A comparative study of FMS tool allocation and part type selection approaches for a varying part type mix

Hankins and Rovito (1984) examined the impact of different tool policies on cutting tool inventory levels and spindle utilization for a flexible manufacturing system (FMS). This study provides a broader perspective of the impact of tool allocation approaches on flow times, tardiness, percent of orders tardy, machine utilization, and robot utilization. Part type selection procedures have been suggested for the FMS prerelease planning problem. However, very little research has specifically evaluated the part type selection procedures across different tool allocation approaches. Also, with the exception of Stecke and Kim (1988, 1991) no other known study has provided any insights on what tool allocation approaches are appropriate when processing different mixes of part types. This research is devoted to addressing those issues.Three tool allocation approaches, three production scheduling rules, and three levels of part mix are evaluated in this study through a similation model of a flexible manufacturing system. The specific impacts of the tool approaches, their interaction effects with the part type selection rules, and their effectiveness at different part type mix levels are provided through the use of a regression metamodel.     

Effects of firm and IT characteristics on the value of e-commerce initiatives: An inductive theoretical framework

We explore the theoretical foundations on how firm and IT characteristics explain the market value variations in e-commerce initiatives by examining the announcements of 946 e-commerce initiatives in the public media. Our approach combines the Event study methodology and Decision tree induction to examine the main and interaction effects of IT and firm characteristics on Cumulative Abnormal Returns (CAR). In particular, we generate complex interaction models that can guide e-commerce investment decisions so managers can know, for example, which combination of IT and firm characteristics are more likely to be viewed positively by investors. The selected study variables as well as explanation of the proposed framework are informed by innovation, resource-based view, transaction cost economics and complementarity theories. We have inductively developed a set of propositions that can be deductively tested to assess the validity of our proposed theoretical framework. Hence our study provides an initial roadmap for theory development on e-commerce and CAR.     

Housing and urban poor

Research Officer, Kwasi Owusu‐Adade, at the Building and Road Research Institute at Kumasi, highlights the role housing plays in the life of the rural migrant and concludes that a greater commitment by government could be demonstrated in practical terms. Low‐income housing requires a supply of land on a rolling basis with the encouragement of locally produced materials, material depots and the provision of basic amenities for illegal settlements which do not seriously inhibit future overall development.     

Chloride ingress and steel corrosion in cement mortars incorporating low-quality fly ashes

In this study, the microstructure and hydration characteristics of ecocement and normal Portland cement mortars blended with low-quality fly ashes were investigated. In addition, the corrosive behaviours of steel bars embedded in the mortars were studied. Several tests including scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) were used for the characterization of the mortars. Electrochemical measurement such as linear polarization resistance and AC impedance spectroscopy were also used to monitor the corrosive behaviours of the embedded steel bars in the mortars. The chloride ingress into the mortars was also studied. The results of the various tests are discussed.     

Optimisation techniques for minimising saw teeth deflection and lumber thickness variation

Lumber size control is an essential element in maximising yield and productivity because a small reduction in rough green target size could lead to substantial savings in wood fibre. One of the key components of rough green target size is sawing variation. In this study, the optimum side clearance of band saw teeth leading to a minimum saw teeth deflection and minimum lumber thickness variation of stellite-tipped and swage-set saws when processing Triplochiton scleroxylon a tropical hardwood were examined. It was observed that the accuracy of kerf width was best with stellite-tipped saws. However, Analysis of variance (ANOVA) at 5% level of significance indicates that there was no significant difference between the accuracy of kerf width of stellite-tipped saws and swage-set saws. It also was observed that at 5% level of significance, the mean kerf width of stellite-tipped saws, which was 4.2 mm, was significantly greater than the mean kerf width of 3.06 mm of the swage-set saws. Sawing variation as indicated by standard deviation of lumber thickness was best for the swage-set saws. A quadratic relationship between sawing variation and side clearance of stellite-tipped saws was established. As the side clearance of the saw increases, the sawing variation decreases until it reaches a minimum value and thereafter, further increase in side clearance of the saw teeth results in an increase in sawing variation. It was observed that an optimum side clearance of 0.69 mm under a saw blade thickness of 1.3 mm was required to produce on the average, a minimum value of 0.42 mm for within-board standard deviation, and 0.59 mm for the total standard deviation. An error margin of less than 1% was achieved when the experimental results for the optimum side clearance was compared with a theoretical assertion.     

The Kinetics of the Sulphate Pulping of Gmelina arborea From Ghana

Investigations concerning the behaviour of Gmelina arborea wood growing in a plantation in Ghana by the Kraft delignification process were carried out in the St. Petersburg (formerly Leningrad) Academy of Forest Technology and Engineering in the Commonwealth of Independent States (Russia).

The basic kinetic data such as the rate constant, order of reaction, temperature dependence and the energy of activation were calculated. The kinetic data obtained indicate that the dielignification of G. arborea is by a process similar to that of diffusion as occurs during chemical reactions. Consequently, the delignification process at temperature which was carried out at selected cooking conditions is not solely controlled by kinetic processes.     

Microbial quality of water in Barekese reservoir and feeder streams in Ghana

Concern is growing in Ghana about the high incidence of water‐related diseases and deaths resulting from use of water contaminated with microorganisms. This water often remains unsafe for human consumption because of inadequate decontamination of microbially infected water. Data are presented in this study on the microbial quality of Barekese reservoir, which is the main drinking water reservoir for the city of Kumasi and its environs (population = 2, 5 million), and nine feeder streams in its catchment. Water samples were collected from 13 sampling sites and analysed for Escherichia coli, total and faecal coliforms. Furthermore, 18 faecal coliform isolates were randomly selected from all sampling sites and confirmed as E. coli using Analytical Profile Index 20E system. Escherichia coli, total and faecal coliforms were enumerated using the most probable number method. Mean bacterial indicator numbers from all sampling sites ranged from 1.45 × 10⁴ to 9.50 × 10⁷ 100 mL^?1 for total coliforms, 1.60 × 10³ to 9.00 × 10⁵ 100 mL^?1 for faecal coliforms and 1.50 × 10¹ to 9.50 × 10³ 100 mL^?1 for E. coli. Indicator numbers exceeded the World Health Organization (0.100 mL^?1) for E. coli and Ghana Water Resources Commission‐Target Water Quality Range of 5–100 100 mL^?1 for total coliforms and 0.100 mL^?1 for faecal coliforms in water used for domestic purposes. The identified isolates in Barekese Reservoir and its feeder streams belonged to Serratia, Enterobacter, Citrobacter, Salmonella and Klebsiella genera. Bacterial numbers were significantly (P < 0.05) higher in the feeder streams, compared with Barekese Reservoir water. This finding indicates the feeder streams pose health risks to local communities that withdraw water from them. The results of this study highlight the urgent need to raise public awareness on the adverse effects of water‐quality degradation through improper waste disposal methods in order to decrease the cost of treating the reservoir water.     

How Internet Security Breaches Harm Market Value

Decision-tree induction is an effective technique for examining the factors influencing abnormal stock market returns when security breaches are announced in the public media. In this article, the authors extend a previous study, specifically identifying new relationships between abnormal returns and firm and attack characteristics and subject them to traditional statistical testing. They relate their results to the confidential, integrity, and availability dimensions of information security and discuss the findings' technical and managerial implications. The Web extra for this article presents detailed event data.     

Compatibility between ecocement produced from incinerator ash and reactive aggregates in ASR expansion of mortars

Recently, in Japan, two new-type hydraulic cements, high early strength type ecocement (HEC) and normal type ecocement (NEC), have been developed using incinerator ashes up to 50% of the raw materials. In this study, the compatibility of these ecocements with various types of reactive aggregates with respect to alkali-silica reaction (ASR) was studied. Ordinary Portland cement (OPC) and blast furnace slag cement (BFSC) were also used for a comparative study. Two types of the accelerated mortar bar expansion test, the JIS A1146 and the Danish methods, were used to clarify the expansion behavior of mortars made with the above cements. The influence of a combination of the chemical and mineralogical compositions of cement and the reactive components of aggregate on both the amount of ASR gel and the expansion rate of the mortar was also investigated. From the results, it was found that the expansion behaviors of mortars due to ASR varied significantly depending on a combination of both the mineralogical composition of cement and the reactive component of aggregate.