900 research outputs found
On the finiteness and stability of certain sets of associated primes ideals of local cohomology modules
Let be a Noetherian local ring, an ideal of and a
finitely generated -module. Let be an integer and
r=\depth_k(I,N) the length of a maximal -sequence in dimension in
defined by M. Brodmann and L. T. Nhan ({Comm. Algebra, 36 (2008), 1527-1536).
For a subset S\subseteq \Spec R we set S_{{\ge}k}={\p\in
S\mid\dim(R/\p){\ge}k}. We first prove in this paper that
\Ass_R(H^j_I(N))_{\ge k} is a finite set for all }. Let
\fN=\oplus_{n\ge 0}N_n be a finitely generated graded \fR-module, where
\fR is a finitely generated standard graded algebra over . Let be
the eventual value of \depth_k(I,N_n). Then our second result says that for
all the sets \bigcup_{j{\le}l}\Ass_R(H^j_I(N_n))_{{\ge}k} are
stable for large .Comment: To appear in Communication in Algebr
High efficient infrared-light emission from silicon LEDs
Since 1965 the number of transistors on a single integrated circuit (IC) forminimum component costs has been almost doubling each 18 months, a phenomenon which is known as Moore’s law. The most advanced ICs contain more than a billion transistors and the line-width used in the next generation CMOS-processes is 32 nm. It is expected that in the coming decade the exponential increase in complexity will start saturating because we are approaching fundamental limits, and new approaches are being explored to push the development further after the\ud
saturation of conventional microelectronic technology. Instead of electrical interconnects, optical integration is suggested to be used in microelectronics. Furthermore,\ud
silicon nowadays remains the first material for IC technology. Meanwhile, a compact high-speed efficient silicon light source being suitable for on-chip integration\ud
process is still missing. The aim of this research is to investigate this missing component.\ud
This dissertation presents an exploration on infrared-light emitting probability in silicon light emitting devices (Si-LEDs) with new approaches to improve the\ud
routinely low emission efficiency of silicon. It starts with a theoretical calculation of the possible internal quantum efficiency in bulk-Si LEDs and SOI-LEDs, after that a model for calculating the relationship between internal and external efficiencies is introduced. Following that the experimentally achieved results from\ud
our realized LED structures implementing the theoretical predictions are exhibited subsequently
On the cofiniteness of generalized local cohomology modules
Let be a commutative Noetherian ring, an ideal of and ,
two finitely generated -modules. The aim of this paper is to investigate the
-cofiniteness of generalized local cohomology modules \displaystyle
H^j_I(M,N)=\dlim\Ext^j_R(M/I^nM,N) of and with respect to . We
first prove that if is a principal ideal then is -cofinite
for all and all . Secondly, let be a non-negative integer such
that \dim\Supp(H^j_I(M,N))\le 1 \text{for all} j Then is
-cofinite for all and \Hom(R/I,H^t_I(M,N)) is finitely generated.
Finally, we show that if or then is
-cofinite for all .Comment: 16 page
Structural Impact Mitigation of Bridge Using Tuned Mass Damper
This paper investigates the application of tuned mass damper (TMD) systems to bridge pier systems for structural impact damage mitigation and thus reduce the risk of collapses. A bridge superstructure and substructures are designed in accordance with The American Association of State Highway and Transportation Officials (AASHTO) specifications. A variety of vessel collision forces are obtained from collision testing of a scaled reinforced concrete pier. The optimal parameters of TMD systems are then determined such that the drift and displacement of the bridge superstructure are minimized for various impact scenarios. The structural impact mitigation performance of the pier equipped with the proposed optimal TMD system is compared with five different TMD systems employing the benchmark TMD optimal parameters. The uncontrolled responses are used as a baseline. It was demonstrated from the extensive simulations that the control effectiveness of the proposed TMD system was 25% better than all of the existing TMD models in reducing structure responses
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