Grey System theory was initiated in 1982 [7]. As far as information is concerned, the systems which lack information, such as structure message, operation mechanism and behaviour document, are referred to as Grey Systems. For example, the human body, agriculture, economy, etc., are Grey Systems. Usually, on the grounds of existing grey relations, grey elements, grey numbers (denoted by 8 ) one can identify which Grey System is, where \"grey\" means poor, incomplete, uncertain, etc. The goal of Grey Systeni and its applications is to bridge the gap existing between social science and natural science. Thus, one can say that the Grey System theory is interdisciplinary, cutting across a variety of specialized fields, and it is evident that Grey System theory stands the test of time since 1982. As the case stands, the developn~ent of the Grey System-as well as theoretical topic-is coupled with clear applications of the theory in assorted fields. The conccept of the Grey System, in its theory and successful application, is now well known in China. The application fields of the Grey System involve agriculture [23, 77-81, 911, ecology [59], economy [61, 102, 103, 1041, meteorology [58, 74,911, medicine [55, 891, history [63, 641, geography [I], industry [61, earthquake [73, 87, 881, geology [76, 1 191, hydrology [98, 1 121, irrigation strategy [261, military affairs, sports [116], traffic [67], management [30, 97, 1051, material science [82, 831, environment [ 1081, biological protection [69,70], judicial system [loo], etc. Projects which have been successfully completed with the Grey System theory and its applications are as follows: 1. Regional econonlic planning for several provinces in China; 2. To forecast yields of grain for some provinces in China:

Introduction to Grey system theory

In this paper the problem of stability of grey linear time-invariant systemsis investigated in virtue of the properiest of non-negative irreducible matrices.Besides,the sufficient criterion for stability of grey linear time-invariant systems aregiven.The criterion obtained here is helpful to the analysis of the stability of lineartime-varying systems as well as grey systems.As an illustrative example of the crite-rion,the sufficient condition is given under which the stability of linear time-varyingsystems is guaranteed.And in terms of the sufficient condition it is much more conve-nient and simpler to judge Whether some linear time-varying systm is stable or not.

Zhou Chaoshu

Papers

Sufficient Condition for Stability of Grey Systems and Its Application in the Analysis of Stability of Linear Time-Varying Systems