2,978 research outputs found
Efficient and Perfect domination on circular-arc graphs
Given a graph , a \emph{perfect dominating set} is a subset of
vertices such that each vertex is
dominated by exactly one vertex . An \emph{efficient dominating set}
is a perfect dominating set where is also an independent set. These
problems are usually posed in terms of edges instead of vertices. Both
problems, either for the vertex or edge variant, remains NP-Hard, even when
restricted to certain graphs families. We study both variants of the problems
for the circular-arc graphs, and show efficient algorithms for all of them
A Partial Test and Development of the DeLone and McLean Model of IS Success
DeLone and McLean’s (1992) comprehensive review of different information system success measures concludes with a model of interrelationships between six IS Success constructs. This paper critically examines the meaning of four of these constructs and the evidence of relationships between them. It then provides results from an empirical test of these relationships. TheempiricalresultsprovidesubstantialsupportforDeLoneandMcLean’smodel. Threefactors,System Quality, Information Quality, and Usefulness, are found to explain 72% of the variance in the overall User Satisfaction measure. Three factors, System Quality, Information Quality, and a measure of the importance of the system to the user, User Involvement, are found to explain 56% of the variance in Usefulness. The paper concludes that of the four measures studied, the best “omnibus” measure of IS success is User Satisfaction. This can be measured using the simple four-question instrument presented in the study
Geometric nonlinear diffusion filter and its application to X-ray imaging
<p>Abstract</p> <p>Background</p> <p>Denoising with edge preservation is very important in digital x-ray imaging since it may allow us to reduce x-ray dose in human subjects without noticeable degradation of the image quality. In denoising filter design for x-ray imaging, edge preservation as well as noise reduction is of great concern not to lose detailed spatial information for accurate diagnosis. In addition to this, fast computation is also important since digital x-ray images are mostly comprised of large sized matrices.</p> <p>Methods</p> <p>We have developed a new denoising filter based on the nonlinear diffusion filter model. Rather than employing four directional gradients around the pixel of interest, we use geometric parameters derived from the local pixel intensity distribution in calculating the diffusion coefficients in the horizontal and vertical directions. We have tested the filter performance, including edge preservation and noise reduction, using low dose digital radiography and micro-CT images.</p> <p>Results</p> <p>The proposed denoising filter shows performance similar to those of nonlinear anisotropic diffusion filters (ADFs), one Perona-Malik ADF and the other Weickert's ADF in terms of edge preservation and noise reduction. However, the computation time has been greatly reduced.</p> <p>Conclusions</p> <p>We expect the proposed denoising filter can be greatly used for fast noise reduction particularly in low-dose x-ray imaging.</p
Discovery and functional annotation of PRSS1 promoter variants in chronic pancreatitis
Recently, our resequencing of the promoter region of PRSS1 in French Caucasian individuals led to the identification of a functional variant (c.-204C > A) that is in perfect linkage disequilibrium with the “chronic pancreatitis (CP)-protective” PRSS1 c.-408C > T variant. Here, we extended the resequencing to 626 French Caucasians (242 idiopathic CP patients and 384 controls). We discovered three additional variants (c.-184G > A, c.-173C > T, and c.-147C > T), each being found only once in either patients or controls. We analyzed these three variants, together with a known PRSS1 promoter variant (c.-30_-28delTCC) long considered to be causative for CP, by luciferase promoter reporter assay in AR42J cells treated with dexamethasone. This analysis revealed that c.-30_-28delTCC resulted in reduced rather than increased PRSS1 gene expression, suggesting that it is not a CP risk factor as originally claimed. We provide evidence that c.-147C > T probably confers protection against CP by reducing the affinity of an ATF4 transcription factor binding site
Intercalation and Delamination of Layered Carbides and Carbonitrides
Intercalation and delamination of two-dimensional solids in many cases is a requisite step for exploiting their unique properties. Herein we report on the intercalation of two-dimensional Ti3C2, Ti3 CN and TiNbC - so called MXenes. Intercalation of hydrazine, and its co-intercalation with N,N-dimethylformamide, resulted in increases of the c-lattice parameters of surface functionalized f-Ti3C2, from 19.5 to 25.48 and 26.8 Å, respectively. Urea is also intercalated into f-Ti3C2. Molecular dynamics simulations suggest that a hydrazine monolayer intercalates between f-Ti3C2 layers. Hydrazine is also intercalated into f-Ti3 CN and f-TiNbC. When dimethyl sulphoxide is intercalated into f-Ti3C2, followed by sonication in water, the f-Ti3C2 is delaminated forming a stable colloidal solution that is in turn filtered to produce MXene \u27paper\u27. The latter shows excellent Li-ion capacity at extremely high charging rates
CFD, potential flow and system-based simulations of fully appended free running 5415m in calm water and waves
5415M, course-keeping, waves, CFD, validation, NATO AVT-161
Abstract. The seakeeping ability of ships is one of the aspects that needs to be assessed during
the design phase of ships. Traditionally, potential flow calculations and model tests are employed
to investigate whether the ship performs according to specified criteria. With the increase of
computational power nowadays, advanced computational tools such as Computational Fluid
Dynamics (CFD) become within reach of application during the assessment of ship designs.
In the present paper, a detailed validation study of several computational methods for
ship dynamics is presented. These methods range from low-fidelity system-based methods, to
potential flow methods, to high-fidelity CFD tools. The ability of the methods to predict motions
in calm water as well as in waves is investigated. In calm water, the roll decay behavior of a
fully appended self-propelled free running 5415M model is investigated first.
Subsequently, forced roll motions simulated by oscillating the rudders or stabilizer fins
are studied. Lastly, the paper discusses comparisons between experiments and simulations in waves
with varying levels of complexity, i.e. regular head waves, regular beam waves and bi-chromatic
waves.
The predictions for all methods are validated with an extensive experimental data set for ship
motions and loads on appendages such as rudders, fins and bilge keels. Comparisons between the
different methods and with the experiments are made for the relevant motions and the
high fidelity CFD results are used to explain some of the complex physics. The course keeping and
seakeeping of the model, the reduction rate of the roll motion, the effectiveness of the fin
stabilizers as roll reduction device and the interaction of the roll motion with other motions are
investigated as well. The paper shows that only high-fidelity CFD is able to accurately
predict all the relevant physics during roll decay, forced oscillation and sailing in waves
- …