Energy, economic and environmental analysis of a BOG re-liquefaction process for an LNG carrier

Due to tighter environmental regulations, newly built liquefied natural gas (LNG) carriers are equipped with a re-liquefaction system to minimize combustion of surplus boil-off-gas (BOG). Thus, this paper comparatively analyzes the re-liquefaction system for a low-pressure gas injection engine according to the refrigerant (no external refrigerant or single mixed refrigerant) with three key performance indicators: energy, economic, and environmental aspects. For an energy efficiency analysis, we proposed several process alternatives and optimized them to minimize the specific power consumption required to liquefy BOG. In economic analysis, minimizing total annualized cost is the objective. For an environmental analysis, CO2 emissions at each optimal point is calculated and comparatively analyzed. The results show that the process without external refrigerant has 10% better performance in terms of economy, while the single mixed refrigerant process is suitable in terms of energy efficiency (6%) and environmental (15%) impact.Energy, economic and environmental analysis of a BOG re-liquefaction process for an LNG carrierpublishedVersio

Utilization of the depolarization ratio derived by AERONET Sun/sky radiometer data for type confirmation of a mixed aerosol plume over East Asia

This is an accepted manuscript of an article published by Taylor & Francis Group in International Journal of Remote Sensing on April 24, 2016. Subject to 12 months' embargo period, embargo end date: April 24, 2017 Young Min Noh, Sung-Kyun Shin, Kwonho Lee, Detlef Müller & Kwanchul Kim (2016) Utilization of the depolarization ratio derived by AERONET Sun/sky radiometer data for type confirmation of a mixed aerosol plume over East Asia, International Journal of Remote Sensing, 37(10): 2008-2025, DOI: 10.1080/01431161.2016.1176274This article confirms the utilization of depolarization ratio derived by ground-based Aerosol Robotic Network (AERONET) Sun/sky radiometer data obtained during a high-PM10 episode at Gwangju, Korea (35.10° N, 126.53° E) in April 2009, in order to determine the nature and source of the atmospheric aerosol associated with this event. Integrated monitoring using satellite and depolarization light detection and ranging (lidar) data, together with model analysis, was also completed for the period of the high-PM10 event. The Sun/sky radiometer-derived particle depolarization ratio values are similar to the lidar-derived values, and these values highlight the effect of dust particles on aerosol observation. High particle depolarization ratios (12.5– 14.2%) were observed when the aerosol plume transported from the west between 5 and 7 April. In contrast, lower particle depolarization ratios (5.8–9.8%) were detected when the aerosol plume was transported from the north on other observation days. Different optical properties are also shown according to the variation of depolarization ratio. High values in the real part of the refractive index (1.47–1.49 at 440 nm), lower values in the imaginary part of the refractive index (0.007–0.009 at 440 nm), and a high proportion of coarser particles were observed during the high depolarization ratio period. In contrast, the atmospheric aerosol transported from the north showed characteristics more commonly associated with smoke, with lower values in the real part of the refractive index (1.41–1.48 at 440 nm), higher values in the imaginary part of the refractive index (0.008–0.011), and a high proportion of fine particles. This indicates that the Sun/sky radiometer-derived depolarization ratio is a useful parameter when estimating the effect of dust particles during high-PM10 events.Peer reviewedFinal Accepted Versio

High-Temperature Optical Properties of Indium Tin Oxide Thin-Films

Indium tin oxide (ITO) is one of the most widely used transparent conductors in optoelectronic device applications. We investigated the optical properties of ITO thin films at high temperatures up to 800 °C using spectroscopic ellipsometry. As temperature increases, amorphous ITO thin films undergo a phase transition at ~ 200 °C and develop polycrystalline phases with increased optical gap energies. The optical gap energies of both polycrystalline and epitaxial ITO thin films decrease with increasing temperature due to electron-phonon interactions. Depending on the background oxygen partial pressure, however, we observed that the optical gap energies exhibit reversible changes, implying that the oxidation and reduction processes occur vigorously due to the low oxidation and reduction potential energies of the ITO thin films at high temperatures. This result suggests that the electronic structure of ITO thin films strongly depends on temperature and oxygen partial pressure while they remain optically transparent, i.e., optical gap energies \u3e 3.6 eV

Spectral signatures of a unique charge density wave in Ta2_2NiSe7_7

Charge Density Waves (CDW) are commonly associated with the presence of near-Fermi level states which are separated from others, or "nested", by a wavector of $\mathbf{q}$. Here we use Angle-Resolved Photo Emission Spectroscopy (ARPES) on the CDW material Ta$_2$NiSe$_7$ and identify a total absence of any plausible nesting of states at the primary CDW wavevector $\mathbf{q}$. Nevertheless we observe spectral intensity on replicas of the hole-like valence bands, shifted by a wavevector of $\mathbf{q}$, which appears with the CDW transition. In contrast, we find that there is a possible nesting at $\mathbf{2q}$, and associate the characters of these bands with the reported atomic modulations at $\mathbf{2q}$. Our comprehensive electronic structure perspective shows that the CDW-like transition of Ta$_2$NiSe$_7$ is unique, with the primary wavevector $\mathbf{q}$ being unrelated to any low-energy states, but suggests that the reported modulation at $\mathbf{2q}$, which would plausibly connect low-energy states, might be more important for the overall energetics of the problem

Long-term variation study of fine-mode particle size and regional characteristics using AERONET data

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).To identify the long-term trend of particle size variation, we analyzed aerosol optical depth (AOD, τ) separated as dust (τD) and coarse-(τPC) and fine-pollution particles (τPF) depending on emission sources and size. Ångström exponent values are also identified separately as total and fine-mode particles (αT and αPF). We checked these trends in various ways; (1) first-order linear regression analysis of the annual average values, (2) percent variation using the slope of linear regression method, and (3) a reliability analysis using the Mann–Kendall (MK) test. We selected 17 AERONET sun/sky radiometer sites classified into six regions, i.e., Europe, North Africa, the Middle East, India, Southeast Asia, and Northeast Asia. Although there were regional differences, τ decreased in Europe and Asian regions and increased in the Middle East, India, and North Africa. Values of τPC and τPF, show that aerosol loading caused by non-dust aerosols decreased in Europe and Asia and increased in India. In particular, τPF considerably decreased in Europe and Northeast Asia (95% confidential levels in MK-test), and τPC decreased in Northeast Asia (Z-values for Seoul and Osaka are −2.955 and −2.306, respectively, statistically significant if |z| ≥ 1.96). The decrease in τPC seems to be because of the reduction of primary and anthropogenic emissions from regulation by air quality policies. The meaningful result in this paper is that the particle size became smaller, as seen by values of αT that decreased by −3.30 to −30.47% in Europe, North Africa, and the Middle East because αT provides information on the particle size. Particle size on average became smaller over India and Asian regions considered in our study due to the decrease in coarse particles. In particular, an increase of αPF in most areas shows the probability that the average particle size of fine-mode aerosols became smaller in recent years. We presumed the cause of the increase in αT is because relatively large-sized fine-mode particles were eliminated due to air quality policies.Peer reviewe