• Journal of the Korea Computer Graphics Society
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• v.24 no.1
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• pp.27-33
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• 2018

This paper presents a new adaptive LSB steganography for high capacity in spatial color images. The number of least signi ficant bit (LSB) of each RGB component in a color image pixel, to replace with the data bits to be hidden, was determine d through analysis of the worst case peak signal noise ratio (PSNR). In addition, the combination of the number of bits is determined adaptively according to image content. That is, 70% of the data to be hidden is proposed to be replaced with 3 bit LSB of two components, 2 bit LSB of the rest component, and 30% be replaced with 4 bit LSB of each RGB compon ent. To find edge areas in an image, delta sorting in local area is also suggested. Using the proposed method, the data cap acity is 9.2 bits per pixel (bpp). The average PSNR value of the tested images with concealed data of up to 60Kbyte was 43.9 db and also natural histograms were generated.

• Journal of Environmental Health Sciences
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• v.32 no.5 s.92
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• pp.462-468
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• 2006

Antibiotics are manufactured and used for specific physiological functions, hence they may exert adverse ecological consequences when they are in contact with nontarget organisms. In the last decade, many reports have been made on the occurrences of various antibiotic compounds in surface water, and their potential impact to the environment has become an increasing concern. This study was conducted to prioritize antibiotic substances with potential environment risk in Korea. Human use antibiotics with an EIC (Expected Introduction Concentration) value greater than $1{\mu}g/l$, US FDA's action limit criteria, were selected. In order to calculate a worst-case EIC for each substance, annual production volume (in kg) of each antibiotic substance was derived using the Korea Pharmaceutical Manufacturers Association (KPMA)'s monetary database. Sixteen substances were preliminarily selected. The EICs of the 16 antibiotic substances were refined with the excretion rate of the parent substances. Ten antibiotic substances were identified to have EIC-corrected greater than $1{\mu}g/l$, which include Amoxicillin ($15.8{\mu}g/l$), Cefaclor ($10.1{\mu}/l$), Roxithromycin ($4.2{\mu}g/l$), Cephradine ($4.5{\mu}g/l$), Cefatrizine ($2.6{\mu}g/l$), Cefadroxil ($3.3{\mu}g/l$), Aztreonam ($2.3{\mu}g/l$), Ceftazidime ($2.8{\mu}g/l$), Ribostamycin ($1.3{\mu}g/l$), and Ceftezole ($1.3{\mu}g/l$). Additional risk assessments for these antibiotic substances are suggested.

• Journal of Korea Multimedia Society
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• v.7 no.7
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• pp.886-895
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• 2004

In this paper, we propose the dynamic allocation scheme of the CPU bandwidth to efficiently integrate and schedule these tasks in the same system, where multimedia tasks and hard real-time tasks can coexist simultaneously. Hard real-time tasks are guaranteed based on worst case execution times, whereas multimedia tasks modeled as soft real-time tasks are served based on mean parameters. This paper describes a server-based allocation scheme for assigning the CPU resource to two types of tasks. Especially for MPEG video streams, we show how to dynamically control the fraction of the CPU bandwidth allocated to each multimedia task. The primary purpose of the proposed method is to minimize the mean tardiness of multimedia tasks while satisfying the timing constraints of hard real-time tasks present in the system. We showed through simulations that the tardiness experienced by multimedia tasks under the proposed allocation scheme is much smaller than that experienced by using other scheme.

• Journal of Korea Multimedia Society
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• v.13 no.10
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• pp.1423-1435
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• 2010

Building wireless sensor networks requires a constituting sensor node to consider the following limited hardware resources: a small battery lifetime limiting available power supply for the sensor node, a low-power microprocessor with a low-performance computing capability, and scarce memory resources. Despite such limited hardware resources of the sensor node, the sensor node platform needs to activate real-time sensing, guarantee the real-time processing of sensing data, and exchange data between individual sensor nodes concurrently. Therefore, in this paper, we propose an energy-efficient real-time task scheduling technique for battery-powered wireless sensor nodes. The proposed energy-efficient task scheduling technique controls the microprocessor's operating frequency and reduces the power consumption of a task by exploiting the slack time of the task when the actual execution time of the task can be less than its worst case execution time. The outcomes from experiments showed that the proposed scheduling technique yielded efficient performance in terms of guaranteeing the completion of real-time tasks within their deadlines and aiming to provide low power consumption.

• The KIPS Transactions:PartA
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• v.8A no.3
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• pp.253-260
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• 2001

It is important to detect races for debugging shared-memoy parallel programs, because the races cause unintended nondeterministic program execution. Previous on-the-fly techniques to detect races can not guarantee the first race detection in nested parallel programs. Detecting the first race is important for debugging parallel programs, since the removal of the first race may make the next occurred races disappear. In this paper, we presents an on-the-fly detection technique to detect all of the first races through the reexecution of the debugged programs. We assume that the debugged parallel program may have one-way nested parallel programs. The number of reexecution is at the least the nesting depth of the program in the worst case. The space complexity is O(VT) and the time complexity to detect race in each access of access history is O(T), where V is number of shared variables and T is the maximum parallelism of the program. This efficiency of our technique in each execution is the same with the previous on-the-fly detection techniques. Therefore, this technique makes debugging parallel programs more effective and practical.

• The Transactions of the Korea Information Processing Society
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• v.6 no.6
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• pp.1678-1685
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• 1999

In most of the existing real-time schedulers producing the total value as large as possible, the service times for all schedulable tasks are computed at each time a new task arrives. If all scheduled tasks would be executed completely before a new task arrives, the schedule may produce the greatest total value. But this is not always true in real situations. In many cases, (a) new tasks arrive(s) before all the scheduled tasks are executed completely. In this paper, we propose a unique scheduling algorithm for real-time tasks. The proposed algorithm determines the service times only for some tasks with earlier deadlines while the existing algorithms determine the service times for all tasks. This partial computation decreases the average scheduling complexity ramatically, even though, in the worst case, the complexity of the proposed algorithm becomes O(N2), which is equal to that of a previous algorithm that has been known as a less complicated one.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.9
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• pp.520-529
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• 2002

This paper presents an approach for scheduling network messages with real-time dynamic algorithms. We present the method that calculates an intermediate relative deadline of the message based on the EDF(Earliest Deadline First) scheduling policy. We adjust the slack of message by using this intermediate relative deadline to allocate a priority of message. The priority of the message can be determined accurately by using the slack that calculates in our approach, which increases the schedulability efficiency of the message. As a result, we reduce the worst-case response time and improve the guarantee ratio of real-time messages. Also, we describe the analysis method to check the schedulability on message sets, and show the efficiency of our approach by comparing the results of the DM(Deadline Monotonic) approach and the existing EDF approach with that of the improved EDF in our approach through the simulation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.1
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• pp.65-72
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• 2013

This case study presents a practical method to reduce resonant vibration of large vertical pumps. The pumps are driven at 400 rpm rated speed by induction motor. The vibration was not significantly large when operated at this rated speed. Large vibration was occurred when the pump was operated below the rated speed for flow control. Due to the large vibration resonance, variable speed operation of the pump was not possible for several months at worst cases. To find an efficient vibration control method, the flexural responses of pumps for both normal and transient operations were measured. The measured modal characteristics were compared with those of finite element analysis. When the pump was operated at a specific rpm, the natural mode whose resonance frequency is twice the rotating angular speed induced the large vibration. The retrofit utilizing stiffeners to reduce this resonant vibration were performed. Effects of designed stiffeners on reducing vibration were validated through tests after actual installation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.157-165
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• 2004

The synchronization algorithm of IEEE 802.11a WLAN(Wireless Local Area Network) has three consecutive processes, which use a short code training symbol, a long code training symbol and a pilot symbol respectively. But in using this synchronization processes, the actual embodiment has two problems. First, the synchronization process has the complex structure using a long code training symbol and a pilot symbol. Second, since the long training symbol is only compensated with the offset correction coefficient, it can not be trusted perfectly. If the equalizer coefficient is obtained in this unstable period, the system performance is degraded. In particular, the system performance becomes worst in case of the 54 Mbps transmission system using the maximum length of data. In this paper, the new algorithm is proposed which can resolve the embodiment complexity of synchronization processes and structural defect, and also it is confirmed by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.181-186
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• 2004

Analysis on sharing between GSO FSS and terrestrial system in the 40㎓ band, related with the problem for sharing between terrestrial services and FSS and identification of HDFSS downlink bands in World Radiocommunication Conference 2003, was practiced by assuming that both systems are operated in Korea. According to results from simulation using the characteristic parameters of GSO FSS and terrestrial FS system in 40 ㎓ described in ITU-R Recommendations, in case that elevation and azimuth angle of antenna of FS station are adjusted to point directly to the geostationary satellite, the GSO system can cause the worst interference to the FS system. This situation is possible to occur in the installation of 40 GHz FS station in urban area where there are high-rise buildings. If high-density FS stations in 40 ㎓ band are operated in the future, interference mitigation techniques to avoid GSO arc should be considered.