适用于汽车冷起动应用的双开关降压／升压技术

一般来说,我们采用降压升压拓扑型拓扑来解决汽车应用中的宽阔输入电压范围及冷起动需求。本文将详细解释冷起动的要求．并介绍两种不同的解决方案。其中一种是传统的SPEIC拓扑,而另一种是较新的多开关降压／升压拓扑。     

Cyclic transfers in school timetabling

In this paper we propose a neighbourhood structure based on sequential/cyclic moves and a cyclic transfer algorithm for the high school timetabling problem. This method enables execution of complex moves for improving an existing solution, while dealing with the challenge of exploring the neighbourhood efficiently. An improvement graph is used in which certain negative cycles correspond to the neighbours; these cycles are explored using a recursive method. We address the problem of applying large neighbourhood structure methods on problems where the cost function is not exactly the sum of independent cost functions, as it is in the set partitioning problem. For computational experiments we use four real world data sets for high school timetabling in the Netherlands and England. We present results of the cyclic transfer algorithm with different settings on these data sets. The costs decrease by 8–28% if we use the cyclic transfers for local optimization compared to our initial solutions. The quality of the best initial solutions are comparable to the solutions found in practice by timetablers.     

Experimental and numerical analysis of a lean premixed stratified burner using 1D Raman/Rayleigh scattering and large eddy simulation

A joint experimental and numerical approach is conducted to investigate a turbulent lean premixed stratified flame (flame TSF-A of the Darmstadt stratified burner). First, the distribution of the temperature and main species is obtained experimentally by 1D Raman/Rayleigh scattering. These measurements are used to provide insight into the physics of stratified combustion and to serve as validation data for numerical models. As a second step Large Eddy Simulations (LES) are carried out using tabulated chemistry combined with a thickened flame approach. The chemistry table uses the progress variable and additionally the mixture fraction as a second controlling variable to account for the variation in equivalence ratio. To test the applicability of the model, the influence of artificial thickening on the simulation of stratified flames is investigated by means of a one-dimensional test case. Furthermore, two different grids are used in the three-dimensional simulations to assess the modeling impact. The data obtained from the measurements and simulations are presented and compared along radial profiles at several axial positions. Further information about the interaction of the reaction zone with the mixing layer has been extracted from the LES which is currently not accessible by experiments.     

X-ray scattering studies of the generation of carbon nanoparticles in flames and their transition from gas phase to condensed phase

The dynamics of particle formation were investigated for a diffusion-like ethylene flame containing a cooling metal plate on which particles condensed. Small-angle and wide-angle X-ray scattering techniques were combined to follow size- and structural changes of the soot particles using a new detector. The high dynamic range allowed continuous monitoring from the gas to the condensed phase of the gradually growing layer depositing on the plate. Different stages in the process of particle formation were observed. In addition the sub-nanometer structure of the deposited material changed rapidly as the flame was turned off. The detection system and methodology presented are of general interest since they can be further developed and applied to the study of reactive systems for materials processing in gas- and condensed phases.     

Surface temperature of decomposing construction materials studied by laser‐induced phosphorescence

Measurements of surface temperature and mass loss of decomposing construction materials during rapid pyrolysis are presented. Experiments have been performed with samples of low‐density fiberboard, medium‐density fiberboard, particleboard and poly(methyl methacrylate) in a single particle reactor at temperatures between 300° and 600°C. Ultraviolet laser light was used to excite micrometer‐sized thermographic phosphor particles that were deposited on the investigated materials, and the temperature was obtained from temporally resolved measurements of the laser‐induced emission. The wood‐based materials show a similar behavior, with small differences being attributed to differences in material properties. The surface temperature rapidly increases to about 400°C when a particle is introduced to the hot reactor. The initial phase is followed by rapid decomposition during which the surface temperature is 380°–540°C. The heating rate is slowed down during the rapid pyrolysis, and again increases as the remaining char is heated to the reactor temperature. The poly (methyl methacrylate), however, melts and at high temperatures can be characterized as a liquid with a boiling point of about 400°C. Thermographic phosphors are concluded to be suitable for high precision remote measurements of the surface temperature of decomposing construction materials, and possibilities for further studies and developments of the technique are discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

Biobased Agents for Single-Particle Detection with Optoacoustics (Small 29/2023)

Optoacoustic (OA, photoacoustic) imaging synergistically combines rich optical contrast with the resolution of ultrasound within light-scattering biological tissues. Contrast agents have become essential to boost deep-tissue OA sensitivity and fully exploit the capabilities of state-of-the-art OA imaging systems, thus facilitating the clinical translation of this modality. Inorganic particles with sizes of several microns can also be individually localized and tracked, thus enabling new applications in drug delivery, microrobotics, or super-resolution imaging. However, significant concerns have been raised regarding the low bio-degradability and potential toxic effects of inorganic particles. Bio-based, biodegradable nano- and microcapsules consisting of an aqueous core with clinically-approved indocyanine green (ICG) and a cross-linked casein shell obtained in an inverse emulsion approach are introduced. The feasibility to provide contrast-enhanced in vivo OA imaging with nanocapsules as well as localizing and tracking individual larger microcapsules of 4–5 µm is demonstrated. All components of the developed capsules are safe for human use and the inverse emulsion approach is known to be compatible with a variety of shell materials and payloads. Hence, the enhanced OA imaging performance can be exploited in multiple biomedical studies and can open a route to clinical approval of agents detectable at a single-particle level.     

3D Two-Photon Microprinting of Nanoporous Architectures

A photoresist system for 3D two-photon microprinting is presented, which enables the printing of inherently nanoporous structures with mean pore sizes around 50 nm by means of self-organization on the nanoscale. A phase separation between polymerizable and chemically inert photoresist components leads to the formation of 3D co-continuous structures. Subsequent washing-out of the unpolymerized phase reveals the porous polymer structures. To characterize the volume properties of the printed structures, scanning electron microscopy images are recorded from ultramicrotome sections. In addition, the light-scattering properties of the 3D-printed material are analyzed. By adjusting the printing parameters, the porosity can be controlled during 3D printing. As an application example, a functioning miniaturized Ulbricht light-collection sphere is 3D printed and tested.     

High‐Performance Materials for 3D Printing in Chemical Synthesis Applications

3D printing has emerged as an enabling technology for miniaturization. High‐precision printing techniques such as stereolithography are capable of printing microreactors and lab‐on‐a‐chip devices for efficient parallelization of biological and biochemical reactions under reduced uptake of reactants. In the world of chemistry, however, up until now, miniaturization has played a minor role. The chemical and thermal stability of regular 3D printing resins is insufficient for sustaining the harsh conditions of chemical reactions. Novel material formulations that produce highly stable 3D‐printed chips are highly sought for bringing chemistry up‐to‐date on the development of miniaturization. In this work, a brief review of recent developments in highly stable materials for 3D printing is given. This work focuses on three highly stable 3D‐printable material systems: transparent silicate glasses, ceramics, and fluorinated polymers. It is further demonstrated that 3D printing is also a versatile technique for surface structuring of polymers to enhance their wetting performance. Such micro/nanostructuring is key to selectively wetting surface patterns that are versatile for chemical arrays and droplet synthesis.