bluuebunny/crossref_metadata_2025 huggingface dataset:
A Mathematical Approach of Voltage Sag Analysis Incorporating Bivariate Probability Distribution in a Meshed System
Authors: Patra Jagannath , Pal Nitai
Published: October 2022

In this paper, different mathematical expressions are derived to compute the residual magnitude of voltage caused by faults along the line and on the bus. Symmetrical and unsymmetrical faults are taken into consideration, and the consequences of the various fault distributions are considered. A new way of assessing a sag is proposed that incorporates the method of fault position and mathematical expression based on sequence currents and voltages. The fault impedance is introduced to obtain a better result. A fast and efficient load flow analysis technique produces quick computational results. In addition, the sag analysis is performed using the bivariate joint discrete probability distribution method that gives a clear idea about the probability of occurrence of sag in a meshed network. The suggested approach is applied in the IEEE 39-bus system and with an existing real-time electrical power distribution system in India.
Waveform Quality Evaluation Method of Variable-Frequency Current Based on Curve Fitting
Authors: Zhao Shengquan , Liu Yaozong
Published: October 2022

Since total harmonic distortion (THD) is mainly used as the evaluation index for the waveform quality of periodic signals, it cannot be applied to variable-frequency signals. However, there is scarce research on the evaluation methods and indicators of variable-frequency signals in the literature. In this paper, an evaluation method of the waveform distortion (WD) of variable-frequency signals based on curve fitting is proposed. First, the variable-frequency current expression of the coefficients to be optimized is obtained through theoretical derivation. Second, the coefficients are optimized by curve fitting in the time domain through the nonlinear least-squares method. Then, the waveform distortion of the variable-frequency current (IWDVF) is calculated. In order to validate the proposed evaluation method, the simulation model of a synchronous motor driven by a cascaded H-bridge five-level inverter is built. The simulation results show that, for the same constant-frequency current, the current THD (ITHD) obtained by the FFT method is the same as the current WD (IWD) obtained by the curve fitting method, which verifies the equivalence of the two methods. The influence of different sampling frequencies on the IWD and ITHD is compared. The higher the sampling frequency, the more sampling points, and the more accurate the results. For the linear variable-frequency current, the IWDVF obtained by the curve fitting method is close to the average value of the ITHD obtained by FFT, which indicates that the time-domain curve fitting method is reasonable to solve the IWDVF. For nonlinear variable-frequency current waveforms, the curve fitting method can also reasonably calculate the IWDVF. The curve fitting method can solve the evaluation problem of the variable-frequency current, and provide an evaluation means for the optimal design of a modulation strategy aiming at the optimal waveform quality of the variable- frequency current.
Simulation Research on Thermal Deviation in 700 °C Ultra-Supercritical Boiler
Authors: Kong Zheng , Liu Jianquan , Zhou Changxin
Published: October 2022

Based on commercial CFD software, a 700 °C ultra-supercritical tangential boiler was simulated by the orthogonal test method, and the thermal deviation of flue gas at the furnace outlet section was used as the optimization index. Three horizontal optimization treatments are designed respectively for the air distribution mode of secondary air (factor A), the reverse tangent angle of the separate over-fire air (factor B), and the upper swing angle of the burner (factor C). The range analysis method, variance analysis method, and weight matrix analysis method are used to determine the factor and level combination of the best optimization effect and the weight of each factor. The research results show that the significance of the influence of each factor on the optimization index is: B > C > A (reverse tangent angle of the separate over-fire air > the upper swing angle of the burner > the secondary air distribution mode); the weight ratios of the three factors are: factor A is 0.080, factor B is 0.543, and factor C is 0.241; based on the three analysis methods, it is concluded that factor B has a highly significant impact on the optimization index, factor C has an impact on the optimization index, and factor A has no impact on the optimization index, and it is determined that the optimal factor and level combination of the orthogonal test is A1B3C3. Under this combination, the thermal deviation in the furnace is 1.349 K, and the problem of thermal deviation is basically eliminated, being 116.066 K lower than the highest thermal deviation of 117.415 K, which is very obvious.
Joint Planning of Offshore Wind Power Storage and Transmission Considering Carbon Emission Reduction Benefits
Authors: Chen Honglin , Yu Hao , Yang Xiaojuan , Lin Yong , Lou Suhua , Peng Sui
Published: October 2022

There are two situations of transmission redundancy and transmission congestion when large-scale offshore wind farms send power out. The energy storage system can store the power blocked by wind power due to insufficient transmission capacity and release it in the period when the wind power output level is low. In this paper, a full-life-cycle cost model is established for energy storage, and a joint planning model for offshore wind power storage and transmission considering carbon emission reduction benefits is established, which integrates power grid transmission benefits, carbon emission reduction benefits, energy storage construction costs, transmission project construction costs and wind abandonment penalty costs. The channel construction and energy storage configuration scheme with the greatest net benefit can be obtained. The relationship between the transmission channel capacity setting and the energy storage parameter configuration under this model is studied, and the combined effect of transmission channel and energy storage system in improving the level of wind power transmission is analyzed. The sensitivity analysis of the influence of the optimal storage and transmission planning scheme of the offshore wind farms is carried out from the perspectives of transmission line engineering cost and transmission channel curve type.
Sensorless Control of High-Speed Motors Subject to Iron Loss
Authors: Cao Yang , Guo Jian
Published: October 2022

It is widely recognized that the iron loss produced by motors at high speeds will directly affect the angle and size of the back electromotive force, and, therefore, it cannot be ignored. In this paper, a high-performance sensorless control algorithm is proposed for high-speed permanent magnet synchronous motors (HSPMSM), taking the iron loss into account. First, the resistance representing the core loss is precalculated by finite element analysis, and then a sliding mode observer with disturbance observation is designed to estimate the rotor position. The observer possesses the advantages of suppressing the chattering phenomenon and enhancing the robustness against uncertainty. Meanwhile, the idea of the characteristic model is used to design an adaptive robust control law to improve the speed control accuracy. Subsequently, a sensorless control scheme is proposed by using the proposed observer in combination with the designed control scheme. The stability of the observer and controller is verified by the Lyapunov theory method. Finally, a simulation example is given to demonstrate the correctness and the effectiveness of the proposed algorithm.
Characterization of a Non-Darcy Flow and Development of New Correlation of NON-Darcy Coefficient
Authors: Elsanoose Abadelhalim , Abobaker Ekhwaiter , Khan Faisal , Rahman Mohammad Azizur , Aborig Amer , Butt Stephen D.
Published: October 2022

Darcy’s law has long been used to describe the flow in porous media. Despite the progress that took place in oil production industry research, it became clear that there is a loss of pressure, especially in the area near the wellbore region, where Darcy’s law is not applicable. For this reason, Forchheimer presented his equation in 1910, where he added a new term to Darcy’s law dealing with pressure loss due to inertial forces by introducing a new term, the β coefficient, into the equation. This paper presents a study of fluid flow through porous media, where water was used as a working fluid. Furthermore, the characteristics of the non-Darcy flow were analyzed by presenting the corresponding pressure and velocity gradient curves for each pressure. Extensive analysis indicates that many of the correlations available in the literature either have defective units or are the product of a small number of experiments. In this study, we benefit from relatively large samples, the radial flow, and the perforation in the middle of the samples. The properties of the samples were measured using mercury intrusion porosimetry. It was found that there is a direct relationship between the porosity and the grain’s size; the greater the size of the grains, the greater the porosity, and vice versa. The non-Darcy coefficient term, β, is found to be inversely proportional to the porosity and permeability. In a previous study, the β was investigated for compressible flow scenarios; however, this study calculated it for an incompressible flow. Finally, by analyzing the β values of both studies, we could deduce new novelty correlations for the β coefficient term, where the permeability, porosity, and tortuosity are included.
Effectiveness of the Chebyshev Approximation in Magnetic Field Line Tracking
Authors: Albanese Raffaele , Chiariello Andrea Gaetano , Fresa Raffaele , Iaiunese Antonio , Martone Raffaele , Zumbolo Pasquale
Published: October 2022

The tracking of magnetic field lines can be very expensive, in terms of computational burden, when the field sources are numerous and have complex geometries, especially when accuracy is a priority, because an evaluation of the field is required in many situations. In some important applications, the computational cost can be significantly reduced by using a suitable approximation of the field in the integrated regions. This paper shows how Chebyshev polynomials are well-suited for field interpolation in magnetic field-line tracking, then discusses the conditions in which they are most appropriate, and quantifies the effectiveness of parallel computing in the approximation procedures.
Evaluation and Optimization of heat Pump Combined District Heating System: A Case Study of China
Authors: Cheng Ling , Yu Zesheng , Xia Shiyao , Li Shixuan , Li Ye , Zhang Huan , Li Bin , Zhang Sirui , Liu Zijian , Zheng Wandong
Published: October 2022

The district heating area in China is continuously increasing, which brings an increase in district heating load. In order to solve the shortage of heating power and realize the carbon neutral target, this study proposes two retrofit schemes for district heating system by integrating air source heat pump and water source heat pump, respectively. Mathematical models are established to study the performance of the integrated systems and a bilevel optimization model is proposed to optimize them. The results show that the air source heat pump combined district heating system has better performance compared to the conventional system, which reduces 50% energy consumption, 10.8% carbon emissions and achieves better economy. The dynamic coupling property of the district heating network and power grid are also considered, and the results indicate that the introduction of air source heat pump can effectively improve the efficiency and stability of power grid and reduce the seasonal fluctuation. The potential of large-scale application of air source heat pump combined system in Beijing is evaluated. The results reveal that retrofit scheme of integrating air source heat pumps into district heating system can cover 2930 MW heating load and bring 362 million Chinese Yuan profit by reducing 219,000 tons of carbon emissions and 539,000 tons of standard coal consumption in 2025.
Investigation on Coalbed Methane Fracturing Using Supercritical CO2 Graphene Cement Slurry System
Authors: Li Dongyuan , Luo Pingya , Peng Xiaojun , Zou Tao , Fu Li , Fu Wanchun , Xie Gang
Published: October 2022

In this study, we innovatively use sulphoaluminate cement slurry and its additives as a fracturing fluid system for supercritical CO2 graphene-permeable cement stone (referred to hereafter as the SCGPCS) fracturing without sand. Utilizing small fluid volumes, small displacement and small pump pressure, we obtain the success of the first field test in an extra-low desorption pressure coal seam. Laboratory experiments have proven that sulphoaluminate cement is suitable as base cements for the SCGPCS system due to their rapid setting and fast hardening characteristics. The reaction of sodium carbonate + aluminum sulfate system and sodium bicarbonate + aluminum sulfate system will generate precipitation to block the internal pore structure of cement stone, leading to a decrease in permeability. Calcium hypochlorite (1.5 wt.%) + urea (0.6 wt.%) system is preferred as a gas-generating agent system for SCGPCS. Sand (30 wt.%) with 300–425 μm particle size is preferred as a structural strength substance for SCGPCS. Graphene poly-gel (referred to hereafter as the GPG) has a high FCI and good CO2 foam stability. GPG (6.0 wt.%) is preferred as a foam stabilizer for SCGPCS. The thickening time of graphene–foam–cement slurry is 138 min at 50 °C, with long pumping time, normal thickening curve and excellent performance. The SCGPCS has a corrosion rate of 11.25 mpy in the formation water and can be stable in the formation. Acid is more corrosive to SCGPCS, and it can be used to improve the permeability of SCGPCS. Field tests have proven that SCGPCS fracturing injected 33 m3 of fluid, of which 27 m3 entered the formation. Graphene–foam–cement slurry was injected into the formation through the casing for 13 m3, with a displacement of 0.4–0.6 m3/min and tubing pressure 8–13 MPa. The formation was fractured with a fracturing crack half-length of 71.58 m, a supported fracturing crack half-length of 56.95 m, and a supported fracturing crack permeability of 56.265 mD.
Experimental and Photothermal Performance Evaluation of Multi-Wall Carbon-Nanotube-Enhanced Microencapsulation Phase Change Slurry for Efficient Photothermal Conversion and Storage
Authors: Wang Changling , Zhang Guiling , Zhang Xiaosong
Published: October 2022

Melamine formaldehyde was used as the shell material and n-eicosane as the core material with the method of in situ polymerization to synthesize microencapsulated phase change materials (MPCMs). To enhance the thermophysical characteristics and photothermal conversion performance of the MPCM slurry, multi-wall carbon nanotubes were added, and the microscopic morphology and thermophysical parameters of the MWCNT-MPCM slurry were analyzed. The thermal conductivity, viscosity, and photothermal conversion properties of the slurry were examined. The results indicated that the synthesized MPCMs were nucleated and unbroken, with a spherical form and a latent heat of phase transition of up to 135.92 kJ/kg. The MPCM was stable when dispersed in water, and its thermal conductivity rose with the temperature but slightly decreased during the phase transition period. The viscosity rose with the addition of the MPCM, with a jump at 20% MPCM content. The addition of MWCNTs had a minor effect on the material’s thermophysical properties. The thermal conductivity increased from 0.55 W/m·°C to 0.6 W/m·°C when MWCNTs were added to the material. The viscosity of a 20% MPCM slurry exceeded 3000 mPa·s when 0.5% MWCNTs were introduced. Under 1 sun of sunlight, the mixture’s peak temperature could reach 60 °C at 0.5% MWCNT concentration. The MWCNT-MPCM slurry is capable of producing efficient solar photothermal conversion without sacrificing other thermophysical properties, and it has several applications in solar energy consumption and thermal engineering.
Principle, Fabrication and Emerging Applications of Nanobottle Motor
Authors: Liu Qingyuan , Wang Lin , Wang Kaiying , Wang Tianhu , Liu Guohua
Published: October 2022

Micro/nano-motors play an important role in energy, environment, and biomedicines. As a new type of nano-motors, nanobottles attract great attention due to their distinct advantages of a large cavity, high specific surface area, bionic streamline structure, and chemotactic motion. Here, we systematically review the development of nanobottle motors from aspects of propulsion mechanisms, fabrication methods and potential applications. Firstly, three types of propulsive modes are summarized, with focus on chemical propulsion, light driving and magnetic actuation. We then discuss the fabrication methods of nanobottles, including the soft-template-based hydrothermal method and the swelling-inducement and wet-chemistry methods. The potential applications of nanobottle motors are additionally highlighted in energy, environmental, and biomedical fields. Finally, the future challenges and outlooks of nanobottle motors are discussed for the further development of this technology.
Reservoir Permeability Calculation under Flow Unit Control
Authors: Cheng Xincai , Zhao Bin , Gao Chuqiao , Gao Ying
Published: October 2022

The No. 2 gas field in the X depression is a low-permeability tight reservoir with a complex lithology, pore structure, and strong physical heterogeneity, and the conventional core porosity–permeability regression method does not meet the requirements of fine evaluation in terms of the accuracy of permeability calculation. The flow unit method has great advantages in improving the accuracy of permeability calculation, but the FZI calculation method is too ideal and weakens the influence of the pore structure’s heterogeneity, and it needs to be verified that the FZI in the study area has a good correlation with the pore structure before it can be used. Therefore, based on analyzing the permeability control factors of low-permeability tight reservoirs, we analyze the correlation between three pore structure characterization parameters and the flow unit index FZI, which proves that the flow unit index FZI in this area can characterize the permeability difference within different flow units. Based on FZI theory and the cumulative frequency division method, we establish a fine evaluation model of four types of reservoirs in the study area. Through the response characteristics and correlation analysis of the conventional logging curves, we select three combined curves, establish a multi-parameter equation, and apply it to the permeability evaluation of the cored section that is not involved in modeling. The application results show that the calculated permeability is in good agreement with the core analysis results, which provides a theoretical basis for the fine evaluation of low-permeability tight reservoirs.
Review on Active Distribution Networks with Fault Current Limiters and Renewable Energy Resources
Authors: El-Ela Adel A. Abou , El-Sehiemy Ragab A. , Shaheen Abdullah M. , Ellien Aya R.
Published: October 2022

To cope with the increasing energy demand, power systems, especially distribution networks, face many challenges. Recently, these networks have become complex and large, and their stability and reliability are not easy to be handled. The integration of renewable energy resources and at the same time limiting their accompanied high fault currents is one of the approvable suggestions. Many solutions have appeared to restrict the fault currents, but fault current limiters (FCLs) arise as an efficient and promising solution to whether to interrupt or limit the fault currents to allowable limits. This paper presents a literature review of the integration of renewable energy resources as distributed generation units (DGs) and FCLs in distribution networks. The DGs can be categorized based on their size and ability to deliver active or reactive power in addition to their fuel. All of solar, wind, water, biomass, geothermal, and fuel cell are utilized as the main engine for these units. Additionally, a survey about FCLs is provided, including their diverse types and applications in either medium- or low-voltage networks. FCLs are divided into reactor, pyrotechnic, non-superconducting (solid state), and the last-developed ones, superconducting FCLs. In addition, the implemented optimization techniques are summarized to correctly employ both FCLs and DGs. These techniques vary between classical and modern, whereas more methods are developed to suit the renewable energy intermittence and uncertainty and the power system operators’ aspirations. Moreover, in this paper, the optimal allocation of diverse types of DGs correlated with FCLs is presented and applied to the real Egyptian distribution network of the East Delta Network (EDN). The results show the avails obtained where the power losses are significantly reduced, with respect to the total load, from 3.59% in the initial case to 0.296%. In addition, the fault current returns to its initial value, removing the percentage of increase of 20.93%.
A Coverage Optimization Algorithm for the Wireless Sensor Network with Random Deployment by Using an Improved Flower Pollination Algorithm
Authors: Jiao Wanguo , Tang Rui , Xu Yun
Published: October 2022

Due to complex terrain and harsh environments, sensor nodes are often randomly scattered in the monitoring area, which may cause coverage holes or network disconnection. Current works move some sensor nodes to certain places to address this problem. However, these works cannot guarantee the coverage and connectivity simultaneously and have larger moving cost in energy. In this paper, we propose a coverage optimization strategy based on the flower pollination algorithm (FPA). First, to solve the shortcomings of the classical FPA in convergence and accuracy, an improved FPA is proposed. Then, the network deployment optimization problem is modeled as a multi-objective optimization problem that guarantees the coverage of target points and the connectivity of the network while minimizing the energy consumption of sensor nodes’ moving. The sensor nodes are selected and moved to the proper position by utilizing the improved FPA to minimize the energy consumed by the sensors’ motion and guarantee the coverage and connectivity. Test results show that the improved FPA has good convergence speed and accuracy compared with other evolutionary algorithms. Simulation results demonstrate that the proposed algorithm can guarantee network connectivity and satisfy the coverage requirement while minimizing the energy consumption of the sensor movement. Consequently, more energy of the sensor node can be used to collect and transmit sensed data. These results indicate that our algorithm can prolong network lifetime and improve monitoring quality in fields such as forest monitoring.
Bayesian Approach for Optimizing Forest Inventory Survey Sampling with Remote Sensing Data
Authors: Pohjankukka Jonne , Tuominen Sakari , Heikkonen Jukka
Published: October 2022

In large-area forest inventories, a trade-off between the amount of data to be sampled and the corresponding collection costs is necessary. It is not always possible to have a very large data sample when dealing with sampling-based inventories. It is therefore important to optimize the sampling design with the limited resources. Whereas this sort of inventories are subject to these constraints, the availability of remote sensing (RS) data correlated with the forest inventory variables is usually much higher. For this reason, the RS and sampled field measurement data are often used in combination for improving the forest inventory estimation. In this study, we propose a model-based data sampling method founded on Bayesian optimization and machine learning algorithms which utilizes RS data to guide forest inventory sample selection. We evaluate our method in empirical experiments using real-world volume of growing stock data from the Aland region in Finland. The proposed method is compared against two baseline methods: simple random sampling and the local pivotal method. When a suitable model link is selected, the empirical experiments show on best case on average up to 22% and 79% improvement in population mean and variance estimation respectively over baselines. However, the results also illustrate the importance of model selection which has a clear effect on the results. The novelty of the study is in the application of Bayesian optimization in national forest inventory survey sampling.
Individual-Tree and Stand-Level Models for Estimating Ladder Fuel Biomass Fractions in Unpruned Pinus radiata Plantations
Authors: Alonso-Rego Cecilia , Fernandes Paulo , Álvarez-González Juan Gabriel , Arellano-Pérez Stefano , Ruiz-González Ana Daría
Published: October 2022

The mild climate and, in recent decades, the increased demand for timber have favoured the establishment of extensive plantations of fast-growing species such as Pinus radiata in Galicia (a fire-prone region in northwestern Spain). This species is characterised by very poor self-pruning; unmanaged pine stands have a worrying vertical continuity of fuels after crown closure because the dead lower branches accumulate large amounts of fine dead biomass including twigs and suspended needles. Despite the important contribution of these dead ladder fuels to the overall canopy biomass and to crown-fire hazards, equations for estimating these fuels have not yet been developed. In this study, two systems of equations for estimating dead ladder fuel according to size class and the vertical distribution in the first 6 m of the crown were fitted: a tree-level system based on individual tree and stand variables and a stand-level system based only on stand variables. The goodness-of-fit statistics for both model systems indicated that the estimates were robust and accurate. At the tree level, fuel biomass models explained between 35% and 59% of the observed variability, whereas cumulative fuel biomass models explained between 62% and 81% of the observed variability. On the other hand, at the stand level, fuel-load models explained between 88% and 98% of the observed variability, whereas cumulative fuel-load models explained more than 98% of the total observed variability. These systems will therefore allow managers to adequately quantify the dead ladder fuels in pure Pinus radiata stands and to identify the treatments required to reduce crown-fire hazard.
The Interconnected Relationship between Auxin Concentration Gradient Changes in Chinese Fir Radial Stems and Dynamic Cambial Activity
Authors: Yang Liwei , Zhu Sheng
Published: October 2022

Auxin has been shown to exhibit a striking concentration gradient distribution in radial sections of angiosperm and gymnosperm species, in which peak auxin levels are concentrated in dividing cambial cells, while the absolute auxin concentration sharply declines toward developing secondary phloem and xylem regions. The coincidence of auxin concentration gradient across shoot tissues and xylem cell developmental gradient has prompted that auxin could act as “a plant morphogen” to provide a positional signal for cambial cell development. However, the specific location of vascular cambium and the lack of mutants altering auxin distribution in shoots of woody species made further verification experiments difficult to explore. To address this issue, different concentrations of exogenous IAA were applied to decapitated Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) trunks in this study to induce the change in the auxin concentration gradient in radial stems, and its effects on cambial activities were examined on the physiological, cellular and molecular levels. Our findings manifested that exogenous IAA treatments resulted in vast changes in endogenous hormone concentrations (including IAA, ZR, GA3 and ABA), cambial cell developmental behaviors and transcriptional activities of genes related to polar auxin transport (PAT), auxin signaling, the biosynthesis and signal transduction of other plant hormones and the genetic control of cambial activity. Based on above findings, we postulated a model of auxin concentration gradient involved in the control of cambial activity and secondary growth in tree trunks. In this model, the contrasting expression of AUX1/LAX and PIN family carriers in distinct Chinese fir wood-forming tissues dynamically modulates PAT into the cambial zone adjacent to the secondary phloem side and secondary xylem tissues, resulting in a sharp and wide auxin spatial gradient distribution across shoots in different stages of secondary growth, respectively. This change in auxin concentration gradient distribution in radial sections in turn acts on cambial developmental behaviors by modulating the expression of auxin signaling genes and key transcription factors and the production of other plant hormones in distinct woody tissues. Findings in this study provide important insights for understanding the biological significance of auxin concentration gradient existing in the radial stems of woody species.
Populus tremula × P. alba Microshoot Secondary Metabolism Response after Paenibacillus sp. Inoculation In Vitro
Authors: Vaitiekūnaitė Dorotėja , Striganavičiūtė Greta , Mishcherikova Valeriia , Sirgedaitė-Šėžienė Vaida
Published: October 2022

Bacterial biostimulants are an eco-friendly alternative to chemical fertilizers. However, before their introduction into open ecosystems, broad-scope studies need to be carried out. Paenibacillus sp. was shown to positively affect poplar root growth. It was hypothesized that alongside these improvements, the Paenibacillus sp. inoculant may affect its host’s secondary metabolism. Populus tremula × P. alba microshoots were inoculated in vitro. Microshoots were tested for chlorophyll, carotenoid, total flavonoid (TFC), total phenol content (TPC) and free radical scavenging capacity during primary growth after 4, 6 and 8 weeks. The results showed that the inoculation decreased shoot phenolics and free radical scavenging capacity after 6 and 8 weeks. Chlorophyll b amounts increased after 6 and 8 weeks. Carotenoid content decreased after 6 weeks, while chlorophyll a and carotenoid levels increased after 8 weeks. Correlation and principal component analyses showed that the inoculant changed the way in which the photosynthesis pigment content relates to TPC, TFC and radical scavenging activity. Overall, these data suggest that the inoculant does statistically significantly affect Populus tree secondary metabolism in the later stages of the initial growth period. This effect may potentially be compensatory in nature.
Optimal Forest Road Density as Decision-Making Factor in Wood Extraction
Authors: Simões Danilo , Cavalcante Felipe Soares , Lima Roldão Carlos Andrade , Rocha Qüinny Soares , Pereira Gilberto , Miyajima Ricardo Hideaki
Published: October 2022

Forest road construction projects mainly depend on factors related to terrain physiography, watershed, and wood harvesting. In the whole tree system, wood extraction is the activity most impacted by the density of forest roads, influencing the extraction distance. One of the alternatives is the optimal forest road density approach, which allows for the minimization of wood extraction costs and the optimization of the productive area. Given the above, the objective of this study was to analyze whether the optimal forest road density in areas of forests planted with eucalyptus allows for maximum productivity and the lowest cost of the road-wood extraction binomial in a whole tree system. The technical and economic analysis of wood extraction was based on the study of time, operational efficiency, productivity, and the cost of wood extraction with a grapple skidder. For the optimal forest road density, the cost of the wood extraction activity was considered, as well as the cost of construction, reconstruction, and maintenance of roads. In addition, the cost of a loss of productive area and the cost of excess forest roads were weighted. The optimal forest road density was 30.49 m ha−1 for an average extraction distance of 81.99 m, with the cost of loss of productive area of 0.49 USD m³ and the excess road of 80.19 m, which represented a cost of 978.31 USD ha−1. It is concluded that the optimal forest road density allows for the identification of excess forest roads, allowing for a reduction in the total cost for the implementation of roads. Therefore, it can be considered an essential variable in the planning of the forest road network, providing improvements in productivity and the costs of wood extraction with a grapple skidder.
Memory Effects of Water Deprivation in European Beech (Fagus sylvatica L.) and Silver Fir (Abies alba Mill.) Seedlings Grown in Mixed Cultivation
Authors: Yang Fengli , Du Baoguo , Burzlaff Tim , Dutta Shourav , Dannenmann Michael , Quan Xueying , Maurer Daniel , Rennenberg Heinz
Published: October 2022

Very limited information is available on the drought tolerance of European beech and silver fir in mixed cultivation, both for mature forests and natural regeneration. Particularly, little information is available regarding the significance on memory effects of drought exposure. Therefore, drought memory was analyzed in seedlings of these species grown in mixed cultivation in the present study. The results showed that previous-year drought hardening mediated enhanced biomass accumulation of beech leaves and root in the subsequent year, but did not impact fir growth. Total carbon (C) content was decreased by drought hardening in both the leaves and roots of beech and previous-year needles and roots of fir, in beech probably as a consequence of increased growth. Previous-year drought hardening had no significant effect on relative water contents, total nitrogen (N), or soluble protein contents in leaves and roots of beech and fir, but resulted in decreased total amino acid contents of beech leaves and fir needles. It further reduced structural N in current-year fir needles and decreased C/N ratios in roots of both beech and silver fir seedlings. Generally, the number of interspecific neighbors had no considerable effect on biomass or total C or N contents, as well as N partitioning in leaves and roots of beech and fir seedlings. The present study highlights that drought hardening induces memory effects in European beech and silver fir seedlings in their mixture in the subsequent year of growth, but these memory effects are stronger in beech than in fir.
Effects of Maize Varieties on Biomass Yield and Silage Quality of Maize–Soybean Intercropping in the Qinghai–Tibet Plateau
Authors: Li Jiayi , Wen Xingjin , Yang Jizhi , Yang Wenyu , Xin Yafen , Zhang Lei , Liu Haiping , He Yaling , Yan Yanhong
Published: October 2022

Forage deficiency is the bottleneck that restricts the development of plateau animal husbandry. Maize (Zea mays L.)–soybean (Glycine max L.) intercropping can improve the forage biomass yield and silage quality. This experiment was conducted in Ganzi Tibetan Autonomous Prefecture to explore the effects of four maize varieties (M1, Rongyu Silage No. 1; M2, Yayu 04889; M3, Demeiya No. 1; M4, Zhenghong 505) on biomass yield, nutritional composition, and silage quality in maize–soybean intercropping. The results showed that M1S had the highest total dry matter yield (18.03 t ha−1), M3S had the highest crude protein (CP) content (8.46% DM), and soybeans had the highest water-soluble carbohydrate (WSC) content (8.55% DM). After silage, the CP content (13.44% DM) of mixed silage in M3S was higher, and the contents of neutral detergent fiber (39.42% DM) and acid detergent fiber (25.42% DM) were lower than those in maize silage alone. The WSC content (4.45% DM) of mixed silage in M3S was higher and the pH value (4.46) and ammonia–nitrogen to total nitrogen (3.97%) were lower than those of soybean silage alone. The results of membership function analysis showed that M3S was the best in fresh feeding and silage utilization, followed by M1S. Therefore, M3S (Demeiya No 1. intercropped with soybeans) is recommended in high-altitude areas.
Fortification of Cow Milk with Moringa oleifera Extract: Influence on Physicochemical Characteristics, Antioxidant Capacity and Mineral Content of Yoghurt
Authors: Lisak Jakopović Katarina , Repajić Maja , Rumora Samarin Ivana , Božanić Rajka , Blažić Marijana , Barukčić Jurina Irena
Published: October 2022

Background: Fermented dairy products are known for their many positive effects on human health and are consumed worldwide. The supplementation of food with plant extracts as sources of valuable nutritional compounds has recently gained a lot of attention. Milk and fermented products are deficient in bioactive components such as phenolic compounds and iron. Moringa oleifera leaf extract is rich in vitamins, minerals (iron), polyphenols, flavonoids, tannins and proteins. Its addition to milk before fermentation might represent an excellent way to enrich fermented milk products. Methods: Yoghurts enriched with moringa extract (ME) (1, 3 and 4-%, v/v) were produced and compared to a control yoghurt without ME. In all samples, acidity, microbiological parameters, syneresis and water holding capacity, rheology parameters, total colour difference, mineral content, total phenols and antioxidant capacity (FRAP method) and sensory properties were determined. Results: The addition of ME to milk before fermentation resulted in a shorter fermentation time, lower yoghurt pH, increased growth of yoghurt bacteria, better rheological properties and an increased total phenols content as well as antioxidant capacity of yoghurts. Moreover, yoghurts with ME addition had a higher mineral content and gained a better sensory score when compared to the control sample.
Plant Proteins as an Alternative Nitrogen Source for Chiral Purity L-Lactic Acid Fermentation from Lignocellulose Feedstock
Authors: Zhang Bin , Wu Lei , Liu Xiucai , Bao Jie
Published: October 2022

High optical purity lactic acid is in high demand as the precursor for synthesizing polylactic acid (PLA). The costs of expensive carbohydrates and nitrogen source materials accounts for a large portion of the production costs in lactic homo-fermentation. The use of lignocellulosic biomass for lactic acid production reduces the cost of the carbohydrate feedstock, but the cost of nitrogen sources is a big challenge when considering the high prices of general nitrogen sources. Low-cost nitrogen materials are vulnerable to being contaminated by exogenous mixed L-lactic acid and D-lactic acid; thus, their feasibility as nitrogen sources for the production of optically pure lactic acid products is hindered. The available reports focus on cost reduction using agro-industrial byproducts as nutrient sources, with these presenting fewer concerns on the effect of the optical purity of lactic acid-product monomers for polymerization. In this study, commonly used low-cost nutrient sources were characterized and screened for high optical purity L-lactic acid fermentation. Corn steep liquor (CSL), a widely used and cheap nutrient for lactic acid fermentation, was found not to be suitable because of its high content of mixed D-/L-lactic acids (up to 20%, w/w). On the other hand, cottonseed meal was found to be completely free of mixed L-/D-lactic acids. Therefore, the cottonseed meal was hydrolyzed with dilute sulfuric acid and used as a nitrogen source for L-lactic acid fermentation using lignocellulose feedstock as a substitution for yeast extract and peptone. The results showed that the final L-lactic acid titer reached 96.5 ± 0.2 g/L from 25% (w/w)-solids loaded pretreated and biodetoxified wheat straw with a yield of 0.31 g/g feedstock and an optical purity of 99.7%. The techno-economic evaluation indicated that the cost of the cottonseed meal was only USD 0.193/kg of lactic acid product, and the minimum lactic acid selling price (MLSP) was USD 0.813/kg of lactic acid product, which was only 25.1% compared to the use of yeast extract and peptone as the nutrients. Cellulosic L-lactic acid production using cottonseed meal as a complex nutrient source showed competitive performance when compared to starch feedstock from food crops.
Impact of Cationic Polyelectrolyte Addition on Mesophilic Anaerobic Digestion and Hydrocarbon Content of Sewage Sludge
Authors: De Simone Simeone , Di Capua Francesco , Pontoni Ludovico , Giordano Andrea , Esposito Giovanni
Published: October 2022

The agricultural spreading of treated sewage sludge is a valid strategy in terms of circular economy for the management of this nutrient-rich waste. Anaerobic digestion (AD) can be applied to stabilize and hygienize sewage sludge, making it suitable for agricultural reuse, while producing biogas to be utilized as an energy vector. However, the presence of contaminants, including petroleum hydrocarbons, could limit the widespread agricultural utilization of sewage sludge. In this context, the impact of dewatering agents, such as cationic polyelectrolytes, on AD efficiency and hydrocarbon biodegradation has been poorly investigated, although it represents a noteworthy aspect when conditioned sludge is digested for agricultural use in centralized biogas plants. This work aims to elucidate the effect of cationic polyelectrolyte addition on biomethanation as well as the degradation and extractability of C10-C40 hydrocarbons during mesophilic AD of sewage sludge. The addition of 26.7 g/kgTS of cationic polyelectrolyte was observed to extend the AD lag phase, although similar methane yields (573–607 mLCH4 per g of degraded volatile solids) were observed for both conditioned and raw sludge. Furthermore, a significant impact on hydrocarbon degradation was observed due to chemical conditioning. Indeed, this work reveals that cationic polyelectrolytes can affect hydrocarbon extractability and suggests moreover that the presence of natural interferents (e.g., biogenic waxes) in sewage sludge may lead to an overestimation of potentially toxic C10-C40 hydrocarbon concentrations, potentially limiting the application of sludge-derived digestates in agriculture.
A Survey of Wi-Fi 6: Technologies, Advances, and Challenges
Authors: Mozaffariahrar Erfan , Theoleyre Fabrice , Menth Michael
Published: October 2022

Wi-Fi is a popular wireless technology and is continuously extended to keep pace with requirements such as high throughput, real-time communication, dense networks, or resource and energy efficiency. The IEEE 802.11ax standard, also known as Wi-Fi 6, promises to provide data rates of up to almost 10 Gb/s, lower energy consumption, and higher reliability. Its capabilities go far beyond Wi-Fi 5 (802.11ac) and novel technical concepts have been introduced for this purpose. As such, the Wi-Fi 6 standard includes Multi-User Orthogonal Frequency Division Multiple Access (MU OFDMA), Multi-User Multiple-Input Multiple-Output (MU MIMO), new mechanisms for Spatial Reuse (SR), new mechanisms for power saving, higher-order modulation, and additional minor improvements. In this paper, we provide a survey of Wi-Fi 6. Initially, we provide a compact technological summary of Wi-Fi 5 and its predecessors. Then, we discuss the potential application domains of Wi-Fi 6, which are enabled through its novel features. Subsequently, we explain these features and review the related works in these areas. Finally, performance evaluation tools for Wi-Fi 6 and future roadmaps are discussed.
Smart Preliminary Channel Access to Support Real-Time Traffic in Wi-Fi Networks
Authors: Chemrov Kirill , Bankov Dmitry , Khorov Evgeny , Lyakhov Andrey
Published: October 2022

Real-time applications (RTA) are an important use case for IEEE 802.11be, a new amendment to the Wi-Fi standard. This amendment introduces new complicated mechanisms to provide low delay and high reliability for RTA, but many of them are not supported by legacy devices that may be present in future Wi-Fi networks. In contrast, the preliminary channel access (PCA) method is designed to satisfy strict RTA requirements even in the presence of legacy devices and does not require significant changes to the Wi-Fi protocol. However, it significantly reduces the capacity for non-RTA traffic. This paper introduces a Smart PCA method, which improves the performance of all the stations in scenarios with multiple RTA stations. Extensive simulation shows that the Smart PCA method guarantees low delays for intensive RTA traffic in these scenarios. Moreover, it doubles the network capacity for the stations with non-RTA traffic.
Study of the Heat Exhaust Coefficient of Lateral Smoke Exhaust in Tunnel Fires: The Effect of Tunnel Width and Transverse Position of the Fire Source
Authors: Liu Qiulin , Xu Zhisheng , Xu Weikun , Tagne Sylvain Marcial Sakepa , Tao Haowen , Zhao Jiaming , Ying Houlin
Published: October 2022

The tunnel width and the transverse fire’s position both impact the heat exhaust coefficient, which is a critical component of the lateral smoke exhaust in tunnel fires. In this research, the tunnel width and the transverse location of the fire source are varied to analyze the heat exhaust coefficient of lateral smoke exhaust. When tunnel width increases, there is a noticeable decrease in the longitudinal temperature of the entrained air and smoke layer in the fire plume. Furthermore, the heat exhaust coefficients are reduced. An increase in the distance between the exhaust vent and the fire source causes an increase in the proportion of hot smoke in the smoke exhaust mass flow, which increases the heat exhaust coefficient. A calculated heat exhaust coefficient was developed using the fire source’s location and the tunnel’s width as inputs, which agrees well with the simulation results. This method can predict the heat exhaust coefficient of the lateral smoke exhaust in tunnel fires. The findings of this study provide insight into how the tunnel width and the location of a transverse fire influence the heat exhaust coefficient.
Genetic Diversity and Population Structure of the Giant Mottled Eel, Anguilla marmorata Quoy & Gaimard, 1824 in Central Vietnam
Authors: Nguyen Anh Tuan , Dao Hoc Tan , Quang Hoang Tan , Hagihara Seishi , Lokman P. Mark , Damsteegt Erin L.
Published: October 2022

The giant mottled eel, Anguilla marmorata, is at high risk of extinction due to overfishing of glass eels and elvers to provide stock for eel farming. In Vietnam, information on the genetic diversity and population structure of this species, which is necessary for resource management, is limited. In order to address this paucity of information, sequencing of the entire mitochondrial control region (mtDNA) was carried out for 176 individuals collected from central Vietnam. The sequences were investigated using various genetic, phylogenetic and population analyses. A total of 165 distinct haplotypes were identified. The percentage of variation within and among populations was 99.26% and 0.74%, respectively. The fixation index was low (0.007) and not significant (p = 0.096). Therefore, panmixia and a lack of significant population genetic structuring seem likely for A. marmorata in central Vietnam. Most sampled eels were genetically similar to eels found in North Pacific populations (Japan, Taiwan and the Philippines), except for one sample from Quang Tri and two samples from Binh Dinh, which had high values of genetic identity (97% to 99%) with South Pacific populations (Tahiti, Fiji, New Caledonia and Papua New Guinea). Taken together, we suggest that A. marmorata from the North and South Pacific populations co-exist in central Vietnam.