Further results on an abstract model for branching and its application to mixed integer programming

Mathematical Programming - A key ingredient in branch and bound (B&B) solvers for mixed-integer programming (MIP) is the selection of branching variables since poor or arbitrary selection...     

Rankine–Hugoniot conditions obtained by using the space–time Hamilton action

In the quadri–dimensional space–time, the variation of Hamilton’s action is a powerful tool to study the process equations for conservative fluid media. In this framework, Hamilton’s principle allows to obtain equation of motions, equation of energy but also Rankine–Hugoniot conditions. The variational method may be a versatile key to obtain the shock-wave conditions for complex media when the equations of processes are not expressed by linear or quasi-linear differential equations.

     

DMulti-MADS: mesh adaptive direct multisearch for bound-constrained blackbox multiobjective optimization

Computational Optimization and Applications - The context of this research is multiobjective optimization where conflicting objectives are present. In this work, these objectives are only available...     

Preface to the special issue of JOGO on the occasion of the 40th anniversary of the Group for Research in Decision Analysis (GERAD).

Journal of Global Optimization -     

Conditional marginal expected shortfall

Extremes - In the context of bivariate random variables $\left (Y^{(1)},Y^{(2)}\right )$ , the marginal expected shortfall, defined as $\mathbb {E}\left (Y^{(1)}|Y^{(2)} \ge Q_{2}(1-p)\right )$ for...     

Thermoelectric power generation

Although the polarisation of the light was discovered at the beginning of the nineteenth century, the Vikings could have used the polarised light around the tenth century in their navigation to America, using a ‘sunstone’ evoked in the Icelandic Sagas. Indeed, the birefringence of the Iceland spar (calcite), a common crystal in Scandinavia, permits a simple observation of the axis of polarisation of the skylight at the zenith. From this, it is possible to guess the azimuth of a hidden Sun below the horizon, for instance. The high sensitivity of the differential method provided by the ordinary and extraordinary beams of calcite at its so-called isotropy point is about two orders higher than that of the best dichroic polariser and permits to reach an accuracy of ±1° for the Sun azimuth (at sunrise and sunset). Unfortunately, due to the relative fragility of calcite, only the so-called Alderney crystal was discovered on board a 16th ancient ship. Curiously, beyond its use as a sunstone by the Vikings, during these last millennia calcite has led to the discovery of the polarisation of the light itself by Malus and is currently being used to detect the atmospheres of exoplanets. Moreover, the differential method for the light polarisation detection is widely used in the animal world.     

Pressure evolution of two polymorphs of Tb 2(MoO 4)3

We have studied the high pressure behavior of the α and β^′-phases of Tb ₂(MoO ₄)₃ using a combination of powder X-ray diffraction and ab initio calculations. The α-Tb ₂(MoO ₄)₃ phase did not undergo any structural phase transition in the pressure range from 0 up to the maximum experimental pressure of 21 GPa. We observed line broadening of the diffraction patterns at pressures above 7 GPa, which may be due to non-hydrostatic conditions. The complete amorphization of the sample was not reached in the pressure range studied, as expected from previous Raman studies. The behavior under pressure of the β^′-Tb ₂(MoO ₄)₃ phase is similar to that of other rare-earths trimolybdates with the same structure at room temperature. A phase transition was observed at 2 GPa. The new phase, which can be identified as the δ-phase, has never been completely characterized by diffraction studies. A tentative indexation has been performed and good refined cell parameters were obtained. We detect indications of amorphization of the δ-Tb ₂(MoO ₄)₃ phase at 5 GPa.     

Optical pressure sensors for high-pressure–high-temperature studies in a diamond anvil cell

We review the various optical pressure sensors that are suitable for high-pressure and high-temperature studies in a diamond anvil cell. Two different kinds of sensors are considered: those based on the pressure shift of a fluorescence line (ruby, SrB₄O₇:Sm²⁺) and those based on the pressure shift of a Raman line (c-BN, diamond). The calibration of those sensors are presented in detail, and discussion is made on their useful pressure and temperature ranges.     

白光LED用Sr3LiMgV3O12:Eu3+单基质荧光粉的研究

采用高温固相法合成了一种新型单基质Sr3-2xLi1+xMgV3O12∶xEu3+荧光粉,研究了其在不同的合成温度及Eu3+掺杂浓度等条件下的发光性能。利用X射线衍射仪(XRD)、扫描电镜(SEM)和荧光光谱仪(PL)等对样品进行表征。荧光光谱表明Sr3-2xLi1+xMgV3O12∶xEu3+荧光粉具有与近紫外芯片相匹配的激发光谱,其宽阔的发射光谱(450～630nm)使得该类物质具有作为白光LED用单基质荧光粉的巨大优势。     

高氧空位浓度对金红石TiO2导电性能影响的第一性原理研究

采用基于密度泛函理论的平面波超软赝势方法研究了 纯的和不同高氧空位浓度金红石型TiO_2-x (x=0, 0.083, 0.125, 0.167, 0.25)超胞的能带结构分布、态密度分布.同时, 采用局域密度近似+U方法调准了带隙.结果表明, 高氧空位浓度越高, 金红石型TiO₂的最小带隙越变窄、电子有效质量越减小, 自由电子浓度越高, 电子迁移率越低、电导率越低.计算结果与实验结果的变化趋势相符合. 关键词： 高氧空位 2')" href="#">金红石型TiO₂ 电导率 第一性原理