A system dynamics approach for modeling construction workers’ safety attitudes and behaviors

Construction accidents are caused by an unsafe act (i.e., a person's behavior or activity that deviates from normal accepted safe procedure) and/or an unsafe condition (i.e., a hazard or an unsafe mechanical or physical environment). While there has been dramatic improvement in creating safer construction environments, relatively little is known regarding the elimination of construction workers’ unsafe acts. To address this deficiency, this paper aims to develop a system dynamics (SD)-based model of construction workers’ mental processes that can help analyze the feedback mechanisms and the resultant dynamics regarding the workers’ safety attitudes and safe behaviors. The developed model is applied to examine the effectiveness of three safety improvement policies: incentives for safe behaviors, and increased levels of communication and immersion in accidents. Application of the model verifies the strong potential of the developed model to provide a better understanding of how to eliminate unsafe acts, and to function as a robust test-bed to assess the effectiveness of safety programs or training sessions before their implementation.     

Effects of Cr and Fe Addition on Microstructure and Tensile Properties of Ti–6Al–4V Prepared by Direct Energy Deposition

The effects of Cr and Fe addition on the mechanical properties of Ti–6Al–4V alloys prepared by direct energy deposition were investigated. As the Cr and Fe concentrations were increased from 0 to 2 mass%, the tensile strength increased because of the fine-grained equiaxed prior β phase and martensite. An excellent combination of strength and ductility was obtained in these alloys. When the Cr and Fe concentrations were increased to 4 mass%, extremely fine-grained martensitic structures with poor ductility were obtained. In addition, Fe-added Ti–6Al–4V resulted in a partially melted Ti–6Al–4V powder because of the large difference between the melting temperatures of the Fe eutectic phase (Ti–33Fe) and the Ti–6Al–4V powder, which induced the formation of a thick liquid layer surrounding Ti–6Al–4V. The ductility of Fe-added Ti–6Al–4V was thus poorer than that of Cr-added Ti–6Al–4V.     

Analysis on the ink transfer mechanism in R2R application

Ink transfer process from the printing roll to the web was investigated using a Computational Fluid Dynamics (CFD) technique for the roll-to-roll (R2R) printing application. A parametric study was conducted to identify the effects of fluid parameters such as viscosity, surface tension and contact angle. To make the present analysis more relevant to the real printing system, a three-dimensional computational configuration for the commercial software was set up using the information obtained from the typical R2R system. Simplified one-dimensional semi-analytic model based on Reynolds equation was compared with the CFD results to assess the validity of the results. Pressure distribution states that 1-D analysis is reasonably good in capturing the flow physics. The 3-D simulation with VOF (Volume of Fluid) shows that viscosity is the most important parameter. Moreover, the larger surface tension resulted in smaller amount of ink transfer.     

Comparative study of quasi-static and normal capacitance–voltage characteristics in amorphous Indium-Gallium-Zinc-Oxide thin film transistors

Capacitance-voltage (C-V) characteristics of amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) thin film transistors (TFTs) are comparatively investigated with two different measurement configurations. Normal gate-to-source/drain (S/D) C-V and quasi-static C-V curves are employed to characterize physical mechanisms with equivalent circuit models for a-IGZO TFTs. The difference between the normal C-V and the quasi-static C-V (QSCV) characteristics is investigated by the dependence on the gate voltage (V_G), measurement configuration, and optical illumination. The discrepancy is analyzed to be due to a high hole barrier in the S/D contact region and a slow response of active bulk charges (Q_loc and Q_free) in the a-IGZO active layer.     

Environmental impacts of products in china

As the Chinese economy has become an integral part of the global supply chain, quantifying the environmental impacts by Chinese industry is indispensible to understanding the environmental performance of products in general. Comprehensive and consistent environmental data infrastructure, however, is lacking in China, hindering such an understanding. In this paper, we demonstrate a simplified method for assembling and harmonizing various data sources to develop a sectoral environmental database for input-output life cycle assessment (IO-LCA). We first identified key substances by analyzing previous normalization studies and other countries' sectoral environmental databases. Data for priority substances were compiled and then adjusted and validated. The database created from this process was then used to analyze the direct and indirect environmental impacts generated by Chinese rural and urban consumptions. Expenditures on food and other basic household needs like heating and cooking were found to play a dominant role in generating environmental impacts in China, while previous studies of industrialized countries also highlighted the importance of transportation. This database provides background information for LCA through, for example, the hybrid approach, and is also conducive to ongoing efforts to develop generic life cycle inventory databases in China.     

Design error reduction: toward the effective utilization of building information modeling

An advocated panacea for reducing design errors and rework in construction and engineering projects is building information modeling (BIM). Yet, it would appear that advocates of BIM have overlooked why and how design errors occur. In this article, the nature of error is explained and the principal underlying causes identified with reference to the normative literature and the authors phenomenological research. A systemic model for reducing design errors is presented and the enabling role of BIM discussed.     

Dimensional changes and phase transformation of TiO2 nanotubes heat-treated under oxygen-containing atmosphere

The purpose of this study was to investigate the dimensional changes and phase transition of nanotubular titanium oxide arrays after heat treatment under an oxygen-containing atmosphere. The thermodynamic background for the oxidation of titanium to titanium oxide was theoretically investigated as a function of the oxygen partial pressure. The anodized titanium nanotubes had lengths between 400 and 500 nm, thicknesses of 11 nm and an amorphous structure. The specimens heat-treated at higher oxygen partial pressures preferentially had rutile phase rather than anatase phase. The thickness of the TiO2 nanotubes was increased at a lower oxygen partial pressure.     

Histomorphometric evaluation of an implant with a nanotubular surface treatment in a beagle femur

This study examined the effects of a nanotubular surface treatment on an implant by anodic oxidation. Forty two screw-shaped implants were classified into 3 groups; machined surface (control group), nanotube formation on the machined surface (group N) and nanotube formation on the RBM surface (group RN). A total of 36 implants were inserted into a beagle femur. Two implants from each group were observed by scanning electron microscopy. Histomorphometric analyses were performed after 4 and 12 weeks. After 4 weeks, the average bone to implant contact (BIC) ratio of groups N and RN was significantly higher than that of the control group (P < .05). After 12 weeks, a nanotubular surface treatment showed a significantly higher BIC ratio only in the marrow space adjacent to the implant apex (P < .05). This in vivo study revealed the enhanced osseointegration of nanotubes.     

Development of sputtered nanoscale titanium oxide coating on osseointegrated implant devices and their biological evaluation

Nanoscale titanium oxide (TiO₂) coating was deposited on titanium (Ti) disks and Ti dental implants using r.f. magnetron sputtering technique. The coating was characterized using grazing angle X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle measurement, profilometry and nano-scratch test. The coating also was evaluated with in vitro cell culture and in vivo dog femur model. Three groups of samples were prepared, including as-sputtered Ti (AS-Ti), sputtered Ti with a post-deposition heat treatment at 600 °C (SH-Ti) and machined Ti (MA-Ti) as controls. The AS-Ti and SH-Ti were dense surfaces consisting of nanoscale grains of 40 nm and 80 nm, respectively. Post-deposition heat treatment increased the coating adhesion. The SH-Ti and AS-Ti significantly decreased the water contact angles compared to the MA-Ti. The nanoscale AS-Ti and SH-Ti significantly improved cell adhesion within the first hour of incubation compared with the MA-Ti. No significant differences were observed in osteoblast proliferation and differentiation in vitro as well as reverse torque and histology in vivo among the three groups. In the present study, it was not observed that the nanoscale dense TiO₂ coating improved the osseointegration compared to the microscale dense Ti.