## Journal of the Chungcheong Mathematical Society

### CONTENTS

A note on the characterizations of the Gumbel distribution based on lower record values
Hyun-Woo Jin and Min-Young Lee
285
Boundedness in functional perturbed differential systems via $t_{\infty}$-similarity
Dong Man Im, Sang Il Choi, and Yoon Hoe Goo
291
Characteristic matrices of some hybrid cellular automata with rules 60 and 102
Jae-Gyeom Kim
305
On $*$-semiderivations and commutativity of prime $*$-rings
Kyung Ho Kim
313
Note on spectrum of linear differential operators with periodic coefficients
Soyeun Jung
323
Calabi--Yau threefolds from building blocks of $G_2$-manifolds
Nam-Hoon Lee
331
On Characterizations of the power distribution via the identical hazard rate of lower record values
Min-Young Lee
337
A study on the set-valued discrete dynamical system $(2^X$, $\overline f )$
Kyung Bok Lee
341