Two-agent scheduling in open shops subject to machine availability and eligibility constraints

Purpose: The aims of this article are to develop a new mathematical formulation and a new heuristic for the problem of preemptive two-agent scheduling in open shops subject to machine maintenance and eligibility constraints. Design/methodology: Using the ideas of minimum cost flow network and constraint programming, a heuristic and a network based linear programming are proposed to solve the problem. Findings: Computational experiments show that the heuristic generates a good quality schedule with a deviation of 0.25% on average from the optimum and the network based linear programming model can solve problems up to 110 jobs combined with 10 machines without considering the constraint that each operation can be processed on at most one machine at a time. In order to satisfy this constraint, a time consuming Constraint Programming is proposed. For n = 80 and m = 10, the average execution time for the combined models (linear programming model combined with Constraint programming) exceeds two hours. Therefore, the heuristic algorithm we developed is very efficient and is in need. Practical implications: Its practical implication occurs in TFT-LCD and E-paper manufacturing wherein units go through a series of diagnostic tests that do not have to be performed in any specified order. Originality/value: The main contribution of the article is to split the time horizon into many time intervals and use the dispatching rule for each time interval in the heuristic algorithm, and also to combine the minimum cost flow network with the Constraint Programming to solve the problem optimally.Peer Reviewe

Capture of CO2 from Coal-fired Power Plant with NaOH Solution in a Continuous Pilot-scale Bubble-column Scrubber

AbstractA continuous pilot-scale bubble-column scrubber with NaOH as the absorbent was used to explore the capture of CO2 gas from a coal-fired power plant. The experimental design was based on the results of previous study. The diameter of the column was 20cm and the height of the column was 2.4 m. According to the S/N ratio, parameters, including absorption rate (RA), absorption efficiency (E), overall mass-transfer coefficient (KGa) and ratio of the gas-liquid flow rate (R), were selected for Taguchi analysis to obtain optimum conditions. A total of eleven experiments were carried out to verify the optimum conditions here. The range of the gas-flow rate (Qg) and liquid-flow rate (QLT) conducted in this work were 48-192 L/min and 1.6-10 L/min, respectively. The input gas concentrations were 9-12.2%. Using a steady-state material balance with a two-film model, RA and KGa could be determined. The results showed that E, RA and KGa were in the range of 30-98%, 1.03x10-4-11.48x10-4mol/s-L and 0.018-0.058 1/s, respectively. The obtained scrubbing factors (φ) were 0.00285-0.146mol/mol-L, while R was in the range of 0.23-24.14. The dynamic behavior of the scrubber was also discussed in this study. The results could be used as a basis for commercial scale operation for the carbon capture at a power plant as well as microalgae cultivation

Isolation and characterization of stromal progenitor cells from ascites of patients with epithelial ovarian adenocarcinoma

<p>Abstract</p> <p>Background</p> <p>At least one-third of epithelial ovarian cancers are associated with the development of ascites containing heterogeneous cell populations, including tumor cells, inflammatory cells, and stromal elements. The components of ascites and their effects on the tumor cell microenvironment remain poorly understood. This study aimed to isolate and characterize stromal progenitor cells from the ascites of patients with epithelial ovarian adenocarcinoma (EOA).</p> <p>Methods</p> <p>Seventeen ascitic fluid samples and 7 fresh tissue samples were collected from 16 patients with EOA. The ascites samples were then cultured in vitro in varying conditions. Flow cytometry and immunocytochemistry were used to isolate and characterize 2 cell populations with different morphologies (epithelial type and mesenchymal type) deriving from the ascites samples. The in vitro cell culture model was established using conditional culture medium.</p> <p>Results</p> <p>The doubling times of the epithelial type and mesenchymal type cells were 36 h and 48 h, respectively, indicating faster growth of the epithelial type cells compared to the mesenchymal type cells. Cultured in vitro, these ascitic cells displayed the potential for self-renewal and long-term proliferation, and expressed the typical cancer stem/progenitor cell markers CD44^high, CD24^low, and AC133⁺. These cells also demonstrated high BMP-2, BMP4, TGF-β, Rex-1, and AC133 early gene expression, and expressed EGFR, integrin α₂β₁, CD146, and Flt-4, which are highly associated with tumorigenesis and metastasis. The epithelial type cells demonstrated higher cytokeratin 18 and E-cadherin expression than the mesenchymal type cells. The mesenchymal type cells, in contrast, demonstrated higher AC133, CD73, CD105, CD117, EGFR, integrin α₂β₁, and CD146 surface marker expression than the epithelial type cells.</p> <p>Conclusion</p> <p>The established culture system provides an in vitro model for the selection of drugs that target cancer-associated stromal progenitor cells, and for the development of ovarian cancer treatments.</p

Study of sponge gourd ascorbate peroxidase and winter squash superoxide dismutase under respective flooding and chilling stresses

AbstractThe objectives of this work were to study the responses of ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), and physiological parameters of bitter melon (BM), sponge gourd (SG), and winter squash (WS) under waterlogged and low temperature conditions. The BM and SG plants were subjected to 0–72h flooding treatments. Moreover, BM and WS plants were exposed to chilling at 12/7°C (day/night) for 0–72h. The results show that different genotypes responded differently to environmental stress according to their various antioxidant enzymes and physiological parameters. The activity of APX in roots and leaves of SG plants significantly higher than that of BM plants during continuous flooding. Significant increases in SOD activity in leaves of WS plants were also observed throughout the entire chilling duration compared to BM plants. On the basis of our observations, we conclude that increased APX and SOD activities provide SG and WS plants with increased waterlogging and chilling stress tolerance, respectively. Both APX and SOD activities can be used for selecting BM lines with the best tolerances to water logging and chilling stresses

The spontaneous emergence of ordered phases in crumpled sheets

X-ray tomography is performed to acquire 3D images of crumpled aluminum foils. We develop an algorithm to trace out the labyrinthian paths in the three perpendicular cross sections of the data matrices. The tangent-tangent correlation function along each path is found to decay exponentially with an effective persistence length that shortens as the crumpled ball becomes more compact. In the mean time, we observed ordered domains near the crust, similar to the lamellae phase mixed by the amorphous portion in lyotropic liquid crystals. The size and density of these domains grow with further compaction, and their orientation favors either perpendicular or parallel to the radial direction. Ordering is also identified near the core with an arbitrary orientation, exemplary of the spontaneous symmetry breaking