• Composites Research
• /
• 제17권5호
• /
• pp.85-95
• /
• 2004

페놀 컴포지트(PC)의 실용화에 관해서 세계에서 가장 발전한 영국의 철도차량, 선박$.$주정과 해양 유전시설 등에서의 실적과, 관련한 상황을 조사하고 일.영 공동의 집필로 지금까지 4회 본지에 보고해 왔다. 본 보고에서 어떤 재료라도 실용화가 비교적 어렵다고는 것을 알 수 있었다. 금번 호에서는 $\ulcorner$건설.건축분야$\lrcorner$를 중심으로 영국에서의 $\ulcorner$PC 실용화$\lrcorner$의 현상을 정리하여 개설한다. 이 분야는 일본뿐만 아니라 영국, 프랑스, 미국에서도 신 재료가 시장에 진입하는 것은 어렵고, 각 국의 PC 관계자의 고통도 모두 마찬가지이다. 최 선단을 가는 영국의 $\ulcorner$PC 실용화$\lrcorner$도, 건축으로는 런던 지하철역 구내 화재 사방사고 이래, 지하철역, 학교. 병원, 시영 아파트 등에 $\ulcorner$PC$\lrcorner$ 화재대책으로써 시설이 뛰어나게 보완되어 $\ulcorner$세계의 모범$\lrcorner$이 되었지만, 지금도 대 지하상가에서 검은 연기 화재에 대한 걱정을 배제할 수 없다.

• The Journal of Advanced Prosthodontics
• /
• 제9권3호
• /
• pp.217-223
• /
• 2017

PURPOSE. This study investigated the effects of silver nanoparticle (SN) loading into hydraulic calcium silicate-based Portland cement on its mechanical, antibacterial behavior and biocompatibility as a novel dental bone substitute. MATERIALS AND METHODS. Chemically reduced colloidal SN were combined with Portland cement (PC) by the concentrations of 0 (control), 1.0, 3.0, and 5.0 wt%. The physico-mechanical properties of silver-Portland cement nanocomposites (SPNC) were investigated through X-ray diffraction (XRD), setting time, compressive strength, solubility, and silver ion elution. Antimicrobial properties of SPNC were tested by agar diffusion against Streptococcus mutans and Streptococcus sobrinus. Cytotoxic evaluation for human gingival fibroblast (HGF) was performed by MTS assay. RESULTS. XRD certified that SN was successfully impregnated in PC. SPNC at above 3.0 wt% significantly reduced both initial and final setting times compared to control PC. No statistical differences of the compressive strength values were detected after SN loadings, and solubility rates of SPNC were below 3.0%, which are acceptable by ADA guidelines. Ag ion elutions from SPNC were confirmed with dose-dependence on the concentrations of SN added. SPNC of 5.0 wt% inhibited the growth of Streptococci, whereas no antimicrobial activity was shown in control PC. SPNC revealed no cytotoxic effects to HGF following ISO 10993 (cell viability > 70%). CONCLUSION. Addition of SN promoted the antibacterial activity and favored the bio-mechanical properties of PC; thus, SPNC could be a candidate for the futuristic dental biomaterial. For clinical warrant, further studies including the inhibitory mechanism, in vivo and long-term researches are still required.

• Korean Chemical Engineering Research
• /
• 제49권5호
• /
• pp.652-656
• /
• 2011

양극산화에 의해 티타니아 나노튜브(TNT) 박막과 나노필름(TNF) 박막을 제조하여 이의 광촉매 반응특성을 연구하였다. TNT 박막이 형성된 티타늄 판에 자외선을 조사하여 용액 내 메틸렌블루의 분해율을 측정하였다. TNT의 길이가 증가할수록 광촉매(PC) 반응에 의한 메틸렌블루 분해율이 증가하였다. 광전자의 재결합을 억제하기 위해 포텐셜을 가해준 광전자촉매(PEC) 반응에서는 전반적으로 분해율이 상승하였으며, 길이에 따른 분해율 차이가 상대적으로 작았다. 튜브형태가 아닌 필름형태의 TNF는 TNT에 비해 낮은 분해율을 나타내었으며, 광촉매 반응에서 분해율의 차이가 더 크게 나타났다.

• Journal of Power Electronics
• /
• 제15권5호
• /
• pp.1348-1357
• /
• 2015

Under traditional unified power quality conditioner (UPQC) control, a UPQC series converter (SC) is mainly used to handle grid-side power quality problems while its parallel converter (PC) is mainly used to handle load-side power quality problems. The SC and PC are relatively independent. The SC is usually in standby mode and it only runs when the grid voltage abruptly changes. In this paper, novel UPQC coordinated control strategies are proposed which use the SC to share the reactive power compensation function of the PC especially without grid-side power quality problems. However, in some cases, there will be a circulating current between the SC and the PC, which will probably influence the compensation fashion, the compensation capacity, or the normal work of the UPQC. Through an active power circulation analysis, strategies with and without a circulating current are presented which fuses the reactive power allocation strategy of the SC and the PC, the composite control strategy of the SC and the compensation strategy of the DC storage unit. Both of the strategies effectively solve the SC long term idle problem, limit the influence of the circulating current, optimize all of the UPQC units and reduce the production cost. An analysis, along with simulation andexperimental results, is presented to verify the feasibility and effectiveness of the proposed control strategies.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2001년도 추계학술발표대회
• /
• pp.906-909
• /
• 2001

곤충병원성 선충으로부터 각각 공생박테리아를 분리하여 flask 상에서 7일간 배양하여 공생박테리아의 성장정도, 단백질 분해 효소의 생성, 배양상등액의 꿀벌부채명나방 유충에 대한 살충성 및 지방산 함량에 관한 연구를 수행한 결과 XR-PC 및 XR-MK의 성장 및 살충성이 가장 우수한 것으로 나타났으며 protease 활성은 XR-DR이 배양 4일째 최대 활성을 보였으며, 지방산 함량의 경우 XR-PC 및 XR-HY가 다른 종의 지방산 함량에 비해 12:0, 14:0, 13:0 iso, 16:1 cis 5, 17:0 cyclo에서 함량의 차이를 나타내었다.

• 한국정보통신학회논문지
• /
• 제15권7호
• /
• pp.1433-1438
• /
• 2011

K-PCS와 US-PCS 듀플렉서의 상대적 감쇠는 -60dB와 -65dB, -51dB와 -53dB를 각각 보여 주었으며, K-PCS와 US-PCS 밴드패스 필터의 상대적 감쇠는 -40dB와 -14dB, -5dB와 -10dB를 각각 보여주었다. 이러한 결과로부터, K-PCS의 수신단과 송신단의 상대적인 영향은 US-PCS에 비해서 작고, 패스밴드의 다양한 커패시턴트는 필터의 특성을 결정하는 데 중요한 역할을 하였다.

• Composites Research
• /
• 제29권5호
• /
• pp.269-275
• /
• 2016

Multiscale hybrid composites, which consist of polymeric resins, microscale fibers and nanoscale reinforcements, have drawn significant attention in the field of advanced, high-performance materials. Despite their advantages, multiscale hybrid composites show challenges associated with nanomaterial dispersion, viscosity, interfacial bonding and load transfer, and orientation control. In this paper, carbon nanotube(CNT)/carbon fiber(CF)/polycarbonate(PC) multiscale hybrid composite were fabricated by a solution process to overcome the difficulties associated with controlling the melt viscosity of thermoplastic resins. The dependence of CNT loading was studied by varying the method to add CNTs, i.e., impregnation of CF with CNT/PC/solvent solution and impregnation of CNT-coated CF with PC/solvent solution. In addition, hybrid composites were fabricated through surfactant-aided CNT dispersion followed by vacuum filtration. The morphologies of the surfaces of hybrid composites, as analyzed by scanning electron microscopy, revealed the quality of PC impregnation depends on the processing method. Dynamic mechanical analysis was performed to evaluate their mechanical performance. It was analyzed that if the position of the value of tan ${\delta}$ is closer to the ideal line, the adhesion between polymer and carbon fiber is stronger. The effect of mechanical interlocking has a great influence on the dynamic mechanical properties of the composites with CNT-coated CF, which indicates that coating CF with CNTs is a suitable method to fabricate CNT/CF/PC hybrid composites.

• 한국소음진동공학회논문집
• /
• 제18권5호
• /
• pp.533-540
• /
• 2008

In this study, a new slab system where a part of precast slab is connected each other by viscoelastic material is proposed and numerical analysis is performed to evaluate the effect of the connection between the material and PC slab on the vibration and noise control. Substructuring is introduced to develop the equation of motion for the slab system. In addition, the optimal properties of viscoelastic material are investigated. For the performance evaluation of the new slab system, the sound power and acceleration responses of the slab are compared with those of two way slab and one way slab, respectively. Numerical analysis results show that the sound power of the new slab system can be reduced by viscoelastic material significantly.

• Structural Engineering and Mechanics
• /
• 제64권5호
• /
• pp.567-577
• /
• 2017

The traditional design procedure of a prestressed concrete (PC) cable-stayed bridge is complex and time-consuming. The designers have to repeatedly modify the configuration of the large number of design parameters to obtain a feasible design scheme which maybe not an economical design. In order to efficiently achieve an optimum design for PC cable-stayed bridges, a multi-parameter optimization technique is proposed. In this optimization technique, the number of prestressing tendons in girder is firstly set as one of design variables, as well as cable forces, cable areas and cross-section sizes of the girders and the towers. The stress and displacement constraints are simultaneously utilized to ensure the safety and serviceability of the structure. The target is to obtain the minimum cost design for a PC cable-stayed bridge. Finally, this optimization technique is carried out by a developed PC cable-stayed bridge optimization program involving the interaction of the parameterized automatically modeling program, the finite element structural analysis program and the optimization algorithm. A low-pylon PC cable-stayed bridge is selected as the example to test the proposed optimization technique. The optimum result verifies the capability and efficiency of the optimization technique, and the significance to optimize the number of prestressing tendons in the girder. The optimum design scheme obtained by the application can achieve a 24.03% reduction in cost, compared with the initial design.

• Computers and Concrete
• /
• 제20권5호
• /
• pp.529-537
• /
• 2017

Excessively elevated temperature can lead to cracks in prestressed concrete (PC) continuous bridge with box girder on the pier top at cement hydration age. This paper presents a case study for evaluating the behavior of PC box girder during the early hydration age using a two-stage computational model, in the form of computer program ANSYS, namely, 3-D temperature evaluation and determination of mechanical response in PC box girders. A numerical model considering time-dependent wind speed and ambient temperature in ANSYS for tracing the thermal and mechanical response of box girder is developed. The predicted results were compared to show good agreement with the measured data from the PC box girder of the Zhaoshi Bridge in China. Then, based on the validated numerical model three parameters were incorporated to analyze the evolution of the temperature and stress within box girder caused by cement hydration heat. The results of case study indicate that the wind speed can change the degradation history of temperature and stress and reduce peak value of them. The initial casting temperature of concrete is the most significant parameter which controls cracking of PC box girder on pier top at cement hydration age. Increasing the curing temperature is detrimental to prevent cracking.