Microstructure and properties of diffusion bonded Ti-6Al-4V parts using brazing-assisted hot isostatic pressing

Ti-6Al-4V couples have been diffusion bonded by hot isostatic pressing (HIPping) after vacuum brazing was used to seal the periphery of the bonding samples so that no encapsulation was required during HIPping. Analytical scanning electron microscopy was used to assess the microstructure of the HIPped interface and tensile and fatigue properties of bonded samples were compared with those of the bulk starting material. The tensile properties of the bonds were shown to be comparable with those of the bulk material, but the fatigue life was slightly downgraded. The fatigue fractures were initiated by inclusions on the bonding interface, caused by contamination before bonding, but the fatigue cracks did not propagate along the bonding interface indicating a strong bond. It is concluded that this technique of vacuum brazing plus HIPping could be used for encapsulation-free HIPping to produce complex-shaped components.     

Impact of finite receiver-aperture size in a non-line-of-sight single-scatter propagation model

In this paper, a single-scatter propagation model is developed that expands the classical model by considering a finite receiver-aperture size for non-line-of-sight communication. The expanded model overcomes some of the difficulties with the classical model, most notably, inaccuracies in scenarios with short range and low elevation angle where significant scattering takes place near the receiver. The developed model does not approximate the receiver aperture as a point, but uses its dimensions for both field-of-view and solid-angle computations. To verify the model, a Monte Carlo simulation of photon transport in a turbid medium is applied. Simulation results for temporal responses and path losses are presented at a wavelength of 260 nm that lies in the solar-blind ultraviolet region.     

Dynamics of control in construction project teams

Control is pervasive in construction project environments. The management of projects through various planning and control tools has therefore been described essentially as rebureaucratization which increases control over individuals, teams and organizations through ideologies of efficiency and performativity. Yet certain characteristics of the project setting make it an ideal climate for the empowerment of individuals and teams. The manifestations of control in five construction project management teams involved in two ongoing construction projects in Hong Kong are examined. The interpretive and exploratory focus of the study favoured the use of a qualitative research design and the case study approach in particular. Control is viewed as all devices and systems employed to ensure that acts, behaviours, outcomes and decisions of individuals, teams and organizations are consistent with meeting organizational or project goals, objectives and strategies. The findings indicate that a portfolio of control modes is implemented in project teams comprising both formal (i.e. behaviour‐ and outcome‐based) and informal (i.e. clan‐ and self‐based) control mechanisms which are not necessarily incompatible. While formal control remains the primary control mode, a portfolio of control appears necessary to augment the inadequacies of formal control due to the evolving nature of the project environment.     

Behaviour-based safety management in Hong Kong's construction industry: the results of a field study

Hong Kong's construction industry has had a poor site safety record for over a decade. Behaviour-based methods of safety management (BSM) have proved successful in other industries and in other countries. Hence, this study aimed to test the effectiveness of BSM by applying goal-setting and feedback interventions to specific areas of safety performance on Hong Kong Housing Authority construction sites. Using a within-group experimental design and with the use of a proportional rating safety measurement instrument, data were collected on the effectiveness of BSM on Hong Kong sites. The data were recognized as time series data; this has been a serious methodological oversight in much previous research. The data were analysed using autoregressive moving averages models, and the results were mixed in that a significant improvement in safety performance occurred in the housekeeping category of intervention but no improvement was observed in the access to heights and bamboo scaffolding categories. Based on these results a goal setting/expectancy theory model of site safety improvement has been synthesized, and the lack of provision of an adequate safety infrastructure has been identified as a serious impediment to improvement.     

Development and validation of a multilevel safety climate measurement tool in the construction industry

Construction organizations are large and complex with decentralized structures, and characterized by non-routine work undertaken by semi-autonomous work groups. Construction workers’ perceptions of safety climate can form at different levels and vary between subunits. A multilevel safety climate measurement tool was proposed, which identified five important safety agents, i.e. client, principal contractor, supervisor, co-workers, and individual workers. Surveys were conducted at three construction projects commissioned by Fonterra Co-operative Group. A total of 356 participants completed the survey. The data was subject to scale reliability analysis and factor analysis. The results showed that all scales achieved satisfactory internal consistency and the multilevel factorial structure was generally supported. At the organizational level, the tool measures clients’ overall safety priority and safety actions, and principal contractors’ general commitment to safety. At the group level, the tool measures supervisors’ safety actions and safety expectations, and co-workers’ general safety values and practices. The tool also measures individual safety responses reflected by safety compliance and safety participation. The measurement tool would help construction organizations to diagnose potential weaknesses in their safety management practices for safety improvement and also help to develop a social and cultural work environment that is supportive of safety at all levels.     

Graphical cogeneration analysis for site utility systems

It is necessary to systematically evaluate site-wide power and heat generation, distribution, and utilization. A new graphical approach based on a Site Grand Composite Curve (SGCC) to targeting cogeneration in site utility systems is proposed to extend Pinch Analysis. The SGCC presents quantitative and visual process targets of heating and cooling requirements, site utility system targets for system steam generation and potential shaft power by steam expansion and condensation. Process indirect heat recovery by intermediate steam levels that can reduce fuel consumption is analyzed readily in the approach. The steam cascade in the SGCC clarifies the Total Site Pinch and site targets of utility very high pressure steam demand and site steam saving. This graphical analysis presents greater clarity for the quantitative interaction between processes and utility system targets than previous approaches. The influence of process variation and steam mains selection on cogeneration improvements is explored much clearer in this straightforward method.     

Lability of Cd,Cu, and Zn in polluted soils treated with lime,beringite, and red mud and identification of a non-labile colloidal fraction of metals using istopic techniques

The use of soil amendments has been proposed as a low input alternative for the remediation of metal polluted soils. However, little information is available concerning the stability, and therefore the longevity, of the remediation treatments when important soil parameters change. In this paper we investigate the effect of pH changes on the lability of heavy metals in soils treated with lime, beringite, and red mud using a modified isotopic dilution technique in combination with a stepwise acidification procedure. Significant amounts of nonlabile (fixed) Cu and Zn were found to be associated with colloids <0.2 microm in the solution phase. The results obtained indicated that the mobility of fixed colloidal metals is significant and increases with soil pH. This must be considered because most of the soil amendments are alkaline and increase soil pH. All the soil amendments significantly decreased the lability of Cd, Zn, and Cu in the soils as a whole. However, when the soils were re-acidified, the labile pool of metals increased sharply and in the case of lime and beringite, the lability of the metals was similar, at equal pH, to the untreated soil. In contrast the lability of metals in the red mud treated soils was always smaller than that in the untreated soils across the range of pH values tested. These results suggest that the mechanism of action of lime and beringite is similar and probably related to increased metal adsorption and precipitation of metal hydroxides and carbonates at high pH. In the case of red mud, a combination of pH dependent and independent mechanisms (possibly solid-phase diffusion or migration into micropores) may be responsible for the metal fixation observed.     

Interaction of wheat and rice starches with yellow mustard mucilage

The effect of yellow mustard mucilage (YMM) on gelatinization and retrogradation of wheat and rice starches were studied. Considerable interactions were observed between YMM and wheat and rice starches which were accompanied by a marked increase in viscosity. DSC studies showed that the presence of YMM did not affect peak gelatinization temperature (T_p) of wheat and rice starches, but slightly increased melting enthalpy (ΔH) and the phase transition temperature range (T_c−T₀). Addition of YMM markedly changed wheat and rice starch gel textures by increasing hardness, adhesiveness, chewiness and springiness. The addition of YMM–locust bean gum (LBG) mixture (9:1) similarly increased the viscosity of wheat and rice starches but decreased gel hardness. The swelling power as well as solubilized starch and amylose were decreased for both starches in the presence of YMM. Syneresis in wheat and rice starches was also decreased by the presence of YMM.     

Assessing the labile arsenic pool in contaminated paddy soils by isotopic dilution techniques and simple extractions

Arsenic (As) contamination of paddy soils threatens rice cultivation and the health of populations relying on rice as a staple crop. In the present study, isotopic dilution techniques were used to determine the chemically labile (E value) and phytoavailable (L value) pools of As in a range of paddy soils from Bangladesh, India, and China and two arable soils from the UK varying in the degree and sources of As contamination. The E value accounted for 6.2-21.4% of the total As, suggesting that a large proportion of soil As is chemically nonlabile. L values measured with rice grown under anaerobic conditions were generally larger than those under aerobic conditions, indicating increased potentially phytoavailable pool of As in flooded soils. In an incubation study, As was mobilized into soil pore water mainly as arsenite under flooded conditions, with Bangladeshi soils contaminated by irrigation of groundwater showing a greater potential of As mobilization than other soils. Arsenic mobilization was best predicted by phosphate-extractable As in the soils.