Using personally controlled air movement to improve comfort after simulated summer commute

People often feel uncomfortably warm and sweaty in their workspace after commuting there by walking or cycling in summer. This is because body heat stored during the commute takes a substantial time to dissipate. People complaining about this uncomfortable transition may cause operators to lower the thermostat setpoint, causing long-term overcooling and wasting energy. In addition, space cooling is slow, requiring minutes to take effect. This study addresses how to improve comfort in the transition by increasing the availability of convective cooling, where the response time is in seconds. Thirty-five subjects (17 men and 18 women) dressed in 0.6 clo en-tered a test room after exercising at 4.4 met for 15 min in 30 ºC. The exercise emulates the commute activity in summer. The test room was controlled to 24, 26, and 28 ºC, with and without the option of cooling using fan-produced horizontal airflow. Subjects were sedentary for 60 minutes, during which subjective thermal responses and physiological responses were measured. The enhanced convective and evaporative heat loss caused by fans significantly shortened the time needed to reach thermal comfort after the exercise-induced thermal stress and improved the final comfort level. Compared to a typical indoor condition of 24 ºC and still air, 26 and 28 ºC with fans provided equal or better comfort more quickly, and inherently required much less energy to do so. Our study suggests that personally controlled air movement should be available in spaces where thermal and metabolic down-steps take plac

Transient human thermophysiological and comfort responses indoors after simulated summer commutes

The current study investigates the transient human physiological and comfort responses during sedentary activity following a period of elevated activity in a hot condition. Such metabolic and thermal down-steps are common in buildings as occupants arrive after commuting in summer. It creates a serious problem for thermostatic control, since arriving occupants find their transition uncomfortably warm at temperatures that resident occupants find comfortable. Fifty-nine participants (29 men, 30 women) dressed in 0.6 clo were tested while sedentary for 60 min in 26 °C, after having been exposed to 30 °C for 15min, during which they performed activities metabolically simulating commuting: sitting (SE- 1.2 met), or doing three levels of stair-step exercises: low (LEx- 2.2 met), medium (MEx - 3.0 met), and high (HEx - 4.4 met). Subjective comfort and physiological responses (metabolic rate, skin temperature, skin blood flow rate, heart rate, core temperature, and skin wettedness) were collected. Results show that sedentary conditions at 26°C became comfortable and acceptable within 2 min, but thermal sensation required much longer to change from ‘warm’ or ‘hot’ to ‘neutral’: 0, 8, 17, 30 min after SE, LEx, MEx, HEx respectively. Skin wettedness and core temperature did not recover within the60 min. The delays are mainly due to body heat stored during the exercise. A room temperature of 26°C may not provide sufficient cooling after summer commuting. Localized convective cooling of transitional spaces and work areas by ceiling or desk fans represent a way to enhance comfort recovery

ONCache: A Cache-Based Low-Overhead Container Overlay Network

Recent years have witnessed a widespread adoption of containers. While containers simplify and accelerate application development, existing container network technologies either incur significant overhead, which hurts performance for distributed applications, or lose flexibility or compatibility, which hinders the widespread deployment in production. We design and implement ONCache (\textbf{O}verlay \textbf{N}etwork \textbf{Cache}), a cache-based container overlay network, to eliminate the overhead while keeping flexibility and compatibility. We carefully analyze the difference between an overlay network and a host network, and find that an overlay network incurs extra packet processing, including encapsulating, intra-host routing, namespace traversing and packet filtering. Fortunately, the extra processing exhibits an \emph{invariance property}, e.g., most packets of the same flow have the same processing results. This property motivates us to cache the extra processing results. With the proposed cache, ONCache significantly reduces the extra overhead while maintaining the same flexibility and compatibility as standard overlay networks. We implement ONCache using eBPF with only 524 lines of code, and deploy ONCache as a plugin of Antrea. With ONCache, container communication achieves similar performance as host communication. Compared to the standard overlay network, ONCache improves the throughput and request-response transaction rate by 12\% and 36\% for TCP (20\% and 34\% for UDP), while significant reduces per-packet CPU overhead. Many distributed applications also benefit from ONCache

Perovskite Origami for Programmable Microtube Lasing

Metal halide perovskites are promising materials for optoelectronic and photonic applications ranging from photovoltaics to laser devices. However, current perovskite devices are constrained to simple low-dimensional structures suffering from limited design freedom and holding up performance improvement and functionality upgrades. Here, a micro-origami technique is developed to program 3D perovskite microarchitectures toward a new type of microcavity laser. The design flexibility in 3D supports not only outstanding laser performance such as low threshold, tunable output, and high stability but also yields new functionalities like 3D confined mode lasing and directional emission in, for example, laser “array-in-array” systems. The results represent a significant step forward toward programmable microarchitectures that take perovskite optoelectronics and photonics into the 3D era. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH

Baiji genomes reveal low genetic variability and new insights into secondary aquatic adaptations

The baiji, or Yangtze River dolphin (Lipotes vexillifer), is a flagship species for the conservation of aquatic animals and ecosystems in the Yangtze River of China; however, this species has now been recognized as functionally extinct. Here we report a high-quality draft genome and three re-sequenced genomes of L. vexillifer using Illumina short-read sequencing technology. Comparative genomic analyses reveal that cetaceans have a slow molecular clock and molecular adaptations to their aquatic lifestyle. We also find a significantly lower number of heterozygous single nucleotide polymorphisms in the baiji compared to all other mammalian genomes reported thus far. A reconstruction of the demographic history of the baiji indicates that a bottleneck occurred near the end of the last deglaciation, a time coinciding with a rapid decrease in temperature and the rise of eustatic sea level

Chebyshev spectral methods for potential field computation

We investigate Chebyshev spectral methods for solving Poisson's equation and the generalized Poisson's equations and apply them to 3-D gravity and DC resistivity modeling. When we approximate a function by a finite sum of Chebyshev polynomials, there are two kinds of errors: truncation and aliasing. We present a cell-average discretization scheme to reduce the aliasing error. Both theoretical analysis and numerical examples show that when there are discontinuities in a function, the cell-average discretization is better than the point injection discretization. We use both the r and collocation methods to solve Poisson's equation V2u = f. We solve the discrete systems by a matrix-diagonalization method. The speed and accuracy of collocation methods are better than those of the r method. For the generalized Poisson's equation V • (oVu) = f, we present a new iterative method. We rewrite the equation in the form of a Poisson's equation, V2u = (f —Va•Vu)la. At each iteration we compute the right hand-side term from the current value of u first. Then we solve the resultant Poisson’s equation by the collocation method. Numerical results show that the convergence rate of the new method is much faster than that of the spectral multi grid method. When there are discontinuities in the source function f and/or the conductivity o, the single-domain Chebyshev spectral method does not converge exponentially. In this case we use the multi-domain Chebyshev spectral method to solve the problem. We divide the whole domain into a number of subdomains so that in each subdomain the function is infinitely differentiable. Then we approximate the function by a separate Chebyshev series in each subdomain. We determine the relations between the Chebyshev polynomials in adjacent subdomains by the interface conditions. In this way we can achieve exponential convergence. In 3-D gravity modeling, we present a method to realize 2-D and 3-D point-injection and cell-average discretizations, use a multi pole expansion to compute the approximate boundary conditions and solve the equations by both single-domain and multi-domain Chebyshev spectral methods. We also extend Okabe's analytic formulation for the gravitational field of a homogeneous, polyhedral body to the potential. Numerical results show that the accuracy of the cell-average discretization is better than that of the point injection discretization. The multi-domain solution is the best. We apply the multi-domain Chebyshev spectral method to 3-D DC resistivity modeling. We discuss the singularity removal and present a modified finite-difference method for comparison. For a two-layered model, the multi-domain Chebyshev spectral solution is far more accurate than the finite-difference solution. For piecewise-constant and piecewise-smooth models the solutions obtained by both methods agree with each other quite well. However, the Chebyshev spectral method is more efficient than the finite-difference method.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Field study on human thermal comfort and indoor air quality in university dormitory buildings

Field studies on the environmental conditions and occupant thermal comfort were carried in air-conditioned buildings and no air-conditioned building in Xi’an, China. The present study aimed to explore the effect of indoor thermal history on the thermal adaptation and indoor air quality of occupants. Based on a field study, 550 and 580 data sets were obtained in naturally ventilated (NV) and spilled air-conditioned dormitory buildings (SAC), respectively. The physical environment parameters and subjective responses were explored. Most of the environment in NV mode were warmer than the current standard upper limit (28 °C). The neutral temperature of the NV group was 26.7 °C, 1.5 higher than that of the SAC group (24.6 °C). The upper limit of 80% acceptable temperature range was 29.2 °C for the NV group, 1.7 °C higher than that of the SAC group (27.5 °C). Compared to the SAC group, a warm indoor thermal history of the NV group produced a shift to higher neutral temperature and higher acceptable temperature. Differences were found in the indoor environment quality and in the occupant’s subjective satisfaction between the two groups. Compared to PMV model, the adaptive model was more applicable to spilt air-conditioned building