bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and fracture characterization of the Jizan group: Implications for subsurface CO2 basalt mineralization
Authors: Fedorik Jakub , Delaunay Antoine , Losi Giacomo , Panara Yuri , Menegoni Niccolo , Afifi Abdulkader M. , Arkadakskiy Serguey , Al Malallah Murtadha , Oelkers Eric , Gislason Sigurður R. , Ahmed Zeyad , Kunnummal Noushad
Published: January 2023

The coastal region of southwest Saudi Arabia contains a thick sequence of Late Oligocene basalts in the Jizan Group, which accumulated along the continental rift that preceded the opening of the Red Sea. These basalts are targeted for the disposal of CO2 emitted from industrial sources by subsurface carbon mineralization processes. The disposal potential of the Jizan Group basalts depends on having adequate permeability along fracture networks capable of conducting injected fluids away from the wellbores. The basalts in the Jizan Group generally lack primary permeability due to hydrothermal alteration, but are cross-cut by a dense network of fractures. In this paper, we describe and interpret the structural geology of the area based on field and geophysical data, and characterize the fracture development in the Jizan Group. The Jizan Group in the area comprises a bimodal suite of 30–21 Ma volcanic and volcaniclastic rocks and lacustrine sediments that accumulated in a continental rift valley similar to the East African rift. It consists predominantly of basaltic lavas that were fed by dense swarms of sheeted basalt dikes intruded parallel to the rift axis. Structurally the area is composed of half grabens bounded from the west by antithetic normal faults, and from the east by a megaflexure. Fractures in the Jizan Group were characterized by ground and aerial digital photogrammetry of outcrops. Mean P21 fracture intensities from 12 scattered meter scale outcrops are in the range 5–54 m−1, which demonstrates that the Jizan Group is highly fractured. Fracture directions are multimodal. The dominant fracture trend is 140–160 N, which is parallel to the sheeted dike swarms and normal faults, and therefore parallel to the paleo-rift axis. Additional conjugate and orthogonal fracture sets are also recognized. The presence of pervasive fracture-based permeability in the Jizan Group will facilitate the injection and mineral carbonation of carbon dioxide in the mafic volcanic rocks in this region.
Tephrostratigraphy of Pleistocene-Holocene deposits from the Detroit Rise eastern slope (northwestern Pacific)
Authors: Derkachev Alexander , Gorbarenko Sergey , Portnyagin Maxim , Zhong Yi , Nikolaeva Nataliya , Shi Xuefa , Liu Yanguang
Published: January 2023

The main goal of the study is to establish the spatial and temporal distribution of pyroclastic material from large explosive eruptions of the volcanoes of Kamchatka, the Kuril, and Aleutian Islands to create a generalized tephrochronological model and reveal patterns of explosive activity in this region. This paper presents new data on the composition of volcanic ash (tephra) found in the Pleistocene deposits of the northwestern Pacific from the eastern slope of the Detroit Rise (northwestern part of the Imperial Ridge), 450–550 km east of the Kamchatka Peninsula. Eleven layers and lenses of tephra aged from 28 to 245 ka, which were previously unknown, were studied in the core Lv63-4-2. Their stratigraphic position and age were determined based on age models developed in this study. Based on the geochemical composition of volcanic glass (determined using an electron microprobe), seven layers were correlated with tephra from several cores in the northwestern Pacific and the Bering Sea. The obtained results supplement the information on large explosive eruptions of volcanoes in the region and their periods of activity. They also allow the development of a generalized tephrochronological model of Quaternary deposits, which is necessary for stratigraphic correlation, and of paleooceanological and paleogeographic reconstructions.
Experimental study on normal deformation characteristics of filled rock joints with typical fluctuation morphology
Authors: Luo Zhanyou , Zheng Wei , Du Shigui , Huang Man , Wang Changshuo
Published: January 2023

The uneven deformation of filled rock joints subjected to ground stress can easily cause instability in engineering rock masses. Fluctuations in morphology and filling are the main factors affecting the normal deformation of filled rock joints. To study the effect of the degree of filling and the degree of morphology fluctuation on the normal deformation of filled rock joints, we conducted a systematic experimental study. First, rock joints with joint roughness coefficients of 1,5, 9, 13, and 17 were selected based on Barton’s typical curves. Then, filled rock joint samples were made using a self-developed filled rock joint sample mold and three-dimensional engraving technology. Lastly, compression tests were carried out to analyze the effect of the degree of filling and the degree of morphology fluctuation on the normal deformation characteristics of filled rock joints. The results show that the degree of filling significantly affects the normal deformation of filled rock joint samples. The normal deformation of filled rock joints has a nonlinear relationship with normal stress. The power function equation can well represent the normal closure deformation behavior of filled rock joints. Additionally, a relationship between the maximum closure deformation of filled rock joints and the degree of filling was established based on Bandis’s empirical formula. The proposed equation takes into account the effect of the degree of filling by replacing the rock joint opening with filling thickness, and the predicted values are in good agreement with the experimental results.
The effect of CRD method and auxiliary construction on surface settlement in shallow-buried tunnels
Authors: Zhang Lin , Pan Yuangui , Chen Kezhu , Zheng Guoqiang , Gao Yang , Chen Peng , Zhong Guoxiang , Chen Panfeng , Xu Fengshou , Zhang Yong , Nan Guangyu , Xue Haobo , Wang Tingshuai , Zhao Peng , Lu Feng
Published: January 2023

Several engineering practices have shown that the excavation of shallow-buried tunnels beneath major roads, as well as the selection of appropriate engineering measures and construction methods, has a significant impact on road surface settlement. Therefore, field monitoring and numerical simulation are adopted in this study to analyze the effect of the cross diaphragm (CRD) excavation method on surface settlement for the under-construction Yüan 1 railroad tunnel. The findings show that during the excavation of the four divisions of the CRD excavation method for shallow-buried tunnels, the amount of surface settlement caused by the excavation of part 1 accounts for 40% of the total surface settlement, followed by the excavation of part 3, accounting for 30% of the total surface settlement, and the difference between the excavation of parts 2 and 4 is insignificant, with part 2 slightly larger than part 4. The main influence of the CRD method on surface settlement for shallow-buried tunnels is 0.64–0.86 times the cavity diameter from the tunnel median, within which the final surface settlement caused by excavation is within the same horizontal range, and beyond which the surface settlement is prone to dramatically decline. By applying advanced grouting and adjusting the construction method of CRD based on the monitoring data, the effect of the CRD excavation method on surface settlement can be controlled.
Perceived control decisions in preparation for a summative achievement test in higher education
Authors: van der Linden Jeroen , van Schilt-Mol Tamara , Nieuwenhuis Loek , van der Vleuten Cees
Published: January 2023

Most courses in higher education finish with one or more assessments which commonly all have to be passed. In these courses, student learning is commonly measured using conventional classroom tests, therefore test preparation is a common task for students. In higher education, compared with students’ prior education, they are faced with a more complex curriculum and have to perform their studies with less guidance and limited resources. Therefore, effective and efficient test preparation is important. A strategy to help students study effectively in the context of test preparation is to make the appropriate control decisions, for instance to cease test preparation on specific content and (re) study other subjects that need attention. These control decisions are an important psychological aspect of the test preparation study process. We conducted a qualitative study on how students made control decisions in a test preparation period for a knowledge test in Educational Sciences. The study was conducted with students of a teacher training program at a University of Applied Sciences in the Netherlands. Results show that different progressions of learning judgments and the self-efficacy of students led to two different saturations. This in turn led to students making either no, inaccurate, or accurate control decisions. This article discusses the impact and practical implications of these insights.
Student evaluation of teacher digitals skills at Granada University
Authors: Alonso-García Santiago , Victoria-Maldonado Juan José , García-Sempere Pablo José , Lara-Lara Fernando
Published: January 2023

The following study is a descriptive/correlational analysis of students’ perception of digital competence in teaching. It is based on the current needs of university students with regard to the digitization of teaching and learning processes. Knowing student satisfaction with teaching digital skills could be used to propose improvements in the quality of university education to the extent that it can channel the various socio-economic demands. The European Higher Education Area is not oblivious to this problem by creating a framework of ambitious objectives for member states where ICT and digital competence of teachers are a priority. The research is carried out at the University of Granada and takes as a reference the framework: Marco Común de Competencia Digital Docente. This Framework in the context of Spain is concerned with indicating which areas educators need to acquire a skill higher degree differentiating between the following levels of classification: basic, intermediate and advanced. A quantitative correlational study was carried out, and an online questionnaire/form was distributed to a random probability sample of 307 students at the University of Granada belonging to different faculties of education. According to the results obtained, the students unanimously share the opinion that, the lecturers at Granada University do not possess a sufficient level of experience or training to competently deliver course content in a purely digital format.
Positioning responsible learning analytics in the context of STEM identities of under-served students
Authors: Grimm Adrian , Steegh Anneke , Çolakoğlu Jasmin , Kubsch Marcus , Neumann Knut
Published: January 2023

Addressing 21st century challenges, professionals competent in science, technology, engineering, and mathematics (STEM) will be indispensable. A stronger individualisation of STEM learning environments is commonly considered a means to help more students develop the envisioned level of competence. However, research suggests that career aspirations are not only dependent on competence but also on STEM identity development. STEM identity development is relevant for all students, but particularly relevant for already under-served students. Focusing solely on the development of competence in the individualisation of STEM learning environments is not only harming the goal of educating enough professionals competent in STEM, but may also create further discrimination against those students already under-served in STEM education. One contemporary approach for individualisation of learning environments is learning analytics. Learning analytics are known to come with the threat of the reproduction of historically grown inequalities. In the research field, responsible learning analytics were introduced to navigate between potentials and threats. In this paper, we propose a theoretical framework that expands responsible learning analytics by the context of STEM identity development with a focus on under-served students. We discuss two major issues and deduce six suppositions aimed at guiding the use of as well as future research on the use of learning analytics in STEM education. Our work can inform political decision making on how to regulate learning analytics in STEM education to help providing a fair chance for the development of STEM identities for all students.
Incident factors in Andalusian university dropout: A qualitative approach from the perspective of higher education students
Authors: Santos-Villalba María Jesús , Alcalá del Olmo Fernández María José , Montenegro Rueda Marta , Fernández Cerero José
Published: January 2023

University dropout is currently one of the main challenges faced by government bodies and state and regional universities. Both personal and institutional reasons can be identified as root causes of university dropout. On a personal level, students accumulate experiences of academic failure that lead them to reflect on the possibility of continuing their studies, while from an institutional point of view, failure can be attributed to educational deficits, reputation, and quality parameters of the university institution itself. Even though more and more universities have educational policies aimed at reducing dropout rates, the dropout figures continue to rise, which shows that this is a complex problem due to the number of variables involved. The main objective of this study is to analyze the factors that influence university dropout among Andalusian students. The methodology is qualitative through a focus group with the participation of 12 students who dropped out of their academic studies in education science degrees at the University of Malaga (Spain). The study population corresponds to students who formalized their enrollment in the first year of the degree in the 2021/22 academic year. The content analysis followed a deductive category development model. The results reveal that the factors that explain the educational abandonment of the students, who are the object of this research, are identification with studies that did not meet their initial expectations, the use of traditionalist methodologies, the development of work activity, and the economic difficulties in covering the costs derived from university education. The main conclusion include the importance of designing educational policies in line with the reality and needs of the students, the use of innovative methodologies that increase the degree of motivation of the students, as well as studying dropouts from a holistic perspective, considering the multiple variables that influence its origin.
Program support matters: A systematic review on teacher- and school related contextual factors facilitating the implementation of social-emotional learning programs
Authors: Ulla Triin , Poom-Valickis Katrin
Published: January 2023

School- and teacher-related contextual factors are those that often influence the quality of social-emotional learning (SEL) program implementation, which in turn has an impact on student outcomes. The current paper was interested in (1) Which teacher- and school-related contextual factors have been operationalized in articles that focus on the relationship between implementation quality indicators 200 and contextual factors in SEL program implementation in schools? (2) Which contextual factors would demonstrate the highest frequency of statistically significant relationships with SEL program implementation quality indicators and could therefore be more essential for ensuring the program outcomes? Determining the more significant contextual factors would allow for more focused and better-informed teacher professional development for supporting students’ social and emotional skills, it can also be useful for hypothesis development for quasi- experimental research designs of SEL program implementation on the school level. A systematic literature search was conducted in seven electronic databases and resulted in an initial sample of 1,281 records and additional journal and citation sampling of 19 additional records. 20 articles met the final inclusion criteria for the study (19 quantitative and one mixed methods). Inductive content analysis and quantitative analysis were employed to map the variables and estimate the relative frequency of statistically significant relationships across studies. Four categories of contextual factors were revealed: program support, school, teacher, and student categories. The results of the study reveal the diversity in contextual factors studied across SEL program implantation quality and bolster the relevance of program support factors (modeling activities during coaching and teacher–coach working relationship) for ensuring implementation quality. A link between teacher burnout and program dosage was revealed. Student factors emerged as a separate contextual level in school, with special attention to student baseline self-regulation that may influence SEL program implementation quality.
Promoting the construction of intelligent knowledge with the help of various methods of cognitively activating instruction
Authors: Schumacher Ralph , Stern Elsbeth
Published: January 2023

How can we promote the construction of intelligent knowledge that facilitates the transfer of knowledge to new situations? This article gives an overview of the current state of empirical research on methods of cognitively activating teaching that promote conceptual change and flexible application of knowledge in new situations. “Cognitively activating” means that these methods promote the active construction of knowledge by facilitating a better understanding of the problem at hand, by activating relevant prior knowledge, and by fostering a better awareness of the limits of one’s own knowledge. Six methods that have each proven successful in boosting learners’ conceptual understanding in experimental studies are presented in this article.
Calcitriol-enhanced autophagy in gingival epithelium attenuates periodontal inflammation in rats with type 2 diabetes mellitus
Authors: Wang Yanan , Huang Maoting , Xu Wanlin , Li Fulong , Ma Chunliang , Tang Xiaolin
Published: January 2023

Type 2 diabetes mellitus (T2DM)-associated periodontitis is a common disease with high prevalence, associated with persistent infection and complicated manifestations. Calcitriol (1 alpha, 25-dihydroxyvitamin D3, 1,25D) is the active form of vitamin D that plays a protective role in immune regulation, bone metabolism, and inflammatory response. In this study, we constructed a T2DM model in rats by combining a high-fat diet with low-dose streptozotocin. The periodontitis model in rats was developed by ligation and Porphyromonas gingivalis (ATCC 33277) inoculation. Rats were randomly divided into five groups: non-diabetic blank, diabetic blank, diabetes with calcitriol treatment, diabetes with 3-methyladenine (3-MA) treatment, or diabetes with calcitriol and 3-MA treatment. The diabetic rats exhibited an intense inflammatory response and decreased autophagy compared with the non-diabetic rats. Intraperitoneal injection of calcitriol and autophagy inhibitor (3-MA) allowed us to explore the effect of calcitriol on inflammation in the gingival epithelium and the role of autophagy in this process. Treatment with calcitriol resulted in the decreased expression of NFκB-p65, p62/SQSTM1 and inflammatory response and increased expression of LC3-II/LC3-I. Application of 3-MA significantly suppressed autophagy, which was apparently retrieved by calcitriol. Antibacterial peptide (LL-37) is the only antimicrobial peptide in the cathelicidin family that is found in the human body, and it exhibits a broad spectrum of antibacterial activity and regulates the immune system. In the present study, our findings indicated that calcitriol-enhanced autophagy may attenuated periodontitis and the decrease of LL-37 was rescued by calcitriol treatment in the gingival epithelial cells of T2DM rats. Our study provides evidence for the application of calcitriol as an adjunctive treatment for T2DM-associated periodontitis.
Graves disease is more prevalent than Hashimoto disease in children and adolescents with type 1 diabetes
Authors: Wang Lu-Ting , Huang Chi-Yu , Lin Chao-Hsu , Cheng Bi-Wen , Lo Fu-Sung , Ting Wei-Hsin , Lee Yann-Jinn
Published: January 2023

Introduction

Autoimmune thyroid disease (AITD) is the most common associated autoimmune disorder in type 1 diabetes (T1D). Early detection of AITD is crucial to optimize glycemic control, growth, and intellectual development. In this prospective cohort study, we sought to characterize the prevalence, incident ages and risk factors of AITD in children and adolescents with T1D.

Materials and methods

Patients with T1D diagnosed at ≤ 18 years at MacKay Children’s Hospital, Taipei, from 1990 to 2019 underwent annual screening for AITD. Institutional Review Board-approved data on age, sex, and disease profile are collected. Statistical analysis was performed by using independent sample t test for continuous variables, chi-squared test for categorical variables, and Kaplan-Meier estimates of cumulative incidence of AITD were calculated. A p value of <0.05 was considered statistically significant.

Results

We prospectively followed up 808 patients with T1D, 761 patients were included in the study. Of these patients, 197 (25.9%) of them had thyroid autoimmunity, meaning positivity of thyroid autoantibodies. Females had a higher prevalence of thyroid autoimmunity than males (59.9%, p = 0.012). Altogether, 5.5% patients developed AITD (4.1% had Graves disease; 1.4% had Hashimoto disease), at a mean age of 17.8 ± 8.5 years. The cumulative incidence of AITD at 30 years of disease duration was 0.29 in the total group and was significantly higher in females (0.39, n = 397) than in males (0.15, n = 364, p<0.001).

Discussion

In Taiwan, the prevalence of AITD in pediatric population with T1D increases with age, a longer disease duration and female sex. For early detection of autoimmune thyroid disease in Taiwanese children and adolescents with T1D, an annual AITD screening program should be implemented.
Mechanisms and therapeutic strategies of immune checkpoint molecules and regulators in type 1 diabetes
Authors: Ding Jia-Tong , Yang Kang-Ping , Lin Kong-Lan , Cao Yu-Ke , Zou Fang
Published: January 2023

Background

Considered a significant risk to health and survival, type 1 diabetes (T1D) is a heterogeneous autoimmune disease characterized by hyperglycemia caused by an absolute deficiency of insulin, which is mainly due to the immune-mediated destruction of pancreatic beta cells.

Scope of review

In recent years, the role of immune checkpoints in the treatment of cancer has been increasingly recognized, but unfortunately, little attention has been paid to the significant role they play both in the development of secondary diabetes with immune checkpoint inhibitors and the treatment of T1D, such as cytotoxic T-lymphocyte antigen 4(CTLA-4), programmed cell death protein-1(PD-1), lymphocyte activation gene-3(LAG-3), programmed death ligand-1(PD-L1), and T-cell immunoglobulin mucin protein-3(TIM-3). Here, this review summarizes recent research on the role and mechanisms of diverse immune checkpoint molecules in mediating the development of T1D and their potential and theoretical basis for the prevention and treatment of diabetes.

Major conclusions

Immune checkpoint inhibitors related diabetes, similar to T1D, are severe endocrine toxicity induced with immune checkpoint inhibitors. Interestingly, numerous treatment measures show excellent efficacy for T1D via regulating diverse immune checkpoint molecules, including co-inhibitory and co-stimulatory molecules. Thus, targeting immune checkpoint molecules may exhibit potential for T1D treatment and improve clinical outcomes.
Early and precocious puberty during the COVID-19 pandemic
Authors: Prosperi Sara , Chiarelli Francesco
Published: January 2023

During the year 2020, the COVID-19 pandemic rapidly became a severe health emergency worldwide. In order to contrast the spread of the novel SARS-CoV-2, many countries implemented extraordinary restrictive measures, such as a strict lockdown and school closures. The pandemic had a great impact on children and adolescents’ daily life, leading to a much more sedentary lifestyle, to larger use of electronic devices and to an increase in stress-related symptoms. These conspicuous changes acted as disruptors of children’s normal development. Since the beginning of the pandemic, many studies reported an increase in the number of precocious puberty cases as well as a faster progression rate of puberty itself, if compared to the pre-pandemic years. In this review, our aim was to evaluate the incidence of new cases of early and precocious puberty during the COVID-19 pandemic, analyzing variations in the timing of puberty and in pubertal progression rate, and to investigate the role of environmental and lifestyle factors during the pandemic in modulating the physiopathology of pubertal development. While a direct effect of SARS-CoV-2 infection remains, at the moment, a remote hypothesis, both physical and psychological factors related to the pandemic seem to have a role in triggering GnRH pulsatile secretion leading to earlier pubertal onset. It is indeed important to stress the need to clarify the exact role of COVID-19 in early pubertal onset comparing data from all over the world; long-term comprehensive studies are also pivotal to explain whether this phenomenon will continue while we resume pre-pandemic habits.
The observability and controllability metrics of power system oscillations and the applications
Authors: Zhao Chenghan , Wang Xitian , Liu Ziyu , Liu Shiyu
Published: January 2023

Power system oscillation has caused many serious accidents in renewable energy grid connection system. The concept of observability and controllability in control theory has been widely applied to power system oscillation study. In this paper, observability metric (OM) and controllability metric (CM) are defined from the perspective of oscillation modes, acting as a novel quantification method to quantify the observability and controllability of power system with distinct or repeated eigenvalues. Furthermore, in order to compare the reflection degree and control effect of signals in different oscillation modes, the mode comprehensive observability metric (MCOM) and comprehensive controllability metric (MCCM) are proposed. The proposed method shows clearer relationship between controllability/observability and oscillation modes by combining the information of conjugate eigenvalues together. The advantages of metrics are illustrated by comparing with theoretical derivations and calculation results of three traditional methods: participation factor, residue method and geometric measures. Finally, the metrics are applied to a subsynchronous damping controller (SSDC) design for better performance in oscillation monitoring and suppression. With the small-signal model and corresponding time-domain simulation, the effectiveness of the proposed method is verified.
Study on reasonable production allocation method of tight sandstone gas reservoir—A case of XX block in ordos basin
Authors: LV Min , CUI Hongjun , LEI Yanyun , Lei Kaiyu , ZHU Yushuang
Published: January 2023

Reasonable production allocation of tight sandstone gas reservoirs is an important basis for efficient development of wells. Combining multiple mathematical models, the modified flowing material balance equation was established considering the variation of viscosity and compressibility, and a reasonable production allocation process was developed. The results show that: ① The flow material balance method ignores the change of compressibility, viscosity and deviation coefficient in the calculation. Compared with the results calculated by the material balance method, the results of the flow material balance method are smaller. ② A modified flowing material balance method is established, verified by the production of 670 wells in the study area during stable period. Compared with the open flow rate method, the error of dynamic reserve allocation method is smaller, with an error of 0.07%. ③ When dynamic reserves are used to allocate production, the initial decline rate of wells is reduced by 74.65% on average, the production on stable period increases by 21.28%, and the time increases by 1.79%. This study provides support for dynamic reserve calculation and reasonable production allocation of gas wells in the study area, and has important guiding significance for the formulation of reasonable development plan and economic and efficient development of tight sandstone gas reservoirs.
Research on arc grounding identification method of distribution network based on waveform subsequence segmentation-clustering
Authors: Wu Yihui , Li Qiong , Long Guohua , Chen Liangliang , Cai Muliang , Wu Wenbao
Published: January 2023

The traditional method of detecting fault current based on threshold judgment method is limited by the current size and is easily disturbed by noise, and it is difficult to adapt to the arc ground fault detection of the distribution network. Aiming at this problem, this paper proposes a single-phase arc-optic ground fault identification method based on waveform subsequence splitting fault segmentation, combined with three-phase voltage-zero sequence voltage waveform feature extraction clustering. First of all, the waveform fault segment is segmented and located, secondly, the characteristic indexes of the time domain and frequency domain of the combined three-phase voltage-zero sequence voltage waveform are established, and the multidimensional feature distribution is reduced by the principal component analysis method, and finally, the characteristic distribution after the dimensionality reduction is identified by the K-means clustering algorithm based on the waveform subsequence. Experimental results show that the arc light grounding fault identification method proposed in this paper achieves 97.12% accurate identification of the test sample.
Identification method of thief zones in carbonate reservoirs based on the combination of static and dynamic data: A case study from the Cretaceous Mishrif Formation in the H oilfield, Iraq
Authors: Li Ruixue , Deng Hucheng , Fu Meiyan , Hu Lanxiao , Xie Xinhui , Zhang Liying , Guo Xiaobo
Published: January 2023

Carbonate reservoirs usually have a strong heterogeneity. The zones with relatively high permeability will form a channel through which fluids can easily flow. These channels are called thief zones. Thief zones have notable effects on oil or gas production, for example, high oil recovery rates at the early stage of the exploitation or an early water breakthrough during the later stage of water flooding development. Therefore, it is essential to have a precise identification of thief zones in carbonate reservoirs. In this research study, a simple approach to identify thief zones based on reservoir permeability gathered from well logging is developed. The thief zones are first identified at wells based on the lower limit value of the thief-zone permeability. This value is determined based on the dynamic production data, indicating that the thief zones identified by applying this criterion can reflect the product characteristics. Then, a zonal inter-well recognition method is adopted to identify the connectivity and distributions of thief zones in the regions far away from the well. This method is applied to identify thief zones for the Cretaceous Mishrif Formation in the H oilfield, Iraq. The reliability of the identification results is tested by the well-group injection test. The distributions of thief zones in the study region are discussed. In the study region, 12 members developed thief zones, while two members (i.e., MC1-3 and MC2-2) did not develop thief zones. Specifically, there are five members having a high level of thief-zone development. They are MB1-2C, MB2-1, MB2-2, MC2-3, and MC3-2. Comparing the distribution of thief zones with that of sedimentary microfacies, it is concluded that the thief-zone development is mainly controlled by the sedimentary microfacies and tends to occur in high-energy shoals.
Voltage monitoring based on ANN-aided nonlinear stability analysis for DC microgrids
Authors: Sun Shengxin , Tang Chenyu , Hailati Gulizhati , Xie Da
Published: January 2023

Due to the low inertia of the DC microgrid, the DC bus voltage is prone to drop or oscillate under disturbance. It is also challenging to supervise the stability of a DC microgrid since it is a highly nonlinear dynamic system with high dimensionality and randomness. To tackle this problem, this paper proposes a new method using ANN-aided nonlinear dynamic stability analysis for monitoring the DC bus voltage, which is combined with two steps. The first step is to establish six corresponding nonlinear accurate discrete iterative models of six switching modes of the PV-battery-load-based DC microgrid system, based on the Poincaré map theory, in order to judge the stability quantitatively with a promoted stability margin index. The second step is to use artificial neural networks (ANNs) to forecast the operating mode of the system when random changes occur in environmental circumstances and load power; this will aid the first step in being efficient and adaptable while determining stability cases. And the employed ANNs are trained with the datasets, including the circuit data, ambient temperature, irradiance, and load power, which are generated by MATLAB/Simulink simulation. Theoretical and simulation analyses are carried out under different operating conditions to validate the proposed method’s efficacy in judging the DC microgrid’s destabilizing oscillation and stable running.
Optimal placement and capacity sizing of energy storage systems via NSGA-II in active distribution network
Authors: Su Rui , He Guobin , Su Shi , Duan Yanru , Cheng Junzhao , Chen Hao , Wang Kaijun , Zhang Chao
Published: January 2023

In recent years, with the rapid development of renewable energy, the penetration rate of renewable energy generation in the active distribution network (ADN) has increased. Because of the instability of renewable energy generation, the operation stability of ADN has decreased. Due to the ability to cut peak load and fill valley load, battery energy storage systems (BESSs) can enhance the stability of the electric system. However, the placement and capacity of BESSs connected to ADN are extremely significant, otherwise, it will lead to a further decline in the stability of ADN. To ensure the effectiveness of the BESSs connected to the grid, this work uses the fuzzy kernel C-means (FKCM) method for scene clustering. Meanwhile, a multi-objective optimization model of BESS configuration is established with the objective of BESS configuration cost, voltage fluctuation, and load fluctuation, and solved by non-dominated sorting genetic algorithm-II (NSGA-II). In this work, the grey target decision method based on the entropy weight method (EWM) is used to obtain the optimal compromise solution from the Pareto non-dominated set. Moreover, the proposed method is tested and verified in the extended IEEE-33 node system and the extended IEEE-69 node system. The results show that the BESSs configuration scheme obtained by NSGA-II can effectively reduce the fluctuation of voltage and load, and improve the stability of ADN operation.
How to promote the energy transition? —An analysis based on the size and technology effect in new energy industry
Authors: Bian Xiaoxia , Chen Peishu , Gao Zhengye , Fang Guochang
Published: January 2023

This paper attempts to explore the dynamic relationship between new energy industry development and energy structure transformation in China. Based on the real option model and stochastic frontier analysis (SFA), the development scale and technical level of the new energy industry are measured at the provincial level. The eastern region is in the lead, but there has been a certain degree of technological efficiency retreat, especially in Liaoning. The new energy industry in the central region has developed rapidly due to the deepening of the industrialization process. With the aid of PVAR model, impulse response function and variance decomposition, the results show that there exists a bidirectional dynamic relationship between the new energy industry and energy structure. In other words, the development of the new energy industry and the energy transition can be mutually predicted. Specifically, technology effect has a positive continuous and dramatic influence on the transformation of energy structure. In turn, the energy transition first elicits a response to size effects, but has a long-term impact on technology effects. This implies that the new energy industry will usher in scale expansion at the early stage of energy transition. It is worth noting that scale expansion will not always accelerate the transition process. At that time, technology played a long-term and central role. Therefore, reasonable expansion of new energy industry scale and efforts to develop new energy technology are important measures to ensure the orderly energy transition.
Current stress optimization control strategy of the buck topology with the variable frequency/amplitude mode
Authors: Li Ning , Li Zhuang , Cao Yujie , Wei Deng , Xiao Zihan , Zhang Yan
Published: January 2023

The Buck circuit is a common topology in DC-DC converter. The existing control strategies have the advantages of short modulation time and high dynamic performance, but they also have the disadvantages of poor active modulation of the working mode of the converter and large current stress. In response to the above problems, an improved frequency/amplitude modulation control strategy is proposed in this paper. The relationship between the output power and the peak inductor current in three modes, namely, Discontinuous Conduction Mode Critical Conduction Mode (CRM) and Continuous Conduction Mode is derived. The precise control strategy of the inductor peak current is introduced based on the traditional voltage loop control strategy to realize the free control of the system working mode and reduce the current stress during the working process. Finally, the experimental platforms of 100V/12V and 220/80V are established respectively. The experimental results show that the flexible switching circuit operating mode in the full load range can be realized under the new control method. In the 100/12V experimental platform, the current stress of the switch tube is optimized by at least 10.7%, and the average system efficiency is improved by 2.21%, with the same main circuit parameters.
Allocating the capacity of shared energy storage for wind farm groups based on the over-limit power export risk
Authors: Zhu Weijun , Song Kexuan , Gu Yilei , Luo Yaogang , Shu Jing , Weng Hua , Li Zhiyi
Published: January 2023

Energy storage in wind farms can stabilize the fluctuation of wind power output. Shared energy storage can reduce the construction cost of energy storage devices and stimulate the enthusiasm of wind farms to invest in energy storage. The wind power base is composed of multiple wind farm groups. Existing research methods did not consider how to allocate shared energy storage among wind farm groups in the wind power base. This paper proposes an energy storage capacity allocation method for wind farm groups. Firstly, a bilevel model for the shared energy storage allocation is established. The upper-level model optimizes the shared energy storage allocation of each wind farm group with the goal of minimizing the over-limit power export risk in the wind power base; The lower-level model calculates the over-limit power export of each wind farm group according to the energy storage capacity allocation and transfers the value of over-limit power export to the upper-level model. The bilevel model can be converted to a two-stage model that can be solved sequentially; The wind power base in Belgium is used for numerical simulation to verify the effectiveness of the proposed model. Finally, the sensitivity of confidence level, total energy storage capacity, and risk preference factor are analyzed.
Assessment of the protection system in response to different grid-tied converters
Authors: Xu Zhi , Alimasibieke Shakenbieke , Zhai Baoyu , Yang Qi , Wang Yuchen
Published: January 2023

The power system is migrating to 100% penetration of the converter-interfaced generation (CIG). The grid-forming converter-based CIG has been proposed to be a solution to replace the synchronous generation (SG) in order to form the grid and achieve the 100% penetration target. However, besides the generation, whether the protection system can coordinate this transition is still an open question. Although the grid-forming converter operates as the same manner as the SG, unlike SG, it physically has constraints on its current output which in transient leads to different operation to the SG. This paper aims to investigate whether these different transients have effects on the protection system, specifically, investigate if the protection system remains reliable when the system migrates to 100% penetration. The investigation is based on the hardware in-the-loop experiment, considering different converter control, different type of the fault, different length of the line and different fault location. The result shows that the grid-forming converter has a reliable coordination with the protection system in response to the fault.
Demand-driven NEV supplier selection: An integrated method based on ontology–QFD–CBR
Authors: Zheng Jin , Li Yong-Hai , Fan Zhi-Ping
Published: January 2023

With the rapid development of new energy vehicles (NEVs), the market competition in the NEV industry is becoming increasingly fierce. Selecting the right supplier has become a critical aspect for NEV manufacturers. Therefore, based on the user’s demand information, selecting a suitable NEV supplier to support the NEV manufacturer’s management decision is a noteworthy research problem. The purpose of this study is to develop an integrated method for demand-driven NEV supplier selection based on ontology–quality function deployment (QFD)–case-based reasoning (CBR). The method is composed of three parts: 1) construction of domain ontology of NEV component supplier selection criteria based on text information mining; 2) extraction of demand attributes and determination of their weight based on latent Dirichlet allocation (LDA) and Kano model, as well as determination of expected attributes and their weights based on QFD; and 3) selection of an NEV component supplier based on CBR. To illustrate the use of the proposed method, an empirical study on the supplier selection of the XP NEV manufacturer is given. This method is helpful in selecting the most suitable component supplier for NEV manufacturers and relevant decision-makers.
Effects of green manure intercropping on soil nutrient content and bacterial community structure in litchi orchards in China
Authors: Yuan Bingchen , Yu Daogeng , Hu An , Wang Yanru , Sun Yuting , Li Chengzhen
Published: January 2023

Green manure intercropping is an agronomic management practice that effectively increases soil nutrients in understory and reduces weed population. However, the influence of different green manures on soil properties and soil bacterial community in litchi orchards in the tropical regions of China remains largely unknown. Here, we examined the effect of intercropping three leguminous green manure crops in litchi orchards of Hainan Province. No intercropping was used as the control. Different green manures increased the contents of different soil nutrients. For example, Desmodium ovalifolium increased the total nitrogen content by 7.93%; Grona heterocarpos increased the ammonium nitrogen content by 558.85%; and Stylosanthes guianensis increased the available phosphorus content by 1207.34%. However, intercropping with D. ovalifoliu and S. guianensis reduced the content of available potassium by 47.29% and 58.48%, respectively. The intercropping of green manure increased the abundance of several microbial genera, including Bradyrhizobium, Serratia, and Bacillus, which are known to facilitate soil nitrogen accumulation, plant growth, and phosphorus dissolution. Compared with no intercropping, the three intercropping treatments significantly improved the contents of soil ammonium nitrogen and soil available phosphorus in the litchi orchard. Therefore, intercropping with green manure crops in litchi orchards is an effective management measure; however, the choice of the green manure crop should be based on the soil conditions of litchi orchards.
Efficient metformin transformation in sulfite/UV process co-present with oxygen
Authors: Gu Yurong , Zhang Yi , Jiang Chengchun , Dong Zijun , Bai Xue
Published: January 2023

UV/sulfite process without oxygen has been extensively explored and used for the degradation of many micro-pollutants. In the present work, a UV/sulfite process in the presence of oxygen was applied to degrade a widely used pharmaceutical compound, metformin (MET). The results showed that the oxygen-involved UV/sulfite process could efficiently degrade MET. At an initial concentration of 2.5 mg/L, 86.0% of MET was removed from the contaminated water within 180 min irradiation at a sulfite dosage of 10 mM, solution pH of 9, and UV intensity of 4,092 μW/cm2. In addition, sulfate radical (SO4•-), hydroxide radical (•OH), hydrogen atom (•H), and hydrated electron (eaq−) were found to be the dominant active species contributing to MET removal in the studied process through scavenging experiments. The increase in UV intensity, sulfite dosage, solution pH, and reaction temperature enhanced MET degradation in the investigated process to a certain extent, whereas the introduction of bicarbonate and fulvic acid slightly suppressed MET degradation. Finally, the degradation products of MET were identified. The oxygen-involved UV/sulfite process exhibited a remarkable denitrification capacity (>80%) in MET. The findings of this study may offer a novel approach for treating emerging contaminants.