大规模机器类通信(massive Machine Type Communications,mMTC)旨在实现海量的物联网设备通信,被广泛应用于工业自动化、智能交通、智慧城市、智慧医疗等领域。面对数量巨大的用户设备,基于授权的随机接入技术存在接入失败概率高和信令...大规模机器类通信(massive Machine Type Communications,mMTC)旨在实现海量的物联网设备通信,被广泛应用于工业自动化、智能交通、智慧城市、智慧医疗等领域。面对数量巨大的用户设备,基于授权的随机接入技术存在接入失败概率高和信令开销大的弊端。为了解决这些弊端,学术界和工业界提出了免授权随机接入(Grant-Free Random Access,GFRA)技术,此技术能够使活跃用户设备在发送导频序列后直接传输数据而无需等待基站授权。因此,在基于免授权接入的mMTC中,基站的一个关键任务是进行用户设备活跃性检测。而在实际场景中,用户设备往往在连续时隙上呈现活跃状态,即存在时间相关性。特别地,利用时间相关性的先验信息可以降低用户设备活跃性的错误检测概率。本文从该出发点提出一种基于最大后验(Maximum A Posteriori,MAP)概率的坐标下降算法。具体而言,该算法首先从最大后验概率的角度构建目标函数,并通过Markov链模拟连续时隙中的状态转移。其次,使用坐标下降法处理接收信号的协方差得到活跃用户设备集合。最后,对当前时隙的用户设备最可能发生的情况进行决策。仿真结果表明,相比经典的活跃用户检测算法,本文算法拥有更低的错误检测概率。并且,当导频序列长度较短及活跃用户数量增加时,仍能表现出较好的检测性能。此外,随着接收天线增多,本文算法相比经典算法的性能增益更显著。展开更多
Background: Hypoglycemia is a traumatic dilemma that has a critical impact on not only the patient’s quality of life but also their families and communities. Improving Patient’s awareness and knowledge regarding hyp...Background: Hypoglycemia is a traumatic dilemma that has a critical impact on not only the patient’s quality of life but also their families and communities. Improving Patient’s awareness and knowledge regarding hypoglycemia symptoms is crucial to avoid serious implications like loss of consciousness and even death. Objective: This study aimed to assess patients’ knowledge of hypoglycemia symptoms and source of diabetes information among insulin users type 2 diabetes. Methods: A single centre, hospital-based, analytical, and cross-sectional study was carried out among diabetic patients using insulin attended to Ribat University Hospital Diabetes Clinic (RUHDC), Khartoum State, Sudan during a period of study. A validated questionnaire was used to obtain socio-demographic characteristics of respondents and the patients’ knowledge regarding hypoglycemia symptoms was assessed whether good, medium or poor. Data were analyzed, using (SPSS). Descriptive (frequencies) and inferential statistics (association used chi-square) were used at a level of confidence p ≤ 0.05. Results: A majority of patients (52%) had poor knowledge of hypoglycemia symptoms and the common symptoms known to patients were hands tremor (67.2%), blurred vision (52.8%) and sweating (65.6%). No associations were found among hypoglycemia symptoms knowledge, socio-demographic and diabetes duration. Only (25.6%) had regular visiting to educating center and physicians were the major source of diabetes knowledge (74.4%). Conclusion: This study proved low patients hypoglycemia symptoms knowledge and physician were the main sources of information about diabetes at RUHDC. Further ideas are required in collaboration and integrated approach to filling the gap of patients’ awareness and multidisciplinary team in diabetes management.展开更多
There are multiple biases in using observational studies to examine treatment effects such as those from prevalent drug users, immortal time and drug indications. We used renin angiotensin system(RAS) inhibitors and s...There are multiple biases in using observational studies to examine treatment effects such as those from prevalent drug users, immortal time and drug indications. We used renin angiotensin system(RAS) inhibitors and statins as reference drugs with proven efficacies in randomized clinical trials(RCTs) and examined their effectiveness in the prospective Hong Kong Diabetes Registry using adjustment methods proposed in the literature. Using time-dependent exposures to drug treatments yielded greatly inflated hazard ratios(HR) regarding the treatment effects of these drugs for cardiovascular disease(CVD) in type 2 diabetes. These errors were probably due to changing indications to use these drugs during follow up periods, especially at the time of drug commencement making time-dependent analysis extremely problematic. Using time-fixed analysis with exclusion of immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of RAS inhibitors for CVD was comparable to that in RCT. The result supported the use of the Registry for performing pharmacoepidemiological analysis which revealed an attenuated low low-density lipoprotein cholesterol related cancer risk with RAS inhibitors. On the other hand, time-fixed analysis with including immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of statins for CVD was similar to that in the RCT. Our results highlight the complexity and difficulty in removing these biases. We call for validations of the methods to cope with immortal time and drug use indications before applying them to particular research questions, so to avoid making erroneous conclusions.展开更多
文摘大规模机器类通信(massive Machine Type Communications,mMTC)旨在实现海量的物联网设备通信,被广泛应用于工业自动化、智能交通、智慧城市、智慧医疗等领域。面对数量巨大的用户设备,基于授权的随机接入技术存在接入失败概率高和信令开销大的弊端。为了解决这些弊端,学术界和工业界提出了免授权随机接入(Grant-Free Random Access,GFRA)技术,此技术能够使活跃用户设备在发送导频序列后直接传输数据而无需等待基站授权。因此,在基于免授权接入的mMTC中,基站的一个关键任务是进行用户设备活跃性检测。而在实际场景中,用户设备往往在连续时隙上呈现活跃状态,即存在时间相关性。特别地,利用时间相关性的先验信息可以降低用户设备活跃性的错误检测概率。本文从该出发点提出一种基于最大后验(Maximum A Posteriori,MAP)概率的坐标下降算法。具体而言,该算法首先从最大后验概率的角度构建目标函数,并通过Markov链模拟连续时隙中的状态转移。其次,使用坐标下降法处理接收信号的协方差得到活跃用户设备集合。最后,对当前时隙的用户设备最可能发生的情况进行决策。仿真结果表明,相比经典的活跃用户检测算法,本文算法拥有更低的错误检测概率。并且,当导频序列长度较短及活跃用户数量增加时,仍能表现出较好的检测性能。此外,随着接收天线增多,本文算法相比经典算法的性能增益更显著。
文摘Background: Hypoglycemia is a traumatic dilemma that has a critical impact on not only the patient’s quality of life but also their families and communities. Improving Patient’s awareness and knowledge regarding hypoglycemia symptoms is crucial to avoid serious implications like loss of consciousness and even death. Objective: This study aimed to assess patients’ knowledge of hypoglycemia symptoms and source of diabetes information among insulin users type 2 diabetes. Methods: A single centre, hospital-based, analytical, and cross-sectional study was carried out among diabetic patients using insulin attended to Ribat University Hospital Diabetes Clinic (RUHDC), Khartoum State, Sudan during a period of study. A validated questionnaire was used to obtain socio-demographic characteristics of respondents and the patients’ knowledge regarding hypoglycemia symptoms was assessed whether good, medium or poor. Data were analyzed, using (SPSS). Descriptive (frequencies) and inferential statistics (association used chi-square) were used at a level of confidence p ≤ 0.05. Results: A majority of patients (52%) had poor knowledge of hypoglycemia symptoms and the common symptoms known to patients were hands tremor (67.2%), blurred vision (52.8%) and sweating (65.6%). No associations were found among hypoglycemia symptoms knowledge, socio-demographic and diabetes duration. Only (25.6%) had regular visiting to educating center and physicians were the major source of diabetes knowledge (74.4%). Conclusion: This study proved low patients hypoglycemia symptoms knowledge and physician were the main sources of information about diabetes at RUHDC. Further ideas are required in collaboration and integrated approach to filling the gap of patients’ awareness and multidisciplinary team in diabetes management.
文摘There are multiple biases in using observational studies to examine treatment effects such as those from prevalent drug users, immortal time and drug indications. We used renin angiotensin system(RAS) inhibitors and statins as reference drugs with proven efficacies in randomized clinical trials(RCTs) and examined their effectiveness in the prospective Hong Kong Diabetes Registry using adjustment methods proposed in the literature. Using time-dependent exposures to drug treatments yielded greatly inflated hazard ratios(HR) regarding the treatment effects of these drugs for cardiovascular disease(CVD) in type 2 diabetes. These errors were probably due to changing indications to use these drugs during follow up periods, especially at the time of drug commencement making time-dependent analysis extremely problematic. Using time-fixed analysis with exclusion of immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of RAS inhibitors for CVD was comparable to that in RCT. The result supported the use of the Registry for performing pharmacoepidemiological analysis which revealed an attenuated low low-density lipoprotein cholesterol related cancer risk with RAS inhibitors. On the other hand, time-fixed analysis with including immortal time and adjustment for confounders at baseline and/or during follow-up periods, the HR of statins for CVD was similar to that in the RCT. Our results highlight the complexity and difficulty in removing these biases. We call for validations of the methods to cope with immortal time and drug use indications before applying them to particular research questions, so to avoid making erroneous conclusions.
