Design techniques for low-voltage analog-to-digital converter

Continuous process scale-down and emerging markets for low-power/low-voltage mobile systems call for low-voltage analog integrated circuits. Switched-capacitor circuits are the building blocks for analog signal processing and will encounter severe overdrive problems when operating at low-voltage conditions. There are several well-known techniques to bypass the problem. These approaches include: (1) The clock boosting schemes (e.g. 2VDD clock signal) which cannot be used in submicron low-voltage CMOS processes as gate oxide can only tolerate the technology's maximum voltage (VDD). (2) The use of scaled/lower threshold transistors, which are not always scalable to very low voltage supplies as it could suffer from an unacceptable amount of leakage current (e.g. the switch may not be fully turned off). (3) The use of bootstrapped clocking, which has added loading and possible reliability issues. (4) The switched-opamp (SO) technique which is fully compatible with low-voltage submicron CMOS processes but the operating speed limited due to slow transients from the opamp being switched off and on. In this thesis, the Opamp-Reset Switching Technique (ORST) topology is proposed for low-voltage operation. Instead of opamps being turned on and off as in the switched-opamp technique, the sourcing amplifier is placed in the unity-gain reset configuration to provide reset level at the output. In this way, high-speed operation is possible. The technique is applied to two ADCs as examples of low-voltage design. The first design is a 10-bit 25MSPS pipelined ADC using pseudo-differential structure. It is fabricated in a 0.35-μm CMOS process. It operates at 1.4V and consumes 21mW of total power. The second design is a two-stage algorithmic ADC with highly linear input sampling circuit. In addition to the low-voltage design techniques used in the pipelined ADC, radix-based digital calibration technique for multi-stage ADC is also proposed. The ADC uses a 0.18-μm CMOS technology. It operates at 0.9V supply with total power consumption of 9mW. Experimental results show that the proposed calibration technique reduces spurious free dynamic range from 47dB to 75dB and improves signal-to-noise and distortion ratio from 40dB to 55dB after calibration

Association between childhood adversities and adulthood depressive symptoms in South Korea: Results from a nationally representative longitudinal study

Objective To examine how childhood adversity (ie, parental death, parental divorce, suspension of school education due to financial strain or being raised in a relative\u27s house due to financial strain) is associated with prevalence and incidence of adulthood depressive symptoms and whether this association differs by gender and by age in South Korea. Design Prospective cohort design. Setting Nationally representative longitudinal survey in South Korea. Participants 11 526 participants in South Korea. Outcome measure Prevalence and incidence of adulthood depressive symptoms were assessed as a dichotomous variable using the Centers for Epidemiologic Studies Depression (CES-D) Scale in 2006 and 2007. Results In the prevalence analysis, each of the four childhood adversities was significantly associated with a higher prevalence of adulthood depressive symptoms. The higher incidence of depressive symptoms was associated with suspension of school education (OR 1.55, 95% CI 1.32 to 1.82) and parental divorce (OR 1.65, 95% CI 1.00 to 2.71). In the age-stratified analyses, prevalence of depressive symptoms was associated with all CAs across different adulthoods, except for parental divorce and late adulthood depressive symptoms. After being stratified by gender, the association was significant for parental divorce (OR 3.76, 95% CI 2.34 to 6.03) in the prevalence analysis and for being raised in a relative’s house (OR 1.89, 95% CI 1.21 to 2.94) in the incidence analysis only among women. Conclusions This study suggests that childhood adversity may increase prevalence and incidence of adulthood depressive symptoms, and the impact of parental divorce or being raised in a relative\u27s house due to financial strain on adulthood depressive symptoms may differ by gender

The Korean urban rural elderly cohort study: study design and protocol

BACKGROUND: Korea is one of the fastest aging countries and is expected to become a super-aged society within 12 years. The Korean Urban Rural Elderly (KURE) study was developed to evaluate the epidemiological characteristics and establish the prevention and management of major disorders of the elderly in Korea. METHODS/DESIGN: The KURE study is a community-based prospective cohort study on health, aging, and common geriatric disorders of Korean elderly persons aged at least 65 years. To construct a cohort reflecting both urban and rural areas, we selected 2 representative communities in the country. To establish multidisciplinary approaches to geriatric health, this study was performed by researchers in the divisions of geriatrics, preventive medicine, endocrinology, and sociology. The baseline examinations began in 2012; the study will follow more than 4,000 elderly Koreans over 10 years. The first and second follow-up health examinations will be performed every 4 years. Every 2 years after each health examination, inter-assessment interview will be conducted to improve participant retention. DISCUSSION: The KURE study will provide longitudinal epidemiologic data on health, aging, and common geriatric disorders of the elderly in Korea. This is a comprehensive, multidisciplinary study of the elderly with respect to biological, physical, socio-economic, and environmental factors. The results of this study will contribute to improve public health and welfare policies for the aging society in Korea

IJA: An Efficient Algorithm for Query Processing in Sensor Networks

One of main features in sensor networks is the function that processes real time state information after gathering needed data from many domains. The component technologies consisting of each node called a sensor node that are including physical sensors, processors, actuators and power have advanced significantly over the last decade. Thanks to the advanced technology, over time sensor networks have been adopted in an all-round industry sensing physical phenomenon. However, sensor nodes in sensor networks are considerably constrained because with their energy and memory resources they have a very limited ability to process any information compared to conventional computer systems. Thus query processing over the nodes should be constrained because of their limitations. Due to the problems, the join operations in sensor networks are typically processed in a distributed manner over a set of nodes and have been studied. By way of example while simple queries, such as select and aggregate queries, in sensor networks have been addressed in the literature, the processing of join queries in sensor networks remains to be investigated. Therefore, in this paper, we propose and describe an Incremental Join Algorithm (IJA) in Sensor Networks to reduce the overhead caused by moving a join pair to the final join node or to minimize the communication cost that is the main consumer of the battery when processing the distributed queries in sensor networks environments. At the same time, the simulation result shows that the proposed IJA algorithm significantly reduces the number of bytes to be moved to join nodes compared to the popular synopsis join algorithm

Association between shift work and obesity among female nurses: Korean Nurses’ Survey

Background: Shift work has been hypothesized as a risk factor for obesity. In this study, we investigated the association between current shift work and body mass index (BMI) among female nurses in Korea. The relationship between duration of shift work and BMI of the participants was also evaluated. Methods: This cross-sectional survey evaluated participants in the Korean Nurses’ Survey, conducted from October to December 2011, using web-based self-administered questionnaires. A total of 9,989 nurses were included among 10,000 who registered on the survey web site (5,287 shift workers and 4,702 non-shift workers). Current shift workers were divided into tertiles of shift work duration (0.08–3.00 years, n = 1,732; 3.08–6.75 years, n = 1,731; and 6.83–38.00 years, n = 1,686). The BMI thresholds of overweight and obesity were ≥23 kg/m2 and ≥25 kg/m2, respectively. Data were analyzed using SPSS software. Results: Mean participant age was 33.2 ± 8.6 years and the mean BMI was 20.9 ± 2.5 kg/m2. There were statistically significant differences in current smoking status, regular drinking habit, dietary habits, regular exercise, sleep problems and self-perceived health status according to duration of shift work. The overall prevalence of overweight/obesity (18.6%) and obesity (7.4%) increased significantly as shift work duration increased from the lowest to highest tertile (P for trend <0.001). Multivariate logistic regression analysis revealed no association between current shift work and BMI. However, after adjusting for potential confounders, the participants with the longest duration of shift work were 1.63 (95% CI, 1.22–2.17) times more likely to be overweight or obese than those with the shortest duration. There was a significant positive association between obesity and shift work duration in the unadjusted analysis; however, it was attenuated and no longer significant in the multivariate model. Conclusions: The duration of shift work was positively associated with prevalence of overweight/obesity in nurses in Korea. Although these findings need to be confirmed in prospective studies, they suggest that special attention should be paid to female nurses with a long duration of shift work

Penetration of the Descending Colon by a Migrating Intrauterine Contraceptive Device

Foreign bodies in the gastrointestinal tract often cause serious complications, such as perforation, obstruction, abscess formation, or hemorrhage. This is a case in which a patient visited our hospital and complained of a vague lower abdominal pain that had been present for three months. She had an intrauterine device (IUD) inserted five years earlier. The abdominal X-ray, computed tomography and colonoscopy revealed that the IUD had penetrated into the descending colon. We tried to remove the IUD by colonoscopy but failed due to pain, so we removed the IUD surgically. Thus, we report a case in which a previously inserted IUD had penetrated into the descending colon and was surgically removed. We also present a brief review of the literature