Sound-absorbing asphalts are particularly useful for reducing noise emissions from vehicular traffic. This solution is perfectly suited for urban areas, in fact the use of sound-absorbing asphalt represents a noise control measure with a negligible environmental impact. In the present work, the results of an experimental investigation on sound-absorbing asphalts were reported. First, the characteristics of the sound-absorbing asphalts used were experimentally found. Then, the measurements of the sound absorption coefficient of the asphalt specimens were investigated. In the final part, numerical simulation model with artificial neural networks of the acoustic coefficient were compared with the data obtained from the measurements. The neural network model showed good Pearson correlation coefficient values (0.894) which can be used with good accuracy to predict the sound absorption coefficient.

Academic success in undergraduate programs is indicative of potential achievements for graduates in their professional careers. The reasons for an outstanding performance are complex and influenced by several principles and factors. An example of this complexity is that success factors might change depending on the culture of students. The relationship of 32 factors with the reported academic performance (RAP) was investigated by using a survey distributed over four key universities in Saudi Arabia. A total of 3565 Saudi undergraduate students completed the survey. The examined factors included those related to upbringing, K-12 education, and structured and unstructured activities. Statistical results validate that many factors had a significant relationship with the RAP. Among those factors, paternal’s education level and work field, type of intermediate and high schools, and the attendance of prayers in mosques were significantly associated with the reported performance. This study provides important insights into the potential root causes of success so that they can be targeted by educators and policy makers in the effort to enhance education outcomes.

Purpose: There is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance parameters. Because of their favorable tribological properties, chemically modified vegetable oils such as palm trimethylolpropane ester (TMP) are one of the potential candidates for the said role. To prove the suitability of TMP for applications involving boundary-lubrication regime such as cam/tappet interface of direct acting valve train system, a logical step forward is to investigate their compatibility with conventional lubricant additives. Design/methodology/approach: In this study, extreme pressure and tribological characteristics of TMP, formulated with glycerol mono-oleate (GMO), molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), has been investigated using four-ball wear tester and valve train test rig. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as reference. Moreover, various surface characterization techniques were deployed to investigate mechanisms responsible for a particular tribological behavior. Findings: In additive-free form, TMP demonstrated better extreme pressure characteristics compared to PAO and lubricant additives which are actually optimized for conventional base-oils such as PAO, are also proved to be compatible with TMP to some extent, especially ZDDP. During cylinder head tests, additive-free TMP proved to be more effective compared to PAO in reducing friction of cam/tappet interface, but opposite behavior was seen when formulated lubricants were used. Therefore, there is a need to synthesize specialized friction modifiers, anti-wear and extreme pressure additives for TMP before using it as engine lubricant base-oil. Originality/value: In this study, additive-free and formulated versions of bio-lubricant are tested for cam/tappet interface of direct acting valve train system of commercial passenger car diesel engine for the very test time. Another important aspect of this research was comparison of important tribological performance parameters (friction torque, wear, rotational speed of tappet) of TMP-based lubricants with conventional lubricant base oil, that is, PAO and its formulated version.

In Saudi Arabia, air-conditioners ACs are responsible for 50% of electricity consumption due to hot weather conditions as well as the delay in implementing ACs standards. In this work, six used split-type and eight used window-type ACs that have ages from 3 to 32 years were tested according to American Society of Heating, Refrigerating and Air-Conditioning Engineers and Saudi Standard, Metrology and Quality Organization cooling test conditions and their performances were compared against new units that have 5.27 kW rated capacity. Test results show that coefficient of performance and cooling capacity of used split-type units compared to new one are 68% and 93%, respectively. For window-type, test results show that coefficient of performance and cooling capacity of used units compared to new one are 55% and 77%, respectively. The effect of replacing used compressor units with a new compressor was experimentally investigated. A model was developed using a commercially available software and was validated with experimental data. An economical map was developed to identify feasible ACs replacement regions. Practical application: Using standard methods this study experimentally quantifies energy savings when used split- and window-type units are replaced with new units. This will help HVAC and energy professionals develop recommendations regarding replacing existing units for a given power tariffs. Additionally, tests were conducted with replacing compressors in used air-conditioners, rather than replacing the entire unit, so as to assist in answering how much energy savings, CO ₂ and payback period can be achieved by simply replacing the compressors.