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排序方式: 共有485条查询结果,搜索用时 46 毫秒
101.
This study explains the role of coagulation in membrane filtration of wastewater for reuse. For this purpose, a coagulation-ultrafiltration (UF) membrane system was used to treat secondary effluent from a nearby wastewater treatment plant using a rotating biological contactor. The study proceeded with the hypothesis that coagulation could affect membrane filtration through two phenomena: change in particle characteristics and contaminant loading reduction. If fouling reduction were observed at a low alum dosage, coagulation would affect membrane performance by changing particle characteristics because contaminant reduction could not be possible at low dosage. If fouling reduction were observed only at a high alum dosage, the role of coagulation would be contaminant loading reduction. Results showed that both phenomena were important. Coagulation improved the membrane performance by changing particle characteristics at a low alum dosage. The improvement was achieved through both a change in particle characteristics and contaminant loading reduction at a high alum dosage. Particle size among various characteristics was found the most important for membrane fouling. Coagulation increased particle size, which led to a reduction of fouling. The beneficial effect from coagulation was observed at both fouling steps of pore blocking/adsorption and cake formation. Coagulation pretreatment was also beneficial for the improvement of the permeate quality in terms of organic matter. 相似文献
102.
A pilot plant study for catalytic decomposition of PCDDs/PCDFs over supported chromium oxide catalysts 总被引:1,自引:0,他引:1
Chromium oxide catalysts supported on TiO2 and Al2O3 were examined in a fixed-bed flow reactor system for the removal of PCE (perchloroethylene), a simulant of 2,3,7,8-TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin), and in a pilot plant employing actual flue gas from a sintering plant for the removal of PCDDs/PCDFs (poly-chlorinated dibenzo-dioxin/poly-chlorinated dibenzo-furan). The 12.5 wt.% chromium oxides supported on TiO2 and Al2O3 revealed excellent stability and performance of PCE removal in the feed gas stream containing water vapor. In a pilot plant study, the catalysts washcoated on the honeycomb reactor revealed 93–95% of PCDDs/PCDFs removal activity over CrOx/Al2O3-HC20 (CrOx/Al2O3 catalyst washcoated on 20 cell-honeycomb), and more than 99% of the decomposition activity over CrOx/TiO2-HC20 (CrOx/TiO2 catalyst washcoated on 20 cell-honeycomb) at 325 °C and 5000 h−1 of reactor space velocity without the de novo synthesis of PCDDs/PCDFs. In particular, CrOx/TiO2-HC20 showed 94% of PCDDs/PCDFs decomposition activity even at 280 °C reaction temperature. The catalyst also exhibited significant NO removal activity. The chromium oxide seems to be a promising catalyst for the removal of PCDDs/PCDFs and NOx contained in the flue gas. 相似文献
103.
Starting from the quaternary Cu47Ti34Zr11Ni8 alloy, the compositional dependence of thermal and elastic properties of Cu-Ti-Zr-Ni alloys was systematically investigated. Quaternary Cu-Ti-Zr-Ni alloys can be cast directly from the melt into copper molds to form fully amorphous strips or rods with the thickness of 3-6 mm. The evidence of the amorphous nature of the cast rods was provided by X-ray spectra. The measured glass transition temperature (Tg) and crystallization temperature (Tx) were obtained for the alloys using differential scanning calorimetry (DSC) at the heating rate of 20 K/s. In the results, the differences between the glass temperature and the crystallization tempera-ture (△Tx=Tx-Tg) are measured with values ranging up to 33-55 K. The reduced glass transition temperature (Trg), which is the ratio of the glass temperature to the liquidus temperature (T1), is often used as an indication of the glass-forming ability of metallic alloys. For the present Cu-Ti-Zr-Ni alloys, this ratio is typically in the range of 0.5838-0.5959, characteristic of metallic alloys with good glass-forming ability. The elastic constants for several selected alloys were measured using ultrasonic methods. The values of the elastic shear modulus, bulk modulus, and Poisson's ratio were also given. 相似文献
104.
Junghoon Kim Jongguk Yim Youngjin Choi 《International Journal of Control, Automation and Systems》2014,12(3):518-529
The conventional Youla parameterization (equivalently Q-Parameterization) approach to solve ?∞ optimal control problems requires solving the well-known matrix dilation optimization as a method for satisfying the ?∞-norm constraint of the closed-loop transfer matrix. As an alternative, this paper presents a constrained doubly coprime factorization so that the ?∞-norm constraint of the closed-loop transfer matrix can be satisfied without the need for matrix dilation optimization. For a given ?∞-norm constraint, a constrained plant is suggested from a state estimator that includes the worst-case disturbance and estimation effects. Then, the constrained doubly coprime factorization is derived from the constrained plant model. All the stabilizing ?∞ controllers are expressed by using the constrained coprime factors. Finally, an application example is provided to demonstrate the effectiveness of the proposed method. 相似文献
105.
Bong-Jo Ryu Kwang-Bok Shin Kyung-Bin Yim Young-Sik Yoon 《Journal of Mechanical Science and Technology》2006,20(9):1355-1360
This paper presents the dynamic stability of a cantilevered Timoshenko beam with a concentrated mass, partially attached to
elastic foundations, and subjected to a follower force. Governing equations are derived from the extended Hamilton’s principle,
and FEM is applied to solve the discretized equation. The influence of some parameters such as the elastic foundation parameter,
the positions of partial elastic foundations, shear deformations, the rotary inertia of the beam, and the mass and the rotary
inertia of the concentrated mass on the critical flutter load is investigated. Finally, the optimal attachment ratio of partial
elastic foundation that maximizes the critical flutter load is presented. 相似文献
106.
Ju-Hyuk Yim Seung-Hyub Baek Hyun-Yong Shin Dow Bin Hyun Jin-Sang Kim 《Journal of Electronic Materials》2013,42(7):2178-2183
We present the effects of In4Se3 addition on thermoelectric properties of n-type Bi2Te2.7Se0.3. In this study, polycrystalline (In4Se3) x -(Bi2Te2.7Se0.3)1?x pellets were prepared by mechanical alloying followed by spark plasma sintering (SPS). The thermoelectric properties such as Seebeck coefficient and electrical and thermal conductivities were measured in the temperature range of 300 K to 500 K. Addition of In4Se3 into Bi2Te2.7Se0.3 resulted in segregation of In4Se3 phase within Bi2Te2.7Se0.3 matrix. The Seebeck coefficient of the (In4Se3) x -(Bi2Te2.7Se0.3)1?x samples exhibited lower values compared with that of pure Bi2Te2.7Se0.3 phase. This reduction of Seebeck coefficient in n-type (In4Se3) x -(Bi2Te2.7Se0.3)1?x is attributed to the formation of unwanted p-type phases by interdiffusion through the interface between (In4Se3) x and (Bi2Te2.7Se0.3)1?x as well as consequently formed Te-deficient matrix. However, the decrease in electrical resistivity and thermal conductivity with addition of In4Se3 leads to an enhanced thermoelectric figure of merit (ZT) at a temperature range over 450 K: a maximum ZT of 1.0 is achieved for the n-type (In4Se3)0.03-(Bi2Te2.7Se0.3)0.97 sample at 500 K. 相似文献
107.
Junyoung Mun Yoon Seok Jung Taeeun Yim Hyun Yeong Lee Hyo-Jin Kim Young Gyu Kim Seung M. Oh 《Journal of power sources》2009,194(2):1068-1074
Four different electrolytes are prepared by dissolving a Li salt in three different room-temperature ionic liquids (RTILs) and also in a conventional organic solvent. The cathodic (electrochemical reduction) stability of these electrolytes is compared at both ambient and elevated temperature by potential cycling on a TiO2-B electrode. At room temperature, the stability of pyrrolidinium- and piperidinium-based RTILs is comparable with that of the carbonate-based organic solvent, which is in contrast to the severely decomposed imidazolium-based RTIL. At elevated temperature (120 °C), the imidazolium-based RTIL undergoes even more significant cathodic decomposition that results in the deposition of a resistive surface film and leads to eventual cell degradation. By contrast, the cathodic decomposition and concomitant film deposition are not serious with pyrrolidinium- and piperidinium-based RTILs even at this high-temperature, so that the TiO2-B/Li cell operates with reasonably good cycle performance. The latter two RTILs appear to be promising solvents for lithium-ion batteries that are durable against occasional exposure to high-temperature. 相似文献
108.
Youn Hee Jun Lee Jeong Il Kim Jong-Min Yim Byung-Seung 《Journal of Materials Science: Materials in Electronics》2022,33(13):10030-10041
Journal of Materials Science: Materials in Electronics - A Cu powder-filled solderable epoxy composite (Cu-SEC), in which Cu powders were applied as reinforcement materials, was developed to... 相似文献
109.
A Robust controller is designed for cascaded nonlinear uncertain systems that can be decomposed into two subsystems; that is, a series connection of two nonlinear subsystems, such as a robot manipulator with actuators. For such systems, a recursive design is used to include the second subsystem in the robust control. The recursive design procedure contains two steps. First, a fictitious robust controller for the first subsystem is designed as if the subsystem had an independent control. As the fictitious control, a nonlinearH∞ control using energy dissipation is designed in the sense ofL 2-gain attenuation from the disturbance caused by system uncertainties to performance vector. Second, the actual robust control is designed recursively by Lyapunov’s second method. The designed robust control is applied to a robotic system with actuators, in which the physical control inputs are not the joint torques, but electrical signals to the actuators. 相似文献
110.
M. S. Kent H. Yim A. Matheson C. Cogdill G. Nelson E. D. Reedy 《The Journal of Adhesion》2013,89(3):267-298
The relationships between fundamental interfacial interactions, energy dissipation mechanisms, and fracture stress or fracture energy in a glassy thermoset/inorganic solid joint are not well understood. This subject is addressed with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The proportions of physical and chemical interactions at the interface, and the in-plane distribution, are varied using self-assembling monolayers of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but interacts only weakly with the methylated tails of the ODTS monolayer. The fracture stress is examined as a function of ODTS coverage in the napkin-ring (nominally pure shear) loading geometry. The relationship between fracture stress and ODTS coverage is catastrophic, with a large change in fracture stress occurring over a narrow range of ODTS coverage. This transition in fracture stress does not correspond to a wetting transition of the epoxy. Rather, the transition in fracture stress corresponds to the onset of large-scale plastic deformation within the epoxy. We postulate that the transition in fracture stress occurs when the local stress that the interface can support becomes comparable to the yield stress of the epoxy. The fracture results are independent of whether the ODTS deposition occurs by island growth (T dep = 10°C) or by homogeneous growth (T dep = 24°C). 相似文献