• 대한전자공학회논문지TC
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• 제48권10호
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• pp.35-42
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• 2011

무선 개인영역 네트워크는 저전력소비, 저가, 소형화 등의 장점을 가지고 있어 개인의 휴대장치와 홈 네트워크, 센서 네트워크 등으로 그 응용범위가 커지고 있다. IEEE 802.15.3 표준에서는 point to point 혹은 peer to peer의 UM(Usage Model)을 기본으로 하였지만, 가정이나 회사 내에서 데이터 통신을 요구하는 장치의 수가 증가하면서 point to multipoint의 UM이 제안되었다. 본 논문에서는 point to multipoint의 UM에서 표준에서는 지원되지 않는 multicast-ACK 메시지를 사용함으로써 동일한 데이터를 다수의 디바이스로 전송하는 경우에 Multicast 전송을 하여 전송률을 향상시켰다. Multicast 전송을 하게 되면 multicast-ACK의 증가로 지연시간이 증가되는 문제가 발생하여 이를 해결하기 위하여 CTA구간에서 데이터 전송이 끝나고 채널이 남는 구간에 multicast ACK를 전송하도록 하였다. 제안한 메커니즘을 수학적 분석을 통해 성능을 표준과 비교하였다.

• 한국항행학회논문지
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• 제21권3호
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• pp.264-271
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• 2017

본 논문에서는 입력된 비행계획을 바탕으로 4차원 궤적을 생성하고, 이 궤적정보를 기반으로 항공기 운동을 나타내는 시뮬레이션 모델을 개발하였다. 4차원 궤적은 BADA에서 제공하는 항공기 성능 계수와 Total Energy Model 및 베지에 곡선을 활용하여 모델링 하였으며, CTA (cntrolled tme of arival) 및 속도를 기준으로 하는 두 가지 항공기 제어 방식을 제안하였다. 시뮬레이션 결과 비행시간 및 경로에 대하여 정의된 궤적과 거의 일치하였으며, 바람 조건에 따른 각 제어 방식 별 차이점을 도출하였다. 본 연구에서 개발된 시뮬레이션 모델을 기반으로, 다양한 항공교통관리 분야 연구에 활용할 수 있을 것으로 기대된다. 향후 연구로 실제 항공기가 운항한 경로와 베지에 곡선간의 차이를 줄이기 위해 최적화 기법을 도입할 필요가 있으며, 이를 통해 개발된 시뮬레이션의 활용도를 높일 수 있다.

• 한국약용작물학회지
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• 제11권4호
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• pp.268-273
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• 2003

To identify the variation of the RAPD patterns between two Atractylodes species, 52 kinds of random primers were applied to each eight of A japonica and A. macrocephala genomic DNA. Ten primers of 52 primers could be used to discriminate between the species and 18 polymorphisms among 67 scored DNA fragments (18 fragments are specific for A. japonica and A. macrocephala) were generated using these primers, 26.9% of which were polymorphic. RAPD data from the 10 primers was used for cluster analysis. The cluster analysis of RAPD markers showed that the two groups are genetically distinct. On the other hand, to identify the variation of the AFLP patterns and select the species specific AFLP markers, eight combinations of EcoRI/MseI primers were applied to the bulked A. japonica and A. macrocephala genomic DNA. Consequently, three combinations of EcoRI/MseI primers (EcoRI /Mse I ; AAC/CTA, AAC/CAA, AAG/CTA) used in this study revealed 176 reliable AFLP markers, 42.0% of which were polymorphic. 74 polymorphisms out of 176 scored DNA fragments were enough to clearly discriminate between two Atractylodes species.

• Archives of Plastic Surgery
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• 제48권2호
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• pp.219-223
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• 2021

Background A micro-arteriovenous fistula (AVF) is a minute, short shunt between an artery and a vein that does not pass through a capillary. We investigated the association between micro-AVFs and lymphedema using computed tomography angiography (CTA) and venous blood gas analysis. Methods In 95 patients with lower limb lymphedema, the presence or absence of early venous return (EVR) was compared between patients with primary and secondary lymphedema. Furthermore, we investigated the difference in the timing of edema onset in patients with secondary lymphedema with or without EVR using CTA. In 20 patients with lower limb lymphedema with confirmed early EVR in a unilateral lower limb, the partial pressure of oxygen (PO₂) was compared between the lower limb with EVR and the contralateral lower limb. Results Secondary lymphedema with or without EVR occurred at an average of 36.0±59.3 months and 93.5±136.1 months, respectively; however, no significant difference was noted. PO₂ was 57.6±11.7 mmHg and 44.1±16.4 mmHg in the EVR and non-EVR limbs, respectively, which was a significant difference (P=0.005). Conclusions EVR and venous blood gas analysis suggested the presence of micro-AVFs in patients with lower extremity edema. Further research is warranted to examine the cause of micro-AVFs, to advance technology to facilitate the confirmation of micro-AVFs by angiography, and to improve lymphedema by ligation of micro-AVFs.

• Advances in concrete construction
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• 제11권5호
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• pp.419-428
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• 2021

The pH of cement-based materials (CBMs) is an important factor for their durability, sustainability, and long service life. Currently, the use of supplementary cementitious materials (SCMs) is becoming mandatory due to economic, environmental, and sustainable issues. There is a decreasing trend in pH of CBMs due to incorporation of SCMs. The determination of numerical values of pH is very important for various low and high volume SCMs blended cement mortars for the better understanding of different defects and durability issues during their service life. In addition, the effect of cement hydration and pozzolanic reaction of SCMs on the pH should be determined at initial and later ages. In this study, the effect of low and high-volume fly ash (FA) and ground granulated ballast furnace slag (GGBFS) cement mortars in different curing conditions on their pH values has been determined. Thermal gravimetric analysis (TGA) was carried out to support the findings from pH measurements. In addition, thermal conductivity (k-value) and strength activity indices of these cement mortars were discussed. The results showed that pH values of all blended cement mortars were less than ordinary Portland cement (OPC) mortar in all curing conditions used. There was a decreasing tendency in pH of all mortars with passage of time. In addition, the pH of cement mortars was not only dependent on the quantity of Ca(OH)₂. The effect of adding SCMs on the pH value of cement mortar should be monitored and measured for both short and long terms.

• Journal of Veterinary Science
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• 제24권1호
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• pp.14.1-14.15
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• 2023

Background: The management of feline hindlimb full-thickness skin defects is challenging. On the other hand, the use of a semitendinosus (ST) myocutaneous flap for their coverage has not been reported. Objectives: To describe the ST flap and compare it with second intention healing for managing hindlimb full-thickness skin defects. Methods: In 12 purpose-bred laboratory domestic short-haired cats, two wounds were made on each tibia. The wounds in group A (n = 12) were covered with ST flaps, and those in group B (n = 12) were left to heal by second intention. In both groups, clinical assessment scoring and planimetry were performed between one-30 d postoperatively. Computed tomography-angiography (CTA) was performed on days zero, 10, and 30, and histological examinations were performed on days zero and 14 and at 6 and 12 mon postoperatively. Results: Statistically significant differences in the clinical assessment scores were observed between groups A and B on days 14 (p = 0.046) and 21 (p = 0.016). On the other hand, the time for complete healing was similar in the two groups. CTA revealed significant differences in the muscle width (day 0 compared to days 10 and 30 [p = 0.001, p = 0.026, respectively], and days 10 to 30 [p = 0.022]), ST muscle density, and the caliber of the distal caudal femoral artery and vein (day 0 compared to day 10 [p < 0.001], and days 10 to 30 [p < 0.001]). Histologically significant differences in inflammation, degeneration, edema, neovascularization, and fibrosis were observed on day 14 compared to zero and 6 mon, but no differences were found between the time interval of 6 and 12 mon. Conclusions: An ST flap can be used effectively to manage hindlimb full-thickness skin defects.

• Journal of Veterinary Science
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• 제24권5호
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• pp.65.1-65.9
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• 2023

Background: Bone subtraction computed tomography angiography (BSCTA) is a useful alternative technique for improving visualization of vessels surrounded by skull bone. However, no studies have compared computed tomography angiography (CTA) and BSCTA for improving the visibility of canine cerebral blood vessels. Objectives: To evaluate the potential benefit of BSCTA for better delineation of brain arteries of the circle of Willis (CoW) in dogs by comparing BSCTA with non-subtraction computed tomography angiography (NSCTA). Methods: Brain CTA was performed for nine healthy beagle dogs using a bolus tracking method with saline flushing. A total dose of 600 mgI/kg of contrast agent with an iodine content of 370 mgI/mL was injected at a rate of 4 ml/s. Bone removal was achieved automatically by subtracting non-enhanced computed tomography (CT) data from contrast CT data. Five main intracranial arteries of the CoW were analyzed and graded on a scale of five for qualitative evaluation. Results: Scores of basilar artery, middle cerebral artery, and rostral cerebral artery in the BSCTA group were significantly higher than those in the NSCTA group (p = 0.001, p = 0.020, and p < 0.0001, respectively). Scores of rostral cerebellar artery (RcA) and caudal cerebral artery (CCA) did not differ significantly between the two groups. However, scores of RcA and CCA in the BSCTA group were higher than those in the NSCTA group. Conclusions: BSCTA improved visualization of intracranial arteries of the CoW with close contact to bone. Thus, it should be recommended as a routine scan method in dogs suspected of having brain vessel disease.

• Korean Journal of Radiology
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• 제22권4호
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• pp.513-524
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• 2021

Objective: To assess the noncontrast two-dimensional single-shot balanced turbo-field-echo magnetic resonance angiography (b-TFE MRA) features of the abdominal aortic aneurysm (AAA) status following endovascular aneurysm repair (EVAR) and evaluate to detect endoleaks (ELs). Materials and Methods: We examined four aortic stent-grafts in a phantom study to assess the degree of metallic artifacts. We enrolled 46 EVAR-treated patients with AAA and/or common iliac artery aneurysm who underwent both computed tomography angiography (CTA) and b-TFE MRA after EVAR. Vascular measurements on CTA and b-TFE MRA were compared, and signal intensity ratios (SIRs) of the aneurysmal sac were correlated with the size changes in the AAA after EVAR (AAA prognoses). Furthermore, we examined six feasible b-TFE MRA features for the assessment of ELs. Results: There were robust intermodality (r = 0.92-0.99) correlations and interobserver (intraclass correlation coefficient = 0.97-0.99) agreement. No significant differences were noted between SIRs and aneurysm prognoses. Moreover, "mottled high-intensity" and "creeping high-intensity with the low-band rim" were recognized as significant imaging findings suspicious for the presence of ELs (p < 0.001), whereas "no signal black spot" and "layered high-intensity area" were determined as significant for the absence of ELs (p < 0.03). Based on the two positive features, sensitivity, specificity, and accuracy for the detection of ELs were 77.3%, 91.7%, and 84.8%, respectively. Furthermore, the k values (0.40-0.88) displayed moderate-to-almost perfect agreement. Conclusion: Noncontrast MRA could be a promising imaging modality for ascertaining patient follow-up after EVAR.

• Korean Journal of Radiology
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• 제22권4호
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• pp.577-583
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• 2021

Objective: To report the authors' experience in performing thoracic endovascular aortic repair (TEVAR) for zone 2 lesions after traumatic aortic injury (TAI). Materials and Methods: This retrospective review included 10 patients who underwent zone 2 TEVAR after identification of aortic isthmus injury by CT angiography (CTA) upon arrival at the emergency room of a regional trauma center from 2016 to 2019. Patients were classified into two groups: those who underwent left subclavian artery (LSA) embolization concurrently with the main TEVAR procedure, and those in whom LSA embolization was not performed during the main procedure, but was planned as a bailout treatment if type II endoleak was noted on follow-up CTA images. Pre-procedural and procedure-related factors and post-procedure prognosis were compared between the groups. Results: There were no differences in pre-procedural factors, occurrence of endoleaks, and post-procedure prognosis (including mortality) between patients in the two groups. The duration of the procedure was shorter in the non-LSA embolization group (61 minutes vs. 27 minutes, p = 0.012). During follow-up, type II endoleak did not occur in either group. Conclusion: Delaying preventative LSA embolization until stabilization of the patient would be desirable when performing zone 2 TEVAR for TAI, in the absence of endoleak on the completion aortography image taken after complete deployment of the stent graft.

• Anatomy and Cell Biology
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• 제56권3호
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• pp.360-366
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• 2023

Increased tortuosity of vessel is associated with high incidence of plaque formation leading to atherosclerosis. Surgical procedures are done after analyzing morphology of middle cerebral artery (MCA). However, literature describing MCA morphology using computed tomography angiography (CTA) is limited, so this study was planned to determine its incidence in Indian population. Datasets of CTA from 289 patients (180 males and 109 females), average age: 49.29±16.16 years (range: 11 to 85 years), from a tertiary care hospital were systematically reviewed for morphology of MCA. Cases involving aneurysms and infarcts were excluded. Four shapes of MCA were recognized: straight, U, inverted U, and S-shaped. MCA was straight in 44% (254/578), U-shaped in 37% (215/578), S shaped in 15% (89/578) and inverted U-shaped in 3% (20/578) cases. In males, MCA was straight in 46% (166/360), U-shaped in 37% (134/360), S-shaped in 16% (58/360) and inverted U-shaped in 4% (14/360) cases. In females, MCA was straight in 42% cases (92/218), U-shaped in 37% (81/218), S-shaped in 17% (36/218) and inverted U-shaped in 4% (9/218). On comparing shape with various age groups using chi square test, U shaped (P≤0.001) and S-shaped (P=0.003) MCA were found to be statistically significant. The incidence of straight shape was higher in advanced age group (>60 years). Knowledge of MCA shape will be useful for clinicians and surgeons in successful endovascular recanalization. Also, this data would help surgeons during neurointerventional procedures.