Poly(3-n-butylthiophene) (P3BT) samples with different average molecular weights and headto-tail regioregularity were crystallized in the form II crystal polymorph either from solution or by annealing with CS 2 vapors. With a combined approach, making also use of literature electron diffraction data, we show that form II is well described by a limit-ordered monoclinic model in space group P2 1 /c with lattice parameters a = 10.76(1) A ˚, b = 7.77(1) A ˚(chain axis), c = 9.44(1) A ˚, and β = 64.66°, yielding a calculated density of 1.29 g/cm 3 in qualitative agreement with proposals by Winokur et al. for the form II structures of regioregular poly(3-octylthiophene) and poly(3-dodecylthiophene) (P3DDT). Our structural model was refined by Rietveld analysis and has been confirmed by molecular mechanics (MM) and molecular dynamics (MD) calculations adopting a thiophene-specific force field developed in our group. Consistent with its higher density and with thermal data, form II shows lower potential energy than the form I 0 crystalline polymorph of P3BT. Both the main-chain and the side-chain conformations closely correspond to those found in form I 0 polymorph. The form II P3BT refined structural model presents an antidirectional looser stacking and tightly interdigitated layering, different from those observed in the form I family of poly(3-alkythiophenes) (P3ATs) and crystallite dimension of 20-30 A ˚along the chain axis. This feature and the lamellar structure implied by the spherulitic morphology are consistent with substantial chain-folding for high molecular weight samples. Oriented X-ray diffraction patterns from thin films of form II P3BT are explained assuming that the stacking axis c, corresponding to the radial, fast growth direction of the bidimensional form II spherulites, is preferentially in the plane of the film, while the layer axis a and the chain axis b approach random orientation around c, at variance with recent literature suggestions. The small crystal dimensions along the chain axis, the looser stacking, the relevance of chain folding and the spherulitic morphology implying film discontinuity suggest that the form II structural family of P3AT's are less viable than the form I polymorphs for molecular electronics applications.
The minimum volume of the nonlinear longitudinal fin with rectangular and triangular profiles by using the modified Newton–Raphson method is presented in this paper. The dimension of the fin profile is regarded as the optimization variable. Furthermore, a mechanism called “volume updating” is added into the modified Newton–Raphson algorithm to obtain the minimum volume of the fin. Two examples are illustrated to demonstrate the proposed method. The obtained results showed that the proposed method can be used efficiently and accurately in finding the minimum volume of the nonlinear longitudinal fin problem with rectangular and triangle profiles.
Mid-priced cars (segment B) are attracting the attention of middle-income families in Vietnam. They often consider choosing one of three vehicles from three different manufacturers, consisting of Hyundai Accent 1.4AT, Toyota Vios 1.5G, and Honda City 1.5L. This study was carried out to rank those three cars. Twelve criteria for rating each car provided by the dealer were used. These criteria are both qualitative and quantitative, and also fall into all three types, including max, min and another (“Yes”, “No”). The importance of each criterion was determined by experts in a survey. They are all knowledgeable about cars. Two multi-criteria decision making (MCDM) methods including R (A simple ranking method for multi-attribute decision making in the industrial environment) and CURLI (Collaborative Unbiased Rank List Integration) method were applied for ranking. This is the first work that has used both methods mentioned above. The result revealed that the rank of the alternatives is the same when both the methods were used. This result gives us a certain confidence when choosing a car. Accordingly, Honda City 1.5L is ranked first. R and CURLI not only succeeded in ranking cars in this study, but also promise to be successful when used in other situations. Moreover, other criteria for evaluating the vehicle options that have not been surveyed in this study are mentioned in the last section of this paper. They need to be further considered to include in other next studies for car selection
Tóm tắt. C¡c nghi ¶n cùu v ùng döng trong caeng nghi»p ¢ chùng tä nhúng °c iºm nêi bªt cõa bi¸n t¦n a bªc bao gçm: ch §t l÷ñng caeng su §t lîn, h i th §p, nhi¹u i»n tø th §p, v tên hao âng ngt th §p. Trong nhúng n«m g¦n ¥y, mët sè mae h¼nh bi¸n t¦n lai ÷ñc ph¡t triºn nh¬m t«ng ch §t l÷ñng i•u khiºn v gi£m ë phùc t¤p trong i•u khiºn cho bi¸n t¦n. Trong sè â, thaeng qua k¸t nèi nèi ti¸p cõa 2 bë bi¸n t¦n NPC ba bªc, bë bi¸n t¦n lai 3/3 NPC ÷ñc h¼nh th nh vîi nhi•u ÷u iºm v÷ñt trëi. B i b¡o tr¼nh b y nhúng kÿ thuªt PWM mîi düa theo ph÷ìng ph¡p sâng mang nh¬m i•u khiºn vªn h nh tèi ÷u cho mae h¼nh gh²p n y. V• m°t nguçn DC, c §u tróc bi¸n t¦n n y ÷ñc c §p nguçn theo c §u tróc nguçn chung (vîi ch¿ mët nguçn DC) hay c §u tróc nguçn ri ¶ng vîi 4 nguçn DC (l c¡c pin m°t tríi). C¡c mae phäng v thüc nghi»m trong b i b¡o s³ ÷ñc thüc hi»n º kiºm tra v ¡nh gi¡ c¡c kÿ thuªt ÷ñc • xu §t.
The goal of this study is to further investigate and to develop a more efficient way in the error estimate and the rate of the convergence for the mesh h, p-refinement procedure in the finite element analysis for two-dimensional and three-dimensional elastostatic mechanics problems. The oscillation of the stress field around singularity points is also considered in the refinement process. In this paper, a-refinement procedure with a h-uniform and p-uniform analysis capability is called a h, p-refinement procedure. We also establish the refinement criterion for the adaptive strategy with h-refinement based on the ratio of error indicator or the enrichment indicator.
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