Youngsoo Shin

Power conscious fixed priority scheduling for hard real-time systems

Power efficient design of real-time systems based on programmable processors becomes more important as system functionality is increasingly realized through software. This paper presents a power efficient version of a widely used fixed priority scheduling method. The method yields a power reduction by exploiting slack times, both those inherent in the system schedule and those arising from variations of execution times. The proposed run-time mechanism is simple enough to be implemented in most kernels. Experimental results show that the proposed scheduling method obtains a significant power reduction across several kinds of applications.

Power optimization of real-time embedded systems on variable speed processors

Power efficient design of real-time embedded systems based on programmable processors becomes more important as system functionality is increasingly realized through software. This paper presents a power optimization method for real-time embedded applications on a variable speed processor. The method combines off-line and on-line components. The off-line component determines the lowest possible maximum processor speed while guaranteeing deadlines of all tasks. The on-line component dynamically varies the processor speed or brings a processor into a power-down mode according to the status of task set in order to exploit execution time variations and idle intervals. Experimental results show that the proposed method obtains a significant power reduction across several kinds of applications.

Architecting voltage islands in core-based system-on-a-chip designs

Voltage islands enable core-level power optimization for System-on-Chip (SoC) designs by utilizing a unique supply voltage for each core. Architecting voltage islands involves island partition creation, voltage level assignment and floorplanning. The task of island partition creation and level assignment have to be done simultaneously in a floorplanning context due to the physical constraints involved in the design process. This leads to a floorplanning problem formulation that is very different from the traditional floorplanning for ASIC-style design. In this paper, we define the problem of architecting voltage islands in core-based designs and present a new algorithm for simultaneous voltage island partitioning, voltage level assignment and physical-level floorplanning. Application of the proposed algorithm to a few benchmark and industrial examples is demonstrated using a prototype tool. Results show power savings of 14%-28%, depending on the constraints imposed on the number of voltage islands and other physical-level parameters.

Partial bus-invert coding for power optimization of application-specific systems

This paper presents two bus coding schemes for power optimization of application-specific systems: partial pus-invert coding and its extension to multiway partial bus-invert coding. In the first scheme, only a selected subgroup of bus lines is encoded to avoid unnecessary inversion of relatively inactive and/or uncorrelated bus lines which are not included in the subgroup. In the extended scheme, we partition a bus into multiple subbuses by clustering highly correlated bus lines and then encode each subbus independently. We describe a heuristic algorithm of partitioning a bus into subbuses for each encoding scheme. Experimental results for various examples indicate that both encoding schemes are highly efficient for application-specific systems.

Coupling-driven bus design for low-power application-specific systems

In modern embedded systems including communication and multimedia applications, large fraction of power is consumed during memory access and data transfer. Thus, buses should be designed and optimized to consume reasonable power while delivering sufficient performance. In this paper, we address a bus ordering problem for low-power application-specific systems. A heuristic algorithm is proposed to determine the order in a way that effective lateral component of capacitance is reduced, thereby reducing the power consumed by buses. Experimental results for various examples indicate that the average power saving from 30% to 46.7% depending on capacitance components can be obtained without any circuit overhead.

Partial bus-invert coding for power optimization of system level bus

We presen t a partial bus-in vertcoding scheme for po wer optim ization of system level bus. In the proposed sch eme, we select a su b-group of bus lines involved in b us encoding to a void unnecessary inversion of b us lines not in the sub-group thereby redu cing th e total number of bus transitions. We propose a heuristic algorithm that selects the sub-grou p of bus lines for b us encoding. Ex periments on benchmark examples in dicate that the partial bus-in vert coding reduces the tot al bus tran sitions b y 62.6% on the av erage, compared to that of the unencoded patterns.

Prevalence of Diabetes and IGT in Yonchon County, South Korea

OBJECTIVE To determine the prevalence of diabetes and impaired glucose tolerance (IGT) in Yonchon County of South Korea and to investigate their associated factors. RESEARCH DESIGN AND METHODS We performed a population-based cross-sectional study with random cluster sampling of residents ≥30 years of age. Among the 3,804 residents sampled, a total of 2,520 participants had a standard 75-g oral glucose tolerance test and answered a detailed questionnaire. We also collected standard anthropometric data. RESULTS If the data for participants in the age range of 30–64 years were adjusted to the standard world population, the prevalence of diabetes was 7.2% and the prevalence of IGT was 8.9%. It was observed that the significant factors associated with diabetes were waist-to-hip circumference ratio, serum triglyceride levels, age, systolic blood pressure, family history of diabetes, and locality. CONCLUSIONS The prevalence of diabetes in Yonchon County was substantially higher than was previously suggested. The risk of diabetes increased with the increased central obesity and metabolic disturbances associated with insulin resistance.

Prevalence of lower urinary tract symptoms in Korean men in a community-based study

Objective: The prevalence of lower urinary tract symptoms was determined in Korean men aged 50 and over. Methods: A community-based, epidemiologic study was performed in Yonchon County, Korea. The Korean version of the International Prostate Symptom Score (I-PSS) was used to assess the severity of urinary symptoms in a representative sample of 514 men. Results: Nocturia and weak stream were the most prevalent symptoms and urgency was the least. Overall, 23.2% of the men were moderately to severely symptomatic: 17.7% in the age group of 50–59 years, 23.3% in that of 60–69 years and 35.3% in that of 70 years and over. The proportion of severely symptomatic men approximately doubled with each decade of age. The ‘quality of life’ score showed a high correlation with the I-PSS. Our estimation indicated that in 1995 approximately 800,000 Korean men had moderate to severe lower urinary tract symptoms that were likely to be associated with benign prostatic hyperplasia. Conclusions: The prevalence of moderate to severe lower urinary tract symptoms in Korean men is substantially similar to that in Caucasians.

Measuring the Burden of Disease in Korea

This paper provides an overview of the Korean Burden of Disease (KBoD) study, which was the first such study to assess the national burden of disease using disability-adjusted life years (DALYs) in an advanced Asian country. The KBoD study generally followed the approach utilized in the original Global Burden of Disease study (GBD), with the exception of the disease classification and epidemiological data estimation methods used, and the relative weightings of disabilities. The results of the present study reveal that the burden of disease per 100,000 of the Korean population originates primarily from; cancer (1,525 Person Years, PYs), cardiovascular disease (1,492 PYs), digestive disease (1,140 PYs), diabetes mellitus (990 PYs), and certain neuro-psychiatric conditions (883 PYs). These results are largely consistent with those of developed countries, but also represent uniquely Korean characteristics.

Prevalence Estimation of Dementia in a Rural Area of Korea

OBJECTIVES: A cross‐sectional survey was conducted to estimate prevalence of dementia and to determine factors related to dementia among residents in a rural area, Yonchon county, Korea, in 1993.