프락토올리고당 50%)에 딸기 중량의 10, 20, 30, 40%를 양파로 대체하여 제조한 딸기잼의 수분, pH, 색도, 총산도, 퍼짐성, 가용성 고형물 함량, 환원당 함량, 안토시아닌 잔존율 및 관능검사를 실시하여 그 품질 특성을 비교 검토하였다. 수분함량, 환원당 함량, 총산도, 펙틴 및 안토시아닌 함량은 딸기가 양파보다 높았고, pH와 가용성 고형물 함량은 양파가 딸기보다 높았다. 대조군 잼에 비해 양파의 첨가량이 많아질수록 수분함량과 총산도는 점차 감소하는 경향을 나타내었고, pH는 점차 증가하였다. 색도는 L값은 양파의 첨가량이 많아질수록 감소하는 경향을 나타내었고, a값은 대조군에 비해 양파를 첨가한 시료가 다소 낮은 값을 나타내었으며, b값은 대조군에 비해 양파를 첨가한 시료가 다소 높은 값을 나타내었다. 대조군 잼에 비해 양파의 첨가량이 많아질수록 가열시간은 길어졌고, 퍼짐성, 가용성고형물 함량, 환원당 함량 및 안토시아닌 잔존율은 점차 감소하는 경향을 나타내었다. 관능검사 결과는 색, 끈기, 광택, 단맛, 신맛, 향, 종합적인 기호도의 모든 항목에서 대조군보다 양파 첨가량이 많아질수록 관능검사 점수가 감소하였다. 한편 잼을 빵에 발라서 관능검사를 실시한 결과 모든 항목에서 대조군보다 양파 첨가량이 많아질수록 관능검사 점수가 감소하였다. 잼만으로 관능검사를 실시했을 때와는 다르게 단맛에서만 다소 점수가 감소하였고, 나머지 모든 항목에서 점수가 증가하였다. 본 실험에서 제시한 시료 배합비율 중에서는 대조군 시료가 모든 관능적인 면에서 가장 좋게 평가되어 기존의 딸기잼에 길들여진 기호도를 바꿀 수는 없었으나, 양파를 딸기 중량의 10%, 20% 첨가했을 때는 관능검사 점수가 다소 떨어지기는 하였지만, 양파 특유의 맛과 향을 지니면서도 상당히 우수한 관능적 품질을 나타내었다. 따라서 다양한 소비자의 기호를 충족시킬 수 있는 기능성이 우수한 잼을 제조하는데 양파를 첨가할 수 있는 새로운 가능성을 제시할 수 있을 것으로 생각된다.

• 한국세라믹학회지
• /
• 제45권8호
• /
• pp.439-442
• /
• 2008

A series of reaction-sintered SiC was fabricated from preforms with varying volume fractions of two resin-coated SiC particles of different sizes (63 and $18{\mu}m$). The electrical resistivity and mechanical strength were eventually optimized at the small particle volume fraction of $0.3{\sim}0.4$, at which point the porosity of the preform was minimized. This study experimentally proves that additional processes after the formation of the preform, such as silicon infiltration and reaction sintering, do not apparently alter the optimum volume fraction of the preform packing, predicted by an existing analytical model based on solid packing. Thus, the volume fraction of particles of different sizes can be determined practically through the solid packing model to fabricate RSSCs with optimal properties.

• 한국주조공학회지
• /
• 제39권6호
• /
• pp.110-115
• /
• 2019

Recently, various studies have been conducted on additive manufacturing technology developed using metal materials. In this study, a numerical analysis was introduced to analyze the effects of the thermal deformation and residual stress which arise during the SLM (selective laser melting) manufacturing process. A phase-transformation mechanism is implemented with the use of the Ti-6Al-4V material, in which a solid-state phase transformation (SSPT) can be induced during a numerical analysis. In this case, the phase of the Ti-6Al-4V material changes from a powder to a solid state and then to the Martensite phase in sequence during heating and cooling steps. The numerical analysis during the SLM process was verified by comparing the results of tensile tests with those from the numerical analysis based on the SSPT material properties.

• 한국물환경학회지
• /
• 제18권4호
• /
• pp.421-433
• /
• 2002

This study was conducted to develope a simple, rapid and solvent-free solid-phase microextraction(SPME) procedure for extracting three organochlorine, one triazine and nine organophosphorus pesticides from water. The optimal conditions of SPME for analyses of organochlorine pesticides were obtained at $250^{\circ}C$ of desorption temperature, 45 minutes of equilibrium time, pH 6 and NaCl 0% addition using $100{\mu}m$ polydimethylsiloxane fiber and those of triazine and organophosphorus pesticides were obtained at $270^{\circ}C$ of desorption temperature, 60 minutes of equilibrium time, pH 6 and NaCl 0% addition using $100{\mu}m$ polydimethylsiloxane fiber. This method showed good lineality for organochlorine pesticides between 0.0001 and $10{\mu}g/L$ with regression coefficients ranging 0.9986~0.9992 and for triazine and organophosphorus pesticides between 0.01 and $10{\mu}g/L$ with regression coefficients ranging 0.9867~0.9998.

• 상하수도학회지
• /
• 제21권6호
• /
• pp.709-715
• /
• 2007

The dewaterability of a sludge can be characterized by two ways: the residual moisture content in the sludge cake after dewatering process, and the filtration of the sludge. Time to filter (TTF) represents filtration processes that are special cases of the flow through a solid matrix concept. TTF characterizes a resistance to filtration. The sludge resistance, in turn, can be subdivided into resistances associated with the solid phase and the liquid phase to evaluate the effect of each of the two phases on sludge dewaterability. In order to determine the dewatering characteristics of the water sludge samples, TTF and zeta potential were measured. For these studies cationic polymer was chosen for water sludge dewatering experiments. The zeta potential of thickener sludges neared from minus values to zero values till 4 days after sampling. The dewaterability of thickener sludges using cationic polymer was deteriorated according to the increase of detention time. As the detention time was increased from 4 to 10 days, the optimal dose of the polymer was increased from 4 to 8mg/L. Therefore, the optimal detention time plays an important part for the dewaterability of a sludge.

• 소성∙가공
• /
• 제17권8호
• /
• pp.570-578
• /
• 2008

A flexible forming apparatus is composed a number of punches which have spherical pin tip shape instead of conventional solid die. The flexible forming tool consisted of punch array in a matrix form was proposed as an alternative forming method to substitute the conventional line heating method which use heat source to induce residual stress along specified heating lines. In this study, application of the flexible forming process to the small scale curved plate forming was conducted. Numerical simulations for both solid and flexible die forming process were carried out to compare the shape of the products between flexible and conventional die forming process. In addition, spring-back analysis was conducted to figure out the feasibility of the flexible forming process comparing with the die forming process in view of final configuration of the specimens. Moreover, experiment was also carried out to confirm the formability of the process. Consequently, it was confirmed that the flexible die forming method has capability and feasibility to manufacture the curved plates for shipbuilding.

• Design & Manufacturing
• /
• 제16권1호
• /
• pp.50-54
• /
• 2022

Coverglass of electronic equipments is thinner and slimmer, so the glass must have good bending strength. In these days, the polishing edge of glass is used by solid tool like grinding wheel. But solid tool leave micro crack or edge chipping in edge of glass. MR polishing is an optimal method by polishing edge of glass. MR polishing is used MR fluid that is a liquid tool. MR polishing doesn't leave tool path or residual stress, micro crack and edge chipping unlike grinding wheel polishing. In this paper, the results of grinding and MR polishing were compared and analyzed to improve bending strength by minimizing edge chipping of cover glass. It was derived that the depth and size of cracks have a significant influence on the bending strength of the glass edge. The edges of the glass using MR grinding were analyzed to have a better surface and higher bending strength than the glass using abrasive wheel grinding. It was confirmed that MR polishing had an effect on strength improvement by effectively removing cracks in the specimen.

• 한국재료학회지
• /
• 제8권10호
• /
• pp.884-889
• /
• 1998

대면적의 비정질 실리콘 박막을 가우스 분포(Gaussian Profile)의 일차원 선형빔(line shape beam)을 가지는 엑시머 레이저를 사용하여 결정화를 시켰다. (Corning 7059 glass)위에 증착된 비정질 실리콘 박막이 재결정화된 실리콘 박막의 경우, 두께에따라 결정화되는 모양이 다르게 나타났다. 따라서 두께에 따라 결정화되는 상태의 변화를 조사하기 위하여 angle wrapping 방법을 새롭게 도입하여 깊이에 따른 Si층이 5${\mu}m$ 이상되도록 angle wrapping한 후에 박막의 두께에 따른 micro-raman spectra를 측정하여 결정화상태에 따른 잔류응력을 조사하였다. 또한 기판의 온도가 상온인 경우에 엑시머 레이저의 밀도가 300mJ/${cm}^2$에서 열처리한 경우에 재결정화된 Si 박막의 잔류응력에 박막의 표면에서 박막의 깊이에 따라 $1.3{\times}10^10$에서 $1.6{\times}10^10$을 거쳐 $1.9{\times}10^10$ dyne/${cm}^2$으로 phase의 변화에 따라 증가하였다. 또한 기판의 온도가 $400^{\circ}C$에서 최적의 열처리 에너지 밀도인 300mJ/${cm}^2$에서는 박막의 깊이에 따른 결정화 상태의변화에 따라 thermal stress 의 값이 $8.1{\times}10^9$에서 $9.0{\times}10^9$를 거쳐 $9.9{\times}10^9$ dyne/${cm}^2$으로 변화하는 것을 알 수 있다. 따라서 liquid phase에서 solid phaserk 변화함에 따라 stress값이 증가하는 것을 알 수 있다.

• 콘크리트학회논문집
• /
• 제26권5호
• /
• pp.643-650
• /
• 2014

일반적으로, 철근콘크리트 슬래브는 재료의 열적특성에 의해 높은 수준의 화재 저항 성능을 보유하고 있다. 그러나, 중공슬래브의 경우 일반 철근콘크리트 슬래브와는 다른 온도분포 및 화재 저항 성능을 보유하고 있을 것으로 예상된다. 중공슬래브는 콘크리트의 축열 효과를 발생시키는 공기층을 만들어내는 중공을 보유하고 있기 때문이다. 이에 연구에서는 중공슬래브의 화재 저항 성능을 평가하는 방법을 Wickstorm이 제안한 방법을 사용하여 제안하였다. 이 연구에서는 본 연구의 연구자가 제안한 도넛형 중공을 보유한 중공슬래브의 화재저항성능에 대한 단순화된 평가 방안을 제시하였다. 또한, 제안된 방법은 중공슬래브에 대한 화재실험을 통해 검증하였다. 이 연구의 결과를 통해 제안된 방법은 화재 발생 이후 중공슬래브의 잔존강도 추정이 가능함을 확인하였으며, 슬래브에 분포되는 온도의 특성을 정확하게 파악할 수 있는 것을 확인할 수 있었다.