荷兰当代住宅变迁:历史、类型及城市设计策略

本文从荷兰填海造田的历史出发,分析了荷兰城市住宅土地开发从密集化到去密集化的演变过程.其中,港口的再开发为各大城市带来了内城复兴的契机,阿姆斯特丹的港口区的各个项目成为城市密度、住宅类型、融资模式、公共参与等的实验场.     

Numerical simulations to support the normalization data reduction technique

The normalization data reduction (NDR) technique is an analytical methodology for characterizing the upper shelf fracture toughness of steels in the ductile regime, both in terms of critical toughness (J_Ic) and resistance to ductile crack extension (J-R curve). It represents an alternative to the more commonly used multi-specimen or single-specimen (unloading compliance and potential drop) techniques.Finite element analyses of a growing crack are executed to evaluate the performance of the technique. This approach has the advantage to remove large uncertainties entailing experimental results. Results demonstrate the precision of the method.     

Red, green, and blue LEDs for white light illumination

The rapid improvement of the white light efficacy achievable with light-emitting diodes (LEDs) opens up new opportunities in the general illumination market. An LED light source made of red, green, and blue LEDs (RGB-LEDs) can provide the unique feature of color variability, allowing the user to select the desired color point of the lamp. The white light color accuracy required in the general illumination market is a challenge for LEDs. The variation in lumen output and wavelength for nominally identical LEDs and the change in these parameters with temperature and time result in an unacceptably high variability in the color point of white light from RGB-LEDs. In this paper, we show that these problems can be overcome with suitable feedback control schemes that can be implemented in a practical LED lamp. We present results of experiment and theoretical modeling that shows the performance that can be achieved with a number of different control schemes     

On a simple wave approximation

Summary An approximation (the linear version of Burgers' equation with appropriate initial data) to a simple wave initial value problem for a set of two linear coupled dissipative partial differential equations is discussed. It has been shown that for the class of square integrable initial functions of which the spectra (Fourier-transforms) have bounded support 2 the approximation is valid for some finite interval of time [0, T()]. For some finite timeT ₁ > T() the approximation may fail. However, fort, it is asymptotically valid again. For the class of initial conditions mentioned above expansions in series of the two solutions, which for every finite interval of time [0, ] are convergent, may be constructed.Detached by Philips Research Laboratories.     

Low-temperature approach to high-yield and reproducible syntheses of high-quality small-sized PbSe colloidal nanocrystals for photovoltaic applications

Small-sized PbSe nanocrystals (NCs) were synthesized at low temperature such as 50-80 °C with high reaction yield (up to 100%), high quality, and high synthetic reproducibility, via a noninjection-based one-pot approach. These small-sized PbSe NCs with their first excitonic absorption in wavelength shorter than 1200 nm (corresponding to size < ～3.7 nm) were developed for photovoltaic applications requiring a large quantity of materials. These colloidal PbSe NCs, also called quantum dots, are high-quality, in terms of narrow size distribution with a typical standard deviation of ～7-9%, excellent optical properties with high quantum yield of ～50-90% and small full width at half-maximum of ～130-150 nm of their band-gap photoemission peaks, and high storage stability. Our synthetic design aimed at promotion of the formation of PbSe monomers for fast and sizable nucleation with the presence of a large number of nuclei at low temperature. For formation of the PbSe monomer, our low-temperature approach suggests the existence of two pathways of Pb-Se (route a) and Pb-P (route b) complexes. Either pathway may dominate, depending on the method used and its experimental conditions. Experimentally, a reducing/nucleation agent, diphenylphosphine, was added to enhance route b. The present study addresses two challenging issues in the NC community, the monomer formation mechanism and the reproducible syntheses of small-sized NCs with high yield and high quality and large-scale capability, bringing insight to the fundamental understanding of optimization of the NC yield and quality via control of the precursor complex reactivity and thus nucleation/growth. Such advances in colloidal science should, in turn, promote the development of next-generation low-cost and high-efficiency solar cells. Schottky-type solar cells using our PbSe NCs as the active material have achieved the highest power conversion efficiency of 2.82%, in comparison with the same type of solar cells using other PbSe NCs, under Air Mass 1.5 global (AM 1.5G) irradiation of 100 mW/cm(2).     

On the use of the crack tip opening angle parameter to explain the ductile crack growth behavior of miniature compact specimens

Experimental crack resistance curves obtained from miniature compact tension, MC(T), specimens were found to be significantly less tough than those obtained on standard one inch 1T-C(T) specimens. In order to investigate the fundamental reasons behind this unexpected result, local approaches to fracture based on the Rice and Tracey void growth model and the crack tip opening angle (CTOA) concept are used. Local crack growth criteria are identified on test results obtained from 1T-C(T) and are used to predict the MC(T) behavior. Results demonstrate that the CTOA parameter is very effective as it allows transferring results from MC(T) to larger specimens, it is easy to implement in a finite element code, it is mesh size insensitive and can be actually measured although its experimental determination is not straightforward. The β parameter derived from the Rice and Tracey void growth model is unable to explain the experimental results. The possible reasons for the poor performance of the β parameter are discussed.     

A new approach to the manufacture of chalcogenide thin film solar cells

Glass beads of 0.2 mm diameter are covered with molybdenum, copper and indium. The copper/indium layers are transformed into copper indium disulfide (CIS) by exposing the glass beads to a hydrogensulfide/argon mixture at temperatures of around 500 °C. The CIS covered glass beads serve as the basis material for the formation of solar cells. The main advantage of this approach is the separation between absorber and cell/module formation. In this paper the different process steps necessary for cell manufacturing are described. Some properties of solar cells made out of CIS covered glass beads are presented.