798 research outputs found
Data_of_WGR for An empirical study on waste generation rates at different stages of construction projects in China
No full textData_of_WGR for An empirical study on waste generation rates at different stages of construction projects in China by Qiankun Wang, Lei Chen, Ruibo Hu, Zhigang Ren, Yanting He, Daoru Liu and Ziqi Zhou in Waste Management & Research</p
Plantations thinning: A meta-analysis of consequences for soil properties and microbial functions
No full textForest conversion to plantations: A meta‐analysis of consequences for soil and microbial properties and functions
No full textOptimization of nonstandard Tripping Protection Scheme for radial and meshed power networks with distributed generation systems
No full textThe operation of modern distribution networks (DNs) tackles serious challenges due to the integration of distributed generations (DGs). The protection scheme is one of these challenges. Particularly, the occurrence of bi-directional short-circuit current flow that affects the reliability, sensitivity and selectivity of traditional overcurrent relays (OCRs). In addition, the future distribution system with DGs is expected that will be occupied by the meshed networks alongside the classical radial design and alternating between the grid-connected and islanded mode, for enhancing their reliability.
The purpose of the present thesis is to introduce practicable protection proposals for such implementations and address pertinent protection issues. In this context, a comprehensive literature review has been introduced in the present thesis critically. The main contribution of this thesis is the introduction of advanced non-standard methods for addressing the coordination problem of OCRs in DNs with a growing integration of DGs in the power system.
Firstly, this thesis presents a novel optimal OCR coordination scheme developed using the non-standard current characteristics (NSTCCs) approach. This approach is specifically designed to adjust OCRs. The proposed equation is contingent on a variable dynamic coefficient based on a logarithmic function curve for improving the flexibility of the curve, thus the optimal coordination between OCRs has been obtained throughout different fault modes. For enhancing the performance of the proposed approach on the OCRs coordination in the DNs, two optimization techniques, namely, the genetic algorithm (GA) and hybrid gravitational search algorithm–sequential quadratic programming (GSA-SQP) have been employed. Moreover, Due to the proposed equation including only one variable coefficient, the NSTCCs has efficaciously contributed to reducing the number of constraints to eliminate significant constraints numbers in the coordination between the overcurrent protective relays. Radial networks, including IEEE 9-bus and IEC MG systems as benchmark as well as meshed networks, namely, IEEE 9 and 30-bus systems have been used to test the proposed protection scheme. The results of the proposed optimal OCRs coordination scheme have been compared to standard and nonstandard characteristics reported in the literature. The results showed a significant improvement in terms of the protection system selectivity and reliability by minimizing the operating time (OT) of OCRs, ensuring the coordination between primary and backup relays and demonstrating the effectiveness of the proposed method throughout minimum and maximum fault modes.
For radial networks based on GA, the reduction percentages of tripping time by using NSTCCs for IEC MG benchmark without DGs (mode 1), DN with DGs (mode 2) and islanded mode (mode 3) compared to the lowest OT value obtained from literature are 42.24%, 60% and 54.74%, respectively. In addition, for the IEEE9-bus radial network, the comparison is between the proposed NSTCCs, standard current characteristics (STCCs) and nonstandard scheme (NSS) recorded in the literature. The overall OT of proposed NSTCCs on mod 1, mode 2 and mode 3 is reduced by 12.06%, 17.33% and 13.55%, respectively compared to STCCs, while it is reduced by 7.05%, 9.91% and 11.42%, respectively compared to NSS. For meshed networks based on the hybrid GSA–SQP algorithm, the NSTCC approach improves the coordination interval time (CTI) between the primary and backup relays. For IEEE 9-bus system meshed network, the sum of CTI values is reduced compared to the sum of CTI values in ref from literature by 16.87%. The OT of proposed NSTCCs is reduced by 78.97% compared to STCC and 21.33% compared to NSS. Furthermore, the NSTCC decreased the total OT in the meshed 30-bus test system by 54.4% and 37.9% compared to the literature methods STCC and NSS, respectively. The suggested NSTCC technique is an important development that could greatly enhance the reliability and selectivity of power systems.
Secondly, this thesis investigates the impact of immoderate fault current owing to the presence of DGs on traditional IEC characteristics. The shape of these characteristics has been adjusted to obtain such characteristics. The non-standard characteristics approach (N-SCA) has been proposed for optimal coordination of OCRs installed in DNs by extending the IEC normal inverse characteristics to fifty plug setting multiplier (PSM). Furthermore, an artificial intelligence hybrid algorithm based on water cycle moth flame optimization (HWCMFO) has been proposed as a new optimization technique in OCRs coordination protection to optimize the maximum PSM limits. Several modes have been implemented and tested with an IEC MG benchmark and carried out in MATLAB and NEPLAN software, the obtained results have illustrated the effectiveness and applicability of N-SCA based on the HWCMFO technique considering the limitation of IEC characteristics. The N-SCA outperforms the conventional approach for various fault locations in the several operational modes.
For mode 1, mode 2 and mode 3, the total OT is reduced by 6.32%, 5.61% and only 0.35%, respectively. Particle swarm optimization (PSO) technique is used for comparative purposes. Using the HWCMFO technique reduced the computing speed compared to PSO by 86.59% for mode 1, 29.69% for mode 2 and 89.18% for islanded mode. Moreover, the best cost function values of the proposed HWCMFO technique is reached at less than the PSO technique for all operational modes. For mode1, mode 2 and mode 3, it is reduced by 74.26%, 63.39% and 65%, respectively. Therefore, it is demonstrated that the presented HWCMFO algorithm is suitable for identifying the global minimum objective function value in the OCR coordination
Crystal and thermal response of cellulose isolation from bamboo by Two different chemical treatments
No full textSustainable manufacturing of a Conformal Load-bearing Antenna Structure (CLAS) using advanced printing technologies and fibre-reinforced composites for aerospace applications
No full textConformal load-bearing antenna structures (CLAS) offer significant advantages in aerospace by reducing drag and weight through highly integrated designs. However, challenges remain in manufacturing, as traditional PCB methods create discontinuous arrays, while directly printed antennas on flexible substrates often lack mechanical strength. Additionally, neither approach integrates well with fibre-reinforced composites, which are widely used in modern aircraft. To address this, the next generation of CLAS must employ continuous surface substrates to maintain aerodynamic profiles and embed antenna systems within composite structures.
This research introduces an innovative CLAS manufacturing method that integrates inkjet-printed silver nanoparticle antennas with composite fabrication. The antenna is printed onto Kapton film, which is then co-cured with woven glass fibre composites to ensure mechanical robustness and compatibility with aerospace materials. Flat and 100mm curvature samples were fabricated to investigate electromagnetic performance, with curvature effects analysed.
Results confirm that the proposed method achieves both reliability and sustainability, producing smoothly curved CLAS with embedded antenna elements. However, frequency shifts and impedance mismatches were observed, attributed to discrepancies in dielectric constants and substrate volume variations. The conformality study revealed that curvature lowers resonant frequencies due to extended effective electric fields.
This research establishes a promising CLAS fabrication approach, integrating sustainable printing with composites. The findings provide a benchmark for future conformal antenna studies and support industry-level advancements in high-integration aerospace antenna systems
Isolation of Soyasaponins I and VI from soybean by semipreparatives HPLC and characterization by mass spectrometry
No full textSaponins are triterpenoid or steroid glycosides naturally occurring in plants. Soyasaponins from soy and other legumes are the primary dietary sources of food saponins. Soyasaponins have been demonstrated to possess multiple health-promoting properties, such as lowering of cholesterol level by inhibiting its absorption, being anti-carcinogenic and antihepatotoxic, and showing anti-replicative properties against HIV [1]. According to their molecular structures, soyasaponins can be divided into two groups, i.e. A and B. Soyasaponins belonging to group A are bidesmosidic saponins having two glycosylation sites on their aglycone moiety (soyasapogenol A), while group B soyasaponins are monodesmosidic saponins having one glycosylation site on two different aglycone moieties (soyasapogenol B and E). Lentils, one of the richest and cheapest sources of vegetable proteins, mainly contain soyasaponin I, also named soyasaponin Bb, and soyasaponin VI, otherwise named g, both belonging to the soyasaponins B group [2]. Because of the difficulties to obtain authentic, high purity soyasaponin standards [3], especially evident for soyasaponin VI that is thermolabile, we started a project aiming at isolating pure soyasaponins I and VI from soybeans, followed by quantitative analysis of soyasaponin content in various Italian cultivars of lentils. Extraction and purification of saponins were performed as follows: dried and finely ground soybeans were extracted with 70% aqueous ethanol at room temperature for 3 h, then the alcoholic solution was filtered and concentrated at temperature < 30°C by a rotary evaporator. The crude extract was purified on a C18 flash-chromatographic column using acetonitrile-water as eluting mixture (gradient); the collected fractions, containing both soyasaponins, were injected in a semipreparative HPLC system equipped with a C18 column using a mixture of methanol/water (83/17), containing 0.25 % of acetic acid, as mobile phase. Each saponin was detected at its specific wavelength: 206 nm for soyasaponin I, and 292 nm for soyasaponin VI. After HPLC analysis, the pure soyasaponins I and VI were collected and their structures identified using the HPLC-ESI-IT (Ion Trap), performing MSn experiments and studying their typical fragmentations. The purified soysaponins were used as pure standards for the quantitation of saponins in various cultivars of lentils.
References
[1] L. Gu, G. Tao, W. Gu, R.L. Prior Journal of Agricultural and Food Chemistry, 2002, 50, 6951-6959.
[2] R.G. Ruiz, K.R. Price, A.E. Arthur, M.E. Rose, M.J.C. Rhodes, R.G. Fenwick Journal of Agricultural and Food Chemistry, 1996, 44, 1526-1530.
[3] J. Hu, S.O. Lee, S. Hendrich, P.A. Murphy Journal of Agricultural and Food Chemistry, 2002, 50, 2587-2594
Investigation of Dietary Factors and Esophageal Cancer Knowledge: Comparison of Rural Residents in High- and Low-incidence Areas
No full textAbstractTo compare the differences in dietary status and knowledge of esophageal cancer (EC) between residents of high- and low-incidence areas. We investigated dietary conditions and EC knowledge among residents in high- and low-EC incidence areas (Yanting and Qingzhen counties). Residents in Yanting consumed more pickled vegetables, salted meat and barbecued food (P < 0.05). Analysis of the past ten-year trend in Yanting consumed fresh vegetables/fruits, beans, sauerkraut, hot food, and barbecued food had gradually increased, and the trend was less than that in Qingzhen County. However, the gradual increasing trend in consumption of pickled vegetables, pickled meat, and spicy food over the past 10 years was greater (P < 0.05). Drinking water in Yanting County was healthier than that in Qingzhen County (P < 0.05). In terms of EC knowledge, the proportions of residents in Yanting who had a clear understanding, knowledge or had heard of EC or knew the common causes, primary symptoms, therapeutic measures, preventive measures, and government interventions for EC were all higher than in Qingzhen (P < 0.05). Residents in Yanting had greater EC knowledge but more harmful dietary habits than those in Qingzhen.</jats:p
Advanced control system for stand-alone diesel engine driven-permanent magnetic generator sets
No full textThe main focus is on the development of an advanced control system for variable speed standalone
diesel engine driven generator systems.
An extensive literature survey reviews the historical development and previous relevant
research work in the fields of diesel engines, electrical machines, power electronic converters,
power and electronic systems. Models are developed for each subsystem from mathematical
derivations with necessary simplifications made to reduce complexity while retaining the
required accuracy. Initially system performance is investigated using simulation models in
Matlab/Simulink.
The AC/DC/AC power electronic conversion system used employs a voltage controlled dc
link. The ac voltage is maintained at constant magnitude and frequency by using a dc-dc
converter and a fixed modulation ratio VSI PWM inverter. The DC chopper provides fast
control of the output voltage by dealing efficiently with transient conditions.
A Variable Speed Fuzzy Logic Core (VSFLC) controller is combined with a classical control
method to produce a novel hybrid controller. This provides an innovative variable speed
control that responds to both load and speed changes. A new power balance based control
strategy is proposed and implemented in the speed controller.
Subsequently a novel overall control strategy is proposed to co-ordinate the hybrid variable
speed controller and chopper controller to provide overall control for both fast and slow
variations of system operating conditions.
The control system is developed and implemented in hardware using Xilinx Foundation
Express. The VHDL code for the complete control system design is developed and the
designs are synthesised and analysed within the Xilinx environment. The controllers are
implemented with XC95108-PC84 and XC4010-PC84 to provide a compact and cheap control
system. A prototype experimental system is described and test results are obtained that show
the combined control strategy to be very effective. The research work makes contributions in
the areas of automatic control systems for diesel engine generator sets and CPLD/FPGA
application that will benefit manufacturers and consumers.EPSR
SERF: A Simple, Effective, Robust, and Fast Image Super-Resolver From Cascaded Linear Regression
No full text
Example learning-based image super-resolution techniques estimate a high-resolution image from a low-resolution input image by relying on high-and low-resolution image pairs. An important issue for these techniques is how to model the relationship between high-and low-resolution image patches: most existing complex models either generalize hard to diverse natural images or require a lot of time for model training, while simple models have limited representation capability. In this paper, we propose a simple, effective, robust, and fast (SERF) image superresolver for image super-resolution. The proposed super-resolver is based on a series of linear least squares functions, namely, cascaded linear regression. It has few parameters to control the model and is thus able to robustly adapt to different image data sets and experimental settings. The linear least square functions lead to closed form solutions and therefore achieve computationally efficient implementations. To effectively decrease these gaps, we group image patches into clusters via k-means algorithm and learn a linear regressor for each cluster at each iteration. The cascaded learning process gradually decreases the gap of highfrequency detail between the estimated high-resolution image patch and the ground truth image patch and simultaneously obtains the linear regression parameters. Experimental results show that the proposed method achieves superior performance with lower time consumption than the state-of-the-art methods.</p
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