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Approach Lies (approach + ly)
Selected AbstractsSurface-Protected Etching of Mesoporous Oxide Shells for the Stabilization of Metal NanocatalystsADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Qiao Zhang Abstract Nanoparticles of transition metals, particularly noble metals, are widely used in catalysis. However, enhancing their stability during catalytic reactions has been a challenge that has limited the full use of the benefits associated with their small size. In this Feature Article, a general "encapsulation and etching" strategy for the fabrication of nanocatalyst systems is introduced in which catalyst nanoparticles are protected within porous shells. The novelty of this approach lies in the use of chemical etching to assist the creation of mesopores in a protective oxide shell to promote efficient mass transfer to encapsulated metal nanoparticles. The etching process allows for the direct transformation of dense silica coatings into porous shells so that chemical species can reach the catalyst surface to participate in reactions while the shells act as physical barriers against aggregation of the catalyst particles. By using the surface-protected etching process, both yolk,shell and core,satellite type nanoreactors are synthesized and their utilization in liquid- and gas-phase catalysis is demonstrated. The thermal and chemical stability of the metallic cores during catalytic reactions is also investigated, and further work is carried out to enhance recyclability via the introduction of superparamagnetic components into the nanoreactor framework. [source] An interpolation-based local differential quadrature method to solve partial differential equations using irregularly distributed nodesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2008Hang Ma Abstract To circumvent the constraint in application of the conventional differential quadrature (DQ) method that the solution domain has to be a regular region, an interpolation-based local differential quadrature (LDQ) method is proposed in this paper. Instead of using regular nodes placed on mesh lines in the DQ method (DQM), irregularly distributed nodes are employed in the LDQ method. That is, any spatial derivative at a nodal point is approximated by a linear weighted sum of the functional values of irregularly distributed nodes in the local physical domain. The feature of the new approach lies in the fact that the weighting coefficients are determined by the quadrature rule over the irregularly distributed local supporting nodes with the aid of nodal interpolation techniques developed in the paper. Because of this distinctive feature, the LDQ method can be consistently applied to linear and nonlinear problems and is really a mesh-free method without the limitation in the solution domain of the conventional DQM. The effectiveness and efficiency of the method are validated by two simple numerical examples by solving boundary-value problems of a linear and a nonlinear partial differential equation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Adaptive robust force control for vehicle active suspensionsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2 2004Supavut Chantranuwathana Abstract In this paper, the modular adaptive robust control (MARC) technique is applied to design the force loop controller of an electro-hydraulic active suspension system. A key advantage of this modular design approach lies in the fact that the adaptation algorithm can be designed for explicit estimation convergence. The effect of parameter adaptation on force tracking performance can be compensated and thus it is possible to guaranteed certain control performance. Experimental results from a quarter-car active suspension test rig show that when realistic external disturbances and measurement noises exist, the modular design achieves a better estimate than the non-modular ARC design. The improved estimation was found to result in control signals with slightly lower magnitude while maintaining similar tracking performance. Copyright © 2004 John Wiley & Sons, Ltd. [source] An adaptive resource reservation for vehicular mobile networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2009I. Ben Hamida This paper presents the time-based bandwidth reservation (TBR) algorithm, suitable for handoff management in cellular systems. TBR is based on real-time measurements of mobile stations (position, velocity and acceleration). The scheme consists in sending reservation requests to the neighboring cells based on an extrapolation of the user's motion. The originality of our approach lies in dynamically adjusting the amount of time for which bandwidth has to be allocated and reserved in a cell. In addition, we propose an optimal channel requests arrangement (CRA) algorithm in order to improve the performance of TBR in terms of resource utilization. Finally, we propose VTBR, an adapted and extended version of TBR for better support of vehicular network specificities where service degradation or forced call termination may occur owing to frequent handoffs. Detailed simulation results for TBR and VTBR schemes and a comparison with the guard channel scheme are presented. The results show that TBR and VTBR can efficiently improve the flow dropping probability. Copyright © 2008 John Wiley & Sons, Ltd. [source] Nano-Level Mixing of ZnO into Poly(methyl methacrylate)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 17 2010Mukesh Agrawal Abstract A simple, facile and versatile approach is presented for the preparation of PMMA/ZnO nanocomposite materials, which possess high transparency, no color, good thermal stability, UV absorption and improved mechanical properties. The employed process involved mixing of ZnO nanoparticles dispersed in DMAc with the PMMA matrix dissolved in the same solvent. The effect of ZnO content on the physical properties of the PMMA matrix is studied. A significant improvement in mechanical properties was observed with the incorporation of 0.5 wt.-% ZnO particles. The beauty of the described approach lies in the fact that despite being a simple and facile approach, it offers nano-level (2,5,nm) mixing of ZnO nanoparticles into a polymer matrix. [source] The ,Origin' of Evil according to Anselm of CanterburyTHE HEYTHROP JOURNAL, Issue 2 2002Daniel Deme Theological debate about the origin of evil derives from the quest after God's goodness and justice. This problem can be constructively discussed only within the framework of a universe that has been created good, and within a corresponding anthropology. Anselm's enquiry proceeds much along these tracks, and is based on the premises of the Platonic-Augustinian view of evil as the privation of good, yet it concludes with a reference to the domain of the irrational and contradiction in which such a discussion must necessarily harbour. The strength and uniqueness of his approach lies in his well defined hermeneutical and epistemological framework: his definition of theology as fides quaerens intellectum on the one hand, and his concept of ordo et pulchritudo universitatis on the other. The aim of this article is to discuss Anselm's answer to the origin of evil in a wider context of his definitions of freedom and theology, trying to consider the issue, as Anselm does, from the point of view of the doctrine of Creation by the Word. His argument will be considered from the standpoint of Systematic Theology, which will enable us to contrast it with the thought of modern thinkers. Therefore the goal of this writing is not primarily to show how unique Anselm's solution is in the history of dogma, but rather to highlight the uniqueness of the manner of his elaboration of this problem within his own theological framework. [source] Longitudinal analysis of androgen deprivation of prostate cancer cells identifies pathways to androgen independenceTHE PROSTATE, Issue 7 2008Jason M. D'Antonio Abstract BACKGROUND Following androgen ablation therapy, the majority of prostate cancer patients develop treatment resistance with a median time of 18,24 months to disease progression. METHODS To identify molecular targets that promote prostate cancer cell survival and contribute to androgen independence, we evaluated changes in LNCaP cell gene expression during 12 months of androgen deprivation. At time points reflecting critical growth and phenotypic changes, we performed Affymetrix expression array analysis to examine the effects of androgen deprivation during the acute response, during the period of apparent quiescence, and following the emergence of a highly proliferative, androgen-independent prostate cancer cell phenotype (LNCaP-AI). RESULTS We discovered alterations in gene expression for molecules associated with promoting prostate cancer cell growth and survival, and regulating cell cycle progression and apoptosis. Additionally, expression of AR co-regulators, adrenal androgen metabolizing enzymes, and markers of neuroendocrine disease were significantly altered. CONCLUSIONS These findings contribute greatly to our understanding of androgen-independent prostate cancer. The value of this longitudinal approach lies in the ability to examine gene expression changes throughout the adaptive response to androgen deprivation; it provides a more dynamic illustration of genes which contribute to disease progression in addition to specific genes which constitute an androgen-independent phenotype. Prostate 68: 698,714, 2008. © 2008 Wiley-Liss, Inc. [source] A new adaptive backstepping Coulomb friction compensator for servo control systems,ASIAN JOURNAL OF CONTROL, Issue 1 2009Jen-te Yu Abstract A new Coulomb friction compensator is proposed for servo control systems in this paper. The novelty of the new approach lies in its capability of assigning the eigenvalues of the resulting closed loop system while attacking the problem. First, based on the standard backstepping methodology, an implicit Lyapunov function, with part of the components being only symbolically constructed at the very beginning, is utilized. To increase the robustness of the system against disturbance and model inaccuracy, an integral term is employed in the design. Using part of the variable gradient method, we are able to turn the implicit Lyapunov function into an explicit one, which is positive definite, and whose time-derivative is negative definite. Second, it will be shown that the resulting closed loop error system is a switched linear system with two possible active modes that share the same set of eigenvalues, which is at our disposal. Unlike the common adaptive control design methods, such as the Control Lyapunov Function approach, in which the gains are typically positive but otherwise arbitrary, and are hence difficult to choose and have a lack of connection with the system's performance, our new scheme imposes two further constraints on the gains. It turns out that we can then match these gains with the coefficients of the desired characteristic equation of the closed loop system. In this respect, the gains are linked to the system's overall performance, which is a new and very appealing feature for such a scheme. Finally, a procedure of constructing a common Lyapunov function is provided to prove exponential stability of the aforementioned switched linear system. In addition, using the invariance principle, we will show the convergence of the estimated Coulomb friction coefficient to its real value. Numerical simulations are given to validate the effectiveness of the design and its robustness against friction time-variations. Compared to existing results, the proposed scheme is much simpler, hence, much more advantageous computationally. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] | |||||||||||||