Impact of different criteria for identifying intra-household interactions: a case study of household time allocation

Activity analysis, Flexible criteria, GIS, Intra-household interactions, Joint activities, Restrictive criteria, Structural equation modeling, Time use, Toronto Travel-Activity Panel Survey,

Exploring day-to-day variability in time use for household members

Studies of activity-travel patterns typically use 1-day or pooled samples, and more often than not, are conducted at the individual level. By default, they assume that activity-travel decisions are uniform from 1 day to the next and individuals are independent from one another. Such assumptions do not reflect reality. This research investigates day-to-day variability in activity time-use patterns of household members while incorporating variations in their interactions. Results from a descriptive analysis and a series of daily structural equation models provide evidence of day-to-day variability in activity time-use patterns. Specifically, time-use patterns on weekdays are substantially different from those on weekends. Furthermore, compared to independent activities, there is a higher proportion of intra-personal variability and a lower proportion of inter-personal variability for joint activities. These findings suggest that transportation planners should not combine independent and joint activities as has been the case in the recent past, nor should they use single-day or pooled models when estimating activity time-use patterns.Activity analysis Intra-household interactions Joint activities Time use Toronto Travel-Activity Panel Survey Variability analysis

An Innovative Survey Design to Understand Sustainable Travel Behaviors: Potential of a Rolling Sample Survey to Replace Traditional Household Travel Surveys

We propose an innovative survey with rolling samples to address a major fiscal challenge faced by many MPOs. Faced with a small, but continuous budget, MPOs are increasingly unable to continue the current survey practice: conducting a large survey every 10 years. A rolling sample design also has other benefits over the current practice. Yet, for its implementation in household travel surveys, many questions exist. Some are technical issues while others are cost and procedural-related. The primary purpose of this project is to understand these issues and provide recommendations for a future household travel survey with rolling samples. It is also expected that a rolling sample design can help us understand travel behavior better for the purpose of VMT reduction. By sampling participants living in very different neighborhoods, it can help us devise better VMT reduction strategies. The second purpose of this project is to assess the potential of a rolling sample design in addressing the potential of land use and infrastructure related strategies for VMT reduction. The research will help transportation planners and analysts to proactively reposition their service in light of the changing budgetary environment by developing a new approach to travel surveys based on small samples but continuous enrollment. This new approach is also more consistent with the recent changes in data collection methods used by the US Census Bureau. Our empirical results demonstrate the reliability of a rolling sample and points to the potential of using it to replacing the traditional household travel surveys. We also demonstrate an innovative parcel-based sampling procedure to allow an empirical examination of the effects of built environments on transportation outcomes based on data collected from continuous enrollment.Pacific Northwest Transportation Consortium Washington State Department of Transportatio

Analysis of Soil Degradation Causes in Phyllostachys edulis Forests with Different Mulching Years

Moso bamboo (Phyllostachys edulis (Carrière) J.Houz.) is famous for its fast growth and biomass accumulation, as well as high annual output for timber and bamboo shoots. Organic mulches are widely used to improve shoots’ production in moso bamboo forests. However, continuous mulching management may cause bamboo forest degradation and affect sustainable development. The objective of this study was to identify the degradation mechanism and to provide a theoretical basis for recovery. A complete randomized block design with four treatments was conducted, including mulching for one year (M1), two years (M2), three years (M3) and no-mulching management (NM). Soil nutrient contents, enzyme activities and microbial biomass were determined. With the increase of mulching years, the soil pH value gradually reduced, causing soil acidification, but the content of soil organic matter was inclined to ascend. Soil total nitrogen (TN), total phosphorus (TP) and total potassium (TK) contents showed an increasing trend, and they were significantly higher in mulching stands than those in NM (p < 0.05). Contents of soil available nutrients (AN, AP and AK) increased, then decreased with the increase of mulching years and peaked in M1. With the increase of mulching years, the soil stoichiometry ratio (C/N, C/P and N/P) gradually increased. Soil invertase, urease and acid phosphatase activities presented a single-peak curve and reached the maximum within one year after mulching. Total microbial biomass and that of individual groups changed greatly after mulching. Soil microbial biomass increased first and then decreased, and it was the largest in M1. The fungi:bacteria ratio decreased in the first year and then began to rise, while the aerobic:anaerobic ratio showed the opposite trend. According to the overall results, M3 leads to soil acidification, imbalance of the nutrients’ proportion, abnormal enzyme activity and change of soil microbial flora, and rotated mulching management (mulching one year and then recuperating one year) should be recommended in practice

Study on ultra-precision compliant mechanisms for nanotechnology applications

Including: 2 parts. Compliant mechanisms provide motion through elastic deformation under the action of external loads. These mechanisms are key functional members in many today's precision machines and devices, such as precision micro-positioning stages, micro actuators, microelectromechanical systems (MEMS) and robots, where micron or even nanometric resolution and accuracy are required for the motion. On the contrary to rigid-body mechanisms, compliant mechanisms consist of monolithic construction without rigid joints or sliders. Thus, they effectively eliminate the wear, backlash, lubrication, and friction problems, which are often encountered by rigid-body mechanisms

Study on ultra-precision compliant mechanisms for nanotechnology applications

Including: 2 parts. Compliant mechanisms provide motion through elastic deformation under the action of external loads. These mechanisms are key functional members in many today's precision machines and devices, such as precision micro-positioning stages, micro actuators, microelectromechanical systems (MEMS) and robots, where micron or even nanometric resolution and accuracy are required for the motion. On the contrary to rigid-body mechanisms, compliant mechanisms consist of monolithic construction without rigid joints or sliders. Thus, they effectively eliminate the wear, backlash, lubrication, and friction problems, which are often encountered by rigid-body mechanisms. Furthermore, their monolithic construction makes the costly assembly process unnecessary and the integration of smart sensors and actuators possible

Experimental and modeling investigation on the viscoelastic-viscoplastic deformation of polyamide 12 printed by multi jet fusion

The viscoelastic-viscoplastic deformation of Multi Jet Fusion-printed polyamide 12 (MJF PA12) was investigated with experimental and numerical approaches. Multi-loading–unloading–recovery tests were conducted to distinguish between the viscoelastic and viscoplastic deformations. The influence of the void defects on deformation of PA12 was investigated through the microcomputed tomography (μCT) and field emission scanning electron microscope. A finite-strain viscoelastic-viscoplastic constitutive model based on the logarithmic stress rate for the matrix of MJF PA12 was developed within the thermodynamic framework as well as an introduction of the accumulated plastic deformation–induced damage into the proposed model. A representative volume element was modeled based on the μCT results of MJF PA12. The simulated results, such as stress–strain and strain–time curves, agreed with the experimental results. Moreover, the model revealed the mechanism that the low tensile ductility of MJF PA12 is caused by the increase in strain localization and narrowing of the shear band.Part of this research was conducted in collaboration with HP Inc. and supported by Nanyang Technological University and the Singapore Government through the Industry Alignment Fund-Industry Collaboration Projects Grant (I1801E0028)

Effect of build direction on tension–tension low cycle fatigue behavior of polyamide 12 parts printed by Multi Jet fusion

The effects of build direction on the tensile properties, tension–tension low cycle fatigue behavior, and failure mechanism of polyamide 12 parts fabricated by Multi Jet Fusion have been investigated by addressing the roles of formed voids, sintering interfaces, and geometrical imperfections. Results indicate that the Young's modulus of bulk material with vertical build direction is higher than that of bulk material with horizontal build direction due to the carbon black enhanced sintering interfaces. The tensile strength of the printed bulk material with horizontal and vertical build directions is comparable. It is found that the anisotropic tension–tension low cycle fatigue behavior for the bulk material is significant, while that for the re-entrant lattice structure is weak. The anisotropic fatigue strength of bulk material is derived from the anisotropic distribution of internal voids and sintering interfaces. The fatigue behavior of the re-entrant lattice structure is determined by the geometrical imperfections. The coalescence of the large voids or clusters of voids contributes to the crack initiation and propagation processes that lead to the failure of the bulk material. While the failure of re-entrant lattice structure is mainly determined by the intersection of strut junction rather than the void defect. This result provides the fatigue data that can be used for the structural design with Multi Jet Fusion polyamide 12 as well as reveals the effects of voids, sintering interfaces, and geometrical imperfections on the fatigue behavior of the printed parts.Nanyang Technological UniversityThis research was conducted in collaboration with HP Inc. and supported by Nanyang Technological University and the Singapore Government through the Industry Alignment Fund-Industry Collaboration Projects Grant (I1801E0028)

Additively manufactured dual-faced structured fabric for shape-adaptive protection

Fabric-based materials have demonstrated promise for high-performance wearable applications but are currently restricted by their deficient mechanical properties. Here, this work leverages the design freedom offered by additive manufacturing and a novel interlocking pattern to for the first time fabricate a dual-faced chain mail structure consisting of 3D re-entrant unit cells. The flexible structured fabric demonstrates high specific energy absorption and specific strength of up to 1530 J kg-1 and 5900 Nm kg-1 , respectively, together with an excellent recovery ratio of ≈80%, thereby overcoming the strength-recoverability trade-off. The designed dual-faced structured fabric compares favorably against a wide range of materials proposed for wearable applications, attributed to the synergetic strengthening of the energy-absorbing re-entrant unit cells and their unique topological interlocking. This work advocates the combined design of energy-absorbing unit cells and their interlocking to extend the application prospects of fabric-based materials to shape-adaptive protection.Published versionThis study was supported by the RIE2020 Industry Alignment Fund – Industry Collaboration Projects (IAF-ICP) Funding Initiative, Singapore and cash and in-kind contribution from the industry partner, HP Inc