• Applied Microscopy
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• 제29권4호
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• pp.405-415
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• 1999

일반적으로 고분자 미세구조 관찰은 microtomming, solution casting, carbon replica, staining법 등을 이용하여 시료를 전처리한 시료를 TEM을 이용하여 관찰한다. 이러한 시편 전처리 법은 높은 재연성 등으로 널리 이용되고 있으나 기기 의존적이거나 시편전처리 과정이 복잡한 단점이 있다. 본 연구는 주사전자현미경을 이용한 고분자미세구조 관찰 및 이를 위한 시편준비법에 관한 것이다. 이를 위하여 본 연구에서는 기존에 제한된 화학적에칭법을 개선하여 각종 polyolefin 종류 및 형상에 맞게 전처리하여 SEM을 이용한 고분자 미세구조 연구를 수행하였다. 본 연구를 통하여 과망간산 에칭방법이 주사전자현미경을 이용한 polyolefin 미세구조 관찰에 적합함을 알 수 있었으며, 에칭조건은 시료의 종류와 관찰대상에 맞게 과망간산/인산, 과망간산/인산/황산 등의 조성과 etchant 의 함량비, 에칭시간의 단순한 조절로 가능하다. 본 연구의 에칭법을 이용하여 관찰한 고분자의 미세구조는 iPP 구정의 characterization, 라멜라 특성연구, 고분자 blend 등 기존 연구의 관찰결과를 잘 재연하고 있어 고분자의 모폴로지 특성 뿐만 아니라 blend와 film등 상업적 제품 연구 및 개발에 유용한 방법임을 알 수 있었다.

• 한국통신학회논문지
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• 제30권11A호
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• pp.1081-1091
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• 2005

기존 DVB-T 시스템에서의 Streaming 방식이 아닌 IPDC(IP Data Casting) 방식으로 전송하는 DVB-H 시스템은 수신기의 소모 전력 감소를 통한 휴대성의 극대화를 위하여 Time-Slicing 기법을 사용한다. 해당 time slot의 Burst에 대해서만 수신기 동작을 수행함으로써 수신기의 전력 효율을 증대시킬 수 있는 Time-Slicing 기법은 각 Burst에 대한 동기 시간의 단축을 통하여 더욱 향상된 절전 효과를 얻을 수 있다. 본 논문에서는 현재 수신된 OFDM 심볼의 파일럿 패턴을 검출하는 고속 분산 파일럿 동기 알고리즘을 제안한다. 제안된 방식은 연속적으로 수신된 두 OFDM 심볼에 대하여 가능한 분산 파일럿 위치의 인접 부반송파 간의 상관을 이용하므로 기존의 DVB-T에 적용된 방식에 비하여 동기 수행 시간을 두 심볼로 크게 줄일 수 있으며, DVB-H 시스템을 위해 노키아에서 제안된 두 가지의 방식 및 기준 신호와의 상관을 이용하는 방식에 비하여 우수한 성능을 나타낸다. 컴퓨터 모의 실험은 ETSI의 EN300 744를 기반으로 수행되었으며, 성능 평가 결과 제안된 방식이 기존 방식에 비하여 보다 효율적이며 안정된 성능을 보임을 확인할 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제25권6호
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• pp.193-198
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• 2021

이 연구에서는 3D 프린팅 복합재료의 레올로지 특성과 출력 패턴에 따른 적층 시험체의 압축강도 특성을 평가하였다. 레올로지 측정결과, 압출 후 60분 후부터 급격한 재료 변화가 나타났으며, 배합직후 대비 1.4배 높은 항복응력과 14.94~25.62% 낮은 소성점도를 나타내었다. 실린더 몰드에 제작한 시험체와 적층 시험체의 압축강도를 비교하였으며, 적층 시험체의 출력패턴은 0°, 45°, 90°를 변수로 하였다. 재령 1~28일까지의 몰드 타설 시험체와 적층 시험체의 압축강도는 출력 패턴과 관계없이 유사한 성능을 나타내었다. 특히, 재령 28일에서는 모든 시험체의 초기 접선탄성계수와 최고 압축강도 및 최대 응력 시 변형률은 거의 동일하게 나타났다. X-ray CT분석을 통한 적층 시험체의 계면 분석결과, 압축강도 측정 후의 시험체의 적층 계면에서의 균열이 발생하지 않은 것을 확인하였으며, 이는 적층 시험체 내의 각각의 계면이 일체화 거동을 한 것으로 판단할 수 있다.

• International Journal of Concrete Structures and Materials
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• 제6권2호
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• pp.65-78
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• 2012

An experimental study was carried out to evaluate fresh properties of a moderately high-strength (high-flowing) self-compacting concrete (SCC) and to investigate shear behavior and performance of deep beams made with SCC. Fresh and hardened properties of normal concrete (NC) and SCC were evaluated. The workability and compacting ability were observed based on casting time and number of surface cavities, respectively. Four-point loading tests on four deep beams (two made with SCC and two with NC) were then conducted to investigate their shear behavior and performance. Shear behavior and performance of beams having two different web reinforcements in shear were systematically investigated in terms of crack pattern, failure mode, and load-deflection response. It was found from the tests that the SCC specimen having a normal shear reinforcement condition exhibited a slightly higher load carrying capacity than the corresponding NC specimen, while the SCC specimen having congested shear reinforcement condition showed a similar load carrying capacity to the corresponding NC specimen. In addition, a comparative study between the present experimental results and theoretical results in accordance with ACI 318 (Building Code Requirements for Reinforced Concrete (ACI 318-89) and Commentary-ACI 318R-89, 1999), Hsu-Mau's explicit method (Hsu, Cem Concr Compos 20:419-435, 1998; Mau and Hsu, Struct J Am Concr Inst 86:516-523, 1989) and strut-and-tie model suggested by Uribe and Alcocer (2002) based on ACI 318 Appendix A (2008) was carried out to assess the applicability of the aforementioned methods to predict the shear strength of SCC specimens.

• 한국주조공학회지
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• 제35권5호
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• pp.109-113
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• 2015

In this study, the measurement of FN (ferrite volume fraction) and the solution annealing ratio at a temperature of $1130^{\circ}C$ were determined with 15A elbow fittings of shell cast SSC13, and the corrosion resistance with and without austenitizing solution annealing were investigated in comparison with AISI304. The delta ferrite phase was observed in the material due to the slow cooling effect of the shell mold casting. However, the delta ferrite phase decreased gradually with the solution annealing at a temperature of $1130^{\circ}C$. The hardness generally decreased with a heat treatment; however, its corrosion resistance was improved with the heat treatment. In addition, when a passivation treatment was applied, its corrosion ratio showed the lowest value. The pattern of general corrosion decreased due to the decrease in the delta ferrite phase with the solution annealing treatment. Consequently, it is suggested that the corrosion resistance of SSC13 elbow fittings can be improved by increasing the ratio of any solution annealing treatment used and by decreasing the ferrite phase. The relationship between the ratio of solution annealing and delta ferrite is expressed as follows: SA (solution annealing ratio,%) = 98 - FN (ferrite volume fraction, %).

• 수산해양교육연구
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• 제25권3호
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• pp.724-732
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• 2013

The purpose of this study is to obtain a basic data on layout of the trawlers' bridge equipment. The task activities of bridge workers involved in the navigation and fishing operation were analyzed by link analysis methods. The results are as follows. It was found that the movement pattern and frequency of bridge workers are different accordance with the bridge work (navigation, casting net, towing net and hauling net). The central workstation of movement of the bridge workers was a radar workstation, a steering workstation and a trawl winch workstation in the bridge work. But the radar did not show up as the center of movement during the hauling net. Workstations related deeply to the central workstations of the movement on the bridge were as below. Radar workstation was related to a GPS plotter, a microphone location for external communication with VHF and MF/HF equipment and a steering in the case of the navigation, the steering, the GPS plotter and the net monitor in the case of the fishing operation. Steering workstation was related deeply to the GPS plotter, the radar in the case of the navigation, a speed controller, the GPS plotter, a fish finder, the net monitor and the microphone location in the case of the fishing operation. Trawl winch workstation showed deep relation with the GPS plotter and the speed control during the fishing operation. Through this study, it was found that Workstations related deeply to the central workstation of the movement of the bridge workers in accordance with the bridge work. The results of this study might be utilized as the basic data on the bridge layout to minimize the fatigue degree due to a physical movement of the bridge workers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.192-192
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• 2009

We have successfully demonstrated the inkjet printing process to fabricate $Al_2O_3$ thick films without a high temperature sintering process. A single solvent system had a coffee ring pattern after printing of $Al_2O_3$ dot, line and area. In order to fabricate the smooth surface of $Al_2O_3$ thick film, we have introduced a co-solvent system which has nano-sized $Al_2O_3$ powders in the mixture of Ethylene glycol monomethyl ester and Di propylene glycol methyl ether. This co-solvent system approached a uniform and dense deposition of $Al_2O_3$ powders on the substrate. The packing density of inkjet-printed $Al_2O_3$ films is more than 70% which is very high compared to the value obtained from the films synthesized by other conventional methods such as casting processes. The characterization of the inkjet-printed $Al_2O_3$ films has been implemented to investigate its thickness and roughness. Also the dielectric loss of the films has been measured to understand the feasibility of its application to 3D integration package substrate.

• Journal of Pharmaceutical Investigation
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• 제24권1호
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• pp.41-48
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• 1994

A new local drug delivery device to treat otitis media (OM) has been developed. This device consists of a biodegradable poly(L-lactic acid) (PLLA) film containing antibiotic (ampicillin, AMP), which can be placed into the middle ear cavity and release the therapeutic concentration of AMP for prolonged period. Biodegradable films containing AMP (10 w/w%) were prepared by solution casting method using a suspension of the drug in a $PLLA/CH_{2}Cl_{2}$ solution (molecular weight of PLLA, 100,000 (100 K) and 300,000 (300 K), respectively). PLLA-AMP films were characterized by FTIR, DSC, and SEM. In vitro release of AMP from AMP-PLLA films were examined. The release pattern of AMP from AMP-PLLA films remained consistent from 1 day to 14 days, and the release rates of AMP from AMP-100K-PLLA film and AMP-300K-PLLA film were $0.7384\;{\mu}g/ml/day$, $0.4107\;{\mu}g/ml/day$, respectively.

• 대한수의학회지
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• 제6권1호
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• pp.57-75
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• 1966

This study was conducted to observe the condition of the ramifications of the bronchus and pulmonary blood vascular system by injecting the vinylite into the bronchial tree and pulmonary blood vessels in 100 normal adult dogs. The results obtained were summarized as follows: 1. Lungs of dog were composed of the same pulmonary territories as in lungs of human. 2. Cardiac lobe corresponding to R.medio-bassalis of human lungs was well developed and situated as a independent cardiac lobe, in ventral side of right lung. 3. Bronchial tree were in the patterns of axial divergency and blood vascular systems were (in general) branched along the bronchial tree, arteries lying near the bronchial tree but veins apart from it. 4. Among the branching patterns of bronchus pulmonary artery and pulmonary vein in each lobe, the type presented most frequently were noted, which were designated basic type by the author. 5. Pulmonary blood vessels were not always branched in accordance with bronchial tree, diverged inmore complex patterns, especially in venous vascular system. 6. Ramus anterior (lobe apicalis) was always observed in all casting specimen. 7. There was a case of peculiar variation patterns of the ramification in the bronchi directing into the left apical and cardiac lobe, arose respectivelly, at independent origin of bifurcation in the left bronchial stem, and a case of peculiar variation pattern of the artery entering left apical lobe and cardiac lobe, had a same origin of the bifurcation at rami pulmonary artery, and then divided respectivelly into the rami medi artery and rami left apical lobe artery. 8. In the classification based on the patterns of bronchial and blood vasculor divergencys, there were a lot of significant combination cases in their patterns.

• 대한치과보철학회지
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• 제42권4호
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• pp.412-424
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• 2004

Statement of problem: Several prosthetic options are available for the restoration of multiple adjacent implants. A passively fitting prosthesis has been considered a prerequisite for the success and maintenance of osseointegration. Passivity is a particular concern with multiple implants because of documented inaccuracies in the casting and soldering process. One way to avoid this problem is to restore the implants individually, however, the restorations of individual adjacent impants requires careful adjustment of interproximal contacts. Purpose: The purpose of this study was to compare the stress distribution pattern and amount surrounding Bicon implants with individual crowns and splinted restorations. Material and method: A photoelastic model of a human partially edentulous left mandible with 3 Bicon implants($4{\times}11mm$) was fabricated. For non-splinted restorations, individual crowns were fabricated on 3 abutments ($4{\times}0.65mm,\;0^{\circ}$, 2.0 mm post, Bicon Inc., Boston, USA) After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal ($8{\mu}m$ shim stock drags without tearing), medium($40{\mu}m)$), and heavy($80{\mu}m$). Splinted 3-unit fixed partial dentures were fabricated and cemented to the model. Changes in stress distribution under simulated non-loaded and loaded conditions(7.5, 15, 30 lb) were analyzed with a circular polaricope. Results: 1. Stresses were distributed around the entire body of fin in Bicon implants. 2. Splinted restorations were useful for distribution of stress around implants especially with higher loads. 3. By increasing the contact tightness between the individually restored three implants, the stress increased in the coronal portion of implants. Conclusions: Ideal adjustment of the contact tightness was important to reduce the stresses around individually restored Bicon implants.