A Risk Score System for Myopia Symptom Warning

Myopia is the leading cause of visual impairments worldwide. Some studies revealed that visual experience in early life affected the final myopia, indicating that environmental factors play an impellent role in the development of myopia. However, risk factors of myopia are still not identified among adolescents in China. A total of 4104 cases of myopia symptom and 3306 emmetropia controls were selected from students in primary and middle schools in Wuhan in 2008. We identified the risk factors associated with myopia symptom by multivariate logistic regression in this cross-sectional study and constructed a risk score system for myopia symptom. The value of the area under the receiver operating characteristic curve (ROC) was 0.735. Furthermore, we followed up 93 students aged 7-9 years for one year and calculated the total points using the score system. We found no significant difference between the final myopia symptom and the results predicted by the total points by pair chi-square test (P>0.05). The score system had a modest ability to estimate the risk factors of myopia symptom. Using this score system, we could identify the students who are at risk of myopia symptom in the future according to their behaviors and environmental factors, and take measures to slow the progress of myopia symptom.

Investigation on energy output structure of explosives near-ground explosion

In order to give the energy output structure of typical explosives near-ground explosion in real ground conditions,the free-field shockwave,ground reflection shockwave and Mach wave overpressure time history of composition B explosive,RDX explosive and aluminized explosive were measured by air pressure sensors and ground pressure sensors.The shape of the free-field shock wave,ground reflection shock wave,and Mach wave and explosion flame were captured by high-speed camera.The experimental results show that,at the same horizontal distance from the initiation point,the peak overpressure of explosive shock wave of composition B explosive,both in the air and on the ground,is less than that of RDX and aluminized explosives.At a distance of 3.0 m from the initiation point,the peak overpressure of aluminized explosives is slightly less than that of RDX explosives.Owing to the exothermic effect of aluminum powder,the pressure drop of aluminized explosives is slower than that of RDX explosives.At 5.0 m from the initiation point,the peak overpressure of aluminized explosives is larger than that of RDX explosives.At the same position from the initiation point,among the three kinds of explosives,the impulse of aluminized explosives is the maximum and the impulse of composition B explosives is the minimum.With the increase of the horizontal distance from the initiation point,the height of Mach triple-points(Mach steam)of the three explosives increases gradually.At the same horizontal distance from the initiation point,there is poorly difference in the height of Mach triple-points between aluminized explosive and RDX explosive,and the height of Mach triple-points of composition B explosive is much smaller than that of other two explosives.The maximum diameter and duration of the fireball formed by aluminized explosives are the largest,followed by composition B explosive,and the maximum diameter and duration of the fireball formed by RDX explosive are the smallest.

Bore-center annular shaped charges with different liner materials penetrating into steel targets

The bore-center annular shaped charge(BCASC)is a new type of shaped charge which can generate a larger-diameter hole in steel targets than classical shaped charges.In this paper,the influence of three liner materials,i.e.molybdenum,nickel and copper,on BCASC formation and penetrating into steel targets was investigated by experiment and numerical simulation.The simulation results were well consistent with the experimental results.This study showed that,at 0.50D standoff distance,the axial velocity of the molybdenum projectile was lower than that of the nickel and copper projectiles.The nickel and copper projectiles had almost the same head velocity.The absolute values of the radial velocity of the molybdenum projectile head was lower than that of the nickel and copper projectiles.However,at 0.75D standoff distance,the absolute values of the radial velocity of the molybdenum projectile head became much greater than that of the nickel and copper projectile heads.The projectile formed by BCASC with the molybdenum liner had the highest penetration depth of 61.5 mm,which was 10.0%and 21.3%higher than that generated by the copper and nickel projectiles.

Chitin-derived fibrous carbon microspheres as support of polyamine for remarkable CO_(2) capture

Supported polyamines are promising candidates for the chemical adsorption of CO_(2),the performance of which is highly dependent on the porous structure of supports.In this work,we synthesized a kind of fibrous carbon microspheres(FCMs)from environmentally friendly and low-cost chitin.The synthesized FCMs have microspheric morphology and fibrous sub-architecture,and the carbon fibers interweave to form pores with large diameters.The flexibility of the pores formed by the interweaving of carbon fibers also enable the supporting of high quantity of polyamines.Given these features,pentaethylenehexamine(PEHA)was physically dispersed in the pores of FCMs to prepare PEHA/FCMs adsorbents,which were systematically characterized and investigated for CO_(2) capture performance.It is found that PEHA/FCMs adsorbents show excellent ability for CO_(2) adsorption,with the highest CO_(2) capacity of 3.90 mmol g^(-1) at 75℃ when using 10 vol%of CO_(2) for determinations.The reversibility of PEHA/FCMs adsorbents for CO_(2) adsorption is also fairly good,and PEHA/FCMs adsorbents have strong ability for the selective adsorption of low-content CO_(2) from N_(2).