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61.
62.
Jonghyeok Lee SeongJun Hwang Yong-gi Hong Jaehyun Park Woo-Jin Byun 《ETRI Journal》2021,43(2):221-231
To resolve energy depletion issues in massive Internet of Things sensor networks, we developed a set of distributed energy beamforming methods with one-bit feedback and clustering for multi-node wireless energy transfer, where multiple single-antenna distributed energy transmitters (Txs) transfer their energy to multiple nodes wirelessly. Unlike previous works focusing on distributed information beamforming using a single energy receiver (Rx) node, we developed a distributed energy beamforming method for multiple Rx nodes. Additionally, we propose two clustering methods in which each Tx node chooses a suitable Rx node. Furthermore, we propose a fast distributed beamforming method based on Tx sub-clustering. Through computer simulations, we demonstrate that the proposed distributed beamforming method makes it possible to transfer wireless energy to massive numbers of sensors effectively and rapidly with small implementation complexity. We also analyze the energy harvesting outage probability of the proposed beamforming method, which provides insights into the design of wireless energy transfer networks with distributed beamforming. 相似文献
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65.
Jaehyun Park Se Hun Joo Yoon‐Jeong Kim Ju Hyun Park Sang Kyu Kwak Seokhoon Ahn Seok Ju Kang 《Advanced functional materials》2019,29(32)
In this work, a highly conductive organic cocrystal is investigated as an anode material for conducting agent‐free lithium‐ion battery (LIB) electrodes. A unique morphology of semiconducting fullerene (C60) and contorted hexabenzocoronene (cHBC) is developed as a cocrystal that efficiently enhances the electron transfer during discharge and charge processes due to the formation of a well‐defined junction between C60 and cHBC. In particular, the present study reveals the exact cocrystal phase of orthorhombic Pnnm using grazing incidence X‐ray diffraction characterization and computational methods. The detailed cocrystal structure analysis indicates that the columnar structure of C60/cHBC cocrystal facilitates the reliable vacant sites for Li+ storage, which ultimately enhances the reversible capacity to 330 mAh g–1 at 0.1 A g–1 with long cyclability of 600 cycles in the absence of a conducting agent. Furthermore, the rate performance of the C60/cHBC cocrystal anode is improved compared to that of the graphite anode, indicating that the cocrystal formation between C60 and cHBC enhances the charge transport at a high current density. It demonstrates that the approach of this study can be a promising strategy for preparing conducting agent‐free organic cocrystal anodes, which also provides a viable design rule for high‐performance LIBs electrodes. 相似文献
66.
Sun Jin Hur Yohan Yoon Cheorun Jo Jong Youn Jeong Keun Taik Lee 《Comprehensive Reviews in Food Science and Food Safety》2019,18(6):1812-1824
Heme iron overload has been implicated as the main cause of the increased risk of cancer due to the consumption of red meat. However, fish and shellfish, teas, and spices contain up to five times more iron than red meat. There is insufficient evidence that iron intake in dietary red meat is the primary causal factor for colorectal cancer. In addition, harmful substances produced during the preparation of red meat, including heterocyclic amines (HCAs), polycyclic aromatic hydrocarbons (PAHs), N‐nitroso compounds, and acrylamide, are extrinsic factors that increase carcinogenicity. HCAs are produced during the cooking of red meat, poultry meat, and fish. PAHs may also be produced during the cooking of diverse food groups, such as dairy products, fruits, vegetables, and cereals. The average daily intake of red meat among Korean individuals is 62 g; the amount of PAHs entering the body via red meat is less than the average amount of PAHs the body is exposed to in the air. Therefore, it is difficult to conclude that dietary red meat is the main cause of colorectal cancer. Rather, there may be an intricate influence of multiple factors, including fruit and vegetable intake, alcohol consumption, smoking, overweight, obesity, and stress. 相似文献
67.
Poly(tetramethylene ether glycol) (PTMG), widely used as a precursor in the fabrication of commodity polymers, is typically produced byacid-catalyzed polymerization of tetrahydrofuran (THF). Herein, we report a detailed investigation of the cationic ring-opening polymerization of THF catalyzed by ferric chloride (FeCl3), which can be considered as a strong Lewisacid. The polymerization reactions were performed in the presence of acetic anhydride at 20°C with FeCl3, which readily produced poly(tetramethylene ether glycol diester) (PTMG_DE). A maximum yield of 79.2% was obtained within 30 min using a FeCl3 to acetic anhydride molar ratio of 5:4. The resulting polymers generally exhibited low molecular weights and a narrow polydispersity index and could be easily converted into PTMG using aqueous NaOH. In contrast with the FeCl3-acetic anhydride system, other iron-based catalysts such as FeCl2 and FeCl3·6H2O did not show any noticeable activity in the polymerization of THF. The proposed mechanism involves initiation of the acetyl cation generated by FeCl3, propagation by nucleophilic addition of THF, and termination by the acetate anion, accounting for the high activity of the FeCl3 catalyst for THF polymerization. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47999. 相似文献
68.
Sang Ho Kang Shin Goo Hur Hee Woo Lee Tae Hyun Nam 《Metals and Materials International》2000,6(4):381-387
Ti-Ni and Ti-Ni-Cu alloy powders have been fabricated by ball milling after which their microstructures and transformation
behaviors were investigated by means of scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis,
transmission electron microscopy and differential scanning calorimetry. The powders of as-milled Ti-Ni-Cu alloys whose Cu-content
is less than 5 at.% were mixtures of crystal and amorphous, whereas those alloy powders whose Cu-content is more than 10 at.%
were crystalline. The B19’ martensite is formed in the Ti-Ni-Cu alloy powders whose Cu-content is less than 10 at.%, whereas
the B19 and B19’ martensites coexist in those whose Cu-content is more than 10 at.%. The martensitic transformation range
became wider with increasing rotating speed, and so endothermic and exothermic peaks obtained from differential scanning calorimetry
were indiscernible. 相似文献
69.
Hyun-Moo Hur Joon-Hyuk Park Won-Hee You Tae-Won Park 《Journal of Mechanical Science and Technology》2009,23(10):2790-2800
A study was conducted to analyze the influence of wheel profile wear on running stability by using a 1/5 scale bogie model.
The critical speed was analyzed by constructing a dynamic model for the bogie model. And the 1/5 scale bogie and a scaled
roller rig prototype were manufactured to verify the feasibility of applying the scale model; a critical speed test was conducted
for worn wheel profile samples. The test results for the scale model were consistent with the simulation results for the scale
model within the range of 5% or less. Also, the variation of the critical speed of the scale model for the wheel profile wear
shows a similar trend with the analysis results of the full scale model. Therefore, using the scale model to analyze the influence
of wheel profile wear on running stability shows sufficient feasibility as a model to analyze the stability of a full scale
bogie. 相似文献
70.
Hong-Kee Lee Jun-Mi Jeon Min Hyung Lee Ho-Nyun Lee Jin-Young Hur 《Metals and Materials International》2013,19(1):119-122
The characteristics of electroless NiCoP films were investigated as a function of Co content. Sheet resistance of a multi-stacked film of SiO2/Ta/Cu/NiP dramatically increased after annealing at 500 °C, but as more Co was co-plated in NiCoP film, the change in sheet resistance of the stacked film of SiO2/Ta/Cu/NiCoP at 500 °C became smaller. A CoP/Cu film showed no change in resistance value after annealing, which indicates the CoP film is the most effective Cu diffusion barrier. X-ray diffraction analysis showed that an as-plated NiP film of amorphous structure is easily crystallized by thermal annealing over 300 °C, while CoP showed an insignificant change in crystal structure by thermal annealing up to 500 °C. This result reveals that the CoP film is capable of preventing the diffusion of Cu at 500 °C due to the thermal stability of CoP film. 相似文献