• Journal of Positioning, Navigation, and Timing
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• v.10 no.2
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• pp.121-130
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• 2021

In this paper, we propose a method to improve the positioning accuracy of TOA based indoor positioning system in NLOS environments. TOA based indoor positioning systems have been studied mostly considering LOS environments. However, it is almost impossible to maintain the LOS environments due to obstacles such as people, furniture, walls, and so on. The proposed method in this study compensates the range error caused by the NLOS environments. We confirmed that positioning accuracy of a proposed method is improved than conventional algorithms through simulation and field test.

• Journal of Environmental Health Sciences
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• v.35 no.4
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• pp.239-248
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• 2009

The Institute of Medicine of the National Academies of Science in the United States concluded in its 2004 report that excessive indoor dampness is a public health hazard and that its prevention should be a public health goal. Water damage in buildings, such as leaks from roofs, walls, or windows, may increase indoor moisture levels. Excessive dampness may promote microbial proliferation in indoor environments, increase occupants' exposure to microbial agents, and eventually produce adverse health effects in building occupants. Epidemiological studies to demonstrate the causal association between exposure to indoor microbial agents and health effects require reliable exposure assessment tools. In this review, I discuss various sampling and analytical methods to assess human exposure to biological agents in indoor environments, their strengths and weaknesses, and recent trends in research and practice in the USA.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.1122-1140
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• 2024

The importance of indoor positioning has grown in numerous application areas such as emergency response, logistics, and industrial automation. In ships, indoor positioning is also needed to provide services to passengers on board. Due to the complex structure and dynamic nature of ship environments, conventional positioning techniques have limitations in providing accurate positions. Compared to other indoor positioning technologies, Bluetooth 5.1-based indoor positioning technology is highly suitable for ship environments. Bluetooth 5.1 attains centimeter-level positioning accuracy by collecting In-phase and Quadrature (IQ) samples from wireless signals. However, distorted IQ samples can lead to significant errors in the final estimated position. Therefore, we propose an indoor positioning method for ships that utilizes a Deep Neural Network (DNN) combined with IQ fingerprint maps to overcome the challenges associated with accurate location detection within the ship. The results indicate that the accuracy of our proposed method can reach up to 97.76%.

• Environmental Engineering Research
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• v.20 no.3
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• pp.237-245
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• 2015

Particulate matter in indoor environments has caused public concerns in recent years. The objective of this research is to explore the influence of radiators on particle size distributions and concentrations. The particle size distributions as well as concentrations above radiators and in the adjacent indoor air are monitored in forty-two indoor environments in Xi'an, China. The temperatures, relative humidity and air velocities are also measured. The particle size distributions above radiators at ten locations are analyzed. The results show that the functional difference of indoor environments has little impact on the particle size distributions above radiators. Then the effects of the environmental parameters (particle concentrations in the adjacent indoor air, temperatures, relative humidities and air velocities) on particle concentrations above radiators are assessed by applying multiple linear regression analysis. Three multiple linear regression models are established to predict the concentrations of $PM_{10}$, $PM_{2.5}$ and $PM_1$ above radiators.

• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.220-228
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• 2007

For many applications particularly in navigation system, a three-dimensional representation improves the usability of information. This paper introduces 3D Graphical User Interface (GUI) of indoor location tracking system, 3D Navigation View. The application provides users a 3D visualization of the indoor environments they are exploring, synchronized with the physical world through spatial information obtained from indoor location tracking system. It adopts widely used Virtual Reality Modeling Language (VRML) to construct, represent, distribute and render 3D world of indoor environments over Internet. Java, an all-purpose programming language is integrated to comprehend spatial information received from indoor location tracking system. Both are connected through an interface called External Authoring Interface (EAI) provided by VRML. Via EAI, Java is given the authority to access and manipulate the 3D objects inside the 3D world that facilitates the indication of user's position and viewpoint in the constructed virtual indoor environments periodically.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.4
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• pp.378-389
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• 2013

In Korea, studies on the indoor air quality have been conducted since mid of 1980s. The turning point occurred in 2003 by establishing the act of the indoor air quality management for public facilities. According to the law, the basic plan for indoor air quality management is prepared by government every five years, affecting greatly governmental policy and related academia and industries. Indoor air quality survey was mostly carried out among indoor air quality researches. After then, assessment of health effect and air cleaning technology were studied. Although various control technologies for particle, bioaerosol, odor, and hazardous chemicals have been applied to indoor environments, breakthrough technologies are needed to solve real problems facing at the applied environments. In the future, issue of indoor air quality is more interested and both management policy and control technology are key factors in order to realize comfort and healthy indoor environments.

• Journal of Environmental Health Sciences
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• v.15 no.1
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• pp.11-18
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• 1989

Indoor radon concentrations, measured in 34 houses and various types of underground environments in the Seoul area during February 1988 - January 1989, varied from 0.9 - 9.9 pCi/l. Radon concentrations in basements of the selected homes were about 1.5 times higher than those levels measured in the first floor. The radon level of the first floor in the energy efficient homes are signficantly higher than the conventional homes. Indoor radon levels in the underground pass were higher than any other types of underground environments. Variations among underground environments were much less than for homes, probably because there was less variability in ventilation.

• Particle and aerosol research
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• v.5 no.3
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• pp.133-138
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• 2009

Airborne microorganisms, termed bioaerosols, are etiological agents of many respiratory and skin diseases. There are high demands of controlling the concentration of bioaerosols, specifically in indoor environments. Here, a new system for controlling indoor bioaerosols is designed and evaluated. An idea of a short time exposure to a thermal energy is used in the design of the equipment. The system was tested in laboratory environments. The experimental results show that the new system can reduce the concentration of viable bioaerosols of indoor laboratory environments.

• Journal of Environmental Science International
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• v.11 no.8
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• pp.801-810
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• 2002

The current paper describes the indoor/outdoor air quality in school environments through analyses of the heavy metal concentrations using Inductive Coupled Plasma(ICP). School environments in a heavy traffic area, two industrial areas, quasi-industrial area, and residential area were evaluated. The results were as follows: (1) The locations with the highest indoor and outdoor concentrations of heavy metals were the industrial areas followed by the heavy traffic area, residential area, and quasi-industrial area in a descending order of magnitude. Plus, the indoor heavy metal concentrations were higher then the outdoor ones. (2) The main heavy metal components were Zn, Al and Ca. Higher concentration levels were found indoors than outdoors. The heavy metal concentrations were also higher in the classrooms than in the corridor or outdoors. (3) The total heavy metal concentrations in the studied areas were highly dependent on the weather elements. including the relative humidity, mixing ratio, and wet-bulb depression. Accordingly, special ventilation systems are recommended to reduce air pollution in school environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.243-257
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• 2010

Rapid developments in wireless sensor networks have extended many applications, hence, many studies have developed wireless sensor network positioning systems for indoor environments. Among those systems, the Global Position System (GPS) is unsuitable for indoor environments due to Line-Of-Sight (LOS) limitations, while the wireless sensor network is more suitable, given its advantages of low cost, easy installation, and low energy consumption. Due to the complex settings of indoor environments and the high demands for precision, the implementation of an indoor positioning system is difficult to construct. This study adopts a low-cost positioning method that does not require additional hardware, and uses the received signal strength (RSS) values from the receiver node to estimate the distance between the test objects. Since many objects in indoor environments would attenuate the radio signals and cause errors in estimation distances, knowing the path loss exponent (PLE) in an environment is crucial. However, most studies preset a fixed PLE, and then substitute it into a radio propagation loss model to estimate the distance between the test points; such method would lead to serious errors. To address this problem, this study proposes a Path Loss Exponent Estimation Algorithm, which uses only four beacon nodes to construct a radio propagation loss model for an indoor environment, and is able to provide enhanced positioning precision, accurate positioning services, low cost, and high efficiency.