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LABORATORY INVESTIGATION OF DIFFERENT EJECTOR GEOMETRIES FOR R-744 TRANSCRITICAL SYSTEMS
ARMIN HAFNER 대한설비공학회 2011 International Journal Of Air-Conditioning and Refr Vol.19 No.3
This work describes measurement results of ejectors manufactured and experimentally investigated at SINTEF Energy Research/NTNU. The ejectors are experimentally investigated in an oil free R-744 test facility in order to focus on the ejector properties and behavior. Five different ejectors were experimentally investigated at equal boundary conditions. The results are promising with pressure lifts close to 9 bars at low mass entrainment ratios of 0.22 and suction pressure ratios of 1.24. At an higher mass entrainment ratio of 0.56 and suction pressure ratio of 1.14 a pressure lift of 6.5 bar was achieved with the smallest mixing section. Best performances were measured with the smallest mixing section diameter (3 mm) and a short nozzle with an ID of 0.9 mm. The results are very promising and show a very good Coefficient of Performance improvement potential for R-744 transcritical process deploying an ejector, as the pressure ratio for a compressor could be reduced by close to 10 bars.
Digital Multimodal Composing: How to Address Multimodal Communication Forms in ELT
Christoph A. Hafner 한국영어교육학회 2020 ENGLISH TEACHING(영어교육) Vol.75 No.3
Digital media play an undeniably influential role in contemporary communication, facilitating new kinds of multimodal forms of representation. However, ELT pedagogy does not always take these multimodal aspects of communication into account in a systematic way. One pedagogical approach that has been developed for this purpose is ‘multimodal composing’ or ‘digital multimodal composing’. This approach caters to the needs of English language learners in the digital age by engaging with multimodal forms of communication in digital media which are ‘embedded’ alongside the reading and writing tasks that make up the core of traditional approaches to ELT. In this article, I provide an overview of scholarly work that has been done in developing this approach. Drawing on a case study of English language learners in Hong Kong, I demonstrate what the approach looks like in practice and suggest how it might be implemented in other contexts, balancing multimodal forms of communication with the traditional demands of the English language curriculum.
All-solid-state disordered LiTiS2pseudocapacitor
Whiteley, Justin M.,Hafner, Simon,Han, Sang Sub,Kim, Seul Cham,Le, Viet-Duc,Ban, Chunmei,Kim, Yong Hyun,Oh, Kyu Hwan,Lee, Se-Hee The Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.30
<P>Pseudocapacitive materials offer an opportunity to bridge the energy storage gap between supercapacitor and battery technologies. Herein is chronicled the first report of pseudocapacitance in a system devoid of liquid electrolytes, using the cathode material LiTiS2. It is demonstrated that due to extreme crystallite reduction to less than 3 nm, additional charge storage is derived by reducing surface Ti<SUP>3+</SUP>to Ti<SUP>2+</SUP>at higher voltages and more reversibly than traditionally shown. Due to facile diffusion pathways in 3-fold coordinated lithium along the TiS2surfaces, disordered LiTiS2can be used as a singular cathode without conductive additives. The result is a system exhibiting nearly 300 mA h g<SUP>−1</SUP>at a rate of C/2 for 1000 cycles. Whereas active materials in liquid cells typically have size limitations before irreversibilities appear, the high pseudocapacitance demonstrated in this report indicates that active materials used in the solid-state could benefit from size reduction. Hopefully, a new avenue of research stems from this work to investigate mixed conductor nano-domains for solid-state battery/capacitor hybrids. The prospect of a solid-state pseudocapacitor unlocks a series of new applications that offer long shelf life, high temperature capabilities, and enhanced safety.</P>
AUF1 promotes let-7b loading on Argonaute 2
Yoon, Je-Hyun,Jo, Myung Hyun,White, Elizabeth J.F.,De, Supriyo,Hafner, Markus,Zucconi, Beth E.,Abdelmohsen, Kotb,Martindale, Jennifer L.,Yang, Xiaoling,Wood III, William H.,Shin, Yu Mi,Song, Ji-Joon,T Cold Spring Harbor Laboratory Press 2015 Genes & development Vol.29 No.15
<P>Yoon et al. discovered that RBP AU-rich-binding factor 1 (AUF1) promotes let-7b loading onto Argonaute 2 (AGO2), the catalytic component of the RNA-induced silencing complex (RISC). In turn, AGO2–let-7 triggered target mRNA decay.</P><P>Eukaryotic gene expression is tightly regulated post-transcriptionally by RNA-binding proteins (RBPs) and microRNAs. The RBP AU-rich-binding factor 1 (AUF1) isoform p37 was found to have high affinity for the microRNA let-7b in vitro (<I>K</I><SUB>d</SUB> = ∼6 nM) in cells. Ribonucleoprotein immunoprecipitation, in vitro association, and single-molecule-binding analyses revealed that AUF1 promoted let-7b loading onto Argonaute 2 (AGO2), the catalytic component of the RNA-induced silencing complex (RISC). In turn, AGO2–let-7 triggered target mRNA decay. Our findings uncover a novel mechanism by which AUF1 binding and transfer of microRNA let-7 to AGO2 facilitates let-7-elicited gene silencing.</P>
Surface-Modified Gold Nanorods for Specific Cell Targeting
Chan-Ung Wang,Yoshie Arai,Insun Kim,장원희,이승현,Jason H. Hafner,정은희,Deokho Jung,권영은 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.10
Gold nanoparticles (GNPs) have unique properties that make them highly attractive materials for developing functional reagents for various biomedical applications including photothermal therapy, targeted drug delivery, and molecular imaging. For <I>in vivo</I> applications, GNPs need to be prepared with very little or negligible cytotoxicitiy. Most GNPs are, however, prepared using growth-directing surfactants, such as cetyl trimethylammonium bromide (CTAB), which are known to have considerable cytotoxicity. In this paper, we describe an approach to remove CTAB to a non-toxic concentration. We optimized the conditions for surface modification with methoxypolyethylene glycol thiol (mPEG) which replaced CTAB and formed a protective layer on the surface of GNPs. The cytotoxicity of pristine and surface-modified gold nanorods (GNRs) was measured in human cell lines derived from hepatic carcinoma, embryonic kidney, umbilical vein endothelia, and thyroid papillary carcinoma. Cytotoxicity assays revealed that treating cells with GNRs do not significantly affect cell viability except for thyroid papillary carcinoma cells. Thyroid cancer cells are more susceptible to residual CTAB, so that CTAB has to be further removed by dialysis in order to use GNRs for thyroid cell targeting. PEGylated GNRs are further modified to present monoclonal antibodies that recognize a specific surface marker, Na-I symporter, for thyroid cells. Antibody-conjugated GNRs specifically targeted human thyroid cells <I>in vitro</I>.
Study on various hot-gas defrosting configurations for CO2-NH3 cascade deep freezer
Arun B. S.,Ninan George,Murali Sariki,Samuel Manoj,Kumar Sumit,Vaishak S.,Dasgupta Mani Sankar,Kochunni Sarun Kumar,Hafner Armin,Widell Kristina Norne 대한설비공학회 2024 International Journal of Air-Conditioning and Refr Vol.32 No.1
Four hot-gas bypass defrosting configurations for CO2-NH3 cascade blast freezer for application in fish processing firm are numerically investigated. Due to the high moisture content of fish, defrosting is necessary after every 4 to 5 h of batch operation. A thermodynamic model for the cascade system and defrosting was developed to study various defrosting configurations formulated by rearranging the existing compressor to operate as a defrosting compressor and with the addition of an external defrosting compressor. From the simulation findings, it can be summarized that the conventional hot-gas bypass defrosting without defrost compressor is suitable for a high-capacity cascade refrigeration system with more than three evaporators. For low cooling capacity refrigeration systems, a defrosting compressor is necessary to elevate the temperature above the cascade condensing temperature. A dedicated defrosting compressor with a power consumption of 3.1 kW and a modified refrigeration/defrosting compressor with a power consumption of 6.8 kW can deliver 33.3 kW of heating at a temperature of +10 °C (45 bar). Incorporating a desuperheater between the main and defrosting compressors reduces compressor temperature and maintains the lubricating oil stability, without change in defrosting energy consumption and less exergy loss. The defrosting efficiency is obtained in the range of 39.7–42% which is in agreement with published literature.
김두근,김홍승,오금윤,김선훈,기현철,김태언,김회종,최영완,Kim, Doo Gun,Kim, Hong-Seung,Oh, Geum-Yoon,Kim, Seon-Hoon,Ki, Hyun-Chul,Kim, Tae-Un,Kim, Hwe Jong,Ma, Ping,Hafner, Christian,Choi, Young-Wan 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.3
We have investigated the optical properties of plamonic waveguide with tapered structure based on InP material for photonic integrated circuit(PIC). The proposed plasmonic waveguide is covered with the Ag thin film to generate the plasmonic wave on metallic interface. The optical characteristics of plasmonic waveguide were calculated using the three-dimensional finite-difference time-domain method. The plasmonic waveguide was fabricated with the lengths of 2 to $10{\mu}m$ and the widths of 400 to 700 nm, respectively. The plasmonic mode and optical loss were measured. The optimum plasmonic length is $10{\mu}m$ and widths are 600 and 700 nm in the fabricated waveguide. This plasmonic waveguide can be directly integrated with other conventional optical devices and can be essential building blocks of PIC.