The rapid development of industry and urban areas, population growth and rising living standards have all resulted in an increased water demand for non-agricultural uses in the North China Plain, therefore decreasing the water availability for irrigation. Technologies that favour a reduced demand and water-saving practices in irrigation are required to assure the sustainability of water use in agricultural production. This paper presents main research results relative to the integration of water and soil management technologies which may contribute to improving the use of water and land in agricultural production, reducing demand for irrigation, and more efficient use of groundwater. Improved estimates of crop irrigation requirements, better irrigation scheduling for the winter wheat crop and improved surface irrigation systems, result in water saving corresponding to about 100 mm in very dry years and up to 250 mm in average years with a small yield increase. These savings represent 16-33% of water use during the wheat crop season. Improvements in soil management lead to improved soil fertility and physical properties (including hydraulic conductivity). These improvements produce potential increases in summer maize yields of between 10 and 20%. Copyright # 2003 John Wiley & Sons, Ltd.key words: evapotranspiration; crop irrigation requirements; irrigation scheduling; basin irrigation; tillage; soil amendments; reduced demand; wheat; maize RÉ SUMÉ Dans la Plaine du Nord de la Chine, le développement rapide de l'industrie et des zones urbaines, la croissance de la population et l'amélioration de leur niveau de vie ont donné lieu à une demande en eau pour des usages non agricoles toujours accrue, ce qui a fortement diminué sa disponibilité pour l'irrigation. Des technologies qui favorisent la réduction de la demande agricole et l'économie d'eau en irrigation sont donc requises pour assurer la durabilité de l'utilisation de l'eau en irrigation. Cet article présente des résultats de recherche relatifs à la gestion de l'eau et du sol à l'échelle de la parcelle qui peuvent contribuer à améliorer l'utilisation de l'eau et de la terre, la réduction de la demande et l'utilisation plus efficiente des eaux souterraines. En irrigation, les solutions proposées concernent l'estimation plus rigoureuse des besoins en eau des cultures irriguées, l'amélioration de la conduite des arrosages et la modernisation des systèmes d'irrigation de surface, ce qui peut conduire à réduire la demande de 100 mm pour les années de sécheresse et jusqu'à 250 mm pour l'année moyenne. Ces réductions représentent à peu près 16 à 33% de l'eau utilisée pour l'irrigation du blé, la principale culture irriguée dans la région. D'autre part, l'amélioration des pratiques de gestion du sol peut conduire à des effets positifs sur les proprietés hydrauliques et la fertilité du sol, ce qui pourrait conduire à augmenter la productivité du maïs en pluvial de 10 à 20% dû tant à une meilleure utilisation des pluies d'été qu'à des conditions de sol plus propi...
In recent years, China has felt the urgent need to address the ecological issues caused by its rapid economic growth. In doing so, one challenge it faces is how to address the interests of the various stakeholders involved. To this end, the Government of China at various levels has been exploring and implementing policies, measures and projects that serve as mechanisms or measures of eco-compensation. This article attempts to capture some of the key policies and practices established to date in China. The article concludes by outlining China's possible future priority actions in eco-compensation and key challenges ahead.
Multi-scale image segmentation and the selection of optimal segmentation parameters are the key processes in the object-oriented information extraction of high-resolution remote sensing images. The accuracy of remote sensing special subject information depends on this extraction. On the basis of WorldView-2 high-resolution data, the optimal segmentation parameters methodof object-oriented image segmentation and high-resolution image information extraction, the following processes were conducted in this study. Firstly, the best combination of the bands and weights was determined for the information extraction of high-resolution remote sensing image. An improved weighted mean-variance method was proposed andused to calculatethe optimal segmentation scale. Thereafter, the best shape factor parameter and compact factor parameters were computed with the use of the control variables and the combination of the heterogeneity and homogeneity indexes. Different types of image segmentation parameters were obtained according to the surface features. The high-resolution remote sensing images were multi-scale segmented with the optimal segmentation parameters. Ahierarchical network structure was established by setting the information extraction rules to achieve object-oriented information extraction. This study presents an effective and practical method that can explain expert input judgment by reproducible quantitative measurements. Furthermore the results of this procedure may be incorporated into a classification scheme.
BackgroundTimolol Maleate is a non-selective beta-adrenergic blocker that is commonly used to treat open-angle glaucoma. Despite its topical administration, ophthalmic timolol enters systemic circulation and produces a systemic beta-adrenergic blockade. We report a case of long-term timolol use that uncovered and worsened an underlying cardiac conduction defect demonstrated as a third degree atrioventricular (AV) block.Case presentationA 62-year old male with a 13-year history of glaucoma was hospitalized due to shortness of breath, dizziness, and amaurosis. Electrocardiography indicated a heart rate (HR) of 29 bpm with complete atrioventricular (AV) block, and the HR was significantly increased with the treatment of isoprenaline. However, the patient experienced bradycardic episodes (− 20 Δbpm) immediately after self-administration of timolol eye drops. The AV block and bradycardia resolved 48-h after timolol cessation. The man was discharged 1 week later with an asymptomatic first-degree A-V block. However, he presented with a worsened A-V block at his one-year checkup.ConclusionWe conclude that chronic topical timolol administration may aggravate a cardiac conduction defect leading to an AV block that is only temporarily resolved by timolol cessation. Patients taking timolol should be routinely monitored for cardiovascular aberrations and if any detected, immediately discontinue timolol therapy. Individuals experiencing timolol induced cardiovascular side effects should receive long term follow-up even if symptoms resolve, as they may be indicative of an underlying conduction defect.
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