Applied Mechanics and Materials Vol. 471

Abstract: This paper presents two important parameters for an electromagnetic energy harvester exploiting various shaker excitation frequencies: (1) number of turns of the coil and (2) length of the beams for the device. This system consists of a cantilever beam based which represent a spring element of the system, permanent NdFeB magnet, coil system and wiring system to be connected to the data acquisition system. It is found that the induced voltage is proportional to the increment of the number of turns and the length of beams. The expected resonance happens at 300 Hz for case (1) and 100 Hz for case (2). The maximum voltage produced by this device is 915.395 millivolts for length 13 cm at 100 Hz excitation and 275.058 millivolts for 1050 turns at 300 Hz excitation. Experimental data have demonstrated that the geometry and number of turns of the coil would affect the performance of the energy harvester while excitation frequency as a non-physical factor also contributes to its effectiveness.

Abstract: Excessive environmental noise and poor air quality can be adverse to human health, living comfort and the environment itself. Measurement of sound pressure levels and air quality in critical areas including libraries, campus areas, public parks and hospitals thus becomes necessary to monitor and mitigate existing noise levels. In a university environment, student activities will be less disrupted if the locations of the activities are sufficiently away from noise sources. The present study is intended to measure sound levels and air quality around the Engineering Complex, Universiti Teknologi Mara, Shah Alam. The measured data is compared with to acceptable sound pressure levels and air quality index specified by the Department of Environment (DOE), Malaysia. Sound pressure levels are measured using the Castle Sound Level Meter Type 6224 and air quality measurement was done by using the BW Gas Alert MicroClip XT device. Both measurements were conducted at five selected stations around the Engineering Complex for three times each weekday for five weeks. Results obtained indicated that sound levels at some locations and time zones are above the thresholds recommended by the DOE. The air quality is acceptable in most locations except the vicinity of a bus stop. With the growing number of students in the university and other factors like construction and redevelopment of existing roads, a continuously increasing noise situations and air pollution proportional to the traffic flow is inevitable.

Abstract: Unattended noise measurements are more and more common for noise assessment in the environment. Multiple sources are usually measured with a random position with respect to the measurement point. Noise generated by ground transportation, leisure activities, construction sites is coming from all directions, although mainly the horizontal direction. Placed vertically and configured for a reference direction of 90° from its axis, the goal is to meet the requirements of the IEC 61672 standard on sound level meters taking into account noise incidence from the horizontal direction. The main technical difficulty is the criterion for the maximum level difference allowed between two random incidence angles (directivity). The objective can be fulfilled using a cone-shaped device on top of the microphone. When measuring attended noise with the instrument in hand, the sound level meter must be pointed at the source according to standard IEC 60651. The purpose of the paper is to describe the different research & development phases to fulfill IEC 61672 sound level meter standard for 0° and 90° reference directions with the same device.

Abstract: Acoustic quality is important in ensuring a healthy and workable working environment. One of green buildings main objective is to reduce the building impact on human health and performance. This was emphasized in most green building rating system under its requirement for Indoor Environmental Quality (IEQ). IEQ highlights the four main points for achieving an improved indoor environment: indoor air quality, acoustics, visual comfort (lighting) and thermal comfort. Although acoustics was mentioned in the IEQ criteria, according to previous surveys and studies; acoustics quality in green buildings were not improving. It seems as though in order to improve on other green building criteria, acoustics performance is bound to become poorer. Through review of previous literature, survey and studies on acoustical performance in green buildings, the objective of this paper is to identify how green building design strategies contribute to the degradation of acoustical environment in green office buildings. Findings shows that design strategies implemented to cater for other green building requirements such as natural ventilation, daylight, reduction of finishes and office layout have unintentionally decrease the acoustical quality.

Abstract: The European Directive 2002/49/EC on the assessment and management of environmental noise obliges European Union Member states to draw noise maps of communities with more than 100,000 inhabitants (agglomerations) and of areas near the major transport infrastructures for the assessment of noise outdoors. The Latvian law On Pollution and the Cabinet Regulation No 597 Procedures for Noise Assessment and Management (Adopted 13 July 2004) were harmonized with this European Directive to provide the legislative background for the local authorities to draw noise maps to be used as a basis for noise reduction plans. Riga Agglomeration strategic noise map was calculated using software IMMI 6.3. The map shows Riga City as rather noisy city because major roads and railway lines cross the city center and close to it. Riga Freeport, located on the banks of river Daugava, with its supply roads and branch-ways also add to contribute in the total noise levels. The European Directive 2002/49/EC on the assessment and management of environmental noise also obliges European Union Member states to draw Noise reduction Action plans. In Latvia, Capital Riga and Daugavpils are required to have the Action Plans. Action Plans must be completed by 18 July 2008. Much to our regret the Riga City noise reduction Action Plan is still under consideration and in process of development because it touches the interests of many parties.

Abstract: The purpose of this paper is to discuss the vibration transmissibility from a cars body to pedal-pad, and the lower extremity, especially on the foot. The vibration transmissibility will occur when the foot interacts with the pedal-pad once the vehicle engine is turned on. The vibrations transmissibility will cause drivers discomfort, especially on the lower extremity due to fatigue and tiredness of the foot. The relationship between vibration transmissibility with the different sizes pedal-pad to the foot, and whether it can contribute to the foot discomfort during handling and controlling pedal-pad while driving is investigated. The variables are the different sizes of pedal-pad. Data was recorded from foot on three different sizes of pedal-pads. The data was measured in root mean square (r.m.s) unit, of the frequency weighted acceleration (m/s²) for every minute. The result for the foot-transmitted-vibration shows the ratio value of medium sized pedal-pad is greater than 1; compared to small sized and large sized pedal-pads which is less than 1. Analysis of One-way Anova shows that the mean of different sizes of pedal-pad is significant. Tukeys post-hoc with HSD (Honestly Significant Difference) test on the foot transmitted-vibration proves that the means for medium size pedal-pad is the highest compared with the small and large size pedal-pads.

Abstract: Exposure to high levels of whole body vibration (WBV) from the seat can present risks to health and safety and cause injuries to drivers. This study presents a study on WBV exposure to Malaysian Army 3-tonne truck drivers using the method defined in International Standard ISO 2631-1:1997. The vehicle that was chosen for this study was based on the highest number of vehicles available within the Malaysian Army services. 3-tonne truck is the most widely used in Malaysian Army services. WBV from the drivers were measured using tri-axial accelerometer and was connected to Brüel & Kjær Vibration Analyser Type 3649, which is capable to produce raw data to calculate the vibration dose value (VDV). The raw data from each axis were analyzed using statistical analysis method, Integrated Kurtosis Algorithm for Z-notch Filter (I-kaz^TM) 3D to determine the vibration values in relation to varying speed of the vehicle. Based on the results, WBV experienced by the drivers can be presented in VDV and I-kaz^TM 3D coefficient which the value will increase proportional to the truck speed.

Abstract: Transmitted vibration from hand to the human body is one of the oscillation sources which are a reason of pain in shoulders, neck and arms. Design vibration isolators or seat suspensions require an accurate biodynamic model which can consider both vibration sources; hand and seat. For this purpose, an artificial neural network model was established which is able predict head acceleration from hand and seat excitation. Average of error in signal prediction in this model is around 3.5%, and this issue made appropriate this biodynamic model to use in the next studies especially for suspension designs.

Abstract: Prevalence of neck-shoulder pain among sewing machine operators is well known. It may be due to the nature and incorrect posture used by sewing machine operators while performing sewing work. However, up till now there is no empirical evidence that can be used to relate the risk factors that would results towards the development of neck and shoulder pain among sewing machine operators. The main objective of this study is to identify and investigate the risk factors that result in neck and shoulder pain among Malaysian sewing machine operators. Twenty female sewing machine operators took part in answering a survey questionnaire to investigate the prevalence of neck and shoulder pain among sewing machine operators. The survey questionnaire was divided into five sections: socio-demographic, work background, workload information, physical exposures and physical musculoskeletal symptoms experienced by workers. Having done that, sewing machine operators who have been screened with neck and/or shoulder pain was evaluated with Rapid Upper Limb Assessment (RULA) to determine the level of workplace risk factors. Subjects without neck and/or shoulder pain were excluded. Results of the study shows that all sewing operators were expose to risk of prolonged sitting, repetitive task and working at high speed. Ninety five percent of sewing machine operators had experienced neck and/or shoulder pain and 80% of them were exposed to high work risk factors that require them to undergo further investigation. Shoulder pain was found to be strongly correlated with high work risk factor among sewing machine operators (p<0.05). In conclusion, occurrence of shoulder pain among sewing operators is due to posture and nature of sewing work.