• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제49권6호
• /
• 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
• /
• 제19권2호
• /
• 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
• /
• 제24권2호
• /
• 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.

• 대한청각학회지
• /
• 제24권2호
• /
• 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
• /
• 제29권5_6호
• /
• 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.

• 치과방사선
• /
• 제21권1호
• /
• pp.99-107
• /
• 1991

저자는 두부규격방사선사진 촬영기에서 건조 두개골 10개의 basal view와 lateral view상에서 측두골의 추체와 접형골의 후상상돌기가 악관절부위에 중첩되지 않는 수평면과 수직면에서의 입사각을 구하였고 Denar사의 Accurad-100의 형태대로 제작하고 고정장치와 cephalostat를 사용하여 촬영된 방사선사진의 재현성을 검토하여 다음과 같은 결과를 얻었다. 중심방사선의 입사각은 수직면에서는 24.5±4.1°, 수평면에서는 3.0±5.7°였으며 재현성을 검정하기 위해 건조두개골의 악관절부위에 임의의 3점을 계측하였든 바 Accurad-100의 형태대로 제작한 고정장치를 이용한 경우에는 AB간의 거리 24.60±0.25㎜, AC간의 거리 16.76±0.27㎜, BC간의 거리 8.79±0.18㎜이었고 cephalostat를 이용한 경우에는 AB간의 거리 29.03±0.14㎜, AC간의 거리 19.95±0.24㎜, BC간의 거리 10.08±0.07㎜로 나타났다. 따라서 이들은 상당히 양호한 재현성을 나타냈으며 특히 cephalostat를 이용한 경우 더욱 재현성이 좋았다.

• 한국멀티미디어학회논문지
• /
• 제19권2호
• /
• 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.

• 한국임상수의학회지
• /
• 제8권1호
• /
• 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.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 하계학술대회 논문집 D
• /
• 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.

• 한국가축번식학회지
• /
• 제22권2호
• /
• 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.