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排序方式: 共有196条查询结果,搜索用时 15 毫秒
71.
Christian Prins Caroline Prodhon Roberto Wolfler Calvo 《Annals of Operations Research》2006,147(1):23-41
This paper deals with the Bi-Objective Set Covering Problem, which is a generalization of the well-known Set Covering Problem.
The proposed approach is a two-phase heuristic method which has the particularity to be a constructive method using the primal-dual
Lagrangian relaxation to solve single objective Set Covering problems. The results show that this algorithm finds several
potentially supported and unsupported solutions. A comparison with an exact method (up to a medium size), shows that many
Pareto-optimal solutions are retrieved and that the other solutions are well spread and close to the optimal ones. Moreover,
the method developed compares favorably with the Pareto Memetic Algorithm proposed by Jaszkiewicz. 相似文献
72.
73.
P. Tim Prins Johanna C. van der Bok Thomas P. van Swieten Stijn O. M. Hinterding Andy J. Smith Andrei V. Petukhov Andries Meijerink Freddy T. Rabouw 《Angewandte Chemie (International ed. in English)》2023,62(28):e202305086
β-NaYF4 nanocrystals are a popular class of optical materials. They can be doped with optically active lanthanide ions and shaped into core-multi-shell geometries with controlled dopant distributions. Here, we follow the synthesis of β-NaYF4 nanocrystals from α-NaYF4 precursor particles using in situ small-angle and wide-angle X-ray scattering and ex situ electron microscopy. We observe an evolution from a unimodal particle size distribution to bimodal, and eventually back to unimodal. The final size distribution is narrower in absolute numbers than the initial distribution. These peculiar growth dynamics happen in large part before the α-to-β phase transformation. We propose that the splitting of the size distribution is caused by variations in the reactivity of α-NaYF4 precursor particles, potentially due to inter-particle differences in stoichiometry. Rate equation modeling confirms that a continuous distribution of reactivities can result in the observed particle growth dynamics. 相似文献
74.
Dinon AZ Prins TW van Dijk JP Arisi AC Scholtens IM Kok EJ 《Analytical and bioanalytical chemistry》2011,400(5):1433-1442
Primers and probes were developed for the element-specific detection of cry1A.105 and cry2Ab2 genes, based on their DNA sequence as present in GM maize MON89034. Cry genes are present in many genetically modified (GM) plants and they are important targets for developing GMO element-specific detection methods. Element-specific methods can be of use to screen for the presence of GMOs in food and feed supply chains. Moreover, a combination of GMO elements may indicate the potential presence of unapproved GMOs (UGMs). Primer-probe combinations were evaluated in terms of specificity, efficiency and limit of detection. Except for specificity, the complete experiment was performed in 9 PCR runs, on 9 different days and by testing 8 DNA concentrations. The results showed a high specificity and efficiency for cry1A.105 and cry2Ab2 detection. The limit of detection was between 0.05 and 0.01 ng DNA per PCR reaction for both assays. These data confirm the applicability of these new primer-probe combinations for element detection that can contribute to the screening for GM and UGM crops in food and feed samples. 相似文献
75.
Juan G. Villegas Christian Prins Caroline Prodhon Andrés L. Medaglia Nubia Velasco 《European Journal of Operational Research》2013
In the truck and trailer routing problems (TTRPs) a fleet of trucks and trailers serves a set of customers. Some customers with accessibility constraints must be served just by truck, while others can be served either by truck or by a complete vehicle (a truck pulling a trailer). We propose a simple, yet effective, two-phase matheuristic that uses the routes of the local optima of a hybrid GRASP × ILS as columns in a set-partitioning formulation of the TTRP. Using this matheuristic we solved both the classical TTRP with fixed fleet and the new variant with unlimited fleet. This matheuristic outperforms state-of-the-art methods both in terms of solution quality and computing time. While the best variant of the matheuristic found new best-known solutions for several test instances from the literature, the fastest variant of the matheuristic achieved results of comparable quality to those of all previous method from the literature with an average speed-up of at least 2.5. 相似文献
76.
Evans BA Fiser BL Prins WJ Rapp DJ Shields AR Glass DR Superfine R 《Journal of magnetism and magnetic materials》2012,324(4):501-507
Magnetic elastomers have been widely pursued for sensing and actuation applications. Silicone-based magnetic elastomers have a number of advantages over other materials such as hydrogels, but aggregation of magnetic nanoparticles within silicones is difficult to prevent. Aggregation inherently limits the minimum size of fabricated structures and leads to non-uniform response from structure to structure. We have developed a novel material that is a complex of a silicone polymer (polydimethylsiloxane-co-aminopropylmethylsiloxane) adsorbed onto the surface of magnetite (γ-Fe2O3) nanoparticles 7-10 nm in diameter. The material is homogenous at very small length scales (<100 nm) and can be crosslinked to form a flexible magnetic material, which is ideally suited for the fabrication of micro- to nanoscale magnetic actuators. The loading fraction of magnetic nanoparticles in the composite can be varied smoothly from 0 to 50 wt% without loss of homogeneity, providing a simple mechanism for tuning actuator response. We evaluate the material properties of the composite across a range of nanoparticle loading, and demonstrate a magnetic-field-induced increase in compressive modulus as high as 300%. Furthermore, we implement a strategy for predicting the optimal nanoparticle loading for magnetic actuation applications, and show that our predictions correlate well with experimental findings. 相似文献
77.
Erica DelGrosso Giulio Ragazzon Leonard J. Prins Francesco Ricci 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5638-5642
We show herein that allostery offers a key strategy for the design of out‐of‐equilibrium systems by engineering allosteric DNA‐based nanodevices for the transient loading and release of small organic molecules. To demonstrate the generality of our approach, we used two model DNA‐based aptamers that bind ATP and cocaine through a target‐induced conformational change. We re‐engineered these aptamers so that their affinity towards their specific target is controlled by a DNA sequence acting as an allosteric inhibitor. The use of an enzyme that specifically cleaves the inhibitor only when it is bound to the aptamer generates a transient allosteric control that leads to the release of ATP or cocaine from the aptamers. Our approach confirms that the programmability and predictability of nucleic acids make synthetic DNA/RNA the perfect candidate material to re‐engineer synthetic receptors that can undergo chemical fuel‐triggered release of small‐molecule cargoes and to rationally design non‐equilibrium systems. 相似文献
78.
Louis H. A. Prins Armand de Vries Mino R. Caira Douglas W. Oliver Sandra van Dyk Sarel F. Malan 《Journal of chemical crystallography》2008,38(9):705-709
Abstract Polycyclic hydrocarbon compounds exhibit a wide variety of biological activities, ranging from antiviral to Parkinson’s disease.
Several structures such as the adamantanes have reached clinical status and are used therapeutically to treat, amongst others,
neurodegenerative disorders such as Alzheimer’s. Polycyclics have also been utilised as carrier molecules to facilitate entry
of drugs into the brain. The synthesis, molecular and crystal structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.02,10.03,14.04,9.09,13.012,15]tetradecane, are reported. NMR spectroscopy was applied for structure elucidation of the novel compound and a rearrangement
mechanism is proposed for its formation. This compound crystallises in the orthorhombic system, space group Pbca (no. 61). The unit cell parameters are: a = 12.3763 (7), b = 11.6597 (6), c = 15.0539 (8) ?,
V = 2172.3 (2) ?3
, and Z = 8 molecules in the unit cell. The reported structure was confirmed by X-ray analysis, which showed that the title molecules
associate into centrosymmetric dimers via N–H···O hydrogen bonding.
Index Abstract The synthesis and structure of a new polycyclic compound, 3-hydroxy-4-aza-8-oxoheptacyclo[9.4.1.02,10.03,14.04,9.09,13.012,15]tetradecane, are reported in this article.
相似文献
79.
Abstract Measurements of the photoluminescence (PL) of strained In0.2Ga0.8As/GaAs and In0.15Ga0.85As/GaAs quantum well structures together with the PL from bulk GaAs, in a diamond anvil cell show that the pressure coefficient of the ground confined state in the wells depends upon well width (LZ). In the thinnest wells, the coefficient is closer to that of the bulk GaAs (10.7 meV/kbar), as expected. However, in the widest wells the coefficients tend to values (9.5meV/kbar for the 15% alloy and 9.1meV/kbar for the 20% alloy) that are significantly lower than the pressure coefficient of unstrained In0.53Ga0.47As (10.9meV/kbar). It is found that the low pressure coefficients can not be explained by the change in uniaxial stress with pressure due to a difference in bulk moduli between the barrier and well. 相似文献
80.