With the recent development of autonomous driving technology, many researchers have studied autonomous mobile robots. Accordingly, they are developing diverse mobile robot actuators. However, most actuators mainly use reducers made of chains, belts, multi-stage gears, etc. So the volume and size of the actuators increase, and power transmission efficiency tends to be relatively low. Therefore, this study has proposed the reducer of the mobile robot actuator using a complex planetary gear train with small volume and high power transmission efficiency, and has confirmed the stability of the proposed reducer through finite element analysis.

Water resources in Republic of Korea have been mainly supplied by the artificial reservoirs and lakes due to severely unbalanced rainfall. rainfall through the year. The lakes and reservoirs in which littoral zones have been damaged in a dry season usually have a big difference between high and low water level. In this study, We examined the effects of artificial floating island (AFI) in the Lake Baekgoki at Jin-Cheon, Chungcheongbuk-do, Korea. Phytoplankton is flora as 29 genera and 39 species, and the dominant species were Synedra acus, Lyngbya sp. and Cryptomonas sp., etc. The plankton numbers gradually decreased after installation of the AFI. In contrast with the phytoplankton, zooplankton individuals increased under the AFI, offering the habitats for zooplankton. Fish fauna were three families and seven species and 76 individuals were counted the AFI. The artificial vegetated island showed the significant effects on the restoration of lake ecosystem.

Among the functions of ecosystem, nutrients cycle is the most important for sustaining natural system. But in modernized and industrialized countries, the product consumes the resources and make wastes. This means that valuable resources are turning to waste through product. Waste water is one of the product from the valuable resources, so waste water is no more waste and it can be used as valuable resources for other process by using natural ecosystem. By the conventional wastewater treatment systems, the “zero discharge” could not be achieved by several factors. Shortage of resources is one of the reasons. Secondly, by the environmental engineering, the pollutants are only transformed from one medium to another. Thirdly, for eliminating the pollutants, fossil fuel must be used, which means another pollution. Self-designed and solar energy based ecotechnology could be an alternative method which solve the local, regional and global environmental problems properly should be found out. Already ecotechnology was defined as “the design of human society with it natural environment for the benefit of both”. By using the functions of ecosystem, such as food web, energy flow, nutrients cycles and homeostasis, pollutants can be eliminated, concentrated and transformed to nature. The major purpose of mechanical wastewater treatment systems is focused on the large quantity of domestic wastewater. But, small quantity of domestic wastewater is not concerned by public treatment because economic and technical difficulty. However, for improvement of water quality of streams and rivers, the small quantity of domestic wastewater must be purified. Here, some eco-technologies for water quality improvement installed in Korea are introduced. The artificial wetland, artificial food web and artificial vegetation island are installed in polluted and ecologically disturbed areas. These methods are not perfectly solving the environmental problems, and they are acting as alternative methods for clean up of polluted and restoration of disturbed ecosystems.

The main goal of e-learning systems is just-in-time knowledge acquisition. Rule-based elearning systems, however, suffer from the mesa effect and the cold start problem, which both result in low user acceptance. E-learning systems suffer a further drawback in rendering the implementation of a natural interface in humanoids difficult. To address these concerns, even exceptional questions of the learner must be answerable. This paper aims to propose a method that can understand the learner’s verbal cues and then intelligently explore additional domains of knowledge based on crowd data sources such as Wikipedia and social media, ultimately allowing for better answers in real-time. A prototype system was implemented using the NAO platform.