• 대한산업공학회지
• /
• 제33권1호
• /
• pp.153-163
• /
• 2007

An adaptive framework paradigm where the bandwidth values of the ongoing calls vary according to the trafficsituations is one of the promising concepts for overcoming poor resource conditions due to handoffs in mobilecellular networks. However, quantifying the level of bandwidth degradation of the ongoing calls in an adaptiveframework is important in view of Quality of Service (QoS) Provisioning. Therefore we introduce new QoSparameters, the Degradation Degree Ratio (DDR), which represents the average portion of the degradationdegree during degradation pehod of a call, and the Degradation Area Ratio (DAR), which represents the averageratio of a call's degradation level considering both the period and the degree of degradation jointly in multi-levelbandwidth service. We also develop a new analytical model for estimating the QoS measures such as theDegradation Pehod Ratio (DPR), DDR and DAR. We show how to calculate the QoS measures and illustrate themethod by numerical examples. The proposed model can be used to determine the optimal parameter of theCAC scheme and analyze the sensitivity ofthe QoS parameters in adaptive networks.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
• /
• pp.229-231
• /
• 1996

We are studied the stability of amorphous and crystalline $Te_{100-x}Ge_x$ (x=10, 15. 25, 40, 50, 60 at.%) thin films by observing the degradation in 8O%RH/$66^{\circ}C$ environment and the reflectance ratio. The degradation was observed with the transmittance and reflectance, the reflectance was measured at 780nm in the wavelength range of diode laser. In amorphous $Te_{100-x}Ge_x$ thin films of below x=4O at.%, the degradation was observed, the thin film of x=10 at.% was shown the degradation degree of 12.5%. In crystalline $Te_{100-x}Ge_x$ thin films of x=10, 40 at.%, the degradation degree were 12.8%, 13%, respectively. The reflectance ratio were shown above 20% in. all composition ratio. Therefore, we are expected that $Te_{100-x}Ge_x$ thin films of x=50, 60 at.% has the long life for the optical recording media.

• 폴리머
• /
• 제29권6호
• /
• pp.599-604
• /
• 2005

생체적합성이 우수한 히아루론산과 생분해성이 우수한 폴리락타이드의 이량체인 락타이드를 결합하여 인체내에서 분해속도를 조절할 수 있는 생체적합성이 우수한 생체재료를 제조하였다. 냉동 건조법을 이용하여 히아루론산과 락타이드를 가교제 1-ethyl-3-(3-dimethyl aminopnpyl) carbodiimide(EDC)로 가교시켰다. 생성된 막을 핵자기 공명분광법으로 분석하여 젖산기 반응도와 EDC 반응도를 결정하였다. 히아루론산에 대한 락타이드의 몰비가 5부터 13까지 증가함에 따라 젖산기 반응도와 EDC 반응도는 증가하였다. 몰비가 커서 젖산기가 많이 첨가되면 팽윤도는 감소하고 취성이 강해졌다. 또 가교제 농도를 증가시키거나 가교 온도를 감소시키면 젖산기가 더욱 첨가되어 팽윤도는 감소하고 탄성률은 증가하였다. 서로 다른 가교도를 가진 막에 대해 약물 방출 실험을 한 결과 막의 가교도가 증가함에 따라 약물의 투과도는 감소하였다. 몰비가 커 젖산기가 많이 첨가된 고분자일수록 늦게 분해되었다. 몰비, 온도, 가교제 농도 등의 운전 변수를 조절하여 막의 기계적 물성과 분해 속도가 적절히 조절될 수 있었다.

• 한국안전학회지
• /
• 제17권4호
• /
• pp.71-79
• /
• 2002

It was attempted to evaluate the degree of degradation of thermally aged 2.25-1Mo steek by ultrasonic monlinear parameter(UNP) measurement and X-ray diffraction analysis of extracted carbide. Artificial aging was performed to simulate the microstructural degradation in 2.25Cr-1Mo steel arising from long time exposure at $540{\circ}C$. Microstructural analysis (number of carbides per unit area) and measurements of mechanical properties(Vickers hardness, DBTT) and degradation evaluation parameters(UNP and intensity ration of X-ray diffraction peak of electrolytically extracted carbide) were performed. Both of UNP and intensity ratio of X-ray diffraction peak for M6C carbide to that of M23C6 carbide(IR) increased abruptly in the initial 1000 hour of aging and then changed little. UNP and IR were proposed as potential parameters to evaluate the degree of aging degradation of 2.25Cr-1Mo steel.

• Bulletin of the Korean Chemical Society
• /
• 제22권12호
• /
• pp.1371-1374
• /
• 2001

Metal doping was adopted to modify TiO2 (P-25) and enhance the photocatalytic degradation of harmful cyanides in aqueous solution. Ni, Cu, Co, and Ag doped TiO2 were found to be active photocatalysts for UV light induced degradation of aqueous cyanides generating cyanate, nitrate and ammonia as main nitrogen-containing products. The photoactivity of Ni doped TiO2 was greatly affected by the state of Ni, that is, the crystal size and the degree of reduction of Ni. The modification effects of some mixed oxides, that is, Ni-Cu/TiO2 were also studied. The activity of Ni-Cu/TiO2 for any ratio of Cu/Ni was higher than that of Ni- or Cu-doped TiO2, and the catalyst at the Cu/Ni ratio of 0.3 showed the highest activity for cyanide conversion.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
• /
• pp.1142-1145
• /
• 2004

ZnO surge arresters continuously endure the operating voltages during the operation course, and in the mean time, which need to withstand occasionally transient voltages of lightning and switching overvoltages. Under these voltages, the ZnO varistors inside arresters would have aging phenomena, one important result of aging phenomena is the increasing of resistive currents of varistors, which leads to the increasing of power losses of varistors. And the operating voltage is continuously applied on the ZnO varistors, there is a degradation phenomenon existing in ZnO varistors. When the degradation reaches a certain degree, then the arrester must stop operation. The degradation is related to the applied voltage ratio, the applied voltage ratio is high, the degradation is quickly. When the power loss is higher than the thermal dispersion ability of house of arrester, then the arrester will thermally breakdown. In this study the thermal stability characteristics of surge arresters for high power wil be discussed on the view point of watt losses and thermal breakdown.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
• /
• pp.233-236
• /
• 2002

This paper describes the properties of between the residual voltage for ${\gamma}$-irradiated in electric power cable using in nuclear power generating station. As these properties related with ${\gamma}$-irradiation dose, it is suggested that these properties can be utilized as a index of irradiation degradation. From theory and experiment We found the residual voltage is not influenced by cable length. We found that residual voltage of basic composite and practical composite have not a difference an occasion be the same cable length. As the ratio of degradation increases, the residual voltage in the initial time range increases and the peak moves to the shorter time. Therefore, We can know the degree of radiation degradation from the position of the peak.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.518-521
• /
• 1999

This paper describes the properties of discharge current and the residual voltage for $^{60}$ C$_{0}$ -${\gamma}$ irradiated cables using in nuclear power generating station. As these properties related with $^{60}$ C$_{0}$ -${\gamma}$ -irradiatiation dose, it is suggested that these properties can be utilized as a index of irradiation degradation. As the ratio of degradation increases, the residual voltage in the initial time range increases and the peak moves to the shorter time. Therefore, I know the degree of radiation degradation from the position of the peak.

• 한국세라믹학회지
• /
• 제30권2호
• /
• pp.164-168
• /
• 1993

Grinding of 3mol% Y-TZP enhanced the texturing of t-ZrO2, which is represented by the increased I(002)t/I(200)t peak intensity ratio, and an asymetric broadening of (111)t peak. The degree of texturing and asymetric broadening depended on a seversity of grinding. The asymetric (111)t peak broadening was resulted by the formation of r-ZrO2. When aged at 25$0^{\circ}C$ for 120h, r-ZrO2 transformed to t-ZrO2 due to the relief of stressed surface area and the amount of tlongrightarrowm transformation inversely varied with the I(002)t/I(200)t. The inverse dependence was interpreted by that the degree of texturing determines the magnitude of residual surface stress and the lattice relaxation of t-ZrO2, which causes the low temperature degradation, is retarded as the residual stress becomes greater.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2000년도 봄 학술발표회논문집
• /
• pp.347-354
• /
• 2000

The seismic behaviors of a bridge system with several simple spans are examined to see the effects of the longitudinal stiffness degradation due to abutment-soil interaction. The abutment-backfill system is modeled as one degree-of-freedom-system with nonlinear spring and linear damper. various soil-conditions surrounding the abutment such as loose sand, medium dense sand, and dense sand are considered in the bridge seismic analysis. The idealized mechanical model for the whole bridge system is modeled by adopting the multiple-degree-of-freedom system, which can consider components such as pounding phenomena, friction at the movable supports, rotational and translational motions of foundations, and the nonlinear pier motions. The stiffness of the abutment is found to be rapidly reduced at the beginning of the earthquakes, and to be converged to constant values shortly after the displacement approaches to the Predefined critical values. It is observed that the maximum relative distanced an maximum relative displacements are generally Increased as the relative density of a soil decreases As the peak ground acceleration increases, the response ratio of the case considering stiffness degradation to the case considering constant stiffness decreases.