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11.
We have derived a nonlinear spatiotemporal differential equation for spacecharge fields from Kukhtarev's material equations in a moving coordinate system and obtained the spatial subharmonic instability boundaries by using linear stability analysis. It is also found that there is an analogy between the temporal subharmonic and the spatial subharmonc instabilities in the sense that the governing differential equations describing the instability boundaries are formally identical. The experiments for generating spatial subharmonic waves are performed in a photorefractive Bi12SiO20 crystal by using conventional moving grating technique. The threshold detunings are experimentally determined and the results are compared with the theory. 相似文献
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14.
A new synthesis procedure for titanium-containing aluminosilicate zeolites has been obtained using a clear colloidal dispersion (sol) which was prepared with titanium isopropoxide, water, hydrochloric acid and colloidal silica, Ludox. When NaY, KL, offretite, mordenite and ZSM-5 zeolites were crystallized from the sol following conventional hydrothermal crystallization procedures, all the aluminosilicate zeolites showed the same X-ray absorption fine structure at the Ti K edge indicating framework Ti. The zeolites showed remarkable catalytic activity for the partial oxidation of cyclohexene using H2O2 as an oxidant and the photocatalytic decomposition of trichloroethene using water. 相似文献
15.
Jeongbae Kim Hee Youl Kwak Dong Won Lee 《Journal of Mechanical Science and Technology》2007,21(12):2159-2167
In this study, we highlighted differences in the standards used in performance tests of solar collectors. We analyzed testing
results for different types of solar collectors to determine the effects of the collector area and mass flow rate, which were
not necessarily consistent across all tests. Our analysis showed that the factor,F′ (τα), including collector efficiency factor (F′), could be correlated with the flow rate or area regardless of the collector type. Moreover, the collector loss coefficient
(F′U
L
) per flow rate or area for an evacuated collector was less that of a flat-plate collector; this was also correlated with
the flow rate or area, regardless of the type of evacuated collector. As a result of this analysis, we propose a modified
heat loss coefficient that includes the effects of all parameters that can be considered in a performance test and show that
this coefficient could better describe the thermal characteristics of various types of solar collectors. 相似文献
16.
Dong?Seop?LeeEmail author J.?Periaux L.?F.?Gonzalez K.?Srinivas E.?Onate 《Structural and Multidisciplinary Optimization》2012,45(3):433-450
There are many applications in aeronautical/aerospace engineering where some values of the design parameters/states cannot
be provided or determined accurately. These values can be related to the geometry (wingspan, length, angles) and or to operational
flight conditions that vary due to the presence of uncertainty parameters (Mach, angle of attack, air density and temperature,
etc.). These uncertainty design parameters cannot be ignored in engineering design and must be taken into the optimisation
task to produce more realistic and reliable solutions. In this paper, a robust/uncertainty design method with statistical
constraints is introduced to produce a set of reliable solutions which have high performance and low sensitivity. Robust design
concept coupled with Multi-Objective Evolutionary Algorithms (MOEAs) is defined by applying two statistical sampling formulas;
mean and variance/standard deviation associated with the optimisation fitness/objective functions. The methodology is based
on a canonical evolution strategy and incorporates the concepts of hierarchical topology, parallel computing and asynchronous
evaluation. It is implemented for two practical Unmanned Aerial System (UAS) design problems; the first case considers robust
multi-objective (single-disciplinary: aerodynamics) design optimisation and the second considers a robust multidisciplinary
(aero-structures) design optimisation. Numerical results show that the solutions obtained by the robust design method with
statistical constraints have a more reliable performance and sensitivity in both aerodynamics and structures when compared
to the baseline design. 相似文献
17.
Hantae Jo Sofia Brito Byeong Mun Kwak Sangkyu Park Mi-Gi Lee Bum-Ho Bin 《International journal of molecular sciences》2021,22(5)
Mesenchymal stem cells (MSCs) are multipotent stem cells derived from adult stem cells. Primary MSCs can be obtained from diverse sources, including bone marrow, adipose tissue, and umbilical cord blood. Recently, MSCs have been recognized as therapeutic agents for skin regeneration and rejuvenation. The skin can be damaged by wounds, caused by cutting or breaking of the tissue, and burns. Moreover, skin aging is a process that occurs naturally but can be worsened by environmental pollution, exposure to ultraviolet radiation, alcohol consumption, tobacco use, and undernourishment. MSCs have healing capacities that can be applied in damaged and aged skin. In skin regeneration, MSCs increase cell proliferation and neovascularization, and decrease inflammation in skin injury lesions. In skin rejuvenation, MSCs lead to production of collagen and elastic fibers, inhibition of metalloproteinase activation, and promote protection from ultraviolet radiation-induced senescence. In this review, we focus on how MSCs and MSC-derived molecules improve diseased and aged skin. Additionally, we emphasize that induced pluripotent stem cell (iPSC)-derived MSCs are potentially advanced MSCs, which are suitable for cell therapy. 相似文献
18.
Woohyeon Shin Jun Seop Kim Heesung Kim Hui Ju Choi Hee Jung Lee Moon Kwang Um Moon Kee Choi Kyeongwoon Chung 《大分子材料与工程》2021,306(5):2100007
Hydrogels are recognized as one of the most promising materials for e-skin devices because of their unique applicable functionalities such as flexibility, stretchability, biocompatibility, and conductivity. Beyond the excellent sensing functionalities, the e-skin devices further need to secure a target-oriented 3D structure to be applied onto various body parts having complex 3D shapes. However, most e-skin devices are still fabricated in simple 2D film-type devices, and it is an intriguing issue to fabricate complex 3D e-skin devices resembling target body parts via 3D printing. Here, a material design guideline is provided to prepare multifunctional hydrogels and their target-oriented 3D structures based on extrusion-based 3D printing. The material design parameters to realize target-oriented 3D structures via 3D printing are systematically derived from the correlation between material design of hydrogels and their gelation characteristics, rheological properties, and 3D printing processability for extrusion-based 3D printing. Based on the suggested material design window, ion conductive self-healable hydrogels are designed and successfully applied to extrusion-based 3D printing to realize various 3D shapes. 相似文献
19.
Polyelectrolyte complexes (PECs) composed of chitosan and hyaluronic acid (HA) were prepared in various pH regions and at different weight ratios. At low pHs, there was a strong ionic interaction between NH groups in chitosan and both COO? and COOH groups in HA due to the deprotonation of HA, whereas weak linkages were formed at high pHs because only the carboxyl groups of HA could interact with NH groups in chitosan. The formation of PECs resulted in a decrease in the crystallinity and thermal stability caused by the interactions between polyions. With variations in the degree of ionization of polyions at various pH conditions, novel PEC sponges were prepared by the freeze drying of PEC solutions. Furthermore, for the evaluation of the wound‐healing effect of PEC sponges with or without an antimicrobial agent (silver sulfadiazine), they were applied to a full‐skin defect of a Wistar rat in vivo. The histology and computerized morphometric analysis of the epidermal healing confirmed the proliferation of fibroblasts in the wound bed and a distinct reduction in infectious agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 925–932, 2003 相似文献
20.
Ozonolysis of cyclododecene was carried out to produce an w-formyl carboxylic acid (12-oxododecanoic acid) which is derived
from zwitterion and aldehyde moiety that are formed during the reaction. The ozonolysis was performed to examine the product
distribution under such reaction variables as temperature, kinds of solvent, and presence of catalyst. The yield of polymeric
ozonide, which is undesirable product, was measured to be dominantly 86% without pyridine catalyst, whereas, only 10.25% with
the catalyst. The optimum reaction condition was to be in MC (methylene chloride) solvent, and in the presence of equimolar
olefin and pyridine catalyst at O°C, at which the yields of polymeric ozonide, 1,12-dodecanedialdehyde, 1,12-dodecanedicarboxylic
acid, and 12-oxo-dodecanoic acid were 10.25%, 26.72%, 26.31%, and 36.72%, respectively. 相似文献