Experimental investigations on the strategies of fighting crickets Velarifictorus micado to manipulate air resistance

Fighting crickets,one species of flightless insects optimally chosen by nature for millions of years,have evolved to fairly smooth and streamlined body surfaces.This article tries to answer the question how the insects manipulate air resistance when travelling through air after take-off without using their wings and meanwhile keep a high efficiency.We found that fighting crickets,Velarifictorus micado,performed two types of movements through air:stable and unstable.The two types both have a high moving efficiency.For the stable type,the moving efficiency is larger than 95%.As a typical example,focusing on the stable type,we firstly predicted each component of aerodynamic drag applied on the crickets and analysed the drag contributions to the initial kinetic energy dissipation.Further investigation revealed the mechanisms of the efficiently moving strategy against air resistance for the insects.The results show that the crickets can spin their hind legs to adjust body posture,thereby changing(increasing or decreasing)the air drag acting on the body to raise the efficiency during aerial movements.This work may advance the understanding of the significance of hind legs to insects’evolution and provide inspiration for future robot or micro aerial vehicle designs.

A method based on potential theory for calculating air ca formation of an air cavity resistance reduction ship

This research is intended to provide academic reference and design guidance for further studies to determine the most effective means to reduce a ship’s resistance through an air-cavity. On the basis of potential theory and on the assumption of an ideal and irrotational fluid, this paper drives a method for calculating air cavity formation using slender ship theory then points out the parameters directly related to the formation of air cavities and their interrelationships. Simulations showed that the formation of an air cavity is affected by cavitation number, velocity, groove geometry and groove size. When the ship’s velocity and groove structure are given, the cavitation number must be within range to form a steady air cavity. The interface between air and water forms a wave shape and could be adjusted by an air injection system.

Computational Solution to the Problems of Projectile Motion under Significant Linear Drag Effect

This paper investigates the computational solution to the problem of projectile motion under a significant linear drag effect. The drag force acting on the particle within the medium of propagation is proportional to the cross-section area of the projectile, the velocity of the particle, and the medium’s density. From zero air resistance force (vacuum) the problems are well known with solutions, but with air resistance (drag force) the problems have no exact analytical solutions which lead to most of the significant scientific research works using numerical methods. Therefore, this study aims to present the analysis of the computational modelling of drag force exerted by the surrounding medium on the linear motion. However, the horizontal and vertical components of differential equations of motion were derived and characterized from the solutions governed by Newton’s 2nd law of motion. The baseball features were presented as the projectile (object) in this work. In addition, the numerical computational results were received from FreeMat. The results were discussed and compared with those from the vacuum. Moreover, the displacements, velocities, range, and trajectories of the projectile were all discussed and a conclusion was made.

Resistance of large caisson in floating transport considering the influence of air

This paper deals with the floating resistance of super large caisson by numerical simulation,and the influence of air resistance on the caisson,which is often ignored by previous researchers,is considered.The floating caisson of Taizhou Highway Bridge’s middle tower pier is investigated,and the software package FLUENT is used to simulate the floating process of largescale rounded rectangular steel caisson.This simulation adopts the volume of fluid(VOF)model with water-air two-phase flow,which can take both the hydraulic resistance and air resistance into account.Subsequently,the analyses on hydraulic resistance and air resistance under different working conditions,such as different flow velocities and different draughts of water are performed,and the results are compared with those calculated by related empirical formula.The comparison shows that the air resistance takes up notable portion in the total resistance on the floating caisson,and the effect of air resistance on the safety of caisson should be paid sufficient attention to rather than be ignored.

Method of branch ariflow for calculatinga complicated mine ventilation networks

The solutions widely used at present for calculating complicated mine ventilation networks are ones in which resistance of the branches and characteristic parameters of the fans are taken as basic input data. But it is time and energy consuming to obtain the branch resistance values. A new solution is developed in this paper in which the branch resistance values are obtained through measuring and evaluating the airflow of the whole ventilation network. Theoretical analysis is made of the establishment of a linear equation series with branch resistance as unknown numbers, an equation series for which one, and only one, result of solutions exists. This solution is programmed in C language and passed on a personal computer. The programmed solution programmed proves of practical use, as demonstrated by specific examples. Being different from other solutions, the method takes the branch airflow and fan working points as basic input data, and the present solution is of greater advantage for calculating ventilation networks of mines in operation.

Effects of herba menthae, borneolum and moschus on nasal sensation of air flow and nasal resistance

Objective Herba menthae, Borneolum and moschus are strongly volatile. Herba menthae, borneolum have been widely used as traditional Chinese medicines in the treatment of nasal congestion. The aim of this study was to determine the effects of herba menthae, borneolum and moschus on nasal sensation of airflow and nasal resistance. Method 52 volunteers (32 females, 20 males, aged from 19 to 32 years) were studied. Only subjects with normal nose functions were included in the study. Those who had had a coryzal illness or allergic rhinitis during the last three weeks excluded from the study. Nasal resistance was measured by active anterior rhinomanometry, using Master PF 2001 rhinomanometry (ICS Corporation, U.S.A.). Nasal sensation was measured with a self made equipment, called “nasal sensation indication scale”. There was a 100cm line scale on the equipment. Each end of the 100cm line scale was defined as either “extremely clear” or “extremely blocked”. The slide control was brought to the center point of the 100cm scale before each scoring of nasal sensation. The center point was the zero point for the scoring of nasal sensation. Each subject expressed his subjective feelings of nasal sensation of airflow by moving the slide control to the appropriate direction. Substances were administered by self made wick inhaler which consisted of a vessel in which the substances were put and a capsule which can spray air. Inhalers A, B, C and D respectively contained a blank wick, herba menthae at a concentration of 100mg dissolved in 1ml vaseline, borneolum at a concentration of 100mg dissolved in 1ml vaseline, moschus Department of Otorhinolaryngology Head and Neck Surgery, Third Clinical College of Bethune University of Medical Sciences, Changchun 130031, China (Wang YP, Dong Z, Yang ZQ and Bu GX) 1g. Each nostril was sprayed three times during the experiment, first the left and then the right. The protocol was as follows. Nasal resistance was measured before the administration of substances. Air control was first administered, followed by the other three kinds of medicines which were administered randomly, so that bias resulting from the order of presentation of substances would be controlled in the final analysis of the results. After inhalation of medicines, nasal sensation and nasal resistance were measured in order. Every two kinds of medicine were administered at an interval of 15 minutes so that any delayed effects could be observed. Results Because original data of nasal resistance and nasal sensation were not normal distribution, the logarithm of the original data were used for statistic analysis. Inhalation of herba menthae, borneolum or moschus all had no obvious influence on nasal resistance (P>0.05), but all caused enhancement of nasal sensation of airflow (P<0.01). Among these medicines the action of herba menthae was the strongest, borneolum and moschus being the second. 4 subjects had a sensation of nasal obstruction after inhalation of the substance, but there was no corresponding increase in nasal resistance. Conclusion The above results clearly demonstrate that herba menthae, borneolum and moschus all cause a highly significant enhancement of nasal sensation of airflow, but had no obvious effects on nasal resistance, in other words, enhancement of sensation of nasal airflow was not accompanied by the decrease of nasal resistance (increase of airflow). Therefore, the enhancement of airflow sensation is just a subjective, false impression and this sort of medicine should be regarded as pseudonasal decongestant.

Influences of substrate temperature on microstructure and corrosion behavior of APS Ni_(50)Ti_(25)Al_(25) inter-metallic coating

In the present investigation, Ni_（50）Ti_（25）Al_（25）（at.%） mechanically alloyed powder is deposited on carbon steel substrate.Before the coating process, the substrate is heated to temperature ranging from room temperature to 400℃. The microstructure, porosity, microhardness, adhesion strength, and corrosion behavior of the coating are investigated at different substrate temperatures. Results show that coating porosity is lower on high temperature surface. Microhardness and adhesion strength of the deposition layer on the substrate without preheating have lower values than with preheating. The polarization test result shows that corrosion performance of the coating is dependent on micro cracks and porosities and the increasing of substrate temperature can improve the quality of coating and corrosion performance.

Comparison effects of lanthanum stearate and antioxidants in epoxidized natural rubber

This work studied possibilities of using lanthanum stearate（LaS t） as an antioxidant in epoxidized natural rubber containing 25 mol.% expoxidation（ENR25） compounds. For comparison purposes, two commercial antioxidant 4010 NA and MB were also used. The influence of LaS t, antioxidant 4010 NA and MB on cure characteristics, mechanical properties, crosslink density, hot air aging and thermo-oxidative degradation were studied. The results indicated that the incorporation of LaS t and antioxidants could accelerate the vulcanization of ENR. The ENR vulcanizates with antioxidant MB had better mechanical properties than 4010 NA and LaS t. Compared with antioxidant 4010 NA and MB, the ENR25 vulcanizates with the addition of LaS t exhibited the best hot air aging resistance and thermo-oxidative stability.