• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.2A
• /
• pp.198-203
• /
• 2008

In this paper, we consider the diffuse type of indoor wireless optical communication (WOC) system. To find the channel characteristics of indoor wireless infrared communication system, we investigate the simulation process to get the impulse response of diffuse type and analyze the scenario of the indoor structure which we have built. The simulation results of the impulse response include power ratio and time delay due to bounce times. We get and discuss the receiving power distribution according to six configurations which have different transmitter and receiver positions and reflection coefficients of the indoor structure assumed. The results of this paper are useful to design the indoor wireless optical communication systems.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.4
• /
• pp.311-322
• /
• 2010

The common life with modern urban residence, spending more than 80~90% of daily life in indoor environment, makes the importance of indoor air quality (IAQ) even higher. Many efforts have made to improve indoor air quality (IAQ), which requires those systematic approaches for field practice. A recent study reported that no general approach cannot be made for IAQ improvement due to the great deal of variety in different indoor environments. Those indoor spaces included in Korean IAQ regulation were classified based on their characteristics and the IAQ guideline was suggested for each group of indoor spaces. Apart from those indoor spaces, the classroom in elementary school has different characteristics. By introducing the systematic approaches, the elementary classroom was surveyed and analyzed to understand its characteristics in due IAQ consideration. Based on the characteristics, there are several IAQ control measures suggested, including ventilation operation, dust mat installation, and white board. $CO_2$ and airborne dust were monitored and analyzed in order to evaluate the effectiveness of each control measure to IAQ. It was found that the general level of $CO_2$ concentration was managed under the IAQ guideline by applying the ventilator operation. The ventilation was also effective to the fugitive airborne particulate in elementary classroom environment.

• Journal of environmental and Sanitary engineering
• /
• v.14 no.4
• /
• pp.85-92
• /
• 1999

Indoor air quality tends to be the dominant contributor to personal exposure because most people spend over 90% of their time indoors. For some contaminants, exposure to indoor air poses a potentially greater health threat than outdoor air exposures. Indoor nitrogen dioxide ($NO_2$) levels are mainly affected gas range, flue gas spillage, kerosene heaters, wood-burning appliances and cigarette smoke. In addition, indoor $NO_2$ levels are influenced by such house characterization as surface reaction and air exchange rate. In this study, the measurements of indoor and outdoor $NO_2$ concentrations were taken using identical protocols, and information was collected on housing characteristics using identical questionnaires in 14 houses out of 15 houses for daily 30 daily 30 days in Brisbane, Australia.The usage of gas range was the most contributing factor in indoor $NO_2$ concentration in relation to house characteristics. Average indoor and outdoor ratios of NO2 concentration in electronic and gas cooking houses were $0.6{\pm}0.1$ and $0.9{\pm}0.2$, respectively. The frequency distributions of $NO_2$ concentration in each house were approximately log-normal Geometric mean of indoor $NO_2$ concentrations of electronic and gas cooking houses for daily 30 days ranged from 2.5 ppm to 11.5 ppm with a mean 6.8 and from 4.7 ppm to 28.6 ppm with a mean 15.6 ppm, respectively. The $NO_2$ concentrations between electronic and gas cooking houses were significantly different (p<0.05). Since each house has different life-style and house characteristics, sampling interval to measure the $NO_2$ levels was recommended above 7 days.

• KIEAE Journal
• /
• v.15 no.5
• /
• pp.107-112
• /
• 2015

Purpose: This study desires to investigate an effect of indoor temperature, humidity, and illuminance targeting a planting system of double-skin facade and cavity space adjacent to the outside within a certain period of winter. Through this, the study suggests a basic material about an energy conservation effect of double window system using planting to reduce heating load of a building in winter, so desires to contribute to indoor thermal comfort effect and illuminance correction study of double window and indoor plant. Method: Considering effects such as day and night climatic elements and air conditions in winter, illuminance measurement was conducted through a double-skin facade of space, a subject of the measurement, on the basis of practical residence time of a resident, and this study analyzed characteristics of indoor illuminance about this. The study measured and compared a change of insolation, dry-bulb temperature, and relative humidity at each indoor-outdoor measuring point, so measured and compared characteristics of an indoor temperature effect by elements of double-skin facade and indoor plant. Result: Through this study, the researcher could determine that indoor plant within double window in winter not only blocks solar radiation but also photosynthesizes, so is somewhat disadvantageous to winter thermal comfort reducing heating load. In addition, solar radiation going through interior plays a role to bring down somewhat high humidity to about 50% of reasonable humidity, so plays a direct role of maintenance of comfortable indoor space. Although there are effects such as blocking of solar radiation and temperature reduction, this has a positive influence on humidity control and proper illuminance distribution. The researcher could determine that illuminance, temperature, and humidity by solar radiation penetration for the whole measuring time play a role to supplement indoor environment mutually.

• Journal of the Korean housing association
• /
• v.18 no.4
• /
• pp.1-7
• /
• 2007

The principle of Korean Traditional Housing was to be harmonized with the nature with shapes according to regional climate and materials easily available from the region. These environmentally friendly characteristics protected indoor environment from climate changes. The characteristics of Korean traditional housing to control indoor environment would be very useful for contemporary housing in that current issues, improving housing amenity and wellbeing, had basic goals same with what Korean Traditional Housing had. Though it could be found characteristics of indoor thermal environment heated by Ondol Heating System, analyses of evaluation made by occupants of the rooms were insufficient because most of the studies had been focused on the measurement of indoor thermal factors. Thus, with an evaluation of occupants for the indoor thermal comfort and an estimation of discomfort derived from the result of vertical temperature distribution, it was studied whether the agreeable indoor range of rooms, of which was Jeonju Hanok Living Experience Center, heated by Ondol Heating System corresponded to the agreeable indoor range presented in references.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.2C
• /
• pp.119-125
• /
• 2011

Start This paper analyzes the propagation characteristics of acoustic signals in indoor environments, which is applicable to indoor positioning system. Indoor stereo sound system is generally valid within $25m^2$. So it is not possible to apply prevalent sound propagation characteristic to indoor positioning system because the prevalent acoustic signals propagation characteristic is defined under free space condition. Therefore, in this paper, we present the propagation characteristics of acoustic signals in indoor environments considering the free space propagation characteristic as well as room characteristic such as humidity, temperature, absorption of atmosphere and so on. To verify the designed propagation model of indoor acoustic signals, this paper presents the propagation characteristics of decreasing sinusoidal signals whose frequencies ate from 1kHz to 20kHz in anechoic room. In addition, this paper also presents the propagation characteristics of decreasing sinusoidal signals which have multiple frequencies.

• Journal of the Korean housing association
• /
• v.17 no.5
• /
• pp.9-16
• /
• 2006

The researches on the environmental friendly buildings have carried out on the materials, environmental property, technical elements and etc., and various buildings with these green materials have built and under construction nowadays and became a new trend of the green building. And recently, new building technique which builds the wall with the soil and wood and very easy to construct (called M Earthen House) was introduced as the green building and rapidly propagated. But the research on the indoor climatic characteristics, the ability to control the environmental comfort and the influence to the human beings of these buildings are not sufficiently identified yet. In this paper, the indoor environmental characteristics and the temperature controlling ability of these buildings in summer season were measured and analysed by the Portable Indoor Air Quality Monitor(BABUC/A, LSI) measuring equipments, ana the subjective test on the thermal environment of the subjects were carried out to evaluate the thermal comfort. The results can be summarized as follows; 1) Compared to the outdoor dry bulb temp.($15.4{\sim}28.7^{\circ}C$), the indoor temp. was $19.5{\sim}26.8^{\circ}C$. It showed the temperature controlling ability of the M earthen house was outstanding. And the indoor relative humidity, compared to the outdoor($45.4{\sim}100%$), was $58.1{\sim}76.4%$, it showed the humidity controlling ability of the M earthen house was also outstanding. 2) The thermal environment was evaluated as 'comfort'(neutral-slightly warm) and the humidity was also evaluated as 'comfort'(neutral-slightly humid). So, the results of the physical and subjective evaluation on the indoor thermal comfort in summer season were 'neutral' and 'comfort' coincidently, it was confirmed that the controlling ability of the indoor temperature and humidity of the M earthen house was very excellent.

• Journal of Environmental Science International
• /
• v.24 no.10
• /
• pp.1273-1283
• /
• 2015

In present study, the temporal characteristics of nine selected volatile organic compounds (VOCs), including four alcohol, 2 aldehyde, and 3 ketone compounds, in high-stories urban apartments over a 2-y period were investigated. The indoor VOC concentrations had generally a decreasing trend over the 2-y follow-up period. For examples, the 2E1H indoor concentration decreased from $10.8{\mu}g/m^3$ for the first two months to $5.1{\mu}g/m^3$ for the last two months. In addition, the DCA and ACT indoor concentrations decreased from 5.0 and $14{\mu}g/m^3$ for the first two months to 2.2 and $6.4{\mu}g/m^3$, respectively, for the last two months. The indoor-to outdoor concentration ratios over the 2-y period were much greater than 1, indicating that indoor VOC concentrations were higher than the outdoor VOC concentrations. Similar to those of the individual VOCs, the indoor-to-outdoor concentration ratios of all three VOC groups were higher than 1 over the 2-y follow-up period, suggesting higher indoor concentrations of the three VOC groups than outdoor concentrations. In consistence with the results of VOC indoor concentrations, the VOC emission rates decreased gradually as time passed, due to the decreased VOC emission strengths of indoor sources. Finally, there was an initial sharp decrease in the indoor VOC concentrations followed by a slower decrease, indicating a multi-exponential decay model for the target VOCs, which was demonstrated by comparison of the residuals and the adjusted coefficient of determination associated with the one and two-exponential fits of each data set.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.22 no.2
• /
• pp.119-127
• /
• 2012

Objectives: The aim of this study is to identify concentration characteristics of indoor and outdoor airborne total fiber particles and asbestos in Gyeongnam Provinces. Methods: This study investigated concentration characteristics of indoor fiber particles from 748 schools and 38 public facilities as well as outdoor particles from 11 sites through PCM (phase contrast microscope). SEM/EDX (scanning electron microscope/energy dispersive using X-ray analysis) was used to obtain physicochemical information of asbestos fiber particles. The study identified asbestos rate in the 15 samples from indoor and outdoor airborne total fiber particles. Results: 1. The average indoor airborne concentrations of total fiber particles were $0.0011{\pm}0007$ f/cc in schools and $0.0015{\pm}0007$ f/cc in public facilities by PCM. Over 90% of the fiber particles were identified as single fibers. 2. The average outdoor airborne concentrations of total fiber particles were $0.0007{\pm}0002$ f/cc, and they were lower than those of indoor airborne concentrations. 3. The results showed that the form of asbestiform was diverse as skein of thread like form and long needle, which was relatively narrower than that of glass fiber and rock wool. 4. The results of SEM/EDX analysis of 15 areas where total fiber particle was relatively high showed that the form was rather similar to that of asbestos, but chemical composition was proven to be non-asbestos. Conclusions: The concentration of indoor and outdoor airborne total fiber particles of Gyeongnam Provinces satisfied the IAQ (Indoor air quality) level of 0.01 f/cc and asbestos was not found in most of the samples by SEM/EDX.

• Journal of the Korean Society for Railway
• /
• v.2 no.3
• /
• pp.18-25
• /
• 1999

A high speed train named Korean High Speed Train (KHST) with its maximum operating speed 350 km/h is now under development. For the successful design of a quiet and comfortable high speed train, it is important to understand the general features of the noise and vibration characteristics of high speed train. This paper reviews extensively collected materials on the noise and vibration characteristics of existing high speed trains. Based on the noise and vibration characteristics of TGV systems, a simple indoor-noise prediction rule is proposed for the TGV-type high speed trains such as KHST The indoor-noise of KHST at 350km/h is expected to be larger than at least 71 dBA. Some important researches conducted for designing KHST during last two years under the G-7 project are also briefly introduced at the last part of this paper.