since 基本就俩解释,用法如下：
（1） 是你所说的 自 ...以后,一般的确都配着完成时使用.
I have started working here since last year.=> 自去年起我就开始在这里工作了（而且仍持续中,所以用完成进行时）
He has missed several classes since the beginning of the semester.=> 他从学期开始就缺了好几堂课.
（2） 是“因为、基于...缘故”的意思,你举出两个例句中的since 都是如此解释.
译文：
1.since very few people are actually concious of thee decision-making norms that their cultures have taught them,they never consider that those norms are far from universal.
因为很少人真正会意识到他们做决定的标准深受个人文化背景影响,他们从不会考虑这些标准并非举世通用的.
2.But since the other side feels the same way about their right way,the results of this teaching effort are usually profoundly non-educational.
但由于另外一边也同样认为他们的方法是正确的,这种教学方式通常离真正的教育相去甚远.