3,187 research outputs found
Robust economic optimization of process design under uncertainty
No full textIn this study, ranges of model parameters are analyzed for robustness measures. In particular, the properties of partial mean and worst-case cost in robust optimization are investigated. The robust optimization models are considered as multiobjective problems having two objectives, the expected performance (i.e. expected cost) and a robustness measure (Suh, M. and Lee, T. ( 2001) Robust optimization method for the economic term in chemical process design and planning. Industrial & Engineering Chemical Research, 40, 5950 - 5959). The robust partial mean model is defined with objectives of expected value and partial mean. The robust worst-case model is defined with the objective of expected value and worst-case. They are proved to guarantee Pareto optimality, which should be satisfied for multiobjective optimization problems. A graphical representation of the meaningful parameter ranges is clearly defined with mathematical proofs. The robustness of the solutions is discussed, based on the analysis of the ranges of the parameters. Three meaningful ranges of the parameters are investigated to choose a proper target value for the robust partial mean model. The worst-case value obtained from the worst-case analysis is recommended as the most effective target value, in order to obtain the optimal solution in a tradeoff between robustness and optimality. The proposed analysis in this study is validated with examples in chemical process design problems
An Analysis and Implementation of High Fairness Arbitration Mechanism by Using Level-table and Static Priority Orders in Shared Bus Architecture
No full textPrognostic value of changes in serum carcinoembryonic antigen levels for preoperative chemoradiotherapy response in locally advanced rectal cancer
No full textBACKGROUND: Preoperative chemoradiotherapy (CRT) is a standard treatment modality for locally advanced rectal cancer. However, CRT alone cannot improve overall survival. Approximately 20% of patients with CRT-resistant tumors show disease progression. Therefore, predictive factors for treatment response are needed to identify patients who will benefit from CRT. We theorized that the prognosis may vary if patients are classified according to pre- to post-CRT changes in carcinoembryonic antigen (CEA) levels.
AIM: To identify patients with locally advanced rectal cancer for preoperative chemoradiotherapy based on carcinoembryonic antigen levels.
METHODS: We retrospectively included locally advanced rectal cancer patients who underwent preoperative CRT and curative resection between 2011 and 2017. Patients were assigned to groups A, B, and C based on pre- and post-CRT serum CEA levels: Both > 5; pre > 5 and post RESULTS: The cohort comprised 145 patients; of them, 27, 43, and 65 belonged to groups A, B, and C, respectively, according to changes in serum CEA levels before and after CRT. Pre- (P < 0.001) and post-CRT (P < 0.001) CEA levels and the ratio of down-staging (P = 0.013) were higher in Groups B and C than in Group A. The ratio of pathologic tumor regression grade 0/1 significantly differed among the groups (P = 0.003). Group C had the highest number of patients showing pCR (P < 0.001). Most patients with pCR showed pre- and post-CRT CEA levels < 5 ng/mL (P < 0.001, P = 0.008). Pre- and post-CRT CEA levels were important risk factors for pCR (OR = 18.71; 95%CI: 4.62-129.51, P < 0.001) and good response (OR = 5.07; 95%CI: 1.92-14.83, P = 0.002), respectively. Pre-CRT neutrophil-lymphocyte ratio and post-CRT T >/= 3 stage were also prognostic factors for pCR or good response.
CONCLUSION: Pre- and post-CRT CEA levels, as well as change in CEA levels, were prognostic markers for treatment response to CRT and may facilitate treatment individualization for rectal cancer
CXCR4-STAT3 Axis Plays a Role in Tumor Cell Infiltration in an Orthotopic Mouse Glioblastoma Model
No full textGlioblastoma multiforme (GBM) is a fatal malignant tumor that is characterized by diffusive growth of tumor cells into the surrounding brain parenchyma. However, the diffusive nature of GBM and its relationship with the tumor microenvironment (TME) is still unknown. Here, we investigated the interactions of GBM with the surrounding microenvironment in orthotopic xenograft animal models using two human glioma cell lines, U87 and LN229. The GBM cells in our model showed different features on the aspects of cell growth rate during their development, dispersive nature of glioma tumor cells along blood vessels, and invasion into the brain parenchyma. Our results indicated that these differences in the two models are in part due to differences in the expression of CXCR4 and STAT3, both of which play an important role in tumor progression. In addition, the GBM shows considerable accumulation of resident microglia and peripheral macrophages, but polarizes differently into tumor-supporting cells. These results suggest that the intrinsic factors of GBM and their interaction with the TME determine the diffusive nature and probably the responsiveness to non-cancer cells in the TME
Chosen logistics processes in Škoda JS
No full textThis master thesis deals with the purchase and sale process in Škoda JS company. The aim of this work is to assess whether the setting of the purchase and sale process is met by the company also within a real business case, in compliance with set controls, and whether the degree of perfect delivery is sufficient. In the introduction, the author specifies the basic terms: logistics, logistic chain, customer benefits, information systems in logistics, buying and selling. The following chapter introduces Škoda JS company, including the sphere of its entrepreneurial activity. This chapter also deals with the nuclear power industry. In the crucial chapter, the author describes the process of purchase and sale in Škoda JS company and compares it with a real business case. In conclusion, the author evaluates discrepancies and suggests recommendations to avoid them
Effect of laser surface modification on the corrosion resistance of Alloy 600
No full textTo improve the corrosion resistance of Alloy 600, a typical alloy for steam-generator tubing in nuclear power plants, the surface of the alloy was modified by melting or alloying with a continuous CO, laser beam. In laser surface melting (LSM), a rapidly solidified surface layer of 300 mu m in thickness was obtained. Anodic polarization measurements showed that the corrosion resistance of the laser-surface-melted specimen was improved slightly. This might be attributed to the elimination of microstructural inhomogeneities, such as precipitates, inclusions and segregated impurities pre-existing at grain boundaries. For laser surface alloying (LSA), chromium was electroplated on the surface of the specimens before laser-beam irradiation. The alloyed layer showed a pore- and oxide-free and very homogeneous microstructure, with a chromium composition of 28-30 at%. The corrosion properties of the alloyed specimen were examined by anodic polarization, electrochemical potentiodynamic reactivation, the modified Huey and slow-strain-rate tests. The properties, in particular intergranular corrosion resistance, were significantly improved compared with those of as-received or LSM specimens. The improvement in corrosion resistance might result from the easy formation of a more stable passive film on the alloyed surface layer with high chromium content. (C) 1998 Elsevier Science S.A. All rights reserved
Numerical modeling of moving interfaces under local equilibrium conditions
No full textA new method is presented to simulate moving interfaces during diffusion-controlled growth under local equilibrium conditions. The position and compositions of the interface are obtained directly from the equilibrium state of the subsystem around the moving interface, without iterative calculation between diffusion fluxes and solute balance conditions. The method is applicable to general multi-component systems, and it ensures the consistency in compositions and solute balance at the interfaces; Those are ascribed to the presented consideration of subsystem around the interface region in a discretized form. Explicit equations of interface compositions and position in discretized variables are also presented for the simplified ternary systems of two solution and compound/solution. The validity and usefulness of the method is demonstrated by simulations of the two important ternary systems; The simulation results illustrate the features of diffusion-controlled growth with different alloy compositions and diffusivities of solutes in both systems.11sciescopu
Investigation of IGSCC behavior of sensitized and laser-surface-melted Alloy 600
No full textAn attempt was made to modify the surface of sensitized Alloy 600, without affecting the bulk properties, by a laser surface melting (LSM) technique in order to improve its resistance to intergranular stress corrosion cracking (IGSCC) in oxidizing environments. A surface layer of 150-200 mu m was melted by a CO2 CW laser beam. The microstructures of the laser-surface-melted specimens were characterized using optical, scanning, and transmission electron microscopy. Slow strain rate tests (SSRTs) at a strain rate of about 4 x 10(-7) s(-1) were carried out in a 0.1 M sodium tetrathionate (Na2S4O6) solution at room temperature in order to evaluate the resistance to IGSCC of the laser-surface-melted specimens. The microstructure of the melted and resolidified layer had a cellular/columnar structure which consisted of cells 1-2 mu m in diameter. The thin, solidified-surface layer was observed to act as an excellent barrier to the initiation and propagation of stress corrosion cracking in the experimental conditions. The fracture mode of the sensitized Alloy 600 changed from a brittle intergranular fracture to a typical ductile transgranular failure. The improved IGSCC resistance of the laser-surface-melted specimens can be attributed in part to Cr redistribution at the boundaries of the cells and grains and in part to the elimination of microstructural inhomogeneities such as precipitates, inclusions at the grain boundaries, during rapid melting and resolidification by the laser surface treatment. (C) 1998 Elsevier Science S.A. All rights reserved
Fabrication of a graded-index polymer optical fiber preform by using a centrifugal force
No full textWe have investigated a fabricating method for a graded index polymer optical fiber preform using a centrifugal force. When two monomers with different densities and refractive indices are polymerized under a centrifugal force, a concentration gradient is generated due to their density difference. Therefore, a graded refractive index can be obtained according to the concentration gradient. When a monomer is polymerized under a centrifugal force, a preform with a hollow is obtained because of volume shrinkage. To compensate for this practically, additional monomer should be filled into the hollow. Monomer should be fed to obtain a continuous gradient of refractive index at the interface before the first polymerized product is perfectly glassified. Two different types of feeding additional monomer were experimented with: monomer-monomer pair (case 1) and monomer-polymer pair (case II). The graded index profile with a proper Deltan (about 0.01) was successfully obtained in either case
Assembly of metal nanoparticle - Carbon nanotube composite materials at the liquid/liquid interface
No full textCarbon nanotubes (CNTs)-mediated self-assembly of metal (AU and Ag) nanoparticles at the liquid/liquid interface in the form of a stable nanocomposite film is reported. The metallic luster results from the electronic coupling of nanoparticles, suggesting the formation of closely packed nanoparticle thin films. The interfacial film could be transferred to mica substrates and carbon-coated transmission electron microscopy (TEM) grids. The transferred films were very stable for a prolonged time. The samples were characterized by UV-vis spectroscopy, scanning electron microscopy (SEM), TEM, and X-ray photoelectron spectroscopy (XPS). SEM and TEM results show that the films formed at the liquid/liquid interface are indeed composite materials consisting of CNTs and nanoparticles. XPS measurements further indicate the presence of the interaction between nanoparticles and CNTs
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