• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.163-166
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• 1997

Aluminium foam material is a highly porous material having complicated cellular structure defined by randomly distributed air pores in metallic matrix. this structure gives the aluminium a set of properties which cannot be achieved by any of conventional treatments. The properties of aluminium foam material significantly depend on its porosity, so that a desired profile of properties can be tailored by changing the foam density. Melting method is the one of foaming processes, which the production has long been considered difficult to realize becaues of such problems as the low foamability of molten metal, the varying size of. cellular structures, solidification shrinkage and so on. These problems, however, have gradually been solved by researchers and some manufacturers are now producing foamed aluminum by their own methods. Most of all, the parameters of solving problem in electric furnace were stirring temperature, stirring velocity, foaming temper:iture, and so on. But it has not considered about those in induction heating, foaming velocity and foaming temperature in semi-solid state yet. Therefore, this paper presents the effects on these parameter to control cell size, quantity and distribution.

• Steel and Composite Structures
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• 제50권3호
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• pp.299-318
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• 2024

The main objective of this paper is to compute the far-field acoustic radiation (sound radiation) of functionally graded plates (FGM) loaded by sinusoidally varying point load subjected to the arbitrary boundary condition is carried out. The governing differential equations for thin functionally graded plates (FGM) are derived using classical plate theory (CPT) and Rayleigh integral using the elemental radiator approach. Four cases, segregated on power-law index k=0,1,5,10, are studied. A novel approach is illustrated to compute sound fields of vibrating FGM plates using the physical neutral surface with an elemental radiator approach. The material properties of the FGM plate for all cases are calculated considering the power law indexes. An in-house MATLAB code is written to compute the natural frequencies, normal surface velocities, and sound radiation fields are analytically calculated using semi-analytical formulation. Ansys is used to validate the computed sound power level. The parametric effects of the power law index, modulus ratios, different constituent of FGM plates, boundary conditions, damping loss factor on the sound power level, and radiation efficiency is illustrated. This work is the benchmark approach that clearly explains how to calculate acoustic fields using a solid layered FGM model in ANSYS ACT. It shows that it is possible to asymptotically stabilize the structure by controlling the intermittent layers' stiffness. It is found that sound fields radiated by the elemental radiators approach in MATLAB, ANSYS and literatures are in good agreement. The main novelty of this research is that the FGM plate is analyzed in the low-frequency range, where the stiffness-controlled region governs the whole analysis. It is concluded that a clamped mono-ceramic FGM plate radiates a lesser sound power level and higher radiation efficiency than a mono-metallic or metal-rich FGM plate due to higher stiffness. It is found that change in damping loss factor does not affect the same constituents of FGM plates but has significant effects on the different constituents of FGM plates.

• 대한환경공학회지
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• 제27권11호
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• pp.1205-1214
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• 2005

본 논문은 중소형 규모의 도시고형 폐기물소각시설 배가스의 수은, 납, 비소, 셀렌과 같은 휘발성중금속의 방출특성을 조사하는데 있다. 대체로, 소형 도시고형 폐기물소각시설에서 배출되는 수은, 납, 비소, 셀렌이 중형 소각시설에서 배출되는 것 보다 높게 나타났다. 이는 중형소각시설에 비하여 소형소각시설의 빈약한 대기오염제어장치의 가동과 높은 배가스 온도에 기인하는 것으로 판단된다. 중소형 소각시설의 배가스 온도는 2개의 온도그룹으로 나누어지는 것을 확인할 수 있다. 첫 번째 온도그룹은 대략 $100^{\circ}C$이고, 두 번째 온도그룹은 $400{\sim}700^{\circ}C$ 정도였다. 2번째 그룹에서의 배가스 중 수은, 납, 비소, 셀렌은 각각 $70.43\;{\mu}g/Sm^3$, $0.94\;{\mu}g/Sm^3$, $9.83\;{\mu}g/Sm^3$, $5.05\;{\mu}g/Sm^3$였다. 첫 번째 온도그룹에서 배가스의 수은, 납, 비소 셀렌은 두 번째 온도그룹의 것보다 낮은 특징을 가지고 있다. 한편, 중형소각시설에서의 수은제거효율은 $55.16{\sim}95.89%$로 나타났다. 이러한 수은의 감소는 폐열보일러의 온도저감이 기여를 하고 있었다. 상기 결과로, 중소형 소각시설에서 휘발성 중금속 제어에 중요한 역할을 하는 것은 배가스의 온도가 큰 역할을 한다. 따라서, 휘발성 중금속의 제거효율을 개선하기 위해서는, 냉각시스템의 온도가 제어되고 대기오염제어장치가 잘 운영되어야 한다.