8 research outputs found
A New Method for Analyzing Integrated Stealth Ability of Penetration Aircraft
AbstractTaking into account the limitations of existing stealth performance analysis methods, a method termed as the integrated stealth performance analysis method is proposed for evaluating the stealth ability of the penetration aircraft. Based on various target radar cross section (RCS) scattering characters, this article integrates the relevant parameters needed for building up target circumferential RCS scattering model and proposes the RCS scattering controlling parameters to control the changing trends of the relevant model RCS scattering characters. According to the radar dynamic detecting characters during the whole penetration course, a dynamic stealth performance evaluating model is proposed accompanied by a series of stealth ability estimation rules. This new analysis method can enhance the integrality and dependability of the stealth analysis conclusions and summarize the relationship between the target RCS scattering characters and their effects on stealth performance. The rules indicated by this relationship can be used as the reference for designing new type of stealth aircraft and setting up specific penetration tactics
Fast Quasi-Optimal Power Flow of Flexible DC Traction Power Systems
This paper proposes a quasi-optimal power flow (OPF) algorithm for flexible
DC traction power systems (TPSs). Near-optimal solutions can be solved with
high computational efficiency by the proposed quasi-OPF. Unlike conventional
OPF utilizing mathematical optimization algorithms, the proposed quasi-OPF
adopts analytical mapping from load information to near-optimal solutions,
hence considerably accelerating the computation. First, we study the mechanism
and physical meaning interpretation of conventional OPF based on a new modeling
method and successfully interpret the mechanism of conventional OPF in flexible
DC TPSs. Then, the analytical mapping from load information to near-optimal
solutions is obtained inspired by the mechanism of conventional OPF, and the
quasi-OPF algorithm is designed based on the mapping. Since the mapping is
based on simple arithmetic, the quasi-OPF algorithm can solve OPF with much
less execution time, achieving subsecond level calculation and a speed-up of 57
times compared to conventional OPF. The effectiveness is verified by
mathematical proofs and a case study with Beijing Metro Line 13. It provides an
insight into the mechanism and physical meaning of OPF, and is a powerful tool
for flexible DC TPSs to analyze the effects of coordinated control, design
real-time control strategies, and solve operational problems in planning
Multi-frequency RCS Reduction Characteristics of Shape Stealth with MLFMA with Improved MMN
AbstractThree new control factors are presented for calculating the multipole mode number (MMN) efficiently and precisely. The effects of these control factors on the number of integral samples and the precision of multilevel fast multipole algorithm (MLFMA) are investigated. A new approach based on control factors which is proven to be able to improve the computational efficiency and reduce the needed memory significantly as well as ensuring the proper precision. For three aircraft models, the improved MLFMA is employed to analyze their multi-frequency scattering characteristics. It is found that aircraft shape can influence radar cross section (RCS) in different frequency zones. Both the multi-frequency RCS reduction characteristics of shape stealth aircraft and the conventional aircraft with stealth design taken into account are investigated, and the results show that shape stealth exhibits significant RCS reduction in the resonance and high-frequency zones, and with a weaker influence in the Rayleigh zone. Compared with radar absorbing material (RAM), shape stealth yields a wider multi-frequency RCS reduction. The above-mentioned results can be applied to stealth design for multiple frequencies or even for all frequencies
A fast power control method based on high-speed communication for the continuous co-phase traction power system
Continuous co-phase traction power system is an effective method to eliminate neutral sections and provide high quality power for both the public grid and the catenary. The substations have the ability to provide cooperative support to each other to reduce capacity and improve system reliability. A fast power control method for substations is needed due to rapid load changes and low overload capability of the system. This paper proposes a fast power control method based on high-speed communication between substations, with additional transient power control to significantly improve the dynamic response of the system
Nonoscillatory solutions for first-order neutral dynamic equations with continuously distributed delay on time scales
Abstract In this paper, we establish the existence of nonoscillatory solutions to the neutral dynamic equation [x(t)−∫abp(t,η)x(g(t,η))Δη]Δ+∫cdω(t,ν)x(h(t,ν))Δν=0 on a time scale T . Some examples are given to illustrate the main results
Exploring the Role of G Protein Expression in Sodium Butyrate-Enhanced Pancreas Development of Dairy Calves: A Proteomic Perspective
The
present study evaluated the effects of sodium butyrate (SB)
supplementation on exocrine and endocrine pancreatic development in
dairy calves. Fourteen male Holstein calves were alimented with either
milk or milk supplemented with SB for 70 days. Pancreases were collected
for analysis including staining, immunofluorescence, electron microscopy,
qRT-PCR, Western blotting, and proteomics. Results indicated increased
development in the SB group with increases in organ size, protein
levels, and cell growth. There were also exocrine enhancements manifested
as higher enzyme activities and gene expressions along with larger
zymogen granules. Endocrine benefits included elevated gene expression,
more insulin secretion, and larger islets, indicating a rise in β-cell
proliferation. Proteomics and pathway analyses pinpointed the G protein
subunit alpha-15 as a pivotal factor in pancreatic and insulin secretion
pathways. Overall, SB supplementation enhances pancreatic development
by promoting its exocrine and endocrine functions through G protein
regulation in dairy calves