7,447 research outputs found
Adaptive design of delta sigma modulators
In this thesis, a genetic algorithm based on differential evolution (DE) is used to generate delta sigma modulator (DSM) noise transfer functions (NTFs). These NTFs outperform those generated by an iterative approach described by Schreier and implemented in the delsig Matlab toolbox. Several lowpass and bandpass DSMs, as well as DSM\u27s designed specifically for and very low intermediate frequency (VLIF) receivers are designed using the algorithm developed in this thesis and compared to designs made using the delsig toolbox. The NTFs designed using the DE algorithm always have a higher dynamic range and signal to noise ratio than those designed using the delsig toolbox
Information-adaptive clinical trials: a selective recruitment design
We propose a novel adaptive design for clinical trials with time-to-event
outcomes and covariates (which may consist of or include biomarkers). Our
method is based on the expected entropy of the posterior distribution of a
proportional hazards model. The expected entropy is evaluated as a function of
a patient's covariates, and the information gained due to a patient is defined
as the decrease in the corresponding entropy. Candidate patients are only
recruited onto the trial if they are likely to provide sufficient information.
Patients with covariates that are deemed uninformative are filtered out. A
special case is where all patients are recruited, and we determine the optimal
treatment arm allocation. This adaptive design has the advantage of potentially
elucidating the relationship between covariates, treatments, and survival
probabilities using fewer patients, albeit at the cost of rejecting some
candidates. We assess the performance of our adaptive design using data from
the German Breast Cancer Study group and numerical simulations of a biomarker
validation trial
Adaptive design of nano-scale dielectric structures for photonics
Using adaptive algorithms, the design of nano-scale dielectric structures for
photonic applications is explored. Widths of dielectric layers in a linear
array are adjusted to match target responses of optical transmission as a
function of energy. Two complementary approaches are discussed. The first
approach uses adaptive local random updates and progressively adjusts
individual dielectric layer widths. The second approach is based on global
updating functions in which large subgroups of layers are adjusted
simultaneously. Both schemes are applied to obtain specific target responses of
the transmission function within selected energy windows, such as discontinuous
cut-off or power-law decay filters close to a photonic band edge. These
adaptive algorithms are found to be effective tools in the custom design of
nano-scale photonic dielectric structures.Comment: 4 pages Revtex, 4 embedded EPS figure
Optimum linear adaptive design of dominant type systems with large parameter variations Semiannual status report, period ending 30 Sep. 1968
Optimum linear adaptive design of dominant type systems with large parameter variation
Adaptive Design of Excitonic Absorption in Broken-Symmetry Quantum Wells
Adaptive quantum design is used to identify broken-symmetry quantum well
potential profiles with optical response properties superior to previous ad-hoc
solutions. This technique performs an unbiased stochastic search of
configuration space. It allows us to engineer many-body excitonic wave
functions and thus provides a new methodology to efficiently develop optimized
quantum confined Stark effect device structures.Comment: 4 pages, 3 encapsulated postscript figure
An Adaptive Design Methodology for Reduction of Product Development Risk
Embedded systems interaction with environment inherently complicates
understanding of requirements and their correct implementation. However,
product uncertainty is highest during early stages of development. Design
verification is an essential step in the development of any system, especially
for Embedded System. This paper introduces a novel adaptive design methodology,
which incorporates step-wise prototyping and verification. With each adaptive
step product-realization level is enhanced while decreasing the level of
product uncertainty, thereby reducing the overall costs. The back-bone of this
frame-work is the development of Domain Specific Operational (DOP) Model and
the associated Verification Instrumentation for Test and Evaluation, developed
based on the DOP model. Together they generate functionally valid test-sequence
for carrying out prototype evaluation. With the help of a case study 'Multimode
Detection Subsystem' the application of this method is sketched. The design
methodologies can be compared by defining and computing a generic performance
criterion like Average design-cycle Risk. For the case study, by computing
Average design-cycle Risk, it is shown that the adaptive method reduces the
product development risk for a small increase in the total design cycle time.Comment: 21 pages, 9 figure
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