Research on the influences of motion characteristics of jetting projectile charge under water

Shaped charge warhead is important for enhancing the damage performance of underwater weapons.This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters(wall thickness,material),charge aspect ratio,and stand-off distance on the movement characteristics of JPC in water.The findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water,the effective length of the JPC in water undergoes two distinct phases:a growth phase and a decrease phase,with the velocity of the JPC decaying exponentially.Increasing the liner thickness,stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the JPC.The optimal ranges for liner thickness and stand-off distance are 0.0363D_(k) to 0.0545D_(k)(D_(k) is the charge diameter),the stand-off distance should be within 1.0D_(k).After the charge aspect ratio higher than 1.25,the charge structure exerts minimal influence the movement characteristics of the JPC in water.Material density plays a crucial role in the velocity decay pattern of the JPC during penetration.JPC with higher densities exhibit superior velocity retention capabilities in water,with the velocity decay pattern converging if the densities are similar.Consequently,copper,tantalum and tungsten liners are deemed appropriate for underwater shaped charge warhead.Finally,the results will provide an important reference for the design of underwater shaped charge warhead.

Experimental research on HEL and failure properties of alumina under impact loading

A series of plate impact experiments on alumina was conducted using a light gas gun in order to further investigate Hugoniot elastic limit(HEL)and failure properties of alumina under shock compression.The velocity interferometer system for any reflector(VISAR)was used to record the rear-free surface velocity histories of the alumina samples.According to the experimental results,the HELs of tested alumina samples with different thicknesses were measured,and the decay phenomenon of elastic wave in shocked alumina was studied.A phenomenological expression between HEL and thickness of sample was presented,and the causes of the decay phenomenon were discussed.The propagation of failure wave in shocked alumina was probed.The velocity and delayed time of failure wave propagation were obtained.The physical mechanism of the generation and propagation of failure was further discussed.

The deformation and failure mechanism of cylindrical shell and square plate with pre-formed holes under blast loading

The deformation and failure mechanism of cylindrical shells and square plate with pre-formed holes under blast loading were investigated numerically by employing the Ansys 17.0 and Ls-Dyna 971.To calibrate the numerical model,the experiments of square plates with pre-formed circle holes were modeled and the numerical results have a good agreement with the experiment data.The calibrated numerical model was used to study the deformation and failure mechanism of cylindrical shells with pre-formed circle holes subjected to blast loading.The structure response and stress field changing process has been divided into four specific stages and the deformation mechanism has been discussed systematically.The local and global deformation curves,degree of damage,change of stress status and failure modes of cylindrical shell and square plate with pre-formed circular holes are obtained,compared and analyzed,it can be concluded as:(1)The transition of tensile stress fields is due to the geometrical characteristic of pre-formed holes and cylindrical shell with arch configuration;(2)The existence of preformed holes not only lead to the increasing of stress concentration around the holes,but also release the stress concentration during whole response process;(3)There are three and two kinds of failure modes for square plate and cylindrical shell with pre-formed holes,respectively.and the standoff distance has a key influence on the forming location of the crack initiating point and the locus of crack propagation;(4)The square plate with pre-formed holes has a better performance than cylindrical shell on blast-resistant capability at a smaller standoff distance,while the influence of pre-formed holes on the reduction of blast-resistant capability of square plate is bigger than that of cylindrical shell.

Effect of toll-like receptor 3 agonist poly I:C on intestinal mucosa and epithelial barrier function in mouse models of acute colitis

AIM To investigate potential effects of poly I:C on mucosal injury and epithelial barrier disruption in dextran sulfate sodium (DSS)-induced acute colitis. METHODS Thirty C57BL/6 mice were given either regular drinking water (control group) or 2% (w/v) DSS drinking water (model and poly I:C groups) ad libitum for 7 d. Poly I:C was administrated subcutaneously (20 mu g/mouse) 2 h prior to DSS induction in mice of the poly I:C group. Severity of colitis was evaluated by disease activity index, body weight, colon length, histology and myeloperoxidase (MPO) activity, as well as the production of proinflammatory cytokines, including tumor necrosis factor-a (TNF-alpha), interleukin 17 (IL-17) and interferon-. (IFN-gamma). Intestinal permeability was analyzed by the fluorescein isothiocyanate labeled-dextran (FITC-D) method. Ultrastructural features of the colon tissue were observed under electron microscopy. Expressions of tight junction (TJ) proteins, including zo-1, occludin and claudin-1, were measured by immunohistochemistry/immunofluorescence, Western blot and real-time quantitative polymerase chain reaction (RT-qPCR). RESULTS DSS caused significant damage to the colon tissue in the model group. Administration of poly I:C dramatically protected against DSS-induced colitis, as demonstrated by less body weight loss, lower disease activity index score, longer colon length, colonic MPO activity, and improved macroscopic and histological scores. It also ameliorated DSS-induced ultrastructural changes of the colon epithelium, as observed under scanning electron microscopy, as well as FITC-D permeability. The mRNA and protein expressions of TJ protein, zo-1, occludin and claudin-1 were also found to be significantly enhanced in the poly I:C group, as determined by immunohistochemistry/immunofluorescence, Western blot and RT-qPCR. By contrast, poly I:C pretreatment markedly reversed the DSS-induced up-regulated expressions of the inflammatory cytokines TNF-alpha, IL-17 and IFN-gamma. CONCLUSION Our study suggested that poly I:C may protect against DSS-induced colitis through maintaining integrity of the epithelial barrier and regulating innate immune responses, which may shed light on the therapeutic potential of poly I:C in human colitis.

Palliative operation procedures for pancreatic head carcinoma

Objective: To investigate the procedure choice of pal-liative operation for carcinoma of the head of the pan-creas (CHP).Methods: The clinical data from 187 patients withCHP treated in the last 20 years were analyzed retro-spectively.Results: The operation mortality rate was 8.6%, themortality of hepatic duct-jejunostomy (HDJS) was nothigher than that of cholecystojejunostomy (CJS) (P>0.05). The postoperative relapse of jaundice and cholan-gitis was significantly lower than that of CJS (P<0.025), while the survival was apparently higher thanthat of CJS (P<0.01). The mortality of HJDS or CJSwith gastrojejunostomy (GJS) was not significantlyhigher than that of the simple procedure without GJS(P>0.05), whereas the survival was significantlyhigher than that of the simple procedure without GJS(P<0.01). The occurrence of duodenal obstructionafter HDJS or CJS was 29.3%.Conclusion: As a palliative operation, Roux-en-Y chole-dochojejunostomy especially in combination with pre-ventive gastrojejunostomy is strongly recommended.

Research and development on hypervelocity impact protection using Whipple shield:An overview

Whipple shield,a dual-wall system,as well as its improved structures,is widely applied to defend the hypervelocity impact of space debris(projectile).This paper reviews the studies about the mechanism and process of protection against hypervelocity impacts using Whipple shield.Ground-based experiment and numerical simulation for hypervelocity impact and protection are introduced briefly.Three steps of the Whipple shield protection are discussed in order,including the interaction between the projectile and bumper,the movement and diffusion of the debris cloud,and the interaction between the debris cloud and rear plate.Potential improvements of the protection performance focusing on these three steps are presented.Representative works in the last decade are mentioned specifically.Some prospects and suggestions for future studies are put forward.

Procedures for congenital choledochal cysts and curative effect analysis in adults

Objective: To evaluate the procedures and timing of operation as well as long-term postoperative effect of congenital choledochal cysts (CCC) in adults. Methods: The procedures and timing of operation, effective rate, re-operation rate and incidence of car- cinoma after operation for 70 adult patients with CCC from January 1980 to June 1999 were analyzed retrospectively. Results: The re-operation rate of external drainage was 86% (6/7). The effective rate of internal drain- age was significantly lower than that of cyst resection (3/10 vs 45/49, X^2=20. 94, P<0.001). The re-op- eration rate and incidence of carcinoma of internal drainage were higher than those of cyst resection (5/ 10 vs 3/49, X^2=13. 64, P<0. 001 and 3/10 vs 3/49, X^2=5. 18, P<0. 025). The reoperation rate of e- mergency surgery was higher than that of selective operation (8/10 vs 6/56, X^2=24. 37, P<0.001). Conclusions: External drainage should be the first- aid measure and the therapy of choice on emergency basis. Internal drainage should never be attempted. Cyst resection with Roux-en-Y hepaticojejunostomy is recommended as the treatment of choice in selective operation.

Experimental research on blast power of fiber reinforced anti-hard target warhead

Fiber reinforced anti-hard-target warhead is a new-type sample munition, which is only designed based on theoretical analysis and numerical simulation in laboratory. This warhead consists of carbon composite casings and high explosive, which can greatly reduce the damage to objects outside the damage range. In order to evaluate its blasting damage effect on concrete target, the three types of charges were researched by means of experiment, which are bare charge, charge with carbon composite material shell and charge with steel shell. Experimental results show that the peak overpressure of charge with carbon fiber composite shell is higher than that of charge with steel shell, but is lower than that of bare charge in the case of the same TNT equivalence. No fragments and fragment effect exist for distant target under the condition of charge with carbon fiber composite shell. However, the experimental result of the charge with steel shell is completely contrary. According to the blast effect in the concrete target, the charge with carbon composite material shell is optimal in matched impedance and detonation propagation.Also, the effective energy produced by the detonation of explosive with carbon composite material shell is the largest.

Application of CRISPR-Cas9 technology in the screening of tumor resistance genes:A review

Drug resistance is a major problem faced by tumor cell-targeted drugs.Currently,functional gene screening is the most common strategy for screening drug resistance genes.In recent years,Crispr-cas9 gene editing technology has been widely used in the functional studies of tumor-related genes due to their characteristics of accuracy,simplicity and efficiency.The principle of CRISPR-Cas9 Library Screening Technology and its application in functional Gene Screening are reviewed.At the same time,the application prospect of the Crispr-Cas9 technology is forecasted.

Research of cavitation characteristics of RCP based on section-constrained blades

To make sure that the bubbles will not block the impeller passage in the process of the transient cavitation, a section-constrained design is adopted in the hydraulic design of the CAP 1400 Reactor Coolant Pump,s(RCP,s) impeller blade, and the cavitation bubble distribution on the suction side of the blade in the CAP 1400 RCP under the transient cavitation condition and the internal pressure pulsation are studied. To study the performance of the section-constrained impeller blade, simulations are carried out by using the CFX software, the cavitation bubble distribution on the suction side and the pulsation dynamics at each monitoring point in different extents of cavitation are obtained based on the Reynolds-averaged N-S equation and the SST k-co equation. The results show that the section-constrained blade has a good constraint capacity on the cavitation, and could enhance the passing ability of the blade in some extent. The main causes of the pressure pulsation inside a pump are the rotor-stator interaction, the separated flow at the round-like pump chamber, and the reflux inside the flow passage. The pressure pulsation inside the impeller and the guide vane is characterized by the significant periodicity, which are both affected by the rotor-stator interaction. And the impeller outlet and the guide vane inlet are more susceptible to the rotor-stator interaction. Studies of the vapor-liquid two-phase flow and the pressure pulsation inside the RCP's impeller with the transient cavitation are of great significance for the prediction of the RCP’s dynamic characteristics after the cavitation, and for the safety and the stable running of the RCP.