Spatio-temporal Keyframe Control of Traffic Simulation using Coarse-to-Fine Optimization

We present a novel traffic trajectory editing method which uses spatio-temporal keyframes to control vehicles during the simulation to generate desired traffic trajectories. By taking self-motivation, path following and collision avoidance into account, the proposed force-based traffic simulation framework updates vehicle's motions in both the Frenet coordinates and the Cartesian coordinates. With the way-points from users, lane-level navigation can be generated by reference path planning. With a given keyframe, the coarse-to-fine optimization is proposed to efficiently generate the plausible trajectory which can satisfy the spatio-temporal constraints. At first, a directed state-time graph constructed along the reference path is used to search for a coarse-grained trajectory by mapping the keyframe as the goal. Then, using the information extracted from the coarse trajectory as initialization, adjoint-based optimization is applied to generate a finer trajectory with smooth motions based on our force-based simulation. We validate our method with extensive experiments

The Viscosity Characteristics for the Mixed Refrigerant HFO-1234yf + HFC-152a

Refrigerants are improved with the development of refrigeration and air conditioning industry. Because of the long-term use of chlorine-containing halogenated hydrocarbon substances, the ozone depletion and global warming become important issues around the world. Searching for refrigerants with low GWP (Global Warming Potential) and zero ODP (Ozone Depletion Potential) is urgent. HFC-134a used to be a widely used refrigerant with zero ODP. However, its high GWP of 1300 and long atmospheric lifetime of 14 years would cause the problem of global warming. Thus, for the sake of environment, the substitution of HFC-134a is imperative. In recent years, HFO-1234yf has been regarded as one of the widely used substitutions of HFC-134a because of low GWP of 4 and similar thermophysical properties to HFC-134a. However, its COP is slightly smaller than that of HFC-134a. In order to make better use of HFO-1234yf, some HFO-1234yf + HFCs or HFO-1234yf + HCs binary mixtures were proposed as alternative refrigerants. HFC-152a with low GWP of 140 and a short atmospheric lifetime of 1.5 years was selected as component in refrigerant mixtures. The mixture HFO-1234yf + HFC-152a is a promising alternative refrigerant. Before the actual application of alternative refrigerants in the refrigeration and air conditioning systems, thermophysical properties of mixed refrigerants need to be carefully investigated. Knowledge of viscosity characteristics, as one of the major concerns in the study of the thermophysical properties of alternative refrigerants, has significant impact on heat transfer and pressure drop in the flow, and viscosity data with high accuracy are of considerable value in the calculation of heat transfer and fluid flow. Â Â Â Â Â Â Thus, in this work, the measurement of liquid viscosity of the mixture was carried out with a new type of gravitational capillary viscometer developed in our previous work. The liquid viscosity experimental system used in this paper consists of a gravitational capillary viscometer made of glass, a pressure vessel with sight glasses, a thermostatic bath system and a measurement system. The measurement system consists of a high accurate temperature measure system (the standard temperature uncertainty is less than 0.011K) and a high accurate pressure measure system (the standard pressure uncertainty is within 1.4 kPa). The expanded uncertainty of dynamic viscosity was 1.58 %. The reliability of the experimental apparatus has been validated with HFO-1234yf and the binary mixture HFC-22 + HFC-134a (0.7 + 0.3, by mole fraction) in previous work. Based on this, the gravitational capillary viscometer was firstly calibrated with HCFC-22, and then, the liquid viscosity data of the binary mixture HFO-1234yf + HFC-152a (0.81 + 0.19, by mole fraction) were given from 278.15 K to 333.15 K. Two most commonly used viscosity models based on the Andrade equation were used to correlate the experimental data of the mixture HFO-1234yf + HFC-152a (0.81 + 0.19, by mole fraction). The correlation results were discussed

The innovative application of learning companions in virtual singapura,”

ABSTRACT Virtual Singapura (VS) is a virtual world based learning environment designed to facilitate learning of the plant transport system. During field studies of VS, we observed that students in virtual world tend to be attracted by visual and auditorial stimuli and be distracted from learning objectives. Also, intensive cognitive load can affect students' learning experience. To address these issues, we propose two types of companion agent, namely curious companion and remembrance companion. Results collected from the field studies indicate advantages of learning companion augmented virtual world in enhancing students' learning experience

UAV first view landmark localization with active reinforcement learning

We present an active reinforcement learning framework for unmanned aerial vehicle (UAV) first view landmark localization. We formulate the problem of landmark localization as that of a Markov decision process and introduce an active landmark-localization network (ALLNet) to address it. The aim of the ALLNet is to locate a bounding box that surrounds the landmark in a first view image sequence. To this end, it is trained in a reinforcement learning fashion. Specifically, it employs support vector machine (SVM) scores on the bounding box patches as rewards and learns the bounding box transformations as actions. Furthermore, each SVM score indicates whether or not the landmark is detected by the bounding box such that it enables the ALLNet to have the capability of judging whether the landmark leaves or re-enters a first view image. Therefore, the operation of the ALLNet is not only dominated by the reinforcement learning process but also supplemented by an active learning motivated manner. Once the landmark is considered to leave the first view image, the ALLNet stops operating until the SVM detects its re-entry to the view. The active reinforcement learning model enables training a robust ALLNet for landmark localization. The experimental results validate the effectiveness of the proposed model for UAV first view landmark localization

Applications of Aluminum Alloys in Rail Transportation

This chapter focus on the latest applications of aluminum alloys in rail transportation field. The typical high-strength aluminum alloys used on high speed train is introduced. The unique properties of aluminum alloys are analyzed. The detailed application is illustrated including car-body, gear box and axle box tie rod. The main challenges encountered in the application are also mentioned. The key manufacturing techniques, such as casting, forming, welding, are analyzed. Finally, the future improvement directions for better application is summarized. It is expected to set up a bridge for materials providers, equipment manufacturers and end-users, thereby promoting the advance of manufacturing technology and application of aluminum alloys in wider fields

Subsidized overexpansion of Chinese firms

This paper examines the economic consequences of public subsidies to listed firms in China. It reveals that public subsidies can significantly increase the chance of firm overinvestment. However, they do not necessarily resolve the underinvestment problem. These results appear robust when we test various types of subsidies separately, as well as when we analyze the influence of subsidies on the investment-Q sensitivity. Further investigation shows that dividend payout has an important moderating role in this relationship between subsidies and investment. Firms with subsidies, especially those that pay higher cash dividends, have lower future stock returns and valuations than comparable non-subsidized firms. Overall, the main findings of this paper signal a clear government failure to correct market failure in the Chinese capital market. © 201