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排序方式: 共有159条查询结果,搜索用时 46 毫秒
31.
32.
Moon-Ju Kim Zhiquan Song Chang Kyu Lee Tae Gyeong Yun Joo-Yoon Noh Mi-Kyung Park Dongeun Yong Min-Jung Kang Jae-Chul Pyun 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(2):2200712
Rapid spread of infectious diseases is a global threat and has an adverse impact on human health, livelihood, and economic stability, as manifested in the ongoing coronavirus disease 2019 (COVID-19) pandemic. Even though people wear a face mask as protective equipment, direct disinfection of the pathogens is barely feasible, which thereby urges the development of biocidal agents. Meanwhile, repetitive respiration generates temperature variation wherein the heat is regrettably wasted. Herein, a biocidal ZnO nanorod-modified paper (ZNR-paper) composite that is 1) integrated on a face mask, 2) harvests waste breathing-driven thermal energy, 3) facilitates the pyrocatalytic production of reactive oxygen species (ROS), and ultimately 4) exhibits antibacterial and antiviral performance is proposed. Furthermore, in situ generated compressive/tensile strain of the composite by being attached to a curved mask is investigated for high pyroelectricity. The anisotropic ZNR distortion in the bent composite is verified with changes in Zn O bond lengths and O Zn O bond angles in a ZnO4 tetrahedron, resulting in an increased polarization state and possibly contributing to the following pyroelectricity. The enhanced pyroelectric behavior is demonstrated by efficient ROS production and notable bioprotection. This study exploring the pre-strain effect on the pyroelectricity of ZNR-paper might provide new insights into the piezo-/pyroelectric material-based applications. 相似文献
33.
34.
Suk-Soo Kim Woo-Jin Lee Su-Il Pyun Dai-Ryong Kim 《Metals and Materials International》1999,5(6):583-588
Effects of applied potential and solution temperatureT
s on the pitting corrosion of pure aluminium (Al) were investigated in 0.01 M NaCl solutions containing various sulphate (SO4
2-) ion concentrations using a potentiodynamic polarisation experiment, the potentiostatic current transient technique, ac impedance
spectroscopy and atomic force microscopy (AFM). The potentiodynamic polarisation curves showed a rise in the pitting potentialE
pir values and a simultaneous increase in anodic current density at potentials much higher than theE
pit value as the SO42~ ion concentration increases. This implies that (SO4
2-) ions impede pit initiation at potentials belowE
pit but enhance pit growth aboveE
pit. This was confirmed from the larger pit growth rate parameterb values of pure Al exposed to (SO4
2-) ion-containing chloride solutions during the abrading action than those exposed to (SO4
2-) ion-free chloride solution. Furthermore, at 7s=25°C, the charge densityQ values for the Al metal dissolution in the presence of (SO4
2-) ions were smaller than the value in its absence. By contrast, as validated by the capacitance values and the AFM images
of the re-anodized specimens, an enhanced metal dissolution was observed in (SO4
2-) ion-containing chloride solutions at 7s=60° and 80°C. From the experimental findings, it is suggested that (SO4
2-) ions act as inhibitors of pitting corrosion on pure Al belowE
pit and at 7s=25°C, whereas they act as promoters at 7s=60 ° and 80°C. This originates from the accelerated dissolution of the bare metal extensively exposed to the temperature-sensitive
Cl ion attack, which occurs at potentials aboveE
pit 相似文献
35.
Inactivation kinetics of Lactobacillus plantarum by high pressure CO2 was investigated to understand the mechanism of microbial inactivation. The inactivation rates increased with pressure, temperature and exposure time, and with decreasing pH of media. Microbial inactivation was governed essentially by penetration of CO2 into cells and its effectiveness could be improved by the enhanced transfer rate. Microbial reduction of 8 log cycles was observed within 120 min under CO2 pressure of 70 kg/cm2 at 30°C. We hypothesized that the cell death resulted from the lowered intracellular pH and damage to the cell membrane due to penetration of CO2. Pressurized CO2 treatment is a potential nonthermal technology for food preservation. 相似文献
36.
Hyeonseok Jeong Sungwoo Cho Daeyeon Kim Hahyung Pyun Daegeun Ha Chonghun Han Minkwan Kang Munsoo Jeong Sanghun Lee 《International Journal of Hydrogen Energy》2012
In a commercialized 300 kW molten carbonate fuel cell (MCFC) power plant, a univariate alarm system that has only upper and lower limits is usually employed to identify abnormal conditions in the system. Even though univariate alarms have already been adopted for system monitoring, this simple monitoring system is limited for using in an extended monitoring system for fault diagnosis. Therefore, based on principal component analysis (PCA), a recursive variable grouping method for a multivariate monitoring system in a commercialized MCFC power plant is presented in this paper. In terms of development, since a principal component analysis model that contains all system variables cannot isolate a system fault, heuristic recursive variable selection method using factor analysis is presented here. To verify the performance of the fault detection, real plant operations data are used. Furthermore, comparison between type 1 and type 2 errors for four different variable groups demonstrates that the developed heuristic method works well when system faults occur. These monitoring techniques can reduce the number of false alarms occurring on site at MCFC power plant. 相似文献
37.
Fatigue characteristics of SAE52100 steel via ultrasonic nanocrystal surface modification technology
Pyun YS Suh CM Yamaguchi T Im JS Kim JH Amanov A Park JH 《Journal of nanoscience and nanotechnology》2012,12(7):6089-6095
Ultrasonic nanocrystal surface modification (UNSM) technology is a novel surface modification technology that can improve the mechanical and tribological properties of interacting surfaces in relative motion. UNSM treatment was utilized to improve the wear resistance fatigue strength of slim bearing rings made of SAE52100 bearing steel without damaging the raceway surfaces. In this study, wear and fatigue results that were subjected to different impact loads of the UNSM treatment were investigated and compared with those of the untreated specimen. The microhardness of the UNSM-treated specimens increased by about 20%, higher than that of the untreated specimens. The X-ray diffraction analysis showed that a compressive residual stress of more than 1,000 MPa was induced after the UNSM treatment. Also, electron backscatter diffraction analysis was used to study the surface structure and nanograin refinement. The results showed that the rolling contact fatigue life and the rotary bending fatigue strength of the UNSM-treated specimens increased by about 80% and 31%, respectively, compared to those of the untreated specimen. These results might be attributed to the increased microhardness, the induced compressive residual stress, and the nanocrystal structure modification after the UNSM treatment. In addition, the fracture surface analysis showed that the fish eye crack initiation phenomenon was observed after the UNSM treatment. 相似文献
38.
Lee J.K. Park K.H. Jang D.H. Cho H.S. Nam E.S. Pyun K.E. Jeong J. 《Photonics Technology Letters, IEEE》2000,12(2):140-142
We demonstrate a kink and beam steering free operation of 0.98-μm GaInAs-GaInP high-power ridge waveguide (RW) lasers utilizing channel ion implantation. The ion-implanted regions along the both sides of the ridge effectively suppressed the excitation of higher order lateral modes, which causes beam steering and kink. The maximum power without beam steering and kink has been achieved over 250 mW for channel ion-implanted RW lasers with 1.8-3.7-μm ridge width, compared to 120-mW maximum power without the channel ion implantation 相似文献
39.
Ilgu Yun Lawrence A. Carastro Ravi Poddar Martin A. Brooke Gary S. May Kyung‐Sook Hyun Kwang Eui Pyun 《ETRI Journal》2000,22(1):38-46
The extraction of model parameters for embedded passive components is crucial for designing and characterizing the performance of multichip module (MCM) substrates. In this paper, a method for optimizing the extraction of these parameters using genetic algorithms is presented. The results of this method are compared with optimization using the Levenberg‐Marquardt (LM) algorithm used in the HSPICE circuit modeling tool. A set of integrated resistor structures are fabricated, and their scattering parameters are measured for a range of frequencies from 45 MHz to 5 GHz. Optimal equivalent circuit models for these structures are derived from the s‐parameter measurements using each algorithm. Predicted s‐parameters for the optimized equivalent circuit are then obtained from HSPICE. The difference between the measured and predicted s‐parameters in the frequency range of interest is used as a measure of the accuracy of the two optimization algorithms. It is determined that the LM method is extremely dependent upon the initial starting point of the parameter search and is thus prone to become trapped in local minima. This drawback is alleviated and the accuracy of the parameter values obtained is improved using genetic algorithms. 相似文献
40.
Su-Il Pyun 《工业材料与腐蚀》1991,42(11):592-597
The present work is concerned with the role of sulphidic inclusions in hydrogen-assisted cracking of low-alloy steels with different sulphur contents. The steels were previously cathodically charged in sulphuric acid solution. Evaluating the susceptibility to hydrogen-assisted cracking in terms of the reduction in area values, the high sulphur steel is less susceptible than the low sulphur steel. The fracture surface of the low sulphur steel appears rather brittle, with local quasi-cleavage fractures around large intergranular fracture facets. In contrast, the fracture surface of the high sulphur steel is characterized predominantly by the microvoid coalescence mode, with a great number of manganese sulphide inclusions. The difference between the two sulphur steels is based upon the concept that the interfaces between sulphidic inclusions and matrix act as trapping sites for hydrogen and thus hydrogen is uniformly distributed over the sulphidic inclusions. 相似文献