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Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 245
Author(s):  
Yong Sun ◽  
Yongli Peng ◽  
Yajiao Zhang

In this work, a flame retardant curing agent (DOPO-MAC) composed of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide DOPO and methyl acrylamide (MAC) was synthesized successfully, and the structure of the compound was characterized by FT-IR and 1H-NMR. The non-isothermal kinetics of the epoxy resin/DOPO-MAC system with 1% phosphorus was studied by non-isothermal DSC method. The activation energy of the reaction (Ea), about 46 kJ/mol, was calculated by Kissinger and Ozawa method, indicating that the curing reaction was easy to carry out. The flame retardancy of the epoxy resin system was analyzed by vertical combustion test (UL94) and limiting oxygen index (LOI) test. The results showed that epoxy resin (EP) with 1% phosphorus successfully passed a UL-94 V-0 rating, and the LOI value increased along with the increasing of phosphorus content. It confirmed that DOPO-MAC possessed excellent flame retardance and higher curing reactivity. Moreover, the thermal stability of EP materials was also investigated by TGA. With the DOPO-MAC added, the residual mass of EP materials increased remarkably although the initial decomposition temperature decreased slightly.


Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 66
Author(s):  
Edyta Nartowska ◽  
Tomasz Kozłowski

This research was conducted with the use of the DSC method; it involved the examination of the unfrozen water content in two model (source) calcium bentonites (≥75% smectite), after one to three freeze-thaw cycles in the natural state, as well as after the ion exchange for a potentially toxic element (Cu2+). The freeze-thaw cycles do not affect the unfrozen water content at a given negative temperature in a statistically significant manner. However, a statistically significant influence of temperature, the initial mass of the water, and the clay type on the change of the unfrozen water content was found. Moreover, the empirical models of predicting the unfrozen water in the bentonite after the exchange for Cu2+ ion were created, for which the parameter was the mass of the water and the mass of the dry soil, at the temperature of −2 °C.


2021 ◽  
Author(s):  
Daniel Mota ◽  
Erick Alves ◽  
Elisabetta Tedeschi

Manuscript submitted to the Twenty-second IEEE Workshop on Control and Modeling for Power Electronics (COMPEL 2021).<div>Abstract: Dual-sequence current controllers of voltage source converters (VSCs) feature two separate rotating reference frames (RRFs), commonly named dq frames, and rely on techniques that isolate the positive and negative sequences of three-phase measurements. One of these techniques is the delayed signal cancellation (DSC). It is performed in the stationary reference frame (SRF), also known as αβ frame. The DSC combines old values of one axis with new values of the other axis of the SRF. The results are, then, transformed into the RRFs for use in the current controller. This filtering process introduces an extra layer of complexity for dual-sequence current controllers, which could otherwise operate solely in the RRFs. This paper introduces a frequency adaptive DSC method that operates directly in the RRF. Moreover, an averaging of two of the proposed DSC filters with contiguous integer delays is employed for reducing discretization errors caused by grid frequency excursions. A formal proof of the equivalence between the αβ and dq DSC methods is presented. Furthermore, computer simulations of a case study support the interpretation of the results.</div>


2021 ◽  
Author(s):  
Daniel Mota ◽  
Erick Alves ◽  
Elisabetta Tedeschi

Manuscript submitted to the Twenty-second IEEE Workshop on Control and Modeling for Power Electronics (COMPEL 2021).<div>Abstract: Dual-sequence current controllers of voltage source converters (VSCs) feature two separate rotating reference frames (RRFs), commonly named dq frames, and rely on techniques that isolate the positive and negative sequences of three-phase measurements. One of these techniques is the delayed signal cancellation (DSC). It is performed in the stationary reference frame (SRF), also known as αβ frame. The DSC combines old values of one axis with new values of the other axis of the SRF. The results are, then, transformed into the RRFs for use in the current controller. This filtering process introduces an extra layer of complexity for dual-sequence current controllers, which could otherwise operate solely in the RRFs. This paper introduces a frequency adaptive DSC method that operates directly in the RRF. Moreover, an averaging of two of the proposed DSC filters with contiguous integer delays is employed for reducing discretization errors caused by grid frequency excursions. A formal proof of the equivalence between the αβ and dq DSC methods is presented. Furthermore, computer simulations of a case study support the interpretation of the results.</div>


Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2284
Author(s):  
Xuemiao Chen ◽  
Ziwen Wu ◽  
Jing Li ◽  
Qianjin Zhao

In this paper, for a class of uncertain stochastic nonlinear systems with input time-varying delays, an adaptive neural dynamic surface control (DSC) method is proposed. To approximate the unknown continuous functions online, the neural network approximation technique was applied, and based on the DSC scheme, the desired controller was constructed. A compensation system is presented to compensate for the effect of the input delay. The Lyapunov–Krasovskii functionals (LKFs) were employed to compensate for the effect of the state delay. Compared with the existing works, based on using the DSC scheme with the nonlinear filter and stochastic Barbalat’s lemma, the asymptotic regulation performance of this closed-loop system can be guaranteed under the developed controller. To certify the availability for the designed control method, some simulation results are presented.


Gels ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 214
Author(s):  
Aneta Lewandowska ◽  
Piotr Gajewski ◽  
Katarzyna Szcześniak ◽  
Agnieszka Marcinkowska

The influence of ene and thiol monomer structure on the mechanical and electrochemical properties of thiol–ene polymeric ionogels were investigated. Ionogels were obtained in situ by thiol–ene photopolymerization of 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATT), 2,4,6-triallyloxy-1,3,5-triazine (TAT), diallyl phthalate (DAP), and glyoxal bis(diallyl acetal) (GBDA) used as enes and trimethylolpropane tris(3-mercaptopropionate) (TMPTP), pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), and pentaerythritol tetrakis(3-mercaptobutyrate) (PETMB) used as thiols in 70 wt.% of ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImNTf2). The mechanical strength of ionogels was studied by puncture resistance and ionic conductivity by electrochemical impedance spectroscopy. The course of photopolymerization by photo-DSC method (differential scanning calorimetry) as well as characterization of compositions and its components (by IR and UV spectroscopy-Kamlet–Taft parameters) were also studied. The resulting ionogels were opaque, with phase separation, which resulted from the dispersion mechanism of polymerization. The mechanical and conductive properties of the obtained materials were found to be largely dependent on the monomer structure. Ionogels based on triazine monomers TAT and TATT were characterized by higher mechanical strength, while those based on aliphatic GBDA had the highest conductivity. These parameters are strongly related to the structure of the polymer matrix, which is in the form of connected spheres. The conductivity of ionogels was high, in the range of 3.5–5.1 mS∙cm−1.


2021 ◽  
Vol 11 (21) ◽  
pp. 10056
Author(s):  
Gulshakhar Kudaibergen ◽  
Madina Zhunussova ◽  
Ellina A. Mun ◽  
Anar Arinova ◽  
Vyacheslav Ogay

The application of biopolymers in tissue engineering is of a great interest due to of their inherent properties such as cell adhesion, biodegradation, bioavailability, and viscoelasticity. In this study, we synthesized cryogels based on biopolymers of gelatin, chitosan, and chondroitin sulfate by cryopolymerization and studied the effect of chondroitin sulfate on changing the physicochemical properties of cryogels such as pore size, pore volume, density, gel fraction, and biodegradation. A macroporous surface of the synthesized polymers has been investigated by SEM. The glass transition temperatures of the crosslinked cryogels, determined by the DSC method, were higher compared to that of the non-crosslinked cryogel used as a reference. The results of the MTT test showed that aqueous extracts of the prepared cryogels had no toxic effect on rat adipose-derived mesenchymal stem cells. The research in this area is of great importance and provides new insights into novel, effective methods for obtaining biopolymers that can be used as carriers of cells.


Author(s):  
I. A. Saranov ◽  
O. B. Rudakov ◽  
K. K. Polansky ◽  
A. S. Ramazanov ◽  
S. A. Balaeva ◽  
...  

The method of differential scanning calorimetry (DSC) is used to characterize the thermophysical properties during melting of samples of milk thistle oil of various geographic origins, seeds and meal. The world experience in applying the DSC method on the study of milk thistle oils is generalized. The temperature measurement program is described. It is shown that, despite the general similarity of the curve profiles of the melting DSC, there are differences in the profiles due to genotypic and phenotypic factors - variety and growing location. The DSC curves of freshly squeezed oil distinguish from the DSC curves after 6 months storage of the oil due to oxidative deterioration and the formation of more refractory partially oxidized triacylglycerols. This fact is relevant to determining the capabilities of the DSC method in controlling the freshness of vegetable oils. The peaks amplitudes in the DSC curves of fresh oil are higher than those of oils that has been stored at room temperature for six months. Double differentiation of the melting curves makes it possible to reveal the temperatures of phase transitions in the case of overlapping endothermic peaks, the establishment of which is difficult without double differentiation. Using the «Netzsch Peak Separation» software to divide the peaks in the melting curves allows at once to estimate the areas of overlapping peaks and increase the informativeness of the DSC data. Thermal analysis of milk thistle seeds and meal reveals that the meal contains a residual amount of oil, in which the proportion of triunsaturated fats is overestimated in comparison to seeds, indicating that triunsaturated fats are more difficult to extract from oil by cold pressing.


Author(s):  
Shahin Jalili ◽  
Reza Khani ◽  
Alireza Maheri ◽  
Yousef Hosseinzadeh

AbstractThis paper investigates the performance of several meta-heuristic algorithms, including Particle Swarm Optimisation (PSO), different variants of Differential Evolution (DE), Biogeography-Based Optimisation (BBO), Cultural Algorithm (CA), Optics-Inspired Optimisation (OIO), and League Championship Algorithm (LCA), for optimum layup of laminated composite plates. The study provides detailed Pseudo codes for different algorithms. The buckling capacity maximisation of a 64-layer laminated composite plate under various load scenarios has been considered as the benchmark problem, in which the design variables are the stacking sequences of layers. A Deep Statistical Comparison (DSC) method is employed to rank the performance of different algorithms. The DSC uses a nonparametric two-sample Kolmogorov-Smirnov test to conduct the performance comparisons between the algorithms. The overall performance rankings obtained from the DSC suggest that the LCA, OIO, and PSO algorithms perform remarkably better in comparison to other algorithms. The comparisons provide some interesting conclusions on the performance of different algorithms.


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