bluuebunny/crossref_metadata_2025 huggingface dataset:
Telerehabilitation: Vestibular Physiotherapy vs. Multicomponent Exercise for Functional Improvement in Older Adults: Randomized Clinical Trial
Authors: López-García Marina , Jiménez-Rejano José Jesús , Suárez-Serrano Carmen María
Published: July 2024

The loss of vestibular and motor function can occur naturally with aging. Vestibular physiotherapy exercises (VE) specifically address vestibular rehabilitation to reduce imbalances and improve physical condition, like therapeutic exercise (TE). During COVID-19, technology was used with the elderly for implementation. Objective: to determine if vestibular exercises are as effective as multicomponent exercises in improving functional capacity using technological tools. Methods: A randomized clinical trial compared two intervention groups of 21 subjects with functional limitations and frailty (average age 76.11 years). The intervention involved multicomponent exercise for the control group (Vivifrail protocol) and vestibular exercises for the experimental group (Cawthorne and Cooksey exercises) for 6 weeks with five sessions per week both groups. Two professionals implemented the exercises, and participants received tailored exercise videos. Primary outcomes were gait speed, dynamic balance, and physical capacity. Results: Both groups showed significant improvements. For physical function measured by SPPB (0–12 points), the multicomponent exercise group improved by 1.97 (0.91; 3.03), p < 0.001, and the vestibular exercise group improved by 1.63 (0.65; 2.60), p = 0.002. For dynamic balance measured by the Timed Up and Go (TUG) test, the multicomponent exercise group improved by −0.88 (−1.33; −0.42), p < 0.001, and the vestibular exercise group improved by −0.79 (−1.21; −0.37), p < 0.001. There were no significant differences between groups. Finally, regarding gait speed, there were no differences in either group between pretest and post-test (p > 0.05). Conclusions: Both multicomponent exercise and vestibular exercises improve functional capacities via telerehabilitation as measured by the SPPB, although vestibular physiotherapy does not show superior outcomes compared to the control group.
Modifying the Characteristics of the Electrical Arc Generated during Hot Switching by Reinforcing Silver and Copper Matrices with Carbon Nanotubes
Authors: Alderete Bruno , Schäfer Christian , Nayak U. Pranav , Mücklich Frank , Suarez Sebastian
Published: July 2024

Switching elements are crucial components in electrical and electronic systems that undergo severe degradation due to the electrical arc that is generated during breaking. Understanding the behavior of the electrical arc and modifying its characteristics via proper electrode design can significantly improve durability while also promoting optimal performance, reliability, and safety in circuit breakers. This work evaluates the feasibility of carbon nanotube (CNT)-reinforced silver and copper metal matrix composites (MMCs) as switching electrodes and the influence of CNT concentration on the characteristics of the arcs generated. Accordingly, three different concentrations per MMC were manufactured via powder metallurgy. The MMCs and reference materials were subjected to a single break operation and the electrical arcs generated using 100 W and 200 W resistive loads were analyzed. The proposed MMCs displayed promising results for application in low-voltage switches. The addition of CNTs improved performance by maintaining the arc’s energy in the silver MMCs and reducing the arc’s energy in the copper MMCs. Moreover, a CNT concentration of at least 2 wt.% is required to prevent unstable arcs in both metallic matrices. Increased CNT content further promotes the splitting of the electrical arc due to a more complex phase distribution, thereby reducing the arc’s spatial energy density.
Underwater Mapping and Optimization Based on Multibeam Echo Sounders
Authors: Zhang Feihu , Tan Tingfeng , Hou Xujia , Zhao Liang , Cao Chun , Wang Zewen
Published: July 2024

Multibeam echo sounders (MBESs) enable extensive underwater environment exploration. However, due to weak correlation between adjacent multibeam sonar data and difficulties in inter-frame feature matching, the resulting underwater mapping accuracy frequently falls short of the desired level. To address this issue, this study presents the development of a multibeam data processing system, which includes functionalities for sonar parameter configuration, data storage, and point cloud conversion. Subsequently, an Iterative Extended Kalman Filter (iEKF) algorithm is employed for odometry estimation, facilitating the initial construction of the point cloud map. To further enhance mapping accuracy, we utilize the Generalized Iterative Closest Point (GICP) algorithm for point cloud registration, effectively merging point cloud data collected at different times from the same location. Finally, real-world lake experiments demonstrate that our method achieves an Absolute Trajectory Error (ATE) of 15.10 m and an average local point cloud registration error of 0.97 m. Furthermore, we conduct measurements on various types of artificial targets. The experimental results indicate that the average location error of the targets calculated by our method is 4.62 m, which meets the accuracy requirements for underwater target exploration.
Regional Difference in Distribution Pattern and Morphological Characteristics of Embayed Sandy Beaches in Zhejiang Province, Eastern China
Authors: Guo Junli , Shi Lianqiang , Zhang Min , Gong Zhaohui , Chen Wei , Xia Xiaoming
Published: July 2024

The distribution pattern and the morphology of sandy beaches have been extensively studied, while those in turbid coastal environments near large river estuaries are still unclear. This study analyzes the distribution pattern, morphological characteristics, and influencing factors of Zhejiang sandy beaches using statistical analysis, based on field data and historical records. Results show that the mean grain size distribution of Zhejiang sandy beaches ranges from fine sand to very coarse sand, and the beach slope and sediment grain size correspond well with the wave heights in the three regions of Zhejiang. The extent of beach headlands in central Zhejiang appeared the largest, suggesting an increased susceptibility to wave erosion due to the less sheltered headlands. Most sandy beaches in Zhejiang formed on the islands and the areas far from the estuaries, showing quantity difference in beach distribution. The comparison of the regional difference in Zhejiang sandy beaches shows that embayment is the main factor affecting the beach distribution pattern and morphological characteristics. The different embayment characteristics provide the space for beach formation and the interaction with the coastal process, the sediment supply, the nearshore hydrodynamic environment, and human intervention also have influence on the morphological characteristics of Zhejiang beaches.
Decoupled Analysis of a Multi-Layer Flexible Pipeline Buried in Clay Subjected to Large Lateral Soil Displacement
Authors: Malta Eduardo Ribeiro , Dong Xiaoyu , Shiri Hodjat
Published: July 2024

Multilayered flexible subsea pipelines may experience significant lateral movements due to manmade and environmental geohazards. These pipelines incorporate several structural and protective layers to resist different loads, and may require additional protection such as trenching, rock placement, or burial. In practice, simplifications are considered due to the complexities and uncertainties involved in the multi-layer pipe structure and the surrounding soil, compromising the pipe structure or the soil behavior. These simplifications are applied either on the pipe by assuming a rigid section or on the soil by representing it as elastic springs, which may result in inaccuracies. This study proposes a decoupled methodology combining the Coupled Eulerian–Lagrangian (CEL) model for soil displacement with a small-strain finite element analysis of the flexible pipe. This approach aims to accurately capture cross-sectional deformations and local stresses due to soil movement while maintaining reasonable computational effort. A parametric analysis was conducted to assess the impact of several variables on failure risk. The deformed cross-section was then used for a collapse analysis to determine critical loads at maximum operational depth. The study showed that modeling parameters such as soil strength and internal diameter might significantly influence pipe failure and the risk of collapse.
Optimization Co-Culture of Monascus purpureus and Saccharomyces cerevisiae on Selenium-Enriched Lentinus edodes for Increased Monacolin K Production
Authors: He Yi , Lai Huafa , Liang Jinxiao , Cheng Lu , He Lixia , Wang Haolin , Teng Qingqing , Cai Wenjing , Wang Rui , Zhu Lisha , Pang Zhengbin , Zhang Dafu , Dong Xingxing , Gao Chao
Published: July 2024

Selenium-enriched Lentinus edodes (SL) is a kind of edible fungi rich in organic selenium and nutrients. Monascus purpureus with high monacolin K (MK) production and Saccharomyces cerevisiae were selected as the fermentation strains. A single-factor experiment and response surface methodology were conducted to optimize the production conditions for MK with higher contents from selenium-enriched Lentinus edodes fermentation (SLF). Furthermore, we investigated the nutritional components, antioxidant capacities, and volatile organic compounds (VOCs) of SLF. The MK content in the fermentation was 2.42 mg/g under optimal fermentation conditions. The organic selenium content of SLF was 7.22 mg/kg, accounting for 98% of the total selenium content. Moreover, the contents of total sugars, proteins, amino acids, reducing sugars, crude fiber, fat, and ash in SLF were increased by 9%, 23%, 23%, 94%, 38%, 44%, and 25%, respectively. The antioxidant test results demonstrated that 1.0 mg/mL of SLF exhibited scavenging capacities of 40%, 70%, and 79% for DPPH, ABTS, and hydroxyl radicals, respectively. Using gas chromatography–ion mobility spectrometry technology, 34 unique VOCs were identified in SLF, with esters, alcohols, and ketones being the main components of its aroma. This study showed that fungal fermentation provides a theoretical reference for enhancing the nutritional value of SL.
The Arrestin-like Protein palF Contributes to Growth, Sporulation, Spore Germination, Osmolarity, and Pathogenicity of Coniella vitis
Authors: Yin Xiangtian , Chen Zihe , Li Tinggang , Liu Qibao , Jiang Xilong , Han Xing , Wang Chundong , Wei Yanfeng , Yuan Lifang
Published: July 2024

Coniella vitis is a dominant phytopathogen of grape white rot in China, significantly impacting grape yield and quality. Previous studies showed that the growth and pathogenicity of C. vitis were affected by the environmental pH. Arrestin-like protein PalF plays a key role in mediating the activation of an intracellular-signaling cascade in response to alkaline ambient. However, it remains unclear whether palF affects the growth, development, and virulence of C. vitis during the sensing of environmental pH changes. In this study, we identified a homologous gene of PalF/Rim8 in C. vitis and constructed CvpalF-silenced strains via RNA interference. CvpalF-silenced strains exhibited impaired fungal growth at neutral/alkaline pH, accompanied by reduced pathogenicity compared to the wild-type (WT) and empty vector control (CK) strains. The distance between the hyphal branches was significantly increased in the CvpalF-silenced strains. Additionally, CvpalF-silenced strains showed increased sensitivity to NaCl, H2O2, and Congo red, and decreased sensitive to CaSO4. RT-qPCR analysis demonstrated that the expression level of genes related to pectinase and cellulase were significantly down-regulated in CvpalF-silenced strains compared to WT and CK strains. Moreover, the expression of PacC, PalA/B/C/F/H/I was directly or indirectly affected by silencing CvpalF. Additionally, the expression of genes related to plant cell wall-degrading enzymes, which are key virulence factors for plant pathogenic fungi, was regulated by CvpalF. Our results indicate the important roles of CvpalF in growth, osmotolerance, and pathogenicity in C. vitis.
Proposal for Effective Management of Geoparks as a Tool for Sustainable Tourism in the Conditions of the Slovak Republic
Authors: Molokáč Mário , Kornecká Enikő , Tometzová Dana
Published: July 2024

Geoparks, as sustainable tourism products, embody a range of values and functions aimed at mitigating the negative impacts of tourism on the landscape. The current increasing trend in establishing and supporting geoparks has extended to the territory of the Slovak Republic, which possesses valuable natural potential. However, effectively harnessing this potential requires a clearly defined management structure aligned with the goals and mission of each geopark. The paper presents the operational aspects of geoparks in Slovakia, providing a comprehensive overview of geopark management followed by a subsequent evaluation. Assessing the management approach yields valuable insights into the ongoing development of Slovak geoparks, serving as a stepping stone for their further advancement. These geoparks are in a state of continual evolution, demanding significant support to ensure their efficient functioning. The study establishes clear quality management criteria for optimal staffing. The main objective of the paper is to demonstrate the need for the professionalization of human resources in geopark management. Additionally, the article concludes with a model for a strategic approach to human resources management, covering all its areas. Geoparks, as a modern product of geotourism and territorial management, represent innovative strategies for protecting and conserving geodiversity. They are closely intertwined with knowledge dissemination, education, and fostering a broader appreciation for the Earth’s value. Moreover, they play a vital role in the sustainable development and preservation of territories.
The Effect of Climate on Strongly Disturbed Vegetation of Bait Sites in a Central European Lower Montane Zone, Hungary
Authors: Rusvai Katalin , Házi Judit , Czóbel Szilárd
Published: July 2024

Human landscape-transforming activities contribute to the global change in vegetation in different forms. Hunting is one of the most ancient human landscape-shaping activities. Feeders for hunting are particularly disruptive to vegetation. In the present study, we conducted a vegetation survey in these highly disturbed places. We investigated the vegetation dynamics over several years in the turkey oak–sessile oak zone, in two areas with different moisture and shade conditions (forest and clearing). Important background factors are the changes in precipitation and temperature. Our results confirm that weed infestation is detectable at bait sites over a long period. The seasonal changes in field weed vegetation, as well as the increase in the number and coverage of weed species at the end of summer, resulting from lifestyle characteristics, were generally detectable in all years and locations, especially in the case of open and more strongly degraded clearings. Meteorological factors played a role in the degree of weed infestation in each year. Degradation was more significant in drought years, while regeneration was also observed in wetter periods. At baits located in the clearing, we showed a positive correlation between the amount of summer precipitation and the total coverage of weed species, as well as between the average spring temperature and the coverage of certain weed species. With the drying of the climate, the disturbed areas are constantly losing their natural value, but wetter weather is not an automatic solution either. Considering that there are approx. 30,000 bait sites in the country, and they are used regularly and very intensively, they can serve as major infection hotspots for alien species in a network.
Evaluating Human Needs: A Study on the Spatial Justice of Medical Facility Services in Social Housing Communities in Guangzhou
Authors: Chao Ruixia , Xue Desheng , Wang Benshuo
Published: July 2024

Mainstream empirical studies on the spatial justice of medical facilities focus on equal accessibility or resource availability based on population scale, overlooking critiques that emphasize the importance of assessing inequality and the multidimensionality of human needs. However, access to medical care, particularly for vulnerable groups in social housing, often demands a higher level of consideration. Evaluating whether people can access the facilities they demand and expect is crucial for improving living standards. This study categorizes medical facilities into primary healthcare and hospital facilities based on their service grade, and integrates survey-based satisfaction into a spatial analysis of cost–distance-based accessibility and gravity-2SFCA-based availability. Analysis reveals that satisfaction primarily correlates with two factors: the distance to primary healthcare and the ease of reaching hospital facilities. While low accessibility to primary healthcare contributes to the evident distribution injustice of medical resources, satisfaction with service quality and scope is more strongly associated with the ease of reaching hospitals. To reduce injustice in social housing, specific remedies are needed to improve the difficult conditions for accessing primary healthcare faced by communities such as Guangdan, Likang, and Jinshazhou. Moreover, improving the easiness of reaching hospital facilities may significantly enhance the resident satisfaction with the level of medical service provided. Findings obtained in this research may not only enlighten Guangzhou’s urban planning, but may also be noteworthy for developing livable cities, which people anticipated.
A Study on the Current Situation of Public Service Facilities’ Layout from the Perspective of 15-Minute Communities—Taking Chengdu of Sichuan Province as an Example
Authors: Sun Yihua , Luo Shixian
Published: July 2024

With the rapid expansion of cities, the construction of 15-minute communities has become an important way to improve the urban living environment and enhance the quality of life of residents. In this study, based on the perspective of a 15-minute community in Chengdu, the current situation of the spatial layout in the 12 main urban districts of 15,941 public service facility points is studied. Additionally, the matching relationship between the supply and demand of five major categories (19 subcategories) of public service facilities and the population is assessed by using the kernel density analysis method, the Gaussian two-step floating catchment area method, the hierarchical analysis method and the bivariate spatial autocorrelation. Finally, suggestions for the optimization of basic service facilities are made in the light of the current development situation in Chengdu. The results show that (1) there is a large spatial heterogeneity in the distribution and accessibility of public service facilities in the study area; (2) there is a mismatch between the supply and demand of public service facilities and the population in Chengdu; and (3) in order to further optimize the allocation of public service facilities, it is necessary to focus first on areas where demand exceeds supply. This study built a framework for assessing the current status of spatial distribution of public service facilities, which measures the 15-minute accessibility of basic public service facilities in a more comprehensive way and bridges the gap of previous single-type studies, which make it difficult to make comprehensive optimization recommendations directly. Meanwhile, the bivariate spatial autocorrelation reveals the areas of mismatch between supply and demand more accurately, and more clearly shows the areas that need to be focused on for optimization by policy makers.
Improving the Estimation Accuracy of Soil Organic Matter Content Based on the Spectral Reflectance from Soils with Different Grain Sizes
Authors: Subi Xayida , Eziz Mamattursun , Wang Ning
Published: July 2024

Accurate and rapid estimation of soil organic matter (SOM) content is of great significance for advancing precision agriculture. Compared with traditional chemical methods, the hyperspectral estimation is superior in rapidly estimating SOM content. Soil grain size affects soil spectral reflectance, thereby affecting the accuracy of hyperspectral estimation. However, the appropriate soil grain size for the hyperspectral analysis is nearly unknown. This study propose a best hyperspectral estimation method for determining SOM content of farmland soil in the Ibinur Lake Irrigation Area (ILIA) of the northwest arid zones of China. The original spectral reflectance of the 20-mesh (0.85 mm) and 60-mesh (0.25 mm) sieved soil were obtained, and the feature wavebands were selected using five types of spectral transformations. Then, hyperspectral estimation models were constructed based on the partial least squares regression (PLSR), support vector machine (SVM), random forest (RF), and extreme gradient boosting (XGBoost) models. Results show that the SOM content had relatively higher correlation coefficient with spectral reflectance of the 0.85 mm sieved soil than that of the 0.25 mm sieved soil. The transformation of original spectral reflectance of soil effectively enhanced the spectral characteristics related to SOM content. Soil grain size obviously affected spectral reflectance and the accuracy of hyperspectral estimation models. The overall stability and estimation accuracy of RF model was significantly higher compared with the PLSR, SVM, and XGBoost. Finally, the RF model combined with the root mean first-order differentiation (RMSFD) of spectral reflectance of the 0.85 mm sieved soil (R2 = 0.82, RMSE = 2.37, RPD = 2.27) was identified as the best method for estimating SOM content of farmland soil in the ILIA.
Ecological Zoning Management Strategies in China: A Perspective of Ecosystem Services Supply and Demand
Authors: Jiang Xiaoyan , Wang Boyu , Fang Qinhua , Bai Peiyuan , Guo Ting , Wu Qi
Published: July 2024

Ecological zoning management aims to ensure ecological functions and improve environmental quality, serving as an essential means to optimize the development and protection of territorial space. However, comprehensive research on ecological zoning management that combines human needs with natural resources is still relatively scarce. In this study, we selected water yield (WY), food provision (FP), and carbon sequestration (CS) as the critical ecosystem services (ES) in China. An InVEST model, ecosystem services supply–demand index (ESI), random forest (RF), and geographically and temporally weighted regression (GTWR) were used to analyze the spatiotemporal characteristics and influencing factors of ES supply and demand, and the four-quadrant model was used to analyze the spatial matching patterns. The results showed that: (1) from 2005 to 2020, the supply and demand of WY, FP, and CS increased. Among them, WY, FP, and CS supply increased by 16.06%, 34%, and 22.53%, respectively, while demand increased by 5.63%, 12.4%, and 83.02%, respectively; (2) the supply of WY and CS follow a “high in the southeast and low in the northwest” pattern, while all of the demands exhibit a “high in the east and low in the west” pattern; and (3) the average ecosystem service supply–demand index (ESI) values for WY, FP, and CS in China are 0.45, 0.12, and −0.24, respectively, showing an overall upward trend. The study identified three dominant functional zones for WY, FP, and CS, and four classification management zones, including protection zones, conservation zones, improvement zones, and reconstruction zones. These research findings provide a scientific basis for future territorial space planning in China and the application of ecosystem service supply and demand in sustainable development.
Correspondence of Consonant Clustering with Particular Vowels in German Dialects
Authors: Link Samantha
Published: July 2024

Recent work found a correspondence between consonant clustering probability in monosyllabic lexemes and the three vowel types, short and long monophthong and diphthong, in German dialects. Furthermore, that correspondence was found to be bound to a North–South divide. This paper explores the preferences in consonant clustering of particular vowels by analyzing the PhonD2-Corpus, a large database of phonotactic and morphological information. The clustering probability of the diphthongs is positively correlated with frequency while the other vowels showed particular preferences that are not positively correlated with frequency. However, all of them are determined by a threefold pattern: short monophthongs prefer coda clusters, diphthongs onset clusters and long monophthong are balanced. Furthermore, it was found that this threefold pattern seems to have evolved from an originally twofold pattern (short monophthong prefers coda clusters and long monophthong and diphthong prefer onset clusters) in Middle High and Low German. This result is then further considered under the aspect of the compensation of the syllable weight and moraicity. Furthermore, some interesting parallels with the syllable vs. word-language typology framework are noted.
Nozzle Wear in Abrasive Water Jet Based on Numerical Simulation
Authors: Chen Xuhong , Yu Hongji , Pan Haihong , Chen Lin , You Hui , Liang Xubin
Published: July 2024

Particle diameters and jet pressure in abrasive water jet (AWJ) are significant jet properties which deserve a better understanding for improving AWJ machining performance. Some influence factors have been verified regarding nozzle wear in abrasive water jet polishing application. A three-dimensional model of a nozzle is established to analyze the influence of internal multi-phase flow field distribution, which is based on Euler-Lagrange methodology. With the increase of jet pressure, the erosion rate decreases; with the increase of the diameter and mass flow rate of the erosion particles, the erosion speed increases as well. When the diameter of the outlet is worn to 1.6 mm, the pressure on the work piece caused by the abrasive water jet increases by more than double compared to the non-worn nozzle; when the diameter of the nozzle outlet is worn to 1.6 mm, the shear force is 2.5 times higher than the shear force when the diameter is 1.0, which means that the jet force is divergent when the diameter is 1.6 mm, and the damage of the work piece is very serious. The obtained results could improve polishing efficiency on the work piece, extend nozzle lifetimes, and guide the future design of AWJ nozzles.
New Calamitic Mesogens Exhibiting Aggregation-Induced Emission (AIE)
Authors: Paul Saurav , Chakraborty Bimal Bhushan , Rao Nandiraju V. S. , Choudhury Sudip
Published: July 2024

Aggregation-induced emitters or AIEgens are generally signified by their stronger photoluminescence in aggregation than in the solution state. Due to high emission efficiency in aggregate and solid states and good processability, organic AIEgens drew attention to the development of advanced luminescent materials. However, as mesogenic materials self-assemble to a different molecular arrangement in different phases, achieving liquid crystallinity and AIE properties in the same molecule would provide a valuable tool to develop solvent-independent AIEgenic materials. With this goal, the present work reports the synthesis of new organic thermotropic liquid crystalline compounds exhibiting aggregation-induced emission (AIE). The synthesized compounds exhibit strong green luminescence in a solid state which sharply quenches upon entering smectic mesophase by heating. This is in addition to the exhibition of dispersion medium (solvent)-dependent emission, thus providing a dual mode of AIE. The mesogenic property of the synthesized compounds was studied by XRD, POM, and DSC. The AIE was studied by fluorescence spectroscopy and variable temperature fluorescence microscopy. A DFT study was carried out to gain an insight into the AIEgenic behavior of the material.
Design of Locally Resonant Acoustic Metamaterials with Specified Band Gaps Using Multi-Material Topology Optimization
Authors: Chen Hongfang , Fu Yu , Ling Ling , Hu Yujin , Li Li
Published: July 2024

Locally Resonant Acoustic Metamaterials (LRAMs) have significant application potential because they can form subwavelength band gaps. However, most current research does not involve obtaining LRAMs with specified band gaps, even though such LRAMs are significant for practical applications. To address this, we propose a parameterized level-set-based topology optimization method that can use multiple materials to design LRAMs that meet specified frequency constraints. In this method, a simplified band-gap calculation approach based on the homogenization framework is introduced, establishing a restricted subsystem and an unrestricted subsystem to determine band gaps without relying on the Brillouin zone. These subsystems are specifically tailored to model the phenomena involved in band gaps in LRAMs, facilitating the opening of band gaps during optimization. In the multi-material representation model used in this method, each material, except for the matrix material, is depicted using a similar combinatorial formulation of level-set functions. This model reduces direct conversion between materials other than the matrix material, thereby enhancing the band-gap optimization of LRAMs. Two problems are investigated to test the method’s ability to use multiple materials to solve band-gap optimization problems with specified frequency constraints. The first involves maximizing the band-gap width while ensuring it encompasses a specified frequency range, and the second focuses on obtaining light LRAMs with a specified band gap. LRAMs with specified band gaps obtained in three-material or four-material numerical examples demonstrate the effectiveness of the proposed method. The method shows great promise for designing metamaterials to attenuate specified frequency spectra as required, such as mechanical vibrations or environmental noise.
Numerical and Experimental Modal Analysis of a Gyroid Inconel 718 Structure for Stiffness Specification in the Design of Load-Bearing Components
Authors: Monkova Katarina , Braut Sanjin , Monka Peter Pavol , Skoblar Ante , Pollák Martin
Published: July 2024

The study aims to investigate the modal properties of a 60 × 70 × 80 mm gyroid structure made of Inconel 718 with 67.5% porosity. The geometry model for sample production was created using the software PTC Creo, whereas the geometry model for numerical analysis was created using the Python application ScaffoldStructures. FE analysis was performed using ANSYS 2024 R1 software. Free boundary conditions were used in experimental modal analysis to ensure feasibility. The analysis identified the first four natural frequencies ranging from 10 to 16 kHz. The results revealed that the first natural frequency corresponds to the first torsional frequency about the Z axis, the second to the first flexural mode in the XZ plane, the third to the first bending mode in the YZ plane, and the fourth to the first torsional mode about the X axis. Small differences between the results of numerical and experimental modal analysis can be attributed to geometric errors in the manufactured sample, careless removal from the platform, and due to reduction in the complexity of the numerical FE model. Employing modal analysis of a component, the stiffness of a lightweight component can be revealed. In the case of the sample with the cellular structure of gyroid type, relatively high stiffness regarding the material savings was identified, which can be advantageously used in many applications.
Ex Situ Stabilization/Solidification Approaches of Marine Sediments Using Green Cement Admixtures
Authors: Yadav Pravendra , Petrella Andrea , Todaro Francesco , De Gisi Sabino , Vitone Claudia , Petti Rossella , Notarnicola Michele
Published: July 2024

The routine dredging of waterways produces huge volumes of sediments. Handling contaminated dredged sediments poses significant and diverse challenges around the world. In recent years, novel and sustainable ex situ remediation technologies for contaminated sediments have been developed and applied. This review article focuses on cement-based binders in stabilizing contaminants through the stabilization/solidification (S/S) technique and the utilization of contaminated sediments as a resource. Through S/S techniques, heavy metals can be solidified and stabilized in dense and durable solid matrices, reducing their permeability and restricting their release into the environment. Industrial by-products like red mud (RM), soda residue (SR), pulverized fly ash (PFA), and alkaline granulated blast furnace slag (GGBS) can immobilize heavy metal ions such as lead, zinc, cadmium, copper, and chromium by precipitation. However, in a strong alkali environment, certain heavy metal ions might dissolve again. To address this, immobilization in low pH media can be achieved using materials like GGBS, metakaolin (MK), and incinerated sewage sludge ash (ISSA). Additionally, heavy metals can be also immobilized through the formation of silicate gels and ettringites during pozzolanic reactions by mechanisms such as adsorption, ion exchanges, and encapsulation. It is foreseeable that, in the future, the scientific community will increasingly turn towards multidisciplinary studies on novel materials, also after an evaluation of the effects on long-term heavy metal stabilization.
Effects of Fineness and Morphology of Quartz in Siliceous Limestone on the Calcination Process and Quality of Cement Clinker
Authors: Nie Donggen , Li Wei , Xie Lilan , Deng Min , Ding Hao , Liu Kaiwei
Published: July 2024

With the increasing depletion of high-quality raw materials, siliceous limestone, sandstone and other hard-to-burn raw materials containing crystalline SiO2 are gradually being used to produce clinker. This study investigates the influence of the quartz content and particle size in siliceous limestone on the calcination process and the resultant quality of cement clinker. Two different siliceous limestones were grinded to different fineness, and calcinated with some other materials. The content of the clinkers was analyzed with the XRD–Rietveld method and the microstructure of the clinkers was observed with laser scanning confocal microscopy (LSCM) and field emission scanning electron microscopy (FESEM). Three key outcomes of this study provide new insights on the use of siliceous limestone in cement production, namely that (i) reducing the fineness values of siliceous limestone from 15% to 0% of residue on a 0.08 mm sieve decreases the quantity of these larger quartz particles, resulting in an increase in C3S content by up to 8% and an increase in 28d compressive strength by up to 4.4 Mpa, which is 62.30 Mpa; (ii) the morphology of quartz—either as chert nodules or single crystals—affects the microstructure of C2S clusters in clinker, finding that chert nodules result in clusters with more intermediate phases, whereas large single crystals lead to denser clusters; (iii) the sufficient fineness values of siliceous limestone SL1 and SL2 are 5% and 7% of residue on a 0.08 mm sieve, respectively, which can produce a clinker with a 28d compressive strength greater than 60 Mpa, indicating that for different kinds of quartz in siliceous limestone, there is an optimum grinding solution that can achieve a balance between clinker quality and energy consumption without having to grind siliceous limestone to very fine grades.
Correction: Hong et al. Textile-Based Adsorption Sensor via Mixed Solvent Dyeing with Aggregation-Induced Emission Dyes. Materials 2024, 17, 1745
Authors: Hong Seong Gyun , Oh Byeong M. , Kim Jong H. , Lee Jea Uk
Published: July 2024

In the original publication [...]
Investigation of Using Calcined Coal Gangue as the Co-Blended Precursor in the Alkali-Activated Metakaolin
Authors: Pan Ye , Lu Zichen , Zhang Liheng , Zhang Hui , Zhang Qin , Sun Zhenping
Published: July 2024

The feasibility and performance of using calcined coal gangue (CCG) to substitute metakaolin (MK) as the precursor to prepare alkali-activated materials (AAMs) were thoroughly evaluated by conducting combined experiments of flowability test, mechanical measurement, calorimetry and microstructure analysis, etc. It was found that the increased substitution ratio of CCG to MK can increase the flowability of the prepared paste by up to 28.1% and decrease its viscosity by up to 55.8%. In addition, a prolonged setting time of up to 31.8% was found with the increased substitution amount of CCG to MK, which can be attributed to the low reactivity of CCG compared to that of MK. Lastly, even though the presence of CCG can lead to a decrease in the early compressive strength of the hardened paste, a highly recovered long-term mechanical property can be found due to the continuous reaction of CCG. All of these results prove the feasibility of using CCG as one co-blended precursor with MK to prepare alkali-activated materials.
Co-Extraction of Aluminum and Silicon and Kinetics Analysis in Carbochlorination Process of Low-Grade Bauxite
Authors: Zhao Xinxin , Liu Yan , Wang Long , Hua Yutong , Cheng Tianhao , Zhang Tingan , Zhao Qiuyue
Published: July 2024

Addressing the issue that the Bayer process is not suitable for low-grade bauxite, carbochlorination was proposed to recover aluminum and silicon from low-grade bauxite. This study focused on the behavior of aluminum and silicon during the carbochlorination process of low-grade bauxite. The impact of various process parameters on the chlorination efficiency was investigated, and the chlorination mechanism and kinetics of aluminum and silicon chlorination in bauxite were analyzed and discussed. Under optimal experimental conditions, the chlorination efficiency of Al2O3 and SiO2 reached 94.93% and 86.32%, respectively. The carbochlorination of aluminum and silicon in bauxite adhered to a shrinking, unreacted core model governed by gas diffusion within the product layer. This process can be bifurcated into two stages. Additionally, calculations were conducted to determine the apparent activation energy and reaction order of the chlorination processes involving Al2O3 and SiO2. Examining the chlorination mechanism revealed that the bauxite carbochlorination encompasses transformations among various minerals. Notably, the aluminum component prefers to participate in the carbothermal chlorination reaction over silicon.
A Comparative Study on the Wear Performance and High-Temperature Oxidation of Co-Free Cermets and Hardmetals
Authors: Biedma Ángel , Sánchez Gabriel , de Nicolás María , Bertalan Claudio , Useldinger Ralph , Llanes Luis , Gordo Elena
Published: July 2024

The present investigation addresses the mechanical properties, wear behaviour, and high-temperature oxidation of cermets and hardmetals based on either Ti(C,N) or WC and a metal binder based on Fe15Ni or Fe15Ni10Cr. This study also includes a commercial-grade WC-Co for comparative purposes. The production of these materials involved a powder metallurgy and sinter-HIP processing route under identical conditions. It is found that WC-based materials have superior mechanical properties, including hardness, fracture toughness, transversal rupture strength (TRS), and wear response, compared to Ti(C,N)-based materials. However, the latter show better oxidation behaviour than the former. Notably, WC-FeNi exhibits a higher hardness and TRS than the commercial-grade material (an increase of 7% and 9%, respectively). The difference in wear behaviour is due to the difference in wear mechanisms. In this regard, cermets wear through a tribolayer of Ti and Fe oxides, while hardmetals primarily wear through abrasion from ploughing. Thus, hardmetals exhibit a lower coefficient of friction (COF) and wear rate than cermets. Furthermore, Ti(C,N)-based materials form a protective layer of TiO2, which enhances their integrity and reduces mass gain. The addition of Cr to the FeNi binder only appears to have a clear effect on the TRS of the materials.
Experimental Study on the Effect of Polycarboxylate Superplasticizer on the Performance of Cement-Based Grouting Materials
Authors: Yu Zhijie , Liu Shujie , Zhang Jiwei , He Wen , Tian Qinghao , Tian Le , Sun Jinze
Published: July 2024

Polycarboxylate superplasticizers BMC-L and BMC-S were utilized as modifiers in the formulation of novel cement-based grouting materials. Indoor tests were conducted on 32 groups of cement slurries, varying by water–cement ratio (0.5:1 and 0.6:1) and modifier content (0, 2‰, 4‰, 6‰, 8‰, 10‰, 12‰, and 14‰), to test their density, funnel viscosity, water separation rate, and stone rate. Four groups of slurry modified with BMC-L were selected as the preferred slurry, and the apparent viscosity test, uniaxial, and triaxial compression test of the slurry stone body were conducted. The study investigated the influence of BMC-L on various properties of the slurry, including its apparent viscosity, uniaxial compressive strength, stress–strain relationships, shear strength parameters, and elastic modulus. Ultimately, the pore structure and phase composition of the slurry stone body were detected by Nuclear Magnetic Resonance (NMR) and X-ray Diffraction (XRD), and the impact of BMC-L on slurry performance was examined from a microstructural perspective. Results indicate that the two polycarboxylate superplasticizers exert minimal influence on the density and water separation rate of the slurry. Within the effective incorporation range of the polycarboxylate superplasticizer, increasing the dosage correlates with a decrease in both the stone rate and viscosity of the slurry. BMC-L significantly enhances the mechanical properties of the slurry stone body by promoting more complete cement hydration and reducing porosity. The uniaxial compressive strength of slurry stone body with a 6 ‰ BMC-L dosage reached 29.7 MPa after 7 days and 38.5 MPa after 28 days of curing, representing increases of 118.4% and 64%, respectively, compared to masonry with 0 BMC-L dosage. The shear strength parameters and elastic modulus of the slurry stone body also showed corresponding increases.
Polarization-Accelerated Seawater Splash Simulation for Rapid Evaluation of Protection Performance of an Epoxy Coating on Carbon Steel
Authors: Xu Yuqing , Song Guangling , Zheng Dajiang , Liu Changsheng , Han Enhou
Published: July 2024

The application of organic coatings is the most cost-effective and common method for metallic equipment toward corrosion, whose anti-corrosion property needs to be improved and evaluated in a short time. To rapidly and rationally assess the anti-corrosion property of organic coatings in the ocean splash zone, a new accelerated test was proposed. In the study, the corrosion protection property of the coating samples was measured by an improved AC-DC-AC test in a simulated seawater of 3.5 wt.% NaCl solution, a simulated ocean splash zone test and a new accelerated test combining the above two tests. The results showed that the corrosion rate of the coating samples was high in the improved AC-DC-AC test, which lost its anti-corrosion property after 24 cycles equal to 96 h. The main rapid failure reason was that the time of the water and corrosive media arriving at the carbon steel substrate under the alternating cathodic and anodic polarization with symmetrical positive and negative electric charges was shortened. The entire impedance of the coating samples was improved by about 1.6 times more than that in the initial early time in the simulated ocean splash zone test, which was caused by the damage effect from the salt spraying, drying, humidifying, salt immersion, high temperature and UVA irradiation being weaker than the enhancement effect from the post-curing process by the UVA irradiation. In the new accelerated test, the samples lost their corrosion resistance after 12 cycles equal to 288 h with the fastest failure rate. On account of the coupling process of the salt spraying, drying, humidifying, salt immersion, high temperature combined with the cathodic and anodic polarization and the UVA irradiation, the penetration and transmission rate of water and corrosive media in the coating were further accelerated, the corrosion rate on the carbon steel substrate was reinforced even larger and the destruction of the top polymer molecules was more serious. The new accelerated test showed the strongest damage-acceleration effect than that in the other two tests.
Improved Energy Density at High Temperatures of FPE Dielectrics by Extreme Low Loading of CQDs
Authors: Wang Huan , Luo Hang , Liu Yuan , Wang Fan , Peng Bo , Li Xiaona , Hu Deng , He Guanghu , Zhang Dou
Published: July 2024

Electrostatic capacitors, with the advantages of high-power density, fast charging–discharging, and outstanding cyclic stability, have become important energy storage devices for modern power electronics. However, the insulation performance of the dielectrics in capacitors will significantly deteriorate under the conditions of high temperatures and electric fields, resulting in limited capacitive performance. In this paper, we report a method to improve the high-temperature energy storage performance of a polymer dielectric for capacitors by incorporating an extremely low loading of 0.5 wt% carbon quantum dots (CQDs) into a fluorene polyester (FPE) polymer. CQDs possess a high electron affinity energy, enabling them to capture migrating carriers and exhibit a unique Coulomb-blocking effect to scatter electrons, thereby restricting electron migration. As a result, the breakdown strength and energy storage properties of the CQD/FPE nanocomposites are significantly enhanced. For instance, the energy density of 0.5 wt% CQD/FPE nanocomposites at room temperature, with an efficiency (η) exceeding 90%, reached 9.6 J/cm3. At the discharge energy density of 0.5 wt%, the CQD/FPE nanocomposites remained at 4.53 J/cm3 with an efficiency (η) exceeding 90% at 150 °C, which surpasses lots of reported results.
Prediction and Dynamic Simulation Verification of Output Characteristics of Radial Piston Motors Based on Neural Networks
Authors: Li Chunjin , Xia Zhengwen , Tang Yongjie
Published: July 2024

Radial piston motors are executive components in hydraulic systems, tasked with providing appropriate torque and speed according to load requirements in practical applications. The purpose of this study is to predict the output torque of radial piston hydraulic motors and confirm their suitable operating conditions. Efficiency determination experiments were conducted on physical models, yielding thirty sets of performance data. Torque (output torque) and mechanical efficiency from the experimental data were selected as prediction targets and fitted using two methods: multiple linear regression and neural networks. A dynamic simulation model was built using Adams2020 software to obtain theoretical torque values, enabling the verification of the alignment between the predicted values and simulation results. The results indicate that the error between the theoretical torque of the dynamic model and the physical experiments is 1.9%, with the error of the neural network predictions being within 2%. The dynamic simulation model can yield highly accurate theoretical torque values, providing a reference for the external load of hydraulic motors; additionally, neural networks offer accurate predictions of output torque, thus reducing experimental testing costs.