Jukka Vanhala - Academia.edu (original) (raw)

Papers by Jukka Vanhala

Smart environments have emerged as a thriving field of research. Understanding user's context... more Smart environments have emerged as a thriving field of research. Understanding user's context is one of the core areas of smart home research. In this study we present a smart home living experiment in which a test subject lived two weeks in the EleHome lab. During this time sensor data was gathered along with annotation data. We used naïve Bayes classifier in a supervised learning setting to recognize a few of the basic contexts and to validate the gathered data. The first results were good for simpler contexts, but further analysis is needed for more complex activities. All in all the study gives us a good baseline for further development of context recognition methods.

Page 1. Textile Electrodes in ECG Measurement Taina Pola1, Jukka Vanhala2 1Institute of electroni... more Page 1. Textile Electrodes in ECG Measurement Taina Pola1, Jukka Vanhala2 1Institute of electronics, Tampere University of Technology PO Box 692, FI-33101, taina.pola@tut. fi Abstract ... Four test persons were used for testing the electrodes. ...

PubMed, 1993

Methods based on the neural network techniques are among the most accurate in the secondary struc... more Methods based on the neural network techniques are among the most accurate in the secondary structure prediction of globular proteins. Here the same principles have been used for the tertiary structure prediction problem. The map of dihedral phi and psi angles is divided into 10 by 10 squares each spanning 36 by 36 degrees. By predicting the classification of each residue in the protein chain in this map a rough tertiary structure can be deduced. A complete prediction system running on a cluster of workstations and a graphical user interface was developed.

Proceedings of the Estonian Academy of Sciences, 2005

Compiler backend is the part of a compiler that is responsible for generating compiled code. By o... more Compiler backend is the part of a compiler that is responsible for generating compiled code. By optimizing the backend, one can easily create a tool chain for a new environment, where some restrictions are to be taken into account. One such restriction is energy consumption, which can be affected by code generation. In this paper, we discuss the different candidate optimizations that we have identified, and whether or not they can be implemented within the scope of the compiler backend.

John Wiley & Sons, Ltd eBooks, Mar 5, 2008

... For some applications the controller has to be able to offer specific services to network nod... more ... For some applications the controller has to be able to offer specific services to network nodes, such as dynamic communication slot assignment for new nodes in the network, interruption handlers for specific events generated by nodes and gateway services to access higher ...

Scientific Reports, May 1, 2016

This article focuses on the fabrication and characterization of stretchable interconnects for wea... more This article focuses on the fabrication and characterization of stretchable interconnects for wearable electronics applications. Interconnects were screen-printed with a stretchable silver-polymer composite ink on 50-μm thick thermoplastic polyurethane. The initial sheet resistances of the manufactured interconnects were an average of 36.2 mΩ/◽, and half the manufactured samples withstood single strains of up to 74%. The strain proportionality of resistance is discussed, and a regression model is introduced. Cycling strain increased resistance. However, the resistances here were almost fully reversible, and this recovery was time-dependent. Normalized resistances to 10%, 15%, and 20% cyclic strains stabilized at 1.3, 1.4, and 1.7. We also tested the validity of our model for radio-frequency applications through characterization of a stretchable radio-frequency identification tag.

This article focuses on characterization of screen printed electrical interconnects for wearable ... more This article focuses on characterization of screen printed electrical interconnects for wearable applications. The interconnects are screen printed with stretchable silver-based ink on a thermoplastic polyurethane film. By optimizing the process parameters, we were able to fabricate 200 μm line widths with spacing of 200 μm. The average sheet resistance is 36.2 mΩ/□, however a significant lot-to-lot deviation was noted. In the strain tests, half of the samples have lost conductivity when 74.1% strain is reached. The normalized resistances of the samples rise linearly to approximately 30 % strain, after which the growth rate and deviation between samples increases significantly. It was also discovered that no cracking can be found from the traces while subjected to strains under 30%.

ABSTRACT Aging people are in risk of social isolation due to direct or indirect effects of aging.... more ABSTRACT Aging people are in risk of social isolation due to direct or indirect effects of aging. Social isolation decreases the quality of life, health and acts against independent living, which is important for both the elderly people and society. Social networking can provide elders a sense of presence with their relatives, friends and healthcare personnel which counteract the effects aging causes to their social connections. In this research a special social networking system is designed and provided for the elderly to answer their communication needs. To collect information on the achieved benefits of the system, a selected group of elders will use the system in their everyday lives in field trials for several months.

Research journal of textile and apparel, Mar 13, 2017

Purpose The purpose of this paper was to offer more reliable dry electrode materials for long-ter... more Purpose The purpose of this paper was to offer more reliable dry electrode materials for long-term measuring and determine how repeated machine washing affects the measured impedance and surface resistance of the sample electrodes. The aim was to manufacture electrodes that could be used for the measurement of ECG. Skin friendly, metal sheet type, electrodes could be a solution. Design/methodology/approach In addition to two conventional electrodes already used in heart rate belts, the authors prepared and tested three different sheet metal electrodes. Three 20-mm-diameter electrodes were manufactured from the following materials: silvered knit, conductive polymer, stainless steel, silver and platinum. Electrode impedance was measured at seven frequencies from 1 Hz to 1 MHz, by placing two electrodes face-to-face. Measurements were taken on unused electrodes and after multiple machine washes at 40°C. Findings Analysis of the measurements indicates that with every material tested, the impedances are elevated after repeated washes. All metallic materials have impedances in the range of 0.01 to 4.5 Ω. Metal sheet electrodes can be integrated comfortably into the textile, and they endure textile maintenance without loss of electrical properties. Practical implications Metal sheet electrodes function well in long-term vital signs monitoring, provide a reliable signal and are resistant to maintenance. For the reasons described in this research, they can be used as a long-term wearable sensor. Originality/value Novel electrode material for long-term measuring research is important in many disciplines such as health care and apparel manufacturing. These findings suggest that pure metal electrodes are better than conductive textiles in long-term measuring.

This paper studies the use of a Bluetooth enabled mobile phone as a controlling device in a smart... more This paper studies the use of a Bluetooth enabled mobile phone as a controlling device in a smart environment. Main focus for the work is partitioning of the functionality and the UI handling between a mobile phone and a smart appliance. There seems to be no single right solution for the partitioning of functions. Instead, there are so many case dependent characteristics that the partitioning of functions should be designed in a case-specific fashion. The results of this work give the basis for designing the partitioning.

Flexible and printed electronics, Oct 9, 2020

3D printing is widely used for manufacturing complex non-functional parts, and recently, the fabr... more 3D printing is widely used for manufacturing complex non-functional parts, and recently, the fabrication of electronics has also attracted research attention. The commercialized process of fused-filament fabrication (FFF), which is still evolving,has been used in the preparation of basic electronic conductors and sensors but only a few studies of more complex structures with integrated circuits and passive components have been reported. Notably, the usage of FFF in wearable stretchable electronics has not been studied previously. We demonstrate that the combination of FFF printing and commonly used stretchable electronics materials and methods enables new wearable stretchable electronics. In this study, thermoplastics were extruded directly onto a stretchable substrate and their adhesion was measured using T-peel tests. The test results were further used in the fabrication of supports for meander-shaped screen-printed interconnects. The elongation of the interconnects with the supports were studied by tensile tests with simultaneous measurements of the electrical conductivity. The results were good, and the adhesion exceeded the constitution of the substrate when the filament and the substrate were of the same material type. The average bond strength was ∼2 N mm −1. Support structures placed close to the meander-shaped interconnects changed the interconnects' deformation under elongation. The average maximum elongation of the interconnects was improved by ∼27% when the supports directed stresses away from the interconnects' weak areas. Conversely, the results were ∼21% lower when the supports directed stresses towards the weak areas. This study demonstrates that it is possible to use direct 3D printing onto highly stretchable substrates. Currently, commercial FFF materials and methods can be used to manufacture supports, frames and other non-functional parts on wearable electronics substrates in a single process step. We believe that in the future, FFF will become a valuable tool in the manufacture of inexpensive and reliable wearable electronics.

Flexible and Printed Electronics

Stretchable electronics can be realized using different manufacturing methods and hybrids thereof... more Stretchable electronics can be realized using different manufacturing methods and hybrids thereof. An example of the latter is the combination of stretchable circuit boards with screen-printing, which will be discussed in this work. The hybrid stretchable electronics structures are based on photolithographically structured and rigid copper islands and screen-printed silver ink interconnections. This enables the assembly of components with a high number of contacts onto the copper islands and deformable silver ink lines between islands. The transition area between islands and lines is critical due to local stress concentration. The effect and potential mitigations were studied by measuring the electrical resistance of test interconnections under mechanical loading. The first set of samples was elongated up to 30% in tensile tests. The second set of samples was elongated 10%, 20%, and 30% in cyclic tests up to 10 000 cycles. After the tests, extensive failure analysis, e.g. scanning e...

Unobtrusive human height and posture

Textile Research Journal, 2017

The research work presents a new design of compression hosiery where compression around a human l... more The research work presents a new design of compression hosiery where compression around a human limb is generated using special air bladders. The pressure inside the air bladders is adjustable. The objective of the research was to study graduated compression and its control on the limb using the prototype with air bladders and two commercial compression products. The compression forces were measured around the limb under a knee in three sectors: a foot, a middle part and an upper part of the leg. Measurements were mainly done in vivo using the limb of a test person – although some pre-trials were done in vitro. During the tests it was concluded that the exact control of the compression was very difficult to achieve due to, for example, the shape and the composition of the limb. Based on the results, the compression values were unstable under the sectors and the graduated compression was nonlinear in the vertical direction for every tested hosiery. There is some analogy concerning th...

2016 IEEE 66th Electronic Components and Technology Conference (ECTC), 2016