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An approximately global optimization method for assortment problems
(1998-03-16)
Li, HL
;
Chang, CT
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Assortment problems occur when we want to cut a number of small rectangular pieces from a large rectangle to get the minimum area within the rectangle. Recently, Chen et al. proposed a useful model for assortment problems. Although Chen et al.'s model is quite promising to find solutions, there are two inadequacies in their model: firstly, the objective function in their model is a polynomial term, which may not lead to a globally optimal solution; secondly, too many 0-1 variables are used to formulate the non-overlapping constraints. We propose a new method to reformulate an assortment model. Our model is not only able to find the approximately global optimal solution, but involves less 0-1 variables for formulating non-overlapping constraints. (C) 1998 Elsvier Science B.V.
An approximate approach of global optimization for polynomial programming problems
(1998-06-16)
Li, HL
;
Chang, CT
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Many methods for solving polynomial programming problems can only find locally optimal solutions. This paper proposes a method for finding the approximately globally optimal solutions of polynomial programs. Representing a bounded continuous variable x(i) as the addition of a discrete variable d(i) and a small variable epsilon(i), a polynomial term x(i)x(j) can be expanded as the sum of d(i)x(j), d(j) epsilon(i) and epsilon(i) epsilon(j). A procedure is then developed to fully linearize d(i)x(j) and d(j) epsilon(i), and to approximately linearize epsilon(i) epsilon(j) with an error below a pre-specified tolerance. This linearization procedure can also be extended to higher order polynomial programs. Several polynomial programming examples in the literature are tested to demonstrate that the proposed method can systematically solve these examples to find the global optimum within a pre-specified error. (C) 1998 Elsevier Science B.V.
Differences in PM10 concentrations measured by beta-gauge monitor and hi-vol sampler
(2001-11-01)
Chang, CT
;
Tsai, CJ
;
Lee, CT
;
Chang, SY
;
Cheng, MT
In this paper. differences between the 24-h average PM10 concentrations of Wedding beta -gauge monitor and Andersen or Wedding hi-vol sampler were studied. When the deliquescent point is not exceeded, PM10 concentrations of the beta -gauge are close to those of the manual samplers. The ratio of beta -gauge PM10 to Andersen PM10 and Wedding PM10 is 1.08 +/-0.06 and 1.09 +/-0.12, respectively. However, when the deliquescent point is exceeded, water absorption by the inorganics of aerosols leads to higher PM10 concentrations of the beta -gauge compared to those of the manual sampler. The ratio of beta -gauge PM10 to Andersen PM10 and Wedding PM10 is 1.21 +/-0.22 and 1.27 +/-0.15, respectively. However., due to evaporation of water from the aerosols collected on the filter tape of the beta -gauge, differences in PM10 concentrations are much less than theoretically calculated. (C) 2001 Elsevier Science Ltd. All rights reserved.
The effect of environmental conditions and electrical charge on the weighing accuracy of different filter materials
(2002-07-03)
Tsai, CJ
;
Chang, CT
;
Shih, BH
;
Aggarwal, SG
;
Li, SN
Different filter materials and electrical charge elimination methods were used to investigate the weighing accuracy of filter papers under different environmental conditions. The results show that the standard deviations (S.D.) of weight data for glass fiber and MCE filters were substantial without environmental control, whether or not the electrical charge eliminators were used. Values of 0.157 and 0.349 mg were determined for glass and NICE filters, respectively. The accuracy of weighing was substantially improved and the S.D. was reduced to 0.01 and 0.09 mg for glass fiber and MCE filters, respectively, after applying the environmental control conditions. For PVC and Teflon filters, the accuracy of weighing was good, even in the uncontrolled environmental conditions, whether or not the electrical charge eliminators were used. The S.D. values of weighing data of PVC and Teflon filters were 0.007 and 0.011 mg, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.
Approximately global optimization for assortment problems using piecewise linearization techniques
(2002-08-01)
Li, HL
;
Chang, CT
;
Tsai, JF
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Recently, Li and Chang proposed an approximate model for assortment problems. Although their model is quite promising to find approximately global solution, too many 0-1 variables are required in their solution process. This paper proposes another way for solving the same problem. The proposed method uses iteratively a technique of piecewise linearization of the quadratic objective function. Numerical examples demonstrate that the proposed method is computationally more efficient than the Li and Chang method. (C) 2002 Elsevier Science B.V. All rights reserved.
An investigation of dust emissions from unpaved surfaces in Taiwan
(2002-11-01)
Tsai, CJ
;
Chang, CT
;
環境工程研究所
;
Institute of Environmental Engineering
One of the critical problems in making an effective strategy to control fugitive road dust is to estimate the emission factor accurately. The paper presents measured results of emission factor at field and in a wind tunnel. For the field study, three unpaved roads in Hsin Chu, Taiwan were tested. For the wind tunnel testing, the tested road dust was also collected from the field. Results of field study indicate that the emission factor of unpaved roads increases with the increasing wind speed, the number of vehicles and the speed of vehicles. It can be predicted as e (g/m(2)day) = 8.72 x 10(-3) x V-w(0.64) X s(0.19) x M-0.05 x V-v(1.32) x N-v(1.11) (V-w, m/s-wind speed, s, %-silt content of road dust; M, %-moisture content of road dust; N-v, #/h-number of vehicles: V-v, km/h-speed of vehicles) by the multi-variable regression technique. The fractions of PM10 and PM2.5, in the TSP reentrained from the unpaved roads are 20.6 +/- 12.9% and 2.3 +/- 1.2%, respectively. The wind tunnel test results show that air acceleration rate and edge effect of the dust surface increase the emission factors considerably. As air acceleration rate increases from 0.1 to 1.5 m/s(2), the emission factor increases linearly from 1.0 x 10(-4) to 7.0 x 10(-4) kg/m(2) s. However, test results show no significant effect of air acceleration and edge effect of dust surface on the threshold wind speed of reentrainment. (C) 2002 Elsevier Science B.V. All rights reserved.
Four-wave mixing between pump and signal in a distributed Raman amplifier
(2003-05-01)
Kung, TT
;
Chang, CT
;
Dung, JC
;
Chi, S
;
交大名義發表
We observed. experimentally four-wave mixing (FWM) between a 14xx-nm pump and a 15xx-nm signal in a forward-pumped distributed Raman amplifier (DRA) over 50 kin of nonzero dispersion-shifted fiber with a zero dispersion wavelength of 1497 nm. The 100-mW pump Fabry-Perot (FP) spectra centered at 1440, 1450, and 1460 nm are reproduced via FWM around the single-wavelength probe signal around 1558, 1548, and 1538 nm, respectively. The suppression of DRA gain by about 2-3 dB was experimentally observed with peak FWM at minimum phase mismatching between two 14xx-nm FP pump wavelengths and two 15xx-nm signal wavelengths. This DRA gain suppression, together with the reproduced pump FP spectrum at 15xx-nm signal band, may limit the usefulness of the forward-pumped DRA, generating spectrally nonuniform FWM-induced noise floors and crosstalk in wavelength-division-multiplexed fiber-optic transmission systems.
A model for the relative humidity effect on the readings of the PM10 beta-gauge monitor
(2003-12-01)
Chang, CT
;
Tsai, CJ
;
環境工程研究所
;
Institute of Environmental Engineering
In the previous paper (Atmos. Environ. 15 (1981) 1087), we found that the PM10 concentrations detected by the Wedding beta-gauge PM10 monitor and those measured by the manual hi-vol PM10 sampler were quite close when the ambient relative humidity (RH) was lower than the deliquescence RH (DRH) of aerosols. However, when the deliquescent point was exceeded, PM10 concentrations of the beta-gauge were found to be higher and differences increased with an increasing ambient RH. In addition, theoretical water mass calculated by a thermodynamic model (ISORROPIA model, (Aquat. Geochem. 4 (1998) 123)) was found to be much higher than the actual values. In this study, models were developed to determine water evaporation loss from collected particles on the filter tape of the beta-gauge during sampling and in the monitoring room. Simulated results show that all absorbed water will evaporate completely at RH lower than about 85%. However, absorbed water does not evaporate completely at RE higher than about 85%, and remaining water in particles accounts for higher beta-gauge readings than the hi-vol concentrations. The simulated daily beta-gauge PM10 concentrations are close to the actual beta-gauge readings obtained previously. (C) 2003 Elsevier Ltd. All rights reserved.
Concentration profiles of acidic and basic air pollutants around an industrial park of Taiwan
(2004-01-01)
Tsai, CJ
;
Aggarwal, SG
;
Chang, CT
;
Hung, IF
;
環境工程研究所
The results of spatial and temporal distribution of acidic and basic air pollutants in ambient air around Hsinchu Science-Based Industrial Park (SBIP), Taiwan during August 2000 to October 2001 are presented. The sampling was performed on 13 different sites around the SBIP for 12 hrs each every month, and a total of 195 samples were collected. The effect of geographical and meteorological conditions, and production volume of the SBIP on the variation of pollutant's concentration was investigated. The spatial distribution shows that comparatively higher concentration of pollutants was found on the sites, which are either low in altitude such as the WS (west-southern) part of SBIP, in the downwind location or close to the factories. In case the wind velocity was low, i.e. below 2 m s(-1), the concentration of pollutant tended to increase and became uniformly distributed around the science park. The temporal distribution shows a decrease in ambient concentration of pollutants from February to June 2001, mainly due to the decline in the production volume of the SBIP in this period. During the whole period of investigation, the concentration of most of the species ( except HF) was found to be lower than the factory-surrounding air quality standard of Taiwan, but in some cases it was higher than the AALG.
Emission characteristics and control efficiency of acidic and basic gases and aerosols from packed towers
(2004-02-01)
Tsai, CJ
;
Chang, CT
;
Liu, TW
;
Huang, CC
;
Chien, CL
Large amount of acidic liquids, such as H2SO4, HF, HCl and HNO3, and basic NH3 liquid are used in high-tech industries in cleaning and etching processes in the Hsinchu Science-Based Industrial Park in Taiwan. The industries use packed towers (or scrubbers) to control emission of these inorganic pollutants, in which acidic gases but not particles are regulated by the Taiwan EPA's strict emission standard for semiconductor industry. To understand whether the emission standard is met and to investigate the emission rates, emission profiles, emission factors, and control efficiencies of various gaseous/aerosol species, measurement of pollutants before and after the packed towers was conducted using a sensitive porous metal sampler during January 2001 to February 2003. Results show that the pollutants are mainly in the gaseous phase, and the control efficiency of pollutants is low and variable when the inlet concentration is low. In addition to the control efficiency data, emission factors before the control device for various gas and particle species have also been developed for estimating the emission rates. (C) 2003 Elsevier Ltd. All rights reserved.

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