Exploring circular water options for a water-stressed city: Water metabolism analysis for Paju City, South Korea

For urban areas with limited water supplies, circular water strategies must be pursued to achieve water security goals. By tracking and balancing all water flows and their potential changes city-wide, urban water metabolism is a useful framework for exploring the effect of circular water strategies on performance. This study focused on a water-stressed city in South Korea, Paju. We first analyzed Paju's current and future water metabolism. We then explored the effects of 10 alternative water management options (implementing four circular water strategies separately or combined, in both conservative and maximum potential cases) on three aspects of water security (water resource efficiency, self-sufficiency, and supply diversification). In 2018, Paju had lower efficiency of water use than our benchmarking case, Seoul, despite Paju's higher level of supply self-sufficiency and diversity. By 2040, the expected growth and increasing water demand of the city would further increase its reliance on water imports, requiring expansion of water infrastructure. However, if Paju employs large-scale wastewater recycling and rainwater harvesting, and reduces its water loss and demand, the combined effect could offset the expected water supply increase between 2018 and 2040, as well as the associated need for additional infrastructure.N

Enhanced electrochemical performance and interdiffusion behavior of sodium ions in onion-derived freeze-dried and KOH-activated carbon for sodium-ion battery anodes

Biomass-derived carbon materials are widely regarded as promising anode materials for sodium-ion batteries (SIBs) owing to their environmental friendliness, high electronic conductivity, stability, and low cost. However, their commercial application is restricted because of their low capacities and poor cycling stabilities. Heteroatom doping and increasing the active specific surface area of carbon materials have proven to be key to solving these problems. In this study, a facile activation and annealing process combined with freeze drying and KOH treatment was used to successfully prepare nitrogen-doped onion-derived carbon materials (dried onion (DO) and freeze-dried onion (FDO)) with high specific surface areas. The obtained carbon materials exhibited excellent electrochemical performances as anodes for SIBs, delivering high discharge reversible capacities of 140.5 (DO) and 151.4 (FDO) mAh/g at a current density of 0.05 A/g after 30 cycles. The capacities reached 45 (DO) and 66 (FDO) mAh/g at 30 A/g. Specifically, FDO//Na3V2(PO4)3@C full cells achieved a reversible capacity of 43.9 mAh/g with a specific energy of 91.5 Wh kg−1 at 5 C after 1,000 cycles, indicating that it provides broad prospects for the energy storage system of SIBs. © 2023 Elsevier B.V.FALS

The Galaxy Environment of Extremely Massive Quasars. I. An Overdensity of H alpha Emitters at z=1.47

We measure a strong excess in the galaxy number density around PG 1630+377, an extremely massive (M (BH) similar or equal to 10(9.7) M (circle dot)) quasar at z = 1.475, using near-infrared narrowband imaging. We identify 79 narrow H-band excess objects in a 525 arcmin(2) area including the vicinity and surroundings of the quasar. These sources are likely H alpha line emitting, star-forming galaxies at z approximate to 1.47. We detect a delta = 6.6 +/- 2.7 overdensity of narrow H-band excess objects located at a projected distance approximate to 2.1 Mpc northeast of the quasar, which is the densest region in the target area. The overdensity is present in BzK color-selected galaxies, while a previously reported overdensity in the immediate vicinity of PG 1630+377 is not, and yet appears as a group-like structure. These megaparsec-scale environments are estimated to merge into a similar or equal to 10(14.7) M (circle dot) cluster at present. Our results support the view that extremely massive black holes form and grow in group-scale environments and later incorporate into a galaxy cluster.N

The Infrared Medium-Deep Survey. II. How to Trigger Radio AGNs? Hints from their Environments

Activity at the centers of galaxies, during which the central supermassive black hole is accreting material, is nowadays accepted to be rather ubiquitous and most probably a phase of every galaxy's evolution. It has been suggested that galactic mergers and interactions may be the culprits behind the triggering of nuclear activity. We use near-infrared data from the new Infrared Medium-Deep Survey and the Deep eXtragalactic Survey of the VIMOS-SA22 field and radio data at 1.4 GHz from the FIRST survey and a deep Very Large Array survey to study the environments of radio active galactic nuclei (AGNs) over an area of ~25 deg2 and down to a radio flux limit of 0.1 mJy and a J-band magnitude of 23 mag AB. Radio AGNs are predominantly found in environments similar to those of control galaxies at similar redshift, J-band magnitude, and (Mu – Mr ) rest-frame color. However, a subpopulation of radio AGNs is found in environments up to 100 times denser than their control sources. We thus preclude merging as the dominant triggering mechanism of radio AGNs. By fitting the broadband spectral energy distribution of radio AGNs in the least and most dense environments, we find that those in the least dense environments show higher radio-loudness, higher star formation efficiencies, and higher accretion rates, typical of the so-called high-excitation radio AGNs. These differences tend to disappear at z > 1. We interpret our results in terms of a different triggering mechanism for these sources that is driven by mass loss through winds of young stars created during the observed ongoing star formation