Y.H. Yau

Thermal comfort study of hospital workers in Malaysia

UNLABELLED This article presents findings of the thermal comfort study in hospitals. A field survey was conducted to investigate the temperature range for thermal comfort in hospitals in the tropics. Thermal acceptability assessment was conducted to examine whether the hospitals in the tropics met the ASHRAE Standard-55 80% acceptability criteria. A total of 114 occupants in four hospitals were involved in the study. The results of the field study revealed that only 44% of the examined locations met the comfort criteria specified in ASHRAE Standard 55. The survey also examined the predicted percentage of dissatisfied in the hospitals. The results showed that 49% of the occupants were satisfied with the thermal environments in the hospitals. The field survey analysis revealed that the neutral temperature for Malaysian hospitals was 26.4 degrees C. The comfort temperature range that satisfied 90% of the occupants in the space was in the range of 25.3-28.2 degrees C. The results from the field study suggested that a higher comfort temperature was required for Malaysians in hospital environments compared with the temperature criteria specified in ASHRAE Standard (2003). In addition, the significant deviation between actual mean vote and predicted mean vote (PMV) strongly implied that PMV could not be applied without errors in hospitals in the tropics. PRACTICAL IMPLICATIONS The new findings on thermal comfort temperature range in hospitals in the tropics could be used as an important guide for building services engineers and researchers who are intending to minimize energy usage in heating, ventilating and air conditioning systems in hospitals operating in the tropics with acceptable thermal comfort level and to improve the performance and well-being of its workers.

Design of new generation femoral prostheses using functionally graded materials: a finite element analysis.

This study aimed to develop a three-dimensional finite element model of a functionally graded femoral prosthesis. The model consisted of a femoral prosthesis created from functionally graded materials (FGMs), cement, and femur. The hip prosthesis was composed of FGMs made of titanium alloy, chrome–cobalt, and hydroxyapatite at volume fraction gradient exponents of 0, 1, and 5, respectively. The stress was measured on the femoral prosthesis, cement, and femur. Stress on the neck of the femoral prosthesis was not sensitive to the properties of the constituent material. However, stress on the stem and cement decreased proportionally as the volume fraction gradient exponent of the FGM increased. Meanwhile, stress became uniform on the cement mantle layer. In addition, stress on the femur in the proximal part increased and a high surface area of the femoral part was involved in absorbing the stress. As such, the stress-shielding area decreased. The results obtained in this study are significant in the design and longevity of new prosthetic devices because FGMs offer the potential to achieve stress distribution that more closely resembles that of the natural bone in the femur.

The Ventilation of Multiple-Bed Hospital Wards in the Tropics: A Review

Abstract Hospital and healthcare facilities have diverse indoor environment due to the different comfort and health needs of its occupants. Currently, most ventilation studies revolve around specialised areas such as operating rooms and isolation rooms. This paper focuses on the ventilation of multiple-bed hospital wards in the tropical climate, taking into account the design, indoor conditions and engineering controls. General ward layouts are described briefly. The required indoor conditions such as temperature, humidity, air movements and indoor air quality in the ward spaces are summarized based on the current guidelines and practices. Also, recent studies and engineering practices in the hospital indoor environment are elaborated. Usage of computational fluid dynamics tools for the ventilation studies is discussed as well. As identified during the review, there is an apparent knowledge gap for ventilation studies in the tropics compared with temperate climates, as fact studies have only been published for hospital wards in countries with a temperate climate. Therefore, it is highlighted that specific tropical studies along with novel engineering controls are required in addressing the ventilation requirements for the tropics.

Mechanical and physical behavior of newly developed functionally graded materials and composites of stainless steel 316L with calcium silicate and hydroxyapatite

This study aimed to investigate the structural, physical and mechanical behavior of composites and functionally graded materials (FGMs) made of stainless steel (SS-316L)/hydroxyapatite (HA) and SS-316L/calcium silicate (CS) employing powder metallurgical solid state sintering. The structural analysis using X-ray diffraction showed that the sintering at high temperature led to the reaction between compounds of the SS-316L and HA, while SS-316L and CS remained intact during the sintering process in composites of SS-316L/CS. A dimensional expansion was found in the composites made of 40 and 50 wt% HA. The minimum shrinkage was emerged in 50 wt% CS composite, while the maximum shrinkage was revealed in samples with pure SS-316L, HA and CS. Compressive mechanical properties of SS-316L/HA decreased sharply with increasing of HA content up to 20 wt% and gradually with CS content up to 50 wt% for SS-316L/CS composites. The mechanical properties of the FGM of SS-316L/HA dropped with increase in temperature, while it was improved for the FGM of SS-316L/CS with temperature enhancement. It has been found that the FGMs emerged a better compressive mechanical properties compared to both the composite systems. Therefore, the SS-316L/CS composites and their FGMs have superior compressive mechanical properties to the SS-316L/HA composites and their FGMs and also the newly developed FGMs of SS-316L/CS with improved mechanical and enhanced gradation in physical and structural properties can potentially be utilized in the components with load-bearing application.

Finite element analysis on longitudinal and radial functionally graded femoral prosthesis

This study focused on developing a 3D finite element model of functionally graded femoral prostheses to decrease stress shielding and to improve total hip replacement performance. The mechanical properties of the modeled functionally graded femoral prostheses were adjusted in the sagittal and transverse planes by changing the volume fraction gradient exponent. Prostheses with material changes in the sagittal and transverse planes were considered longitudinal and radial prostheses, respectively. The effects of cemented and noncemented implantation methods were also considered in this study. Strain energy and von Mises stresses were determined at the femoral proximal metaphysis and interfaces of the implanted femur components, respectively. Results demonstrated that the strain energy increased proportionally with increasing volume fraction gradient exponent, whereas the interface stresses decreased on the prostheses surfaces. A limited increase was also observed at the surfaces of the bone and cement. The periprosthetic femur with a noncemented prosthesis exhibited higher strain energy than with a cemented prosthesis. Radial prostheses implantation displayed more strain energy than longitudinal prostheses implantation in the femoral proximal part. Functionally graded materials also increased strain energy and exhibited promising potentials as substitutes of conventional materials to decrease stress shielding and to enhance total hip replacement lifespan.

A review on predicted mean vote and adaptive thermal comfort models

This paper presents a literature review of the Fanger’s predicted mean vote and adaptive thermal comfort models developed in different buildings and climates. An important premise of this paper is the fact that Fanger’s model underestimates the thermal impression in the actual case and thus is no longer valid for use in certain climates. As a consequence, many researchers have developed adaptive models from field studies for different climates and countries. However, there is still no adaptive model that can be applied in designing air-conditioning systems for different buildings in all tropical climate countries. Based on this comprehensive review, an internationally recognized adaptive model is needed to achieve better thermal conditions in a variety of buildings such as hospitals, offices, factories, lecture halls, museums, hotels and libraries in the tropics. Practical application: The new conclusions from the comprehensive review on an adaptive thermal comfort model in buildings in the tropics could be used as an important guide for building service engineers and researchers. Their intentions are to minimize energy usage in heating, ventilation and air conditioning (HVAC) systems in buildings such as hospitals, offices and lecture halls operating in the tropics while maintaining an acceptable thermal comfort level and thus improving the performance and well-being of the occupants.

A Field Study on Thermal Comfort of Occupants and Acceptable Neutral Temperature at the National Museum in Malaysia

A field study was conducted to investigate the thermal environment and occupants’ comfort in the National Museum of Malaysia. The occupants’ thermal perceptions in the museum were measured and characterised. The response of the occupants has indicated that the thermal conditions inside the museum did not satisfactorily fulfil the ASHRAE Standard 55, because only 78% of the occupants were satisfied with their environment. Besides, actual mean vote (AMV) and predicted mean vote (PMV) were compared. The Fanger’s model gave a neutral operative temperature of 22.2°C from the PMV, whereas the questionnaire data used in the mean thermal sensation vote (MTSV) of the present study gave a higher value (22.5°C) for the neutral operative temperature. The preferred operative temperature was found to be 22.3°C. The minimum air temperature in three galleries was below the lower limit of the temperature range of 18–22°C as recommended by Museums Australia Victoria. The mean indoor humidity was too high compared to the optimal range of 55 ± 5% relative humidity (RH). The mean air velocity, ≤0.15 m·s−1, in each gallery was satisfactory. Findings of this study are very useful for designing heating, ventilating and air-conditioning (HVAC) systems with energy-saving methodology for museum buildings in tropical regions.

Adaptive thermal comfort model for air-conditioned hospitals in Malaysia

This article presents an adaptive thermal comfort model study in the tropical country of Malaysia. A number of researchers have been interested in applying the adaptive thermal comfort model to different climates throughout the world, but so far no study has been performed in Malaysia. For the use as a thermal comfort model, which better applies to hot and humid climates, the adaptive thermal comfort model was developed as part of this research by using the collected results from a large field study in nine hospitals with 293 workers. The relationship between the operative temperature and behavioral adaptations was determined. In the developed adaptive model, the acceptable indoor neutral temperatures lay within the range of 23.3–26.5℃, with outdoor temperatures ranging between 25.4℃ and 35.0℃. The most comfortable temperature for hospital workers was 26.4℃. Practical implications: The new conclusions from the adaptive thermal comfort model in hospitals in the tropics could be used as an important guide for building services engineers and researchers. Their intentions are to minimize energy usage in HVAC systems in hospitals operating in the tropics while maintaining an acceptable thermal comfort level and thus improving the performance and well-being of hospital workers.

Field analysis of indoor air quality in high rise and low rise green offices with radiant slab cooling systems in Malaysia

Even though the green building concept is fairly new in Malaysia, the development of this industry has been growing in recent years prior to the launch of Malaysia’s own standard, namely the Green Building Index (GBI). One of the criteria assessed in the GBI is the energy efficiency, which takes about 21% of the overall assessment. Considering this, the passive design has been included in the green building concept to reduce the energy usage without compromising occupant thermal comfort. This study attempts to assess the passive design effectiveness in terms of indoor air quality in green office buildings in the tropics. Two green office buildings that incorporated the radiant slab cooling and conventional cooling system have been selected as case studies. A detailed assessment in terms of thermal comfort parameters (temperature and relative humidity), indoor pollutants’ concentration (carbon dioxide, carbon monoxide and formaldehyde) and air movement was carried out. The results showed that the thermal comfort parameters fall within the Malaysian Standard (MS1525:2007) and ASHRAE Standard-55 2010 except for the air movement in both buildings. Based on the results obtained, future buildings using the radiant slab cooling can have a better comfort level from the lesson learned from both buildings.

Effect of geometrical parameters on the performance of longitudinal functionally graded femoral prostheses.

This study aimed to assess the performance of different longitudinal functionally graded femoral prostheses. This study was also designed to develop an appropriate prosthetic geometric design for longitudinal functionally graded materials. Three-dimensional models of the femur and prostheses were developed and analyzed. The elastic modulus of these prostheses in the sagittal plane was adjusted along a gradient direction from the distal end to the proximal end. Furthermore, these prostheses were composed of titanium alloy and hydroxyapatite. Results revealed that strain energy, interface stress, and developed stress in the femoral prosthesis and the bone were influenced by prosthetic geometry and gradient index. In all of the prostheses with different geometries, strain energy increased as gradient index increased. Interface stress and developed stress decreased. The minimum principal stress and the maximum principal stress of the bone slightly increased as gradient index increased. Hence, the combination of the femoral prosthetic geometry and functionally graded materials can be employed to decrease stress shielding. Such a combination can also be utilized to achieve equilibrium in terms of the stress applied on the implanted femur constituents; thus, the lifespan of total hip replacement can be prolonged.