Autor: Li, Jun - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Review of Lattice Boltzmann Method Applied to Computational Aeroacoustics
Autorzy:: Shao, Weidong
Li, Jun
Tematy:: lattice Boltzmann method
computational aeroacoustics
dispersion
dissipation
perfectly matched layers
discontinuous Galerkin method; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/177111.pdf Link otwiera się w nowym oknie
Opis:: This paper presents the research studies carried out on the application of lattice Boltzmann method (LBM) to computational aeroacoustics (CAA). The Navier-Stokes equation-based solver faces the difficulty of computational efficiency when it has to satisfy the high-order of accuracy and spectral resolution. LBM shows its capabilities in direct and indirect noise computations with superior space-time resolution. The combination of LBM with turbulence models also work very well for practical engineering machinery noise. The hybrid LBM decouples the discretization of physical space from the discretization of moment space, resulting in flexible mesh and adjustable time-marching. Moreover, new solving strategies and acoustic models are developed to further promote the application of LBM to CAA.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Short-term wind power combined prediction based on EWT-SMMKL methods
Autorzy:: Li, Jun
Ma, Liancai
Tematy:: combined model
empirical wavelet transform
prediction
soft margin multiple kernel learning
wind power
model łączony
empiryczna transformacja falkowa
przewidywanie
miękki margines uczenia wielokrotnego jądra
energia wiatrowa; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/1955182.pdf Link otwiera się w nowym oknie
Opis:: Since wind power generation has strong randomness and is difficult to predict, a class of combined prediction methods based on empirical wavelet transform (EWT) and soft margin multiple kernel learning (SMMKL) is proposed in this paper. As a new approach to build adaptive wavelets, the main idea is to extract the different modes of signals by designing an appropriate wavelet filter bank. The SMMKL method effectively avoids the disadvantage of the hard margin MKL method of selecting only a few base kernels and discarding other useful basis kernels when solving for the objective function. Firstly, the EWT method is used to decompose the time series data. Secondly, different SMMKL forecasting models are constructed for the sub-sequences formed by each mode component signal. The training processes of the forecasting model are respectively implemented by two different methods, i.e., the hinge loss soft margin MKL and the square hinge loss soft margin MKL. Simultaneously, the ultimate forecasting results can be obtained by the superposition of the corresponding forecasting model. In order to verify the effectiveness of the proposed method, it was applied to an actual wind speed data set from National Renewable Energy Laboratory (NREL) for short-term wind power single-step or multi-step time series indirectly forecasting. Compared with a radial basic function (RBF) kernel- based support vector machine (SVM), using SimpleMKL under the same condition, the experimental results show that the proposed EWT-SMMKL methods based on two different algorithms have higher forecasting accuracy, and the combined models show effectiveness.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Calculation of the dynamic characteristics of ship’s aft stern tube bearing considering journal deflection
Autorzy:: Yang, Hongjun
Li, Jun
Li, Xiaolong
Tematy:: journal deflection
aft stern tube bearing
dynamic characteristic; Pokaż więcej
Wydawca:: Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Powiązania:: https://bibliotekanauki.pl/articles/259603.pdf Link otwiera się w nowym oknie
Opis:: Dynamic properties are vital for the working reliability of aft stern tube bearings. However, the determination of such properties currently involves several simplifications and assumptions. To obtain its dynamic characteristics accurately, the aft stern tube bearing was divided into several bearing segments. The oil film reaction force was considered in the calculation of shaft alignment, and the journal deflection and actual oil film thickness were obtained accordingly. Subsequently, the perturbed Reynolds equation was solved using the finite difference method when the dynamic characteristics of journal bearings with finite width were evaluated. Then, a calculation program was developed and verified by comparing with the results of other studies. Finally, the dynamic characteristics were calculated under different revolutions. The results showed that the stiffness at the vertical direction of the aft stern tube bearing was several times that of the horizontal direction and varied with the revolutions of the shafting system. These findings can provide the foundation for the precise calculation of the journal trajectory under dynamic conditions, as well as for the evaluation of the oil film thickness. Moreover, the results led to favorable conditions for the accurate calculation of the shafting whirling vibration.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: The Role of China’s Exchange Rate on the Trade Balance of Sub‑Saharan Africa: a Gravity Model Approach
Rola kursu walutowego Chin w bilansie handlowym państw Afryki Subsaharyjskiej: zastosowanie modelu grawitacyjnego
Autorzy:: Khan, Hameed
Khan, Umair
Jiang, Li Jun
Khan, Muhammad Asif
Hasanat Shah, Syed
Tematy:: handel dwustronny
Chiny
ASS
bilateral trade
China
SSA; Pokaż więcej
Wydawca:: Uniwersytet Łódzki. Wydawnictwo Uniwersytetu Łódzkiego
Powiązania:: https://bibliotekanauki.pl/articles/633205.pdf Link otwiera się w nowym oknie
Opis:: Niniejsze opracowanie prezentuje rezultaty badania wpływu kursu walutowego Chin na bilans handlowy 41 państw Afryki Subsaharyjskiej w latach 1994–2016. Przy zastosowaniu rozszerzonego modelu grawitacyjnego, pogrupowane i niepogrupowane wyniki badania potwierdzają słuszność podejścia elastycznościowego i absorpcyjnego do bilansu handlowego. Podobnie test wrażliwości, dokonany poprzez podział analizowanego okresu na dwa podokresy (2005–2016 i 1994–2004), potwierdza słuszność podejścia elastycznościowego i absorpcyjnego do bilansu handlowego.
This study seeks to investigate theimpactof China’sexchange rate onthe trade balance of 41 Sub‑aharan African countries for the period from 1994 to 2016. Using an augmented gravity model, the grouped and ungrouped results of the study confirm the elasticity and absorption approaches of the trade balance. Similarly, the robustness check, by dividing the sample period into two sub‑eriods (2005–016 and 1994–004), also confirms the elasticity and absorption approaches of the trade balance.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Theoretical Simulations on Physicochemical Performance of Novel High-energy BHDBT-based Propellants
Autorzy:: Wang, Ke
Huang, Hai-tao
Xu, Hui-xiang
Li, Huan
Li, Jun-qiang
Fan, Xue-zhong
Pang, Wei-qiang
Tematy:: molecular dynamic
BHDBT
migration
mechanical properties
safety; Pokaż więcej
Wydawca:: Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Powiązania:: https://bibliotekanauki.pl/articles/27787879.pdf Link otwiera się w nowym oknie
Opis:: Based on Energy Calculation Star program and molecular dynamic method, three designed 2,3-bis(hydroxymethyl)-2,3-dinitro-1,4-butanediol tetranitrate-based (BHDBT) propellants are firstly reported and their physicochemical performance are investigated. Results suggest that compared with HMX-based and CL-20-based propellants, the specific impulses of all BHDBT-based propellants surpass or approximate 280 s, which indicates the latter have the potential to be high-energy propellants. The diffusion coefficient of plasticizers in BHDBT-based propellant decrease as the temperature reduces, and reduce in the order: Bu-NENA > TMETN > BTTN. The densities of all BHDBT-based propellants surpass or approximate 1.7 g/cm3. The comparison of elastic constants, Poisson’s ratios and K/G values indicates that the mechanical properties of three BHDBT-based propellants increase in the order (by plasticizer): Bu-NENA < TMETN < BTTN. The bond length analysis of C–NO2 and O–NO2 bond in BHDBT suggests that the former is the trigger bond in the BHDBT-based propellants, and the safety of BHDBT-based propellants and BHDBT crystal decreases in the order: GAP/BTTN/Al/BHDBT > GAP/Bu-NENA/Al/BHDBT ≈ GAP/TMETN/Al/BHDBT > BHDBT. In conclusion, GAP/BTTN/Al/BHDBT propellant has the potential to be a novel high-energy propellant.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: First-Principles Calculations for Structural, Elastic, Electronic and Thermodynamic Properties of $HfZn_{2}$ under Pressure
Autorzy:: Li, Guo-Jun
Shi, Lan-Ting
Hu, Cui-E
Cheng, Yan
Ji, Guang-Fu
Tematy:: C15 Laves-phase
elastic properties
electronic structure
vibrational properties
quasi-harmonic approximation; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1398192.pdf Link otwiera się w nowym oknie
Opis:: By using density functional theory within the Perdew-Burke-Ernzerhof generalized gradient approximation implemented in the VASP code, we study the structural, elastic, electronic, and thermodynamic properties of C15 Laves-phase compound $HfZn_{2}$. Comparing the lattice constants calculated from the Perdew-Burke-Ernzerhof generalized gradient approximation and local density approximation, we find that the former is in better agreement with the experimental data. The elastic constants of $HfZn_{2}$ calculated by strain-stress method indicate that they keep stable up to 100 GPa. The bonding characteristics are discussed by analyzing the energy band structure, charge density distribution and charge density difference. Phonon dispersion curves and phonon density of states of HfZn_{2} at the different pressure are predicted for the first time. In addition, there is no imaginary frequency in the phonon band at different pressure, which also shows that $HfZn_{2}$ is stable up to 100 GPa. Vibrational models are also illustrated based on phonon and group theory. The thermodynamic properties under high temperature and high pressure are calculated by different thermodynamic models. The heat capacity at constant pressure and low temperature calculated by quasi-harmonic approximation is more close to the measurement than that calculated by quasi-harmonic Debye models.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Development and verification of a high-precision laser measurement system for straightness and parallelism measurement
Autorzy:: Xu, Peng
Li, Rui Jun
Zhao, Wen Kai
Chang, Zhen Xin
Ma, Shao Hua
Fan, Kuang Chao
Tematy:: straightness
parallelism
laser measurement system
machine tool; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/1849049.pdf Link otwiera się w nowym oknie
Opis:: A laser measurement system for measuring straightness and parallelism error using a semiconductor laser was proposed. The designing principle of the developed system was analyzed. Addressing at the question of the divergence angle of the semiconductor laser being quite large and the reduction of measurement accuracy caused by the diffraction effect of the light spot at the long working distance, the optical structure of the system was optimized through a series of simulations and experiments. A plano-convex lens was used to collimate the laser beam and concentrate the energy distribution of the diffraction effect. The working distance of the system was increased from 2.6 m to 4.6 m after the optical optimization, and the repeatability of the displacement measurement is kept within 2.2 m in the total measurement range. The performance of the developed system was verified by measuring the straightness of a machine tool through the comparison tests with two commercial multi-degree-of-freedom measurement systems. Two different measurement methods were used to verify the measurement accuracy. The comparison results show that during the straightness measurement of the machine tool, the laser head should be fixed in front of the moving axis, and the sensing part should move with the moving table of the machine tool. Results also show that the measurement error of the straightness measurement is less than 3 m compared with the commercial systems. The developed laser measurement system has the advantages of high precision, long working distance, low cost, and suitability for straightness and parallelism error measurement.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Development and verification of a high-precision laser measurement system for straightness and parallelism measurement
Autorzy:: Xu, Peng
Li, Rui Jun
Zhao, Wen Kai
Chang, Zhen Xin
Ma, Shao Hua
Fan, Kuang Chao
Tematy:: straightness
parallelism
laser measurement system
machine tool; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/1849061.pdf Link otwiera się w nowym oknie
Opis:: A laser measurement system for measuring straightness and parallelism error using a semiconductor laser was proposed. The designing principle of the developed system was analyzed. Addressing at the question of the divergence angle of the semiconductor laser being quite large and the reduction of measurement accuracy caused by the diffraction effect of the light spot at the long working distance, the optical structure of the system was optimized through a series of simulations and experiments. A plano-convex lens was used to collimate the laser beam and concentrate the energy distribution of the diffraction effect. The working distance of the system was increased from 2.6 m to 4.6 m after the optical optimization, and the repeatability of the displacement measurement is kept within 2.2 m in the total measurement range. The performance of the developed system was verified by measuring the straightness of a machine tool through the comparison tests with two commercial multi-degree-of-freedom measurement systems. Two different measurement methods were used to verify the measurement accuracy. The comparison results show that during the straightness measurement of the machine tool, the laser head should be fixed in front of the moving axis, and the sensing part should move with the moving table of the machine tool. Results also show that the measurement error of the straightness measurement is less than 3 m compared with the commercial systems. The developed laser measurement system has the advantages of high precision, long working distance, low cost, and suitability for straightness and parallelism error measurement.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Development and verification of a high-precision laser measurement system for straightness and parallelism measurement
Autorzy:: Xu, Peng
Li, Rui Jun
Zhao, Wen Kai
Chang, Zhen Xin
Ma, Shao Hua
Fan, Kuang Chao
Tematy:: straightness
parallelism
laser measurement system
machine tool; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/1849006.pdf Link otwiera się w nowym oknie
Opis:: A laser measurement system for measuring straightness and parallelism error using a semiconductor laser was proposed. The designing principle of the developed system was analyzed. Addressing at the question of the divergence angle of the semiconductor laser being quite large and the reduction of measurement accuracy caused by the diffraction effect of the light spot at the long working distance, the optical structure of the system was optimized through a series of simulations and experiments. A plano-convex lens was used to collimate the laser beam and concentrate the energy distribution of the diffraction effect. The working distance of the system was increased from 2.6 m to 4.6 m after the optical optimization, and the repeatability of the displacement measurement is kept within 2.2 m in the total measurement range. The performance of the developed system was verified by measuring the straightness of a machine tool through the comparison tests with two commercial multi-degree-of-freedom measurement systems. Two different measurement methods were used to verify the measurement accuracy. The comparison results show that during the straightness measurement of the machine tool, the laser head should be fixed in front of the moving axis, and the sensing part should move with the moving table of the machine tool. Results also show that the measurement error of the straightness measurement is less than 3 m compared with the commercial systems. The developed laser measurement system has the advantages of high precision, long working distance, low cost, and suitability for straightness and parallelism error measurement.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Intervention effects of greenspace exposure on human microbiota : a randomized controlled trial in Chinese young adults
Autorzy:: Dong, Guang-Hui
Huang, Ji-Lin
Markevych, Iana
Dadvand, Payam
Yang, Bo-Yi
Heinrich, Joachim
Li, Jun-Yi
Chen, Chen
Browing, Matthew H.E.M.
Li, Chuang
Zheng, Zi-Han
Jiang, Jian-Cheng
Zhao, Tian-Yu
Zhu, Xiao-Qi
Wang, Zhi
Wang, Lu
Opis:: Enriching human microbiota has been proposed as a mechanism by which greenspace exposure improves human health. The existing evidence is scarce with few studies able to evaluate causality. We conducted a randomized controlled trial of 30 healthy undergraduate students to explore the intervention effects of greenspace on human gut and oral microbiota alpha-diversity, composition, differential genera and functional pathways. The study participants were divided into three groups, including outdoor greenspace (GS) group, outdoor non-greenspace (NGS) group, and indoor group, who visited a park, an open space without vegetation, and a classroom, respectively, for two hours per day over seven days. Differences in microbial alpha-diversity and composition across various groups were tested using Wilcoxon test and permutational multivariate analysis of variance, respectively. Linear discriminant analysis effect size analysis was performed to test differences in genera and functional pathways. Greenspace intervention significantly increased gut microbiota alpha-diversity, especially the observed Amplicon Sequence variant indexes and the Faith indexes (both p <0.05). In addition, the intervention substantially changed the composition of gut microbiota, of which the relative abundances of potentially beneficial bacteria increased. Further, the greenspace intervention affected several functional pathways of gut microbiota, including "substance dependence", "specific types of cancer", and "viral infectious diseases". However, we did not find any significant effect of greenspace intervention on oral microbiota. Our results suggest that greenspace intervention diversifies the gut microbiota and alters its composition. These findings could help to reinforce the potential of increasing people’s access to greenspace as a public health intervention.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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