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ABSTRACT: The first objective of this paper is to present a new approach to econometric modeling of producer behavior. Substitution is determined by observable variables, such as prices of output and inputs and shares of inputs in the value of output. Our principal innovation is to represent the rate and biases of technical change by unobservable or latent variables. This representation is considerably more flexible than the constant time trends employed in the previous literature. An added advantage of the new representation is that the latent variables can be projected into the future, so that the rate and bias of technical change can be incorporated into econometric projections. The second objective of this paper is to present a new econometric model of aggregate demand and labor supply for the United States. We also analyze the allocation full wealth among time periods for households distinguished by a variety of demographic characteristics. The model is estimated using 1 Acknowledgements: Corresponding author: e-mail, djorgenson@harvard.edu, phone, 617-495-4661, fax: 617-495-4660. We are indebted to Jon Samuels, Johns Hopkins University, for help with the data employed in this paper. We are also grateful to Mun S. Ho, Resources for the Future, and James H. Stock, Harvard University, for valuable suggestions. Finally, we are grateful for useful comments to three anonymous referees and an Associate Editor and to participants in seminars at the Copenhagen Business School and the Department of Economics, Harvard University, and in the Summer Meeting of the Korean Econometric Society. Financial support for this research was provided by the Climate Economics Division of the Environmental Protection Agency. The usual disclaimer applies. 2 micro-level data from the Consumer Expenditure Surveys supplemented with price information obtained from the Consumer Price Index. An important feature of our approach is that aggregate demands and labor supply can be represented in closed form while accounting for the substantial heterogeneity in behavior that is found in household-level data. As a result, we are able to explain the patterns of aggregate demand and labor supply in the data despite using a parametrically parsimonious specification.
04/2010;
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ABSTRACT: Polymer light-emitting diodes(PLEDs) devices based on MEH-PPV were fabricated. The performance of PLEDs device with inserting insulating layer PEO nserted between the metal cathode and emissive polymer was enhanced. Furthermore, when cathode Al was modified by PEO/LiF, the threshold, the luminescence intensity, the efficiency and stability of the device were improved significantly. Experiment results show that the improvement of the device performance is caused by the introduction of PEO. The PEO between the metal cathode and emissive polymer works as the carrier barrier for carriers, and the injection of holes is restrained by the accumulation of holes on the surface. Meanwhile, electron injection is enhanced, and the dissociation of exciton is reduced.
Guang pu xue yu guang pu fen xi = Guang pu 08/2007; 27(7):1276-8. · 0.84 Impact Factor
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ABSTRACT: In the present paper, polymer-based light-emitting diode employing N-vinylcarbazole (PVK) doped with dilute phosphorescent dye factris-(2-phenylpyridine) iridium [Ir(ppy)3] and fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) as active layer was fabricated in order to compare the formation cross-sections of triplet exciton and singlet exciton. According to the changes in the electroluminescence (EL) spectrum and the relative intensity of photoluminescence (PL) spectrum, we deduce that the exciton formation cross-section of Ir(ppy)3 is larger than that of DCJTB.
Guang pu xue yu guang pu fen xi = Guang pu 04/2007; 27(3):420-2. · 0.84 Impact Factor
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ABSTRACT: Photoconductive properties of the composite devices made up of cadmium selenide nanocrystals and polymer poly[2-methoxy-5-(2'-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) were investigated. The photocurrent action spectrum for a nanocomposite device corresponded to the absorption of MEH-PPV and CdSe nanocrystals, indicating that the absorption of the CdSe nanocrystals and MEH-PPV contributed to the photocurrent. The photocurrent was attributed to the exciton dissociation and charge transfer between the interface of CdSe nanocrystals and MEH-PPV. The photocurrent action spectra of the nanocomposite device was wider than that of the pure MEH-PPV device, and the photocurrent was enhanced in comparison with the pure MEH-PPV device due to the introduction of CdSe nanocrystals.
Guang pu xue yu guang pu fen xi = Guang pu 01/2007; 26(12):2169-72. · 0.84 Impact Factor
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ABSTRACT: Photoconductive devices with organic (polyvinylcarbazole-PVK)/inorganic (zinc-sulfide--ZnS) thin-film heteropairing were fabricated. In external field, the excitation profile of the steady-state photoconductivity and the primary photoexcitation process of hybrid devices were presented and discussed. Comparison of photoconductivity of the devices and absorption spectra of PVK and ZnS implied that both layers absorption contributes to the photocurrent, but the effective part is at the interface of PVK and ZnS. The dependence of maximum photocurrent on the applied voltage and the dark and illuminated current spectra indicates the ultrafast charge transfer at the interface.
Guang pu xue yu guang pu fen xi = Guang pu 09/2004; 24(8):918-21. · 0.84 Impact Factor
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ABSTRACT: This article addresses a production planning optimization problem of overall refinery. The authors formulated the optimization problem as mixed integer linear programming. The model considers the main factors for optimizing the production plan of overall refinery related to the use of run-modes of processing units. The aim of this planning is to decide which run-mode to use in each processing unit in each period of a given horizon, to satisfy the demand, such as the total cost of production and inventory is minimized. The resulting model can be regarded as a generalized lot-sizing problem where a run-mode can produce and consume more than one product. The resulting optimization problem is large-sized and NP-hard. The authors have proposed a column generation-based algorithm called branch-and-price (BP) for solving the interested optimization problem. The model and implementation of the algorithm are described in detail in this article. The computational results verify the effectiveness of the proposed model and the solution method.
Chinese Journal of Chemical Engineering.
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Chemical Physics Letters 443:374-377. · 2.34 Impact Factor
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ABSTRACT: The purpose of this paper is to present a new approach to econometric modeling of substitution and technical change. Substitution is determined by observable variables, such as prices of output and inputs and shares of inputs in the value of output. Our principal innovation is to represent the rate and biases of technical change by unobservable or latent variables. This representation is considerably more flexible than the constant time trends employed in the previous literature. An added advantage of the new representation is that the latent variables can be projected into the future, so that the rate and bias of technical change can be incorporated into econometric projections.
Journal of Econometrics.
