Comparison of two measurement devices for obtaining horizontal force-velocity profile variables during sprint running

This study established the magnitude of systematic bias and random error of horizontal force-velocity (F-v) profile variables obtained from a 1080 Sprint compared to that obtained from a Stalker ATS II radar device. Twenty high-school athletes from an American football training group completed a 30 m sprint while the two devices simultaneously measured velocity-time data. The velocity-time data were modelled by an exponential equation fitting process and then used to calculate individual F-v profiles and related variables (theoretical maximum velocity, theoretical maximum horizontal force, slope of the linear F-v profile, peak power, time constant tau, and horizontal maximal velocity). The devices were compared by determining the systematic bias and the 95% limits of agreement (random error) for all variables, both of which were expressed as percentages of the mean radar value. All bias values were within 6.32%, with the 1080 Sprint reporting higher values for tau, horizontal maximal velocity, and theoretical maximum velocity. Random error was lowest for velocity-based variables but exceeded 7% for all others, with slope of the F-v profile being greatest at ±12.3%. These results provide practitioners with the information necessary to determine if the agreement between the devices and the magnitude of random error is acceptable within the context of their specific application.

The missing mass

In response to the Lateral Thoughts quiz “Sporting chance”, in which question 8 asked for a rough estimate of the theoretical maximum height a pole vaulter could jump, and why the actual world record is slightly above this.

Heuristic compactness maximization algorithm for two-dimensional single-atom traps rearrangement

We establish an algorithm and computational results based on heuristic rearrangement of randomly filled array toward a defect-free and compact array. In this approach, the vacancies are filled from the inner layer that is related to the distance from the center of each loading site. By rearranging the position of atoms that maximize the compactness of the system layer by layer, the algorithm is set to iterate until the compactness reaches its local maximum. The results show that by applying the algorithm, the compactness of the system converges up to ∼97% of the theoretical maximum.

On the genera of polyhedral embeddings of cubic graph

In this article we present theoretical and computational results on the existence of polyhedral embeddings of graphs. The emphasis is on cubic graphs. We also describe an efficient algorithm to compute all polyhedral embeddings of a given cubic graph and constructions for cubic graphs with some special properties of their polyhedral embeddings. Some key results are that even cubic graphs with a polyhedral embedding on the torus can also have polyhedral embeddings in arbitrarily high genus, in fact in a genus {\em close} to the theoretical maximum for that number of vertices, and that there is no bound on the number of genera in which a cubic graph can have a polyhedral embedding. While these results suggest a large variety of polyhedral embeddings, computations for up to 28 vertices suggest that by far most of the cubic graphs do not have a polyhedral embedding in any genus and that the ratio of these graphs is increasing with the number of vertices.

Hybrid Rockets as Post-Boost Stages and Kick Motors

Hybrid rockets are attractive as post-boost stages and kick motors due to their inherent safety and low cost, but it is not clear from previous research which oxidizer is most suitable for maximizing ΔV within a fixed envelope size, or what impact O/F shift and nozzle erosion will have on ΔV. A standard hybrid rocket design is proposed and used to clarify the impact of component masses on ΔV within three 1 m3 envelopes of varying height-to-base ratios. Theoretical maximum ΔV are evaluated first, assuming constant O/F and no nozzle erosion. Of the four common liquid oxidizers: H2O2 85 wt%, N2O, N2O4, and LOX, H2O2 85 wt% is shown to result in the highest ΔV, and N2O is shown to result in the highest density ΔV, which is the ΔV normalized for motor density. When O/F shift is considered, the ΔV decreases by 9% for the N2O motor and 12% for the H2O2 85 wt% motor. When nozzle erosion is also considered, the ΔV decreases by another 7% for the H2O2 85 wt% motor and 4% for the N2O motor. Even with O/F shift and nozzle erosion, the H2O2 85 wt% motor can accelerate itself (916 kg) upwards of 4000 m/s, and the N2O motor (456 kg) 3550 m/s.

Application of Virtual Display Technology of LCD Backlight Spectrum Optimization Algorithm Based on Linear Programming

In order to make the color of image display more realistic, optimize the use of energy, and improve the light efficiency of the module through reasonable spectral distribution, this paper proposes a backlight spectral optimization algorithm based on linear programming. With the goal of maximizing the backlight luminous efficiency, the theoretical maximum of the luminous efficiency of the backlight spectrum can be achieved by constructing a linear programming model. The research process is to obtain the optimal distribution of transmittance spectrum by linear programming method on the premise of ensuring the color gamut standard of display system. The results show that the light efficiency can be increased to 335.5 lm/W, while the original light efficiency of the system is less than 150 lm/W. With the goal of maximizing the light efficiency, light sources with narrow bandwidths such as lasers and quantum dot materials can be used to simulate and reconstruct these characteristic wavelengths. There will be easier to approach the ideal optimization spectrum and achieve the theoretical maximum luminous efficiency of 610.8 lm/W.

Theoretical maximum contribution of dominance complementation to heterosis

Heterosis refers to the superiority of F1 hybrid over its inbred parents. Although heterosis has been widely used in the production of maize and rice, its genetic basis remains a matter of conjecture. Without the roles of overdominance and/or epistasis in heterosis, elite hybrids would finally lose their advantage over inbred lines possessing the vast majority of superior alleles. Here we demonstrate the theoretical maximum contribution of dominance complementation to heterosis with a focus on diploid plants, and compare our theoretical results with the experimental observations. The comparisons indicate that the theoretical maximum contribution of dominance complementation to heterosis is inadequate to explain heterosis exhibited by the elite maize hybrids and cannot be reached by the actual contribution of dominance complementation to heterosis. The gap between heterosis and the actual contribution of dominance complementation to heterosis in the elite maize hybrids should be attributed to the roles of overdominance and/or epistasis in heterosis. These findings imply that the advantage of elite hybrids over elite inbred lines can be maintained even when the vast majority of superior alleles accumulate in inbred lines.

An Intelligent Load Control-Based Random Access Scheme for Space-Based Internet of Things

Random access is one of the most competitive multiple access schemes for future space-based Internet of Things (S-IoT) due to its support for massive connections and grant-free transmission, as well as its ease of implementation. However, firstly, existing random access schemes are highly sensitive to load: once the load exceeds a certain critical value, the throughput will drop sharply due to the increased probability of data collision. Moreover, due to variable satellite coverage and bursty traffic, the network load of S-IoT changes dynamically; therefore, when existing random access schemes are applied directly to the S-IoT environment, the actual throughput is far below the theoretical maximum. Accordingly, this paper proposes an intelligent load control-based random access scheme based on CRDSA++, which is an enhanced version of the contention resolution diversity slotted ALOHA (CRDSA) and extends the CRDSA concept to more than two replicas. The proposed scheme is dubbed load control-based three-replica contention resolution diversity slotted ALOHA (LC-CRDSA3). LC-CRDSA3 actively controls network load. When the load threatens to exceed the critical value, only certain nodes are allowed to send data, and the load is controlled to be near the critical value, thereby effectively improving the throughput. In order to accurately carry out load control, we innovatively propose a maximum likelihood estimation (MLE)-based load estimation algorithm, which estimates the load value of each received frame by making full use of the number of time slots in different states. On this basis, LC-CRDSA3 adopts computational intelligence-based time series forecasting technology to predict the load values of future frames using the historical load values. We evaluated the performance of LC-CRDSA3 through a series of simulation experiments and compared it with CRDSA++. Our experimental results demonstrate that in S-IoT contexts where the load changes dynamically, LC-CRDSA3 can obtain network throughput that is close to the theoretical maximum across a wide load range through accurate load control.

Enantioselective preparation of mechanically planar chiral rotaxanes by kinetic resolution strategy

Asymmetric synthesis of mechanically planar chiral rotaxanes and topologically chiral catenanes has been a long-standing challenge in organic synthesis. Recently, an excellent strategy was developed based on diastereomeric synthesis of rotaxanes and catenanes with mechanical chirality followed by removal of the chiral auxiliary. On the other hand, its enantioselective approach has been quite limited. Here, we report enantioselective preparation of mechanically planar chiral rotaxanes by kinetic resolution of the racemates via remote asymmetric acylation of a hydroxy group in the axis component, which provides an unreacted enantiomer in up to >99.9% ee in 29% yield (the theoretical maximum yield of kinetic resolution of racemate is 50%). While the rotaxane molecules are expected to have conformational complexity, our original catalysts enabled to discriminate the mechanical chirality of the rotaxanes efficiently with the selectivity factors in up to 16.

Formation of p-Unsubstituted Phenols in Base-catalyzed Lignin Depolymerization

Lignin valorization is one of the biggest challenges for developing biomass-based chemical industry. Recent innovative works has enabled depolymerization of lignin to the monomers with the yield close to theoretical maximum. The main product is a mixture of phenols derived from the cleavage of β-O-4 linkages between phenylpropanoid units. However, the obtained highly functionalized phenols are not common in current industry and, therefore, needs further processing for the utilization in intended applications. The present study shows that simple phenols without functional groups at para-position form selectively in base-catalyzed depolymerization of lignin. The yield is not sufficiently high, up to 6.9% on a carbon basis under the examined conditions, but the selectivity among released lignin monomers reaches 80%. The study also discusses the mechanism of p-unsubstituted phenols formation.