Search

Copyright of Automotive Digest is the property of Automotive Digest Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Steel bridge, as one of the main structural types in bridge design, has been widely used in rail transit. However, the train-induced vibro-acoustic problem of the bridge has become increasingly prominent. The vibration and noise characteristics must be more significant and complex than steel truss bridge because of too many components. Viscoelastic damping materials (VDMs) have the characteristics of both viscous liquid and elastic solid, and have better damping performance than other damping materials. Therefore, VDM plays an important role in vibration and noise reduction technology. In applications, VDM is usually combined with constraining materials to form composite viscoelastic damping materials (CVDM). In this paper, based on the dynamic receptance method and superposition principle, the coupling model of vehicle–track–bridge in the frequency domain is first established, and then the vibration and noise prediction model of a steel truss bridge with CVDM is established based on RUK theory and statistical energy analysis (SEA) method. Based on the prediction model, the natural dynamic characteristics of typical components of steel truss bridges with CVDM were investigated, and the control mechanism and influence rule of CVDM on train-induced vibration and noise of steel bridges were revealed. [ABSTRACT FROM AUTHOR]

Vibro-acoustic systems in aviation engineering could operate in a thermal environment and suffer from high-frequency dynamic excitations. The high-frequency vibro-acoustic problems are commonly solved by the Statistical Energy Analysis method, in which the Coupling Loss Factor is the key parameter for modeling vibro-acoustic systems. This work investigates the CLFs of vibro-acoustic systems under thermal environment. First, based on the modal data considering different thermal effects, the modal CLFs between structural modes and acoustic modes are predicted by the Statistical modal Energy distribution Analysis. Then, the CLFs between the structural subsystem and the acoustic subsystem are calculated. The simulation models employed in this research include the coupled plate-cavity system and the cylindrical shell-cavity system. The influence of thermal effects on the CLFs is discussed. For the investigated cases, in which the boundaries of structural susbsystem are set to simply supported, the results demonstrate that the CLFs decrease with increasing temperature when only the temperature-dependent material properties are considered. However, when only the additional stress stiffness is considered, the CLFs experience a more dramatic decrease compared to when only the temperature-dependent material properties are taken into account. Moreover, when both effects are considered, the influence of the additional stress stiffness has a leading effect on the CLFs. The proposed method can be conveniently applied to various vibro-acoustic systems operating in the thermal environment. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to analyze and evaluate the consumption of thermal energy in a coal mining enterprise with separate business units, in the context of securing energy reserves and effectively managing the consumption of this energy. Design/methodology/approach: Based on the aggregation and analysis of historical data of thermal energy consumption, the method of statistical analysis of aggregated data from individual business units of the coal mining company was applied. Findings: The applied statistical analysis of the aggregate data made it possible to verify the planned short-and long-term activities for each group of facilities of the coal mining company. Research limitations/implications: The further direction of the research requires verification of the obtained results of the statistical analysis, after completing the data of thermal energy consumption in the following years and correlating the obtained results with the introduced pro-efficiency measures in the enterprise so as to clarify the division of the enterprise's facilities into individual groups. Practical implications: Statistical analysis of thermal energy consumption, can become an effective tool to support the process of managing pro-efficiency measures in mining enterprises with separate business units. Social implications: The right approach of coal mining companies to thermal energy analysis and management can contribute to securing energy reserves for the local environment in which the company operates. Originality/value: The presented classification of facilities into groups A, B and C and the use of statistical analysis to verify the introduced measures to reduce thermal energy consumption have not yet been introduced and tested in the Polish coal mining industry. [ABSTRACT FROM AUTHOR]

In light of continuous advancements in science and technology, the global economy is experiencing rapid growth. However, this growth has been accompanied by significant depletion of natural resources and environmental degradation. Consequently, there is a burgeoning global emphasis on energy conservation, emissions reduction, and sustainable development. In this study, based on the Science Citation Index Expanded (SCIE) and Social Science Citation Index (SSCI) databases from 1990 to 2022, a statistical analysis of energy conservation and emission reduction in alignment with Sustainable Development Goals (SDGs)-related publications was undertaken using biblimometric methods. The findings reveal that (1) In recent years, there has been a discernible increase in global research on this subject, especially since 2009, with a sustained trend of exceeding 100 publications per annum. China prominently contributing to this domain, the proportion reached 34.2%, reflecting a growing emphasis on eco-friendly development trends. (2) Due to the burgeoning significance of energy conservation and emission reduction, there has been a notable escalation in research efforts pertaining to "Energy and Fuels," "Environmental Science" and "Green and Sustainable Science and Technology" and other related subjects. (3) Regarding the keyword analysis, "renewable energy" as the most frequently encountered term, often paired with "CO2 emissions." This association underscores the pivotal role of renewable energy technologies in advancing green development initiatives and mitigating emissions. (4) China, United States and United Kingdom occupy central positions in terms of both paper publication volume and collaborative networks, collectively accounting for about 54.7%, and these countries are pivotal contributors to the scholarly discourse on sustainable development and environmental conservation. (5) From 1990 to 2022, the top 20 cited articles predominantly address diverse sub-goals of Sustainable Development Goal 7, with a common emphasis on enhancing energy efficiency, sustainability and renewable energy. These findings furnish valuable analytical insights for subsequent researchers investigating energy conservation and emission reduction as well as sustainable development endeavors. [ABSTRACT FROM AUTHOR]

The objective of this research is to develop an improved uniaxial static compaction method to address the limitations of the traditional Proctor's dynamic approach for soil compaction. This new approach offers reduced labor, enhanced soil density, and increased compactness. The study compares of static soil compaction characteristics with various soil parameters and explores the concept of Equivalent Static Compaction Energy (ESCE). A diverse range of fine-grained soils with varying range of plasticity was investigated, and a significant correlation of compaction parameters attained by static compaction was observed with the corresponding value of static compaction energy, degree of saturation, void ratio, and plastic limit of soil. The research resulted in the creation of constant-energy curves for static compaction, which were compared to dynamic compaction curves from four compaction attempts. From the study, the ESCE corresponding to standard Proctor, reduced standard Proctor, and reduced modified Proctor tests were found to be within the range of 180-340, 155-308, and 532-664 KJ/m3, respectively. It was also observed for the static compaction method that after reaching the maximum level of compaction, the dry unit weight of the soil specimen remains constant with further increases in compaction energy. [ABSTRACT FROM AUTHOR]

The interior noise caused by the pantograph area is greater than that caused by other areas, and the impact of this pantograph area becomes more significant as the speed of high-speed trains increases, especially above 350 km/h. This study proposes an active jet method for pantograph cavities to control noise at the source. First, a predictive model for the interior noise of pantograph carriages was established by jointly adopting large eddy simulation-statistical energy analysis methods. Then, numerical simulations were conducted to determine the external noise sources and interior sound pressure level at different speeds (300, 350, 400, and 450 km/h). Finally, active jets at different speeds (97.2, 111.1, 125, and 140 m/s) were used to analyze the reduction in interior noise. Results showed that the active jet method decreased the average overall sound pressure level of the acoustic cavity in the horizontal plane. When the train speed reached 450 km/h, the optimal reduction in interior noise was approximately 7.5 dB in the horizontal plane for both the standing and sitting postures. The proposed method can efficiently reduce interior noise in the pantograph area. [ABSTRACT FROM AUTHOR]

Current research on noise and vibration control of high-speed maglev trains pays more attention to far-field noise, while the level of interior noise has a direct impact on the ride comfort and should be placed equal weight on. In this paper, inter-coach space, one of the main pressure fluctuation sources of a specific type of high-speed maglev train with a design speed of 600 km·h−1, is taken as the research object. The turbulent and acoustic components of wall pressure fluctuations (WPF) are separated based on a wavenumber-frequency analysis approach, and then each component is applied as different forms of source input to the vibroacoustic model, namely, finite element method-boundary element method (FEM-BEM) and statistical energy analysis (SEA) for low- and high-frequency ranges respectively, to investigate the contribution of both components to interior acoustic cavity in all frequency range. It can be seen quantitatively from the results that the amplitude of turbulent component is generally much higher than that of the acoustic one, but it can be vice versa when it comes to the interior response. The conclusion drawn in this paper are able to provide guidance for future researches on more targeted interior noise control of high-speed maglev trains. [ABSTRACT FROM AUTHOR]

The interior noise caused by the pantograph area is greater than that caused by other areas, and the impact of this pantograph area becomes more significant as the speed of high-speed trains increases, especially above 350 km/h. This study proposes an active jet method for pantograph cavities to control noise at the source. First, a predictive model for the interior noise of pantograph carriages was established by jointly adopting large eddy simulation–statistical energy analysis methods. Then, numerical simulations were conducted to determine the external noise sources and interior sound pressure level at different speeds (300, 350, 400, and 450 km/h). Finally, active jets at different speeds (97.2, 111.1, 125, and 140 m/s) were used to analyze the reduction in interior noise. Results showed that the active jet method decreased the average overall sound pressure level of the acoustic cavity in the horizontal plane. When the train speed reached 450 km/h, the optimal reduction in interior noise was approximately 7.5 dB in the horizontal plane for both the standing and sitting postures. The proposed method can efficiently reduce interior noise in the pantograph area.

Despite the fact that there is an existing body of literature addressing the computation of Coupling Loss Factors (CLFs) via the Finite Element Method (FEM), no publications have sufficiently taken into account real structural joints in their approach. Previous research has focused on academic cases of trivial connections, rarely involving more than two steel plates. To enable Statistical Energy Analysis (SEA) on a real ship, a methodology for determining CLFs for non-trivial systems is proposed, considering realistic boundary conditions and irregularities that can occur in marine structures. Based on the method, a library of CLFs is created by selecting the tested connections to enable modelling of about 90% of the acoustic paths on an existing jack-up vessel. Boundary conditions were set by introducing spring elements with a stiffness calibrated to the type of connection and taking the adjacent structure into account. In previous works, CLFs were determined for basic connections of rectangular plates. The lack of scantling variations, ignoring discontinuities and only defining parallel edges in the considered models, lead to the overestimation of energy transmission in real structures. To consider the influence of the above, random deviations from the initial stiffness of the springs at individual edges and point restraints at random points are introduced in this paper.

This paper studies sound transmission through a thin cylindrical shell of finite length. The structure is subjected to an exterior turbulent boundary layer (TBL) excitation and the boundary conditions of its two ends are considered as simply-supported. The classical shell theory (CST) is employed to derive wave propagation in the cylindrical shell, and the Corcos model is applied to describe pressure fluctuation due to TBL. According to the existence of two axial and radial modes, a complete convergence study is presented. To examine sound transmission through the structure, a comprehensive parameters study is provided on the resulting power spectral density (PSD) of the kinetic energy. To validate the results of the present method, the statistical energy analysis (SEA) method is used. For this purpose, modeling is performed by SEA in VA One software, which shows the high accuracy of the results of the present method. The analytical predictions suggest that the sound insulation performance of such a finite length structure is enhanced considerably by increasing the thickness of the shell in a broad-band frequency range. Similar effects on sound transmission are observed for Young's modulus and density of the shell particularly in the low and high-frequency ranges, respectively. Whereas, enhancing the turbulent pressure and freestream velocity adversely affects sound radiation into the structure. [ABSTRACT FROM AUTHOR]

The statistical energy analysis (SEA) method was popularly employed to handle the high-frequency dynamics problems in many engineering fields such as aerospace and shipping. The damping loss factor and coupling loss factor were the major parameters in the SEA theory, and they can usually be identified with the measured external input power and structural modal energy. The measurement errors of the input power and modal energy were not considered in the traditional parameter identification, where the accuracy of the identified results was relatively low. The interval mathematics method was applied to the parameter identification in this study, and the measurement errors of the input power and modal energy were fully considered. The effects of the measurement errors on the parameter identification were revealed, and the accuracy of the identified results was improved. The work can be helpful for the structure design and safety analysis. [ABSTRACT FROM AUTHOR]

The excessive use of energy from fossil fuels, which corresponds to population, industrialisation, and unsustainable economic growth, is the cause of carbon dioxide production and climate change. The Water–Energy–Food (WEF) nexus is an applicable conceptual framework that helps manage the balance between human development and natural resource constraints, and it becomes a valuable tool to address the challenges of resource depletion and clean energy. This article aims to analyse the relationship between the WEF nexus and clean energy through a statistical analysis and a systematic review of knowledge on energy sustainability. The methodology involves the selection of bibliographic information databases such as Scopus and Web of Science (WoS), a statistical analysis, specifically the Scientometrics applied to the information obtained, and the identification of 179 scientific publications related to the study variables through a screening process called Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The interaction of green energy and sustainability with the WEF nexus has been approached mainly by developed countries such as China (10%), the United States (9.49%), India (7.26%), and Brazil (5.02%). The review of 55 scientific papers identified strategies that balance economic growth and environmental impact, applying clean energy systems (e.g., solar and wind), and the importance of adaptation to the subsystems of the WEF nexus. This study also highlights adaptability to climate change in rural and urban communities. Therefore, it is consistent with the four pillars of sustainable development (Economic: 7 papers, Environmental: 22, Social: 18, and Cultural: 8). This study highlights the following: (a) the importance of the use of renewable energy either in mixed systems and consumption, energy storage, and seeking energy efficiency in systems adapted to diverse environments and (b) the relevance of community participation in the decision-making process for the use of clean energy, such as a strategy for climate change adaptation. [ABSTRACT FROM AUTHOR]

The understanding of eco-evolutionary dynamics, and in particular the mechanism of coexistence of species, is still fragmentary and in need of test bench model systems. To this aim we developed a variant of SELEX in vitro selection to study the evolution of a population of ~1015 single-strand DNA oligonucleotide 'individuals'. We begin with a seed of random sequences which we select via affinity capture from ~1012 DNA oligomers of fixed sequence ('resources') over which they compete. At each cycle ('generation'), the ecosystem is replenished via PCR amplification of survivors. Massive parallel sequencing indicates that across generations the variety of sequences ('species') drastically decreases, while some of them become populous and dominate the ecosystem. The simplicity of our approach, in which survival is granted by hybridization, enables a quantitative investigation of fitness through a statistical analysis of binding energies. We find that the strength of individual resource binding dominates the selection in the first generations, while inter- and intra-individual interactions become important in later stages, in parallel with the emergence of prototypical forms of mutualism and parasitism. [ABSTRACT FROM AUTHOR]

The molecular mechanisms of mesoporous silica nanomaterial (MSN) loading by gemcitabine and ibuprofen molecules, respectively, are elucidated as functions of pore geometry. Based on a small series of MSN archetypes, we use molecular dynamics simulations to systematically explore molecule-by-molecule loading of the carrier material. Apart from predicting the maximum active pharmaceutical ingredient (API) loading capacity, more detailed statistical analysis of the incorporation energy reveals dedicated profiles stemming from the interplay of guest-MSN salt-bridges/hydrogen bonding in concave and convex domains of the silica surfaces - which outcompete interactions among the drug molecules. Only after full coverage of the silica surface, we find secondary layer growth stabilized by guest-guest interactions exclusively. Based on molecular models, we thus outline a two-step type profile for drug release from MSN networks. Subject to the MSN structure, we find 50–75 % of the API within amorphous domains in the inner regions of the pores – from which drug release is provided at constant dissociation energy. In turn, the remaining 50–25 % of drug molecules are drastically hindered from dissociation. [ABSTRACT FROM AUTHOR]

The wall pressure fluctuation caused by a turbulent boundary layer is an important source of noise and vibration in high-speed trains. Considering that railway vehicles are usually made of extruded profiles, a simple and reliable model is needed to predict the vibroacoustic characteristics of extruded profiles excited by a TBL in the early stages of design. A hybrid finite element and statistical energy analysis model is established for computing the vibroacoustic response of finite-sized panels excited by a TBL. In the hybrid model, the wall pressure fluctuation of the TBL is modelled in the wavenumber domain. The panels are modelled using FEs, and acoustic waves in the fluid space below the panels are modelled using SEA. The TBL wall pressure acting on the top surface of the panels is resolved into equivalent nodal forces with discretization of the structure using FEs, achieved by calculating the cross-spectrum matrix of the wall pressure in the spectral domain and using jinc functions with smooth boundary and symmetric properties as shape functions. The reciprocity between direct and reverberant fields couples the acoustic fields to the structure. Once the response of the hybrid model is determined, sound transmission through the panels can be calculated. By following the procedures outlined in this paper, the range of wall pressure model selection for TBL has extended and reduced computational time and provides a basis for the acoustic optimization design of extruded profiles. [ABSTRACT FROM AUTHOR]

Purpose: Electromobility significantly changes the approach to road transport. Therefore, we decided to evaluate the implementation of electric vehicles in road transport in selected countries and compare Poland with the leaders in the transformation taking place in Europe. Design/methodology/approach: Statistics on electromobility and national energy systems were obtained from Eurostat. We used statistical measures to measure the extent of progress of the introduced electric mobility solutions. We identified leaders in road transport transformation using the TOPSIS method. Findings: The successful implementation of electromobility solutions in road transport across Europe is limited to a handful of countries that we have identified. Most countries do not have sufficiently developed grid infrastructure and charging stations. Poland compares very unfavourably with the leaders in road transport transformation and occupies roughly the same distant position in the rankings. Research limitations/implications: The most recent data available are from 2021. In addition, some countries did not provide Eurostat with complete data on road transport and energy policy. It would be worthwhile to re-examine the study with completed data to understand the impact of the disrupted supply chains and the war in Ukraine that occurred in 2022. Originality/value: This interdisciplinary study combines green logistics, statistical analysis of energy policy and multi-criteria optimisation. We propose a new way of evaluating consumer interest in electric vehicles. In addition, our set of criteria in the TOPSIS method includes an assessment of a country's energy security. [ABSTRACT FROM AUTHOR]

From Gerretsen's 1979 Applied Acoustics paper through four series of standards including ISO 12354 and ISO 10848, a significant amount of effort has gone into creating a standardized prediction method that uses standardized laboratory measured values to predict the apparent sound reduction index to demonstrate compliance with regulations. The terms and equations in the prediction method have evolved over time as researchers have evaluated the results of the prediction method, especially in the case of lightweight constructions for which statistical energy analysis is not well suited. To reflect the changes to other equations in the prediction method over the past 40 years, this paper suggests an update to the relationship in ISO 12354-1 between the in situ flanking sound reduction index and the laboratory measured flanking normalized level difference. The suggested changes are of importance for Type B elements such as timber and steel framed walls and floors for which the prediction of flanking transmission according to ISO 12354 requires the measurement of the level difference in laboratory flanking facilities. [ABSTRACT FROM AUTHOR]

Owing to rapid climate change, large-scale floods have occurred yearly in cities worldwide, causing serious damage. We propose a real-time urban flood-monitoring technology as an urban disaster prevention technology for sustainable and secure smart cities. Our method takes advantage of the characteristic that water flow is regularly detected at a certain distance with a constant Doppler velocity within the radar observation area. Therefore, a pure flow energy detection algorithm in this technology can accurately and immediately detect water flow due to flooding by effectively removing dynamic obstacles such as cars, people, and animals that cause changes in observation distance, and static obstacles that do not cause Doppler velocities. Specifically, in this method, the pure flow energy is detected by generating a two-dimensional range–Doppler relation map using 1 s periodic radar observation data and performing statistical analysis on the energy detected on the successive maps. Experiments to verify the proposed technology are conducted indoors and in real river basins. As a result of conducting experiments in a narrow indoor space that could be considered an urban underpass or underground facility, it was found that this method can detect flooding situations with centimeter-level accuracy by measuring water level and flow velocity in real time from the time of flood occurrence. And the experimental results in various river environments showed that our technology could accurately detect changes in distance and flow speed from the river surface. We also confirmed that this method could effectively eliminate moving obstacles within the observation range and detect only pure flow energy. Finally, we expect that our method will be able to build a high-density urban flood-monitoring network and a high-precision digital flood twin. [ABSTRACT FROM AUTHOR]

Energy finite element analysis (EFEA) has been successfully applied to steady-state response prediction over the past three decades. Compared with other energy-based methods, such as statistical energy analysis (SEA), EFEA can consider more local structural information without increasing the computational consumption too much, which makes it attractive. Inspired by the transient local energy approach (TLEA), a general transient energy balance equation was derived by assuming that the plane wave condition is satisfied. The properties of the energy balance equation were studied, and the analytical solutions with different initial conditions were provided. Utilizing the derived transient energy balance equation, transient EFEA is proposed, which has the same advantages as EFEA. A general formula is presented for the energy transmission coefficients of any number of coupled in-plane beams. The present approach was validated using a single beam and a coupled collinear beam structure under unloading conditions. The coupled collinear beams were also investigated using constant and quasi-static input power. The validation results show that TEFEA can accurately predict the local response of the structure. All of these results were compared with those of finite element analysis (FEA), simplified TEFEA (sTEFEA), transient statistical energy analysis (TSEA), and analytical formulas. [ABSTRACT FROM AUTHOR]

The excessive noise present within an aircraft cabin during flight operations constitutes a notable origin of fatigue, stress, and communication impediments for both pilots and passengers. Ensuring the comfort, well-being, and safety of passengers and crew members necessitates the accurate anticipation of noise levels. This study concerns the computation of structure-borne noise levels within the cabin of a tiltrotor aircraft. This investigation employed two distinct methodologies: advanced transfer path analysis (ATPA) and statistical energy analysis (SEA). To assess the results obtained with the ATPA approach, the acquired outcomes were compared with empirically measured sound pressure levels during airplane mode operations. The contributions of air-borne and structure-borne noises were calculated with the ATPA methodology. On the other hand, the structure-borne noise was calculated with a hybrid experimental–SEA model with ACTRAN software, and its results were compared with those of the ATPA method. The results show a good agreement between these methods at high frequencies, while at low frequencies, certain adjustments or modifications to the SEA model are necessary to predict the noise levels. [ABSTRACT FROM AUTHOR]

Public buildings consume the largest proportion of total energy consumption and carbon dioxide emissions in the building sector of China. Enhancing building energy efficiency becomes a necessary way to reduce greenhouse gas emissions and energy waste. In this study, 10-year real data from 2000 buildings covering five different types of public buildings in a hot summer and cold winter zone in eastern coastal China were investigated to analyze energy-saving potential (ESP) and the impacts of various influencing factors on building energy performance. The concept of energy consumption limit (ECL) was proposed and used for identifying high energy-consuming buildings and the calculation of ESP. Hotels, shopping malls, and office buildings were the top three types of buildings with high ESP. ESP for the high energy-consuming buildings based on the benchmark limits was more than 18%, and that for three-star hotels and shopping malls was 51%. In addition, a correlation analysis between energy consumption and influencing factors was carried out, which laid the foundation for the development of building energy performance assessment and diagnosis tools. [ABSTRACT FROM AUTHOR]

In this paper, the authors investigate energy harvesting on railway bridges. A tuning process based on a statistical analysis of the mechanical energy generated by a lumped‐mass model is presented and validated. A cantilever‐based energy harvester configuration is applied, and the optimal design of 3D printed energy harvesters is studied. The electromechanical behaviour of the device is represented by an analytical model for the estimation of the energy harvested from train‐induced bridge vibrations. A genetic algorithm constrained to geometry and structural integrity is used to solve the optimisation problem. The design flexibility and energy performance are maximised by 3D printing of the substructure of the harvester. An optimal device prototype with PAHT CF15 substructure is designed and manufactured for a real bridge in the Madrid‐Sevilla High‐Speed line. The prototype is experimentally validated under laboratory conditions. Finally, the performance of energy harvesting is evaluated from in situ experimental data measured by the authors. The results allow quantifying the energy harvested in a time window of five hours and twenty‐seven train passages. [ABSTRACT FROM AUTHOR]

Building a valid Statistical Energy Analysis (SEA) model is far from straightforward in real life applications because it has to comply with certain requirements. Since intuition-based SEA subsystems do not always entirely meet these, more advanced methods such as clustering techniques have been proposed for model building. This paper focuses on the comparison of different clustering techniques from SEA model validity point of view in the case of a simplified car body model. Besides the compliance with the SEA theory, each obtained model is compared to a reference finite element simulation to assess its accuracy. [ABSTRACT FROM AUTHOR]

Chemical and structural features of (2 ¯ 01) β -Ga 2 O 3 interfaces with SiO 2 and Al 2 O 3 gate oxides formed by low pressure chemical vapor deposition (SiO 2) and atomic layer deposition (Al 2 O 3) were investigated by analytical electron microscopy in order to identify features that may explain electrical properties recently observed in the same samples. Cross-sectional transmission electron microscopy at the Ga 2 O 3 /SiO 2 interface revealed nanoscale interfacial roughness increasing with higher post-deposition annealing temperature. At the Ga 2 O 3 /Al 2 O 3 interface, a few nanometers of epitaxial Al 2 O 3 was seen prior to the complete crystallization of the gate oxide film after tens of seconds exposure to the electron beam. Multivariate statistical analysis of electron energy loss spectroscopy signals showed evidence of interdiffusion between Al and Ga into the substrate and gate oxide, respectively, which was more pronounced following post-deposition annealing at elevated temperatures. The interdiffusion provides an explanation for the increased interface trap density previously reported in these devices. These results identify issues with the processing methods of the gate oxide affecting the performance and reliability of β -Ga 2 O 3 metal–oxide–semiconductor devices. [ABSTRACT FROM AUTHOR]

The power injection method (PIM) is an experimental method used to identify the statistical energy analysis (SEA) parameters (called loss factors – LFs) of a vibroacoustic system. By definition, LFs are positive real numbers. However, it is not uncommon to obtain negative LFs during experiments, which is considered a measurement error. To date, a recently proposed method, called Monte Carlo filtering (MCF), of correcting negative coupling loss factors (CLFs) has been validated for systems that meet SEA assumptions. In this article, MCF was validated for point connections and in conditions where SEA assumptions are not met (systems with low modal overlap, non-conservative junctions, strong coupling). The effect of removing MCF bias on the results was also examined. During the experiments, it was observed that the bias is inversely proportional to the damping loss factor of the examined subsystems. The obtained results confirm that the PIM, combined with MCF, allows to determine non-negative SEA parameters in all considered cases.

The frequency-domain vibration model of the vehicle-track structure is established based on the symplectic-spectral element method (S-SEM). To this end, the vehicle is considered as 10-degree-of-freedom, and the rail is modeled by an infinite Timoshenko beam supported by discrete sprung fasteners. Further, the track slab and base plate are regarded as two-dimensional Timoshenko beams supported by uniformly distributed sprung elements. Using the pseudo excitation method (PEM), the track irregularity is viewed as the pseudo load. The vibration response and the internal force of the single-layer or multi-layer beam models are obtained by solving the corresponding S-SEM-based equations. The spectral forces are also applied in frequency bands to the finite element (FE) and statistical energy analysis (SEA) acoustic models. The steel-concrete composite bridge deck is simulated with composite plate materials. The effectiveness of the proposed method is verified by comparing the predicted results with those obtained from the field test. The achieved results reveal that multi-layer beam structures effectively consume energy, and elastic fasteners and steel springs are capable of effectively reducing bridge noise. [ABSTRACT FROM AUTHOR]

The study of the efficiency of photovoltaic modules in outdoor conditions allows determining their correct operation and to detect abnormal behavior. Most efficiency models developed use experimental data that are difficult to obtain as they require specialized equipment and a long measurement time under laboratory conditions to identify or adjust the model parameters. In this article, we propose a linear equation that estimates the efficiency of photovoltaic modules using irradiance and back panel temperature measurements as input variables. The main contribution is that the parameters of the proposed model can be obtained directly from the reference information (IEC61853-1 power values) without any data regression. The proposed model was validated using experimental data obtained from three different climatic zones during a whole year. The model shows the best fit to the data of four analyzed models, and its normalized root mean square deviation for all photovoltaic modules is less than 3.6%; this dispersion could be explained by the fact that the outdoor data have an uncertainty of around 3.0%. [ABSTRACT FROM AUTHOR]

Nowadays, radiofrequency (RF) is a vital component of harvesting RF energy from the ambient environment to power ultra‐low‐power applications in wireless communication. This article presents an RF energy harvesting system for a frequency range of (0.58–3 GHz) to harvest RF energy from the ambient source. The system's design consists of four major modules: a coplanar waveguide antenna (CPW), a bandpass filter (BF), an L‐type impedance matching network, and a four‐stage Villard voltage multiplier (VM) circuit. First, A CPW antenna is designed suitably to harvest RF energy from GSM 900/1800, 3G, and Wi‐Fi frequency bands. Next, a BF is designed and simulated in Agilent advanced design system software for the same frequency range to attenuate the RF signals that are not in this specific frequency range. Then, an RF power conditioning circuit prototype comprising an L‐type impedance matching network and a four‐stage Villard VM circuit was integrated and fabricated on an FR4 substrate. The four‐stage rectifier circuit is designed to convert the RF signal into DC output voltage and maximize the output voltage. The performance of the RF energy harvesting system is validated through simulation and measured results. All the RF energy harvesting system elements have been connected, and the prototype is tested at various indoor and outdoor locations of Sri Sivasubramaniya College of Engineering, Chennai, India. It is observed that the prototype system can harvest energy from input power levels as low as −30 dBm. The simulated results of the RF energy harvesting system achieve an output voltage of 2.5 V with a maximum efficiency of 62.5%. The harvested output voltage at a distance of 100 m from the RF cell tower at the indoor location is 59.5 mV and at the outdoor location 271.6 mV. The harvested output voltage is used to energies the ultra‐low‐power applications. Finally, the performance of the RF energy harvesting system is analyzed by statistical techniques. The two types of analysis are Taguchi's method and analysis of variance. The RF energy harvester impact factors are VM and BF. A statistical test (P) is used to determine the significant factors on the RF output voltage. [ABSTRACT FROM AUTHOR]

An implementation in a typical L joined plate system has been proposed to investigate the effects of damping and coupling on vibration energy transmission through plates junction. A combined statistical energy analysis (SEA) and finite element method (FEM) approach characterizing the dynamic behavior of the panels has been considered. Within the procedure, the wave approach has been used to obtain the coupling loss factor (CLF) and the apparent coupling loss factor (ACLF) obtained by experimental statistical energy analysis (ESEA) together with FEM. The influence of the frequency spectrum, excitation, damping, and panel edge boundary conditions on the coupling parameters has been observed. It is demonstrated in the ESEA/FEM procedure that the boundary conditions influence the coupling factors more significantly at low frequencies, and for the higher values of damping used the results approximate those of the wave approach, which in general tends to occur at high frequencies. Variations in the energy transmission is observed in agreement with the coupling changes. [ABSTRACT FROM AUTHOR]

The similitude theory helps to understand the physical behaviors of large structures through scaled models. Several papers have studied the similitude of shock issues. However, the dynamic similitude for shock responses of coupled structures is rarely incorporated in open studies. In this paper, scaling laws are derived for the shock responses and spectra of coupled structures. In the presented scaling laws, the geometric distortion and energy loss are considered. The ability of the proposed scaling laws is demonstrated in the simulation and experimental cases. In both cases, the similitude prediction for the prototype's time-domain waveform and spectrum is conducted with the scaled model and scaling laws. The simulation and experimental cases indicate that the predicted shock responses and spectra agree well with those of the prototype, which verifies the proposed scaling laws for predicting shock responses. [ABSTRACT FROM AUTHOR]

Today, the use of wind energy by wind turbines has grown significantly, and this development is due to the production of required energy and tourism attraction of wind turbines. But according to the standard technologies used in this industry, the operating costs are very high. For this reason, before the construction of wind farms, potential measurements should be done along with economic analysis. Therefore, in this research, a statistical analysis of wind farms has been done. In the statistical analysis, Weibull and Rayleigh distribution functions were used to predict the wind speed of the studied area. MATLAB software is used to model prediction functions. Among the important results of wind speed prediction by the Weibull distribution function, it can be mentioned that the wind speed is variable between 0.6 and 7 m/s in the studied area. The total power density and wind energy in the 10 years are equivalent to 28 W/m2 and 810/0534 kWh/m2 at the height of 10 m calculated. [ABSTRACT FROM AUTHOR]

L-Theanine is a multifunctional nonprotein amino acid found naturally in tea leaves. It has been developed as a commercial product for a wide range of applications in the food, pharmaceutical, and healthcare industries. However, L-theanine production catalyzed by γ-glutamyl transpeptidase (GGT) is limited by the low catalytic efficiency and specificity of this class of enzymes. Here, we developed a strategy for cavity topology engineering (CTE) based on the cavity geometry of GGT from B. subtilis 168 (CGMCC 1.1390) to obtain an enzyme with high catalytic activity and applied it to the synthesis of L-theanine. Three potential mutation sites, M97, Y418, and V555, were identified using the internal cavity as a probe, and residues G, A, V, F, Y, and Q, which may affect the shape of the cavity, were obtained directly by computer statistical analysis without energy calculations. Finally, 35 mutants were obtained. The optimal mutant Y418F/M97Q showed a 4.8-fold improvement in catalytic activity and a 25.6-fold increase in catalytic efficiency. The recombinant enzyme Y418F/M97Q exhibited a high space-time productivity of 15.4 g L-1 h-1 by whole-cell synthesis in a 5 L bioreactor, which was one of the highest concentrations reported so far at 92.4 g L-1. Overall, this strategy is expected to enhance the enzymatic activity associated with the synthesis of L-theanine and its derivatives. Key points • Cavity topology engineering was used to modify the GGT for L-theanine biocatalysis. • The catalytic efficiency of GGT was increased by 25.6-fold. • Highest productivity of L-theanine reached 15.4 g L-1h-1(92.4 g L-1) in a 5 L bioreactor. [ABSTRACT FROM AUTHOR]

Over the past several decades, a medical physics service group covering 35 clinical sites has provided routine monthly output and energy quality assurance for over 75 linear accelerators. Based on the geographical spread of these clinics and the large number of physicists involved in data acquisition, a systematic calibration procedure was established to ensure uniformity. A consistent measurement geometry and data collection technique is used across all machines for every calendar month, using a standardized set of acrylic slabs. Charge readings in acrylic phantoms are linked to AAPM's TG‐51 formalism via a parameter denoted kacrylic, used to convert raw charge readings to machine output values. Statistical analyses of energy ratios and kacrylic values are presented. Employing the kacrylic concept with a uniform measurement geometry of similar acrylic blocks was found to be a reproducible and simple way of referencing a calibration completed in water under reference conditions and comparing to other machines, with the ability to alert physicists of outliers. [ABSTRACT FROM AUTHOR]

To detect human survivors trapped in buildings after earthquakes by using structure-borne sound it is necessary to have knowledge of vibration transmission in collapsed and fragmented reinforced-concrete buildings. In this paper, statistical energy analysis (SEA) is considered for modelling vibration transmission in seismically damaged, reinforced concrete, beam-to-column junctions where the connection between the beam and the column is made only via the steel reinforcement. An ensemble of 30 randomly damaged beam-to-column junctions was generated using a Monte Carlo simulation with FEM. Experimental SEA (ESEA) is then considered with two or three subsystems to determine the coupling loss factors (CLFs) between the beam and the column with either bending modes or the combination of all mode types. It is shown that bending modes dominate the dynamic response and that the uncertainty of predicting the CLFs using FEM with ESEA is sufficiently low that it should be feasible to estimate the coupling even when the exact angle between the beam and the column is unknown. In addition, the use of two rather than three subsystems for the junction significantly decreases the number of negative coupling loss factors with ESEA. An initial analysis of the results in this paper was presented at the 50th International Congress and Exposition on Noise Control Engineering.

Monte Carlo Filtering (MCF) is one of the methods of Experimental Statistical Energy Analysis (E-SEA), which allows the correction of negative LFs (Loss Factors). In this article, a modification of the MCF method, called DESA (Diagonal Expansion of the Search Area), is proposed. The technique applies a non-uniform extension of the search area when generating a population of normalized energy matrices. The degree of expansion of the search area is controlled by the Diagonal Penalty Factor (DPF). The authors demonstrated the method’s effectiveness on a system that could not be identified in several frequency bands by the classical MCF method. After applying DESA, it was possible to fill in the problematic bands that were missing CLF (coupling loss factor) and DLF (damping loss factor) values. The paper also proposes a way to minimize the errors introduced by using overly high DPF values.

ObjectivesThis paper aims to solve the problem of the prediction and control of the bow sonar self-noise. MethodsA self-noise simulation model of the ship's sonar platform based on the entire ship is established by statistical energy analysis (SEA). Based on the prediction results, the self-noise reduction effects of a sound absorption wedge, polyurethane and concave-shaped acoustic baffle are studied. The effects of the sound transmission window on flow-induced noise are then discussed in the two aspects of material and structure. ResultsThe results show that bow sonar self-noise can be reduced to a certain extent by laying a sound absorption wedge on the non-transparent interface, and bow sonar mechanical noise can be effectively reduced by laying polyurethane material, while the noise reduction effects of flow-induced noise and propeller noise are relatively small. Bow sonar mechanical noise and propeller noise can be effectively controlled by setting a concave-shaped acoustic baffle. Compared with a single-layer glass reinforced plastic (GRP) window with the same thickness, a sandwich titanium alloy window can better suppress flow-induced noise on the bow sonar platform. ConclusionsThe simulation results provide a theoretical basis and data support for the noise reduction design of bow sonar platforms.

The conical shape structures are widely employed in many practical applications such as aircraft, rockets, tanks, and submarines. Prediction of sound transmission loss is often required at the design and evaluation stages of such structures. In this paper, an analytical model is proposed using the statistical energy analysis (SEA) technique to predict the sound transmission loss of a conical shape acoustic enclosure in a broad frequency range. The proposed model is verified experimentally using the sound intensity experimental technique. It was found that the analytical predictions are in good agreement with the measured transmission loss, specifically at the ring and critical frequencies. The percentage error between predicted and measured lower ring frequency is 5.1% and that for the upper ring frequency is 0.4%. The percentage error between predicted and measured critical frequency is 2.7%. The results obtained indicate that the developed analytical model can be used as an efficient design tool to predict the acoustic performance of conical shape structures. [ABSTRACT FROM AUTHOR]

This article is a discussion on the necessity of the assumption of diffuse field in statistical energy analysis and the validity of the coupling power proportionality which states that the vibrational power exchanged between coupled subsystems is proportional to the difference of their modal energies. It is proposed to re-formulate the coupling power proportionality in terms of local energy density instead of modal energy. We show that this generalized form remains valid even if the vibrational field is not diffuse. Three causes of lack of diffuseness have been studied: coherence of rays in symmetrical geometries, nonergodic geometries, and the effect of high damping. Numerical simulations and experimental results conducted on flat plates in flexural vibration are provided to support these statements. [ABSTRACT FROM AUTHOR]