Numerical calculation of coupled damage effects on ship subjected to internal blast loading of warhead北大核心CSCD

［Objective］This paper studies the coupled damage effects of a ship's structure due to the internal blast loading of a warhead. ［Methods］Blast tests with cased charge data are conducted to verify the effectiveness of the coupled SPH-FEM approach, and numerical calculations are then performed on real ship compartment scale model tests to analyze the coupled fragmentation and shockwave damage effects of an explosion in a confined cabin.［Results］The results show that the fragments caused by the detonation of the warhead will first cause local damage to the cabin structure. The shockwave will exacerbate the local damage, and blasted openings will further increase the space for the propagation and diffusion of the shockwave inside the chamber, which will in turn cause damage to the adjacent structures. The simple equivalence of the warhead to a bare charge does not give a true picture of the effect of the warhead on the ship's structure, and fragmentation plays a significant role in the detonation of the warhead.［Conclusions］The results of this study show that employing the coupled SPH-FEM numerical method to calculate the coupling damage effects on a ship's structure can accurately reproduce the warhead damage pattern in tests, thereby providing support for the improved assessment of the damage of naval structures under warhead detonation. © 2022 Chinese Journal of Ship Research. All rights reserved.     

高海拔隧道施工劳动强度与供氧浓度关系研究北大核心CSCD

为研究高海拔隧道施工人员供氧浓度问题,文章通过骑行试验得到了不同人员在海拔高度为590~4000 m,氧气浓度为20.9%~29%,骑行功率为0、50 W、75 W、100 W工况下的生理指标,得到测试对象的劳动强度指数,分析研究得到以下结论:(1)在同一海拔高度、相同劳动强度工况下,提升环境氧气浓度,可以显著降低人员劳动强度指数;(2)劳动强度指数的减少与氧气浓度的增加并不是线性关系,当环境氧气浓度超过25%时,劳动强度指数的降低程度有限;(3)拟合得到了劳动负荷为100 W且氧气浓度为20.9%~25%时施工人员的劳动强度指数与海拔高度及供氧浓度的关系式。     

Development and prospects of key technology for submarine atmospheric environment control北大核心CSCD

Air regeneration, harmful gas purification and atmospheric composition monitoring are the key technologies of submarine atmospheric environment control systems. After years of development, China has made great progress in such systems, which have developed from ensuring the safety requirements of submariner and equipment operation to ensuring the health of submariner and reliability of system for long-term underwater operation. This paper reviews the development history of submarine atmospheric environment control technologies and introduces their future development prospects. The developers of integrated atmospheric environment control technology should learn from foreign submarine and aerosphere equipment technologies, which aim to support long-term submerged operation and comfort demands, and better adapt to future submarine technology development and evolving mission, in order to constantly enhance the level of submarine cabin air quality of the Chinese navy. © 2022 Journal of Clinical Hepatology. All rights reserved.     

Applying Public Participation Geographic Information Systems for Coastal Wading Bird Conservation

Coastal estuaries in the northern Gulf of Mexico are important habitat for wading birds, but are threatened by land use and ecological changes. Conservation has been demonstrated to be more effective when stakeholders are included in the decision-making process. Public Participation Geographic Information Systems (PPGIS) facilitates the inclusion of stakeholder preferences in the planning process by allowing a direct spatial comparison with other ecological data. In this study, we used a PPGIS survey of residents of two counties on Alabama’s Gulf Coast to identify wading bird conservation hotspots as identified by local residents. Additionally, we assessed the ability of general public respondents to accurately identify wading bird habitat, determined whether participants associated wading bird habitat with particular land cover types, and examined whether respondents identified areas with high wading bird species richness. We found that respondents could accurately identify suitable wading bird habitat on a map of the study area, but underrepresented riparian forest, which is an important habitat for many wading bird species. Additionally, participants tended to prioritize areas that support higher wading bird species richness. Thus, this study demonstrated how PPGIS can function as an important tool for incorporating both stakeholder management preferences and identifying knowledge gaps.     

Revisiting urban hierarchy and specialization from a maritime perspective

ABSTRACT

Port–city relationships have attracted paramount attention from a variety of scientific disciplines for several decades, such as geography, history, planning, regional science, sociology, and economics to name but a few. Yet, the extent to which maritime traffic specialization obeys the same spatial distribution than other economic activities remains underexplored today. This article tackles these lacunae head-on by proposing an empirical analysis of the way vessel tonnage per main categories of flows (e.g. containers, bulks, passengers) coincides with the demographic size of the world’s coastal and inland city-regions, using novel data on global inter-port vessel movements and harmonized population data over the period 1977–2008. Our main results confirm that such traffic is far from being randomly distributed, as its volume, value, and diversity concentrate at the top of the urban hierarchy. This research motivates the need to further integrate physical connectivity into the study of cities and their development mechanisms.     

Lateral controller design for an unmanned vehicle via Kalman filtering

This paper proposes a lateral control system for an unmanned vehicle that is designed to improve the responsiveness of the system with the use of a PD control. The vehicle heading error can be stabilized, and the transient response characteristics can be improved using the proposed controller. A mathematical model of the vehicle dynamics using two degrees of freedom was developed for the controller design. The waypoint tracking method for autonomous navigation was tested with incorporation of the Point-to-Point algorithm with position and heading measurements received from GPS receivers via Kalman filtering. The performance of the designed controller was verified through experiments with a real vehicle.     

Computational model for analyzing the kinematics and compliance characteristics of a commercial vehicle’s front suspension system

This paper develops a computational model that can analyze the kinematics and compliance characteristics of the front suspension of a commercial vehicle. This computational model is called the flexible multi-body dynamic model because it is developed by interfacing the finite element model of the multi-leaf spring with the dynamic model of the front suspension. In this paper, the bump mode and roll mode tests are performed with a suspension parameter measuring device (SPMD). An excitation load for creating the bump mode and roll mode motion is applied on the left and right tires slowly in in-phase and out-of-phase modes. In the test, wheel rate, toe angle change, caster angle change, and camber angle change, which together represent the wheel alignment, are measured along with the longitudinal and lateral wheel center loci which together represent the wheel center trajectory change. The reliability of the developed computational model is verified by comparing the simulation results with the SPMD test results. The developed flexible multi-body computational model will provide useful information on kinematics and compliance characteristics in the earliest stages of the commercial vehicle design process.     

Modeling and control of an anti-lock brake and steering system for cooperative control on split-mu surfaces

The brake and steering systems in vehicles are the most effective actuators that directly affect the vehicle dynamics. In general, the brake system affects the longitudinal dynamics and the steering system affects the lateral dynamics; however, their effects are coupled when the vehicle is braking on a non-homogenous surface, such as a split-mu road. The yaw moment compensation of the steering control on a split-mu road is one of the basic functions of integrated or coordinated chassis control systems and has been demonstrated by several chassis suppliers. However, the disturbance yaw moment is generally compensated for using the yaw rate feedback or using wheel brake pressure measurement. Access to the wheel brake pressure through physical sensors is not cost effective; therefore, we modeled the hydraulic brake system to avoid using physical sensors and to estimate the brake pressure. The steering angle controller was designed to mitigate the non-symmetric braking force effect and to stabilize the yaw rate dynamics of the vehicle. An H-infinity design synthesis was used to take the system model and the estimation errors into account, and the designed controller was evaluated using vehicle tests.     

Design optimization of an injection mold for minimizing temperature deviation

The quality of an injection molded part is largely affected by the mold cooling. Consequently, this makes it necessary to optimize the mold cooling circuit when designing the part but prior to designing the mold. Various approaches of optimizing the mold cooling circuit have been proposed previously. In this work, optimization of the mold cooling circuit was automated by a commercial process integration and design optimization tool called Process Integration, Automation and Optimization (PIAnO), which is often used for large automotive parts such as bumpers and instrument panels. The cooling channels and baffle tubes were located on the offset profile equidistant from the part surface. The locations of the cooling channels and the baffle tubes were automatically generated and input into the mold cooling computer-aided engineering program, Autodesk Moldflow Insight 2010. The objective function was the deviation of the mold surface temperature from a given design temperature. Design variables in the optimization were the depths, distances and diameters of the cooling channels and the baffle tubes. For a more practical analysis, the pressure drop and temperature drop were considered the limited values. Optimization was performed using the progressive quadratic response surface method. The optimization resulted in a more uniform temperature distribution when compared to the initial design, and utilizing the proposed optimization method, a satisfactory solution could be made at a lower cost.     

Research on the Brayton cycle design conditions for reliquefaction cooling of LNG boil off

This paper analyses the Brayton cooling cycle for the reliquefaction of the boil off on liquefied natural gas (LNG) vessels. By performing a thermodynamic study, we analysed and evaluated the conditions, parameters and energy consumption required in the process, including the influence of the choice and variation of diverse factors on the operating conditions and power.