Synthesis,characterization, and thermal stability of novel wholly para-oriented aromatic poly(ether-amide-hydrazide)s bearing pendant groups and their corresponding poly(ether-amide-1,3,4-oxadiazole)s

Four novel wholly para-oriented aromatic poly(ether-amide-hydrazide)s containing various pendant groups on their aromatic rings were synthesized from p-aminosalicylic acid hydrazide (PASH) with an equimolar amount of either 4,4′-(1,4-phenylenedioxy)dibenzoyl chloride (1a), 4,4′-(2,5-tolylenedioxy)dibenzoyl chloride (1b), 4,4′-(2-tert-butyl-1,4-phenylenedioxy)dibenzoyl chloride (1c), or 4,4′-(2,5-biphenylenedioxy)dibenzoyl chloride (1d) via a low temperature solution polycondensation reaction. A polyamide-hydrazide without the ether and pendant groups, poly[4-(terephthaloylamino)salicylic acid hydrazide, PTASH, is also investigated for comparison. It was synthesized from PASH and terephthaloyl chloride by the same synthetic route. The polymer intrinsic viscosities ranged from 4.5 to 2.47 dlg⁻¹ in N,N-dimethyl acetamide (DMAc) at 30 °C and decreased with the introduction of the ether and pendant groups into the polymer. All the polymers were soluble in DMAc, N,N-dimethyl formamide (DMF), and N-methyl-2-pyrrolidone (NMP) and their solutions could be cast into flexible films with good mechanical strengths. Further, they exhibited a great affinity to water sorption. Their solubility and hydrophilicity increased with introduction of the ether and pendant groups into the polymer. The prepared polymers could be thermally cyclodehydrated under nitrogen atmosphere into the corresponding poly(ether-amide-1,3,4-oxadiazole)s approximately in the region of 300–450 °C. The introduction of the flexibilizing ether linkages and the pendant groups into the polymer improves the solubility of the resulting poly(ether-amide-1,3,4-oxadiazole)s compared to poly(amide-1,3,4-oxadiazole) free from these groups.     

Interaction of Soil Air Permeability and Soil Vapor Extraction

A new theoretical model to analyze the measurements obtained from a typical soil column venting experiment is proposed. The principles of mass transfer, Darcy's law, and air compressibility in the form of pressure-volume relationships were coupled to calculate the contaminant concentration in the gas phase (air), and the rate of contaminant removal. The proposed model relates soil air permeability with the contaminant removal and is capable of calculating the variation of soil air permeability with time during the venting process. The contaminated sand sample was idealized as a system of straight capillary tubes in the direction of flow, lined by the liquid contaminant. A closed-form solution for radial diffusion of the contaminants in a cylinder, coupled with axial advection of air, was used to model contaminant removal. The results from the mass transfer model were then used to trace the change of soil air permeability with time. The model also uses, as an alternative approach, a modified form of Darcy's law for compressible flow.     

Efficient Tree Structures for High Utility Pattern Mining in Incremental Databases

Recently, high utility pattern (HUP) mining is one of the most important research issues in data mining due to its ability to consider the nonbinary frequency values of items in transactions and different profit values for every item. On the other hand, incremental and interactive data mining provide the ability to use previous data structures and mining results in order to reduce unnecessary calculations when a database is updated, or when the minimum threshold is changed. In this paper, we propose three novel tree structures to efficiently perform incremental and interactive HUP mining. The first tree structure, Incremental HUP Lexicographic Tree ({rm IHUP}_{{rm {L}}}-Tree), is arranged according to an item's lexicographic order. It can capture the incremental data without any restructuring operation. The second tree structure is the IHUP Transaction Frequency Tree ({rm IHUP}_{{rm {TF}}}-Tree), which obtains a compact size by arranging items according to their transaction frequency (descending order). To reduce the mining time, the third tree, IHUP-Transaction-Weighted Utilization Tree ({rm IHUP}_{{rm {TWU}}}-Tree) is designed based on the TWU value of items in descending order. Extensive performance analyses show that our tree structures are very efficient and scalable for incremental and interactive HUP mining.     

Development of a GaAs monolithic surface acoustic wave integratedcircuit

An oscillator technology using surface acoustic wave (SAW) delay lines integrated with GaAs MESFET electronics has been developed for GaAs-based integrated microsensor applications. The oscillator consists of a two-port SAW delay line in a feedback loop with a four-stage GaAs MESFET amplifier. Oscillators with frequencies of 470, 350, and 200 MHz have been designed and fabricated. This oscillator technology is most suitable for sensor applications but can logically be extended to radio-frequency oscillator and filter applications by methods well known for other piezoelectric substrates     

Prediction of hub corner stall characteristics of a highly loaded low speed single stage fan

In this paper a numerical investigation has been presented on the stall mechanism of a highly loaded Single Stage Low Speed Fan designed for the research test facility to be installed at North Western Polytechnic University (NWPU) Xi’an, China. The results presented are for the design point, near stall and just stall operating conditions at design speed. Design point studies have been found to be an indicative of stall area. Unsteady method of domain scaling has been used to compute the results at near stall and just stall conditions. It has been found that unlike the conventional tip leakage flow of the rotor, stator hub section is mainly responsible for the stall of the fan. The flow mechanism has been discussed with correlation to the design variables and previous investigations. Commercial CFD code NUMECA FINE/Turbo has been used for computations; results have been compared with results obtained from commercial CFD code ANSYS-CFX. The loss prediction of latter code is conservative than the former. The stall mechanism predicted by both codes is analogous.     

A Real-Time Data Mining Approach for Interaction Analytics Assessment: IoT Based Student Interaction Framework

Students’ interaction and collaboration with the fellows and teachers using the Internet of Things (IoT) based interoperable infrastructure is a convenient way. Measuring student attention is an essential part of the educational assessment for students’ interaction. As new learning styles develop, new tools and assessment methods are also needed. The focus in this paper is to develop IoT based interaction framework and analysis of the student experience in electronic learning (eLearning) so that the students can take full advantage of the modern interaction technology and their learning can increase to a high level. This setup has a data collection module, which is implemented using Visual C# programming language and computer vision library. The number of faces, number of eyes, and status of eyes are extracted from the video stream, which is taken from a video camera. The extracted information is saved in a dataset for further analysis. The analysis of the dataset produces interesting results for student learning assessments. Modern learning management systems can integrate the developed tool to consider student-learning behaviors when assessing electronic learning strategies. The tools are also developed for the data collection on both student and teacher ends. Correlation of data and hidden meaning are extracted to make the learning experience and teaching performance better and adaptable. IoT based infrastructure provides the facilities to fellow students about location awareness, fellows’ accessibility, social behavior and helping hand.     

Zero Configuration Networking: Implementation, performance, and security

The ubiquitous access to wired and wireless networks is making information access possible from anywhere, anytime, and any device. Today, end-users are also highly mobile, often equipped with a range of portable devices, and they expect service availability when they require it. In addition, they do not want to be burdened by complex configurations before they can discover and use services. The Zero Configuration (Zeroconf) Networking technology promises to alleviate this configuration burden by allowing users to discover services and devices with little end-user intervention. We compare two popular implementations of Zeroconf namely, Avahi and Mono.Zeroconf running on Linux and Windows XP operating systems, respectively. We evaluate their performance using service discovery time as the performance metric. Our empirical results show that Linux Avahi yields almost 99% improvements in service discovery time over Windows Mono.Zeroconf. We also discuss security solutions that can be deployed to enhance the security of Zeroconf networks. We further investigate the performance of the IP Security (IPSec) protocol when used by our Mono.Zeroconf implementation running on the Windows XP platform. With IPSec, service discovery time increases by almost 45% with our prototype implementation.     

密度和纤维取向对炭/炭复合材料烧蚀性能的影响(英文)

采用不同的预制体和致密化方法制备了密度不同的5种炭/炭复合材料(密度范围1.77g/cm3～1.85g/cm3)。用氧-乙炔焰对试样进行了烧蚀试验,并用SEM表征了烧蚀后材料的形貌。结果表明:烧蚀后,与乙炔焰成30o角的纤维变成楔形,而与火焰平行的纤维变成直径为3.5μm～4.5μm的针状,针状纤维更易被火焰烧蚀而钝化。部分宏观孔(直径为1.0mm～1.26mm)、针状微孔及界面裂纹等缺陷处更易被烧蚀而变成烧蚀坑。包裹纤维的沥青炭层由于热解炭基体的不连续而出现了严重的剥蚀。高密度材料(1.85g/cm3)具有良好的抗烧蚀性能。     

Mucoadhesive elementary osmotic pump tablets of trimetazidine for controlled drug delivery and reduced variability in oral bioavailability

The objectives of this work was preparation and evaluation of the mucoadhesive elementary osmotic pump tablets of trimetazidine hydrochloride to achieve desired controlled release action and augmentation of oral drug absorption. The drug-loaded core tablets were prepared employing the suitable tableting excipients and coated with polymeric blend of ethyl cellulose and hydroxypropyl methylethylcellulose E5 (4:1). The prepared tablets were characterized for various quality control tests and in vitro drug release. Evaluation of drug release kinetics through model fitting suggested the Fickian mechanism of drug release, which was regulated by osmosis and diffusion as the predominant mechanism. Evaluation of mucoadhesion property using texture analyzer suggested good mucoadhesion potential of the developed osmotic systems. Solid state characterization using Fourier-transform infrared spectroscopy, differential scanning calorimetry and powder X-ray diffraction spectroscopy confirmed the absence of any physiochemical incompatibilities between drug and excipients. Scanning electron microscopy analysis showed the smooth surface appearance of the coated tablets with intact polymeric membrane without any fracture. In vivo pharmacokinetic studies in rabbits revealed 3.01-fold enhancement in the oral bioavailability vis-à-vis the marketed formulation (Vastarel MR®). These studies successfully demonstrate the bioavailability enhancement potential of the mucoadhesive elementary osmotic pumps as novel therapeutic systems for other drugs too.