The progress of stabilization of two compositions of acrylic fibres with various orientations has been followed by a variety of techniques. The thermooxidative treatments for stabilization have been carried out in a continuous process and also in a batch process under free shrinkage, constant length and constant tension conditions. The morphological model of acrylic fibres consists of an alternating sequence of laterally ordered and laterally disordered regions along the fibre direction. This structure is consistent with the observations based on small-angle X-ray scattering of copper- impregnated precursor fibres and thermomechanical response, thermal stress development, calorimetry, wide- and small-angle X-ray scattering and sonic modu-lus measured at different extents of stabilization. Lateral as well as orientational order in these fibres can be increased markedly through a high-temperature deformation process prior to stabilization. An increase in perfection and extent of order is observed in the early stages of stabilization. There is also a simultaneous decrease in the orientation of the disordered phase at this stage and the extent of this decrease depends on the axial constraints imposed on the fibre. Little difference in the rate of stabilization is observed as measured by density or oxygen uptake for fibres with different extents of orientation, lateral order or restraint. Fibres containing itaconic add, a stabilization catalyst did show an increased rate of stabilization. Inferences have been drawn regarding additional research pertaining to achieving high order in precursor fibres, minimizing orientational relaxation during oxidative stabilization, and the techniques for monitoring the extents of the stabilization treatment and the changes in relevant morphological parameters. 相似文献
A heterogeneous finite element model with randomly distributed inhomogeneities has been developed for the determination of
the forming limit diagram (FLD) for thin aluminum sheet material based on the prediction of localized necking. The strength
difference between the inhomogeneities and the matrix is ascertained either from the fluctuation of the experimental stress-strain
curve or from a micromechanical analysis that uses a representative particle field. By changing the specimen geometry and
friction conditions, different stress states (or strain paths) are achieved. A plot of the critical Oyane fracture parameter
is used to identify the limit strain state. Also, a plot of equivalent plastic strain rate is used to distinguish the boundary
of intense shear bands and hence to identify where to take the measurement point. Both a plane stress model and a three-dimensional
(3-D) model are adopted to predict the shear banding phenomenon and hence the FLD. The predicted FLD agrees well with the
measurements from a recent round robin experimental FLD involving several independent research laboratories. The Taguchi method
is applied to assess how the various parameters involved in the heterogeneous model affect the calculated forming limit strain. 相似文献
In recent years, Vehicular ad hoc networks (VANETs) could facilitate the decision-making progress of the drivers for example trip planning with the consideration of traffic. In the VANET, the Sybil attack is a very serious attack that collapses the security. In literature, some of the methods are reviewed to detect Sybil attacks in VANETs, but it fails to achieve Sybil attack detection. Hence, in this paper, Emperor Penguin Optimization-based Routing protocol (EPORP) is developed for detecting the Sybil attack which enhances the VANETs security. The main motive of the research is detecting the Sybil attack in VANETs for enhancing the secure operation. In the proposed approach, the Sybil attack will be detected with the help of the Rumour riding technique. To enhance the security of the VANETs, the Split XOR (SXOR) operation is utilized. In the SXOR operation, the optimal key is selected with the help of Emperor Penguin Optimization (EPO). The proposed method is implemented in the NS2 platform and performances are evaluated by metrics such as delay, throughput, delay, encryption time, and decryption time. The proposed method is compared with existing methods such as Whale Optimization Algorithm (WOA), Particle Swarm Optimization (PSO), and Firefly Algorithm (FA) respectively. While analyzing the delivery ratio, the proposed method has 0.96 s, and the WOA, PSO, and FA are 0.94, 0.92, and 0.90 respectively. From the analysis, the proposed method has a high delivery ratio value compared with the WOA, PSO, and FA methods. Similarly, the other parameters are analyzed and compared with the existing methods.
Context: The conventional liquid ophthalmic delivery systems exhibit short pre-corneal residence time and the relative impermeability to the cornea which leads to poor ocular bioavailability.
Objective: The aim of this study was to apply quality by design (QbD) for development of dexamethasone sodium phosphate (DSP) and tobramycin sulfate (TS)-loaded thermoresponsive ophthalmic in situ gel containing Poloxamer 407 and hydroxyl propyl methyl cellulose (HPMC) K4M for prolonging the pre-corneal residence time, ocular bioavability and decreases the frequency of administration of dosage form. The material attributes and the critical quality attributes (CQA) of the in situ gel were identified. Central composite design (CCD) was adopted to optimize the formulation.
Materials and methods: The ophthalmic in situ forming gels were prepared by cold method. Materials attributes were the amount of Poloxamer 407 and HPMC and CQA identified were Gel strength, mucoadhesive index, gelation temperature and % of drug release of both drug.
Results and discussion: Optimized batch (F*) containing 16.75% poloxamer 407 and 0.54% HPMC K4M were exhibited all results in acceptable limits. Compared with the marketed formulation, optimized in situ gel showed delayed Tmax, improved Cmax and AUC in rabbit aqueous humor, suggesting the sustained drug release and better corneal penetration and absorption.
Conclusion: According to the study, it could be concluded that DSP and TS would be successfully formulated as in situ gelling mucoadhesive system for the treatment of steroid responsive eye infections with the properties of sustained drug release, prolonged ocular retention and improved corneal penetration. 相似文献
Titanium is widely used as medical implant material and as condenser material in the nuclear industry where its integrity is questioned due to its susceptibility to bacterial adhesion. A systematic investigation on the influence of thermally (50–800 °C) stabilized titanium (TS-Ti) nano oxide towards bacterial adhesion was carried out. The results showed that below 350 °C significant bacterio-phobicity was observed, while above 500 °C significant affinity towards bacterial cells was recorded. Conventional characterization tools such as HR-TEM and XRD did not provide much insight on the changes occurring on the oxide film with heat treatment, however, attenuated total reflection fourier transform infrared spectroscopy (ATR-FTIR) of the surface showed significant changes in the spectral pattern as a function of increasing heat treatment. It was observed that elevated OH, N–H and C=O groups and rutile titania on the TS-Ti oxide films led to higher affinity for bacterial adhesion. On the other hand low temperature TS-Ti nanooxide films (<350 °C) showed high C–H groups and decreased OH groups on their surface, which possibly contributed towards their bacterio-phobicity. The TS-Ti nanooxide film grown at 50 °C was observed to be the most efficient anti-bacterial adhesion interface, while the 800 °C interface was the one showing highest affinity towards bacterial adhesion. This study confirms the successful application of ATR-FTIR technique for nano-oxide film characterization and towards understanding the variations in bacterial interaction of such nano interfaces. 相似文献
In this paper, we develop mathematical models for simultaneous consideration of suitability and optimality in asset allocation. We use a hybrid approach that combines behavior survey, cluster analysis, analytical hierarchy process and fuzzy mathematical programming. 相似文献
View materialization is an important way of improving the performance of query
processing. When an update occurs to the source data from which a materialized view is
derived, the materialized view has to be updated so that it is consistent with the source
data. This update process is called view maintenance. The incremental method of view
maintenance, which computes the new view using the old view and the update to the
source data, is widely preferred to full view recomputation when the update is small in
size. In this paper we investigate how to incrementally maintain views in object-relational
(OR) databases. The investigation focuses on maintaining views defined in OR-SQL, a
language containing the features of object referencing, inheritance, collection, and aggregate
functions including user-defined set aggregate functions. We propose an architecture and
algorithms for incremental OR viewmaintenance. We implement all algorithms and analyze
the performance of them in comparison with full view recomputation. The analysis shows
that the algorithms significantly reduce the cost of updating a vieww hen the size of an
update to the source data is relatively small.
Received 23 May 2000 / Revised 27 March 2001 / Accepted in revised form 30 April 2001
Correspondence and offprint requests to: Jixue Liu, School of Computer and Information Science, University of South Australia, Mawson Lakes, Adelaide SA5084, Australia.
Email: jixue.liu@unisa.edu.auau 相似文献
This letter presents a filtering directional coupler (FDC) with enhanced coupling and high directivity simultaneously. The proposed FDC is composed of a pair of coupled lines instead transmission line of a directional coupler. This coupled lines resonator increases the design parameters by which even/odd mode phase velocity can be compensated to improve the directivity and coupling level. The coupling enhancement can be explained by analyzing the even mode and odd mode circuit of the proposed coupler. A prototype of the proposed coupler is designed which provides a high directivity of 44 dB for 6 dB coupling level at 1 GHz frequency. The proposed coupler is designed, fabricated, and tested. 相似文献
Twitter is a radiant platform with a quick and effective technique to analyze users’ perceptions of activities on social media. Many researchers and industry experts show their attention to Twitter sentiment analysis to recognize the stakeholder group. The sentiment analysis needs an advanced level of approaches including adoption to encompass data sentiment analysis and various machine learning tools. An assessment of sentiment analysis in multiple fields that affect their elevations among the people in real-time by using Naive Bayes and Support Vector Machine (SVM). This paper focused on analysing the distinguished sentiment techniques in tweets behaviour datasets for various spheres such as healthcare, behaviour estimation, etc. In addition, the results in this work explore and validate the statistical machine learning classifiers that provide the accuracy percentages attained in terms of positive, negative and neutral tweets. In this work, we obligated Twitter Application Programming Interface (API) account and programmed in python for sentiment analysis approach for the computational measure of user’s perceptions that extract a massive number of tweets and provide market value to the Twitter account proprietor. To distinguish the results in terms of the performance evaluation, an error analysis investigates the features of various stakeholders comprising social media analytics researchers, Natural Language Processing (NLP) developers, engineering managers and experts involved to have a decision-making approach. 相似文献