The performance improvement of a cascade thermoacoustic engine by adjusting the acoustic impedance in the regenerator

A novel cascade configuration consisting of one standing wave unit and one travelling wave unit arranged in series is studied in this paper. Theoretically, a straight‐line cascade engine provides an efficient energy conversion, reduces the difficulties of fabrication and allows no Gedeon streaming. In order to achieve such a powerful cascade thermoacoustic engine, the regenerator of the travelling wave unit must be operated in high impedance and travelling wave phasing region. Various techniques of phase adjustment by modifying the configurations and geometrical dimensions of the system are investigated both numerically and experimentally in order to adjust the position of the sweet spot as well as to promote the acoustic impedance in the regenerator. It is found that the effective tuning methods with less modification here are accomplished by changing the volume of down‐cavity and reducing the flow area of down‐resonator by inserting the pencil. The exploration also shows that the acoustic field in the system is quite sensitive to the effect of down‐resonator length. The performance of the proposed system is clearly improved after the phase‐adjustment schemes are completely implemented, in which the regenerator works within the sweep spot zone with high acoustic impedance. Copyright © 2016 John Wiley & Sons, Ltd.     

Tidal energy leasing and tidal phasing

In addition to technical and economic constraints, tidal energy leasing is generally governed by demand for sites which contain the highest tidal streams, and does not take into account the phase relationship (i.e. the time lag) between sites. Here, the outputs of a three-dimensional tidal model are analysed to demonstrate that there is minimal phase diversity among the high tidal stream regions of the NW European shelf seas. It is therefore possible, under the current leasing system, that the electricity produced by the first generation of tidal stream arrays will similarly be in phase. Extending the analysis to lower tidal stream regions, we demonstrate that these lower energy sites offer more potential for phase diversity, with a mean phase difference of 1.25 h, compared to the phase of high energy sites, and hence more scope for supplying firm power to the electricity grid. We therefore suggest that a state-led leasing strategy, favouring the development of sites which are complementary in phase, and not simply sites which experience the highest current speeds, would encourage a sustainable tidal energy industry.     

A Long-Read Sequencing Approach for Direct Haplotype Phasing in Clinical Settings

The reconstruction of individual haplotypes can facilitate the interpretation of disease risks; however, high costs and technical challenges still hinder their assessment in clinical settings. Second-generation sequencing is the gold standard for variant discovery but, due to the production of short reads covering small genomic regions, allows only indirect haplotyping based on statistical methods. In contrast, third-generation methods such as the nanopore sequencing platform developed by Oxford Nanopore Technologies (ONT) generate long reads that can be used for direct haplotyping, with fewer drawbacks. However, robust standards for variant phasing in ONT-based target resequencing efforts are not yet available. In this study, we presented a streamlined proof-of-concept workflow for variant calling and phasing based on ONT data in a clinically relevant 12-kb region of the APOE locus, a hotspot for variants and haplotypes associated with aging-related diseases and longevity. Starting with sequencing data from simple amplicons of the target locus, we demonstrated that ONT data allow for reliable single-nucleotide variant (SNV) calling and phasing from as little as 60 reads, although the recognition of indels is less efficient. Even so, we identified the best combination of ONT read sets (600) and software (BWA/Minimap2 and HapCUT2) that enables full haplotype reconstruction when both SNVs and indels have been identified previously using a highly-accurate sequencing platform. In conclusion, we established a rapid and inexpensive workflow for variant phasing based on ONT long reads. This allowed for the analysis of multiple samples in parallel and can easily be implemented in routine clinical practice, including diagnostic testing.     

一起换热器提前失效案例的分析及启示

针对某公司卧式列管换热器的腐蚀穿孔问题,对失效的换热器进行了宏观形貌、微观形貌、腐蚀产物能谱、金相组织及材料化学成分等分析,结果表明,这是一起由厌氧的硫酸盐还原菌引起的微生物腐蚀。并从中得到几点启示,可为今后解决此类问题提供参考。     

基于工频滤波的线路绝缘及定相测试仿真

架空输电线路多回、交叉跨越等情况将导致临近线路产生感应电压,同塔架设的输电线路感应电压甚至高达上千伏,若用兆欧表对其进行绝缘及定相测试,则设备存在被烧毁的风险。本文基于RC分压原理设计了一种工频滤波器,将其装到兆欧表和被测线路之间,能够有效降低兆欧表承受的工频感应电压,同时装置的引入对线路绝缘及定相测试结果无影响。用PSCAD对工频滤波器、兆欧表和同塔双回输电线路进行建模,通过系统仿真得出工频滤波器参数的合理范围。仿真结果表明将工频滤波器用于输电线路绝缘及定相测试可以有效保护兆欧表,而且测试结果不受影响,是一种简单可行的方法。     

大尺度城市设计中的时序问题——以南京东山新市区中心为例

大尺度城市设计项目中,建设时序并非被动的实施计划,它也影响到未来的城市形态。城市设计中建设时序的关键在于把握影响空间发展格局的关键时段和关键节点,来推动其他部分的实施。本文以南京东山新市区中心为例,探讨了在大尺度城市设计中,将城市形态的最终产品分解为若干个过程式的分阶段形态的方法,并根据各阶段特点采用不同的控制力度,把总体的城市形态设计转变为基于建设时序的"形态过程"指引。     

Optimization of the phasing of electrodes in four-arc welding of gas transmission pipes with a wall thickness of 6–10 mm

The optimum phasing of the electrodes and the conditions of four-arc submerged-arc welding of thin wall pipes (6–10 mm), resulting in the height of the convex region and the width of the welded joint not greater than 2.5 and 20 mm, respectively, are determined.     

基于色差分析的鼓膜穿孔图像边缘跟踪算法

鼓膜穿孔图像的边缘分析是确定鼓膜穿孔破损百分率的根本依据.针对利用耳内窥镜采集的图像特点,从实用角度出发,设计滑动小窗口来搜索初始特征点,提出一种基于色差分析指导的自适应边缘跟踪方法,实现了图像边缘特征点的全自动定位.实验表明,该方法快速而有效.     

FT8燃气轮机特殊功能的实践

介绍了FT8燃气轮机具有的黑启动、快速启动、孤立-有差、孤立-无差、调相等5种特殊的启动和发电模式。指出燃气轮机电厂在目前主要用作调峰与事故应急电源的情况下,应充分地试验与完善其特殊功能,以满足电厂与电网公司双方的要求。     

直流定相在输电线路相位检定中的应用

在新建的输电线路投入运行前和运行中输电线路的连接方式变动时,如线路T接、线路改道、多处换相作业等有可能使线路三相连接关系发生变化,投运前应核对输电线路两端的相位。提出输电线路相位检查中直流定相的相位检定方法,通过直流定相可有效地判断输电线路相位是否正确、线路有无接地或相间短路等问题,保证电网的安全稳定运行。