Research into the Energy Output of Asymmetric Cylindrical Structure under Internal Explosion Loading

The energy output characteristic of an asymmetric cylindrical structure under internal explosion loading has significant research value in the field of the national defense industry. This paper took the D-shaped structure as the research object. Three groups of experiments (D-90°, D-120°, D-150°) were carried out. The D-shaped structure showed that fragments are concentrated in the middle and are sparse on both sides. Moreover, the fragment density decreased with the increase of the azimuth angle. The fragment velocities, which were measured from high-speed photography and an oscilloscope, coincided well with each other, and decreased with an increase in the central angle. Compared with the cylindrical structure, the fragment energy gain of the D-shaped structure is significant; the total energy and energy density of the three D-shaped structures were very close to each other. This indicates that D-120° is the optimal solution among the three D-shaped structures and it can provide guidance for the future design of D-shaped structures to achieve higher energy output

Rapid Evaluation and Analysis of the Deformation of Filled Cylindrical Casing with Deforming Charge Width Based on Self-Compiled MATLAB Program

The casing of deformable warheads warps under the action of deforming charges. The deformation profiles may be concave-, convex-, or D-shaped, but they are all symmetrical. The D-shape is considered the optimal deformation profile. The width of the deformed surface affects the number of fragments in the target area. In order to evaluate the deformable surface width of the cylindrical casing, a criterion α was established and its optimum range was determined as 20 to 30%. Based on our previous theoretical analysis, a MATLAB program that can rapidly evaluate the projectile deformation surface was compiled, which was verified using LS-DYNA and experiments. The laws influencing the deforming charge width on the deformed surface of the filled cylindrical casing were also studied using the MATLAB rapid evaluation program. As the deforming charge width increased, the deformation profile of the casing gradually transferred from “inner-concave” to the “outer-convex”. In addition, a formula that can better reflect the relationship between the deforming charge width φ and the criterion value α was fitted and verified. The conclusions obtained in this paper provide rapid guidance for the structural design of deformable warheads

Prediction of Consumption Choices of Low-Income Groups in a Mixed-Income Community Using a Support Vector Machine Method

To examine how cross-strata neighboring behavior in a mixed-income community can influence the consumption choices of individuals in low-income groups, and to improve the prediction accuracy of the consumption choice model of low-income groups for small sample sizes, we developed a support vector machine (SVM) algorithm based on the influence of neighboring behavior. We substituted the predicted latent variables into the SVM classifier and constructed an SVM prediction model with latent variables based on reference group theory. We established the model parameters using cross-validation and used low-income residents from a mixed-income community in Shanghai as study objects to empirically test the model’s performance. The results show that the SVM selection model with latent variables has good prediction accuracy. The proposed model’s accuracy was improved by 1.29% on the basis of the particle swarm optimization (PSO)-SVM model without latent variables, and by 19.35% on the basis of the SVM model with latent variables. The proposed model can be employed to predict the consumption choices of individuals in low-income groups. This paper offers a theoretical reference for investigating neighboring behavior in a mixed-income community and the consumption choices of individuals in low-income groups and is practically important for urban community planning systems

The Dispersion Rule of Fragments about the Asymmetric Shell

In order to obtain the dispersion rule of fragments about the asymmetric shell subjected to internal blast loading, two different cross section structures, concave-shaped and convex-shaped, were carried out by experimental and numerical methods. The simulation results well coincided with the experimental results, and the spatial distribution and fragment velocity were obtained. The optimal curvatures for the different concave structures changed from 4r to 6r (r represents the charge radius), as the central angle of concave structure changed from 90° to 120°. However, the optimal curvature changed weakly when the central angle of concave structure was larger than 120°. In addition, a formula which can rapidly predict the projection angle range was fitted for the convex structure. The conclusions can provide a reference for concave-shaped and convex-shaped structures to achieve a higher effectiveness of fragments

Parallel Control to Fragments of a Cylindrical Structure Driven by Explosive inside

By analyzing the fragmentation distributions of a cylindrical structure and a specific structure, the necessity of parallel control to the fragments is presented. The shell shape of structures has an influence on the fragment spatial distribution. A new design method for the shell shape is proposed. To facilitate the establishment of the numerical model and the machining for relative experiments, the mathematical description of the theoretical calculated generatrix of the shell is simplified. The fragment spraying processes of the designed structures are simulated, and end effects are analyzed. Based on the theoretical design and plentiful simulation data, the relationships between the size of the parallel fragmentation structure and the optimized curvature radius of the shell are expressed by an equation. The equation is validated by numerical means and can be a reliable reference to the design of the parallel fragmentation structure

Analysis and Prediction of Dockless Shared Bike Demand Evolving Around Urban Rail Transit Stations: Case Study in Shenzhen, China

Abstract The emergence of dockless shared bikes (DSB) has led to their use as an important transfer mode to urban rail transit (URT) stations. However, in highly populated areas such as subway stations in peak hours, there is increasing concern about the imbalance between the demand and supply of shared bikes. To promote smoother subway transfer trips using shared bikes, it is very important to estimate the DSB demand, especially the disparity in the volume of bike pick-up and drop-off demand around subway stations. This research first utilizes the Shenzhen metro usage data and DSB usage data, analyzes data regarding subway and shared bike usage, discusses their potential transfer uses, and finds great disparity in DSB demand between different subway stations. The catchment area method is used to estimate bike usage as a potential transfer mode to the subway, where the catchment area is defined as a radius of 150 m from the subway station center. The DSB trip demand is categorized into two types: pick-up and drop-off. The most recent deep learning method, adaptive graph convolutional recurrent network (AGCRN), is used to predict the DSB demand more accurately because of its ability in enabling the modeling of relationships between entities in a self-adapted graph, and the prediction is compared with long short-term memory (LSTM), spatiotemporal neural network (STNN), diffusion convolutional recurrent neural network (DCRNN), and Graph WaveNet. Results show that methods with graphs (STNN, DCRNN, Graph WaveNet, and AGCRN) perform better than LSTM, and methods with adaptive graphs (Graph WaveNet and AGCRN) outperform methods with static graphs in terms of mean absolute error (MAE), root-mean-square error (RMSE), and mean absolute percentage error (MAPE). DSB prediction results show that AGCRN performs the best in this study. More data, particularly land use data and URT station volume data, are expected to improve the predictive accuracy of the method due to potentially improved graph representation of station characteristics and subway station volume correlations. And with more accurate prediction results, it will be possible to achieve a better balancing strategy for bike operation optimization for better bike usage, and thus for a higher transfer rate of DSB to subway

Effect of intubation in lateral position on placement of a double-lumen tube in patients undergoing unilateral video-assisted thoracic surgery: a randomied clinical trialResearch in context

Summary: Background: Approximately one-third of patients who undergo double-lumen tube (DLT) intubation in the conventional supine position experience DLT malposition. No randomized study investigates the effect of DLT intubation in the lateral position. We therefore aimed to evaluate the effect of intubation in lateral position on placement of a DLT compared to supine intubation, and to test primary hypothesis that lateral DLT intubation could reduce the incidence of DLT malposition. Methods: We randomly allocated 108 patients undergoing video-assisted thoracic surgery to receive DLT intubation in the comfortable and surgically required lateral position (lateral group) or in the supine position (supine group) from October to December 2022. The primary outcome was the incidence of DLT malposition defined as movement >1.0 cm to correct the DLT position. The secondary outcomes included intubation time, the frequency and duration of fibreoptic bronchoscopy, the need for re-intubation, intra-operative vital signs, and post-operative recovery. This trial is registered with the Chinese Clinical Trial Registry (ChiCTR2200060794). Findings: The incidence of DLT malposition was significantly lower in the lateral group (1/53 [2%]) than that in the supine group (16/53 [30%]; RR [95% confidence interval] of 0.06 [0.01–0.46]; P < 0.001). Lateral DLT intubation decreased the intubation time, the frequency and duration of fibreoptic bronchoscopy. The incidence of hypotension, post-operative sore throat, and upper-arm discomfort was lower in the lateral group. Other secondary outcomes were similar between groups. Interpretation: Lateral DLT intubation reduced the incidence of DLT malposition for patients undergoing video-assisted thoracic surgery. These results support that lateral DLT intubation offers more benefits and may be a superior option compared to conventional supine intubation. Funding: National Natural Science Foundation of China and of Zhejiang Province