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81.
针对半轴套管多工位热挤压自动化生产线工艺调试过程中,正挤压工序冲连皮时,管端易出现连皮粘连缺陷的问题,探讨了有可能造成连皮粘连的原因。通过对工艺流程和现场情况进行综合分析,提出了圆柱形坯料周向温度加热不均是关键的影响因素。采用Deform有限元分析软件,模拟了不同加热温差条件下,反挤压和冲连皮时材料变形及材料剪断过程。通过对模拟结果的分析,揭示了连皮粘连机理,并可知,当坯料周向加热温差小于30℃时,连皮可顺利冲下。根据模拟得出的合理温差,进行现场试验,实际情况与模拟结果具有较高的一致性,生产出的产品锻件切口平齐、连皮撕裂带分布均匀,有效地解决了连皮粘连的问题。 相似文献
82.
Marina A. Marchenko Victoria V. Nefedova Daria S. Yampolskaya Galina V. Kopylova Daniil V. Shchepkin Sergey Y. Bershitsky Natalia A. Koubassova Andrey K. Tsaturyan Dmitrii I. Levitsky Alexander M. Matyushenko 《International journal of molecular sciences》2020,21(22)
Tropomyosin (Tpm) is one of the major actin-binding proteins that play a crucial role in the regulation of muscle contraction. The flexibility of the Tpm molecule is believed to be vital for its functioning, although its role and significance are under discussion. We choose two sites of the Tpm molecule that presumably have high flexibility and stabilized them with the A134L or E218L substitutions. Applying differential scanning calorimetry (DSC), molecular dynamics (MD), co-sedimentation, trypsin digestion, and in vitro motility assay, we characterized the properties of Tpm molecules with these substitutions. The A134L mutation prevented proteolysis of Tpm molecule by trypsin, and both substitutions increased the thermal stability of Tpm and its bending stiffness estimated from MD simulation. None of these mutations affected the primary binding of Tpm to F-actin; still, both of them increased the thermal stability of the actin-Tpm complex and maximal sliding velocity of regulated thin filaments in vitro at a saturating Ca2+ concentration. However, the mutations differently affected the Ca2+ sensitivity of the sliding velocity and pulling force produced by myosin heads. The data suggest that both regions of instability are essential for correct regulation and fine-tuning of Ca2+-dependent interaction of myosin heads with F-actin. 相似文献
83.
84.
Research was conducted to evaluate the effects of using food-grade ingredients on cave aged Cheddar cheese as either a surface coating or in nets to prevent infestation by Tyrophagus putrescentiae growth at different environmental conditions. Food grade coating formulations with 1) xanthan gum and propylene glycol (XG+PG) and 2) carrageenan, propylene glycol alginate, and PG (CG+PGA+PG) were made and infused into nets. Jars with cave aged Cheddar cheese cubes that were inoculated with 20 mites were stored in an environmental chamber for 14 d at temperature and relative humidity (RH) combinations of 10, 15, and 20 °C and 75 ± 2 and 85 ± 2% RH. When averaged over RH, mite counts were fewer on control cheese cubes at 10 °C when compared to 15 °C and 20 °C, regardless of whether nets were used or not. However, mites were able to reproduce on untreated cheese cubes at all temperatures. The CG+PGA+PG and XG+PG coatings and nets controlled mite reproduction, as evidenced by harboring less than the initial inoculation level of 20 mites. Sensory results indicated that CG+PGA+PG and XG+PG coated Cheddar cheese at 10 °C and 75% RH and netted Cheddar cheese at 10 or 15 °C and 75% RH did not differ (P > 0.05) from the control with respect to sensory attributes. The treatments at 15 °C and 85% RH and 20 °C caused the cheese to be softer and more bitter than control cheese. In conclusion, the CG+PGA+ 40% PG and XG+40% PG treatments of both coatings and nets inhibited the growth of mites, and the use of nets lessened the impact of food grade coatings on the sensory properties of the Cheddar cheese. 相似文献
85.
Nabil T. Eldabe Galal M. Moatimid Abdelhafeez A. ElShekhipy Naglaa F. Aballah 《亚洲传热研究》2019,48(5):1946-1962
The influence of inconstant electrical conductivity and chemical reaction on the peristaltic motion of non‐Newtonian Eyring‐Prandtl fluid inside a tapered asymmetric channel is investigated. The system is concerned by a uniform external magnetic field. The heat and mass transfer are considered. The problem is controlled mathematically by a system of nonlinear partial differential equations which describe the velocity, temperature, and nanoparticle concentration of the fluid. By means of long wavelength and low Reynolds numbers, our system is simplified. It is explained by using the multi‐step differential transform method as a semi‐analytical technique. The distributions of velocity, temperature, nanoparticle concentration, as well as pressure gradient and pressure rise are obtained as a function of the physical parameters of the problem. The effects of these parameters on these distributions are deliberated numerically and illustrated graphically through a set of figures. The results indicate that the parameters play a significant role in controlling the velocity, temperature, nanoparticle concentration, pressure gradient, and pressure rise. 相似文献
86.
Various active substances, antioxidant activities and primary differential metabolite profiles were investigated to assess the nutritional quality of radish sprouts steamed for 0–300 s. The levels of flavonoids, total phenolic content and isothiocyanate in radish sprouts decreased with increased steaming time, and DPPH radical scavenging activity levels and superoxide dismutase levels also exhibited a downward trend (P < 0.05). By contrast, total phenolic acid, ferric-reducing antioxidant power and reducing power levels exhibited significant increases in the early short-term steaming process (P < 0.05). Steaming for 30 s promoted the accumulation of vitamin B2, whereas, steaming for 300 s promoted the accumulation of phospholipids and myristic acid to a greater extent than steaming for 30 s. Overall, there was a partial non-decreased nutritional indicator in short-term steaming of radish sprouts, and a longer steaming time positively affected the differential metabolites. 相似文献
87.
《International Journal of Hydrogen Energy》2022,47(16):9485-9503
A low-carbon energy transition is permeating many industrialized countries due to the overuse of fossil fuels and the climate change. Some countries stress the hydrogen energy in optimizing their energy structures. This article examines both the markets and the policies of the hydrogen industry in the World's Top 4 largest economies. To make the comparative analysis more logical, a novel conceptual model for energy transition -- the institution-economics-technology-behavior framework -- has been adopted to make a multi-dimensional discussion. The results show that: (1) From the perspective of strategic intention, developing hydrogen energy is conductive to the energy transition. (2) From the horizontal comparison, each country has its own advantages, however, the main driving factors are different. (3) From the vertical comparison, the hydrogen energy development in each country is still in the stage of quantitative change, and the inflection point of qualitative change has not been reached yet. 相似文献
88.
Lukáš Kolek Vít Šisler Patrícia Martinková Cyril Brom 《Journal of Computer Assisted Learning》2021,37(5):1348-1369
This study investigates a video game's effects on implicit and explicit attitudes towards depicted historical events in the short- and long-term on a sample of 148 young adults. We used, as an intervention tool, a serious game Czechoslovakia 38–89: Borderlands that deals with the expulsion of the Sudeten Germans from the former Czechoslovakia after the WWII. Results showed more negative pretest-posttest explicit attitude changes towards the expulsion on a general level (d = −0.34) and a specific level (d = −0.53) compared to the control group. Over the long-term, group differences in attitude change remained significant for the specific level (d = −0.44), but not for general one (d = −0.16). Exploratory analysis on the item level indicated that especially attitudes towards the expulsion's (un)fairness were affected by the game. However, no significant changes were found in implicit attitudes in the experimental group. This study is the first of such scale to empirically investigate video games' effects on a society's historical awareness. 相似文献
89.
For better synthesis and use of WB3 triborides surface coatings, structural, electronic and optical properties of hexagonal and trigonal hP4, hP8, hP16 and hR24-WB3 triborides were predicted through the first-principles calculation. The formation enthalpies revealed that all of these WB3 are energetically stable, and hR24-WB3 is the best stable phase. Electronic properties showed that these WB3 have strong B-B covalent bonds mixed with W-B covalent-ionic bonds. The calculated reflectivity that these WB3 triborides can be used as optical shielding devices for FUV radiation. Moreover, Nd-YAG laser with wavelength of 1064?nm is available for synthetizing hP4, hP8 and hP16-WB3 coatings, while the laser with wavelength of 532?nm is suitable for hR24-WB3 coatings. The calculated static dielectric constants and refractive index indicated that the optical anisotropy for these WB3 is in a sequence of hP8-WB3 >?hP4-WB3 >?hP16-WB3 >?hR24-WB3. 相似文献
90.