Xiaojun Fan

• Doctor of Philosophy
• Postdoctoral researcher at ETH Zurich

This paper investigates the integration of data center waste heat into district heating networks, evaluating its potential from technical, energy, economic, and environmental perspectives. It offers a comprehensive review of global efforts to recover waste heat from data centers, focusing on existing research, practical applications, and the effect...

Building energy management increasingly utilises Machine Learning (ML) to use data from sensor-rich environments. A significant challenge in this context is managing high-dimensional data, which can affect model performance. This study addresses this by applying multi-target feature selection, an underexplored method that reduces dimensionality by...

As an alternative to Polysomnography (PSG), Fitbit Alta HR (Fitbit) could provide an easier way to monitor sleep. Since the accuracy of Fitbit sleep monitoring is unknown, this study was conducted to compare the sleep monitoring performance of Fitbit and PSG. Nine healthy young adults (5 males and 4 females; 24 ± 2 years old; Pittsburgh Sleep Quali...

In developed nations, 2/3 of the population fail to obtain the recommended 7-9 hours of sleep, with large consequences for health and productivity. A potent stimulus in regulating sleep and wake balance is light received at a light-sensitive retinal protein called melanopsin, found in our retinal cells, otherwise known as intrinsically retinal gang...

The ongoing project 'Bedroom Ventilation and Sleep Quality' investigates the effects of bedroom ventilation on sleep quality and next-day cognitive performance. As part of the project, 84 bedrooms in the Greater Copenhagen area of Denmark were inspected during the 2020 heating season. In the first week, participants slept under environmental condit...

A four-week-long field intervention experiment was conducted in twenty-nine bedrooms with extract ventilation systems and air inlet vents. During the first week no interventions took place. In the three weeks that followed, each participant slept for one week under a low, medium, and high ventilation rate condition in a balanced order. These condit...

Humans emit carbon dioxide (CO2) as a product of their metabolism. No measurements of CO2 emission rates (CERs) of elderly sleeping people have yet been reported. This study performed such measurements and examined the possible mechanisms impacting CERs. Sixteen participants (8 males) aged ≥65 years old slept alone for a whole night under each of t...

Indoor Air Quality (IAQ) and sleep quality measurements over a period of two weeks were performed all night in 40 bedrooms in Denmark during the heating season. In the first week, the bedroom conditions were typical of what participants would normally experience during sleep. In the second week, the participants were asked to open the doors or wind...

Parameters describing the bedroom environment and sleep quality were measured overnight for one week in 84 randomly selected actual bedrooms in Denmark from September to December 2020. The median age of participants was 26 years (interquartile range (IQR) (Laverge et al., 2015; Fan et al., 2021; Berglund et al., 1999; Zhang et al., 2016; Bjorvatn e...

Wrist skin temperature has been validated to be sensitive to the thermal state of awake people, but its correlation with thermal state of sleeping people has not been investigated. In the present study four human subject experiments were performed on both young and elderly subjects in different seasons (winter, transition, summer). Their skin tempe...

Ten healthy young adults slept one by one in a specially designed and constructed sleep capsule located in a climate chamber at two temperatures (24 and 28 °C) and two ventilation rates that ensured that the resulting CO2 concentrations were 800 and 1700 ppm. Subjectively rated sleep quality was reduced at 28 °C and reduced ventilation, while sleep...

Sleep is essential for the health of elderly people, but few studies have made connection between their sleep quality and their bedroom environment. This study performed field measurements in Shanghai, China, to investigate the bedroom thermal environment and ventilation and their associations with the sleep quality of elderly subjects in summer. F...

Poor air quality has been shown to reduce sleep quality. There is a limited number of studies reporting how occupants rate the air quality in their bedrooms. The present study sheds the light on this issue. It was conducted in actual bedrooms and asked occupants to rate air quality once awake in the morning using an online sleep diary. The study wa...

Humans emit carbon dioxide (CO2) as a product of their metabolism. Its concentration in buildings is used as a marker of ventilation rate (VR) and degree of mixing of supply air, and indoor air quality (IAQ). The CO2 emission rate (CER) may be used to estimate the ventilation rate. Many studies have measured CERs from subjects who were awake but li...

We performed a survey of the types of bedroom ventilation in Danish dwellings (January–February 2020) and the associated subjective sleep quality. Five hundred and seventeen people responded. Their median age was 33 years old and 55.4% of them were males. We used an online questionnaire and collected information on the type of bedroom ventilation,...

Good sleep is essential for our health and daytime functioning; seven to nine hours of sleep each night are recommended for people age 18 to 64.(1,2) Noise, light, temperature and air quality affect our sleep. However, very few regulations address indoor air quality (IAQ) in bedrooms, and even fewer studies examine the relationship between sleep qu...

Sleep is essential for our health and well-being. Some research suggests that air quality influences sleep quality in bedrooms, but the evidence is limited. Research, until now, has focused on how indoor air quality affects health, comfort, and cognitive performance during waking hours. Less information is available on the levels of indoor air qual...