Experimental Analysis of the Mechanics of Sport Climbing Falls

International audienceRock climbing falls can be safely stopped and are often a routine part of the sport. However, safety may be compromised not only by equipment failure but also due to the climbers' misjudgment of the situation. Current literature and other resources are either based on laboratory experiments or lacking specific and systematic measurements of the relevant parameters of lead climber falls. Only one recent theoretical paper describes the physics of lead climber falls under realistic conditions. To provide research-based safety guidance for the climber community systematic studies of various scenarios are needed. In this study experimental data were collected and analyzed from lead climber falls on an actual climbing route, recording all positions prior to and after the fall as well as climber and belaye

Magnetic properties of low temperature phase MnBi of island structure

The magnetic and structural properties of island-structured LTP MnBi fabricated onto MgO single crystal substrates are discussed. The size and height of the “Volmer-Weber” type islands vary from place to place but are averagely a few microns and sub-microns, respectively. From the wetting angle (40 ∼ 60°) of those islands, the surface energy ΥMnBi of LTP MnBi is found to be 0.5∼0.8 J/m2. Those MnBi islands possesses the magnetic anisotropy constant Ku and saturation magnetization Ms close to those for bulk over a temperature range of 5 to 400 K. There seems to be a correlation between Ku and lattice constant c measured at 300K. The Ku is found to be inversely proportional to Ms5 over the temperature range from 5 K to 400 K, as compared to the Ms8 dependence for those fabricated onto fused silica glass substrates

Analysis of low voltage regulator efficiency based on ferrite inductor

Low voltage regulator based on ferrite inductor, using single- and two-phase topologies, were designed and simulated in MATLAB. Simulated values of output voltage and current were used to evaluate the buck converter (i.e., low voltage regulator) for power efficiency and percentage ripple reduction at frequencies between 1 and 10 MHz with variable loads from 0.024 to 4 ohms. The parameters, such as inductance of 20 nH, quality factor of 15 of fabricated ferrite inductor and DC resistance (DCR) of 8.3 milli ohms, were used for efficiency analysis of the converter. High current around 40 A was achieved by the converter at low load values. Low output voltage in the range of 0.8-1.2 V was achieved. The simulated results for the single- and two-phase converter were compared for maximum efficiency and lowest ripple in output voltage and current. The maximum efficiency of 97 % with load of 0.33 ohms and the lowest ripple current of about 2.3 mA were estimated for the two-phase converter at 10 MHz. In summary, the two-phase converter showed higher efficiency and lower ripple voltage and current than those of the single-phase converter. In addition, the efficiency of single- and two-phase converters based on ferrite inductor was compared to single- and two-phase converters based on air-core inductor. It was found that the power efficiency of the two-phase converter using ferrite inductor was 10 % higher than the converter using air-core inductor at 10 MHz with a load of 0.024 ohms. (Published By University of Alabama Libraries

Study of structural and magnetic properties of intermetallic thin films

Intermetallic thin films have tunable magnetic properties. The magnetic phases of intermetallic thin films were tuned by changing the alloy composition of the intermetallic system. L10 Fe50Pt50 thin film has high magnetic anisotropy which makes them ideal candidates for the thin film recording media. Magnetic phases of Fe50Pt50 can be tuned by the addition of third element like Mn by forming Fe50-x Mnx Pt50 ternary alloy system. In this work magnetic phases of ordered Fe rich Fe50-xMnxPt50 and Mn rich Fe50-xMnxPt50 thin films of Fe50-x Mnx Pt50 alloy system is investigated. Fe rich Fe50-xMnxPt50 thin films are epitaxially grown on a- Al2O3 and MgO (100) substrates, while Mn rich Fe50-xMnxPt50 thin films are grown on MgO (100) substrates. The change in the magnetic properties in Fe rich Fe50-xMnxPt50 thin films due to presence of tetragonal phase and the prediction of a the presence of a new low temperature phase in the Mn rich Fe50-xMnxPt50 thin films is verified. These intermetallic films are produced in a Ultra High Vacuum sputtering system with Reflective High Energy Electron Diffraction and Auger electron spectroscopy. RHEED is used to verify epitaxy and Auger electron spectroscopy measures chemical composition. (Published By University of Alabama Libraries