Film formation from PS/AL2O3 nanocomposites prepared by dip‐drawing method

In this study, steady state fluorescence (SSF) and UV–vis (UVV) techniques were used to examine film formation from pyrene (P) labeled polystyrene (PS) latex/Al₂O₃ (PS/Al₂O₃) composites prepared by the dip‐drawing method. The effects of dip‐drawing rates and dipping time in Al₂O₃ sol on film formation behavior and the morphology of PS/Al₂O₃ films were investigated. Films were prepared first by casting PS dispersion on clean glass substrates which creates a close‐packed array of PS sphere (203 nm) templates. These templates were then covered with Al₂O₃ utilizing the dip‐drawing method for various dip‐drawing rates and dipping times in Al₂O₃ sol. The film formation of these composites was studied by annealing them at a temperature range of 100°C to 270°C and monitoring the scattered light (I_sc), fluorescence (I_P), and transmitted light (I_tr) intensities after each annealing step. The structural properties of the composite films were analyzed with a scanning electron microscope (SEM). The results demonstrated that the film formation behavior and morphology of composites depended mainly on dipping time, and no dependence on the dip‐drawing rate was observed. The optical results indicated that PS/Al₂O₃ films undergo complete film formation independent of the dip‐drawing rate and dipping time. Additionally, the film formation stages were modeled and the corresponding activation energies were determined. After completion of film formation, PS polymers were extracted to obtain porous Al₂O₃ thin films. Highly ordered porous structures were observed for long dipping time in Al₂O₃ sol but no change was observed for different dip‐drawing rates, confirming the optical data. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Partitioning behavior of trace elements during pilot-scale fluidized bed combustion of high ash content lignite

This study describes the partitioning of 20 trace elements (As, B, Ba, Cd, Co, Cr, Cu, Hg, Li, Mn, Mo, Ni, P, Pb, Sb, Se, Sn, Tl, V, Zn) and eight major and minor elements (Al, Ca, Fe, K, Mg, Na, Si, Ti) during the combustion of high ash content lignite. The experiments were carried out in the 0.3 MW(t) Middle East Technical University (METU) atmospheric bubbling fluidized bed combustor (ABFBC) test rig with and without limestone addition. Inert bed material utilized in the experiments was bed ash obtained previously from the combustion of the same lignite without limestone addition in the same test rig. Concentrations of trace elements in coal, limestone, bottom ash, cyclone ash and filter ash were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Partitioning of major and minor elements are influenced by the ash split between the bottom ash and fly ash and that the major proportion of most of the trace elements (As, Ba, Cr, Hg, Li, Mo, Ni, Sn, V, Zn) are recovered in fly ash. Limestone addition shifts the partitioning of Ba, Cr, Mo, Ni, Sn, V, Zn from bottom ash to fly ash.     

Power and area efficient MOSFET-C filter for very low frequency applications

New circuit design techniques for implementing very high-valued resistors are presented, significantly improving power and area efficiency of analog front-end signal processing in ultra-low power biomedical systems. Ranging in value from few hundreds of M\Upomega\hbox{M}\Upomega to few hundreds of G\Upomega\hbox{G}\Upomega, the proposed floating resistors occupy a very small area, and produce accurately tunable characteristics. Using this approach, a low-pass MOSFET-C filter with tunable cutoff frequency (f _C  = 20 Hz–184 kHz) has been implemented in a conventional 0.18 μm CMOS technology. Occupying 0.045 mm²/pole, the power consumption of this filter is 540 pW/Hz/pole with a measured IMFDR of 70 dB.     

A 10-bit 50-MS/s redundant SAR ADC with split capacitive-array DAC

A new architecture for successive-approximation register analog-to-digital converters (SAR ADC) using generalized non-binary search algorithm is proposed to reduce the complexity and power consumption of the digital circuitry. The proposed architecture is based on the split capacitive-array DAC with a simple switching logic as compared to the conventional non-binary SAR ADC architecture. A 10-bit 50-MS/s SAR ADC is designed based on the proposed architecture in a 0.18 μm CMOS technology. Simulation results show that at a supply voltage of 1.2 V, the SAR ADC achieves a peak signal-to-noise-and-distortion ratio of 59.5 dB, and a power consumption of 1.3 mW, resulting in a figure of merit of 33 fJ/conversion-step.     

Failure mechanism of FBGA solder joints in memory module subjected to harmonic excitation

This paper investigates the failure mechanism of Fine-pitch Ball Grid Array (FBGA) solder joints of memory modules due to harmonic excitation by the experiments and the finite element method. A finite element model of the memory module was developed, and the natural frequencies and modes were calculated and verified by experimental modal testing. Modal damping ratios are also obtained and used in the forced vibration analysis. The experimental setup was developed to monitor resistance variation of FBGA solder joints due to the harmonic excitation under Joint Electron Devices Engineering Council (JEDEC) standard service conditions. Experiments showed that the failure of the solder joints of the memory module under vibration mainly occurs due to resonance. Forced vibration analysis was performed to determine the solder joints having high stress concentration under harmonic excitation. It showed that failure occurs due to the relative displacement between PCB and package and solder joints are the most vulnerable part of the memory module under vibration. It also showed that cracked solder joints in the experiments match those in the simulations with the highest stress concentration.     

Electrical analysis of a hybrid photovoltaic-hydrogen/fuel cell energy system in Denizli, Turkey

In recent years, hybrid photovoltaic-hydrogen/fuel cell energy systems have been popular as energy production systems that are clean, environmental-friendly, modular, and independent from fossil fuels. In February 2007, a clean energy research facility consisting of a 5 kWp photovoltaic system and a 2.4 kWp hydrogen-fuel cell system was built to investigate these energy production technologies at Pamukkale University in Denizli, Turkey. In this hybrid energy system, electricity is generated by photovoltaic panels. Generated electrical energy is stored chemically in batteries and metal hydride hydrogen canisters. Hydrogen electrolyzed from water is transformed to DC electrical energy by two fuel cells in the case of its necessity. DC electricity produced by photovoltaic panels and fuel cells is converted to AC by two inverters for the requirements of the building. In this study, an electrical energy analysis of the building, in terms of energy efficiency, harmonics, voltage changes, voltage and current sags, voltage and current swells, transients, power outage, frequency changes etc., is performed to evaluate the power quality of the hybrid energy system. In addition, some measurements such as insulation resistance, loop impedance, line impedance, grounding resistance, and specific resistance of the ground are measured to obtain the electrical characteristics of the system.     

Characterisation of Wolbachia-like bacteria isolated from the parthenogenetic stored-product pest psocid Liposcelis bostrychophila (Badonnel) (Psocoptera)

The widespread psocid, Liposcelis bostrychophila, is a stored-product pest of grain and farinaceous foods. Its ubiquity is in part due to its parthenogenetic reproduction which is shown to be the result of the presence of rickettsial bacteria in the ovaries and developing oocytes. Based on similarities in 16S rDNA sequences, the bacteria are identified as Wolbachia-like. There is little difference in these sequences among a number of L. bostrychophila populations from around the UK and there was no correlation with patterns of similarity among the insect 12S rDNA sequences.Treatment with antibiotics and heat reduced or removed the bacterial infections. Rifampicin (1%) produced aposymbiotic psocids within 4 weeks and the egg production in such treated individuals was greatly reduced. Tetracycline and maintenance at a temperature of 37°C reduced the bacterial loads in the oocytes but did not significantly impact egg production. Closely related bisexual psocid species have no detectable 16S rDNA, which supports EM observations, and were unaffected by the antibiotic treatments.     

Overcoming the limitations of current meta-analysis of randomised controlled trials

For a meta-analysis to give definitive information, it should meet at least the minimum standards that would be expected of a well-designed, adequately powered, and carefully conducted randomised controlled trial. These minimum standards include both qualitative characteristics--a prospective protocol, comparable definitions of key outcomes, quality control of data, and inclusion of all patients from all trials in the final analysis--and quantitative standards--an assessment of whether the total sample is large enough to provide reliable results and the use of appropriate statistical monitoring guidelines to indicate when the results of the accumulating data of a meta-analysis are conclusive. We believe that rigorous meta-analyses undertaken according to these principles will lead to more reliable evidence about the efficacy and safety of interventions than either retrospective meta-analysis or individual trials.     

K and Ca content of fresh green tea, black tea, and tea residue determined by X-ray fluorescence analysis

Summary X-Ray fluoresence (XRF) can be successfully used for the qualitative and quantitative elemental analysis of various agricultural products. Its simplicity, high throughput and the possibility of automation make it useful for screening large numbers of samples. The K and Ca content of 138 samples of fresh green tea, black tea and black tea residues were determined by applying the XRF system. Such a method of mineral analysis of food products is not very common. Tea from different teagrowing areas of Turkey, green tea of different shooting periods, black tea processed at different tea plants and tea residues from these black tea were analysed. The K content of green tea, processed black tea and tea residues after brewing were found to have ranges of 19,049–26,254 mg/kg, 21,904–26,883 mg/kg and 9,468–13,778 mg/kg, respectively. In the same samples the Ca content was determined as 3,580–4,799 mg/kg, 3,370–4,823 mg/kg, and 3,743–5,733 mg/kg, respectively. These findings were compared with the results of atomic emission techniques and it was concluded that the XRF system could be effectively used for quantitative analysis of the K and Ca content of tea samples.

---

Die Bestimmung des K- und Ca-Gehaltes von frischem Tee, schwarzem Tee und Teerückstand durch die X-Ray-Fluoreszenz-Technik

Zusammenfassung Mit der X-Ray Fluoreszenztechnik können die qualitativen und quantitativen Bestimmungen der Mineralstoffe in verschiedenen Produkten erfolgreich durchgeführt werden. Mit dieser Methode wurde der Ca- und K-Gehalt von 138 Proben untersucht, und zwar frischer Tee, schwarzer Tee und Teerückstand. Diese Methode ist in der Lebensmitteltechnologie, insbesondere bei der Mineralstoffbestimmung nicht üblich. Die Teeproben stammten aus verschiedenen Teeanbaugebieten der Türkei. In dieser Arbeit wurden die Wirkung der Sproßperiode, der Verarbeitungstechnik und des Anbaugebietes auf den Ca- und K-Gehalt der Teeproben untersucht. Der durchschnittliche K-Gehalt betrug: in frischem Tee 19049–26254 mg/kg, in schwarzem Tee 21904–26883 mg/kg, in Teerückstand 9468–13778 mg/kg; der Ca-Gehalt 3580–4799 mg/kg, 3370–4823 mg/kg und 3473–5733 mg/kg.

     

基于BERT及双向GRU模型的慕课用户评论情感倾向性分析

以实现慕课网用户评论的情感倾向性分析为目的,本文提出一种基于BERT和双向GRU模型的用户评论情感倾向性分类方法。首先使用BERT模型提取课程评论文本的特征表示,其次将获取的词语特征输入BiGRU网络实现用户评论的情感特征的提取,最后用Softmax逻辑回归的方式进行情感倾向性分类。实验结果表明基于BERT和双向GRU模型的评论情感倾向性分类模型的F1值达到92.5%,提高了用户情感倾向性分析的准确率,从而验证了方法的有效性。