Energy efficient drive train for a high-performance battery chain saw
Up to today, small two-stroke gasoline engines are the major power source for professional outdoor power equipment such as hedge trimmers, chain saws, blowers, cut-off saws.
Velocity, Depth-of-Cut, and Physical Property Effects on Saw Chain Cutting
A better understanding of saw-chain cutting mechanics is needed for more efficient chainsaw designs. The effects of varying key parameters such as workpiece moisture content, workpiece density, cutting velocity, and depth-of-cut, while established for other types of cutting, are largely unexplored and/or unpublished for saw chains. This study contributes to filling this gap through experimentation and analysis. Experiments were conducted using a custom-built saw-chain testing apparatus to measure relevant forces over a range of workpiece moisture contents, workpiece densities, cutting velocities, and depths-of-cut. Analysis consisted of fitting linear regression models to experimental data, identifying trends, and exploring optimum cutting conditions. Results showed that over the range of values included in the study, workpiece moisture content and density had effects that depended on the depth-of-cut. Cutting velocity had a small effect, and depth-of-cut had a large effect. All trends fit well with linear models; however, depth-of-cut required one linear fit for small-to-mid values and a second fit for mid-to-large values. Maximum efficiency was found to occur at a depth-of-cut equal to the transitional value between fits. These results provide basic relationships that can lead to the more effective and efficient use and design of chainsaws.
In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs
Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.