“…During the past decades, the Keller-Segel models of type (1.1) have been studied extensively by many authors, where the main issue of the investigation is whether the solutions of the models are bounded or blow-up (see e.g., Cieślak et al [7,4,5,6], Calvez and Carrillo [2], Keller and Segel [15,16], Horstmann et al [11,12,13], Osaki [20,19], Painter and Hillen [21], Perthame [22], Rascle and Ziti [23], Wang et al [28,29], Winkler [31,32,33,34,35,37], Zheng [39]). Especially, in the absence of the logistic source (i.e.…”