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  • MDPI AG  (124)
  • 11
    In: Processes, MDPI AG, Vol. 10, No. 6 ( 2022-06-12), p. 1179-
    Abstract: The S reservoir in the X Oilfield in Iraq has great development potential due to its rich geological reserves. However, the low permeability and strong heterogeneity of the reservoir lead to great differences in reservoir stimulation performance. In this study, an integrated reservoir model and differential stimulation mode are put forward to solve the above problems. First, the feasibility of fracturing is evaluated by laboratory experiments. Second, an integrated reservoir model is established, which mainly includes a rock mechanics model, fracturing simulation model, and numerical simulation model, and correct the integrated model by fracturing operation curves and production dynamic curves. Third, three types of stimulation areas are classified according to the combination of sweet spot types, and three different stimulation modes are proposed. In conclusion, a small-scale stimulation mode should be applied in the Type I area to maximize economic benefits. In the Type II area, the medium-scale stimulation mode should be performed to ensure certain productivity while achieving certain economic benefits. In the Type III area, the large-scale stimulation mode should be employed to obtain certain productivity while economic benefits must be above a limit. The differential stimulation model proposed in this paper has made a great reference for the efficient development of low-permeability carbonate rocks.
    Type of Medium: Online Resource
    ISSN: 2227-9717
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2720994-5
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  • 12
    In: Energies, MDPI AG, Vol. 16, No. 17 ( 2023-08-30), p. 6307-
    Abstract: Converter blocking is a serious malfunction encountered in high voltage direct current (HVDC) transmission systems. During sending-end converter blocking, the resultant active power and reactive power surplus in the sending-end power system lead to a severe increase in bus voltage and grid frequency. Consequently, this poses a substantial threat to the stability of the power system. Traditional control techniques generally control the frequency and voltage separately, which makes it challenging to regulate them jointly. This research paper introduces a collaborative approach for optimal control of voltage and frequency to address this issue. State space models for converter bus voltage and grid frequency prediction are developed using the bus voltage sensitivity matrices and system swing equation. The regulation of the converter bus voltage and grid frequency are intrinsically integrated using the explicit model predictive control (EMPC). When blocking occurs and results in an increase in the converter bus voltage and grid frequency, the EMPC controller regulates the output of active power and reactive power from the wind farm to realize the cooperative regulation of the converter bus voltage and grid frequency. The applicability and effectiveness of this strategy have been confirmed through simulation studies.
    Type of Medium: Online Resource
    ISSN: 1996-1073
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2437446-5
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  • 13
    In: Symmetry, MDPI AG, Vol. 14, No. 1 ( 2022-01-08), p. 107-
    Abstract: Rigid-flexible composite pouch piles with expanded bottom (RFCPPEB) are generally considered as new symmetrical piles in practical engineering, but their bearing characteristics and design method are still not completely understood. The objective of this study is to investigate the vertical bearing performance and the optimal design scheme of RFCPPEB. Hence, laboratory modeling tests for this symmetric structure and an ABAQUS three-dimensional (3D) numerical simulation analysis were used to study the vertical bearing characteristics on bottom-expanded piles and rigid-flexible composite piles with expanded bottom. The vertical bearing capacity, shaft resistance, pile tip resistance distribution rule, and load sharing ratio of RFCPPEB were analyzed and verified using different bottom expansion dimensions and cemented soil thicknesses. The results revealed that the optimal bottom expansion ratio of rigid bottom-expanded piles was 1.8 when the ratio of pile body to bottom-expanded pile head was 9:1. When the bottom expansion ratio (D/d) was increased, the bearing capacity of bottom-expanded piles was significantly increased at D/d = 1.4 and D/d = 1.8 compared to that of D/d = 1.0, reaching 1.67 and 2.29 times, respectively, while for D/d = 1.6 and D/d = 2.0, the ultimate bearing capacity remained unchanged. Besides, shaft resistance played an important role in the bearing process of the rigid bottom-expanded piles and RFCPPEB. When the shaft resistance was increased, the ultimate bearing capacity of the pile foundation was significantly improved. The shaft resistance of RFCPPEB was increased with increasing cemented soil thickness. The increases in the shaft resistance and thickness of the cemented soil showed a nonlinear growth, and the maximum shaft resistance was approximately 75 cm from the pile top. When the diameter of the expanded head was 1.8 times the diameter of the pipe pile and slightly larger than the thickness of the cemented soil (0.5 times the diameter of the pipe pile), the optimal amount of concrete 425.5 kN/m3 required for per unit volume around piles was obtained, with the RFCPPEB ultimate bearing capacity of 7.5 kN. For RFCPPEB, the soil pressure at the pile tip was directly proportional to the pile top load under small load and was decreased in the form of a half quadric curve under large load. It reached the most reasonable position where the slope of the quadric curve was the largest when the thickness of the cemented soil was larger than 0.5 times the diameter of the pipe pile.
    Type of Medium: Online Resource
    ISSN: 2073-8994
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2518382-5
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  • 14
    In: Sustainability, MDPI AG, Vol. 14, No. 10 ( 2022-05-19), p. 6195-
    Abstract: Rural revitalization places higher demands on the productive–living–ecological (P-L-E) spaces of towns and cities. It is necessary, therefore, to identify, evaluate, and optimize P-L-E spaces to better guide spatial planning. Existing studies typically evaluate a single space, lacking a comprehensive consideration of whole-area integration. This study, therefore, developed a coupled spatial/developmental suitability evaluation system for Feixi County, Anhui Province, China, combining spatial quality evaluation, a coupled coordination model, and future land-use simulation (FLUS) model. The spatial quality of Feixi County in 2010, 2015, and 2020 was obtained by applying the evaluation system to the spatial development pattern. The results were analyzed and verified using the landscape pattern index and development suitability evaluation. The results showed the following: (1) The coupling coordination degree of the region increased from 0.131 to 0.372, changing from low to moderate coordination. (2) Based on the FLUS model to better capture the uncertainty and stochastic basis of the development in the study area. The kappa coefficient and Figure of Merit (FoM) index of the land-use simulation accuracy verification index were 0.7647 and 0.0508, respectively, and the logistic regression ROC values were above 0.75, thus meeting accuracy requirements. This demonstrated that the simulation model—based on a factor library of the evaluation of resource and environmental carrying capacity and suitability for development and construction—could better reflect future land-use changes. (3) The simulation showed that under the baseline development scenario, the area’s spatial layout is too concentrated in terms of construction land, ignoring P-L-E coordination. Under the ecological optimization scenario, high-quality ecological space is ensured, but other types of spaces are lacking. Under the comprehensive guidance scenario, lagging ecological space is optimized and P-L-E spatial development is enhanced through aggregation, clustering, concentration and integration. This way, the spatial quantity structure and distribution form can meet P-L-E spatial development needs in Feixi County. In this study, on the basis of scientific assessment of the current P-L-E space, the FLUS model was applied to carry out a scenario simulation according to different objectives. Moreover, based on the construction of the coupling system of human–nature system, the driving factors were improved to enhance the prediction accuracy of the FLUS model. This study’s findings can help improve the scientificity, flexibility and management efficiency of Feixi County’s P-L-E spatial layout, thereby supporting its sustainable development.
    Type of Medium: Online Resource
    ISSN: 2071-1050
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2518383-7
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  • 15
    In: Remote Sensing, MDPI AG, Vol. 13, No. 22 ( 2021-11-20), p. 4694-
    Abstract: Landslides pose a constant threat to the lives and property of mountain people and may also cause geomorphological destruction such as soil and water loss, vegetation destruction, and land cover change. Landslide susceptibility assessment (LSA) is a key component of landslide risk evaluation. There are many related studies, but few analyses and comparisons of models for optimization. This paper aims to introduce the Tree-structured Parzen Estimator (TPE) algorithm for hyperparameter optimization of three typical neural network models for LSA in Shuicheng County, China, as an example, and to compare the differences of predictive ability among the models in order to achieve higher application performance. First, 17 influencing factors of landslide multiple data sources were selected for spatial prediction, hybrid ensemble oversampling and undersampling techniques were used to address the imbalanced sample and small sample size problem, and the samples were randomly divided into a training set and validation set. Second, deep neural network (DNN), recurrent neural network (RNN), and convolutional neural network (CNN) models were adopted to predict the regional landslides susceptibility, and the TPE algorithm was used to optimize the hyperparameters respectively to improve the assessment capacity. Finally, to compare the differences and optimization effects of these models, several objective measures were applied for validation. The results show that the high-susceptibility regions mostly distributed in bands along fault zones, where the lithology is mostly claystone, sandstone, and basalt. The DNN, RNN, and CNN models all perform well in LSA, especially the RNN model. The TPE optimization significantly improves the accuracy of the DNN and CNN (3.92% and 1.52%, respectively), but does not improve the performance of the RNN. In summary, our proposed RNN model and TPE-optimized DNN and CNN model have robust predictive capability for landslide susceptibility in the study area and can also be applied to other areas containing similar geological conditions.
    Type of Medium: Online Resource
    ISSN: 2072-4292
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2513863-7
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  • 16
    In: Polymers, MDPI AG, Vol. 15, No. 18 ( 2023-09-11), p. 3727-
    Abstract: Polyethylene oxide (PEO)-based solid-state electrolytes for lithium-ion batteries have garnered significant interest due to their enhanced potential window, high energy density, and improved safety features. However, the issues such as low ionic conductivity at ambient temperature, substantial ionic conductivity fluctuations with temperature changes, and inadequate electrolyte interfacial compatibility hinder their widespread applications. Electrospinning is a popular approach for fabricating solid-state electrolytes owing to its superior advantages of adjustable component constitution and the unique internal fiber structure of the resultant electrolytes. Thus, this technique has been extensively adopted in related studies. This review provides an overview of recent advancements in optimizing the performance of PEO solid-state electrolytes via electrospinning technology. Initially, the impacts of different lithium salts and their concentrations on the performance of electrospun PEO-based solid-state electrolytes were compared. Subsequently, research pertaining to the effects of various additives on these electrolytes was reviewed. Furthermore, investigations concerning the enhancement of electrospun solid-state electrolytes via modifications of PEO molecular chains are herein detailed, and lastly, the prevalent challenges and future directions of PEO-based solid-state electrolytes for lithium-ion batteries are summarized.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2527146-5
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  • 17
    In: Veterinary Sciences, MDPI AG, Vol. 10, No. 7 ( 2023-06-25), p. 413-
    Abstract: In this study, we reported the isolation, identification, and molecular characteristics of nine BVDV strains that were isolated from the serum of persistently infected cattle. The new strains were designated as BVDV TJ2101, TJ2102, TJ2103, TJ2104, TJ2105, TJ2106, TJ2107, TJ2108 and TJ2109. The TJ2102 and TJ2104 strains were found to be cytopathic BVDV, and the other strains were non-cytopathic BVDV. An alignment and phylogenetic analysis showed that the new isolates share 92.2–96.3% homology with the CP7 strain and, thus, were classified as the BVDV-1b subgenotype. A recombination analysis of the genome sequences showed that the new strains could be recombined by the major parent BVDV-1a NADL strain and the minor parent BVDV-1m SD-15 strain. Some genome variations or unique amino acid mutations were found in 5′-UTR, E0 and E2 of these new isolates. In addition, a potential linear B cell epitopes prediction showed that the potential linear B cell epitope at positions 56–61 is highly variable in BVDV-1b. In conclusion, the present study has identified nine strains of BVDV from persistently infected cattle in China. Further studies on the virulence and pathogenesis of these new strains are recommended.
    Type of Medium: Online Resource
    ISSN: 2306-7381
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2768971-2
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  • 18
    In: Coatings, MDPI AG, Vol. 12, No. 6 ( 2022-06-01), p. 762-
    Abstract: As a key core component of cotton pickers, the spindle is prone to wear of the hook teeth. This research explores the wear characteristics of the spindle hook teeth of cotton pickers under different working areas. The sampled spindles were cut, the element composition and hardness of the spindle hook tooth coating and substrate were determined, the surface morphology of the spindle hook tooth was characterized, and its wear area and coating thickness were extracted. Results show that the main constituent elements of the coating and substrate are Cr and Fe, respectively, the hardness of the coating is about 1020 HV0.1, and the hardness of the substrate is 470~840 HV0.1. During the field operation, scratches appeared on the surface of the coating, the coating thickness layer gradually decreased, and the coating peeled off as the operating area increased. Afterward, scratches and oxidized particles appeared on the surface of the substrate, the wear rate accelerated, and the wear area gradually increased. The wear of the spindle hook teeth started to appear from the front and rear tooth tips up to the tooth edge, the back of the tooth, and the doffering edge, hence forming a long boot-shaped wear area.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2662314-6
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  • 19
    Online Resource
    Online Resource
    MDPI AG ; 2022
    In:  Agronomy Vol. 12, No. 6 ( 2022-06-10), p. 1399-
    In: Agronomy, MDPI AG, Vol. 12, No. 6 ( 2022-06-10), p. 1399-
    Abstract: Water ionization is an efficient physical water treatment technology, and crop water and nutrient use efficiencies can be improved using ionized water for irrigation. In order to explore the effect of ionized water on soil nitrification and nitrifying microorganisms, we conducted a laboratory soil incubation experiment with the addition of ionized water and ordinary water under different soil water contents (equal to 30%, 60%, 100% and 175% of the field capacity, θFC). During the soil incubation, we analyzed soil inorganic nitrogen transformation, ammonia oxidation gene abundances and nitrifying microbial community structure. The results showed that, no matter adding ordinary water or ionized water, the soil nitrification rate and the abundance of ammonia oxidizing bacteria in the 100%θFC treatment were significantly higher than those in other water conditions, while the abundance of ammonia oxidizing archaea was not affected by the soil water content. With the same soil water content, the nitrification rate of ionized water treatment was stronger than that of the ordinary water treatment. Although the absolute abundance of ammonia-oxidizing microorganisms in ionized water treatment was significantly lower than that of ordinary water (p 〈 0.05), the relative abundance of some dominant nitrifying microbial genera in the ionized water treatment was significantly higher (p 〈 0.05). The dominant genera may play a key role in the nitrification process. The results show that ionized water irrigation can significantly promote the nitrification of silt loam soil, especially under 100%θFC conditions, and may regulate soil nitrification by affecting some dominant nitrifying microorganisms. This study provides a theoretical basis for understanding the biological regulation mechanism of ionized water irrigation on soil nutrient transformation and for application of ionized water to field irrigation.
    Type of Medium: Online Resource
    ISSN: 2073-4395
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2607043-1
    SSG: 23
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  • 20
    In: Cells, MDPI AG, Vol. 11, No. 2 ( 2022-01-14), p. 277-
    Abstract: Chimeric RNAs (chiRNAs) play many previously unrecognized roles in different diseases including cancer. They can not only be used as biomarkers for diagnosis and prognosis of various diseases but also serve as potential therapeutic targets. In order to better understand the roles of chiRNAs in pathogenesis, we inserted human sequences into mouse genome and established a knockin mouse model of the tamoxifen-inducible expression of ASTN2-PAPPA antisense chimeric RNA (A-PaschiRNA). Mice carrying the A-PaschiRNA knockin gene do not display any apparent abnormalities in growth, fertility, histological, hematopoietic, and biochemical indices. Using this model, we dissected the role of A-PaschiRNA in chemical carcinogen 4-nitroquinoline 1-oxide (4NQO)-induced carcinogenesis of esophageal squamous cell carcinoma (ESCC). To our knowledge, we are the first to generate a chiRNA knockin mouse model using the Cre-loxP system. The model could be used to explore the roles of chiRNA in pathogenesis and potential targeted therapies.
    Type of Medium: Online Resource
    ISSN: 2073-4409
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2661518-6
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