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전자기력에 의한 연주 Slab 내의 교반유동에 관한 수치적 연구
이재헌,이성우,신영길,김희창 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.1
A Numerical study was performed for the two-dimensional turbulent stirring flow created by linear motor in a continuous casting system. A k-εturbulent model was applied to solve time-averaged turbulent momentum equations within the computation domain. Four different situations in a stirring system being consisted of two-dimensional slab of 1 m(width) × 0.2 m(height) have been investigated, that is : Model (A) : W =0.1 m and B_0=0.01 tesla, Model (B) : W =0.3 m and B_0=0.01 tesla, Model (C) : W =0.1 m and B_0=0.02 tesla, Model (D) : W =0.3 m and B_0=0.02 tesla, where W is the length of linear motor and B_0 is the magnetic flux applied on the motor-side-surface of the slab. The results shows that the flow characteristics depends mainly on the magnetude of B_0 not on W. The order of the magnitudes of turbulent intensity at four flow situations were almost same. However, the magnitude of turbulent viscosity became much less in case of greater B_0 than in smaller B_0. Therefore it is recommended that the stirrer with greater B_0 should be used to make finer stirring action.
이재헌,박명식 대한기계학회 1993 대한기계학회논문집 Vol.17 No.8
A numerical investigation has been carried out for the flow characteristics after exchange of some filters from the original layer to the new low pressure loss layer with equal filtering efficiency. The solution domain includes upper plenum, filter layer, clean space, access panels, and lower plenum. The concept of the distributed pressure resistance was applied to describe the momentum loss in filter layer and access panels. The evolution of the flow field is simulated using the low Reynolds number k-.epsilon. over bar turbulent model and SIMPLE algorithm based on the finite volume method. As a result, after the exchange of filter layer the power requirement can be reduced by 8-9 percent. The results also demonstrate that the perpendicularity of the flow near access panels may become worse at new filter layer than origianl filter layer. But the situation can be recovered by adjusting the jopening ratio of access panels.
통합공정관리에서 출력변수와 입력변수를 탐지하는 절차의 비교
이재헌 한국데이터정보과학회 2011 한국데이터정보과학회지 Vol.22 No.4
Two widely used approaches for improving the quality of the output of a process are statistical process control (SPC) and automatic process control (APC). In recent hybrid processes that combine aspects of the process and parts industries, process variations due to both the inherent wandering and special causes occur commonly, and thus simultaneous application of APC and SPC schemes is needed to effectively keep such processes close to target. The simultaneous implementation of APC and SPC schemes is called integrated process control (IPC). In the IPC procedure, the output variables are monitored during the process where adjustments are repeatedly done by its controller. For monitoring the APC-controlled process, control charts can be generally applied to the output variable. However, as an alternative, some authors suggested that monitoring the input variable may improve the chance of detection. In this paper, we evaluate the performance of several monitoring statistics, such as the output variable, the input variable, and the difference variable, for efficiently monitoring the APC-controlled process when we assume IMA(1,1) noise model with a minimum mean squared error adjustment policy. 통계적 공정관리 (statistical process control; SPC)와 자동공정관리 (automatic process control; APC)는 공정의 품질을 향상시키기 위하여 가장 널리 사용하는 방법이다. 이 두 종류의 관리절차는 서로 독립적으로 적용되고 연구되어져 왔지만, 현대의 생산 공정은 공정 자체가 복잡하고 혼합된 양상을 나타내기 때문에 두 관리절차를 병행하여 사용함으로써 관리효과를 증대시킬 수 있게 된다. 이와 같이 수정과 탐지를 동시에 사용하여 공정을 좀 더 효율적으로 관리하고자 하는 절차를 통합공정관리 (integrated process control; IPC)라고 한다. IPC의 기본절차는 잡음이 내재하는 공정에 대하여 수정조치를 취하고, 이러한 수정활동 중 공정에 이상원인이 발생했는지 관리도를 통하여 이를 탐지하는 것이다. APC로 조정된 공정을 관리할 경우 일반적으로 출력변수를 관리통계량으로 사용하고 있으나, 입력변수를 관리통계량으로 사용하는 연구 결과들도 있다. 이 논문에서는 누적이동평균(integrated moving average; IMA) (1,1) 잡음모형과 최소평균제곱오차 (minimum mean square error; MMSE) 수정을 가정할 경우, 출력변수, 입력변수, 그리고 출력변수와 입력변수의 정보를 모두 이용하는, 즉 출력과 입력변수의 차이변수를 사용하는 절차의 효율을 비교하고 있다.