148 research outputs found
A Study on Dislocation Mechanisms of Toughening in Cu-Graphene Nanolayered Composite
No full textWe investigated the role of graphene interfaces in strengthening and toughening of the Cu-graphene nanocomposite by a combination of in situ transmission electron microscopy (TEM) deformation and molecular dynamics (MD) simulations. In situ TEM directly showed that dislocation plasticity is strongly confined within single Cu grains by the graphene interfaces and grain boundaries. The weak Cu-graphene interfacial bonding induces stress decoupling, which results in independent plastic deformation of each Cu layer. As confirmed by the MD simulation, the localized deformation made by such constrained dislocation plasticity results in the nucleation and growth of voids at the graphene interface, which acts as a precursor for crack. The graphene interfaces also effectively block crack propagation promoted by easy delamination of Cu layers dissipating the elastic strain energy. The toughening mechanisms revealed by the present study will provide valuable insights into the optimization of the mechanical properties of metal–graphene nanolayered composites.
A 915 MHz, 499 μW, –99 dBm, and 100 kbps BFSK Direct Conversion Receiver
No full textThis paper presents an ultra-low power (ULP) high sensitivity binary frequency-shift keying (BFSK) direct conversion receiver (RX) for the internet of things (IoT). By employing a combination of a 2-stage ring voltage-controlled oscillator (VCO) and a 50 %-to-25 % duty conversion passive mixer, the power consumption is dramatically reduced. The prototype of the proposed RX which is implemented in a 55 nm CMOS technology shows −99 dBm sensitivity for 915 MHz 100 kbps BFSK signal while dissipating 499 µW from 0.9 V supply
Role of graphene in reducing fatigue damage in Cu/Gr nanolayered composite
No full textNanoscale metal/graphene nanolayered composite is known to have ultrahigh strength as the graphene effectively blocks dislocations from penetrating through the metal/graphene interface. The same graphene interface, which has a strong sp2 bonding, can simultaneously serve as an effective interface for deflecting the fatigue cracks that are generated under cyclic bendings. In this study, Cu/Gr composite with repeat layer spacing of 100 nm was tested for bending fatigue at 1.6% and 3.1% strain up to 1,000,000 cycles that showed for the first time a 5-6 times enhancement in fatigue resistance compared to the conventional Cu thin film. Fatigue cracks that are generated within the Cu layer were stopped by the graphene interface, which are evidenced by cross-sectional scanning electron microscopy and transmission electron microscopy images. Molecular dynamics simulations for uniaxial tension of Cu/Gr showed limited accumulation of dislocations at the film/substrate interface, which makes the fatigue crack formation and propagation through thickness of the film difficult in this materials system. © 2017 American Chemical Society3
The origin of jerky dislocation motion in high-entropy alloys
No full textDislocations in single-phase concentrated random alloys, including high-entropy alloys (HEAs), repeatedly encounter pinning during glide, resulting in jerky dislocation motion. While solute-dislocation interaction is well understood in conventional alloys, the origin of individual pinning points in concentrated random alloys is a matter of debate. In this work, we investigate the origin of dislocation pinning in the CoCrFeMnNi HEA. In-situ transmission electron microscopy studies reveal wavy dislocation lines and a jagged glide motion under external loading, even though no segregation or clustering is found around Shockley partial dislocations. Atomistic simulations reproduce the jerky dislocation motion and link the repeated pinning to local fluctuations in the Peierls friction. We demonstrate that the density of high local Peierls friction is proportional to the critical stress required for dislocation glide and the dislocation mobility
Human-Interactive, Active-Matrix Displays for Visualization of Tactile Pressures
No full textHuman-interactive displays involve the interfacing of a stimuli-responsive sensor with a human-readable response. Human-readable responses include the five recognized senses, i.e., sight (vision), hearing (audition), taste (gustation), smell (olfaction), and touch (somatosensation). Vision is considered to be the most informative human stimulus so that the visualization of electrical, thermal, and mechanical data is important for various applications. Herein, the fabrication of human-interactive displays is demonstrated in which active-matrix arrays of pressure-sensitive Si transistors with air dielectric layers are fully integrated with pixels of organic light-emitting diodes (OLEDs). In this way, the luminance of the individual OLED pixels can be increased locally by pressing the display, and the luminance is dependent on the magnitude of the applied pressure. Furthermore, the air dielectric layer of transistors provides outstanding electrical properties, including high transconductance and negligible hysteresis. 3D integration of these transistors with dual-side emissive OLED pixels is also demonstrated. Local pressing increases the light intensity of OLED pixel and then the underlaid Si channel can absorb this light successively to generate additional photocurrents from the pressure-sensitive transistor, further enhancing its sensitivity. This human-interactive display can visualize tactile pressure directly, suggesting the substantial promise as next generation displays for intelligent human-machine interfacing
CO electro-oxidation reaction on Pt nanoparticles: Understanding peak multiplicity through thiol derivative molecule adsorption
No full textThe electro-oxidation of CO adsorbed on Pt nanoparticles is an important reaction in fuel cells. Despite extensive research, the underlying concept for peak multiplicity is not yet clearly understood. We investigated CO electro-oxidation features by scan-rate-dependent Tafel analysis and a model system experiment based on adsorption of 3-mercaptopropionic acid (3-MPA). The results suggest that the first main oxidation peak corresponds to the competition between OH adsorption and the interaction between adsorbed CO and OH. Modifying the Pt surface with 3-MPA can reduce the OH coverage, which in turn reduces the width of the first peak. However, the peak potential is not significantly dependent on OH coverage. Considering that the free surface is large enough for OH adsorption on Pt at high potential, the second peak shows few features that depend on OH coverage; the second peak is mainly influenced by the Pt-CO interaction. (C) 2016 Elsevier B.V. All rights reserved1111sciescopu
Data for 'Microbial carbon use efficiency along an altitudinal gradient'
No full textThis dataset is related to the manuscript “Microbial carbon use efficiency along an altitudinal gradient“ by Kevin Mganga, Outi-Maaria Sietiö, Nele Meyer, Christopher Poeplau, Sylwia Adamczyk, Christina Biasi, Subin Kalu, Matti Räsänen, Per Ambus, Hannu Fritze, Petri Pellikka, and Kristiina Karhu. Corresponding author: Outi-Maaria Sietiö ([email protected]
Injectable tissue prosthesis for instantaneous closed-loop rehabilitation
No full textTo construct tissue-like prosthetic materials, soft electroactive hydrogels are the best candidate owing to their physiological mechanical modulus, low electrical resistance and bidirectional stimulating and recording capability of electrophysiological signals from biological tissues1,2. Nevertheless, until now, bioelectronic devices for such prostheses have been patch type, which cannot be applied onto rough, narrow or deep tissue surfaces3–5. Here we present an injectable tissue prosthesis with instantaneous bidirectional electrical conduction in the neuromuscular system. The soft and injectable prosthesis is composed of a biocompatible hydrogel with unique phenylborate-mediated multiple crosslinking, such as irreversible yet freely rearrangeable biphenyl bonds and reversible coordinate bonds with conductive gold nanoparticles formed in situ by cross-coupling. Closed-loop robot-assisted rehabilitation by injecting this prosthetic material is successfully demonstrated in the early stage of severe muscle injury in rats, and accelerated tissue repair is achieved in the later stage. © 2023, The Author(s), under exclusive licence to Springer Nature Limited.11Nsciescopu
The effect of dynamic written corrective feedback for learners of Korean
No full textThis study investigates the effectiveness of dynamic written corrective feedback (DWCF) for intermediate learners of Korean as a foreign language (KFL) compared to traditional types of written corrective feedback. DWCF is an innovative method of providing written corrective feedback on students\u27 writing that has primarily been used in English as a second language (ESL) settings. It aims to improve learners\u27 linguistic accuracy and requires multilayered interaction between teachers and students. Although DWCF has been effectively used to increase linguistic accuracy in various ESL settings, it has not yet been widely applied to other language learning settings. This study demonstrates the extent to which DWCF increases the linguistic accuracy of intermediate KFL learners and determines DWCF\u27s impact on fluency and complexity. The treatment group (n = 9) was managed with DWCF and the control group (n = 10) wrote six essays over a 12-week period. The pre- and post-test results were analyzed to determine differences in linguistic accuracy, fluency, and complexity between the two groups. A mixed-model repeated measures ANOVA revealed that the treatment group\u27s accuracy significantly increased compared to the control group, whereas there was no significant difference in fluency or complexity for either group. Limitations and suggestions for future research are discussed in the conclusion
A Study of Artwork on Emotion Concealed by Childlike Behavior
No full text학위논문 (석사) -- 서울대학교 대학원 : 미술대학 조소과, 2020. 8. 이종건.본연구는본인이내면에서경험한이상과현실사이의대립된간극을좁히기위한행위로부터시작하였다. 본인은성장하면서독립적으로세상을헤쳐나가는동시에심리적인안정감을찾기위해, 경험하고싶지않은대상들을본인이선호하는이미지로둔갑시키고자하였다. 이이미지는본인의개인적인만족감을충족시키고이상적인세계에가까워질수있는매개체역할을한다. 또한, 작업을통해본인이지속해서꿈꿔온환상의세계를구축하고, 이것을다른사람들과일상속에서공유하고자했다.
이상과현실은서로대립하면서양가적인심상적특성을만들어낸다. 이러한관계는현대사회가성인에게부여하는자유라는의미속에숨어있는관습적인통념과규율그리고제도사이에서생겨난다. 본인은대립하는두관계사이에선채균형을유지함으로써괴리감을극복하고자했다. 이상은현실을좀더긍정적인방향으로이끌어주고, 현실은즐거움속에서도현재의삶에충실해조화롭게어울려살아가게끔중심을잡아준다. 이러한관점으로바라보았을때, 본인이하는일들은내면의나를표출함으로써어른으로성장한나가동심의환상세계에한발자국더가깝게만들어주는역할을한다. 그결과, 본인은작업을통해두관계사이에서균형을유지한다.
작업을진행할때에는본인의감정과작업사이의상호작용, 그리고경험의과정 이전반적으로중요하게작용했다. 경험의과정은작업의재료와구성과색감에온전히배어있다. 본인은이과정안에서나타나는심리적상호작용을표출하고공유하고자하였다. 이어서이일들을통해나는무엇을좋아하고, 왜좋아하는지그리고무엇을꿈꾸며살아가는지에대한궁금증을해소하고자했다. 그러므로본인은외부의사건이나이야기보다는본인의삶과내면의심리에집중해서작업을이끌어갔다.
본논문에서는동심속환상의세계를꿈꾸는내면의나와어른으로성장해현실의삶을살아가고있는나 사이의균형유지를위해본인이작업에서의도한네가지요소인핑크, 틈, 놀이, 포장에대하여소개하였다. 핑크는작품의표면색상으로주로사용하였으며, 시각적인효과뿐만아니라심리적인경험에영향을미친다. 이는본인이어린시절타의로접하게되어지금은스스로선호하는색으로, 어린시절기억을통해감각적으로선명히떠오르는내면의동심과연결된다. 두번째로틈은본인이이상과현실의세계에서느끼는괴리감을중재시켜주는물리적인공간이다. 이는어른이된본인의머릿속에서이상과현실의사이를자유롭게오갈수있는통로의역할을한다. 다음으로, 본인의내면적갈등을해소하고균형을유지하기위한방식으로사용한놀이의행위에관하여서술하였다. 그리고마지막포장에서는, 작업을지속하면서느끼는양가적인모순된감상에관해설명했다. 이는순수한동심으로부터느끼는긍정적인감정과주입식교육의결과물인포장된감정에대한부정적인감정을이야기한다.
본인은작업을통해내면의아이와순수함을끄집어내어어른이된자아가경험하는내면적대립과간극을좁히고모호하게만들었다. 이에두관계는대화하고상호반응하며, 그결과서로가긍정적인방향으로발전해간다. 본인의작업은관습적인틀에갇힌어른의동심을넘어, 아이같은무한한상상의세계와순수성으로가까워지게만드는역할을한다. 반면에, 마음속깊은곳에서는온전하지못한감정이라고느끼면서무조건적으로믿었던긍정적인감정에의문을던지는새로운계기가된다. 이의문은작업을통해, 본인개인의내면적갈등에서비롯된미묘한불편함에서, 모범화된어른혹은성숙한여성이라는보편적가치에가두려는사회적시스템에대한반문으로확장되었다. 본인은본연구를통해관습적인사회적인식에지속적으로반문을던지며, 독립된개체로서자아의정체성을탐구하고확립하고자한다.
주요어:양가적심상, 놀이, 환상세계, 현실세계, 간극, 균형This study begins with the authors action to reduce the gap between the internally experienced ideal and the reality. During the growth period, in order to cope with the world independently and to seek psychological stability, the author used to transform the objects that are not experienced favorably into the preferred images. The images satisfied the author personally and served as a mediator to reach an ideal world. Through the present artwork, the author tried to establish the world that has continuously been fantasized and to share it with others in daily life.
While opposing each other, the ideal and the reality create ambivalent images. Such a relation occurs in the customarily accepted ideas, rules and systems, as they are hidden in the meaning of freedom, which is given to the adults by the modern society. The author tried to overcome the gap by keeping a balance between the ideal and the reality. The ideal guides the reality in a more positive direction, whereas the reality keeps a balance to be faithful to and harmonized with the current life while enjoying the life. From this kind of viewpoint, the authors artwork enables the author to express what is inside in order for the author, as a grown-up, to come one step closer to the fantasized world of childish innocence. Hence, the artwork enables the author to maintain a balance between the ideal and the reality.
The interaction between the authors emotion and the artwork as well as the process of experiences was crucial to the artwork. The process of experiences is fully reflected to the materials, composition and colors of the artwork. The author desired to express and share the psychological interaction that occurs in the process. The author also wanted to find the answers to the questions, What do I like?, Why do I like that?, and What am I dreaming of? Therefore, when preparing the artwork, the author was focusing on the authors own life and the internal psychological state, rather than external events or stories.
The present thesis introduces the four elements of the authors artwork that were employed to keep a balance between the internal ego that is dreaming of the fantasized world of childish innocence and the person that is living in the real world as a grown-up: pink, crack, play, and packaging. Pink, used as the main color of the artwork, not only gives a visual effect but also affects the psychological experiences. Encountered in the childhood by others will but favored now by the authors own will, the color is connected with the internal world of childish innocence that is clearly recalled to the mind through the memories of the childhood. Crack is a physical space that mediates the gap between the authors ideal and the real world. The gap serves as a channel that allows the author to freely travel in the mind between the ideal and the reality after becoming an adult. The act of play is the authors means to resolve the internal conflicts and maintain a balance. Finally, packaging describes the ambivalent and contradictory feelings during the work of art. The packaging represents both the positive feelings toward the world of childish innocence and the negative feelings about the emotions packaged or decorated by the learning by rote.
Through the artwork, the author has drawn the childish innocence that is deep in the heart and mind in order to reduce and blur the internal conflicts experienced by the author after being grown-up. The childish innocence and the real world of grown-ups converse and interact with each other to develop in a positive direction. The authors artwork enables the viewers to not only recall the world of childish innocence confined in the customary framework of the grown-ups but also come closer to the unrestricted world of imagination and innocence. In addition, the authors artwork provides an opportunity to raise a question, deeply in the heart, about the feelings that have been unconditionally believed to be positive, as the feelings are recognized as incomplete ones. This question has been extended through the present artwork, from a subtly uncomfortable feeling originating with the authors internal conflicts to a counter-question regarding the social system that has attempted to confine the author in the universal value of exemplary adult or mature woman. In the present study, the author has continuously raised questions about the traditional social recognition, and explored and established the authors identity as an independent individual.
Key words : ambivalent image, play, fantasized world, real world, gap, balanceⅠ. 들어가며 1
II. 본론 4
1. 핑크8
2. 틈 16
3. 놀이 24
4. 포장 31
III. 작품 소개 38
Ⅳ. 마치며 69
작품 목록 72
참고 도판 목록 74
참고 문헌 75
Abstract 7Maste
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