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Tytuł:
Threshold effect of economic growth on domestic waste production : evidence from China
Autorzy:
Yang, Li
Wang, Hong-Yan
Yi, Lan
Shi, Xiang-Zhen
Deng, Wei
Powiązania:
https://bibliotekanauki.pl/articles/2203127.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
domestic waste
per capita GDP
source reduction
panel threshold regression model
Opis:
Since the implementation of the compulsory sorting of domestic waste policy in China, the participation rate of residents is low, which leads to the unsatisfactory result of terminal reduction of domestic waste. Therefore, the problem of domestic waste reduction still needs to rely on source reduction. Based on the panel data of 29 provincial capitals in China from 2009 to 2018, this study conducts a comprehensive threshold effect test on per capita GDP and other influencing factors of domestic waste production, conducts panel threshold regression for the factors with threshold value, and explores the nonlinear relationship between per capita GDP and domestic waste production under the influence of different threshold variables. The results show that when the urban population density is less than 272 people/km2, the increase of 1% of per capita GDP will lead to a decrease of 0.251% in the domestic waste production, otherwise, it will lead to an increase of 0.249%; when the per capita consumption expenditure is less than the threshold value of 10,260 yuan/year, the influence coefficient of per capita GDP is 0.155, which increases to 0.207 above the threshold. When the share of tertiary industry is taken as the threshold variable, the two threshold values are 61% and 71% respectively. Through the analysis of control variables, it has been found that population size and amount of courier per capita have significant positive effects on domestic waste production, while gas permeability and the number of non-governmental organizations have significant negative effects.
Źródło:
Archives of Environmental Protection; 2022, 48, 4; 13--24
2083-4772
2083-4810
Pojawia się w:
Archives of Environmental Protection
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Three Insensitive Energetic Co-crystals of 1-Nitronaphthalene, with 2,4,6-Trinitrotoluene (TNT), 2,4,6-Trinitrophenol (Picric Acid) and D-Mannitol Hexanitrate (MHN)
Autorzy:
Hong, D.
Li, Y.
Zhu, S.
Zhang, L.
Pang, C.
Powiązania:
https://bibliotekanauki.pl/articles/1063066.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
co-crystal
insensitive energetic material
crystal structure
explosive properties
Opis:
Co-crystallization is proposed as an effective method to alter the physicochemical properties of energetic materials, e.g. density, sensitivity and solubility. As reported in this paper, it was found that 1-nitronaphthalene could form cocrystals with TNT, picric acid and MHN in a 1:1 molecular ratio. The sensitivity and thermal stability of the 1-nitronaphthalene co-crystals was greatly improved compared with that of pure TNT, picric acid and MHN. In addition, the melting points of TNT, picric acid and MHN were lowered through co-crystallization with 1-nitronaphthalene. The electrostatic potential surface of 1-nitronaphthalene, calculated by the DFT method, showed that the electron-rich 1-nitronaphthalene has a tendency to be a proton donor and to co-crystallize with other energetic materials. The structures of the co-crystals of 1-nitronaphthalene with TNT and picric acid were characterized by single crystal X-ray diffraction (SXRD). The 1-nitronaphthalene/MHN co-crystal was studied by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and FTIR.
Źródło:
Central European Journal of Energetic Materials; 2015, 12, 1; 47-62
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Minimum Spectral Radius of Signless Laplacian of Graphs with a Given Clique Number
Autorzy:
Su, Li
Li, Hong-Hai
Zhang, Jing
Powiązania:
https://bibliotekanauki.pl/articles/30148000.pdf
Data publikacji:
2014-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
clique number
kite graph
signless Laplacian
spectral radius
Opis:
In this paper we observe that the minimal signless Laplacian spectral radius is obtained uniquely at the kite graph $PK_{n-\omega,\omega}$ among all connected graphs with $n$ vertices and clique number $\omega$. In addition, we show that the spectral radius $\mu$ of $PK_{m,\omega}$ $(m\geq1)$ satisfies $$\frac{1}{2}(2\omega-1+\sqrt{4\omega^{2}-12\omega+17})\leq\mu\leq 2\omega-1.$$ More precisely, for $m>1$, $\mu$ satisfies the equation \[ \mu-\omega-\frac{\omega-1}{\mu-2\omega+3}=a_m\sqrt{\mu^2-4\mu}+\frac{1}{t_1}, \] where $a_m=\frac{1}{1-t_1^{2m+3}}$ and $t_{1}=\frac{\mu-2+\sqrt{(\mu-2)^{2}-4}}{2}$. At last the spectral radius $\mu(PK_{\infty,\omega})$ of the infinite graph $PK_{\infty,\omega}$ is also discussed.
Źródło:
Discussiones Mathematicae Graph Theory; 2014, 34, 1; 95-102
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Laplacian spectrum of some digraphs obtained from the wheel
Autorzy:
Su, Li
Li, Hong-Hai
Zheng, Liu-Rong
Powiązania:
https://bibliotekanauki.pl/articles/743220.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
digraph
Laplacian matrix
eigenvalue
wheel
Opis:
The problem of distinguishing, in terms of graph topology, digraphs with real and partially non-real Laplacian spectra is important for applications. Motivated by the question posed in [R. Agaev, P. Chebotarev, Which digraphs with rings structure are essentially cyclic?, Adv. in Appl. Math. 45 (2010), 232-251], in this paper we completely list the Laplacian eigenvalues of some digraphs obtained from the wheel digraph by deleting some arcs.
Źródło:
Discussiones Mathematicae Graph Theory; 2012, 32, 2; 255-261
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Gas6 gene rs8191974 and Ap3s2 gene rs2028299 are associated with type 2 diabetes in the northern Chinese Han population
Autorzy:
Kazakova, Elena
Zghuang, Tianwei
Li, Tingting
Fang, Qingxiao
Han, Jun
Qiao, Hong
Powiązania:
https://bibliotekanauki.pl/articles/1038636.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
Type 2 diabetes mellitus
Gas6 gene
Ap3s2 gene
single nucleotide polymorphisms
epidermal growth factor (EGF)-like
Opis:
Previous studies in other countries have shown that single nucleotide polymorphisms (SNPs) in the growth arrest-specific gene 6 (Gas6; rs8191974) and adapter-related protein complex 3 subunit sigma-2 (Ap3s2; rs2028299) were associated with an increasedrisk for type 2 diabetes mellitus (T2DM). However, the association of these loci with T2DM has not been examined in Chinese populations. We performed a replication study to investigate the association of these susceptibility loci with T2DM in the Chinese population.We genotyped 1968 Chinese participants (996 with T2DM and 972controls) for rs8191974 in Gas6 and rs2028299 near Ap3s2, and examined their association with T2DM using a logistic regression analysis. We also analyzed the correlation of genotypes and clinical phenotypes. The distribution of the T allele of SNP rs8191974 in the Gas6 gene was significantly different between T2DM cases and controls when compared with the C allele (P<0.05, OR: 0.80, 95% CI: 0.69-0.94). The occurrence of the CT genotype and the dominant model was also significantly less frequent in the T2DM cases vs. controls when compared with the CC genotype (CT vs. CC: P<0.05, OR: 0.75, 95% CI:0.62-0.90; TT+CT vs. CC: P<0.05, OR:0.75, 95% CI:0.63-0.90). In SNP rs2028299, the allele C showed no statistically significant differencein distribution between the control and T2DM groups when compared with allele A. However, in male populations, the dominant model was statistically more frequent when compared with genotype AA (CC+CA vs. AA: P<0.05, OR:1.29, 95% CI:1.02-1.64), and in obesity-stratified analysis, we also observed a significant difference in the distribution of the dominant model between the T2DM cases and controls in subjects with BMI≥24 kg/m2 and BMI<28kg/m2 (CC+CA vs. AA: P<0.05, OR: 6.33, 95% CI:4.17-9.61). In conclusion, our study shows that SNPsrs8191974 and rs2028299 are significantly associated with T2DM in the Chinese population.
Źródło:
Acta Biochimica Polonica; 2017, 64, 2; 227-231
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Teacher stress among public primary and secondary schoolteachers in Datong, a city of Shanxi Province, China: association between teacher stress and standardized workload
Autorzy:
Zhang, Xiaojuan
Guo, Jungang
Ma, Li
Xu, Ruijun
Wang, Jinfang
Yang, Yonghong
Shen, Hong
Powiązania:
https://bibliotekanauki.pl/articles/2203017.pdf
Data publikacji:
2023-05-23
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
stress
occupational health
China
workload
primary and secondary schoolteachers
occupational health strategy
Opis:
Objectives The policy of the standardized workload has been implemented among primary and secondary schoolteachers in Shanxi Province. The aim of this cross-sectional cohort study is to assess teacher stress among primary and secondary schoolteachers in Datong, a city of Shanxi Province and the association between teacher stress and the quantified workload. Material and Methods Three hundred and fifty schoolteachers in 10 public primary schools, 187 schoolteachers in 6 secondary schools and 268 non-teachers in 21 education institutes were recruited. A single-item rating assessment of work-related stress was completed by using the Exposure to Job Stress measure with modification. The quantified workload included class size, teaching hours, and subjects. Descriptive and logistic regression analyses were carried out. Results In 805 participants, the pro- portion of primary and secondary schoolteachers with moderate stress was significantly greater. The results of Spearman’s correlation and logistic regression analyses showed that the occupations of the primary and secondary schoolteachers had higher stress risk. Further, the stratified results showed that among the primary schoolteachers, the independent stress risk factor was larger class size; while among the secondary schoolteachers, the stress associated factor was more weekly teaching hours. Conclusions After standardization of the workload, there remain higher levels of work stress among primary and secondary schoolteachers. Notwithstanding, the stress state in teachers is manageable and they may be faced with controllable stressors.
Źródło:
International Journal of Occupational Medicine and Environmental Health; 2023, 36, 2; 161-176
1232-1087
1896-494X
Pojawia się w:
International Journal of Occupational Medicine and Environmental Health
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on fluoride fixation effect of Bayan Obo rare earth iron ore and three sodium agents under microwave irradiation
Autorzy:
Guo, Jing
Wen, Ming
Li, Jie
Hong, Xunhai
Zhang, Wenhao
Wang, Yonglun
Powiązania:
https://bibliotekanauki.pl/articles/2146846.pdf
Data publikacji:
2022
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Bayan Obo rare earth iron ore
microwave roasting
sodium agent fluoride fixation
Opis:
To investigate the fluorine fixation of Bayan Obo rare-earth iron ores in beneficiation and metallurgy processes, the effect of three sodium agents, namely, sodium hydroxide, sodium carbonate, and sodium bicarbonate, on fluorine fixation under the action of microwaves was investigated using Xray diffraction, chemical detection, and orthogonal experiments. The effects of different types of sodium, roasting temperatures, sodium ratios, and roasting times on the fluorine fixation rate were evaluated. Results show that compared with conventional roasting, the fluorine fixation efficiency of Bayan Obo rare-earth iron ore under the action of microwave is superior after the formulation of the sodium agent, which is crucial for the study. Among the three sodium agents, the fluorine fixation effect of NaHCO3 can be used as the preferred sodium agent. Orthogonal experiments showed that the factors influencing the magnitude of the fluorine fixation rate are the roasting temperature, sodium agent ratio, and roasting constant temperature time in the order of priority. The optimal conditions for the fluorine fixation process are the microwave roasting temperature of 973.15 K, sodium bicarbonate ratio of 40%, and roasting time of 60 min. The highest fluorine fixation rate of 86.72% can be obtained. The findings of this study can provide a reference for the development of green and economic recovery processes for Bayan Obo rare-earth iron ores.
Źródło:
Physicochemical Problems of Mineral Processing; 2022, 58, 1; 63--76
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Review of Carbon Emission and Carbon Neutrality in the Life Cycle of Silk Products
Autorzy:
Liu, Shuyi
Liu, Hong
Meng, Yudong
Li, Qizheng
Wang, Laili
Powiązania:
https://bibliotekanauki.pl/articles/2171952.pdf
Data publikacji:
2022
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Biopolimerów i Włókien Chemicznych
Tematy:
carbon footprint
carbon neutrality
silk product
life cycle
Opis:
Silk is a distinctive and significant category of natural structural protein fiber. With a remarkable structure and versatility, silk has emerged as a topic of scientific study perennially because of its chemical, physical and biological properties. Meanwhile, in order to have an omnifaceted understanding of silk, the environmental performance of silk production is also worthy of attention. With the concern of global warming, efforts are increasingly focused on understanding and addressing carbon emission in the life cycle of silk products. However, the majority of current studies give priority to the carbon emission of either just one or a few stages of silk products’ life cycle, or to a specific type of silk product. On the basis of a review of literature on the life cycle assessment of silk products, this study presents a full-scale review of the quantification of the carbon emission and carbon neutrality of cocoon acquisition, industrial production of silk products, distribution, consumption, and recycling. The analysis revealed that the carbon sequestration by photosynthesis at the stage of cocoon acquisition could not be ignored. It is of importance to establish complete and unified system boundaries when quantifying carbon emissions in the industrial production of silk products. Reasonable models of washing times and washing modes are needed to assess carbon emissions in the domestic laundry of silk products. At the end of life phase of silk products, the positive impact on carbon emission in the phase of silk recycling is noteworthy. This study will help interested scholars, manufacturers and consumers to gain an in-depth understanding of the carbon emissions and carbon neutrality of silk products, and it is also of great value for exploring new production processes for reducing carbon emissions of silk products.
Źródło:
Fibres & Textiles in Eastern Europe; 2022, 2 (151); 1--7
1230-3666
2300-7354
Pojawia się w:
Fibres & Textiles in Eastern Europe
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Response of vitamins A, E, hematological and serum biochemical markers in Crucian carp (Carassius auratus gibelio) exposed to environmental Pb2+ and Cd2+
Autorzy:
Khan, Sher
Zhou, Peiyuan
Liu, Xiaoyu
Li, Hong
Li, Jingna
Rehman, Zia ur
Ahmad, Ijaz
Powiązania:
https://bibliotekanauki.pl/articles/1039010.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
vitamins A and E
hematology
serum chemistry
Crucian carp (Carassius auratus gibelio)
Cd2+
Pb2+
Opis:
Toxicity of Pb2+ and Cd2+ is a widespread issue in the world; however, few studies have been conducted to understand their effect at environmentally realistic concentration in a mixture. In the present study, Crucian carp was exposed to Pb2+ (30 µg·l-1), Cd2+ (100 µg·l-1) and their mixture (30+100 µg·l-1) for 96 h and 21 d period to assess changes in the liver and muscle vitamin A and E content, and hematological and serum biochemical parameters. The results indicated significant decline in the level of antioxidant vitamins A, E and alterations in the hematological and serum biochemical indices. The toxicity revealed anemia, impairment of the liver and kidney with evident responses after 21 d exposure due to additive effect of Pb2+ and Cd2+ in mixture. Moreover, the differential response of vitamins A, E and blood parameters to low levels of waterborne Pb2+ and Cd2+ in freshwater fish can be used as biomarkers for monitoring contamination of aquatic environment.
Źródło:
Acta Biochimica Polonica; 2015, 62, 3; 581-587
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on the Critical Sizes for Detonation of Cube-shaped Transfer Charges
Autorzy:
Zhao, Xiang-run
Jin, Shi-xin
Huang, Jin-hong
Li, Chao-zhen
Yan, Li-wei
Powiązania:
https://bibliotekanauki.pl/articles/358353.pdf
Data publikacji:
2019
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
explosive train
transfer charge
shock wave sensitivity
minimum safe separation distance
Opis:
In order to obtain the minimum size, thickness and safe separation distance, for the cube-shaped transfer charges used in MEMS (micro-electromechanical system) explosive trains, an explosive train using a JO-9C(III) cube-shaped transfer charge was designed for experimental research. Detonation transfer experiments and detonation interruption experiments were conducted in turn. In initial experiments, the electric detonators were all in the armed position, but different thicknesses of the cube-shaped transfer charges were used. In the later experiments, the thickness of the transfer charges were unchanged, but the separation distances were different. The detonation path of the transfer charge under unsafe conditions was analyzed using the shock wave attenuation law. The results showed that the minimum thickness ranged from 0.2 mm to 0.4 mm, the minimum safe separation distance ranged from 0.4 mm to 0.6 mm; and the cube-shaped transfer charge is detonated by a shock wave from a steel gap rather than air clearance when the safe separation distance is less than the minimum threshold. The thickness design value of the cube-shaped transfer charge (JO-9C(III)) should not be less than 0.6 mm, and the safe separation distance design value of the MEMS explosive train should not be less than 1 mm.
Źródło:
Central European Journal of Energetic Materials; 2019, 16, 1; 91-104
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on speed control of high speed trains based on hybrid modeling
Autorzy:
Hou, Tao
Tang, Li.
Niu, Hong-xia
Zhao, Tingyang
Powiązania:
https://bibliotekanauki.pl/articles/27311802.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
high-speed train
hybrid modeling
speed control
error compensation
pociąg ekspresowy
modelowanie hybrydowe
kontrola prędkości
kompensacja błędów
Opis:
With the continuous improvement of train speed, the automatic driving of trains instead of driver driving has become the development direction of rail transit in order to realize traffic automation. The application of single modeling methods for speed control in the automatic operation of high-speed trains lacks exploration of the combination of train operation data information and physical model, resulting in low system modeling accuracy, which impacts the effectiveness of speed control and the operation of high-speed trains. To further increase the dynamic modeling accuracy of high-speed train operation and the high-speed train's speed control effect, a high-speed train speed control method based on hybrid modeling of mechanism and data drive is put forward. Firstly, a model of the high-speed train's mechanism was created by analyzing the train's dynamics. Secondly, the improved kernel-principal component regression algorithm was used to create a data-driven model using the actual operation data of the CRH3 (China Railway High-speed 3) high-speed train from Huashan North Railway Station to Xi'an North Railway Station of "Zhengxi High-speed Railway," completing the mechanism model compensation and the error correction of the speed of the actual operation process of the high-speed train, and realizing the hybrid modeling of mechanism and data-driven. Finally, the prediction Fuzzy PID control algorithm was developed based on the natural line and train characteristics to complete the train speed control simulation under the hybrid model and the mechanism model, respectively. In addition, analysis and comparison analysis were conducted. The results indicate that, compared to the high-speed train speed control based on the mechanism model, the high-speed train speed control based on hybrid modeling is more accurate, with an average speed control error reduced by 69.42%. This can effectively reduce the speed control error, improve the speed control effect and operation efficiency, and demonstrate the efficacy of the hybrid modeling and algorithm. The research results can provide a new ideal of multi-model fusion modeling for the dynamic modeling of high-speed train operation, further improve control objectives such as safety, comfort, and efficiency of high-speed train operation, and provide a reference for automatic driving and intelligent driving of high-speed trains.
Źródło:
Archives of Transport; 2023, 66, 2; 77--82
0866-9546
2300-8830
Pojawia się w:
Archives of Transport
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Remaining useful life prediction model of the space station
Model predykcji pozostałego czasu pracy stacji kosmicznej
Autorzy:
Li, Xiaopeng
Huang, Hong-Zhong
Li, Fuqiu
Ren, Liming
Powiązania:
https://bibliotekanauki.pl/articles/301774.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
space station
remaining useful life prediction
key equipment
key activity
Monte Carlo simulation
stacja kosmiczna
przewidywanie pozostałego czasu pracy
kluczowy sprzęt
kluczowe działania
symulacja Monte Carlo
Opis:
Space station is a very complex system, and its remaining useful life will be affected by the key equipment, cosmonauts’ maintenance activities as well as space environments. It is important for the operation management of a space station to predict its remaining useful life (RUL). A valid RUL prediction model is the key foundation for this issue, which motivates the research presented in this paper. Firstly, different types of space station life are defined. Secondly, the function and performance requirements as well as the operation mission program of the space station are analysed, which are further used to confirm the model development precondition. A life prediction model is then proposed by synthetically taking account of the safety, reliability and maintainability restrictions. Finally, the data requirement for supporting the RUL prediction is determined. Based on this work, a comprehensive procedure for RUL prediction model development is constructed for the operation management engineers of the space station. If the data of the development and operation is adequate, RUL prediction of the space station can be well implemented, and can be further leveraged to support the space station operation management.
Stacja kosmiczna stanowi wysoce złożony system, którego pozostały czas pracy (ang. remaining useful time, RUL) zależy od kluczowego sprzętu, czynności konserwacyjnych przeprowadzanych przez kosmonautów, a także warunków panujących w kosmosie. Zarządzanie operacyjne stacją kosmiczną wymaga przewidywania RUL. Podstawą tego zagadnienia jest stworzenie prawidłowego modelu predykcji RUL, co jest przedmiotem niniejszej pracy. W artykule, w pierwszej kolejności, zdefiniowano różne kategorie czasu pracy stacji kosmicznej na orbicie. Następnie, przeanalizowano wymagania dotyczące funkcji i eksploatacji stacji a także program jej misji operacyjnych. Wyniki tych analiz wykorzystano do weryfikacji wstępnych warunków koniecznych do budowy modelu. W dalszej kolejności, zaproponowano model predykcji czasu pracy stacji, który w sposób syntetyczny uwzględnia ograniczenia dotyczące bezpieczeństwa, niezawodności i możliwości konserwacji. Na koniec określono rodzaje danych wspierających predykcję RUL. Na podstawie opisanych etapów prac skonstruowano kompleksową procedurę opracowywania modeli predykcji RUL dla inżynierów zarządzania operacyjnego pracujących na stacjach kosmicznych. Jeśli dane dotyczące rozwoju i operacji są prawidłowe, zaprojektowany algorytm predykcji pozostałego czasu pracy stacji kosmicznej można z powodzeniem zaimplementować, a także rozszerzyć tworząc skuteczne narzędzie wsparcia personelu zarządzającego pracą stacji kosmicznej.
Źródło:
Eksploatacja i Niezawodność; 2019, 21, 3; 501-510
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reliability evaluation for vhf and uhf bands under different scenarios via propagation loss model
Ocena niezawodności propagacji fal radiowych pasm VHF i UHF w różnych warunkach terenowych z wykorzystaniem modelu utraty mocy sygnału
Autorzy:
Li, Xiang
Huang, Hong-Zhong
Li, Yi-Fan
Li, Yan-Feng
Powiązania:
https://bibliotekanauki.pl/articles/301184.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
propagation
reliability estimation
lognormal distribution
VHF radio propagation
UHF radio propagation
propagacja
ocena niezawodności
rozkład lognormalny
propagacja fal radiowych VHF
propagacja fal radiowych UHF
Opis:
The significant effect of path loss on the reliability of very high frequency (VHF) and ultrahigh frequency (UHF) bands propagation has drawn much attention. Previous works mainly focus on the reliability evaluation for infrastructures and basic equipment, however, its propagation reliability has not been taken into full consideration. This paper proposes a new method for evaluating the reliability of the wireless communication based on the analysis of the traditional outdoor wave propagation loss models. In the reliability evaluation of the radio communication, we firstly consider the transmission frequency, the antenna height, the cell type and the communication distance. Then, we use a lognormal distribution to fit the random distribution curve of the communication distance so that the relationship between the path loss value and the reliability can be analysed. We further derive the probability distribution function (PDF) and the cumulative distribution function (CDF) of the path loss value from different antenna correction factors, cell type correction factors and terrain correction factors. Finally, we calculate the radio communication reliability values at different frequencies based on the threshold of the propagation loss value. Compared with the reliability degree only considering the communication distance threshold, the influence of environmental factors on the reliability of the VHF and the UHF radio propagation has been analysed.
W literaturze przedmiotu, wiele uwagi poświęca się ostatnio znaczącemu wpływowi utraty mocy sygnału (ang. path loss) na niezawodność rozchodzenia się fal tworzących pasma o bardzo wysokiej częstotliwości (VHF) i ultra wysokiej częstotliwości (UHF). Wcześniejsze prace koncentrują się głównie na ocenie niezawodności infrastruktury i podstawowego wyposażenia, nie uwzględniając w pełni niezawodności propagacji fal. W niniejszym artykule zaproponowano nową metodę oceny niezawodności komunikacji bezprzewodowej opartą na analizie tradycyjnych modeli utraty mocy sygnału podczas propagacji fal radiowych w środowisku zewnętrznym. Oceniając niezawodność komunikacji radiowej, w pierwszej kolejności rozważano częstotliwość transmisji, wysokość anteny, typ komórki oraz odległość komunikacyjną. Następnie, za pomocą rozkładu lognormalnego, dopasowano krzywą rozkładu losowego odległości komunikacyjnej, co pozwoliło na analizę związku między wartością utraty mocy sygnału a niezawodnością. W dalszej kolejności, z wartości różnych współczynników korekcji anteny, typu komórki oraz terenu wyprowadzono funkcję rozkładu prawdopodobieństwa oraz dystrybuantę wartości utraty mocy sygnału. Na koniec obliczono wartości niezawodności komunikacji radiowej dla różnych zakresów częstotliwości w oparciu o próg wartości utraty mocy sygnału. Przedstawiona analiza wykracza poza elementarne obliczenia niezawodności na podstawie maksymalnej odległości komunikacyjnej biorąc także pod uwagę wpływ czynników środowiskowych na niezawodność propagacji fal radiowych VHF i UHF.
Źródło:
Eksploatacja i Niezawodność; 2019, 21, 3; 375-383
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reliability estimation for momentum wheel bearings considering frictional heat
Ocena niezawodności łożysk kół zamachowych z uwzględnieniem ciepła tarcia
Autorzy:
Huang, Hong-Zhong
Yu, Kang
Huang, Tudi
Li, He
Qian, Hua-Ming
Powiązania:
https://bibliotekanauki.pl/articles/1365209.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
momentum wheel bearings
finite element analysis
frictional heat
stress-strength interference model
łożyska kół zamachowych
analiza MES
ciepło tarcia
model obciążeniowo-wytrzymałościowy
Opis:
Momentum wheels are the key components of the inertial actuators in the satellites, and the momentum wheel bearings are weak links of momentum wheels as they operate under harsh conditions. The reliability estimation for momentum wheel bearings are helpful to guarantee the mission successes for both momentum wheels and satellites. Hence, this paper put emphasis into reliability estimation of a momentum wheel bearing considering multiple coupling operating conditions and frictional heat by using the finite element analysis. The stress-strength interference model is employed to calculate the reliability of the momentum wheel bearing. A comparative analysis for reliability estimation with and without frictional heat of the momentum wheel bearing is conducted. The results show that the frictional heat cannot be ignored in the reliability analysis of momentum wheel bearings.
Koła zamachowe są kluczowymi elementami składowymi siłowników bezwładnościowych w satelitach. Ich łożyska stanowią słaby punkt podczas pracy w trudnych warunkach. Ocena niezawodności łożysk kół zamachowych pozwala zapewnić powodzenie misji zarówno w odniesieniu do samych kół zamachowych, jak i satelitów. Dlatego też niniejszy artykuł poświęcono zagadnieniu oceny niezawodności łożyska koła zamachowego z wykorzystaniem analizy metodą elementów skończonych przy uwzględnieniu wielu sprzężonych warunków pracy oraz ciepła tarcia. Do obliczenia niezawodności łożyska koła zamachowego zastosowano model obciążeniowo-wytrzymałościowy. Przeprowadzono także analizę porównawczą oceny niezawodności łożyska koła zamachowego z uwzględnieniem lub bez uwzględnienia ciepła tarcia. Wyniki pokazują, że w analizie niezawodności łożysk kół zamachowych nie można pominąć ciepła tarcia.
Źródło:
Eksploatacja i Niezawodność; 2020, 22, 1; 6-14
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reliability assessment of wind turbine generators by fuzzy universal generating function
Autorzy:
Huang, Tudi
Xiahou, Tangfan
Li, Yan-Feng
Qian, Hua-Ming
Liu, Yu
Huang, Hong-Zhong
Powiązania:
https://bibliotekanauki.pl/articles/1841742.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Polskie Naukowo-Techniczne Towarzystwo Eksploatacyjne PAN
Tematy:
reliability assessment
double fed induction generator
multi-state system
fuzzy universal generating function
Opis:
Wind power has been widely used in the past decade because of its safety and cleanness. Double fed induction generator (DFIG), as one of the most popular wind turbine generators, suffers from degradation. Therefore, reliability assessment for this type of generator is of great significance. The DFIG can be characterized as a multi-state system (MSS) whose components have more than two states. However, due to the limited data and/or vague judgments from experts, it is difficult to obtain the accurate values of the states and thus it inevitably contains epistemic uncertainty. In this paper, the fuzzy universal generating function (FUGF) method is utilized to conduct the reliability assessment of the DFIG by describing the states using fuzzy numbers. First, the fuzzy states of the DFIG system’s components are defined and the entire system state is calculated based the system structure function. Second, all components’ states are determined as triangular fuzzy numbers (TFN) according to experts’ experiences. Finally, the reliability assessment of the DFIG based on the FUGF is conducted.
Źródło:
Eksploatacja i Niezawodność; 2021, 23, 2; 308-314
1507-2711
Pojawia się w:
Eksploatacja i Niezawodność
Dostawca treści:
Biblioteka Nauki
Artykuł
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