• Communications for Statistical Applications and Methods
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• v.8 no.2
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• pp.383-394
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• 2001

This paper is a generalization of single and two-level skip-lot sampling plans to n-level. On every skipping inspection of the n-level skip-lot sampling plan, not only the number of consecutive lots to be accepted but also the fraction of lots to be inspected can be freely choosed. The general formulas of the operating characteristic function, average fraction inspected, average sample number and average outgoing quality in n-level skip-lot sampling plan are derived. The operating characteristic curves, average sample number and average outgoing quality of a reference plan, two-level and five-level skip-lot sampling plans are compared.

• Journal of the Korean Operations Research and Management Science Society
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• v.30 no.4
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• pp.71-81
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• 2005

This Paper focuses on the effects of outside competition on an optimal echelon base stock level in a two stage supply chain. This is new in that we have been studying the effects of inside competition within a supply chain up to now. It is known that the optimal echelon base stock level with inside competition within a supply chain is less than the global optimal echelon base stock level without inside competition. This is due to the ' public goods ' nature of inventory. That is, more inventory is better, but one wants the other to invest more, thus resulting in under-investment. However, this phenomenon becomes weaker as outside competition increases. We show that as outside competition becomes stronger, the ' public goods ' effects decrease and the optimal echelon base stock level increases. If the level of competition is sufficiently high, the optimal echelon base stock level goes even higher than the global optimal echelon base stock level. We develop a theoretical model for the analysis and conduct a numerical analysis.

• Journal of Power Electronics
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• v.9 no.4
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• pp.593-603
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• 2009

This paper proposes and describes the design and operational principles of a three-phase three-level nine switch voltage source inverter. The proposed topology consists of three bi-directional switches inserted between the source and the full-bridge power switches of the classical three-phase inverter. As a result, a three-level output voltage waveform and a significant suppression of load harmonics contents are obtained at the inverter output. The harmonics content of the proposed multilevel inverter can be reduced by half compared with two-level inverters. A Fourier analysis of the output waveform is performed and the design is optimized to obtain the minimum total harmonic distortion. The full-bridge power switches of the classical three-phase inverter operate at the line frequency of 50Hz, while the auxiliary circuit switches operate at twice the line frequency. To validate the proposed topology, both simulation and analysis have been performed. In addition, a prototype has been designed, implemented and tested. Selected simulation and experimental results have been provided.

• Journal of the Semiconductor & Display Technology
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• v.13 no.4
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• pp.43-48
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• 2014

Two-level inverter has some disadvantages like high harmonics contained in the output current, efficiency limit and stress to switching device as IGBT and FET. Many researches have reported multi-level inverter to complement two-level inverter of problems. In this paper, we suggest MPPT algorithm of multi-string three-level solar inverter that considered nowadays. We added midpoint controller in order to implement the MPPT algorithm because the three-level inverter has to need midpoint controller and procured the stability of direct current link. We verify the superiority of multi-string T-Type inverter and the algorithm we suggested with solar irradiance variation experiment and MPPT efficiency measurement. The MPPT efficiency was confirmed with a high efficiency more than 99.97%.

• The Korean Journal of Applied Statistics
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• v.6 no.2
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• pp.277-287
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• 1993

This paper is a generalization of single- and two-level skip-lot sampling plans to n-level, which can considerably reduce inspection cost when the level of submitted quality is high. In every skipping inspection of the generalized sampling plan, not only skipping parameters but also inspection fractions can be freely choosed. The general formula of the operating characteristic function for the n-level skip-lot sampling plan is derived. Also the operating characteristic curves of a reference plan, two-level and three-level skip-lot sampling plans are compared.

• Phonetics and Speech Sciences
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• v.6 no.4
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• pp.67-77
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• 2014

This study investigated (1) whether Korean learners of English use discourse-level prosody in L2 production as native speakers of English do, and (2) whether discourse-level prosody is also found in the Korean language, as is evident in the prosody of native speakers of English. The study compared the production of the same 15 sentences in two types of reading materials, sentence-level and discourse-level. This study analyzed the onset pitch, sentence mean pitch and pause length to examine the paratone (intonational paragraph) realization in discourse-level speech. The results showed that in L2 discourse-level prosody, the Korean speakers were limited in displaying paratone and did not made significant difference between sentence-level and discourse-level prosody. On the other hand, in L1 discourse-level text, both English and Korean participants demonstrated paratone using pitch. However, there were differences in using prosodic cues between two groups. In using pauses, the ES group paused longer before both the orthographically marked and not marked topic sentences. The KS group paused longer only before the orthographically marked topic sentence in both L1 and L2 text reading. In the comparison of sentence-level and discourse-level prosody, the topic sentences were marked by different prosodic cues. English participants used higher sentence mean pitch, and the Korean participants used higher onset pitch.

• Journal of Korean Neurosurgical Society
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• v.50 no.5
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• pp.441-445
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• 2011

Objective : There are technical limitations of multi-level posterior pedicle screw fixation performed by the percutaneous technique. The purpose of this study was to describe the surgical technique and outcome of minimally invasive multi-level posterior lumbar interbody fusion (PLIF) and to determine its efficacy. Methods : Forty-two patients who underwent mini-open PLIF using the percutaneous screw fixation system were studied. The mean age of the patients was 59.1 (range, 23 to 78 years). Two levels were involved in 32 cases and three levels in 10 cases. The clinical outcome was assessed using the visual analog scale (VAS) and Low Back Outcome Score (LBOS). Achievement of radiological fusion, intra-operative blood loss, the midline surgical scar and procedure related complications were also analyzed. Results : The mean follow-up period was 25.3 months. The mean LBOS prior to surgery was 34.5, which was improved to 49.1 at the final follow up. The mean pain score (VAS) prior to surgery was 7.5 and it was decreased to 2.9 at the last follow up. The mean estimated blood loss was 238 mL (140-350) for the two level procedures and 387 mL (278-458) for three levels. The midline surgical scar was 6.27 cm for two levels and 8.25 cm for three level procedures. Complications included two cases of asymptomatic medial penetration of the pedicle border. However, there were no signs of neurological deterioration or fusion failure. Conclusion : Multi-level, minimally invasive PLIF can be performed effectively using the percutaneous transpedicular screw fixation system. It can be an alternative to the traditional open procedures.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1996.06a
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• pp.175-180
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• 1996

In this paper, a new image segmentation method based on merging of two low contrast neighbor regions iteratively is proposed. It is suitable for very low bit rate coding. The proposed method reduces efficiently contour information and preserves subjective and objective image quality. It consists of image segmentation using 4-level hierarchical structure based on mathematical morphology and 1-level region merging structure using the contrast difference of two adjacent neighbor regions. For each segmented region of the third level, two adjacent neighbor regions having low contrast difference value in fourth level based on contrast difference value is merged iteratively. It preserves image quality and shows the noticeable reduction of the contour information, so that it can improve the bottleneck problem of segmentation-based coding at very low bit rate.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.453-458
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• 2004

This study proposes a new two-level condensation scheme for the construction of a reduced system. In the first step, the candidate area is selected for the construction of the reduced system by energy estimation in element-level. In the second step, primary degrees of freedom are selected by sequential elimination from the candidate degrees of freedom linked to the selected elements. Numerical examples demonstrate that the proposed method saves the computational cost effectively and provides a reduced system which predicts the eigenvalues accurately. Moreover, the well-constructed reduced system can present the reliable behavior of the structure under arbitrary dynamic loads comparing to that of global system. Time integration in a reduced system can save the computing time remarkably. Through a few numerical examples, the efficiency and reliability of the proposed scheme are verified.

• Journal of Chest Surgery
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• v.28 no.3
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• pp.274-279
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• 1995

To evaluate clinical pattern and operative outcome of atherosclerotic obstructive disease in the lower extremity, surgical experience in 25 patients between September 1987 and June 1994 was analyzed. There were 24 male patients and 1 female patient. The age of the patients ranged between 36 and 77 years[mean:60.9 years . Disabing intermittent claudication, rest pain, or ischemic gangrene[or ulceration was the operative indication. The patients were classified into three groups according to the level of obstruction: Aortoiliac level[11 cases/44% , femoropopliteal level[6 cases/24% , and whole level[8 cases/32% . Anatomic bypass with prosthetic graft was performed in all cases: aortobifemoral or aortofemoral bypass in 15 procedures, iliofemoral bypass in 5 procedures, femoropopliteal bypass in 13 procedures. The perioperative mortality rate was 12%. Two patients received postoperative major amputation. Twenty two patients were followed-up for 1 to 70 months[mean: 21 months . Late graft obstruction occurred in two patients. The cumulative patency rate at 3 years was 69.5%. The cumulative limb salvage rate at 3 years was 92.0%.