Groundwater plays a major role in agro-hydrological processes in the North China Plain (NCP). The NCP is facing a water deficit, due to a rapid decline in the water table because of the double cropping system. A two crop (maize and wheat) rotation is required to balance the food supply and demand, which leads to an imbalance between evapotranspiration (ET) and precipitation. Thus, there has been a decline of about 1.35 m yr−1 of groundwater (Luancheng Agroecosystem Experimental Station (LAES), NCP) during the last 10 years. Lysimeter experiments were conducted under different irrigation treatments (flood, surface drip, and subsurface drip) to account for ET in the selection of a suitable irrigation method. Subsurface drip irrigation reduced ET by 26% compared to flood irrigation, and 15% compared to surface drip irrigation, with significant grain yield and biomass formation due to decreased evaporation losses. Grain yield, yield components, and above ground biomass were similar in subsurface drip and flood irrigation. However, these biomass parameters were lower with surface drip irrigation. Furthermore, subsurface drip irrigation increased the crop water productivity (24.95%) and irrigation water productivity (19.59%) compared to flood irrigation. The subsurface irrigated plants showed an increase in net photosynthesis (~10%), higher intrinsic water use efficiency (~36%), lower transpiration rate (~22%), and saved 80 mm of water compared to flood irrigation. Our findings indicate that subsurface drip irrigation can be adopted in the NCP to increase water use efficiency, optimize grain yield, and minimize water loss in order to address scarcity.
Energy crisis and environmental pollution have become global problems, and the increasing use of energy has caused climate change. Electric vehicle (EV) is regarded as the future of the automotive industry, because of the lesser impact on the environment than traditional vehicles. In recent years, electric vehicles have developed rapidly. However, the development of charging points and service cannot adapt to the development trend of EV. In urban areas, the distribution characteristics of street lighting and charging points are similar. Therefore, the street lighting pole with EV charging is proposed. However, due to the capacity limit of public grid, the single hybrid pole is only suitable for slow charging. This paper proposes hybrid poles group based on renewable energy, street lighting, and EV charging, which can realize fast charging and slow charging based on DC micro-grid with help of energy storage device. For studying the suitable number in a group of smart hybrid pole, the efficiency model of smart hybrid poles group is proposed. The efficiency model indicates that the group approach has better performance than the single pole, which provides a theoretical basis for practical construction.Energies 2018, 11, 3445 2 of 17 of car to pole is about 8:1, so it is less than the theoretical ratio of 1:1~1.2. Currently, it needs to build more charging poles [6]. In 2020, 435 thousand charging points will be built in Beijing to satisfy the requirement for 600 thousand EV. Moreover, the lack of an adequate publicly accessible charging infrastructure is considered to be a major obstacle to the growth of European market [15].Charging facilities generally include private points and charging station. In recent years, it has been suggested that EV charging points can be integrated with the existing street lighting network, because the distribution characteristic of street lighting in the urban area is similar with the distribution characteristic of charging points. Therefore, the street lighting pole with EV charging system is presented [16]. Smith et al. introduced the concept of a DC Lighting and Charging network to increase the power transfer capability of the lighting cables in order to enable charging of EVs at a higher energy efficiency than AC [16]. In addition, BMW and Ubitricity company, respectively, have deployed a street-light charging solution [17,18], which contribute to a greener city. However, this single street-light charging pole is only suitable for EV slow charging because the power of public grid for a single pole is not enough for EV fast charging.For handling the incompatibility between fast charging and the power limit, the hybrid poles group method with renewable energy, street lighting, and EV charging systems are proposed based on DC micro-grid in this paper. The energy storage devices in hybrid poles group can collaboratively work with the help of DC micro-gird and provide enough electric power for fast charging.The remainder of the paper is organized as follows: Section 2 presents the archi...
As the quantity of direct current (DC) load and wireless power transmission (WPT) devices are continuously increasing in building, in order to efficiently utilize renewable energy (which outputs DC power) such as photovoltaic (PV), especially for building integrated photovoltaic (BIPV), and regeneration energy from elevators (which also outputs DC power), a novel building power distribution system architecture is explored in consideration of the characteristics of supply and demand-side in this paper. The proposed architecture is a hybrid framework integrated with conventional alternating current (AC) power distribution system, DC power distribution and WPT system. The applied AC and DC hybrid power distribution system has higher conversion efficiency than a single AC power system, which indicates that the former is becoming an important trend of building power distribution. In addition, the results of experimental test in a case study suggest that the proposed architecture can provide fine service for efficient application of renewable energy and regeneration energy in building. The obtained results also can serve as a foundation to promote the development of building power distribution system and related practical application in building.
Recommender systems have been widely deployed on E-commerce websites. The cold start problem of making effective recommendations to new users without any historical data on the website is still challenging. These new users often have some available information, such as search keywords, before visiting the website. It is natural to use the information to predict users' preference, such that an immediate recommendation is possible. In this paper, we propose a new product recommendation approach for new users based on the implicit relationships between search keywords and products. The relationships between keywords and products are represented in a graph and relevance of keywords to products is derived from attributes of the graph. The relevance information will be utilized to predict preferences of new users. A preliminary experiment is conducted and shows that our approach outperforms the traditional approach (Recommending Most Popular Products).
Elevators were reported to cause an important part of building energy consumption. In general, each elevator has two operation states: The load state and power regeneration state. During operation, it has the potential to save energy by using regeneration power efficiently. In existing research, a set of energy storage devices are installed for every elevator, which is highly costly. In this paper, an energy conservation approach for elevators based on a direct current (DC) micro-grid is proposed, which has better economy. Then, an innovative energy-efficient device for the elevator group is designed based on a supercapacitor with similar characteristics and lifetimes. In a high-rise building case study, the experimental test and field data collection show that the innovative approach could result in a high energy efficiency within 15.87–23.1% and 24.1–54.5%, respectively. It is expected that the proposed method and designed device could be employed practically, saving energy consumption for elevator reconstruction.
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