BRAKING FORCES DURING BICYCLE PEDALING: AN EXAMINATION OF THE FULL CRANK ROTATION

Pedalling skills are evaluated using angular impluse of negative crank torque (INCT) that occurs in pulling phase (180-360° of crank rotation that 0° is top dead center. INCT has the effect of inhibit crank rotation (“braking force“). The aim of study was to obtain findings to reduce INCT for improving cyclists\u27 pedalling skills. We examined the relationship between INCT and kinetic pedalling data through the full crank rotation. Fifteen male cyclists performed constant pedalling at 80%Vo2max and 90rpm. Kinetic and kinematic pedalling data were measured by the pedal-shaped force platform (KISTLER) and by a 3D motion capture system (VICON). A negative correlation was indicated 80-250° of crank rotation between horizontal pedal force (Fh) and INCT (pNCT occurring in pulling phase was affected by amount of Fh in pushing phase

Effects of large amounts of hydrogen on the fatigue crack growth behavior of torsional prestrained carbon steel

The effects of large amounts of hydrogen on the fatigue crack growth properties of torsional prestrained ferritic–pearlitic low-carbon steel were investigated. Hydrogen-precharged specimens were produced by conducting cathodic charge to the virgin material and to torsional prestrained JIS-S10C and JISS25C steels (hereafter S10C and S25C steels). Rotating bending fatigue tests were conducted in air at room temperature. Hydrogen content, CH, increased with torsional prestrain for both S10C and S25C steels; the CH of the torsional prestrained S25C steel precharged with hydrogen was lower than that of S10C at the same torsional prestrain. No clear difference between the maximum CH values of the torsional fractured S10C and S25C hydrogen-precharged steel specimens. With respect to crack initiation, there was no obvious difference between the uncharged and precharged specimens in spite of the large amount of CH induced by torsional prestrain. The acceleration of fatigue crack growth by hydrogen was the main cause of the decreased fatigue life. For the virgin material, hydrogen had no obvious effect on the fatigue crack growth rate. In contrast, for the torsional prestrained materials, the acceleration ratios, {(da/dN)H/(da/dN)U}, increased with the torsional prestrain and CH. However, {(da/dN)H/(da/dN)U} did not exceed the value of about 30, even when a large amount of hydrogen was charged (10.0 ? CH ? 30.3 mass ppm). A hydrogen content threshold was found; hydrogen content above this limit enhances the growth of the non-propagated crack, even for metals with lower hardness (HV < 200)

Ultrafast melting of charge-density wave fluctuations at room temperature in 1T−TiSe2{1T-TiSe_2} monitored under non-equilibrium conditions

We investigate the ultrafast lattice dynamics in ${1T-TiSe_2}$ using femtosecond reflection pump-probe and pump-pump-probe techniques at room temperature. The time-domain signals and Fourier-transformed spectra show the $A_{1g}$ phonon mode at 5.9 THz. Moreover, we observe an additional mode at $\approx$ 3 THz, corresponding to the charge-density wave (CDW) amplitude mode, which is generally visible below T$_c \approx 200\$K. We argue that the emergence of the CDW amplitude mode at room temperature can be a consequence of fluctuations of order parameters, based on the additional experiment using the pump-pump-probe technique, which exhibited suppression of the AM signal within the ultrafast time scale of $\sim$ 0.5 ps.Comment: 15 pages, 3 figures, Applied Physics Letters, in pres

Photo-induced Tellurium segregation in MoTe2\mathrm{MoTe_2}

We report on the coherent phonon spectroscopy of polymorphic $\mathrm{MoTe_2}$ single crystals using a femtosecond-pulsed laser to investigate the relationship between structural phase transitions and photo-thermal effects induced by high-density laser excitation. Even when a femtosecond pulsed laser was used, which generally induces fewer heat accumulation effects than the case for a CW laser, tellurium segregation was observed in coherent phonon spectra with increasing excitation density, while no structural phase transition among polymorphs of $\mathrm{MoTe_2}$ was observed. The use of higher photon-energy excitation, however, was found to suppress tellurium segregation.Comment: 15 pages, 4 figures, accepted for Physica Status Solidi (RRL) - Rapid Research Letter

Generation of Embryonic Stem Cell Lines from Immature Rabbit Ovarian Follicles

In mammalian ovaries, many immature follicles remain after the dominant follicles undergo ovulation. Here we report the successful production of rabbit embryonic stem cells (ESCs) from oocytes produced by in vitro culture of immature follicles and subsequent in vitro maturation treatment. In total, we obtained 53 blastocysts from oocytes that received intracytoplasmic sperm injection followed by in vitro culture. Although only weak expression of POU5f1 was observed in the inner cell masses of in-vitro-cultured follicle-derived embryos, repeated careful cloning enabled establishment of 3 stable ESC lines. These ESC lines displayed the morphological characteristics of primed pluripotent stem cells. The ESC lines also expressed the pluripotent markers Nanog, POU5f1, and Sox2. Further, these ESCs could be differentiated into each of the 3 different germ layers both in vitro and in vivo. These results demonstrate that immature follicles from rabbits can be used to generate ESCs. Moreover, the use of rabbit oocytes as a cell source provides an experimental system that closely matches human reproductive and stem cell physiology.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140197/1/scd.2012.0300.pd

Experimental Demonstration of Coexistence of Microwave Wireless Communication and Power Transfer Technologies for Battery-Free Sensor Network Systems

This paper describes experimental demonstrations of a wireless power transfer system equipped with a microwave band communication function. Battery charging using the system is described to evaluate the possibility of the coexistence of both wireless power transfer and communication functions in the C-band. A battery-free wireless sensor network system is demonstrated, and a high-power rectifier for the system is also designed and evaluated in the S-band. We have confirmed that microwave wireless power transfer can coexist with communication function

Effect of Reduction in Thickness and Rolling Conditions on Mechanical Properties and Microstructure of Rolled Mg-8Al-1Zn-1Ca Alloy

A cast Mg-8Al-1Zn-1Ca magnesium alloy was multipass hot rolled at different sample and roll temperatures. The effect of the rolling conditions and reduction in thickness on the microstructure and mechanical properties was investigated. The optimal combination of the ultimate tensile strength, 351 MPa, yield strength, 304 MPa, and ductility, 12.2%, was obtained with the 3 mm thick Mg-8Al-1Zn-1Ca rolled sheet, which was produced with a roll temperature of 80°C and sample temperature of 430°C. This rolling process resulted in the formation of a bimodal structure in the α-Mg matrix, which consequently led to good ductility and high strength, exclusively by the hot rolling process. The 3 mm thick rolled sheet exhibited fine (mean grain size of 2.7 μm) and coarse grain regions (mean grain size of 13.6 μm) with area fractions of 29% and 71%, respectively. In summary, the balance between the strength and ductility was enhanced by the grain refinement of the α-Mg matrix and by controlling the frequency and orientation of the grains