高压液压能源系统热特性及热控制仿真分析

高压液压技术是未来飞机液压系统的主要发展趋势,由于损耗功率增加,系统温度变化将更加剧烈并影响飞行安全,因此,高压液压系统的热特性与热控制技术是未来飞机液压系统设计需要考虑的一个重要因素。以某高压液压能源系统为例,对液压能源系统的主要液压元件进行生热和散热机理分析。利用AMESim软件开展液压系统温度特性分析,权衡系统是否需要热交换器。结果表明:热交换器有效降低系统油液温度至安全温度内;同时,得到燃油-液压油热交换器位于不同位置、系统在不同飞行阶段下不同环境温度、机翼处管路引入冷气流等工况下温度变化趋势,为飞机高压液压能源系统热设计提供参考。     

Plasticity role in strength behavior of cement-phosphogypsum stabilized soils

Dredged soil and phosphogypsum are frequently regarded as wasted materials, which require further treatment to control their environmental impact. Hence, phosphogypsum is proposed as a binder to stabilize dredged soil, aiming at efficiently reducing and reusing these waste materials. In this study, the engineering properties of cement-phosphogypsum stabilized dredged soils were investigated through a series of unconfined compression tests, and the effects of plasticity index of original soils on the strength improvement were identified. Then, the microstructure test and mineralogical test were performed to understand the mechanism of physical role of original soils in strength improvement. The results revealed that the unconfined compressive strength significantly decreased with the increase in plasticity index at the same binder content. The essential factor for strength improvement was found to be the formation of cementitious materials identified as calcium silicate hydrate (CSH), calcium aluminate hydrate (CAH), and ettringite (Aft). The normalized integrated intensity of cementitious materials (CSH + CAH + Aft) by pore volume decreased with the increase in plasticity index. Consequently, the density of cementitious materials filling the soil pores controlled the effectiveness of strength improvement. More cementitious materials per pore volume were observed for the original soils with lower values of plasticity index. That is, the higher strength of stabilized soils with lower values of plasticity index was attributed to a packed structure forming by integrated fabric through denser cementitious components. It can be anticipated from the above findings that the effectiveness of stabilization treatment will significantly reduce with the increase in plasticity of origin soil.     

Prevalence and profile of Salmonella from samples along the production line in Chinese beef processing plants

This work investigated the prevalence of Salmonella, the serotypes and antibiotic resistance of the isolated strains from four beef processing plants of China. The prevalence of Salmonella in hide (n = 70), feces (n = 70), pre-evisceration carcass (n = 70), post-evisceration carcass (n = 70), post-washing carcass (n = 70), chilled carcass (n = 80), and raw meat (n = 80) samples was 20.0%, 18.6%, 1.4%, 1.4%, 2.9%, 1.3%, and 1.3%, respectively. Among the four plants, there were significant differences in the prevalence of Salmonella on hides and in feces. During the processing, Salmonella was significantly reduced after hide removal. Seven serotypes of Salmonella were identified among the eighty-three isolates. Salmonella Agona was the dominant serotype (p < 0.05, 53.0%), followed by Salmonella Senftenberg (16.9%), Salmonella Meleagridis (10.8%), and Salmonella Derby (9.6%). None of the isolated strains were found to be resistant to sixteen commonly used antimicrobial agents. The results of this study indicate that Salmonella contamination is common in samples along the production line, with S. Agona as dominant serotype. Specific measures should be taken to prevent and/or treat Salmonella contamination in corresponding products in Chinese beef processing plants. Furthermore, the current research might provide baseline information of Salmonella prevalence profile in Chinese beef processing plant, which could be used for the future study.     

Continuous quality and shelf life monitoring of retail-packed fresh cod loins in comparison with conventional methods

This study investigated the applicability of a new photochromic time-temperature indicator (TTI) to monitor the quality and shelf life of fresh cod loins in retail packs at different storage conditions; also compared this automatic monitoring method with other methods of quality control, such as sensory, chemical and microbiological analyses; and with a shelf life prediction model. TTI placed on the bottom of the packs effectively reflected the temperature condition of the product. TTI with the initial square value of 61 was suitable for continuous monitoring of the quality and shelf life of the product repacked on day 6 after processing. The estimated product shelf lives based on TTI and on the square-root model for relative rate of spoilage of fresh seafood were well correlated.     

Starch hydrolysis in autogenerative high pressure digestion: Gelatinisation and saccharification as rate limiting steps

Autogenerative high pressure digestion (AHPD) provides an integrated biogas upgrading technology, capable of producing biogas with a CH₄ content exceeding 95% at pressures up to 90 bar. Hydrolysis is generally regarded as the rate-limiting step in the anaerobic digestion of complex organic matter, governing the volatile fatty acid (VFA) production rate for subsequent conversion to methane. Starch hydrolysis rates in AHPD systems were studied and the potential risk for VFA accumulation was assessed. Under the anticipated practical moderate pressure conditions at 30 °C, experimental CH₄-content of the biogas improved from 49 to 73 ± 2% at atmospheric and elevated pressure, respectively. Furthermore, no significant effect of pressure on the hydrolysis was found. Like under atmospheric pressure, gelatinisation was the rate-limiting step for particulate starch (0.05 d⁻¹) and saccharification for gelatinised starch (0.1 d⁻¹). Because no effect was observed on starch, an effect on the hydrolysis rate of more complex organic matter like (ligno-)cellulose is also not anticipated.     

Compression of facial images using the K-SVD algorithm

The use of sparse representations in signal and image processing is gradually increasing in the past several years. Obtaining an overcomplete dictionary from a set of signals allows us to represent them as a sparse linear combination of dictionary atoms. Pursuit algorithms are then used for signal decomposition. A recent work introduced the K-SVD algorithm, which is a novel method for training overcomplete dictionaries that lead to sparse signal representation. In this work we propose a new method for compressing facial images, based on the K-SVD algorithm. We train K-SVD dictionaries for predefined image patches, and compress each new image according to these dictionaries. The encoding is based on sparse coding of each image patch using the relevant trained dictionary, and the decoding is a simple reconstruction of the patches by linear combination of atoms. An essential pre-process stage for this method is an image alignment procedure, where several facial features are detected and geometrically warped into a canonical spatial location. We present this new method, analyze its results and compare it to several competing compression techniques.     

三角帆蚌贝壳的微结构及尺寸变化特征

天然生物经历了亿万年的不断进化,已经形成了近乎完美的结构。天然生物材料结构的研究是仿生研究的基础,本文以三角帆蚌贝壳为研究对象,利用SEM和AFM,描述了三角帆蚌贝壳的微结构特征,包括其角质层、棱柱层、珍珠层及界面和晶带的形貌,揭示文石晶片及各层间的尺寸变化规律。研究表明:角质层内部分布大量裂纹,珍珠层与棱柱层无明显过渡界面,珍珠层内发现条状晶带结构缺陷;贝壳壳体和珍珠层厚度随0生长线向外呈现先增大后减小的变化趋势,且单层文石晶片的厚度不均,最厚处可达最薄处的2倍多。对三角帆蚌贝壳的结构进行了深入研究,为其优异的力学性能提供了理论依据,为未来的仿生结构设计提供了新思路和新想法。      

基于近邻关系的离群约简搜索算法

针对传统离群点检测过程中属性多、维度大等问题,结合粗糙集理论,提出一种基于近邻关系的离群约简搜索算法。利用属性约简技术解决对象不相容的问题,并有效缩减离群搜索的属性空间。计算任意点与其他所有点间的距离和,通过计算基于近邻的加权离群因子来判定离群点,并在通用数据集上进行测试。实验结果表明,该离群检测算法的搜索精度较高。     

变电站二次系统设备屏柜线套标签智能识别系统

给出了一种变电站二次系统设备屏柜线套标签智能识别系统的设计方案,阐述了构成该系统各模块之间的信号传递流程。通过基于人工智能深度学习算法的定位和识别拍摄的屏柜端子排现场接线照片,获取接线线套标签信息,将其与电子图纸中的接线标准信息进行对比,生成检查报告对运维人员进行接线错误实时警告提醒。从而减轻变电站运维人员的劳动强度,缩短操作时间,消除因接线错误所引起的变电站运行安全隐患。     

Carbon-Nitride Popcorn—A Novel Catalyst Prepared by Self-Propagating Combustion of Nitrogen-Rich Triazenes

The interest in development of non-graphitic polymeric carbon nitrides (PCNs), with various C-to-N ratios, having tunable electronic, optical, and chemical properties is rapidly increasing. Here the first self-propagating combustion synthesis methodology for the facile preparation of novel porous PCN materials (PCN3-PCN7) using new nitrogen-rich triazene-based precursors is reported. This methodology is found to be highly precursor dependent, where variations in the terminal functional groups in the newly designed precursors (compounds 3–7) lead to different combustion behaviors, and morphologies of the resulted PCNs. The foam-type highly porous PCN5, generated from self-propagating combustion of 5 is comprehensively characterized and shows a C-to-N ratio of 0.67 (C₃N_4.45). Thermal analyses of PCN5 formulations with ammonium perchlorate (AP) reveal that PCN5 has an excellent catalytic activity in the thermal decomposition of AP. This catalytic activity of PCN5 is further evaluated in a closer-to-application scenario, showing an increase of 18% in the burn rate of AP-Al-HTPB (with 2 wt% of PCN5) solid composite propellant. The newly developed template- and additive-free self-propagating combustion synthetic methodology using specially designed nitrogen-rich precursors should provide a novel platform for the preparation of non-graphitic PCNs with a variety of building block chemistries, morphologies, and properties suitable for a broad range of technologies.