• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1999년도 가을 학술발표회 논문집
• /
• pp.131-136
• /
• 1999

In this study, novel activated silicate grout solution for injection grouting was prepared by the reaction of ordinary waterglass with alkaline earth metal salts mixture by means of the high-speed stirring method with strong shearing force, and its chemical and physical properties were investigated. The variation of its gelation time plotted with the amount of dilution water showed that this novel silicate had better gelation characteristics in comparison with ordinary waterglass. And some other engineering characteristics of this grout such as durability and mechanical properties were investigated experimentally. The whole experimental results established that this novel silicate grout was a good alternative with an existing ordinary waterglass grouting method.

• 소성∙가공
• /
• 제11권4호
• /
• pp.312-322
• /
• 2002

In this study, an innovative semi-solid die casting technology to replace heavier cast iron compressor parts with lightweight aluminum castings was proposed, and the application possibility for home-appliance component was investigated. The most important factors regarding the semi-solid die casting process are the reheating process of the raw materials to the semi-solid state, specifications of the forming machine, the optimal injection conditions and die design. Materials used in this study were A3S7 and hSn alloys fabricated by the electromagnetic stirring process. The optimal injection conditions for semi-solid die casting process were Presented with the reheating conditions of the semi-solid materials. To investigate the effect of plunger tip shape on the formability and mechanical properties in semi-solid die casting process for complicated shape part, two kinds of plunger tip shape with long and short plunger tip taper are proposed.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 추계학술대회
• /
• pp.1016-1020
• /
• 2003

In this paper, we present a technology of producing anew chaotic micromixer, named Micromixer with Arranged Blocks(MAB), and the experimental result of the mixing performance. Chaotic mixing was successfully achieved by introducing periodic perturbation in the field of the channel flow by means of slanted blocks. The MAB was made by an RP(Rapid Prototyping) technology. We performed flow visualization experiments for the quantification of the mixing performance with the MAB. Lyapunov exponent was measured to be 0.3557 and 0.1305 for the block height 0.8 and 0.2 times the channel width.

• Environmental Engineering Research
• /
• 제25권4호
• /
• pp.470-478
• /
• 2020

Spent coffee grounds (SCG), the residue after brewing coffee beverage, is a promising biodiesel feedstock due to its high oil contents (15-20%). However, SCG should be pretreated to reduce the high free fatty acid content, which hampers transesterification reaction. To overcome this, we explored a direct transesterification reaction of SCG using ultrasound irradiation and identified the optimal sonication parameters. A high fatty acid methyl ester (FAME) content, up to 97.2%, could be achieved with ultrasound amplitude of 99.2 ㎛, irradiation time of 10 min, and methanol to oil ratio of 7:1 in the presence of potassium hydroxide concentration of 1.25 wt.%. In addition, we demonstrated that ultrasound irradiation is an efficient method to produce biodiesel from untreated SCG in a short time with less energy than the conventional mechanical stirring method. The physical and chemical properties of the SCG biodiesel met the requirements for an alternative fuel to the current commercial biodiesel.

• 설비공학논문집
• /
• 제19권8호
• /
• pp.607-614
• /
• 2007

This paper investigated that the functional group and chemical structure of additives affect ice adhesion in aqueous solutions cooling with stirring. In order to compare the effect on the ice adhesion in aqueous solutions, the functional group like carboxyl (-COOH), hydroxyl(-OH) or amine($-NH_{2}$) one were compared each other. Among the functional group, the strength of the hydrogen bonding force order is amine, hydroxyl and carboxyl one. It supports that ethylene diamine 7 mass% solution including amine group was effective to suppress the ice adhesion, though it is corrosive. Also, the ice adhesion were effectively resisted and formed lots of ice slurries in cooling experiment of 7 mass% solution of 1, 2-and 1, 3-propanediol which is different molecular structure but equal molecular weight each other.

• 한국세라믹학회지
• /
• 제53권6호
• /
• pp.670-675
• /
• 2016

Calcium phosphate crystallites were prepared by wet chemical method for use in artificial bone. In order to obtain ${\beta}$-tricalcium phosphate (TCP), nano-crystalline calcium phosphate (CaP) was precipitated at $37^{\circ}C$ and at $pH5.0{\pm}0.1$ under stirring using highly active $Ca(OH)_2$ in DI water and an aqueous solution of $H_3PO_4$. The precipitated nano-crystalline CaP solution was kept at $90^{\circ}C$ for the growth of CaP crystallites. Through the growing process of CaP crystallites, we were able to obtain various sizes of rectangular CaP crystallites according to the crystal growing times. Dry nano-crystalline CaP powders at $37^{\circ}C$ were mixed with dry macro-crystalline CaP crystallites and the shaped mixture sample was fired at $1150^{\circ}C$ to make a ${\beta}-TCP$ block. Several tens of nm powders were uniformly coated on the surface, which was comprised of powders of several tens of ${\mu}m$, using a vibrator. The mixing ratio between the nanometer powders and the micrometer powders greatly affected the mechanical strength of the mixture block; the most appropriate ratio of these two materials was 50 wt% to 50 wt%. The sintered block showed improved mechanical strength, which was caused by the solid state interaction between the nano-crystalline ${\beta}-TCP$ and the macro-crystalline ${\beta}-TCP$.

• Journal of Welding and Joining
• /
• 제23권5호
• /
• pp.61-68
• /
• 2005

Dissimilar joining of Al 6013-T4 alloys and austenite stainless steel was carried out using friction stir welding technique. Microstructures near the weld zone and mechanical properties of the joint have been investigated. Microstructures in the stainless steel side were composed of the heat affected zone and the plastically deformed zone, while those in the Al alloy side were composed of the recrystallized zone including stainless steel particles, the thermo-mechanically affected zone and the heat affected zone. TEM micrographs revealed that the interface region was composed of the mixed layers of elongated stainless steel and ultra-fine grained Al alloy with lamella structure and intermetallic compound layer. Thickness of the intermetallic layer was approximately 300nm and was identified as the A14Fe with hexagonal close packed structure. Mechanical properties, such as tensile and fatigue strengths were lower than those of 6013 Al alloy base metal, because tool inserting location was deviated to Al alloy from the butt line, which resulted in the lack of the stirring.

• 대한기계학회논문집B
• /
• 제30권5호
• /
• pp.430-437
• /
• 2006

The mixing effect is studied by comparing rotating and oscillating stirrers in the micro channel. The cases of Re=10 to 80 with various stirring speeds are considered to analysis the effect of Re and stirrer speed for the mixing. Under Re=20, the oscillating stirrer represents better mixing rate than the rotating stirrer up to the critical stirrer speed which has a maximum efficiency. Over Re=30, the results of oscillating and rotating stirrer show that the faster the stirrer speed, the higher the mixing effect within the concerned stirrer speed range and the oscillating stirrer keeps the higher mixing rate. It was found that the mixing effect is a function which has an optimum of the Reynolds number and the stirrer speed. The D2Q9 Lattice Boltzmann Method is used due to the merits of calculation for the unsteady flow with moving boundary.

• 한국기계기술학회지
• /
• 제13권3호
• /
• pp.65-71
• /
• 2011

The concrete mixer truck which is in charge of raw materials in civil engineering construction of the concrete loading, transport, placement, is used $6m^3$, $7m^3$ class in domestic(Korea). But in the case of the international construction fields are utilized $9m^3$ or above class because of the large-scale engineering and construction circumstances. In this paper, to develop a large $9m^3$ class mixer drum and the mixer drum in order to complement the technical and discharge that is responsible for stirring the blades by applying optimal design through implementation of the optimal shape of the concrete in the drum maintenance and placement of high-quality effects on increasing discharge such as advanced conventional drum mixer is to secure and differentiated technology. Large, heavy weight in development and uphold the drum mixer vehicle sub-frame is required to settle the design of the existing class mixer drum frames per $6m^3$ changed to account for changes in slope and length using CATIA V5 3D modeling work was performed.

• 한국주조공학회지
• /
• 제17권2호
• /
• pp.170-179
• /
• 1997

A noble technique has been developed for fabricating in situ formed $TiC_p/Al$ composites. In this process, fairly stable TiC particles were in situ synthesized in liquid aluminum by the interfacial reaction between an Al-Ti melt and SiC, which is a comparatively unstable carbide from the view-point of thermodynamics. It is possible in the present process to generate TiC particles of nearly 1 ${\mu}m$ in diameter, even utilizing SiC of 14 ${\mu}m$ as raw material. However, the dispersion behavior of TiC particles in the matrix depends on the size of the raw material SiC. Decomposing finer SiC makes the dispersion of TiC particles more uniform and the mechanical properties of composites are improved accordingly. The structure of in situ composites and their mechanical properties are affected by the fabrication temperature and the stirring time. It has been found that the most suitable condition for fabrication should be applied depending on the size of the raw material, even if the same kinds of carbide are used. Furthermore, although Al-Ti-Si system intermetallic compounds are detected in a $TiC_p/Al-Si$ composite which is fabricated by conventional melt-stirrng method, these compounds can not be observed in a $TiC_p/Al-Si$ composite made by this in situ production method. Hence the mechanical properties of the in situ $TiC_p/Al-Si$ composite are superior to those of the conventional $TiC_p/Al-Si$ composites.