MODELLING OF RESPONSES FROM ORTHOGONAL METAL CUTTING OF MILD STEEL USING CARBIDE INSERT TOOL

The purpose of this research was to develop models for the prediction of responses from orthogonal metal cutting process that are responsible for the machinability ratings of this technological system. Mild steel work-piece material that is representative sample for various industrial applications was machined. The various industrial applications of this representative sample range from mechanical shafts to fasteners, screws and hydraulic jack. These machine elements require high degree of surface finish. A fifteen-run based Box-Behnken response surface design was created using widely established machining parameters, namely cutting speed, feed rate and depth of cut. The optimum predicted responses from the orthogonal cutting process for the optimal process parameters are 0.1742 micron, 0.4933 micron, 0.1845 micron, 0.3673 micron, 794.6839 seconds and 19.642 seconds for the Ra, Rz, Rq, Rt, TL and M/C time respectively. The associated desirabilities for these optimum responses are 1.000000, 1.000000, 1.000000, 1.000000, 0.524122, and 0.361858 respectively.   http://dx.doi.org/10.4314/njt.v36i1.1

IDENTIFYING THE CRITICAL CAUSES OF CONFLICT IN CONSTRUCTION PROJECTS IN NIGERIA

Completing construction projects entails inputs from various professional disciplines; this makes projects prone to conflicts. It has been acknowledged that management of conflict is crucial to improving project performance. Thus, understanding the causes of conflicts in construction project will ease the process of conflict management. This study sets out to gain an in depth understanding of the causes of conflicts in Nigeria using mixed method research approach. Both questionnaire survey and interview were used to capture the perspective of consultants and contractors on causes of conflicts. Based on the responses, it was evident that poor financial projection on the client’s side is the most significant cause of conflicts. Furthermore, it was found that there are no differences in the perception of both groups of respondents. This finding was also evident from interviews. Thus, there is a need for clients to develop procedures of engaging competent and experienced consultants so as to reduce the likelihood of conflicts.  http://dx.doi.org/10.4314/njt.v35i2.

CAUSES OF CONFLICTS IN CONSTRUCTION PROJECTS IN NIGERIA: CONSULTANT’S AND CONTRACTOR’S PERSPECTIVE

Construction projects are prone to conflicts. This is due to the multiplicity of individuals handling different phases of the projects. Empirical evidence from previous studies shows that conflicts affects projects outcomes, if not properly managed. Identification of the significant causes of conflicts is critical to minimizing the likelihood of conflicts occurring in projects. Thus, this study was aimed at identifying and assessing causes of conflicts in Nigeria based on the perception of consultants and contractors. To achieve the study’s objectives, a 64-item questionnaire was used to collect information on experiences of construction professionals on the causes of conflicts in Nigerian construction projects. Responses from 69 professionals working for consultants and contractors were analysed. Seven significant causes of conflicts in the Nigerian context were identified. Based on the survey results, poor financial projections on the client’s side was identified as the most significant cause of conflicts. Furthermore, it was found that there are no difference in the perception of both groups of respondents. Taken together, these findings support strong recommendations on the need for effective management of finance on the client side, and engagement of experienced consultants in project. Implementation of these recommendations will minimize the likelihood of conflicts occurring in construction projects.  http://dx.doi.org/10.4314/njt.v35i2.

Kronecker Product Analytical Approach to ANOVA of Surface Roughness Optimization

The Fishers-Yates algorithm has remained the most widely used statistical approach that involves the use of sum of squares of treatments or blocks in the determination of mean square errors (MSEs) needful for the computation of F-statistic prior to the decision making based on the acceptance or rejection of the null hypothesis. A review of literature on design of experiments shows a trend away from uncritical acceptance of the approach, thus confirming that sustained effort is being made to develop a new method. As part of this effort, this paper attempts to develop a novel approach for determining the MSEs in designed experiment. Using the new method, the combination of controllable variables that optimized most the surface finish of machined workpiece materials was determined with Kronecker product analysis which was enhanced by the use of MATLAB software package. The response value for the surface roughness, Xijklmn, obtained from the model developed was 1.5368μm. Residual analysis carried out indicates that the model output was adequate. The analytical method explored can be used to develop a statistical software package that will be helpful in the computation of sums of squares of observation as well as make decision on the null hypothesis without recourse to Fisher’s table.Keywords: Kronecker product, Sum of Squares, Mean sum of squares, Optimization

Serious complications of pancreatoduodenectomy correlate with lower rates of adjuvant chemotherapy: Results from the recurrence after Whipple's (RAW) study

Introduction: Adjuvant chemotherapy (AC) can prolong overall survival (OS) after pancreatoduodenectomy (PD) for pancreatic ductal adenocarcinoma (PDAC). However, fitness for AC may be influenced by postoperative recovery. We aimed to investigate if serious (Clavien-Dindo grade ≥ IIIa) postoperative complications affected AC rates, disease recurrence and OS. Materials and methods: Data were extracted from the Recurrence After Whipple's (RAW) study (n = 1484), a retrospective study of PD outcomes (29 centres from eight countries). Patients who died within 90-days of PD were excluded. The Kaplan-Meier method was used to compare OS in those receiving or not receiving AC, and those with and without serious postoperative complications. The groups were then compared using univariable and multivariable tests. Results: Patients who commenced AC (vs no AC) had improved OS (median difference: (MD): 201 days), as did those who completed their planned course of AC (MD: 291 days, p < 0.0001). Those who commenced AC were younger (mean difference: 2.7 years, p = 0.0002), more often (preoperative) American Society of Anesthesiologists (ASA) grade I-II (74% vs 63%, p = 0.004) and had less often experienced a serious postoperative complication (10% vs 18%, p = 0.002). Patients who developed a serious postoperative complication were less often ASA grade I-II (52% vs 73%, p = 0.0004) and less often commenced AC (58% vs 74%, p = 0.002). Conclusion: In our multicentre study of PD outcomes, PDAC patients who received AC had improved OS, and those who experienced a serious postoperative complication commenced AC less frequently. Selected high-risk patients may benefit from targeted preoperative optimisation and/or neoadjuvant chemotherapy