Development of a new solar thermal engine system for circulating water for aeration

This paper presents a numerical study about the performance of a Beta Stirling solar thermal engine system. This system is composed of a solar collector box connected to a regenerator hydraulic system and a transmitting power system. The objective of the system is to offer a new alternative to help solving stagnant water pollution in hot countries like Thailand by circulating water in canals, lakes, ponds etc. for aeration using solar energy.The purpose of this study is to determine the power output and actual heat transfer on the performance of the solar thermal engine. The solar thermal engine is analyzed using a mathematical model based on the first law of thermodynamics for processes with finite speed, with particular attention to the energy balance at the receiver. The result of calculations showed that the regenerator volume and phase angle must be chosen carefully to fulfill the requirement that total fluid mass in the system is constant and to obtain maximum power output throughout the day.     

虚拟现实技术在绿色基础设施健康效益评估中的应用

快速的城市化进程在不经意间将人类与自然环境割裂开来。因此所带来的日益严重的城市污染和人们进行户外活动的局限性,对人的身心健康和认知都产生了影响。城市规划师可以通过绿色基础设施营建来降低城市化带来的负面影响,如自然式公园、生态滤沟、植物墙和行道树等。然而,哪些绿色基础设施要素能否用于改善人们的健康福祉仍不十分明确。研究人员在绿色基础设施健康效益研究中引入虚拟现实技术（VR）,为循证设计提供科学可靠的依据。VR技术仅需要较低的成本和专业技术。受试者佩戴仪器进入沉浸式虚拟世界,过程中同步采集心理和生理指标,用于预测不同自然场景对健康和认知功能的长期影响。通过对VR系统、内容创作、实验设计、健康指标测量和安全注意事项的方法论进行概述,使读者了解VR技术如何用于研究,并作为一种替代治疗的手段,用于改善绿色基础设施的健康福祉,为VR技术的研究应用提供理论与实践基础。     

健康的生态系统服务和人居环境：泰国北部的机遇与挑战

健康的生态系统服务对于人类健康至关重要。设计师、规划师和学者们需要共同协作创造更具韧性的建成环境。然而,当前的研究成果仍然较难应用到具体的现实场景中。不管是在城市还是乡村,设计师、规划师和学者们都需要了解现状当中的问题,为提出解决方案而进行充分的调研和设计探讨。然而理论和实践的差距仍可能导致进度的滞后。从城市规划师、风景园林师和学者的角度审视泰国北部建成环境中的三大议题：环境公平、食物安全和空气质量。讨论设计师和学者们在解决上述问题过程中可合作努力的方向,涉及循证设计、研究方法和设计评估。最后提出了一个致力于改善健康生态系统和人居环境关系的新范式。     

Exact indexing for massive time series databases under time warping distance

Among many existing distance measures for time series data, Dynamic Time Warping (DTW) distance has been recognized as one of the most accurate and suitable distance measures due to its flexibility in sequence alignment. However, DTW distance calculation is computationally intensive. Especially in very large time series databases, sequential scan through the entire database is definitely impractical, even with random access that exploits some index structures since high dimensionality of time series data incurs extremely high I/O cost. More specifically, a sequential structure consumes high CPU but low I/O costs, while an index structure requires low CPU but high I/O costs. In this work, we therefore propose a novel indexed sequential structure called TWIST (Time Warping in Indexed Sequential sTructure) which benefits from both sequential access and index structure. When a query sequence is issued, TWIST calculates lower bounding distances between a group of candidate sequences and the query sequence, and then identifies the data access order in advance, hence reducing a great number of both sequential and random accesses. Impressively, our indexed sequential structure achieves significant speedup in a querying process. In addition, our method shows superiority over existing rival methods in terms of query processing time, number of page accesses, and storage requirement with no false dismissal guaranteed.     

Local Structure of Magnetoelectric BiFeO3–BaTiO3 Ceramics Probed by Synchrotron X-Ray Absorption Spectroscopy

The novel Cu- and Mn-doped and Cu/Mn codoped 0.75BiFeO₃–0.25BaTiO₃ magnetoelectric ceramics were successfully prepared by a solid-state reaction method. The dielectric, ferroelectric, ferromagnetic, and magnetoelectric properties were determined and all the results suggested that Cu and Mn dopants occupied different B-site lattices in the 0.75BiFeO₃–0.25BaTiO₃ structure. To identify the preferential sites of Cu and Mn in the lattice, Synchrotron X-ray Absorption Spectroscopy (SXAS) measurements were carried out. A combination of both measured and simulated XAS results with a linear combination fitting (LCF) revealed that in Cu- and Mn-doped 0.75BiFeO₃–0.25BaTiO₃ ceramics both Mn and Cu substituted at Fe-site and Ti-site with slightly different proportion. On the other hand, both dopants were found to occupied different sites in Cu/Mn codoped 0.75BiFeO₃–0.25BaTiO₃ ceramics.     

High Solid‐State Near Infrared Emissive Organic Fluorophores from Thiadiazole[3,4‐c]Pyridine Derivatives for Efficient Simple Solution‐Processed Nondoped Near Infrared OLEDs

Many efforts have been dedicated to developing near infrared (NIR) fluorescent emitters with strong emission especially in the range of 700–1000 nm due to their potential applications in biomedical and optoelectronic fields. However, high solid state NIR emission fluorophores are still rare for applications. Herein, two efficient donor‐π‐acceptor type NIR emitters, C3HTP and C4HTP , are designed and synthesized by end‐capping two isomeric bis(n‐hexylthienyl)thiadiazole[3,4‐c]pyridines as π‐acceptor with structural bulky, electron rich tercarbazole moiety. They exhibit excellent solid state NIR emission with an emission peak at 725 nm, especially C3HTP , reaching a record high photoluminescence quantum yield (Φ_PL) of 34% for NIR organic fluorescent materials. By taking advantage of their Φ_PL values in the film state (Φ_PL = 10–34%), suitable energy levels (highest occupied molecular orbital (HOMO) level ≈ ?5.3 eV), high hole mobility (5.49 × 10^?8 cm² V^?1 s^?1) as well as good amorphous film forming ability by solution casting, they are used to fabricate a nondoped emissive layer (EML) in simple double‐layer solution processed NIR electroluminescent (EL) devices. The device containing C3HTP as the EML shows a NIR emission peaking at 726 nm and excellent EL performance with a high external quantum efficiency of 1.51%, which is the best solution processed nondoped NIR organic light‐emitting diodes reported to date. Importantly, this represents an advance in near infrared organic fluorescent materials and EL devices that meet the requirements of many applications.     

CoFe_2O_4-BaTiO_3颗粒复合材料的频率相关电磁性能

通过湿法球磨制备CoFe2O4-BaTiO3颗粒复合材料,研究材料成分和调制频率与电磁效应的关系。结果表明：电磁效应系数随着调制频率由400Hz增加到1000Hz而增加。由于CoFe2O4的电导率在400-1000Hz范围内对频率敏感,电磁效应的曲线特性而发生改变。在烧结过程中形成第三相Ba2Fe2O5,从而导致电磁效应的下降。     

Magnetic Hysteresis and Electrical Impedance Spectra of Hard Magnetic SmCo5 and Soft Magnetic Co30Ag70 Composites

在磁场下,采用振动样品磁强计和电阻抗测试仪来研究加入 0%,5% 和 10%(质量分数)的硬磁钐钴的钴银合金在矫顽场不变的情况下,颗粒状复合材料的剩余磁化强度伴随钐钴质量分数的增加而增加。在 10 kHz~100 kHz 区间,各复合材料的电阻抗均未表现大的变化。但是,在 200 kHz~1 MHz 区间,由于趋肤效应,电阻抗迅速增加。当磁场为 3.3 kA/m,所有的阻抗谱都发生了微移。其中,未加钐钴的钴银合金阻抗谱发生了最大的偏移。这些结果确定了在磁场下材料软磁特性与其电阻抗的关系。     

Ferroelectromagnetic characteristic of Na-doped 0.75BiFeO3–0.25BaTiO3 multiferroic ceramics

BiFeO₃-based materials are expected to have both ferroelectricity and ferromagnetism simultaneously. In this study, effects of Na-doping (0.5, 1.0, 3.0, and 5.0 mol%) on ferromagnetic and ferroelectric properties of 0.75BiFeO₃–0.25BaTiO₃ ceramics which have been fabricated by the solid state reaction technique are studied. The effects of Na-doped 0.75BiFeO₃–0.25BaTiO₃ ceramics on the crystal structure, and magnetic and electrical properties were investigated and discussed. Rhombohedrally distorted 0.75BiFeO₃–0.25BaTiO₃ showed weak ferromagnetic and ferroelectric properties. In addition, ferroelectric and ferromagnetic properties of 0.75BiFeO₃–0.25BaTiO₃ have been controlled by Na doping, and the maximum values of magnetization and polarization were observed at 5.0 mol%.