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Kepler data for three SRS: stars, V616 Lyrae, V607 Lyrae, and V621 Lyrae, were analyzed to study their period structure. Two of the stars had confirmed SRS light curve characteristics. V616 Lyr shows two strong periods at 16.91 days and 8.18 days. V607 Lyr shows one strong period at 13.55 days. V616 Lyr and V607 Lyr also display amplitude changes common to the SR stars. Variability was not detected for V621 Lyr. Evidence for solar-like oscillations in V616 Lyr is presented. 

As a result of constantly increasing data center utilization, many challenges have appeared for thermal engineers over the last few decades. Advanced cooling systems for servers are of significant interest, particularly, technologies which can also reduce electricity usage. One known technology called Organic Rankine Cycle (ORC) is considered a viable alternative for this purpose. It can both the heat from a server and then transfer the server heat into a power cycle to generate electricity. This study consists of the design and construction of an experimental prototype of 20kW of waste heat, representing two common rack servers operating at full capacity. The range of server waste heat temperatures is between 60°C to 85°C, which is far below the normal operating range for ORCs. This ultra-low-grade waste heat leads to an expected thermal efficiency between 2%-8%. Tests on the experimental rig showed a maximum thermal efficiency of 3.33%. The system is both absorbing all the waste heat from the data center and at the same time providing an economic benefit back to the data center in form of electricity. Through experimental investigation, this study provides the first evidence for using ORC system as a valid solution for ultra-low-grade waste heat recovery. 

Abstract In this work, we present polarization profiles for 23 millisecond pulsars observed at 820 and 1500 MHz with the Green Bank Telescope as part of the NANOGrav pulsar timing array. We calibrate the data using Mueller matrix solutions calculated from observations of PSRs B1929+10 and J1022+1001. We discuss the polarization profiles, which can be used to constrain pulsar emission geometry, and present both the first published radio polarization profiles for nine pulsars and the discovery of very low-intensity average profile components (“microcomponents”) in four pulsars. We obtain the Faraday rotation measures for each pulsar and use them to calculate the Galactic magnetic field parallel to the line of sight for different lines of sight through the interstellar medium. We fit for linear and sinusoidal trends in time in the dispersion measure and Galactic magnetic field and detect magnetic field variations with a period of 1 yr in some pulsars, but overall find that the variations in these parameters are more consistent with a stochastic origin. 

ABSTRACT We present 10 main-sequence ALPINE galaxies (log (M/M⊙) = 9.2−11.1 and $${\rm SFR}=23-190\, {\rm M_{\odot }\, yr^{-1}}$$) at z ∼ 4.5 with optical [O ii] measurements from Keck/MOSFIRE spectroscopy and Subaru/MOIRCS narrow-band imaging. This is the largest such multiwavelength sample at these redshifts, combining various measurements in the ultraviolet, optical, and far-infrared including [C ii]158 $$\mu$$m line emission and dust continuum from ALMA and H α emission from Spitzer photometry. For the first time, this unique sample allows us to analyse the relation between [O ii] and total star-formation rate (SFR) and the interstellar medium (ISM) properties via [O ii]/[C ii] and [O ii]/H α luminosity ratios at z ∼ 4.5. The [O ii]−SFR relation at z ∼ 4.5 cannot be described using standard local descriptions, but is consistent with a metal-dependent relation assuming metallicities around $$50{{\ \rm per\ cent}}$$ solar. To explain the measured dust-corrected luminosity ratios of $$\log (L_{\rm [OII]}/L_{\rm [CII]}) \sim 0.98^{+0.21}_{-0.22}$$ and $$\log (L_{\rm [OII]}/L_{\rm H\alpha }) \sim -0.22^{+0.13}_{-0.15}$$ for our sample, ionization parameters log (U) < −2 and electron densities $$\log (\rm n_e / {\rm [cm^{-3}]}) \sim 2.5-3$$ are required. The former is consistent with galaxies at z ∼ 2−3, however lower than at z > 6. The latter may be slightly higher than expected given the galaxies’ specific SFR. The analysis of this pilot sample suggests that typical log (M/M⊙) > 9 galaxies at z ∼ 4.5 to have broadly similar ISM properties as their descendants at z ∼ 2 and suggest a strong evolution of ISM properties since the epoch of reionization at z > 6. 

UPS (Uninterruptible Power Supply) units and batteries are essential subsystems in data centers or telecom industries to protect equipment from electrical power spikes, surges and power outages. UPS units handle electrical power and dissipate a large amount of heat, and possess a high efficiency. Therefore, cooling units (e.g., CRACs) are needed to manage the thermal reliability of this equipment. On the other hand, battery operating conditions and reliability are closely related to the ambient temperature according to battery manufacturers; reliability increases when the ambient room temperature is around 25ºC. This study analyzed different room configurations and scenarios using the commercial CFD software 6Sigma Room DCXTM. As a first approach, we evaluated the thermal behavior and cooling degradation using standard thermal performance metrics SHI (Supply Heat Index) and RHI (Return Heat Index). These are frequently implemented in data centers to measure the level of mixing between cold and hot air streams. The results from this evaluation showed that standard cooling practices are inefficient, as values for the two metrics differed considerably from industry recommendations. We also considered a metric from the second law of thermodynamics using exergy destruction. This technique allowed us to find the mechanisms that increase entropy generation the most, including viscous shear and air stream mixing. Reducing exergy destruction will result in lessening lost thermodynamic work and thus reduce energy required for cooling. Typically, UPS and batteries are located in different rooms due to the hydrogen generation by the batteries. The integration of both equipment in the same room is a new concept, and this study aims to analyze the thermal performance of the room. Adding controllability showed improvements by reducing the exergy destruction due to viscous dissipation while slightly increasing thermal mixing in the rooms. Ducting the return flows to avoid flow mixing increased pressure drop, but reduced heat transfer between the hot and cold air streams, which in turn, improved the thermal performance. In the study, we determined the optimal configuration and possible strategies to improve cooling while maintaining desirable battery temperatures. 

Aims. The dust content of normal galaxies and the dust mass density (DMD) at high- z ( z  > 4) are unconstrained given the source confusion and the sensitivity limitations of previous observations. The ALMA Large Program to INvestigate [CII] at Early times (ALPINE), which targeted 118 ultra-violet (UV)-selected star-forming galaxies at 4.4 <  z  < 5.9, provides a new opportunity to tackle this issue for the first time with a statistically robust dataset. Methods. We exploited the rest-frame far-infrared (FIR) fluxes of 23 galaxies individually detected in their continuum emission, as well as stacked continuum images, to measure the dust content of the 118 UV-selected ALPINE galaxies. We focused on the dust scaling relations and, by comparison with predictions from chemical evolution models, we probed the evolutionary stage of UV-selected galaxies at high- z . By using the observed correlation between the UV luminosity and the dust mass, we estimated the DMD of UV-selected galaxies at z  ∼ 5, weighting the galaxies by means of the UV luminosity function. The derived DMD is compared with the value we estimated from ten ALPINE galaxies blindly detected in the FIR continuum, at the redshift of the ALPINE targets. Results. Our ALMA survey allows the exploration for the first time of the dust content in normal star-forming galaxies at z  > 4 in a statistically robust sample of sources. The comparison of the observed dust scaling relations with chemical evolution models suggests that ALPINE galaxies are not likely progenitors of disc galaxies, but of intermediate- and low-mass proto-spheroids, resulting in present-day bulges of spiral or elliptical galaxies. Interestingly, this conclusion is in line with the independent morphological analysis that shows that the majority (∼70%) of the dust-continuum detected galaxies have a disturbed morphology. The DMD obtained at z  ∼ 5 from UV-selected sources is ∼30% of the value obtained from blind FIR-selected sources, showing that the UV selection misses the most dust-rich, UV-obscured galaxies.