Autonomous Navigation with Deep Reinforcement Learning in Carla Simulator

With the rapid development of autonomous driving and artificial intelligence technology, end-to-end autonomous driving technology has become a research hotspot. This thesis aims to explore the application of deep reinforcement learning in the realizing of end-to-end autonomous driving. We built a deep reinforcement learning virtual environment in the Carla simulator, and based on it, we trained a policy model to control a vehicle along a preplanned route. For the selection of the deep reinforcement learning algorithms, we have used the Proximal Policy Optimization algorithm due to its stable performance. Considering the complexity of end-to-end autonomous driving, we have also carefully designed a comprehensive reward function to train the policy model more efficiently. The model inputs for this study are of two types: firstly, real-time road information and vehicle state data obtained from the Carla simulator, and secondly, real-time images captured by the vehicle's front camera. In order to understand the influence of different input information on the training effect and model performance, we conducted a detailed comparative analysis. The test results showed that the accuracy and significance of the information has a significant impact on the learning effect of the agent, which in turn has a direct impact on the performance of the model. Through this study, we have not only confirmed the potential of deep reinforcement learning in the field of end-to-end autonomous driving, but also provided an important reference for future research and development of related technologies

A case ship study on practical design and installation of carbon absorption and solidification system

Onboard carbon capture and storage is an excellent solution to reduce the greenhouse gas emissions from shipping. This paper focuses on a case ship study on design and installation of a practical carbon absorption and solidification system which was proposed in authors’ previous work (Peilin and Haibin, 2014). The design process is based on authors’ previous work of simulation on lab-scale experiment. The specifications of the selected ship will be presented and utilized for its modelling. The processes of simulation illustrate modifications of simulation model, design of physical model, application of orthogonal design method, introduction of equipment and software and analysis of results. This paper also presents tank design, positioning and CAD drawing of the system on board after all processes and systems are derived. This paper demonstrates general processes of carbon absorption and solidification system design for a case ship so that design of the system for a new ship could follow the same procedures

Analysis on numerical simulations of CO2 absorption process of carbon solidification system

Carbon dioxide (CO2) emission control has been a popular topic since global warming affects our living conditions on the planet. Carbon Capture and Storage (CCS) is a feasible solution for mitigating the global warming effect by capturing the CO2 from power stations and industrial processes and storing them underground. There are great many of active CCS projects onshore. International Maritime Organization (IMO) has adopted guidelines for CO2 emission control by improving ship energy efficiency. The project is aiming to apply CCS on ships by capturing the CO2 emission from the engine exhaust gases and solidifying them for easy storage. It will enable ships to comply with various regional and international CO2 emission regulations and also maintain the efficiency of waterborne transportation. The simulation of carbon absorption develops and investigates the multiphase reaction model in CFD software, focusing on bubble column effect with chemical reaction. This paper presents the analysis of the numerical simulation of the CO2 absorption process. Simulation results illustrate the pressure distribution of solution and gas path and velocity in solution. This numerical simulation results also indicates the impact of environment temperature on chemical reaction rate. A comparison between experiment and simulation results is presented to figure out the impact of initial NaOH solution concentration on gas absorption process. An optimized NaOH solution concentration is figured out and will be used for further practical design of absorption system for ships

CFD simulations of absorption reaction in carbon solidification processes

Carbon capture and storage (CCS) is a promising task solution for reduction of CO2 emission from ships. To meet the IMO proposed target of 20% CO2 reduction from shipping by 2020, proposal of solidifying CO2 separated from engine exhaust had been made and tested by the authors. Laboratory experiment [1] on CO2 absorption has illustrated the feasibility of solidifying carbon onboard ships. To further verify the accuracy of results from CO2 absorption experiment, simulation with computational fluid dynamics (CFD) of the CO2 absorption and solidification processes is carried out, including system modelling and meshing, reactions simulating and post-CFD treatments. Eulerian multiphase model and species transport model are applied for the simulation. These models will present the interaction between gas phase (CO2) and chemical solution in both physical phase interactions and chemical reactions between the species. The mass fractions of Na2CO3 in solution are monitored during the absorption process. Conclusions has been reached that the simulation results have a good agreement with the experiment results

A life cycle assessment on carbon capture and solidification method on ship

Greenhouse gas reduction has become a severe topic in the shipping industry and researchers are striving to investigate different GHG reduction technologies to determine their feasibility especially on the environment impact. However, there is no specific evaluation process currently available so this paper presents a Life Cycle Assessment for a carbon emission reduction method to introduce Life Cycle Assessment as a systematic evaluation approach which can guide policy makers to evaluate the performances and help ship owners to select suitable reduction technologies. The carbon reduction method proposed by authors was proved to be cost effective in previous works and this paper applies life cycle analysis focusing on all stages of ship life to investigate, determine and compare the feasibility of this method. The environmental impacts are considered to be the most significant standard for the assessment. From the results of the assessment, the proposed reduction method meets the carbon reduction target and can lead to a lower global warming potential while leveling up the carbon reduction target. This paper also indicates, to achieve carbon reduction target set up by regulations, a marginal target will be necessary due to the energy requirement and efficiency of the method/system as well as the consideration of activities in different life stages. It is also recommended that the evaluation of carbon reduction method could apply Life Cycle Assessment so that policy makers and ship owners are provided with comparable results for reasonable decision makings

Experimental and numerical analysis on impacts of significant factors on carbon dioxide absorption efficiency in the carbon solidification process

Onboard carbon capture and storage is an excellent solution to reduce the greenhouse gas emissions from shipping. This paper focuses on the absorption process and CO2 gas flow rate, the geometry of absorption tank and the concentration of absorption solution are key factors affecting the absorption efficiency. This paper will illustrate the experimental results of the impacts of these factors on the CO2 absorption efficiency. Meanwhile, results from CFD simulations of effects of the key factors on CO2 absorption rates will be presented in this paper. Pressure distributions, solution concentration and velocity of CO2 gas and solution are derived from the simulations. The results of the simulations provide fundamentals and insight understanding of the design of a proto-type demonstration system onboard a case ship. In addition to the key factors, the effect of atmosphere temperature was simulated and analyzed. Comparisons between the experiment and simulation have been conducted and the results have shown a good agreement. Optimized values of the factors are obtained from the comparisons and analyses. The numerical simulations of temperature effects on CO2 absorption rate and optimized temperature for the absorption process are also presented in the paper

Reviews on current carbon reduction technologies and experimental and numerical analysis on financial feasibility and practical application of a carbon absorption method

Global warming has become a popular topic and IMO’s regulations have come in forces to reduce carbon emission from international shipping by improving the energy efficiency with EEDI and EEOI. Carbon capture and storage is an alternative method utilizing different technologies to capture the CO2 from emission sources and storage/utilize them to reduce the carbon emission from exhaust gas or the content of CO2 in atmosphere. This paper reviews current carbon capture method and introduces a chemical absorption technology for carbon reduction on ships, which is a feasible method and applied by onshore industry. Experimental analysis indicates the average absorption rate for carbon dioxide feed in can reach 68%. A financial analysis is presented to evaluate a case ship in comparison with liquefaction method which indicates the absorption method is cost effective and earns profit after selling the final product from the chemical processes at the destination of a voyage. This paper also presents the design, analysis and validation of the numerical simulation model and a case ship study of practical absorption system installation is conducted based on the validated model

Parallel Graph Connectivity in Log Diameter Rounds

We study graph connectivity problem in MPC model. On an undirected graph with $n$ nodes and $m$ edges, $O(\log n)$ round connectivity algorithms have been known for over 35 years. However, no algorithms with better complexity bounds were known. In this work, we give fully scalable, faster algorithms for the connectivity problem, by parameterizing the time complexity as a function of the diameter of the graph. Our main result is a $O(\log D \log\log_{m/n} n)$ time connectivity algorithm for diameter-$D$ graphs, using $\Theta(m)$ total memory. If our algorithm can use more memory, it can terminate in fewer rounds, and there is no lower bound on the memory per processor. We extend our results to related graph problems such as spanning forest, finding a DFS sequence, exact/approximate minimum spanning forest, and bottleneck spanning forest. We also show that achieving similar bounds for reachability in directed graphs would imply faster boolean matrix multiplication algorithms. We introduce several new algorithmic ideas. We describe a general technique called double exponential speed problem size reduction which roughly means that if we can use total memory $N$ to reduce a problem from size $n$ to $n/k$, for $k=(N/n)^{\Theta(1)}$ in one phase, then we can solve the problem in $O(\log\log_{N/n} n)$ phases. In order to achieve this fast reduction for graph connectivity, we use a multistep algorithm. One key step is a carefully constructed truncated broadcasting scheme where each node broadcasts neighbor sets to its neighbors in a way that limits the size of the resulting neighbor sets. Another key step is random leader contraction, where we choose a smaller set of leaders than many previous works do