Health Of Occupants Research Articles

Daylight performance of collector-diffuser combinations in light pipe systems at different geographical locations

Incorporating daylight inside occupied spaces has several benefits, including reduced lighting load, improved mental and physical health of occupants, and increased productivity during working hours. Several Innovative daylighting systems that utilize advanced technologies and design approaches are devised and tested to bring natural light into occupied spaces. Amongst them, the Tubular Daylighting Devices (TDD) have immense potential to trap the sunlight and carry it to enclosed/dimly lit areas, especially in tropical climates.The careful selection of system components dictates TDD's spatial and temporal illumination performance. The present study aims to analyze and correlate the performance of various TDD systems with different collector-diffuser configurations widely reported in the literature and used commercially. The study uses the Daily Useful Daylight Illuminance (DUDI) paradigm and uniformity criterion to assess the performance of carefully chosen collectors, namely, hemispherical dome, prismatic dome, and faceted collector, with the selected diffusers: flat plate acrylic, hemispherical dome, flat prismatic, and flat Fresnel lens. The study encompasses the identification, modeling, and simulation of different configurations throughout the year at four chosen cities in India. Results indicate that the maximum and average lighting level measured is high in the case of the hemispherical collector when paired with flat diffusers at all seasons and cities considered for the study. A matrix of different configurations of system components is tabulated for each location based on a predefined criterion. The increase in diameter of the tube improved the lighting level above 150 lx even at a distance of 1.5 m from the center, and splitting the light pipe into two pipes of an equivalent cross-sectional area improved the end illumination levels at the periphery of the room (10–25 %) making it better in terms of both illuminance and uniformity when paired with hemispherical/faceted collector and flat diffuser.

Enhanced selectivity of a 3D-printed microfluidic gas detector towards different volatile organic compounds (VOCs) for the effective monitoring of indoor air quality in vehicles

In the age of connected mobility, monitoring volatile organic compounds (VOCs) inside the vehicle plays a pivotal role in effectively controlling in-cabin air quality conditions. In this context, it is imperative to develop new monitoring devices that not only detect VOCs at low concentrations, but also can discern those compounds that pose a major risk to the health and comfort of occupants. Microfluidic gas detectors have recently emerged as a promising solution for the cost-effective discretization of VOCs in interior environments. Although microfluidic gas detectors may not yet reach the accuracy of other analytical methods, these devices offer a simple and compact design, can work at room-temperature, and do not require a carrier gas to operate; which represent a clear competitive advantage for their implementation in the vehicle. This work intends to study the feasibility of a 3D-printed microfluidic gas detector for the semi-selective detection of VOCs inside the vehicle cabin. In particular, this research aims to analyze whether the selectivity of these devices can be improved by (i) optimizing the thickness of the polymer layer on the walls of the microchannel, and (ii) understanding the influence of the chemical affinity between VOCs and the coating polymer. Empirical results reveal that thicker polymer films enable to enhance and expand the retention capabilities of the microchannel. Additionally, the Hansen solubility parameters are presented as a suitable tool to analyze and determine how polymer-analyte affinity, in combination with other intrinsic properties of analytes, influences the elution of contaminants from the microfluidic channel as well.

Phytoarchitecture Design Requires a Plant Selection Framework to Combat Air Contaminants in Building Areas Sustainably

Empowerment of plants to maintain the indoor and outdoor air quality of a building area promises occupant health and sustainable use of the building. In supporting plants' functional role, this study proposes a novel approach for a general framework for selecting plants. The method to achieve the objectives of this study was based on previous empirical studies conducted in various places under different environmental quality conditions. The essential findings of the selected literature became part of the technical feasibility process in selecting plants. Significant results indicate the mechanism of controlling airborne contaminants by plants through aerial parts and growth media. Gaseous pollutants can be absorbed along with carbon dioxide absorption, while particulate matter is deposited on the leaf surface. Some other contaminants enter the plant growth medium, which plants can process with microbes in the root zone. The use of plants for indoor and outdoor phytoremediation is various plant species, sourced and selected from a retrospective study, locally available and standard plants, and popular plants. These findings were developed to include assessments of contaminant-plant interactions and plant-specific experiments. The implications of the plant selection framework can be one of the promising methods in designing sustainable building phytoarchitectures.

EXPLORING THE GREEN BUILDING PROSPECTS IN MALAYSIA

Green building refers to any development project or building that, in its design, construction, and building operation is environmentally responsible, resource-efficient, and eliminates or reduces the negative effects on the environment. Although green buildings provide enormous benefits to the environment, economy, and society, the public is still unaware of these benefits. The public’s lack of knowledge, experience, and awareness of green buildings led to market barriers becoming one of the primary reasons for the poor implementation of green buildings in Malaysia. Thus, the objective of this study is to explore the benefits and the contributing factors of green building towards sustainability in Malaysia. Most of the green building developments are in the Klang Valley. This study focused on the public within the Klang Valley area. A total of 500 questionnaires were distributed via online platforms. A total of 80 respondents were received for the survey. The data were analysed by using SPSS software. Descriptive analysis is used to analyse the data to obtain a mean value, and the score is ranked accordingly. The results summarised that the top three benefits of green building include reduced waste and pollution, improved environmental quality, and enhanced indoor environmental quality. Energy efficiency, improved occupant health and comfort, and greater building value are major factors that contribute to the sustainability of green buildings.

Impact of indoor environmental quality weighting schemes on office architectural design decisions

The importance of indoor environmental quality (IEQ) cannot be overstated, as it impacts the health and satisfaction of occupants. To evaluate overall indoor comfort, all four IEQ domains must be considered together. However, there is a lack of guidance on how to prioritize each domain and corresponding metrics, particularly during the early design stage. Therefore, this study investigates the effect of different weighting schemes on commercial building design elements to have high overall comfort. First, a parametric modeling approach for a shoe-box office building is developed to quantify IEQ domains using various design parameters. Subsequently, multiple weighting options are defined, resulting in an aggregated IEQ score. Next, high-performance designs are identified and compared based on each weighting scheme for two different climates. Results show that, as long as all four comfort domains are considered, the choice of weighting scheme does not significantly affect the selection of high-performance designs. Therefore, an equal weighting scheme is suggested for the early stage. This paper presents an original approach to support design decisions and the mutual weightings of IEQ factors.

Field Survey Analysis of CO2 Concentration and Its Impact on Sleep Efficiency in University Dormitory

This study aims to investigate the impact of carbon dioxide (CO2) levels on sleep efficiency in university dormitories. The quality of the indoor environment, including CO2 concentrations, can significantly influence the health and comfort of dormitory occupants. Poor sleep efficiency can lead to long-term cognitive disturbances and health problems. Therefore, understanding the relationship between CO2 levels and sleep efficiency in the university dormitory environment is crucial to improving the living conditions of students. The study was carried out through field surveys at Diponegoro University Dormitory. The real-time CO2 data in the rooms was measured using a logger monitoring device. In addition, the sleep efficiency of the students was evaluated using sleep tracking devices and sleep journals filled out by the participants. Other data, such as ventilation rates and room temperature, were also collected as determinants of environmental quality. The results of the analysis revealed a significant association between CO2 levels (665.33 ± 207,20 ppm) and sleep efficiency (86,71 ± 3,11 %). High levels of CO2 were found to be associated with lower sleep efficiency, leading to sleep disturbances and irregular sleep patterns. Other environmental factors, such as ventilation rates, were also relevant to sleep efficiency.

Monitoreo de la Salud de los Ocupantes de Vehículos Inteligentes: Una Revisión

Technological innovations have pursued to improve the quality of life of people. These innovations have led to the development of high-tech smart equipments, vehicles, monitoring systems, and so on. Smart healthcare monitoring systems have become an important tool for monitoring the health of patients, company employees, athletes, among others. This work is a review of the scientific works and studies of the last ten years, the state of the art regarding the techniques employed for monitoring the health of occupants of smart vehicles. Through a systematic review of the studies reported in the literature, we quantified articles published and identified the most relevant works with the use of the Proknow-C technique. The databases employed for our review were ScienceDirect, Web of Science, Scopus and Google Scholar. Approximately 1337 works were found. Once selected the 16 most relevant papers, we applied the conceptual maps technique to construct a comprehensive overview linking the contributions of works and correlating them to the main research approaches adopted in the literature. This review brings meaningful contributions to help the scientific community to have a comprehensive understanding of the subject and to make advances.

SYNTAX OF SPATIAL PATTERN OF INFORMAL SETTLEMENT AREA OF SENTRA TAHU CIBUNTU, BANDUNG

Sentra Tahu Cibuntu, a tofu supplier industry in Bandung Raya, is categorized as an informal settlement because it formed spontaneously due to national road infrastructure development in Bandung City. The designation of an ordinary settlement as a center positively impacts the city's economic growth. On the other hand, the high demand for housing for tofu makers became a new problem that resulted in an increasingly unplanned settlement growth pattern. Spatial patterns in informal settlements need to be identified as a benchmark for estimating the direction of settlement development in the future. Both designers and policymakers can determine the design strategy of the area to improve the quality of informal settlements. This research uses the space syntax approach to analyze integration on the Sentra Tahu Cibuntu axial map. Primary data was obtained through field observations combined with mapping from satellite imagery. The mapping data is processed using DepthMapX software to produce an axial map that shows the integration value, which describes the real setting. The results of the syntactic analysis are combined with the results of field observations to obtain an overview of building functions, activities, and environmental characteristics. The lower integration value is interpreted as low accessibility to residential areas, so residents have high vulnerability to security and safety, limited infrastructure, limited social activities, and low quality of occupant health. Designers can use the results of these findings as a consideration in designing inclusive and sustainable residential areas through innovative designs.

Analytical Hierarchical Process as a Multicriteria Decision Tool in Material Selection for Prefabricated Wood Buildings

The popularity of prefabricated wooden buildings is increasing in North America, but choosing suitable materials for these structures can be complicated. This can lead to problems like financial losses, production delays, and lower quality. Therefore, the main goal of this study was to use the Analytical Hierarchy Process (AHP) decision-making tool to rank the criteria for material selection for prefabricated wood buildings in Canada and the United States. The methodology involved surveys experts in the prefabricated wood construction industry from Canada and the United States. The data obtained from the questionnaires utilized for the AHP analysis were modeled using R programming language. The results revealed that for structural materials, the top five subcriteria were safety and security of building occupants (0.234), location, shape, and height of the building (0.218), comfort, satisfaction, and well-being of the building (0.155), occupant health (0.121), and availability of materials (0.098). For selecting envelope materials, the top five subcriteria were comfort, satisfaction, and well-being of the building (0.252), safety and security of building occupants (0.206), location, shape, and height of the building (0.178), occupant health (0.132), and availability of materials (0.078).

Preliminary Study on the Emission Dynamics of TVOC and Formaldehyde in Homes with Eco-Friendly Materials: Beyond Green Building

This preliminary study investigates the emission characteristics of formaldehyde (HCHO) and total volatile organic compounds (TVOC) in indoor environments, comparing the effects of eco-friendly materials and general materials. The study analyzes the concentration changes over time in the living rooms of experimental units to assess the effectiveness of eco-friendly materials in reducing indoor air pollutants. The results show that eco-friendly materials exhibit lower initial emissions of TVOC than general materials, gradually decreasing over time. Compared to the eco-friendly material unit, the general material unit takes longer to reach acceptable TVOC concentrations. The emission pattern of HCHO differs from TVOC, with the highest peak occurring on the seventh day. Major individual VOCs, except for benzene, exhibit a similar decreasing trend for TVOC over time. Eco-friendly materials demonstrate significant reductions in emissions compared to general materials in various material applications, including parquet flooring, wallpaper, built-in furniture, and kitchen furniture. However, the difference in emissions for door and window frames using eco-friendly materials is minimal. These findings emphasize the effectiveness of eco-friendly materials in reducing indoor air pollutants and provide valuable insights for creating healthier living environments. Further research is needed to optimize the application of eco-friendly materials in specific components and investigate their long-term impact on indoor air quality and occupant health.

A Systematic Approach to Evidence-Based Design for Measurable Health and Wellness Outcomes: Curating and Translating Evidence to Practice.

Evaluating evidence from peer-review literature for use in evidence-based design is often challenging for the design disciplines, requiring access to the peer-reviewed literature, expertise in evaluating methods and findings, and translating the results into actionable design and operational recommendations. The purpose of this methods paper is to elucidate the process for systematic evaluation of research to translate evidence into practical application to improve design for occupant health and wellness. Researchers have found strong connections in environmental design influence on health and wellness that have proven to be substantiative in the effort to improve health and well-being. Design has the capacity to encourage healthy choices and decisions within the built environment. Translation of evidence into applied design solutions may improve public health. A protocol is presented that culminates in the translation of evidence into design recommendations focused on improving occupant health. The protocol includes preparation for the literature search and review, search strategy, study selection, data analysis, and development of the literature review. After evaluation of the evidence is completed, there were several positive findings in the example that stakeholders could utilize to improve the health of building occupants with programs and design to support nutrition, physical activity, and circadian entrainment. There are a variety of software tools and processes to utilize in the curation of evidence to improve the built environment with relevant design recommendations and operational considerations affecting the personal, social, and economic health of our society.

Effect of temperature on VOC emissions and odor from vehicle carpet

Volatile organic compounds (VOCs) released from carpets deteriorate the air quality in the confined vehicle interior. The wide range of temperatures experienced by vehicle carpets impacts VOC and odor emissions, affecting the physical and mental health of occupants. We investigated the VOC emissions and odor characteristics of vehicle carpets at 25, 40, 50, and 60 °C, respectively. An approach was developed for simultaneous objective sampling and subjective evaluation in a 1 m3 chamber with controlled temperature, humidity, and ventilation. Sensory panelists were screened and trained to evaluate the odor intensity, preference, and type. The emitted VOC types and concentrations increased with temperature; there were 4.5 times more VOC types at 60 °C than at 25 °C. The emission of aromatic compounds, heterocyclic compounds, acids, esters, and ketones significantly increased with temperature. The interaction between odorants affected odor characteristics at the four temperatures; the dominant odors were plastic-like and stinky at 25 °C, rubber- and leather-like at 40 and 50 °C, and aroma at 60 °C. Further quantitative and qualitative exploration of substances, odors, and health effects from carpet emissions at different temperatures could help improve the vehicle environment.

Assessment of Window Size and Layout Impact on a View Quality Perception in a Virtual Reality Environment

ABSTRACT Window views are key factors that affect buildings’ occupants psychological and physiological comfort and wellbeing. Window design should consider the holistic impacts on building energy, lighting performance, and the connection to the outdoors provided by the view which is usually overlooked. In this study, view perception, stress recovery, physiological, and psychological affect were evaluated in virtual environments of five different conditions varying the physical dimensions of a window located in the same office space with an urban view. This allowed three window-to-wall ratios (i.e. 10%, 20%, and 30%) and two different window layouts (i.e. narrow and wide) to be compared. Twenty-five participants were recruited. Subjective self-assessments on view perception (e.g. content and complexity), self-assessment and physiological measures (e.g. skin conductance and heart rate variability) stress recovery besides psychological affect were measured. Participants performed a Stroop-test to induce stress that was immediately followed by a period of recovery facilitated by exposure to one of the five window conditions. Results showed that increased window size advocated higher view perception assessments, increased stress recovery, and positive psychological affect. Measurements of skin conductance and heart rate variability also corroborated these findings. Differences in window layout were also revealed, but only for 10% WWRs. Therefore, WWR is not a reliable indicator for view perception for small window sizes, indicating that layout preference is dependent on window size. This study highlights the importance of considering view perception for occupant health and wellbeing when sizing window openings, since these may not necessarily align with other design criteria.

A Review of the Role of Indoor Fungi in Sick Building Syndrome

Sick building syndrome (SBS) is a group of non-specific symptoms associated with the built environment, including mucosal symptoms in the eyes, nose, throat, and skin, and general symptoms such as headache and fatigue. Currently, more attention has been paid to the impact of buildings on the health and well-being of occupants, so SBS has become a global concern. Indoor microbial agents such as fungi are important in causing this syndrome. Fungi are eukaryotic microorganisms that occur in indoor air. Among the fungi, Cladosporium, Aspergillus, Stachybotrys, and Penicillium have a significant role in causing SBS. Fungi can contribute to this syndrome in different ways. Thus, this review article attempts to investigate the role of fungi and how to intervene in these microorganisms in SBS. To this end, keywords such as: "air," "indoor," "fungi," and "sick building syndrome" were searched. Articles published in scientific databases, such as Google Scholar, PubMed/MEDLINE, Elsevier, and Scopus were used.

Effect of background noise on speech privacy

There is a need for speech privacy in many building environments, which is often affected by various factors such as human perception, acoustic separation of partitions, and background noise levels. Previous studies have classified speech privacy rating between spaces based on partition separation and internal noise in receiving spaces. However, the typical design process often overlooks a holistic approach to speech privacy. Green buildings, focused on sustainability, have recently gained global attention. They aim to reduce environmental impact while ensuring comfort and health for occupants through energy-efficient HVAC systems, sustainable insulation, and low emissivity glazing. Despite their benefits, energy-efficient HVAC systems can emit minimal noise levels. The low internal noise levels in green buildings can often adversely affect the speech privacy rating between spaces. The Green Building Council of Australia have recently addressed the requirement of speech privacy by introducing the need for minimum internal noise levels in the Green Star Buildings, in addition to the acoustic separation requirements between spaces. This paper aims to investigate the need for minimum internal noise levels to address the requirement of speech privacy holistically rather than addressing acoustic separation and internal noise levels as individual components of acoustic design.

Combined Effects of Exterior Shading and A/C Heat Rejection on Building Energy Consumption and Indoor Air Pollution Exposure

Exterior shading devices and outdoor units can be closely coupled since these two building components are commonly installed next to each other. This study uses a coupled EnergyPlus-Fluent modeling approach to examine how a combination of exterior shading and heat rejection from outdoor units can affect the ambient outdoor environment of a building, and how changes in the ambient outdoor environment can influence cooling loads and indoor PM2.5 exposure. Three exterior shading devices were simulated, including horizontal overhangs, vertical overhangs, and vertical fins. Data from wind-tunnel experiments and field measurements were used to ensure the accuracy of the airflow model, energy model, and pollution model developed in this study. Results indicate that horizontal overhangs could almost offset the increase in cooling loads due to increased ambient outdoor temperatures caused by heat rejection. The use of vertical overhangs did not always mean lower demand for space cooling when heat rejection was considered. Heat rejection, horizontal overhangs, and vertical overhangs could help reduce indoor PM2.5 exposure, while indoor air pollution was worse after the implementation of vertical fins. This study shows how exterior shading devices and outdoor units can be coupled to achieve better building energy efficiency and improved occupant health.

Risk factors for moisture damage presence and severity in Finnish homes

Moisture-damaged buildings are a prominent issue in Finland, but with limited information on damage prevalence, degree of severity and risk factors. This paper analyses 14,996 Finnish detached and semidetached houses that have undergone a standardised moisture assessment of interior spaces and at-risk structures inside the building envelope. Confirmed damage (a binary indicator of damage presence) and a damage index (an ordinal indicator of severity) were calculated for each home and their association with different building and area characteristics estimated. Frequently damaged structures include pre-1950s log walls, walls contacting soil, wooden ground floors and false plinths. Around 15% of surveyed houses had risk structure damage, 19% had at least one confirmed damage anywhere in the house and 49% had either confirmed, likely or possible damage. The greatest risk factor for confirmed damage was house age (odds ratio = 1.48 (95% confidence interval (CI) = 1.45–1.51) for each decade since construction), with nearly half of all houses built pre-1939 damaged. Other risk factors explained a third of the effect of building age, and included log external walls, fibreboard roofs, absence of mechanical ventilation, detached properties and wind-driven rain precipitation. Results can support targeted remediation efforts, protect health and estimate exposure–response relationships for moisture damage. Practice relevance Moisture damage in homes causes various health concerns for occupants, and in colder climates such as Finland such damage often occurs within the building structure. This study finds confirmed moisture damage in 19% of surveyed Finnish homes. Most damage was within the building structure, supporting the need for surveys investigating inside known-risk structures. Older homes had much higher damage risk, reflecting different construction methods and ageing, but also suggesting modern building standards are helping to reduce damage. Increased risk in higher wind-driven precipitation regions indicates a need for regulations and research that improve the resilience of all housing to the projected increases in driving rain from climate change. Understanding the building characteristics and structures that increase moisture risk can support targeted remediation and maintenance in vulnerable buildings, conserve older buildings and avoid demolition, and help protect occupant health.

Indoor Air Quality Assessment in the Office of the Transformer Manufacturing Factory in Selangor, Malaysia

Introduction: As humans spend 90% of their time inside, indoor air quality (IAQ) is critical for occupant health. The primary concern associated with low IAQ is its impact on employees’ health, comfort, and productivity. In accordance with the Industry Code of Practice on Indoor Air Quality 2010 (ICOP IAQ 2010), a ten-parameter assessment was conducted in the office of the transformer manufacturing factory in Selangor, Malaysia. Methods: The measured parameters are temperature, air movement, relative humidity, carbon dioxide (CO2), carbon monoxide (CO), formaldehyde (CH2O), particulate matter (PM10), total volatile organic compounds (TVOCs), total fungal count (TFC), and total bacterial count (TBC). This study employed both qualitative and quantitative approaches by distributing questionnaires (N = 42), and measuring the indoor air quality parameters with integrated equipment at selected stations and comparing them to the ICOP IAQ 2010 standard. Results: A majority of the measures, with the exception of air movement, CO2, and TBC, complied with the ICOP IAQ 2010 standards. The one-way ANOVA test showed that there were significant differences (p < 0.05) for the parameters of temperature, PM10, and TVOCs. The Chi-Square test revealed that sleepiness was a symptom of the sick building syndrome, affecting both male and female employees the most frequently and significantly. Conclusion: Air movement, CO2, and TBC values that did not meet ICOP IAQ 2010 requirements revealed poor IAQ at the study site, which could have a negative influence on the employees’ health. To cut down on air pollution, the improvement on the ventilation system should be done to reduce the risks to the employees’ health.

From existing conventional building towards LEED certified green building: case study in Bangladesh

Green Building refers to the planning, design, construction, and operation of buildings considering indoor environment quality, occupant health, using energy, water, and other resources more efficiently; and reducing waste, pollution, and the overall environmental impact. Among the Green Building guidelines, Leadership in Energy and Environmental Design (LEED) offers a certification and rating system by which buildings are certified in different categories. The LEED rating system is used to rate an existing building how much it is fulfilling the criteria of Green Building (GB) or not. This research explored how an existing conventional building can be retrofitted to satisfy green building standards. An academic building of KUET has been selected for the study. A field survey and Participatory Rural Appraisal (PRA) tools (i.e., Focus Group Discussion (FGD), Key Informant Interview (KII)) were used for the data collection and then the data was analyzed by comparative analysis concerning the LEED 2009 rating system for assessing the building. The New Academic building receives 31 points out of 110 and so cannot earn any certification level. The lacking for which the points were not gained is identified and the installation of water and energy efficiency features, rooftop gardening is suggested as retrofitting options to earn the green building certification level.

Impact of Indoor Environmental Quality on Students’ Comfort in High School Buildings during the Summer Season in an Extreme Climate

Maintaining a satisfactory indoor environmental quality (IEQ) is an integral element of improving occupant health and well-being. In particular, IEQ is an essential factor in some facilities, such as school buildings, to improve student academic performance. This study employed an objective and subjective measurement approach to assess IEQ in a government high school (GHS) and a private high school (PHS) located in Oman, which is characterized by its extreme hot climate. A total of 212 high school students were surveyed during the summer season across 10 different classrooms to ascertain their perception of IEQ situations. The results suggested that most of the observed IEQ factors, including air temperature, relative humidity, and lighting levels across the classrooms in GHS and PHS, satisfied the ASHRAE standard, except the indoor air temperature, which was slightly above the maximum threshold of the European Standard (EN). The average indoor sound levels (>60 dB) exceeded critical limits of 35 dB for school buildings, which may pose the risk of high annoyance (HA) to 30% of students. Satisfactory predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) scores were obtained from both schools when they were evaluated against the ASHRAE standard compared with the EN standard. The maximum proportion of the students reported their classroom’s air temperature (33%), relative humidity (25%), and air movement (47%) levels as not acceptable, and thermal comfort (33%), visual comfort (22%), and air quality (41%) as bad (P < 0.001). Multiple regression analysis revealed a strong linear relationship between indoor air temperature (R2 = 0.89) and other IEQ parameters, while PPD (R2 = 0.45) and PMV (R2 = 0.17) showed a weak relationship with outdoor environmental factors. Outdoor air temperature and humidity levels accounted for greater changes in indoor air temperature levels in the PHS than in the GHS. Providing increased urban vegetation, green façade, and retrofitting and the utilization of passive cooling could help improve IEQ in Oman schools.