| 9611. |
- Krpic, Z., et al.
(författare)
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Green HPC : MPI vs. OpenMP on a shared memory system
- 2012
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Ingår i: MIPRO 2012 - 35th International Convention on Information and Communication Technology, Electronics and Microelectronics - Proceedings. - 9789532330724 ; , s. 246-250
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Konferensbidrag (refereegranskat)abstract
- A power consumption of a high performance computer (HPC) system has been an issue lately. Many programming techniques are still relying on performance gain, but only few of them are concerning energy footprint of the increased computing power. MPI and OpenMP are considered as a core scientific HPC programming libraries for distributed-memory and shared-memory computer systems respectively. Each of them brings performance when used on a parallel system, but there are dissimilarities in their performance per watt ratio. The key is to find the best appliance for each of them on a shared-memory computer system.
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| 9612. |
- Krpic, Zdravko, et al.
(författare)
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Towards a Common Software-to-hardware Allocation Framework for the Heterogeneous High Performance Computing
- 2014
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Ingår i: 38th International Computer Software and Applications Conference Workshops (COMPSACW). ; , s. 378 - 383
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Konferensbidrag (refereegranskat)abstract
- In the domain of high performance computing, software deployment on heterogeneous distributed processing units has been in practice for many years. However, new hardware technologies, increased complexity of software and significant increase of requirements demand new methods that can manage these concerns in an efficient way. In this paper we propose a new optimization framework that in a systematic way addresses a general allocation model, the software and deployment architectures, and, based on the user preferences, provides a software deployment solution regardless of number of quality attributes used. Additionally, we present the input models to the allocation process capable of describing a number of software and hardware configurations, and a two-step allocation algorithm capable of harnessing these models.
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| 9613. |
- Krueger, Joel, et al.
(författare)
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Acculturation of hygiene norms among immigrants to Sweden
- 2023
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Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Hygiene norms in Sweden are generally loose compared to most other countries. Does this looseness affect the hygiene norms among people who immigrate to Sweden from other countries? In a study of hygiene norms among immigrants to Sweden, the change in the physical environment and material living conditions, acculturation to Swedish culture and norms, and selection effects were all expected to lead immigrant hygiene norms to be closer to Swedish looseness. However, in a sample of 447 immigrants from 12 different countries, immigrants reported hygiene norms that were even stricter than those found in their countries of origin. We propose an explanation based on a combination of uncertainty about prevailing hygiene norms and the social risk and stigma associated with being perceived as unhygienic. We conclude that acculturation processes may rely on mechanisms that are domain specific.
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| 9614. |
- Krustok, Ivo, et al.
(författare)
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Algae biomass cultivation in nitrogen rich biogas digestate.
- 2015
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 72:10, s. 1723-1729
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Tidskriftsartikel (refereegranskat)abstract
- Because microalgae are known for quick biomass growth and nutrient uptake, there has been much interest in their use in research on wastewater treatment methods. While many studies have concentrated on the algal treatment of wastewaters with low to medium ammonium concentrations, there are several liquid waste streams with high ammonium concentrations that microalgae could potentially treat. The aim of this paper was to test ammonium tolerance of the indigenous algae community of Lake Malaren and to use this mixed consortia of algae to remove nutrients from biogas digestate. Algae from Lake Malaren were cultivated in Jaworski's Medium containing a range of ammonium concentrations and the resulting algal growth was determined. The algae were able to grow at NH4-N concentrations of up to 200 mg L(-1) after which there was significant inhibition. To test the effectiveness of the lake water algae on the treatment of biogas digestate, different pre-cultivation set-ups and biogas digestate concentrations were tested. It was determined that mixing pre-cultivated suspension algae with 25% of biogas digestate by volume, resulting in an ammonium concentration of around 300 mg L(-1), produced the highest algal growth. The algae were effective in removing 72.8 ± 2.2% of NH4-N and 41.4 ± 41.4% of PO4-P.
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| 9615. |
- Krustok, Ivo, et al.
(författare)
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ALGAE BIOMASS CULTIVATION WITH AMMONIUM RICH WASTEWATERS AS SUBSTRATE : THE POTENTIAL FOR SIMULTANEOUS WASTEWATER TREATMENT AND ENERGY RECOVERY
- 2014
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Konferensbidrag (refereegranskat)abstract
- Ammonia rich wastewaters pose risk to recipient waters and the atmosphere, and can be difficult to treat in wastewater treatment plants (WTTP) due to toxicity to the microbes in conventional biological treatment systems. This article presents an idea on how to use a combination of bacteria and microalgae for efficient treatment of wastewaters with high ammonia concentrations (200-1400 mg/L). The challenge in this research is that most algae species are sensitive to high ammonia concentrations (>1 mM)(Abalde and Mezzamo, 2009). Despite the numerous wastewaters that contain high ammonia concentrations, i.e. landfill leachate, piggery manure, reject water and biogas digestate, the progress in finding sustainable treatment methods is taking time. This despite the fact that climate change, eutrophication and eco-toxicity is negatively affected by this commonly occurring component. Further, nitrogen is a valuable nutrient that in conventional WWTP is just released into the air without any recycling or recovery.In this article, we present a study where algae were cultivated as a mean for treatment of wastewater reject water and swine manure from a piggery farm. The algae inoculum was pretreated from lake water, sampled in mid Sweden during summer algae blooms. Lake Mälaren is a shallow lake with a rich algae consortia, optimized for the local climate. During seasonal algae blooms, the lake demonstrates the extremely rapid growth rate of the algae such as cyanobacteria, green algae and diatoms. Algae inoculum, wastewater substrate and dilution media (tap water) were mixed in various ranges of ammonium concentrations to evaluate the nutrient removal and algae biomass growth. During the algae cultivation experiment, chlorophyll, optical density and TS were used as indicators for algae biomass growth. Flow Injection System (FIA) was used for nutrient analysis.The two main findings in this research are that algae growth is inhibited by ammonia but that it is possible to grow algae in readily high ammonia concentrations. Moreover, significant amount of ammonium were removed by algae during the cultivation in the reactors.
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| 9616. |
- Krustok, Ivo, 1987-, et al.
(författare)
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Characterization of algal and microbial community dynamics in a wastewater photo-bioreactor using indigenous algae from lake mälaren
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Microalgae grown in photo-bioreactors can be a valuable source for biomass especially when combined with the treatment of wastewater. While most published research has been studying pure cultures, consortia of algae and bacteria from the wastewater have more complex dynamics affecting both the biomass production and pollutant removal. In this paper we investigate dynamics of algal and bacterial communities in mixed culture photo-bioreactors using chlorophyll and real-time PCR analysis. Wastewater photo-bioreactors were inoculated with water from a nearby lake to add native algae species. The results indicated a decline in bacterial 16S rDNA copy numbers before algae started to multiply. The photo-bioreactors inoculated with lake algae produced more biomass and grew faster than the algae originating only from wastewater. The reactors were effective in removing ammonia from the wastewater which seemed work to mostly through nitrification thus causing an increase in nitrate concentration. There was also an increase in Cr, Co and Ni ion concentrations during the experiment suggesting they may have moved from organic complexes to the water phase as free ions.
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| 9617. |
- Krustok, Ivo, 1987-, et al.
(författare)
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Characterization of algal and microbial community growth in a wastewater treating batch photo-bioreactor inoculated with lake water
- 2015
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Ingår i: Algal Research. - : Elsevier. - 2211-9264. ; 11:Sept, s. 421-427
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Tidskriftsartikel (refereegranskat)abstract
- Microalgae grown in photo-bioreactors can be a valuable source of biomass, especially when combined with wastewater treatment. While most published research has studied pure cultures, the consortia of algae and bacteria from wastewater have more complex community dynamics which affect both the biomass production and pollutant removal. In this paper we investigate the dynamics of algal and bacterial growth in wastewater treating batch photo-bioreactors. The photo-bioreactors were inoculated with water from a nearby lake. Lake water was obtained in August, November and December in order to add native algal species and study the effects of the season. The photo-bioreactors inoculated with lake water obtained in August and November produced more biomass and grew faster than those that only contained the algae from wastewater. The results indicated a rapid decline in bacterial abundance before algae began to multiply in reactors supplemented with lake water in November and December. The reactors were also successful in removing nitrogen and phosphorous from wastewater.
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| 9618. |
- Krustok, Ivo, 1987-
(författare)
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Communities of microalgae and bacteria in photobioreactors treating municipal wastewater
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Everyone who uses water produces wastewater. This inevitability creates several problems that increase with the growth of the population and industry. What to do with the wastewater, how to purify it and how to design the infrastructure are all important questions that each municipality has to deal with, taking into account ever growing demands to reduce environmental impact. In these conditions scientists and engineers have turned to biological processes to help treat the water. Currently the most commonly used wastewater treatment method known as the activated sludge process involves bacteria that help break down the pollutants. While it has been used successfully for around 100 years now, it has many limitations when faced with modern demands. As an alternative, microalgae reactors, commonly known as photobioreactors, have been suggested.Microalgae are microscopic water organisms that can use photosynthesis to form sugars from CO2 and water. To do this they require energy from light, hence the photo part of the photobioreactor. In addition to taking up CO2 from their environment, they take up nutrients such as nitrogen and phosphorous compounds. This is a reason why microalgae have great potential for use in wastewater treatment. When grown in wastewater together with the microorganisms already present, they are able to reduce the amount of pollutants by taking them up into their cells, effectively purifying the water.Since wastewater has its own microbial community, the biological processes taking place in a wastewater treating photobioreactor are more complex compared to growing a single species of algae in a sterile medium. With the work presented in this licentiate, we characterized the algae and bacterial communities present in photobioreactors treating wastewater in addition to finding the most optimal ways to grow algae originating from a local lake in a wastewater medium. We looked at the species found, most important metabolic pathways, growth dynamics for both algae and bacteria and water purification dynamics.Overall, we were successful in inoculating municipal wastewater from Västerås wastewater treatment plant with algae from Lake Mälaren. The dominant algae growing in our systems belonged to the genera Scenedesmus, Desmodesmus and Chlorella. We also saw that the bacterial community was involved in synthesis of vitamins essential for algae growth. The information presented in this thesis is another step towards a better design of control and monitoring systems in full-scale photobioreactor plants.
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| 9619. |
- Krustok, Ivo, 1987-, et al.
(författare)
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Comparative analysis of the metagenomes extracted from wastewater treating photobioreactors
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The metagenomes of lab-scale municipal wastewater treating batch photobioreactors were studied with a focus on nitrogen metabolism, pathogen abundance and antibiotic resistance genes. Previous studies based on the dataset showed that in general, as algae growth in the reactors increased, nitrogen metabolism and virulence genes decreased. With this study, a more detailed view of these gene groups is presented.
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| 9620. |
- Krustok, Ivo, et al.
(författare)
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CULTIVATION OF INDIGENOUS ALGAE FOR INCREASED BIOGAS PRODUCTION
- 2013
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Konferensbidrag (refereegranskat)abstract
- There is an increased demand for biogas in the society and one way to meet this is to use cultivated microalgae as fermentation substrate. In the present study, a co-digestion experiment was established where municipal food waste was fermented with harvested microalgae cultivated in lake water. The experiment was carried out as a laboratory batch experiment with fermentation bottles, where 0, 12, 25 and 37% of the food waste was replaced with harvested microalgae, respectively. The results showed that the biogas production was generally improved after addition of microalgae. During the first 25 days of fermentation, replacement of 12% food waste with microalgae gave the highest biogas production rate. However, higher proportions of microalgae (25% and 37%) slightly decreased the gas production rate compared to 12% and compared to using food waste alone.
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