bluuebunny/crossref_metadata_2025 huggingface dataset:
Some resonance effects of non-typical trains and railway bridges investigated by a frequency-domain method
Authors: Auersch Lutz
Published: June 2024

The resonances of railway bridges have often been analysed for short bridges under periodical high-speed trains, for simply supported one-span bridges, for the fundamental bridge mode, and by time-domain analyses. Many time-consuming calculations have been performed to establish simplified rules for standards. In this contribution, the passage of different (existing, new and hypothetic) trains over different (simply supported, integral, multi-span, continuous) bridges will be analysed in frequency domain by using three separated spectra with the purpose to get a better physical insight in the phenomena. At first, the excitation spectrum of the modal forces is built by the mode shape and the passage time of the train over the bridge. The second spectrum is the frequency response function of the bridge which include the modal frequency, damping and mass. The third part is the spectrum of the axle sequence of an arbitrary train which is not limited to periodical or specific (conventional, articulated, regular or standard) trains and which does not include any bridge parameters. The final solution in frequency domain is obtained as the product of these three complex, strongly varying spectra for the dominating bridge mode or in general as the sum of these products over all relevant bridge modes. The time domain solution is obtained via the inverse Fourier transform, and the resulting time histories have been successfully compared with some measurement results. The method is applied to the vertical and torsional modes of a mid-long single-span bridge on elastomeric bearings under standard train speeds, to a short two-span bridge under high-speed traffic, and to a long three-span integral bridge under long periodical freight trains. Different resonance and cancellation effects have been found for systematically varied train speeds according to the axle sequence of the whole train which is dominated by the two locomotives in that case. To be more specific, the first torsional mode of the mid-span bridge is excited for a train speed of 100 km/h whereas the second bending mode is excited for a train speed of 160 km/h. In both cases, the other mode is suppressed by the minima of the axle-distance spectra. In addition, the case of the German high-speed train ICE4, a Maglev train on a viaduct, and the very high-speed hyperloop case will be discussed briefly. In general, it is shown that resonance effects are also worth to be studied for freight and passenger trains with lower speeds.
Dynamic response of structures with a friction-yield damper
Authors: Titirla M D
Published: June 2024

In this study, the effects of an energy dissipation device in a reinforced concrete building are presented. The damper that is used in this study is part of the passive energy dissipation systems and absorbs the seismic energy through yielding in bending and frictional forces that occur in the metallic elements of the damper. The existence of this friction-yield damper: (i) increases the stiffness of the structure, (ii) absorbs seismic energy, (iii) and controls the axial forces occurring at the diagonal steel braces. The first step of this study is to present the dynamic response of this damper, testing it experimentally under cyclic loading. These experimental results have been compared to the finite element model of the damper results. In addition, a three-story reinforced concrete building is studied in this paper. It is being analysed using push-over and time history analysis, as regards three different cases, (i) the benchmark r/c building (BM3), (ii) the strengthening building with steel diagonal braces (DS3), and (iii) the strengthening building with the investigated damper (DS3-Damper). A comparison of the strengthening solution is presented and further useful results are observed.
On the critical velocity of a mass moving along an infinite beam supported by three viscoelastic layers
Authors: Dimitrovová Z , Mazilu T
Published: June 2024

Numerical assessment of the dynamic behaviour of structures subject to moving loads are under huge development, as are other approaches, to mention e.g. (semi)analytical methods and methods based on frequency-domain moving Green’s function. This contribution is focused on an infinite beam supported by three viscoelastic layers, which, due to its computational efficiency and relatively good approximation of reality, is a quite common model of a railway line. New developments that are presented concern the instability of a moving mass. The critical velocity in this context will be used for the lowest velocity that separates stable and unstable behaviour. The two above-mentioned methods are compared in terms of computational efficiency and accuracy of the obtained results. All results are presented in dimensionless form to cover a wide range of possible scenarios. When the frequency-domain moving Green’s function is used to calculate the critical velocity via D-decomposition method, then a little damping should be considered for numerical stability. The semianalytical approach, on the other hand, can deal with both undamped and damped structures without any problems. Nevertheless, the final results obtained by the two methods (in the Green’s function approach under the assumption of very low damping) are identical.
Studying the effect of delamination on Ostrovsky wave packet propagation in waveguides
Authors: Tranter Matthew R , Tamber Jagdeep S
Published: June 2024

This paper considers the scattering of Ostrovsky wave packets in a delaminated two-layer waveguide with a soft bonding between the layers. The lower layer is significantly denser than the upper layer, so the displacements are described by Boussinesq-Klein-Gordon (BKG) equations in bonded regions or Boussinesq equations in the delaminated regions. A semi-analytical approach is developed using asymptotic multiple-scales expansions, which is less expensive than direct numerical modeling, and good agreement is shown between the two methods. In delaminated regions, the Ostrovsky wave packet evolves into a series of rank ordered solitons with dispersive radiation, and when these solitons re-enter a bonded region, they each evolve into Ostrovsky wave packets, with the lead Ostrovsky wave packet being most distinct. The numerical results are then linked to material parameters, which can motivate physical experiments with a wide range of materials to determine if this measure can be used to control delamination.
Where is the end of a Bridge (model)?
Authors: Bunce Andrew , Hester David , Brennan Daniel S.
Published: June 2024

Bridge SHM solutions have been developed to assist with the assessment and monitoring of bridges. State of the art bridge SHM solutions tend to be data based, where machine learning algorithms are trained using large, historical bridge datasets, and outlier analysis is subsequently used for anomaly detection. However, most bridges lack the required healthy state data for machine learning approaches to be considered, and many bridges are not in a healthy condition to collect the required data from. A population based structural health monitoring (PBSHM) approach has recently been proposed that seeks to facilitate knowledge transfer between similar structures. The approach proposes that if two structures are similar enough, there could be scope to make SHM inferences between the structures. The ability to make inferences between bridges, which are currently monitored in isolation, would be highly valuable as a bridge management tool, particularly if datasets could be leveraged between bridges through transfer learning. However, before knowledge can be shared between bridges, there is first a need to identify bridges that are similar enough for inferences to be made. The PBSHM approach proposes the use of Irreducible Element (IE) models to describe structures, which allows Attributed Graphs (AG) to generated and compared for similarity using graph theory techniques. The general method for comparing structures was trialled on bridges previously, however the resulting similarity metrics were for the whole bridge as opposed to particular common zones of interest e.g. the deck. This paper instead proposes that bridges be modelled as subsections of structures that interact via shared boundaries (i.e., points of articulation such as bearings), as opposed to whole structures. Bridge datasets are often limited to the part of the bridge that was investigated, i.e., datasets particular to bridge decks, abutments etc. Therefore, the extents of the IE models proposed in this paper are set to only include elements that would pertain to a particular dataset. In particular, two beam and slab bridges are each described with bridge deck, abutment and pier IE models to trial the concept. The revised extents of the bridge IE models reduced the number of elements being compared, resulting in increased resolution graph comparisons being carried out and more meaningful similarity metrics between the bridge parts being achieved.
Numerical assessment of the dynamic load allowance on long-span modular steel bridges considering vehicle-bridge interaction
Authors: Chordà-Monsonís J , Moliner E , Martínez-Rodrigo MD , Zacchei E , Tadeu A , Romero A
Published: June 2024

Dynamic effects caused by vehicles on bridges is a key aspect to consider on the designing, monitoring and maintenance of the roadway infrastructure. This is particularly important in the case of modular truss bridges as they face operational restrictions when spans lengths are larger than 60 m. In the recent years, new efforts are being directed to develop fully-functional modular steel bridges of substantially larger spans. For this purpose, it is essential to fully understand the dynamic effect of vehicles on such structures. This paper provides a detailed study on two modular steel bridges considering span lengths from 120 to 140 m. A 3D coupled vehicle-bridge model is used to simulate the vehicle-bridge interaction and evaluate the dynamic load allowance of the structures. Different profiles of road irregularities are generated and their influence is investigated. The results reveal the importance of defects that excite vertical bouncing modes of the vehicle. The effects of considering different span lengths and vehicle speeds are also discussed. Finally, the dynamic load allowance obtained for the bridges under study is compared to that calculated with the expressions given in several design codes.
Residual Life Assessment of Steel Truss Bridge due to Coupled Action of Corrosion and Fatigue
Authors: Ghosh Diptarka , Ashwin Kumar P. C.
Published: June 2024

Steel trusses have often been used as medium to long-span railway-over-bridge structures due to their rapid installation and reliable performance. However, fatigue reduces the service life of these steel bridges. Rapid stress reversals are generated in steel bridges due to the high-speed movement of trains. The damage is further intensified with aging of the structure, due to corrosion. This coupled action of corrosion and rapid stress reversals increase the stress concentration in steel bridges, especially in the vicinity of existing initial defects. Thus, the focus of the current study is to develop a relationship between the residual fatigue life and the coupled deterioration due to corrosion and rail loads, provided in standard railway design guidelines. For the present study, a 63m railway-over-bridge structure modeled in professional design and analysis software is subjected to eleven 25t rail loads taken from Research Designs and Standards Organisation (RDSO) guidelines. The rainflow-counting algorithm has been used to convert critical member’s stress histories into an equivalent set of constant amplitude stress reversals. The obtained equivalent stress histories are applied to the critical member of the steel bridges exclusively modeled using ANSYS. From the numerical results obtained, the residual fatigue life is calculated in terms of number of equivalent sets of varying stress reversal that the simulated member can withstand before failure.
An Efficient Non-intrusive Strategy For Weakly Coupled Fluid-structure Interaction
Authors: Alhayki Eman , Dettmer Wulf G. , Perić Djordje
Published: June 2024

Computational efficiency has remained one of the major barriers constraining the development of computational approaches for simulating many industrial problems involving fluid-structure interaction. The most efficient algorithms are the partitioned staggered solution approaches. These methods require one execution of the solid and fluid sub-solvers per time step. However, such strategies usually lack robustness and efficiency. This work proposes robust second-order accurate staggered solution schemes for fluid-structure interaction. These approaches are based on linear combinations of higher-order predictors and are based on Dirichlet-Neumann coupling. The schemes are unconditionally stable to a high amount of added mass and are suitable for code coupling. The schemes are developed and tested in the setting of one-dimensional model problems, including two dimensional flow around a flexibly supported cylinder.
CFD-Corrected Aerodynamic Influence Matrices and Aplications on Aeroelastic Phenomena
Authors: Utku Gungor O , Burak Nuzumlalı A , Ozkesiciler Müslüm , Kocan Cagrı , Sakarya Evren
Published: June 2024

The main aim of this study is solution of aeroelastic problems such as flutter, gust and control reversal analysis with Computational Fluid Dynamic (CFD) corrected unsteady aerodynamic instead of inviscid linear results calculated by Doublet Lattice Method (DLM). The DLM is the essential tool for calculating unsteady aerodynamic loads in aeroelasticity. Besides the essential advantages of the DLM, it is based on linear potential flow approach and is only valid for subsonic flow with the assumption of thin airfoil geometry. On the other hand, wing tunnel experiments and high fidelity methods such as Reynolds Avaraged Navier Stoke equations (RANS) are traditional ways to improve aerodynamic behavior fidelity. While the experiments and the CFD based solutions give valid results even for transonic region, the cost of them are higher than the conventional DLM method. Hence, the CFD correction methods have been implemented to increase fidelity of the DLM calculations without computational burdens. The challenge here lies in, the mapping/interpolation of external CFD results to DLM boxes and the generation of correction matrices. The authors presents the CFD interpolation and its commercial application on common sense aeroelastic phenomena; flutter, gust and control reversal analysis which are mentioned in aircraft certification documents with CFD corrected aerodynamic. Once the the methods are applied to models in the frame of industrial mandatories. The comparison is made between with and without the CFD correction.
Numerical evaluation of empirical equations for the prediction of building vibrations due to vibratory rollers
Authors: Cao S , Achmus M
Published: June 2024

Vibrations due to construction activities and the resultant oscillation and potential damage of adjacent structures is an important issue in soil dynamics. To prevent damage, the intensity of building vibration on the subsoil and also on the building must be predicted. In most application cases, empirical equations are used to estimate the intensity of vibration (in terms of peak vibration velocity). However, these equations normally do not take site-specific soil conditions into account, but consider an energy term dependent on the construction machine and the distance of the operating machine to the considered building. In the paper, building vibrations due to vibratory rollers are considered. First, empirical approaches from literature are described and compared. Then, a numerical simulation model is presented, which allows the determination of peak vibration velocities due to vibratory roller operation of the soil in the free field as well as of a footing. A parametric study is conducted which shows the effects of subsoil conditions (i.e. soil layering and soil stiffnesses) and footing dimensions on the vibration intensities at varying distances to the vibratory roller. From a comparison of free field and foundation peak velocities, also transmission coefficients from soil to footing are determined.
Evaluation of Soil-Structure Interaction for Different RC Structural Systems and Foundation Sizes
Authors: Bapir Baban , Abrahamczyk Lars , Afroz Ayesha
Published: June 2024

Past earthquakes and contemporary research reveal that dynamic soil-structure interaction (SSI) could significantly alter the structural response of a building during an earthquake. These effects are functions of several parameters, including structural system, foundation type and geotechnical characteristics of the subsoil. Previous studies discovered that SSI effects are more prominent for structures supported by shallow foundations. However, increasing the foundation size for high-rise buildings tends to decrease the SSI effects in lateral deflections and foundation rocking. Further, the structural response of wall-frame structures differs from Moment-Resisting Frame (MRF) structural system. The present article extends earlier findings to investigate the influences of shallow foundation size on the seismic response of short and medium heights of reinforced concrete buildings resting on soft soil deposits. In addition, the inertial soil-structure interaction effects on MRF and wall-frame systems are studied and compared. A nonlinear Winkler foundation model (BNWF) is adopted to represent the soil domain. The model allows accounting for plastic deformation in the subsoil and considers the soil damping. The structural elements are modelled based on distributed plasticity mechanism to capture the inelastic response of the structures. A 3-storey, 6-storey and 12-storey building with various foundation sizes and different structural systems are numerically simulated in OpenSees software. The buildings are subjected to five moderate earthquake records for time history analysis in the time domain. The results are expressed in terms of period lengthening, lateral deflection, inter-storey drift, and base shear forces. The results reveal a noticeable influence of foundation size on dynamic characteristics and seismic response of MRF structures. Increasing foundation length decreases the structures’ lateral deflection and base shear forces. However, these effects are less observable for the short-height structure. On the other hand, the wall-frame system is relatively more influenced by SSI effects than the MRF system. The effects of period elongation and increasing base shear forces due to SSI are more noticeable for wall-frame systems, and these effects are maximum for stiffer structures. Similarly, the increase in maximum lateral displacement and storey drift is higher in wall-frame buildings compared to MRF structures, particularly in the lower stories of the building.
An equivalent modeling method for coupling stiffness of metal braided sleeve based on hyper-elastic material function
Authors: Jianrun Zhang , Xinran Chen , Dacheng Huang
Published: June 2024

Metal hoses are important connecting components in pipelines, used for compensation in length and vibration reduction in system. Due to the complex structure of the metal braided sleeve on the outer layer of the metal hose and the nonlinear stiffness caused by coupling with the metal corrugated pipe during the combination process, modeling and calculation are difficult. In this paper, an equivalent modeling method for the coupling stiffness of metal braided sleeve based on Hyper-elastic material function is proposed. The parameters of Hyper-elastic material function are obtained through experiments. Experiments and simulations show that this method has a high accuracy, which propose an efficient way to solve the problems in theoretical analysis and simulation modeling of metal hose.
Design and Modelling of a Centrifugal Pump Using Autodesk Inventor Professional
Authors: Ngcukayitobi Miniyenkosi
Published: June 2024

Centrifugal pumps find wide-ranging applications across various fields, yet the majority of these pumps continue to be produced using conventional manufacturing methods. These methods involve processes such as milling, cutting, and drilling, which, while effective, are less inclined towards achieving energy, environmental, and economic sustainability. This has spurred researchers to explore innovative approaches to enhance the sustainability of production processes. One notable advantage of 3D printing lies in its capacity for rapid prototyping. This term denotes the ability to swiftly fabricate, design, and evaluate a bespoke component in the shortest possible time. The driving force behind this research endeavor is to furnish comprehensive guidance on the design and modelling of a centrifugal pump utilizing Autodesk Inventor Professional software. To ensure synchronized operation, a coupling unit was employed to link the pump and motor shafts, ensuring they rotate at identical speeds and within the same plane. This unit plays a critical role in transmitting both speed and torque. The modelling of the impeller, the pivotal component of the centrifugal pump, entailed the following steps: creating a model for the lower flared section, fashioning the upper flared part, shaping the impeller blades, generating a circular series of blades to yield the remaining seven, designing a reinforcement solid for secure attachment to the axis, sculpting the lower wear ring, and fashioning the central aperture to accommodate the rotating shaft.
A Study on the Effects of Clearance Joints on the Dynamic Response of a Planar Deployable Structure
Authors: Yao Huaibo , Liang Lei , Ma Wenlai , Zhao Yang
Published: June 2024

This article investigates the influence of clearance joints on the dynamic characteristics of deployable structures and the contact characteristics inside clearance joints. An explicit dynamic modeling method is employed to formulate the governing equation of the structure, integrating the contact forces. Initially, a planar deployable structure is subjected to analysis to discern the effects of clearance joints. Subsequently, two distinct dynamic analyses are meticulously conducted to discern the nuanced effects of clearance size. The outcomes offer conclusive insights; clearance joints substantially influence dynamic responses and prolong the structure’s vibration period. The unrestrained motion of joints contributes to increased kinetic energy within the structure. Furthermore, a larger clearance size exacerbates these effects. In conclusion, the findings underscore the significant effects on the structure’s dynamic characteristics, which should be seriously taken into consideration in the design and modeling process. This necessitates meticulous consideration in designing and analyzing high-precision space structures to ensure accurate predictions and optimal performance.
Effect of Maglev Suspension on the Aerodynamics of Multiple Vehicles Moving in a Low-Pressure Tube
Authors: Alzhrani Seraj , Abdulla Mohammed , Juhany Khalid A , AlQadi Ibraheem
Published: June 2024

The concept of high-speed vehicles traveling in a low-pressure closed system has attracted global attention as an innovative, efficient, and safe mode of transport. So far, most the studies on Hyperloop aerodynamics has considered a single vehicle moving in a confined space, but limited work has been devoted to the succession of vehicles system. This paper deals with the analysis of vehicle suspension gap for multiple vehicles system running in a low-pressure environment. The vehicle’s system is traveling at Mach number = 0.7 in a low operating pressure of 10,000 Pa and blockage ratio of 0.36. Each vehicle is equipped with a compressor and jet exit to provide the thrust force. Three running vehicles at various vehicle-to-vehicle distances, Xv (0.25, 0.5, 1, 2Lv), were numerically investigated using RANS. The analysis was carried out at a gap distance of 75 mm. The obtained results showed that the suspension gap significantly impacts the aerodynamic performance of the entire system. The flow structure behind each vehicle was investigated, and its influence on thrust was presented. It was observed that the drag on the trailing vehicle is approximately six times the drag on the leading vehicle. The high drag on the trailing vehicle is attributed to the development of shock waves at its rear part.
Structural and Optical Characterization of Dual Phased AlScN Thin Film Co-Sputtered on Sapphire
Authors: Ahmad Ateed , James Raju K C
Published: June 2024

In the present report, the structural and optical characteristics of RF sputtered Al52Sc48N (ASN) was studied with X-ray diffraction (XRD), Raman spectroscopy and UV-Vis reflection spectroscopy. XRD spectra shows three distinct peaks at 35.31˚, 40.80˚ and 59.32˚ of which two of them belong to cubic phase while one of them suggest a hexagonal structure. The Raman spectra show some unusual broadening of the peaks with a huge redshift. The addition of Sc has induced a great amount of strain in ASN which is reflected in the redshift of Raman peaks, smaller grain size calculated by Scherrer equation and micro cracks observed in FESEM images. The reflectivity spectra show interference fringe pattern at higher wavelength with the pattern diminishing gradually as the bandgap threshold approaches. An abrupt drop in reflection around 254 nm is observed which is believed to be of Surface Plasmon Resonance of Al. The refractive index was calculated using envelope method and it shows a typical inverse behaviour with respect to the wavelength. The thickness of the film as calculated by cross sectional SEM image is almost similar to that calculated using envelope method of UV-Vis reflection spectra.
Synthesis, Properties, and Structural Studies of Bismuth-Barium Tellurite Glasses Doped with Dy2O3
Authors: Mujeeb Syed , Eraiah B
Published: June 2024

A series of a new glass sample has been prepared with glass composition xDy2O3-(10-x) Bi2O3-20BaO-70TeO2 (where x=0,1,2,3,4,5, and 6 and mol %) have been produced through the traditional melt-quenching approach. The XRD (“X-Ray Diffraction”) pattern indicates that the glass system is amorphous by nature. The prepared glass system’s density has been examined with Archimedes’ principle, and the associated molar volume was estimated. Dy2O3 increases the density of the glass system, and it is observed that the molar volume is inversely related to the glass density. The absorption spectra from the wavelength range 200nm – 1100nm are applied to assess the glass’s optical properties. The direct and indirect optical band gap were computed using Tauc’s plots from the absorption spectra. The energy gap variation with the concentration of Dy2O3 has been discussed. The refractive index has also been calculated using the energy band gap values. Other physical parameters like electronic polarizability, and dielectric constant molar volume have been calculated. The structural and optical properties were examined via FTIR and RAMAN spectrometers.
Analysing CMOS performance: A comprehensive study of operational characteristics in low-temperature environments
Authors: Cui Chuanjie
Published: June 2024

This article aims to methodically analyse and consolidate the experimental findings from previous research on the operational behaviour of Complementary Metal-Oxide-Semiconductor (CMOS) technology in low-temperature conditions. Recognizing the extensive array of empirical data available, the focus is on delineating and systematizing the functional attributes of CMOS devices when subjected to such environmental parameters. The study involves a comparative review of diverse scholarly sources, identifying and categorizing the operational features of CMOS in low-temperature scenarios. This endeavour seeks to distil these findings into clear, initial conclusions, drawing upon a comprehensive examination of relevant literature and database compilations. Structurally, the paper commences with an introductory exposition on CMOS, followed by a detailed literature review cantered on its performance in low-temperature contexts, leading to the analysis of collected data and ensuing discussions. The synthesis of these insights aims to enhance the understanding and generalization of CMOS operational dynamics in low-temperature environments, contributing to a cohesive body of knowledge in this specialized field.
Research progress on piezoelectric acoustic transducers: Principles, materials, performance, and applications
Authors: Zhu Jishen
Published: June 2024

Piezoelectric acoustic transducers enable the mutual conversion between mechanical energy and electrical energy. In recent years, piezoelectric transducers, as efficient and reliable sustainable energy harvesting devices, have demonstrated unique application value in various disciplines such as physics, acoustics, and engineering. This paper comprehensively reviews the current research status and future development directions of acoustic transducers. Firstly, the physical mechanism of the piezoelectric effect is thoroughly analyzed, and the basic operating mode of piezoelectric acoustic transducers is systematically explained. Furthermore, the characteristics and design directions of different types of piezoelectric materials are comprehensively reviewed, with a focus on exploring material innovation approaches to enhance performance. Moreover, various design methods, including layered, integrated, and curved structures, are summarized with emphasis on their crucial roles in improving sensitivity and adaptability. Techniques improving performance were also reviewed. Given the unique nature of piezoelectric effect, the research outlines applications of transducers in sonar systems, structural monitoring systems, and micro-piezoelectric systems. Through the above review, this paper provides profound insights into the research on piezoelectric acoustic transducers, emphasizing in-depth investigations in specific areas. It offers researchers from backgrounds including materials science, acoustics, and electronics different directions, ideas, and methods, thereby promoting innovation in wireless, sensing, and energy fields.
Design remote wireless sensor node solar power fire detection system to prevent high temperature’s fire
Authors: Wu Zheyu
Published: June 2024

This paper introduces a basic remote wireless sensor node solar power fire detection system model. It aims at the design and analysis of a closed-loop converter circuit aimed at voltage regulation within the range of 2V to 5V. The circuit employs a microcontroller for the purpose of maintaining a stable output voltage of 9V. Efficiency testing has been conducted to quantify input and output voltages as well as currents, yielding efficiency curves across various load resistor values, all surpassing the 70% threshold. The circuit has been tailored for optimizing battery charging and discharging processes and incorporates a sleep system to enhance the longevity of the wireless sensor node. Furthermore, the integration of temperature sensors is thoroughly discussed. In conclusion, this study displays the successful creation of wireless sensor nodes featuring efficient voltage regulation and extended battery life.
Design of 1000-1100nm fiber laser based on neodymium ion
Authors: Liu Yuan
Published: June 2024

Nd3+ ions have a large emission cross-section in the 1000 ∼ 1100 nm band. In this study, we focus on the spectral properties of Nd3+ ions, simulate the power transfer equation of the Nd-doped ion fiber laser. The design of the Nd-doped fiber laser is aimed at laser generation by considering parameters such as absorption cross section, particle number concentration, loss coefficient, and reflectivity of the front and rear cavity mirrors. The experimental process begins with the design of specific parameters for the two cavity mirrors at 1060 nm using Matlab, based on the required reflectivity parameters. The simulation demonstrates that laser generation begins at a pump light power of 9.8 W, and the laser power reaches 36.8 W. Observe the propagation power of the signal light and pump light, when the pump light propagates in the forward direction, the forward propagation power of the pump light will decrease. This paper summarizes and innovates the numerical simulation parameters of Nd-doped ion fiber laser. The specific innovations are reflected in the proposed new emission cross section of pump light and absorption cross section of signal light, as well as the novel mathematical model for designing the front cavity mirror and the back cavity mirror. The experiments provide better data support for the preparation of 1000 ∼ 1100 nm doped Nd-doped fiber lasers.
In praise of cooking gas subsidies: transitional fuels to advance health and equity
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Authors: Gould Carlos F , Bailis Rob , Balakrishnan Kalpana , Burke Marshall , Espinoza Sebastián , Mehta Sumi , Schlesinger Samuel B , Suarez-Lopez José R , Pillarisetti Ajay
Published: June 2024

Households that burn biomass in inefficient open fires—a practice that results in $1.6 trillion in global damages from health impacts and climate-altering emissions yearly—are often unable to access cleaner alternatives, like gas, which is widely available but unaffordable, or electricity, which is unattainable for many due to insufficient supply and reliability of electricity services. Governments are often reluctant to make gas affordable. We argue that condemnation of all fossil fuel subsidies is short-sighted and does not adequately consider subsidizing gas for cooking as a potential strategy to improve public health and reduce greenhouse gas emissions.
Influence of fieldwork in geo-education
Authors: Nam Nguyen Thi Que , Hieu Nguyen Thi Le , Chi Hoang Thi Phuong
Published: June 2024

Fieldwork is an indispensable method in geo-education which provides young people with a fundamental understanding of how the human and natural world work. However, fieldwork in the curriculum is gradually being reduced due to a few reasons such as risks, sickness, expense, and effectiveness. Therefore, a study was conducted to clarify the influence of fieldwork on three aspects of students: knowledge, skills, and attitudes through a survey of 112 students from 2 groups that participated in different number of field trips: a one-trip group and a more-than-two-trip group. Hierarchical cluster analysis also classified five clusters of attitudes about field trips: Addict, Explorer, Acceptor, Non-fan, and Skeptic. However, Mann-Whitney test found that there was not significantly different between the two groups of student experienced different numbers of field trips and cluster of attitudes. The analysis results show that there are statistically significant differences between the two groups of students in several aspects of knowledge and skills. To make fieldwork more effective, the study proposes to have more informative surveys, more research subjects such as field teachers, staff; thereby making appropriate adjustments to meet the outcome of the course and the development of geo-education in modern world.
Aquatic invertebrates and their correlation with the basic abiotic factors in the coastal water of Can Gio, Southern Vietnam
Authors: Pham A D , Dao T S
Published: June 2024

Macroinvertebrates metrics are reliable indicators to assess the environmental quality and ecological health. In water systems, estuarine areas are sinks and sources of nutrients and pollutants, and strongly influenced by anthropogenic activities and emission from inland. Benthic macroinvertebrates and zooplankton living in estuary and coastal are not very active organisms hence heavily impacted by surrounding environmental conditions. In this study, we assessed the water quality at the tropical coastal of Can Gio located in Southern Vietnam, based on the aquatic invertebrates and environmental variables. The organisms were monitored at 20 sampling sites along the Can Gio coastal in November 2021, April, June and August 2022. Totally, 45 invertebrate species were recorded in the Can Gio coastal. The zooplankton and benthic macroinvertebrate abundance, respectively, varied between 900 to 13,000 individuals/m3, and ranged from 30 to 120 individuals/m2. The copepods and polychaetes were dominant in both species number and abundance of the zooplankton and benthic macroinvertebrates, respectively. The water quality at the Can Gio coastal during the monitored period was from low pollution to high-moderate pollution based on the invertebrate structure, abundance and indices. The results also showed the correlation between environmental variables (e.g., turbidity and dissolved oxygen) and species richness and abundance of aquatic invertebrates. Our study revealed the important and valuable application of aquatic invertebrates for the environmental quality monitoring to protect the border of the most mangrove biosphere reserve in Vietnam.
Study on COD and color removal efficiency in textile dyeing wastewater by iron electro-coagulation technology combined with persulfate
Authors: Nam Ngo Thi Phuong , Cuong Nguyen Ngoc , Trung Le Duc
Published: June 2024

Electrocoagulation (EC) is an attractive method for treating many types of wastewater due to its advantages. The purpose of this study is to investigate the effect of persulfate addition on the efficiency of textile wastewater treatment through the removal percentage of COD and color parameters. Persulfate is proven to significantly enhance the rate and efficiency of pollutant removal in textile wastewater. The removal percentage of COD could reach 91.33 ± 1.23% and 97.99% ± 0.52% was the highest removal percentage of the color parameter at the optimal reaction parameters. The effluent concentration meets the standards according to Vietnam national technical regulation on textile industry wastewater. By using persulfate, the COD and color removal efficiency increased by 17.53 ± 2.69% and 8.81 ± 0.91%, respectively, compared to the single electrocoagulation process. The amount of sludge generated in the system is 0.542 ± 0.0357 kg/m3, significantly reduced compared to the flocculation process of 0.875 ± 0.0295 kg/m3.
Assessment of awareness, consensus, and willingness to enforce regulations’ household waste separation in Ho Chi Minh City, Vietnam
Authors: Mai Le Thi Tuyet , Thao Do Phuong , Anh Hoang , Hai Pham Viet , Chau Nguyen Lam Hong
Published: June 2024

The amount of household solid waste is increasing seriously in Vietnam, because of population growth, urbanization, and economic growth. Reducing the waste volume liberated to the environment needs community participation and people’s awareness about the waste segregation at sources and hand to reuse and recycling. Realizing the value of waste classification would mobilize residents to classify domestic waste and nurture more residents’ habits. Knowing the factors influencing the individual waste separation intention supports building effective environmental campaigns. By applying the Theory of Planned Behaviour (TPB), this study determined factors correlated with residents’ waste classification intention in Ho Chi Minh City (HCMC), Vietnam. An extension of the TPB model was undertaken. This extension incorporated three additional factors, namely, propaganda, awareness, and consensus about household waste separation regulations to predict individual separation intention in HCMC, Vietnam. With a sample size of 250 residents, SPSS 20.0 software is used to analyze data. This study supports policymakers regarding formulating laws and regulations in terms of raising waste classification intention and community recycling plans.
Evaluation of factors influencing the quality of life of residents living close to Northwest Solid Waste Treatment Complex Cu Chi districts, Ho Chi Minh City
Authors: Mai Le Thi Tuyet , Chau Nguyen Lam Hong , Thao Do Phuong , Anh Hoang
Published: June 2024

Ho Chi Minh City (HCMC) grapples with a significant surge in waste generation, a consequence of urban expansion and development. The escalating waste poses a threat to the well-being of residents, particularly those in proximity to waste treatment facilities. This study delves into the impact of the Northwest Solid Waste Treatment Complex (NSWTC), a key waste treatment facility in HCMC, on residents residing in its immediate vicinity. The assessment encompasses 120 subjects living within a semi-permanent radius of 5 km from NSWTC. The residents’ Quality of Life (QoL) is quantitatively evaluated using the WHO QoL assessment scale (WHOQOL-BREF), comprising 26 survey questions categorized into four domains: living environment, physical health, psychological well-being, and socio-economic conditions. The identification of these domains is facilitated through bivariate and multivariate logistic analyses. Utilizing SPSS 20.0 software for data analysis, the findings reveal that a noteworthy 76.7% of subjects exhibit a subpar QoL. The overall QoL score, averaging 49.08 ± 18.82, falls considerably below acceptable standards, attributing this decline to environmental factors such as odours, dust, falling waste, water quality, and socio-economic conditions.
Assessing water quality of the Saigon River under the impact of industrial wastewater incidents
Authors: Thuy Nguyen Thi Diem , Mai Nguyen Thi Huynh , Linh Do Quang
Published: June 2024

The Saigon River, as its economic potential and clusters and industrial parks evolve, is threatened by a high potential for water pollution. The objective is to evaluate the water quality (BOD5 and COD) under the influence of industrial wastewater incidents in the Saigon River using MIKE 21FM model. The results of model calibration and validation have high reliability with NSE values larger than 0.65 for the flow simulation and percentage error values less than 25% for the water quality simulation. Subsequently, the study proceeds to develop hypothetical scenarios in case untreated wastewater from industrial parks is charged directly into the Saigon River with actual discharge volumes of 15,811 m3/day and 30,000 m3/day. The results indicated that when an incident occurs at a location 1.3 km upstream from the Hoa Phu pumping station with a discharge volume of 15,811 m3/day, that has the most consequential impact, in terms of time and concentration of water pollutants on the pumping station. Specifically, the water quality at the pumping station area experiences a remarkable decrease after one and three hours of incidents in the dry and rainy seasons, respectively. In general, the impacts of industrial wastewater incidents vary depending on their location. An incident beneath the Hoa Phu pumping station on the Saigon River is expected to have a faster impact on the raw water source during the dry season compared to the rainy season.
Prediction of surface urban heat island in Ho Chi Minh City, Viet Nam using remote sensing and logistic regression model
Authors: Pham Chi Cuong , Nguyen Ngoc Tuyen , Tran Quang Tra , Nguyen Nhu Ngoc
Published: June 2024

Urban heat island is a concerning environmental issue in major cities, particularly in Ho Chi Minh City. With a high rate of urbanization, the city’s extensive impervious surface area contributes to land surface temperature increase, leading to the expansion of the urban heat island phenomenon. This study was conducted in the Ho Chi Minh city region from 2009 to 2020, images from Landsat 5 (TM) and Landsat 8 (OLI/TIRS) satellites were employed to estimate land surface temperature (LST), examine the spatial distribution of the urban heat island (SUHI), and analyze changes in impervious surface area (ISA). A logistic regression model was established to predict the relationship between SUHI and ISA, with the percentage of ISA calculated by the Kernel Density Estimation method (KDE). The results revealed that the impervious surface area in the city doubled from 2009 to 2020, accounting for 29.54% of the city’s area, which correlated with a significant expansion of SUHI from 37,000 ha to 53,000 ha. The SUHI predicting model exhibited good discrimination ability (AUC = 0.98) and total accuracy of 96% through Hosmer & Lemeshow Test in R. The probability of the predicted SUHI showed a high correlation (R2 = 0.885) with the actual SUHI. In areas where ISA increased from 60% to 80%, the probability of SUHI occurrence also increased from 52.85% to 98%. This study presented a novel approach, utilizing statistical modeling to accurately quantify SUHI based on changes in impervious surface density. This method can contribute to an effective evaluation of heat-related health risks, provide the government and urban planners with a precise orientation in management toward sustainable development.
Factors affecting the change of agricultural livelihoods of farmers adapting to water resource reduction in the highland area in An Giang province, Vietnam
Authors: Nguyen Cam T H , Febriamansyah Rudi , Pham Van H T , Tran Hieu V
Published: June 2024

Currently, water shortages are affecting agricultural production in the Mekong Delta region of Vietnam. Consequently, most farmers have changed their current cropping patterns to other patterns that need less water. The factors affecting this change have not so far been deeply analyzed, especially in the higher terrain areas of the delta. This study intends to identify and understand factors causing change in the agricultural livelihoods of farmers in the highland area of An Giang province. Farm household surveys (90 households) were used to collect information on the changes in agricultural livelihoods and identify the causal factors. Multinomial logistic regression was applied to analyze these affecting factors, based on variables in household livelihood assets. The results show that farmers have at least three livelihood choices: change from rice to vegetable, change from rice to rice and-vegetable, and change from rice to fruit. The results from multinomial logistic regression show that livelihood choices are affected by households’ types of assets: human (number of employees involved, perception of farmers); natural (cultivated land area, the distance between the water source and the cultivated land area); financial (household income); and social (relationship with friends and relatives). Therefore, to increase the sustainability of existing livelihood models, it is necessary to improve the capacity of farmers through technical training sessions, promote social networks within the farming community and provide financial support policies for farmers.
Troubles with Words
Authors: Strawson Galen
Published: June 2024

Chapter 1 discusses problems of mutual misunderstanding—both chronic and acute—that arise in philosophy on account of terminological divergences and unclarities. It considers how philosophers fall into thought ruts, and lock on to narrow ways of hearing particular words, in such a way that they cease to be able to respond rationally to arguments. It reviews the greatest catastrophe that has occurred in metaphysics in the last three centuries: the rise of ‘epistemologized metaphysics’. One classical example of epistemologized metaphysics is the illegitimate conversion of Hume’s non-metaphysical, semantic-cum-epistemological claim regarding what we can know about causation (only regularity) into a metaphysical claim about what causation is (only regularity). The chapter then briefly introduces the key notions of the book: stuff, quality, structure. And it defines naturalism in an unorthodox way: the first commitment of the true naturalist must be to qualia, or the reality of consciousness.