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18
result(s) for
"Imagawa, Hikaru"
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Study on Winter Comfort Temperature in Mixed Mode and HVAC Office Buildings in Japan
by
Uno, Tomoko
,
Mori, Taro
,
Nakaya, Takashi
in
Air conditioning
,
Energy consumption
,
Equipment and supplies
2022
Comfort temperature is important to investigate because the chosen office indoor temperatures affect the energy used in a building, and a thermally comfortable environment makes the occupants be more productive. The effects of temperature on comfort are broadly recognized for thermal comfort. Japanese office buildings are well equipped with air-conditioning systems to improve the thermal comfort of the occupants. The main objectives of this research were to compare the winter comfort temperature in mixed mode (MM) and heating, ventilation and air-conditioning (HVAC) office buildings and to investigate the relationship between the comfort temperature and the indoor air temperature. This study measured the thermal environmental conditions of the office buildings and surveyed the thermal comfort of the occupants. The field survey was conducted during winter in seven office buildings located in the Aichi prefecture of Japan. In total, 4466 subjective votes were collected from 46 occupants. The result suggested that the occupants were found to be more satisfied with the thermal environment of MM buildings than that of HVAC office buildings. Overall, 95% of comfort temperatures were in the range 22~28 °C in MM and HVAC buildings, which were higher than the indoor temperature of 20 °C recommended by the Japanese government. The comfort temperature was highly correlated to the indoor air temperature of the MM buildings than to that of HVAC buildings. This indicated that the occupants were more adapted towards the given thermal environment of MM buildings.
Journal Article
Development of Adaptive Model and Occupant Behavior Model in Four Office Buildings in Nagasaki, Japan
2023
A field survey of indoor environmental measurements and questionnaires on thermal sensation, overall comfort, and behaviors was conducted in four office buildings in Japan by visiting each office every month over a duration of more than a year during the coronavirus disease 2019 (COVID-19) pandemic. The indoor environment was measured concurrently. We obtained 1047 votes from office workers in their 20s to 60s. The regression and Griffiths’ methods were used to calculate the indoor comfort temperature. A logistic regression analysis was used to develop the occupant behavior model. Over 70% of the occupants found the indoor environment comfortable at a mean comfort temperature of 23.2 to 25.9 °C. Gender differences were observed in thermal sensation and overall comfort, but a gender difference was observed only in the cooling mode for the indoor comfort temperature. An adaptive model was developed for the office buildings in Nagasaki city to predict the indoor comfort temperature from the outdoor air temperature. The proportions of heating, cooling, and fan usage can be predicted from the outdoor air temperature using a logistic regression analysis. The adaptive model and occupant behavior model are useful for the indoor temperature control of the existing buildings and thermal simulation of the new building design.
Journal Article
Development of the adaptive model for thermal comfort in office buildings of Aichi prefecture, Japan
2023
This study was undertaken to investigate seasonal adaptation to temperature in Japanese offices, with a view to suggesting an adaptive model for them. We measured temperatures in seven office buildings and conducted thermal comfort transverse surveys of occupants for over a year in the Aichi prefecture of Japan. We collected 1,228 samples. The occupants were found to be highly satisfied with the thermal environment in their offices. Even though the Japanese government recommends the indoor temperature of 28 °C for cooling and 20 °C for heating, we found that the comfort temperature was 2.8 °C lower in cooling mode and 4.3 °C higher in heating mode, in line with the actual indoor temperatures. The monthly variation in the temperature in the investigated offices was significantly lower than had been found in dwellings. An adaptive relationship can be derived to estimate the indoor comfort temperature from the prevailing outdoor temperature for similar office buildings.
Journal Article
Study on adaptive model and behavioural adaptation for thermal comfort of Japanese office buildings
2023
This study focuses on the behavioural aspects of the occupants in Japanese office buildings. The behavioural adaptations such as window opening, heating/cooling use, clothing adjustments are important contributor factors for the adaptive thermal comfort. Therefore, understanding the behavioural aspects of the office workers can lead to have the guidelines to explain the mechanism of the adaptive model. The main aim of this study is to identify the differences in behavioural adaptation of the occupants in Japanese office buildings. Environmental parameters such as air temperature, relative humidity, and so on were measured in five mixed-mode office buildings located in Aichi prefecture were analysed for 15 months’ survey with 35 occupants. Thermal comfort survey together with the occupants’ behavioural survey were conducted in these office buildings. An adaptive relationship can be derived to estimate the indoor comfort temperature estimated by Griffiths method from the prevailing outdoor temperature. The results suggest that the proportion of heating and cooling use is related to the outdoor air temperature. The proportion of clothing adjustment is different for the different modes and are correlated to the outdoor air temperature. The acknowledge of the adaptive thermal comfort and the occupant behaviour of the selected buildings will be fruitful in designing the building with maximum thermal comfort in the future.
Journal Article
Development of an adaptive model for thermal comfort in the office buildings of Nagasaki City, Japan
2023
Thermal comfort in office buildings is instrumental in improving the productivity of employees while maintaining their health. The primary objectives of this research were to analyze the comfort temperature in Japanese office buildings and investigate its relationship with outdoor air temperature. Additionally, we examined the differences in comfort temperatures with respect to closed and opened windows to factor in the increase in the opening of windows during the COVID-19 pandemic when air-conditioning systems were operated. We investigated the environmental conditions of office buildings and the thermal comfort of the occupants through monthly visits to each office building over a year. Field data were collected from four office buildings located in Nagasaki City, with 1047 votes obtained from 143 participants. The survey indicated that the occupants were highly satisfied with the thermal environment in their offices. The correlation between indoor comfort temperature and outdoor temperature was high in the FR mode. Based on the analysis, we developed an adaptive model for office buildings in Nagasaki City and compared it with existing adaptive models used for buildings in other regions of Japan. The proposed model is useful for energy-saving designs that bring out human adaptive capacity.
Journal Article
Study on winter indoor thermal environment of temporary shelters built in Nepal after massive earthquake 2015
by
Thapa, Rita
,
Shukuya, Masanori
,
Imagawa, Hikaru
in
Air temperature
,
Digital data
,
Earthquakes
2019
After massive earthquake 2015, thousands of Nepalese who lost their permanent houses by the hardest hits were forced to live in makeshift temporary shelters. The people residing in these shelters are facing extreme coldness that causes various health-related problems in winter. The field measurement on indoor thermal environment was conducted in one of the district hit by massive earthquake, Lalitpur. The indoor and outdoor air temperatures of five shelters were measured by a set of thermometers with digital data loggers at the ten minute intervals in winter. The mean indoor and mean outdoor air temperatures during the measured night-time were found to be from 10.3°C and 7.6°C; they were lower than lower limit value of acceptable indoor temperature at 11°C found from our previous research. We analyzed the thermal characteristics of those shelters measured for seeking whether the improvement is possible or not and also how much of it is affordable. Thus, in this study, we evaluated the indoor thermal environment by estimating the heat-transmission characteristics of the used materials in these investigated shelters. The total heat loss coefficient estimated in five shelters per respective floor areas ranged from 11.2 to 15.4 W/(m2·K). These values obtained are very large due to low thermal insulation materials used. The paper ends with important lesson that reduce the total heat loss coefficient needs to reduce down to 2∼7 W/(m2·K) for realising the need to indoor air temperature above at 11°C could be 70% of nighttime hours. Such reduction of heat loss was found to be realized by adding affordable materials, i.e. cellular polyethylene foam and clothes for respective walls and roof.
Journal Article
Development of Single and Combined Fan-Use Models in Japanese Dwellings
2019
Thermal adjustment is one of the most important behaviours. In daily life, we use some behavioural adjustments for thermal comfort. Especially, fan use is most common adaptive behaviour for the active thermal adjustments. The occupant behaviour stochastic models were proposed by some previous studies. However, the relative proportion of each behaviour has not yet been fully understand. It is important to estimate the proportion of each behaviour relatively because the selection of abehaviour is determined in relation to each others. In our previous study, the stochastic models of window opening/closed, cooling and heating use were integrated to one model. The integrated fan use model is useful for understanding the occupant behaviour. The objective of this research is to clarify the fan use in relation to the window opening and cooling use. The occupant behaviour surveys were conducted in 120 dwellings during a four-year period in Kanto region of Japan. From this survey, we have collected 36, 114 responses. The major findings are: 1) The proportion of fan use was highest in summer; 2) The stochastic model of fan use was explained by outdoor air temperature, and the combined stochastic model of \"fan use\" and \"window opening or cooling use\" were also developed; and 3) The proportion of \"combined fan use\" was higher than that of \"fan single use\". The results indicated that the residents use the fan together with some other thermal adjustments. The knowledge of this research, as the next step of research, will be implemented in building thermal simulation.
Journal Article
Vasohibin as an endothelium-derived negative feedback regulator of angiogenesis
by
Hasegawa, Yasuhiro
,
Imagawa, Keiichi
,
Shimizu, Kazue
in
Amino Acid Sequence
,
Amino acids
,
Angiogenesis
2004
Negative feedback is a crucial physiological regulatory mechanism, but no such regulator of angiogenesis has been established. Here we report a novel angiogenesis inhibitor that is induced in endothelial cells (ECs) by angiogenic factors and inhibits angiogenesis in an autocrine manner. We have performed cDNA microarray analysis to survey VEGF-inducible genes in human ECs. We characterized one such gene, KIAA1036, whose function had been uncharacterized. The recombinant protein inhibited migration, proliferation, and network formation by ECs as well as angiogenesis in vivo. This inhibitory effect was selective to ECs, as the protein did not affect the migration of smooth muscle cells or fibroblasts. Specific elimination of the expression of KIAA1036 in ECs restored their responsiveness to a higher concentration of VEGF. The expression of KIAA1036 was selective to ECs, and hypoxia or TNF-alpha abrogated its inducible expression. As this molecule is preferentially expressed in ECs, we designated it \"vasohibin.\" Transfection of Lewis lung carcinoma cells with the vasohibin gene did not affect the proliferation of cancer cells in vitro, but did inhibit tumor growth and tumor angiogenesis in vivo. We propose vasohibin to be an endothelium-derived negative feedback regulator of angiogenesis.
Journal Article