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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Coarse Woody Debris in Industrially Managed Pinus taeda Plantations of the Southeastern United States

Pittman, Judd R. 25 August 2005 (has links)
Coarse woody debris (CWD) plays an influential role in forested ecosystems by adding organic matter to soils, stabilizing the soil environment, providing wildlife habitat, preventing soil erosion, providing seedling establishment habitat, and involvement in the nutrient cycle. Most CWD research has been conducted in old-growth and unmanaged, second-growth forests. However, less is understood about CWD in intensively managed ecosystems, such as industrialized southern pine plantations. The objectives of this study were to determine the climatic and ecological factors that affect the decomposition rate of CWD, to predict the decomposition rate, specific gravity, and time since death (TSD) using multiple linear regression in industrial loblolly pine (Pinus taeda L.) plantations in the southeastern United States. The study sites for this project were part of a long-term, loblolly pine thinning study maintained by the Loblolly Pine Growth and Yield Research Cooperative at Virginia Tech. Measurements included piece size, position, and decay class. Samples of CWD were collected and analyzed to determine their mass and density. Decomposition rate of CWD was significantly different across position classes and decay classes: disk decomposition rates were significantly negatively correlated with disk diameter, large and small end piece diameter, estimated disk height, and disk dry weight. Average annual precipitation and average annual temperature were not significantly correlated with CWD disk decomposition rate. / Master of Science
2

跨國新產品銷售預測模式之研究-以電影為例 / Models Comparing for Forecasting Sales of a New Cross-National Product - The Case of American Hollywood Motion Pictures

李心嵐, Lee, Hsin-Lan Unknown Date (has links)
現今市場競爭愈來愈激烈,迫使廠商紛紛至海外尋求產品消費市場,在跨國銷售的背景之下,需要有更多可以確定國家選擇、預測銷售及估計需求的方法。而其中可以滿足這些需求的方法之中,就是研究產品跨國擴散型態,藉以瞭解後進國家與領先國家中新產品如何擴散且會如何互相影響 (Douglas and Craig, 1992)。 在眾多的跨國產品中,本研究選擇好萊塢電影做為實證分析的對象。 經由集群分析,本研究發現(一)台灣高首週票房且口碑佳的電影,會遇到假日人潮、有很高的美國總票房、以及很高的美國首週票房;(二)美國影片在美國及台灣映演的每週票房趨勢有差異存在;(三)片商沒有做好影片在台灣映演的檔期歸劃;(四)三群電影中,在影片類型沒有明顯地區別。 經由十二個新產品銷售預測模型的建立:對數線性迴歸模式(LN-Regression Model)(不考慮新產品領先國擴散經驗)(以OLS估計)、卜瓦松迴歸模式(Poisson Regression Model) (不考慮新產品領先國擴散經驗)(以MLE估計)、負二項分配迴歸模式(Negative Binomial Distribution Regression Model) (不考慮新產品領先國擴散經驗)(以MLE估計)、Exponential Decay模式(以OLS估計)+迴歸方程式體系(不考慮新產品領先國擴散經驗)(以SUR估計)、Exponential Decay模式(以OLS估計)+迴歸方程式體系(考慮新產品領先國擴散經驗)(以SUR估計)、Exponential Decay模式+層級貝氏迴歸模式(考慮新產品領先國擴散經驗)、Bass連續型擴散模式(以NLS估計)+迴歸方程式體系(不考慮新產品領先國擴散經驗(以SUR估計)、Bass連續型擴散模式(以NLS估計)+迴歸方程式體系(考慮新產品領先國擴散經驗(以SUR估計)、Bass離散型擴散模式(以OLS估計)+迴歸方程式體系(不考慮新產品領先國擴散經驗)(以SUR估計)、Bass離散型擴散模式(以OLS估計)+迴歸方程式體系(考慮新產品領先國擴散經驗)(以SUR估計)、層級貝氏BASS離散型擴散模式+迴歸方程式體系(不考慮新產品領先國擴散經驗)(以SUR估計)、層級貝氏BASS離散型擴散模式+迴歸方程式體系(考慮新產品領先國擴散經驗)(以SUR估計)。本研究發現:(一)在考慮影響後進國的新產品擴散速度時,領先國的擴散經驗為絕對必要的考慮因子;(二)必須使用Bass連續型擴散模式做為建構新產品銷售預測模型的基礎;(三)必須使用Bass連續型擴散模式的NLS估計法估計Bass模型的創新係數p、模仿係數q及市場潛量m。

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