Tool For Tuning Research Articles

Optical Enhancement in Heteroleptic Ru(II) Polypyridyl Complexes Using Electron-Donor Ancillary Ligands

Organic dyes are a viable alternative to silicon for energy conversion. Using simulations from first-principles, we show that chemical manipulation is a powerful tool for tuning the optical absorption spectra of a special class of dyes in a way that is convenient for exploitation in dye-sensitized solar cells. Specifically, we have carried out density functional theory calculations on three Ru(II) polypyridyl complexes with electron-donor ancillary ligands. These complexes were recently developed to study how different electron-donor ancillary ligands affect the photophysical and electrochemical properties of these dyes for light harvesting and photon-to-electron conversion efficiency. We found that the electron-donor ancillary ligands significantly enhance the light harvesting in the visible and the near-infrared regions relative to the reference dye N3. Furthermore, we detected a decrease in the ionization potential, which improves the energy alignment with the redox potentials of the electrolyte. These findings demonstrated that better organic materials for energy applications were developed.

Advanced semi-active engine and transmission mounts: tools for modelling, analysis, design, and tuning

This paper is focused on modelling, design, and testing of semi-active magneto-rheological (MR) engine and transmission mounts used in the automotive industry. The purpose is to develop a complete analysis, synthesis, design, and tuning tool that reduces the need for expensive and time-consuming laboratory and field tests. A detailed mathematical model of such devices is developed using multi-physics modelling techniques for physical systems with various energy domains. The model includes all major features of an MR mount including fluid dynamics, fluid track, elastic components, decoupler, rate-dip, gas-charged chamber, MR fluid rheology, magnetic circuit, electronic driver, and control algorithm. Conventional passive hydraulic mounts can also be studied using the same mathematical model. The model is validated using standard experimental procedures. It is used for design and parametric study of mounts; effects of various geometric and material parameters on dynamic response of mounts can be studied. Additionally, this model can be used to test various control strategies to obtain best vibration isolation performance by tuning control parameters. Another benefit of this work is that nonlinear interactions between sub-components of the mount can be observed and investigated. This is not possible by using simplified linear models currently available.

ELASTIC: A Large Scale Dynamic Tuning Environment

The spectacular growth in the number of cores in current supercomputers poses design challenges for the development of performance analysis and tuning tools. To be effective, such analysis and tuning tools must be scalable and be able to manage the dynamic behaviour of parallel applications. In this work, we present ELASTIC, an environment for dynamic tuning of large-scale parallel applications. To be scalable, the architecture of ELASTIC takes the form of a hierarchical tuning network of nodes that perform a distributed analysis and tuning process. Moreover, the tuning network topology can be configured to adapt itself to the size of the parallel application. To guide the dynamic tuning process, ELASTIC supports a plugin architecture. These plugins, called ELASTIC packages, allow the integration of different tuning strategies into ELASTIC. We also present experimental tests conducted using ELASTIC, showing its effectiveness to improve the performance of large-scale parallel applications.

ELASTIC: A Large Scale Dynamic Tuning Environment

The spectacular growth in the number of cores in current supercomputers poses design challenges for the development of performance analysis and tuning tools. To be effective, such analysis and tuning tools must be scalable and be able to manage the dynamic behaviour of parallel applications. In this work, we present ELASTIC, an environment for dynamic tuning of large- scale parallel applications. To be scalable, the architecture of ELASTIC takes the form of a hierarchical tuning network of nodes that perform a distributed analysis and tuning process. Moreover, the tuning network topology can be configured to adapt itself to the size of the parallel application. To guide the dynamic tuning process, ELASTIC supports a plugin architecture. These plugins, called ELASTIC packages, allow the integration of different tuning strategies into ELASTIC. We also present experimental tests conducted using ELASTIC, showing its effectiveness to improve the performance of large-scale parallel applications.

Оптимизация приложений для заданных статических компиляторов и целевых архитектур: методы и инструменты

The paper describes the workflow for optimizing programs for performance targeting the fixed hardware architecture with static compilation using GCC and LLVM compilers as examples. We present some of the optimizations performed and the corresponding evaluation results. We also describe TACT, a tool for automatic compiler tuning for the given application, and its example use cases both for an application developer and a compiler engineer. We give the sample of TACT optimization results.

Structure and special chemical reactivity of interface-stabilized cerium oxide nanolayers on TiO2(110)

Novel interface-stabilized ceria nanophases have been grown on TiO2(110) by physical vapor deposition. At low coverage, dumbbell nanostructures constituted by reconstructed titania and ceria clusters are formed, while long range ordered nanoxides can be obtained by increasing the ceria dose. Scanning tunneling microscopy and photoemission spectroscopy were used to characterize the electronic properties of the films, showing that the TiO2 substrate can effectively stabilize ceria in reduced form over a wide range of experimental conditions. Epitaxial coupling is a very useful tool for tuning the chemical properties of mixed oxide systems. The special electronic properties of the films have a direct counterpart in the chemical activity, which has been investigated by temperature programmed desorption using methanol as a probe molecule. The experimental results indicate an exceptional activity of the ceria-titania interface in the selective dehydration of methanol to formaldehyde at an unprecedented low temperature (330 K).

Tuning of a dynamic boiler model using a nonlinear multivariate optimisation method

Wide and complex process models set challenges to the modelling work. Especially the determination and tuning of the parameters of complex models are often laborious and time-consuming. The strong cross-interconnection of modelled variables also makes tuning work more difficult. Efficient tuning tools can be used to accelerate tuning work. In this paper it is proposed how a nonlinear multivariable optimisation method can be adapted for the tuning of the parameters of a dynamic circulating fluidized bed (CFB) drum boiler model, which based on the first principle laws of mass and energy. In the fine-tuning example, the tuneable variables are the gas side heat transfer coefficients and the water side local resistance coefficients of the heat exchanger model blocks into the flue gas duct.

GMATE: Dynamic Tuning of Parallel Applications in Grid Environment

Performance is a main issue in parallel application development. Dynamic tuning is a technique that changes certain applications' parameters on-line to improve their performance adapting the execution to actual conditions. To perform that, it is necessary to collect measurements, analyze application behavior and carry out tuning actions during the application execution. Computational Grids present proclivity for dynamic changes in the environment during the application execution. Therefore, dynamic tuning tools are necessary to reach the expected performance indexes of applications on those environments. This paper addresses the dynamic tuning of parallel/distributed applications on Computational Grids. We analyze Grid environments to determine their characteristics and we present the development of dynamic tuning tool GMATE enabled for such environments. The performance analysis is based on performance models that indicate how to improve the application execution. A particular problem which provokes performance bottlenecks is the load imbalance in Master/Worker applications. A heuristic to dynamically tune granularity of work and number of workers is proposed. Finally, we describe the experimental validation of the performance model and its applicability on a set of real parallel applications.

Binding of Mazindol and Analogs to the Human Serotonin and Dopamine Transporters

Mazindol has been explored as a possible agent in cocaine addiction pharmacotherapy. The tetracyclic compound inhibits both the dopamine transporter and the serotonin transporter, and simple chemical modifications considerably alter target selectivity. Mazindol, therefore, is an attractive scaffold for both understanding the molecular determinants of serotonin/dopamine transporter selectivity and for the development of novel drug abuse treatments. Using molecular modeling and pharmacologic profiling of rationally chosen serotonin and dopamine transporter mutants with respect to a series of mazindol analogs has allowed us to determine the orientation of mazindol within the central binding site. We find that mazindol binds in the central substrate binding site, and that the transporter selectivity can be modulated through mutations of a few residues in the binding pocket. Mazindol is most likely to bind as the R-enantiomer. Tyrosines 95 and 175 in the human serotonin transporter and the corresponding phenylalanines 75 and 155 in the human dopamine transporter are the primary determinants of mazindol selectivity. Manipulating the interaction of substituents on the 7-position with the human serotonin transporter Tyr175 versus dopamine transporter Phe155 is found to be a strong tool in tuning the selectivity of mazindol analogs and may be used in future drug design of cocaine abuse pharmacotherapies.

Architecturing Nanospace via Thermal Rearrangement for Highly Efficient Gas Separations

The ability to monitor free volume formation during space-making treatments is critical for the ultrafine tuning of nanospace for efficient gas separation. Here, investigating the polymer thermal rearrangement using synchrotron in situ small-angle X-ray scattering for the first time and combining this information with transport theory, we elucidate the evolution of nanospace features in polymer-based gas separation membranes. The proposed nanospace monitoring technique encompasses the structure–property relationships, therefore offering a powerful tool for tuning the polymer properties for particular gas-related clean energy applications. These results demonstrate that the fine control of the nanospace dimension and magnitude leads to a drastic improvement in gas separation performance above any material to date.

A Probability-One Homotopy Method for Stabilizer Parameter Tuning

A probability-one homotopy method for standard and least-square partial pole assignment problems is presented in this paper. The suggested method enjoys superior theoretical properties and it is very reliable. Implementation innovations, including the development of an efficient algorithm for computing the second order derivatives of eigenvalues, rescaling and eigenvalue tracking, are reported in detail. Simulation results of ten test systems including the East China power system with 465 machines and 3296 buses are described, showing that the suggested method is a reliable parameter tuning tool and it has the potential for solving real-world stabilizer parameter tuning problems.

Modification of electrospun poly(ε-caprolactone) mats by formation of a polyelectrolyte complex between poly(acrylic acid) and quaternized chitosan for tuning of their antibacterial properties

Novel antibacterial nanofibrous mats from poly(ε-caprolactone) (PCL) were prepared using the formation of polyelectrolyte complex as a tool for tuning the properties of the mats. Two approaches were applied: (i) coating the surface of PCL mats with crosslinked poly(acrylic acid) (PAAcr) followed by the formation of a polyelectrolyte complex (PEC) with N,N,N-trimethylchitosan iodide (TMCh) and (ii) grafting of PAA on the surface of PCL mats and subsequent PEC formation between grafted PAA and TMCh. The formation of PEC-based coating on the fiber surface was demonstrated by means of scanning electron microscopy (SEM), attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The microbiological screening revealed that in contrast to the pristine PCL mats, the PEC-coated PCL mats are effective in inhibiting the growth of the Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli as well as in suppressing the adhesion of pathogenic bacteria S. aureus.

An efficient imperialist competitive algorithm for scheduling in the two-stage assembly flow shop problem

This paper considers a two-stage assembly flow shop problem where m parallel machines are in the first stage and an assembly machine is in the second stage. The objective is to minimise a weighted sum of makespan and mean completion time for n available jobs. As this problem is proven to be NP-hard, therefore, we employed an imperialist competitive algorithm (ICA) as solution approach. In the past literature, Torabzadeh and Zandieh (2010) showed that cloud theory-based simulated annealing algorithm (CSA) is an appropriate meta-heuristic to solve the problem. Thus, to justify the claim for ICA capability, we compare our proposed ICA with the reported CSA. A new parameters tuning tool, neural network, for ICA is also introduced. The computational results clarify that ICA performs better than CSA in quality of solutions.

Sustainable Thermoplastic Elastomers Derived from Fatty Acids

Vegetable oils are an attractive source for polymers due to their low cost, abundance, annual renewability, and ease of functionalization. Stearyl and lauryl acrylate, derived from vegetable oils such as soybean, coconut, and palm kernel oil, have been polymerized through reversible addition–fragmentation chain transfer polymerization, resulting in poly(styrene-b-(lauryl acrylate-co-stearyl acrylate)-b-styrene) (SAS) triblock copolymers. Varying the length of the side chain on the polyacrylate midblock (C18 and C12 in stearyl and lauryl acrylate repeat units, respectively) is a convenient tool for tuning the physical properties of the triblock copolymers. The SAS triblock copolymers exhibit properties appropriate for thermoplastic elastomer (TPE) applications. Small-angle X-ray scattering and transmission electron microscopy experiments have elucidated the microphase-separated morphology of the SAS triblock copolymers, consistent with a spherical morphology lacking long-range order. The physical propertie...

Nanocomposite materials for rapid-response interior air humidity buffering in closed environments

Three different mesoporous silica (MS) samples were selected as template materials for designing novel, high-performance desiccants to give rapid-response temperature and humidity buffering in closed environments. The aim was to investigate how the functional properties of the MS materials can be tuned to suit differing psychrometric conditions in closed environments, and to inform the design process by conducting sensitivity analysis using building performance simulation software. Their humidity buffering performance was compared with other materials using WUFI Pro v5.1 to conduct numerical hygrothermal simulations. The MS materials had more than two orders of magnitude greater humidity buffering than traditional interior building materials (e.g. painted gypsum plaster) due to their high vapour storage capacity and high dynamic vapour sorption (DVS) response rates. Analysis showed that the gradient of the w 50–w 80 portion of the absorption branch isotherm is the most sensitive parameter when using the hygrothermal numerical model as a design tool for materials tuning.

QUASI-CHEMICAL REACTIONS IN IRRADIATED SILICON

Normal 0 There are described the quasi-chemical reactions that take place between radiation defects and impurities in irradiated silicon. It has been experimentally investigated single-crystalline n- and p-type silicon doped, respectively, with phosphorus or boron, irradiated with high-energy electrons or protons and subjected to the high-temperature isochronous annealing. Rates of quasi-chemical reactions are found to be dependent on the charge-states of reactants and then controllable by varying the irradiation conditions – beam-intensity, irradiation temperature and IR light exposure during the irradiation, as well as temperature of annealing of the previously irradiated samples. It is shown that the quasi-chemical reactions can serve as effective tools for tuning the electronic properties of silicon, the basic material of micro- and nanoelectronics .

Improving the Catalytic Activity of Semiconductor Nanocrystals through Selective Domain Etching

Colloidal chemistry offers an assortment of synthetic tools for tuning the shape of semiconductor nanocrystals. While many nanocrystal architectures can be obtained directly via colloidal growth, other nanoparticle morphologies require alternative processing strategies. Here, we show that chemical etching of colloidal nanoparticles can facilitate the realization of nanocrystal shapes that are topologically inaccessible by hot-injection techniques alone. The present methodology is demonstrated by synthesizing a two-component CdSe/CdS nanoparticle dimer, constructed in a way that both CdSe and CdS semiconductor domains are exposed to the external environment. This structural morphology is highly desirable for catalytic applications as it enables both reductive and oxidative reactions to occur simultaneously on dissimilar nanoparticle surfaces. Hydrogen production tests confirmed the improved catalytic activity of CdSe/CdS dimers, which was enhanced 3-4 times upon etching treatment. We expect that the demonstrated application of etching to shaping of colloidal heteronanocrystals can become a common methodology in the synthesis of charge-separating nanocrystals, leading to advanced nanoparticles architectures for applications in areas of photocatalysis, photovoltaics, and light detection.

ChemInform Abstract: Mechanochemical Synthesis of Hydrogen Storage Materials

AbstractReview: 282 refs.

Efficient computer-aided design of ceramic block duplexers

An efficient CAD technique for the design of ceramic block duplexers is presented in this work. The technique makes use of an accurate equivalent circuit extracted from first electromagnetic principles. This circuit is used as the basic tuning tool, which speeds up the design process by avoiding the time consuming electromagnetic simulator. It also indicates the necessary structural changes to achieve the desired response.

Simultaneous ion beam profile scan using a single laser source

We report on the world's first experiment of a simultaneous profile scan of the hydrogen ion (${\mathrm{H}}^{\ensuremath{-}}$) beam using a laser wire system. The system was developed and brought to operational level of application at the superconducting linac of the Spallation Neutron Source accelerator complex. The laser wire profile scanner is based on a photodetachment process and therefore can be conducted on a 1-MW neutron production ${\mathrm{H}}^{\ensuremath{-}}$ beam in a nonintrusive manner. The new simultaneous profile scanning system allows one to simultaneously measure profiles of the ${\mathrm{H}}^{\ensuremath{-}}$ beam at nine different locations of the linac with high speed and accuracy, and therefore provides a unique tool for accelerator tuning and physics study. This paper describes the design, optical system and software platform developments, and measurement results of the simultaneous profile scanning system.