• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.866-872
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• 2010

In this paper, we developed a digital soldering station based on PID controller, which supply stable power by controlling the current of heater of soldering iron. The proposed system designed PID controller to converge quickly to the set up temperature by user, and regain the lost of heat by external factors quickly. PID controller, designed by Ziegler-Nichols' tuning method, decides triac's trigger timing using setting temperature and present temperature to control the phase of AC 24V power that supply to the heater. Also, we give the function that shows present temperature and setting temperature of iron, and working time by graphic LCD. And during the rest time, we decided the power saving and extension of iron tip by dropping to the optimal temperature. Two experiments had implemented in $25^{\circ}C$ laboratory to confirm the performance of proposed method. The first experiment took 12sec, 13sec, 16sec, 18sec, reaching to $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$, $480^{\circ}C$ respectively which result showed shorten of rising time than previous method. In the loading experiment of $300^{\circ}C$, $400^{\circ}C$, $480^{\circ}C$ steady state showed temperature drop of $3.8^{\circ}C$, $4.1^{\circ}C$, $4.5^{\circ}C$ which result showed the low temperature deviation than previous method.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.1
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• pp.66-72
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• 2004

PID control has been well used for several decades. For PID algorithms, some tuning methods are used for selecting PID parameters and with these selected parameters, PID control system is designed. But in some cases various kinds of performance indices are used instead of well-known tuning rules, and so variable type of performance index must be tested so that the designed control system meets the some specifications. For 2 DOF PID controller design this paper presents a linear combinational type of performance indices constituting of index for robust performance, which is obtained by h infinity norm of a weighted complementary sensitivity function, including other time domain indices such as error, energy and changing rate of control input. By numerical methods, the optimal 2 DOF PID parameters are obtained. Therefore various types of 2 degree of freedom PID controllers such as I-PD controller are used so that this two degree of freedom PID controllers may give more desirable output characteristics. Simulations are done with MATLAB m file and mdl files.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.470-473
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• 2018

Using High-order Modulation in wideband system is sensitive to change of wireless channel environment as well as changes in ripple characteristics that can occur when baseband signals pass through RF equipment. Therefore, it is necessary to design and RF tuning that minimizes ripple characteristics change, which is difficult to implement systematically and takes a long time. In this paper, we analyze the fixed ripple characteristics of the baseband signal distored through the RF transmitting and receiving equipment. And the function of compensating the compensation filter by the modem receiver is implemented in 256 TCM. Also, it is confirmed that SNR and received sensitivity are improved by applying a digital compensation filter in a channel with poor RF equipment ripple characteristics.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.693-701
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• 2020

In this paper, SQL statements are analyzed to improve database performance in the current course registration system. The performance of the current database was measured through the execution plan of the SQL statements used in the transactions related to the course registration. Through the SQL analysis, the complemented SQL statements confirmed the improved performance. Overall, the performance of the course registration database system was improved through the analysis of the execution plan, and some improvement methods of the course registration SQL were shown as test results. The improved method is to reorganize the tables and index tables related to the course registration through database tuning, and utilize the SQL function to implement an optimized system that has evolved into a course database system with improved performance. The enrollment system re-adjusted by the proposed method showed excellent results in terms of performance compared to the previous enrollment system, and the integrated performance test result reduced the response time by 1.8 to 18 times.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.1
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• pp.70-77
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• 2001

This paper present a fuzzy mxlel of describing reacton features for ozon contactor in advanced water treatn-ent systems. Input and output variables are chosen by considenng the object of ozon processing and several parameters related to management of water quahty. Dissolved organic carbon concentration, $UV_{254}$ absorptIon and $KM_NO_4$ consumption are proposed as common variables in input and outp.lt variables. Furthermore own concentration, raw water's temperature and contact time are suggested as input variables, Membership hmctions for input variables have triangular type share and the grades in each lrembership function are determined by investigating process data gathered at pilot planl The decision parts of fuzzy model have linear combination form of input variables and coefficients included in such linear equations are computedd with process clata in the sense of least square error Also fuzzy trodel suggested in this paper is partitioned by 3 independent fuzzy rnxlels using the characteristics of having no interactions armng output variables. As a result, such fuzzy mxlel has rrerits in computation and comprehension. According to simulatIon results, fuzzy moIel's outputs give almost similar data to process output under same input conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.9
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• pp.2064-2072
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• 2015

To improve performance, most of Web Services produce and manage User Access Logs. Through the Access Logs, the record provides information about time when the most traffic happens and logs and which resource is mostly used. Then, the log can be used to analyze. However, in case of increasing high traffics of Web Services at the specific time, the performance of Web Service leads to deterioration because the number of processing User Access Logs is increasing rapidly. To solve this problem, we should improve the system performance, or tuning is needed, but it makes a problem cost a lot of money. Also, after it happens, it is not necessary to build such system by spending extra money. Therefore, this paper described the effective Web Service's performance as using improved User Access Log performance. Also, to process the newest data in bulk, this paper includes a method applying some parts of NoSQL using Redis.

• Journal of KIISE
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• v.42 no.1
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• pp.107-113
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• 2015

In a database system, updates on pages that are made by a transaction should be stored in a secondary storage before the commit is complete. Generic secondary storages have volatile DRAM caches to hide long latency for non-volatile media. However, as logs that are only written to the volatile DRAM cache don't ensure durability, logging latency cannot be hidden. Recently, a flash SSD with capacitor-backed DRAM cache was developed to overcome the shortcoming. Storage devices, like those with a non-volatile cache, will increase transaction throughput because transactions can commit as soon as the logs reach the cache. In this paper, we analyzed performance in terms of transaction throughput when the SSD with capacitor-backed DRAM cache was used as log storage. The transaction throughput can be improved over three times, by committing right after storing the logs to the DRAM cache, rather than to a secondary storage device. Also, we showed that it could acquire over 73% of the ideal logging performance with proper tuning.

• The KIPS Transactions:PartD
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• v.16D no.2
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• pp.191-200
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• 2009

Location based services (LBSs) have drawn huge attention as the growing number mobile devices and wireless technology demand more pervasive information access. In LBSs, Constraint nearest neighbor queries are one of the important queries of human to fulfill his desired quickly through wireless technology. We propose new query processing of constrained nearest neighbor query on the air to support mobile clients which demand optimal uses of wireless broadcast channel and using minimum battery power of client. First we proposed NN query processing with constrained region and then explain the novel NN query processing with various types of constraints. We have proposed novel algorithms to support Constrained Nearest Neighbor queries on the air based on Distributed Spatial Index and Bitmap-based Spatial Index.

• Journal of Korea Water Resources Association
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• v.54 no.8
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• pp.617-628
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• 2021

Drought is a major natural disaster that causes serious social and economic losses. Local drought forecasts can provide important information for drought preparedness. In this study, we propose a new machine learning model that predicts drought by using historical drought indices and meteorological data from 10 sites from 1981 to 2020 in the southeastern part of the Korean Peninsula, Busan-Ulsan-Gyeongnam. Using Bayesian optimization techniques, a hyper-parameter-tuned Random Forest, XGBoost, and Light GBM model were constructed to predict the evaporative demand drought index on a 6-month time scale after 1-month. The model performance was compared by constructing a single site model and a regional model, respectively. In addition, the possibility of improving the model performance was examined by constructing a fine-tuned model using data from a individual site based on the regional model.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.3
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• pp.111-116
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• 2023

The WiscKey database, which optimizes overhead by compaction of the LSM tree-based Key-Value database, stores the value in a separate file, and stores only the key and value addresses in the database. Each time an fsync system call function is used to ensure data integrity in the process of storing values. In previously conducted studies, workload performance was reduced by up to 5.8 times as a result of performing the workload without calling the fsync system call function. However, it is difficult to ensure the data integrity of the database without using the fsync system call function. In this paper, to reduce the overhead of the fsync system call function while performing workloads on the WiscKey database, we use NVDIMM caching techniques to ensure data integrity while improving the performance of the WiscKey database.