Forest gaps restrict the restoration of temperate secondary forest to broad-leaved Korean pine forest in zonal climax vegetation by affecting the growth of Korean pine(Pinus koraiensis).However,the photo synthetic ada...Forest gaps restrict the restoration of temperate secondary forest to broad-leaved Korean pine forest in zonal climax vegetation by affecting the growth of Korean pine(Pinus koraiensis).However,the photo synthetic adaptability of Korean pine to gap size and position within the gap is unclear.In order to explore the adaptability of young Korean pine(35 years) to different gap sizes in Xiaoxing’anling,photo synthetic capacity and microenvironmental factors(leaf temperature,light transmittance) of Korean pine needles in three positions in the gap(central,transition,and edge areas) were investigated.Three gaps were identified in the secondary Populus davidiana forest:a large 201 m^(2) gap,a middle 112 m^(2) gap,and a small 50 m^(2) gap;12 m^(2) of the understory was sampled as a control.The results show that:(1) maximum net photosynthetic rate(P_(max)) in needles of Korean pine growing in the large gap was higher than in the small gap,and P_(max) in the centre in the same gap was higher than in the transition and edge areas;(2) light saturation point(LSP) and photosynthetic quantum yield(AQY)of needles in the large gap were higher than in the small gap,while the light compensation point(LCP) and chlorophyll contents of needles were lower in the small gap;and,(3)P_(max) had a significant positive correlation with temperature and light transmittance.It is suggested that the larger the gap in secondary Populus davidiana forests,the greater the change in light intensity and temperatures,the stronger the light adaption of Korean pine needles and the higher the photosynthetic capacity.Therefore,in the recovery of broadleaved/Korean pine forests,suitable gaps should be created and gap microhabitats fully utilized to accelerate the restoration process.展开更多
In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the fille...In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.展开更多
A new method using lead coated glass fiber to produce continuous wire for battery grid of electric vehicles （EVs） and hybrid electric vehicles （HEVs） was introduced. Under equal flow, both the maximum and minimum ...A new method using lead coated glass fiber to produce continuous wire for battery grid of electric vehicles （EVs） and hybrid electric vehicles （HEVs） was introduced. Under equal flow, both the maximum and minimum theoretical value of gap size were studied and estimation equation was established. The experimental results show that the gap size is a key parameter for the continuous coating extrusion process. Its maximum value （Hmax） is 0.24 mm and the minimum one （Hmin） is 0.12mm. At a gap size of 0.18 mm, the maximum of metal extrusion per unit of time and optimal coating speed could be obtained.展开更多
Under the condition of equal flow, the maximum and minimum theoretical values of gap size were studied and an estimation equation was established for the clad extrusion of the brittle core cladded by plastic metal mat...Under the condition of equal flow, the maximum and minimum theoretical values of gap size were studied and an estimation equation was established for the clad extrusion of the brittle core cladded by plastic metal materials. The results show that the gap size is a key parameter for the continuous clad extrusion and the molding speed. Its maximum value (Hmax) is 0.24mm and the minimum one (Hmin) is 0.12mm. At a gap size of 0.18mm, the maximum of metal extrusion per unit of time and the optimal coating speed can be obtained.展开更多
Subri River Forest Reserve(SR)is the most extensive forest area in Ghana with an accompanying rich floral species.Over the years,logging from both legally prescribed and illegal operations remain the predominant fores...Subri River Forest Reserve(SR)is the most extensive forest area in Ghana with an accompanying rich floral species.Over the years,logging from both legally prescribed and illegal operations remain the predominant forest disturbance in SR.Gap creation following logging is crucial in determining tree species composition and diversity.Hence,the study evaluated the composition and diversity of naturally regenerated tree species in logging gaps of different sizes and,again examined the roles of these tree species in fulfilling the economic and ecological agenda of sustainable forest management after logging in SR.Twelve gaps were randomly selected:4 each were grouped into small size(≤200 m^(2)),medium size(201–300 m^(2)),and large size(≥300 m^(2)).Data were gathered from 1 m^(2) circular area at gap centres and repeatedly inside 1 m width strip along 20 m individual N-S-E-W transects.Species diversity differed significantly between gap sizes.Higher diversity indices were measured in large size gaps.Gap sizes shared similar species.There were significant differences among various height groupings of tree species across all three gap sizes.Pioneers preferred medium to large size gaps,while shadetolerant tree species preferred small size gaps for their abundance.Vulnerable and Lower Risk Near Threatened tree species under Conservation Status and,Premium and Commercial tree species under Utilisation Status preferred small size gaps for their proliferation and conservation.Therefore,we recommend the single tree-based selective logging for ensuring creations of small to medium size(200–300 m^(2))gaps through adjustments to the logging permit process,revision of Allocation Quota Permit,strict adherence to the 40-year polycyclic selection system,along with more dedicated enforcement and monitoring.Changes along these protocols would tremendously facilitate natural regeneration of different suites of timber species resulting in the improvement of the overall biodiversity conservation associated with the forest,more sustainable forest harvests and more income to those who receive permits.展开更多
Forest gaps are important in forest dynamics and management, but little is known about how soil fauna influence the degradation of recalcitrant litter components in different-sized forest gaps. This investigation uses...Forest gaps are important in forest dynamics and management, but little is known about how soil fauna influence the degradation of recalcitrant litter components in different-sized forest gaps. This investigation uses litterbags with two different mesh sizes (0.04 and 3 mm) to control the meso- and microfauna entering the bags to quantify the contribution of soil fauna to the degradation of recalcitrant components (including condensed tannins, total phenol, lignin and cellulose) during litter decomposition. The experiment was conducted in seven different forest gap sizes in Pinus massoniana plantations over 1 year. One closed-canopy site (CC) and forest gap sizes of 100, 225, 400, 625, 900, 1225 and 1600 m^2 were created in a P. massoniana plantation in the Sichuan basin of China;the CC was treated as the control. Cinnamomum camphora foliage from local native trees was used in all forest gap experiments. We found the following:(1) Gap size had significant effects on the degradation rates (E) of condensed tannins and lignin and on the contributions of soil fauna;medium-sized gaps also presented high degradation rates. Soil fauna obviously contributed to the degradation of recalcitrant foliar litter components in medium-sized gaps.(2) The highest contribution to degradation (40.98%) was recorded for lignin, and the lowest contribution (0.29%) was recorded for condensed tannins. The results indicate that medium-sized gaps (900 m^2) were conducive to the degradation of recalcitrant litter components by soil fauna.展开更多
Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest ...Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.展开更多
Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of ...Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of a directional band gap. Experiments reveal that two distinct beams emerge at crystal output, in agreement with the numerical results obtained through the finite-element method. Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space. Split beams propagate in equal amplitude, whereas beam splitting is destructed for oblique incidence above a critical incidence angle.展开更多
Amorphous silicon （a-Si）, nanocrystalline silicon （nc-Si） and hydrogenated nanocrys- talline silicon （nc-Si：H） films were fabricated by using chemical vapor deposition （CVD） system. The a-Si and nc-Si thin fi...Amorphous silicon （a-Si）, nanocrystalline silicon （nc-Si） and hydrogenated nanocrys- talline silicon （nc-Si：H） films were fabricated by using chemical vapor deposition （CVD） system. The a-Si and nc-Si thin films were irradiated with 94 MeV Xe-ions at fluences of 1.0 × 10^11 ions/cm2, 1.0 × 10^12 ions/cm^2 and 1.0 × 10^13 ions/era2 at room temperature （RT）. The nc-Si：H films were irradiated with 9 MeV Xe-ions at 1.0 ×10^12 Xe/cm^2, 1.0 × 10^13 Xe/cm2 and 1.0×10^14 Xe/cm2 at RT. For comparison, mono-crystalline silicon （c-Si） samples were also irradiated at RT with 94 MeV Xe-ions. All samples were analyzed by using an UV/VIS/NIR spectrometer and an X-ray powder diffractometer. Variations of the optical band-gap （Eg） and grain size （D） versus the irradiation fluence were investigated systematically. The obtained results showed that the optical band-gaps and grain size of the thin films changed dramatically whereas no observable change was found in c-Si samples after Xe-ion irradiation. Possible mechanism underlying the modification of silicon thin films was briefly discussed.展开更多
基金This research was funded by national key research and development project of the"13th Five-Year Plan"of China-(2017YFC0504102).
文摘Forest gaps restrict the restoration of temperate secondary forest to broad-leaved Korean pine forest in zonal climax vegetation by affecting the growth of Korean pine(Pinus koraiensis).However,the photo synthetic adaptability of Korean pine to gap size and position within the gap is unclear.In order to explore the adaptability of young Korean pine(35 years) to different gap sizes in Xiaoxing’anling,photo synthetic capacity and microenvironmental factors(leaf temperature,light transmittance) of Korean pine needles in three positions in the gap(central,transition,and edge areas) were investigated.Three gaps were identified in the secondary Populus davidiana forest:a large 201 m^(2) gap,a middle 112 m^(2) gap,and a small 50 m^(2) gap;12 m^(2) of the understory was sampled as a control.The results show that:(1) maximum net photosynthetic rate(P_(max)) in needles of Korean pine growing in the large gap was higher than in the small gap,and P_(max) in the centre in the same gap was higher than in the transition and edge areas;(2) light saturation point(LSP) and photosynthetic quantum yield(AQY)of needles in the large gap were higher than in the small gap,while the light compensation point(LCP) and chlorophyll contents of needles were lower in the small gap;and,(3)P_(max) had a significant positive correlation with temperature and light transmittance.It is suggested that the larger the gap in secondary Populus davidiana forests,the greater the change in light intensity and temperatures,the stronger the light adaption of Korean pine needles and the higher the photosynthetic capacity.Therefore,in the recovery of broadleaved/Korean pine forests,suitable gaps should be created and gap microhabitats fully utilized to accelerate the restoration process.
文摘In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.
文摘A new method using lead coated glass fiber to produce continuous wire for battery grid of electric vehicles （EVs） and hybrid electric vehicles （HEVs） was introduced. Under equal flow, both the maximum and minimum theoretical value of gap size were studied and estimation equation was established. The experimental results show that the gap size is a key parameter for the continuous coating extrusion process. Its maximum value （Hmax） is 0.24 mm and the minimum one （Hmin） is 0.12mm. At a gap size of 0.18 mm, the maximum of metal extrusion per unit of time and optimal coating speed could be obtained.
基金Project(2000 78) supported by the Key Science and Technology Project of Shandong Province
文摘Under the condition of equal flow, the maximum and minimum theoretical values of gap size were studied and an estimation equation was established for the clad extrusion of the brittle core cladded by plastic metal materials. The results show that the gap size is a key parameter for the continuous clad extrusion and the molding speed. Its maximum value (Hmax) is 0.24mm and the minimum one (Hmin) is 0.12mm. At a gap size of 0.18mm, the maximum of metal extrusion per unit of time and the optimal coating speed can be obtained.
基金funded by the Internal Grant Agency of Mendel University in Brno(LDF_VP_2019015)the Framework of Bilateral Mobility Program for Traineeship of Doctoral Students,MENDELU。
文摘Subri River Forest Reserve(SR)is the most extensive forest area in Ghana with an accompanying rich floral species.Over the years,logging from both legally prescribed and illegal operations remain the predominant forest disturbance in SR.Gap creation following logging is crucial in determining tree species composition and diversity.Hence,the study evaluated the composition and diversity of naturally regenerated tree species in logging gaps of different sizes and,again examined the roles of these tree species in fulfilling the economic and ecological agenda of sustainable forest management after logging in SR.Twelve gaps were randomly selected:4 each were grouped into small size(≤200 m^(2)),medium size(201–300 m^(2)),and large size(≥300 m^(2)).Data were gathered from 1 m^(2) circular area at gap centres and repeatedly inside 1 m width strip along 20 m individual N-S-E-W transects.Species diversity differed significantly between gap sizes.Higher diversity indices were measured in large size gaps.Gap sizes shared similar species.There were significant differences among various height groupings of tree species across all three gap sizes.Pioneers preferred medium to large size gaps,while shadetolerant tree species preferred small size gaps for their abundance.Vulnerable and Lower Risk Near Threatened tree species under Conservation Status and,Premium and Commercial tree species under Utilisation Status preferred small size gaps for their proliferation and conservation.Therefore,we recommend the single tree-based selective logging for ensuring creations of small to medium size(200–300 m^(2))gaps through adjustments to the logging permit process,revision of Allocation Quota Permit,strict adherence to the 40-year polycyclic selection system,along with more dedicated enforcement and monitoring.Changes along these protocols would tremendously facilitate natural regeneration of different suites of timber species resulting in the improvement of the overall biodiversity conservation associated with the forest,more sustainable forest harvests and more income to those who receive permits.
基金supported by the National Natural Science Foundation of China(Grant Number 31370628)the National Science and Technology Support Project of China(Grant Number2011BAC09B05)the Sichuan Provincial Science and Technology Support Project(Grant Number 12ZC0017)
文摘Forest gaps are important in forest dynamics and management, but little is known about how soil fauna influence the degradation of recalcitrant litter components in different-sized forest gaps. This investigation uses litterbags with two different mesh sizes (0.04 and 3 mm) to control the meso- and microfauna entering the bags to quantify the contribution of soil fauna to the degradation of recalcitrant components (including condensed tannins, total phenol, lignin and cellulose) during litter decomposition. The experiment was conducted in seven different forest gap sizes in Pinus massoniana plantations over 1 year. One closed-canopy site (CC) and forest gap sizes of 100, 225, 400, 625, 900, 1225 and 1600 m^2 were created in a P. massoniana plantation in the Sichuan basin of China;the CC was treated as the control. Cinnamomum camphora foliage from local native trees was used in all forest gap experiments. We found the following:(1) Gap size had significant effects on the degradation rates (E) of condensed tannins and lignin and on the contributions of soil fauna;medium-sized gaps also presented high degradation rates. Soil fauna obviously contributed to the degradation of recalcitrant foliar litter components in medium-sized gaps.(2) The highest contribution to degradation (40.98%) was recorded for lignin, and the lowest contribution (0.29%) was recorded for condensed tannins. The results indicate that medium-sized gaps (900 m^2) were conducive to the degradation of recalcitrant litter components by soil fauna.
基金supported by grants from the National Basic Research Program of China(973 Program)(2012CB416906)National Nature Scientific Foundation of China(31330016)
文摘Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.
基金Project supported by Akdeniz University Scientific Research Projects Coordination Unit
文摘Beam splitting upon refraction in a triangular sonic crystal composed of aluminum cylinders in air is experimentally and numerically demonstrated to occur due to finite source size, which facilitates circumvention of a directional band gap. Experiments reveal that two distinct beams emerge at crystal output, in agreement with the numerical results obtained through the finite-element method. Beam splitting occurs at sufficiently-small source sizes comparable to lattice periodicity determined by the spatial gap width in reciprocal space. Split beams propagate in equal amplitude, whereas beam splitting is destructed for oblique incidence above a critical incidence angle.
基金supported by the Major State Basic Research Development Program of China(973Program,No.2010CB832902)the Knowledge Innovation Program of the Chinese Academy of Sciences(No.KJCX2-YW-N35)
文摘Amorphous silicon （a-Si）, nanocrystalline silicon （nc-Si） and hydrogenated nanocrys- talline silicon （nc-Si：H） films were fabricated by using chemical vapor deposition （CVD） system. The a-Si and nc-Si thin films were irradiated with 94 MeV Xe-ions at fluences of 1.0 × 10^11 ions/cm2, 1.0 × 10^12 ions/cm^2 and 1.0 × 10^13 ions/era2 at room temperature （RT）. The nc-Si：H films were irradiated with 9 MeV Xe-ions at 1.0 ×10^12 Xe/cm^2, 1.0 × 10^13 Xe/cm2 and 1.0×10^14 Xe/cm2 at RT. For comparison, mono-crystalline silicon （c-Si） samples were also irradiated at RT with 94 MeV Xe-ions. All samples were analyzed by using an UV/VIS/NIR spectrometer and an X-ray powder diffractometer. Variations of the optical band-gap （Eg） and grain size （D） versus the irradiation fluence were investigated systematically. The obtained results showed that the optical band-gaps and grain size of the thin films changed dramatically whereas no observable change was found in c-Si samples after Xe-ion irradiation. Possible mechanism underlying the modification of silicon thin films was briefly discussed.
