• 경영과학
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• 제31권2호
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• pp.65-70
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• 2014

This paper considers a single machine scheduling problem to determine release and processing times where both the release times and processing times are linearly decreasing functions of resources. The objective is to minimize the sum of the associated resource consumption cost and scheduling cost including makespan, sum of completion times, maximum lateness, or sum of lateness. This paper proves that the scheduling problem is NP-hard in the strong sense even if the release times are constant.

• 한국광물학회지
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• 제23권4호
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• pp.297-303
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• 2010

본 연구에서는 파쇄 메커니즘이 상이한 파쇄기(함마 크럿셔와 롤 크럿셔)와 파쇄회로(개회로 및 폐회로)를 사용하여 각각의 파쇄기 종류에 따른 백운석 파쇄산물의 입도분포와 파쇄특성에 대해 알아보았다. 함마 크럿셔로 파쇄한 경우, 100 mesh 이하의 미분이 약 34 wt.%로 롤 크럿셔로 파쇄한 경우보다 약 3 배 이상 높았다. 또한 14~25 mesh 산물은 롤 크럿셔로 파쇄할 경우, 함마 크럿셔로 파쇄한 경우에 비하여 약 20 wt.% 이상 많이 생성되었다. 35 mesh 이하의 산물은 함마 크럿셔로 파쇄 시 전체의 약 80 wt.% 정도였다. 두 파쇄기 모두 개회로에 비해 폐회로 파쇄 시 미분의 발생률이 감소하였다. 광석에 따른 적절한 파쇄기 및 파쇄회로의 선택에 따라 목적하는 입도의 산물을 효율적으로 얻을 수 있다.

• Journal of Biosystems Engineering
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• 제40권3호
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• pp.296-304
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• 2015

Purpose: The balance between miscanthus production and its cost effectiveness depends greatly on its moisture content during post processing. The objective of this research was to measure the moisture content using a non-destructive and non-contact methodology for in situ applications. Methods: The moisture content of comminuted miscanthus was controlled using a closed chamber, a humidifier, a precision weigher, and a real-time monitoring software developed in this research. A CMOS sensor equipped with $50{\times}$ magnifier lens was used to capture magnified images of the conditioned materials with moisture content level from 5 to 30%. The hypothesis is that when light is incident on the comminuted particles in an inclined manner, higher moisture content results in light being reflected with a higher intensity. Results: A linear regression analysis for an initiative hypothesis based on general histogram analysis yielded insufficient correlations with low significance level (<0.31) for the determination coefficient. A significant relationship (94% confidence level) was determined at level 108 in a reverse accumulative histogram proposed based on a revised hypothesis. A linear regression model with the value at level 108 in the reverse accumulative histogram for a magnified image as the independent variable and the moisture content of comminuted miscanthus as the dependent variable was proposed as the estimation model. The calibrated linear regression model with a slope of 92.054 and an offset of 32.752 yielded 0.94 for the determination coefficient (RMSE = 0.2%). The validation test showed a significant relationship at the 74% confidence level with RMSE 6.4% (n = 36). Conclusions: To compensate the inconsistent significance between calibration and validation, an estimation model robust against various systematic interferences is necessary. The economic efficiency of miscanthus, which is a promising energy resource, can be improved by the real-time measurement of its crucial material properties.