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Thermal pre-oxidation of polyacrylonitrile (PAN) fibers is a time-consuming and energy-consuming step in the production of PAN-based carbon fibers. In this paper, the effect of temperature on the ...structures and properties of PAN fibers cyclized in the supercritical carbon dioxide (Sc-CO₂) medium was studied. The thermal behaviors of the PAN fibers were investigated by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The cyclization reaction was sensitive to the heating temperature and gas atmosphere. The FT-IR results of the PAN fibers treated in the Sc-CO₂ confirmed that the degree of cyclization increased with the increase of the cyclization temperature. Compared with the PAN fibers treated in the air, the PAN fibers treated in the Sc-CO₂ showed a higher degree of cyclization even at the same temperature. These findings might be related to the osmotic action of Sc-CO₂ causing the fibers to be further arranged in a regular manner, which was favorable for the cyclization reaction. Moreover, as one kind of high diffusion and high heat transfer media, the heat release during the cyclization of PAN fibers could be quickly removed by Sc-CO₂, which achieved the progress of the rapid-entry cyclization reaction.
Background
The rapid increase in the detection rate of thyroid cancer over the past few decades has caused some unexpected economic burdens. However, that of papillary thyroid carcinoma (PTC) seems ...to have had the opposite trend, which is worthy of further comprehensive exploration.
Methods
The Surveillance, Epidemiology, and End Results 18 database was used to identify patients with PTC diagnosed during 2003-2017. The incidence trends were analyzed using joinpoint analysis and an age-period-cohort model.
Results
The overall PTC incidence rate increased from 9.9 to 16.1 per 100 000 between 2003 and 2017. The joinpoint analysis indicated that the incidence growth rate began to slow down in 2009 (annual percentage change APC = 3.1%, 95% confidence interval CI = 1.9%–4.4%). After reaching its peak in 2015, it began to decrease by 2.8% (95% CI = −4.6% to −1.0%) per year. The stratified analysis indicated that the incidence patterns of different sexes, age groups, races, and tumor stages and sizes had similar downward trends, including for the localized (APC = −4.5%, 95% CI = −7% to −1.9%) and distant (APC = −1.3%, 95% CI = −2.7% to −.1%) stages, and larger tumors (APC = −4%, 95% CI = −12% to 4.7%). The age-period-cohort model indicated a significant period effect on PTC, which gradually weakened after 2008-2012. The cohort effect indicates that the risk of late birth cohorts is gradually stabilizing and lower than that of early birth cohorts.
Conclusion
The analysis results of the recent downward trend and period effect for the incidence of each subgroup further support the important role of correcting overdiagnosis in reducing the prevalence of PTC. Future research needs to analyze more-recent data to verify these downward trends.
The influences of various m-γ-PGA (0.08-0.20%,
/
) concentrations on the properties of minced beef meat paste in terms of rheological properties, texture, moisture distribution, and microstructures ...were evaluated. The results indicated that m-γ-PGA enhanced the water-holding capacity, gel strength, texture, and whiteness of the minced beef meat paste. Based on the microstructural results, m-γ-PGA helped form a more organized and compact gel, thereby limiting the migration of water through the gel matrix. In contrast to the control group, the water-holding property, gel strength, and whiteness of minced meat paste gels with m-γ-PGA content of 0.12% increased from 75.89%, 584.51 g·cm, and 61.83 to 79.91%, 780.87 g·cm, and 62.54, respectively (
< 0.05), exhibiting the highest water-holding property and gel strength. Thus, m-γ-PGA exhibits great potential for minced meat paste products as a healthy gel water retainer and enhancer in low-fat meat products.
In order to improve the interface combination property between an aramid fiber (AF) and an epoxy resin matrix, the surface modification of AF with epichlorohydrin (ECH) assisted by supercritical CO2 ...(ScCO2) was investigated. The fiber surface was characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and dynamic contact angle (DCA) analysis. At the same time, we utilized interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) to characterize the bond strength between the fiber and epoxy resin. An ideal modification effect of the fiber surface was acquired when the fiber treated with ECH in ScCO2 compared with the fiber treated in pure ScCO2. The results showed that ECH could be successfully grafted onto the fiber surface under an anhydrous aluminum chloride (AlCl3) catalyst in ScCO2, and the relative content of oxygen on the fiber surface increased after modification; simultaneously, the morphology of the fiber surface became rougher and the fiber's wettability was upgraded. Finally, the IFSS property of the fiber with the epoxy resin increased, and the ILSS property of the AF-reinforced resin composites was also improved compared with those of the untreated materials.
This paper proposes a combined cooling, heating and electric power (CCHP) system based on demand side response. In order to improve the economy of the system, a two-stage optimal scheduling scheme is ...proposed with the goal of minimizing the total operating cost of the system and maximizing user satisfaction. The optimal operation of the system was divided into two optimization problems, including the demand side and the supply side. In the first stage, combined with user satisfaction, from the new point of view that users are prone to excessive behavior due to time-of-use electricity prices, the cooling, heating and power load curves are optimized. In the second stage, an economic dispatch model that includes operating costs in terms of energy, maintenance and environment is established. An improved artificial bee colony (IABC) algorithm is used to solve the optimal energy production scheme based on the demand curves optimized in the first stage. Case studies are conducted to verify the efficiency of the proposed method. Compared with the CCHP system that does not consider demand response, this method reduced operation cost on typical days in summer and winter by 5.20% and 5.76%, respectively.
Aiming at the economic dispatch problem for an interconnected system with wind power integration, and in order to realize the goals of system economy and improvement of the cross-regional consumption ...level of wind energy, a decentralized coordination dispatch model is established in this paper. In this model, a DC tie-line is cut by the branch cutting method and used as a coupling variable. A virtual upper-level dispatch center is established, and the economic dispatch problem to be solved is decomposed into a master optimization problem for the upper-level dispatch center and subsidiary optimization problems for the lower-level dispatch centers. For solving this model, an improved Harris hawks optimization (HHO) algorithm called the chaotic mutation Harris hawks optimization (CMHHO) algorithm is proposed. In the CMHHO algorithm, tent mapping and the “DE/pbad-to-pbest/1” strategy are introduced, and a new nonlinear escape energy factor adjustment is proposed. Through an algorithm comparison experiment and a simulation experiment with two examples, the superiority of the CMHHO algorithm, the effectiveness of the proposed model and the applicability of the CMHHO algorithm to the proposed model are verified. The model proposed is of great significance for solving the economic dispatch problem for an interconnected system with wind power integration.
The reasonable and efficient use of the abundant biomass resources in rural areas has not been realized. Therefore, the concept of a combined cooling, heating, and power (CCHP) microgrid system, ...considering biomass pyrolysis and gasification, has been developed by researchers. A biomass gasification device can fully use biomass resources and can play a role in absorbing wind energy. Meanwhile, in order to minimize the operating cost of each micropower supply unit, as well as the environmental pollution costs, researchers have also established an optimal scheduling model for CCHP microgrids, which uses the sparrow search algorithm. In this paper, we have improved upon the traditional sparrow algorithm to solve the problems of its uneven population distribution, poor global search ability, and the risk of falling into local optima, through the development of the random walk sparrow search algorithm (RSSA). First, a sinusoidal chaotic map is used to generate the early-generation sparrow population with a uniform distribution in space. Second, in this study we add a sharing factor to the discoverer’s optimization process to enhance information sharing and the global research capability among individuals in this field. Finally, a random walk strategy is used to form new participants to improve the algorithm’s skill in locally searching for optimal locations. Taking the CCHP microgrid with grid-connected action as a case study, we concluded that compared with the optimization outcomes of the SSA, the total costs incurred by RSSA in summer and winter were reduced by 2.2% and 3.1%, respectively. Compared with the optimization findings for the chaotic SSA algorithm, the total costs incurred using the RSSA algorithm under typical summer and winter days were reduced by 0.14% and 0.13%, respectively. The productiveness of the RSSA algorithm for solving the CCHP microgrid economic dispatch issues has thus been verified.
Kernel size and weight are important determinants of grain yield in maize. In this study, multivariate conditional and unconditional quantitative trait loci (QTL), and digenic epistatic analyses were ...utilized in order to elucidate the genetic basis for these kernel-related traits. Five kernel-related traits, including kernel weight (KW), volume (KV), length (KL), thickness (KT), and width (KWI), were collected from an immortalized F2 (IF2) maize population comprising of 243 crosses performed at two separate locations over a span of two years. A total of 54 unconditional main QTL for these five kernel-related traits were identified, many of which were clustered in chromosomal bins 6.04-6.06, 7.02-7.03, and 10.06-10.07. In addition, qKL3, qKWI6, qKV10a, qKV10b, qKW10a, and qKW7a were detected across multiple environments. Sixteen main QTL were identified for KW conditioned on the other four kernel traits (KL, KWI, KT, and KV). Thirteen main QTL were identified for KV conditioned on three kernel-shape traits. Conditional mapping analysis revealed that KWI and KV had the strongest influence on KW at the individual QTL level, followed by KT, and then KL; KV was mostly strongly influenced by KT, followed by KWI, and was least impacted by KL. Digenic epistatic analysis identified 18 digenic interactions involving 34 loci over the entire genome. However, only a small proportion of them were identical to the main QTL we detected. Additionally, conditional digenic epistatic analysis revealed that the digenic epistasis for KW and KV were entirely determined by their constituent traits. The main QTL identified in this study for determining kernel-related traits with high broad-sense heritability may play important roles during kernel development. Furthermore, digenic interactions were shown to exert relatively large effects on KL (the highest AA and DD effects were 4.6% and 6.7%, respectively) and KT (the highest AA effects were 4.3%).
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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