Use
the fast Fourier transform function fft to analyse following signal. Plot the ORIGINAL signal, and the magnitude of its
spectrum linearly and logarithmically. Apply Hamming window to reduce the
leakage.
.
The hamming window can be coded in Matlab as
for n=1:N
hamming(n)=0.54+0.46*cos((2*n-N+1)*pi/N);
end;
where
N is the data length in the FFT.
We introduce a sub-cell WENO reconstruction method to evaluate spatial derivatives in the high-order ADER scheme. The basic idea in our reconstruction is to use only r stencils to reconstruct the point-wise values of solutions and spatial derivatives for the 2r-1 th order
ADER scheme in one dimension, while in two dimensions, the dimension-by-dimension sub-cell reconstruction approach for spatial derivatives is employed. Compared with the ORIGINAL ADER scheme of Toro and Titarev (2002) [2] that uses the direct derivatives of reconstructed polynomials for solutions to evaluate spatial derivatives, our method not only reduces greatly the computational costs of the ADER scheme on a given mesh,
but also avoids possible numerical oscillations near discontinuities, as demonstrated by a number of one- and two-dimensional numerical tests. All these tests show that the 5th-order ADER scheme based on our sub-cell reconstruction method achieves the desired accuracy, and is essentially non-oscillatory and computationally cheaper for problems with discontinuities.
Our ORIGINAL effort in writing this book was to create a starting point for those in
the business community who did not have a high level of technical expertise but
needed to have some understanding of the technical functions of their information
and communication technologies (ICT) in a corporate environment. As was true
with the first edition of this book, if you are already an engineer, find some other
form of pleasure reading—this text is not designed for you!
Since the ORIGINAL publication of Manual 74 in 1991, and the preceding
“Guidelines for Transmission Line Structural Loading” in 1984, the
understanding of structural loadings on transmission line structures has
broadened signifi cantly. However, improvements in computational capa-
bility have enabled the transmission line engineer to more easily deter-
mine structural loadings without properly understanding the parameters
that affect these loads. Many seasoned professionals have expressed
concern for the apparent lack of recent information on the topic of struc-
tural loadings as new engineers enter this industry. The Committee on
Electrical Transmission Structures is charged with the responsibility to
report, evaluate, and provide loading requirements of transmission struc-
tures. This task committee was therefore formed to update and revise the
1991 manual.
Thepredecessorvolumeofthisbookwaspublishedin1996.Intheyears
since then, some things have changed and some have not.
Two of the things that have not changed are the desire for better
models and faster simulations. I performed the ORIGINAL simulations on
my “hyperfast” 133-MHz computer! At the time, I thought if I could just
getafastercomputer,allofourSPICEproblemswouldbehistory,right?
TodayIamsimulatingonacomputerthathasa2.6-GHzprocessorwith
512 MB of RAM, and I would still say that simulations run too slow.
The computer technology has evolved, but so have the models. In 1996
wewereperformingsimulationson100-kHzpowerconverters,whereas
today I routinely see 1- and 2-MHz power converters.
In this new edition of the book, only minor changes were made to the ORIGINAL
nine chapters but three new chapters treat topics of increasing interest to GPS
users and equipment developers. One topic, improving the GPS receiver sensi-
tivity may extend their operations into buildings, which is becoming important
for emergency rescue and urban warfare.
The basic topic of this book is solving problems from system and control theory using
convex optimization. We show that a wide variety of problems arising in system
and control theory can be reduced to a handful of standard convex and quasiconvex
optimization problems that involve matrix inequalities. For a few special cases there
are “analytic solutions” to these problems, but our main point is that they can be
solved numerically in all cases. These standard problems can be solved in polynomial-
time (by, e.g., the ellipsoid algorithm of Shor, Nemirovskii, and Yudin), and so are
tractable, at least in a theoretical sense. Recently developed interior-point methods
for these standard problems have been found to be extremely efficient in practice.
Therefore, we consider the ORIGINAL problems from system and control theory as solved.
摘要：本文在分析1GBT的動態開關特性和過流狀態下的電氣特性的基礎上，通過對常規的IGBT推挽驅動電路進行改進，得到了具有良好過流保護特性的IGBT驅動電路。該電路簡單，可靠，易用，配合DSP等控制芯片能達到很好的驅動效果Abstract：Based on the studies on the dynamic switching and over-current characteristics of IGBT，this paper makes some improvments to the ORIGINAL push-pull driving circuit，obtains a new IGBT driving circuit which has a good over-current protection function.The circuit is simple，reliable and easy to use.Combined with controlling chips such as DSP it will do a great job in driving applications.關鍵詞：IBGT：開關特性；驅動；過流保護；Key Words:IGBT；switching characteristics；driving:over-current protection
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