Availability in mobile application in IaaS cloud

Deploying software system into IaaS cloud takes infrastructure out of user's control, which diminishes visibility and changes system administration. Service outages of infrastructure services and other risks to availability have caused concern for early users of cloud. In this thesis existing web application, which is deployed in IaaS cloud, was evaluated for availability. Whole spectrum of different cloud related incidents that compromises provided service was examined. General view from availability point of view of the case Internet service was formed based on interviews. Big cloud service providers have service level agreements effective and long cloud outages are rare events. Cloud service providers build mutually independent domains or zones into infrastructure. Internet availability is largely determinative of users' perceived performance of site. Using multiple cloud service providers is a solution to cloud service unavailability. Case company had discovered requirements for availability and sufficiently prevented threats. Case company was satisfied in cloud services and there is no need to withdraw from cloud. User is a significant threat to the dependability of system, but there are no definite means to prevent user from damaging system. Taking routinely and regularly backups of data outside the cloud is the core activity in IT crisis preparedness. Application architecture was evaluated and found satisfactory. Software system contains managed database service and load balancer as an advanced feature from IaaS provider. Both services give crucial support for the availability of the system. Examined system has conceptually simple stateless recovery.Ohjelmiston käyttö IaaS -pilvessä saattaa infrastruktuurin käyttäjän kontrollin ulottumattomiin, mikä heikentää näkyvyyttä ja muuttaa järjestelmän hallintaa. Palvelukatkot infrastruktuuripalveluissa ja muut riskit saatavuudelle ovat aiheuttaneet varovaisuutta pilvipalveluiden varhaisissa käyttäjissä. Tässä diplomityössä evaluoitiin olemassa olevan ja IaaS -pilvessä käytettävän web-sovelluksen saatavuutta. Kokonainen kirjo erilaisia pilveen liittyviä tapahtumia, jotka keskeyttävät tarjotun palvelun, tutkittiin. Yleiskuva saatavuuden näkökulmasta katsottuna muodostettiin haastattelujen pohjalta. Suurilla pilvipalveluiden tarjoajilla on voimassa olevat palvelutasosopimukset ja pitkät palvelukatkot ovat harvinaisia tapahtumia. Pilvipalveluiden tarjoajat rakentavat infrastruktuuriin toisistaan riippumattomasti toimivia alueita. Suurelta osalta määräävä tekijä käyttäjien kokeman sivuston suorituskyvyn kannalta on Internetin kautta palveluun liittymisen saatavuus. Useamman pilvipalvelun tarjoajan käyttäminen on ratkaisu pilvipalvelun saatavuuteen. Case-yritys oli löytänyt vaatimukset saatavuudelle ja riittävällä tavalla estänyt riskien toteutumisen. Case-yritys oli tyytyväinen pilvipalveluihin ja pilvestä pois vetäytymiselle ei ole tarvetta. Käyttäjä on merkittävä riski järjestelmän luotettavuudelle, mutta ei ole varmoja tapoja estää käyttäjää vahingoittamasta järjestelmää. Keskeinen toiminto tietotekniseen kriisiin varautumisessa on rutiininomainen ja säännöllinen varmuuskopioiden teko. Sovelluksen arkkitehtuuria evaluoitiin ja se havaittiin tarpeita vastaavaksi. Ohjelmistojärjestelmä sisältää palveluntarjoajan ylläpitämän tietokantapalvelun ja web-palvelimien tietoliikenteen kuorman tasaajan IaaS -palvelun edistyneinä ominaisuuksina. Molemmat palvelut tukevat ratkaisevasti järjestelmän saatavuutta. Tarkastellussa järjestelmässä on käsitteellisesti yksinkertainen tilaton järjestelmän palautuminen

Soil organic carbon and clay content as deciding factors for net nitrogen mineralization and cereal yields in boreal mineral soils

To achieve appropriate yield levels, inherent nitrogen (N) supply and biological N fixation are often complemented by fertilization. To avoid economic losses and negative environmental impacts due to over-application of N fertilizer, estimation of the inherent N supply is critical. We aimed to identify the roles of soil texture and organic matter in N mineralization and yield levels attained in cereal cultivation with or without N fertilization in boreal mineral soils. First, the net N mineralization and soil respiration were measured by laboratory incubation with soil samples varying in clay and organic carbon (C) contents. Secondly, to estimate the inherent soil N supply under field conditions, both unfertilized and fertilized cereal yields were measured in fields on clay soils (clay 30-78%) and coarse-textured soils (clay 0-28%). In clay soils (C 2.5-9.0%), both the net N mineralization and the cereal yields (without and with fertilization) decreased with increasing clay/C ratio. Moreover, in soils with high clay/C ratio, the agronomic N use efficiency (additional yield per kg of fertilizer N) varied considerably, indicating the presence of growth limitations other than N. In coarse-textured soils, the yield increase attained by fertilization increased with increasing organic C. Our results indicate that for clay soils in a cool and humid climate, the higher the clay content, the more organic C is needed to produce reasonable yields and to ensure efficient use of added nutrients without high N losses to the environment. For coarse soils having a rather high mean organic C of 2.3%, the organic C appeared to improve agronomic N use efficiency. For farmers, simple indicators such as the clay/C ratio or the use of non-N-fertilized control plots may be useful for site-specific adjustment of the rates of N fertilization. Highlights We aimed to identify simple indicators of inherent soil N supply applicable at the farm level. In clay soils, the net N mineralization was found to correlate negatively with the clay/C ratio. In coarse-textured soils, agronomic N use efficiency improved with increasing soil organic C. Clay soils with high clay/C ratio are at risk of low yield levels.Peer reviewe

Impact of earthworm Lumbricus terrestris living sites on the greenhouse gas balance of no-till arable soil

We studied the effect of the deep-burrowing earthworm Lumbricus terrestris on the greenhouse gas (GHG) fluxes and global warming potential (GWP) of arable no-till soil using both field measurements and a controlled 15-week laboratory experiment. In the field, the emissions of nitrous oxide (N2O) and carbon dioxide (CO2) were on average 43 and 32% higher in areas occupied by L. terrestris (the presence judged by the surface midden) than in adjacent, unoccupied areas (with no midden). The fluxes of methane (CH4) were variable and had no consistent difference between the midden and non-midden areas. Removing the midden did not affect soil N2O and CO2 emissions. The laboratory results were consistent with the field observations in that the emissions of N2O and CO2 were on average 27 and 13% higher in mesocosms with than without L. terrestris. Higher emissions of N2O were most likely due to the higher content of mineral nitrogen and soil moisture under the middens, whereas L. terrestris respiration fully explained the observed increase in CO2 emissions in the laboratory. In the field, the significantly elevated macrofaunal densities in the vicinity of middens likely contributed to the higher emissions from areas occupied by L. terrestris. The activity of L. terrestris increased the GWP of field and laboratory soil by 50 and 18 %, but only 6 and 2% of this increase was due to the enhanced N2O emission. Our results suggest that high N2O emissions commonly observed in no-till soils can partly be explained by the abundance of L. terrestris under no-till management and that L. terrestris can markedly regulate the climatic effects of different cultivation practises.Peer reviewe

MIMO Extension to DVB-SH

DVB-SH is a hybrid satellite-terrestrial system combining a satellite component and a complementary ground component to provide service in all types of environments, i.e., outdoor and indoor coverage in urban, sub-urban and rural. This paper reports the studies on multiple-input multiple-output (MIMO) extension to the existing DVB-SH standard. MIMO techniques are considered in this paper for achieving increased spectral efficiency and reliability in the challenging satellite and hybrid channel environment

MIMO Evolution Beyond 5G Through Reconfigurable Intelligent Surfaces and Fluid Antenna Systems

With massive deployment, multiple-input-multiple-output (MIMO) systems continue to take mobile communications to new heights, but the ever-increasing demands mean that there is a need to look beyond MIMO and pursue the next disruptive wireless technologies. Reconfigurable intelligent surface (RIS) is widely considered a key candidate technology block to provide the next generational leap. The first part of this article provides an updated overview of the conventional reflection-based RIS technology, which complements the existing literature to include active and semiactive RIS, and the synergies with cell-free massive MIMO (CF mMIMO). Then, we widen the scope to discuss the surface-wave-assisted RIS that represents a different design dimension in utilizing metasurface technologies. This goes beyond being a passive reflector and can use the surface as an intelligent propagation medium for superb radio propagation efficiency. The third part of this article turns the attention to the fluid antenna, a novel antenna technology that enables a diverse form of reconfigurability that can combine with RIS for ultrahigh capacity, power efficiency, and scalability. This article concludes with a discussion of the potential synergies that can be exploited between MIMO, RIS, and fluid antennas

Valuing companies in M&A situations:a study of Finnish small & middle-sized companies

The goal of this study is to examine valuation in small and middle-sized, private companies’ mergers and acquisitions in Finland. This study attempts to answer the following questions: How are companies valuated in M&A in the small and middle-sized, private firm context? What are the most critical issues affecting valuation and M&A processes in this context? This research uses qualitative methods as information gathering from private companies is challenging. These methods enable to reflect issues of interest even on a small sample. We use method triangulation as the topic is studied by numerous procedures. First, there’s a questionnaire directed for companies involved in M&A. Second, the results from the first phase are presented to experts who give their own opinions on the matter. Finally, previously gathered views are scrutinized with academic outlook. Therefore this study attempts to create a discussion between academics and practitioners on the matter of valuation in small, private company M&A. Results of this paper are ample. Valuation should be seen as a part of the M&A process and this procedure should be properly planned and executed in order to harness the expected value. There are many ways to derive a value for the target and one can’t unambiguously determine the best method. The selection of the method depends on the expertise of the analyst and on the information available. There are special issues in private company valuation. The unreliability of the information used in valuation and personification of the company should be taken into consideration. Availability of funds for the transaction has also crucial role on the process. The results of this study should not be completely removed from their context as qualitative methods usually resemble case studies. This research provides guidelines for future work on this issue, as similar studies made with this research structure have apparently not been done. For a company involved in M&A this paper gives information on where to focus in the process

Non-linear self-interference cancelation for full-duplex transceivers based on Hammerstein-Wiener model

Abstract The main challenge in a full-duplex transceiver design is created by the self-interference caused by the coupling of the transmitted signal to the transceiver’s own receiver. The effect of the non-linear operation of both the power amplifier at the transmitter and the low noise amplifier at the receiver are considered in the self-interference cancelation. The performance of three self-interference cancelers are studied: linear cancelation, auto-regressive moving-average (ARMA) based cancelation and a neural network (NN) based canceler. The NN based cancelation outperforms both the linear and ARMA based canceler but requires considerably more operations than the other two

Analog self-interference cancellation with automatic gain control for full-duplex transceivers

Abstract The main challenge in full-duplex transceiver design is the self-interference (SI). Analog SI isolation is performed at radio frequency (RF) by using an antenna design based on the characteristic modes theory and using active cancelation principle. Two different structures based on using a vector down-converter and a complex multiplier are used for analog baseband SI cancellation. Cancellers are tuned using a automatic gain control (AGC) enhanced variable-step steepest descent algorithm while transmitting a data signal to a distant node in half-duplex mode. Simulations show that the inclusion of AGC into the tuning process speeds up the convergence significantly