Development of modified graphite felt electrodes for the vanadium redox flow battery

Redox flow batteries (RFBs) are one of the most promising candidates for stationary large-scale energy storage systems with regard to cost, cycle life, design flexibility, and safety. Among various RFBs, vanadium redox flow batteries (VRFBs) have the advantage of overcoming the cross-contamination of both electrolytes because VRFBs use the same V ion as the active species in both the anolyte and the catholyte. In spite of the various advantages of VRFBs, the performance of VRFBs needs to be further improved for the commercialization. The performance of VRFBs is significantly affected by the electrochemical activity of the electrode because the vanadium ion redox reactions take place at the graphite felt electrode surface during the charge-discharge process. To improve the electrochemical activity of graphite felt electrodes, facile methods for preparing nitrogen-doped carbon coated graphite felt electrodes using nitrogen-containing materials were developed. First, 1-ethyl-3-methylimidazolium dicyanamide (EMIM dca), an ionic liquid containing a high content of nitrogen, was used as an effective precursor for nitrogen doping on graphite felt surfaces. The effect of EMIM dca derived nitrogen doped graphite felt on the performance of VRFBs was investigated by various physical and electrochemical analyses. When employed in charge-discharge tests, the single cells with the nitrogen doped graphite felts showed outstanding performance. The improved performance is attributed to the high nitrogen content on the graphite felt, which increased the electrocatalytic activity of vanadium redox reactions. Second, polyacrylonitrile (PAN), which contains 26 wt% of nitrogen atoms, was employed to fabricate nitrogen-doped carbon materials on graphite felt surfaces. PAN was coated on graphite felt to improve the performance of VRFB single cell electrodes by utilizing the mechanism of the process of manufacturing carbon fiber from PAN. After optimizing the amount of PAN coated, a single cell with PAN derived nitrogen-doped graphite felt showed higher performance than a single cell with electrodes prepared by conventional treatment methods. In addition to improving the performance of the electrode by chemical methods, we examined the effect of local porosity of the electrodes on the electrolyte flow field in VRFBs at high current densities. The optimization of local porosity of the graphite felt electrode was carried out to improve the performance of VRFBs at high current density region.Redox-Fluss-Batterien (RFBs) gehören zu den vielversprechendsten Kandidaten für stationäre Energiespeichersysteme im großen Maßstab in Hinblick auf Kosten, Lebensdauer, Designflexibilität und Sicherheit. Vanadium-Redox-Fluss-Batterien (VRFBs) haben gegenüber anderen RFBs den Vorteil, dass sie keine Kreuzkontamination der Elektrolyte aufweisen, da VRFBs das gleiche V-Ion als aktive Spezies sowohl im Anolyten als auch im Katholyten verwenden. Trotz der verschiedenen Vorteile von VRFBs muss die Leistung von VRFBs für die Kommerzialisierung weiter verbessert werden. Die Leistung von VRFBs wird erheblich von der elektrochemischen Aktivität der Elektrode beeinflusst, da die Vanadiumionen-Redoxreaktionen an der Oberfläche der Graphitfilzelektrode während des Lade-Entlade-Prozesses stattfinden. Um die elektrochemische Aktivität von Graphitfilzelektroden zu verbessern, wurden einfache Verfahren zur Herstellung stickstoffdotierter kohlenstoffbeschichteter Graphitfilzelektroden unter Verwendung stickstoffhaltiger Materialien entwickelt. Zunächst wurde 1-Ethyl-3-methylimidazolium dicyanamid (EMIM dca), eine ionische Flüssigkeit mit hohem Stickstoffgehalt, als wirksame Vorstufe für die Stickstoffdotierung auf Graphitfilzoberflächen verwendet. Die Auswirkung von mit Stickstoff dotiertem Graphit, der von EMIM dca abgeleitet ist, auf die Leistung von VRFBs wurde durch verschiedene physikalische und elektrochemische Analysen untersucht. Bei Verwendung in Lade-Entlade-Tests zeigten die Einzelzellen mit den stickstoffdotierten Graphitfilzen eine hervorragende Leistung. Die verbesserte Leistung wird auf den hohen Stickstoffgehalt des Graphitfilzes zurückgeführt, der die elektrokatalytische Aktivität von Vanadium-Redox-Reaktionen erhöhte. Zweitens wurde Polyacrylnitril (PAN), das 26 Gew.-% Stickstoffatome enthält, verwendet, um mit Stickstoff dotierte Kohlenstoffmaterialien auf Graphitfilzoberflächen herzustellen. PAN wurde auf Graphitfilz aufgetragen, um die Leistung von VRFB-Einzelzellenelektroden zu verbessern, indem der Mechanismus des Prozesses zur Herstellung von Kohlenstofffasern aus PAN genutzt wurde. Nach Optimierung der Menge an beschichtetem PAN zeigte eine Einzelzelle mit PAN-abgeleitetem stickstoffdotiertem Graphitfilz eine höhere Leistung als eine Einzelzelle mit über herkömmliche Behandlungsmethoden hergestellten Elektroden. Zusätzlich zur Verbesserung der Leistung der Elektrode durch chemische Methoden untersuchten wir den Effekt der lokalen Porosität der Elektroden auf das Elektrolytflussfeld in VRFBs bei hohen Stromdichten. Die Optimierung der lokalen Porosität der Graphitfilzelektrode wurde durchgeführt, um die Leistung von VRFBs im Bereich hoher Stromdichte zu verbessern

History and conservation of gardens in Korea

An assessment of the conservation of historic gardens in Korea reveals that this is still in a rather rudimentary state; there appears to be a general lack of understanding about historic gardens, about what is important within them and how their value may best be preserved. The official understanding of historic gardens is as tangible artefacts, yet art historical aspects of gardens are rarely a consideration even though there is a basic understanding of significance of these issues. More importantly there appears to be a lack understanding of the importance of the social and cultural context of gardens. This thesis offers seeks to explore this context in order to review modem attitudes to historic gardens and their value, in terms of international and local, cultural and political ethics. The legal framework for garden conservation is subjected to critical review, with suggestions being made as to the way ahead. Korea has a rich garden heritage, yet modem historical writing fails to explain the economic, social, cultural and political contexts of gardens, or how they were created, improved and maintained. As a result only a few gardens have been officially recognized as heritage; there are only fourteen gardens amongst a total of some 9806 sites designated as tangible cultural heritage. Moreover, in these fourteen cases protection is reliant primarily on the fact that they form the curtilage of a protected building, rather than because of their own value. Thus those historic gardens that have been well preserved owe their state of conservation to the fact that they are included in cultural heritage sites which have been designated on the basis of other elements' perceived value. Another consequence of the value of gardens not being recognized is that their full potential as tourist destinations has not been realized. Without concerted efforts to promote gardens it is unlikely that they will be properly protected. With the majority of people in Korea living high above the ground in apartment buildings, it requires considerable thought as to how they might become interested in historic garden culture. Yet with issues of global warming and sustainability causing increasing concern, energy consuming apartment living is perhaps an outmoded way of life that should be reconsidered. The historic courtyard typology, adapted to local climate conditions, should once again be considered as aú model for development. This would also enable a more sustained revival of local garden culture. This research identifies five ways of developing the conservation of historic gardens in Korea: first, historic gardens must be identified; conservation ethics must be reconsidered so that they take better account of garden heritage, particularly taking account of the proposed Global Landscape Charter; education and academic research is an essential basis for the understanding of historic gardens' conservation, and must be promoted; and the contribution a revival of garden culture can make to a sustainable future should be recognized. It will be a consequence of the shift in perspective that a greater understanding of the contribution gardens have made, that the high-rise building typology which has dominated Korea's development in the past halfcentury can be reassessed. Instead of seeing it as a reactive solution, we can gain much from incorporating conservation and its values as part of process which is integral to a sustainable future

Three Songs by John Duke, Poems by Edwin Arlington Robinson Luke Havergal, Miniver Cheevy, Richard Cory

John Duke is a composer who strongly believed that in a good song words became assimilated by the music. Although John Duke was an active pianist, having much knowledge of keyboard music, he devoted himself to writing art songs. The reason why his compositions include so few piano works and many songs is that he had a core belief, i.e., vocal utterance is the basis of the music's mystery. I, as a singer, discovered that Duke's choices for the texts of songs are tasteful. The range in mood of the poems that he used for his songs runs from sprightly wit to biting irony, sometimes to unabashed romanticism or even to a meditation. Most of his songs create a mood based on meanings of the texts, and Duke used the music to support the stories of the texts. The poems that I would like to present in my performance research document areby Edwin Arlington Robinson: "Luke Havergal," "Miniver Cheevy" and "Richard Cory ". These quite serious poems depict ironies as well as human emotions in a brokensociety. John Duke did not follow the traditions in composition of American art songs inthe twentieth century, but created his own musical language, a great mixture of sounds oftraditional European classical music and sophisticated modem American poems.I would like to discuss the general styles of Robinson's poetry, emphasizing poeticmeanings of three songs and the musical characteristics of each setting by John Duke.</p

Kaggok (Korean Art Songs) Its Origin and Development

Today, I would like to discuss the various stages of Kaggok, which are Korean art songs written in western classical music style. Since Korea did not open its culture to the Western world until 1882, music in Korea was based on their own traditions. In other words, scales, rhythms, and harmony in Korean music were set up independently within its own tradition, the result of which meant that traditional Korean music sounds completely different and cannot be played properly using western instruments. The only exceptions to this were the influences from the various missionaries who brought western music to Korea, as well as the occupation of Japan in Korea (beginning in 1910). The western culture Japan had already encountered was unavoidably brought with them into Korea. As a result, western styles of singing began to replace traditional technique. Indeed even composition was influenced by western music conventions. People began to mix Korean text with melodies from westernized music. These are the origins of Kaggok.</p

Franz Schubert's "WINTERREISE" As a teaching tool for the college-level singer

Musicians agree that Winterreise is a masterwork. And it also offers us important artisticvalues as well as a sensitive humanism. For a singer , learning and performing a song cyclerequires rigorous voice training and musicianship. Although singers reach at certain level ofsinging ability, they might hesitate to perform the song cycle because they are concerned aboutadvanced voice techniques or complexity of understanding the text. The compositional styles ofwriting songs provide helpful guidance for singing well , and considering the texts as well asdetailed descriptions of musical demands support singing intelligently. Through the performanceand research I have done , as a voice instructor, I believe that college level voice students canlearn and perform the song cycle. This paper will address proper approaches in voice techniquesand interpretative music skills to learn the song cycle for male voice students of college level.</p

Experimental Investigation for Tensile Performance of GFRP-Steel Hybridized Rebar

Tensile performance of the recently developed “FRP Hybrid Bar” at Korea Institute of Civil Engineering and Building Technology (KICT) is experimentally evaluated by the authors. FRP Hybrid Bar is introduced to overcome the low elastic modulus of the existing GFRP bars to be used as a structural member in reinforced concrete structures. The concept of material hybridization is applied to increase elastic modulus of GFRP bars by using steel. This hybridized GFRP bar can be used in concrete structures as a flexural reinforcement with a sufficient level of elastic modulus. In order to verify the effect of material hybridization on tensile properties, tensile tests are conducted. The test results for both FRP Hybrid Bar and the existing GFRP bars are compared. The results indicate that the elastic modulus of FRP Hybrid Bar can be enhanced by up to approximately 250 percent by the material hybridization with a sufficient tensile strength. To ensure the long-term durability of FRP Hybrid Bar to corrosion resistance, the individual and combined effects of environmental conditions on FRP Hybrid Bar itself as well as on the interface between rebar and concrete are currently under investigation

Ball Trajectory Inference from Multi-Agent Sports Contexts Using Set Transformer and Hierarchical Bi-LSTM

As artificial intelligence spreads out to numerous fields, the application of AI to sports analytics is also in the spotlight. However, one of the major challenges is the difficulty of automated acquisition of continuous movement data during sports matches. In particular, it is a conundrum to reliably track a tiny ball on a wide soccer pitch with obstacles such as occlusion and imitations. Tackling the problem, this paper proposes an inference framework of ball trajectory from player trajectories as a cost-efficient alternative to ball tracking. We combine Set Transformers to get permutation-invariant and equivariant representations of the multi-agent contexts with a hierarchical architecture that intermediately predicts the player ball possession to support the final trajectory inference. Also, we introduce the reality loss term and postprocessing to secure the estimated trajectories to be physically realistic. The experimental results show that our model provides natural and accurate trajectories as well as admissible player ball possession at the same time. Lastly, we suggest several practical applications of our framework including missing trajectory imputation, semi-automated pass annotation, automated zoom-in for match broadcasting, and calculating possession-wise running performance metrics

A NUMERICAL STUDY ON THE OPEN WATER PERFORMANCE OF A PROPELLER WITH SINUSOIDAL PITCH MOTION

When a ship operates in waves, the ship moves with 6 degrees-of-freedom, and a propeller at the stern of the ship cannot avoid moving due to the ship motion. Therefore, it is important to analyse the propulsion performance while considering the ship motion in waves for efficient ship operation. The pitch motion of the ship has a dominant effect on the variation of the propeller performance and results in sinusoidal pitch motion of the propeller. In this study, a numerical analysis was done using a KP458 model propeller with a diameter of 10 cm, which was designed for the KLVCC2 body plan. The propeller performance was calculated using computational fluid dynamics (CFD) at several constant tilt angles. Numerical simulations were then conducted with sinusoidal pitch motion in several conditions of varying pitch angle. The variations of the thrust and torque of the propeller in sinusoidal pitch motion were compared with the results obtained in constant tilt angles

Differential Genomic Imprinting and Expression of Imprinted microRNAs in Testes-Derived Male Germ-Line Stem Cells in Mouse

BACKGROUND: Testis-derived male germ-line stem (GS) cells, the in vitro counterpart of spermatogonial stem cells (SSC), can acquire multipotency under appropriate culture conditions to become multipotent adult germ-line stem (maGS) cells, which upon testicular transplantation, produce teratoma instead of initiating spermatogenesis. Consequently, a molecular marker that can distinguish GS cells from maGS cells would be of potential value in both clinical and experimental research settings. METHODS AND FINDINGS: Using mouse as a model system, here we show that, similar to sperm, expression of imprinted and paternally expressed miRNAs (miR-296-3p, miR-296-5p, miR-483) were consistently higher (P<0.001), while those of imprinted and maternally expressed miRNA (miR-127, miR-127-5p) were consistently lower (P<0.001) in GS cells than in control embryonic stem (ES) cells. DNA methylation analyses of imprinting control regions (ICR), that control the expression of all imprinted miRNAs in respective gene clusters (Gnas-Nespas DMR, Igf2-H19 ICR and Dlk1-Dio3 IG-DMR), confirmed that imprinted miRNAs were androgenetic in GS cells. On the other hand, DNA methylation of imprinted miRNA genes in maGS cells resembled those of ES cells but the expression pattern of the imprinted miRNAs was intermediate between those of GS and ES cells. The expression of imprinted miRNAs in GS and maGS cells were also altered during their in vitro differentiation and varied both with the differentiation stage and the miRNA. CONCLUSIONS: Our data suggest that GS cells have androgenetic DNA methylation and expression of imprinted miRNAs which changes to ES cell-like pattern upon their conversion to maGS cells. Differential genomic imprinting of imprinted miRNAs may thus, serve as epigenetic miRNA signature or molecular marker to distinguish GS cells from maGS cells