.back{
	width:100%;
	}
	.back .bk{
	width:1200px;
	margin:0 auto;
	border-bottom: 1px solid #c5c5c5;
	padding-left: 30px;
	}
	.back .bk a{
	color: #555555;
    line-height: 36px;
	font-family: Arial;
	text-decoration:none;
	}
	.wrap{
	width:1200px;
	margin:0 auto;
	}
	.wrap ul{
	padding-left:0;
	}
	.wrap .class_xw_center{
	margin-top:50px;
	}
	.mb30{
	margin-bottom:30px;
	}
	.wn{
	width:100%;
	overflow:hidden;
	}
	.wrap_1226{
	max-width:1226px;
	margin:0 auto;
	}
	.letter1{
	width:55%;
	margin-top:160px;
	}
	.left_letter{
	float: left;
    width: 48%;
    text-align: center;
    margin-top: 200px;
    line-height: 60px;
	}
	.right_img{
	float: right;
    box-shadow: 0px 0px 10px 0px #828282;
    margin: 3px 1px 3px 0;
	}
	.mb10{
	margin-bottom:10px;
	}
	#mobile-column{display:none;}
	
	.back{
	width:100%;
	}
	.back .bk{
	width:1200px;
	margin:0 auto;
	border-bottom: 1px solid #c5c5c5;
	padding-left: 30px;
	}
	.back .bk a{
	color: #555555;
    line-height: 36px;
	font-family: Arial;
	text-decoration:none;
	}
	
	.department{
	overflow:hidden;
	}
	.left_img{
	float: left;
    box-shadow: 0px 0px 10px 0px #828282;
    margin: 3px 1px 3px 3px;
	}
	.right_letter{
	float: right;
    width: 55%;
    text-align: center;
    margin-top: 200px;
    line-height: 60px;
	}
	.letter2{
	margin-top: 130px;
	}
	.img_three{
	float: left;
    box-shadow: 0px 0px 10px 0px #828282;
    margin: 3px 35px 3px 4px;
	}
	.img_three:nth-child(3){
	margin-right:0;
	}
	.equipment img{
	max-width: 100%;
    max-height: 100%;
    text-align: center;
	}
	.img_two{
	float: left;
    box-shadow: 0px 0px 10px 0px #828282;
    margin: 3px 50px 3px 4px;
	}
	.img_two:nth-child(2){
	margin-right: 0;
	}
	.mb50{
	margin-bottom:50px;
	}
	.letter3{
	margin-top: 110px;
	}
	.letter4{
	margin-top: 100px;
    width: 54%;
	}
	.img_bottom{
	float: left;
    box-shadow: 0px 0px 10px 0px #828282;
    margin: 3px 33px 100px 4px;
	}
	.img_bottom:nth-child(3){
	margin-right:0;
	}
	 .hb{
	width:800px;
	margin:100px auto;
	text-align:center;
	}