Designing Buildings for Maintenance: Designers' Perspective

The degree to which the design of a building embraces maintenance considerations has a major impact on its performance. A survey was conducted of the largest 211 building design firms in the United States to investigate the relationship between design practices and maintenance considerations. The findings shed light on the extent to which maintenance issues are considered when designers specify building materials and service equipment; the level of designers' knowledge in maintenance-related issues; the degree to which design personnel is exposed to training in maintenance-related matters; the extent to which designers consult property managers and maintenance consultants; the relative importance of maintenance issues to other design factors; the level of difficulty in cleaning, inspecting, repairing, and replacing various building components; and the magnitude and frequency of maintenance-related complaints that designers receive from clients and tenants. The performance of buildings is likely to be enhanced if designers are cognizant of maintenance-related matters.     

Cytotoxic assessment of flying barb fish (Esomus metallicus) from a gold mine area with heavy metal contamination

This study aimed to investigate contamination by heavy metals including arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and manganese (Mn) and to conduct a cytotoxic assessment of Esomus metallicus from a gold mine area compared with that from the non-affected area. The E. metallicus samples were collected downstream of a gold mine area. The heavy metal concentrations were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The average amounts of As, Cd, Cr, Pb and Mn in water and E. metallicus samples from the gold mine area were 0.368 ± 0.009, 0.008 ± 0.006, 0.009 ± 0.001, 0.006 ± 0.002, 1.438 ± 0.058 mg/L, 0.65 ± 0.25, 0.03 ± 0.03, 2.12 ± 0.05, 0.25 ± 0.07 and 18.28 ± 6.82 mg/kg, respectively. The difference of As, Cr and Mn concentrations in E. metallicus samples between gold mine and non-affected areas was statistically significant (p < 0.05) except for Cd and Pb. The diploid chromosome number of E. metallicus from both areas was 2n = 50. There are six types of chromosomal aberrations including centric fragmentation (CF), centric gap (CG), single chromatid gap (SCG), fragmentation (F), deletion (D) and polyploidy (P). The most common chromosomal aberration type in the samples from the gold mine area was CG, and the difference in chromosomal aberration and the number of cells with chromosomal aberrations in E. metallicus between the study areas was statistically significant (p < 0.05). The percentages of chromosomal aberrations in the E. metallicus samples from gold mine and non-affected areas were 14.66 and 3.00, respectively.     

Algorithms for flexible flow shop problems with unrelated parallel machines, setup times, and dual criteria

In textile industries, production facilities are established as multi-stage production flow shop facilities, where a production stage may be made up of parallel machines. This known as a flexible or hybrid flow shop environment. This paper considers the problem of scheduling n independent jobs in such an environment. In addition, we also consider the general case in which parallel machines at each stage may be unrelated. Each job is processed in ordered operations on a machine at each stage. Its release date and due date are given. The preemption of jobs is not permitted. We consider both sequence- and machine-dependent setup times. The problem is to determine a schedule that minimizes a convex combination of makespan and the number of tardy jobs. A 0–1 mixed integer program of the problem is formulated. Since this problem is NP-hard in the strong sense, we develop heuristic algorithms to solve it approximately. Firstly, several basic dispatching rules and well-known constructive heuristics for flow shop makespan scheduling problems are generalized to the problem under consideration. We sketch how, from a job sequence, a complete schedule for the flexible flow shop problem with unrelated parallel machines can be constructed. To improve the solutions, polynomial heuristic improvement methods based on shift moves of jobs are applied. Then, genetic algorithms are suggested. We discuss the components of these algorithms and test their parameters. The performance of the heuristics is compared relative to each other on a set of test problems with up to 50 jobs and 20 stages.