bluuebunny/crossref_metadata_2025_split huggingface dataset:
Series and parallel resonance active damping of three‐phase buck‐type dynamic capacitor for reactive compensation and harmonic suppression
Authors: Chao Zeyun , Chen Xinwen , Dai Ke , Wu Qi , Zhang Yuxiao , Dai Ziwei 
Published: April 2020

Series and parallel resonance tend to occur and cause harmonic distortion when the distribution system contains a shunt power capacitor to compensate inductive load and dynamic capacitor (D‐CAP) to suppress harmonics. This study focuses on the series and parallel resonance active damping of three‐phase buck‐type D‐CAP, so as to achieve better power quality control. Two virtual resistor damping methods for series resonance, D‐CAP power capacitor voltage or D‐CAP front‐end buffer inductor current feedback, are introduced and compared. Then, parallel resonance is damped by generating certain harmonic currents in the phase with the selective harmonic voltage at the point of common coupling (PCC), equivalent to controlling the D‐CAP as a virtual harmonic resistor. In addition, the power balance of D‐CAP is interpreted to ensure no additional energy control loop is needed for the active damping. To further improve the parallel resonance damping, the self‐adjusted damping gain is proposed by the closed‐loop regulation of harmonics in PCC voltage. Finally, coordinated control between reactive and multiple harmonic currents is introduced for the whole combined control to avoid over‐modulation. A wide variety of experimental results from a 33 kVar/220 V laboratory prototype are provided to demonstrate the validity of the combined control.
Characterization of phosphate-solubilizing bacteria isolated from acidic Ultisol soil, South Borneo
Authors: Jaya G I , Utami S N H , Widada J , Yusuf W A 
Published: April 2020

Abstract
Borneo Island is an area crossed by the equator, which is characterized by high rainfall and stable warm temperatures condition. In these condition, the soil experiences advance weathering so that the content of Fe2+ and Al 3+ in the soil is very high. This causes many problems, such as high fixation of P by poisonous Fe and Al so that P elements become unavailable for plant. Plant Growth Promoting Rhizobacteria (PGPR) can support the growth of plants by the Al and Fe chelation mechanism so that the plants are not poisoned by the toxic elements and P nutrients can be available for plants. The purpose of this study was to isolate Phosphate Solubilizing Bacteria (PSB) from acidic ultisol soil. The results showed that among isolated PSB, PL1 isolates and PL2 isolates had the highest value of P solubilizing index. DNA of these 2 potential isolates were extracted and then amplified gDNA showed 1330-1500 bp.
Compatibility of variety and planting pattern of Maize (Zea mays) in early Ganitri (Elaeocarpus ganitrus Roxb.) based agroforestry in dry land
Authors: Rohandi A , Swestiani D 
Published: April 2020

AbstractAgroforestry in dry-land is an effort to increase land productivity and to support food security program. Practicing the proper agroforestry in the early age is very essential not only to optimize the annual crop yield but also giving benefit to the tree growth.Ganitri (Elaeocarpus ganitrusRoxb.) is a tree species that produce beads with high economic value for religious purpose in Southeast Asia and India. Meanwhile, maize is one of staple food throughout Southeast Asia which support food security program. This research aimed to discover the suitable maize variety and planting pattern for early agroforestry in order to get optimum yield and able to supportganitrigrowth as the main tree. Randomized block design with split plot design was conducted with 2 factors and 3 replications. The main plot was maize variety (single cob and double cobs) and the sub-plot was the planting pattern (two rows and three rows of maize inganitrialleys). The hypothesis of this research was maize varieties and planting pattern inganitribased agroforestry had influence on maize production and the growth ofganitri.The result shows that interaction between maize variety and planting pattern have significant effect on the average height of maize in the early and end of growth, nevertheless it does not give any significant response on the early growth ofganitriexcept for the branch number. The utilization of double cobs variety with three rows of maize in between trees gave higher yield, 4.55 t ha−1dry kernels in total. This planting pattern has the potency to be applied in order to optimize the land-use on earlyganitri-based agroforestry in dry land.
The utilization of trees by endangered primate species Javan slow loris (Nycticebus javanicus) in shade-grown coffee agroforestry of Central Java
Authors: Sari D F , Budiadi  , Imron M A 
Published: April 2020

Abstract
Although human intervention remains high, a shade-grown coffee agroforestry in Kemuning, Central Java still have important roles for biodiversity conservation. Among various fauna, the Javan slow loris (Nycticebus javanicus), a critically endangered species, can survive in this agroforestry system. The use of spatial method on shade-grown coffee agroforestry seems unusual. We aim to investigate the utilization of tree and other vegetation by Javan slow lorises in a shade-grown coffee agroforestry ecosystem in Kemuning Forest. We followed two individuals (male and female) of slow lorises from December 2018 until May 2019 using radio collar. We recorded both vertical and horizontal positions of each individual based on their position on trees at two spatial dimensions (vertical and horizontal). To explore whether lorises select certain tree species, we laid 275 plots (20×20m) in their habitat and using Chi-square test for the analysis. Our findings show that both male and female of Javan slow loris in shade-grown coffee agroforestry use different forest stratum for their activity. The female used 42.11% of their time to do exploratory activity in the outer part of the canopy, regardless the vertical position, and 43.76% in the middle part (vertical position) and the outer part (horizontal position) of the canopy. While the male mostly uses the inner part of the canopy (52.57%) and upper part of the canopy for feeding activity (64.37%). Both male (Chi-square test = 264.05, p < 0.05) and female (Chi-square test = 357.35, p < 0.05) lorises select tree species for their behavior. We provide here evidence of biodiversity conservation services by shade-grown coffee agroforestry practices in Indonesia. The intensity of coffee management under tropical trees seems does not impact significantly to the presence and behavior of slow loris, however precautionary measures to reduce poaching should be done as this endangered species threatened by illegal activity. Benefivial values from managing shade-grown coffee agroforestry for generating income for locals such as wildlife-friendly coffee production can also be alternative hand in hand to reduce poaching.
Smallholder farmers’ perception on oil palm agroforestry
Authors: Susanti A , Marhaento H , Permadi D B , Hermudananto  , Budiadi  , Imron M A , Maimunah S , Susanto D , Bakhtiar I , Lembasi M 
Published: April 2020

Abstract
Oil palm has become a prominent agricultural commodity in Indonesia. It is widely adopted mainly as monoculture plantations both by smallholders and large scale companies. Evidence shows that these massive monoculture practices have led to adverse impacts to environmental and social systems as well as unsustainable growth of the producing regions. Particularly, smallholder farmers have encountered difficulties to cope with the fluctuating oil palm price. We argue that adding perennial trees and other agricultural crops or combining with livestock breeding in the form of agroforestry could become an alternative for smallholder farmers to deal with this problem. Oil palm agroforestry (OPAF) has been voluntarily adopted by smallholder farmers at limited scales. This article aims at analysing smallholder farmers’ perception on oil palm agroforestry in terms of production and potential contribution to improve environment. Intensive fieldworks were conducted in Jambi and Central Kalimantan to investigate smallholder farmers’ perception on oil palm agroforestry. This research reveals that the relatively large proportion of smallholder farmers perceived that (a) oil OPAF produces less of oil palm fresh bunch fruits and demands more complex management compared to those with monoculture system, (b) OPAF helps smallholder farmers to cope with the FFB price fluctuation and improves household food security, and (c) OPAF improves environmental quality in general. From these results, we learned that smallholder farmers have various perceptions on OPAF which are ranged from very positive to very negative. These smallholder farmers’ perceptions could become important factors which determine their decisions in adopting or not adopting OPAF. Therefore, more efforts are needed to improve farmers’ confidence in adopting oil palm agroforestry. Furthermore, we need more evidence on how oil palm agroforestry system could provide a socially, economically and environmentally feasible alternative to monoculture system.
Strengthening of farmer groups institutions in the development of community forests based on Jamblang (Syzygium cummini Linn) agroforestry
Authors: Palmolina M , Sudomo A , Mulyana S 
Published: April 2020

Abstract
The existence of farmer’s groups is important for increasing community forest productivity. The final impact is the sustainability of the environment and the community’s welfare with the pattern of community forests. The purpose of the research is to find out the structure and dynamic of farmer groups for institutional strengthening. The research was conducted in Cipari Hamlet, Linggajaya Village, Cisitu Subdistrict, Sumedang Regency, from 2015 to 2017. The research used a qualitative approach and descriptive explanation of a case. Data collection was conducted by doing in-depth interviews with 3 (three) informants, and using questionnaires on 22 (twenty two) respondents who are members of the “Lingga Murni” forest farmer group. The result showed that the forest farmer group “Lingga Murni” was a modern group, as seen from the existence of an organizational structure (but there was no forestry section) and some institutional activities that have already left the sub-district. But the collection of decisions was not by deliberation but directly from the group leader. The Lingga Murni farmer group did not accommodate the opinions of all members. Alternative development agency priorities were the establishment of a forestry section in the organizational structure to accommodate community forest activities, as well as the creation of work plans with the aim of improving the performance of its members, from program design to evaluation of activities.
Effect of altitude on thermal balance of a heavy-duty diesel engine
Authors: Rao Xiaoxuan , Huang Ronghua , Huang Runwu , Zhou Pei , Zhang Yu , Huang Sheng 
Published: April 2020

Abstract
Diesel engines working at high altitudes are prone to thermal failure. In this paper, a series of experiments and simulations were conducted to analyze the thermal balance, in-cylinder heat transfer, and performance of diesel engines at various altitudes. A six-cylinder four-stroke diesel engine was used to conduct the thermal balance tests at altitudes from 0 m to 4500 m. The experiment results show that the engine thermal efficiency declines from 37.8% to 33.9% at the rated speed as altitude rises. The heat loss through cooling water has no significant change in trend and remains about 22%-24% in most conditions. The heat loss through exhaust decreases as altitude rises and accounts for 26.7%-39.8% of total energy. The unaccounted losses increase greatly as altitude rises but it makes up no more than 12.1% of total energy at all altitudes. To acquire more detailed in-cylinder heat transfer parameters, a one-dimensional in-cylinder simulation was conducted. The simulation results show that the in-cylinder heat transfer coefficient and heat fluxes increase first and then decrease as altitude rises. In addition, with the increase of altitude, the in-cylinder average gas temperature substantially increases. This study has practical significance for reducing thermal load of the engines working at high altitudes.
Numerical simulation research of subcooled flow boiling based on MUSIG model under low pressure
Authors: Zhou Pei , Huang Ronghua , Zhang Yu , Huang Sheng , Rao Xiaoxuan 
Published: April 2020

Abstract
Subcooled boiling heat transfer is widely used in modern high-power and high-load internal combustion engines (ICEs) because of its efficient heat transfer characteristics. In the present work, a numerical simulation of subcooled boiling under low-pressure conditions is performed on CFX with a user-defined program. Lee’s subcooled boiling experiment results are used for calculations. The bubble departure diameter is simulated by Du’s model. In order to apply the simulation method to engine cooling system with complex channel, the Favre Averaged Drag Model and Tomiyama Lift Force Model are used which makes up for shortcomings of the experience factor needed to be adjusted. The Multiple Size Group (MUSIG) model considering the effects of vapor bubbles coalescence and breakup is used to describe the different sizes of bubbles in the liquid phase. A qualitatively good agreement with the experimental data is achieved without changing model parameters, which lays a good foundation for the application of the simulation method in an engine cooling system.
Formation mechanism and distribution characteristics of micro residual oil in ultra-high water cut reservoirs a case study of yangsanmu oilfield
Authors: Zhang Shuo , Zhang Tao , Zhang Xianguo , Yan Mingming 
Published: April 2020

Abstract
The formation mechanism and distribution characteristics of microscopic remaining oil are the basis for efficient development and enhanced oil recovery of heavy oil reservoirs in ultra-high water cut stage. This paper takes Yangsanmu heavy oil reservoir in Huanghua depression as an example, micro-displacement simulation experiment based on microscopic pore structure analysis. Through parallel experiments, the remaining oil displacement effects of water flooding combined with polymer flooding, water flooding and surfactant polymer system combination, water flooding and poly-alkaline ternary composite flooding were compared. The formation mechanism and distribution pattern of remaining oil under different displacement medium conditions were studied to find a reasonable displacement medium system. The experimental results show that the formation of microscopic remaining oil in the study area is related to the stripping effect, the flow around, the pinch action occurs, the run through effect and the adherent flow. The distribution types of remaining oil are mainly angular type, pore wall oil film type, throat retention type, dispersed oil drop type and porphyritic remaining oil in macropores. The analysis of residual oil saturation under different displacement media shows that the combined flooding effect of water flooding and poly-alkaline ternary composite flooding are the best, followed by water flooding and surfactant polymer system combination flooding. This study provides guidance for the remaining oil exploration plan of the ultra-high water cut stage heavy oil reservoir in this area.
Prediction of circulating water loss based on support vector machine and neural network
Authors: Yin Aiming , Cao Fan , Jin Xuliang , Dong Lei , Nie Jinfeng , Ma Lin 
Published: April 2020

Abstract
Based on the operational data of the circulating water system in a thermal power plant, BP neural network and support vector machine regression were used to establish the prediction model of circulation water system evaporation and wind blow loss. The trail method was used to improve the BP neural network prediction model, and for the prediction model of support vector machine regression, the kernel function and the corresponding parameters were selected through optimization. The results showed that the mean square error of the simulation results of the two models were 0.071 and 0.070 respectively in summer and 0.046 and 0.047 respectively in winter, this meets the prediction requirements of project and demonstrates high prediction accuracy. With the evaluation index of neural network model, the simulation and prediction results of the two models were compared and analysed. The results showed that the simulation results of two model were basically the same, but the support vector machine model training sample time is shorter, the convergence speed is faster, and the overall network model performance is better.
Highly robust LCL three-phase grid-connected inverter under non-ideal grid
Authors: Zhang Ziyuan , Fu Ziyi , Dong Yanjie 
Published: April 2020

Abstract
A current-voltage dual-loop grid-connected control strategy for a conventional grid-connected inverter that is susceptible to instability under a non-ideal grid is designed. The effects of grid impedance and fluctuations in this strategy are considered. The influence of power network impedance change on LCL filter is analysed, the small signal model of phase-locked loop is established, and the design methods of system parameters and controller parameters to improve the robustness of the system are given. Finally, through MATLAB/Simulink simulation, current and voltage output of grid-connected inverters and grid-connected current quality parameters are obtained under different working conditions, verifying the correctness and feasibility of theoretical derivation.
Evaluation of the performance of a hybrid cooling/heating system combining groundwater direct cooling with groundwater heat pump for rural buildings
Authors: Fang Qi , Zhang Yufeng 
Published: April 2020

Abstract
With the remarkable improvement of villagers’ living standard and the requirement of building energy efficiency, it becomes imperative to rely on renewable sources of energy and make a more efficient use of energy to solve the problem of cooling/heating for the rural buildings. This paper presents a new hybrid cooling/heating system, which combines groundwater direct cooling system (GWDCs) with groundwater heat pump system (GWHPs). The system is installed in an office building in Youhao Street, Duliu town, Jinghaicounty, Tianjin, China. The feasibility of the system is verified and the performance of the system is experimentally evaluated both in cooling and heating modes. It is found that the average GWDCs COPS is approximately 3.85 in the cooling season, while the average heat pump COP and the overall system’s COPS of GWHPs are about 5.05 and 2.8 respectively. The results obtained from the experiment show that these systems could be used safely, reliably and efficiently at the lowest cost for the rural buildings in Tianjin, China.
Clustering and modelling of rheological parameters for anaerobic digestion materials (ADMs) and its application for feed pump selection
Authors: Yang Yang , Zhu Hongguang 
Published: April 2020

Abstract
Anaerobic digestion technology is a promising technology for renewable energy and environmental protection. Rheological properties of anaerobic digestion materials (ADMs) are the essential parameters for transporting and mixing system design. Anaerobic slurry with high total solid(TS) is a Non-Newton fluid fit for power law model, its apparent viscosity is a function of consistency coefficient K and non-dimensional rheology index n. At present, studies on rheological parameters of ADMs mostly focus on specific single raw material, and the TS content has the greatest influence on rheological parameters. By comparing the rheological properties of different ADMs in literatures, it was found that the large difference among the rheological parameters comes from not only different types of ADMs (due to different components), but also the same type (due to different ways of pretreatment), which makes it difficult for the selection of rheological parameter model in biogas design. In this work, 20 different ADMs were clustered into 5 types by statistical method and then their rheological parameters were conducted. The five types of ADMs respectively are: low fiber content slurry, high fiber content slurry, straw manure mixture, straw suspension and digested sludge. The rheological parameter models of the five types can be written as K as an exponential function of TS, and n as a linear function of TS, which the range of TS is 4%-10%. Furthermore, the rheological parameter models were applied to the selection of feed pump of a 6000m3 biogas plant in Funan county of Anhui province, China. In this paper, the values of K and n of 20 ADMs were calculated when TS equals to 4%, 6%, 8% and 10%, and the optimal classification results were obtained by comparing the three results between hierarchical clustering method and K-Means clustering method.
Pore-scale model of two phase flow in 2D porous media: Influences of interfacial tension and heterogeneity effects on CO2 injection in the tight oil reservoir
Authors: Wang Deqiang , Cheng Linsong , Cao Renyi , Jia Pin , Guan Yun , Liu Hao 
Published: April 2020

Abstract
The CO2 injection in tight reservoir is different from the conventional reservoir. For the porous media, the pore throat in the matrix reaches the level of nanopore, and the heterogeneity leads to huge difference during CO2 injection. For the interaction of fluids, the reduction of interfacial tension caused by CO2 is benefit to enhance oil recovery. To reveal the mechanism, pore scale model from tight formation is built and the influences of interfacial tension and heterogeneity are investigated. First, the migration of two-phase interface is studied by coupled with level set (LS) equation and Navier-Stokes (NS) equation. And finite element method (FEM) with interfacial adaptive mesh refinement is employed to solve the equation system. The results reach highly agreement compared with analytical solution and phase field method. Then, the pore throat distribution characteristics of porous media model are built by the scanning electron micrograph (SEM). Finally, based on the real porous media model from the SEM image, the influences of interfacial tension and heterogeneity are investigated. The pore scale model considering fluid and medium mechanism during CO2 injection provides a better understanding of interfacial tension and heterogeneity effect in tight oil reservoirs.
Hydrogeochemical features and origin of geothermal water of carbonate rocks in the NE Guanzhong Basin, China
Authors: Xu Panpan , Zhang Qiying , Qian Hui 
Published: April 2020

Abstract
A great number of geothermal waters in carbonate rocks are located in the NE Guanzhong Basin. Hydrogeochemical features and genesis of geothermal waters in carbonate rocks were investigated by hydrogeochemical and statistical methods. The results show that the geothermal water in carbonate rocks is basically fresh water with the dominant water type of Na-HCO3. The hydrogeochemistry of geothermal water is governed by water-rock interaction, and the reservoir environment of geothermal water is open. The origin of geothermal water can be the atmospheric infiltration water. This study is aimed to provide the scientific basis for the sustainable development and utilization of geothermal waters of carbonate rocks in Guanzhong Basin.