Formation and evolution of marginal contact binaries with larger temperature difference between their two components remain inexplicable to date. To get a better understanding of the nature of such population we investigate on an individual, NSVS 7358116, by analysing observational data obtained from ground-based and space-based telescopes. It is found that NSVS 7358116 is a marginal contact totally eclipsing binary with a small fill-out factor by 3 per cent but large temperature difference by 2000 K or t-ratio by 0.3. This suggests that the two components are only geometrically contact but not in thermal contact. By collecting all available targets in literature, we compiled a table of 80 non-thermal equilibrium contact binaries (nTCBs) including 53 STRONG t-ratio samples and 27 WEAK t-ratio samples. We performed statistical distribution analysis on physical parameters which reveals that STRONG t-ratio samples will evolve to WEAK t-ratio samples through heat and mass transfer along with angular momentum loss, meanwhile thickening their common envelop. This current investigation is acted as only an appetizer, because more exploration on nTCBs and its evolutionary connection with related populations will follow.

Algol-type binaries (Algols) have aroused extensive interests due to the idiosyncratic evolutionary stages of both components. To better understand the evolutionary properties of such characteristic population, we collected mostly double-lined samples and performed systematic work concentrated on their physical constraints. It is found that orbital period cut-off for the OB and AF type Algols are P(OB) >0.482 d, P(AF) >0.358 d; constraints on mean density and surface gravity of the secondary components are $\overline{\rho }_2$(OB) < 0.144 ρ⊙, $\overline{\rho }_2$(AF) < 0.26 ρ⊙, log g2(OB) < 4.719 cgs and log g2(AF) < 4.517 cgs. Limitations of a(OB) >3.48 R⊙ and a(AF) >2.29 R⊙ have been deduced from the a - P relation. Moreover, statistical analysis of secular period changes reveal that Algols with higher f1 and relevant shorter period generally show weak period change. It hints that there is some connections between f1 and orbital evolution. Systems with lower f1 have the chance to evolve from classic Algols to SD2-type near contact binaries; systems with higher f1 obey the evolutionary channel from SD2-type near contact binaries to contact binaries. However, it seems that SD2-type near contact binaries could not evolve toward classic Algols. As a natural lab Algols are producing peculiar stellar experimental samples via complicated astrophysical processes, which will enhance our understanding on the physical properties and evolution of such binary populations.