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INTENSIFICATION OF GRASSLAND-BASED DAIRY PRODUCTION AND ITS IMPACTS ON LAND, NITROGEN AND PHOSPHORUS USE EFFICIENCIES

Jouke OENEMA, Oene OENEMA

《农业科学与工程前沿（英文）》 2021年第8卷第1期页码 130-147 doi: 10.15302/J-FASE-2020376

摘要： Many grassland-based dairy farms are intensifying production, i.e., produce more milk per ha of land in response to the increasing demand for milk (by about 2% per year) in a globalized market. However, intensive dairy farming has been implicated for its resources use, ammonia and greenhouse gas emissions, and eutrophication impacts. This paper addresses the question of how the intensity of dairy production relates to N and P surpluses and use efficiencies on farms subjected to agri-environmental regulations. Detailed monitoring data were analyzed from 2858 grassland-based dairy farms in The Netherlands for the year 2015. The farms produced on average 925 Mg·yr milk. Milk production per ha ranged from<10 to>30 Mg·ha ·yr . Purchased feed and manure export strongly increased with the level of intensification. Surpluses of N and P at farm level remained constant and ammonia emissions per kg milk decreased with the level of intensification. In conclusion, N and P surpluses did not differ much among dairy farms greatly differing in intensity due to legal N and P application limits and obligatory export of manure surpluses to other farms. Further, N and P use efficiencies also did not differ among dairy farms differing in intensity provided the externalization of feed production was accounted for. This paper provides lessons for proper monitoring and control of N and P cycling in dairy farming.

关键词： ammonia externalization feed forage maize front runners manure production milk yield nitrogen surplus

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A review on front end conversion in ocean wave energy converters

Nagulan SANTHOSH,Venkatesan BASKARAN,Arunachalam AMARKARTHIK

《能源前沿（英文）》 2015年第9卷第3期页码 297-310 doi: 10.1007/s11708-015-0370-x

摘要： Harvesting the energy from ocean waves is one of the greatest attractions for energy engineers and scientists. Till date, plenty of methods have been adopted to harvest the energy from the ocean waves. However, due to technological and economical complexity, it is intricate to involve the majority of these energy harvesters in the real ocean environment. Effective utilization and sustainability of any wave energy harvester depend upon its adaptability in the irregular seasonal waves, situation capability in maximum energy extraction and finally fulfilling the economic barriers. In this paper, the front end energy conversions are reviewed in detail which is positioned in the first stage of the wave energy converter among other stages such as power take off (PTO) and electrical energy conversion. If the recent development of these front end energy conversion is well known then developing wave energy converter with economic and commercial viability is possible. The aim of this review is to provide information on front end energy conversion of a point absorber and emphasize the strategies and calamity to be considered in designing such kinds of devices to improve the energy harvesting competence. This will be useful to the engineers for speeding up the development of a matured point absorbing type wave energy converter.

关键词： wave energy converter point absorbers power take off (PTO) front end energy conversion

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Ultramicrostructure and clinical implications of satellite foci in front of the head of pterygium

LIU Haixia, XIANG Nan, ZHOU Xiongwu, HU Weikun, LI Guigang, ZHANG Hong

《医学前沿（英文）》 2007年第1卷第2期页码 211-214 doi: 10.1007/s11684-007-0040-4

摘要： In our previous studies, grey satellite foci were found in the front of heads of pterygia. This research was designed to investigate the ultramicrostructure and clinical implications of these satellite foci. The satellite foci were observed and counted under slit lamp biomicroscope. The patients with eye pterygia were divided into groups in terms of occupation, sex, age, length of history, grade of congestion, and size of the heads. The SPSS 13.0 software was used for statistical analysis. The cap areas and satellite foci were ultramicrostructurally examined. Among the total 62 eyes with pterygium, satellite foci were found in 34. The overall incidence of satellite foci was 54.8%. There were no significant differences in incidence among the subjects of different sex, age, and length of history. There were significant differences in incidence among the patients of different occupation, grades of congestion, and size of heads. Higher grades of congestion, outdoor occupations and larger pterygium heads were associated with higher incidence of satellite foci. High grades of congestion and bigger heads were also correlated with the number of satellite foci. Length of history bore no correlation with number of satellite foci. Histologically, the components of the cap areas and the foci were identical, with both consisting of mass of active fibroblasts. The activated fibroblasts existed in the natural tissue planes between Bowman s layer and basal cell layer. The fibroblasts in the satellite foci and the cap areas of a pterygium show some features of tumor cells and may play a vital role in the development and progression of a pterygium. The presence and amount of satellite foci around a pterygium can be used as an indicator for the speed of its growth.

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A family of non-conforming crack front elements of quadrilateral and triangular types for 3D crack problems

Guizhong XIE, Fenglin ZHOU, Hao LI, Xiaoyu WEN, Fannian MENG

《机械工程前沿（英文）》 2019年第14卷第3期页码 332-341 doi: 10.1007/s11465-019-0540-3

摘要： This study focuses on establishing non-conforming crack front elements of quadrilateral and triangular types for 3D crack problems when the dual boundary element method is applied. The asymptotic behavior of the physical variables in the area near the crack front is fully considered in the construction of the shape function. In the developed quadrilateral and triangular crack front elements, the asymptotic term, which captures the asymptotic behavior of the physical variable, is multiplied directly by the conventional Lagrange shape function to form a new crack front shape function. Several benchmark numerical examples that consider penny-shaped cracks and straight-edge crack problems are presented to illustrate the validity and efficiency of the developed crack front elements.

关键词： Taylor expansion crack front elements stress intensity factors dual boundary element method

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Influence of using amorphous silicon stack as front heterojunction structure on performance of interdigitated

Rui JIA,Ke TAO,Qiang LI,Xiaowan DAI,Hengchao SUN,Yun SUN,Zhi JIN,Xinyu LIU

《能源前沿（英文）》 2017年第11卷第1期页码 96-104 doi: 10.1007/s11708-016-0434-6

摘要： Interdigitated back contact-heterojunction (IBC-HJ) solar cells can have a conversion efficiency of over 25%. However, the front surface passivation and structure have a great influence on the properties of the IBC-HJ solar cell. In this paper, detailed numerical simulations have been performed to investigate the potential of front surface field (FSF) offered by stack of n-type doped and intrinsic amorphous silicon (a-Si) layers on the front surface of IBC-HJ solar cells. Simulations results clearly indicate that the electric field of FSF should be strong enough to repel minority carries and cumulate major carriers near the front surface. However, the over-strong electric field tends to drive electrons into a-Si layer, leading to severe recombination loss. The n-type doped amorphous silicon (n-a-Si) layer has been optimized in terms of doping level and thickness. The optimized intrinsic amorphous silicon (i-a-Si) layer should be as thin as possible with an energy band gap ( ) larger than 1.4 eV. In addition, the simulations concerning interface defects strongly suggest that FSF is essential when the front surface is not passivated perfectly. Without FSF, the IBC-HJ solar cells may become more sensitive to interface defect density.

关键词： amorphous silicon front surface field simulations interdigitated back contact-heterojunction solar cells