Effects of parameters of Helmholtz resonator on transmission loss of hybrid muffler

Expansion chamber and Helmholtz resonators are widely used in noise control. In this paper, they are combined to use as a hybrid muffler. The analysis is done to investigate the influence of the parameters of Helmholtz resonator on transmission loss. The transfer matrix method is used in the analysis. The result of transmission loss from the transfer matrix method is validated with the result from experimental two-load method using four microphones impedance tube. After had the transmission loss of the hybrid muffler been validated, the study was proceeded to investigate the effects of parameters of Helmholtz resonator on the transmission loss. The root mean square value of transmission loss were also calculated to compare the transmission losses clearly. In this paper, we investigated the effect of length of the neck of Helmholtz resonator, the effect of diameter of the neck of Helmholtz resonator, the effect of the length of the Helmholtz resonator cavity and the effect of the diameter of the Helmholtz resonator cavity for stationary medium. It is found that the transmission loss is increased when the diameter of the neck of Helmholtz resonator is increased. When the length of the neck is reduced, the transmission loss is increased. The transmission loss can also be increased by reducing the diameter of resonator cavity. It is better to increase the transmission loss at low frequencies by increasing the length of the resonator cavity

Experimental modal analysis of vehicle exhaust system to determine hanger location using root mean square value

Vibration of exhaust system due to the engine operation and the condition of the road surface which is transferable to the body through the hanger affects the noise, vibration and harshness performance of the vehicle, and the life time of the hangers. In order to solve this problem of the automobile exhaust system, experimental modal analysis was carried out by utilizing a sample exhaust system of passenger car as a research object within the frequency of interest. LMS Test. Lab was used to perform modal analysis. This study estimated the dynamic characteristics of the exhaust system such as natural frequencies and mode shapes. Using frequency response function at every measuring point, root mean square value (RMS) of vibrating energy was calculated to select hanger location of exhaust system where the RMS value is comparatively small. Experimental modal analysis is an efficient tool to study and estimate the dynamic properties of the exhaust system, and calculating RMS value is also an easy method to find hanger location of the exhaust system utilizing frequency response function

Moderating effect of goal orientation on the relationship between academic self-efficacy, learner characteristics and learning achievement in an open distance learning (ODL) based higher education institution

This study focuses on factors influencing learning achievement in an Open-Distance- Learning environment of a higher education institution. This study explores the relationship between academic self-efficacy and individual learner characteristics on learning achievement (learning transfer, generalisation, and maintenance). Moreover, this study investigates the role of learner goal orientation. The objectives of the study are, first, to investigate a proposed model to represent theoretical relationship between academic self-efficacy, learner characteristics and learning achievement. Secondly, to confirm learner goal orientation moderates the relationship between learner selfefficacy and training effectiveness. The measures employed in the study are adopted from past studies; goal orientation, self-efficacy and learning achievement using a fivepoint Likert scale. The study utilised purposive sampling. Respondents are postgraduate students from Open University Malaysia (OUM). Analysis was done by using SmartPLS. Findings indicate that hypothesis were supported

Vibration fault detection and classifaction based on the fft and fuzzy logic

Vibration fault exhibit a multifaceted and nonlinear behavior generation in rotated machines, for example in a steam turbine (ST). Vibration fault (VF) is collectedin the form of acceleration, velocity, and displacement via the vibration sensor. This fault damages the turbines if it strays into the danger zone. This paper first models the VF in a time domain to transfer the frequency domain via an FFT technique. The signals were applied to the fuzzy system to be used by the VF for classification via sugeno and mamdani Fuzzy Inference System (FIS) to generate the signal that will reflect the VF in the event it is embedded into the protection system. The Membership Function (MF) sets depends on practical work in a power plant, and the ISO is interested in ST vibration zones. The outcomes of the sugeno fuzzy property is the generation of stable and usable signals that can be used within the protection system, mostly owing to its efficiency in detecting vibrational faults. The results from this work can be utilized to prevent VF from generating on ST via increased processing that will feed signals for ST controls

Numerical modelling of multiple tuned mass damper equipped with magneto rheological damper for attenuation of building seismic responses

TMD is basically designed to be tuned to the dominant frequency of a structure which the excitation frequency will resonate the structural motion out of phase to reduce unwanted vibration. However, a single unit TMD is only capable of suppressing the fundamental structural mode and for multimode control, more than one TMD is needed. In this study, a 3-storey benchmark reinforced structural building subjected to El Centro seismic ground motion is modelled as uncontrolled Primary Structure (PS) by including properties such as stiffness and damping. For the case of controlled PS which the passive mechanism is included to the system, optimum parameters of both TMD and Multiple TMD (MTMD) are designed to be tuned to the dedicated structural modes where the performance is dependent on parameters such as mass ratio, optimum damping ratio, and optimum frequency ratio. The input and output components of structural system arrangements are then characterized in the transfer function manner and then converted into state space function. For enhancement of the passive system, Magneto-Rheological (MR) damper is added to both single TMD and MTMD passive system. The response analysis is executed using both time history and frequency response analysis. From the analysis, semi-active case is the most effective mechanism with 99% displacement reduction for the third and second floors, and 98% for the first floor, compared to the uncontrolled case. It is concluded that the MR damper significantly contributed to the enhancement of the passive system to mitigate structural seismic vibration

The Role of Technology Advancement in Improving the Current Practice of Ambulance Decontamination in Malaysia: A Scoping Review

Abstract In Malaysia, the current methodology for decontaminating ambulances is by manually cleaning surfaces with Environmental Protection Agency (EPA) approved disinfecting solutions as contrast to previous practice using water and soap. The solutions used are registered with National Pharmaceutical Regulatory Agency (NPRA) Ministry of Health Malaysia (NPRA) to ensure adherence to international standard of practice.  The manual decontamination practices are effective if strictly conducted following guidelines. However, the proper cleaning and decontamination of an ambulance is an important task that frequently overlooked. It creates a risk to healthcare providers and their patients for subsequent ambulance trip. To ensure the patient compartment is absent from multitudes of infectious pathogen especially Covid-19, is not only an escalating challenge for healthcare providers as it is an unseen, but also poses a real threat to them and their patient. The healthcare managers should consider technologies that can provide a safer, effective and more efficient cleaning and decontamination of an ambulances. We proposed to adapt a new approach of decontamination by using a vapour based disinfection method coupled with germicidal enhancement using ultra violet. It utilizes an EPA-approved hospital disinfectant to decontaminate surfaces in the patient care compartment after every patient transport. A nozzle, placed inside the patient care compartment, disperses a mist of disinfectant solution that designed to meet standard requirement. The enhancement of germicidal effect using an ultra violet ray will disinfect and ensure a free patient compartment from an infectious organism. This decontamination system directly integrated into a new or existing ambulance. It is convenient, timesaving, hands-off solution for decontaminating of an ambulance and importantly creates a safer practice. Keywords: Ambulance service, decontamination, Vapour-based, safe practice

Relationship between Islamic concept and ethical behaviour akhlak) of being in love among youth

The word love is synonymous with values of goodness. Romantic relationship needs guidance from religious knowledge in order to sustain an ethical love relationship. This is to avoid involvement in social illness. The impact of being unethical in loving behaviour includes increasing number of adultery and baby dumping cases. The aim of this study is to determine the relationship between Muslim youth understanding, attitude and practice on the Concept of Love (COL) in Islam with values in Ethical Love Behaviour (ELB). The study was conducted among students at three types of higher education institutions in Malaysia which include public, private and the public Islamic universities with a total of 599 respondents. The age of the respondents are from 18 to 23 years old (mean=19.5). Respondents were asked to complete Likert type and self-administered questionnaire assessing respondents’ understanding and attitude towards dimensions of love and values in ELB. The psychological measurement tools in this study were developed by the researchers and named as the Instrument of Love in Islam (ICDI) and Ethics of Love (IAP). Findings show that understanding and attitude towards love in Islam is high; however, the practical aspect is moderate. The COL in Islam has a significant relationship with values in ELB. The findings of this study highlight the contributions of understanding and possessing positive attitude towards the COL in sustaining youth’s meaningful participation in values of ELB. The implication of this study suggests that understanding and appreciation of love is particularly relevant to youth in order to address problems of wrongful behaviours that result from misunderstanding of the concept of love

Sound from high-Reynolds number flow over bluff bodies

Purpose - This paper aims to investigate the aerodynamic sound generated from flow over bluff bodies at a high Reynolds number. By taking circular and square cylinders as two representative geometries for the cross-section of bluff bodies, this study aims to clarify the difference in flow formation and sound generation between the two types of bluff bodies. Furthermore, the possibility for a downstream flat plate to be used as sound cancellation passive mechanism is also discussed in this study. Design/methodology/approach - Sound source from the near field is numerically solved by using the Unsteady Reynolds-Averaged Navier Stokes equations. While for the sound at far-field, the compact sound theory of Curle's analogy is used. Findings - Magnitude of the generated sound is dominant by the aerodynamic forcer fluctuations, i.e. lift and drag, where the lift fluctuation gives the strongest influence on the sound generation. The square cylinder emits 4.7 dB higher than the sound emitted from flow over the circular cylinder. This relates to the longer vortex formation length for the case of square cylinder that provides space for more vortex to dissipate. It is suggested that downstream flat plate is possible to be applied for a sound cancellation mechanism for the case of circular cylinder, but it would be more challenging for the case of square cylinder. Practical implications - This study include implications for the development of noise reduction study especially in high-speed vehicles such as the aircrafts and high-speed trains. Originality/value - This study identified that there is possible method for sound cancellation in flow over bluff body cases by using passive control method, even in flow at high Reynolds number