• International Journal of Internet, Broadcasting and Communication
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• 제13권2호
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• pp.27-35
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• 2021

NAND flash memory-based SSD needs an internal software, Flash Translation Layer(FTL) to provide traditional block device interface to the host because of its physical constraints, such as erase-before-write and large erase block. However, because useful host-side information cannot be delivered to FTL through the narrow block device interface, SSDs suffer from a variety of problems such as increasing garbage collection overhead, large tail-latency, and unpredictable I/O latency. Otherwise, the new type of SSD, open-channel SSD exposes the internal structure of SSD to the host so that underlying NAND flash memory can be managed directly by the host-level FTL. Especially, I/O data classification by using host-side information can achieve the reduction of garbage collection overhead. In this paper, we propose a new scheme to reduce garbage collection overhead of open-channel SSD by separating the journal from other file data for the journaling filesystem. Because journal has different lifespan with other file data, the Write Amplification Factor (WAF) caused by garbage collection can be reduced. The proposed scheme is implemented by modifying the host-level FTL of Linux and evaluated with both Fio and Filebench. According to the experiment results, the proposed scheme improves I/O performance by 46%~50% while reducing the WAF of open-channel SSDs by more than 33% compared to the previous one.

• 한국수산과학회지
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• 제56권6호
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• pp.826-832
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• 2023

Clostridium perfringens causes diarrhea and other diseases in humans and animals. We investigated the prevalence, toxin gene profiles, and antimicrobial resistance of C. perfringens isolated from commercial jeotgal sample. C. perfringens was isolated from 11 of 22 commercial jeotgals. All C. perfringens strains were positive for the alpha toxin gene, but not for the beta, epsilon, iota, CPE or NetB toxin genes; therefore, all strains were identified as type A C. perfringens. However, the beta2 toxin gene was identified in 54.5% of isolates. Disk diffusion susceptibility tests showed that most isolates were resistant to kanamycin (90.9%), nalidixic acid (72.7%), oxacillin (54.5%), erythromycin (27.3%), ciprofloxacin (9.1%) and clindamycin (9.1%). However, all strains were susceptible to 14 other antimicrobial including amoxicillin, ampicillin, and chloramphenicol. The average minimum inhibitory concentrations against C. perfringens of clindamycin, kanamycin, and nalidixic acid were 128.0, 128.0, and 54.0 ㎍/mL, respectively. These results provide new insight into the necessity for sanitation of commercial jeotgal, and provide evidence to help reduce the risk of contamination with antimicrobial-resistant bacteria.

• 대한치과보철학회지
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• 제38권2호
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• pp.200-213
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• 2000

Lasers have given dentistry a new rapid, economic, and accurate technique for metal joining. Although laser welding has been recommended as an accurate technique, there are some limitations with this technique. For example, the two joining surfaces must have a tight-fitting contact, which may be difficult to achieve in some situations. The tensile samples used for this study were made from a custom-made pure titanium and type III gold alloy plates. 27 of 33 specimens were sectioned perpendicular to their long axis with a carborundum disk and water coolant. Six specimens remained and served as the control group. A group of 6 specimens was posed as butt joints in custom parallel positioning device with a feeler gauge at each of three gaps : 0.00, 0.25. and 0.50mm. All specimens were then machined to produce a uniform cross-sectional dimension, none of the specimens was subjected to any subsequent form of heat treatment. Scanning electron microscopy was performed on representative tested specimens at fractured surfaces in both the parent metal and the weld. Vickers hardness was measured at the center of the welds with a micropenetrometer using a force of 300gm for 15 seconds. Measurement was made at approximately $200{\mu}m\;and\;500{\mu}m$ deep from each surface. One-way analysis of variance (ANOVA) and Scheffe's test was calculated to detect differences between groups. The purpose of this study is to compare the strength and properties of the joint achieved at various butt Joint gaps by the laser welding of type III gold alloy and pure titanium tensile specimens in an argon atmosphere. The results of this study were as follows : 1. When indexing and welding pure titanium, there was no decrease in ultimate tensile strength as compared with the unsectioned alloys for indexing gaps of 0.00 to 0.50mm, although with increasing gap size may come increased distortion (p>0.05). 2. When indexing and welding type III gold alloy, there were significant differences in ultimate tensile strength among groups with weld gaps of 0.00mm, 0.25 and 0.50mm, and the control group. Group with butt contact without weld gap demonstrated a significant higher ultimate tensile strength than groups with weld gaps of 0.25 and 0.50mm (p<0.05). 3. When indexing and welding the different metal combination of type III gold alloy and pure titanium, there were significant differences in ultimate tensile strength between groups with weld gaps of 0.00, 0.25, and 0.50mm. However, the mechanical properties of the welded joint would become too brittle to be acceptable clinically (p<0.05). 4. The presence of large pores in the laser welded joint appears to be the most important factor in controlling the tensile strength of the weld in both pure titanium and type III gold alloy.

• 한국식품과학회지
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• 제33권5호
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• pp.582-588
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• 2001

단체급식용으로 납품되는 생계육에서 Salmonella를 분리하여 생육제어를 위한 생리특성을 분석하였다. 계육의 총균수는 표피의 내부 살부위에서도 표피 균수의 약 10%정도가 검출되었으며 75 개 계육시료로부터 선택배지를 사용하여 분리한 후 최종적으로 51 주의 Salmonella를 동정하였다. 이들 균주 중 약 70%의 Salmonella는 4종 이상의 항생제에 내성을 보이는 다제내성균으로 보여 국내에서의 기 분리균에 비해서 높은 비율의 항생제에 대한 내성을 나타내었다. 이들 Salmonella에 대한 여러 가지 위생처리제인 유기산의 중 lactic acid와 trisodium phosphate를 agar disk diffusion으로 표준균주인 S. typhimurium ATCC 14028, S. typhimurium ATCC 12023, S. heidelberg and S. enteritidis(isolated from egg)와 비교하였다. Lactic acid는 분리된 Salmonella나 표준균주 모두 비슷한 정도의 내성을 보여 주었고 오히려 분리 Salmonella는 더 내성이 적었다. 그러나 최근에 중요시되는 trisodium phosphate에는 표준균주에 비하여 분리된 wild type에서 내성이 강한 균주가 거의 절반에 가까운 정도로 많음을 알 수가 있었다. 또한 trisodium phosphate에 대한 내성은 처리시간과 처리 후 재생배지에 따라 다르게 보여서 이들은 환경에 따 라 내성이 다르게 나타난다는 것을 알았다. 계육에 오염된 Salmonella는 wild type이므로 실제 위생처리제로 사용할 때는 좀더 철저한 처리가 요망되었다. 그러므로 집단 급식소에 납품되는 계육은 브로일러 사육단계에서의 항생제 관리와 도계과정으로부터 세균오염을 줄여야 하는 노력과 함께 이러한 식중독균의 제어를 위한 위생처리제에 대한 지속적인 기술개발도 필요할 것이다.

• Restorative Dentistry and Endodontics
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• 제38권1호
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• pp.26-30
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• 2013

Objectives: The aim of this study was to investigate the relationship between the apical foramen morphology and the length of merged canal at the apex in type II root canal system. Materials and Methods: This study included intact extracted maxillary and mandibular human premolars (n = 20) with fully formed roots without any visible signs of external resorption. The root segments were obtained by removing the crown 1 mm beneath the cementum-enamel junction (CEJ) using a rotary diamond disk. The distance between the file tip and merged point of joining two canals was defined as Lj. The roots were carefully sectioned at 1 mm from the apex by a slow-speed water-cooled diamond saw. All cross sections were examined under the microscope at ${\times}50$ magnification and photographed to estimate the shape of the apical foramen. The longest and the shortest diameter of apical foramen was measured using ImageJ program (1.44p, National Institutes of Health). Correlation coefficient was calculated to identify the link between Lj and the apical foramen shape by Pearson's correlation. Results: The average value of Lj was 3.74 mm. The average of proportion (P), estimated by dividing the longest diameter into the shortest diameter of the apical foramen, was 3.64. This study showed a significant negative correlation between P and Lj (p < 0.05). Conclusions: As Lj gets longer, the apical foramen becomes more ovally shaped. Likewise, as it gets shorter, the apical foramen becomes more flat shaped.

• International Journal of Air-Conditioning and Refrigeration
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• 제14권1호
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• pp.7-13
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• 2006

Because the usage of CFC and HCFC based refrigerants are restricted due to the depletion of ozone layer, the $NH_3$ gas, in the experiment is evaluated to the performance characteristics for the superheat control to improve the energy efficiency. The experiment is carried out about the condensing pressure of refrigeration system from 1,500 kPa to 1,600 kPa through the degree of superheat from 0 to $10^{\circ}C$ at each condensing pressure. As a result, in the case of shell and tube type of heat exchanger, the COP is more efficient than other cases at the degree of superheat $1^{\circ}C$ at each condensing pressure. In the case of shell and disk type of heat exchanger, the COP is the most efficient at the degree of superheat 0.

• 자원리싸이클링
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• 제10권1호
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• pp.56-65
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• 2001

원전 안전주입계통 역지밸브의 유지보수 작업과 관련하여 작업자 방사성 피폭저감과 고가 부품의 재사용을 위해 방사능으로 오염된 이들 밸브를 화학제염법으로 제염을 수행하였다. 화학제염 후 역지밸브 내부 틈새에 잔류한 미세 고형입자를 제거하기 위해 초음파세척을 병행하였다. 역지밸브 disk arm holder를 사용한 사전 시험결과를 토대로 제염공정과 제염시약량을 결정하였으며 제염에 의한 부식산화물 용해거동, 방사능 제거거동과 재료부식거동을 조사하였다. 화학제염에 이은 초음파 적용결과, 초기 방사능의 93-95%가 제거되었으며 역지밸브 구성재질인 Type 304 stainless steel, Inconel-600 및 Stellite-6 에 대한 일반부식량은 각각 $ 2.1$\times10^{-2}$ , $6.0\times10^{-2}$ 및 1.7 mil 로써 일반부식 허용한계치의 3.3%, 24.0 % 및 2.7% 수준을 나타내어 제염효과와 재질건전성 면에서 효과적이었다.

• 한국산학기술학회논문지
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• 제16권1호
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• pp.50-55
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• 2015

본 연구에서는 공동 주택의 수전 개방 조건에서, 감압밸브 내부 오리피스 형상이 캐비테이션 발생에 미치는 영향에 대하여 살펴보았다. 이를 위하여 감압밸브 내부의 유로형상을 9가지 유형으로 구별하여 제시하고, 3차원 유한해석 코드인 ANSYS CFX를 사용하여 감압밸브 내의 유동해석을 수행하였다. 급격한 단면 변화가 일어나는 오리피스에서 최저 압력과 최대 속도가 발생하였다. 최대속도가 존재하는 부위에서 0 이상 증기체적비를 나타내어 캐비테이션이 발생함을 확인하였다. 유로 길이가 긴 형상에 비하여 돌연 확대관 형상의 모델에서 유체의 최대 속도가 낮게 나타났다. 돌연확대관 형상의 경우에는 매우 작은 증기체적비를 나타내고 있으며, 돌연확대의 정도가 클수록 증기체적비는 낮게 나타났다. 따라서 감압밸브의 케비테이션 발생을 방지하기 위해서는 돌연확대의 형상을 갖도록 설계하는 것이 타당하다고 판단된다.

• 한국대기환경학회지
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• 제20권4호
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• pp.451-463
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• 2004

The performance of disk-type catalytic filters impregnated by TiO$_2$ or TiO$_2$-3Al$_2$O$_3$ㆍ 2SiO$_2$ supports and V$_2$O$_{5}$ catalyst was evaluated for selective catalytic reduction (SCR) of NO with ammonia as a reductant. XRD, FT -IR, BET and SEM were used to characterize the catalytic filters prepared in this work. Optimal V$_2$O$_{5}$ loading and reaction temperature for V$_2$O$_{5}$/TiO$_2$ catalytic filters were 3-6 wt.% and 350-40$0^{\circ}C$ at GHSV 14,300 $hr^{-1}$ in the presence of oxygen, respectively. With increasing the V$_2$O$_{5}$ loading from 0.5 to 6 wt%, NO conversion increased from 24 to 96% at 40$0^{\circ}C$ and 14.300$hr^{-1}$, and maintained at 80% over in the V$_2$O$_{5}$ loading range of 3-6 wt.% and then dropped at V$_2$O$_{5}$ loading of 7wt.% over. In comparing V$_2$O$_{5}$/ TiO$_2$ and V$_2$O$_{5}$/ TiO$_2$-3Al$_2$O$_3$ㆍ2SiO$_2$ catalytic fillers, which have same 3wt.% V$_2$O$_{5}$ loading, the V$_2$O$_{5}$/ TiO$_2$-3A1$_2$O$_3$ㆍ2SiO$_2$ catalytic filter showed higher activity than V$_2$O$_{5}$/ TiO$_2$ catalytic filter, but higher differential pressure drops owing to its low air permeability. low air permeability.

• Journal of Oral Medicine and Pain
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• 제20권2호
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• pp.407-420
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• 1995

This study was performed to evaluate and compare conservative treatment results by several parameters such as age, sex, symptom duration, type and timing of joint sound, parafunctional habits, splint type, and diagnostic classification. There have been too many articles reporting long term results of conservative treatment but articles related to comparison of treatment results by patients' self-evaluation have been rarely reported. For this study 258 patients with temporomandibular disorders(TMDs) were selected and examined by routine diagnostic procedure for TMDs. The subjects were classified into 5 TMDs subgroups ad treated with conservative treatments involving splints, physical modalities, jaw exercises, and counseling. Visual analogue scale(VAS) about pain, joint sound, and mouth opening limitation was recorded respectively during treatment period. From the VAS data and treatment duration, VAS treatment index(VAS Ti) was calculated. The obtained results were as follows : 1. Pain was the most frequent main symptom in subjects with temporomandibular disorders, and main symptom for mouth opening limitation was comparatively less than for pain or sound in disk displacement with reduction group or in degenerative joint disease group. 2. Degenerative joint disease group had the most poor treatment results and highest occlusal index of Helkim's index. 3. Good prognosis for conservative treatment was observed in acute group, under 6 months than chronic group, 6months over in symptom duration, and subjects with 40 years over in age showed the most poor prognosis. 4. Subjects treated with anterior repositioning splint had better treatment results than subjects treated with centric relation splint, but statistical significance in VAS Ti and treatment duration was not observed. 5. Treatment results according to affected side, types and point of joint sound did not show consistent statistical results. 6. The result for conservative treatment was observed poor in subjects with bruxism and clenching. 7. In studying coincidence between preferred chewing and affected side, frequency of preferred chewing side, in unilateral affection, was higher in ipsilateral than in contralateral side.