• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.49 no.6
• /
• pp.339-346
• /
• 2023

Objectives: This analysis details the characteristics of dental trauma in South Korea during the coronavirus disease 2019 (COVID-19) (DC) pandemic and compares them in patients before and after COVID-19 (BC and AC, respectively). Materials and Methods: Data were collected from medical records of patients who visited Seoul National University Bundang Hospital's Emergency Dental Care Center during three 12-month periods: BC, DC, and AC (BC from March 1, 2019 to February 29, 2020; DC from March 1, 2020 to February 28, 2021; AC from March 1, 2022 to February 28, 2023). A retrospective review was conducted to investigate patient age, sex, time of visit, cause, and diagnosis. The study included 1,544 patients: 660 BC, 374 DC, and 510 AC. Results: Significant difference in age and sex was not observed among the three periods; 1-9 years of age was the largest group (38.3% in BC, 29.6% in DC, and 27.8% in AC), and the percentage of male patients was greater than of female patients (male proportion as 63.5% in BC, 67.4% in DC, and 64.9% in AC). The number of patients generally peaked at a Saturday night in spring (for BC: May, Saturday, 18:00-19:59; for DC: March, Saturday, 18:00-19:59; for AC: April as the second most (October as the most peaked), Saturday, 20:00-21:59). The primary etiology of the dental trauma was identical in the three periods: falls, followed by sports. The most frequent diagnosis was laceration, followed by tooth avulsion and jaw fracture. Conclusion: Significant differences were not found between the characteristics and patterns of dental trauma in the BC, DC, and AC periods. However, due to the pandemic and social distancing, activities decreased and associated dental trauma-related incidents declined.

• Journal of Contemporary Eastern Asia
• /
• v.19 no.2
• /
• pp.169-178
• /
• 2020

Thomas L. Friedman's "Our New Historic Divide: B.C. and A.C. ― The World Before Corona and the World After" column is becoming the talk of the times. Whoever talks about the post-Corona world mentions "BC/AC" as a new concept. However, people seem to be overusing the term "BC/AC" while overlooking the specific context that Friedman emphasized. So, taking into account the cultural differences and contexts of the East and the West highlighted in Friedman's column, we devised the "BC/AC" ten-paradigm hypothesis. We hope these ten cultural shifts will be the first step in examining the post-Corona world.

• Journal of Audiology & Otology
• /
• v.24 no.2
• /
• pp.79-84
• /
• 2020

Background and Objectives: Hearing can be elicited in response to vibratory stimuli delivered to fluid in the external auditory meatus. To obtain a complete audiogram in subjects with normal hearing in response to pure tone vibratory stimuli delivered to fluid applied to the external meatus. Subjects and Methods: Pure tone vibratory stimuli in the audiometric range from 0.25 to 6.0 kHz were delivered to fluid applied to the external meatus of eight participants with normal hearing (15 dB or better) using a rod attached to a standard clinical bone vibrator. The fluid thresholds obtained were compared to the air conduction (AC), bone conduction (BC; mastoid), and soft tissue conduction (STC; neck) thresholds in the same subjects. Results: Fluid stimulation thresholds were obtained at every frequency in each subject. The fluid and STC (neck) audiograms sloped down at higher frequencies, while the AC and BC audiograms were flat. It is likely that the fluid stimulation audiograms did not involve AC mechanisms or even, possibly, osseous BC mechanisms. Conclusions: The thresholds elicited in response to the fluid in the meatus likely reflect a form of STC and may result from excitation of the inner ear by the vibrations induced in the fluid. The sloping fluid audiograms may reflect transmission pathways that are less effective at higher frequencies.

• Korean Journal of Audiology
• /
• v.24 no.2
• /
• pp.79-84
• /
• 2020

Background and Objectives: Hearing can be elicited in response to vibratory stimuli delivered to fluid in the external auditory meatus. To obtain a complete audiogram in subjects with normal hearing in response to pure tone vibratory stimuli delivered to fluid applied to the external meatus. Subjects and Methods: Pure tone vibratory stimuli in the audiometric range from 0.25 to 6.0 kHz were delivered to fluid applied to the external meatus of eight participants with normal hearing (15 dB or better) using a rod attached to a standard clinical bone vibrator. The fluid thresholds obtained were compared to the air conduction (AC), bone conduction (BC; mastoid), and soft tissue conduction (STC; neck) thresholds in the same subjects. Results: Fluid stimulation thresholds were obtained at every frequency in each subject. The fluid and STC (neck) audiograms sloped down at higher frequencies, while the AC and BC audiograms were flat. It is likely that the fluid stimulation audiograms did not involve AC mechanisms or even, possibly, osseous BC mechanisms. Conclusions: The thresholds elicited in response to the fluid in the meatus likely reflect a form of STC and may result from excitation of the inner ear by the vibrations induced in the fluid. The sloping fluid audiograms may reflect transmission pathways that are less effective at higher frequencies.

• Journal of applied mathematics & informatics
• /
• v.29 no.5_6
• /
• pp.1603-1608
• /
• 2011

Let R be a ring with identity. If a, b, $c{\in}R$ such that a+b+c = 1, then the distributive laws from addition over multiplication hold in R, that is a+(bc) = (a+b)(a+c) when ab = ba, and (ab)+c = (a+c)(b+c) when ac = ca. An application to obtains, if A,B are idempotent matrices and AB = BA = 0 then there exists an idempotent matrix C such that A + BC = (A + B)(A + C), and also A + BC = (I - C)(I - B). Some other cases and applications are also presented.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.21 no.1
• /
• pp.99-107
• /
• 1991

The purpose of this study was to decide the proper projection angle that could avoid the superimposition of the petrous portion of temporal bone and posterior clinoid process in cephalometric lateral and basal view of the 10 dry skulls and to analyze the reproducibility of a modified Accurad-100 head holder device from Denar Co. and a cephalostat head holder in 30 transcranial radiographs of the dry skull. The results were obtained as follows: The vertical angle was 24.5±4.1° and the horizontal angle was 3.0 ±5.7°. The distances between arbitrary 3 points which were on the TMJ area were as follows: AB 16.76±0.27㎜, BC 8.79±0.18㎜ in the transcranial radiographs using modified Accurad-100 head holder, AB 29.03±0.14㎜, AC 19.95±0.24㎜, BC 10.08±0.07㎜ in the transcranial radiographs using cephalostat.

• Journal of Korea Multimedia Society
• /
• v.19 no.2
• /
• pp.128-137
• /
• 2016

In mobile communication, air conduction(AC) speech signal had been commonly used, but it was easily affected by ambient noise environment such as emergency, military action and rescue. To overcome the weakness of the AC speech signal, bone conduction(BC) speech signal have been used. The BC speech signal is transmitted through bone vibration, so it is affected less by the background noise. In this paper, we proposed noise cancellation algorithm of the BC speech signal using noise feature of decomposed bands. The proposed algorithm consist of three steps. First, the BC speech signal is divided into 17 bands using perceptual wavelet packet decomposition. Second, threshold is calculated by noise feature during short time of separated-band and compared to absolute average of the signal frame. Therefore, the speech and noise parts are detected. Last, the detected noise parts are removed and then, noise eliminated bands are re-synthesised. In order to confirm the efficiency of the proposed algorithm, we compared the proposed algorithm with conventional algorithm. And the proposed algorithm has better performance than the conventional algorithm.

• Journal of Veterinary Clinics
• /
• v.8 no.1
• /
• pp.27-30
• /
• 1991

Transferrin type of stallions and their foals in total of 56 was analysed. Phenotype showed 8 types(AA, AB, AC, AD, AE, BB, BC, BD), while gene frequencies A ; 0.410, B ; 0.455, C : 0.063, D ; 0.063, E ; 0.09 There were not negative factors in the result of idenification of real paternity but showed AC type that is abscent in their parents.

• Proceedings of the KIEE Conference
• /
• 1997.07c
• /
• pp.1133-1136
• /
• 1997

This study established AC-DC system model including DC Link, and then BC Link equation was derived from the model. The equation was included into the calculational algorithm of AC system and solved using fast decoupled method. To minimize the line loss of AC-DC system, optimum theory was applied to the equations.

• Korean Journal of Animal Reproduction
• /
• v.22 no.2
• /
• pp.153-161
• /
• 1998

This study was conducted to examine the viability of nuclear transfer bovine embryos following embryo transfer. Donor embryos were treated with nocodazole to arrest their cell-cycle-stage at mitotic(M) phase. After releasing from nocodazole blastomeres were separated and transferred into the enucleated oocytes(BC), or cultured in medium with aphidicolin. Freshly cleaved blastomeres within 1.5h after cleavage(AC) and non-cleaved ones up to 3h after releasing from nocodazole(NC) were transferred into the enucleated oocytes. Blastocysts derived from nuclear transfer were transferred to Day 7~8 recipient cows. Some blastocysts were vitrified and thawed before embryo transfer. Developmental rates to the blastocyst stage were higher in AC(18.1%, P<0.05) than BC(8.6%) and NC(5.1%). Blastocyst development slightly enhanced with aphidicolin(1~2$\mu\textrm{g}$/ml) treatment(16.9~22.6%) compared to non treated control(11.1%). Survival rate fo vitrified nuclear transfer embryos after thawing was 75%(24/32). Twnety-three vitrified nuclear transfer embryos and 3 fresh ones were transferred to 23 recipients, 6 heads were pregnant and 1 male calf(24 kg) was born from a recipient cow recevied one vitrifiedthawed nuclear transfer embryo at 277 days after embryo transfer. This result suggests that the nuclear transfer embryos can developed to term after vitrification andembryo transfer.