Comparative analysis of air permeability between UHPC and epoxy-coated normal concrete for hyperloop tube structures.

This study evaluates the air permeability of epoxy-coated normal concrete and ultra-high performance concrete (UHPC) for use in Hyperloop tube structures, where maintaining ultra-low air permeability is crucial to preserving the vacuum environment. While UHPC is recognized for its exceptionally low permeability due to its dense microstructure, this research explores epoxy-coated conventional concrete as a cost-effective alternative. Using a vacuum-based permeability test simulating Hyperloop's near-vacuum conditions, the study found that epoxy-coated concrete significantly reduced air permeability compared to uncoated concrete, with specimens coated on both sides approaching near-zero permeability.

GIS-Based Analysis of Volatile Organic Compounds in Bucheon, Korea, Using Mobile Laboratory and Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry Methods.

Recently, volatile organic compounds (VOCs) have been shown to act as precursors of secondary organic particles that react with ultraviolet rays in the atmosphere and contribute to photochemical smog, global warming, odor, and human health risks, highlighting the importance of VOC management. In this study, we measured VOC concentrations in various contexts including industrial and residential areas of Bucheon, Korea, through mobile laboratory and proton-transfer-reaction time-of-flight mass spectrometry methods to determine winter VOC concentrations and visualized the data based on spatial information. Regional characteristics, temperature/humidity, atmospheric conditions, wind speed, traffic volume, etc.

Multivariate disturbance filtering in auditory fNIRS signals using maximum likelihood gradient estimation method: Feasibility study using sound quality indices.

Functional near-infrared spectroscopy (fNIRS) technology has been widely used to analyze biomechanics and diagnose brain activity. Despite being a promising tool for assessing the brain cortex status, this system is susceptible to disturbances and noise from electrical instrumentation and basal metabolism. In this study, an alternative filtering method, maximum likelihood generalized extended stochastic gradient (ML-GESG) estimation, is proposed to overcome the limitations of these disturbance factors.

The composition of the bacterial communities collected from the PM samples inside the Seoul subway and railway station.

Health implications of indoor air quality (IAQ) have drawn more attention since the COVID epidemic. There are many different kinds of studies done on how IAQ affects people's well-being. There hasn't been much research that looks at the microbiological composition of the aerosol in subway transit systems.

BT100, a three-in-one, multipurpose disinfecting, deodorizing, and air-cleaning solution with an effective, gradual, and continuous gaseous chlorine dioxide-releasing substance.

Aerosols carrying viruses that are released from the oral cavity of infected individuals are the primary, if not the only, means of transmission during viral respiratory disease epidemics. This makes crowded rooms and tiny, enclosed public areas like bathrooms prime environments for the transmission of diseases. Volatile organic compounds (VOCs) and formaldehyde are two contaminants that pose serious threats to human health and well-being in indoor environments.

Determinants of wearer satisfaction factors for harnesses in upper-limb assistive wearable robots.

Wearable robots are increasingly being deployed for use in industrial fields. However, only a few studies have focused on the usability of wearable robots. The present study evaluated the factors affecting the usability of a harness in securing a wearable robot to the body because the harness directly affects the work efficiency, and thus its design and use require careful consideration.

Characterization of bacterial species and antibiotic resistance observed in Seoul, South Korea's popular Gangnam-gu area.

Public transportation facilities, especially road crossings, which raise the pathogenic potential of urban environments, are the most conducive places for the transfer of germs between people and the environment. It is necessary to study the variety of the microbiome and describe its unique characteristics to comprehend these relationships. In this investigation, we used 16 S rRNA gene sample sequencing to examine the biological constituents and inhalable, thoracic, and alveolar particles in aerosol samples collected from busy areas in the Gangnam-gu district of the Seoul metropolitan area using a mobile vehicle.

Determination of the Spatial Distribution of Air Pollutants in Bucheon, Republic of Korea, in Winter Using a GIS-Based Mobile Laboratory.

Driven by industrialization and urbanization, urban air pollution can increase respiratory, heart, and cerebrovascular diseases, and thus mortality rates; as such, it is necessary to improve air quality through the consideration of individual pollutants and emission sources. In Republic of Korea, national and local governments have installed urban and roadside air quality monitoring systems. However, stations are lacking outside metropolitan regions, and roadside stations are sparsely distributed, limiting comparisons of pollutant concentrations with vehicle traffic and floating population levels.

Effectiveness of Tap Water in Reducing the Generation of Ultrafine Wear Particles from the Wheel-Rail Contact by Eliminating the Water Vapor Effect.

This study aimed to assess the impact of tap water application on reducing the generation of ultrafine particles from the wheel-rail contact using a twin-disk rig under dry and wet conditions, with train velocities of 45 and 80 km/h. A small amount of 0.3 L/min tap water was applied at the wheel-rail contact, and a diffusion dryer was used to eliminate water vapor.

MWCNT-Coated Glass Fabric/Phenol Composite Heating Panel Fabricated by Resin Infusion Process.

MWCNTs (multiwalled carbon nanotubes) were applied to fiber-reinforced composite materials with phenolic resin having flame retardance for the composite heating panels of railroad vehicles. Instead of dispersing MWCNTs in the matrix, the surface of a pristine plain-weave glass fiber fabric was coated with MWCNTs through a series of dip-coating and drying processes, followed by the resin infusion of the phenolic resin to make the composite heating panel. Before and after the resin infusion process, low percolation thresholds of 0.

Field studies on low and fast compressibility of cement-mixed gravel in railway embankment construction.

The cement-mixed gravel, which is used in the construction of railway embankment, is a relatively more expensive material compared to sandy soil. Having said that, it is used where small residual settlement is required for example, abutment transition zone, due to characteristic of higher strength than sandy soil. In this paper, the time-dependent settlement were evaluated using field data measured over a long period of time at two RSR (Reinforced Subgrade for Railways) construction sites using two different backfill materials (sandy soil and cement-mixed gravel).

Resilience and social change: Findings from research trends using association rule mining.

This study analyzed the historical development of with respect to multidisciplinary aspects using association rule mining (ARM). ARM is a rule-based machine-learning approach tailored to identify validated relations among multiple variables in a large dataset. This study collected author keywords from all -related literature in the Web of Science database and examined the changes in validated -related topics using ARM.

Electromagnetic drag forces between HTS magnet and tube infrastructure for hyperloop.

Maglevs are typically accelerated using electromagnetic propulsion and levitation. High-temperature superconducting (HTS) magnets along with electrodynamic suspension (EDS) and linear synchronous motors are one of the best options for Hyperloop. However, the strong magnetic fields generated by HTS magnets on the pods inevitably interact with the magnetic and conductive structures in the vacuum tubes, along with the tube itself, while the pods move through the tubes.

Systematic literature review on impacts of COVID-19 pandemic and corresponding measures on mobility.

Unlabelled: The unprecedented COVID-19 outbreak has significantly influenced our daily life, and COVID-19's spread is inevitably associated with human mobility. Given the pandemic's severity and extent of spread, a timely and comprehensive synthesis of the current state of research is needed to understand the pandemic's impact on human mobility and corresponding government measures. This study examined the relevant literature published to the present (March 2023), identified research trends, and conducted a systematic review of evidence regarding transport's response to COVID-19.

Independent Heating Performances in the Sub-Zero Environment of MWCNT/PDMS Composite with Low Electron-Tunneling Energy.

The structural stability of various structures (railroads, bridges, buildings, etc.) is lowered due to freezing because of the decreasing outside temperature in winter. To prevent damage from freezing, a technology for de-icing has been developed using an electric-heating composite.

Evaluation of Health Economic Loss Due to Particulate Matter Pollution in the Seoul Subway, South Korea.

Evaluating an illness's economic impact is critical for developing and executing appropriate policies. South Korea has mandatory national health insurance in the form of NHIS that provides propitious conditions for assessing the national financial burden of illnesses. The purpose of our study is to provide a comprehensive assessment of the economic impact of PM exposure in the subway and a comparative analysis of cause-specific mortality outcomes based on the prevalent health-risk assessment of the health effect endpoints (chronic obstructive pulmonary disease (COPD), asthma, and ischemic heart disease (IHD)).

Fine Particulate Matter (PM) Sources and Its Individual Contribution Estimation Using a Positive Matrix Factorization Model.

The effective management and regulation of fine particulate matter (PM) is essential in the Republic of Korea, where PM concentrations are very high. To do this, however, it is necessary to identify sources of PM pollution and determine the contribution of each source using an acceptance model that includes variability in the chemical composition and physicochemical properties of PM, which change according to its spatiotemporal characteristics. In this study, PM was measured using PMS-104 instruments at two monitoring stations in Bucheon City, Gyeonggi Province, from 22 April to 3 July 2020; the PM chemical composition was also analyzed.

Human Health Impacts of Residential Radon Exposure: Updated Systematic Review and Meta-Analysis of Case-Control Studies.

This study investigated the impact of residential radon exposure on human cancers (i.e., lung cancer and childhood leukemia) through a systematic review and meta-analysis of case−control studies.

Applicability Evaluation of Surface and Sub-Surface Defects for Railway Wheel Material Using Induced Alternating Current Potential Drops.

The majority of catastrophic wheelset failures are caused by surface opening fatigue cracks in either the wheel tread or wheel inner. Since failures in railway wheelsets can cause disasters, regular inspections to check for defects in wheels and axles are mandatory. Currently, ultrasonic testing, acoustic emissions, and the eddy current testing method are regularly used to check railway wheelsets in service.

Effect of gelatin treatment on tow deformation in resin-impregnated glass fiber.

The potential use of gelatin materials in the liquid composite molding manufacturing (LCM) process was investigated, with specific focus on the reinforcement deformation phenomenon. The adoptability of gelatin as a binder in a composite material with glass fiber for application in the LCM process was evaluated by analyzing the permeability and microscopic structure of the gelatin-coated glass fiber. To assess the tow deformation, the permeability of the non-crimped unidirectional glass fiber mat was evaluated at different flow rates that could be applied in the LCM process.

Study on the Ventilation Method to Maintain the PM Concentration in a Subway Cabin below 35 μg/m.

The city of Seoul will limit the maximum particulate matter (PM) concentration to ≤35 μg/m (from 2024). Herein, a numerical parametric study was conducted on the PM removal efficiency of the heating, ventilation, and air conditioning (HVAC) filters installed in the ceiling of subway cabins. The PM concentration distribution was explored according to the flow rate and flow rate ratio of the air introduced into the cabin.

Optimized parameters for effective SARS-CoV-2 inactivation using UVC-LED at 275 nm.

The spread of SARS-CoV-2 infections and the severity of the coronavirus disease of 2019 (COVID-19) pandemic have resulted in the rapid development of medications, vaccines, and countermeasures to reduce viral transmission. Although new treatment strategies for preventing SARS-CoV-2 infection are available, viral mutations remain a serious threat to the healthcare community. Hence, medical devices equipped with virus-eradication features are needed to prevent viral transmission.