9,722 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
Performance Evaluation of Distributed-Antenna Communications Systems Using Beam-Hopping
No full textDigital beamforming (DBF) techniques are capable of improving the performance of communications systems significantly. However, if the transmitted signals are conflicted with strong interference, especially, in the direction of the transmitted beams , these directional jamming signals will severely degrade the system performance. In order to efficiently mitigate the interference of the directional jammers, in this contribution a beam-hopping (BH) communications scheme is proposed. In the proposed BH communications scheme, only one pair of the beams is used for transmission and it hops from one to the next according to an assigned BH pattern. In this contribution a range of expressions in terms of the average SINR performance have been derived, when both the uplink and downlink are considered. The average SINR performance of the proposed BH scheme and that of the conventional single-beam (SB) as well as multiple-beam (MB) assisted beam-processing schemes have been investigated. Our analysis and results show that the proposed BH scheme is capable of efficiently combating the directional jamming, with the aid of utilizing the directional gain of the beams generated by both the transmitter and the receiver. Furthermore, the BH scheme is capable of reducing the intercept probability of the communications. Therefore, the proposed BH scheme is suitable for communications, when several distributed antenna arrays are available around a mobile
Tun hu: (du mu ju ji).
No full text復工之前 -- 母女們 -- 囤戶.吳天著.Drama.Wu Tian zhu.Fu gong zhi qian -- Mu nü men -- Tun hu
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
Flow dynamics on a U shaped channel flow: a numerical study
No full textThe paper deals with the numerical simulation of river channel flows at laboratory scale. The adopted geometry
consists of a U shaped trapezoidal smooth open channel with fixed slope. The branches, 3m of length each, are linked with a joint, 0.40m long, realizing two 90 degrees bends. The system is fed upstream with a water discharge under critical conditions while a Cipolletti weir is set downstream to control flow profiles.
Steady flow movements are obtained by means of two different softwares: a pure Lagrangian developed by the author, based on the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) technique and Flow3D®, a commercial CFD software based on a Finite Volume formulation of the Navier Stokes equations in the Eulerian framework. Depending on the assumed boundary conditions, velocity profiles and water interfaces at certain cross sections are deducted by using the codes. Results are discussed and compared, showing a satisfactory agreement
Crystal and thermal response of cellulose isolation from bamboo by Two different chemical treatments
No full textHU Protein Induces Incoherent DNA Persistence Length
No full textHU is a highly conserved protein that is believed to play an important role in the architecture and dynamic compaction of bacterial DNA. Its ability to control DNA bending is crucial for functions such as transcription and replication. The effects of HU on the DNA structure have been studied so far mainly by single molecule methods that require us to apply stretching forces on the DNA and therefore may perturb the DNA-protein interaction. To overcome this hurdle, we study the effect of HU on the DNA structure without applying external forces by using an improved tethered particle motion method. By combining the results with DNA curvature analysis from atomic force microscopy measurements we find that the DNA consists of two different curvature distributions and the measured persistence length is determined by their interplay. As a result, the effective persistence length adopts a bimodal property that depends primarily on the HU concentration. The results can be explained according to a recently suggested model that distinguishes single protein binding from cooperative protein binding.Imaging Science and TechnologyApplied Science
Sustainable 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
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