Inter-organizational collaboration in software product development

Digitalization changes many industries since manufacturers are increasing the automation level in their products. Novel business needs require developed softwares, and that often leads companies to use external skills in software development either by hiring more software engineers or by purchasing tailored softwares from software companies. However, prices in the software industry can be high, and hiring new software engineers or purchasing tailored softwares may not be the most cost-effective method to get softwares into products. Co-developing softwares with other companies could be a potential method for sharing the costs and benefits of the product development processes. The objective of this thesis was to investigate different companies’ interests towards deep collaboration models, such as contractual alliances and joint ventures, in software development. Other objective was to examine what benefits and risks these collaboration models include, as well as which are the enablers and barriers for such collaboration. Research data was gathered by interviews with product development managers and directors as well as with technology managers and directors of different companies. Results showed that software co-development in a contractual alliance aroused moderate interest, whereas forming a joint venture for software co-development aroused less interest among the interviewees. Main benefits that interviewees saw in a deep collaboration in product development were the possibility to increase the speed and creativity in the processes while sharing the costs and risks of the development work. The main risks in deep collaboration were the uncertainty in collaboration costs, risk of getting too dependent of the partner and risk of getting unfair share of the jointly created value. Trust, open knowledge sharing and sufficient contracting skills were seen as the main enablers for deep collaboration, whereas limited time and complex contracting were the main barriers for deep inter-organizational collaboration

The logic behind secondary buyouts: Empirical evidence from Finland

The purpose of this thesis is to study the logic behind the secondary buyouts in Finland between 2002 and 2014 using the hand-collected sample of buyouts. The thesis investigates whether the secondary buyouts are motivated by efficiency gains or driven by market conditions or liquidity demand. In addition, the role of collusion in secondary buyouts is examined. Finally, this thesis studies how secondary buyout are priced. Value creation is the basis of private equity industry. Previous academic literature shows private equity buyouts has positive impact on target companies’ operating performance. In the context of value creation the logic of secondary buyout is still a puzzle. This thesis investigates with year-by-year examination the development of the operating performance after secondary buyouts. In order to find out the alternative motives for secondary buyouts, probit model is used to find out how equity and debt market condition and liquidity demand effect on the exit route. To examine the role of collusion in secondary buyouts cross-participation matrix is built to identify possible trade patterns. The pricing of secondary buyouts is studied with comparable industry transaction method against first-time buyouts using the Ordinary Least Squares regression. Evidence of the study do not show efficiency gains for target companies in secondary buyouts. Results suggests that market condition is the main driver of secondary buyouts. When debt market is favorable, the probability of exiting through secondary buyout increases significantly. On the other hand, favorable equity market is found to increase the probability of other exit routes, IPO and the selling strategic buyer, although with less significant results. In addition, results also shows that secondary buyouts are associated with higher value compared to first-time buyouts. The higher value is significantly driven by favorable debt market condition and the size of the target company.fi=Opinnäytetyö kokotekstinä PDF-muodossa.|en=Thesis fulltext in PDF format.|sv=Lärdomsprov tillgängligt som fulltext i PDF-format

Evolution of eccentric stellar disks around supermassive black holes: the complex disk disruption dynamics and the milliparsec stars

We study the 10 Myr evolution of parsec-scale stellar disks with initial masses of $M_{\mathrm{disk}} = 1.0$ - $7.5 \times 10^4 M_\odot$ and eccentricities $e_\mathrm{init}=0.1$-$0.9$ around supermassive black holes (SMBHs). Our disk models are embedded in a spherical background potential and have top-heavy single and binary star initial mass functions (IMF) with slopes of $0.25$-$1.7$. The systems are evolved with the N-body code $\texttt{BIFROST}$ including post-Newtonian (PN) equations of motion and simplified stellar evolution. All disks are unstable and evolve on Myr timescales towards similar eccentricity distributions peaking at $e_\star \sim 0.3$-$0.4$. Models with high $e_\mathrm{init}$ also develop a very eccentric $(e_\star\gtrsim0.9)$ stellar population. For higher disk masses $M_\mathrm{disk} \gtrsim3 \times10^4\;\mathrm{M_\odot}$, the disk disruption dynamics is more complex than the standard secular eccentric disk instability with opposite precession directions at different disk radii - a precession direction instability. We present an analytical model describing this behavior. A milliparsec population of $N\sim10$-$100$ stars forms around the SMBH in all models. For low $e_\mathrm{init}$ stars migrate inward while for $e_\mathrm{init}\gtrsim0.6$ stars are captured by the Hills mechanism. Without PN, after $6$ Myr the captured stars have a sub-thermal eccentricity distribution. We show that including PN effects prevents this thermalization by suppressing resonant relaxation effects and cannot be ignored. The number of tidally disrupted stars is similar or larger than the number of milliparsec stars. None of the simulated models can simultaneously reproduce the kinematic and stellar population properties of the Milky Way center clockwise disk and the S-cluster.Comment: 33 pages, 28 figures, submitted into MNRA

Odling och uppdragande av ädla lövträd och klibbal

sidott

Forming Galaxies in Cosmological Zoom-in Simulations

In this Master's thesis, I have reviewed the theory of galaxy formation and evolution from primordial fluctuations to present-day galaxies. I have also examined the procedure for creating initial conditions for cosmological Zoom-in simulations. The main aim of this thesis was to perform groundwork in the field of Zoom-in simulations at the Department of Physics of the University of Helsinki for my future PhD studies. I have prepared a total number of 10 high-resolution multi-mass Zoom-in initial conditions, five of which contains dark matter and baryons and the rest consisting of dark matter only. The Zoom-in initial conditions were calculated using the P-GenIC N-body initial conditions code using the Alcyone cluster at the Department of Physics in July and August 2013. The computation of the Zoom-in initial conditions took approximately 41 days in wall-clock time using 24 processors. The ten Zoom-in simulations were run on the supercomputer Sisu at CSC, the Finnish IT Center for Science in September and October 2013 using the N-body simulation code GADGET-3. The code calculated the Newtonian gravitational force using the TreePM method. The gas dynamics was computed with the SPH algorithm and the properties of the interstellar medium and star formation were modeled using a statistical subgrid model. The simulation runs took approximately from one hour to one week of wall-clock time using 64 processors. The ten simulated galaxies were searched for contamination from low-resolution particles. The high-resolution regions of the galaxies were not contaminated, validating the preparation method of the Zoom-in initial conditions. The basic properties of the galaxies at z=0 were analyzed, including virial radii and virial masses, circular rotation curves and density profiles. Finally, star formation histories and colors of the simulated galaxies were extracted. The properties of the simulated galaxies were consistent with previous studies in the field of Zoom-in simulations (Naab et al. 2007, Johansson et al. 2012). Thus, I conclude that the aims set for this Master's thesis were successfully completed. After the groundwork has been conducted, it is convenient to move to future studies in the field of cosmological structure formation simulations. The focus of the future work will be in improving the simulation codes and in developing more realistic astrophysical feedback models. Increased spatial resolution and improved feedback models of the simulations can lead to significant progress on the most demanding challenges in the field of cosmological structure formation simulations

Modeling supermassive black hole dynamics in galactic-scale numerical simulations

The presence of supermassive black holes (SMBHs) is ubiquitous in all massive galaxies in the local Universe. In the standard cosmological model, galaxies grow in a process of hierarchical merging and through accretion of matter from the intergalactic medium. Correspondingly, SMBHs grow by accreting gas from their surroundings and through merging with other SMBHs. Thus, present-day SMBHs are expected to have a complicated past merger history. Merging SMBHs leave imprints both on the central regions of their host galaxies and the gravitational wave background. In this thesis, which consists of four peer-reviewed publications, we investigate SMBH binary dynamics in realistic galactic environments and study the effect of merging SMBHs on their early-type host galaxies. For this research, a novel numerical simulation code KETJU was developed. The first two publications present the simulation code KETJU. The KETJU code combines the widely-used galactic-scale simulation code GADGET-3 and an extremely accurate small-scale SMBH dynamics integrator AR-CHAIN. The numerical methods used in KETJU and their practical implementation are thoroughly presented. In addition, we validate the performance of KETJU in comparison simulations with direct N-body codes used in the literature. The energy conservation of the code and parallel scaling behaviour are also demonstrated. We study the effect of the chosen stellar mass resolution on the evolution of the SMBH binaries in a series of galaxy merger simulations. We find that the dependence of the SMBH binary hardening rate on the mass resolution of the simulation is weaker if more realistic multi-component galaxy initial conditions are used. Finally, we show that with a proper treatment of SMBH dynamics in galactic-scale simulations, SMBH mergers are delayed by a few 100 million years compared to the SMBH merger criteria commonly used in the literature. The last two articles study the formation of large stellar cores in massive elliptical galaxies. Using KETJU, we run a series of early-type galaxy merger simulations with SMBHs to investigate the core scouring process responsible for creating cores in massive galaxies. We systematically study the effect of the initial SMBH mass and the initial stellar density profile slope on the surface brightness, the velocity anisotropy profiles and the core scaling relations of the merger remnant. Throughout the two studies we find that more cuspy initial stellar density profiles provide a better match to the final observed properties of core elliptical galaxies. We show that elliptical galaxies built up in a series of minor mergers have larger cores than major merger remnants, as expected, but on the other hand have less anisotropic velocity distributions in their core regions. Finally, we present a simple merger model which for the first time simultaneously produces an early-type galaxy with a flat central core, a tangentially biased central stellar population and kinematically decoupled central regions. These properties of cored early-type galaxies have previously been difficult to explain in one single formation scenario.Tähtitieteelliset havainnot ovat vahvistaneet että jokaisen massivisen galaksin keskustassa sijaitsee supermassiivinen musta aukko. Kosmologian standardimallissa galaksit kasvavat hierarkisesti törmäilemällä ja yhteensulautumalla muiden galaksien kanssa sekä vetämällä puoleensa kaasua galaksienvälisestä avaruudesta. Supermassiiviset mustat aukot kasvavat samaan tapaan: aukkoon päätyvä kaasu kasvattaa sen massaa, ja mustat aukot voivat myös yhteensulautua toistensa kanssa. Täten lähiavaruuden supermassiiviset mustat aukot ovat elinaikanaan yhteensulautuneet monien toisten supermassiivisten mustien aukkojen kanssa. Supermassiivisten mustien aukkojen yhteensulautumiset tuottavat voimakkaasti gravitaatiosäteilyä sekä muokkaavat galaksien keskusalueiden rakennetta. Tässä artikkeliväitöskirjassa tutkin supermassiivisten mustien aukkojen binäärien (vrt. kaksoistähti) ratadynamiikkaa massiivisten ellipsigalaksien keskustoissa sekä yhteensulautuvien binäärien vaikutusta emogalaksiinsa. Tutkimustyötä varten kehitettiin uusi numeerinen simulaatiokoodi KETJU. Artikkeliväitöskirjani sisältää neljä vertaisarvioitua julkaisua. Kaksi ensimmäistä julkaisua käsittelevät KETJU-koodin toimintaa. KETJU yhdistää laajasti käytetyn galaksisimulaatiokoodi GADGET-3:n erittäin tarkkaan AR-CHAIN-rataintegraattoriin, jota käytetään mustien aukkojen dynamiikan tutkimiseen. Artikkelit esittelevät KETJU:ssa käytetyt numeeriset menetelmät sekä niiden käytännön tason toteutuksen koodissa. KETJU:n numeerinen tarkkuus varmistetaan tarkastelemalla säilyviä fysikaalisia suureita ja vertaamalla simulaatiotuloksia kirjallisuudessa esiintyvien N:n kappaleen suorasummauskoodien tulosten kanssa. KETJU-koodin rinnakkaistuvuus supertietokoneissa tarkastetaan skaalautuvuustesteissä. Lisäksi tarkastelen galaksitörmäyssimulaatioiden massaresoluution vaikutusta binäärien rataelementtien evoluutioon. Simulaatiosarjan päätulos on että massaresoluution vaikutus rataelementtien evoluutioon on heikompi jos simulaatioiden galaksialkuehdot koostuvat realistisesta tähtikomponentista ja pimeän aineen halosta. Lisäksi osoitan että KETJU-koodilla ajetuissa simulaatioissa supermassiivisten mustien aukkojen yhteensulautuminen viivästyy sadoilla miljoonilla vuosilla verrattuna aikaisempiin yksinkertaisiin simulaatiomenetelmiin. Väitöskirjan kaksi viimeistä artikkelia keskittyvät massiivisten ellipsigalaksien keskusalueisiin. Ajan sarjan ellipsigalaksitörmäyssimulaatioita KETJU-koodia käyttäen tutkiakseni kuinka simulaatioissa syntyvät binäärit uurtavat syntyneen galaksin tähtikomponenttiin matalatiheyksisen core-alueen. Tutkin systemaattisesti alkuehtojen mustien aukkojen massan ja tähtikomponentin tiheysprofiilin vaikutusta syntyvän galaksin pintakirkkausjakaumaan, nopeusanisotropiaan sekä core-alueen ominaisuuksien korrelaatioihin. Tutkimusartikkelit osoittavat että jyrkemmät tähtikomponentin alkutiheysjakaumat johtavat paremmin havaittuja ellipsigalakseja vastaaviin tuloksiin. Useissa galaksitörmäyksissä syntyvillä simuloiduilla ellipsigalakseilla on suuremmat core-alueet, mutta core-alueen tähtien nopeusjakauma on isotrooppisempi kuin yhdessä törmäyksessä syntyneillä galakseilla. Väitöskirjan viimeisessä artikkelissa esitän yksinkertaisen galaksitörmäysmallin joka samanaikaisesti selittää core-ellipsigalaksien keskusosien kaikki keskeiset rakenneosat: matalan tiheyden, anisotropian sekä kinemaattisesti erillisten ja irtikytkeytyneiden komponenttien olemassaolon. Aikaisempien mallien on ollut hyvin vaikea selittää kaikki kolme core-galaksien ominaisuutta yhdellä muoduostumismekanismilla

Differential power analysis attack against Advanced Encryption Standard

Tiedon joutuminen ulkopuolisten tahojen haltuun halutaan usein estää käyttämällä salausalgoritmeja. Symmetriset salauslalgoritmit ovat eräs tapa suorittaa salaus. Symmetriset salausalgoritmit käyttävät salaukseen ja salauksen purkamiseen samaa salausavainta. Differentiaalinen tehoanalyysihyökkäys on sivukanavahyökkäys. Sivukanavahyökkäyksissä käytetään hyväksi sauslaitteen vuotamaa tietoa. Differentiaalisessa tehoanalyysihyökkäyksessä hyväksikäytetään elektronisen salauslaitteen tehonkulutuksen riippuvuutta laitteen käyttämästä salausavaimesta. Hyökkäyksellä on mahdollista selvittää salauslaitteen käyttämä salausavain. Differentialiseen tehoanalyysihyökkäykseen tarvitaan salauslaitteen salaamaa salattua tietoa ja tehonkulutusmittauksia laitteesta. Hyökkäykseen tarvitaan oskilloskooppi ja tietokone, joiden avulla mitataan salauslaitteen tehonkulutus ja suoritetaan laskenta. Salatun tiedon ja avainarvausten avulla lasketaan salauslaitteen mahdollisesti tuottamia välituloksia. Välitulosten avulla arvioidaan salauslaitteen tehonkulutusta. Korrelaatioanalyysillä tunnistetaan oikea avainarvaus. Tässä työssä suoritettiin differentiaalinen tehoanalyysihyökkäys kahta AES-salauslaitetta vastaan. Salauslaitteen salausavain saatiin selville yhdellä kolmesta kokeillusta AES-toteutuksesta.It is often desirable that information is not readable by outsiders. To make information unreadable for outsiders an encryption algorithm is used. Symmetric encryption algorithms uses secred key for encryption and decryption. Differential power analysis attack is a side-channel attack. The attack takes advantage of information about the secret key that leaks trough encryption device's power consumption. Goal of the attack is to find the secret key. Encrypted information and power consumption measurements are needed for differential power analysis attack. An oscilloscope is used to measure the encryption device's power consumption. A computer is used to calculate results. Possible intermediate values are calculated by encrypted information and key guesses. Intermediate values are used to approximate power consumption of the encryption device. Correlation analysis is used to distinguish the correct key guess. In this work differential power analysis attack is performed against two different AES encryption devices. Secret key was found while using one of the three AES implementations that are investigated

FROST: a momentum-conserving CUDA implementation of a hierarchical fourth-order forward symplectic integrator

We present a novel hierarchical formulation of the fourth-order forward symplectic integrator and its numerical implementation in the GPU-accelerated direct-summation N-body code FROST. The new integrator is especially suitable for simulations with a large dynamical range due to its hierarchical nature. The strictly positive integrator sub-steps in a fourth-order symplectic integrator are made possible by computing an additional gradient term in addition to the Newtonian accelerations. All force calculations and kick operations are synchronous so the integration algorithm is manifestly momentum-conserving. We also employ a time-step symmetrisation procedure to approximately restore the time-reversibility with adaptive individual time-steps. We demonstrate in a series of binary, few-body and million-body simulations that FROST conserves energy to a level of $|\Delta E / E| \sim 10^{-10}$ while errors in linear and angular momentum are practically negligible. For typical star cluster simulations, we find that FROST scales well up to $N_\mathrm{GPU}^\mathrm{max}\sim 4\times N/10^5$ GPUs, making direct summation N-body simulations beyond $N=10^6$ particles possible on systems with several hundred and more GPUs. Due to the nature of hierarchical integration the inclusion of a Kepler solver or a regularised integrator with post-Newtonian corrections for close encounters and binaries in the code is straightforward.Comment: 18 pages, 7 figures. Accepted for publication in MNRA