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331.
Based on the assumption of adiabatic equilibrium stages, a rigorous calculation procedure applicable to a multicomponent batch
distillation with a distillate receiver under total reflux condition was developed. Provided that the operating conditions
including the desired product purity of the most volatile component in the receiver are specified, the proposed model estimates
the volume of the distillate receiver, changes in compositions in the receiver and still, concentration profiles of the column,
and the batch time required to complete the separation. In order to test the validity of the proposed model, experimental
data for the separation of acetone-methanol-2-propanol mixture using a 10 cm I.D. column having six theoretical stages were
compared with the simulation results for the two cases when the distillate receiver is initially empty and initially full. 相似文献
332.
The biodegradable polylactide (PLA) and polylactide‐co‐glycolides (PLGAs) are being widely investigated for use as scaffolds in bone and ligament reconstruction. The glass transition temperatures (Tg) for these polymers are generally greater than 37°C, causing PLA and PLGA devices to possess brittle characteristics in physiological conditions. To evaluate the possibility of obtaining PLGA polymers with Tg values below 37°C, we evaluated the determinants of Tg in PLA and PLGA copolymers. The Tg, changes in specific heat capacity (ΔCp), and enthalpic relaxation (ΔHg) in two consecutive heating cycles were correlated with lactide/glycolide content and intrinsic viscosity [η] for PLA, PLGAs 90:10, 75:25, 65:35, and 50:50. A linear correlation was observed between Tg and intrinsic viscosity, with 0.1 dL/g increase in viscosity resulting in an increase in Tg by about 3.55°C. The selection of PLA and PLGA copolymers with [η] values <0.19 dL/g, corresponding to a viscosity average molecular weight of <70 kDa, will obtain PLA/PLGA polymers with Tg values below 37°C. The lowest attainable Tg values were found to be 28–30°C. Intrinsic viscosity also correlated with ΔCp differences between aged and rapidly cooled polymers, and is therefore important in predicting free volume changes within these polymers upon aging. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1983–1987, 2006 相似文献
333.
Kyu Sun Lee Byoungyull Yang Sang Yeon Pyo Hyung Gyoon Kim Dong Hyun Lee Sang Done Kim 《Korean Journal of Chemical Engineering》2006,23(4):658-662
The effects of flow rates of hot air and cooling water on drying percentage and energy efficiency of cotton lint in a cylindrical
type drum tumbler dryer (0.54m-ID×0.34m-high) have been determined. Drying of the lint is mainly affected by flow rate of
hot air, which is a function of the diameter ratio (DM/DF) of motor and fan pulley and motor capacity. During the drying process in the tumbler dryer, temperatures and humidity before
and after were measured to determine the drying characteristics. The volumetric flow rate of hot air increases with increasing
the diameter ratio of the motor and fan pulley, whereas the volumetric flow rate of hot air decreases with an increase in
the mass flow rate of the cooling water through the condenser. The energy consumed by the motor relied more on the diameter
ratio of the motor and fan pulley as opposed to the mass flow rate of cooling water. Despite the increase in the drying percentage
with increasing the diameter ratio of the motor and fan pulley and the mass flow rate of the cooling water, the energy efficiency
decreased. 相似文献
334.
335.
This work aims to understand a SCC failure mode of thermally treated steam generator tubing materials in high temperature water containing lead. The effect of lead contents on the anodic polarization curves of alloy 600 (UNS NO6600) and alloy 690 (UNS NO6900) has been studied in a solution of pH 10 at 200 °C and 315 °C. Lead increased the active peaks of alloy 600 and alloy 690 in mild alkaline water at high temperatures. A reduction of PbO to a metallic lead in alloy 690 is easier than that of alloy 600. When lead was added into the solution, a relative ratio of Cr from among the main metallic elements (Cr, Fe, and Ni) of alloy 600 and alloy 690 decreased in the outer corrosion film. Alloy 690 TT showed a transgranular stress corrosion cracking (TGSCC) in a 10 M NaOH solution with 5000 ppm of lead. Intergranular stress corrosion racking (IGSCC) was observed in the 100 ppm lead condition, and some TGSCC was detected on the fracture surface of the alloy 600 MA cracked in the 10,000 ppm lead solution. IGSCC seemed to be retarded by a crack blunting around the grain boundaries, and the TG cracking mode of the thermally treated alloy 600 and 690 seemed to be related to a crack blunting at the grain boundary carbide and a film dissolution by lead in an alkaline solution. 相似文献
336.
Tae Hyun Baek Lei Chen Dong Pyo Hong 《Journal of Mechanical Science and Technology》2011,25(10):2535-2543
For isotropic material structure, the stress in the vicinity of crack tip is generally much higher than the stress far away
from it. This phenomenon usually leads to stress concentration and fracture of structure. Previous researches and studies
show that the stress intensity factor is one of most important parameter for crack growth and propagation. This paper provides
a convenient numerical method, which is called hybrid photoelasticity method, to accurately determine the stress field distribution
in the vicinity of crack tip and mixed-mode stress intensity factors. The model was simulated by finite element method and
isochromatic data along straight lines far away from the crack tip were calculated. By using the isochromatic data obtained
from finite element method and a conformal mapping procedure, stress components and photoelastic fringes in the hybrid region
were calculated. To easily compare calculated photoelastic fringes with experiment results, the fringe patterns were reconstructed,
doubled and sharpened. Good agreement shows that the method presented in this paper is reliable and convenient. This method
can then directly be applied to obtain mixed mode stress intensity factors from the experimentally measured isochromatic data
along the straight lines. 相似文献
337.
Lipids, particularly phospholipids (PLs), are key components of cellular membrane. PLs play important and diverse roles in cells such as chemical‐energy storage, cellular signaling, cell membranes, and cell–cell interactions in tissues. All these cellular processes are pertinent to cells that undergo transformation, cancer progression, and metastasis. Thus, there is a strong possibility that some classes of PLs are expected to present in cancer cells and tissues in cellular physiology. The mass spectrometric soft‐ionization techniques, electrospray ionization (ESI), and matrix‐assisted laser desorption/ionization (MALDI) are well‐established in the proteomics field, have been used for lipidomic analysis in cancer research. This review focused on the applications of mass spectrometry (MS) mainly on ESI‐MS and MALDI‐MS in the structural characterization, molecular composition and key roles of various PLs present in cancer cells, tissues, blood, and urine, and on their importance for cancer‐related problems as well as challenges for development of novel PL‐based biomarkers. The profiling of PLs helps to rationalize their functions in biological systems, and will also provide diagnostic information to elucidate mechanisms behind the control of cancer, diabetes, and neurodegenerative diseases. The investigation of cellular PLs with MS methods suggests new insights on various cancer diseases and clinical applications in the drug discovery and development of biomarkers for various PL‐related different cancer diseases. PL profiling in tissues, cells and body fluids also reflect the general condition of the whole organism and can indicate the existence of cancer and other diseases. PL profiling with MS opens new prospects to assess alterations of PLs in cancer, screening specific biomarkers and provide a basis for the development of novel therapeutic strategies. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 37:107‐138, 2018 相似文献
338.
Won?Pyo?HongEmail author Seok-Woo?Lee Hon-Zong?Choi Min?Yang?Yang 《Journal of Mechanical Science and Technology》2003,17(3):336-342
Increasing demand on precision machining using computerized numerical control (CNC) machines have necessitated that the tool
move not only with the smallest possible position error but also with smoothly varying feedrates in 3-dimensional (3D) space.
This paper presents the simultaneous 3D machining process investigated using a retrofitted PC-NC milling machine. To achieve
the simultaneous 3-axis motions, a new precision interpolation algorithm for 3D Non-Uniform Rational B-Spline (NURBS) curve
is proposed. With this accurate and efficient algorithm for the generation of complex 3D shapes, a real-time NURBS interpolator
was developed using a PC and the simultaneous 3D machining was accomplished satisfactorily. 相似文献