375 research outputs found
Development of Coal Mill and Aggregate Load Area Models in Power Systems using Genetic Algorithms
Quality and reliability is one of the most important issues. in power
generation and distribution. With the recent advances in computer and
network technology, the Operational Information Systems (OIS) have been
installed in almost all power plants and substations. The data stored in
databases covers long periods of time, which presents a challenge as how
to extract the useful, task-oriented knowledge from the data to improve
power system reliability and power quality. The thesis presents the
research work in development of mathematical models for power systems
by analysing the data available from on-site measurement using
evolutionary computation techniques. The project contributes to aspects in
power generation and distribution: coal mill modelling and electrical load
area modelling.
Coal-fired power stations are now obliged to vary their outputs in response
to changing electricity demand and are required to operate more flexibly
with more varied coal specifications. The operations of a mill need to be
controlled to respond effectively to changes in plant load and coal quality.
Combustion optimization relies heavily on optimization of the mill output.
Frequently start-ups and shut-downs of mills bring the impact on power
plant to achieve both low NOx and CO2 emissions. Operational safety and
efficient combustion require better understanding to the milling process.
The work described in the thesis has three new contributions: 1)
Development of an improved normal grinding coal mill process model
which provide more accurate prediction of mill states than the previous
version; 2) Development of a new multi-segment coal mill model which
covers the whole milling process from start-ups to shut-downs; 3)
Development of a prototype software programme to implement the multisegment
mill model on-line. The software has been passed to RWEnPower PIc. for further test.
Stable operation of a power system depends on the ability to continuously
match the electrical output of generation units to the electrical load. So it is
important to have a reliable mechanism to predict the power load on time.
Model based approach is one of the options. With the sponsorship from the
National Grid Transco PIc, a study of modelling electricity area load has
been carried out through this project A methodology using evolutionary
computation techniques based on system measurements to construct power
system area load models and achieve distribution network reduction is
proposed in the thesis. Three aggregate load area model (ALAM)
approaches entitled Voltage-Two-Step, Current-Two-Step and Direct-OneStep
have been studied in the thesis. Simulations studies are carried out for
these three approaches, and it found that the Direct-One-Step offers the
best performance among the three ALAM approaches. Verification studies
are performed through the project and some rules for constructing a good
ALAM are obtained
A new model-based approach for power plant Tube-ball mill condition monitoring and fault detection
AbstractWith the fast growth in intermittent renewable power generation, unprecedented demands for power plant operation flexibility have posed new challenges to the ageing conventional power plants in the UK. Adding biomass to coal for co-fired power generation has become widely implemented practices in order to meet the emission regulation targets. These have impacted the coal mill and power plant operation safety and reliability. The Vertical Spindle mill model was developed through the authors’ work before 2007. From then, the new research progress has been made in modelling and condition monitoring for Tube-ball mills and is reported in the paper. A mathematical model for Tube-ball milling process is developed by applying engineering principles combined with model unknown parameter identifications using a computational intelligent algorithm. The model describes the whole milling process from the mill idle status, start-up to normal grinding and shut-down. The model is verified using on-site measurement data and on-line test. The on-line model is used for mill condition monitoring in two ways: (i) to compare the predicted and measured mill output pressure and temperatures and to raise alarms if there are big discrepancies; and (ii) to monitor the mill model parameter variation patterns which detect the potential faults and mill malfunctions
First order transition in PbCu(PO)O () containing CuS
Lee et al. reported that the compound LK99, with a chemical formula of
PbCu(PO)O (), exhibits room-temperature
superconductivity under ambient pressure. In this study, we investigated the
transport and magnetic properties of pure CuS and LK-99 containing CuS.
We observed a sharp superconducting-like transition and a thermal hysteresis
behavior in the resistivity and magnetic susceptibility. However, we did not
observe zero-resistivity below the transition temperature. We argue that the
so-called superconducting behavior in LK-99 is most likely due to a reduction
in resistivity caused by the first order structural phase transition of CuS
at around 385 K, from the phase at high temperature to the
phase at low temperature
Mechanisms of Sodium-glucose Cotransporter 2 Inhibitors in Heart Failure
Heart failure is an end stage cardiac disease that has been associated with high mortality and rehospitalization rates in previous decades, in spite of standard anti-heart failure therapy, thus posing a major social and economic burden on public health. Several studies have demonstrated that sodium-glucose cotransporter 2 inhibitors (SGLT2i), anti-hyperglycemic drugs whose function is independent of islet function, have significant positive effects on prognosis and quality of life, by decreasing mortality and readmission rates in patients with heart failure. To increase general clinicians’ understanding and facilitate the practical application of SGLT2i in the treatment of heart failure, the mechanisms through which SGLT2i alleviate heart failure is reviewed herein
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