利用2021-09全球80个MGEX测站进行PPP实验,以国际GNSS服务组织(IGS)发布的ZTD产品为参考进行比较分析。结果表明,多系统联合估计ZTD在精度上具有较大优势,GPS+BDS双系统比单GPS系统平均RMSE精度提高约0.6 mm, GPS+BDS+GLONASS+Galileo...利用2021-09全球80个MGEX测站进行PPP实验,以国际GNSS服务组织(IGS)发布的ZTD产品为参考进行比较分析。结果表明,多系统联合估计ZTD在精度上具有较大优势,GPS+BDS双系统比单GPS系统平均RMSE精度提高约0.6 mm, GPS+BDS+GLONASS+Galileo四系统比双系统精度提高约0.9 mm,单系统条件下GPS的ZTD估计精度高于BDS。在精度空间分布上,随着纬度升高ZTD估计精度提升较为明显,当纬度大于50°时,四系统PPP估计的ZTD精度优于5 mm。在纬度基本不变的情况下,观测站海拔升高可提升ZTD估计精度。在模糊度固定的情况下,ZTD估计精度明显提升,单GPS系统估计ZTD的平均绝对误差(MAE)和均方根误差(RMSE)分别为7.6 mm和8.4 mm,相比于浮点解分别提高约11%和12%,平均收敛时间加快20 min。展开更多
时间频率传递的结果会受到非模型化误差和观测噪声的影响,其噪声常为高频信号,构建低通滤波器可在一定程度上消除观测值序列中的高频噪声信号.本文对Vondrak滤波函数的本质进行剖析,通过IGG3算法对钟差序列进行定权并采用频率响应法选...时间频率传递的结果会受到非模型化误差和观测噪声的影响,其噪声常为高频信号,构建低通滤波器可在一定程度上消除观测值序列中的高频噪声信号.本文对Vondrak滤波函数的本质进行剖析,通过IGG3算法对钟差序列进行定权并采用频率响应法选择适合的滤波因子;对不同的链路分别进行卫星双向时间频率传递(two-way satellite time and frequency transfer,TWSTFT)、基于软件接收机的卫星双向时间传递(two-way satellite time and frequency transfer based on software defined receiver,SDR-TWSTFT)和短基线共视时间频率传递实验,并对钟差结果采用抗差Vondrak滤波进行平滑去噪.结果表明:滤波后的钟差序列能够很好地反映原始钟差序列的趋势;平滑后的TWSTFT钟差结果,日波动效应得到了有效的抑制,精度有明显提升;对于共视钟差结果,精度有明显提升,与精密单点定位(precise point positioning,PPP)时间传递结果的差值保持在−1.0~1.0 ns范围内.展开更多
天门冬氨酸氨基转移酶(AST)与丙氨酸氨基转移酶(ALT)比值(AAR),传统上用于肝脏功能评估,近年来研究发现它与肝外疾病,如心血管疾病、代谢综合征和肾脏功能等存在关联。尿白蛋白肌酐比(ACR)作为肾脏敏感指标,在预测心血管风险、脑卒中、...天门冬氨酸氨基转移酶(AST)与丙氨酸氨基转移酶(ALT)比值(AAR),传统上用于肝脏功能评估,近年来研究发现它与肝外疾病,如心血管疾病、代谢综合征和肾脏功能等存在关联。尿白蛋白肌酐比(ACR)作为肾脏敏感指标,在预测心血管风险、脑卒中、糖尿病和全因死亡率方面具有重要意义。本文旨在探讨AST/ALT比值与ACR相关潜在机制的关联性,以利用这两个指标全面评估人体健康,并通过它们的关系,利用肝损伤指标预测肾脏状况,从而对肾病患者实施早期临床管理。The ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT), traditionally known as the AST/ALT ratio (AAR), has been used for the assessment of liver function. Recent studies have identified its association with extrahepatic diseases, such as cardiovascular diseases, metabolic syndrome, and renal function. The urinary albumin-to-creatinine ratio (ACR) serves as a sensitive marker for kidney health and holds significant prognostic value in predicting cardiovascular risks, stroke, diabetes, and all-cause mortality. This article aims to explore the correlation between the AST/ALT ratio and ACR in chronic kidney disease, to utilize these two indicators for a comprehensive assessment of human health. Furthermore, by understanding their relationship, liver injury markers can be used to predict kidney conditions, thereby facilitating early clinical management for patients with kidney disease.展开更多
文摘时间频率传递的结果会受到非模型化误差和观测噪声的影响,其噪声常为高频信号,构建低通滤波器可在一定程度上消除观测值序列中的高频噪声信号.本文对Vondrak滤波函数的本质进行剖析,通过IGG3算法对钟差序列进行定权并采用频率响应法选择适合的滤波因子;对不同的链路分别进行卫星双向时间频率传递(two-way satellite time and frequency transfer,TWSTFT)、基于软件接收机的卫星双向时间传递(two-way satellite time and frequency transfer based on software defined receiver,SDR-TWSTFT)和短基线共视时间频率传递实验,并对钟差结果采用抗差Vondrak滤波进行平滑去噪.结果表明:滤波后的钟差序列能够很好地反映原始钟差序列的趋势;平滑后的TWSTFT钟差结果,日波动效应得到了有效的抑制,精度有明显提升;对于共视钟差结果,精度有明显提升,与精密单点定位(precise point positioning,PPP)时间传递结果的差值保持在−1.0~1.0 ns范围内.
文摘天门冬氨酸氨基转移酶(AST)与丙氨酸氨基转移酶(ALT)比值(AAR),传统上用于肝脏功能评估,近年来研究发现它与肝外疾病,如心血管疾病、代谢综合征和肾脏功能等存在关联。尿白蛋白肌酐比(ACR)作为肾脏敏感指标,在预测心血管风险、脑卒中、糖尿病和全因死亡率方面具有重要意义。本文旨在探讨AST/ALT比值与ACR相关潜在机制的关联性,以利用这两个指标全面评估人体健康,并通过它们的关系,利用肝损伤指标预测肾脏状况,从而对肾病患者实施早期临床管理。The ratio of aspartate aminotransferase (AST) to alanine aminotransferase (ALT), traditionally known as the AST/ALT ratio (AAR), has been used for the assessment of liver function. Recent studies have identified its association with extrahepatic diseases, such as cardiovascular diseases, metabolic syndrome, and renal function. The urinary albumin-to-creatinine ratio (ACR) serves as a sensitive marker for kidney health and holds significant prognostic value in predicting cardiovascular risks, stroke, diabetes, and all-cause mortality. This article aims to explore the correlation between the AST/ALT ratio and ACR in chronic kidney disease, to utilize these two indicators for a comprehensive assessment of human health. Furthermore, by understanding their relationship, liver injury markers can be used to predict kidney conditions, thereby facilitating early clinical management for patients with kidney disease.
