Hybrid Nanogenerators for Ocean Energy Harvesting: Mechanisms,Designs, and Applications

The ocean holds vast potential as a renewable energy source, but harnessing its power has been challenging due to low-frequency and high-amplitude stimulation. However, hybrid nanogenerators (HNGs) offer a promising solution to convert ocean energy into usable power efficiently. With their high sensitivity and flexible design, HNGs are ideal for low-frequency environments and remote ocean regions. Combining triboelectric nanogenerators (TENGs) with piezoelectric nanogenerators (PENGs) and electromagnetic nanogenerators (EMGs) creates a unique hybrid system that maximizes energy harvesting. Ultimately, hybrid energy-harvesting systems offer a sustainable and reliable solution for growing energy needs. This study provides an in-depth review of the latest research on ocean energy harvesting by hybrid systems, focusing on self-powered applications. The article also discusses primary hybrid designs for devices, powering self-powered units such as wireless communication systems, climate monitoring systems, and buoys as applications. The potential of HNGs is enormous, and with rapid advancements in research and fabrication, these systems are poised to revolutionize ocean energy harvesting. It outlines the pros and cons of HNGs and highlights the major challenges that must be overcome. Finally, future outlooks for hybrid energy harvesters are also discussed.     

Estimation of health hazards resulting from a radiological terrorist attack in a city

In recent years, the concern for protection of urban populations against terror attacks involving radiological, biological or chemical substances has attracted increasing attention. It sets new demands to decision support and consequence assessment tools, where the focus has traditionally been on accidental exposure. The aim of the present study was to illustrate issues that need to be considered in evaluating the radiological consequences of a 'dirty bomb' explosion. This is done through a worked example of simplified calculations of relative dose contributions for a specific 'dirty bomb' scenario leading to atmospheric dispersion of 90Sr contamination over a city area. Also, the requirements of atmospheric dispersion models for such scenarios are discussed.     

Effect of sintering temperature on the electrical and gas sensing properties of tin oxide powders

Tin oxide is an n-type semiconducting material having superior properties that can be utilized in several applications. The warning and detection of several dangerous gases in the environment are possible by utilizing gas sensors. The comprehensive functionality of these sensors could help to reduce the risk of severe health hazards and unexpected explosion risks. Tin oxide-based gas sensors exhibit reliable gas sensing performances along with respectful sensitivity and selectivity. Tin oxides in micro-and nano-particle forms provide an extremely high surface-to-volume ratio, which is favorable for gas sensors. Processing and synthesis of tin oxide particles accompany high-temperature processes, and this paper focuses on studying the effect of sintering temperatures on the structural and grain size of the commercially available tin oxide particles. The surface morphology of the tin oxide samples sintered at three different temperatures of 1100, 1200, 1300 ^°C shows a clear difference in the grain size and further affecting the dielectric properties of the materials. The gas sensing performances of three tin oxide samples are investigated by fabricating a pellet-type gas sensor. The sensor with the sintering temperature of 1200 ^°C exhibits the best gas-sensing performance with high response and low limit of detection (LOD). Our results suggest that the sintering temperature plays a vital role in deciding the dielectric properties and grain sizes, which are important parameters that affect the gas sensing behavior of tin oxide micro-and nano-particles.     

300% Enhancement of Carrier Mobility in Uniaxial‐Oriented Perovskite Films Formed by Topotactic‐Oriented Attachment

Organic–inorganic perovskites with intriguing optical and electrical properties have attracted significant research interests due to their excellent performance in optoelectronic devices. Recent efforts on preparing uniform and large‐grain polycrystalline perovskite films have led to enhanced carrier lifetime up to several microseconds. However, the mobility and trap densities of polycrystalline perovskite films are still significantly behind their single‐crystal counterparts. Here, a facile topotactic‐oriented attachment (TOA) process to grow highly oriented perovskite films, featuring strong uniaxial‐crystallographic texture, micrometer‐grain morphology, high crystallinity, low trap density (≈4 × 10¹⁴ cm^?3), and unprecedented 9 GHz charge‐carrier mobility (71 cm² V^?1 s^?1), is demonstrated. TOA‐perovskite‐based n‐i‐p planar solar cells show minimal discrepancies between stabilized efficiency (19.0%) and reverse‐scan efficiency (19.7%). The TOA process is also applicable for growing other state‐of‐the‐art perovskite alloys, including triple‐cation and mixed‐halide perovskites.     

Effect of dihydroxydiphenyl ether on poly(ether ether ketone)

A series of modified poly(ether ether ketone) (PEEK) polymers were synthesized by introduction of addition ether groups from dihydroxydiphenyl ether (DHDE) into the PEEK structure. The inherent viscosity of the DHDE-modified PEEK increased with reaction time at 320 °C. DSC thermograms showed the melting points of the obtained PEEK decreased with the increase of the DHDE content in the backbone. The degradation temperature (T_d) was slightly decreased by the introduction of DHDE. The crystallinity as measured via the X-ray diffraction (XRD) increases with the introduction of DHDE into the modified PEEK. The crystalline structure was identified as an orthorhombic structure with lattice constants a = 7.72 Å, b = 5.86 Å, and c = 10.24 Å. Due to the glass transition temperature (T_g) and the melting temperature (T_m) decreasing with the increase of the DHDE content in the reaction system. the processability of the resultant PEEK could be improved through this DHDE modification.     

Roles of bulk carbon content on grain size,carbide reactions and intergranular rupture life in 2.25cr martensitic heat resistant steels

The steel of a higher bulk carbon content shows the denser precipitation distribution of carbides after the solution treatment followed by tempering. Such a carbide distribution produces the smaller prior austenite grain size after the welding simulation at a high temperature. Because the equilibrium segregation concentration of phosphorus decreases with decreasing prior austenite grain size, the specimen of the higher bulk carbon content shows therefore the longer intergranular rupture life. The rupture life is also increased by the partitioning of phosphorus pre-segregated at prior austenite grain boundary/carbide interfaces onto the fresh surface of precipitates formed on the surface of pre-formed carbides. The intergranular rupture life is additionally increased by the repulsive segregation between carbon and phosphorus which decreases the overall phosphorus segregation concentration at the prior austenite grain boundaries.     

Kinetic and mechanistic modeling of acid‐catalyzed degradation of polymers with various cracking catalysts

A new approach is presented that combines kinetic and mechanistic considerations which take into account chemical reactions and catalyst deactivation in the modeling of the catalytic degradation of polymers. Though acid‐catalyzed hydrocarbon cracking reactions involve a large number of compounds, reactions and catalyst deactivation and are very complex, the model gives a good representation of experimental results from the degradation of polyethylene and polypropylene over fluidized acidic catalysts. This model provides the benefits of product selectivity for the chemical composition such as alkanes, alkenes, aromatics, and coke in relation to the effect of structurally different polymer feeds, the performance of the catalyst and the selection of their particle sizes, and the influence of different reaction temperatures. It is an improvement of the currently available empirical “lumping” techniques which usually are severely restricted in terms of product definitions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Finite-Element Simulations of Full-Scale Modular-Block Reinforced Soil Retaining Walls under Earthquake Loading

A finite-element procedure was used to simulate the dynamic behavior of four full-scale reinforced soil retaining walls subjected to earthquake loading. The experiments were conducted at a maximum horizontal acceleration of over 0.8 g, with two walls subjected to only horizontal accelerations and two other walls under simultaneous horizontal and vertical accelerations. The analyzes were conducted using advanced soil and geosynthetic models that were capable of simulating behavior under both monotonic and cyclic loadings. The soil behavior was modeled using a unified general plasticity model, which was developed based on the critical state concept and that considered the stress level effects over a wide range of densities using a single set of parameters. The geosynthetic model was based on the bounding surface concept and it considered the S-shape load-strain behavior of polymeric geogrids. In this paper, the calibrations of the models and details of finite-element analysis are presented. The time response of horizontal and vertical accelerations obtained from the analyses, as well as wall deformations and tensile force in geogrids, were compared with the experimental results. The comparisons showed that the finite-element results rendered satisfactory agreement with the shake table test results.