Abstract
A comprehensive understanding of the mechanisms underlying bone fatigue failure is crucial for advancing treatment strategies. In this regard, this study presents a novel approach to quantify crack propagation in cortical bone tissue through fatigue testing under mode I loading. To closely replicate real bone damage mechanisms, pre-cracked bone samples were subjected to cyclic loading. A compliance-based beam method and cubic B-spline interpolation method were employed to accurately extract fatigue coefficients and reduce experimental noise, yielding refined modified Paris law coefficients. A cohesive zone model for high-cycle fatigue was used to simulate crack propagation, capturing the nonlinear material response by means of the cohesive zone length, mimicking the non-negligible fracture process zone. The goal is to validate the followed experimental procedure. This study offers valuable insights into the fatigue and fracture mechanisms in cortical bone, providing a more accurate and realistic framework for characterizing fatigue life compared to previous methodologies. Coefficients produced from the cohesive model may be readily integrated into simulation tools commonly used in many areas of engineering, allowing biomechanical experts to create more robust designs that simulate actual world conditions for application in implants and orthopaedic structures.

Abstract
The need for real-time and scalable oceanographic monitoring has become crucial for coastal management, marine traffic control and environmental sustainability. This study investigates the integration of sensor technology into marine cables to enable real-time monitoring, focusing on tidal cycles and wave characteristics. A 2000 m cable demonstrator was deployed off the coast of Portugal, featuring three active repeater nodes equipped with pressure sensors at varying depths. The goal was to estimate hourly wave periods using fast Fourier transform and calculate significant wave height via a custom peak detection algorithm. The results showed strong coherence with tidal depth variations, with wave period estimates closely aligning with forecasts. The wave height estimations exhibited a clear relationship with tidal cycles, which demonstrates the system's sensitivity to coastal hydrodynamics, a factor that numerical models designed for open waters often fail to capture. The study also highlights challenges in deep-water monitoring, such as signal attenuation and the need for high sampling rates. Overall, this research emphasises the scalability of sensor-integrated smart marine cables, offering a transformative opportunity to expand oceanographic monitoring capabilities. The findings open the door for future real-time ocean monitoring systems that can deliver valuable insights for coastal management, environmental monitoring and scientific research.

Abstract
ObjectiveThe capacity of hair to absorb water causes changes in its physical and cosmetic properties under different environmental conditions. Hence, the control of hair volume in variable relative humidity settings is an important topic in cosmetics. The behaviour of two types of hair, Caucasian and Asian, was studied regarding their volume change in different relative humidity conditions. The ability of a peptide as a hair volume treatment was evaluated in two climate control formulations. MethodsTresses of the two types of hair were tested in two relative humidity (RH) conditions: (A) variable relative humidity (2h 40% RH, followed by 2h 90% RH and 2h of 40% RH), and (B) continuous high relative humidity (90% RH for 6h). Changes in the hair tress volume were assessed throughout time. Hair treated with two climate control formulations, with and without a peptide (KP peptide), were tested under the two relative humidity conditions. ResultsCaucasian hair had a higher change in volume compared to the Asian hair in variable and high relative humidity conditions. The hair volume increase when subject to high air humidity, and it was lower with the incorporation of a peptide into climate control formulations. ConclusionCaucasian hair showed higher volume than Asian hair when submitted to both relative humidity conditions. The incorporation of the peptide into the climate control formulations, a base (mostly composed of water approximate to 94%) and an ethanolic, was found to reduce the volume of Caucasian hair tresses. The presence of the peptide improved the hair volume change more than 60% in high relative humidity conditions.

Abstract

Abstract
Underwater wireless communication systems are becoming a priority in terms of research and technological development due to the increasing demand for exploring the oceans’ potential in areas such as pharmaceutical, oil, minerals, environmental and biodiversity. This demand is increasing exponentially with the need for high data rate and near-real-time communications between submerged mobile and static agents. The existing wireless communication technologies using electromagnetic waves or lasers are not very efficient due to the large attenuation in aquatic environment. Ultrasound reveals a lower attenuation, and thus has been used in underwater long-distance communications. But the underwater acoustic medium is one of the less reliable communication channels which represent major challenges for communications. With relatively slow sound speed propagation (~1500 m/s) the delay may represent a problem for communications with real-time applications. A theoretical model of an underwater communication system was also developed. The model allows to emulate the emitter, the hydrophone and the underwater acoustic channel, which includes attenuation, environmental noise, Doppler Effect, multipath and propagation delay. This model supported the study of wireless communications by emulating the transmission of acoustic signals using different types of digital modulations. The acoustic signal attenuation, multipath, ambient noise in several environments theoretical results were compared to those obtained experimentally. Allowing to conclude that the model represents a suitable approximation to the real subaquatic communication channel for the evaluation of digital acoustic communications. An optimization study of ultrasound transducers for underwater communications was addressed, focusing on a piston type emitter operating in the thickness mode (d33). It was discussed how the acoustic impedance, thickness, resonance frequency and structure affect the transducer performance. This work allowed a better understanding of the emitter transducer characteristics allowing reaching the optimum point of operation for specific applications. Focusing on underwater communication, the transducer was optimized by finite element computer simulations. The results were compared with experimental tests and show that four-layer structures increase up to 16 dB in performance when compared to single-layer transducer disks. For high data-rates and real-time applications it was necessary to develop ultrasound transducers able to work at high frequencies and wideband, with suitable responses to digital modulations. It was thus also included a comparison study that shows how the acoustic impedance influences the performance of an ultrasonic emitter when using different digital modulations and operating at frequencies between 100 kHz and 1 MHz and some tens of meters of distance. It is presented a Finite Element Method (FEM) and a MATLAB/Simulink simulation with an experimental validation to evaluate two types of piezoelectric materials: one based in ceramics (high acoustic impedance) with a resonance design and a polymer based (low acoustic impedance) system, designed to optimize the performance when using digital modulations. The transducers performance for Binary Amplitude Shift Keying (BASK), On-Off Keying (OOK), Binary Phase Shift Keying (BPSK) and Binary Frequency Shift Keying (BFSK) modulations with a 1 MHz carrier at 125 kbps baud rate were compared. The transducers materials used were the ceramics PZT-5H and the polymer PVDF. The results show that PVDF transducer has a better performance to digital modulations than PZT-5H transducer, providing the signal full demodulation for all digital modulations tested. On the other hand, the PZT-5H transducer showed a higher output, but fails to perform accurate modulated signals. Finally, the system was validated by the implementation of a full duplex point-to-point communication at 1 Mbps using OOK modulation with a 1 MHz single carrier. The system was successfully tested in a swimming pool at a distance of 6 meters with a 1 Mbps rate, achieving a 3x10-3 Bit Error Rate (BER) using just 1.4 W of power consumption. These results represent an advance in underwater acoustic communications, being the first practical system to achieve data rates up to 1 Mbps.;O desenvolvimento de sistemas de comunicação subaquáticos sem fios está a tornar-se uma prioridade na comunidade científica no sentido de aumentar o desenvolvimento tecnológico. Este facto deve-se à crescente necessidade de exploração do potencial dos oceanos em áreas científicas diversas como farmacêutica, petrolífera, mineral, ambiental e até do próprio estudo da biodiversidade. Essa necessidade aumenta exponencialmente com a necessidade de comunicações de alto débito e em tempo real entre agentes submersos móveis e estáticos. As tecnologias de comunicações sem fios existentes, nomeadamente as que utilizam ondas eletromagnéticas ou lasers não são muito eficientes, devido, em grande parte, à atenuação no ambiente subaquático. Os ultrassons revelam uma menor atenuação tendo sido, por isso, utilizados em comunicações subaquáticas em longas distâncias. Contudo o canal acústico subaquático definisse como um dos mais difíceis, devido em parte as suas características únicas, o que apresenta ser um enorme desafio. Como a velocidade de propagação do som é relativamente lenta (~1500 m/s), o atraso pode representar um problema para as aplicações em tempo real. Foi desenvolvido um modelo teórico do sistema de comunicações subaquáticos que permite emular o emissor, o hidrofone e o canal acústico subaquático. No canal acústico subaquático foi simulado o efeito da atenuação, ruído ambiente, efeito de Doppler, multipath e atraso de propagação. Este modelo é indicado para o estudo das comunicações subaquáticas, emulando a transmissão de sinais acústicos utilizando diferentes tipos de modulações digitais. Neste estudo foram testados, a atenuação do sinal acústico, multipath, ruído em diversos ambientes e os resultados teóricos foram comparados com os obtidos experimentalmente. Permitindo concluir que o modelo representa uma aproximação adequada do canal de comunicação, permitindo a avaliação das comunicações digitais acústicas. Inclui ainda um estudo de otimização de transdutores de ultrassons para comunicações subaquáticos, tendo como base o emissor do tipo pistão, operando ao longo da espessura (d33). Foi analisada ainda a forma como a impedância, espessura, frequência de ressonância acústica e estrutura afetam o desempenho do transdutor. Este trabalho permitiu uma melhor compreensão das características do transdutor emissor que permitem atingir o ponto ótimo de operação para aplicações específicas. Tendo como base a comunicação subaquática, o transdutor foi otimizado usando os resultados de simulações pelo Método dos Elementos Finitos. Os resultados foram comparados com os testes experimentais, onde se mostra que as estruturas de quatro camadas podem aumentar até 16dB no desempenho quando comparados com discos de transdutor de única camada. Para aplicações em tempo real e de elevado debito, foi necessário desenvolver transdutores de ultrassons capazes de operar em banda larga a altas frequências, com resposta adequada às modulações digitais. Foi, portanto, incluído também um estudo comparativo que mostra como a impedância acústica influencia o desempenho do emissor de ultrassons quando se utilizam modulações digitais a operar com frequências entre 100 kHz e 1 MHz abrangendo distâncias de algumas dezenas de metros. São apresentadas simulações por Método de Elementos Finitos (MEF) e MATLAB/Simulink com validação experimental de modo a avaliar dois tipos de materiais piezoelétricos: um com base cerâmica PZT-5H (alta impedância acústica) com um design de ressonância e outro de base de polimérica PVDF (baixa impedância acústica), otimizado para modulações digitais. O desempenho dos transdutores foi comparado para as modulações: Binary Amplitude Shift Keying (BASK), On-Off Keying (OOK), Binary Phase Shift Keying (BPSK) e Binary Frequency Shift Keying (BFSK) com uma portadora de 1 MHz a 125 kbps. Os resultados mostram que o transdutor de PVDF tem um melhor desempenho do que transdutor PZT-5H, proporcionando a desmodulação completa do sinal para todas as modulações digitais testadas. Por outro lado, o transdutor de PZT-5H mostrou uma potência acústica mais elevada, embora não consiga produzir sinais modulados precisos. Finalmente, o sistema foi validado através da implementação de uma comunicação ponto-aponto bidirecional de 1 Mbps utilizando uma modulação OOK com uma portadora de 1 MHz. O sistema foi testado com sucesso numa piscina a uma distância de 6 metros com uma taxa de 1 Mbps, com um BER (Bit Error Rate) de 3x10-3, utilizando apenas 1,4 W de consumo de potência. Estes resultados representam um avanço nas comunicações acústicas subaquáticas, sendo o primeiro sistema prático de atingir velocidades até 1 Mbps.

Abstract
The manufacturing process of thermoregulation products with polyester (PES) fabric and conductive polymers such as poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) with proper wearability, comfort, and high performance is still a challenge due to low adhesion, environment instability and nonuniform coatings. This study presents a simple and effective method for producing thermoregulatory PES fabrics using the Joule heating effect. Textiles treated with dielectric barrier discharge (DBD) plasma were functionalized with PEDOT:PSS incorporating secondary dopants, such as dimethyl sulfoxide (DMSO) and glycerol (GLY). PEDOT:PSS was used because it does not compromise the mechanical properties of base materials. DBD plasma treatment was applied to PES to improve the substrate's functional groups and consequently increase adhesion and homogeneity of the PEDOT:PSS on the substrate. The polymer were applied to the textiles by dip-pad-drycure method ensuring uniform distribution and homogeneous heating of the materials. The samples' conductivity, impedance, potential and Joule effect, and their morphological, chemical and thermal properties were studied. Control samples without plasma treatment and secondary dopants were also prepared. The results showed that the DBD-treated samples, coated with 5 layers of PEDOT:PSS, doped with DMSO 7 % (w/v), displayed the best conductivity and Joule effect performance reaching 44.3 degrees C after 1 h.