Poplar alkaline peroxide mechanical pulp(APMP)was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested.The raw poplar APMP fibers are stiff and ...Poplar alkaline peroxide mechanical pulp(APMP)was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested.The raw poplar APMP fibers are stiff and have been detached from the lamella during APMP pulping process.During the refining process,the APMP fibers did not swell and fibrillate;they were easily broken and formed into fragments.The breaking length of formed hand sheets increased as the heating degree increased because lots of hydrogen bonds were formed between fibers and fine pieces.The tear strength of hand sheets first increased and then decreased as the beating degree changed from 17 to 70~SR.The maximum tear strength was achieved at 61~SR of the beating degree.These results indicated that the hydrogen bond between the fibers was the main factor influencing the tear index followed by the fiber length.Along with the increase of the beating degree,the sheet density increased while the opacity decreased.展开更多
In the northeastern United States, whole-tree harvesting is widely used to supply fuel to biomass energy facilities, but questions remain regarding its long-term sustainability. We have previously reported findings in...In the northeastern United States, whole-tree harvesting is widely used to supply fuel to biomass energy facilities, but questions remain regarding its long-term sustainability. We have previously reported findings indicating no short-term decrease in forest productivity in whole-tree harvested sites when compared with similar conventionally (stem-only) harvested sites. Here we present additional results of the same study, but focus on the effect harvest treatment has on the species composition of the regenerating forest. Within northern hardwood forests in central New Hampshire and western Maine, regeneration surveys were conducted on four (4) small clearcuts in 2010 and twenty-nine (29) small clearcuts in 2011. The species and diameter of trees > 2 m in height were recorded within 1 m or 2 m-radius plots and used to calculate the biomass fraction of each species. The 2010 study additionally measured the density of trees 2 m in height and the diversity of understory non-tree species. Non-metric multidimensional scaling and multi-response permutation procedures were used to determine the effect of harvest treatment had on community-wide tree species composition. Potential differences were also examined on a species-by-species basis. Both analytic methods indicated no significant differences in species composition of tree species or understory communities. Within the limits of our data, we conclude that no significant effects of residue removal on species composition are observed within our sample of northern hardwood sites at this early stage of stand development.展开更多
Acoustoelastic coupling occurs when a hollow structure’s in-vacuo mode aligns with an acoustic mode of the internal cavity.The impact of this coupling on the total dynamic response of the structure can be quite sever...Acoustoelastic coupling occurs when a hollow structure’s in-vacuo mode aligns with an acoustic mode of the internal cavity.The impact of this coupling on the total dynamic response of the structure can be quite severe depending on the similarity of the modal frequencies and shapes.Typically,acoustoelastic coupling is not a design feature,but rather an unintended result that must be remedied as modal tests of structures are often used to correlate or validate finite element models of the uncoupled structure.Here,however,a test structure is intentionally designed such that multiple structural and acoustic modes are well-aligned,resulting in a coupled system that allows for an experimental investigation.First,coupling in the system is identified using a measure termed the magnification factor.Next,the structural-acoustic interaction is measured.Modifications to the system demonstrate the dependency of the coupling on changes in the mode shape and frequency proximity.This includes an investigation of several practical techniques used to decouple the system by altering the internal acoustic cavity,as well as the structure itself.These results show that acoustic absorption material effectively decoupled the structure while structural modifications,in their current form,proved unsuccessful.Readily available acoustic absorptive material was effective in reducing the coupled effects while presumably adding negligible mass or stiffness to the structure.展开更多
Over the past few years, more and more higher education institutions have pledged to achieve carbon neutrality and designed and adopted Climate Action Plans. Although many higher institutions are adopting climate acti...Over the past few years, more and more higher education institutions have pledged to achieve carbon neutrality and designed and adopted Climate Action Plans. Although many higher institutions are adopting climate action plans, few are integrating resil-ience principles and priorities, which are essential for understanding institutions’ adaptive capacity for dealing with climate change. There is little existing research on how higher education institutions can implement climate resilience programs, behav-iors, and policies into their planning process and campus-communities. To address this gap, this case study explores Arizona State University’s process of designing and implementing a climate resilience plan and outlines best practices other higher educa-tion institutions can utilize to create their own climate resilience plan. We critically discuss the importance of climate resilience at the higher education level, outline steps necessary for designing an inclusive and holistic climate resilience plan, and provide examples of important techniques used to design the climate resilience plan.展开更多
文摘Poplar alkaline peroxide mechanical pulp(APMP)was refined in a PFI mill at varied revolution and the properties of the refined fibers and the resulting hand sheets were tested.The raw poplar APMP fibers are stiff and have been detached from the lamella during APMP pulping process.During the refining process,the APMP fibers did not swell and fibrillate;they were easily broken and formed into fragments.The breaking length of formed hand sheets increased as the heating degree increased because lots of hydrogen bonds were formed between fibers and fine pieces.The tear strength of hand sheets first increased and then decreased as the beating degree changed from 17 to 70~SR.The maximum tear strength was achieved at 61~SR of the beating degree.These results indicated that the hydrogen bond between the fibers was the main factor influencing the tear index followed by the fiber length.Along with the increase of the beating degree,the sheet density increased while the opacity decreased.
文摘In the northeastern United States, whole-tree harvesting is widely used to supply fuel to biomass energy facilities, but questions remain regarding its long-term sustainability. We have previously reported findings indicating no short-term decrease in forest productivity in whole-tree harvested sites when compared with similar conventionally (stem-only) harvested sites. Here we present additional results of the same study, but focus on the effect harvest treatment has on the species composition of the regenerating forest. Within northern hardwood forests in central New Hampshire and western Maine, regeneration surveys were conducted on four (4) small clearcuts in 2010 and twenty-nine (29) small clearcuts in 2011. The species and diameter of trees > 2 m in height were recorded within 1 m or 2 m-radius plots and used to calculate the biomass fraction of each species. The 2010 study additionally measured the density of trees 2 m in height and the diversity of understory non-tree species. Non-metric multidimensional scaling and multi-response permutation procedures were used to determine the effect of harvest treatment had on community-wide tree species composition. Potential differences were also examined on a species-by-species basis. Both analytic methods indicated no significant differences in species composition of tree species or understory communities. Within the limits of our data, we conclude that no significant effects of residue removal on species composition are observed within our sample of northern hardwood sites at this early stage of stand development.
文摘Acoustoelastic coupling occurs when a hollow structure’s in-vacuo mode aligns with an acoustic mode of the internal cavity.The impact of this coupling on the total dynamic response of the structure can be quite severe depending on the similarity of the modal frequencies and shapes.Typically,acoustoelastic coupling is not a design feature,but rather an unintended result that must be remedied as modal tests of structures are often used to correlate or validate finite element models of the uncoupled structure.Here,however,a test structure is intentionally designed such that multiple structural and acoustic modes are well-aligned,resulting in a coupled system that allows for an experimental investigation.First,coupling in the system is identified using a measure termed the magnification factor.Next,the structural-acoustic interaction is measured.Modifications to the system demonstrate the dependency of the coupling on changes in the mode shape and frequency proximity.This includes an investigation of several practical techniques used to decouple the system by altering the internal acoustic cavity,as well as the structure itself.These results show that acoustic absorption material effectively decoupled the structure while structural modifications,in their current form,proved unsuccessful.Readily available acoustic absorptive material was effective in reducing the coupled effects while presumably adding negligible mass or stiffness to the structure.
文摘Over the past few years, more and more higher education institutions have pledged to achieve carbon neutrality and designed and adopted Climate Action Plans. Although many higher institutions are adopting climate action plans, few are integrating resil-ience principles and priorities, which are essential for understanding institutions’ adaptive capacity for dealing with climate change. There is little existing research on how higher education institutions can implement climate resilience programs, behav-iors, and policies into their planning process and campus-communities. To address this gap, this case study explores Arizona State University’s process of designing and implementing a climate resilience plan and outlines best practices other higher educa-tion institutions can utilize to create their own climate resilience plan. We critically discuss the importance of climate resilience at the higher education level, outline steps necessary for designing an inclusive and holistic climate resilience plan, and provide examples of important techniques used to design the climate resilience plan.
