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Soft stimulation treatment of geothermal well RV-43 to meet the growing heat demand of Reykjavik
(2021-11) Hofmann, Hannes; Zimmermann, Günter; Huenges, Ernst; Regenspurg, Simona; Aldaz, Santiago; Milkereit, Claus; Heimann, Sebastian; Dahm, Torsten; Zang, Arno; Grigoli, Francesco; Karvounis, Dimitrios; Broccardo, Marco; Wiemer, Stefan; Hjörleifsdóttir, Vala; Kristjánsson, Bjarni Reyr; Hersir, Gylfi Páll; Ásgeirsdóttir, Ragnheiður St; Magnússon, Rögnvaldur; Árnadóttir, Sigurveig; Department of Engineering
Reykjavik is almost entirely heated by geothermal energy. Yet, recent growth of the city significantly increased the heat demand. Past experiences in Iceland's capital region showed that hydraulic stimulation of existing geothermal wells is suited to improve hydraulic performance and energy supply. However, fluid injection may also trigger felt or even damaging earthquakes, which are of concern in populated areas and pose a significant risk to stimulation operations. Consequently, soft stimulation concepts have been developed to increase geothermal well performance while minimizing environmental effects such as induced seismicity. In a demonstration project of hydraulic soft stimulation in October 2019, more than 20.000 m³ of water were injected into well RV-43 in Reykjavik in multiple stages and with different injection schemes. The hydraulic performance of the well was improved without inducing felt seismicity. An a priori seismic risk assessment was conducted and for the first time the risk was continuously updated by an adaptive traffic light system supported by a sophisticated realtime microseismic monitoring. Our results confirm that it is possible to improve the performance of geothermal wells in Reykjavik and worldwide with acceptable technical, economic, and environmental risks. Here we provide an overview of the entire stimulation project including site description, stimulation design, zonal isolation, logging, seismic risk assessment and mitigation measures, realtime seismic, hydraulic and chemical monitoring, and stimulation results and challenges.
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Compact and high gain 4 × 4 circularly polarized microstrip patch antenna array for next generation small satellite
(2021-10-01) Elahi, Manzoor; Trinh-Van, Son; Yang, Youngoo; Lee, Kang Yoon; Hwang, Keum Cheol; Department of Engineering
In this article, a high gain and compact 4 × 4 circularly polarized microstrip patch antenna array is reported for the data transmission of the next-generation small satellite. The radiating element of the circularly polarized antenna array is realized by the conventional model of the patch with truncated corners. A compact two-stage sequential rotational phase feeding is adopted that broadens the operating bandwidth of the 4 × 4 array. A small stub is embedded in the sequential rotational feed, which results in better performance in terms of the S-parameters and sequential phases at the output ports than sequential rotational feed without open stub. A prototype of the array is fabricated and measured. Fulfilling the application requirements of the next-generation small satellites, the array has the left-handed circularly polarized gain of more than 12 dBic with the axial ratio level below 1.5 dB in the ±10◦ angular space with respect to the broadside direction for the whole bandwidth from 8.05 GHz to 8.25 GHz. Moreover, the left-handed circularly polarized gain varies from 15 to 15.5 dBic in the desired band. The radiation patterns are measured; both the co-and X-pol are validated.
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Introduction to the fourth annual lifelog search challenge, LSC'21
(Association for Computing Machinery, Inc, 2021-09-01) Gurrin, Cathal; Jónsson, Björn Þór; Schöffmann, Klaus; Dang-Nguyen, Duc Tien; Lokoč, Jakub; Tran, Minh Triet; Hürst, Wolfgang; Rossetto, Luca; Healy, Graham; Department of Computer Science
The Lifelog Search Challenge (LSC) is an annual benchmarking challenge for comparing approaches to interactive retrieval from multi-modal lifelogs. LSC'21, the fourth challenge, attracted sixteen participants, each of which had developed interactive retrieval systems for large multimodal lifelogs. These interactive retrieval systems participated in a comparative evaluation in front of an online live-audience at the LSC workshop at ACM ICMR'21. This overview presents the motivation for LSC'21, the lifelog dataset used in the competition, and the participating systems.
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What is a Visual Novel?
(2021-09) Camingue, Janelynn; Carstensdottir, Elin; Melcer, Edward F.; Department of Computer Science
Visual Novel (VN) is a widely recognizable genre of narrative-focused games that has grown in popularity over the past decade. Surprisingly, despite being so widely recognizable, there is not a singular definition to help guide the design and analysis of such games - -with academic definitions and implementations ranging from "interactive textbooks"to "adventure games with multi-ending stories". In this paper, we present a unified definition of VNs drawn from an analysis of 30 prior academic definitions. We also examined 54 existing VNs to further refine our definition and employ a deeper analysis of the interactivity within VNs. We highlight key features of VNs that arise in our definition, and discuss resulting implications for the design of VNs. This work is relevant for narrative game designers and researchers, affording a more unified structure and clearer guidelines to identify, analyze, and design future VN games.
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The design of RIP belts impacts the reliability and quality of the measured respiratory signals
(2021-09) Montazeri, Kristofer; Jonsson, Sigurdur Aegir; Agustsson, Jon Skirnir; Serwatko, Marta; Gislason, Thorarinn; Arnardottir, Erna S.; Department of Engineering; Department of Computer Science
Purpose: Evaluate the effect of respiratory inductance plethysmography (RIP) belt design on the reliability and quality of respiratory signals. A comparison of cannula flow to disposable cut-to-fit, semi-disposable folding and disposable RIP belts was performed in clinical home sleep apnea testing (HSAT) studies. Methods: This was a retrospective study using clinical HSAT studies. The signal reliability of cannula, thorax, and abdomen RIP belts was determined by automatically identifying periods during which the signals did not represent respiratory airflow and breathing movements. Results were verified by manual scoring. RIP flow quality was determined by examining the correlation between the RIP flow and cannula flow when both signals were considered reliable. Results: Of 767 clinical HSAT studies, mean signal reliability of the cut-to-fit, semi-disposable, and disposable thorax RIP belts was 83.0 ± 26.2%, 76.1 ± 24.4%, and 98.5 ± 9.3%, respectively. The signal reliability of the cannula was 92.5 ± 16.1%, 87.0 ± 23.3%, and 85.5 ± 24.5%, respectively. The automatic assessment of signal reliability for the RIP belts and cannula flow had a sensitivity of 50% and a specificity of 99% compared with manual assessment. The mean correlation of cannula flow to RIP flow from the cut-to-fit, semi-disposable, and disposable RIP belts was 0.79 ± 0.24, 0.52 ± 0.20, and 0.86 ± 0.18, respectively. Conclusion: The design of RIP belts affects the reliability and quality of respiratory signals. The disposable RIP belts that had integrated contacts and did not fold on top of themselves performed the best. The cut-to-fit RIP belts were most likely to be unreliable, and the semi-disposable folding belts produced the lowest-quality RIP flow signals compared to the cannula flow signal.

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