495 research outputs found
Multicriteria sustainability evaluation of transport networks for selected European countries
As an essential economic activity, transportation has complex interactions with the environment and society. Since the concept of sustainable development has become one of the top priorities for nations, there has been a growing interest in evaluating the performance of transport systems with respect to sustainability issues. The main purpose of this study is to introduce a decision making framework to assess the sustainability of the transport networks in a multidimensional setting and a technique to identify non-compromise alternatives. We also propose an elucidation technique to identify according to which criteria a system needs to be improved and how much improvement is required to attain a certain level of sustainability. The proposed methods are applied to a set of selected European countries within a case study
A Buffer Stocks Model for Stabilizing Price of Staple Food with Considering the Expectation of Non Speculative Wholesaler
This paper is a study of price stabilization in the
staple food distribution system. All stakeholders experience
market risks due to some possibility causes of price volatility.
Many models of price stabilization had been developed by
employing several approaches such as floor-ceiling prices,
buffer funds, export or import taxes, and subsidies. In the
previous researches, the models were expanded to increase the
purchasing price for producer and decrease the selling price
for consumer. Therefore, the policy can influence the losses for
non-speculative wholesaler that is reflected by the descending
of selling quantity and ascending of the stocks. The objective of
this model is not only to keep the expectation of both producer
and consumer, but also to protect non-speculative wholesaler
from the undesirable result of the stabilization policy. A
nonlinear programming model was addressed to determine the
instruments of intervention program. Moreover, the result
shows that the wholesaler behavior affects the intervention
costs.
Index Terms Buffer stocks, Price stabilization, Nonlinear
programming, Wholesaler behavior
Improving the performance of cascade correlation neural networks on multimodal functions
Intrinsic qualities of the cascade correlation algorithm make it a popular choice for many researchers wishing to utilize neural networks. Problems arise when the outputs required are highly multimodal over the input domain. The mean squared error of the approximation increases significantly as the number of modes increases. By applying ensembling and early stopping, we show that this error can be reduced by a factor of three. We also present a new technique based on subdivision that we call patchworking. When used in combination with early stopping and ensembling the mean
improvement in error is over 10 in some cases
Capacity Integration into a Microgrid, a Tool for Electrical Energy Supply Cost Reduction in Nigeria- Covenant University as a Case Study
The cost implication of running a cluster
of stand-alone power generating plants was
investigated using the generating capacities of the
generators and consumption (load) profile obtained
from a campus based substation. Analysis of the
results revealed a lot of unused available capacity
within the system which invariably increases the
operating cost of power generation within the
campus. Integrating the power generators into a
microgrid was suggested where there will be a
common pool of energy sources and all loads
attached to the network. The proposed network
model seeks to reduce power plant engagement by
integrating the generating power plants into a
microgrid system. To overcome the challenge of
synchronization in the AC platform as the power
generators are dissimilar, the network is designed to
operate as a DC microgrid where the AC generating
plants and loads will be interfaced by converters
(rectifiers) and inverters respectively. This method
reduced the unused capacity being wasted by
reducing power plant engagement and consequently
reducing the running cost of power generation in
the campus
Optimizing Hydroelectric Power Generation: The Case of Shiroro Dam
Abstract—Hydroelectric power, one of the most important
sources of mass generation of electric power, is a renewable
source of energy. The amount of electricity that can be
produced by a hydro-electricity generating system depends on
systemic variables viz; plant efficiency, volumetric water flow
through the turbine and the head of the water from the water
surface to the turbine. The availability of the Water in the
reservoir is a function of some hydrological variables principal
among which are rainfall, reservoir inflows and evaporation.
Understanding the dynamics of these variables, and the
correlation between them are core to proper planning and
management of a hydroelectric power station. In this Study,
simple mathematical methods that include linear programming
and statistical analysis based on simulation techniques were
used to evaluate vital parameters based on the hydrologic data
obtained from the Hydrologic Units of the Shiroro Power
Stations in Nigeria. The overall aim of the study is to idealize
power generation at Shiroro dam in and out of rain season so
as to ensure optimum generation of electricity all year round in order
to achieve energy sufficiency in Nigeria
Experimental investigation of heat transfer effectiveness on finned-tube thermoacoustic heat exchanger
Heat exchangers are some of the most important parts in thermoacoustic devices. In an oscillatory flow condition, the flow and temperature fields around the heat exchangers can be quite complex and it may significantly affect their heat transfer behaviour. As a result, one cannot directly apply the heat transfer correlations for a steady flow to the design of heat exchangers operating in oscillatory flow conditions. However, the fundamental knowledge of heat transfer in oscillatory flow is still not well established. The aim of the current work is to establish the heat transfer correlation for a few selected finned-tube heat exchangers, by measuring the heat transfer from the heat exchangers to the oscillatory flow in a range of operating conditions. Among the main parameters considered are fin spacing, fin length, thermal penetration depth, and gas displacement amplitude, and their effect on the thermal performance of heat exchangers. The results are presented in term of heat transfer effectiveness, which is the ratio of actual heat transfer rate to the maximum possible heat transfer rate. The correlations are proposed between the heat transfer effectiveness and the ratios of the fin length to the displacement amplitude and the fin spacing to the thermal penetration depth. The uncertainties associated with all the measurement data are also considered
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The experimental and numerical approach of two-phase flows by wall jets on rough beds in open channel flow
YesThis paper presents the results of investigations
carried out to study the effect of horizontal wall jets on a fixed
rough bed in an open channel. The study used both numerical
and experimental approaches. The numerical and experimental
studies are compared for validation. The main objective of this
study is to understand the effect of wall jets on a horizontal
fixed rough bed in an open channel.
The experimental study investigated the effect of wall jets on
a fixed horizontal bed, with a known roughness in an open
channel flume. A sid-looking Acoustic Doppler Velocimetry
(ADV) was used to measure the velocity profile of the flow at
different flow zones. The wave monitor was used to measure the
free surface during the experiments.
Computational fluid dynamics CFD simulations were
conducted in a rectangular channel to compare with the
laboratory tests using the volume of fluid VOF multiphase
method and K- ࢿ model. The two phase (water and air) was
used in this study. Computer simulations for the model were
used to predict the fluid horizontal velocity (u) revealing the
characteristics of the wall jet over different flow zones
(developing, fully developed and recovering zones).
The results showed that the velocity profiles distribution in
the stream wise direction in the channel were reasonable. The
reverse velocity was close to the wall jet and the maximum
reverse velocity was observed near the water surface. Also the
results showed that the depression was close to the wall jet.
The agreement between the results obtained from the
numerical and the experimental data were reasonable
Liver CT enhancement using Fractional Differentiation and Integration
In this paper, a digital image filter is proposed to enhance the Liver CT image for improving the classification of tumors area in an infected Liver. The enhancement process is based on improving the main features within the image by utilizing the Fractional Differential and Integral in the wavelet sub-bands of an image. After enhancement, different features were extracted such as GLCM, GRLM, and LBP, among others. Then, the areas/cells are classified into tumor or non-tumor, using different models of classifiers to compare our proposed model with the original image and various established filters. Each image is divided into 15x15 non-overlapping blocks, to extract the desired features. The SVM, Random Forest, J48 and Simple Cart were trained on a supplied dataset, different from the test dataset. Finally, the block cells are identified whether they are classified as tumor or not. Our approach is validated on a group of patients’ CT liver tumor datasets. The experiment results demonstrated the efficiency of enhancement in the proposed technique
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