Estimation in mixed models via layer triangular transformation

A new alternative for estimating parameters in some mixed linear models is presented and illustrated. The approach is based on the same layer triangular transformation of the model matrix as proposed earlier by Öfversten (Biometrics 49 (1993)) for the derivation of some exact tests for variance components. Using the same preliminary transformation for both testing and estimation gives us an integrated set of procedures for the full analysis of some widely used mixed linear models. The proposed procedures are computationally stable and space saving.     

SQUID magnetometers for low-frequency applications

We present a novel formulation for SQUID operation, which enables us to evaluate and compare the sensitivity and applicability of different devices. SQUID magnetometers for low-frequency applications are analyzed, taking into account the coupling circuits and electronics. We discuss nonhysteretic and hysteretic single-junction rf SQUIDs, but the main emphasis is on the dynamics, sensitivity, and coupling considerations of dc-SQUID magnetometers. A short review of current ideas on thin-film, dc-SQUID design presents the problems in coupling and the basic limits of sensitivity. The fabrication technology of tunnel-junction devices is discussed with emphasis on how it limits critical current densities, specific capacitances of junctions, minimum linewidths, conductor separations, etc. Properties of high-temperature superconductors are evaluated on the basis of recently published results on increased flux creep, low density of current carriers, and problems in fabricating reliable junctions. The optimization of electronics for different types of SQUIDs is presented. Finally, the most important low-frequency applications of SQUIDs in biomagnetism, metrology, geomagnetism, and some physics experiments demonstrate the various possibilities that state-of-the-art SQUIDs can provide.     

User level performance analysis of multi-hop in-band backhaul for 5G

In recent years, mobile access networks operating at millimeter wavelengths have received a great deal of attention, as they promise previously unattainably high mobile data rates. At these frequencies, mobile access links are expected to use highly directional beamforming antennas, which are also well suited to backhaul links. Therefore, access points can efficiently act as self-backhauled relays by using the same spectrum, circuits and antennas for mobile access and backhaul links, thus forming a multi-hop in-band backhaul network. The contributions of our paper are extensive simulations to investigate user level performance in such multi-hop networks. We specifically take into account the momentary data traffic of every link in order to calculate the interference. Results quantify the detrimental effect of interference on user level performance. Furthermore, the potential benefit of using the combination of in-band and dedicated backhaul links is evaluated. Additionally, this paper investigates the user level effects of the sudden loss of a link in the backhaul mesh network, and underlines the importance of effective rerouting algorithms. The feasibility of the in-band concept is demonstrated, and we can confirm that the user level experience will surpass the performance provided by previous generation mobile networks.     

Achieving agility using business model stress testing

Business Model (BM) Innovations aim at making systemic changes in the business logic of companies when they are bringing innovative products and services to the market. Companies should be sensitive to changes in their business environment and able to modify their BMs in an agile way. To assess the agility of BMI during specific market entry situations, this paper uses a method that stress tests the value proposition and the components of a BM against contingent uncertainties. We present three qualitative case studies of companies that differ in their market entry approach. Starting from their strategic orientation, these case companies’ stress test their Business models and BM components, using a scenario-based identification of uncertainties. The BM Stress Test method contributes to a quick understanding of the components their BM needs to monitor, reconsider, or improve. Such stress testing helps enhance business agility. The research contributes to market strategy and business modelling research by introducing BM Stress Testing as a new method that can achieve and maintain agility regarding BM uncertainties.     

Compatibilization of Poly(propylene)/Polyamide 6 Blends with Functionalized Poly(propylene)s Prepared with Metallocene Catalyst

Summary: Propylene was copolymerized with 10‐undecen‐1‐ol using dimethylsilanylbis(2‐methyl‐4‐phenyl‐1‐indenyl)zirconium dichloride as catalyst and MAO and TIBA as cocatalysts. Comonomer incorporations from 0.1 to 0.9 mol‐% (0.5 to 3.6 wt.‐%) were obtained. These hydroxyl functionalized copolymers were applied as compatibilizers to PP/PA6 blend with a composition of 70/30. For comparison, hydroxyl functionalized polyethylene prepared with metallocene catalyst and commercial MAH grafted ethylene butyl acrylate (E/BA/MAH) and poly(propylene) (PP‐g‐MAH) were also used as compatibilizers. Effects of the compatibilizers on morphology and mechanical and thermal properties of the blends were studied. Enhanced adhesion between the blend components was observed in morphology and dynamic mechanical studies. Although improvement in toughness was not as pronounced as expected, there were indications that the hydroxyl functionalized propylene copolymers prepared with metallocene catalysts could serve as a new type of compatibilizer in polymer blends.

SEM micrograph (5 000×) of an PP/PA6/PP‐co‐OH4 blend.     

Screw optimization of a co-rotating twin-screw extruder for a binary immiscible blend

The effect of the screw configuration of a closely intermeshing co-rotating twin-screw extruder on residence time and mixing efficiency was studied for an uncompatibilized immiscible PA6/PP (80:20) bend. Alternative screw configurations were investigated systematically. The residence time distribution (RTD) was found to be a poor indicator of the total mixing efficiency, whereas the mixing intensity function yielded considerably better information. High shear stress, sufficient residence time, and high fill ratio in the melting section of the screw were the most important factors in achieving good dispersion of the minor phase. The evolution of morphology along the screw axis depended strongly on the screw configuration. The downstream flow characteristics after the screw end determined the final morphology of the blend.     

Use of epoxy reactivity for compatibilization of PP/PBT and PP/LCP blends

Binary blends of a reactive ethylene-based terpolymer with polybutylene terephthalate (PBT) and with a liquid crystalline polyester (LCP) were studied to clarify the possible interactions between the blended polymers. The aim was to determine the suitability of the reactive terpolymer containing epoxy reactivity as a compatibilizer in blends of polypropylene (PP) and these two polyesters. The binary blends exhibited increased viscosity during blending, changes in the crystallization of the PBT phase, and an intimate contact between the blended polymers, which pointed to strong interactions or chemical reactions between the compatibilizer and both PBT and LCP. FTIR analysis confirmed the reaction of the epoxide and formation of new esters. Most probably the carboxyl end groups of the polyesters reacted with the epoxy group of the compatibilizer. In the second part of the work the same terpolymer was shown to act as a compatibilizer in PP/PBT and PP/LCP blends. This behavior was based on good mixing with the PP phase and on the chemical reactivity or strong interactions with the polyesters demonstrated in the investigations on binary blends. Addition of 5 wt% of the compatibilizer improved the impact strength, especially in PP/PBT blends where synergistic behavior was found at compositions of 80/20 and 20/80. In PP/LCP blends, the compatibilizer significantly improved the impact strength of unnotched samples at 20 wt % LCP content. In both blends, the compatibilizer reduced the size of the dispersed domains and caused them to attach better in the matrix. © 1995 John Wiley & Sons, Inc.     

Challenges and industry practices for managing software variability in small and medium sized enterprises

Software variability is an ability to change (configure, customize, extend) software artefacts (e.g. code, product, domain requirements, models, design, documentation, test cases) for a specific context. Optimized variability management can lead a software company to 1) shorter development lead time, 2) improved customer and improved user satisfaction, 3) reduced complexity of product management (more variability, same $) and 4) reduced costs (same variability, less $). However, it is not easy for software companies, especially small and medium size of enterprises to deal with variability. In this paper we present variability challenges and used practices collected from five SMEs. Our study indicates that increased product complexity can lead growing SMEs to the time-consuming decision-making. Many of the analyzed medium size of companies also expect improved tool support to help them to boost their productivity when managing increasingly complex products and increasing amount of variants In fact, in many of the analysed SMEs, a high level of automation in design, release management and testing are or become a key factor for market success By introducing the challenges and used practices related to variability the paper deepens understanding of this highly relevant but relatively under-researched phenomenon and contributes to the literature on software product line engineering.     

Readout methods for an inductively coupled resonance sensor used in pressure garment application

The methods needed to inductively read a passive resonance sensor in pressure measurement are studied. A simple dual-layer pressure sensor, a small portable phase response measurement unit and the methods to extract a coupling coefficient compensated resonance frequency are presented. The functionality and accuracy of the measurement are tested in a test rig and demonstrated in a realistic measurement environment. According to the test measurements, the overall performance of this wireless system is promising and the accuracy is within the typical range of the measurements made in the field of pressure garments.     

Probabilistic simulation of fire endurance of a wooden beam

This paper presents a probabilistic simulation approach to assessment of the fire endurance of a wooden load-bearing beam in a fire. The approach introduces several novel modelling techniques developed by VTT, such as the probabilistic fire simulator which is an interface enabling to run fire simulation models in the Monte Carlo mode and the time-dependent event-tree method which enables to take into account the active fire safety measures such as detectors, first-aid fire fighting, sprinklers and fire brigade intervention. Also the simulation of the response to heat and the mechanical performance of the structure are carried out using the Monte Carlo technique. The charring rate of the wooden beam is calculated by a new model that includes explicitly the principal sources of uncertainties and variabilites. The results show explicitly the effectiveness of different fire safety measures in reducing the risk of structural failure.