On parallel p-equidistant ruled surfaces by using mofied orthogonal frame with curvature in E³

In this paper, it is investigated Ruled surfaces according to modified orthogonal frame with curvature in 3-dimensional Euclidean space. Firstly, we give apex angle, pitch and drall of closed ruled surface in E³. Then, it characterized the relationship between these invariant of parallel p-equidistant ruled surfaces.

Effect of triangular oil pockets on friction reduction

The effect of the apex angle of triangular oil pockets created on a disc surface on friction was studied. Experiments were carried out using an Optimol SRV5 tribotester equipped with a pin-on-disc module under unidirectional lubricated sliding. Both the sample and counter sample was made of steel of 45 Hardness Rockwell C (HRC) hardness. Only 1 ml of oil was put to the inlet side of the contact area at the beginning of each test. All textured surfaces had the same pit-area ratio and an average depth of dimples. Oil pockets were positioned in the spiral array. It was found that the effect of the apex angle of triangular dimples on friction reduction was important. When the normal load was lower, the smallest coefficient of friction was achieved for the sliding pair with a disc apex angle of 60°. Under a larger normal load, a higher apex angle corresponded to a higher coefficient of friction.

DESIGNING A TEMPORARY COLD PROTECTIVE GEAR CONSTRUCTED BY FOLDING NEWSPRINT PAPER CONSIDERING HEAT-RETAINING PROPERTY AND RIGIDITY

During the cold season, the cold protective products are often short during evacuation life after a natural disaster. If evacuees can make and wear simple cold protective gears by using materials obtainable on site, it will reduce the burden on the evacuees in emergent situation. Therefore, we investigated the structure constructed by folding newsprint paper, which can improve the heat retention effect and be applied to various body shapes. Focusing on the glide reflection structure repeating a smaller chamber, the basic size was determined by experiments with reference to the accordion shape, and the experimental results indicated that the heat retention effect was significantly greater than that of a mere air layer and those of ordinary fabrics. Next, it was found that the apex angle of structure had no significant difference in the heat retention effect. Then, the dimensions of the structure were determined to maintain the air layer under the pressure of the clothes by simulation of structural analyses. Finally, we made a temporary cold protective gear that can practically cover the trunk of the body and found that the heat retention effect was significantly higher than that of unprocessed newsprint and that of accordion shape.

Numerical analysis and mechanic theoretical derivations for optimizing the V-thread profiles in dental implant system

Background The thread design of the dental implant is an important feature to be considered in the optimization of the dental implant structure. The present study aimed to investigate the effects of V-thread profile design dimensions, including depth, width, pitch, thread helix angle and triangle thread apex angle on the mechanical characteristics of the bone-implant interface. A total of 588 V-thread implant system models were constructed to investigate the effects of the dimension parameters on the stress distribution generated around the bone-implant interface under vertical occlusal force. Furthermore, the force transfer at the bone-implant interface was analyzed theoretically to analyze the force transmission mechanism at bone-implant for an optimized V-thread profile in the implants. Results The optimum thread pitch ranged from 1.0 mm to 1.2 mm, when the triangle thread depth and width was 0.1 mm. The theoretically derived results showed that, with the same implant diameter, when the thread depth was 0.1 mm and the thread pitch was 0.9 mm, the optimal thread width was found to be 0.1026 mm. This derived result was consistent with the simulation analysis results. Conclusions To design the optimal V-shape threads, the implant and thread dimensions, such as the implant diameter, thread pitch, thread width, thread helix angle and triangle thread apex angle should be comprehensively considered. The optimal designed thread in this study can dissipate the chewing load, as a result of the appropriate ratio of tensile force and shear force on bone-implant interface. The optimum designed thread profile can take full advantage of the carrying capacity of the tensile and shear of the bone, thereby bearing a high chewing load.

Pressure Losses at Moderate Reynolds Numbers in Diamond-Shaped Cylinders Arrays: Application to Microregenerators

Cylinders with an elliptical, oblong, lenticular, sinus, or diamond transveral shape are very interesting geometries for the design of compact heat exchangers. This work investigates the role of the porosity and of the apex angle of diamond-shaped cylinders networks on the pressure losses, at moderate Reynolds numbers, inside microheat regenerators. The design of the geometry under test has been chosen so that the cross section of the flow remains almost constant along the path of the flow between cylinders. Experiments have been performed at 1 ⩽ Re ⩽ 30 and a porosity range 0.40<ε<0.90 for an apex angle of α=33deg. Numerical simulations have been conducted using the same Reynolds and porosity ranges but varying the apex angle 33deg ⩽ α ⩽ 90deg. Experimental measurements and dimensional analysis have shown that the friction factor can be affected by the porosity. Two-dimensional numerical simulations confirmed that the friction factor increases with the porosity but also with the apex angle. An analysis at the scale of a channel flanked by adjacent cylinders has provided an original correlation able to describe easily the evolution of the Poiseuille number and the collective effects on the drag coefficient as a function of α and ε. Such a diamond-shaped design is found to induce much lower Poiseuille numbers than those expected from conventional stacked spheres, woven wires, and circular cylinders arrays. The findings of this study can help for better understanding the optimization of low pressure drop regenerators and how to reduce associated hydraulic power.

Axisymmetric landslides on top-shaped asteroids

Spin rates of minor planets or asteroids are known to have been affected by several agents including but not limited to tidal fly-bys, impacts and solar radiation. Surface processes like landslides occur as a result of such rotational changes. We study the evolution of landslides on top-shaped rubble pile asteroids like 101955 Bennu and 162173 Ryugu, with the underlying core modeled as two solid cones fused back to back. Using a depth averaged avalanche theory applicable to granular flows we solve for axisymmetric landslides occurring at various spin rates and regolith friction. Static regions on the surface corresponding to different spin rates are identified from an equilibrium analysis. We then solve for landslides initiated at different latitudes. It is found that landslides equilibrate at lower latitudes as the spin rate is increased. Beyond a critical spin rate regolith is shed from the equator. This critical spin is higher for a lower value of the semi-apex angle of the cone.