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912.
An experimental study was performed to investigate the effect of surface coating on the critical heat flux for downward facing boiling on the outer surface of a hemispherical vessel. Steady-state boiling experiments were conducted in the subscale boundary layer boiling (SBLB) facility using test vessels with metallic microporous coatings to obtain the local boiling curves and the local critical heat flux (CHF) limits. Similar heat transfer performance was observed for microporous aluminum and microporous copper coatings. When compared to the corresponding data without coatings, the boiling curves for the coated vessels were found to shift upward and to the right. This meant that the CHF limit was higher with surface coating and that the minimum film boiling temperatures were located at higher wall superheats. In particular, the microporous coatings were found to enhance the local CHF values appreciably at all angular locations explored in the experiments. Results of the present study showed that the microporous aluminum coating was very durable. Even after many cycles of steady state boiling, the vessel coating remained rather intact, with no apparent changes in color or structure. Although similar heat transfer performance was observed for microporous copper coatings, the latter were found to be much less durable and tended to degrade after several cycles of boiling. 相似文献
913.
Abstract A continuum-based configuration design sensitivity analysis method is presented for kinematically driven mechanical systems. Configuration design variable for mechanical systems are defined. The 3-1-3 Euler angle is used as the orientation design variable. The reassembly process for a mechanical system after a configuration design change is eliminated by imposing kinematic admissibility conditions of the velocity field. The direct differentiation method is used to derive design sensitivity equations. Numerical examples are presented to demonstrate the validity and effectiveness of the proposed method. 相似文献
914.
Ji‐Hoon Kim Sunyoung Lee In‐Nam Kang Moo‐Jin Park Do‐Hoon Hwang 《Journal of polymer science. Part A, Polymer chemistry》2012,50(16):3415-3424
An alternating copolymer composed of heal‐to‐tail‐structured 3,4′‐dihexyl‐2,2′‐bithiophene (DHBT) and pyrene units [poly(DHBT‐alt‐PYR)] was synthesized using a Stille coupling reaction for use in photovoltaic devices as a p‐type donor. For the reduction of the bandgap energy of poly(DHBT‐alt‐PYR), 4,7‐bis(3′‐hexyl‐2,2′‐bithiophen‐5‐yl)benzo[c][1,2,5]thiadiazole (BHBTBT) units were introduced into the polymer. Poly(DHBT‐co‐PYR‐co‐BHBTBT)s were synthesized using the same polymerization reaction. The synthesized polymers were soluble in common organic solvents and formed smooth thin films after spin casting. The optical bandgap energies of the polymers were obtained from the onset absorption wavelengths. The measured optical bandgap energy of poly(DHBT‐alt‐PYR) was 2.47 eV. As the BHBTBT content in the ter‐polymers increased, the optical bandgap energies of the resulting polymers decreased. The bandgap energies of poly(50DHBT‐co‐40PYR‐co‐10BHBTBT) and poly(50DHBT‐co‐20PYR‐co‐30BHBTBT) were 1.84 and 1.73 eV, respectively. Photovoltaic devices were fabricated with a typical sandwich structure of ITO/PEDOT:PSS/active layer/LiF/Al using the polymers as electron donors and [6,6]‐phenyl C71‐butyric acid methyl ester as the electron acceptor. The device using poly(50DHBT‐co‐20PYR‐co‐30BHBTBT) showed the best performance among the fabricated devices, with an open‐circuit voltage, short‐circuit current, fill factor, and maximum power conversion efficiency of 0.68 V, 5.54 mA/cm2, 0.35, and 1.31%, respectively. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
915.
916.
Oh Kuen Kwon Jun Ha Lee Jungchul Park Ki-Sub Kim Jeong Won Kang 《Current Applied Physics》2013,13(2):360-365
A tunable graphene-nanoribbon (GNR)-resonator was investigated via classical molecular dynamics simulations. Resonance frequencies increased with increasing externally applied gate-force and axial-strain, and could be tuned above several hundred GHz. Tunable resonance frequencies achieved from the gate force were higher than those achieved from the axial-strain. The operating frequencies of GNR-resonators without axial-strain or with small axial-strains were most widely tuned by the gate, and almost linearly increased with increasing mean deflection. As the axial strain increased, the tunable ranges of the GNR-resonators were exponentially decreased, although the operating frequencies increased. GNR-resonators without axial-strain could be applied to wide-range-tuners, whereas GNR-resonators with high axial-strain could be applied to high-frequency-fine-tuners. 相似文献
917.
918.
Yong Hee Kim Nam Seob Baek Kook Hwa Kim Sang-Don Jung 《Journal of Sol-Gel Science and Technology》2012,64(2):304-308
We present herein a simple protocol of growing a patterned ZnO nanowire by etching of ZnO seed layer in the tetramethyl ammonium hydroxide (TMAH) solution. The ZnO seed layer was fabricated by sol–gel method using zinc acetate solution and patterned by using photolithographic method. Patterned ZnO seed layer as etched in the TMAH solution, followed by growth of ZnO nanowires by hydrothermal method. Remarkable point of present ZnO seed layer patterning is that development of UV-exposed photoresist and etching of ZnO seed layer is subsequently processed in aqueous TMAH solution without interruption. The grown ZnO nanowires were analyzed using XRD patterns to exhibit high purity and degree of crystallinity, and showed very good pattern fidelity. 相似文献
919.
Relationships between structure,ionization profile and sensitivity of exogenous anabolic steroids under electrospray ionization and analysis in human urine using liquid chromatography–tandem mass spectrometry 下载免费PDF全文
Eunju Cha Sohee Kim Hee Won Kim Kang Mi Lee Ho Jun Kim Oh‐Seung Kwon Jaeick Lee 《Biomedical chromatography : BMC》2016,30(4):555-565
The relationships between the ionization profile, sensitivity, and structures of 64 exogenous anabolic steroids (groups I–IV) was investigated under electrospray ionization (ESI) conditions. The target analytes were ionized as [M + H]+ or [M + H–nH2O]+ in the positive mode, and these ions were used as precursor ions for selected reaction monitoring analysis. The collision energy and Q3 ions were optimized based on the sensitivity and selectivity. The limits of detection (LODs) were 0.05–20 ng/mL for the 64 steroids. The LODs for 38 compounds, 14 compounds and 12 compounds were in the range of 0.05–1, 2–5 and 10–20 ng/mL, respectively. Steroids including the conjugated keto‐functional group at C3 showed good proton affinity and stability, and generated the [M + H]+ ion as the most abundant precursor ion. In addition, the LODs of steroids using the [M + H]+ ion as the precursor ion were mostly distributed at low concentrations. In contrast, steroids containing conjugated/unconjugated hydroxyl functional groups at C3 generated [M + H ? H2O]+ or [M + H ? 2H2O]+ ions, and these steroids showed relatively high LODs owing to poor stability and multiple ion formation. An LC‐MS/MS method based on the present ionization profile was developed and validated for the determination of 78 steroids (groups I–V) in human urine. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
920.
Sunyoung Kim Dan-Bi Kim Wenjie Jin Junghyuck Park Wonjin Yoon Yunyeol Lee 《Natural product research》2018,32(10):1193-1197
We evaluated organosulphur compounds in Allium vegetables, including garlic, elephant garlic and onion, using high-performance liquid chromatography. Among organosulphur compounds, elephant garlic had considerable γ-glutamyl peptides, and garlic had the highest alliin content. Onion had low level of organosulphur compounds than did elephant garlic and garlic. In addition, antioxidant capacities were evaluated by oxygen radical absorbance capacity (ORAC) values and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging assay. The results showed that garlic had the highest antioxidant capacity, followed by elephant garlic and onion. Furthermore, a positive correlation was observed between antioxidant activities and organosulphur compounds (R > 0.77). Therefore, our results indicate that there was a close relationship between antioxidant capacity and organosulphur compounds in Allium vegetables. 相似文献