• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.8
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• pp.1102-1114
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• 2002

An electret filter is composed of permanently charged electret fibers and is widely used in applications requiring high collection efficiency and low-pressure drop. In this work, the collection efficiency of the filter media used in manufacturing cabin air filters was investigated by using poly-disperse particles when submicron particles were loaded. Long-term experiments were conducted by applying two different charging states, which were spray electrification and charge equilibrium by bipolar ionization. In order to investigate the effect of particle loading in filter media, NaCl particles were generated from 0.1% and 1% solutions by an atomizer. Liquid DOS particles were used to evaluate the effect of liquid particles on the collection efficiency of an electret filter. The results show significant effect of charge amount and size distribution of loading particles on the collection performance of a filter media in submicron region. Smaller particles loaded in electret fibers cause a more rapid degradation in collection efficiency and have lower minimum efficiency with time. The pressure drop of a filter media do rarely increase when the collection efficiency decreases to the minimum value. For the larger particles charged by spray electrification, which have charge amounts more than that of Boltzmann equilibrium charge distribution, the pressure drop of a filter media slowly increases in comparison with that of equilibrium charged particles. For DOS particles it is shown that the charging level of an electret filter severely decreases and the collection efficiency is below 10% in some particle size range.

• Journal of Radiation Industry
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• v.4 no.1
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• pp.85-89
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• 2010

The radioactive experiments are carried out for diagnosis of a variety of industrial processes in terms of the operation condition and the efficiency by measuring the residence time distribution. However, it is not easy to interpret the residence time distribution using the conventional methods when the flow rate is not constant and a number of processes are coupled in a complicated manner. In these cases, they can be analyzed by describing the system with mathematical models that can be defined with the state-space equations. In this paper, the residence time distribution of sludge was measured with a radiotracer, $^{46}Sc-EDTA$, in the digester of which the flow rate varies with time. The digester was assumed as a linear time variant system since the flow rate changed during the experiment and the operation efficiency of the digester was calculated by applying the state-spae equations.

• Journal of Distribution Science
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• v.19 no.5
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• pp.5-12
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• 2021

Purpose: Research on supply chain sustainability is important for exporters When the factor of sustainable development is considered by the businesses as well as governments of all countries. Research on supply chain sustainability is important for exporters. Sustainable supply chain management and supply chain dynamics will help enterprises adapt to changes in the business environment. This study analyzes the impact of sustainable supply chain management, and supply chain dynamic capabilities on the sustainable development of exporting enterprises in Vietnam. Research design, data, and methodology: The research model and survey are designed based on previous studies after surveying export enterprises. With 185 samples collected from export enterprises. The Structural Equation Modeling (SEM) analysis technique is used. Data analysis is performed on SPSS and AMOS software (Reliability test, Confirmatory Factor Analysis, SEM). Results: Sustainable supply chain management and supply chain dynamic capabilities all have positive effects on the sustainable development of businesses (sustainable development is measured by distribution: measuring economic efficiency, social efficiency, and environmental performance). Conclusions: From the results of this study, the authors also made several recommendations to help export enterprises develop sustainability based on sustainable supply chain management and supply chain dynamic capabilities.

• The KSFM Journal of Fluid Machinery
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• v.19 no.5
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• pp.20-27
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• 2016

The Francis-99 is a workshop initiated by the Norwegian University of Science and Technology (NTNU), Norway, and Lulea University of Technology (LTU), Sweden, in order to further validate the capabilities of the CFD technologies. The goal of the first workshop is to determine the state of the art of numerical predictions for steady operating conditions. When performing the CFD analysis, some geometry details are often neglected. In case of Francis Turbine, labyrinth seals are usually not include in the simulation domain, this may lead to inaccurate prediction of turbine efficiency. In this study, the CFD analysis for Francis-99 Workshop model has been performed for full domain of machine including top and bottom labyrinth seals. The efficiency value and distribution of velocity and pressure have been investigated and compared to the experimental data obtained from NTNU. By comparing the results, it was found that: With the top and bottom labyrinth seals in the domain, the CFD result was significantly improved in prediction of efficiency at all the operating point, especially at part load.

• Journal of Korean Society on Water Environment
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• v.25 no.5
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• pp.674-681
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• 2009

Characteristics of organic matters (OM) in wastewater and the removal efficiencies were investigated using the influent and the effluent samples collected from 21 wastewater treatment plants. The OM characteristics investigated included biodegradability, humic content, specific UV absorbance (SUVA), the distribution percentage of refractory OM (R-OM), and synchronous fluorescence spectra. The types of wastewater (sewage, livestock waste/night soils, industrial waste) were easily distinguished by comparing the synchronous fluorescence spectra of the influent wastewater. The prominent peak of protein-like fluorescence (PLF) was observed for livestock waste/night soils whereas sewage exhibited a unique fluorescence peak at a wavelength of 370 nm. Irrespective of the wastewater types, the distribution percentage of R-OM increased from the influent to the effluent. Livestock waste/night soils showed the highest removal efficiency among all the three types of wastewater. There was no statistical difference of the removal efficiency between a traditional activated sludge and biological advanced treatment processes. Removal efficiency based on dissolved organic carbon DOC presented good correlations with the distribution percentage of R-OM and fulvic-like fluorescence (FLF) of the influent. The prediction for DOC removal efficiency was improved by using multiple regression analyses based on some selected OM characteristics and mixed liquid suspended solid (MLSS).

• Journal of Distribution Science
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• v.22 no.10
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• pp.91-102
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• 2024

Purpose: This study exploresthe impact of e-service quality (e-SQ) on satisfaction, trust, and loyalty within Chinese online travel retail distribution agencies (OTRDAs) using the SOR (stimulus-organism-response) model. In addition, this research examines the mediating roles of satisfaction and trust in the relationship between e-SQ and loyalty. In the model, e-SQ encompasses four sub-dimensions, such as information, efficiency, reliability, and security. Research design, data, and methodology: Data were collected from 401 respondents through an online survey. The data were analyzed using SPSS 25.0 and SmartPLS 4.1 to test the relationships among the variables. Results: The findings reveal that information, efficiency, reliability, and security positively influence satisfaction and trust. Both satisfaction and trust, in turn, significantly enhance loyalty. Mediation analysisindicatesthat satisfaction and trust partially mediate the relationship between e-SQ and loyalty. Conclusions: The study highlights the direct effects of e-SQ components on satisfaction and trust, as well as their indirect effects on loyalty within the OTRDA framework. Notably, trust exerts a stronger influence on loyalty than satisfaction, underscoring the importance of trust as a mediator in the satisfaction-loyalty relationship. Consequently, customer loyalty programs for OTRDAs should prioritize trust evaluations alongside satisfaction measures.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.9
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• pp.2590-2608
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• 2023

The high-altitude and mobility characteristics of unmanned aerial vehicles (UAVs) have made them a key element of new radio systems, particularly because they can exceed the limits of terrestrial networks. However, at high altitudes, UAVs can be significantly affected by intercell interference at a high line-of-sight probability. To mitigate this drawback, we propose an algorithm that selects the optimal beam to reduce interference and maximize transmission efficiency. The proposed algorithm comprises two steps: constructing a user-location-based fingerprint database according to the user types presented herein and cooperative beam selection. Simulations were conducted using cellular cooperative downlink systems for analyzing the performance of the proposed method, and the signal-to-interference-plus-noise cumulative distribution function and spectral efficiency cumulative distribution function were used as performance analysis indicators. Simulation results showed that the proposed algorithm could reduce the effect of interference and increase the performance of the desired signal. Moreover, the algorithm could efficiently reduce overheads and system cost by reducing the amount of resources required for information exchange.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.796-805
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• 2016

In many wireless sensor network (WSN) applications, the information transmitted by an individual entity or node is of limited use without the knowledge of its location. Research in node localization is mostly geared towards multi-hop range-free localization algorithms to achieve accuracy by minimizing localization errors between the node's actual and estimated position. The existing localization algorithms are focused on improving localization accuracy without considering efficiency in terms of energy costs and algorithm convergence time. In this work, we show that our proposed localization scheme, called DV-maxHop, can achieve good accuracy and efficiency. We formulate the multi-objective optimization functions to minimize localization errors as well as the number of transmission during localization phase. We evaluate the performance of our scheme using extensive simulation on several anisotropic and isotropic topologies. Our scheme can achieve dual objective of accuracy and efficiency for various scenarios. Furthermore, the recently proposed algorithms require random uniform distribution of anchors. We also utilized our proposed scheme to compare and study some practical anchor distribution schemes.

• Journal of Distribution Science
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• v.20 no.9
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• pp.97-107
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• 2022

Purpose: Online-To-Offline Food Delivery Services (O2O-FDS) is a new element in hotel supply chain that digitalizes traditional food delivery practices using new technologies. Targeting hotel guests, the present research is to explore the role of trust in the relationship between food delivery app on loyalty, price efficiency, and convenience. This new perspective is an essential value addition in the field of hotel marketing in relation to O2O-FDS. Research design, data and methodology: The present research conducted the mediator variable regression analysis as a main statistical methodology to identify the connections between three main constructs using total 244 South Korean participants that were recruited from the professional research company in Korea. Results: The statistical findings based on three steps of mediator regression approach strongly indicate that the trust of food delivery app in the hotel sector plays a moderating role in the relationship between price efficiency and convenience of food delivery app and customer loyalty of food delivery app in the hotel business. Conclusions: This research concludes that hotel practitioners must strive to provide adequate information on food delivery applications in order to increase price efficiency and convenience relative to traditional food and beverage services, influencing consumer trust in food delivery technology.

• Journal of Welding and Joining
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• v.5 no.1
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• pp.23-33
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• 1987

Plasma arc cutting is a fusion cutting process in which a gas constricted arc is employed to produce high temperature, high velocity jet at the workpiece. Even though the plasma arc cutting has been wid¬ely used in the industry, very little work has been done on the analysis of the process. In this paper, the kerf width was numerically analyzed by soving the temperature distribution in base metal under consideration of the latent heat effect. In modelling the heat flow problem, the heat intensity of the plasma arc was assumed to have a Gaussion distribution in the transverse direction and expone¬ntially decreasing in the thickness direction. The thermal efficiency and the heat input ratio of the top surface were experimentally deterimned for various thickness and cutting conditions, and used in numerical calculation of the kerf width. The experimental results were in eonsiderabely good agreement with the theoretically predicted kerf width.