Hydrogen storage technologies and implications of real-life applications:a review of case studies

Abstract. Hydrogen is seen as the solution for a carbon-neutral future. It can be used as a fuel for traffic, transportation, industry, and energy generation. Green hydrogen is produced from renewable energy sources. It can be produced in overgeneration periods and be utilized when needed, creating energy storage. The objective of the thesis was to find out the best hydrogen storage technologies for each purpose currently available for implementation, and options that are being developed. In addition, hydrogen strategies in the European Union and Finland were analyzed. Based on that knowledge, one case study of long-term seasonal hydrogen storage and one short-term hydrogen storage, which levels daily renewable energy generation fluctuations, are analyzed. The case studies were based on modelling. The short-term case study examinesan electrical testing laboratory, located in Saudi Arabia’s eastern region. The long-term case study is located in Finland. In addition, a real-life hydrogen project is analyzed to show the impacts of the integration of hydrogen storage technologies in the energy system. Calculations based on statistical data and technological parameters were used as a research method. The results of the analysis show that compressed hydrogen, liquefied hydrogen, and metal hydrides are far-developed and most-used storage methods. Cryo-compressed hydrogen, liquid organic hydrogen carriers, physically adsorbed hydrogen, and complex metal hydrides are still developing technologies. The advantages of integrating hydrogenstorage into the energy system lie in its ability to minimize the unmet demand by storing green hydrogen produced in low-demand periods and utilizing it later. This reduces the demand for fossil-based energy, preventing carbon dioxide emissions. In addition, hydrogen storage would have a positive effect on the prices of renewable energy systems

New Classes of Distributed Time Complexity

A number of recent papers -- e.g. Brandt et al. (STOC 2016), Chang et al. (FOCS 2016), Ghaffari & Su (SODA 2017), Brandt et al. (PODC 2017), and Chang & Pettie (FOCS 2017) -- have advanced our understanding of one of the most fundamental questions in theory of distributed computing: what are the possible time complexity classes of LCL problems in the LOCAL model? In essence, we have a graph problem $\Pi$ in which a solution can be verified by checking all radius-$O(1)$ neighbourhoods, and the question is what is the smallest $T$ such that a solution can be computed so that each node chooses its own output based on its radius-$T$ neighbourhood. Here $T$ is the distributed time complexity of $\Pi$. The time complexity classes for deterministic algorithms in bounded-degree graphs that are known to exist by prior work are $\Theta(1)$, $\Theta(\log^* n)$, $\Theta(\log n)$, $\Theta(n^{1/k})$, and $\Theta(n)$. It is also known that there are two gaps: one between $\omega(1)$ and $o(\log \log^* n)$, and another between $\omega(\log^* n)$ and $o(\log n)$. It has been conjectured that many more gaps exist, and that the overall time hierarchy is relatively simple -- indeed, this is known to be the case in restricted graph families such as cycles and grids. We show that the picture is much more diverse than previously expected. We present a general technique for engineering LCL problems with numerous different deterministic time complexities, including $\Theta(\log^{\alpha}n)$ for any $\alpha\ge1$, $2^{\Theta(\log^{\alpha}n)}$ for any $\alpha\le 1$, and $\Theta(n^{\alpha})$ for any $\alpha <1/2$ in the high end of the complexity spectrum, and $\Theta(\log^{\alpha}\log^* n)$ for any $\alpha\ge 1$, $\smash{2^{\Theta(\log^{\alpha}\log^* n)}}$ for any $\alpha\le 1$, and $\Theta((\log^* n)^{\alpha})$ for any $\alpha \le 1$ in the low end; here $\alpha$ is a positive rational number

Flow correlations from a hydrodynamics model with dynamical freeze-out and initial conditions based on perturbative QCD and saturation

We extend the applicability of the hydrodynamics, perturbative QCD and saturation -based EKRT (Eskola-Kajantie-Ruuskanen-Tuominen) framework for ultrarelativistic heavy-ion collisions to peripheral collisions by introducing dynamical freeze-out conditions. As a new ingredient compared to the previous EKRT computations we also introduce a nonzero bulk viscosity. We compute various hadronic observables and flow correlations, including normalized symmetric cumulants, mixed harmonic cumulants, and flow–transverse-momentum correlations, and compare them against measurements from the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC) . We demonstrate that the inclusion of the dynamical freeze-out and bulk viscosity allows a better description of the measured flow coefficients in peripheral collisions and enables the use of an extended centrality range when constraining the properties of QCD matter in the future.Peer reviewe

Antimicrobial resistance conferred by OXA-48 β-lactamases:towards a detailed mechanistic understanding

OXA-48-type β-lactamases are now routinely encountered in bacterial infections caused by carbapenem-resistant Enterobacterales. These enzymes are of high and growing clinical significance due to the importance of carbapenems in treatment of health care-associated infections by Gram-negative bacteria, the wide and increasing dissemination of OXA-48 enzymes on plasmids, and the challenges posed by their detection. OXA-48 confers resistance to penicillin (which is efficiently hydrolyzed) and carbapenem antibiotics (which is more slowly broken down). In addition to the parent enzyme, a growing array of variants of OXA-48 is now emerging. The spectrum of activity of these variants varies, with some hydrolyzing expanded-spectrum oxyimino-cephalosporins. The growth in importance and diversity of the OXA-48 group has motivated increasing numbers of studies that aim to elucidate the relationship between structure and specificity and establish the mechanistic basis for β-lactam turnover in this enzyme family. In this review, we collate recently published structural, kinetic, and mechanistic information on the interactions between clinically relevant β-lactam antibiotics and inhibitors and OXA-48 β-lactamases. Collectively, these studies are starting to form a detailed picture of the underlying bases for the differences in β-lactam specificity between OXA-48 variants and the consequent differences in resistance phenotype. We focus specifically on aspects of carbapenemase and cephalosporinase activities of OXA-48 β-lactamases and discuss β-lactamase inhibitor development in this context. Throughout the review, we also outline key open research questions for future investigation

ARGUMENTOINTIA PAINOTTAVA LUONNONTIETEEN KOULUOPETUS – KATSAUS TAVOITTEISIIN

Tässä artikkelissa tarkastellaan argumentointia painottavan luonnontieteen kouluopetuksen tavoitteita kansainvälisen tutkimuskirjallisuuden pohjalta. Tarkasteluun valittiin 14 luonnontieteen kouluopetuksen kansainvälistä tutkimusartikkelia, joissa esiintyvät kuvaukset argumentoinnin tavoitteista luokiteltiin niissä esiintyvien teemojen perusteella. Tavoitekuvauksista erottui kolme pääteemaa: koulussa opetettavien luonnontieteiden autenttisuuden lisääminen, oppilaiden ajattelu- ja vuorovaikutustaitojen kehittymisen tukeminen sekä sisältötiedon osaamisen ja luonnontieteellisen sivistyksen syventäminen. Autenttisen kuvan välittäminen luonnontieteistä oppilaille näyttäytyi edellytyksenä muiden oppimistavoitteiden saavuttamiselle. Tavoitteiden tunnistaminen edesauttaa argumentoinnin painottamista suomalaisessa luonnontieteen opetuksessa.Tässä artikkelissa tarkastellaan argumentointia painottavan luonnontieteen kouluopetuksen tavoitteita kansainvälisen tutkimuskirjallisuuden pohjalta. Tarkasteluun valittiin 14 luonnontieteen kouluopetuksen kansainvälistä tutkimusartikkelia, joissa esiintyvät kuvaukset argumentoinnin tavoitteista luokiteltiin niissä esiintyvien teemojen perusteella. Tavoitekuvauksista erottui kolme pääteemaa: koulussa opetettavien luonnontieteiden autenttisuuden lisääminen, oppilaiden ajattelu- ja vuorovaikutustaitojen kehittymisen tukeminen sekä sisältötiedon osaamisen ja luonnontieteellisen sivistyksen syventäminen. Autenttisen kuvan välittäminen luonnontieteistä oppilaille näyttäytyi edellytyksenä muiden oppimistavoitteiden saavuttamiselle. Tavoitteiden tunnistaminen edesauttaa argumentoinnin painottamista suomalaisessa luonnontieteen opetuksessa

Dynamic relaxation of the elastic properties of hard carbon films

The effect of enhanced atomic mobility on the growth of hard carbon films was examined. Tetrahedrally bonded amorphous carbon films were deposited by condensing energetic carbon ions using an arc-discharge deposition method. The deposition temperature varied between 50 and 400 °C. The dependence of elastic properties on deposition temperature was examined by determining the frequency-dependent propagation velocity of ultrasonic surface acoustic waves induced by a laser. A remarkable decrease in elastic coefficient was revealed above the deposition temperature of 300 °C and complete relaxation was obtained at 400 °C. This observation was analyzed by using a simple model which was in turn supported by molecular dynamics simulations. The relaxation turns out to be a thermally activated, dynamic process with an activation energy of 0.57 eV. Possible relaxation mechanisms associated with the migration of atoms or defects on a growing surface are discussed.Peer reviewe