• 한국농공학회논문집
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• 제60권5호
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• pp.69-80
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• 2018

This study investigated climate change influences over crop water requirement (CWR) and irrigation water requirement (IWR) of the wheat-rice cropping system of Upper Chenab Canal (UCC) command in Punjab Province, Pakistan. PRECIS simulated delta-change climate projections under the A1B scenario were used to project future climate during two-time slices: 2030s (2021-2050) and 2060s (2051-2080) against baseline climatology (1980-2010). CROPWAT model was used to simulate future CWRs and IWRs of the crops. Projections suggested that future climate of the study area would be much hotter than the baseline period with minor rainfall increments. The probable temperature rise increased CWRs and IWRs for both the crops. Wheat CWR was more sensitive to climate-induced temperature variations than rice. However, projected winter/wheat seasonal rainfall increments were satisfactorily higher to compensate for the elevated wheat CWRs; but predicted increments in summer/rice seasonal rainfalls were not enough to complement change rate of the rice CWRs. Thus, predicted wheat IWRs displayed a marginal and rice IWRs displayed a substantial rise. This suggested that future wheat production might withstand the climatic influences by end of the 2030s, but would not sustain the 2060s climatic conditions; whereas, the rice might not be able to bear the future climate-change impacts even by end of the 2030s. In conclusion, the temperature during the winter season and rainfall during the summer season were important climate variables controlling water requirements and crop production in the study area.

• Restorative Dentistry and Endodontics
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• 제29권3호
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• pp.267-272
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• 2004

The purpose of this in vitro study was to evaluate the effect of surface defects and cross-sectional configuration of NiTi rotary files on the fatigue life under cyclic loading. Three NiTi rotary files ($K3^{TM},{\;}ProFile^{\circledR},{\;}and{\;}HERO{\;}642^{\circledR}$) with ＃30/.04 taper were evaluated. Each rotary file was divided into 2 subgroups : control (no surface defects) and experimental group (artificial surface defects), A total of six groups of each 10 were tested. The NiTi rotary files were rotated at 300rpm using the apparatus which simulated curved canal (40 degree of curvature) until they fracture. The number of cycles to fracture was calculated and the fractured surfaces were observed with a scanning electron microscope. The data were analyzed statistically. The results showed that experimental groups with surface defects had lower number of cycles to fracture than control group but there was only a statistical significance between control and experimental group in the $K3^{TM}$ (p<0.05), There was no strong correlation between the cross-sectional configuration area and fracture resistance under experimental conditions. Several of fractured files demonstrated characteristic patterns of brittle fracture consistent with the propagation of pre-existing cracks. This data indicate that surface defects of NiTi rotary files may significantly decrease fatigue life and it may be one possible factor for early fracture of NiTi rotary files in clinical practice.

• Journal of Korean Neurosurgical Society
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• 제61권6호
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• pp.707-715
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• 2018

Objective : To investigate the potential risk of approach-related complications at different access angles in minimally invasive lateral lumbar interbody fusion. Methods : Eighty-six axial magnetic resonance images were obtained to analyze the risk of approach-related complications. The access corridor were simulated at different access angles and the potential risk of neurovascular structure injury was evaluated when the access corridor touching or overlapping the corresponding structures at each angle. Furthermore, the safe corridor length was measured when the corridor width was 18 and 22 mm. Results : When access angle was $0^{\circ}$, the potential risk of ipsilateral nerve roots injury was 54.7% at L4-L5. When access angle was $45^{\circ}$, the potential risk of abdominal aorta, contralateral nerve roots or central canal injury at L4-L5 was 79.1%, 74.4%, and 30.2%, respectively. The length of the 18 mm-wide access corridor was largest at $0^{\circ}$ and it could reach 44.5 mm at L3-L4 and 46.4 mm at L4-L5. While the length of the 22 mm-wide access corridor was 42.3 mm at L3-L4 and 44.1 mm at L4-L5 at $0^{\circ}$. Conclusion : Changes in the access angle would not only affect the ipsilateral neurovascular structures, but also might adversely influence the contralateral neural elements. It should be also noted to surgeons that alteration of the access angle changed the corridor length.

• Restorative Dentistry and Endodontics
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• 제48권1호
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• pp.4.1-4.10
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• 2023

Objectives: This study aimed to compare the torsional and cyclic fatigue resistance of ProGlider (PG), WaveOne Gold Glider (WGG), and TruNatomy Glider (TNG). Materials and Methods: A total of 15 instruments of each glide path system (n = 15) were used for each test. A custom-made device simulating an angle of 90° and a radius of 5 millimeters was used to assess cyclic fatigue resistance, with calculation of number of cycles to failure. Torsional fatigue resistance was assessed by maximum torque and angle of rotation. Fractured instruments were examined by scanning electron microscopy (SEM). Data were analyzed with Shapiro-Wilk and Kruskal-Wallis tests, and the significance level was set at 5%. Results: The WGG group showed greater cyclic fatigue resistance than the PG and TNG groups (p < 0.05). In the torsional fatigue test, the TNG group showed a higher angle of rotation, followed by the PG and WGG groups (p < 0.05). The TNG group was superior to the PG group in torsional resistance (p < 0.05). SEM analysis revealed ductile morphology, typical of the 2 fracture modes: cyclic fatigue and torsional fatigue. Conclusions: Reciprocating WGG instruments showed greater cyclic fatigue resistance, while TNG instruments were better in torsional fatigue resistance. The significance of these findings lies in the identification of the instruments' clinical applicability to guide the choice of the most appropriate instrument and enable the clinician to provide a more predictable glide path preparation.

• Restorative Dentistry and Endodontics
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• 제46권4호
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• pp.53.1-53.11
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• 2021

Objectives: This study evaluates the bond strength and marginal adaptation of mineral trioxide aggregate (MTA) Repair HP and Biodentine used as apical plugs; MTA was used as reference material for comparison. Materials and Methods: A total of 30 single-rooted teeth with standardized, artificially created open apices were randomly divided into 3 groups (n = 10 per group), according to the material used to form 6-mm-thick apical plugs: group 1 (MTA Repair HP); group 2 (Biodentine); and group 3 (white MTA). Subsequently, the specimens were transversely sectioned to obtain 2 (cervical and apical) 2.5-mm-thick slices per root. Epoxy resin replicas were observed under a scanning electron microscope to measure the gap size at the material/dentin interface (the largest and smaller gaps were recorded for each replica). The bond strength of the investigated materials to dentin was determined using the push-out test. The variable bond strengths and gap sizes were evaluated independently at the apical and cervical root dentin slices. Data were analyzed using descriptive and analytic statistics. Results: The comparison between the groups regarding the variables' bond strengths and gap sizes showed no statistical difference (p > 0.05) except for a single difference in the smallest gap at the cervical root dentin slice, which was higher in group 3 than in group 1 (p < 0.05). Conclusions: The bond strength and marginal adaptation to root canal walls of MTA HP and Biodentine cement were comparable to white MTA.

• 한국해안·해양공학회논문집
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• 제27권4호
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• pp.202-216
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• 2015

가용한 토지의 부족으로 현재 우리나라 인공운하에서 흔히 관측되는 협수로에서는 고립파 형태의 항주파가 생성되는 것으로 추정된다. 본고에서는 이러한 가설을 확인하기 위해 수치모의를 수행하였다. 수치모의는 삼차원 Navier Stokes 식과 VOF에 기초하여 수행되었으며, 수치모형의 검증은 현재 우리에게 가용한 운하 설계기준 중 가장 빈번히 언급되는 PIANC (1987) 설계안과 본고에서 유도된 해석해에 기초하여 수행되었다. 모의결과, 고립파형태의 항주파가 관측되었으며, 하안 인근에서 계측된 선수파 파고의 경우 수치모의 결과는 PIANC (1987) 설계안을 상회하였으며 상당히 오랜 기간 (이십초 내외) 지속되었다. 선미파의 경우는 하회하였다. 이러한 결과는 광역수로에서 관측되는 항주파의 일반적인 특성과는 상이한 것으로 좁은 수로 폭이 항주파 특성에 영향을 미치는 것으로 판단된다. 또한 선박의 협수로 통과시 선박을 중심으로 양안으로 진행되는 흐름과, 반사로 인해 양안에서 선박으로 진행되는 흐름이 교대로 출현하였으며 이 때 최대 0.90 m/s의 유속이 전 수심대역에서 비교적 균일하게 유지되어, 상당한 쇄굴이 진행될 수 있다고 판단된다.

• Restorative Dentistry and Endodontics
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• 제32권4호
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• pp.385-396
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• 2007

이 연구의 목적은 Mtwo 전동 파일의 사용에 있어서 제조사가 제안한 single length technique과 crown-down technique의 근관성형효율과 안전성을 비교하고 Mtwo 전동 파일의 변형된 사용방법을 제안하고자 하는 것이다. 기구의 종류와 사용방법에 따라 60개의 레진 블록 근관 모형 (Endo Training Bloc; Benstply Maillefer, Ballaigues, Switzerland)을 세 군으로 나누어 20개씩 표본을 성형하였다. MT군은 Mtwo 파일 (VDW, Munich, Germany)을 제조사의 추천방법인 single length technique으로, MC군은 Mtwo 파일을 crown-down technique으로 형성하였고, 대조군인 PT군은 ProTaper (Denstply Maillefer, Ballaigues, Switzerland)를 사용하였다. 모든 기구는 250 r.p.m., torque 2.2 N로 고정한 전동 모터 (X-smart; Denstply Maillefer, Ballaigues, Switzerland)로 사용하였다. 근관 성형 후, 스캐너로 근관 형성 전후의 이미지를 채득하여 중첩 비교함으로써 근단부로부터 1, 2, 3, 4, 5, 6, 7, 8 mm 높이에서의 중심변위율을 산출하였다. 순수 기구조작 시간 및 기구조작 동안의 binding빈도를 기록하였다. 근관 성형 후, 레진 블록의 무게 감소를 측정하였고 근관 성형에 사용된 파일의 파절이나 변형 및 근관 성형 후 형태의 이상을 조사하였다. 세 실험군의 측정 및 산출된 자료를 일원배치 분산분석 및 Duncan's Multiple Range Test로 사후 검정을 시행하여 비교하였으며, Fisher's exact test으로 근관의 이형성, 기구의 변형 그리고 기구 binding 등 발생 빈도를 유의 확률 95%에서 통계 검정하였다. 그 결과는 다음과 같다. 1. 근관의 만곡도 감소, 중심변위율, 레진 블록의 무게 감소, 기구 변형 등은 세 군간에 유의한 차이가 없었다 (p > 0.05). 2. 기구 조작 시간은 보면 MT군과 MC군이 PT군보다 짧았다 (p < 0.05). 3. Elbow는 MT군이 MC군에서 PT군보다 더 많이 형성되었다 (p < 0.05). Ledge는 세 군 모두에서 나타나지 않았다. 4. 파일 binding 횟수는 MC군이 가장 적고 PT군이 가장 많았다 (p < 0.05). 이상의 결과를 볼 때, Mtwo 전동 파일을 crown-down technique으로 사용하는 것이 single length technique과 유사한 성형 효율을 보이면서도 더 안전할 것으로 추정된다.

• Restorative Dentistry and Endodontics
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• 제30권2호
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• pp.79-85
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• 2005

최근, 다양한 경사도의 니켈-티타늄 근관기구와 더불어 다양한 경사도의 gutta-percha cone이 소개되었다. 효율적인 근관 충전을 위해서는 짧은 시간에 적은 수의 기구 및 재료를 사용하여 균일한 gutta-percha로 근관을 충전할 필요가 있다. 본 연구에서는 0.06 경사도의 니켈-티타늄 전동화일로 형성된 만곡 근관에서 측방 가압법으로 근관충전시 비표준화 medium 크기 master gutta-percha cone의 충전효율을 ISO 표준화 규격의 master cone과 비교하여 평가하고자 하였다. 60개의 모형레진 만곡근관에서 0.06 경사도의 니켈-티타늄 전동화일 ($ProTaper^{TM},\;ProFile^{(R)}$, Dentsply-Maillefer, Ballaigues, Switzerland)을 사용하여 근단부 근관이 30번 크기가 되게 crown-down법으로 근관을 형성하였다. 근관은 master gutta-percha cone, AH 26 실러 (Dentsply-DeTrey, Konstanz, Germany), 그리고 type A accessory cone (Dentsply-Maillefer, Ballaigues, Switzerland)을 사용하여 측방가압법으로 충전하였으며, 이 때 사용된 master gutta-percha cone(Diadent, Chongju, Korea)과 Finger spreader(B type, Dentsply-Maillefer, Ballaigues, Switzerland)에 따라 임의로 15개씩 4개의 군으로 나누어 실험하였는데, St/SS 군에서는 ISO 표준화 규격의 30번 master cone과 스테인레스 스틸 finger spreader를, St/NT 군에서는 ISO 표준화 규격의 30번 master cone과 니켈-티타늄 finger spreader를, Non-St/SS 군에서는 비표준화 medium 규격 master cone과 스테인레스 스틸 spreader를, 그리고 Non-St/NT 군에서는 비표준화 medium 크기 master cone과 니켈-티타늄 finger spreader를 각각 사용하였다. 충전된 근관은 $37^{\circ}C$, 상대습도 $100\%$하에서 24시간 보관한 후, 치근단 1, 3및 5 mm수준에서 횡절단하여 입체현미경 하에서 관찰하고 컴퓨터에 저장한 다음, $Auto^{(R)}$CAD 2000 프로그램을 이용하여, 형성된 근관 및 gutta-percha 충전물의 외형을 추적하여 근관내 gutta-percha 면적비를 계산하였다. Gutta-percha 면적비의 결과치는 two-way ANOVA를, 그리고 accessory cone 수는 one-way ANOVA 및 Duncan's multiple range test를 이용하여 통계 분석하여 다음과 같은 결과를 얻었다. 스테인레스 스틸 finger spreader를 사용한 경우 및 니켈-티타늄 finger spreader를 사용한 경우 공히, 모든 치근단 수준에서 비표준화 medium 크기 master cone 사용군이 ISO 표준화 규격의 master cone 사용군에 비해 유의하게 높은 gutta-percha 면적비를 나타내었다 (p < 0.01). 비표준화 medium크기 master cone 사용군에서는 표준화 규격의 master cone 사용군에 비해 유의하게 적은 수의 accessory cone이 사용되었다 (p < 0.01).

• Restorative Dentistry and Endodontics
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• 제24권1호
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• pp.40-48
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• 1999

This study was designed to examine the specificities of the designed primers for F. nucleatum and F. necrophorum and to compare the PCR results using clinical samples with those of the anaerobic culture method. F. nucleatum and F. necrophorum spp. are frequently isolated in infected root canals, and they are related to periapical diseases. F. nucleatum(VPI 10197) and F. necrophorum(ATCC 25286) were used as references for PCR reaction, and thirty five teeth with one canal and periapical lesion were used. The samples were cultured anaerobically and identified using Rapid ID 32A(BioMerieux Vitek, Inc., France) as biochemical battery. In the GenBank database, species-specific PCR primers(nuc1/nuc2 primers for F. nucleatum and nec1/nec2 primers for F. necrophorum) were designed from the 16S ribosomal DNA(rDNA) sequences of F. nucleatum(accession number M58683) and F. necrophorum(accession number AF044948). PCR procedures of F. nucleatum(VPI 10197) and F. necrophorum (ATCC 25286) were simulated on a computer software. Amplify(v.1.2${\beta}$ for Macintosh). 820 bps and 817 bps of nucleotides were expected, respectively. Using extracted DNAs with QiaAmp tissue kit(Qiagen co., Germany), PCR was done. The results were as follows : 1. The nuc1/nuc2 primers produced an amplicon of 820 bps and the nec1/nec2 primers produced an amplicon of 817 bps. 2. The nuc1/nuc2 primers and the nec1/nec2 primers were specific and did not react with species other than the designated ones(i.e. nuc1/nuc2 primers did not produce amplicons for F. necrophorum, and vice versa.). And the PCR products of Porphyromonas endodontalis(ATCC 35406), Porphyromonas gingivalis(ATCC 33277), Prevotella intermedia(ATCC 25611), and Prevotella nigrescens(ATCC 33563), frequently isolated in infected root canals and periapical lesions, were not amplified by the primers specific for Fusobacterium nucleatum and Fusobacterium necrophorum. 3. This method utilizing PCR could detect F. nucleatum and F. necrophorum in clinical samples, while anaerobic culture method could detect neither.

• 한국농공학회논문집
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• 제59권3호
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• pp.83-96
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• 2017

This study presented a surface water quality modeling framework considering the spatial resolution of pollutant load estimation to better represent stream water quality characteristics in the Saemangeum watershed which has been focused on keeping its water resources sustainable after the Saemangeum embankment construction. The watershed delineated into 804 sub-watersheds in total based on the administrative districts, which were units for pollutant load estimation and counted as 739 in the watershed, Digital Elevation Model (DEM), and agricultural structures such as drainage canal. The established model consists of 7 Mangyung (MG) sub-models, 7 Dongjin (DJ) sub-models, and 3 Reclaimed sub-models, and the sub-models were simulated in a sequence of upstream to downstream based on its connectivity. The hydrologic calibration and validation of the model were conducted from 14 flow stations for the period of 2009 and 2013 using an automatic calibration scheme. The model performance to the hydrologic stations for calibration and validation showed that the Nash-Sutcliffe coefficient (NSE) ranged from 0.66 to 0.97, PBIAS were -31.0~16.5 %, and $R^2$ were from 0.75 to 0.98, respectively in a monthly time step and therefore, the model showed its hydrological applicability to the watershed. The water quality calibration and validation were conducted based on the 29 stations with the water quality constituents of DO, BOD, TN, and TP during the same period with the flow. The water quality model were manually calibrated, and generally showed an applicability by resulting reasonable variability and seasonality, although some exceptional simulation results were identified in some upstream stations under low-flow conditions. The spatial subdivision in the model framework were compared with previous studies to assess the consideration of administrative boundaries for watershed delineation, and this study outperformed in flow, but showed a similar level of model performance in water quality. The framework presented here can be applicable in a regional scale watershed as well as in a need of fine-resolution simulation.