Performance Evaluation of Precast Concrete Using Microwave Heating Form

The purpose of this study is to evaluate the temperature distribution, strength development, porosity, scanning electron microscopy observation, shrinkage, and surface properties of concrete in order to apply microwave heat curing to the precast method and to analyze the CO2 emissions and economic feasibility of microwave heat curing. The heating of a steel form by microwave heating enabled concrete to be efficiently cured at a temperature within a range of _5 _C. After the curing, demolding strength could be cleared through the densification of the concrete by decreasing the porosity of the concrete. Microwave heat curing exhibited excellent performance compared to conventional steam curing in terms of efficient temperature control, occurrence of cracks due to shrinkage, surface condition of concrete after curing, economic efficiency, and CO2 emissions. However, verification and supplementation based on actual data are necessary so that environments applicable to the various sizes and shapes of forms can be prepared

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Assessment of the Applicability of a Thawing-Guided Drainage System for Old Railway Tunnel Icicle Prevention in Cold Weather

As train failures from icicles annually recur in old railway tunnels in cold weather, fundamental measures to prevent the formation of icicles within the tunnels are necessary for the safe operation of trains and efficient maintenance of old tunnels. This study develops and tests a thawing-guided drainage system for old railway tunnels. The proposed system consists of heating panels, supporting stands, and the drainageways for discharging leaked water. A heating panel is composed of a film heater, thermal insulator, and a steel plate. The heater installed on a steel plate supplies the heat source to prevent icicle formation. This system uses a low-power module lining structure, which fundamentally prevents the formation of icicles from cracks in old railway tunnels and induces the drainage of thermally melted icicles to the outside of the track. A prototype system was installed in the Seungbu tunnel (a railway tunnel) and monitored over 3 weeks in winter from 22 December 2021 to 12 January 2022. The icicle prevention and guided drainage performances were verified at an ambient temperature of about −10 °C, with an internal temperature for maintaining the system above 0 °C over the whole test period. The proposed system is judged by the fact that the applicability of the developed system has been verified in consideration of the following three aspects: usability in the operational railway line, effectiveness through icicle prevention performance, and operational safety which does not interfere with train operations

Design of a Shipboard Outside Communication Network and Its Testbed Using PLC: For Safety Management during the Ship Building Process

For the shipbuilding industry worldwide, work-related accidents at the construction site have been a major concern. Workers at the shipyards are consistently exposed to dangerous environments and their intensity of work is quite high. Considering the complexity of the shipbuilding process, efficient communications between workers are essential in the workplace, but current communication methods, which mostly use wireless technologies, are sometimes limited by the structural blocks, creating shadow areas where the radio bands cannot reach. As a countermeasure, SUNCOM Co., Ltd in the Republic of Korea has developed the PLC-based communication system followed by establishing a test-bed facility in cooperation with SK Telecom Co., Ltd and the Hyundai Heavy Industries Co., Ltd. This system and applied technologies are expected to reduce accidents in the field and be applied for other industries having the same problem, providing an uninterrupted communication environment and safer working conditions. The solution adopted this time can provide mobile communication services inside the ship during shipbuilding, thereby enabling rapid processing of work reports and instructions and fast responses to disaster occurrence, contributing to improvements in work efficiency in shipbuilding yards and ensuring workers’ safety

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This research reviewed and compared the railway noise standards of major railway countries because the control of railway noise has become more important recently. In order to satisfy demand for railway vehicles capable of higher speeds and to reduce maintenance, concrete slab track is becoming more popular due to its high rigidity compared to conventional ballasted track. However, since concrete slab track has unfavorable acoustic characteristics in terms of reflecting sound, it increases the noise level compared to ballasted track. Sound absorbable concrete slab track could be an effective solution to reduce railway noise; this research suggests the important features that need to be considered to design sound absorbable concrete slab track. In order to develop concrete with high sound absorbing capability, various measurement methods for porosity and sound absorption coefficient, and evaluation methods to represent sound absorption coefficient in a single parameter, were reviewed and analyzed. In addition, analytical sound absorption rate models were analyzed by comparison with the experimental results recently conducted by the authors. © 2018 The Korean Society for Railway

Microstructural characteristics of sound absorbable porous cement-based materials by incorporating natural fibers and aluminum powder

As transportation on roads and railways has become an essential means enabling the development of cities, residents living near roads and railways face undesirable noise pollution. To reduce this noise pollution, sound absorbable porous cement-based materials have great potential in terms of high sound absorption ability at a wide frequency range. Because sound absorption performance is primarily related to pore characteristics, this study mainly focuses on the development and evaluation of highly porous structures in cement-based materials by incorporating natural fibers and aluminum powder. The fresh and hardened properties of porous cement-based materials are investigated with respect to workability, compressive strength, and water absorption capacity. Furthermore, the porous network in the materials is characterized by microstructural observation using an optical microscope and X-ray computed tomography. A sound absorption test is also conducted to highlight the influences of the material porosity on sound absorption performance. Experimental results indicate that a combination of natural fibers and aluminum powder has a synergistic effect for forming highly porous structures that improve sound absorption performance. (C) 2020 Elsevier Ltd. All rights reserved

Performance Evaluation of Precast Concrete Using Microwave Heating Form

The purpose of this study is to evaluate the temperature distribution, strength development, porosity, scanning electron microscopy observation, shrinkage, and surface properties of concrete in order to apply microwave heat curing to the precast method and to analyze the CO2 emissions and economic feasibility of microwave heat curing. The heating of a steel form by microwave heating enabled concrete to be efficiently cured at a temperature within a range of ±5 °C. After the curing, demolding strength could be cleared through the densification of the concrete by decreasing the porosity of the concrete. Microwave heat curing exhibited excellent performance compared to conventional steam curing in terms of efficient temperature control, occurrence of cracks due to shrinkage, surface condition of concrete after curing, economic efficiency, and CO2 emissions. However, verification and supplementation based on actual data are necessary so that environments applicable to the various sizes and shapes of forms can be prepared

Assessment of Heavy Metal and Oil-Contaminated Silty Sand Treatment by Electrical Resistance Heating Method

The feasibility of the electrical resistance heating method developed in this study was evaluated for the remediation of multi-contaminated silty sand in terms of environmental and geotechnical aspects. The multi-contaminated silty sand sampled in this study was polluted with 21,081 mg/kg of heavy oils, as well as heavy metals. Silty sand, treated using the electrical resistance _heating method was environmentally, as well as geotechnically, compared with the multi-contaminated silty sand in terms of residual concentration, leaching, shear modulus and modified California bearing ratio (CBR). The remediation test was conducted with a target temperature of 700 °C. The removal efficiency of total petroleum hydrocarbon (TPH) was estimated as 99.99% after remediation in 48 h; most of the heavy metals, as some of the contaminants, were isolated as a crystal in treated silty sand without any harmful leakage, and heavy oil was fully extracted with a form of mist and dust. Moreover, it was also geotechnically found that the decontamination process, including the removal of heavy metals and oils, had an effect on the increase in the internal friction angle, shear modulus and modified CBR of treated silty sand. In conclusion, it is shown that the electrical resistance heating method developed in this study is an environmentally and geotechnically effective technology for the recovery of clean construction fill material from hazardous-waste-contaminated silty sand

Assessment of Heavy Metal and Oil-Contaminated Silty Sand Treatment by Electrical Resistance Heating Method

The feasibility of the electrical resistance heating method developed in this study was evaluated for the remediation of multi-contaminated silty sand in terms of environmental and geotechnical aspects. The multi-contaminated silty sand sampled in this study was polluted with 21,081 mg/kg of heavy oils, as well as heavy metals. Silty sand, treated using the electrical resistance _heating method was environmentally, as well as geotechnically, compared with the multi-contaminated silty sand in terms of residual concentration, leaching, shear modulus and modified California bearing ratio (CBR). The remediation test was conducted with a target temperature of 700 °C. The removal efficiency of total petroleum hydrocarbon (TPH) was estimated as 99.99% after remediation in 48 h; most of the heavy metals, as some of the contaminants, were isolated as a crystal in treated silty sand without any harmful leakage, and heavy oil was fully extracted with a form of mist and dust. Moreover, it was also geotechnically found that the decontamination process, including the removal of heavy metals and oils, had an effect on the increase in the internal friction angle, shear modulus and modified CBR of treated silty sand. In conclusion, it is shown that the electrical resistance heating method developed in this study is an environmentally and geotechnically effective technology for the recovery of clean construction fill material from hazardous-waste-contaminated silty sand

Chloride-induced corrosion of steel fiber near the surface of ultra-high performance concrete and its effect on flexural behavior with various thickness

The results of experimental investigation of ultra-high performance concrete (UHPC) by evaluating the flexural response are presented in order to qualitatively evaluate the effects of chloride-induced corrosion. The third-point bending test is carried out using the hydraulic servo-controlled testing machine. The experimental variables are thickness of specimen (10, 25 and 50 mm), immersion duration, and mixture design of UHPC. The specimens are immersed in 10 wt% NaCl solution up to a year to induce corrosion. The effect of chloride-induced corrosion of steel fiber of UHPC is evaluated in terms of compressive strength, flexural strength and flexural toughness. The experimental results indicate that there is no significant loss in flexural strength and toughness for the specimens which were thicker than 25 mm over a period up to 365 days of immersion in chloride solution; whereas, the specimen with thickness of 10 mm showed about 10% decrease in maximum stress and corresponding toughness after 180 days of the immersion. Furthermore, it is revealed by comparing the compressive strength with and without fibers that the presence of steel fibers in UHPC under corrosive environments do not lead to substantial strength decrease