Journal of Environmental Engineering (Transactions of AIJ)
Online ISSN : 1881-817X
Print ISSN : 1348-0685
ISSN-L : 1348-0685
Volume 86 , Issue 780
Showing 1-9 articles out of 9 articles from the selected issue
  • Jun MUTO, Jun MUNAKATA, Naoko SANO
    2021 Volume 86 Issue 780 Pages 121-130
    Published: 2021
    Released: February 28, 2021

     It is important to consider discomfort glare in designing comfortable office environment. Architectural Institute of Japan has set UGR and PGSV as design criteria for discomfort glare, but those indicators do not completely reflect the needs for lighting environments due to differences in work behavior. For example, when performing a task that requires concentration, worker may prefer a glare environment to increase one's level of alertness. From the subjective glare and the degree of awakening during work behavior, it is considered necessary to examine the method of indicators that are more suited to actions. Therefore, we focused on the relationship between discomfort glare and EEG, and conducted two experiments with different presentation luminance range. The number of subjects was 10 (5 males and 5 females) in both Experiments 1 and 2, and the age were 21-24 in Experiment 1 and 22-25 in Experiment 2. The experiments were conducted in a space with simulated windows, assuming an office space. The experimental factors were luminance levels of the window and subject' conditions ("Task" is the task of looking at the monitor and doing the calculation work, and "No task" is a task to view the monitor without doing anything). In Exp. 1, luminance levels of the window were 2000, 8000, 14000, 20000 cd/m2, and in Exp. 2, 2000, 5000, 8000, 14000 cd/m2. The measurement indexes were EEG, GSV, and subjective evaluations.

     As the result, it was found that in Exp1, the rising tendency of GSV with respect to the increase of the window brightness corresponds to the decreasing tendency of the β-wave component of the visual cortex with the increase of the window brightness during work. The [Visibility of monitor] evaluation also decreases as the brightness increases, which suggests that the visual information processing during calculation decreases as the monitor visibility decreases and glare increases. As the result of Exp. 2, the brightness of the window had no effect on the EEG. In subjective evaluation including glare evaluation, effects of the brightness of the window were observed. The difference between the results of Experiments 1 and 2 is considered to be due to the difference in the maximum brightness condition. Comparing the results of brain response and subjective evaluation between Experiments 1 and 2, β power of visual cortex tends to be suppressed in Experiment 2, and the information processing state of visual cortex tends to be lower than that of Experiment 1. In the subjective evaluation, the feeling of being surrounded in light was high in Experiment 2 and the visibility of the monitor was low in Experiment 2. Therefore, the awakening state in Experiment 2 was lower than that in Experiment 1 as the visibility of the monitor decreased. The GSV value discrepancy between two experiments with different presented luminance ranges shows that the GSV value tends to be high in Experiment 2 without the high luminance condition. It is suggested that in Experiment 1 with high-brightness conditions, the awareness level of the brain is higher than in Experiment 2, while the GSV value is lower.

     From the results of this study, it is inferred that occasionally sending a line of sight to a highly bright window surface may be effective for work. On the other hand, it is also suggested that the glare feeling is also influenced by the total amount effect due to the brightness around the window. In the lighting plan including the windows as the office environment, consideration for both of the perceived glare feeling and the substantial brain activity are important.

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  • Yukiko SEIKE, Sohei TSUJIMURA, Takashi ISHIZUKA
    2021 Volume 86 Issue 780 Pages 131-139
    Published: 2021
    Released: February 28, 2021

     In situations where workplaces and values of workers are drastically changing because of the work style reform, a new perspective is required for the comfort evaluation of sound environment. The caption evaluation method is a popular landscape or location evaluation method that is exceedingly useful, owing to the capability of measuring high order concepts, such as comfort. However, this method requires capturing photographs. Therefore, it is difficult to apply this evaluation to a sound environment, and there are no examples of such an implementation. We proposed a method based on this method omitting the process of taking photos and evaluated the comfort of the sound environment. We aim to address the following.

     ・To confirm the usability of the proposed method for the comfort evaluation of a sound environment.

     ・To understand the evaluation structure for the comfort of the sound environment in a workplace.

     ・To extract evaluation items that influence the comfort of sound environment.

     We conducted this study in two stages. First, we carried out a field experiment for the workers using caption evaluation method without the process of taking photos. The subjects walked around the workplace and searched for an environment or sound environment that made them feel “comfortable”, “uncomfortable” or “curious”. They noted the environment or sound, feature, and their feeling. From this experiment, we clarified the construction of an evaluation of workers’ comfort of a sound environment. In the workplace owing to the high sound levels of air conditioners or machines, many workers experienced it as noisy and answered with “uncomfortable”. However, in a biotope, the sounds of nature, e.g., a bird’s tweet or sound of stream made workers feel calm or refreshed and they answered with “comfortable”.

     Next, to extract the evaluation items that contribute to comfortability of sound environment in the new workplace and validate the proposed method, we selected sound sources and evaluation items from the above results and carried out a subjective experiment in the laboratory. From this experiment, we found that workers have positive impressions from the sound of nature, and show negative impressions from other sounds. The extraction of the comfort evaluation model by multiple regression analysis indicated that the evaluation items contributing to comfort differ with the types of sound source. For example, when workers hear the PC operation sound, they feel “focused”, “quiet”, and “comfortable”. In this situation, it is considered that the workers’ image is of work. However, the level of comfort will improve when they hear the sound of stream and feel “calm”, “pleasant” and “do not care”. This comfort evaluation model assumes a relaxed situation. The proposed method is validated owing to the high coefficient of determination for all of these models.

     As mentioned above, we revealed the evaluation items for the sound environment that contribute to the workplace comfort. We confirmed the usefulness of extracting the evaluation items by the impression evaluation method based on the caption evaluation method that is proposed in this research and applying it for the comfort evaluation of the sound environment in a workplace. In the future, we will obtain the data from various workplaces to design a comfortable workplace sound environment through this method, and examine the type of space and activity content.

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  • The effects of surrounding acoustic environment on learning and conversation activities
    Naoya MARUYAMA, Keiji KAWAI
    2021 Volume 86 Issue 780 Pages 141-150
    Published: 2021
    Released: February 28, 2021

     Learning commons (LC) is a space provided in a library to support active learning for users. LC is typically equipped with information technology equipment and space for group discussion so that users can utilize them for exploring information and making discussions. On the other hand, since LC is a space where people are encouraged discussing, acoustic problems may occur such as noise intrusion into other quiet zones or disturbance on concentration of neighboring users in learning due to loud conversation of other groups. However, not many years have passed since the introduction of LC and therefore there are few studies on the acoustic environment of LC.

     In this study, we investigated acoustic environment and user’s subjective evaluation in a LC in a university library by conducting a field survey and acoustic measurement. In the acoustic measurement, referring on ISO 3382-3, a standard for open plan offices, we measured sound pressure level distribution and impulse responses in the LC spaces and obtained spatial decay of speech and speech transmission index (STI). In the field survey, noise measurements, observation and questionnaire survey to users were performed for two days in the LC and a silent zone for comparison. The questionnaire consisted of two questions about learning preference and eight questions about subjective evaluation on spatial impression, including ease of conversation or discussion, noisiness and so on. A total of 541 people responded to the questionnaire in two days. We observed number of users, number of groups, and conversation volume every 10 minutes, and noise levels were obtained every 10 minutes, and these data were connected with the time period of the stay of each respondent.

     Major results are following:

     (1) The noise level in the LC was approximately 45-60 dB, and 30-40 % of the users were making a conversation.

     (2) Answers to the question of preference of learning style and learning environment tended to be different between the users of the LC and the silent zone, such that the users of the LC tended to prefer group learning rather than individual learning.

     (3) User’s subjective evaluations of spatial impression was negatively affected by loud conversations and the existence of loud conversation at the neighboring table affected the evaluation of being bothered and loosing concentration.

     (4) Regarding with acoustics, the spatial decay rate of speech (D2,s) tend to be high in the space with low height of ceiling compared to the space with high ceiling and this factor affected the decay of STI with background noise.

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  • Study on the prediction model of the discomfort glare based on the visual system
    Kazuto TAKASE, Naoya HARA
    2021 Volume 86 Issue 780 Pages 151-157
    Published: 2021
    Released: February 28, 2021

     In order to realize a comfortable visual environment, a high-resolution photometric image taken with a wide-field camera is useful for evaluating the visual environment. However, its resolution is uniform in the whole image, and there is a problem in applying directly the photometric image to the evaluation of the visual environment because the resolution in the visual field is not uniform. In this study, we aim to develop a prediction model to evaluate the visual environment based on the visual system. This paper targets the discomfort glare, which must be carefully considered in designing and planning in order to realize a comfortable visual environment in an indoor space.

     UGR, PGSV, and DGP, which are currently commonly used as prediction indexes of discomfort glare, are derived from a different experiment in which the conditions for each target object in the index are set as the main variable for the rating of discomfort glare. So they are applied individually to target objects respectively. Therefore the applying range of an index is limited and the characteristics of the rating of discomfort glare in prediction indexes are different. The evaluation method for the visual environment, aimed at in this study, based on the visual system has a common structure that can reflect the fundamental characteristics of the visual system for the light and information transfer even in different application targets. The evaluation method has a wide range of applicability by incorporating a universal visual system applicable to a wide range of conditions, not limited to the condition range of the development process, into the evaluation index derivation process.

     The basic model that reflects the visual characteristics proposed in this paper assumes that the BCD is determined by a certain amount of light flux incident on one receptive field on the retina at a certain receptive field sensitivity in the visual field. Then, this incident light flux is calculated with reflecting visual characteristics such as the scattering characteristic of the eye optical system and the receptive field characteristic of the visual nerve system, and the BCD luminance is predicted based on the derivation formula. In addition, it is possible to specify visual characteristic values within the visual field by optimizing the model against the results of the subjective evaluation experiment in which the BCD luminance is judged in the visual field in which light sources of various solid angles are presented at various eccentric angles on a uniform background luminance. The suitability of the prediction method of BCD luminance was verified by the error of BCD luminance estimated by the prediction model for BCD luminance obtained in the experiment.

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  • Experiment with human subjects exposed to different square-wave airflows
    Shinya MORIKAMI, Yusaku NISHIMURO, Kunio MIZUTANI, Yukari IINO, Taiki ...
    2021 Volume 86 Issue 780 Pages 159-166
    Published: 2021
    Released: February 28, 2021

     Natural cross ventilation not only removes the heat load generated indoors, but also increases convective and evaporative heat loss from human skin to improve indoor thermal comfort of residential houses in the summer season. Opening of windows to increase air movement through cross ventilation has been always used as an environmental adaptive behavior in many countries including Japan. Existing research about fluctuating airflow mainly focused on sinusoidal or random airflow. This study investigated the perceptual and physiological responses of 10 college-aged subjects to square wave airflows of different cycles (2 min, 10 min and 30 min) under different temperature levels ( 28 ℃ and 32 ℃). Their thermal sensation, thermal comfort, thermal pleasure, and air movement sensation were investigated. In addition to subjective perceptions, a physiological parameter and skin temperature were also monitored. Main conclusions are obtained as follows:

     (1) The skin temperature difference among different body parts were smaller under the air temperature (32℃) than that under 28 ℃. The variation in skin temperature also showed an individual difference.

     (2) Under air temperature of 32 ℃, no subject reported “hot” thermal sensation when exposed to square-wave air flow with 2-min or 10-min cycles. However, subjects reported “hot” thermal sensation for 28% of the exposure time to airflow with 30-min cycle.

     (3) Subjects’ pleasantness showed a decreasing tendency under the square-wave airflow with 30-minute cycle period under both 28 ℃ and 32 ℃ thermal exposure. The mean pleasantness was highest in the condition of 32 ℃ air temperature with square-wave airflow (10-min cycle).

     (4) The mean thermal sensations reported by subjects were lower than corresponding PMV values, indicating the cooling effect of dynamic airflows on human thermal comfort in warm environment.

     In future research, it is necessary to increase sample size to enable analysis of the effects of gender and age on the cooling effect of cross ventilation on thermal comfort.

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  • Kaori NOMURA, Naoki KAGI, Naohide SHINOHARA
    2021 Volume 86 Issue 780 Pages 167-174
    Published: 2021
    Released: February 28, 2021

     Semi volatile organic compounds (SVOC), such as di-n-butyl phthalate (DnBP) and di-(2-ethylhexy) phthalate (DEHP), are known to be ubiquitous in indoor environments and frequently detected from house dust. It is reported that the levels of SVOC concentration in indoor floor dust have correlations with asthma and allergies of the inhabitants. SVOCs have a tendency to be adsorbed onto surfaces of airborne particles and house dust in indoor environments because of their low vapor pressures. Many studies investigated SVOC adsorption mechanisms on airborne particle, but few studies on settled dust particles had been carried out experimentally. The aim of this study was to investigate SVOC adsorption characteristics on settled particles by experiments.

     In this study, in order to investigate the adsorption on dust surface, the test dust particles were directly placed on PVC sheets that emitted DEHP. Assuming usual cleaning frequency is about three days, dust particles on the sheet were exposed for three days. Three types of PVC sheets and seven kinds of particles were selected for the experiment. Exposure time and amount of deposition were changed as the experimental conditions. The dust concentration was analyzed with TD-GC/MS. The amounts of bleed-out on the PVC sheets surface were also measured as the indicator of SVOC emission rate by wiping with quartz filters dipped into methanol.

     As a result of the experiments, DEHP concentration in dust increased in proportion to the exposure period, and the emission from materials can affect the adsorption rate. Moreover, adsorption rate increased as amount of bleed-out. Various kinds of particles were examined for this experiment. In terms of amount of DEHP per dust weight, there are no characteristics of adsorption among each dust particles. Nevertheless, taking into account for surface area of each dust, a linear relationship between the surface area and the amount of DEHP was observed clearly regardless of the types of dust particles.

     Based on the experimental results, DEHP adsorption predictive model was built. Indoor particles are present as airborne particles or house dust. Therefore, DEHP detected from house dust may have been adsorbed in both of their states. In this study, the predictive model was built in consideration of the amount of adsorption during suspending and deposition. When the DEHP adsorption amount to house dust was estimated based on the model, it was indicated that coarse particles contribute to elevate DEHP concentration on particle per material surface area. Moreover, exposure time can influence adsorption on house dust.

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  • Yuki MATSUDA, Ryozo OOKA
    2021 Volume 86 Issue 780 Pages 175-183
    Published: 2021
    Released: February 28, 2021

     Information and communication technology including internet of things have developed significantly in recent years. Building Digital-Twin which simulates a real product or building is expected to contribute to data-driven operations by connecting a cyber space and physical space seamlessly. The aim of this study is building a Digital-Twin of building facilities and realization of data-driven operation planning. In this paper, it is described that ANN models imitating all air conditioning system was built and its predictive accuracy was evaluated.

     An architecture of ANN model is forward propagation neural network which has an input layer, two hidden layers and an output layer. Each conditions of hidden layer nodes and input historical data are 4. A learning method to build models is back-propagation method, an algorithm is Adam and a loss function is RMSE. The predictive accuracy of models were evaluated for representative three days in summer and winter and MAE was applied as the evaluation function. The target building is the research institute which has an absorption chiller heater utilizing waste heat, a cogeneration system, AHUs and the others.

     As the result, the finding and issue are follows.

     (1) The ANN model has high predictive accuracy less than MAE 0.05. Also, the model can predict an efficiency of equipment.

     (2) In the case of this system, the predictive accuracy was improved under the condition of the ANN model had 800 hidden layer nodes and more 4 steps input historical data.

     (3) The items with high prediction accuracy regardless of the season were water temperature, pressure, and air temperature.

     (4) It was confirmed that the predictive accuracy decreased when the set point of equipment was changed. It is considered that the predictive accuracy is improved by continuous training of the ANN model.

     (5) Measured values and predicted values were significantly different when the failure occurred. It was suggested that a defect could be found by monitoring that values.

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  • Yasuyuki ISHIDA, Maho ONODA, Hironori WATANABE, Hiromi UEDA, Akashi MO ...
    2021 Volume 86 Issue 780 Pages 185-195
    Published: 2021
    Released: February 28, 2021

     The use of sea breeze with a huge cool potential has been regarded as one of the effective countermeasures against urban heat island phenomenon, and many studies have reported the effect of sea breeze on reducing air temperature. On the other hand, atmospheric observations have been conducted to understand the characteristics of wind in the urban boundary layer. Especially, in recent years, with the development of remote sensing technology, many studies to measure the mean or turbulent characteristics of wind above the city have been conducted using Doppler lidars. However, the relationship between sea breeze above the city and temperature and humidity near the ground has not been clarified precisely. In this study, to examine the relationships between sea breeze and temperature near the ground in summer, a concurrent measurement of wind velocities above the city center using two Doppler lidars, and air temperature and humidity at multiple observation points was conducted in Sendai, a coastal city of Japan. The results were classified into days with wind from inland and sea breeze, and compared. A time series of the vertical distributions of wind direction, speed and the vertical component of wind velocity vector, and power spectrum of vertical fluctuations of the wind were analyzed with a time series of air temperature and humidity for each day.

     In the day with inland wind, the difference between the time series of air temperature measured at points located in inland to coastal areas was small. From the measurements taken by the Doppler lidars, the inland wind was observed at the height near the ground to over 1,000 m. The results also showed that the higher the altitude, the larger the scalar value of horizontal wind velocity. Until 9:30, small fluctuations in vertical wind velocity above the city were observed uniformly across all heights. From that time onward, the vertical fluctuations with large power were confirmed at the height of around 400 m and 600 m, while the power at the height of around 100 m and 200 m was low.

     In the day with sea breeze, the rise of air temperature stopped or moderated in order of distance from the coastal line. In the central part of the city, the temperature rise was stopped until 15:00. Based on the results of Doppler lidars, the sea breeze started to be observed at around 8:30, and in the afternoon, the layer of inland wind was observed on the layer of sea breeze. Regarding the vertical fluctuations of wind, though there were small fluctuations in the morning as with the day of inland wind, a strong and long lasting upflow with large power occurred when the sea breeze was observed at 9:30, unlike the day with inland wind. Therefore, it was considered that the strong vertical fluctuation contributed to the stagnation of the rise of air temperature at 9:30. From that time onward, it was considered that the rise of air temperature was stopped until 15:00 due to the vertical mixing between the air near the ground and the air above the city at the height of around 200 m.

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  • - Indoor Temperature and Humidity in Relation to Dampness Index Proposed by Authors -
    Kenichi HASEGAWA, Naoki KAGI, Jun SAKAGUCHI, Naohide SHINOHARA, Yasuyu ...
    2021 Volume 86 Issue 780 Pages 197-204
    Published: 2021
    Released: February 28, 2021

     A recent meta-analysis of dampness in homes has shown that dampness and mold in indoor environments are factors in approximately 30-50% of all respiratory and asthma-related health ailments. Although the specific indoor dampness factors related to such issues have yet to be fully explored, there are clear and urgent needs for improved architectural techniques and optimized occupant behavior patterns that can prevent or eliminate excessive dampness inside buildings. Furthermore, if the underlying structures linking dampness to adverse health effects could be more closely estimated through epidemiological surveys, prevention methodologies for serious problems related to indoor dampness might be discovered. With these points in mind, we previously proposed a home dampness estimation method based on occupants’ self-reported answers to questions regarding indoor dampness during winter. This resulted in an indoor dampness index covering a range from 0 to 24 that classifies houses into four ranks, with those in Rank 4 presenting the most serious dampness-related problems.

     To clarify the relationship between home dampness levels and indoor environmental quality, another questionnaire survey was conducted and several physical environmental items such as indoor temperature, humidity, and microbial flora from floor dust were measured in 119 detached East Japan houses during the winter season. Herein, we describe the surveyed results and the distribution of the dampness index. The questionnaire also included child health-related symptoms that show onsets within 3 months, and the prevalence of each symptom is presented in relation to each dampness index rank. The characteristics of indoor temperature and humidity resulting from home dampness levels were also clarified by comparing the dampness index and measured results of these physical items.

     Analyzing the survey results, we found that the prevalence of nasal- and eye-related symptoms increased approximately in tandem with the dampness index ranking. In particular, more than 50% of the children residing in Rank 4 homes reported nasal problems, and there was a high prevalence of throat and skin symptoms in Rank 3 homes. However, despite these values, there are still no clear links between the dampness index and the reported health-related symptoms.

     Next, the statistical values of temperature, relative humidity, and the humidity ratio during evening time in living rooms and bedrooms were analyzed for each dampness index rank. To test the significance of these associations, Kruskal-Wallis testing was performed to determine whether the samples in each dampness index rank originate from the same distribution. Moreover, the significant differences among each rank’s samples were tested in multiple comparisons. As for temperature results, no significant association was found among the dampness index ranks. This presumes that living room temperatures are affected by heating behaviors at the time of occupancy.

     On the other hand, both the relative humidity level and the humidity ratio were found to be strongly associated with the dampness index rankings; with higher humidity levels in the living room and bedroom presaging higher dampness index ranks. In addition, the relative humidity and humidity ratios in Rank 2, 3, and 4 living rooms were significantly higher in comparison with Rank 1 living rooms, while the median relative humidity values in Rank 4 living rooms and bedrooms were around 50% and 70%, respectively. Significantly, the humidity ratios in Rank 4 homes were found to be the highest among the surveyed houses and it was expected that these houses had severe environmental problems related to indoor dampness.

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