The finite element analysis of a fractured tibia applied by composite bone plates considering contact conditions and time-varying properties of curing tissues

This paper addresses the use of composite bone plates in healing long-bone fractures such as transverse fractures of the tibia using finite element analysis, that takes into consideration contact conditions and material property variations of calluses in relation to the healing period. For the time-varying properties of calluses in relation to the healing period, stepwise material properties were imposed on the callus part based on the time elapsed, and the loading conditions were coupled with the callus properties based on the length of the healing period. The strain distributions at the fracture site were calculated according to the stacking sequence of the bone plate and healing time. The analysis results showed that composite bone plates with stacking sequences of [0]_12T for the Kevlar/BCP composites generated the most appropriate strain distributions at the fracture site during the early healing process.     

Maximizing the weighted number of just-in-time jobs in flow shop scheduling

In this paper we consider the maximization of the weighted number of just-in-time jobs that should be completed exactly on their due dates in n-job, m-machine flow shop problems. We show that a two-machine flow shop problem is NP-complete. When job weights are all identical, we show that the problem can be solved in polynomial time. We also show that a three-machine flow shop problem with identical job weights is NP-hard in the strong sense by reduction of the 3-partition problem.     

RuO2/GaN Schottky contact formation with superiorforward and reverse characteristics

This is a first time report of a ruthenium oxide (RuO₂) Schottky contact on GaN. RuO₂ and Pt Schottky diodes were fabricated and their characteristics compared. When the RuO₂ Schottky contact was annealed at 500°C for 30 min, the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the RuO₂ were dramatically improved. The annealed RuO₂ /GaN Schottky contact exhibited a reverse leakage current that was at least two or three orders lower in magnitude than that of the Pt/GaN contact along with a very large barrier height of 1.46 eV, which is the highest value ever reported for a GaN Schottky system     

A new genetic algorithm for lot-streaming flow shop scheduling with limited capacity buffers

Lot-streaming is the process of splitting a job (lot) into a number of smaller sublots to allow the overlapping of operations between successive machines in a multi-stage production system. The use of sublots usually results in substantially shorter job completion times for the corresponding schedule. A new genetic algorithm (NGA) is proposed for an n-job, m-machine, lot-streaming flow shop scheduling problem with equal size sublots and limited capacity buffers with blocking in which the objective is to minimize total earliness and tardiness penalties. NGA replaces the selection and mating operators of genetic algorithms (GAs), which often lead to premature convergence, by new operators (marriage and pregnancy operators) and also adopts the idea of inter-chromosomal dominance and individuals’ similarities. Extensive computational experiments have been conducted to compare the performance of NGA with that of GA. The results show that, on the average, NGA outperforms GA by 9.86 % in terms of objective function value for medium to large-scale lot-streaming flow-shop scheduling problems.     

Single machine scheduling problems with resource dependent release times

We consider two single machine scheduling problems with resource dependent release times that can be controlled by a non-increasing convex resource consumption function. In the first problem, the objective is to minimize the total resource consumption with a constraint on the sum of job completion times. We show that a recognition version of the problem is NP-complete. In the second problem, the objective is to minimize the weighted total resource consumption and sum of job completion times with an initial release time greater than the total processing times. We provide some optimality conditions and show that the problem is polynomially solvable.     

Estimation of Amylose Content of Starches after Precipitation of Amylopectin by Concanavalin-A

The estimation of the amylose content of starches has been studied by precipitating the amylopectin with concanavalin-A and then, after denaturing the remaining concanvalin-A by heat, determining the unprecipitated glucan in the supernatant by (a) hydrolysis with amyloglucosidase: α-amylase followed by glucose oxidase-peroxidase reagent, (b) colorimetrically with phenol-sulphuric acid or (c) by colour with iodine.     

Finite element analysis using interfragmentary strain theory for the fracture healing process to which composite bone plates are applied

The present paper deals with finite element analyses to estimate the healing efficiency of fractured long bones to which various composite bone plates are applied. To estimate the callus modulus according to the healing period, interfragmentary strain theory was used, and the iterative process for updating the newly determined callus properties in every finite element was implemented by a user-defined sub-routine constructed by the Python code. The results of analysis revealed that a composite bone plate made of a plain weave carbon/epoxy composite whose Young’s modulus was in the range of 30–70 GPa produced a positive effect on the healing efficiency relieving stress-shielding effect. This result can be used in the detailed design of high-performing composite bone plates to determine more effective shapes and stacking sequences for better healing efficiency.     

An application of genetic algorithms to lot-streaming flow shop scheduling

A Hybrid Genetic Algorithm (HGA) approach is proposed for a lot-streaming flow shop scheduling problem, in which a job (lot) is split into a number of smaller sublots so that successive operations can be overlapped. The objective is the minimization of the mean weighted absolute deviation of job completion times from due dates. This performance criterion has been shown to be non-regular and requires a search among schedules with intermittent idle times to find an optimal solution. For a given job sequence, a Linear Programming (LP) formulation is presented to obtain optimal sublot completion times. Objective function values of LP solutions are used to guide the HGA's search toward the best sequence. The performance of the HGA approach is compared with that of a pairwise interchange method.     

Autotoxic Compounds from Fresh Alfalfa Leaf Extracts: Identification and Biological Activity

Many investigators have attempted to identify the allelochemicals in alfalfa (Medicago sativa), that cause autotoxicity. The autotoxic compounds from fresh alfalfa leaves were separated and quantified, and their biological activity was determined. Chemical separation procedures involved an 80% methanol extract of fresh alfalfa leaves, treatment with activated charcoal, microcrystalline cellulose thin-layer chromatography (MCTLC), and finally separation by Sephadex LH-20 column chromatography. The various fractions were examined further by high-performance liquid chromatography (HPLC). Preliminary identification by HPLC analysis resulted in peaks with retention times close to those of chlorogenic (m/z = 354) and salicylic acid (m/z = 138) standards, and these compounds were confirmed with GC-MS. Several other peaks remain unidentified. Chlorogenic acid occurs in relatively large amounts (0.39 mg/g) in alfalfa aqueous extracts as compared to salicylic acid (0.03 mg/g), and bioassays suggest that chlorogenic acid is involved in alfalfa autotoxicity.