This paper is a contribution to graded model theory, in the context of mathematical fuzzy logic. We study characterizations of classes of graded structures in terms of the syntactic form of their first-order axiomatization. We focus on classes given by universal and universal-existential sentences. In particular, we prove two amalgamation results using the technique of diagrams in the setting of structures valued on a finite MTL-algebra, from which analogues of the Łoś-Tarski and the Chang-Łoś-Suszko preservation theorems follow.

中文翻译：

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数学模糊逻辑中一阶结构类的句法表征。

本文在数学模糊逻辑的背景下，对分级模型理论做出了贡献。我们根据一阶公理化的句法形式研究分级结构类别的表征。我们专注于由通用和通用存在句子给出的类。特别是，我们使用图的技术在有限MTL代数上确定的结构设置中证明了两种合并结果，随后是Łoś-Tarski和Chang-Łoś-Suszko保存定理的类似物。