Applied Mechanics and Materials Vol. 926

Abstract: The micro-perforated panel (MPP) absorber has provided better noise control solutions in the medium to high-frequency range than the traditional fibrous porous absorbers regarding absorption characteristics and durable features in challenging environments. But, the low-frequency performance of the MPP absorber with a constrained air back cavity is not satisfactory. Researchers in the last decades proposed many solutions to enhance the acoustic performance of the absorbers, but the cost and complexities involved limited their wide applications. In this paper, the back cavity is partitioned to have a multi-cavities arrangement behind the MPP, which facilitates the multiple Helmholtz resonator (HR) effects. Maa model for the MPP absorber is modified to accommodate multiple HR effects and find the acoustic impedance and sound absorption coefficient of the proposed absorber. The individual absorption peaks of the absorber can be tuned along the frequency axis to have wideband absorption characteristics. 3D printed MPP sample with a multi-cavities structure is mounted in two microphone impedance tube setup to validate the predicted results.

Abstract: This study investigates the drying kinetics of Irish potato slices using an Arduino controlled convective heat dryer. The experiment examines drying temperatures of 60, 65, 70, and 75°C, coupled with potato slice thicknesses of 3 and 5 mm. The drying process is crucial in preserving food products and extending their shelf life. Understanding the drying kinetics of potato slices under different conditions is essential for optimizing the drying process and maintaining product quality. The experimental setup allows for precise control of drying parameters, facilitating accurate data collection. The research aims to analyze the drying characteristics, including drying rate, moisture content, and drying time, at various temperature and thickness combinations. From the mathematical models obtained, it is evident that correlation coefficients closest to unity is at 70°C for chip thickness of 3 mm whereas the correlation coefficients closest to unity is at 60°C for chip thickness of 5 mm. Also, it is clearly observed that the efficiency of the system is highest with chip thickness of 3 mm dried at 70°C and performance evaluation results indicate that dryer efficiency is contingent on both temperature and thickness of the chips. These findings contribute to enhancing the efficiency and effectiveness of convective heat drying methods for potato slices, offering insights into temperature and thickness effects on the drying process. This study provides valuable information for food processing industries seeking to improve drying techniques for potato products.

Abstract: The accurate estimation of thermal contact conductance (TCC) at material contact interfaces is cru cial for determining the temperature distribution in a system, particularly in vacuum conditions such as outer space. Improper estimates of TCC, especially in vacuum environments, may result in under design of thermal management systems resulting in the formation of hot spots, leading to material and system failure. This study introduces two inverse techniques for determining the TCC at the contact interface. The validity of the proposed inverse methods is established by comparing TCC values at the interface with those obtained from experiments performed using the ASTM D5470-17 standard, which is applicable under the assumption of one-dimensional heat transfer. Experiments are meticu lously conducted to ensure the validity of the one-dimensional heat transfer assumption. The variation observed in the TCC estimates obtained from experiments and the inverse methodology is discussed to establish the validity of the proposed inverse techniques. Consequently, these techniques offer ap plicability in scenarios where one-dimensional heat transfer is compromised due to factors such as asperity distribution, vacuum conditions, or low thermal conductivity of the specimen.

Abstract: Mechanical fatigue is an essential phenomenon that occurs when the structures are exposed to dynamic, fluctuating loadings. Especially automotive components are regularly exposed to random vibration loadings. Vibration fatigue failures may arise even in components that meet static requirements and are stable and robust, because of dynamic and fluctuating loadings. The primary focus of this study is the research of the vibration fatigue. Hence, in addition to the analyses, the tests are conducted. In order to study the analyses and tests, aluminum cross-section beams are designed and manufactured. The notched sections added to the beam geometry to acquire a more distinct fatigue life compared to other parts of the beams. The results obtained from the experimental tests are used to correlate the effect of notch parameters on fatigue life.

Abstract: High-performance volume holographic grating (VHG) is an important coupling element for a holographic waveguide system. Small angular bandwidth and low diffraction efficiency restrict the applications of VHGs. Based on asymmetrical recording, a reflection VHG with large angular bandwidth and high diffraction efficiency are designed and prepared. The relationship between the recording angles and the diffraction efficiency is discussed first and several combinations of the recording angles are found. Then the relationship between the recording angles and the angular bandwidth is further analyzed, which could obtain the optimal recording setup. The experimental results show that when the incident angle of the reference light and signal light is 10° and 59°, the angular bandwidth of the fabricated VHG reaches 25° and the diffraction efficiency is 90%. However, the wavelength shift happens. The recording angle is modified to improve wavelength shift. The method proposed in this paper could help design a VHG with large angular bandwidth and high diffraction efficiency.

Abstract: Vehicle theft is a major issue, underscoring the shortcomings of conventional security systems that frequently depend on expensive and sophisticated sensors. In order to solve this problem, a smart car security system that combines GPS and GSM technology with biometric fingerprint authentication on an affordable Arduino-based platform is created. The main goal is to improve car security by using fingerprint recognition, which uses distinct and difficult-to-copy biometric data, to guarantee that only authorized individuals may access the vehicle. The technology offers a high degree of security by prohibiting unauthorized people from entering the car using fingerprint authentication. Moreover, the system makes use of GSM technology to provide instantaneous notifications in the case of unlawful entry attempts and to allow real-time communication between the owner and the car. The owner may act quickly to safeguard their car thanks to this instant notice. The precise tracking capabilities provided by GPS technology further improve the security framework and are crucial for the prompt recovery of stolen cars. The owner may feel secure knowing that their vehicle's position is always tracked thanks to this extensive tracking technology. The main focus of the issue statement is the requirement for an inexpensive, dependable, and easy-to-use vehicle security system that can overcome the shortcomings of traditional systems. Many car owners are unable to use traditional systems since they are frequently costly and complicated. Using GPS modules for position tracking, GSM modules for communication, and fingerprint sensors for identification, the system is designed and implemented according to the approach. This method offers a flexible solution that may be extensively used while also ensuring high security and system adaptability to different vehicle kinds. This all-encompassing strategy seeks to lower theft rates, improve owner happiness, and offer a strong security framework that can be customized to fit different kinds of vehicles.

Abstract: Ceiling cassette air-conditioning units play a pivotal role in the HVAC industry, renowned for their high efficiency, especially in high-rise buildings. However, the routine maintenance of these units poses significant challenges. The current methods are labor-intensive, time-consuming, and wasteful of water, leading to adverse effects on workers' health due to chemical exposure and the physical strain of manual cleaning. In response, this research proposes an innovative solution leveraging Arduino, high-pressure water nozzles, and electronic components to revolutionize maintenance procedures. By automating cleaning processes, this system aims to reduce both the time required for servicing and the physical exertion demanded from workers while also minimizing water wastage and eliminating exposure to harmful chemicals. This study comprehensively evaluates the effectiveness of this technological intervention against conventional methods, highlighting its potential to not only optimize maintenance efficiency but also enhance worker safety and well-being.

Abstract: This article focuses on the development and testing of a sensor-based motorcycle restraint system equipped with an automated braking mechanism. The system integrates ultrasonic sensors, a DC linear motor, and an Arduino microcontroller to enhance motorcycle safety by detecting obstacles and applying brakes automatically. A prototype was constructed using a wooden frame and bicycle wheels to emulate the motorcycle's dynamics. The braking system utilized a genuine motorcycle drum brake, and the DC linear motor was linked to activate the brake lever based on sensor feedback. LED strips and a buzzer provided visual and audible warnings, indicating the presence and proximity of obstacles. The system was tested under various conditions to evaluate its responsiveness, accuracy, and dependability. The findings revealed that the ultrasonic sensors provided precise distance measurements, allowing for a timely response in obstacle detection scenarios. The automatic braking mechanism demonstrated a 65% reduction in reaction time compared to manual braking, improving rider safety significantly. The system also managed to reduce the braking distance at speeds of 50 km/h, demonstrating its efficacy in emergency situations. Data collected during prototype testing indicated that the system effectively engaged the brake within a 10 cm detection range, issued appropriate warnings, and accurately monitored brake wear. Despite some limitations, such as environmental sensitivity and the prototype's use of simplified materials, the research underscores the system's potential to enhance motorcycle safety. Future recommendations include improving sensor reliability in adverse weather conditions, upgrading the prototype to mimic full-scale motorcycle dynamics, and incorporating additional features like traction control and rider-assist technology.

Abstract: The aircraft's navigation system routinely makes use of the Global Navigation Satellite System (GNSS) during numerous phases of a flight. A primary concern is Ionospheric Gradients, which might impact the global positioning system's positional accuracy. Data from a single GNSS reference station is required for Ionospheric Spatial Gradient estimation using the well-known Time-Step Method. Temporal decorrelation faults are one type of inaccuracy that accompany the Time-Step Method. Conversely, the Station-Pair technique uses two GNSS reference stations that are closely separated to estimate the Spatial Gradient. When GNSS stations are far apart, the Station-Pair Method is ineffective in determining delay gradients in ionospheric plasma at short baselines. An attractive alternative is Satellite-Pair Method which uses observations from a single GNSS reference station. Satellite-Pair approach compares the Ionospheric delays of two satellites that are being monitored by the same receiver at the same time. GNSS data for the year of January to December 2021 was obtained from the mid latitude stations p502 (Imperial County, California) with Geographical Latitude and Graphical Longitude 32°58'55.2"N and 115°25'19.2"W and p509 (Holtville, California) with Geographical Latitude and Graphical Longitude 32°48'40.18"N and 115°22'48.95"W located in California, USA. The maximum Ionospheric Spatial Gradient for disturbed day (15 June 2021) using Satellite-Pair Method is found to be 4.6047 mm/100km, whereas for Existing Time-Step and Station-Pair Methods are 2.2089 mm/100km and 1.8859 mm/100km.The Spatial Gradients are found to be occurred mostly between 2000hrs to 2200hrs UT.