• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.24 no.2
• /
• pp.161-197
• /
• 2020

Total variation minimization is standard in mathematical imaging and there have been numerous researches over the last decades. In order to process large-scale images in real-time, it is essential to design parallel algorithms that utilize distributed memory computers efficiently. The aim of this paper is to illustrate recent advances of domain decomposition methods for total variation minimization as parallel algorithms. Domain decomposition methods are suitable for parallel computation since they solve a large-scale problem by dividing it into smaller problems and treating them in parallel, and they already have been widely used in structural mechanics. Differently from problems arising in structural mechanics, energy functionals of total variation minimization problems are in general nonlinear, nonsmooth, and nonseparable. Hence, designing efficient domain decomposition methods for total variation minimization is a quite challenging issue. We describe various existing approaches on domain decomposition methods for total variation minimization in a unified view. We address how the direction of research on the subject has changed over the past few years, and suggest several interesting topics for further research.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.31 no.4
• /
• pp.114-120
• /
• 2008

The control chart is widely used statistical process control(SPC) tool that searches for assignable cause of variation and detects any change of process. Generally, ${\bar{X}}-R$ control chart and ${\bar{X}}-S$ are most frequently used. When the production run is short and process parameter changes frequently, it is difficult to monitor the process using traditional control charts. In such a case, the coefficient of variation (CV) is very useful for monitoring the process variability. The CV control chart is an effective tool to control the mean and variability of process simultaneously. The CV control chart, however, is not sensitive at small shift in the magnitude of CV. In this paper, we propose an CV-EWMA (exponentially weighted moving average) control chart which is effective in detecting a small shift of CV. Since the CV-EWMA control chart scheme can be viewed as a weighted average of all past and current CV values, it is very sensitive to small change of mean and variability of the process. We suggest the values of design parameters and show the results of the performance study of CV-EWMA control chart by the use of average run length (ARL). When we compared the performance of CV-EWMA control chart with that of the CV control chart, we found that the CV-EWMA control chart gives longer in-control ARL and much shorter out-of-control ARL.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.9 no.2
• /
• pp.73-82
• /
• 1989

When the flood occurs in the alluvial rivers, the rivers adjust to the flood by means of the mechanism of the river bed variations and its morphological changes to pass that safely, the numerical model was developed to simulate the process of the alluvial river bed variation due to flood wave and carried out by the flood routing for flood wave and the sediment routing for river bed variation. The flood wave, river bed variation, and bed material size distribution may be analysed and predicted by this model. The ability of this model to predict the process of river bed response was proved by the application to the reach from Paldang dam to Indogyo site. In view of the flood analysis considering the sediment process, the effects of river bed variation for the flood routing may be negligible because the river bed variation is smaller than the unsteady flow variation during the same period. By the application of this model, it is shown that, in occurring of sequential flood events, the variation of the river bed and bed material size distribution due to flood wave is more dependent on the first flood event than the latter flood events, and that the river bed variation in this reach of the downstream Han river is dependent on the degradation and the coarsening of bed materials.

• Archives of Reconstructive Microsurgery
• /
• v.22 no.2
• /
• pp.48-51
• /
• 2013

Purpose: The lessor saphenous vein is an anatomical index in various surgical methods involving an approach to the popliteal fossa. However, occasionally, there have been some cases where the surgical process was difficult because the lessor saphenous vein was not found in the popliteal fossa during the operation process. The aim of this study is to determine the frequency of the anatomical variation of lessor saphenous vein not found in the popliteal fossa with a review of the literature. Materials and Methods: This study was conducted on 83 cases of selective neurectomy for hypertrophic calf performed in our clinic from March 1997 to June 2013. There were 42 patients, with a mean age of 32.8 years old. We confirmed the existence of the lessor saphenous vein in the popliteal fossa during the operation process. Results: Among 83 cases during this study period, the lesser saphenous vein was not found in four cases. In one patient, no lesser saphenous vein was found on either side of the popliteal fossa, and in two patients, no lesser saphenous vein was found on the left side of the popliteal fossa. As a result, the frequency of variation was found to be 4.8%. Conclusion: Due to the anatomical variation of the lessor saphenous vein, it may not be found in the midline of the popliteal fossa. Based on the literature review, several possibilities for failure to observe the lesser saphenous vein could be suggested. If surgeons are well aware of these possibilities, the steadier operation could be performed.

• Korean Journal of Construction Engineering and Management
• /
• v.2 no.4 s.8
• /
• pp.117-126
• /
• 2001

The purpose of this study is to present a way of Variation Control in building construction process. The study suggest a way of the application method of shielding, decoupling concept and also Poka-yoke device to control variation that occurs from uncertainty in construction industry with lots of waste factors. The main contents of the study are as follows; (1) It's suggested strategy to apply shielding, decoupling as variation control technique. (2) Current Poka-yoke devices are investigated and analyzed. As a future research, it is required to study continuously on the more effective application method of Poka-yoke device and on existing examples in domestic construction sites for the process improvement.

• Journal of the Society of Naval Architects of Korea
• /
• v.54 no.5
• /
• pp.387-392
• /
• 2017

There is a constant demand for hull variation related to ship design. Various input variables are generally given to achieve the objective functions assigned by each variation process. When dealing with geometric shapes accompanied by nonlinear operations during the variation process, vague relationships or uncertainties among input variables are commonly observed. Therefore, it is strongly recommended to identify those uncertainty factors in advance. A method to modify the shape of a closed hull form with a new area and a centroid had been introduced as a new process of hull variation. Since uncertainty between input variables still existed in the method, however, it was not easy for the user to enter the area and the corresponding centroid. To overcome this problem, a method is presented in this paper to provide the feasible region of centroids for a given area. By utilizing the concept and techniques used in the statistics such as the number of samples, probability, margin error, and level of confidence, this method generates the distribution of possible centroids along the regression curve. The result shows that the method helps the user to choose an appropriate input value following his or her design intention.

• Journal of Environmental Health Sciences
• /
• v.34 no.6
• /
• pp.423-432
• /
• 2008

In this study, we investigated the possibility of auto control and the proper operating factors in the BNR(Biological Nutrient Removal) process using an NADH(Reduced Nicotinamide Adenine Dinucleotide) fluorometer, which characterized the emitted fluorescence when activated by flashes of UV light at 460 nm. In terms of finding adequate operating parameters, results indicted that nitrification efficiency decreased in the controlled DO while denitrification efficiency decreased in the controlled pH. The above results indicated that controlled operating condition after combination with NADH, DO and pH was resonable. Result obtained from the correlation between NADH and pH showed that variation trend of influent loading was similar to those of NADH and pH, and also the variation cycle was repeated on a daily basis. Consequently, this result showed the increase of BOD loading caused the nitrification efficiency to decrease because air-flow, required for nitrification, was reduced, and so the NADH value was increased. From these results, it is possible to use NADH flourimetry to assess the variation of organic load and nitrification efficiency in the case of small change in influent pH such as in sewage and also to handle and operate the load variation in the auto control system using the NADH fluorometer.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.04a
• /
• pp.218-223
• /
• 2000

A both mixing process of electro-magnetic stirring and mechanical process technique were used to fabricate particulate metal matrix composites(PMMCs) for variation of particle size. The PMMCs were tested for their tensile test for with and without heat treatment with T6. PMMCs fabrication processing conditions for both electrical and mechanical process are also suggested. In order to thixoforming of PMMCs, fabricated billet are reheated by using the optimal coil designed as a function of length between PMMC billet and coil surface, coil diameter and billet length. The effect of reinforcement distribution on billet temperature variation are investigated with calculated solid fraction theory proposed as a function of matrix alloy and volume fraction of reinforcement.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1428-1429
• /
• 2011

This paper variation of stranded cable conductor with CIP(Cold Isostatic Press) technology. Conductor as cable material takes majority costs. Thus many experiments have been done on conductor compaction. The core technology is to maintain the resistance of circular stranded conductor after compaction process, while reducing the weight of conductor diameter, but by increasing filling factor. Testing by varying the compaction ratio using 300SQ conductor, conductor after CIP process shows lower resistance rather than conductor before CIP process.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.2
• /
• pp.57-59
• /
• 2001

We investigated the maximum controllable current characteristics of the CB-BRT (Corrugated p-Base-Base Resistance Controlled Thyristor), which suppresses the snap-back effectively and increases the maximum controllable current(MCC) by employing the corrugated p-base. Experimental result shows that, when compared with conventional BRT, the MCC of the CB-BRT exhibits good stability on various process parameters. The MCC of the CB-BRT is larger than that of the conventional BRT by 50%, and the variation of the MCC in CB-BRT, caused by variation of the process parameters, is only 20% of that of the conventional BRT.