Browse Topic: Environment
Both concrete guardrails and corrugated beam guardrails have certain wind resistance that can easily hinder wind speed in sections with severe wind-blown sand and snow. This can further cause sand and snow particles to accumulate on the road surface, thereby reducing the friction coefficient of the road surface and having adverse effects on the safety of operating road traffic. The study analyzed the formation mechanism of wind-blown sand and snow, analyzed the functional characteristics of guardrail structure, and explored the SB-level low wind resistance metal beam-post guardrail structure from the perspective of reducing wind resistance area and considering the characteristics of protective vehicles. The main conclusions are as follows: (1) In areas with high wind speed and abundant sand and snow, the roadbed guardrail will have a blocking effect on the wind due to its cross-sectional size, causing wind-blown sand and snow on the road surface. The low wind resistance guardrail can be adopted in key areas, and the metal beam-post guardrail type can be adopted. (2) Considering the types of vehicles protected by SB-level guardrails, the guardrail structure adopts the form of upper and lower beams, with the upper beam mainly protecting large vehicles (buses and trucks) and the lower beam protecting cars. (3) The connection type between beams and posts varies depending on the cross-sectional shape of the tube. Considering the low wind resistance characteristics and structural protection capabilities, circular pipe beams with good wind resistance and square pipe beams with better cross-sectional bending resistance can be used as a beam structure. Circular pipe beams are connected to posts using channel-shaped, while square pipe beams are connected to posts using C-shaped connectors.
In recent years, global automotive manufacturers have been steadfastly engaged in the pursuit of advanced technical solutions to address the increasingly stringent noise pollution standards mandated by national and international regulatory authorities for their domestic and export markets respectively. Aligned with this overarching objective, the Engine Design and Development team at Maruti Suzuki India Limited (MSIL) has undertaken focused efforts to reduce powertrain-induced noise and vibration (NV). Recognizing that the engine unit’s principal static subsystems, namely the intake and exhaust assemblies and critical structural components such as the cylinder head (CH) and cylinder block (CB), serve as primary sources of acoustic emissions, special emphasis was placed on their refinement. Additionally, particular attention was directed toward the engine’s rotating and reciprocating components, especially the camshaft and crankshaft assemblies, to minimize overall measured sound pressure levels.
Long-term orbital missions require highly independent life-support systems, maintaining ecological stability under limited external support and subsystem attenuation. Conventional strategies are typically based on fixed threshold rules or deterministic mass-balance models and cannot adapt to disturbances or multi-objective trade-offs between resource safety and environmental load. This paper proposes a reinforcement learning framework for managing micro closed-loop ecological systems under reliability decay and environmental constraints. A reinforcement learning controller based on Proximal Policy Optimization (PPO) is trained to learn stable regulation policies with random disturbances. A dynamic state model is constructed to describe the coupled and time-sequential elements, ranging from water storage, oxygen concentration, energy reserve, subsystem reliability to ecological load. Degradation propagation is integrated into the transition dynamics through reliability-dependent recycling efficiency. Simulation experiments demonstrate that the proposed policy maintains all resource variables within the safety margins while reducing ecological imbalance compared with traditional strategies. Consequently, the proposed framework provides an expandable control architecture for independent regulation of space station life-support systems.
To investigate the effect of negative pressure environment on the aging behavior of solid propellants, a 60-day negative pressure accelerated aging test was carried out on SG-2 propellant with five working conditions: atmospheric pressure at room temperature, atmospheric pressure at 80°C, and negative pressure at 40°C/60°C/80°C. Combined with Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), the functional group evolution law and thermal decomposition kinetic characteristics of the periphery zone and core zone of the propellant were analyzed. The results show that the propellant exhibits significant inhomogeneous aging characteristics under negative pressure aging. The functional group structure in the periphery zone is more stable in the early aging stage; in the middle stage, components such as DNT and C2 in the core zone migrate to the periphery zone; in the late stage, the undegraded components in the core zone continuously supplement the periphery zone, making the functional group integrity of the periphery zone better than that of the core zone. DSC tests combined with Kissinger and Ozawa methods show that the thermal decomposition activation energy of the propellant decreases continuously with the increase of aging temperature under negative pressure environment, and the activation energy drops to 428.91 kJ/mol after aging at negative pressure 80°C. High temperature accelerates the volatilization of NG, the cross- linking of NC molecular chains and the consumption of stabilizer, leading to the easy breakage of O-NO₂ groups and the significant deterioration of thermal stability. This study clarifies that the aging mechanism of the propellant under negative pressure environment is the synergistic effect of component migration and diffusion, functional group decomposition and molecular chain cross-linking, which provides a theoretical basis for the storage and application of solid propellants in negative pressure service scenarios such as deep space exploration.
With the rapid development of information technology, electronic devices in aerospace, data centers and other fields have faced increasingly severe thermal runaway issues. Two-phase heat transfer technology, with its superior heat dissipation performance, has attracted growing attention and research. A test rig was established to investigate the flow boiling characteristics of R134A within rectangular enhanced flow channels. The test conditions are listed below: heat load ranging from 100W to 3000W, vapor quality from 0.05 to 0.7, and flow rate from 5 L/h to 240 L/h. The results indicate: With the increase of inlet flow rate, The phase change pressure drop gradually increases within the rectangular enhanced flow channels. Similarly, the relationship holds true for phase change pressure drop and cold plate heat load, showing a distinct linear relationship. Under constant heat load, the phase change flow resistance within rectangular enhanced flow channels gradually decreases with increasing the vapor quality. The pressure drop changes dramatically when the vapor quality is below 0.3 and becomes significantly more gradual when the vapor quality exceeds 0.4. Under the test conditions, the maximum density of heat flux is approximately 230 W/cm^2, corresponding to a maximum temperature rise of about 22°C in the heating unit. The equivalent maximum two-phase heat transfer coefficient exceeds 12,000 W/(m^2K). When the cold plate outlet vapor quality is between 0.4 and 0.7, the flow resistance within the rectangular enhanced flow channels is relatively low, and the cooling performance is relatively high. It is recommended that two phase system should be designed within this vapor quality range.
Aiming at the constraint issues of adjacent spacecraft solar panel collision avoidance and formation keeping in the pose tracking control of spacecraft formation, this paper proposes a distributed relative position and attitude cooperative control strategy on the basis of high-order control barrier functions. First, nominal control strategies for relative position and attitude tracking using the sliding mode control method to achieve high-precision tracking of relative motion are de-signed. Then, high-order control barrier functions suitable for solar panel collision avoidance and spacecraft formation keeping constraints are constructed. The control strategy constraints satisfying safety specifications are derived based on the forward invariant set theory. Finally, a quadratic programming optimization framework is established by combining the nominal control strategies and constraint conditions and then we obtain the optimal control strategy by solving this framework. Numerical simulations verify that the designed control scheme achieves precise tracking of relative position and attitude for spacecraft formation, avoids collisions between solar panels of adjacent spacecraft and prevents excessive loosening of the formation configuration.
In addressing the challenges of deep purification of cadmium (Cd) heavy metal contamination and membrane fouling control in spacecraft drinking water sources and recirculation systems, this study adopts a coagulation-ultrafiltration coupled process, with polyaluminium chloride (PACl) as the coagulant and sodium polyacrylate (PAANa) as the complexing agent. A systematic investigation was carried out to examine the effects of key operating parameters—including coagulant dosage, complexing agent dosage, and humic acid (HA) concentration—on Cd removal efficiency, floc morphological characteristics, and ultrafiltration membrane resistance distribution. The results indicate that for simulated raw water containing 0.05 mg/L Cd and (50 ± 0.5) NTU turbidity, under the optimized conditions of 20 mg/L PACl, 20 mg/L PAANa, and pH = 7, the Cd concentration in the effluent treated by the coagulation-ultrafiltration coupled process is reduced to as low as 0.004 mg/L, which meets and even exceeds the hygiene standard limits for both spacecraft drinking water and domestic drinking water. HA was found to promote floc growth and enhance the complexation-based removal of Cd, yet it exacerbates membrane surface adsorption and gel layer fouling. Membrane resistance analysis reveals that gel layer resistance and concentration polarization resistance are the primary sources of fouling, and membrane fouling can be effectively mitigated through rational regulation of operating parameters. This coagulation-ultrafiltration coupled process is characterized by high purification efficiency, stable effluent quality, and strong modularity. It is well adapted to the requirements for closed-loop circulation of spacecraft water resources and drinking water safety assurance, and can provide technical support for water circulation systems in manned spacecraft, drinking water purification at launch sites, and in-situ water treatment during deep space exploration.
For a company concerned with end-of-life automotive recycling, it makes sense to have a “metal” attitude. INDRA's slogan - Car destruction and automotive recycling specialist since 1985 - certainly fits the bill. INDRA, a subsidiary of The Future is Neutral (itself a subsidiary of the Renault Group and SUEZ), has been around for over 40 years and was on hand at the massive Automechanika Frankfurt expo, an event focused on the automotive aftermarket, in early September to promote Design For Recycling (DFR) and more options for recycling old cars. Since automobiles are at least 85% recyclable and at least 95% recoverable, INDRA said, it can fairly be thought of as a “main resource.” The problem is that new vehicles usually contain less than 30% recycled materials, which is why the company has a mission to collect and dismantle end-of-life vehicles and then reuse, revalue, and recycle their components and materials. With vehicle complexity increasing, older vehicles sticking around longer, and new regulations coming into effect, EVL services are in high demand.
A worn-out heavy-duty engine covered in oily grime is an attractive core that's in hot demand by engine remanufacturers. “Even though that engine assembly is non-working, there's tremendous value in the components and the parts that can be brought back to like-new condition for reuse,” said Kevin Schrag, manager of John Deere Reman, a remanufacturing engine and parts operation for off-highway vehicles. Heavy-duty engines have been one of the top sectors for remanufacturing activity for many years. “Many factors make heavy-duty engines ideal for remanufacturing. As durable products, the engine and its components are designed to last, and remanufacturing extends the functionality,” said Dr. Nabil Nasr, founder and current board member of the Remanufacturing Industries Council and the CEO of the REMADE Institute.
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