Research on Pesticide Residues of Cypermethrin in Lettuce

In order to find the effective method to reduce pesticide residues in vegetables, and promote the healthy development of vegetable industry. The paper used chlorothalonil, fenvalerate, dimethoate widely used pesticides as experimental material, using GC method to measure residual dynamics of vegetable pesticide. The results show that： fenvalerate, dimethoate, chlorothalonil pesticide residues in lettuce was higher than that tomato in the application day, respectively reach at 42.9%, 44.9%, 57.8%, pesticide degradation rate in open land were significantly higher than those in greenhouse within 5-20 days. The test showed that： the degradation of pesticide amount is in 8.77%r-19.64% within 1 days. The initial concentration of pesticides on vegetables are relevant with surface area of vegetable edible parts; the degradation speed of pesticide degradation rate in greenhouse vegetable is obviously slower than the open field vegetable; pesticide deposition phenomenon is an important factor affecting the pesticide residues in greenhouse.

Model-driven degradation modeling approaches:Investigation and review

The second law of thermodynamics implies that any animate and inanimate systems degrade and inevitably stops functioning.It is irreversible over time that can be labeled as‘‘the degradation arrow of time".From perspective of products’reliability design,it is essential to build appropriate models of describing the degradation arrow of time.The current modeling approaches mainly include the model-driven(having assumed forms based on cognitive experience of mankind)and data-driven(using data learning techniques without form hypothesis)approaches.In this paper,we just investigate and review the model-driven degradation approaches,hoping to provide suggestions of the model construction or selection for scholars or engineers.First,for the single mechanism,degradation law models and stochastic process models are classified as separately depicting the tendency and fluctuation of degradation.For the degradation law model,we propose the concept of meta-models as original types for various personal models.For the stochastic process model,two main types including the non-monotonic and monotonical types are presented.Then,four multi-mechanism degradation types are discussed,that are competitive degradation,multi-stage degradation,coexistence of degradation and impact,and coexistence of degradation and failure.Besides,for the multi-performance degradation,independent and coupling models are introduced.The forms,connotations,applicability and insufficiency of these models are described with a series of examples from the literature and our own experiences.The final explicit suggestions about the potential future work are provided for the development of new degradation models.