• Journal of Information Technology Services
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• v.16 no.1
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• pp.73-82
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• 2017

Recently in-memory data stream processing has been actively applied to various subjects such as query processing, OLAP, data mining, i.e., frequent item sets, association rules, clustering. However, finding regular periodic patterns of events in an infinite data stream gets less attention. Most researches about finding periods use autocorrelation functions to find certain changes in periodic patterns, not period itself. And they usually find periodic patterns in time-series databases, not in data streams. Literally a period means the length or era of time that some phenomenon recur in a certain time interval. However in real applications a data set indeed evolves with tiny differences as time elapses. This kind of a period is called as a pseudo-period. This paper proposes a new scheme called FPMH (Finding Periods using Multiple Hash functions) algorithm to find such a set of pseudo-periods over a data stream based on multiple hash functions. According to the type of pseudo period, this paper categorizes FPMH into three, FPMH-E, FPMH-PC, FPMH-PP. To maximize the performance of the algorithm in the data stream environment and to keep most recent periodic patterns in memory, we applied decay mechanism to FPMH algorithms. FPMH algorithm minimizes the usage of memory as well as processing time with acceptable accuracy.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.252-252
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• 2011

Rainfall-runoff models are calibrated and validated by using a same data set such as observations. The past climate change effects the present rainfall pattern and also will effect on the future. To predict rainfall-runoff more preciously we have to consider the climate change pattern in the past, present and the future time. Thus, in this study, the climate change represents changes in mean precipitation and standard deviation in different patterns. In some river basins, there is no enough length of data for the analysis. Therefore, we have to generate the synthetic data using proper distribution for calculation of precipitation based on the observed data. In this study, Kajiyama model is used to analyze the runoff in the dry and the wet period, separately. Mean and standard deviation are used for generating precipitation from the gamma distribution. Twenty hypothetical scenarios are considered to show the climate change conditions. The mean precipitation are changed by -20%, -10%, 0%, +10% and +20% for the data generation with keeping the standard deviation constant in the wet and the dry period respectively. Similarly, the standard deviations of precipitation are changed by -20%, -10%, 0%, +10% and +20% keeping the mean value of precipitation constant for the wet and the dry period sequentially. In the wet period, when the standard deviation value varies then the mean NSE ratio is more fluctuate rather than the dry period. On the other hand, the mean NSE ratio in some extent is more fluctuate in the wet period and sometimes in the dry period, if the mean value of precipitation varies while keeping the standard deviation constant.

• Health Policy and Management
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• v.26 no.1
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• pp.71-78
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• 2016

The value of using health insurance claim database is continuously rising in healthcare research. In studies where comorbidities act as a confounder, comorbidity adjustment holds importance. Yet researchers are faced with a myriad of options without sufficient information on how to appropriately adjust comorbidity. The purpose of this study is to assist in selecting an appropriate index, look back period, and data range for comorbidity adjustment. No consensus has been formed regarding the appropriate index, look back period and data range in comorbidity adjustment. This study recommends the Charlson comorbidity index be selected when predicting the outcome such as mortality, and the Elixhauser's comorbidity measures be selected when analyzing the relations between various comorbidities and outcomes. A longer look back period and inclusion of all diagnoses of both inpatient and outpatient data led to increased prevalence of comorbidities, but contributed little to model performance. Limited data range, such as the inclusion of primary diagnoses only, may complement limitations of the health insurance claim database, but could miss important comorbidities. This study suggests that all diagnoses of both inpatients and outpatients data, excluding rule-out diagnosis, be observed for at least 1 year look back period prior to the index date. The comorbidity index, look back period, and data range must be considered for comorbidity adjustment. To provide better guidance to researchers, follow-up studies should be conducted using the three factors based on specific diseases and surgeries.

• Journal of information and communication convergence engineering
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• v.5 no.4
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• pp.369-373
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• 2007

RFID systems large volume of data, it can lead to slower queries. To achieve better query performance, we can partition into active and some nonactive data. In this paper, we propose two approaches of partitioning for efficient query support. The one is average period plus delta partition and the other is adaptive average period partition. We also present the system architecture to manage active data and non-active data and logical database schema. The data manager check the active partition and move all objects from the active store to an archive store associated with an average period plus data and an adaptive average period. Our experiments show the performance of our partitioning methods.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.29.3-29.3
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• 2008

1RXS J062518.2+733433. The X-ray data was obtained in April 6, 2006 with the XMM-Newton and the optical data with CCD R filter at the 1m telescope of the Lemonsan observatory in 2005-2006 for 11 nights. This source is classified as a magnetic cataclysmic variable with a spin period of 1187.3 s in the optical region. We determine the spin period to be $1187.26\pm0.11$ s using the X-ray data, which is well consistent with the optical studies. However, we find that the pulse profile of the data (0.2-10 keV) folded at the period is different from the quasi-sinusoidal optical profile and is dependent on the selected X-ray energy bands. The results of period searching with times of extrema will be also presented.

• Journal of Korean Academy of Rural Health Nursing
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• v.8 no.1
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• pp.25-32
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• 2013

Purpose: The purpose of this study was to investigate the changing process of work activities of community health practitioners in medically vulnerable areas. Methods: For the study an historical research method was used, based on literature data and collected literature data related to the work of community health practitioners from 1940 to 2013. Results: There were 45 records according to the literature data about the work activities of the practitioners. Analysis of the process of work activities by time period was based on the historical records: first, the introduction period (1940~1980) saw the "community health practitioners begin their work activities"; second, the development period (1981~1997) involved "provision of comprehensive health and medical service"; third, the stagnation period (1998~2005) characterized by "attempts at new role changes in a crisis"; fourth, the expansion period (2006~2011) "focused on the work of health promotion"; and finally, the stable period (2012~the present) observed "work activities of community health practitioners recognized." Conclusion: Results showed five topics in the process of work activities of community health practitioners by time period. The results offer basic data to investigate work activities of these practitioners and enable discussions about the future of community healthcare.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2159-2166
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• 2016

In the IEEE 802.11 DCF (Distributed Coordination Function) protocol, the binary exponential backoff algorithm is used to avoid data collisions. However, as the number of stations increases of, the collision probability tends to grow and the overall network performance is reduced. To solve this problem, this paper proposes a data transmission scheme based on the channel reservation method. In the proposed scheme, channel time is divided into reservation period and contention period. During the reservation period, stations succeeded in channel reservation transmit their own data packets in sequence without contention. During the contention period, each station sends its data packets through contentions as in DCF. During both the reservation period and the contention period, each station sends a request for channel reservation for the next reservation period to an AP (Access Point). After receiving such a channel reservation request from each station, the AP decides whether the reservation is succeeded and sends the result via a beacon frame to each station. Performance of the proposed scheme is analyzed through simulations. The simulation results show that the proposed scheme tends to reduce the collision probability of DCF and to improve the overall network performance.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.3
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• pp.287-291
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• 2000

The study was based on 1921 service period records of Nili Ravi buffaloes maintained at six dairy farms in Pakistan during the period 1978 to 1994. The mean service period was $237.57{\pm}4.5$ days in the over all data. The highest mean service period ($393.59{\pm}16.18$ days) was at MDF Rawalpindi and the lowest ($199.15{\pm}14.35$ days) was at MDF Peshawar. The difference was significant p<0.001. Late maturing buffaloes showed significantly longer service period as compared to early maturing buffaloes. Parity and seasonal effects on Service Period were studied. There was an overall trend of reduction in the length of service period with the increase in parity. The mean ($287.54{\pm}6.89$ days) service period was (highest) in parity number one and lowest in parity number eight ($107.95{\pm}19.72$ days). The difference was highly significant. In overall data significantly lower service periods were seen in buffaloes calving in spring+winter as compared to summer+fall.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.205-208
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• 2009

In this paper, a MAS information management method is proposed for the WiMedia MAC protocol. WiMedia MAC configures a fully distributed network based on Ad-hoc method. WiMedia devices communicate during Superframe which is a communication unit in WiMedia MAC. Each superframe which consist of 256 MASs is divided into two periods, beacon period and data period. In data period, devices communicate with each other using the received channel access information during the beacon period. Due to only $12{\mu}s$ timing allowance between beacon period and data period, the process of the MAS information management cannot be completed in time if entire process handle by software. Therefore, we propose a novel MAS information management method using hardware module. With our proposed method, a WiMedia device is satisfied with the processing time that is required in WiMedia MAC protocol.

• Journal of Sensor Science and Technology
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• v.26 no.6
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• pp.408-413
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• 2017

In this paper, we newly developed a byte-inverted transmission method for flicker-free visible light communication (VLC). The VLC transmitter sends original data in the former half period of the clock, and inverted data and in the latter half period of the clock. The VLC receiver receives the original data in the in the former half period of the clock. In this system, we used 480Hz clock that was generated from the 60Hz power line. The average optical power of the LED array in the transmitter is constant, thus flicker-free, in the observation time longer than the period of the clock that is about 2ms. This period is shorter than the maximum flickering time period (MFTP) of 5ms that is generally considered to be safe. This configuration is very useful in constructing indoor wireless sensor networks using LED light because it is flicker-free and does not require additional transmission channel for clock transmission.