Josephine Lau

• PhD
• Professor (Associate) at University of Nebraska–Lincoln

During the COVID-19 pandemic, meatpacking workers were disproportionately affected by disease. Large outbreaks at meatpacking facilities resulted in loss of life and threatened the well-being of workers across the globe. Much work was done throughout the pandemic to understand and prevent these outbreaks. This study combined ventilation system eval...

This study examines the effect of portable air purifiers on the indoor air quality of elementary school classrooms. In this first year of a two-year study, the research team installed portable air purifiers in 200 classrooms spanning more than 20 school buildings in Nebraska. The research team measured several air quality and thermal parameters;...

This study aimed to investigate the effect of portable air purifiers on the indoor air quality in classrooms. In this pilot study, the research team monitored air quality parameters in twenty classrooms from three school buildings of a school district located in the state of Nebraska in Spring 2022. The classrooms were assigned into four groups, wi...

In the past decade, the term 'global aging' has gained much attention among researchers, policymakers, civil societies, and governments worldwide. The continuous decline in fertility rates and increased life expectancy have resulted in an ongoing demographic transition where the share of adults aged 65 or older is increasing and outnumbering childr...

This study monitored indoor environmental data in 144 classrooms in 31 schools in the Midwestern United States for two consecutive days every fall, winter, and spring during a two-year period; 3,105 pupils attended classrooms where the measurements were conducted. All classrooms were ventilated with mechanical systems that had recirculation; there...

Although many long-term care (LTC) facilities have implemented measures to isolate infectious residents from the general population, most are not designed for airborne infection control, and guidance for retrofitting existing LTC spaces for airborne isolation is limited. The purpose of this study was to evaluate the effect of ventilation, negative...

The COVID-19 pandemic created needs for (a) estimating the existing airborne risk of infection from SARS-CoV-2 in existing facilities and new designs and (b) estimating and comparing the impacts of engineering and behavioural strategies for contextually reducing that risk. This paper presents the development of a web application to meet these needs...

The objective of this study was to investigate associations between indoor air quality (IAQ) in K-12 classrooms and student academic performance. During the academic years 2015-2017, various IAQ factors in 220 classrooms in the US were measured seasonally, excluding summer. Measurements were taken during occupied and unoccupied times in several cla...

(1) The association of the indoor environmental conditions in classrooms with illness-related absenteeism (IRA) was not well investigated. In addition, studying the association between heating and non-heating seasons were very limited; (2) To fill this knowledge gap, a research team collected various indoor air quality (IAQ) and thermal comfort con...

This study explores the effects of indoor air quality (IAQ) and thermal comfort (TC) factors on student academic performance. IAQ and TC of 45 classrooms (11 schools) in the United States midwestern region were measured during the academic year 2015-16 in three seasons during occupied and unoccupied periods. Measurements during occupied times inclu...

Indoor air quality (IAQ) data of 220 classrooms in the Midwestern region of the US were measured during 2015–2017. During three seasons (fall, winter, and spring), indoor and outdoor CO2 concentrations of each classroom were measured under both occupied and unoccupied conditions. To calculate ventilation rates from the collected CO2 data, three mai...

The objective of this study is to investigate the impacts of indoor environmental factors on students' academic achievement. The thermal, indoor air quality (IAQ), acoustics, and lighting conditions gathered from 220 classrooms in the Midwest region of the United States were studied. The data have been collected under occupied and unoccupied condit...

In this 2-year, seasonally-repeated study, the research team surveyed the baseline conditions of indoor air quality (IAQ)and thermal conditions (TC)of 220 classrooms in the Midwestern region (Nebraska and Iowa)of the United States of America. Seasonal variations of each IAQ and TC variable and correlations between variables were also examined. CO 2...

Current research being conducted at the University of Nebraska-Lincoln seeks to determine the impact of indoor environmental conditions in K-12 classrooms on student achievement. The indoor environmental conditions being investigated include indoor air quality, thermal, lighting, and acoustics. The data being gathered on indoor air quality and ther...

Recently, the requirement to continuously collect bioaerosol samples using shorter response times has called for the use of real-time detection. The decreased cost of this technology makes it available for a wider application than military use, and makes it accessible to pharmaceutical and academic research. In this case study, real-time bioaerosol...

With funding from the U.S. Environmental Protection Agency’s (EPA) Healthy Schools initiative, a research team from the University of Nebraska– Lincoln (UNL) is currently working on establishing how environmental conditions in K-12 school buildings impact student scholastic achievement. The objectives of the research project are: (1) to study compr...

Since 2006, High Performance Incentive (HPI) grants has been provided to qualified public schools in the state of California. This supplemental grant is available for new and modernization (additions to a site) school construction projects to promote the use of high performance attributes. The attributes are assessed by a High Performance Rating Cr...

Here, an absorption type refrigerating performance test bench equiped with an electric vibration system was built. The vibration-strengthed effect of heat transfer performance of an absorption type chiller was studied. The results showed that vibration can effectively improve the heat transfer performance of the absorption chiller and increase it's...

In Part 1 of this article, a CO2-based dynamic reset was proposed and evaluated as an energy-saving demand-controlled ventilation strategy by reducing the outdoor airflow rate when the occupancy is under design occupancy. Further energy-saving potential still exists when the zone primary airflow rate is modulated or reset instead of only resetting...

This article describes a case study the authors conducted in an elementary school in the Midwest. The objective was to evaluate the performance of ultraviolet germicidal irradiation (UVGI) to reduce the bioaerosol concentration in a classroom. Two fourth grade classrooms with the same dimensions were studied. One classroom was designated as the UVG...

Upper room ultraviolet germicidal irradiance (UVGI) has been shown to reduce the concentration of bioaerosols in controlled chambers. However, there is a lack of experimental results on the reduction of bioaerosol concentrations by UVGI devices in actual uncontrolled buildings. This study was carried out in an American elementary school in the Midw...

http://www.tandfonline.com/eprint/4srPjbFY4jMXayZDHASX/full Demand controlled ventilation (DCV) is used to reduce the system outdoor airflow (OA) when the occupancy of the system is under design occupancy. However, the new versions of ASHRAE Standard 62.1-2010 make DCV more difficult to implement for multiple zone HVAC systems. This article propos...

Demand control ventilation is one of the most energy efficient ways to achieve the optimum indoor air quality (IAQ). The interest in it has led to a lot of research and publications particularly for single duct VAV system with terminal reheat since the update of the ASHRAE standard 62 in 2004. However, the VAV terminal box (TBX) control algorithms...

In this study, real-time bioaerosol monitors (RTM) based on the mechanism of detecting biological fluorescence of airborne particulates were applied in elementary school classrooms, along with upper-room UVGI devices installed. Continuous samples were collected in each visiting days from October to next year January. The RTMs have observed a lower...

Fault detection and diagnosis (FDD) is an effective way to automatically detect the existing faults of a rooftop unit (RTU) and increase the reliability and availability of system. Most existing FDD methods use thermodynamic signals as fault indicators. Recently, however, major concerns have arisen in regards to whether refrigerant-related temperat...

Significant process intensification (PI) of heat and mass transfer is indispensable in building compact and energy efficient absorption refrigeration systems. High potentials exist to achieve the required PI through (1) development of active heat and mass transfer enhancement techniques and (2) combining the active enhancement mechanism with proven...

There are many potential benefits in applying dedicated outdoor air systems (DOAS) such as it is easier to ensure proper ventilation; decoupling latent and sensible loads control; providing energy use and demand reduction and better indoor environmental quality (IEQ). To realize the ventilation benefit of DOAS the OA must be supplied to each occupi...

A virtual flow measuring is integrated with the best efficiency staging and the loop differential pressure (DP) reset method to unleash pump power saving potentials from a variable flow primary pump system. Based on the measured pump head, speed, and power, the virtual measuring determines the pump operation condition in an accurate and fast way. T...

Significant process intensification (PI) of heat and mass transfer is indispensable in building compact and energy efficient absorption refrigeration systems. High potentials exist to achieve the required PI through (1) development of active heat and mass transfer enhancement techniques and (2) combining the active enhancement mechanism with proven...

This study uses ray-tracing software to calculate the fluence distribution in ultraviolet germicidal irradiation devices with different surface reflectivities and lamp configurations. Of five validation cases considered, one incorporating anisotropic duct surface reflectivity and wind-chill correction of lamp output gave the best agreement with pla...

Most designers provide dilution ventilation by introducing outdoor air at a rate determined by zone population, zone area, occupancy category, and ventilation-system type to promote acceptable indoor air quality (IAQ). Demand-controlled ventilation (DCV) is a ventilation system capability that provides for the automatic reduction of outdoor air int...

Human beings are facing threats from bio-aerosols like pollens, mold, bacteria and viruses in indoor environments. Improving indoor air quality by applying air cleaners in air handling units can reduce high-energy consumption of ventilation and extra expenses related to absences from work, reduced productivity and medical treatments. Currently, the...

Airborne infectious diseases have been a concern in buildings for many years, even more so now with recent serious health threats such as H1N1, SARS, the Avian Flu and others. In-duct ultraviolet germicidal irradiation (UVGI) is currently being used to help control infectious airborne diseases in many buildings such as healthcare facilities. Many f...

Ultraviolet germicidal irradiation (UVGI) uses UVC radiation produced by low pressure mercury vapor lamps to control biological air contaminants. Ambient air velocity and temperature have a strong effect on lamp output by influencing the lamp surface cold spot temperature. In-duct UVGI systems are particularly susceptible to ambient effects due to...

In-duct ultraviolet germicidal irradiation (UVGI) systems treat moving air streams in heating, ventilation, and air-conditioning (HVAC) systems to inactivate airborne microorganisms. UVGI system performance depends on air temperature, velocity, cumulative operating time, variations in exposure time and other factors. Annual simulations of UVGI effi...

The output of low pressure mercury vapor lamps used in ultraviolet germicidal irradiation (UVGI) applications depends strongly on the lamp surface cold spot temperature. The objective of this study is to develop a model to predict the output variation of these lamps in flow conditions typical of ventilation systems. Experiments were performed to ac...

Ultraviolet germicidal irradiation (UVGI) is the use of ultraviolet (UV) energy (electromagnetic radiation with a wavelength shorter than that of visible light) to kill or inactivate viral, bacterial, and fungal species. The UV spectrum is commonly divided into UVA (wavelengths of 400 nm to 315 nm), UVB (315 nm to 280 nm), and UVC (280 nm to 200 nm...

Ultraviolet germicidal irradiation (UVGI), typically utilizing 254 nm radiation from low pressure mercury vapor lamps, is being applied in HVAC systems to inactivate infectious airborne microorganisms in health care, security, and general air quality applications. Simulation can play a useful role in the design of application-appropriate systems. A...

This paper reported the investigation of the performance of floor-supply displacement ventilation with swirl diffusers or perforated panels under a high cooling load (nearly 90 W/m2). The experiment was carried out in a full-scale environmental chamber to obtain reliable data on the floor-supply displacement ventilation for the validation of a comp...

Many studies have shown that floor–supply displacement ventilation systems are better than mixing ventilation systems. The benefits include indoor air quality, thermal comfort and reduced energy use. The energy benefits depend on the climate conditions. This research compared the energy use of a floor–supply displacement ventilation system in a lar...

A glazed atrium is a common feature in shopping centres and in the lobbies of residential and commercial buildings. This research aimed to discover the vertical temperature distribution and cooling load reduction relating to displacement ventilation in atrium spaces. The air temperatures at different levels (0.1, 0.7, 1.2, 1.7, 3, 5 and 7 m), withi...

With the booming of the Internet, the TCP is widely used in both wired and wireless networks. In mobile ad hoc networks, the topology changes frequently due to mobile nodes, which leads to significant packet losses and network throughput degradations. This is due to the fact that the TCP fails to distinguish the link failure induced packet losses f...

This paper proposes a novel reactive power-based source routing (PBSR) protocol for wireless mobile ad hoc communications. The routing scheme adjusts the node's transmission power to keep the connectivity of the network topology and controls its components' life times to follow the variation of the network conditions. PBSR is a source routing and i...