Kirjasto-oppi tieteenalaksi - informaatiotutkimuksen ja interaktiivisen median oppiaineen alkutaival : informaatiotutkimus 40 vuotta

Katsaus perustuu kirjoittajan Informaatiotutkimus 40 vuotta-seminaarissa joulukuussa 2011 pitämään esitykseen siitä, miten nykyinen oppiaine informaatiotutkimus ja interaktiivinen media sai alkunsa.

Power semiconductor nonlinearities in active du/dt output filtering

This doctoral thesis introduces an improved control principle for active du/dt output filtering in variable-speed AC drives, together with performance comparisons with previous filtering methods. The effects of power semiconductor nonlinearities on the output filtering performance are investigated. The nonlinearities include the timing deviation and the voltage pulse waveform distortion in the variable-speed AC drive output bridge. Active du/dt output filtering (ADUDT) is a method to mitigate motor overvoltages in variable-speed AC drives with long motor cables. It is a quite recent addition to the du/dt reduction methods available. This thesis improves on the existing control method for the filter, and concentrates on the lowvoltage (below 1 kV AC) two-level voltage-source inverter implementation of the method. The ADUDT uses narrow voltage pulses having a duration in the order of a microsecond from an IGBT (insulated gate bipolar transistor) inverter to control the output voltage of a tuned LC filter circuit. The filter output voltage has thus increased slope transition times at the rising and falling edges, with an opportunity of no overshoot. The effect of the longer slope transition times is a reduction in the du/dt of the voltage fed to the motor cable. Lower du/dt values result in a reduction in the overvoltage effects on the motor terminals. Compared with traditional output filtering methods to accomplish this task, the active du/dt filtering provides lower inductance values and a smaller physical size of the filter itself. The filter circuit weight can also be reduced. However, the power semiconductor nonlinearities skew the filter control pulse pattern, resulting in control deviation. This deviation introduces unwanted overshoot and resonance in the filter. The controlmethod proposed in this thesis is able to directly compensate for the dead time-induced zero-current clamping (ZCC) effect in the pulse pattern. It gives more flexibility to the pattern structure, which could help in the timing deviation compensation design. Previous studies have shown that when a motor load current flows in the filter circuit and the inverter, the phase leg blanking times distort the voltage pulse sequence fed to the filter input. These blanking times are caused by excessively large dead time values between the IGBT control pulses. Moreover, the various switching timing distortions, present in realworld electronics when operating with a microsecond timescale, bring additional skew to the control. Left uncompensated, this results in distortion of the filter input voltage and a filter self-induced overvoltage in the form of an overshoot. This overshoot adds to the voltage appearing at the motor terminals, thus increasing the transient voltage amplitude at the motor. This doctoral thesis investigates the magnitude of such timing deviation effects. If the motor load current is left uncompensated in the control, the filter output voltage can overshoot up to double the input voltage amplitude. IGBT nonlinearities were observed to cause a smaller overshoot, in the order of 30%. This thesis introduces an improved ADUDT control method that is able to compensate for phase leg blanking times, giving flexibility to the pulse pattern structure and dead times. The control method is still sensitive to timing deviations, and their effect is investigated. A simple approach of using a fixed delay compensation value was tried in the test setup measurements. The ADUDT method with the new control algorithm was found to work in an actual motor drive application. Judging by the simulation results, with the delay compensation, the method should ultimately enable an output voltage performance and a du/dt reduction that are free from residual overshoot effects. The proposed control algorithm is not strictly required for successful ADUDT operation: It is possible to precalculate the pulse patterns by iteration and then for instance store them into a look-up table inside the control electronics. Rather, the newly developed control method is a mathematical tool for solving the ADUDT control pulses. It does not contain the timing deviation compensation (from the logic-level command to the phase leg output voltage), and as such is not able to remove the timing deviation effects that cause error and overshoot in the filter. When the timing deviation compensation has to be tuned-in in the control pattern, the precalculated iteration method could prove simpler and equally good (or even better) compared with the mathematical solution with a separate timing compensation module. One of the key findings in this thesis is the conclusion that the correctness of the pulse pattern structure, in the sense of ZCC and predicted pulse timings, cannot be separated from the timing deviations. The usefulness of the correctly calculated pattern is reduced by the voltage edge timing errors. The doctoral thesis provides an introductory background chapter on variable-speed AC drives and the problem of motor overvoltages and takes a look at traditional solutions for overvoltage mitigation. Previous results related to the active du/dt filtering are discussed. The basic operation principle and design of the filter have been studied previously. The effect of load current in the filter and the basic idea of compensation have been presented in the past. However, there was no direct way of including the dead time in the control (except for solving the pulse pattern manually by iteration), and the magnitude of nonlinearity effects had not been investigated. The enhanced control principle with the dead time handling capability and a case study of the test setup timing deviations are the main contributions of this doctoral thesis. The simulation and experimental setup results show that the proposed control method can be used in an actual drive. Loss measurements and a comparison of active du/dt output filtering with traditional output filtering methods are also presented in the work. Two different ADUDT filter designs are included, with ferrite core and air core inductors. Other filters included in the tests were a passive du/dtfilter and a passive sine filter. The loss measurements incorporated a silicon carbide diode-equipped IGBT module, and the results show lower losses with these new device technologies. The new control principle was measured in a 43 A load current motor drive system and was able to bring the filter output peak voltage from 980 V (the previous control principle) down to 680 V in a 540 V average DC link voltage variable-speed drive. A 200 m motor cable was used, and the filter losses for the active du/dt methods were 111W–126 W versus 184 W for the passive du/dt. In terms of inverter and filter losses, the active du/dt filtering method had a 1.82-fold increase in losses compared with an all-passive traditional du/dt output filter. The filter mass with the active du/dt method was 17% (2.4 kg, air-core inductors) compared with 14 kg of the passive du/dt method filter. Silicon carbide freewheeling diodes were found to reduce the inverter losses in the active du/dt filtering by 18% compared with the same IGBT module with silicon diodes. For a 200 m cable length, the average peak voltage at the motor terminals was 1050 V with no filter, 960 V for the all-passive du/dt filter, and 700 V for the active du/dt filtering applying the new control principle.

Sosiaalisen median käyttö rekrytoinnissa työnantajan näkökulmasta

Tutkielmassa perehdytään siihen, mitä motiiveja yrityksillä on käyttää sosiaalista mediaa rekrytointiprosessissaan. Tämän lisäksi on pohdittu, mitkä sosiaalisen median kanavat ovat tärkeimpiä rekrytoinnin tarpeisiin ja mitä riskejä niiden käytössä voi olla rekrytoinnissa.

Liiketoimintamallit suomalaisissa sosiaalisen median palveluissa

Viime vuosina erilaisten sosiaalisten median palveluiden tarjonta internetissä on kasvanut huomattavasti. Herää kysymys, miten on mahdollista tarjota jotain ilmaiseksi, mutta saada silti aikaan merkittäviä tuloja. Tämän tutkimuksen tarkoituksena oli tutkia sitä, millaiset liiketoimintamallit vaikuttavat suomalaisten sosiaalisen median palveluiden taustalla. Lisäksi analysoitiin mallien eroja ja yhtäläisyyksiä. Tutkimuskohteiksi valittiin neljä erilaista sivustoa, joiden kävijämäärät ovat suuria. Tutkimus toteutettiin laadullisena tapaustutkimuksena. Aineisto kerättiin asiantuntijahaastatteluin. Lisäksi perehdyttiin valmiiseen aineistoon, jota löytyi muun muassa tutkimuskohteiden internet-sivuilta, lehtiartikkeleista sekä asiantuntijoiden aikaisemmista haastatteluista. Aineisto analysoitiin Osterwalderin ja Pigneurin (2010) liiketoimintamallien käsitekehikkoa apuna käyttäen. Tutkimustuloksista selvisi, että sosiaalisen median palveluissa hyödynnetään edelleen paljon mainosrahoitteisuutta. Kuitenkaan ainoastaan mainosten varaan rakentaminen ei usein enää riitä. Tämän vuoksi on yleistä, että erilaisia malleja yhdistellään. Yrityksillä on paljon vaihtoehtoja, joista ne voivat valita itselleen sopivimmat. Loppukäyttäjiä ei yleensä veloiteta palvelun käytöstä. Sen sijaan tulovirtoja voidaan saada esimerkiksi yritysasiakkailta, mainostajilta tai muilta yhteistyökumppaneilta. Liiketoimintamalleissa esiintyi paljon yhtäläisyyksiä. Etenkin palveluiden kustannusrakenteet, avainresurssit ja -prosessit muistuttivat paljon toisiaan. Arvolupauksille yhteistä oli se, että palvelun tavoitteena oli helpottaa käyttäjien arkea. Asiakastyytyväisyyteen panostaminen ja etenkin suhteet maksaviin asiakkaisiin koettiin yleisesti tärkeinä. Jokaisen palvelun liiketoimintamallista oli löydettävissä myös eroavaisuuksia. Kun tarkasteltiin kunkin osa-alueen toteutusta, havaittiin, että ne saattoivat poiketa paljonkin toisistaan. Koska liiketoimintamallit koostuvat erilaisista yhdistelmistä, muodostuu niistä usein ainutlaatuisia. Etenkin se, millaisia rahastusmalleja ja kanavia käytettiin sekä miten niitä oli yhdistelty, vaihteli palvelusta toiseen. Liiketoimintamallit tarjoavat paljon mahdollisuuksia jatkotutkimuksia silmällä pitäen. Tästä tutkimuksesta voi olla hyötyä myös niille tahoille, jotka tutkivat aihealuetta tulevaisuudessa. Mielenkiintoista olisi tutkia kokonaan uudenlaisia malleja, jotka ovat vasta kehitteillä. Myös nousevien toimialojen, kuten peli- ja mobiiliteollisuuden tarkastelu saattaisi olla hedelmällistä.

Tv-viihde sosiaalisen median pyörityksessä : Conan O'Brienin tapaus

Teemanumero: Tv-viihde.

Sosiaalisen median muodostama uhka taisteluosaston operaatioturvallisuudelle joukkojen perustamisvaiheessa

Operaatioturvallisuus (OPTU) nykyajan konseptina on suhteellisen tuore. Aihetta on tutkittu Persianlahdensodan ajoilta asti. Suomen Puolustusvoimat tulkitsee operaatioturvallisuutta yleisesti ottaen samalla tavalla kuin Yhdysvaltojen asevoimat. Sosiaalinen media (SOME) on konseptina myös tuore ilmiö (2007). Sosiaalisen median käyttöaste yhteiskunnassamme on merkittävä. Sosiaalinen media mahdollistaa vaivattoman tiedon jakamisen, joka puolestaan vaikuttaa operaatioturvallisuuteen. Sosiaalista mediaa ja operaatioturvallisuutta on tutkittu laajasti joko yksittäisinä konsepteina tai osana muita kokonaisuuksia. Operaatioturvallisuutta ei ole kuitenkaan käsitelty sosiaalisen median näkökulmasta laajamittaisesti. Suomessa aihe-aluetta on tarkasteltu rauhanturvaajien toimintaympäristössä ja sen yleiskäyttöä rauhan aika-na. Joukkojen perustamisvaihetta ei ole käsitelty. Modernina ilmiönä on syytä ymmärtää so-siaalisen median mahdollistamaa uhkaa taisteluosaston (TSTOS) operaatioturvallisuudelle joukkojen perustamisvaiheessa. Päätutkimuskysymys on: Millainen uhka sosiaalinen media on taisteluosaston operaatiotur-vallisuudelle ja miten siltä voidaan suojautua joukkojen perustamisvaiheen aikana? Alaky-symykset, jotka tukevat tutkimusta ovat: Mitä operaatioturvallisuus tarkoittaa konseptina? Minkälainen sosiaalinen media on toimintaympäristönä? Miten vastustaja tiedustelee sosiaa-lisessa mediassa (OSINT)? Minkälaisen vaikutuksen operaatioturvallisuuden puute sosiaali-sen median toimintaympäristössä luo taisteluosastolle? Aineisto koostuu internetlähteistä sekä kirjallisista lähteistä oppaiden, artikkelien ja uutisten muodossa. Johtopäätöksenä on todettavissa, että operaatioturvallisuuden kannalta on syytä kieltää sosiaalisen median käyttöä sekä poistaa sosiaalisen median palveluita mahdollistavat laitteet joukkojen perustamisvaiheessa. Operaatioturvallisuuden laiminlyöminen sosiaalisen median toimintaympäristössä jo rauhanajan koulutuksessa voi johtaa pahimmassa tapaukses-sa siihen, että joukot on saatettu toimintakyvyttömään tilaan ennen laajamittaista sotaa. Ope-raatioturvallisuuden tärkeyttä sosiaalisessa mediassa on koulutettava henkilökunnalle ja va-rusmiehille jo rauhan aikana. Tutkija kehottaa Puolustusvoimia ottamaan tarkemmin kantaa älypuhelimien ja sosiaalisen median käyttöön rauhan- ja joukkojen perustamisvaiheen aika-na.

Median digitalisoituminen ja yhdistetty tieto

Esitys Kansalliskirjaston Finto-palvelun ja arkistosektorin KDK-yhteistyöverkoston järjestämässä seminaarissa: Linkity! Kohti yhteentoimivaa metatietoa 3.9.2014.

Metabolism of diglycine and triglycine by non-filtering kidneys

We have studied the metabolism of diglycine and triglycine in the isolated non-filtering rat kidney. Kidneys from adult male Wistar Kyoto rats weighing 250-350 g were perfused with Krebs-Henseleit solution containing either 1 mM diglycine or triglycine. The analysis of the peptide residues and their components was performed using an amino acid microanalyzer utilizing ion exchange chromatography. Diglycine was degraded to a final concentration of 0.09 mM after 120 min (91%); this degradation occurred predominantly during the first hour, with a 56% reduction of the initial concentration. The metabolism of triglycine occurred similarly, with a final concentration of 0.18 mM (82%); during the first hour there was a 67% reduction of the initial concentration of the tripeptide. Both peptides produced glycine in increasing concentrations, but there was a slightly lower recovery of glycine, suggesting its utilization by the kidney as fuel. The hydrolysis of triglycine also produced diglycine, which was also hydrolyzed to glycine. The results of the present study show the existence of functional endothelial or contraluminal membrane peptidases which may be important during parenteral nutrition.

Normal median near nerve potential

In routine studies of sensory nerve conduction, only fibers e7 µm in diameter are analyzed. The late components which originate from thinner fibers are not detected. This explains why a normal sensory action potential (SAP) may be recorded in patients with peripheral neuropathies and sensory loss. In the present study we investigated the late component of the median SAP with a near nerve needle electrode technique in 14 normal volunteers (7 men and 7 women), aged 34.5 ± 14.8 years. The stimulus consisted of rectangular pulses of 0.2-ms duration at a frequency of 1 Hz with an intensity at least 6 times greater than the threshold value for the main component. Five hundred to 2000 sweep averagings were performed. The duration of analysis was 40 or 50 ms and the wave analysis frequency was 200 (-6 dB/oct) to 3000 Hz (-12 dB/oct). We used an apparatus with a two-channel amplifier system, 200 MW or more of entry impedance and a noise level of 0.7 µVrms or less. The main component mean amplitude, conduction velocity and latency and the late component mean amplitude, conduction velocity and latency were respectively (mean ± SD): 26.5 ± 5.42 µV, 56.8 ± 5.42 m/s, 3.01 ± 0.31 ms, 0.12 ± 0.04 µV, 16.4 ± 2.95 m/s and 10.6 ± 2.48 ms. More sophisticated equipment has an internal noise of 0.6 µVrms. These data demonstrate that the technique can now be employed to study thin fiber neuropathies, like in leprosy, using commercial electromyographs, even in non-academic practices

Adaptive Markov chain Monte Carlo and Bayesian filtering for state space models

This thesis is concerned with the state and parameter estimation in state space models. The estimation of states and parameters is an important task when mathematical modeling is applied to many different application areas such as the global positioning systems, target tracking, navigation, brain imaging, spread of infectious diseases, biological processes, telecommunications, audio signal processing, stochastic optimal control, machine learning, and physical systems. In Bayesian settings, the estimation of states or parameters amounts to computation of the posterior probability density function. Except for a very restricted number of models, it is impossible to compute this density function in a closed form. Hence, we need approximation methods. A state estimation problem involves estimating the states (latent variables) that are not directly observed in the output of the system. In this thesis, we use the Kalman filter, extended Kalman filter, Gauss–Hermite filters, and particle filters to estimate the states based on available measurements. Among these filters, particle filters are numerical methods for approximating the filtering distributions of non-linear non-Gaussian state space models via Monte Carlo. The performance of a particle filter heavily depends on the chosen importance distribution. For instance, inappropriate choice of the importance distribution can lead to the failure of convergence of the particle filter algorithm. In this thesis, we analyze the theoretical Lᵖ particle filter convergence with general importance distributions, where p ≥2 is an integer. A parameter estimation problem is considered with inferring the model parameters from measurements. For high-dimensional complex models, estimation of parameters can be done by Markov chain Monte Carlo (MCMC) methods. In its operation, the MCMC method requires the unnormalized posterior distribution of the parameters and a proposal distribution. In this thesis, we show how the posterior density function of the parameters of a state space model can be computed by filtering based methods, where the states are integrated out. This type of computation is then applied to estimate parameters of stochastic differential equations. Furthermore, we compute the partial derivatives of the log-posterior density function and use the hybrid Monte Carlo and scaled conjugate gradient methods to infer the parameters of stochastic differential equations. The computational efficiency of MCMC methods is highly depend on the chosen proposal distribution. A commonly used proposal distribution is Gaussian. In this kind of proposal, the covariance matrix must be well tuned. To tune it, adaptive MCMC methods can be used. In this thesis, we propose a new way of updating the covariance matrix using the variational Bayesian adaptive Kalman filter algorithm.

Excitotoxic median raphe lesions aggravate working memory storage performance deficits caused by scopolamine infusion into the dentate gyrus of the hippocampus in the inhibitory avoidance task in rats

The interactions between the median raphe nucleus (MRN) serotonergic system and the septohippocampal muscarinic cholinergic system in the modulation of immediate working memory storage performance were investigated. Rats with sham or ibotenic acid lesions of the MRN were bilaterally implanted with cannulae in the dentate gyrus of the hippocampus and tested in a light/dark step-through inhibitory avoidance task in which response latency to enter the dark compartment immediately after the shock served as a measure of immediate working memory storage. MRN lesion per se did not alter response latency. Post-training intrahippocampal scopolamine infusion (2 and 4 µg/side) produced a more marked reduction in response latencies in the lesioned animals compared to the sham-lesioned rats. Results suggest that the immediate working memory storage performance is modulated by synergistic interactions between serotonergic projections of the MRN and the muscarinic cholinergic system of the hippocampus.