• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.883-893
• /
• 2016

This paper presents a comprehensive analysis of the spurious turn-on phenomena in phase-shifted full-bridge (PSFB) converters. The conventional analysis of the spurious turn-on phenomenon does not establish in the PSFB converter as realizing zero voltage switching (ZVS). Firstly, a circuit model is proposed taking into account the parasitic capacitors and inductors of the transistors, as well as the parasitic elements of the power circuit loop. Second, an exhaustive investigation into the impact of all these parasitic elements on the spurious turn-on is conducted. It has been found that the spurious turn-on phenomenon is mainly attributed to the parasitic inductors of the power circuit loop, while the parasitic inductors of the transistors have a weak impact on this phenomenon. In addition, the operation principle of the PSFB converter makes the leading and lagging legs have distinguished differences with respect to the spurious turn-on problems. Design guidelines are given based on the theoretical analysis. Finally, detailed simulation and experimental results obtained with a 1.5 kW PSFB converter are given to validate proposed analysis.

• Parasites, Hosts and Diseases
• /
• v.59 no.4
• /
• pp.421-426
• /
• 2021

A 12-year nationwide survey (2008-2019) was performed to investigate the prevalence of Enterobius vermicularis infection among preschool children in Seoul, 4 large cites (Busan, Incheon, Daegu, and Ulsan), and 9 provinces (grouped into 5 localities) in the Republic of Korea (=Korea). The survey was carried out once a year by 16 regional offices of the Korea Association of Health Promotion. The cello-tape perianal swab method (1 smear per child) was applied to detect eggs of E. vermicularis and other helminths. According to the results, the egg positive rate of E. vermicularis infection in 2008-2009 was 1.8-2.0%, but it decreased gradually to 0.6% in 2019 (P<0.05). The prevalence was significantly higher in boys (0.7-5.0%, mean 1.8%) than in girls (0.5-2.8%, mean 1.3%) (P<0.05). The 2 most southern localities, Jejudo (Province) and Jeolla-do (inclusive of Jeollabuk-do and Jeollanam-do) and a mid-western province, Gyeonggi-do, revealed higher prevalences, whereas Seoul and Gangwon-do showed lower prevalences. The results indicate that a low-grade prevalence of E. vermicularis infection (less than 4%) has been maintained for the recent 12 years among preschool children in Korea. Continuous monitoring of enterobiasis in the child age group is necessary in Korea.

• Structural Engineering and Mechanics
• /
• v.87 no.3
• /
• pp.283-296
• /
• 2023

Free-vibration and buckling analyses of plate problems are investigated with the aid of the strain gradient notation finite element method (SGN-FEM). As SGN-FEM employs physically interpretable polynomials in developing finite elements, parasitic shear sources, which are the cause of shear locking, can be precisely identified and subsequently eliminated. This allows two mutually complementary objectives to be defined in this work, namely, evaluate the efficiency of free-vibration and buckling results provided by corrected models, and study the severity of parasitic shear effects on plate models performance. Parasitic shear are flexural terms erroneously present in shear strain polynomials. It is reviewed here that six parasitic shear terms arise during the formulation of the four-node Mindlin plate element. Two parasitic shear terms have been identified in the in-plane shear strain polynomial while other two have been identified in each of the transverse shear strain polynomials. The element is corrected a-priori, i.e., during development, by simply removing the spurious terms from the shear strain polynomials. The computational implementation of the element in its two versions, namely, containing the parasitic shear terms (PS) and corrected for parasitic shear (SG), allows for assessments of the accuracy of results and of the deleterious effects of parasitic shear in free vibration and buckling analyses. This assessment of the parasitic shear effects is a novelty of this work. Validation of the SG model is done comparing its results with analytical results and results provided by other numerical procedures. Analyses are performed for square plates with different thickness-to-length ratios and boundary conditions. Results for thin plates provided by the PS model do not converge to the correct solutions, which indicates that parasitic shear must be eliminated. That is, analysts should not rely on refinement alone. For thick plates, PS model results can be considered acceptable as deleterious effects are really critical in thin plates. On the other hand, results provided by the SG model converge well for both thin and thick plates. The effectiveness of the SG model is established via high-accuracy results obtained in several examples. It is concluded that corrected SGN-FEM models are efficient alternatives for free-vibration and buckling analysis of Mindlin plate problems, and that precise elimination of parasitic shear is a requirement for sound analyses.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.34D no.1
• /
• pp.1-7
• /
• 1997

In this paper, several parasitic elements are added to the circular microstrip antenna in order to increase its bandwidth. Three kinds of parasitic elements such as cone, circular plate, and ring types are applied and input VSWRs, radiation patterns, and input impedances are measured. The optimal sizes of each parasitic element are obtianed and the variations of the bandwidth according to the height from the patch are also measured. In thid case of the ring type, the optimum bandwidth is obtained at the height of 10mm from the patch to the parasitic element. In the cases of conical and circular plate types, the maximum bandwidth is obtained at the hight of 45mm form the patch to the parasitic elements.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.5
• /
• pp.1294-1303
• /
• 1996

In this paper, the microstrip anntenna with broad bandwidth is designed using parasitic element. In the designed cofiguration, parasitic element of the same resonating length but different width which is coupled to the nonradiating edge of a rectangular patch antenna. The driven element aloe is fed and the other part is operated as parasitic element. So the different patchs are resonating at differnt frequencies and this multiple resonance increase the bandwidth. The overall size of the antenna is not increased by adding parasitic element to a driven patch. Compared to the available wideband microstrip antennas, the designed antenna structure is bery compact. A theoretical explanation of the rectangular patch antenna coupled with prarsitic is analyzed by extending the theory of coupled microstrip lines. The theoretical and experimental results for a patch coupled with a single parasitic are presented.

• The Korean Journal of Cytopathology
• /
• v.6 no.1
• /
• pp.36-40
• /
• 1995

In the past, parasitic diseases were a major problem in public health in Korea. In recent years, however, nematodiasis that used be prevalent are no longer a serious problem. Instead some cestodiasis, particularly cysticercosis and sparganosis have become comparatively more important in recent years. Parasitic infestation of soft tissue is presented as a subcutaneous nodule or mass with nonspecific clinical manifestations. We experienced 4 cases of parasitic infestation in the soft tissue diagnosed by fine needle aspiration (FNA). Three out of four cases were histologically confirmed, two out of four cases were cysticercosis and one case was confirmed as sparganosis. FNA may be useful in providing a diagnosis in cases of parasitic infestation.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.34D no.6
• /
• pp.20-32
• /
• 1997

An optimum parasitic inductance is observed for maximizing the modulation bandwidth of the multiple quantum well (MQW) electro-absorption optical modulator. For 1.1 pF device cpaacitance of the current MQW optical modulator, the optimum parasitic inductances for maximum bandwidth are calculated for different terminating resistors. In ase of 50.ohm. terminating resistor, the 3-dB modulation bandwidth can be increased 45% wider by using the optimum parasitic inductance than nothing parasitic inductance. This calculated optimum inductance can be practically implemented, since the parasitic inductance of bondwires can be accurately analyzed using the method of moments (MoM) and controlled by changing the length and shpae of bondwires.

• The Plant Pathology Journal
• /
• v.37 no.5
• /
• pp.446-454
• /
• 2021

Plant-parasitic nematodes are not only an important constraint on agricultural crop production, but also cause both direct and indirect damage to turfgrass, which is a ground cover plant. However, studies on plant-parasitic nematodes of turfgrass in Korea are scarce. A survey for plant-parasitic nematodes was carried out on 13 golf courses in Korea. The results yielded 28 species/taxa belonging to 16 genera and 12 families of plant-parasitic nematodes. Among the isolated species, Helicotylenchus microlobus, Mesocriconema nebraskense, Tylenchorhynchus claytoni, Mesocriconema sp., and Meloidogyne graminicola were the most prevalent species in all management zones. Twelve species were new records of plant-parasitic nematodes in Korea. Highest maximum densities were showed by T. claytoni, Paratylenchus nanus, M. nebraskense, M. graminicola, and H. microlobus. Diversity (H'), was significantly higher in fairways compared to tees and greens, though species evenness (J') and dominance (D) showed no statistically significant differences. This information is crucial in nematode problem diagnosis, and the subsequent formulation of management strategies.

• Parasites, Hosts and Diseases
• /
• v.54 no.6
• /
• pp.797-801
• /
• 2016

Heishui county, located in northwest Sichuan province, southwestern China, is an endemic area of zoonotic visceral leishmaniasis (VL) and is the most intractable area. VL is never destroyed in it. Asymptomatic dogs (Leishmania parasites have been diagnosed but clinically healthy) are considered to be a potential reservoir host in zoonotic VL area, and most can lead to infection of individuals, that is a new challenge for controlling VL in humans. The present study aimed to assess the Leishmania infection rate of asymptomatic dogs in Heishui county. Total 105 asymptomatic domestic dogs were gathered from 4 districts in Heishui county to investigate the infection rate with serological and molecular methods based on ELISA and kinetoplast minicircle DNA(kDNA) PCR, respectively. Out of 105 dogs, 44 (41.9%) were positive by more than 1 method; 21 (20.0%) were positive by ELISA, and 30 (28.6%) were positive by kDNA-PCR. Our study showed that Leishmania infection of domestic dogs which is clinically healthy is prevalent in the studied district, and the asymptomatic dogs infected by Leishmania may be the primary reason for the prevalence of visceral leishmaniasis in the area.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.26 no.5
• /
• pp.483-491
• /
• 2015

This paper describes the design optimization of parasitic elements used for TACAN broadband antenna. We deployed parasitic elements arranged in a circular array to electronically rotate the antenna instead of employing a mechanically rotated antenna to generate the composite radiation pattern of 15 Hz and 135 Hz including bearing information and to meet the harmonic contents specification of MIL-STD-291C. We performed the simulation for optimization of the parasitic elements and fabricated the antenna composed of 16 parasitic elements of 15 Hz and 63 parasitic elements of 135 Hz. With harmonics magnitude reduction by increasing the number of steps using vector composition of the reflectors, the measured result meets the specification of MIL-STD-291C.