Biomimetic Anti-Abrasion Surfaces of a Cone Form Component Against Soil

The geometrical surfaces of soil-burrowing animals were imitated and modeled on a cone component, the measuring tip part of a soil cone penetrometer. These biomimetic surfaces are concave dimples, convex domes and two wavy forms. The conventional cone surface and the biomimetic cone surfaces were analyzed in ANSYS 11.0 program to estimate cone equivalent stress and soil equivalent stress. Results show that biomimetic surfaces with the geometrical structures have lower cone equivalent stresses and soil equivalent stresses than that with conventional (smooth) surface. The least maximum cone equivalent stress and least maximum soil equivalent stress were recorded for biomimetic surfaces with concave dimples and wavy form-2 respectively. The two-body abrasive wear of biomimetic cone surfaces and conventional (smooth) cone surface were run on a rotary disk type of abrasive wear testing machine. The biomimetic cone surfaces were found to have lower abrasive wear than the conventional surface. It was found that and biomimetic cone surface with concave dimples has the lowest abrasive wear among the all tested surfaces.     

Forces and Straw Cutting Performance of Double Disc Furrow Opener in No-Till Paddy Soil

Conservation tillage is an energy efficient and low cost tillage system to improve soil environment compared with conventional tillage systems. However, the rice residue management becomes an “impossible to achieve” task due to high soil moisture content at harvest time and the thickness of rice straw. Disc type furrow openers are used for both seed drilling as well as straw cutting during no tillage sowing. A study was conducted to evaluate the draft requirement and straw cutting performances of different sized furrow openers in no-till paddy soil conditions. Double disc furrow opener was tested on an in-field traction bench for three working depths, i.e. 30, 60 and 90 mm, and three forwarding speeds, i.e. 0.1, 0.2 and 0.3 m/s. The draft and vertical forces on the disc were recorded with load cells. These sensors were connected to a data acquisition system developed with hardware and software. The results revealed that the size of the furrow opener, operating depth and the forwarding speed had significant effects (P<0.05) on the horizontal and vertical forces, and the straw cutting performance. Mean values of the draft were 648.9, 737.2 and 784.6 N for the opener with diameters of 330, 450 and 600 mm respectively, and the vertical forces for similar openers were 904.7, 1553.9 and 1620.4 N, respectively. Furthermore, the mean straw cutting efficiencies for the double disc opener with diameters of 330, 450 and 600 mm were 39.36, 78.47 and 65.46%, respectively. The opener with 450 mm diameter provided higher straw cutting efficiency as compared to 600 mm diameter disc, while lowest straw cutting efficiency was observed with 330 mm diameter disc. The 450 mm diameter opener provided the highest straw cutting efficiency (88.6%) at 90 mm working depth and expressed optimum performance compared with other furrow openers.     

The mechanical effects of different levels of cement penetration at the cement–bone interface

The mechanical effects of varying the depth of cement penetration in the cement–bone interface were investigated using finite element analysis (FEA) and validated using companion experimental data. Two FEA models of the cement–bone interface were created from micro-computed tomography data and the penetration of cement into the bone was varied over six levels each. The FEA models, consisting of the interdigitated cement–bone constructs with friction between cement and bone, were loaded to failure in tension and in shear. The cement and bone elements had provision for crack formation due to excessive stress. The interfacial strength showed a strong relationship with the average interdigitation (r²=0.97 and r²=0.93 in tension and shear, respectively). Also, the interface strength was strongly related with the contact area (r²=0.98 and r²=0.95 in tension and shear, respectively). The FEA results compared favorably to the stiffness–strength relationships determined experimentally. Overall, the cement–bone interface was 2.5 times stronger in shear than in tension and 1.15 times stiffer in tension than in shear, independent of the average interdigitation. More cracks occurred in the cement than in the bone, independent of the average interdigitation, consistent with the experimental results. In addition, more cracks were generated in shear than in tension. In conclusion, achieving and maintaining maximal infiltration of cement into the bone to obtain large interdigitation and contact area is key to optimizing the interfacial strength.     

The structural proteins of scaleless-mutant chick epidermis.

Epidermis isolated from the anterior tarsometatarsus region of scaleless mutant chick legs was found to contain only α fibrous protein rather than the usual feather one. The polyacrylamide disc electrophoretic pattern of structural proteins isolated from mutant epidermis was also different from that of normal tissue. X-ray diffraction analysis of the claw of mutant chicks, however, showed the usual feather pattern. These results indicated that failure of scale induction rather than a defect in synthesis of feather protein is the abnormality in the mutant chick.     

Effects of Biomimetic Surface Designs on Furrow Opener Performance

The effects of biomimetic designs of tine furrow opener surface on equivalent pressure and pressure in the direction ofmotion on opener surface against soil were studied by finite element method (FEM) simulation and the effects of these designson tool force and power requirements were examined experimentally.Geometrical structures of the cuticle surfaces of dungbeetle (Copris ochus Motschulsky) were examined by stereoscopy.The structures of the cuticle surfaces and Ultra High Mo-lecular Weight Polyethylene (UHMWPE) material were modeled on surface of tine furrow opener as biomimetic designs.Sevenfurrow openers were analyzed in ANSYS program (a FEM simulation software).The biomimetic furrow opener surfaces withUHMWPE structures were found to have lower equivalent pressure and pressure in the direction of motion as compared to theconventional surface and to the biomimetic surfaces with textured steel-35 structures.It was found that the tool force and powerwere increased with the cutting depth and operating speed and the biomimetic furrow opener with UHMWPE tubular sectionridges showed the lowest resistance and power requirement against soil..     

A novel approach to in vivo mitral valve stress analysis

Three-dimensional (3-D) echocardiography allows the generation of anatomically correct and time-resolved geometric mitral valve (MV) models. However, as imaged in vivo, the MV assumes its systolic geometric configuration only when loaded. Customarily, finite element analysis (FEA) is used to predict material stress and strain fields rendered by applying a load on an initially unloaded model. Therefore, this study endeavors to provide a framework for the application of in vivo MV geometry and FEA to MV physiology, pathophysiology, and surgical repair. We hypothesize that in vivo MV geometry can be reasonably used as a surrogate for the unloaded valve in computational (FEA) simulations, yielding reasonable and meaningful stress and strain magnitudes and distributions. Three experiments were undertaken to demonstrate that the MV leaflets are relatively nondeformed during systolic loading: 1) leaflet strain in vivo was measured using sonomicrometry in an ovine model, 2) hybrid models of normal human MVs as constructed using transesophageal real-time 3-D echocardiography (rt-3DE) were repeatedly loaded using FEA, and 3) serial rt-3DE images of normal human MVs were used to construct models at end diastole and end isovolumic contraction to detect any deformation during isovolumic contraction. The average linear strain associated with isovolumic contraction was 0.02 ± 0.01, measured in vivo with sonomicrometry. Repeated loading of the hybrid normal human MV demonstrated little change in stress or geometry: peak von Mises stress changed by <4% at all locations on the anterior and posterior leaflets. Finally, the in vivo human MV deformed minimally during isovolumic contraction, as measured by the mean absolute difference calculated over the surfaces of both leaflets between serial MV models: 0.53 ± 0.19 mm. FEA modeling of MV models derived from in vivo high-resolution truly 3-D imaging is reasonable and useful for stress prediction in MV pathologies and repairs.     

Biomimetic Composite Structural T-joints

Biological structural fixed joints exhibit unique attributes,including highly optimized fiber paths which minimize stress concentrations.In addition,since the joints consist of continuous,uncut fiber architectures,the joints enable the organism to transport information and chemicals from one part of the body to the other.To the contrary,sections of man-made composite material structures are often joined using bolted or bonded joints,which involve low strength and high stress concentrations.These methods are also expensive to achieve.Additional functions such as fluid transport,electrical signal delivery,and thermal conductivity across the joints typically require parasitic tubes,wires,and attachment clips.By using the biomimetic methods,we seek to overcome the limitations which are present in the conventional methods. In the present work,biomimetic co-cured composite sandwich T-joints were constructed using unidirectional glass fiber,epoxy resin,and structural foam.The joints were fabricated using the wet lay-up vacuum bag resin infusion method.Foam sandwich T-joints with multiple continuous fiber architectures and sandwich foam thickness were prepared.The designs were tested in quasi-static bending using a mechanical load frame.The significantweight savings using the biomimetic approaches is discussed,as well as a comparison of failure modes versus architecture is described.     

Experimental Investigation into Soil-Cutting Performance of the Claws of Mole Rat (Scaptochirus moschatus)

The geometrical characteristics of the fore claw toes of mole rats Scaptochirus moschatus were analyzed. It was found that the middle three toes play the major role in soil-cutting performance. So the middle three toes were selected as the prototype for designing the biomimetic specimens. The biomimetic specimens were manufactured using reverse engineering and rapid prototype technology. The scales of the second toe (one of the middle three toes) and the angle between the back side and the palm side of the second toe were taken as the main geometrical structure parameters for designing the comparative specimen. The horizontal soil-cutting tests were conducted to examine the effects of the biomimetic geometrical structure on the soil-cutting resistance. The results show that the resistance of the biomimetic specimen is 12.80% smaller than the comparative specimen, which indicates that the toe geometry has a significant effect on its soil-cutting performance. The investigation into the effect of toe arrangement suggests that the tip positions of the middle three toes in arc curve arrangement is helpful to reduce soil-cutting resistance.     

Dietary high protein and vitamin C mitigate stress due to chelate claw ablation in Macrobrachium rosenbergii males

Stress due to claw ablation was tested in Macrobrachium rosenbergii males. Dietary high protein and vitamin C were supplemented for amelioration of stress. We used four different treatments: fed with 25% protein and a normal dose (0.12%) of vitamin C (T(1)); 35% protein and a normal dose (0.12%) of vitamin C (T(2)); 25% protein and a high dose (0.24%) of vitamin C (T(3)); and high protein 35% and a high dose (0.24%) of vitamin C (T(4)) for 30 days. All test prawns (T(1) to T(4)) were subjected to ablation of their second chelate legs after the 15th day of the feeding trial. A control treatment was maintained without claw ablation and fed with 25% protein. Haemolymph glucose, hepatopancreatic glycogen, muscle ascorbate and enzyme activities (glucose 6 phosphatase (G6Pase), fructose-1,6-bisphosphatase (FBPase), lactate dehydrogenase (LDH), Alanine aminotransferase (ALT) in hepatopancreas) were tested at different recovery periods (0, 6, 24 h, 7 and 14 days). Results indicate a high glucose level immediately after claw ablation and a concomitant increase in gluconeogenic enzymes (G6Pase and FBPase). However, glycogen reserves were regained in the treatments due to claw ablation stress after 24 h. LDH and ALT activity decreased in the hepatopancreas of M. rosenbergii up to 24 h after claw ablation. Overall results indicate that claw ablation is stressful to M. rosenbergii and high protein and vitamin C diet may mitigate stress due to claw ablation.     

Stem Nematode-Fusarium Wilt Complex in Alfalfa as Related to Irrigation Management at Harvest Time

A high moisture level in the top 10 cm of soil at time of cutting of alfalfa increased the incidence of plant mortality and Fusarium wilt in soil infested with Ditylenchus dipsaci and Fusarium oxysporum f. sp. medicaginis in greenhouse and field microplot studies. Ranger alfalfa, susceptible to both D. dipsaci and F. oxysporum f. sp. medicaginis, was less persistent than Moapa 69 (nematode susceptible and Fusarium wilt resistant) and Lahontan alfalfa (nematode resistant with low Fusarium wilt resistance). In the greenhouse, the persistence of Ranger, Moapa 69, and Lahontan alfalfa plants was 46%, 64%, and 67% respectively, in nematode + fungus infested soil at high soil moisture at time of cutting. This compared to 74%, 84%, and 73% persistence of Ranger, Moapa 69, and Lahontan, respectively, at low soil moisture at time of cutting. Shoot weights as a percentage of uninoculated controls at the high soil moisture level were 38%, 40%, and 71% for Ranger, Moapa 69, and Lahontan, respectively. Low soil moisture at time of cutting negated the effect D. dipsaci on plant persistence and growth of subsequent cuttings, and reduced Fusarium wilt of plants in the nematode-fungus treatment; shoot weights were 75%, 90%, and 74% of uninoculated controls for Ranger, Moapa 69, and Lahontan. Similar results were obtained in the field microplot study, and stand persistence and shoot weights were less in nematode + fungus-infested soil at the high soil-moisture level (early irrigation) than at the low soil-moisture level (late irrigation).