Two-dimensional structures of ferroelectric domain inversion in LiNbO3 by direct electron beam lithography

We report on the fabrication of domain-reversed structures in LiNbO3 by means of direct electron beam lithography at room temperature without any static bias. The LiNbO3 crystals were chemically etched after the exposure of electron beam and then, the patterns of domain inversion were characterized by atomic force microscopy (AFM). In our experiment, an interesting phenomenon occurred when the electron beam wrote a one-dimensional (1-D) grating on the negative c-face: a two-dimensional (2-D) dotted array was observed on the positive c- face, which is significant for its potential to produce 2-D and three-dimensional photonic crystals. Furthermore, we also obtained 2-D ferroelectric domain inversion in the whole LiNbO3 crystal by writing the 2-D square pattern on the negative c-face. Such a structure may be utilized to fabricate 2-D nonlinear photonic crystal. AFM demonstrates that a 2-D domain-reversed structure has been achieved not only on the negative c-face of the crystal, but also across the whole thickness of the crystal.Comment: 17 pages, 4 figure

Analysis of traffic noise distribution and influence factors in Chinese urban residential blocks.

To improve the acoustic environment of residential blocks, noise mapping is employed in this study to analyze traffic noise distribution and the influence factors of four types of residential blocks in China. The study shows that high-rise small blocks have the highest average noise level (Lavg) for ground and building facades, followed by small low-rise blocks while modern residential blocks yield the lowest value. An analysis of the standard deviation (STD) of spatial statistical noise level (Ln) shows that the STD of the ground and building façade of two types of small blocks is higher than that of other blocks. The analysis of influence factors indicates that the lot area of residential block has significant negative correlation with ground and building facade average noise level (Lavg), and street coverage ratio (SCR) has significant positive correlation with ground and building facade average noise level (Lavg). In low-rise and high-rise small blocks, ground space index (GSI) has significant negative correlation with ground and building facade average noise level (Lavg); street interface density (SID) has significant positive correlation with the STDs of ground and building facade noise. Floor space index (FSI) shows significant positive correlation with the STDs of ground and building facade noise in low-rise small block

Research progress on the acoustic environments of healthy buildings / 健康建筑声环境研究进展

Building and urban acoustic environments greatly contribute to the quality of healthy buildings. This paper first discusses the developmental transitions from noise control to soundscape construction, and the changing focus from negative effects on public health to the promotion of health benefits. During this transition, the impacts of acoustic environments on human health have been investigated from various research perspectives, from concept to theory to methods. In current soundscape research, sound environment designs are based on health concepts. Innovative results have been introduced from this focus. First, the impacts of soundscape perception on human health and the psychophysiological effects of soundscape have been extensively reviewed. Reduced negative soundscapes are significantly positively correlated with the self-reported health conditions of subjects. Especially, soundscapes reported as positive (e.g., pleasant and calm) are significantly positively correlated with environmental stress restoration. The physiology and neurophysiology of soundscapes are emerging subjects that require extensive further research. Research on the restorative effects of urban public open spaces has included the development of relevant theories and practice, experimental studies of restorative performance and its influencing factors, and sensitivity studies, which measure the response magnitude of physiological indicators to typical soundscapes. The restorative quality of public open spaces in the urban context is of particular interests. Soundscapes in public open spaces are known to directly affect the psychology, physiology, and attention span of individuals. They also exert an indirect recovery effect through audio-visual interactions. A study on the sensitivity study of physiological indicators analyzed the change of the physiological signals over time, the type of scenery, and the restoration effect was quantified from the relationships among different subjective scales. Stressed children exposed to different potentially restorative soundscapes perceive the restorative sound scenery differently from adults. The effect of noise on the cognitive performance of children is primarily reflected in the degree of subjective annoyance, and children's test performances do not significantly depend on the varying noise conditions. In specific spaces such as hospitals, the acoustic environment is known to affect inpatient health and the efficiency of hospital staff. Studies have confirmed that improving the acoustic environment benefits the resting ability, sleep, and mood of inpatients, and this can also improve the efficiency of hospital staff. With the broadening and deepening of acoustic environment research and the effective development of research tools, indicator systems and research paradigms will become more standardized. Such standardization will further deepen the research and lead to evaluative standards. Much scope remains for investigating the impact mechanism and efficiency of various soundscape restorative treatments in urban public open spaces. Furthermore, the health effects of soundscape treatments for other specific groups of people and other specific spaces should be elucidated. Finally, research should move from revealing the influence patterns and tendencies of soundscapes toward the active design of healthy acoustic environments. / 建筑及城市声环境是健康建筑质量的重要组成部分. 本文首先讨论了从噪声控制到声景营造, 即从降低负 面健康影响到促进公众健康的发展趋势, 在这个从观念到理论到方法的转化过程中, 声环境对人的健康影响有了 更为科学的研究视角和操作方法, 与基于健康理念的声环境设计共同成为声景研究持续关注的焦点. 在此基础上, 介绍了一些近期的创新研究成果, 包括声景感知对健康效应的影响, 及声景的心理生理学方面的系统性综述研究; 基于恢复性环境理论的城市公共开放空间声景恢复性效应的理论发展和实证研究进展、典型声景的生理指标变 化的敏感性研究; 针对特定群体健康影响的研究, 包括儿童恢复性声景研究、环境噪声对儿童认知能力的影响研 究; 针对特定空间的声环境健康研究, 包括医院声环境对住院病人健康、对医护人员工作效率的影响等. 总体而言, 声景的生理学和神经生理学研究尚处于起步阶段, 有许多方面值得研究; 城市公共开放空间声景恢复性效应, 其影 响机理和主动调节层面还有值得深入研究的内容; 针对特定人群和特定空间的声景健康研究还将拓展到其他人群 和空间, 研究也将从客观影响规律走向基于健康的声环境主动设

Overall effects of temperature steps in hot summer on students' subjective perception, physiological response and learning performance

University students are very likely to experience temperature steps before class in hot summer. This study aims to investigate the overall effects of step changes on students' subjective perception, physiological response and learning performance, so as to explore an optimal thermal condition for classrooms in hot summer. Four typical temperature step conditions (S6: 34 °C-28 °C, S8: 34 °C-26 °C, S10: 34 °C-24 °C, S12: 34 °C–22 °C) were developed to conduct experiments on sixteen participants. It has been found that after temperature steps, no more than 62.5% of students consistently found thermally acceptable at 22 °C; students felt the most acceptable and comfortable at 26 °C; the effect of thermal environment on workload was not significant in most cases, especially for memory-related tasks; students' negative mood was less at 26 °C than at 28 °C and 22 °C. When the temperature step was less than S12, blood pressure and blood oxygen saturation were insensitive to temperature steps; core temperature continued to rise during the first 5 min and then decreased significantly when the temperature step exceeded S8. No significant difference in learning performance was found among the four conditions; the differences in relative performance between thermal conditions were <2%, and are not likely to have practical meaning in building management practice. Overall, the optimal thermal condition is 26 °C, and it is recommended to set the indoor temperature between 24 and 28 °C

Enhancement of Gear Fault Detection Using Narrowband Interference Cancellation

The development of enhanced fault detection ability for gearbox systems has received considerable attention in recent years. Detecting the gear fault easier is very important for maintenance action. This has driven the need in research for enhanced gear fault detection method. The goal is to extract periodic impulse signal from the very noise signal which mainly contains the narrowband signals. This can be done by enhancing the impulsive signals while suppressing the narrowband signals. This paper used a new method, Narrowband Interference Cancellation, to detect the gear fault. This method reserves the impulsive signal produced by gear fault and removes the other signals out. The methodology is demonstrated on a gearbox run-to-failure test. The results show that Narrowband Interference Cancellation can enable the gear fault detection easier

Interference through quantum dots

We discuss the effect of quantum interference on transport through a quantum dot system. We introduce an indirect coherent coupling parameter alpha, which provides constructive/destructive interference in the transport current depending on its phase and the magnetic flux. We estimate the current through the quantum dot system using the non-equilibrium Green's function method as well as the master equation method in the sequential tunneling regime. The visibility of the Aharonov-Bohm oscillation is evaluated. For a large inter-dot Coulomb interaction, the current is strongly suppressed by the quantum interference effect, while the current is restored by applying an oscillating resonance field with the frequency of twice the inter-dot tunneling energy.Comment: 10 pages, 3 figure

The effects of residential area building layout on outdoor wind environment at the pedestrian level in severe cold regions of China

In recent years, there has been a frequent occurrence of extremely cold conditions which has had a serious impact on the life of residents of buildings in various locations around the world. However, there have only been a very limited number of studies on the effects of residential area building layout on the winter wind environments, which led to a lack of quantitative guidance for residential area planning in severely cold regions. This study aims to reveal the relationship between (1) the residential areas' building density, floor area ratio, wind projection angle, average building height, and relative position of high-rise buildings, and; (2) the mean wind velocity ratio at pedestrian level in severe cold regions. In this study, the pedestrian-level outdoor wind environments in 24 typical residential areas of Harbin, China, are simulated using ENVI-met software. The results show that the relative position of high-rise buildings in multi-high-level mixed residential areas has little influence on the mean wind velocity ratio, and the maximum difference is 0.04. The factors of building layout have little influence on the mean wind velocity ratio of multistory residential areas. However, a significant linear correlation exists between the mean wind velocity ratio of high-rise residential areas and both the building density and wind projection angle. The prediction model of the mean pedestrian-level wind velocity ratio was then established