Annual report pursuant to Section 13 and 15(d)

Other long-term assets (Schedule of Carrying Amounts Related to Acquired Intangible Assets) (Details)

v3.19.1
Other long-term assets (Schedule of Carrying Amounts Related to Acquired Intangible Assets) (Details) - USD ($)
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Other Long-term Assets Schedule Of Carrying Amounts Related To Acquired Intangible Assets    
Patents at beginning, net $ 509,649 $ 550,799
Additions 59,597 26,850
Less: amortization expense 61,904 68,000
Patents at ending, net $ 507,342 $ 509,649