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1.
Virpi Oksman Ville Ollikainen Elina Noppari Carlos Herrero Antti Tammela 《Multimedia Systems》2008,14(2):105-114
Recently, mobile TV has been launched in several countries. While mobile TV integrates television contents into mobile phones,
the most personal of communication devices, it becomes interesting to know how this feature will be used throughout the day
and in varying contexts of everyday life. This paper presents empirical results on the use of mobile TV with different delivery
mechanisms and both quantitative and qualitative results on how end-users prefer to use mobile TV contents in different situations.
The data is based on ongoing empirical research in Finland in 2006 and 2007. The mobile TV services under study included both
news and entertainment contents, and were tested in 3G, DVB-H and Wi-Fi networks using different delivery paradigms: broadcast,
on-demand and download. To explore the use of different delivery methods and content consumption, we have developed a mobile
TV service protoype, called Podracing. The analysis shows that users appreciated up-to-date information and information-rich
media forms and contents especially for mobile news delivery. There was high demand for only the latest news on mobiles. The
real-time property was considered important. Most of the users looked at the headlines or followed the news several times
a day – much more often than the traditional TV and news prime times would allow. 相似文献
2.
Ville T. Heikkilä Maria Paasivaara Casper Lasssenius Daniela Damian Christian Engblom 《Empirical Software Engineering》2017,22(6):2892-2936
In a large organization, informal communication and simple backlogs are not sufficient for the management of requirements and development work. Many large organizations are struggling to successfully adopt agile methods, but there is still little scientific knowledge on requirements management in large-scale agile development organizations. We present an in-depth study of an Ericsson telecommunications node development organization which employs a large scale agile method to develop telecommunications system software. We describe how the requirements flow from strategy to release, and related benefits and problems. Data was collected by 43 interviews, which were analyzed qualitatively. The requirements management was done in three different processes, each of which had a different process model, purpose and planning horizon. The release project management process was plan-driven, feature development process was continuous and implementation management process was agile. The perceived benefits included reduced development lead time, increased flexibility, increased planning efficiency, increased developer motivation and improved communication effectiveness. The recognized problems included difficulties in balancing planning effort, overcommitment, insufficient understanding of the development team autonomy, defining the product owner role, balancing team specialization, organizing system-level work and growing technical debt. The study indicates that agile development methods can be successfully employed in organizations where the higher level planning processes are not agile. Combining agile methods with a flexible feature development process can bring many benefits, but large-scale software development seems to require specialist roles and significant coordination effort. 相似文献
3.
4.
It is shown that the (infinite) tiling problem by Wang tiles is undecidable even if the given tile set is deterministic by all four corners, i.e. a tile is uniquely determined by the colors of any two adjacent edges. The reduction is done from the Turing machine halting problem and uses the aperiodic tile set of Kari and Papasoglu. 相似文献
5.
In this paper we propose a soft-output RAKE receiver for CDMA mobile terminals using low spreading factor and/or high-order modulation constellations for high data rates. Based on the outputs of theRAKE correlator fingers, the receiver produces symbol or bit metrics for soft decision decoding. The formulation of these metrics is derived analytically taking into account the multipath propagation, interfering users and channel estimation errors. Simulations show thata performance gain is achieved when low spreading factors or high-order modulation constellations are used. 相似文献
6.
Marjo Kettunen Riitta J. Silvennoinen Nikolay Houbenov Antti Nykänen Janne Ruokolainen Jani Sainio Viljami Pore Marianna Kemell Mikael Ankerfors Tom Lindström Mikko Ritala Robin H. A. Ras Olli Ikkala 《Advanced functional materials》2011,21(3):510-517
Chemical vapor deposition of a thin titanium dioxide (TiO2) film on lightweight native nanocellulose aerogels offers a novel type of functional material that shows photoswitching between water‐superabsorbent and water‐repellent states. Cellulose nanofibrils (diameters in the range of 5–20 nm) with native crystalline internal structures are topical due to their attractive mechanical properties, and they have become relevant for applications due to the recent progress in the methods of their preparation. Highly porous, nanocellulose aerogels are here first formed by freeze‐drying from the corresponding aqueous gels. Well‐defined, nearly conformal TiO2 coatings with thicknesses of about 7 nm are prepared by chemical vapor deposition on the aerogel skeleton. Weighing shows that such TiO2‐coated aerogel specimens essentially do not absorb water upon immersion, which is also evidenced by a high contact angle for water of 140° on the surface. Upon UV illumination, they absorb water 16 times their own weight and show a vanishing contact angle on the surface, allowing them to be denoted as superabsorbents. Recovery of the original absorption and wetting properties occurs upon storage in the dark. That the cellulose nanofibrils spontaneously aggregate into porous sheets of different length scales during freeze‐drying is relevant: in the water‐repellent state they may stabilize air pockets, as evidenced by a high contact angle, in the superabsorbent state they facilitate rapid water‐spreading into the aerogel cavities by capillary effects. The TiO2‐coated nanocellulose aerogels also show photo‐oxidative decomposition, i.e., photocatalytic activity, which, in combination with the porous structure, is interesting for applications such as water purification. It is expected that the present dynamic, externally controlled, organic/inorganic aerogels will open technically relevant approaches for various applications. 相似文献
7.
Ville Saari Jussi Mustola Jarkko Jussila Jussi Ryynänen Saska Lindfors Kari Halonen 《Analog Integrated Circuits and Signal Processing》2008,54(2):77-84
SiGe BiCMOS low-pass filter for a multicarrier WCDMA base-station receiver is described in this paper. The 4th-order Chebyshev
filter with a 0.1-dB passband ripple is designed to drive a high-resolution A/D converter. The −3-dB frequency of the implemented
filter can be programmed to four different bandwidths: 2.5, 5, 7.5, and 10 MHz depending on the number of received WCDMA channels.
The filter achieves +9.7-dBV in-band IIP3, +20-dBV out-of-band IIP3, and 8.5-nV/√Hz input-referred noise density with 10-MHz
bandwidth. The circuit uses a 2.5 V supply and has been fabricated in a 0.25-μm SiGe BiCMOS process. 相似文献
8.
The monogenic signal is the natural 2D counterpart of the 1D analytic signal. We propose to transpose the concept to the wavelet domain by considering a complexified version of the Riesz transform which has the remarkable property of mapping a real-valued (primary) wavelet basis of L2(R2) into a complex one. The Riesz operator is also steerable in the sense that it give access to the Hilbert transform of the signal along any orientation. Having set those foundations, we specify a primary polyharmonic spline wavelet basis of L2(R2) that involves a single Mexican-hat-like mother wavelet (Laplacian of a B-spline). The important point is that our primary wavelets are quasi-isotropic: they behave like multiscale versions of the fractional Laplace operator from which they are derived, which ensures steerability. We propose to pair these real-valued basis functions with their complex Riesz counterparts to specify a multiresolution monogenic signal analysis. This yields a representation where each wavelet index is associated with a local orientation, an amplitude and a phase. We give a corresponding wavelet-domain method for estimating the underlying instantaneous frequency. We also provide a mechanism for improving the shift and rotation-invariance of the wavelet decomposition and show how to implement the transform efficiently using perfect-reconstruction filterbanks. We illustrate the specific feature-extraction capabilities of the representation and present novel examples of wavelet-domain processing; in particular, a robust, tensor-based analysis of directional image patterns, the demodulation of interferograms, and the reconstruction of digital holograms. 相似文献
9.
Ferenets R Lipping T Anier A Jäntti V Melto S Hovilehto S 《IEEE transactions on bio-medical engineering》2006,53(6):1067-1077
Entropy and complexity of the electroencephalogram (EEG) have recently been proposed as measures of depth of anesthesia and sedation. Using surrogate data of predefined spectrum and probability distribution we show that the various algorithms used for the calculation of entropy and complexity actually measure different properties of the signal. The tested methods, Shannon entropy (ShEn), spectral entropy, approximate entropy (ApEn), Lempel-Ziv complexity (LZC), and Higuchi fractal dimension (HFD) are then applied to the EEG signal recorded during sedation in the intensive care unit (ICU). It is shown that the applied measures behave in a different manner when compared to clinical depth of sedation score--the Ramsay score. ShEn tends to increase while the other tested measures decrease with deepening sedation. ApEn, LZC, and HFD are highly sensitive to the presence of high-frequency components in the EEG signal. 相似文献
10.