Search Results (143)

Accurate localization plays a critical role in enabling underwater vehicle autonomy. In this work, we develop a robust infrastructure-based localization framework that estimates the position and orientation of underwater vehicles using only range measurements from long baseline (LBL) acoustic beacons to multiple on-board receivers. The proposed framework integrates three key components, each formulated as a convex optimization problem. First, we introduce a robust calibration function that unifies multiple sources of measurement error—such as range-dependent degradation, variable sound speed, and latency—by modeling them through a monotonic function. This function bounds the true distance and defines a convex feasible set for each receiver location. Next, we estimate the receiver positions as the center of this feasible region, using two notions of centrality: the Chebyshev center and the maximum volume inscribed ellipsoid (MVE), both formulated as convex programs. Finally, we recover the vehicle’s full 6-DOF pose by enforcing rigid-body constraints on the estimated receiver positions. To do this, we leverage the known geometric configuration of the receivers in the vehicle and solve the Orthogonal Procrustes Problem to compute the rotation matrix that best aligns the estimated and known configurations, thereby correcting the position estimates and determining the vehicle orientation. We evaluate the proposed method through both numerical simulations and field experiments. To further enhance robustness under real-world conditions, we model beacon-location uncertainty—due to mooring slack and water currents—as bounded spherical regions around nominal beacon positions. We then mitigate the uncertainty by integrating the modified range constraints into the MVE position estimation formulation, ensuring reliable localization even under infrastructure drift. Full article

This study utilizes waste wheat straw fibers and discarded tea bags as novel raw materials for developing new thermal insulation and sound absorption composites. Wood adhesive (WA) is used to bind the polymer raw materials. Loose polymers and different composites are experimentally developed in different concentrations. Sound absorption and thermal conductivity coefficients are obtained for the developed boards. Bending moment analysis and the moisture content of the boards are reported in addition to a microstructure analysis of the straw fibers from wheat. The results indicate that as the wheat straw fiber’s percentage increases in the composite, the thermal conductivity coefficient decreases, the flexure modulus decreases, the sound absorption coefficient increases at some frequencies, and the moisture content increases. The range of thermal conductivity and the noise reduction coefficient are 0.042–0.073 W/m K and 0.35–0.6 at 24 °C for the polymer raw materials, respectively. The corresponding values for the composites are 0.054 and 0.0575 W/m K and 0.45–0.5, respectively. The maximum moisture content percentages for the polymers and composites are 6.5 and 1.15, respectively. The composite flexure modulus reaches maximum and minimum values of 4.59 MPa and 2.22 MPa, respectively. These promising results promote these polymer and composite sample boards as more convenient insulation materials for green buildings and could replace the conventional petrochemical thermal insulation ones. Full article

This paper explores the potential of the Ozobot EVO mobile robot as an educational tool for teaching Python programming. While the robot is currently designed for younger students through color and block programming, it is not yet widely utilized for teaching text-based coding. The Ozobot’s compatibility with Python presents a valuable opportunity for students to visualize their programming concepts through the robot’s actions, offering a more engaging alternative to console-based learning. The increasing use of the Raspberry Pi, a single-board computer programmed in Python, has necessitated the inclusion of Python in the curriculum. However, students often find learning Python challenging and demotivating. To enhance STEM education and student motivation, this paper proposes sample Python code for the Ozobot EVO, aiming to encourage educators to integrate the robot into their teaching. I suggest some Python code examples for the Ozobot EVO. This is to help educators see how they can use the robot in their lessons. Specifically, code examples for controlling motion, sound, light, and combinations of these functionalities are presented. When students see the robot react immediately to their code, they can understand programming ideas much better than just seeing text in the Python console. The Ozobot EVO mobile robot offers a solid foundation for learning Python programming. Full article

The study presented in this paper investigates the influence of coating polymers on the acoustic properties of resonant spruce wood. It evaluates absorption, acoustic reflection, and resonance frequency spectrum characteristics in both unvarnished and varnished samples, with the interface between the coating polymer and the wood modifying the acoustic response. The novelty of the research consists in evaluating the acoustic and dynamic parameters of resonant spruce wood boards, varnished with varnishes with different chemical properties (oil-based varnish, spirit varnish, nitrocellulose varnish). The study focuses on the influence of the type of varnish and the thickness of the varnish film on the frequency spectrum, damping coefficient, quality factor, acoustic absorption coefficient, and sound reflection. The sound absorption coefficient increases with the number of varnish layers and is influenced by the sound’s frequency range, the type of varnish, and the quality of the wood—factors that collectively enhance acoustic performance. For instance, oil-based varnish applied in 5 or 10 layers contributes to a fuller sound at a frequency of 1.5 kHz. In contrast, spirit varnish, which has a lower acoustic absorption coefficient at this frequency, and a reduced damping coefficient, can lead to a nasal tone, although the frequency spectrum turns out to have the richest. Applying more than 10 layers of varnish softens the sound when using oil-based varnish but sharpens it with spirit varnish on resonant wood. Thus, the acoustic performance of a soundboard can be tailored by selecting the appropriate varnishing system and number of layers applied. However, a detailed analysis of the timbre of musical instruments finished with these varnishes is necessary to confirm their influence on the acoustic quality of the instruments. Full article

The perceived acoustic comfort on board modern yachts has recently been the subject of specific attention by the most important classification societies, which have issued new guidelines and regulations for the evaluation of noise and vibrations. The evaluation of the acoustic insulation performance of the internal partitions of yachts is, therefore, a very current topic. The estimation of the acoustic performance of internal partitions can be very complex; on the one hand, on-board measurements can be extremely difficult, but on the other hand, manual or software calculation is extremely complex or potentially affected by non-negligible errors, which is also due to the high amount of highly detailed information required. This paper explores the possibility of using simplified models, commonly used in building construction, to determine the acoustic insulation of the internal partitions of yachts in the design phase, without having to resort, even from the beginning, to very advanced calculation tools such as those based on the Finite Elements Method or Statistical Energy Analysis. Using a 44 m yacht as a case study, this paper presents the results of a series of acoustic simulations of single partitions and compares them with the results of an on-board measurement campaign. From the comparison of the obtained results, it was possible to state that the simulations of single partitions (therefore, those not of the whole vessel) can be useful in the design phase to verify compliance with the acoustic requirements requested by the classification societies. Considering that the propagation of sound and vibrations through the structures is a determining factor for the correct acoustic design of the vessel and therefore for the achievement of adequate levels of acoustic comfort, the analysis with simplified models (which consider the single partition) can be extremely useful in the preliminary phase of the design process. Subsequently, starting from the data acquired in the first simulation phase, it is possible to proceed with more complex simulations of specific situations and of the whole vessel. Full article

In this study, we present two configurations of piezo-actuated microspeakers, which were fabricated by combining a self-developed aerosol deposition method with the metal MEMS microfabrication process. The stainless steel used was structurally designed to enhance the displacement amplitude of the speaker, which is related to its sound pressure level. The two packaged speakers were measured using the IEC 60318-4 standard. The package around the speaker contains a printed circuit board with the dimensions in 20.0 mm × 13.0 mm × 3.0 mm. In an enclosed field test, the bimorph single-layer (BSL) configuration reached sound levels of 98.4 dB and 92.4 dB using driving voltages of 30 Vpp and 15 Vpp at 1 kHz, respectively; however, the bimorph multi-layer (BML) configuration reached higher levels of 108.2 dB and 102.2 dB under the same conditions. Full article

This paper presents the development of an energization system prototype for IoT sensor nodes using Peltier cells as energy harvesters; its operation is optimized by applying a maximum power point tracking algorithm (MPPT) to capture as much electrical energy as possible, even if the cell temperature conditions have variations. In the IoT sensor node, a power management algorithm that works in accordance with the measurement and transmission operations can extend the node operating time, to obtain a greater amount of information and reducing the need for battery maintenance. The proposed methodology consists of developing an energization system, as well as the IoT sensor node. The energization system consists of a block of Peltier cells to obtain up to 4 V, a SEPIC-type DC-DC converter, and a 3.7 V lithium battery for energy storage. The converter works in a closed loop with the MPPT algorithm and delivers a voltage that guarantees the maximum power transfer to the battery. The sensor node was developed based on the ESP8266 development board, it allows data acquisition of temperature, humidity, light intensity, presence, and sound. The node transmits this information to the Ubidots platform for real-time visualization; to take advantage of its processing capacity, MPPT and energy management algorithms are also implemented. The results showed that to obtain a minimum voltage of 3.3 V in the energization system, a temperature difference of $59\pm 1$ °C between the plates of the Peltier cells is required. The MPPT algorithm allows working at the maximum power point and keeps the power delivered to the battery stable, with small transients when the information is transmitted; however, the overshoot and the settling time are reduced and do not affect the node operation. Full article

Straw–concrete combined floor slabs consist of straw boards, shear-resistant connectors, and concrete slabs. These slabs offer various advantages over traditional reinforced concrete slabs due to the straw boards’ properties of excellent insulation and sound absorption. Research using ABAQUS software created 15 composite floor models to study the impact of connection methods, bond strength, connector spacing, and thickness of straw and concrete on the flexural performance. Results indicated that the composite floor slab with adhesive bonding had a 7.34% and 17.34% higher load-carrying capacity than the bolt-connected and self-tapping screw-connected composite floor slabs, respectively. Increasing bond strength from 40 MPa to 60 MPa improved the load-carrying capacity of self-tapping nail-connected slabs by 80.84%. Connector spacing negatively correlated with slab capacity, while increasing the thickness of straw boards or concrete slabs enhanced the ultimate load-carrying capacity, with the latter having a more significant effect. Midspan deflection and flexural capacity were calculated using the converted cross-section method and static calculation formulas, with theoretical and simulated values showing good agreement, offering guidance for engineering applications. Full article

Purpose: This study examines the role of board gender diversity in shaping corporate financial decisions, particularly in terms of debt structure and risk management. Focusing on the Tehran Stock Exchange, it explores how female representation on boards influences long-term and short-term leverage decisions, focusing on the moderating effect of board compensation. Design/Methodology: Utilising a quantitative ex post facto design, the study analyses data from 114 companies listed on the Tehran Stock Exchange between 2017 and 2021. Multivariate regression techniques, including year- and industry-fixed effects, are employed to investigate the relationship between board gender diversity, debt structure, and risk-taking behaviour. Findings: The results reveal a significant negative relationship between female board representation and long-term debt, suggesting that companies with more female directors tend to adopt more conservative debt structures, thereby reducing risk. Additionally, the findings demonstrate that board compensation moderates this relationship by curbing managerial risk-taking, further improving financial decision-making. Originality/Value: This research provides novel insights into the intersection of board gender diversity and risk management in financial decision-making, particularly in the context of a developing economy like Iran. It also offers practical implications for firms seeking to optimise their debt structures while maintaining sound risk management practices. Full article

High-speed craft (HSC) present unique challenges regarding on-board noise levels, affecting crew safety, comfort, and operational efficiency. This study investigates noise exposure and mitigation strategies aboard three Ro-Pax HSC vessels operating in southern Spain, with a focus on noise sources, regulatory compliance, and crew health. Full-scale experimental measurements were conducted in critical on-board locations, and noise maps were developed to identify areas where sound levels exceed International Maritime Organization (IMO) and European Directive 2003/10/EC thresholds. Results highlight that engine rooms and propulsion systems are the primary sources of excessive noise, with significant transmission to passenger and crew accommodation areas. Noise exposure calculations reveal that several crew roles, particularly engineers and deckhands, face exposure to hazardous noise levels during routine operations. Mitigation strategies, including improved insulation, noise mapping, and the implementation of hearing protection, are recommended to enhance on-board acoustic conditions. This research contributes to a deeper understanding of noise pollution on HSC vessels and proposes practical interventions to reduce exposure, improving overall maritime safety and occupational health. Full article

Background/Objectives: Patients requiring haemodialysis often perceive the cost of their travels to the dialysis centres as a significant burden. The study aimed to collect a first Swiss national data set on transport costs and assess their impact on patients and their relatives. Methods: In addition to interviews with patients, a quantitative survey was developed and distributed online using a voluntary sampling strategy. Data were analysed by means of descriptive statistics. A Sounding Board of patients, relatives, and healthcare professionals accompanied all steps of the project. Results: A total of 6 dialysis patients were interviewed; 437 respondents of the national survey met the inclusion criteria. Patients travel a median distance of 7.5 km to their dialysis centres. For 78% of them, the journey takes up to 30 min, and nearly half use their private car as their main mode of transport. The median annual transport costs are CHF 2925 (mean = CHF 5041). Approximately half of the patients perceive transport costs as a burden or limitation, yet only about 30% receive financial support, for which there is no standard process. Patients requiring financial support reported difficulties navigating the system. Conclusions: This study highlighted that many dialysis patients are burdened by transport costs and receive limited financial support and counselling services. Implementation of a standardised process for financial support should be explored. Full article

In this paper, the development of a low-cost acoustic sensor is presented based on an import-substituting element base as a cheap alternative to professional sensors or analog sensors. An Arduino board, a microphone module, a microSD card module, and other modules were used. To improve the accuracy of the data taken from the microphone, it was calibrated using a reference noise meter, using a logarithmic smoothing method to calculate the sound level in decibels, and an equation was formulated for converting the obtained ADC values into decibels. The code of the program executed by the sensor was developed and sewn into the device. The data captured from the microphone are stored in a CSV file with the date and time of the captured data. Full article

This paper focuses on the novel and unique training provision of acoustics relevant for noise, vibration, and harshness (NVH), focused on the ISO-362 standard highlighting important design aspects for electric vehicles. A case study of the practical implementation of off-site vehicle testing supporting an acoustics module is described, detailing a time-constrained test for automotive pass-by-noise and tyre-radiated noise with speed. Industrial test standards are discussed, with education as a primary motivation. The connections between low-cost, accessible equipment and future electric vehicle acoustics are made. The paper contains a full equipment breakdown to demonstrate the ability to link digital data transfer, analogue-to-digital communication, telemetry, and acquisition skills. The benchmark results of novel pass-by-noise and tyre testing are framed around discussion points for assessments. Inexpensive Arduino Uno boards provide data acquisition with class 1 sound pressure meters, XBee radios provide telemetry to a vehicle, and a vehicle datalogger provides GPS position with CANBUS data. Data acquisition is triggered through the implementation of light gate sensors on the test track, with the whole test lasting 90 minutes. Full article

A tremendous amount of waste black tea bags (BTBs) and date palm surface fibers (DPSFs), at the end of their life cycle, end up in landfills, leading to increased pollution and an increase in the negative impact on the environment. Therefore, this study aims to utilize these normally wasted materials efficiently by developing new composite materials for thermal insulation and sound absorption. Five insulation composite boards were developed, two were bound (BTB or DPSF with polyvinyl Acetate resin (PVA)) and three were hybrids (BTB, DPSF, and resin). In addition, the loose raw waste materials (BTB and DPSF) were tested separately with no binder. Thermal conductivity and sound absorption coefficients were determined for all boards. Thermal stability analysis was reported for the components of the tea bag (string, label, and bag) and one of the composite hybrid boards. Mechanical properties of the boards such as flexural strain, flexural stress, and flexural elastic modulus were determined for the bound and hybrid composites. The results showed that the thermal conductivity coefficients for all the hybrid composite sample boards are less than 0.07 at the ambient temperature of 24 °C and they were enhanced as the BTB ratio was reduced in the hybrid composite boards. The noise reduction coefficient for bound and all hybrid composite samples is greater than 0.37. The composite samples are thermally stable up to 291 °C. Most composite samples have a high flexure modulus between 4.3 MPa and 10.5 MPa. The tea bag raw materials and the composite samples have a low moisture content below 2.25%. These output results seem promising and encouraging using such developed sample boards as eco-friendly thermal insulation and sound absorption and competing with the synthetic ones developed from petrochemicals in building insulation. Moreover, returning these waste materials to circulation and producing new eco-friendly composites can reduce the number of landfills, the level of environmental pollution, and the use of synthetic materials made from fossil resources. Full article

Financial institutions should prioritize the adoption of comprehensive Environmental, Social, and Corporate Governance (ESG) disclosure policies to improve their market reputation and decrease capital expenditures. The current study’s research objective is to investigate the impact of both inside and outside executives on the successive adoption of ESG strategies, based on the sustainable leadership theoretical framework and the bottom-up corporate governance theory. Data for the current study were obtained from the Refinitiv Eikon database and analyzed through using the entropy weight and TOPSIS techniques. The research suggests that including fully autonomous board members has the potential to improve the transparency of firms’ ESG criteria. This result was derived from an analysis of data pertaining to the behavior of CEOs and non-executives at the company level in Fiscal Year (FY) 2023. The verification of the soundness and dependability of this finding has been carried out by scrutinizing the problem of endogeneity and diverse techniques of data representation. Furthermore, our study has disproven the idea that having CEOs on the board of directors may significantly improve the ESG performance of financial institutions. Consequently, the research proposes that adopting a strict policy of board independence has the capacity to alleviate the environmental, social, and governance repercussions that arise from the control of internal executives, namely CEOs. Full article