Matakuliah
Tahun
: H0062/Teori Sistem
: 2006
Pendahuluan
Pertemuan 9
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Contoh Modeling
Watershed Modeling
(http://water.usgs.gov/osw/techniques/watershed.html)
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Overview
The interdisciplinary nature and increasing complexity of environmental
and water-resource problems require the use of modeling
approaches that can incorporate knowledge from a broad range of
scientific disciplines. Selection of a model to address these
problems is difficult given the large number of available models and
the potentially wide range of applications, data constraints, and
spatial and temporal scales of application. Coupled with these
issues are the problems of study area characterization and
parameterization after a model is selected. Guidelines for parameter
estimation are sparse, and the user commonly has to make
decisions based on an incomplete understanding of the relation
between parameter values and physical measures of watershed
characteristics. The U.S. Geological Survey is currently addressing
these issues by developing a watershed modeling framework that
promotes models that are problem- and-scale specific and that
provides a capability to evaluate alternative modeling and parameter
estimation approaches.
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Conceptually, the framework is an integrated system of
computer software designed to provide the modeling
tools needed to support a broad range of model
applications and model user skills. The framework
supports the (1) application and analysis of existing
models, (2) modification and enhancement of existing
models for problem-specific applications, and (3)
research, devleopment, testing, and application of new
models. The framework uses a module library that
contains modules for simulating a variety of physical
processes. A model is created by selectively coupling
appropriate modules from the library to create a suitable
model for a desired application. When existing modules
do not provide appropriate process algorithms, new
modules can be developed.
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A wide range of pre-processing and postprocessing capabilities and model optimization
and sensitivity analysis tools are also major
components of a watershed modeling
framework. Pre-processing capabilities include a
range of data management and analysis tools
and geographic information system (GIS) tools
to provide watershed delineation,
characterization, and parameterization
capabilities. Post- processing tools include
graphical and statistical analysis tools for use in
analyzing and interpreting results.
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Continued advances in the physical and
biological sciences, GIS technology,
computer technology, and data resources
will increase the need for a set of dynamic
tools capable of providing a simple
interface between research and
operational applications. A watershed
modeling framework provides a flexible
mechanism for integrating scientific and
technological capabilities with resource
planning and management requirements.
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Modeling Parameter Heterogeneity in
Cross Country Growth Regression
Models
(http://ideas.repec.org/p/ucy/cypeua/0212.html)
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Given the failure of the conventional linear Solow growth model to
establish reliable results in the analysis cross-country growth
performance, this paper proposes a new framework using the
concept of hierarchy of time-scales. By hierarchy of time scales, I
mean that slower moving variables such as culture, play a major role
in determining medium moving variables such as institutions, and
which in turn play a major role in determining faster moving
variables such as the conventional determinants of economics
growth. This approach provides a systematic way of thinking about
the heterogeneity in the cross-country growth performance. In the
context of the Solow growth model the hierarchical approach
suggests a local generalization of the Solow growth model in the
form of a semiparametric varying parameter model along the lines of
Hastie and Tibshirani (1992). Using the varying coefficient model,
this paper studies two examples. In the first example the parameters
of the model vary according to initial human capital while in the
second they vary according to a measure of ethnic diversity. The
results suggest that there exists substantial parameter heterogeneity
in the cross-country growth process.
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