In recent years, people pay more and more attention to travel safety and travel risks. Tourism risk perception is a quantitative assessment of tourism security. Destination risk perception of tourists directly affects tourists purchase intention. The asymmetry of the objective existence of tourist safety information and the subjective perception of tourists determines that tourists are extremely sensitive to travel risks. The inevitability of tourism risks requests that tourists have a certain level knowledge of destination environment. This study aimed to systematically review existing researches of tourism risk perception. The study shows: (1) Tourism risk perception includes three views, which were subjective feelings, objective evaluation and the cognition of exceeding the threshold portion of the negative consequences or negative impact that may occur during travel. (2) The subjective factors of tourism risk perception were the physical characteristics and psychological processes. The objective factors include physical risk, economic risk, equipment risk, social risk, psychological risk, time risk and opportunity loss. (3) The multi-dimensional model and the two-factor model were the two main types of risk perception assessment models. The survey (with interviews) and mathematical statistical analysis were the main research methods. Besides, this article highlights three points. (1) There is a certain critical value for travel risk perception of tourists; (2) cognitive ability is an important factor affecting the level of tourists objective risk perception; and (3) quantitative assessment of tourism risk perception level is helpful to the tourism decision making and destination management.

Ambitious targets to reduce emissions caused by aviation in the light of an expected ongoing rise of the air transport demand in the future drive the research of propulsion systems with lower CO 2 emissions. Regional hybrid electric aircraft (HEA) powered by conventional gas turbines and battery powered electric motors are investigated to test hybrid propulsion operation strategies. Especially the role of the battery within environmentally friendly concepts with significantly reduced carbon footprint is analyzed. Thus, a new simulation approach for HEA is introduced. The main findings underline the importance of choosing the right power-to-energy-ratio of a battery according to the flight mission. The gravimetric energy and power density of the electric storages determine the technologically feasibility of hybrid concepts. Cost competitive HEA configurations are found, but do not promise the targeted CO 2 emission savings, when the well-to-wheel system is regarded with its actual costs. Sensitivity studies are used to determine external levers that favor the profitability of HEA.

Abstract:The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL) searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF) and Hybrid Laminar Flow Control (HLFC) to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS) solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today's turbulent aircraft.

Abstract:It is always a strong motivation for aeronautic researchers and engineers to reduce the aircraft emissions or even to achieve emission-free air transport. In this paper, the impacts of different game-changing technologies together on the reduction of aircraft fuel consumption and emissions are studied. In particular, a general tool has been developed for the technology assessment, integration and also for the overall aircraft multidisciplinary design optimization. The validity and robustness of the tool has been verified through comparative and sensitivity studies. The overall aircraft level technology assessment and optimization showed that promising fuel efficiency improvements are possible. Though, additional strategies are required to reach the aviation emission reduction goals for short and medium range configurations.