• 한국항행학회논문지
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• 제13권2호
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• pp.208-213
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• 2009

본 연구는 모바일 환경에서 신경망 기법을 이용하여 서비스 호가 요구하는 대역폭의 크기를 예측하고, 목표 핸드오프호 손실확률 이하로 유지시키는 신경망 자원예측에 의한 적응 호 수락제어기법을 제안한다. 이 기법은 목표 핸드오프호의 손실확률을 설정하여 그 기준치 이상으로 핸드오프호의 손실확률이 발생하면 예약 대역폭의 양을 증가시켜부정확한 예측으로 인해 핸드오프호의 손실확률이 증가되는 것을 방지하여 핸드오프호의 GoS(Grade of Service)를 보장하기 위함이다. 제안한 신경망 자원예측과 목표 핸드오프호 손실확률에 기초한 적응 호수락제어기법의 성능을 기존의 호 수락제어기법과 비교하여 핸드오프호 손실확률을 기준치 이하로 유지할 수 있음을 보인다.

• Mycobiology
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• 제38권1호
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• pp.26-32
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• 2010

The cyclic AMP (cAMP) pathway plays a major role in growth, sexual differentiation, and virulence factor synthesis of pathogenic fungi. In Cryptococcus neoformans, perturbation of the cAMP pathway, such as a deletion in the gene encoding adenylyl cyclase (CAC1), causes defects in the production of virulence factors, including capsule and melanin production, as well as mating. Previously, we performed a comparative transcriptome analysis of the Ras- and cAMP- pathway mutants, which revealed 163 potential cAMP-regulated genes (38 genes at a 2-fold cutoff). The present study characterized the role of one of the cAMP pathway-dependent genes (serotype A identification number CNAG_ 06576.2). The expression patterns were confirmed by Northern blot analysis and the gene was designated cAMP-regulated gene 1 (CAR1). Interestingly, deletion of CAR1 did not affect biosynthesis of any virulence factors and the mating process, unlike the cAMP-signaling deficient cac1$\Delta$ mutant. Furthermore, the car1$\Delta$ mutant exhibited wild-type levels of the stress-response phenotype against diverse environmental cues, indicating that Car1, albeit regulated by the cAMP-pathway, is not essential to confer a cAMP-dependent phenotype in C. neoformans.

• 한국대기환경학회지
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• 제21권2호
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• pp.155-160
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• 2005

Removal of methyl mercaptan was investigated using adsorption on virgin activated carbon (VAC) and modified activated carbons with acidic chemicals in the present work. CAC, NAC, AAC and SAC were represented as activated carbons modified with HCI, HNO$_{3}$, CH$_{3}$COOH and H$_{2}$S0$_{4}$ ,respectively The pore structures were evaluated using nitrogen isotherm. The surface properties of virgin activated carbon and modified activated carbons were characterized by EA, pH of carbon surface and acid value from Boehm titration. The modification of activated carbon with acidic chemicals resulted in a decrease in BET surface area, micropore volume and surface pH, but an increase in acid value. The order of the adsorption capacity of activated carbons was NAC>AAC>SAC>CAC>VAC, and in agreement with that of acid value of activated carbons, whereas in disagreement with that of micropore volume of activated carbons. It appeared that chemical adsorption played an important role in methyl mercaptan on modified activated carbons with acidic chemicals compared to virgin activated carbon. Modifying activated carbon with acidic chemicals enabled to significantly enhance removal of methyl mercaptan.

• 한국환경농학회지
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• 제32권1호
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• pp.70-77
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• 2013

우리나라는 2007년부터 원료축산물에 대한 동물용의약품 잔류허용기준 설정을 강화하면서 관련 시험법을 식품공전에 등재하여 활용하고 있다. 더불어 국외에서는 국제식품규격위원회와 유럽연합의 규제 강화 추이에 따라 불검출기준 물질에 대한 MRL 설정 등 낮은 농도의 정량한계를 가지는 검증된 분석법 개발 등이 활발히 진행되고 있다. 따라서 본 연구는 가금류 중 잔류허용기준은 아직 설정되어 있지 않으나, 식품안전성 조사 및 연구 등을 위해서는 시험법의 확립이 필요한 nitroxoline의 닭고기 근육 중 잔류시험법을 개발하고자 하였다. 분석에 사용된 검체는 닭고기의 근육을 이용하였다. 검체에 아세트로니트릴을 가하여 추출한 후, 이를 감압 농축하여 메탄올로 녹인 다음 MCX 카트리지로 정제한 후 HPLC-PDA에 주입하였다. 기기분석은 C18 컬럼을 사용하였고, 0.1 % TBAOH-인산용액과 메탄올을 기울기 조건으로 하여 360 nm에서 측정하였다. 또한, 액체크로마토그래프-질량분석기를 통해 확인시험을 수행하였으며, 모든 검증은 CAC 가이드라인(CAC/GL 16, 1993; CAC/GL 71, 2009) 규정에 따라 실시하였다. 그 결과, nitroxoline의 LOQ는 0.02 mg/kg 수준이었고, 회수율은 72.9~88.1 %로 나타났다. 또한, 변동계수는 2.5~11.7 %로 CAC 가이드라인(CAC/GL 16, 1993; CAC/GL 71, 2009) 규정에 만족하는 수준이었다. 따라서 개발된 분석법은 잔류동물용의약품의 분석에 있어 보다 신속하고 경제적인 분석 및 모니터링에 적용 가능할 것으로 기대된다.

• Restorative Dentistry and Endodontics
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• 제48권1호
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• pp.3.1-3.14
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• 2023

Objectives: This study evaluated the effect of different nanoparticulated zinc oxide (nano-ZnO) and conventional-ZnO ratios on the physicochemical properties of calcium aluminate cement (CAC). Materials and Methods: The conventional-ZnO and nano-ZnO were added to the cement powder in the following proportions: G1 (20% conventional-ZnO), G2 (15% conventional-ZnO + 5% nano-ZnO), G3 (12% conventional-ZnO + 3% nano-ZnO) and G4 (10% conventional-ZnO + 5% nano-ZnO). The radiopacity (R_ad), setting time (S_et), dimensional change (D_c), solubility (S_ol), compressive strength (C_st), and pH were evaluated. The nano-ZnO and CAC containing conventional-ZnO were also assessed using scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Radiopacity data were analyzed by the 1-way analysis of variance (ANOVA) and Bonferroni tests (p < 0.05). The data of the other properties were analyzed by the ANOVA, Tukey, and Fisher tests (p < 0.05). Results: The nano-ZnO and CAC containing conventional-ZnO powders presented particles with few impurities and nanometric and micrometric sizes, respectively. G1 had the highest Rad mean value (p < 0.05). When compared to G1, groups containing nano-ZnO had a significant reduction in the S_et (p < 0.05) and lower values of D_c at 24 hours (p < 0.05). The C_st was higher for G4, with a significant difference for the other groups (p < 0.05). The S_ol did not present significant differences among groups (p > 0.05). Conclusions: The addition of nano-ZnO to CAC improved its dimensional change, setting time, and compressive strength, which may be promising for the clinical performance of this cement.

• 대한방사선기술학회지:방사선기술과학
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• 제34권4호
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• pp.305-314
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• 2011

분진에 노출된 집단의 흉부 디지털영상에서 진폐 소견에 따라 흉부 저선량 CT영상에서 발견된 소견을 비교 분석하였다. 2007년 4월부터 2008년 8월 사이 일개 진폐정밀건강진단기관에 내원한 진폐정밀건강진단 대상자 남자 328명에 대해 저선량 CT촬영을 실시하였고, 진폐 판독경험이 많은 1명의 영상의학과 전문의가 판독하였다. 흉부 디지털영상의 진폐 소견은 국제노동기구 흉부 영상 분류법(ILO, 2000)따라 아날로그 표준 사진을 참조하여 2명의 영상의학과 전문의가 합의 판독한 결과로부터 얻었고, 소음영의 병형에 따라 진폐 소견이 없는군(87명, 26.5%)과 있는군(241명, 73.5%)으로 분류하였다. 진폐 소견이 있는군에서 나이(60.9 vs. 65.0, p<0.001)와 분진노출기간(17.0 vs. 19.2, p=0.024)이 통계학적으로 유의하게 높았지만, 흡연력은 차이가 없었다. 전체 대상자 328명 중 245명(74.7%)이 저선량 CT영상에서 13 종류의 소견이 발견되었다. 진폐 소견이 없는군 보다 있는군에서 관상동맥 석회화 소견이 통계학적으로 의미 있게 높은 빈도를 보였고(25.3% vs. 36.9%, p=0.049), 벌집모양 소견도 높은 빈도를 보였다(1.2% vs. 6.2%, p=0.079). 하지만, 저선량 CT영상에서 진폐 소음영을 시사하는 작은 결절은 진폐 소견이 없는 군에서 더 높은 빈도를 보여 흉부 디지털영상이 민감도가 낮았다. 이상의 결과에서 분진 노출에 의한 진폐 소견이 저선량 CT영상의 관상동맥 석회화 소견과 유의한 관련성을 보였지만, 독립적인 위험요인임을 규명하기 위해서는 관상동맥 혈관 조영술을 이용한 전향적인 추가 연구가 필요할 것으로 사료된다.

• 한국통신학회논문지
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• 제35권5B호
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• pp.741-752
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• 2010

The ability to seamlessly switch between the macro networks and femtocell networks is a key driver for femtocell network deployment. The handover procedures for the integrated femtocell/macrocell networks differ from the existing handovers. Some modifications of existing network and protocol architecture for the integration of femtocell networks with the existing macrocell networks are also essential. These modifications change the signal flow for handover procedures due to different 2-tier cell (macrocell and femtocell) environment. The handover between two networks should be performed with minimum signaling. A frequent and unnecessary handover is another problem for hierarchical femtocell/macrocell network environment that must be minimized. This work studies the details mobility management schemes for small and medium scale femtocell network deployment. To do that, firstly we present two different network architectures for small scale and medium scale WCDMA femtocell deployment. The details handover call flow for these two network architectures and CAC scheme to minimize the unnecessary handovers are proposed for the integrated femtocell/macrocell networks. The numerical analysis for the proposed M/M/N/N queuing scheme and the simulation results of the proposed CAC scheme demonstrate the handover call control performances for femtocell environment.

• 설비공학논문집
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• 제23권8호
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• pp.571-579
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• 2011

Heat pump systems for commercial building with variable refrigerant flow(VRF) are expanding a market due to high energy efficiency, lower maintenance cost and easy installation comparing with the conventional heat pump with the constant refrigerant flow. In general, heat pump systems degrade the energy efficiency in the extremely low temperature regions. In this study, VRF heat pump system with refrigerant heating is experimentally investigated to overcome the low heating performance in the extremely low temperature regions. VRF heat pump system with refrigerant heating is found out the sufficient heating performance in the -25 degree temperature condition comparing with the conventional heat pump system and is obtained more than 2,500 kPa high pressure in the evaporator at low temperature.

• Structural Engineering and Mechanics
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• 제40권5호
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• pp.595-616
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• 2011

Impact experiments have been carried out on concrete slabs. The first group was traditionally manufactured, densely reinforced concrete targets, and the next were ordinary Portland and calcium aluminate cement based HPSFRC (High performance steel fiber reinforced concrete) and SIFCON (Slurry infiltrated concrete) targets. All specimens were hit by anti-armor tungsten projectiles at a muzzle velocity of over 4 Mach causing destructive perforation. In Part I of this article, production and experimental procedures are described. The first group of specimens were ordinary CEM I 42.5 R cement based targets including only dense reinforcement. In the second and third groups, specimens were produced using CEM I 42.5 R cement and Calcium Aluminate Cement (CAC40) with ordinary reinforcement and steel fibers 2 percent in volume. In the fourth group, SIFCON specimens including 12 percent of steel fibers without reinforcement were tested. A high-speed camera was used to capture impact and residual velocities of the projectile. Sample tests were performed to obtain mechanical properties of the materials. In the companion Part II of this study, numerical investigations and simulations performed will be presented. Few studies exist that examine high-velocity impact effects on CAC40 based HPSFRC targets, so this investigation gives an insight for comparison of their behavior with Portland cement based and SIFCON specimens.

• Computers and Concrete
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• 제11권2호
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• pp.105-121
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• 2013

This paper investigates the parameters that control the design of Fiber Reinforced Polymer (FRP) reinforced concrete flexural members proportioned following the ACI 440.1R-06. It investigates the critical parameters that control the flexural design, such as the deflection limits, crack limits, flexural capacity, concrete compressive strength, beam span and cross section, and bar diameter, at various Mean-Ambient Temperatures (MAT). The results of this research suggest that the deflection and cracking requirements are the two most controlling limits for FRP reinforced concrete flexural members.