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Issue Info: 
  • Year: 

    2018
  • Volume: 

    49
  • Issue: 

    1
  • Pages: 

    133-142
Measures: 
  • Citations: 

    0
  • Views: 

    192
  • Downloads: 

    53
Abstract: 

Recently, multi-TIME stepping methods have become very popular among scientistdue to their high stability in problems with critical conditions. One importantshortcoming of these methods backs to their high amount of uncontrolled amplitudeDECAY. This study proposes a new multi-TIME stepping method in which the TIME stepis split into two sub-steps. The first sub-step is solved using the well-knownNewmark method and for the second sub-step an extended version of Newmarkmethod is applied. In fact, similarity in basic formulas of the mentioned methodsmakes it available to control the amount of amplitude DECAY in responses obtainedby the proposed method; in other words, the amplitude DECAY in the proposed methodis controlled through constant parameters of the two methods applied on each substep. The precision assessment of the proposed method is performed using numericalapproaches and revealed the minor period elongation error of the proposed methodin comparison with other existing methods. In addition to this, the unconditionalstability region of constant parameters is also determined through computation ofspectral radius of the proposed method. Finally, practical assessment of the proposedmethod is performed through several numerical examples.

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Journal: 

CRYSTENGCOMM

Issue Info: 
  • Year: 

    2012
  • Volume: 

    14
  • Issue: 

    -
  • Pages: 

    1382-1386
Measures: 
  • Citations: 

    1
  • Views: 

    99
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2016
  • Volume: 

    42
  • Issue: 

    3
  • Pages: 

    551-563
Measures: 
  • Citations: 

    1
  • Views: 

    689
  • Downloads: 

    0
Abstract: 

According to key role of dead trees in maintaining biodiversity in forest ecosystems, the awareness of the full DECAY dead trees TIMEs, play an important role in developing in forest protection and management program. This research was done in the Asalem forest to investigate DECAY dynamic of dead beech trees. A total of 90 sample cuts of dead beech stumps were randomly selected and studied. For each sample, species, diameter and degree of DECAY stumps were recorded. To determine the density of dead wood, cut samples were taken with the length, width and height of 5 cenTIMEters per two perpendicular directions to the cross-section of each sample. The results showed that the DECAY TIME of 95% and 50% of the dry mass of beech stumps take a 49 and 22 years, respectively. According to the results, the DECAY constant of this tree species varied 0. 01 to 0. 07. Meanwhile in this research the total TIME of dead wood recruitment in the four DECAY class estimated totally 36 years and 2, 17, 12 and 6 years, respectively. Results showed there is no significant relationship between DECAY rate and wood extracts. According to the results in the maintaining dead wood as source of biodiversity in the forest ecosystems, the dynamic of density and volume of dead wood must be considered. Introduction Today, the dead woods are important to the conservation of biodiversity in forest ecosystems. The importance of maintaining diversity in natural ecosystems, has led to the formation of different perspectives of the forestry projects. In the most forestry projects, especially in the conservational projects and management based on the ecological point of view, one of the main objectives of forestry plans is maintaining biological diversity in forest ecosystems (Bollmann & Mü ller 2012). In addition, biodiversity have been introduced as one of the main quantitative indicators to evaluate the sustainable management of forest ecosystems and high variability in forest ecosystems demonstrate the health and sustainability of ecosystems (Parviainen & Vä stilä 2011). Researchers have figured out the importance of dead trees in the 1970s. Most publications have been proved its importance in biodiversity (Mü ller and Schnell, 2003; Schuck et al., 2004), nutrient cycling (Hafner and Groffman, 2005; Santiago and Amanda, 2005), natural regeneration (Yan et al., 2007; Sefidi et al., 2013) wildlife habitat (Harmon et al., 1986; Hunter, 1990) Due to the change in the overall attitude toward forest management and conservation approaches, and highlights the role of forests in carbon sequestration and storage, today aware of the TIME of trees stay in the forest can help managers of forest in regulating forestry plans. According to dynamics of the dead trees volume in the forest ecosystem, knowledge of the changes in volume over TIME will be very helpful to maintain dead woods in different period’ s forestry project. This research attempts to answer these questions; (1) the total DECAY TIME of a dead beech in natural conditions it takes a few years? And (2) each of the four DECAY classes naturally spent how many year. The answers to these questions can help us to achieve the main objective of this research provide appropriate quantitative information from the DECAY rates of oriental beech trees Method and Material This study was conducted at Asalem Forest (37° 36' N, 48° 52'E). The climate of the area is temperate with an annual mean temperature from 7. 3 to 8. 3 C and an annual mean precipitation of 586– 885 mm. Forests occupy plateaus on moderately inclined slopes, largely free of rocks with limestone bedrock. Caspian forests occupy an approximate area of 2, 000, 000 ha being dominated by oriental beech (Fagus orientalis Lipsky). The field sampling for the case study was carried out in August 2014. A chronological sequence of samples for 0, 2, 5, 11, 15, 19 and 25 years after the harvesting period was established) Mü ller-Using and Bartsch, 2003). In total, 90 stumps of beech were chosen randomly for dead wood carbon measurements. Stumps were considered as a representative of dead trees, because their mortality age was specified and it was possible to establish chornosequence plots (Harmon et al., 1986). Consequently, the sample a cube shape with 4cm length was removed from two opposite parts of a cross-section using chain saw and axe. Consequence plots were a representative of the defined DECAY class in this forest. DECAY class of stumps was specified by visual characteristics which were observed in the structure of the bark and tissue of the wood (Albercht, 1990; Sefidi & Marvie-Mohadjer, 2010). All statistical analyses were performed using SAS 9. 3 software. Analyses of variance (ANOVA) were used to detect differences in carbon contents, C concentration and wood density of beech and hornbeam trees. Tukey’ s HSD procedure was used to determine significant differences in the mean density of wood with years at α =0. 05 level. Discussion of Results The findings showed that the decrease in wood density over TIME follows a negative exponential function. Based on the results the total DECAY TIME of the about 95% dead wood can be estimate or in other words TIME of reduction to estimate the 95% of the timber weight can be estimated, which is consistent with the findings of studies in northern Iran (Alidadi et al., 2015) and correspond in other similar areas in forests (Yang et al., 2010; Garrett et al., 2012; Mü ller & Bartsch, 2009). The results of this research in the Asalem of beech forests revealed that the TIME required to DECAY and lose 95% of the weight of a beech tree dead wood lasts about 46 years. Different results for different tree species have been reported. The DECAY TIME varies among different species. The rate of DECAY in trees in addition to the sites geomorphic features (Fukasawa, 2015) and environmental conditions such as climate (Russell et al., 2014) that are influential in the DECAY process (Dunn & Bailey, 2012) are also influenced by genetic species there. Numerous studies have mentioned the differences between species in the rate of DECAY. Mackensen et al. (2003) reported differences in the rate of DECAY in the eucalyptus species. The tree species of E. radiata and E. elata showed differences in the rate of decomposition of the wood. In addition conifers and broadleaf tree species also varies by the chemicals properties of wood caused to e differences in the DECAY rates (Mackensen et al., 2003). Studies of (Palmetto & Tohi, 2014) showed differences in the DECAY of tree species due to differences in moisture content and density of trees. In the in Mazandaran province, Alidadi et al (2015) reported the total TIME of beech dead wood DECAY need to approximately 36 years. The contradiction in the results can be caused by different climatic condition between two study sites. In the European beech forests Mü ller & Bartsch (2009) reported 30 years for total DECAY of beech trees. Diffrences caused by environmental factors like climate and also initial density of tree species. In addition to the aforementioned, the chemical characteristics of wood can also be more effective on the activity of microorganisms and the development of DECAY process. Conclusion Today, we are witnessing a change in attitude and overall approach the managers of the forestry sector to the management of our forest ecosystems. In the concepts based on the conservation of biodiversity in forest, the health of ecosystem has been an important position. T According to the findings of this research it is recommended that in the maintenance of dead trees in the forest ecosystems, beside to the volume of dead trees in the forest floor, the dynamics and volume changes over TIME to be considered.

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Issue Info: 
  • Year: 

    2025
  • Volume: 

    13
  • Issue: 

    2
  • Pages: 

    235-249
Measures: 
  • Citations: 

    0
  • Views: 

    8
  • Downloads: 

    0
Abstract: 

In this paper, we consider a general class of nonautonomous abstract delayed evolution equations with a nonlinear source term. Under appropriate assumptions on the TIME-independent operator and the initial data, we establish global existence using the method of steps and employing classical results from the theory of inhomogeneous evolution problems. Then, by assuming that the operator associated with the non-delayed part of the system generates an exponentially stable semigroup, we obtain an exponential DECAY estimate. This is achieved through a direct proof based on Duhamel's formula combined with Gronwall's inequality, under Lipschitz continuity conditions on the nonlinear source term. Finally, we conclude the paper by providing illustrative examples that validate the generalized setting of our system.

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Conference: 

IRAN PHYSICS CONFERENCE

Issue Info: 
  • Year: 

    2005
  • Volume: 

    0
Measures: 
  • Views: 

    154
  • Downloads: 

    0
Keywords: 
Abstract: 

IN THIS RESEARCH, WE USE QUARK MODEL AND STANDARD MODEL FOR THE CALCULATION OF THE DECAY RATE OF C QUARK IN TREE-LEVEL AND PENGUIN. THEN, WE COMPARE THE THEORETICAL RESULT WITH THE EXPERIMENTAL VALUES. THE THEORETICAL RESULTS ARE NEARLY SIMILAR TO THE OBSERVED EXPERIMENTAL VALUES.

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Issue Info: 
  • Year: 

    2014
  • Volume: 

    22
  • Issue: 

    4
  • Pages: 

    624-635
Measures: 
  • Citations: 

    1
  • Views: 

    835
  • Downloads: 

    0
Abstract: 

Due to their significance for carbon sequestration and ecosystem management, information on DECAY dynamic of deadwood and its total DECAY TIME are of great importance to ecologists and forest managers. This study was conducted in Kheirud forest of Nowshahr to study the DECAY process of beech and hornbeam deadwood. Therefore, 72 beech and hornbeam dead trees were randomly selected. For each sample tree, information on species, diameter, DECAY classes and slope gradient were recorded. The cubic cut samples with 5 cm length, width and height in two perpendicular aspects were taken from each DECAYing stump.30 and 16 years of DECAYing TIME were shown to be needed for 95% dry mass of dead beech and hornbeam logs, respectively. In addition, the required periods for passing through all stages of DECAY for beech and hornbeam dead trees were 27 and 21 years, respectively. A strong relation (R2=0.8) between density and DECAY stage of dead trees was indicated. Therefore, the density of dead wood was concluded to significantly decline with increased DECAY stage in both species.

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Author(s): 

HUNTINGTONS SAMUEL

Journal: 

WORLD POLITICS

Issue Info: 
  • Year: 

    1965
  • Volume: 

    17
  • Issue: 

    3
  • Pages: 

    386-430
Measures: 
  • Citations: 

    1
  • Views: 

    156
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

SCHWARZE F.W.M.R.

Issue Info: 
  • Year: 

    2007
  • Volume: 

    21
  • Issue: 

    -
  • Pages: 

    133-170
Measures: 
  • Citations: 

    1
  • Views: 

    232
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2019
  • Volume: 

    -
  • Issue: 

    87
  • Pages: 

    48-54
Measures: 
  • Citations: 

    0
  • Views: 

    541
  • Downloads: 

    0
Abstract: 

In this research work, different terbium doped lutetium aluminium garnet nano crystalline powders were prepared by the co-precipitation method in different sizes at different annealing temperatures. The structural properties and size of the different nano crystalline powders prepared at different temperatures were investigated by the X-ray diffraction pattern and TEM. Also, the atomic structure of different nano crystals in garnet forming was studied by Fourier Trans from Infrared (FTIR) method. The impact of different crystallite sizes on the absorption energy was investigated by the UV-visible spectroscopy. The emission and excitation spectra of terbium doped lutetium aluminium garnet nano-structure powders were measured at room temperature. The DECAY TIME of different nano crystalline with different sizes was examined at room temperature. The change of nanocrystalline size affects the DECAY TIME. Also, the investigation of terbium doped garnet emission spectra showed that this material can be used as an appropriate scintillator for detection systems such as medical diagnostic and therapeutic.

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Issue Info: 
  • Year: 

    2019
  • Volume: 

    12
  • Issue: 

    46
  • Pages: 

    101-125
Measures: 
  • Citations: 

    0
  • Views: 

    2289
  • Downloads: 

    0
Abstract: 

Rehabilitation and renovation are of the major challenges with which urban management is facing in developing countries. Identifying physical and functional status of these textures is important for planning, managing, and maintaining them. Urban DECAY in Nahavand covers an area of 166 hectares consisting of seventeen dead tissues in the neighborhoods. The areas, despite the capabilities in physical, socio-economic and cultural – historical matters, are deficient somehow. In this study, SWOT analysis was used in order to assess the situation of urban DECAY in Nahavand. The research method used in this article was analytical and documents-literature and field observations were used in order to obtain the necessary data. The results of this study showed that the urban DECAY of Nahavand because of being ignored by officials and authorities of the city has turned into a serious problem experiencing disorder in social, economic, infrastructural, and bioenvironmental grounds. The city officials have not had any contribution to remove the existing problems either. It seems that any change in their approaches toward the mentioned texture, not as a threat but as an opportunity, most of the problems in the city can be removed and the potentials of Nahavand can be realized to develop this city fundamentally.

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