Automatic feature selection for context recognition in mobile devices

In mobile devices there exist several in-built sensor units and sources which provide data for context reasoning. More context sources can be attached via wireless network connections. Usually, the mobile devices and the context sources are battery powered and their computational and space resources are limited. This sets special requirements for the context recognition algorithms. In this paper, several classification and automatic feature selection algorithms are compared in the context recognition domain. The main goal of this study is to investigate how much advantage can be achieved by using sophisticated and complex classification methods compared with a simple method that can easily be implemented in mobile devices. The main result is that even a simple linear classification algorithm can achieve a reasonably good accuracy if the features calculated from raw data are selected in a suitable way. Usually context recognition algorithms are fitted to a particular problem instance in an off-line manner and modifying methods for on-line learning is difficult or impossible. An on-line version of the Minimum-distance classifier is presented in this paper and it is justified that it leads to considerably higher classification accuracies compared with the static off-line version of the algorithm. Moreover, we report superior performance for the Minimum-distance classifier compared to other classifiers from the view point of computational load and power consumption of a smart phone.     

A prognostic method for the embedded failure monitoring of solder interconnections with 1149.4 test bus architecture

This paper describes the feasibility of accurate low frequency measurements in predicting the breakdown of modern lead free ball grid array (BGA) interconnections. In these measurements, performed partly with 1149.4 analogue boundary scan, ceramic BGA modules measuring 15×15 mm in width, with 9×9 ball matrixes, were attached on an FR-4 printed wiring board (PWB) and thermally cycled over a temperature range of −40 to +125 °C. The condition of corner interconnections was monitored using the developed measurement methods and construction. In-situ measurements were performed with a datalogger during temperature cycling, accompanied with 1149.4 mixed-signal test bus measurements of corner interconnections performed between cycling intervals. In addition, the measurements were complemented by scanning acoustic microscopy and, X-ray. Monitoring corner interconnections by a simple, low-frequency voltage measurement method with embedded test constructions gives an early warning indication well before the electrical interconnection failures. Of two studied interconnection compositions, the ones with plastic core solder balls (PCSB) proved to be more reliable than the ones with 90/10 PbSn balls.     

Semiconductor and thermoluminescent dosimetry of pulsed soft X ray plasma sources

A multichannel detection system having a dynamic range of approximately 1 x 10(-9) Gy --20 Gy was developed with the use of commercially produced Si-photodiodes and TLDs for accurate measurement of X ray energy emitted from plasma-focus facility and from laser-produced plasmas. The proof of linearity of the employed detectors accomplished by a comparison of their responses to a broad band spectrum of X rays emitted from plasmas, is reported. It is demonstrated that TLDs irradiated with no protective filter show an incorrect response due to overloading in the sub-keV range and repopulation of dosimetric peaks induced by the UV radiation. The measurement of the power of undesirable secondary X ray sources driven by the primary plasma inside the interaction chamber was performed on the basis of analysis of space dependence of X ray intensity with respect to the assumed r(-2) decrease in the intensity far away from the plasma.     

Direct photolithographic deforming of organomodified siloxane films for micro-optics fabrication

Direct photolithographic deforming of hybrid glass films is used to fabricate optical structures. The structure is fabricated in polyethylene-oxide-acrylate modified hybrid glass films with (1) binary and gray-scale photomasks using a mercury UV-lamp exposure and (2) maskless UV-laser patterning. Fabrication of isolated lenslets, lens arrays, and gratings is presented, including the associated exposure patterns. The hybrid glass material yields light-induced deformation peak-to-valley (p.v.) heights up to 12.8 microm with mercury UV-lamp exposure and p.v. deformation heights up to 6.8 microm with 365-nm UV-laser exposure. The fabricated lenslets' surface data are presented as Zernike-polynomial fit coefficients. Material synthesis and processing-related aspects are examined to understand and control the material's deformation under exposure. The hybrid glass material exhibits a maximum spectral extinction coefficient of 1.6 x 10(-3) microm(-1) at wavelengths ranging from 450 to 2,200 nm and has a refractive index of 1.52 at 632.8 nm. The fabricated structures exhibit rms surface roughness between 1 and 5 nm.     

Dependence between $$\varvec{\upeta }$$-factor and crack location relative to a fusion boundary between hard and soft materials in a SE(B) specimen

The current solutions in ASTM E1820 and E1921 for the calculation of the J-integral are not necessary directly applicable for strength mismatched welds. The problem is connected to the \(\eta \)-factor relating the experimentally measured work to the J-integral. Previous, investigations on \(\eta \)-factors for welds have focused mainly on cracks at the center of the weld. However, characterisation of the \(\eta \)-factor at other locations is also important since the crack can form anywhere in the weld. In this study, the \(\eta \)-factors for SE(B) specimens were investigated, with focus on the effect of the crack location relative to the fusion boundary between a hard base metal and a soft weld metal of a dissimilar metal weld. The results show a dependence between the \(\eta ^{\textit{CMOD}}\)-factor, the distance of the crack to the fusion boundary, the size of the remaining ligament, and the size of the plastic deformation zone. This dependence cannot be generalised based on this study alone, but the results give insight for developing an analytical \(\eta ^{\textit{CMOD}}\)-equation for strength mismatched specimens.     

Flow-optimized random access for wireless multihop networks

We study elastic traffic performance in time-slotted wireless random access networks, where the link access probabilities are adjusted at flow level each time a new flow (file transfer) arrives or a flow in progress terminates. By defining the capacity sets of such networks we carry out performance analysis in a dynamic setting, where the flows come and go and share the resources according to the balanced fairness principle. We derive flow throughput analytically for three special scenarios and devise an algorithm for general networks. At low loads, flow-optimized random access yields almost the same performance as optimal/deterministic scheduling.     

Improving the integrity of IR based online moisture measurement used in the paper and board industry

The automatic control of product moisture content in the paper industry is based upon online moisture measurement. Furthermore, the automatic control of other quality variables such as coat weight may also rely on the moisture measurement. The integrity of infrared radiation (IR) based online moisture measurement systems was studied by performing basic calibrations at the mills with references sealed between two glass plates. The calibrations were performed according to the EN ISO/IEC 17025 standard which is a requirement for calibration laboratories. The observed measurement errors were 2.9% moisture in the first time calibrations at the 95% confidence level. It is demonstrated that these errors can be reduced to under 0.5% moisture by applying traceable methods in the basic calibration, thus improving the integrity of online moisture measurements. Also a standardised algorithm, based on the experience from the performed calibrations, is proposed to ease the adjustment of different moisture measurement systems.     

Estimation of drag forces caused by natural woody vegetation of different scales

To reliably estimate water levels and velocities in vegetated rivers and floodplains, flow resistance models based on physical plant properties are advantageous. The purpose of this study is （1） to assess the suitable parameterization of woody riparian vegetation in estimating the drag forces, （2） to address the effect of plant scale on the drag estimates and reconfiguration, and （3） to evaluate the applicability of three recently developed flow resistance models. Experiments on four tree species in a towing tank together with detailed characterization of tree properties were carried out to establish a novel dataset. Despite the variability in the tree height （0.9 m-3.4 m）, the stem, leaf and total areas proved to be suitable characteristic dimensions for estimating the flow resistance at different scales. Evaluations with independent data revealed that the tested models produced reasonable results. The performance of the models was controlled by the parameter values used rather than the model structure or the plant scale.     

Context-aware pervasive service composition and its implementation

Incorporating service composition and pervasive computing into managing users’ complex everyday activities calls for the Pervasive Service Composition paradigm for everyday life. In this paper, we propose the concept of Context-Aware Pervasive Service Composition (CAPSC), which aims at enabling a pervasive system to provide user service compositions that are relevant to the situation at hand. We investigate CAPSC requirements and design a CAPSC architecture by taking into account context-aware peer coordination, context-aware process service adaptation, and context-aware utility service adaptation. We present a proof of concept application prototype as well.