Effect of initiation manners on the scattering characteristics of semi-preformed fragment warhead

The lethality of a semi-preformed fragment warhead is closely related to the expand velocity and spatial distribution of the fragments from ruptured metal casing. The topic of how to improve the utilization of charge of have been drawing great attention from researchers and designer in this filed. In present paper,in order to investigate the influence of charge initiation manners on the scattering characteristics of semi-preformed fragment warhead, the numerical simulations and experimental test are conducted.Firstly, the influence of grid density on numerical results is investigated, and a proper numerical model with relatively high accuracy and effectiveness is determined. Then. numerical simulations of three kinds of different initiation position of a semi-preformed fragment warhead are carried out. An experimental test of the explosion of a semi-preformed fragment warhead is carried out. By comparing and analyzing the numerical results and experimental data, it is found that the initiation manners have great influence on scattering characteristics of semi-preformed fragment warhead. The researcher work of this paper would provide an effective alternative method to optimize the design of warhead.

Clinical effect of ultrasound-guided nerve block and dexmedetomidine anesthesia on lower extremity operative fracture reduction

BACKGROUND Lower extremity fractures are mainly treated by surgical reduction,but this operation is often affected by the patient’s level of agitation and the type of anesthesia used.The main treatment for lower-extremity fractures is operative reduction.However,operations can often be affected by both agitation and the degree of anesthesia.Therefore,it is of great importance to develop an effective anesthesia program to effectively ensure the progress of surgery.AIM To discuss the effect of ultrasound-guided nerve block combined with dexmedetomidine anesthesia in lower extremity fracture surgery.METHODS A total of 120 hospital patients with lower extremity fractures were selected for this retrospective study and divided into an observation group(n=60)and a control group(n=60)according to the anesthesia scheme;the control group received ultrasound-guided nerve block;the observation group was treated with dextromethomidine on the basis of the control group,and the mean arterial pressure,heart rate(HR),and blood oxygen saturation were observed in the two groups.RESULTS The mean arterial pressure of T1,T2 and T3 in the observation group were 94.40±7.10,90.84±7.21 and 91.03±6.84 mmHg,significantly higher than that of the control group(P<0.05).The observation group’s HR at T1 was 76.60±7.52 times/min,significantly lower than that of the control group(P<0.05);The observation group’s HR at T2 and T3 was 75.40±8.03 times/min and 76.64±7.11 times/min,significantly higher than that of the control group(P<0.05).The observation group’s visual analog score at 2 h,6 h and 12 h after operation was 3.55±0.87,2.84±0.65 and 2.05±0.40.the recovery time was 15.51±4.21 min,significantly lower than that of the control group(P<0.05).Six hours post-anesthesia,epinephrine and norepinephrine in the observation group were 81.10±21.19 pg/mL and 510.20±98.27 pg/mL,significantly lower than that of the control group(P<0.05),and the mini-mental state exam score of the observation group was 25.51±1.15,significantly higher than that in the control group(P<0.05).CONCLUSION Ultrasound-guided nerve block combined with dexmedetomidine has a good anesthetic effect in the operation of lower limb fractures and has little effect on the hemodynamics of patients.

Life cycle assessment for waste acid treatment in zinc smelting

Lift cycle assessment(LCA)methodology was applied to evaluating and comparing two waste acid disposal processes in zinc smelting.The results indicate that environmental impacts of gas−liquid vulcanization technologies are human toxicity,abiotic depletion potential,and global warming risk,which are mainly caused in neutralizing−evaporating−crystallization unit and electrodialysis unit.As for traditional lime neutralization method,vulcanization unit is the main factor.In this regard,the total environmental impact of traditional lime neutralization method is much higher than that of gas−liquid vulcanization technologies.Furthermore,the sensitive analysis shows that electricity and sodium sulfide(60%)are sensitive factors in two waste acid disposal technologies.In addition,the total cost of disposing a functional unit waste acid in traditional lime neutralization process is nearly 27 times that of the gas−liquid vulcanization waste acid disposal technologies.

Research of 6-DOF Serial-Parallel Mechanism Platform for Stability Training of Legged-Walking Robot

The concept of legged-robot stability training with a training platform is proposed and a serial-parallel mechanism platform with 6 degrees of freedom is designed for this target. The designed platform is composed of 4-DOF parallel mechanism with spherical joints and prismatic pairs,and 2-DOF serial mechanism with prismatic pairs. With this design,the platform has advantages of low platform countertop,big workspace,high carrying capacity and high stiffness. On the basis of DOF analysis and computation of space mechanism,weight supporting auxiliary mechanism and raceways-balls supporting mechanism are designed,so as to improve the stiffness of designed large platform and payload capacity of servo motors. And then the whole structure design work of the platform is done. Meanwhile,this paper derives the analytical solutions of forward kinematics, inverse kinematics and inverse dynamics. The error analysis model of position and orientation is established. And then the simulation is done in ADAMS to ensure the correctness and feasibility of this design.

Revisiting the Parallel Strategy for DOACROSS Loops

DOACROSS loops are significant parts in many important scientific and engineering applications,which are generally exploited pipeline/wave-front parallelism by loop transformations.However,previous work almost statically performs iterations in parallel threads,thus causing a waste of computing resources in thread synchronization.This paper proposes a brand-new parallel strategy for DOACROSS loops that provides a dynamic task assignment with reduced dependences to achieve wave-front parallelism through loop tiling.The proposed strategy uses a master-slave parallel mode and some customized structures to realize dynamic and flexible parallelization,which effectively avoids threads from waiting in communication.An efficient tile size selection(TSS)approach is also proposed to preserve data reuse in cache for tiled codes.The experimental results show that the proposed parallel strategy obtains good and stable speedups over six typical benchmarks with different problem sizes and different numbers of threads on an Intel■Xeon■32-core serve?.And it outperforms two static strategies,a barrier-based strategy and a post/wait-based strategy,by 32% and 20% in average performance,respectively.This strategy also yields a better performance than a mutex-based dynamic strategy.Besides,it has been demonstrated that the proposed TSS approach can achieve a near-optimal performance and is comparable with a state-of-the-art TSS approach.