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Wyszukujesz frazę "Chen, Chang" wg kryterium: Autor


Tytuł:
Weighted integrability and L¹-convergence of multiple trigonometric series
Autorzy:
Chen, Chang-Pao
Powiązania:
https://bibliotekanauki.pl/articles/1291177.pdf
Data publikacji:
1994
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
multiple trigonometric series
rectangular partial sums
Cesàro means
weighted integrability
L¹-convergence
conditions of generalized bounded variation
Opis:
We prove that if $c_{jk} → 0$ as max(|j|,|k|) → ∞, and $∑_{|j|=0±}^∞ ∑_{|k|=0±}^∞ θ(|j|^⊤)ϑ(|k|^⊤)|Δ_{12}c_{jk}| < ∞$, then f(x,y)ϕ(x)ψ(y) ∈ L¹(T²) and $∬_{T²} |s_{mn}(x,y) - f(x,y)|·|ϕ(x)ψ(y)|dxdy → 0$ as min(m,n) → ∞, where f(x,y) is the limiting function of the rectangular partial sums $s_{mn}(x,y)$, (ϕ,θ) and (ψ,ϑ) are pairs of type I. A generalization of this result concerning L¹-convergence is also established. Extensions of these results to double series of orthogonal functions are also considered. These results can be extended to n-dimensional case. The aforementioned results generalize work of Balashov [1], Boas [2], Chen [3,4,5], Marzuq [9], Móricz [11], Móricz-Schipp-Wade [14], and Young [16].
Źródło:
Studia Mathematica; 1994, 108, 2; 177-190
0039-3223
Pojawia się w:
Studia Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Uniform convergence of double trigonometric series
Autorzy:
Chen, Chang-Pao
Chen, Gwo-Bin
Powiązania:
https://bibliotekanauki.pl/articles/1287625.pdf
Data publikacji:
1996
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Opis:
It is shown that under certain conditions on ${c_{jk}}$, the rectangular partial sums $s_{mn}(x,y)$ converge uniformly on $T^2$. These conditions include conditions of bounded variation of order (1,0), (0,1), and (1,1) with the weights |j|, |k|, |jk|, respectively. The convergence rate is also established. Corresponding to the mentioned conditions, an analogous condition for single trigonometric series is $∑_{|k|= n}^∞ |Δc_k| = o(1/n)$ (as n → ∞). For O-regularly varying quasimonotone sequences, we prove that it is equivalent to the condition: $nc_{n} = o(1)$ as n → ∞. As a consequence, our result generalizes those of Chaundy-Jolliffe [CJ], Jolliffe [J], Nurcombe [N], and Xie-Zhou [XZ].
Źródło:
Studia Mathematica; 1996, 118, 3; 245-259
0039-3223
Pojawia się w:
Studia Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-parameter Hardy-Littlewood inequality and its variants
Autorzy:
Chen, Chang-Pao
Luor, Dah-Chin
Powiązania:
https://bibliotekanauki.pl/articles/1206123.pdf
Data publikacji:
2000
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Opis:
Let s* denote the maximal function associated with the rectangular partial sums $s_{mn}(x,y)$ of a given double function series with coefficients $c_{jk}$. The following generalized Hardy-Littlewood inequality is investigated: $||s*||_{p,μ}≤C_{p,α,β} {Σ_{j=0}^∞Σ_{k=0}^∞(j̅ )^{p-α-2}(k̅)^{p-β-2}|c_{jk}|^p }^{1/p}$, where ξ̅=max(ξ,1), 0 < p < ∞, and μ is a suitable positive Borel measure. We give sufficient conditions on $c_{jk}$ and μ under which the above Hardy-Littlewood inequality holds. Several variants of this inequality are also examined. As a consequence, the ||·||_{p,μ}-convergence property of $s_{mn}(x,y)$ is established. These results generalize the work of Askey-Wainger [1], Balashov [2], Boas [3], Chen [5], [6], [8], [9], Marzug [15], Móricz [16]-[18], [19], Móricz-Schipp-Wade [20], Ram-Bhatia [22], Stechkin [24], Weisz [26]-[28], and Young [30].
Źródło:
Studia Mathematica; 2000, 139, 1; 9-27
0039-3223
Pojawia się w:
Studia Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Almost everywhere convergence of Laguerre series
Autorzy:
Chen, Chang-Pao
Lin, Chin-Cheng
Powiązania:
https://bibliotekanauki.pl/articles/1290468.pdf
Data publikacji:
1994
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
almost everywhere convergence
Cesàro means
Laguerre polynomials
Riesz means
Opis:
Let $a ∈ ℤ^+$ and $f ∈ L^p (ℝ^+), 1 ≤ p ≤ ∞ $. Denote by $c_j$ the inner product of f and the Laguerre function $ℒ^a_j$. We prove that if ${c_j}$ satisfies $lim_{λ↓1} \overline lim_{n→∞} ∑_{n
Źródło:
Studia Mathematica; 1994, 109, 3; 291-301
0039-3223
Pojawia się w:
Studia Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An intelligent multimodal framework for identifying children with autism spectrum disorder
Autorzy:
Chen, Jingying
Liao, Mengyi
Wang, Guangshuai
Chen, Chang
Powiązania:
https://bibliotekanauki.pl/articles/331151.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
autism spectrum disorder
eye fixation
facial expression
cognitive level
improved random forest
spektrum zaburzeń autystycznych
wyraz twarzy
poziom poznawczy
las losowy
Opis:
Early identification can significantly improve the prognosis of children with autism spectrum disorder (ASD). Yet existing identification methods are costly, time consuming, and dependent on the manual judgment of specialists. In this study, we present a multimodal framework that fuses data on a child’s eye fixation, facial expression, and cognitive level to automatically identify children with ASD, to improve the identification efficiency and reduce costs. The proposed methodology uses an optimized random forest (RF) algorithm to improve classification accuracy and then applies a hybrid fusion method based on the data source and time synchronization to ensure the reliability of the classification results. The classification accuracy of the framework was 91%, which is higher than that of the RF, support vector machine, and discriminant analysis methods. The results suggest that data on a child’s eye fixation, facial expression, and cognitive level are useful for identifying children with ASD. Because the proposed framework can separate ASD children from typically developing (TD) children, it can facilitate the early identification of ASD and may improve intervention programs for children with ASD.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2020, 30, 3; 435-448
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on the Acoustic Scattering Characteristics of Multi-Sections Conning Tower Geometries in Monostatic Configuration
Autorzy:
Han, Lin-Jiang
Song, Hao
Chen, Chang-Xiong
Peng, Xi-Rui
Peng, Zi-long
Powiązania:
https://bibliotekanauki.pl/articles/2141632.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
conning tower
Kirchhoff approximation
target strength
monostatic configuration
Opis:
The overall acoustic echo of a submarine is greatly dependent on the conning tower. For enhancing the acoustic stealth performance of a submarine, it is necessary to research an innovative design scheme of the conning tower to reduce its target strength (TS). The aim of this work is to reduce the TS of a conning tower by varying its geometry and streamlining. The accuracy in modelling the acoustic scattering of a conning tower using the Kirchhoff approximation (KA) was validated, compared with finite element analysis (FEA). Several angular conning tower geometries were designed to analyze the effect of streamlining and the number of lateral facets on TS using the KA method. In consideration of the actual situation, the acoustic effect of backing medium was analyzed by compared water-filled elastic hulls with rigid hulls. From the observed TS calculation results, it is shown that the non-streamlined four lateral-facet conning tower geometries are optimal for acoustic stealth performance during the range of incidence angles from −10° to 10°, whereas the streamlined versions have better performance at incidence angles beyond this range. Furthermore, elastic hulls and rigid hulls provide similar spatial distribution regularities in monostatic configuration with the rigidity affecting the magnitude of the TS.
Źródło:
Archives of Acoustics; 2022, 47, 3; 307-317
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physiological responses of the eustigmatophycean Nannochloropsis salina to aqueous diesel fuel pollution
Autorzy:
Mohammady, Nagwa Gamal-El-Din
Chen, Yean-Chang
El-Mahdy, Abd-El-Ruhman Aly
Mohammad, Rania Farag
Powiązania:
https://bibliotekanauki.pl/articles/47635.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Oceanologii PAN
Tematy:
microalga
diesel fuel pollution
physiological response
Nannochloropsis salina
eustigmatophycean microalga
Opis:
The marine eustigmatophycean microalga Nannochloropsis (Monallantus) salina Hibberd was cultivated in a batch culture in the presence of various concentrations (0, 25, 50, 75 and 100%) of an aqueous extract of diesel fuel oil in order to assess the influence of the pollutant on the growth and certain physiological responses of the microalga. The growth data revealed a significant negative effect of the various pollutant concentrations on the algal cell number (p≤0.05). However, at the midlogarithmic growth phase (day 8), the algal cells were analysed for chlorophyll a, β-glucan, amino acid pool, C/N ratio and elemental composition. According to our results, N. salina was significantly affected by the pollution with regard to the different physiological parameters examined, and this significance may be negative, positive or variable. The effect of the pollutant on cellular β-glucan and the total amount of amino acids was negative;h owever, the composition of the cellular amino acid pool remained unaffected. A positive effect of the pollutant on cellular chl a and the C/N ratio was observed. In addition, the pollutant showed variable effects on the composition of different elements, as shown by energy-dispersive X-ray microanalysis. Also, an existence correlation between different elements was statistically reported.
Źródło:
Oceanologia; 2005, 47, 1
0078-3234
Pojawia się w:
Oceanologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal buckling of temperature-dependent functionally graded Timoshenko beams
Autorzy:
Chen, Wei-Ren
Chen, Chun-Sheng
Chang, Heng
Powiązania:
https://bibliotekanauki.pl/articles/139902.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
thermal buckling
functionally graded material
transformed-section method
temperature-dependent properties
Opis:
Thermal buckling behavior of a functionally graded material (FGM) Timoshenko beam is studied based on the transformed-section method. The material and thermal properties of the FGM beam are assumed to vary across the beam thickness according to a power-law function, a sigmoid function and an exponential function. The results of buckling temperature for the FGM beams with respective temperature-dependent and temperature-independent properties under uniform and non-linear temperature rises are presented. Some results are compared with those in the published literature to verify the accuracy of the present work. The effects of the material distributions, temperature fields, temperature-dependent properties and slenderness ratios on the thermal buckling behaviors of FGM beams are discussed. It is believed that the present model provides engineers with a simple and effective method to study the effects of various parameters of the FGM beam on its thermal buckling behavior.
Źródło:
Archive of Mechanical Engineering; 2019, LXVI, 4; 393-415
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study of the nonlinear dynamics of a smooth and discontinuous oscillator with different smoothness parameters and initial values
Autorzy:
Chang, Yujian
Chen, Enli
Feng, Ming
Powiązania:
https://bibliotekanauki.pl/articles/281961.pdf
Data publikacji:
2019
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
SD oscillator
experimental system
nonlinear dynamic characteristic
initial value sensitivity
smoothness parameters
Opis:
The dynamic response of a nonlinear system is very sensitive to initial conditions. Both the irrational nonlinearity and the large displacement of a smooth and discontinuous (SD) oscillator have been studied in this paper. An experimental study has been conducted on a model of the SD oscillator with different initial conditions and smoothness parameters. Experimental results indicate that tiny variation in the initial displacement will lead to different kinds of vibrations, and the system exhibits a wide range of nonlinear dynamical phenomena with the change of smoothness parameters. All experimental results are in good conformity with numerical simulation results.
Źródło:
Journal of Theoretical and Applied Mechanics; 2019, 57, 4; 935-946
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A roadway in close distance to coal seam in deep mine: location selection and supporting practice based on creep characteristics of surrounding rocks
Autorzy:
Wang, Xufeng
Wang, Jiyao
Chen, Xuyang
Chang, Zechao
Powiązania:
https://bibliotekanauki.pl/articles/2073870.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
kopalnia głębinowa
pokłady węgla
pełzanie
deep mine
close distance
coal seam group
location of roadway
creep
Opis:
In deep mines, since the broken surrounding rocks & high-stress level of a roadway being near a coal seam, the creep characteristics of surrounding rocks should be considered as the main influencing factor in the selection for the roadway’s location of the lower coal seam. Both VI15 and VI16-17 coal seams of the Pingdingshan No. 4 Coal Mine, in China, Henan province, are close coal seams with a depth of around 900 m. According to the traditional formula calculation results, when the lower coal seam roadway is staggered 10 m to the upper coal seam goaf, the roadway pressure behaviour is significant, and the support becomes difficult. In this paper, the properties of surrounding rock were tested and the influence of lower coal seam on the stress state of surrounding rock is analysed by numerical simulation, and systematic analysis on the stress and creep characteristics of the surrounding rock of the mining roadway and its effects on the deformation is performed. The results demonstrated that the roadway’s locations in the lower coal seam can be initially divided into three zones: the zone with accelerated creep, the transition creep zone and the insignificant creep zone. The authors believed that the roadway layout in an insignificant creep zone can achieve a better supporting effect. Based on the geological conditions of the roadway 23070 of the VI16-17 coal seam of the Pingdingshan No. 4 Coal Mine, combined with the above analysis, a reasonable location of roadway (internal offset of 30 m) was determined using numerical simulation method. The reliability of the research results is verified by field measurement. The above results can provide a reference for selecting the roadway’s location under similar conditions.
Źródło:
Archives of Mining Sciences; 2021, 66, 3; 407--419
0860-7001
Pojawia się w:
Archives of Mining Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Social Impacts on the Maritime Education – a Case Study of National Kaohsiung Marine University in Taiwan
Autorzy:
Hu, Jia-Shen
Chang, S. W.
Chen, T. S.
Powiązania:
https://bibliotekanauki.pl/articles/116312.pdf
Data publikacji:
2008
Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Tematy:
Maritime Education and Tr
Maritime Education
human resources
Shipping Industry
educational reform
STCW-95
Quality Assurance
Opis:
Recent developments in Taiwan toward the technology intensive country, the employment of cost effective foreign labors by shipping companies, the widespread of universities and the internationalization of shipping industries propose considerable threats on the quality assurance of maritime education. A resultant crisis for lacking on-board seafarers with managerial levels has urged the consolidation of governmental, private and educational organizations in the attempts to further improve the quality of maritime education and to promote the on-board career incentives. The process from the formulation of problems to the implementation of strategies undertaken by the National Kaohsiung Marine University (NKMU) is reviewed. A chain reaction initiated from the degradation of students’ entry performances due to the widespread of universities has formed a viscous cycle leading to the outsourcing of foreign human resources by shipping industry. Strategies in the aspects of course reform, joint ventures of lectureship with shipping industry, pre-courses for students’ extended career plans and the establishment of educational center that consolidates the departments of navigation, marine engineering and fishery in NKMU are illustrated.
Źródło:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2008, 2, 2; 197-203
2083-6473
2083-6481
Pojawia się w:
TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Noether Theorems and Discrete Variational Integrators in Field Theory
Autorzy:
Xia, Li-Li
Chen, Li-Qun
Liu, Chang-Xin
Powiązania:
https://bibliotekanauki.pl/articles/1398640.pdf
Data publikacji:
2015-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
02.20.Sv
11.30.-j
Opis:
The discrete analogue of the Noether-type identities in field theory is investigated by means of the difference discrete variational principle in which the difference is regarded as an entire geometric object. The discrete counterparts of the Noether theorems are obtained. It is proved that there exists the discrete version of the Noether conservation law in field theory. The discretization for the nonlinear Schrödinger equation is presented to illustrate the results.
Źródło:
Acta Physica Polonica A; 2015, 127, 3; 669-673
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimal screw orientation for the fixation of cervical degenerative disc disease using nonlinear C3-T2 multi-level spinal models and neuro-genetic algorithms
Autorzy:
Chang, T.-K.
Hsu, C.-C.
Chen, K.-T.
Powiązania:
https://bibliotekanauki.pl/articles/306375.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
stabilizacja
optymalizacja
kątownik
bioinżynieria
cervical plate
insertion angle
fixation stability
optimization
Opis:
Purpose: Anterior cervical discectomy and fusion is a common surgical procedure performed to remove a degenerative or herniated disc in cervical spine. Unfortunately, clinical complications of anterior cervical plate (ACP) systems still occur, such as weak fixation stability and implant loosening. Previous researchers have attempted to ameliorate these complications by varying screw orientations, but the screw orientations are mainly determined according to the investigator’s experiences. Thus, the aim of this study was to discover the optimal screw orientations of ACP systems to achieve acceptable fixation stability using finite element simulations and engineering algorithms. Methods: Three-dimensional finite element models of C3-T2 multi-level segments with an ACP system were first developed to analyze the fixation stability using ANSYS Workbench 14.5. Then, artificial neural networks were applied to create one objective function, and the optimal screw orientations of an ACP system were discovered by genetic algorithms. Finally, the numerical models and the optimization study were validated using biomechanical tests. Results: The results showed that the optimal design of the ACP system had highest fixation stability compared with other ACP designs. The neuro-genetic algorithm has effectively reduced the time and effort required for discovering for the optimal screw orientations of an ACP system. Conclusions: The optimum screw orientation of the ACP system could be successfully discovered, and it revealed excellent fixation stability for the treatment of cervical degenerative disc disease. This study could directly provide the biomechanical rationale and surgical suggestion to orthopedic surgeons.
Źródło:
Acta of Bioengineering and Biomechanics; 2015, 17, 3; 59-66
1509-409X
2450-6303
Pojawia się w:
Acta of Bioengineering and Biomechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Saving water used for vegetable production by applying regulated deficit irrigation practices
Autorzy:
Chang, Y.-S.
Lin, K.-H.
Chen, Y.-J.
Wu, C.-W.
Chang, Y.-J.
Powiązania:
https://bibliotekanauki.pl/articles/13003875.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Przyrodniczy w Lublinie. Wydawnictwo Uniwersytetu Przyrodniczego w Lublinie
Źródło:
Acta Scientiarum Polonorum. Hortorum Cultus; 2021, 20, 3; 27-36
1644-0692
Pojawia się w:
Acta Scientiarum Polonorum. Hortorum Cultus
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mild Method to Synthesize TATB by Amination of 1,3,5-Trialkoxy-2,4,6-Trinitrobenzene under Phase Transfer Catalysis Conditions
Autorzy:
Chang, T.
Li, B.
Chen, L.
Ge, L.
Lu, M.
Powiązania:
https://bibliotekanauki.pl/articles/358103.pdf
Data publikacji:
2017
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
TATB
phase transfer catalysis
atmospheric amination reaction
Opis:
Nucleophilic amination, as a vital step in the synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using 1,3,5-trialkoxy-2,4,6-trinitrobenzene (TORTNB) and aqueous ammonia as the starting materials and catalyzed by phase transfer catalysis (PTCs) under mild conditions is described. Various phase transfer catalysts, such as crown ethers, tertiary amines, quaternary ammonium salts, poly ethers and cyclodextrin, and various experimental parameters, such as no. of equivalents of PTC, mole ratio of ammonium hydroxide to the starting material, reaction time, reaction temperature and cycle times of the organic phase were investigated. The crown ethers, especially 18-crown-6, show good catalytic activity and re-usability for the amination of 1,3,5-triethoxy-2,4,6-trinitrobenzene giving a yield of 96.52%. This makes for a safe process and suitable for scale-up, because the reactions are carried out under atmospheric conditions. The material synthesised by the new system was characterized by DSC, SEM and LPS.
Źródło:
Central European Journal of Energetic Materials; 2017, 14, 1; 47-59
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Age Structures and Air Pollution: What Role Does Gender Play?
Struktura wiekowa i zanieczyszczenie powietrza: jaką role odgrywa płeć?
Autorzy:
Liu, Jiliang
Wang, Wei
Chen, Yin E
Chang, Chun-Ping
Powiązania:
https://bibliotekanauki.pl/articles/371266.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Komitet Człowiek i Środowisko PAN
Tematy:
age structure
gender
carbon emission
panel cointegration
panel causality
struktura wiekowa
płeć
emisja ditlenku węgla
kointegracja paneli
przyczynowość panelu
Opis:
We investigate the influence of age structure and gender on air pollution, dividing the age structure into four groups and use CO2 emissions as a measure of air pollution, which can be separated into four categories to ob-tain more complete findings, then employing panel cointegration techniques and panel-based error correction models. The data are collected from 29 OECD and 40 non-OECD countries in the period 1990-2014. For case of total CO2 emissions, younger (people under 30) and older people (people 65 and above) emit less than people in the intermediate age group, but the impact of age group on CO2 emissions is different when looking at CO2 emissions from coal, gas, and oil. While we take gender into account, the causality between age structure and CO2 emissions becomes significant, especially for the relationship between population and total CO2 emissions in OECD and non-OECD countries. We also note that more people who are aged 15-29 increase total CO2 emis-sions in OECD countries and more people who are aged 30-44 decrease CO2 emissions from coal in non-OECD countries. Our findings suggest that an energy and environmental policy should consider both age structure and gender effects on environmental issues.
Artykuł przedstawia wyniki badań odnoszących się do wpływu zmiennych struktury wiekowej i płci na zanie-czyszczenia powietrza, wyróżniając cztery grupy wiekowe i wykorzystując poziom emisji CO2 jako wskaźnik zanieczyszczeń powietrza, który można podzielić na 4 kategorie, a następnie wykorzystaliśmy techniki kointe-gracji paneli i oparte na panelach modele korekcji błędów. Dane zebrano z 29 krajów należących do OECD i 40 spoza tej organizacji, obejmują one lata 1990-2014. W przypadku całkowitej emisji CO2 okazało się, że osoby młodsze (poniżej 30 roku życia) oraz starsze (powyżej 65 roku życia) odpowiedzialne są za mniejszą emisję niż osoby w wieku średnim, przy czym występują różnice odnoszące się do poszczególnych grup wiekowych w odniesieniu do emisji CO2 z różnych źródeł: węgla, gazu i ropy. Biorąc pod uwagę płeć, zależność pomiędzy strukturą wiekową a emisjami CO2 okazuje się być znaczącą, szczególnie w aspekcie relacji pomiędzy populacją a całkowitą emisją CO2. Zauważyliśmy ponadto, że osoby w wieku 15-29 z krajów OECD bardziej przyczyniają się do wzrostu całkowitej emisji CO2, a w przypadku krajów nie należących do OECD osoby w wieku 30-44 bardziej odpowiedzialne są za obniżenie emisji CO2 z węgla. Przeprowadzone badania umożliwiają postawienie hipotezy, według której polityka energetyczna i środowiskowa w kontekście zagadnień odnoszących się do środowiska powinna uwzględniać zarówno strukturę wieku jak i płci.
Źródło:
Problemy Ekorozwoju; 2019, 14, 1; 43-52
1895-6912
Pojawia się w:
Problemy Ekorozwoju
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the Microstructure and Strengthening Mechanisms of Ti-6Cu-8Nb-xCr3C2 Alloy through Vacuum Sintering Process
Autorzy:
Chang, Shih-Hsien
Weng, Chen-Yu
Huang, Kuo-Tsung
Liang, Cheng
Powiązania:
https://bibliotekanauki.pl/articles/2106558.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
vacuum sintering
Ti-6Cu-8Nb-Cr3C2 alloy
hardness
transverse rupture strength
EBSD
Opis:
This study mixes four different powders to produce Ti-6Cu-8Nb-xCr3C2 (x = 1, 3, and 5 mass%) alloys in three different proportions. The experimental results reveal that when 5 mass% Cr3C2 was added to the Ti-6Cu-8Nb alloys, the specimen possessed optimal mechanical properties after sintering at 1275°C for 1 h. The relative density reached 98.23%, hardness was enhanced to 67.8 HRA, and the transverse rupture strength (TRS) increased to 1821.2 MPa, respectively. The EBSD results show that the added Cr3C2 in situ decomposed into TiC and NbC during the sintering process, and the generated intermetallic compounds (Ti2Cu) were evenly dispersed in the Ti matrix. Furthermore, the reduced Cr atom acts as a β-phase stabilizing element and solid-solution in the Ti matrix. Consequently, the main strengthening mechanisms of the Ti-6Cu-8Nb-xCr3C2 alloys include dispersion strengthening, solid-solution strengthening, and precipitation hardening.
Źródło:
Archives of Metallurgy and Materials; 2022, 67, 3; 815--825
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental study on vibration of a rotating pipe in still water and in flow
Autorzy:
Geng, Xinge
Wu, Weiguo
Liu, Erpeng
Lin, Yongshui
Chen, Wei
Rheem, Chang-Kyu
Powiązania:
https://bibliotekanauki.pl/articles/32916494.pdf
Data publikacji:
2023
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
flow-induced vibration
rotating pipe
vibration frequency
whirl
VIV
Opis:
To illustrate the vibration characteristics of a rotating pipe in flow, experiments were conducted for a pipe in flow, a rotating pipe in still water and a rotating pipe in flow. For the pipe in flow without rotation, the trajectory diagram is ‘8’ shaped. For the rotating pipe in still water, a multiple frequency component was induced, and a ‘positive direction whirl’ was found. For the flow and rotation, at a flow velocity of 0.46 m/s, the vibration is dominated by the combination of flow and rotation. With an increase in rotating frequency, the trajectory of the rotating pipe varies from an ‘8’ shape to a circular shape and the ‘reverse direction whirl’ is induced, which is different from ‘positive direction’ in still water. The vibration frequency ratio increases uniformly with flow velocity. At a flow velocity of 1.02 m/s, at which the frequency is close to the theoretical natural frequency, the vibration frequency ratio is f*≈1. Predominantly governed by vortex-induced vibration (VIV), the vibration behavior of a rotating pipe subjected to fluid flow conditions has been found to exhibit complete vanishing of whirl. The vibration characteristics of a rotating pipe in flow are studied by the experiments which is benefit for structural drilling design.
Źródło:
Polish Maritime Research; 2023, 1; 65-77
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation and calibration of thermal and salinity layering in surface water resources using Ce-Qual-W2 model
Autorzy:
Chen, Tzu-Chia
Yu, Shu-Yan
Wang, Chang-Ming
Xie, Sen
Barazandeh, Hanif
Powiązania:
https://bibliotekanauki.pl/articles/2048504.pdf
Data publikacji:
2021
Wydawca:
Instytut Technologiczno-Przyrodniczy
Tematy:
Ce-Qual-W2 model
salinity
surface water
thermal layering
water quality modelling
water resources
Opis:
In the discussion of water quality control, the first and most effective parameter that affects other variables and water quality parameters is the temperature situation and water temperature parameters that control many ecological and chemical processes in reservoirs. Additionally, one of the most important quality parameters studied in the quality of water resources of dams and reservoirs is the study of water quality in terms of salinity. The salinity of the reservoirs is primarily due to the rivers leading into them. The control of error in the reservoirs is always considered because the outlet water of the reservoirs, depending on the type of consumption, should always be standard in terms of salinity. Therefore, in this study, using the available statistics, the Ce-Qual-W2 two-dimensional model was used to simulate the heat and salinity layering of the Latyan Dam reservoir. The results showed that with warming and shifting from spring to late summer, the slope of temperature changes at depth increases and thermal layering intensifies, and a severe temperature difference occurs at depth. The results of sensitivity analysis also showed that by decreasing the wind shear coefficient (WSC), the reservoir water temperature increases, so that by increasing or decreasing the value of this coefficient by 0.4, the average water temperature by 0.56°C changes inversely, and the results also show that by increasing or decreasing the value of the shade coefficient by 0.85, the average water temperature changes by about 7.62°C, directly.
Źródło:
Journal of Water and Land Development; 2021, 51; 117-123
1429-7426
2083-4535
Pojawia się w:
Journal of Water and Land Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Feasibility study on preparation of magnesium titanate in carbonthermic reduction of vanadium titanomagnetite concentrates
Autorzy:
Chen, Chao
Sun, Ti-Chang
Kou, Jue
Wang, Xiao-Ping
Zhao, Yong-Qiang
Powiązania:
https://bibliotekanauki.pl/articles/110181.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
vanadium titanomagnetite
carbonthermic reduction
magnesium titanate
formation mechanism
Opis:
Effect of temperature and Mg:Ti ratio on phase composition and microstructure of reduced pellets was investigated to verify the feasibility of preparation of magnesium titanate by adding MgO in carbonthermic reduction of the vanadium titanomagnetite concentrates (VTC). Thermodynamic analysis results showed that magnesium titanate is more easily generated than FeTi2O5 or TiO2 by the reaction of FeTiO3 and MgO under the reductive atmosphere, which was confirmed by the discovery of magnesium titanate at roast experiment. It was found that the optimum conditions for reduction of VTC pellets were temperature of 1250 ºC and Mg:Ti ratio of 2, and the main phases of reduction product were metallic Fe and magnesium titanate (Mg2TiO4). However, trace iron impurities in Mg2TiO4 particles were found by energy-dispersive spectroscopy (EDS), so further purification is required.
Źródło:
Physicochemical Problems of Mineral Processing; 2019, 55, 2; 417-425
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photo-oxidative Aging Behaviors of Acrylic Coatings during UV Irradiation Investigated by Positron Annihilation Spectroscopy
Autorzy:
Zhao, Xipo
Cai, Xiaolin
Liu, Chang
Chen, Ting
He, Chunqing
Fang, Pengfei
Peng, Shaoxian
Powiązania:
https://bibliotekanauki.pl/articles/1033253.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
Acrylic coating
UV irradiation
positron annihilation spectroscopy
Opis:
Slow positron annihilation spectroscopy, contact angle and scanning electron microscope (SEM) were employed to investigate the surface polarity and morphologies as functions of aging time in acrylic coatings during UV-a irradiation. The S parameter plots of each exposed sample are lower than that of the virgin sample in the whole range of E. The S parameter plots become lower as the exposing longer time, indicated that the irradiation generated more polar groups and increased the oxidation layer depth. Combined with surface morphology and the surface energy of acrylic coating, the variation of contact angle, and surface energy, polar component and dispersive component is related with surface polarity and morphologies.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1527-1530
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Finite element analysis of three-point bending of a T-beam structural biaxial highly oriented polymer material
Analiza metodą elementów skończonych zginania trójpunktowego belki teowej wykonanej z wysoko zorientowanego dwuosiowo materiału polimerowego
Autorzy:
Wei, C.-L.
Chang, Y.
Lee, Y.-C.
Lee, R.
Luo, T.-W.
Chen, J.-H.
Powiązania:
https://bibliotekanauki.pl/articles/946988.pdf
Data publikacji:
2018
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
Tematy:
solid phase processing
highly oriented polymer (HOP)
orthotropic materials
T-beam
three-point bending
finite element
proces w fazie stałej
wysoko zorientowany polimer
materiały ortotropowe
belka teowa
zginanie trójpunktowe
elementy skończone
Opis:
Polymers with biaxial aligned molecular chains are also orthotropic materials, which are characterized by high tensile strength and low shear strength in the length direction. When orthotropic materials are used as structural shapes with poor shear strength, they are likely to undergo premature failure under shear stress. Therefore, in three-point bending, the cross-section of the entire profile not only bears tensile stress and compressive stress in the length direction, but also simultaneously exhibits shear stress. This study analyzes the distribution of tensile stress, compressive stress and shear stress in the length direction of highly oriented polymers (HOP) by finite element analysis to find the most suitable length-to-height ratio for these materials when used as structural shapes. The finite element analysis software, Abaqus, is utilized to simulate HOP T-beam to analyze the load stress of a T-beam. With a fixed cross–section area, as the length of the material changes, its shear strength also changes. Accordingly, the order of occurrence of tensile failure and shear failure can be investigated. The simulation reveals that when the length-to-height ratio is between 4 : 1 and 20 : 1, a zone of stress in which tensile failure and shear failure occur can be found. This result can be exploited in the design and development of structural beam.
Polimery o dwuosiowo zorientowanych łańcuchach makrocząsteczek są materiałami ortotropowymi, wykazującymi dużą wytrzymałość na rozciąganie oraz niewielką wytrzymałość na ścinanie w kierunku długości. Elementy konstrukcyjne wytworzone z materiału ortotropowego o małej wytrzymałości na ścinanie są podatne na przedwczesne uszkodzenie pod wpływem naprężeń ścinających. Przy zginaniu trójpunktowym w przekroju ich profilu występują zarówno naprężenia rozciągające i ściskające w kierunku podłużnym, jak i naprężenia ścinające. Metodą elementów skończonych analizowano rozkład naprężeń rozciągających, ściskających i ścinających w kierunku podłużnym wysoko zorientowanych polimerów (HOP) w celu określenia optymalnego stosunku długości do wysokości w kształtach konstrukcyjnych. Do symulacji naprężeń obciążeniowych w zginaniu trójpunktowym belki teowej wykorzystano program komputerowy Abaqus. Stwierdzono, że przy stałej powierzchni przekroju poprzecznego belki jej wytrzymałość na ścinanie zmienia się wraz ze zmianą długości. Badano również kolejność występowania uszkodzeń pod wpływem działania sił rozciągających i ścinających. Symulacja wykazała, że przy stosunku długości do wysokości w zakresie od 4 : 1 do 20 : 1 występuje strefa naprężeń, w której mogą się pojawiać uszkodzenia w wyniku rozciągania lub ścinania. Uzyskane wyniki można wykorzystać w projektowaniu i optymalizacji belek konstrukcyjnych.
Źródło:
Polimery; 2018, 63, 3; 219-223
0032-2725
Pojawia się w:
Polimery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Semi-quantitative analysis study of the impact of microwave treatment on fly ash
Autorzy:
Ma, Xian Yun
Nie, Yi Miao
Guo, Jia Le
Chen, Yang
Chang, Zhen Jia
Wang, Ling
Liu, Shu Xian
Wang, Long
Powiązania:
https://bibliotekanauki.pl/articles/27323647.pdf
Data publikacji:
2023
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
microwave
fly ash
semi-quantitative analysis
adsorption
XRD refinement
infrared fitting
NMR
Opis:
Pre-processing provides an effective way for fly ash's high value-added utilization. However, the shortcomings of pre-processing methods such as grinding and flotation are apparent with many disadvantages that make it more challenging to use efficiently. Microwave heating helps the SiO2-Al.2O3 bond break, not only can make the structural change of the material can also promote the chemical reaction process. In the article, XRD, SEM, FT-IR, ammonia nitrogen adsorption, and other methods were used to analyze the changes in the properties of fly ash before and after microwave pre-treatment, the change in adsorption performance of fly ash before and after microwave treatment was analyzed. The study found that under microwave conditions of 600 W and 15 min, the adsorption rate of ammonia nitrogen by fly ash reached a maximum of 29.67%. The intensity of mullite and amorphous diffraction peaks decreased after 20 min at 600 W. The Si-O-(Si, Al) and Si-O-(Si) bonds showed significant changes at 15 min and 20 min under 600 W conditions. Based on the results, the microwave conditions were selected at 600 W for different periods, and semi-quantitative analysis was carried out by XRD-Rietveld, infrared peak fitting, and nuclear magnetic resonance. The XRD-Rietveld analysis showed that the amorphous phase content reached 46.18% at 15 min. In the infrared peak fitting, the fitting area at 1300-900 cm-1 and 600-400 cm-1 peaks at 56.92% at 25 min and 17.5% at 15 min, respectively. The silicon-oxygen network's degree of connection and polymerization was reduced after 15 min of microwave treatment for the nuclear magnetic resonance analysis. By combining specific surface area measurements, it was discovered that the maximum specific surface area attained a value of 3.122 m2/g at 15 min.
Źródło:
Physicochemical Problems of Mineral Processing; 2023, 59, 6; art. no. 174897
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entry into vocational rehabilitation program following work-related hand injury: Potential candidates
Autorzy:
Chen, Yueh-Hsia
Hsu, Chung-Yin
Lien, Shwu-Huei
Yu, Shu-Jung
Chang, Jen-Mu
Su, Shanq-Wen
Chao, Yuan-Hung
Powiązania:
https://bibliotekanauki.pl/articles/2177083.pdf
Data publikacji:
2015-09-23
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
rehabilitation
vocational
return to work
occupational injuries
hand injuries
Opis:
Objectives This case-control study aimed to investigate the predictors of return to work (RTW) following work-related major forearm, wrist or hand injury at the preparation stage of return to work. Material and Methods A total of 80 clients were recruited and divided into 2 groups depending on their readiness of RTW. The groups were compared with each other with regard to their demographics, compensation status, hand injury severity, health perception, and time off work (TOW) using correlation coefficient. Predictors of RTW were measured by logistic regression analysis. Results There were no significant differences in demographics and the severity of hand injury between 2 groups. Self-perceived physical functioning (p = 0.04), vitality (p = 0.01), mental health (p = 0.03) and TOW (p = 0.001) were significantly different between Action group and Preparation group. With binary logistic regression analysis, self-perceived vitality (odds ratio (OR) = 1.041) and TOW (OR = 0.996) were shown to be strongly predictive of RTW at the preparation stage of return to work. Conclusions This study has shown that shorter TOW and better self-perceived vitality could predict early readiness for RTW after major work-related forearm, wrist or hand injury.
Źródło:
International Journal of Occupational Medicine and Environmental Health; 2016, 29, 1; 101-111
1232-1087
1896-494X
Pojawia się w:
International Journal of Occupational Medicine and Environmental Health
Dostawca treści:
Biblioteka Nauki
Artykuł

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