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Urban heat islands (UHI) are a widely documented phenomenon that adversely increases urban overheating and, among other effects, contributes to heat-related mortalities and morbidities in urban areas. Consequently, comprehensive UHI-mitigating measures are essential for improving urban microclimate environments and contributing to salutogenic urban design practices. This study proposed urban cooling strategies involving different tree percentages and leaf area densities in a dense urban area during the summertime in Korea. The cooling effects of sixteen various combinations of proposed scenarios based on common urban tree types were studied via in-situ field measurements and numerical modeling, considering both vegetated and exposed areas. It was observed that by changing the characteristics of the leaf area density (LAD) per plant of our vegetated base area—for instance, from 4% trees to 60% trees, from a low LAD to a high LAD—the daily average and daily maximum temperatures were reduced by approximately 3 °C and 5.23 °C, respectively. The obtained results demonstrate the usefulness of urban trees to mitigate urban heating, and they are particularly useful to urban designers and policymakers in their efforts to minimize UHI effects.
Atefeh Tamaskani Esfehankalateh; Jack Ngarambe; Geun Yun. Influence of Tree Canopy Coverage and Leaf Area Density on Urban Heat Island Mitigation. Sustainability 2021, 13, 7496 .
AMA StyleAtefeh Tamaskani Esfehankalateh, Jack Ngarambe, Geun Yun. Influence of Tree Canopy Coverage and Leaf Area Density on Urban Heat Island Mitigation. Sustainability. 2021; 13 (13):7496.
Chicago/Turabian StyleAtefeh Tamaskani Esfehankalateh; Jack Ngarambe; Geun Yun. 2021. "Influence of Tree Canopy Coverage and Leaf Area Density on Urban Heat Island Mitigation." Sustainability 13, no. 13: 7496.
Spectral power distribution (SPD) is an essential element that has considerable implications on circadian energy and the perception of lit environments. The present study assessed the potential influences of SPD on energy consumption (i.e., considering circadian energy), visual comfort, work performance and mood. Two lighting conditions based on light-emitting diode (LED) and organic light-emitting diode (OLED) were used as proxies for SPDs of different spectral content: dominant peak wavelength of 455 nm (LED) and 618 nm (OLED). Using measured photometric values, the circadian light (CL), melatonin suppression (MS), and circadian efficacy (CE) of the two lighting sources were estimated via a circadian-phototransduction model and compared. Additionally, twenty-six participants were asked to evaluate the said lit environments subjectively in terms of visual comfort and self-reported work performance. Regarding circadian lighting and the associated energy implications, the LED light source induced higher biological actions with relatively less energy than the OLED light source. For visual comfort, OLED lighting-based conditions were preferred to LED lighting-based conditions, while the opposite was true when considering work performance and mood. The current study adds to the on-going debate regarding human-centric lighting, particularly considering the role of SPD in energy-efficient and circadian lighting practices.
Jack Ngarambe; Inhan Kim; Geun Yun. Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance. Sustainability 2021, 13, 4852 .
AMA StyleJack Ngarambe, Inhan Kim, Geun Yun. Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance. Sustainability. 2021; 13 (9):4852.
Chicago/Turabian StyleJack Ngarambe; Inhan Kim; Geun Yun. 2021. "Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance." Sustainability 13, no. 9: 4852.
The urban heat island is a vastly documented climatological phenomenon, but when it comes to coastal cities, close to desert areas, its analysis becomes extremely challenging, given the high temporal variability and spatial heterogeneity. The strong dependency on the synoptic weather conditions, rather than on city-specific, constant features, hinders the identification of recurrent patterns, leading conventional predicting algorithms to fail. In this paper, an advanced artificial intelligence technique based on long short-term memory (LSTM) model is applied to gain insight and predict the highly fluctuating heat island intensity (UHII) in the city of Sydney, Australia, governed by the dualistic system of cool sea breeze from the ocean and hot western winds from the vast desert biome inlands. Hourly measurements of temperature, collected for a period of 18 years (1999–2017) from 8 different sites in a 50 km radius from the coastline, were used to train (80%) and test (20%) the model. Other inputs included date, time, and previously computed UHII, feedbacked to the model with an optimized time step of six hours. A second set of models integrated wind speed at the reference station to account for the sea breeze effect. The R2 ranged between 0.770 and 0.932 for the training dataset and between 0.841 and 0.924 for the testing dataset, with the best performance attained right in correspondence of the city hot spots. Unexpectedly, very little benefit (0.06–0.43%) was achieved by including the sea breeze among the input variables. Overall, this study is insightful of a rather rare climatological case at the watershed between maritime and desertic typicality. We proved that accurate UHII predictions can be achieved by learning from long-term air temperature records, provided that an appropriate predicting architecture is utilized.
Geun Young Yun; Jack Ngarambe; Patrick Nzivugira Duhirwe; Giulia Ulpiani; Riccardo Paolini; Shamila Haddad; Konstantina Vasilakopoulou; Mat Santamouris. Predicting the magnitude and the characteristics of the urban heat island in coastal cities in the proximity of desert landforms. The case of Sydney. Science of The Total Environment 2019, 709, 136068 .
AMA StyleGeun Young Yun, Jack Ngarambe, Patrick Nzivugira Duhirwe, Giulia Ulpiani, Riccardo Paolini, Shamila Haddad, Konstantina Vasilakopoulou, Mat Santamouris. Predicting the magnitude and the characteristics of the urban heat island in coastal cities in the proximity of desert landforms. The case of Sydney. Science of The Total Environment. 2019; 709 ():136068.
Chicago/Turabian StyleGeun Young Yun; Jack Ngarambe; Patrick Nzivugira Duhirwe; Giulia Ulpiani; Riccardo Paolini; Shamila Haddad; Konstantina Vasilakopoulou; Mat Santamouris. 2019. "Predicting the magnitude and the characteristics of the urban heat island in coastal cities in the proximity of desert landforms. The case of Sydney." Science of The Total Environment 709, no. : 136068.
Light pollution is a serious environmental issue with many adverse effects on human health and the ecosystem as a whole. Accordingly, many countries have issued laws and regulations to limit the effects of artificial lighting at night (ALAN). The Republic of Korea and China are among the few countries that have drafted laws to curb light pollution. In the present study, we gathered data related to light pollution regulations and ordinances in both China and Korea. We then carried out a comparative analysis of the light pollution laws of both countries. We found that, although the two countries share a similar socio-economic background, they have different approaches to the issue of light pollution. The information provided in this study serves as a guideline to countries that wish to develop their own light pollution policies. In addition, the conclusions provided in our study offer potential improvements to local and national light pollution policies in both the Republic of Korea and China.
Wu Guanglei; Jack Ngarambe; Gon Kim. A Comparative Study on Current Outdoor Lighting Policies in China and Korea: A Step toward a Sustainable Nighttime Environment. Sustainability 2019, 11, 3989 .
AMA StyleWu Guanglei, Jack Ngarambe, Gon Kim. A Comparative Study on Current Outdoor Lighting Policies in China and Korea: A Step toward a Sustainable Nighttime Environment. Sustainability. 2019; 11 (14):3989.
Chicago/Turabian StyleWu Guanglei; Jack Ngarambe; Gon Kim. 2019. "A Comparative Study on Current Outdoor Lighting Policies in China and Korea: A Step toward a Sustainable Nighttime Environment." Sustainability 11, no. 14: 3989.
The thermal environment in bedrooms is important for high-quality sleep. Studies confirm that, even during sleep, the human body remains sensitive to the ambient air temperature. This study assesses how changing indoor air temperatures at different sleep stages affects the subjective evaluation of sleep quality. We compare reports from two identical sleeping environments with different thermal control systems: an IoT-based control system that adjusts the indoor air temperature according to the sleep stage and a fixed control system that maintains a constant temperature throughout the night. Ten subjects participated in the experiments and completed a questionnaire about their sleep quality. Our results show that, overall, the subjects experienced better sleep in the room with the IoT-based control system than in the one with a fixed thermal control. The mean differences in sleep satisfaction levels between the two sleeping environments were generally statistically significant in favor of the room with the IoT-based thermal control. Our results thus illustrate the suitability of using the IoT to control the air conditioning in bedrooms to provide improved sleep quality.
Jack Ngarambe; Geun Young Yun; Kisup Lee; Yeona Hwang. Effects of Changing Air Temperature at Different Sleep Stages on the Subjective Evaluation of Sleep Quality. Sustainability 2019, 11, 1417 .
AMA StyleJack Ngarambe, Geun Young Yun, Kisup Lee, Yeona Hwang. Effects of Changing Air Temperature at Different Sleep Stages on the Subjective Evaluation of Sleep Quality. Sustainability. 2019; 11 (5):1417.
Chicago/Turabian StyleJack Ngarambe; Geun Young Yun; Kisup Lee; Yeona Hwang. 2019. "Effects of Changing Air Temperature at Different Sleep Stages on the Subjective Evaluation of Sleep Quality." Sustainability 11, no. 5: 1417.
Light pollution is ranked high among recent forms of environmental degradation. While there have been many studies focusing on the diverse effects of artificial lighting on human health, wild life, etc., studies related to the social-economic impact of light pollution have been neglected. In the current paper, we assessed the relationship between economic development and light pollution. Using collected field data of illuminance levels as a measure of light pollution and land prices as an indicator of economic development, we drew conclusions about the effects of economic development on light pollution. The results did not show an inverted-U relationship between the two variables, hence denouncing the Environmental Kuznets Curve (EKC) theory. A regression analysis test showed an R-squared value of 0.322 at p > 0.215. Looking at the obtained results, which show no statistical significance between the two variables, we advise that local light pollution regulation laws and policies be equally stringent throughout districts/cities, regardless of economic status.
Jack Ngarambe; Hong Soo Lim; Gon Kim. Light pollution: Is there an Environmental Kuznets Curve? Sustainable Cities and Society 2018, 42, 337 -343.
AMA StyleJack Ngarambe, Hong Soo Lim, Gon Kim. Light pollution: Is there an Environmental Kuznets Curve? Sustainable Cities and Society. 2018; 42 ():337-343.
Chicago/Turabian StyleJack Ngarambe; Hong Soo Lim; Gon Kim. 2018. "Light pollution: Is there an Environmental Kuznets Curve?" Sustainable Cities and Society 42, no. : 337-343.
We carried out field measurements to determine the contribution of advertisement and decorative lighting to local light pollution in Seoul. We used the lighting limits set by the “Light Pollution Prevention Act”, which regulates light pollution, as measuring criteria. Our results show that both advertisement and decorative lighting are significant contributors to local light pollution in Seoul. Thirty percent of advertisement lighting measured in our study areas exceeded the legal limits. Moreover, we found that certain types of advertisement lighting are more likely to cause light pollution than the others. In addition, 73% of the decorative lighting found in our sample areas exceeded the legal limits. Based on our findings, we suggest that local light pollution policies establish a curfew time when all advertisement and decorative lighting must be completely turned off. Such an approach is essential in reducing lighting levels in outdoor environments. Furthermore, it lessens the burden on law enforcement personnel, who otherwise must ensure that advertisement and decorative lighting levels are kept within the legal limits. In light of the ongoing debate over the role of lighting in public well-being and the sustainability of cities, the present study provides a discussion on the status and management policy of light pollution caused by advertisement and decorative lighting.
Jack Ngarambe; Gon Kim. Sustainable Lighting Policies: The Contribution of Advertisement and Decorative Lighting to Local Light Pollution in Seoul, South Korea. Sustainability 2018, 10, 1007 .
AMA StyleJack Ngarambe, Gon Kim. Sustainable Lighting Policies: The Contribution of Advertisement and Decorative Lighting to Local Light Pollution in Seoul, South Korea. Sustainability. 2018; 10 (4):1007.
Chicago/Turabian StyleJack Ngarambe; Gon Kim. 2018. "Sustainable Lighting Policies: The Contribution of Advertisement and Decorative Lighting to Local Light Pollution in Seoul, South Korea." Sustainability 10, no. 4: 1007.
Light pollution has been receiving increased attention worldwide. Scientific research has provided convincing evidence that ties artificial lighting to health-related issues. Consequently, the involved parties are now leaned towards the implementation of regulations to help limit the use of artificial lighting. Many countries, together with international organizations, have embarked on setting standards and regulations aimed at halting the excessive and improper usage of artificial lighting, there-by eradicating light pollution and its effects. In Korea, outdoor lighting at night is a common phenomenon. Moreover, as the economic development grows even further, the use of artificial lighting is expected to increase making Korea vulnerable to the adverse effects of artificial lighting. In this study, we discuss the issue of light pollution based on field measurements conducted in Seoul, South Korea. The measurements were undertaken to broaden the understanding and assessment of light pollution. During the investigation, we noted that the most severe forms of light pollution were found in developed urban and densely commercialized areas. Currently, there are ongoing light pollution measurement projects around the entire Korea. It would be informative to see how the rest of South Korea compares to the Capital, Seoul in terms of light pollution levels.
Hong Lim; Jack Ngarambe; Jeong Kim; Gon Kim. The Reality of Light Pollution: A Field Survey for the Determination of Lighting Environmental Management Zones in South Korea. Sustainability 2018, 10, 374 .
AMA StyleHong Lim, Jack Ngarambe, Jeong Kim, Gon Kim. The Reality of Light Pollution: A Field Survey for the Determination of Lighting Environmental Management Zones in South Korea. Sustainability. 2018; 10 (2):374.
Chicago/Turabian StyleHong Lim; Jack Ngarambe; Jeong Kim; Gon Kim. 2018. "The Reality of Light Pollution: A Field Survey for the Determination of Lighting Environmental Management Zones in South Korea." Sustainability 10, no. 2: 374.