电力电子技术中虚拟原型和综合多目标优化技术研究(上)

新的拓扑结构,新的调制方法和未来的宽能带隙的半导体器件技术将会满足电力电子系统更高效率,更高功率密度和更低成本的要求。但是,在设计过程中通过使用多范畴/多目标优化,亦即对设计变量都用最优值,也能显著地提高目前技术系统的性能。为了实现这些优化,首先需要对主电路建立一个综合的数学模型,包括热模型,DM和CM EMI滤波器模型。基于这些模型,可以得到诸如效率,功率密度等的多目标优化。优化可以充分地使用所有的设计自由度,也允许确定根据诸如功率半导体器件的品质因数或磁芯材料的性质等基本技术决定的系统性能的敏感度。而且,能够容易地比较不同拓扑结构和识别固有性能的限制。本文首先描述设计一个电力电子变换器的主要功能要素的分析途径和一个线性设计过程。接着连接诸如电、磁、热和热-机设计范畴的元件模型,讨论基于这些连接模型的各个设计变量的优化。最后,研究不同范畴的耦合和实施这些耦合的等效电路的利用实例。     

Application of fuzzy logic for evaluation of the level of social acceptance of waste treatment

The social aspect is very important in sustainability assessment of waste treatment technique, as well as making decision on their application and planning. In recent years, it is becoming evident that a waste treatment technique, which ignores social aspects, is doomed to failure. The most commonly used social indicators are: number of jobs created, level of social acceptance, public knowledge, public health etc. The most of them are qualitative and measuring the sustainability and quantifying the social dimension of sustainability are difficult tasks. This paper presents the application of fuzzy logic for evaluating the social indicator—level of social acceptance. The fuzzy set theory and fuzzy logic were used to develop a model for the evaluation of level of social acceptance, due to the lack of data, uncertainties, and qualitative character of indicators and also to provide effective way to include knowledge and gained experience on the process. A questionnaire was applied as instrument for data collection. The fuzzy model was verified using the city of Ni? as a case study. The results obtained using the developed fuzzy model, shows that the highest level of social acceptance in the city of Ni? is for recycling (57.47 %) and the lowest level of social acceptance is for incineration (17.74 %). The presented study suggests an innovative methodology for evaluation of level of social acceptance of certain waste treatment based on fuzzy logic approach and can be used for ranking of waste management scenarios in the sustainability assessment.     

Identification of Secretory Compounds from the European Callipodidan Species <Emphasis Type="Italic">Apfelbeckia insculpta</Emphasis>

Defensive secretions of the callipodidan species Apfelbeckia insculpta contain a p-cresol as the main component and phenol in traces. This is the first identification of these compounds in a European callipodidan species. The repugnatory glands of A. insculpta are of the spirobolid type and consist of a spherical reservoir, a simple duct, and a valvular cuticular infolding that opens onto the lateral surface of the millipede via a pore.     

Substituted imino and amino derivatives of 4-hydroxycoumarins as novel antioxidant,antibacterial and antifungal agents: Synthesis and in vitro assessments

A series of imino and amino derivatives of 4-hydroxycoumarins were synthesised and evaluated for antioxidant potential, through different in vitro models such as (DPPH) free radical-scavenging activity, linoleic acid emulsion model system, reducing power assay and phosphomolybdenum method. Also, antimicrobial activity of obtained coumarins was evaluated against 13 bacteria and eight fungi. All prepared compounds possessed good antioxidant activity and among them a p-nitrophenol derivative with IC₅₀ at 25.9 μM possessed radical-scavenging activity which was comparable to BHT. Observed data for antibacterial activity indicated strong activity of all tested amino derivatives, while imines showed better antifungal properties.     

Characterizing the structure of pharmaceutical granules obtained by wet granulation with varying amounts of water via Raman chemical imaging

A pharmaceutical formulation containing metformin hydrochloride (MET), hydroxypropyl cellulose (HPC), and microcrystalline cellulose (MCC) was wet granulated with varying amounts of water and the structure of the obtained granules was characterized by Raman chemical mapping. Univariate Raman mapping was found to be satisfactory for producing the images of the two components of interest (HPC and MCC). In addition to the images, the average Raman spectra from the maps as well as the micro-Raman spectra from the hot pixels were analyzed. HPC is found to strongly respond to the addition of water, with its domain dissipating and Raman bands becoming weaker as the water addition increases. MCC is also responsive to water, reacting similarly to HPC but to a much smaller extent and only for the largest amounts of water. Granules made with increasing water content also have improved tabletting properties and flow.     

Effects of Al2O3 particle reinforcement on the lubricated sliding wear behavior of ZA-27 alloy composites

The present investigation deals with the effect of Al₂O₃ particle reinforcement on the lubricated sliding behavior of ZA-27 alloy. The composites with 3, 5, and 10 wt% of Al₂O₃ particles were produced by the compocasting procedure. Tribological properties of alloy and composites were studied, using block-on-disk tribometer at different specific loads and sliding speeds. The test results revealed that composite specimens exhibited significantly lower wear rate, but higher coefficient of friction than the matrix alloy specimens in all the combinations of applied loads and sliding speeds. The improved antiwear characteristics of the composites were influenced by positive effects of higher frictional heating on compatibility of the composite phases and suppressing micro-cracking tendency. Due to that, effects of reinforcing hard particles were manifested through the reduced wear rate of composites, especially in conditions of higher load, lower sliding speeds and higher Al₂O₃ particle content. In present wear tests, the significant forming of mechanically mixed layers was not noticed, what is confirmed by the SEM microphotographs.     

Study of multicycle melting and freezing of sodium thiosulphate pentahydrate

The behaviour of sodium thiosulphate pentahydrate in the course of repeated use as a heat-storing medium can be predicted, cycle by cycle, on the basis of a generalised phase-transition equation adapted for incongruently melting material. An indice is derived for this purpose and named ‘coefficient of true phase-transition reversibility’. Its predictive value is shown for three additional incongruently melting materials well known as heat-storing media: CaCl₂.6H₂O, Na₂SO₄.10H₂O and the mixture Na₂SO₄.10H₂O + 2/3NH₄Cl + 2/3NaCJ.     

A biometric identification system based on eigenpalm and eigenfinger features

This paper presents a multimodal biometric identification system based on the features of the human hand. We describe a new biometric approach to personal identification using eigenfinger and eigenpalm features, with fusion applied at the matching-score level. The identification process can be divided into the following phases: capturing the image; preprocessing; extracting and normalizing the palm and strip-like finger subimages; extracting the eigenpalm and eigenfinger features based on the K-L transform; matching and fusion; and, finally, a decision based on the (k, l)-NN classifier and thresholding. The system was tested on a database of 237 people (1,820 hand images). The experimental results showed the effectiveness of the system in terms of the recognition rate (100 percent), the equal error rate (EER = 0.58 percent), and the total error rate (TER = 0.72 percent).     

Torque calculation between circular coils with inclined axes in air

In this paper we derive new semi‐analytical expressions for calculating the electromagnetic torque between inclined circular coils in air. The torque calculation has been obtained from the corresponding mutual inductance between inclined circular coils using the filament method. The coils of rectangular cross‐section whose centers are at the same and the different axes have been considered. From this general case it is possible to calculate the torque between all possible coil combinations either with rectangular or neglected cross‐section. Results obtained by the presented approach are in very good agreement with already published data. This method can be used for industrial electromagnetic devices such as torque sensors, transducers and torque‐measuring devices. Copyright © 2010 John Wiley & Sons, Ltd.     

Nanomotion Detection Method for Testing Antibiotic Resistance and Susceptibility of Slow‐Growing Bacteria

Infectious diseases are caused by pathogenic microorganisms and are often severe. Time to fully characterize an infectious agent after sampling and to find the right antibiotic and dose are important factors in the overall success of a patient's treatment. Previous results suggest that a nanomotion detection method could be a convenient tool for reducing antibiotic sensitivity characterization time to several hours. Here, the application of the method for slow‐growing bacteria is demonstrated, taking Bordetella pertussis strains as a model. A low‐cost nanomotion device is able to characterize B. pertussis sensitivity against specific antibiotics within several hours, instead of days, as it is still the case with conventional growth‐based techniques. It can discriminate between resistant and susceptible B. pertussis strains, based on the changes of the sensor's signal before and after the antibiotic addition. Furthermore, minimum inhibitory and bactericidal concentrations of clinically applied antibiotics are compared using both techniques and the suggested similarity is discussed.