Wireless Internet over LMDS: architecture and experimentalimplementation

LMDS is currently a promising emerging technology in broadband fixed wireless communications. The cellular structure, high data rates, and flexibility make it perfect for multimedia, digital television, and interactive services. These high-bandwidth multimedia services received most of the research attention until lately. There has been a clear gap when considering UDP/TCP/IP and other data services over LMDS. We examine the ramifications of using standard TCP/IP data communication over a two-layer LMDS system. We argue that the former emphasis only on multimedia and ATM-based communication over LMDS was a mistake. The most exciting prospect for LMDS should be in the role of enabling Internet and data services together with multimedia. We introduce a basic architecture for two-layer IP-LMDS based on a trial network built between 1996 and 2000     

Quality-oriented optimization of wave soldering process by using self-organizing maps

In this paper, the optimal process parameters of a wave soldering process were defined. The optimization was performed in respect to soldering quality by minimizing a cost function describing the total repairing cost of a wave-soldered printed circuit board (PCB). The data analysis stages were as follows. First, the process data were coded into inputs for a self-organizing map (SOM). Next, a function for the repairing cost was constructed and used to find the optimal map neurons. At the last phase, the optimal parameters were approximated on the basis of the reference vectors of the optimal neurons. The results showed clearly potential in the optimization of the wave soldering process, especially in the visualization of the optimal process conditions. Therefore, it would be useful to exploit the method more widely in the electronics industry.     

Textural changes in metallurgical coke prepared with polyethylene

The effect of high-density polyethylene （HDPE） on the textural features of experimental coke was investigated using polar- ized-light optical microscopy and wavelet-based image analysis. Metallurgical coke samples were prepared in a laboratory-scale furnace with 2.5%, 5.0%, 7.5%, 10.0%, and 12.5% HDPE by mass, and one sample was prepared by 100% coal. The amounts and distribution of textures （isotropic, mosaic and banded） and por~s were obtained. The calculations reveal that the addition of HDPE results in a decrease of mosaic texture and an increase of isotropic texture. Ethylene formed from the decomposition of HDPE is considered as a probable reason for the texture modifications. The approach used in this study can be applied to indirect evaluation for the reactivity and strength of coke.     

Behaviour of oat globulins in lactic acid fermentation of oat bran

Oat bran fermentation (OBF) is used to produce non-dairy yogurt-type products. Such products may be designed being rich in probiotic bacteria and/or dietary-fibre. Oat bran is, however, also rich in proteins, especially 12 S globulins. Understanding the behaviour of globulins in OBF would thus offer a basis for further exploitation of proteins in the product design. The behaviour of oat globulins was monitored during a model OBF in order to study changes in protein solubility and possible protein hydrolysis. Proteins were extracted from OBF samples with a buffered and a non-buffered extraction procedure. The extracts were analyzed with SDS-PAGE and a Lowry assay. Combined effect of pH and NaCl-concentration on the solubility of oat globulin isolate was studied. The solubility of oat globulins decreased during OBF; this appeared as their shift from the salt-soluble fraction to the residual protein fraction. The shift in oat globulin solubility was due to the acidifying conditions present in OBF, which lead to the unfolding of globulins and also apparently induced protein aggregation. No major protein hydrolysis was observed during OBF.     

Circular correlation based identification of switching power converter with uncertainty analysis using fuzzy density approach

Switching power converters are extensively used in powering various electronics loads and processes. The proper functioning of those processes may be vital for the every day life of the society. Therefore, the reliable operation of the switched-mode converters is of prime importance and the functioning has to be verified reliably both during the design phase and in the production. It has been shown lately that the main deficiencies in the verification process are related to the dynamics of the converter which can be characterized with a certain set of transfer functions. This paper investigates the frequency response measurement methods by means of which the transfer functions can be identified fast and accurately being economically feasible to apply also in the production phase. Multi-period maximum length pseudo random binary sequence (m.l.b.s.) is used as the excitation signal and the transfer functions are identified from the measurement data with circular cross-correlation method. The measurement uncertainty is computed by means of fuzzy density approach yielding a certain confidence band around the measured nominal response. The proposed methods are verified both by simulations and experimental data from high-frequency switched-mode converters.     

Sulphide-induced stress corrosion cracking and hydrogen absorption of copper in deoxygenated water at 90°C

Stress corrosion cracking (SCC) of oxygen-free phosphorous-alloyed copper was investigated in sulphide- and chloride-containing deoxygenated water at 90°C with sulphide concentrations of 0.001 and 0.00001 M. Several intergranular defects were found in the specimen exposed to the high sulphide environment. Similar defects were not found in the low sulphide environment, where only slight corrosion on grain boundaries and slip lines occurred. Hydrogen content measurements show an increase in hydrogen uptake of the plastically deformed specimens, which is dependent on the sulphide concentration and on plastic deformation of copper. However, the highest hydrogen content was measured in friction stir welds, welded in air without shielding gas, and tested in the high sulphide environment. The embedded oxide particles in the weld metal act as local hydrogen trapping sites and selectively react with the sulphide solution. A relatively thick air-formed oxide film covers the copper canisters when deposited, which transforms into a sulphide film in the repository conditions. Thus, some of the coupon specimens were pre-oxidised. The conversion of the pre-existing Cu₂O film into Cu₂S film occurs quickly and the transformation is almost 100% efficient. The structure and properties of the Cu₂S films, susceptibility of copper to sulphide-induced SCC and hydrogen uptake of copper in reducing, anoxic repository conditions are discussed.     

Hydrogen embrittlement of nodular cast iron

Ferritic nodular cast iron, intended for use as the material for inserts of canisters for long-term geological disposal of spent nuclear fuel, was studied for hydrogen sensitivity. In the canisters, the insert provides the mechanical strength against external loads. Hydrogen was charged from 0.1 N H₂SO₄ solution in free-corrosion tests and under controlled cathodic potential. Hydrogen uptake and trapping were then measured using thermal desorption spectroscopy. The hydrogen desorption rate after hydrogen charging manifests two distinct peaks. Plastic deformation during hydrogen charging increases the hydrogen uptake considerably. Hydrogen reduces the elongation to fracture and time to fracture in slow strain rate testing and constant load testing (CLT), respectively. Especially, the strain rate in CLT is dramatically increased. The appearance of hydrogen-induced cracking in the ferrite phase changes from ductile dimple fracture to brittle cleavage fracture due to hydrogen charging, which initiates from the interphases of the graphite nodules. The results are discussed in terms of the role of hydrogen and the graphite nodules in hydrogen embrittlement of ductile cast iron.     

This is not classified: everyday information seeking and encountering in smart urban spaces

We present a multipronged comparative study of citizens’ self-proclaimed information needs and actual information seeking behavior in smart urban spaces. We first conducted several user studies to identify the types of information services that citizens believed to be useful in urban setting utilizing methods ranging from contextual inquiry with lo-fi prototypes to “card sorting” exercise with a separate set of participants, and finally to implementing selected services. We then made a sizeable constructive intervention into the urban space by deploying in a city center 12 large, interactive public displays called “hotspots” to offer a wide range of previously identified information services. We collected comprehensive qualitative and quantitative data on the usage of the hotspots and their services by the general public during 13 months. Our study reveals discrepancies between a priori and a posteriori information seeking strategies extracted from the self-proclaimed information needs and the actual usage of the hotspots.