Polymorphic behavior of gondoic acid and phase behavior of its binary mixtures with asclepic acid and oleic acid

Molecular properties of polymorphic forms of gondoic acid [cis-C_20:1Δ11ω9 (GOA)] have been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical microscopy, and Raman scattering, in comparison to those of six principal unsaturated fatty acids: oleic acid [cis-C_18:1Δ9ω9 (OA)], erucic acid [cis-C_22:1Δ13ω9 (ERA)], petroselinic acid [cis-C_18:1Δ6ω12 (PSA)], asclepic acid [cis-C_18:1Δ11ω7 (APA)], palmitoleic acid [cis-C_16:1Δ9ω7 (POA)], and elaidic acid [trans-C_18:1Δ9ω9 (ELA)]. In addition, phase behavior of binary mixtures of GOA and APA and OA was examined by XRD and DSC. The polymorphic structures of GOA are quite similar to those of APA, ERA, POA, and partly to OA. In particular, DSC and Raman scattering studies have shown that gondoic acid exhibits conformational disordering on heating at the ω-chain, a chain segment between the double bond and CH₃ group, as a transition from all-trans (γ form) to gauche-rich (α form) conformations. A miscible mixing phase was observed in the mixture of GOA and APA, yet eutectic phases were observed in the GOA and OA mixtures. This is a remarkable contrast because the binary mixture systems of varying combinations of cis-unsaturated fatty acids examined so far exhibited either eutectic nature or molecular compound formation. It is expected that specific molecular interactions between GOA and APA that originate from the equivalence of the length of the Δ-chain, the chain segment between the cis-double bond and COOH group, and also from the presence of the γ-α order-disorder transformation would be operating to form the miscible mixing phase.     

Modelling the dynamics of the students’ academic performance in the German region of the North Rhine-Westphalia: an epidemiological approach with uncertainty

Student academic underachievement is a concern of paramount importance in Europe, where around 15% of the students in the last high school courses do not achieve the minimum knowledge academic requirement. In this paper, we propose a model based on a system of differential equations to study the dynamics of the students’ academic performance in the German region of the North Rhine-Westphalia. This approach is supported by the idea that both good and bad study habits, are a mixture of personal decisions and influence of classmates. This model allows us to forecast the student academic performance by means of confidence intervals over the next few years.     

Robust consensus algorithm for multi-agent systems with exogenous disturbances under convergence conditions

In this paper, a robust consensus algorithm is developed and sufficient conditions for convergence to consensus are proposed for a multi-agent system (MAS) with exogenous disturbances subject to partial information. By utilizing H_∞ robust control, differential game theory and a design-based approach, the consensus problem of the MAS with exogenous bounded interference is resolved and the disturbances are restrained, simultaneously. Attention is focused on designing an H_∞ robust controller (the robust consensus algorithm) based on minimisation of our proposed rational and individual cost functions according to goals of the MAS. Furthermore, sufficient conditions for convergence of the robust consensus algorithm are given. An example is employed to demonstrate that our results are effective and more capable to restrain exogenous disturbances than the existing literature.     

Boundary feedback stabilization of the telegraph equation: Decay rates for vanishing damping term

We study a semilinear mildly damped wave equation that contains the telegraph equation as a special case. We consider Neumann velocity boundary feedback and prove the exponential stability of the closed loop system. We show that for vanishing damping term in the partial differential equation, the decay rate of the system approaches the rate for the system governed by the wave equation without damping term. In particular, this implies that arbitrarily large decay rates can occur if the velocity damping in the partial differential equation is sufficiently small.     

On solutions to fuzzy stochastic differential equations with local martingales

This paper deals with a class of fuzzy stochastic differential equations (FSDEs) driven by a continuous local martingale under the Lipschitzian condition. Such equations can be useful in modeling hybrid systems, where the phenomena are simultaneously subjected to two kinds of uncertainties: randomness and fuzziness. The solutions of the FSDEs are the fuzzy stochastic processes, and their uniqueness is considered to be in a strong sense. Thus, the existence and uniqueness of solutions to the FSDEs under the Lipschitzian condition is first proven. Moreover, some asymptotic properties of the solutions to the FSDEs are investigated. Finally, an illustrating example on the interest term model is provided.     

Nucleating activity of the quinacridone and phthalocyanine pigments in polypropylene crystallization

The nucleating ability of two organic pigments, quinacridone and phthalocyanine, in nonisothermal polypropylene (PP) crystallization was investigated. The investigations were carried out using DSC and polarizing microscopy. The efficiency of pigments in the nucleation process was determined in a simple test comparing the crystallization temperature of the PP‐containing pigments with respect to the pure polymer. Both pigments revealed good nucleating activity. In the presence of pigments the increment of the crystallization temperature and the increase of nucleation rate were observed. The nucleating efficiency of pigments was confirmed in investigations of the obtained structure. The nucleating activity of pigments was explained by their features fulfilling several requirements for good nucleating agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3957–3964, 2003     

Influence of the synthesis conditions on the curing behavior of phenol–urea–formaldehyde resol resins

The curing behavior of synthesized phenol–urea–formaldehyde (PUF) resol resins with various formaldehyde/urea/phenol ratios was studied with differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The results indicated that the synthesis parameters, including the urea content, formaldehyde/phenol ratio, and pH value, had a combined effect on the curing behavior. The pH value played an important role in affecting the shape of the DSC curing curves, the activation energy, and the reaction rate constant. Depending on the pH value, one or two peaks could appear in the DSC curve. The activation energy was lower when pH was below 11. The reaction rate constant increased with an increase in the pH value at both low and high temperatures. The urea content and formaldehyde/phenol ratio had no significant influence on the activation energy and rate constant. DMA showed that both the gel point and tan δ peak temperature (T_tanδ) had the lowest values in the mid‐pH range for the PUF resins. A different trend was observed for the phenol–formaldehyde resin without the urea component. Instead, the gel point and T_tanδ decreased monotonically with an increase in the pH value. For the PUF resins, a high urea content or a low formaldehyde/phenol ratio resulted in a high gel point. The effect of the urea content on T_tanδ was bigger than that on the gel point because of the reversible reaction associated with the urea component. Too much formaldehyde could lead to more reversible reactions and a higher T_tanδ value. The effects of the synthesis conditions on the rigidity of the cured network were complex for the PUF resins. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1368–1375, 2005     

Pattern synthesis of time‐modulated conformal arrays by an improved differential evolution algorithm

In this article, an improved differential evolution algorithm (IDE) based on two different colonies is proposed and applied to time‐modulated conformal arrays syntheses. The whole population of IDE is divided into two parts. The one part searches the solution globally while the other searches the neighborhood of the solution provided by the previous one. Benchmark functions are provided to testify IDE. Furthermore, IDE is applied to synthetize sum‐difference patterns with a 1 × 16 elements time‐modulated circular array and low sidelobe level (SLL) patterns with an 8 × 12 elements time‐modulated cone array. After optimization, the sideband level (SBL) of the circular array at the first sideband frequency is ?1.00 dB. The SLL and SBL at the first sideband frequency of the cone array are lower than ?30.00 and ?20.00 dB, respectively. Experiment results verify the superior performance of IDE. Moreover, to accelerate the computation speed, graphics processing unit parallel computing technique is introduced into pattern synthesis and the acceleration ratios of more than 23 times can be achieved. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:697–705, 2014.     

A global energy optimization framework for 2.1D sketch extraction from monocular images

The 2.1D sketch is a layered image representation, which assigns a partial depth ordering of over-segmented regions in a monocular image. This paper presents a global optimization framework for inferring the 2.1D sketch from a monocular image. Our method only uses over-segmented image regions (i.e., superpixels) as input, without any information of objects in the image, since (1) segmenting objects in images is a difficult problem on its own and (2) the objective of our proposed method is to be generic as an initial module useful for downstream high-level vision tasks. This paper formulates the inference of the 2.1D sketch using a global energy optimization framework. The proposed energy function consists of two components: (1) one is defined based on the local partial ordering relations (i.e., figure-ground) between two adjacent over-segmented regions, which captures the marginal information of the global partial depth ordering and (2) the other is defined based on the same depth layer relations among all the over-segmented regions, which groups regions of the same object to account for the over-segmentation issues. A hybrid evolution algorithm is utilized to minimize the global energy function efficiently. In experiments, we evaluated our method on a test data set containing 100 diverse real images from Berkeley segmentation data set (BSDS500) with the annotated ground truth. Experimental results show that our method can infer the 2.1D sketch with high accuracy.     

Isothermal crystallization behavior of polypropylene catalloys

The isothermal crystallization behavior of polypropylene (PP) catalloys and neat PP were studied with differential scanning calorimetry and polarized optical microscopy (POM). The crystallization kinetics of the samples were described with the well‐known Avrami equation. The crystallization rate depended remarkably on the content of the ethylene component in the PP catalloys. The crystallization half‐time increased obviously with the increase of the ethylene component in the PP catalloys. We also observed by POM that in isothermal crystallization, there were many more nuclei in the PP catalloys than that in neat PP and with an increase of the ethylene component, the average size of the spherulites decreased obviously. Even when ethylene content was as high as 27%, the crystallization rate still increased apparently, and this was quite different from common PP melting blends, in which the crystallization rate decreased when the ethylene content was relatively high because of the obstruction effect of dispersed droplets to the spherulite growth of the PP matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 877–882, 2004