消除串扰自激的工程应用实例

在实际工程中,系统在设计加工出来以后,电路结构都已经确定,但是在调试过程中会出现各种问题,要求有大量调试的经验。文章以C波段的接收机的调试为例,给出了几种消除串扰自激的实例应用,从而很好的解决了射频高增益放大器由于串扰信号进入而引起自激的现象,使得系统工作状态正常稳定,为工程实践提出一些经验,借鉴。     

Needle-disk electrospinning inspired by natural point discharge

Point discharge is a natural phenomenon which principle and application are both under active investigation. In this work, a needle-disk electrode spinneret was designed through the combination of the point discharge concept and the merits of typical needleless electrospinning (disk as spinneret). The desired outcome for point electrode system is to produce a controllable process of jet formation, with respect to the control of jet site and amount of jets under a lower applied voltage value. Two comparisons were used: (i) in comparison to the typical needleless electrospinning method (disk electrospinning), the needle-disk electrospinning produce finer and more uniform nanofibers. Further numerical simulation results confirmed that the needle-disk electrode induced electric field intensity which is 5.33 times higher than that of disk electrode under the same parameters; (ii) both the numerical simulation and experimental results showed that needle-disk electrospinning can produce competitive quality of nanofibers accompanied by enhanced throughput, compared with the traditional single-needle electrospinning method. Finally, we demonstrate that needle-disk electrospinning produces nanofiber with super-high throughput of 13.5 g/h, which is 183 times higher than traditional electrospinning under similar spinning conditions.     

Estimation of the kinetic parameters of chlorinated polyvinyl chloride waste pyrolysis by particle swarm optimization

Chlorinated polyvinyl chloride (CPVC) is a widely-used material in various fields with excellent properties. However, CPVC waste is one of the most intractable solids to dispose of. With the development of pyrolysis technology, some advantages have been exhibited, for example, it is flexible to convert solid waste into clean products by pyrolysis, which can be used as energy. Therefore, pyrolysis is considered as an effective method to dispose of solid waste. Especially, kinetic parameters are significant for pyrolysis, which contributes to reactor design and waste management. To better apply the kinetic parameters of CPVC to dispose of waste, thermogravimetric experiments were conducted to obtain the kinetic parameters and establish the reaction mechanism. The Tang, distributed activation energy model, and Advanced Vyazovkin methods were used to calculate the activation energy, and the reaction order was obtained by the Coats-Redfern method. The results showed that the reaction consisted of two stages, and the average activation energy of the corresponding stage was 153.27 and 290.55 kJ/mol, respectively. However, the abovementioned parameters by traditional methods were not enough to characterize the whole pyrolysis behaviors, then the obtained kinetic parameters were further optimized and extra parameters were computed by the Particle Swarm Optimization algorithm.     

Physicochemical characterization and thermal behavior of hexosomes containing ketoconazole as potential topical antifungal delivery system

Objective: The main purpose of this article is to show the valuable characteristics that liotropic liquid crystal systems possess to be employed as new drug delivery systems.

Significance: Colloidal aqueous dispersions of lyotropic liquid crystal mesophases such as the identified as cubosomes and hexosomes, and so on, have received considerable attention due to their unique nanostructures and their thermodynamic properties, which provide the potential as a sustained drug release matrix. Additionally, their large surface area and similarity with the liquid crystal structures of intercellular lipids of stratum corneum enhances the interaction with the skin and mucous, increasing the potential for topical drug delivery efficiency of biopharmaceutical class II drugs as the antifungal ketoconazole.

Methods: This article presents the results in morphological characteristics, particle size, ζ potential, flow, thermal behavior and drug release studies of hexosomes containing ketoconazole (LHLC-K) obtained with glycerol monooleate, propylene glycol monolaurate, poloxamer, and water mixtures.

Results: This colloidal system exhibits a Newtonian-type flow and a hexagonal nanostructure with a median particle size of 107?±?20?nm and ζ potential of +4.45?±?0.50?mV. Through differential scanning calorimetry studies, the LHLC-K demonstrated physical and chemical stability for more than six months and mesophasic thermal reversibility between 10 and 50?°C. Finally, LHLC-K releases ketoconazole following a kinetics described by the first order model.

Conclusions: Physicochemical properties of the hexosomes containing ketoconazole are important for topical mycosis treatment administration, conditions of storage, and for its incorporation into the formulation of semi-solid dosage forms.     

Electric current–assisted direct joining of silicon carbide

Conventional direct joining technologies are difficult to use with silicon carbide (SiC) materials, especially for fiber composite forms of SiC, because of the harsh conditions required. To reduce the temperature and/or process time required for the direct joining process, an electric current–assisted joining (ECAJ) method was studied. Joining of low–resistivity grade, nitrogen doped β-SiC was demonstrated at a relatively low nominal temperature of 1750 °C with a 10 min hold by enhancing the passage of current through the material. The joining mechanism is discussed in terms of localized overheating and accelerated self-diffusion at the interface. In the case of joining at 2160 °C for 1 min, rapid crystal growth of textured SiC was found at the interface. This study indicates that rapid ECAJ-based direct joining is a practical and appropriate method for joining SiC-based materials.     

无监督网络对抗生成模型的研究

一般的学习模型都是基于一个假设的随机分布,然后通过训练真实数据来拟合出模型。网络模型复杂并且数据集规模也不小,这种方法简直就是凭借天生蛮力解决问题。Goodfellow认为正确使用数据的方式,是先对数据集的特征信息有insight之后,再干活。无监督学习是当下较为流行的话题,但也是困难较为繁多的话题。目前无监督学习可以分成以下两类,分别是确定型的自编码方法以及概率型的受限波尔兹曼机,其目标主要是使受限玻尔兹曼机达到稳定状态时原数据出现的概率最大。如何更快速更有效地地搭建模型以及如何做实验并有效地获得相关的实验结论是人们讨论的重点。在研究中,在判别模型中增加正则化,用卷积层代替池化层,在生成模型中输出层使用tanh激活函数激活,这样使得最终运算的准确率和损失率大大下降,并减少了冗余成分。     

Understanding the structural evolution of Au/WO2.7 compounds in hydrogen atmosphere by atomic scale in situ environmental TEM

Hydrogen energy is a resuscitated clean energy source and its sensitive detection in air is crucial due to its very low explosive limit. Metal oxide decorated with noble metal nanoparticles has been used for the enhancement of gas detection and exhibits superior sensitivity. Understanding the intrinsic mechanism of the detection and the enhancement mechanism is thus becoming a fundamental issue for the further development of novel metal/oxide compound gas-sensing materials. However, the correlation between the microstructural evolution, the charge transport and the complex sensing process has not yet been directly revealed and its atomic mechanism is still debatable. In this study, an Au/WO_2.7 compound was synthesized and exhibited a strongly enhanced gas sensitivity to many reductive gases, especially H₂. Aberration-corrected environmental transmission electron microscopy was used to investigate the atomic-scale microstructural evolution in situ during the reaction between H₂ and Au/WO_2.7 compound. Swing and sintering processes of the Au particles on the WO_2.7 surface were observed under heating and gaseous environments, and no injection of hydrogen atoms was suggested. First principle calculations verified the swing and sintering processes, and they can be explained by the enhancement of H₂ sensitivity.

     

Target setting with minimum improving costs in data envelopment analysis: A mixed integer linear programming approach

This study addresses a problem called cost‐minimizing target setting in data envelopment analysis (DEA) methodology. The problem is how to make an inefficient decision‐making unit efficient by allocating to it as few organizational resources as possible, assuming that the marginal costs of reducing inputs or increasing outputs are known and available, which is different from previous furthest and closest DEA targets setting methods. In this study, an existed cost minimizing target setting heuristics approach based on input‐oriented model is examined to show that there exist some limitations. This study develops a simple mixed integer linear programming to determine the desired targets on the strongly efficient frontier based on non‐oriented DEA model considering the situation in the presence of known marginal costs of reducing inputs and increasing outputs simultaneously. Some experiments with the simulated datasets are conducted, and results show that the proposed model can obtain more accurate projections with lower costs compared with those from furthest and closest target setting approaches. Besides, the proposed model can be realistic and efficient in solving cost‐minimizing target setting problem.     

Computerized spatial language generation for object location

Spatial language is the syntax used for object or place locations. Because an object location is inherently relative, it implies a frame of reference, which in turn may be aided by a reference object, other than the one to be located. This reference object is commonly selected based on its perceptual salience, that is, its more prominent features. Computer systems linked to various research areas have been developed to facilitate the communication and/or interpretation of spatial language for localization tasks. In this paper is presented a literature review of computer systems that adopt spatial language and perceptual salience for object location.