Zeroth-order complex-amplitude modulation with dielectric Fourier-type dififractive elements

Abstract

Diffraction by a lamellar grating with slowly modulated groove width and depth is considered. By mathematical design of the diffractive microstructure the zeroth diffraction order of the carrier grating may be modulated in amplitude and phase and thereby split into some specified on-axis far-zone diffraction pattern. The noise, which in diffractive optics normally appears in the immediate neighbourhood of the signal, is shifted angularly into the surroundings of the higher diffraction orders of the carrier grating. Therefore a large frame of virtually zero intensity can be formed around the original signal without brute force optimization. This is of interest in, for example, several space-invariant optical interconnection and photonic switching schemes that employ diffractive beam-splitter elements.     

Particle Image Velocimetry (PIV) application in the measurement of indoor air distribution by an active chilled beam

We study the turbulent air flow behaviours of the attached plane jet discharged from an active chilled beam in a room using Particle Image Velocimetry (PIV). PIV is an innovative technology to study indoor air flow which began in the eighties of the last century for the measurement of whole air flow fields in fractions of a second. Here an experimental PIV system was built to reveal the structure of a turbulent attached plane jet in the entrainment process of the ambient air downstream from the jet slot. For the particle seeding in the PIV experiments, a few different particles were tested with the attached jet PIV application in a room. The results presented in this paper show the clear structure of the turbulent attached plane jet in the entrainment process after issuing from the chilled beam slot. The PIV visualisation results proved that the jet will attach to the ceiling and become fully turbulent a short distance downstream from the slot. The jet velocity vector fields show that the volume flow rate of the attached plane jet increases because of the large vortex mixing mechanism in the outer region of the jet. In three measurement cases, the air jet grows faster at a Reynolds number of 960 than at Reynolds numbers of 1320 and 1680. The calculated spreading angles in the cases with lower Reynolds numbers have similar values compared with the visualisation results.     

Macroscopically Aligned Ionic Self‐Assembled Perylene‐Surfactant Complexes within a Polymer Matrix

Ionic self‐assembled (ISA) surfactant complexes present a facile concept for self‐assembly of various functional materials. However, no general scheme has been shown to allow their overall alignment beyond local polydomain‐like order. Here we demonstrate that ionic complexes forming a columnar liquid‐crystalline phase in bulk can be aligned within polymer blends upon shearing, taken that the matrix polymers have sufficiently high molecular weight. We use an ISA complex of N,N′‐bis(ethylenetrimethylammonium)perylenediimide/bis(2‐ethylhexyl) phosphate (Pery‐BEHP) blended with different molecular weight polystyrenes (PS). Based on X‐ray scattering studies and transmission electron microscopy the pure Pery‐BEHP complex was found to form a two‐dimensional oblique columnar phase where the perylene units stack within the columns. Blending the complex with PS lead to high aspect ratio Pery‐BEHP aggregates with lateral dimension in the mesoscale, having internal columnar liquid‐crystalline order similar to the pure Pery‐BEHP complex. When the Pery‐BEHP/PS blend was subjected to a shear flow field, the alignment of perylenes can be achieved but requires sufficiently high molecular weight of the polystyrene matrix. The concept also suggests a simple route for macroscopically aligned nanocomposites with conjugated columnar liquid‐crystalline functional additives.     

Flavonol glycosides in wild and cultivated berries of three major subspecies of Hippophaërhamnoides and changes during harvesting period

Flavonol glycosides are an important group of bioactive components of sea buckthorn (Hippophaë rhamnoides). The content and profile of flavonol glycosides of some major subspecies and most cultivars as well as the variation amongst the harvesting years and dates are largely unknown. This study investigated flavonol glycosides in wild berries of two major subspecies H. rhamnoides ssp. rhamnoides and ssp. sinensis and berries of eight cultivars of ssp. rhamnoides and mongolica by reverse phase high performance liquid chromatography combined with diode array detection. The major flavonol glycosides were isorhamnetin-3-O-glucoside-7-O-rhamnoside, isorhamnetin-3-O-rutinoside, isorhamnetin-3-O-glucoside, isorhamnetin-3-O-sophoroside-7-O-rhamnoside, quercetin-3-O-rutinoside, quercetin-3-O-glucoside and quecertin-3-O-sophoroside-7-O-rhamnoside. The total content of flavonol glycosides fell in the range of 27–130 mg per 100 g fresh berries with considerable variation amongst the origins and the harvesting years. Compared with the berries of ssp. sinensis and ssp. mongolica, the berries of ssp. rhamnoides contained high levels of isorhamnetin-3-O-glucoside-7-O-rhamnoside and isorhamnetin-3-O-glucoside and lower levels of quercetin-3-O-rutinoside and quercetin-3-O-glucoside. In the wild berries of ssp. sinensis, the contents of flavonol glycosides reached maxima around late September to early October and decreased thereafter, whereas a general decreasing trend was seen in the cultivated berries of ssp. rhamnoides from the end of August to the end of October.     

Indoor Climate and the Performance of Ventilation in Finnish Residences

The purpose of the study was to gather information about the actual ventilation and indoor air quality and to evaluate the differences between houses and apartments with different ventilation systems. A sample of 242 dwellings in the Helsinki metropolitan area was studied over periods of no weeks during the 1988-1989 heating season. The mean air-exchange rates had a high variation (average 0.52 l/h, range 0.07-1.55 l/h). The ASHRAE minimum value of 0.35 l/h was not achieved in 28% of the dwellings. The air-exchange rates were significantly her in the houses than in the apartments (averages 0.45/0.64 l/h, p < 0.001); in the natural ventilation systems they, were slightly her than in the mechanical systems. The average temperature in the bedrooms was approximately 22 °C (range 18–27 °C), slightly but significantly higher in the apartment than in the houses. The average dust depositions were higher in the balanced ventilation systems than in the other systems. The median radon concentration was 82 Bq/m³ (range 5-866 Bq/m³); the Finnish target value of 200 Bq/m³ was exceeded in 17% of the houses but in none of the apartment. The measurements indicate that the indoor air quality in Finnish dwellings is not always satisfactory with reference to human health and comfort.     

DSP system integration and prototyping with FPGAS

Field Programmable Gate Arrays (FPGAs) offer a cost-effective and flexible technology for DSP ASIC prototype development. In this article, the fast ASIC prototyping concept based on the use of multiple FPGAs is reviewed in different engineering applications. The design experiences of the proposed approach, applied to four different DSP ASIC design projects are presented. The design experiences concerning the selection of the design methodology, application architectures and prototyping technologies are analyzed with respect to efficient system integration and ASIC migration from the FPGA prototype onto first-time functional silicon. Novel prototyping techniques based on using configurable hardware modellers concerning the same objective are studied. Some future goals are outlined to develop an integrated, multipurpose DSP ASIC prototyping environment.     

Integrated Water Resources Management along the Senegal River: Introducing an Analytical Framework

Integrated water resources management has become a trendy paradigm, although the issue is anything but new. In West Africa the past few decades have been rich with such attempts. Along the Senegal River their success has been very limited. The situation has instead polarized strongly across the dilemma of whether to prioritize a few macro-scale development goals or to develop the livelihood of the poor along the river. One of the crucial steps to move on is to develop a clear and transparent formulation of the problem. An approach that uses Bayesian networks is presented and applied in this study.     

Minimizing the assembly cycle time on a revolver gantry machine

In printed circuit board (PCB) manufacturing the revolver head gantry machines are nowadays popular because of their flexibility, accuracy and high speed. The operation control of this kind of machines includes, for example, selecting the nozzles into the revolver, assigning the component reels to feeder slots, and determining the pick-up and placement sequences of the components. We consider in this article the feeder assignment and the pick-up and placement sequencing problems.