• Journal of Power Electronics
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• 제10권1호
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• pp.1-8
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• 2010

A new scheme for sliding-mode control (SMC) of DC-DC converters with a constant switching frequency is proposed. The scheme is based on the averaging model and the output signal of the controller is $d^+$ or $d^-$ instead of the on or off signal of a direct sliding-mode (SM) controller or the continuous signal d = $u_{eq}$ of an indirect SM controller. Two approaches using the new scheme are also proposed and the design procedures for a buck converter are given in detail. The first approach called constant $d^+$ and $d^-$ SMC is simple, cost effective and dynamically fast. In order to improve the dynamic characteristics of the reaching phase and to alleviate chattering, the second approach called reaching law SMC is also presented. Analyses and simulation results demonstrate the feasibility of the proposed scheme.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제26권2호
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• pp.204-212
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• 1990

The SMC composite, now being considered in certain structural applications, is anticipated to experience repeated loading during service. Thus, understanding of the fatigue behavior is essential in proper use of the composite material. In this paper, using the SMC composite composed of E-glass chopped strand and unsaturated polyester resin three point bending fatigue tests are carried out to investigate the fatigue crack propagating behavior under various cyclic stresses and fatigue damage of various microcrack forms. The following results are obtained from this study; 1) Most of the total fatigue life of the SMC composite is consumed at the initial extension or the growth of the macroscopic crack. 2) A Paris' type power-law relationship between the crack propagation rate and stress intensity factor range is obtained, and the value of material constant m is much higher (m=9~11)than that of other metals. 3) In case of high cyclic stress the fatigue damage show high microcrack density and short crack length, but in case of low cyclic stress does it vice versa. 4) Fatigue damage is characterized by microcrack density, crack length and distribution of crack orientation.

• Journal of Practical Agriculture & Fisheries Research
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• 제7권1호
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• pp.109-117
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• 2005

This study was carried out to determine effects of the feeding length of spent mushroom composts from selenium-enriched mushroom (Se-SMC) on meat quality and carcass characteristics in finishing Hanwoo steers. A total of 20 steers were used in this trial with four treatments. Treatments included control (no Se-SMC), Se-SMC groups of three different feeding lengths (2, 4, and 6 months). After the completion for each feeding length, steers were slaughtered and then loin muscle (Longissimus dorsi) was sampled to evaluate meat quality characteristics. Chemical compositions of the loin, except for protein content, were not different across treatments. Protein content was highest in 6 months feeding groups, however, it was lowest in 4 months. Physical property and meat color (L*, a* and b* values) were not affected by the feeding length of Se-SMC. However, water holding capacity (WHC) for Se-SMC feeding treatments was significantly more improved (p<0.05) in comparison with the control group, showing 63.8 (2 months), 64.4 (4 months), 64.2 (6 months), and 59.5% (control), respectively. Grades for meat quality and quantity, and carcass characteristics were not affected by feeding length of Se-SMC. Our results showed that Se-SMC supplementation was not significantly associated with parameters for meat quality and carcass characteristics. However, as feeding Se-SMC lengthens, WHC for loin was more improved, suggesting that the improved WC may result in the expression of antioxidant effect.

• Composites Research
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• 제31권1호
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• pp.8-11
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• 2018

Sheet molding compound (SMC) is one of the most economical fiber reinforced composite fabrication processing for automotive applications. In this study, we studied the optimum formulation for the production of SMC which shows low specific gravity without lowering the mechanical properties by using glass bubble (GB) which is a low specific gravity filler and glass fiber (GF) as a reinforcing material. The tensile strength increased with the increase of the GF in the SMC, and the specific gravity decreased with the increase of the GB. The synergistic effect of improving the mechanical properties as the specific gravity is lowered is found in the optimum formulation. The synergy effect was confirmed by the internal structure analysis that the dispersion effect of the crack propagation of the GB and the improvement of the binding force between the fiber and the matrix due to the incorporation of the GB.

• Journal of the Korean Society of Marine Environment & Safety
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• 제24권7호
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• pp.953-959
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• 2018

This paper deals with controlling surge oscillations of a mooring vessel system under large external disturbances such as wind, waves and currents. A control synthesis based on Sliding Mode Control (SMC) with a Super-Twisting Algorithm (STA) has been applied to suppress nonlinear surge oscillations of a two-point mooring system. Despite the advantages of robustness against parameter uncertainties and disturbances for SMC, chattering is the main drawback for implementing sliding mode controllers. First-order SMC shows convergence within the desired level of accuracy, in which chattering is the main obstacle related to the destructive phenomenon. Alternatively, STA completely eliminates chattering phenomenon with high accuracy even for large disturbances. SMC based on STA is an effective tool for the motion control of a nonlinear mooring system because it avoids the chattering problems of a first-order sliding mode controller. In addition, the error trajectories of controlled mooring systems implemented by means of STA form in the bounded region. Finally, the control gain effect of STA can be observed in sliding surface and position trajectory errors.

• Journal of the Korean Arthroscopy Society
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• 제8권1호
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• pp.37-44
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• 2004

Purpose: To evaluate the optimal number of additional half hitches for achieving an optimal knot-holding capacity (KHC) of Lockable sliding knots. Methods: Four configurations of arthroscopic knots (Duncan loop, Field knot, Giant knot, and SMC knot) were tested for their knot-holding capacity. For each knot configuration, 6 sequential knots were made including the initial sliding knot and additional 5 knots by incrementing one half hitches at a time. Each added half-hitch were in reversing half-hitches with alternate posts (RHAPs) fashion. For each sequential knot configuration, 12 knots were made by No. 2 braided sutures. On the servo-hydraulic material testing system (Instron 8511, MTS, Minneapolis, MN), cyclic loading, load to clinical failure (3-mm displacement), load to ultimate failure, and mode of failure were measured. Results: Most of the initial loop without additional half-hitch showed dynamic failure with cyclic loading. The mean displacement after the end of cyclic loading decreased with each additional half-hitches. SMC and Giant knot reached plateau to 0.1 mm or less displacement after one additional half-hitch, shereas Field and Duncan loop needed 3 additional half-hitches. The SMC and Duncan knots needed 1 additional half-hitch to reach greater than 80N at clinical failure, whefeas the other 2 knots needed2 additional half-hitches. For the load exceeding 100N for clinical failure, the SMC knot required 3 additional half-hitches and the other three knots needed 4 additional half-hitches. As the number of additional half-hitches incremented, the mode of failure switched from pure loop failure (slippage) to material failure (breakage). Duncan loop showed poor loop security in that even with 5 additional half-hitches, some failed by slippage (17%). On the other hand, after 3 additional half-hitches, the 3 other knots showed greater than 75% of failure by material breakage mode (SMC and Field 92%, Giant 75%). Conclusion: Even with its own locking mechanism, lockable sliding knot alone does not withstand the initial dynamic cyclic load. For all tested variables, SMC knot requires a minimum of 2 additional half-hitches. Duncan knot may need more than 3 additional half-hitches for optimal security. All knots showed a mear plateau in knot security with 3 or more additional half-hitches.

• Journal of Genetic Medicine
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• 제8권2호
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• pp.119-124
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• 2011

Purpose: Supernumerary marker chromosome (SMC) could be associated with various phenotypic abnormalities based on the chromosomal origin of SMCs. The present study aimed to determine the genomic contents of SMCs using chromosomal microarray and to analyze molecular cytogenetic characterizations and clinical phenotypes in patients with SMCs. Materials and Methods: Among patients with SMCs detected in routine chromosomal analysis, SMCs originating from chromosome 15 were excluded from the present study. CGH-based oligonucleotide chromosomal microarray was performed in 4 patients. Results: The chromosomal origins of SMCs were identified in 3 patients. Case 1 had a SMC of 16.1 Mb in 1q21.1-q23.3. Case 2 showed 21 Mb gain in 19p13.11-q13.12. Case 3 had a 4.5 Mb-sized SMC rearranged from 2 regions of 2.5 Mb in 22q11.1-q11.21 and 2.0 Mb in 22q11.22-q11.23. Conclusion: Case 1 presented a wide range of phenotypic abnormalities including the phenotype of 1q21.1 duplication syndrome. In case 2, Asperger-like symptoms are apparently related to 19p12-q13.11, hearing problems and strabismus to 19p13.11 and other features to 19q13.12. Compared with cat-eye syndrome type I and 22q11.2 microduplication syndrome, anal atresia in case 3 is likely related to 22q11.1-q11.21 while other features are related to 22q11.22-q11.23. Analyzing SMCs using high-resolution chromosomal microarray can help identify specific gene contents and to offer proper genetic counseling by determining genotype-phenotype correlations.

• Journal of Information Processing Systems
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• 제3권1호
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• pp.21-25
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• 2007

We propose several practical SMC protocols for privacy-preserving cooperative scientific computations. We consider two important scientific computations which involve linear equations: the linear systems of equations problem and the linear least-square problem. The protocols proposed in this paper achieve acceptable security in the sense of Du-Zhan's paradigm and t-wise collusion-resistance, and their communication complexity is O(tm), where t is a security parameter and m is the total number of participants. The complexity of our protocol is significantly better than the previous result O($m^2/{\mu}$) of [4], in which the oblivious transfer protocol is used as an important building block.

• The Korean Journal of Mycology
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• 제40권3호
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• pp.152-158
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• 2012

The lignocellulytic enzymes including a-amylase (EC 3.2.1.1), lignin peroxidase (EC 1.11.1.14), laccase (EC 1.10.3.2), xylanase (EC 3.2.1.8), ${\beta}$-xylosidase (EC 3.2.1.37), ${\beta}$-glucosidase (EC 3.2.1.21) and cellulase (EC 3.2.1.4) were extracted from spent mushroom compost (SMC) of Pleurotus eryngii. Different extraction buffers and conditions were tested for optimal recovery of the enzymes. The optimum extraction was shaking incubation (200 rpm) for 2 h at $4^{\circ}C$. ${\alpha}$-Amylase was extracted with the productivity range from 1.20 to 1.6 Unit/SMC g. Cellulase was recovered with the productivity range from 2.10 to 2.80 U/gf. ${\beta}$-glucosidase and ${\beta}$-xylosidase productivities showed lowest recovery producing 0.1 U/g and 0.02 U/g, respectively. The P. eryngii SMCs collected from three different mushroom farms showed different recovery on laccase and xylanse, cellulase. Furthermore, the water extracted SMC was compared to commercial enzymes for its industrial application in decolorization and cellulase activity.

• Transactions of the Korean Society of Mechanical Engineers
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• 제13권1호
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• pp.87-95
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• 1989

The fatigue crack propagation of random short fiber SMC composite material was investigated. In macroscopic viewpoint, SMC composite material was treated as isotropic material and was analyzed in terms of conventional fracture mechanics. Experiments were conducted on mode I and mixed respectively and various loading level was applied to each mode. Fatigue crack growth can be explained in three steps and most of fatigue life is consumed in initial crack growth. In this experiments, power law, i.e, da/dN=C(C.DELTA.K)$^{m}$ , between fatigue crack growth rate and stress intensity factor range, was valid and the value of the exponent m is about 10, which is much higher than that of other metals. Fracture mechanism was also investigated by SEM fractographic study.