▁Conf u cian , ▁T ao ist , ▁and ▁traditional ▁astronom ical ▁systems . ▁This ▁took ▁Ku ai ▁several ▁years , ▁and ▁the ▁first ▁palace ▁and ▁walls ▁of ▁the ▁City ▁were ▁completed ▁only ▁after ▁ 1 3 ▁years . ▁ ▁References ▁ ▁Further ▁reading ▁C ao ▁X un , ▁Ku ai ▁X i ang , ▁Encyclopedia ▁of ▁China ▁ ▁Category : 1 3 9 8 ▁birth s ▁Category : 1 4 8 1 ▁death s ▁Category : Arch itect s ▁from ▁Su z hou ▁Category : Ch inese ▁architect s ▁Category : Engine ers ▁from ▁Ji ang su ▁Category : For b idden ▁City ▁Category : M ing ▁dynast y ▁people <0x0A> </s> ▁In ▁mat roid ▁theory , ▁a ▁Syl v ester ▁mat roid ▁is ▁a ▁mat roid ▁in ▁which ▁every ▁pair ▁of ▁elements ▁belongs ▁to ▁a ▁three - element ▁circuit ▁( a ▁triangle ) ▁of ▁the ▁mat roid . ▁ ▁Example ▁The ▁- point ▁line ▁( i . e ., ▁the ▁rank ▁ 2 ▁uniform ▁mat roid ▁on ▁ ▁elements , ▁) ▁is ▁a ▁Syl v ester ▁mat roid ▁because ▁every ▁pair ▁of ▁elements ▁is ▁a ▁basis ▁and ▁every ▁triple ▁is ▁a ▁circuit . ▁ ▁A ▁Syl v ester ▁mat roid ▁of ▁rank ▁three ▁may ▁be ▁formed ▁from ▁any ▁Ste iner ▁triple ▁system , ▁by ▁defining ▁the ▁lines ▁of ▁the ▁mat roid ▁to ▁be ▁the ▁tri ples ▁of ▁the ▁system . ▁Syl v ester ▁mat roid s ▁of ▁rank ▁three ▁may ▁also ▁be ▁formed ▁from ▁Syl v ester – G alla i