继电保护隐藏故障造成输电线路连锁跳闸的概率模型

继电保护隐藏故障是造成输电线路连锁跳闸的主要原因。通过分析继电保护装置隐藏故障的动作机理，定义了隐藏故障的风险区域，并利用保护装置隐藏故障概率和风险区域故障概率的计算，建立了输电线路连锁跳闸的概率模型。该模型计入了多条输电线路具有不同故障概率对触发继电保护装置隐藏故障的影响，可以评估继电保护系统因隐藏故障造成连锁误切线路的概率。最后，利用实际数据进行的算例分析验证了模型的合理性，计算结果对电力系统可靠性分析及连锁故障风险评估具有参考价值。     

Fabrication of Millimeter-Wave Electromagnetic Bandgap Crystals Using Microwave Dielectric Powders

Electromagnetic bandgap (EBG) structures active in the 90–110 GHz region widely used by security imaging radar were created using different ceramics by a rapid prototyping method informed by finite difference time domain modeling. This solid free-forming method uses a high volatility solvent-based ceramic paste extruded through fine nozzles allowing ceramic powders to be assembled on a multiaxis building platform avoiding machining, etching, or the alignment of loose rods and created to designs downloaded directly from a computer file. Lattices were made from two high dielectric constant ceramics: La(Mg_0.5, Ti_0.5)O₃ and (Zr_0.8, Sn_0.2)TiO₄ and compared with those of Al₂O₃ demonstrating three EBG structures with different dimensions and dielectric constants but with the same bandgap. The effects of manufacturing tolerances on bandgap frequency are investigated by simulation.     

Content-based image retrieval using color vector angle difference histogram

Abstract

This paper presents an innovative method to represent an image for image retrieval in Content-Based Image Retrieval (CBIR), using a color vector angle differences histogram approach (CVADH), which is different from the existing histograms, such as color histograms, gray level co-occurrences (GLCM), color distribution entropy (CDE), or just counting the frequency number of pixels or neighbors. In contrast to other methods, the CVADH takes account of the color difference and spatial information of two pixels in RGB color space. Furthermore, it directly leverages color clues to extract shape features to show differences given different backgrounds. Experimental results show that the scheme is more efficient than traditional ones that have been developed for CBIR.     

简单醇热法制备ZnO纳米棒及其抗菌性能研究

通过Zn(NO3)2.6H2O和NaOH的醇溶液制备ZnO,利用XRD和TEM对产物进行表征,产物为具有较高的结晶度和纯度的ZnO纳米棒,直径约为30nm,长度约为130～500nm。取市售ZnO和产物,采用抑菌圈法对3种常见致病菌作药物敏感试验,并测定了产物对金黄色葡萄球菌的最小杀菌浓度(MBC)。结果表明,产物与市售ZnO试剂均对大肠杆菌不敏感,对金黄色葡萄球菌和白色念珠菌有不同程度的敏感,且产物比市售试剂抑菌效果更为明显,产物对金黄色葡萄球菌的最小杀菌浓度(MBC)为1.5%。     

含储氢合金炸药的能量研究

通过水下试验和空中爆炸试验研究了RDX基含储氢合金炸药的能量释放,并与含铝炸药进行比较。水下能量的研究发现,在金属粉质量分数为30％时,组分适当的含储氢合金炸药水下爆炸比气泡能和总能量高于相应含铝炸药,含A-30、A-60合金炸药的比气泡能分别比含铝炸药提高9．3％和5．1％,总能量分别提高7．0％和3．0％;空中爆炸研究发现,在相同爆心距处,含储氢合金炸药的爆炸冲击波压力和冲量与含铝炸药相当。试验结果表明：由于储氢合金中的氢元素能够通过燃烧放热和产生水蒸气并促进铝、硼金属的氧化,因此可以提高爆炸的总体能量输出。     

Understanding the Host–Guest Interaction Between Responsive Core‐Crosslinked Hybrid Nanoparticles of Hyperbranched Poly(ether amine) and Dyes: The Selective Adsorption and Smart Separation of Dyes in Water

The host–guest interaction between polymer nanoparticles and guest molecules plays a key role in fields such as controlled drug delivery, separation, and nanosensors. To understand this host–guest interaction, a series of hybrid polymer nanoparticles (SiO_1.5‐hPEA NPs) are designed and prepared based on hyperbranched poly(ether amine) (hPEA) with the different hydrophobicity and functional groups. Their adsorption behavior to twelve hydrophilic dyes in aqueous solution is studied. The core‐crosslinked hybrid nanoparticles (SiO_1.5‐hPEA NPs) are prepared by direct dispersion of hPEA containing trimethoxysilyl moieties (TMS‐hPEA) in aqueous solution, which exhibit sharp multiresponse to temperature, pH, and ionic strength in aqueous solution. The effect of molecular structure of TMS‐hPEA on the host–guest interaction between SiO_1.5‐hPEA NPs and hydrophilic dyes is investigated in detail. The obtained SiO_1.5‐hPEA NPs interact selectively with different hydrophilic dyes in aqueous solution. The distribution coefficient (K) for partitioning of dyes between SiO_1.5‐hPEA NPs and water is proposed to define the strength of the host‐guest interaction between the nanoparticles and dyes. K increases with the increasing hydrophobicity of the hPEA backbone regardless of their charge states of SiO_1.5‐hPEA NPs and dyes. A methodology is demonstrated for the smart separation of a mixture of dyes in water using SiO_1.5‐hPEA NPs.     

美国大都市区最新综合交通规划比较研究

美国大都市区综合交通规划已经过半个多世纪的发展.我国城市交通发展面临的交通拥堵、交通安全、交通环境等问题日益突出,学习和借鉴美国大都市区新一轮的交通规划经验十分必要.本文对美国25个大都市区最新一轮综合交通规划报告进行系统整理,总结了25个大都市区综合交通规划的远景、总体目标以及实现目标的对策.针对当前中国城市交通问题对综合交通规划编制提出了建议.     

海上勘探开发一体化钻完井关键技术研究与实践

勘探开发一体化是缩短海上油气田建产周期、降低开发成本的有效手段,但海上油气田工程设施建造周期长、油气管网相对较少,对钻完井作业提出了更高要求.本文针对不同水深、不同类型和不同井口型式等探井转开发井特殊要求,建立了浅水探井井口再利用技术、一井多目标钻完井技术、简易移动式平台井口稳定性技术和深水探井转开发井井筒完整性评估技...     

Novel methods to fabricate macroporous 3D carbon scaffolds and ordered surface mesopores on carbon filaments

New methods for fabrication of 3D macroporous carbon scaffolds and synthesis of mesopores on carbon surfaces are proposed. Ordered macroporous filamentary carbon structures were made by rapid prototyping using solvent-based extrusion freeforming which allows the scaffold to be designed on computer and downloaded directly to a building platform. The surface of extruded filaments was decorated with 20?C25?nm open mesopores by coating with nano-silica as a hard template followed by pyrolysis and dissolution of the silica. This left an open mesoporous surface to serve as a host for catalysts or enzymes while retaining integrity in the core for electrical and mechanical performance. The combination of these two methods could be used to make different hierarchical, multi-functional carbon structures which could be applied in fuel cells as the catalyst carrier and biofuel cell electrode.     

Method to correct the distortion caused by amplified stimulated emission as motivated by LIF-based flow diagnostics

Amplified stimulated emission (ASE) represents a significant issue in two-photon laser-induced fluorescence (TPLIF). The ASE effects are nonlinear and nonlocal, i.e., the ASE effects distort the LIF signal nonlinearly, and the distortion at one location depends on conditions at other locations. In this sense, the ASE effects pose a greater challenge to quantitative TPLIF than quenching and ionization. This work therefore seeks a method to correct such distortion. The method uses two LIF measurements, one with low signal-to-noise ratio (SNR) and negligible ASE distortion and another with high SNR but significant distortion, to generate a faithful measurement with high SNR. Extensive simulations were performed to evaluate the performance of this method for practical applications.