Weightlifting: an applied method of technical analysis

Weightlifting is a highly technical sport which is governed by interactions of phases to optimise the load lifted. Given the technicality of the snatch and clean and jerk, understanding key stable components to identify errors and better prescribe relevant exercises are warranted. The aim of this article is to present an applied method of analysis for coaches that considers the biomechanical underpinnings of optimal technique through stable interactions of the kinetics and kinematics of the lifter and barbell at key phases of the lift. This paper will also look to discuss variable components which may differentiate between athletes and therefore provide a foundation in what to identify when coaching weightlifting to optimise load lifted whilst allowing for individual variances

Potential structural material problems in a hydrogen energy system

Potential structural material problems that may be encountered in the three components of a hydrogen energy system - production, transmission/storage, and utilization - were identified. Hydrogen embrittlement, corrosion, oxidation, and erosion may occur during the production of hydrogen. Hydrogen embrittlement is of major concern during both transmission and utilization of hydrogen. Specific materials research and development programs necessary to support a hydrogen energy system are described

Reassessing Railroads and Growth: Accounting for Transport Network Endogeneity

Motivated by the seminal work of Robert Fogel on U.S. railroads, I reformulate Fogel's original counter- factual history question on 19th century U.S. economic growth without railroads by treating the transport network as an endogenous equilibrium object. I quantify the effect of the railroad on U.S. growth from its introduction in 1830 to 1861. Specifically, I estimate the output loss in a counterfactual world with- out the technology to build railroads, but retaining the ability to construct the next-best alternative of canals. My main contribution is to endogenize the counterfactual canal network through a decentralized network formation game played by profit-maximizing transport firms. I perform a similar exercise in a world without canals. My counterfactual differs from Fogel's in three main ways: I develop a structural model of transport link costs that takes heterogeneity in geography into account to determine the cost of unobserved links, the output distribution is determined in the model as a function of transport costs, and the transport network is endogenized as a stable result of a particular network formation game. I find that railroads and canals are strategic complements, not strategic substitutes. Therefore, the output loss can be quite acute when one or the other is missing from the economy. In the set of Nash stable networks, relative to the factual world, the median value of output is 45% lower in the canals only counterfactual and 49% lower in the railroads only counterfactual. With only one of the transportation technologies available, inequality in output across cities would have been lower in variance terms but sharply higher in terms of the maximum-minimum gap. Such a stark output loss is due to two main mechanisms: inefficiency of the decentralized equilibrium due to network externalities and complementarities due to spatial heterogeneity in costs across the two transport modes

Dynamics of Locomotor Fatigue during Supra-critical Power Exercise

Purpose; We aimed to measure 1) the dynamics of locomotor fatigue during constant supra-critical power cycling, and 2) the magnitude of any reserve in locomotor power at intolerance to constant and ramp-incremental cycling in recreationally-active volunteers. Methods; Fifteen participants (7 women and 8 men, 22±3 yr, 3.34±0.67 L.min-1 V[Combining Dot Above]O2peak) completed ramp-incremental and very-heavy constant power (205±46 W) exercise to the limit of tolerance. Immediately following intolerance, the ergometer was switched into the isokinetic mode and participants completed a short (~5 s) maximal isokinetic effort at 70 rpm. The time course of locomotor fatigue during constant supra-critical power exercise was characterized with these short maximal isokinetic sprints at 30, 60, 120, 180 s and at the limit of tolerance. Each bout was terminated following the isokinetic sprint. Results; Constant power exercise duration was 312±37 s. Isokinetic power production at 30, 60, 120, 180 s and the limit of tolerance (at 312±37 s) was 609±165, 503±195, 443±157, 449±133, and 337±94 W, respectively. Of the total decline in isokinetic power, ~36% occurred within the first minute of exercise and significant (p<0.05) reductions in isokinetic power occurred at all time-points vs the baseline maximal isokinetic power (666±158 W). Additionally, a significant power reserve of 132±74 W (64% of the task requirement) and 119±80 W (47%) was present at the limit of constant power and ramp-incremental exercise, respectively. Conclusions; Locomotor fatigue occurred rapidly during supra-critical power exercise with pseudo-exponential kinetics. Instantaneous isokinetic power production at the limit of tolerance exceeded that of the task requirement, regardless of the constant, or ramp work rate profile. Thus, the perceptual and physiologic limits were dissociated at the limit of tolerance in recreationally-active volunteers

The effects of display variables and secondary loading on the dual axis critical task performance

The effects of scanning displays for separated instruments, separated versus combined displays, and the effects of secondary loading are investigated. An operator rating scale for handling qualities is established analogous to the Cooper Harper Scale

Ar-40/Ar-39 Ages of Maskelynite Grains from ALHA 77005

We present Ar-40/Ar-39 measurements for twelve small (20-60 micro-g) maskelynite samples from the heavily shocked martian meteorite ALHA 77005. The reported modal composition for ALHA 77005 is 50-60% olivine (Fa28), 30-40% pyroxene (Wo5Fs23En72), approx.8% maskelynite (An53), and approx.2% opaques by volume [1]). The meteorite is usually classified as a lherzolite. Previous Studies - Ar-40/Ar-39 results from previous work display disturbed release spectra [2,3]. In study [2], Ar-40/Ar-39 measurements on a 52-mg whole-rock sample produced an extremely disturbed release spec-trum, with all calculated apparent ages > 1 Ga, (Fig. 1). In a subsequent study [3], a light and a dark phase were analyzed. A 2.3-mg sample of the light, relatively low-K phase produced a disturbed release spectrum. For the first 20% of the Ar-39(sub K), most of the apparent ages exceeded >1 Ga; the remaining 80% yielded ages between 0.3-0.5 Ga. The integrated age for this phase is 0.9 Ga