• Archives of Reconstructive Microsurgery
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• v.19 no.1
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• pp.68-79
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• 2010

Lower abdominal tissue is regarded as an ideal donor site for the breast reconstruction because it provides large skin territory and huge amount of soft tissues enough to the breast size. However it is not easy for the surgeon to reconstruct the really natural breast, and needs the learning curve with long time experience. Author represent the various reconstruction procedures for the breast using lower abdominal tissue such as muscle sparing free TRAM, DIEP, and SIEA free flaps to reinsure like breast. Indications, and selection of reconstructive methods, surgical timing, selection of donor sites and recipient vessel of these flaps were reviewed. In addition, detailed procedures, surgical tips and secondary adjuvant procedures are described for more symmetry of reconstructed breast. The muscle sparing free TRAM, DIEP, and SIEA free flaps would be enough to provide supple, huge amount of well vascularized tissue for the breast, if these flaps were selected for the appropriate indication according to patient's general condition, obesity, the opposite breast and abdominal tissue condition. Lower abdominal tissue was able to provide versatile designs with sufficient adipose tissue without compromising the integrity of abdominal wall.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.7
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• pp.1411-1417
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• 2009

In this paper, we consider the design of $H_{\infty}$ control of linear discrete-time systems having no mathematical model. The basic approach is to use Q-learning which is a reinforcement learning method based on actor-critic structure. The model-free control design is to use not the mathematical model of the system but the informations on states and inputs. As a result, the derived iterative algorithm is expressed as linear matrix inequalities(LMI) of measured data from system states and inputs. It is shown that, for a sufficiently rich enough disturbance, this algorithm converges to the standard $H_{\infty}$ control solution obtained using the exact system model. A simple numerical example is given to show the usefulness of our result on practical application.

• Journal of Applied Reliability
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• v.15 no.1
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• pp.6-11
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• 2015

Maintenance plays an important role in keeping product availability, reliability and quality at an appropriate level. In this paper, two-types of maintenance policies are studied following the expiration of two-dimensional (2D) free replacement warranty. Both the fixed-maintenance-period policy and the variable-maintenance-period policy are based on a specified region of the warranty defined in terms of age and usage where all failures are minimally repaired. An accelerating failure time (AFT) model is used to allow for the effect of usage rate on product degradation. The maintenance model that arises following the expiration of 2D warranty is discussed. The expected cost rates per unit time from the user's point of view are formulated and the optimal maintenance policies are determined to minimize the expected cost rate to the user. Finally numerical examples are given to illustrate the optimal maintenance polices.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.62
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• pp.1-10
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• 2001

The electronics industry is fast growing segment of manufacturing and service industries. It is important that the manufacturer develops a product with adequate life cycle, high quality, and low failure rate in the specified time period. Environmental Stress Screening(ESS) and burn-in are widely used in the electronic industry to assist in the elimination of early failure. In this research, we construct optimal cost model of combined ESS and burn-in under various warranty policy and establish optimal testing times for given environments. Also we conduct sensitivity analysis on various parameter. The results of this study are summarized as follows. Comparing free warranty policy to rebate warranty policy, optimal ESS time is longer under free warranty policy, and optimal burn-in time is longer under rebate warranty policy. Free warranty policy higher than rebate warranty policy in total cost.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.10
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• pp.900-906
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• 2010

This note proposes vibration-free motor control through modified LQG/LTR methodology. A conventional LQG/LTR method is a design tool in the frequency domain. However, unlike the conventional one, the proposed one is a time response based design method. This feature is firstly designed by parameterized settling time control gain through the target loop design procedure and the feature is secondly realized by loop transfer recovery. In order to show convergence to the target loop transfer functions, asymptotic behaviors of the open and the closed loop transfer functions are shown. At the conclusion, it is verified that the proposed method is robustly stable to parametric uncertainties through ${\mu}$-plot.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.19 no.39
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• pp.89-98
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• 1996

This paper is concerned with cost analysis model in free -replacement policy under the periodic maintenance policy The free-replacement policy with minimal repairable item is considered as follows; in a manufacturer's view point operating unit is periodically replaced, if a failure occurs between minimal repair and periodic maintenance time, unit is remained in a failure condition. Also unit undergoes minimal repair at failures in minimal-repair interval. Then total expected cost per unit time is calculated according to maintenance period Tin a viewpoint of consumer's. The expected costs are included repair cost and usage cost: operating, fixed, minimal repair and loss cost. Numerical example is shown in which failure time of item has beta distribution.

• Journal of the Korea Society of Computer and Information
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• v.24 no.9
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• pp.21-27
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• 2019

In this paper, we propose a deep auto-encoder-based pipe leak detection (PLD) technique from time-series acoustic data collected by microphone sensor nodes. The key idea of the proposed technique is to learn representative features of the leak-free state using leak-free time-series acoustic data and the deep auto-encoder. The proposed technique can be used to create a PLD model that detects leaks in the pipeline in an unsupervised learning manner. This means that we only use leak-free data without labeling while training the deep auto-encoder. In addition, when compared to the previous supervised learning-based PLD method that uses image features, this technique does not require complex preprocessing of time-series acoustic data owing to the unsupervised feature extraction scheme. The experimental results show that the proposed PLD method using the deep auto-encoder can provide reliable PLD accuracy even considering unsupervised learning-based feature extraction.

• Korean Journal of Head & Neck Oncology
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• v.23 no.1
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• pp.26-31
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• 2007

Background and Objectives：Microvascular free flap reconstruction has been revolutionized in last two decades, and became a standard option in the reconstruction of head and neck defects. We intended to review our experiences of 51 microvascular free flap for head and neck defects during 5-year period and to analyze the types of flaps according to primary sites, success and complication rates. Subjects and Methods：From Oct. 2001 through Dec. 2005, fifty one free flap reconstructions were performed in forty nine patients at ENT department of Soonchunhyang university bucheon hospital. Primary sites, pathology, T-stage, operative time, time interval of oral feeding, and various reconstructive factors such as recipient and donor vessels, free flap related complications, failure rates and salvage rates were retrospectively analyzed. The relation between complication rates and preoperative risk factors were statistically analyzed. Results：Methods of reconstruction were radial forearm free flap(RFFF)(n=28, 54.9%), anterolateral thigh free flaps(n=9, ALTFF)(17.6%), rectus abdominis free flap(n=7, RAFF)(13.7%), jejunal free flap(n=5, JFF)(9.8%), and miscellanous(n=2, 4.0%) in order. In free flap related complications, failure of free flap occurred in seven cases(13.7%) and pharyngocutaneous fistula occurred in five cases(9.8%) among fifty one free flaps. The overall success rate of free flaps was 86.3%. Salvage of free flaps was possible only one among eight cases(12.5%). In positive preoperative risk factor groups, failure of free flap was higher than in negative risk factor group. However, it was not statistically significant. Conclusion：We confirmed that free flap reconstructions are highly versatile and reliable options for use in the reconstruction of various soft tissue defects of the head and neck. Free flaps have gained great popularity given its versatility, ability for a two-team approach, and minimal donor site morbidity. However, complications related to microvascular surgery may be overcome by increased surgical experience and by intensive flap monitoring in early postoperative period.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.45
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• pp.301-307
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• 1998

This paper proposes free warranty interval for repairable items when the failure types of item are considered. Failure types are classified into major failure and minor failure. If major failure occurs during warranty period, the item is replaced and if minor failure occurs during warranty period, the item is minimally repaired. This paper determines the optimum free warranty interval which minimizes total expected cost of the free warranty cost model. Numerical example is shown in which failure time of item has weibull distribution.

• Archives of Plastic Surgery
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• v.42 no.5
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• pp.608-613
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• 2015

Background The purpose of this study was to compare postoperative morbidities and functional outcomes of pectoralis major myocutaneous (PMMC) flap and cutaneous free flap reconstruction approaches in hypopharyngeal squamous cell carcinoma patients. Methods We retrospectively reviewed records from 99 patients who underwent hypopharyngeal reconstruction with a cutaneous free flap (n=85) or PMMC flap (n=14) between 1995 and 2013. Morbidity was classified into hospitalization, medical, or flap-related complications. Functional outcomes were classified into oral re-alimentation and decannulation time. Results The overall flap-related complication rate was higher in the PMMC flap group (n=8, 57.1%; P=0.019), but the medical morbidity rate was higher in the cutaneous free flap group (n=68, 80%; P=0.006). The rate of pneumonia was higher in the cutaneous free flap group (n=48, 56.5%; P=0.020). Pulmonary premorbidity was the variable most significantly associated with pneumonia (odds ratio=3.012, P=0.012). There was no statistically significant difference in oral re-alimentation and decannulation time between the two groups. Conclusions Although the functional superiority of free flaps has been reported in many studies, our results do not support this hypothesis. One limitation of our study is the relatively smaller flap size and fewer PMMC flap cases compared with the cutaneous free flap group. The low postoperative medical morbidity incidence rate in the PMMC flap group was clinically significant; however, the free flap group had more flap-related complications. Thus, PMMC flaps should be considered a viable option, especially for patients with pulmonary premorbidities.