A letter of congratulations for the launching of Global Health Journal from WHO Representative in China

Dear President Hao Yang, My heartfelt congratulations to you and your colleagues at the People's Medical Publishing House for successfully launching of the Global Health Journal this week in Xi'an.The launching of the journal is the culmination of many years of hard work and persistence.

Real-time UAV path planning based on LSTM network

To address the shortcomings of single-step decision making in the existing deep reinforcement learning based unmanned aerial vehicle(UAV)real-time path planning problem,a real-time UAV path planning algorithm based on long shortterm memory(RPP-LSTM)network is proposed,which combines the memory characteristics of recurrent neural network(RNN)and the deep reinforcement learning algorithm.LSTM networks are used in this algorithm as Q-value networks for the deep Q network(DQN)algorithm,which makes the decision of the Q-value network has some memory.Thanks to LSTM network,the Q-value network can use the previous environmental information and action information which effectively avoids the problem of single-step decision considering only the current environment.Besides,the algorithm proposes a hierarchical reward and punishment function for the specific problem of UAV real-time path planning,so that the UAV can more reasonably perform path planning.Simulation verification shows that compared with the traditional feed-forward neural network(FNN)based UAV autonomous path planning algorithm,the RPP-LSTM proposed in this paper can adapt to more complex environments and has significantly improved robustness and accuracy when performing UAV real-time path planning.

Role of elemental reduction in microstructure,microcrack,and mechanical properties of GH3230 by laser powder bed fusion

Two kinds of pre-alloyed GH3230 powders,each with different Si and Mn compositions,were employed to fabricate components through laser powder bed fusion(LPBF).Microstructural analysis reveals that microcrack formation in the GH3230 sample results from both microsegregation and thermal cycling-induced strain.Both samples with different contents of Si and Mn exhibit typical epitaxial growth of columnar dendrites with directional anisotropy,indicating minimal variation in microstructure under identical thermal cycling conditions.The occurrence of hot cracking is influenced by various factors,with chemical composition playing a crucial role.The presence of these cracks significantly impacts the mechanical properties of the component.The ultimate tensile strength and elongation of the GH3230-L sample,which has reduced Si and Mn content,show significant improvements compared to the GH3230 sample.The ultimate tensile strength increases from 735.0 MPa to 790.0 MPa,and elongation rises substantially from 11.3%to 35.2%.Thermodynamic simulations confirm that variations in Si and Mn content influence hot cracking sensitivity.Reducing Si and Mn levels narrows the solidification range,which helps to minimize the formation of hot cracks by enhancing liquid filling at grain boundaries.

A Constrained Local Neighborhood Approach for Efficient Markov Blanket Discovery in Undirected Independent Graphs

When learning the structure of a Bayesian network,the search space expands significantly as the network size and the number of nodes increase,leading to a noticeable decrease in algorithm efficiency.Traditional constraint-based methods typically rely on the results of conditional independence tests.However,excessive reliance on these test results can lead to a series of problems,including increased computational complexity and inaccurate results,especially when dealing with large-scale networks where performance bottlenecks are particularly evident.To overcome these challenges,we propose a Markov blanket discovery algorithm based on constrained local neighborhoods for constructing undirected independence graphs.This method uses the Markov blanket discovery algorithm to refine the constraints in the initial search space,sets an appropriate constraint radius,thereby reducing the initial computational cost of the algorithm and effectively narrowing the initial solution range.Specifically,the method first determines the local neighborhood space to limit the search range,thereby reducing the number of possible graph structures that need to be considered.This process not only improves the accuracy of the search space constraints but also significantly reduces the number of conditional independence tests.By performing conditional independence tests within the local neighborhood of each node,the method avoids comprehensive tests across the entire network,greatly reducing computational complexity.At the same time,the setting of the constraint radius further improves computational efficiency while ensuring accuracy.Compared to other algorithms,this method can quickly and efficiently construct undirected independence graphs while maintaining high accuracy.Experimental simulation results show that,this method has significant advantages in obtaining the structure of undirected independence graphs,not only maintaining an accuracy of over 96%but also reducing the number of conditional independence tests by at least 50%.This significant performance improvement is due to the effective constraint on the search space and the fine control of computational costs.

Mechanical Properties and Thermal Shock Resistance of SrAl_(2)Si_(2)O_(8) Reinforced BN Ceramic Composites

Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric properties.However,their densification during sintering still poses challenges for researchers,and their mechanical properties are rather unsatisfactory.In this study,SrAl_(2)Si_(2)O_(8)(SAS),with low melting point and high strength,was introduced into the h-BN ceramics to facilitate the sintering and reinforce the strength and toughness.Then,BN-SAS ceramic composites were fabricated via hot press sintering using h-BN,SrCO_(3),Al_(2)O_(3),and SiO_(2) as raw materials,and effects of sintering pressure on their microstructure,mechanical property,and thermal property were investigated.The thermal shock resistance of BN-SAS ceramic composites was evaluated.Results show that phases of as-preparedBN-SAS ceramic composites are h-BN and h-SrAl_(2)Si_(2)O_(8).With the increase of sintering pressure,the composites’densities increase,and the mechanical properties shew a rising trend followed by a slight decline.At a sintering pressure of 20 MPa,their bending strength and fracture toughness are(138±4)MPa and(1.84±0.05)MPa·m^(1/2),respectively.Composites sintered at 10 MPa exhibit a low coefficient of thermal expansion,with an average of 2.96×10^(-6) K^(-1) in the temperature range from 200 to 1200℃.The BN-SAS ceramic composites prepared at 20 MPa display higher thermal conductivity from 12.42 to 28.42 W·m^(-1)·K^(-1) within the temperature range from room temperature to 1000℃.Notably,BN-SAS composites exhibit remarkable thermal shock resistance,with residual bending strength peaking and subsequently declining sharply under a thermal shock temperature difference ranging from 600 to 1400℃.The maximum residual bending strength is recorded at a temperature difference of 800℃,with a residual strength retention rate of 101%.As the thermal shock temperature difference increase,the degree of oxidation on the ceramic surface and cracks due to thermal stress are also increased gradually.

Intelligent extraction of road cracks based on vehicle laser point cloud and panoramic sequence images

In light of the limited efficacy of conventional methods for identifying pavement cracks and the absence of comprehensive depth and location data in two-dimensional photographs,this study presents an intelligent strategy for extracting road cracks.This methodology involves the integration of laser point cloud data obtained from a vehicle-mounted system and a panoramic sequence of images.The study employs a vehicle-mounted LiDAR measurement system to acquire laser point cloud and panoramic sequence image data simultaneously.A convolutional neural network is utilized to extract cracks from the panoramic sequence image.The extracted sequence image is then aligned with the laser point cloud,enabling the assignment of RGB information to the vehicle-mounted three dimensional(3D)point cloud and location information to the two dimensional(2D)panoramic image.Additionally,a threshold value is set based on the crack elevation change to extract the aligned roadway point cloud.The three-dimensional data pertaining to the cracks can be acquired.The experimental findings demonstrate that the use of convolutional neural networks has yielded noteworthy outcomes in the extraction of road cracks.The utilization of point cloud and image alignment techniques enables the extraction of precise location data pertaining to road cracks.This approach exhibits superior accuracy when compared to conventional methods.Moreover,it facilitates rapid and accurate identification and localization of road cracks,thereby playing a crucial role in ensuring road maintenance and traffic safety.Consequently,this technique finds extensive application in the domains of intelligent transportation and urbanization development.The technology exhibits significant promise for use in the domains of intelligent transportation and city development.

Fundamental Interaction Bridging Elements, in Supplement to the Standard Model

An interdisciplinary-field research brings new elements in bridging the gravitational interaction with the Standard Model, by focusing on 3 factors. The involvement of inductive and capacitive-like phase shifts in the gravitational interaction, the exploration of swapping between parameters of time and space, and the provision of a way to handle imaginary terms. The existence of phase shifts in the gravitational interaction is documented via re-interpretation of older quantitative predictions, and is specifically linked to the Higgs field mechanism. Same as in electronics, a phase shift splits energy into real and imaginary coordinates. This allows to quantitatively treat inertia as an inductive-like potential, alongside the swapping of parameters of time and space. That also allows to treat the Bernoulli pressure in quantitative analogy to a magnetic potential, as well as barrier penetration in quantitative symmetry to the crossing of displacement-current through a capacitor. The findings shed light on how fields & forces, including reaction forces function, while the role of imaginary numbers is analyzed. Interaction of fields with quantum particles is discussed to involve a Fourier-series effect that results in energy quantization. The role of phase shifts becomes essential in bridging between wave nature and effects of relativity, and the Weinberg angle is explained to have the role of an inductive-like shift. The precise value of this angle is proposed to link to elementary particles’ properties like spin, or the value of quarks’ charge. Symmetries introduced allow to address the abundance of matter over antimatter in certain analogy to theory from electronics, to address galaxy rotation curves through an interaction involving negative energy, and more. The new concepts open up room for advancements in energy exploitation over interdisciplinary areas.

Feasibility study of renewable e-methanol production:A substitution pathway from blue to green

Producing renewable e-methanol from e-hydrogen and diverse carbon sources is an essential way for clean methanol preparation.Despite this,the technical and economic feasibility of different e-methanols has yet to be thoroughly compared,leaving the most promising pathway to achieve commercialization yet evident.This paper reports a preliminary analysis of the lifecycle greenhouse gas(GHG)emissions and costs of four renewable e-methanols with different carbon sources:bio-carbon,direct air capture(DAC),fossil fuel carbon capture(FFCC),and fossil.The results indicate that renewable e-methanol costs(4167−10250 CNY/tonne)2−4 times the market rate of grey methanol.However,with the carbon tax and the projected decline in e-H2 costs,blue e-methanol may initially replace diesel in inland navigation,followed by a shift from heavy fuel oil(HFO)to green e-methanol in ocean ship-ping.Furthermore,the e-H2 cost and the availability of green carbon are vital factors affecting cost-effectiveness.A reduction in e-H2 cost from 2.1 CNY/Nm3 to 1.1 CNY/Nm3 resulting from a transition from an annual to a daily scheduling period,could lower e-methanol costs by 1200 to 2100 CNY.This paper also provides an in-depth discussion on the challenges and opportunities associated with the various green carbon sources.

再入飞行器冷热结构一体化设计及分析

针对多层热结构存在的热短路和连接方式复杂问题,设计了防/隔热双层热结构与冷结构一体化。在典型服役环境条件下,采用有限元法对热结构组件与冷结构进行了强度和热匹配分析,计算发现气动力对组件强度影响不大;惯性力作用下,组件的薄弱环节是螺钉和隔热层;再入热环境条件下,连接件位置出现应力集中现象。完成的强度及热匹配分析结果可应用于再入飞行器冷热结构一体化设计。

Diurnal variation of number concentration and size distribution of ultrafine particles in the urban atmosphere of Beijing in winter

Number concentration and distribution of airborne particles in the size range 5.6 to 560 nm diameter were measured in Beijing for a 15-d period in winter 2005. Dally average number concentrations of nucleation mode （5.6-20 um）, Aitken mode （20-100 um）, and accumulation mode （100-560 um） particles, and total particles were 17500, 32000, 4000, and 53500 cm^-3, respectively. Average particle size distribution was monomodal with a mode diameter of about 40 um at night and bimodal with mode diameters of about 10 and about 40 um during the daytime. New particle formation events, which were connected to diurnal variation of nucleation mode particles, were observed in more than half of the observation days. The events often started around 10：00-11：00 Chinese Standard Time （CST） and ended up after 3-4 h. Concentrations of Aitken and accumulation mode particles increased from midnight and reached their maxima at about 10：00 CST, and then decreased and became the lowest in the afternoon. Analysis of diurnal cycles in traffic volume and meteorological parameters revealed that the accumulation of the particles in Aitken and accumulation modes in the morning was influenced by formation of an inversion and increase in vehicle emission, and dispersion of such particles in the afternoon was associated with more effective vertical mixing and higher wind speed.

Experimental Simulation for Fracture of Gun Propellant Charge Bed

The simulation of compression and fracture of charge bed in chamber is one of the key problems in the study of launch safety of gun propellant charge. A new kind of experimental device that can be used for simulation is given. Its structure and operational principle are introduced. Using a semi-closed vessel as a source of compression force, the device can simulate any kind of dynamic environment in a gun propellant charge. Using the low temperature inert gas （N2） as the compression medium, the device can not only ensure that the simulation is real, but also protect the fragmentized propellant from combustion after experiment. Using the device, many simulation experiments have been accomplished, and dynamic environment of propellant fracture is acquired. With the experiments, fragmentized propellant for the compression and fracture of charge bed is obtained. Results of experiments show that the new device can be used to study the principle of the compression and fracture of charge bed.

In situ synthesis and hardness of TiC/Ti_5Si_3 composites on Ti-5Al-2.5Sn substrates by gas tungsten arc welding

TiC/TisSi3 composites were fabricated on Ti-5A1-2.5Sn substrates by gas tungsten arc welding （GTAW）. Identification of the phases was performed using X-ray diffraction （XRD）. The microstructures were analyzed using scanning electron microscopy （SEM） combined with energy-dispersive X-ray spectrometry （EDS） and optical microscopy （OM）. The Vickers hardness was measured with a micro-hardness tester. The TiC/TisSi3 composites were obtained in a double-layer track, and the Vickers hardness of the track increased by two to three times compared with the Ti-5A1-2.5Sn substrate.

Effects of ZrO_2 Nanoparticles on the Microstructure and Thermal-protective Properties of PEO Coating on Al-12.5%Si Alloy

PEO ceramic coatings including ZrO_2-Al_2O_3-SiO_2 in three phases were prepared on an Al-12.5%Si alloy in electrolyte solutions containing ZrO_2 nanoparticles. The microstructures and phases of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. The compactness of the coating increased significantly and the hindrance of the Si element on plasma electrolytic oxidation process was effectively weakened. The growth rate of the coating was improved substantially with the addition of ZrO_2 nanoparticles. The PEO ceramic coatings are primarily composed of SiO_2 and high temperature steady phases such as a-Al_2O_3 and c-ZrO_2. Both the content of c-ZrO_2 and the heat-insulating property of the coating increased significantly. The ceramic coatings with special microstructure and composition formed in the solutions containing ZrO_2 nanoparticles possess excellent heat insulation performance and thermal shock resistance.

Gas–liquid mass transfer and flow phenomena in a peirce–smith converter: A numerical model study

A numerical model was established to simulate the flow field in a Peirce–Smith converter bath, which is extensively adopted in copper making. The mean phase and velocity distribution, circular area, and mean wall shear stress were calculated to determine the optimal operation parameter of the converter. The results showed that the slag phase gathered substantially in the dead zone. The circular flow was promoted by increasing the gas flow rate, Q, and decreasing the nozzle height, h. However, these operations significantly aggravate the wall shear stress. Reducing the nozzle diameter, d, increases the injection velocity, which may accelerate the flow field. However, when the nozzle diameter has an interval design, the bubble behaviors cannot be combined, thus, weakening the injection efficiency. Considering the balance between the circular flow and wall shear stress in this model, the optimal operation parameters were Q = 30000–35000 m^3/h, h = 425–525 mm, and d = 40 & 50 mm.

Gas–liquid mass transfer and flow phenomena in the Peirce–Smith converter: a water model study

A water model with a geometric similarity ratio of 1：5 was developed to investigate the gas-liquid mass transfer and flow charac- teristics in a Peirce-Smith converter. A gas mixture of CO2 and Ar was injected into a NaOH solution bath. The flow field, volumetric mass transfer coefficient per unit volume （Ak/V; where A is the contact area between phases, V is the volume, and k is the mass transfer coeffi- cient）, and gas utilization ratio （t/） were then measured at different gas flow rates and blow angles. The results showed that the flow field could be divided into five regions, i.e., injection, strong loop, weak loop, splashing, and dead zone. Whereas the Ak/V of the bath increased and then decreased with increasing gas flow rate, and n steadily increased. When the converter was rotated clockwise, both Ak/F and t/increased. However, the flow condition deteriorated when the gas flow rate and blow angle were drastically increased. Therefore, these para- meters must be controlled to optimal conditions. In the proposed model, the optimal gas flow rate and blow angle were 7.5 m3.h-1 and 10°, respectively.

Online hierarchical recognition method for target tactical intention in beyond-visual-range air combat

Online accurate recognition of target tactical intention in beyond-visual-range (BVR) air combat is an important basis for deep situational awareness and autonomous air combat decision-making, which can create pre-emptive tactical opportunities for the fighter to gain air superiority. The existing methods to solve this problem have some defects such as dependence on empirical knowledge, difficulty in interpreting the recognition results, and inability to meet the requirements of actual air combat. So an online hierarchical recognition method for target tactical intention in BVR air combat based on cascaded support vector machine (CSVM) is proposed in this study. Through the mechanism analysis of BVR air combat, the instantaneous and cumulative feature information of target trajectory and relative situation information are introduced successively using online automatic decomposition of target trajectory and hierarchical progression. Then the hierarchical recognition model from target maneuver element, tactical maneuver to tactical intention is constructed. The CSVM algorithm is designed for solving this model, and the computational complexity is decomposed by the cascaded structure to overcome the problems of convergence and timeliness when the dimensions and number of training samples are large. Meanwhile, the recognition result of each layer can be used to support the composition analysis and interpretation of target tactical intention. The simulation results show that the proposed method can effectively realize multi-dimensional online accurate recognition of target tactical intention in BVR air combat.

Morphology and tribological properties of Ni/n-SiO_2 composite coatings by pulse-reverse current brush-plating

Ni/n-SiO2 composite coating was electrodeposited by brush-plating with pulse-reverse current（RC）. The morphology, hardness, and tribological properties of the coating were investigated and compared with those of Ni and composite coatings electrodeposited with direct current（DC）. The results indicate that Ni/n-SiO2 composite coating electrodeposited by RC, because of RC and the nano powders, has denser coating, finer crystal grains, higher hardness（HV650.0, nearly 1.5 times higher than that of Ni coating electrodeposited by DC） and lower friction coefficient（nearly 0.62）, as a result, in the wearing experiment, the Ni/n-SiO2 composite coating electrodeposited by RC has the least worn loss. So this kind of coating has better wear resistance. And RC electro brush-plating can be used as a new technology of brush-plating in the area of wear resistance.

Lessons in bridge damage learned from the Wenchuan earthquake

A strong earthquake occurred in Wenchuan County, Sichuan Province, China, on May 12, 2008. Shortly after the earthquake, the Turner-Fairbank Highway Research Center of the Federal Highway Administration, in partnership with the Research Institute of Highways, the Ministry of Communication of China, led a reconnaissance team to conduct a post-earthquake bridge performance investigation of the transportation system in the earthquake affected areas. The U.S. transportation system reconnaissance team visited the area during July 20 24, 2008. This paper presents the findings and lessons learned by the team.

Research on the Application of Explosive Network in the Shaped Charge Warhead

With respect to the problems of that the shaped charge warhead currently uses a cover method to improve the penetration power, a method using an explosive network technology as the detonation mode of shaped charge warhead is proposed. In the context of some shaped charge warhead, a synchronous explosive network prototype is designed according to some charge structure parameters, such as the liner and main grain. From the performance comparison test, it can be known that the explosive network not only stably detonates, but also largely improves the penetration power and stability. Experimental results show that explosive network technology is an effective method for improving the penetration power. The results lay a solid foundation for the engineering application of the technology in the shaped charge warhead.

Water model experiments of multiphase mixing in the top-blown smelting process of copper concentrate

We constructed a 1：10 cold water experimental model by geometrically scaling down an Isa smelting furnace. The mixing processes at different liquid heights, lance diameters, lance submersion depths, and gas flow rates were subsequently measured using the conductivity method. A new criterion was proposed to determine the mixing time. On this basis, the quasi-equations of the mixing time as a function of different parameters were established. The parameters of the top-blown smelting process were optimized using high-speed photography. An excessively high gas flow rate or excessively low liquid height would enhance the fluctuation and splashing of liquid in the bath, which is unfavorable for material mixing. Simultaneously increasing the lance diameter and the lance submersion depth would promote the mixing in the bath, thereby improving the smelting efficiency.