• 한국통신학회논문지
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• 제30권2A호
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• pp.80-89
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• 2005

IEEE 802.11과 802.11e는 애드 혹 환경을 위해 DCF와 EDCA 모드를 제공한다. DCF와 EDCA 모드는 CSMA/CA를 사용하는 경쟁 기반의 프로토콜로써, 구현이 용이하고 시스템의 부하가 작은 경우에는 효율적으로 동작한다. 그러나 시스템의 부하가 증가할수록 충돌이 증가하여 그 성능이 현저하게 감소한다. 반면 제어 기반 동작 프로토콜인 PCF와 HCCA 모드는 스테이션들이 중앙 조정자의 폴링에 의하여 통제되고, 충돌이 발생하지 않는다. 그러나 시스템의 부하가 적을 때, 소수의 스테이션들만이 전송할 수 있는 기회를 가지기 때문에 효율적이지 않다. 보다 중요한 문제는 PCF와 HCCA 모드는 애드 혹 네트워크에서는 사용이 불가능하다는 것이다. 따라서 본 논문에서는 경쟁 기반의 매커니즘을 수행하기 전에 폴링의 개념을 추가하여, 애드 혹 환경에서 QoS 제공을 위해 DCF와 EDCA 모드에 폴링 매커니즘을 적용한 우선순위 기반 분산 폴링 매커니즘 (Priority-based Distributed Polling Mechanism)을 제안한다. PDPM은 시스템의 부하가 큰 경우 대부분의 충돌을 피할 수 있는 장점을 가지며, 부하가 적을 경우는 경쟁 기반의 매커니즘을 유지할 수 있다. 또한 IEEE 802.11e와 비교하여 보다 적은 충돌과 높은 처리율을 제공한다.

• Journal of Korean Neurosurgical Society
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• 제56권3호
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• pp.224-229
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• 2014

Objective : To report long-term clinical and radiological outcomes of minimally invasive posterior cervical foraminotomy (MI-PCF) performed in patients with unilateral single-level cervical radiculopathy. Methods : Of forty-six patients who underwent MI-PCF for unilateral single-level radiculopathy between 2005 and 2013, 33 patients were included in the study, with a mean follow-up of 32.7 months. Patients were regularly followed for clinical and radiological assessment. Clinical outcome was measured by visual analogue scale (VAS) for the neck/shoulder and arm, and the neck disability index (NDI). Radiological outcome was measured by focal/global angulation and disc height index (DHI). Outcomes after MI-PCF were evaluated as changes of clinical and radiological parameters from the baseline. Mixed effect model with random patients' effect was used to test for differences in the clinical and radiological parameters repeat measures. Results : There were no complications and all patients had an uneventful recovery during the early postoperative period. VAS scores for neck/shoulder and arm improved significantly in the early postoperative period (3 months) and were maintained with time (p<0.001). NDI improved significantly post-operatively and tended to decrease gradually during the follow-up period (p<0.001). There were no statistically significant changes in focal and global angulation at follow-up. Percent DHIs of the upper adjacent or operated disc were maintained without significant changes with time. During the follow-up, same site recurrence was not noted and adjacent segment disease requiring additional surgery occurred in two patients (6%) on the contra-lateral side. Conclusion : MI-PCF provides long-term pain relief and functional restoration, accompanied by good long-term radiological outcome.

• 한국식품영양과학회지
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• 제24권1호
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• pp.98-104
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• 1995

미이용자원의 효율적인 이용을 위해서 고등어 내장으로부터 항산화물질을 추출하여 그 효과를 알아보고자 본 실험을 행하였다. 내장으로 부터 총지질을 추출하여 다시 헥산 추출물, 사염화탄소-메탄올 추출물(1 : 1, 1 : 3, 1 : 9, v/v), 인지질, 포스파티딜콜린(PC), PC를 제외한 나머지 인지질획분(PCF)로 추출하여 $40^{\circ}C$ 항온기에서 10일간 산화억제실험을 하였다. 그 결과 헥산 추출물은 총지질이나 사염화탄소-메탄올 보다 산화억제 효과가 낮았고 사염화탄소-메탄올(1 : 1, 1 : 3, 1 : 9, v/v) 추출물은 극성이 높을수록 효과가 컸다. 극성지질인 인지질(PL)과 인지질을 구성하는 포스파티딜콜린(PC)과 그 나머지 획분(PCF=PC free PL)도 모두 현저한 산화억제 효과를 나타내었으며 그 중에서도 PC가 가장 효과적인 것을 알 수 있었다. PC의 항산화 효과를 알아보기 위해 천연 및 합성산화제와의 효과를 비교한 결과 PC첨가군이 다른 항산화제 보다 2~3배 산화억제력이 높게 나타났다. 이상의 결과를 종합해보면 인지질의 항산화작용을 인정할 수 있으며 그 주체는 PC임을 알 수 있다. 수산폐기물로 부터 항산화물질의 이용이라는 대단히 긍정적인 결과와 함께 어유의 산화안정효과에 대단히 큰 영향을 미치리라고 예상된다.

• Physical Therapy Rehabilitation Science
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• 제7권4호
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• pp.147-153
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• 2018

Objective: This study investigated the effects of air stacking training (AST) on pulmonary function, respiratory strength, and peak cough flow (PCF) in persons with cervical spinal cord injury (CSCI). Design: Randomized controlled trial. Methods: A total of 24 persons with CSCI were randomly allocated to the AST group (n=12) or the incentive spirometry training (IST) group (n=12). Patients with CSCI received AST or IST for 15 minutes, with 3 sessions per week for 4 weeks, and all groups performed basic exercises for 15 minutes. In the AST group, after the subject inhaled the maximal amount of air as best as possible, the therapist insufflated additional air into the patient's lung using an oral nasal mask about 2-3 times. In the IST group, patients were allowed to hold for three seconds at the maximum inspiration and then to breathe. The pre and post-tests measured forced vital capacity (FVC), forced expiratory volume one at second (FEV1), maximal expiratory pressure (MEP), maximal inspiratory pressure (MIP) and PCF. Results: Both groups showed significant improvements in FVC, FEV1, MEP, MIP and PCF values after training (p<0.05). The FVC in the post-test and the mean change of FVC, FEV1, MIP were significantly higher in the AST group than the IST group (p<0.05). Conclusions: The findings of this study suggested that AST significantly improved pulmonary function, respiratory strength, and PCF in persons with CSCI. Therefore, AST should be included in respiratory rehabilitation programs to improve coughing ability, pulmonary function and respiratory muscle strength.

• Geomechanics and Engineering
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• 제31권5호
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• pp.477-488
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• 2022

Pile composite foundation (PCF) has been commonly applied in practice. Existing research has focused primarily on semi-infinite media having equal pile lengths with little attention given to the effects of inclined bedrock and dissimilar pile lengths. This investigation considers the effects of inclined bedrock on vertical loaded PCF with dissimilar pile lengths. The pile-soil system is decomposed into fictitious piles and extended soil. The Fredholm integral equation about the axial force along fictitious piles is then established based on the compatibility of axial strain between fictitious piles and extended soil. Then, an iterative procedure is induced to calculate the PCF characteristics with a rigid cap. The results agree well with two field load tests of a single pile and numerical simulation case. The settlement and load transfer behaviors of dissimilar 3-pile PCFs and the effects of inclined bedrock are analyzed, which shows that the embedded depth of the inclined bedrock significantly affects the pile-soil load sharing ratios, non-dimensional vertical stiffness N₀/wdE_s, and differential settlement for different length-diameter ratios of the pile l/d and pile-soil stiffness ratio k conditions. The differential settlement and pile-soil load sharing ratios are also influenced by the inclined angle of the bedrock for different k and l/d. The developed model helps better understand the PCF characteristics over inclined bedrock under vertical loading.

• 대한두경부종양학회지
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• 제11권2호
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• pp.167-172
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• 1995

Pharyngocutaneous fistula(PCF) is one of the complications following total laryngectomy in laryngeal and hypopharyngeal cancer. Fistula lead to delayed wound healing, more serious complications such as carotid blow-out, prolonged hospitalization, significant patient morbidity and occasional mortality. Identification of patients at high risk for fistula formation, appropriate preventive measures, and appropriate management are the head and neck surgeon's responsibility. So we analyzed the clinical data of pharyngocutaneous fistula which was developed after total laryngectomy. Following results were obtained: 1) Occurrence of PCF increases with salvage surgery compared to curative surgery. 2) Early detection and effective management of PCF are the key factors to decreasing the hospitalization period. 3) Constructing a pharyngostoma seems to be an ideal method of preventing dangerous complications and ultimately closing the fistula. 4) Simultaneous reconstruction is necessary in the high risk group.

• 한국전문물리치료학회지
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• 제22권3호
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• pp.12-22
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• 2015

The purpose of this study was to investigate the effect of taping on knee joint for patellofemoral compressive force (PCF) during stair descent for elderly women. Ten healthy elderly women voluntarily participated in this study. A three-dimensional motion analysis system and force plates were used to analyze the movements of the joints for the lower extremities. The results were as follows: There were no significant differences for the maximum PCF, maximum quadriceps contraction force and maximum knee extension moment (p>.05) but, there was a pattern decreasing all values with the taping during stair descent. There were significant differences for the knee and ankle angle on the event of maximum PCF (p<.05) and there was a pattern decreasing all values with the taping during stair descent. Therefore, taping on the knee would be effective to relieve the pain like patellofemoral pain syndrome in the knee joint.

• Steel and Composite Structures
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• 제21권3호
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• pp.605-628
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• 2016

The energy absorption characteristics of diamond core sandwich cylindrical columns under axial crushing process depend greatly on the amount of material which participates in the plastic deformation. Both the single-objective and multi-objective optimizations are performed for columns under axial crushing load with core thickness and helix pitch of the honeycomb core as design variables. Models are optimized by multi-objective particle swarm optimization (MOPSO) algorithm to achieve maximum specific energy absorption (SEA) capacity and minimum peak crushing force (PCF). Results show that optimization improves the energy absorption characteristics with constrained and unconstrained peak crashing load. Also, it is concluded that the aluminum tube has a better energy absorption capability rather than steel tube at a certain peak crushing force. The results justify that the interaction effects between the honeycomb and column walls greatly improve the energy absorption efficiency. A ranking technique for order preference (TOPSIS) is then used to sort the non-dominated solutions by the preference of decision makers. That is, a multi-criteria decision which consists of MOPSO and TOPSIS is presented to find out a compromise solution for decision makers. Furthermore, local and global sensitivity analyses are performed to assess the effect of design variable values on the SEA and PCF functions in design domain. Based on the sensitivity analysis results, it is concluded that for both models, the helix pitch of the honeycomb core has greater effect on the sensitivity of SEA, while, the core thickness has greater effect on the sensitivity of PCF.

• 소성∙가공
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• 제29권4호
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• pp.179-187
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• 2020

Existing composite forming processes such as the autoclave, prepreg compression forming (PCF), RTM, etc. require high production costs because of their long processing time. On the other hand, microwave heating process (MHP) can reduce the production costs since both mold and composite material can be heated directly. The aim of this study is to manufacture a mold consisting of polytetrafluoroethylene (PTFE), quartz glass, stainless steel clamps, and polyether ether ketone (PEEK) bolts for fabricating FML based on self-reinforced polypropylene (SRPP) using the MHP. First, the flame test was carried out prior to the MHP to check the temperature on the mold and whether the spark occurred at the mold and the edge of the FML. Second, the uniaxial tensile test was then conducted to obtain the mechanical properties of the FML manufactured by the MHP. The mechanical properties were compared with those of the FML fabricated by the PCF. As a result, the MHP using the PTFE mold can manufacture the FML more rapidly than the PCF, and obtain acceptable mechanical properties.

• 한국광학회지
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• 제18권1호
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• pp.14-18
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• 2007

실리카 코어 주변에 주기적인 공기층을 가지는 광자결정 광섬유는 넓은 파장 영역을 통한 단일모드의 구현 또는 1옥타브 이상의 광대역 연속광 발생과 같은 기존의 광섬유로는 불가능한 독특한 특성을 갖도록 유연하게 설계할 수 있다. 광자결정 광섬유의 설계에 사용되는 변수로는 공기층의 직경과 간격이 있으며 이러한 변수의 조절을 위한 공정을 도입하여 넓은 파장영역을 통한 단일모드 구현과 높은 비선형 특성을 가지는 광자결정 광섬유를 각각 제작 하였고 수치적 계산과 실험을 통해 그 특성을 살펴보았다.