Improved design of the transmission mechanism of the of 4‑cylinder double‑acting Stirling engine

Four-cylinder U-shaped transmission mechanism design is closely related to operational stability, efficiency and life expectancy of Stirling engine system, as any deficiency of design of transmission mechanism may cause excessive reciprocating inertia force, centrifugal inertia force and counter-torque. Those intense forces and torques will transfer through the crankshaft bearings and the crankcase to supporting, resulting in the vibration of the Stirling engine and reducing the system operation stability and efficiency. According to features of four cylinder U-shaped drive mechanism, this paper built the counterweight theoretical model of transmission mechanism to obtain the values of counterweight and counter-balanced phase angle on crankshaft and output shaft. On this basis, dynamics simulation model of transmission mechanism can be established by multi-body dynamics simulation platform. Simulation results indicate that through certain improvement based on original design, the speed fluctuation coefficient of output shaft, left and right crankshafts is reduced by 19.2 %, 40.5 % and 37.4 % respectively; vibration displacement of the center of mass in output shaft is decreased by 19.5 %; average dynamic force and moment on engine body is diminished by 15.84 % and 20 % respectively; the weight of the flywheel can be declined by 50 % under steady working conditions. Above simulation results could verify the feasibility and effectiveness of improvement program aimed at dynamic balance. Meanwhile, this paper improves the power density of engine through the appropriate design of flywheel, striving to provide theoretical support for the design of transmission mechanism in Stirling engines

Iterative Signal Processing for Integrated Sensing and Communication Systems

Integrated sensing and communication (ISAC), with sensing and communication sharing the same wireless resources and hardware, has the advantages of high spectrum efficiency and low hardware cost, which is regarded as one of the key technologies of the fifth generation advanced (5G-A) and sixth generation (6G) mobile communication systems. ISAC has the potential to be applied in the intelligent applications requiring both communication and high accurate sensing capabilities. The fundamental challenges of ISAC system are the ISAC signal design and ISAC signal processing. However, the existing ISAC signal has low anti-noise capability. And the existing ISAC signal processing algorithms have the disadvantages of quantization errors and high complexity, resulting in large energy consumption. In this paper, phase coding is applied in ISAC signal design to improve the anti-noise performance of ISAC signal. Then, the effect of phase coding method on improving the sensing accuracy is analyzed. In order to improve the sensing accuracy with low-complexity algorithm, the iterative ISAC signal processing methods are proposed. The proposed methods improve the sensing accuracy with low computational complexity, realizing energy efficient ISAC signal processing. Taking the scenarios of short distance and long distance sensing into account, the iterative two-dimensional (2D) fast Fourier transform (FFT) and iterative cyclic cross-correlation (CC) methods are proposed, respectively, realizing high sensing accuracy and low computational complexity. Finally, the feasibility of the proposed ISAC signal processing methods are verified by simulation results

Improved design of the transmission mechanism of the of 4‑cylinder double‑acting Stirling engine

Four-cylinder U-shaped transmission mechanism design is closely related to operational stability, efficiency and life expectancy of Stirling engine system, as any deficiency of design of transmission mechanism may cause excessive reciprocating inertia force, centrifugal inertia force and counter-torque. Those intense forces and torques will transfer through the crankshaft bearings and the crankcase to supporting, resulting in the vibration of the Stirling engine and reducing the system operation stability and efficiency. According to features of four cylinder U-shaped drive mechanism, this paper built the counterweight theoretical model of transmission mechanism to obtain the values of counterweight and counter-balanced phase angle on crankshaft and output shaft. On this basis, dynamics simulation model of transmission mechanism can be established by multi-body dynamics simulation platform. Simulation results indicate that through certain improvement based on original design, the speed fluctuation coefficient of output shaft, left and right crankshafts is reduced by 19.2 %, 40.5 % and 37.4 % respectively; vibration displacement of the center of mass in output shaft is decreased by 19.5 %; average dynamic force and moment on engine body is diminished by 15.84 % and 20 % respectively; the weight of the flywheel can be declined by 50 % under steady working conditions. Above simulation results could verify the feasibility and effectiveness of improvement program aimed at dynamic balance. Meanwhile, this paper improves the power density of engine through the appropriate design of flywheel, striving to provide theoretical support for the design of transmission mechanism in Stirling engines

Integrated Sensing and Communication Signals Toward 5G-A and 6G: A Survey

Integrated sensing and communication (ISAC) has the advantages of efficient spectrum utilization and low hardware cost. It is promising to be implemented in the fifth-generation-advanced (5G-A) and sixth-generation (6G) mobile communication systems, having the potential to be applied in intelligent applications requiring both communication and high-accurate sensing capabilities. As the fundamental technology of ISAC, ISAC signal directly impacts the performance of sensing and communication. This article systematically reviews the literature on ISAC signals from the perspective of mobile communication systems, including ISAC signal design, ISAC signal processing algorithms and ISAC signal optimization. We first review the ISAC signal design based on 5G, 5G-A and 6G mobile communication systems. Then, radar signal processing methods are reviewed for ISAC signals, mainly including the channel information matrix method, spectrum lines estimator method and super resolution method. In terms of signal optimization, we summarize peak-to-average power ratio (PAPR) optimization, interference management, and adaptive signal optimization for ISAC signals. This article may provide the guidelines for the research of ISAC signals in 5G-A and 6G mobile communication systems.Comment: 25 pages, 13 figures, 8 tables. IEEE Internet of Things Journal, 202

Preparation, Characterization, and Structure Trends for Graphite Intercalation Compounds Containing Pyrrolidinium Cations

New graphite intercalation compounds (GICs) containing N,N-n-alkyl substituted pyrrolidinium cation intercalates (Py[subscript n.m], n, m = alkyl chain lengths) are obtained via cationic exchange from stage-1 donor-type GIC [Na(ethylenediamine)₁.₀]C₁₅. Powder X-ray diffraction and thermogravimetric analyses are used to determine the GIC structures and compositions. [Py₄.₈]C₄₇·0.71DMSO and [Py₈.₈]C₄₈ with intercalate monolayers are obtained as stage-1 GICs with gallery expansions of 0.48 nm, whereas [Py₁.₁₈]C₄₇ and [Py₁₂.₁₂]C₈₀·0.25DMSO form stage-1 GICs with intercalate bilayers and gallery expansions of 0.81 nm. The gallery dimensions require that alkyl chain substituents orient parallel to the encasing graphene sheets. Smaller intercalate cations such as Py₁.₄, Py₄.₄, and Py₁.₈ either form high-stage GICs or do not form stable intercalation compounds. These results, along with those reported for graphite intercalation of other quaternary ammonium cations, indicate trends in graphite chemistry where larger intercalates form more stable and lower-stage GICs, and the graphene sheet charge densities can be correlated to the intercalate footprint areas

Effects of forage type on the rumen microbiota, growth performance, carcass traits, and meat quality in fattening goats

Forages fed to goats influence ruminal microbiota, and further contribute to affect growth performance, meat quality and its nutritional composition. Our objective for current study was to investigate the effects of different forages on growth performance, carcass traits, meat nutritional composition, rumen microflora, and the relationships between key bacteria and amino acids and fatty acids in the longissimus dorsi and semimembranosus muscles of goats. Boer crossbred goats were separately fed commercial concentrate diet supplemented with Hemarthria altissima (HA), Pennisetum sinese (PS), or forage maize (FG), and then slaughtered 90 days after the beginning of the experiment. Growth performances did not vary but carcass traits of dressing percentage, semi-eviscerated slaughter percentage, and eviscerated slaughter percentage displayed significant difference with the treatment studied. Meats from goats fed forage maize, especially semimembranosus muscles are rich in essential amino acids, as well as an increase in the amount of beneficial fatty acids. Our 16S rRNA gene sequencing results showed that the Firmicutes, Bacteroidetes, and Proteobacteria were the most dominant phyla in all groups but different in relative abundance. Further, the taxonomic analysis and linear discriminant analysis effect size (LEfSe) identified the specific taxa that were differentially represented among three forage treatments. The spearman’s correlation analysis showed that rumen microbiota was significantly associated with the goat meat nutritional composition, and more significant positive correlations were identified in semimembranosus muscles when compared with longissimus dorsi muscles. More specifically, the lipid metabolism-related bacteria Rikenellaceae_RC9_gut_group showed positively correlated with meat amino acid profile, while genera Oscillospiraceae_UCG-005 were positively correlated with fatty acid composition. These bacteria genera might have the potential to improve nutritional value and meat quality. Collectively, our results showed that different forages alter the carcass traits, meat nutritional composition, and rumen microflora in fattening goats, and forage maize induced an improvement in its nutritional value

Developing a Reliable Service System of Charity Donation During the Covid-19 Outbreak

Drawing upon the functional characteristics of blockchain technology, this article envisages the feasibility and reliability of developing a charity donation service system loaded onto blockchain in response to the complex service demands encountered by charity operators due to the Covid-19 epidemic. With blockchain technology's support as the underlying data book, this article focuses on the practical issues of charity donation fund and material allocation, as well as information release and sharing, charity donation organization, and organization self-management. The paper thereby discusses the key technologies in terms of overall structure design, specific service sector, and functional design of the donation service system and further summarizes the operational mechanism of the system as combined with the needs of help-seeking, receiving, and management users. It is argued that all the above proposals have the potential to alleviate the trust crisis of charity services in China in view of low transparency. The paper expects to provide a useful reference for charity business innovation propelled by blockchain technology

TMR-Array-Based Pipeline Location Method and Its Realization

Pipeline inspection is important to ensure the safe operation of pipelines. Obtaining the location of an underground pipeline is a prerequisite for most inspection technologies. Existing pipeline location methods can find a pipeline’s location, but they require multiple measurements and cannot be used by automatic inspection robots. In this paper, a tunnel magnetoresistance (TMR)-sensor-array-based pipeline location method is proposed to solve this problem. Firstly, a detection probe is designed using a TMR sensor array. It is calibrated by the improved ellipsoid fitting method to measure the magnetic field around the pipeline accurately. Secondly, a relative pipeline-position-locating method is proposed by detecting the phases of the magnetic induction signals at different frequencies. Thirdly, a three-dimensional pipeline location method is proposed. The horizontal and vertical distances and the angle between the pipeline and the probe are calculated by measuring the magnetic induction amplitude. Finally, a simulation model and a test platform are established, and the experimental results illustrate that, by adopting the TMR array, the three-dimensional pipeline location method can locate a pipeline in real time in three dimensions with good accuracy

Hyperspectral Image Recovery Using Non-Convex Low-Rank Tensor Approximation

Low-rank tensors have received more attention in hyperspectral image (HSI) recovery. Minimizing the tensor nuclear norm, as a low-rank approximation method, often leads to modeling bias. To achieve an unbiased approximation and improve the robustness, this paper develops a non-convex relaxation approach for low-rank tensor approximation. Firstly, a non-convex approximation of tensor nuclear norm (NCTNN) is introduced to the low-rank tensor completion. Secondly, a non-convex tensor robust principal component analysis (NCTRPCA) method is proposed, which aims at exactly recovering a low-rank tensor corrupted by mixed-noise. The two proposed models are solved efficiently by the alternating direction method of multipliers (ADMM). Three HSI datasets are employed to exhibit the superiority of the proposed model over the low rank penalization method in terms of accuracy and robustness