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41.
Measurements of five variations of a toroidal point-contact dc superconducting quantum interference device (SQUID) are presented. The energy resolution and other parameters of these SQUIDs are examined and compared with the predictions of the Resistively Shunted Junction model. For these SQUIDs, the measured minimum energy resolution was approximately 2×10–30 J/Hz. Excess noise in the point contacts was found to limit the energy resolution of the SQUIDs. A comparison between the typical junction parameters and noise obtained for our niobium-niobium point contacts and those of others is given. TheI–V characteristics of the junctions showed the effects of Joule heating. The white voltage noise spectral density was found to have an approximately parabolic dependence on the average voltage for bias currents larger than the critical current. While this parabolic dependence is consistent with heating effects in the junctions, the amplitude of the noise cannot be explained in terms of a heating model. The low-frequency noise of the point contacts has also been investigated. 相似文献
42.
Ungyu Paik Jeong-Gu YeoMoon-Hwan Lee Vincent A HackleyYeon-Gil Jung 《Materials Research Bulletin》2002,37(9):1623-1631
The electrokinetic behavior of BaTO3 particles in an aqueous medium exhibited a hysteresis loop with titration direction. As BaTiO3 suspension was titrated toward acidic pH, the amount of Ba2+ dissolution strongly increased, and in the subsequent titration toward alkaline pH, Ba2+ adsorbed and/or reprecipitated on the Ba-depleted BaTiO3 surface. This dissolution-reprecipitation cycle results in the observed hysteresis behavior. An attempt was made to identify the responsible species of the adsorbed/reprecipitated compound by XPS in conjunction with electrokinetic titrations. 相似文献
43.
Jeom Kee Paik 《钢结构》2008,23(9):77-77
作为作者系列研究成果[Paik J K.Ultimate strength of perforated steel plates under edge shear loading.Thin-Walled Structures,2007,45:301-6,Paik J K.Ultimate strength of perforated steel plates under axial compressive loading along short edges.Ships Offshore Struct,2007,2(3):(inpress)]的终结篇,与前期论文在边缘剪力或单轴压力荷载方面进行了对比,目的是研究双轴受压和边缘剪力作用下多孔钢板的极限强度特点,这是船舶和船舶型海洋结构在货物和水压作用下的一个典型受力模式。板的约束考虑为四边简支,中心区域为圆形孔。一系列ANSYS非线性有限元分析中考虑了不同的板尺寸(厚度)。在有限元分析基础上,推导出组合荷载下多孔板的极限强度交互关系公式,可用于可靠性分析或规范中极限强度的预测。 相似文献
44.
45.
Jung‐Min Moon Bong‐Soo Kim Hyun‐Jong Paik Jang‐Oo Lee Emiko Mouri Kohji Yoshinaga 《Polymer Engineering and Science》2010,50(6):1067-1074
Silica nanoparticles with well‐defined, highly grafted dense poly(methyl methacrylate) (MMA) were prepared by surface‐initiated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) of methyl methacrylate with an initiator‐fixed silica particle in the presence of air. Two different polymerizations of MMA were carried out under the same conditions using tris[2‐(dimethylamino)ethyl]amine (Me6TREN) and N,N,N′,N′,N″‐pentamethyldiethylene‐triamine (PMDETA) as the ligand, respectively. In the CuCl2/PMDETA system, polymerization appeared to be more controlled with a lower polydisperisty compared with the CuCl2/Me6TREN system. The monolayer of these particles was formed at the air–water interface using Langmuir‐Blodgett (LB) technique. Multilayers of the particles were fabricated by repetition of LB depositing. A surface pressure–area (π–A) measurement and SEM observation were used to characterize the particle arrays. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers 相似文献
46.
Jong Hoo Paik Sahn Nahm Young Sik Kim Hyun Min Park Hwack Joo Lee Jae Dong Byun 《Journal of Materials Science》2003,38(3):621-628
The crystal structure of (Ba1–x
La
x
)[Mg(1 + x)/3Nb(2–x)/3]O3 (BLMN) ceramics with 0 x 1 was investigated using X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). When the La content, x, was above 0.1, the 1:2 ordered hexagonal structure found in Ba(Mg1/3Nb2/3)O3 (BMN) was transformed into the 1:1 ordered cubic structure. The 1:1 ordered cubic structure was maintained up to x = 0.7. When x exceeded 0.7, however, BLMN exhibited a 1:1 ordered monoclinic structure, rather than a 1:1 ordered cubic structure. La(Mg2/3Nb1/3)O3 (LMN) has a 1:1 ordered monoclinic P21/n structure with a = 5.6004 Å, b = 5.6414 Å, c = 7.9346 Å, and = 89.9819°. The monoclinic LMN has the in-phase and the anti-phase tilt of oxygen octahedra. The anti-parallel shift of A-site cations was also found in LMN. 相似文献
47.
AbstractThis study examines how R&D intensity and open innovation affect the technological capabilities of firms in newly-developed countries, such as South Korea. East Asian latecomers are transitioning from a catch-up phase toward becoming leaders, and they are engaging in open innovation activities to drive this transition. This research quantitatively analyzes three kinds of open innovation activities—outside-in, inside-out, and coupled—to investigate their influence upon technological capabilities, while also considering the effect of R&D intensity. Data from 75 South Korean medium-sized firms were analyzed, and two major findings are reported. First, technological capabilities are enhanced by some open innovation activities and by R&D intensity. Second, R&D intensity negatively moderates the impact of open innovation activities on technological capabilities. Therefore, it may be concluded that firms with relatively low R&D intensity will gain the most benefit from increasing their open innovation activities. 相似文献
48.
Young‐Min Kim Hyun‐Dong Paik Dong‐Sun Lee 《Journal of the science of food and agriculture》2002,82(9):998-1002
Fresh oysters and ground beef were wrapped in antimicrobial films coated with a bacteriocin (nisin or lacticin NK24) incorporated into a polyamide binder layer. The packaged foods were stored at 3 and 10 °C and changes in counts of total aerobic bacteria and coliform bacteria were monitored together with appropriate quality attributes in order to determine the influence of the bacteriocin‐coated films on quality preservation and shelf‐life extension. Compared to plain low‐density polyethylene film, plastic films with incorporated bacteriocins slowed down microbial growth on packaged oysters and ground beef at both temperatures, contributed in some degree to the preservation of chemical quality and extended shelf‐life significantly. The effects of the antimicrobial films on the suppression of coliform bacterial growth were more pronounced at 10 than at 3 °C , while the effects on total aerobic bacteria were consistently evident at both temperatures. There was no difference in food quality preservation between the two types of antimicrobial film. © 2002 Society of Chemical Industry 相似文献
49.
Synthesis of BaCu(B2 O5 ) Ceramics and their Effect on the Sintering Temperature and Microwave Dielectric Properties of Ba(Zn1/3 Nb2/3 )O3 Ceramics 总被引:1,自引:0,他引:1
Min-Han Kim Jong-Bong Lim Jae-Chul Kim Sahn Nahm Jong-Hoo Paik Jong-Hee Kim Kyeong-Soon Park 《Journal of the American Ceramic Society》2006,89(10):3124-3128
BaCu(B2 O5 ) ceramics were synthesized and their microwave dielectric properties were investigated. BaCu(B2 O5 ) phase was formed at 700°C and melted above 850°C. The BaCu(B2 O5 ) ceramic sintered at 810°C had a dielectric constant (ɛr ) of 7.4, a quality factor ( Q × f ) of 50 000 GHz and a temperature coefficient of resonance frequency (τf ) of −32 ppm/°C. As the BaCu(B2 O5 ) ceramic had a low melting temperature and good microwave dielectric properties, it can be used as a low-temperature sintering aid for microwave dielectric materials for low temperature co-fired ceramic application. When BaCu(B2 O5 ) was added to the Ba(Zn1/3 Nb2/3 )O3 (BZN) ceramic, BZN ceramics were well sintered even at 850°C. BaCu(B2 O5 ) existed as a liquid phase during the sintering and assisted the densification of the BZN ceramic. Good microwave dielectric properties of Q × f =16 000 GHz, ɛr =35, and τf =22.1 ppm/°C were obtained for the BZN+6.0 mol% BaCu(B2 O5 ) ceramic sintered at 875°C for 2 h. 相似文献
50.
The high molecular weight (MW) polypropylene with average particle size of 60 nm was synthesized by controlled growth mechanism using Ziegler–Natta catalyst. The atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies showed that PP nanoparticles were spherical in shape. Structure and crystallinity were concomitantly studied through Fourier transform infrared spectroscopy and X‐ray diffraction, respectively. It shows nanospherical PP particles with more crystallinity (~ 75%) compared with macrosized PP (~ 59%). In addition, differential scanning calorimetry studies revealed the finite particle size effect on Tg and the scale dependence Tg followed a first order exponential trend. As particle size goes down to nano‐ scale from macrosize, continuous elevation of Tg's were observed from ?25 to ?11°C. This phenomenon was directed to configuration entropy of single spherical nanoparticles of PP. The mechanical properties and surface roughness were also evaluated through AFM. At last, the properties of nanosized PP were compared with micron and macrosized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献