【目的】杂草是限制油菜丰产的重要因素之一,养分的合理管理对杂草防控起到关键作用。本研究在大田条件下,探究氮、磷、钾肥施用量对油菜与杂草生物量及养分竞争的影响,为生态控草和农业可持续发展提供依据。【方法】在湖北省武穴市开...【目的】杂草是限制油菜丰产的重要因素之一,养分的合理管理对杂草防控起到关键作用。本研究在大田条件下,探究氮、磷、钾肥施用量对油菜与杂草生物量及养分竞争的影响,为生态控草和农业可持续发展提供依据。【方法】在湖北省武穴市开展田间试验,采用单因素试验设计,设置氮(0、90、180和270 kg N·hm^(-2),分别用N0、N1、N2和N3表示)、磷(0、45、90和135 kg P_(2)O_(5)·hm^(-2),分别用P0、P1、P2和P3表示)、钾(0、60、120和180 kg K_(2)O·hm^(-2),分别用K0、K1、K2和K3表示)各4个不同用量梯度田间试验。在油菜成熟期,测定油菜籽产量、油菜和杂草的生物量及相应的养分含量,计算养分积累量,分析油菜与杂草的养分竞争关系及其对肥料用量的响应。【结果】施肥显著提高油菜籽产量、地上部总生物量和相应的养分积累量,在氮、磷、钾3种养分中,油菜生长和养分吸收对缺磷最敏感。N0、P0和K0处理的油菜籽产量分别为560、227和1490 kg·hm^(-2),分别只占相应最高产量(N3、P3和K3处理)的18.2%、7.5%和50.1%,油菜地上部总生物量随着养分的投入变化趋势与籽粒产量一致。N0、P0和K0处理的油菜相应养分积累量依次为19.96、0.88和26.21 kg·hm^(-2),分别占相应最高养分积累量的12.24%、3.72%、22.26%。杂草生物量和相应的养分积累量随着3种养分施用量的增加不断下降(磷肥用量试验P2处理最高除外),N0、P0和K0处理的杂草生物量分别为1365、3060和1535 kg·hm^(-2),分别是相应最低杂草生物量(N3、P2和K3处理)的7.59倍、5.19倍和3.61倍;N0、P0和K0处理杂草的相应养分积累量依次为17.60、1.91和9.38 kg·hm^(-2),分别是相应最低杂草养分积累量(N3、P2和K3处理)的3.78倍、1.54倍和1.52倍。与磷和钾相比,杂草与油菜对氮的养分竞争力更强,在各氮肥处理时杂草的氮含量均高于油菜。施肥提高了油菜与杂草的生物量和相应养分积累量的比值,除不施磷处理外,其他所有处理的油菜与杂草的生物量和相应养分积累量的比值均大于1,且这个比值随施肥量的增加而不断提高(磷肥用量试验P2处理最高除外),说明充足的养分供应可以显著提高油菜的生长势及养分吸收能力,发挥了抑制杂草的作用。【结论】冬油菜田间杂草的危害程度受养分供应状况的控制,施肥有效弥补了油菜生长前期除草剂不能完全控制整个生育期杂草的不足,氮、磷、钾肥充足施用能显著降低杂草生物量和相应的养分积累量,油菜与杂草竞争能力对3种养分的响应程度为磷>氮>钾。展开更多
Today's Internet architecture provides only "best effort" services,thus it cannot guarantee quality of service(QoS) for applications.Software Defined Network(SDN)is a new approach to computer networking ...Today's Internet architecture provides only "best effort" services,thus it cannot guarantee quality of service(QoS) for applications.Software Defined Network(SDN)is a new approach to computer networking that separates control plane and forwarding planes,and has the advantage of centralized control and programmability.In this paper,we propose HiQoS that provides QoS guarantees using SDN.Moreover,HiQoS makes use of multiple paths between source and destination and queuing mechanisms to guarantee QoS for different types of traffic.Experimental results show that our HiQoS scheme can reduce delay and increase throughput to guarantee QoS.Very importantly,HiQoS recovers from link failure very quickly by rerouting traffic from failed path to other available path.展开更多
As one of Qo S(Quality of Service) metrics, delay is critical important to delay sensitive applications, such as interactive video, network game and online surgery. In this paper, we exploit SDN(Software Defined Netwo...As one of Qo S(Quality of Service) metrics, delay is critical important to delay sensitive applications, such as interactive video, network game and online surgery. In this paper, we exploit SDN(Software Defined Networking) advantages to solve delay Qo S problem. Our work mainly focuses on SDN based queuing delay estimation with real traffic and end-to-end delay control. First, we propose a queuing estimation model and extended it for end-to-end delay of the whole path. It is proved to be feasible and accurate with experimental results in SDN environment. Second, in order to demonstrate the use of our proposed model, we also implement an end-to-end delay control application in SDN. It fulfills specific delay Qo S requirements by dynamically switching flows to a suitable queue based on estimation results and delay requirements.展开更多
文摘【目的】杂草是限制油菜丰产的重要因素之一,养分的合理管理对杂草防控起到关键作用。本研究在大田条件下,探究氮、磷、钾肥施用量对油菜与杂草生物量及养分竞争的影响,为生态控草和农业可持续发展提供依据。【方法】在湖北省武穴市开展田间试验,采用单因素试验设计,设置氮(0、90、180和270 kg N·hm^(-2),分别用N0、N1、N2和N3表示)、磷(0、45、90和135 kg P_(2)O_(5)·hm^(-2),分别用P0、P1、P2和P3表示)、钾(0、60、120和180 kg K_(2)O·hm^(-2),分别用K0、K1、K2和K3表示)各4个不同用量梯度田间试验。在油菜成熟期,测定油菜籽产量、油菜和杂草的生物量及相应的养分含量,计算养分积累量,分析油菜与杂草的养分竞争关系及其对肥料用量的响应。【结果】施肥显著提高油菜籽产量、地上部总生物量和相应的养分积累量,在氮、磷、钾3种养分中,油菜生长和养分吸收对缺磷最敏感。N0、P0和K0处理的油菜籽产量分别为560、227和1490 kg·hm^(-2),分别只占相应最高产量(N3、P3和K3处理)的18.2%、7.5%和50.1%,油菜地上部总生物量随着养分的投入变化趋势与籽粒产量一致。N0、P0和K0处理的油菜相应养分积累量依次为19.96、0.88和26.21 kg·hm^(-2),分别占相应最高养分积累量的12.24%、3.72%、22.26%。杂草生物量和相应的养分积累量随着3种养分施用量的增加不断下降(磷肥用量试验P2处理最高除外),N0、P0和K0处理的杂草生物量分别为1365、3060和1535 kg·hm^(-2),分别是相应最低杂草生物量(N3、P2和K3处理)的7.59倍、5.19倍和3.61倍;N0、P0和K0处理杂草的相应养分积累量依次为17.60、1.91和9.38 kg·hm^(-2),分别是相应最低杂草养分积累量(N3、P2和K3处理)的3.78倍、1.54倍和1.52倍。与磷和钾相比,杂草与油菜对氮的养分竞争力更强,在各氮肥处理时杂草的氮含量均高于油菜。施肥提高了油菜与杂草的生物量和相应养分积累量的比值,除不施磷处理外,其他所有处理的油菜与杂草的生物量和相应养分积累量的比值均大于1,且这个比值随施肥量的增加而不断提高(磷肥用量试验P2处理最高除外),说明充足的养分供应可以显著提高油菜的生长势及养分吸收能力,发挥了抑制杂草的作用。【结论】冬油菜田间杂草的危害程度受养分供应状况的控制,施肥有效弥补了油菜生长前期除草剂不能完全控制整个生育期杂草的不足,氮、磷、钾肥充足施用能显著降低杂草生物量和相应的养分积累量,油菜与杂草竞争能力对3种养分的响应程度为磷>氮>钾。
基金supported partly by NSFC(National Natural Science Foundation of China)under grant No.61371191 and No.61472389
文摘Today's Internet architecture provides only "best effort" services,thus it cannot guarantee quality of service(QoS) for applications.Software Defined Network(SDN)is a new approach to computer networking that separates control plane and forwarding planes,and has the advantage of centralized control and programmability.In this paper,we propose HiQoS that provides QoS guarantees using SDN.Moreover,HiQoS makes use of multiple paths between source and destination and queuing mechanisms to guarantee QoS for different types of traffic.Experimental results show that our HiQoS scheme can reduce delay and increase throughput to guarantee QoS.Very importantly,HiQoS recovers from link failure very quickly by rerouting traffic from failed path to other available path.
基金supported by the project of 111 Intelligence Introduction for Innovation at Communication University of ChinaNSFC under grant No.61371191,No.61472389 and No.61201236ETH Zurich for the valuable discussion about H2020 MAMI project related to TCP modeling in this work
文摘As one of Qo S(Quality of Service) metrics, delay is critical important to delay sensitive applications, such as interactive video, network game and online surgery. In this paper, we exploit SDN(Software Defined Networking) advantages to solve delay Qo S problem. Our work mainly focuses on SDN based queuing delay estimation with real traffic and end-to-end delay control. First, we propose a queuing estimation model and extended it for end-to-end delay of the whole path. It is proved to be feasible and accurate with experimental results in SDN environment. Second, in order to demonstrate the use of our proposed model, we also implement an end-to-end delay control application in SDN. It fulfills specific delay Qo S requirements by dynamically switching flows to a suitable queue based on estimation results and delay requirements.
