Wyniki wyszukiwania - Biblioteka Nauki

1

Bounded oscillation for a class of even order neutral difference equations

100%

Lin X. , Shen J.

Fasciculi Mathematici

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2002

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tom Nr 33

37-47

EN

We investigate bounded oscillation for the even order neutral delay difference equation delta'' (x(n) -cx(n-m) = pn(x-k), where u is even. The sufficient conditions obtained in this paper improve and generalize the results in related literature.

2

The boundary value problem of higher order differential equations with delay

100%

He Z. , Shen J.

Demonstratio Mathematica

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2013

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tom Vol. 46, nr 1

87--100

EN

In the paper, Guo–Krasnoselskii’s fixed point theorem is adapted to study the existence of positive solutions to a class of boundary value problems for higher order differential equations with delay. The sufficient conditions, which assure that the equation has one positive solution or two positive solutions, are derived. These conclusions generalize some existing ones.

3

Existence of positive solutions to BVPs of higher order delay differential equations

100%

Shen J. , Dong J.

|

2009

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tom Vol. 42, nr 1

53-64

EN

The paper is concerned with the existence of positive solutions for the nonlinear eigenvalue problem with singularity and the superlinear semipositone problem of higher order delay differential equations. The main results are obtained by using Guo-Krasnoselskii's fixed point tbearem In cones. These results extend some of the existing literature.

4

Asymptotic behavior of solutions of impulsive differential equations with positive and negative coefficients

100%

Wei G. , Shen J.

Fasciculi Mathematici

|

2005

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tom Nr 36

109-119

EN

This paper is concerned with the impulsive delay differential equations with positive and negative coefficients Sufficient conditions are obtained for every solution of the above equation tends to a constant as t —> &infin. KEY WORDS: asymptotic behavior, Liapunov functional, delay differential equation, impulse, coefficients.

5

Analysis and measure of novel stereo-garage driven by linear induction motor

80%

Lu Q. , Ye Y. , Shen J.

Archives of Electrical Engineering

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2015

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tom Vol. 64, nr 4

669--678

EN

The car access time is a key parameter, especially in a huge stereo-garage, where this one should be decreased as much as possible. This paper proposes a novel stereo-garage. Adopting the linear induction motors (LIMs), the system has a simple structure and rapid response capability. In the stereo-garage, several LIMs are installed below the crossbeam on a lifting platform, and several LIMs are fixed on the top of a moving frame. During the operation of LIMs, the moving frame moves forward and backward to reach the required parking place, whereas the crossbeam moves horizontally in order to take or store the vehicle rapidly. All these LIMs are the same and should be designed at a low frequency. The influences of key structure parameters and dynamic performances are investigated, based on FEM. The predicted results are validated by a prototype. Finally, the designed LIMs are successfully applied in two 8-layer stereo-garages.

6

Past and recent lake eutrophication evidenced by microfossil (over 160 years) diatom succession in sediments, Lake Xingyun (Southwest China)

80%

Ji M. , Li Y. , Shen J.

|

tom 61

|

nr 4

EN

Eutrophication, disappearance of aquatic vegetation and fish introduction are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. This study investigated the effects of eutrophication, aquatic vegetation and fish introduction on the diatom community of Lake Xingyun by examining the changes of microfossil diatom assemblage. Results showed that diatom assemblages changed with increasing trophic level, decreasing aquatic vegetation and fish introduction. A mesotrophic, alkaliphilous species, Aulacoseira ambigua, was dominant in Lake Xingyun before 1950, which indicated the lake was mesotrophic in the period. Epiphytic diatom species (Achnanthes minutissima, Denticula sp., Gomphonema pumilum) presented high relative concentration between 1950–1980, which indicated aquatic vegetation had a higher cover in this period. The number of diatom species varied from 20 to 66, and to 52 with the change of aquatic vegetation from the past to present. Epiphytic diatoms except Achnanthes minutissima disappeared with the decrease of aquatic vegetation after 1980. Since 1980, with the sharply rising of TP and TN concentration, mesotrophic species (Aulacoseira ambigua) disappeared and eutrophic species (Cyclostephanos dubius, Fragilaria crotonensis, Aulacoseira granulata, Nitzschia palea) were dominant. It indicates the lake has evolved towards eutrophication after 1980. Our study indicated that change of trophic status and aquatic vegetation are important driving factors affecting diatom community composition in Lake Xingyun, but that fish introductions have also been an additional factor.

7

Recent advances on renewable energies and carbon capture

80%

Zhang K. , Shen J. , Zhang J. , Han H.

Polish Journal of Environmental Studies

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2019

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tom 28

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nr 4

EN

In recent years, environmental pollution caused by excessive exploitation and utilization of the Earth’s fossil fuels, extreme exploitation of land resources, and excessive emissions of carbon dioxide (CO2) has caused people to think about how to reduce CO2 emissions and capture the existing CO2 in the atmosphere. The reduction of CO2 emissions can be summarized into two aspects. Firstly, people could use renewable energy to provide energy support for economic and social development. These renewable energies mainly include solar energy; wind energy, hydro, and marine energies; geothermal energy; and biomass energy. The second aspect is the sequestration and conversion of CO2. CO2 is also a form of carbon resource that can be a favorable alternative to traditional carbon resources. The utilization of CO2 can solve both environmental pollution and depletion of traditional carbon resources at the same time. In this paper, the development of five renewable energy sources and their applications in China were discussed, and the methods of effective sequestration and conversion of CO2 were presented. Energy and environment are closely related to the development of modern society. The problems caused by excessive CO2 emissions cannot be ignored and the sequestration of the greenhouse effect requires joint efforts of mankind.

8

Energy Management for Grid-connected Micro Grid with Renewable Energies and Dispatched Loads

80%

Liu Y. , Jiang C. , Shen J. , Zhou X.

Przegląd Elektrotechniczny

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2012

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tom R. 88, nr 5b

87-92

EN

This paper focused on energy management program for grid-connected micro grid with renewable generation and electric vehicles. The proposed program, including energy purchase and self-scheduling problems, aimed to minimize energy cost based on forecasting of loads, prices and renewable generations and was solved with genetic algorithm and pattern search methods. Furthermore, it adopts the expectation model and Monte Carlo methods to solve the uncertainty problems. Simulation results proved the effectiveness of the proposed program.

PL

Analizowano zarządzanie energią w sieci typu microgrid. Celem jest minimalizacja kosztów bazująca na przewidywaniu obciążenia. Wykorzystano algorytmy genetyczne oraz metodę Monte Carlo.

9

Short Term Load Forecasting Based on WLS-SVR and TGARCH Error Correction Model in Smart Grid

80%

Hou L. , Yang S. , Wang X. , Shen J.

Przegląd Elektrotechniczny

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2013

|

tom R. 89, nr 3b

170--175

EN

Smart grid is the main development goal of future power grid while the short-term load forecasting is the significant premise of making management, power supply and trading plan in market circumstance. The forecasting accuracy directly determined the safety and economy of electric system. Support Vector Machines (SVM), as the new machine learning method, has applied successfully to short-termed load forecasting. However, research finds out that the singular points of the initial data have impact on forecasting accuracy. So in this paper, firstly, based on the analysis of SVM, we render Weighted Least Square and Support Vector Regression (WLS-SVR) applying to short-termed load forecasting, which overcomes the disadvantage of singular points. Secondly, we offer Threshold Generalized Autoregressive Conditional Heteroskedasticity (TGARCH) model to construct error prediction model to modify the initial predicted value. Finally, according to the PJM historical data, we get the results showing that the accuracy is greatly improving by implementing our methods which makes our methods founded.

PL

W artykule przedstawiono model przewidywania krótkookresowego obciążenia sieci elektroenergetycznej. W proponowanym rozwiązaniu wykorzystano metodę SVM (ang. Support Vector Machine). W celu eliminacji istniejącego wpływu wartości syngularnych na dokładność wyniku, zastosowano regresję ze średnią ważoną. Dodatkowo wykorzystano model TGARCH w określaniu błędów predykcji. Przedstawiono wyniki badań weryfikacyjnych, przeprowadzonych na rzeczywistych danych.

10

Bryophyte diversity in karst sinkholes afected by diferent degrees of human disturbance

80%

Liu R. , Zhang Z. , Shen J. , Wang Z.

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tom 88

|

nr 2

11

Past and recent lake eutrophication evidenced by microfossil (over 160 years) diatom succession in sediments, Lake Xingyna (Southwest China)

80%

Ji M. , Li Y. , Shen J.

|

2013

|

tom Vol. 61, nr 4

729--737

EN

Eutrophication, disappearance of aquatic vegetation and fish introduction are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. This study investigated the effects of eutrophication, aquatic vegetation and fish introduction on the diatom community of Lake Xingyun by examining the changes of microfossil diatom assemblage. Results showed that diatom assemblages changed with increasing trophic level, decreasing aquatic vegetation and fish introduction. A mesotrophic, alkaliphilous species, Aulacoseira ambigua, was dominant in Lake Xingyun before 1950, which indicated the lake was mesotrophic in the period. Epiphytic diatom species (Achnanthes minutissima, Denticula sp., Gomphonema pumilum) presented high relative concentration between 1950–1980, which indicated aquatic vegetation had a higher cover in this period. The number of diatom species varied from 20 to 66, and to 52 with the change of aquatic vegetation from the past to present. Epiphytic diatoms except Achnanthes minutissima disappeared with the decrease of aquatic vegetation after 1980. Since 1980, with the sharply rising of TP and TN concentration, mesotrophic species (Aulacoseira ambigua) disappeared and eutrophic species (Cyclostephanos dubius, Fragilaria crotonensis, Aulacoseira granulata, Nitzschia palea) were dominant. It indicates the lake has evolved towards eutrophication after 1980. Our study indicated that change of trophic status and aquatic vegetation are important driving factors affecting diatom community composition in Lake Xingyun, but that fish introductions have also been an additional factor.

12

Proof of Multicopy via Proof of File Position in Cloud

80%

Zhang H. , Cao Z. , Dong X. , Shen J.

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tom Vol. 157, nr 1/2

141--151

EN

For disaster recovery, we store backups of a file in several positions far away from each other. If we delegate this task to an untrusted cloud service provider, a verification method is desired. In this paper, we construct a generic transformation from “proof of retrievability” to “proof of multicopy”. We present this work in two stages. In the first stage, we propose a generic protocol of “proof of file position” based on an arbitrary secure “proof of retrievability” protocol. In the second stage, we propose a “proof of multicopy” protocol based on our “proof of file position” protocol. Both of our protocols are provably secure.

13

Effects of selenium on the growth and photosynthetic characteristics of flue-cured tobacco (Nicotiana tabacum L.)

71%

Jiang C. , Zu C. , Shen J. , Shao F. , Li T.

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tom 84

|

nr 1

EN

The objective of this study was to investigate the effect of Selenium (Se) supply (0, 3, 6, 12, 24 mg kg−1) on the growth, photosynthetic characteristics, Se accumulation and distribution of flue-cured tobacco (Nicotiana tabacum L.). Results showed that low-dose Se treatments (≤6 mg kg−1) stimulated plant growth but high-dose Se treatments (≥12 mg kg−1) hindered plant growth. Optimal Se dose (6 mg kg−1) stimulated plant growth by reducing MDA content and improving photosynthetic capability. However, excess Se (24 mg kg−1) increased MDA content by 28%, decreased net photosynthetic rate and carboxylation efficiency by 34% and 39%, respectively. The Se concentration in the roots, stems, and leaves of the tobacco plants significantly increased with increasing Se application. A linear correlation (R = 0.95, P < 0.01) was observed between Se level and tobacco plant tissue Se concentration. This correlation indicated that the tobacco plant tissues were not saturated within the concentration range tested. The pattern of total Se concentration in the tobacco plant tissues followed the order root > leaf > stem. The Se concentration in the roots was 3.17 and 7.57 times higher than that in the leaves and stems, respectively, after treatment with 24 mg kg−1 Se. In conclusion, the present study suggested that optimal Se dose (6 mg kg−1) improved the plant growth mainly by enhancing photosynthesis, stomatal conductance, carboxylation efficiency and Rubisco content in the flue-cured tobacco leaves. However, the inhibition of excess Se on tobacco growth might be due to high accumulation of Se in roots and the damage of photosynthesis in leaves.

14

Methane-oxidizing microorganism properties in Landfills

61%

Mei J. , Wu Y. , Qian F. , Chen C. , Shen J. , Zhao Y.

Polish Journal of Environmental Studies

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2019

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tom 28

|

nr 5

EN

Bio-oxidation of methane in a landfill environment is important for mitigating global methane emissions into the atmosphere. In the present study, the characteristics of methane bio-oxidation and methane-oxidizing microorganisms were studied by enrichment cultivation using fresh and aged leachate (collected from Qizishan Landfill, Suzhou, China). Both aerobic and anaerobic methane oxidation were detected, methane oxidation capacities of the culture liquid were 5.24–7.26 µmol/mL/d under aerobic conditions and 4.41-3.70 µmol/mL/d under anaerobic conditions. The stoichiometry of anaerobic oxidation of methane (AOM) showed the complexity of AOM mechanisms in the leachate culture, with the types of sulfate-dependent, denitrification-dependent and iron-dependent AOM. The 16S rRNA gene sequence analysis and SEM analysis results showed that the genus Methylocystis was the dominant bacteria in aerobic cultures (relative abundance 35.96–78.37%). Genus Moheibacter (41.38%) and Cupriavidus (43.08%) were the most dominant taxa in anaerobic cultures, with aerobic methanotrophs Methylocaldum and Methylocystis in low abundance, and no anaerobic methane-oxidizing archaea (ANME) was found. Further research is needed to confirm whether aerobic methanotrophs can oxidize methane under anaerobic conditions.