和田师专学生档案管理系统的设计与实现

该文以和田师专学生档案管理为研究背景,结合学生档案管理系统的设计与实现,研究了基于分布式应用系统原理、设计和实现的问题。全国各大专院校及一些中专和中学的校园网建设已进入蓬勃发展的阶段。校园网建成以后,需要在校园网上建设一个全校范围的、开放的、分布的学生档案管理系统。文中论述了符合新疆特色的大专学校学生档案管理系统的一般构成,论述了校园网络与学生档案管理系统的关系。     

Performance evaluation of framework of VoIP/SIP server under virtualization environment along with the most common security threats

Neural Computing and Applications - Virtualization is the central point empowering cloud infrastructure. Many services, such as web-based applications, databases, and instant messaging servers, are...     

Quality practices in design organizations

Design organizations play a major role in the construction industry: they are the media that transfer the requirements of the client to the contractor and ensure that they are met. Thus they need to provide a high quality of service to ensure that their client's project achieves the best possible standards of cost, time and quality. Seventy quality practices (QP) were identified as having a bearing on the quality of service provided by the local design organizations. These quality practices were grouped into fifteen sections termed quality sections (QS). The prevalence of these practices among the local design organizations was surveyed and determined. The results indicate a significant need for improvement in the quality sections ‘working relationship’, ‘employee training and education’, and ‘performance quality audit’. The study reveals the need for the establishment of a design code, and evaluation standards for local design organizations.     

Composite mixed matrix membranes incorporating microporous carbon molecular sieve as filler in polyethersulfone for CO2/CH4 separation

Membrane technology has been considered a key factor for sustainable growth in high-efficiency gas separation. Current mixed matrix membranes (MMMs) technology is rising, but these membranes in the dense structure are having difficulties in operating at high pressures and scale up for commercialization. The purpose of this research is to synthesize composite MMMs (CMMMs) consisting of polyethersulfone (PES), carbon molecular sieve (CMS 1–5 wt %), and Novatex 2471 nonwoven fabric (support layer). The membranes' physical, chemical, and thermal properties were evaluated by different analytical equipment. The morphology of both PES and PES-CMS composite membranes had a porous and asymmetric structure, in which CMS was uniformly distributed in the polymer matrix. The thermal properties showed that the membranes were stable up to 350 °C with a single glass transition temperature. The functional groups in the membrane were confirmed by spectral analysis. The gas performance results showed that carbon dioxide permeance increased with increased CMS concentration and methane permeance decreased due to the hindering effect of CMS under similar operating conditions. The highest selectivity achieved was 12.774 using CMMM of 5 wt % of CMS at 10 bar, which on average was 137.80%, improved selectivity compared to pure PES membrane. The support layer was able to withstand high operating pressures and showed the ability to scale up. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48476.     

Growth and aflatoxin production by Aspergillus parasiticus in a medium at different pH values and with or without pimaricin

A glucose-yeast extract-salt medium containing 0, 5, 7.5, 10, 15 or 20 micrograms pimaricin/ml with an initial pH of 3.5 or 5.5 was inoculated with Aspergillus parasiticus WB 108 and incubated at 15 degrees or 28 degrees C. The pH, weight of mycelium and amount of aflatoxin produced were determined after 3, 7, and 10 days and after 14, 21, and 30 days when incubation was at 28 degrees or 15 degrees C, respectively. Increasing the concentration of pimaricin in the medium with an initial pH of 5.5 decreased the amounts of aflatoxin B1 and G1 produced after 3 days of incubation. When the initial pH of the medium was 3.5, no growth or toxin production occurred after 3 days of incubation in the medium containing 7.5 micrograms or more of pimaricin/ml. The presence of 20 micrograms of pimaricin/ml inhibited growth and toxin production after 7 days of incubation. When cultures were incubated at 15 degrees C, there was a lag phase which extended from 9 to 16 days, and the amounts of aflatoxin produced decreased with an increasing concentration of pimaricin. Pimaricin did not completely inhibit the growth and aflatoxin production by A. parasiticus. Pimaricin, in combination with a low pH, low temperature or 4% or 6% NaCl, initially caused slow mycelial growth and low toxin production, but the mold overcame the inhibitory effects and produced substantial amounts of mycelium and toxin.     

Prevalence of Salmonella in broilers at retail outlets, processing plants and farms in Malaysia

A study was conducted to estimate the prevalence of Salmonella among broilers retailed at wet-markets and processing plants. Litter and feed samples obtained from both broiler and breeder farms were also examined for Salmonella. A total of 158 out of 445 (35.5%) and 52 out of 104 (50.0%) broiler carcasses obtained from wet-markets and processing plants were contaminated with Salmonella, respectively. Salmonella was isolated from 14 out of 98 (14.3%) samples of intestinal content. Litter samples from broiler and breeder farms were positive for Salmonella, 8/40 (20%) and 2/10 (20%), respectively. Salmonella isolates (230) belonging to 15 different serovars were isolated. Predominant serovars were S. enteritidis, S. muenchen, S. kentucky and S. blockley.     

Spectrum blind reconstruction and direction of arrival estimation of multi-band signals at sub-Nyquist sampling rates

In this paper we consider the problem of spectrum blind reconstruction (SBR) and direction of arrival (DOA) estimation of constituent sources of a disjoint multi-band signal (MBS) at sub-Nyquist sampling rates. Transformation of the problem into frequency domain indicates that the steering vector is a function of both the carrier frequency and its corresponding DOA. Employing the existing two dimensional frequency-DOA search algorithms suffers from the drawbacks of increased computational complexity and ambiguity issues. To overcome these drawbacks, in this paper we propose a simple modification to the receiver architecture by introducing an additional delay channel at every sensor. Estimation algorithms based on ESPRIT is then employed to estimate the carrier frequencies, while MUSIC algorithm is employed to estimate their corresponding DOAs. Using the knowledge of both these parameters, the MBS spectrum is then reconstructed. A two-dimensional iterative grid refinement algorithm is also described to further improve the estimation accuracy in the presence of noise. Identifiability issues are addressed and the conditions for unique identifiability are discussed. Furthermore, by assuming a two dimensional uniform array the advantages of the proposed approach in terms of identifiability is also provided. We further show that an \(M \ge N+1\) sensors and an overall sampling rate of at least \(2(N+1)B\) would be sufficient to achieve SBR and DOA estimation of an MBS comprising of N disjoint bands each of maximal bandwidth B. Numerical simulations are finally presented which verifies the validity of the proposed approach and compares the performance against appropriate bounds.     

Compact Frequency and Bandwidth Reconfigurable Microwave Filter

This paper details the construction and working of a compound reconfigurable filter capable of frequency and bandwidth reconfiguration in the frequency range from 2 to 3 GHz. The switching between frequency and bandwidth reconfiguration is inherited by two PIN diodes. Bandwidth tuning is facilitated by tuning two transmission zeros individually using varactor diodes, giving flexibility in reconfiguring the upper and lower pass edges. The two transmission zeros are obtained using simple concentric square loop resonators. The maximum bandwidth obtained is 1.5 times the minimum bandwidth offered by the filter. Hence the filter can be used for dynamic bandwidth allocation. This prototype is fabricated and validated in real-time. The simulated and measured results are analogous to each other.

     

Integrated Vivaldi antenna for UWB/diversity applications in vehicular environment

This article presents the design of a three‐port diversity antenna capable of producing three‐directional radiation pattern for vehicular communications. The proposed antenna consists of three uncorrelated Vivaldi antennas that are interconnected and developed on a single printed circuit board. Unlike many other antennas reported for the vehicular environment, the proposed antenna offers ultra‐wideband characteristics with end‐fire radiation pattern leading to high realized antenna gain. The integrated antenna has a footprint of 65 × 40 × 1.6 mm³ and offers 6 GHz impedance bandwidth extending from 5 to 11 GHz. The port‐to‐port isolation is greater than 20 dB within the operating bandwidth. Furthermore, the diversity performance of the proposed three‐port antenna system is evaluated and presented. The calculated envelope correlation coefficient, diversity gain, and mean effective gain are well above the minimum requirement. The prototype antenna is fabricated and the experimental results are presented.     

Gain enhanced multipattern reconfigurable antenna for vehicular communications

This article presents the design and implementation of a high‐gain tunable dual‐band pattern reconfigurable antenna for vehicular communications. The proposed antenna consists of a slotted patch loaded with a double‐side FSS acting as superstrate. The proposed slotted antenna operates at 2.45 and 3.5 GHz and the frequency tuning over the dual‐band is accomplished by employing a varactor diode for tuning the center frequency from 2.41 to 2.62 GHz and from 3.38 to 3.65 GHz at lower and upper frequency bands, respectively. To obtain pattern reconfiguration, the slotted patch is divided into four regions by using two diagonal lines of vias. By properly choosing the excitation port combinations, 14 different radiation patterns are realized with a maximum realized gain of 8.4 and 7.9 dB. Further enhancement of gain is achieved using frequency‐selective surface (FSS) screens which act as a partially reflecting surface. The unique feature of this design is to provide reflection coefficient with high reflectivity in two predetermined frequency ranges. The prototype antenna is fabricated and the measurement results are reported. The experimental results show that the prototype antenna with FSS offers tunable dual‐band with beam reconfigurable properties.