Use of Material Interfaces in DEM to Simulate Soil Fracture Propagation in Mode I Cracking

Mode I fracture is common in geomechanics in desiccation cracking, hydraulic fracture, and pressuremeter testing. The cohesive crack model has been used extensively and successfully in numerical modeling of such fracture in concrete and steel but has not been applied in modeling of soil fracture to the same extent. It is argued that the cohesive crack model may be more appropriate than linear elastic fracture mechanics (LEFM) for soils because it takes into account finite tensile strength and any likely plasticity during fracture. With special reference to the Universal Distinct Element Code (UDEC) computer program, a methodology of using interfaces in the distinct element method (DEM) of analysis to model fracture has been validated herein, and this approach is considered to be useful in geomechanical modeling applications. The methodology is based on the cohesive crack approach and shows how softening laws could be back-calculated from load-displacement curves of test specimens. It has been validated using three geometries: a tension test with a rectangular cross section, a notched three-point bend beam, and a compact tension test. Approximate softening laws for St. Albans clay from Canada are proposed.     

An extended transaction to maintain consistency and recovery in multidatabase systems

A complete practical solution to transaction management preserving multidatabase consistency in the presence of multidatabase updates and failures is presented. The approach developed does not require support for the two-phase commit (2PC) protocol in the participating local database management systems (LDBMSs). Furthermore, it does not violate local autonomy; the source code of the LDBMSs is not modified in any way and the multidatabase system (MDBS) does not access or modify any control information of the LDBMS. The principles of the 2PC protocol in the process of global transaction commitment are adopted. The presented method does not rely on any specific concurrency control mechanism for LDBMSs. Consideration is given to global transaction failures due to subtransaction aborts by the LDBMSs and local site crashes. The recovery process is based on undo operations. While a global transaction is in progress, the tables accessed by subtransactions of this transaction at each local site are locked using specially initiated table locks. These locks are stored and maintained in the local database itself as control tables. The approach taken is easy to implement, and its limitations are discussed.     

A study on estimation of damage accumulation of glass fibre reinforce plastic (GFRP) composites under a block loading situation

Many cumulative damage theories have been used in lifetime calculation of GFRP composite components. However, it is well known that linear damage accumulation models are inadequate for predicting the cumulative damage in GFRP compositeas due to their dominant viscoelastic characteristics. This paper discusses the outcomes of application of damage accumulation models proposed by Palmgren-Miner [Miner MA. Cumulative damage in Fatigue. J Appl Mech 1945;12(September):A159–64], Broutman and Sahu [Broutman LJ, Sahu SA. New theory to predict cumulative fatigue damage. In: Fiberglass reinforced plastics, composite materials: testing and design (second conference), ASTM STP 497; 1972. p. 170–88], Hashin and Rotem [Hashin Z, Rotem A. A cumulative damage theory of fatigue failure. J Mater Sci Eng 1978;(34):147–60] and Epaarachchi and Clausen [Epaarachchi Jayantha A, Clausen Philip D. On predicting the cumulative fatigue damage in glass fibre reinforced plastic (GFRP) composites under step/discrete loading. Composites Part A: Appl Sci Manuf 2005;36(9):1236–45], to calculate the lifetime of GFRP composite samples under repeated block loading situations.     

A fuzzy–logic controller for an electrically driven steering system for a motorcar

This paper presents an application where a Fuzzy-Logic Controller (FLC) is used at a supervisory level to implement mutual coordination of the steering of the two front wheels of a motorcar. The two front wheels are steered by two independent discrete time state feedback controllers with a view to optimize the steering slip angles. The functions of the two controllers are tied together by way of a FLC. Because of the presence of unmodelled dynamics and disturbances acting on the two sides, it is difficult to achieve the desired performance using conventional control systems. This is the primary reason that FLC is emploged to solve the problem. The results show that the implemented system achieved desired coupling between the two independent systems and thereby reduces the difference between the two steered angles.     

Modeling of creep and shrinkage behavior of polymeric films used in magnetic tapes

For ever increasing high recording densities of magnetic tape drives, improved dimensional stability of the polymeric films used as magnetic tape substrates is required. During storage and use, creep and shrinkage occur simultaneously and it needs to be minimized. To obtain constitutive relationships for creep and shrinkage, these contributions need to be separated and modeled. A mathematical model based on Kelvin–Voigt models has been developed to characterize simultaneous creep and shrinkage behavior to obtain the constitutive relationships for creep and shrinkage. Experiments have been performed to separate out creep and shrinkage effects and this model has been used to compensate the effect of shrinkage on creep data and to get true creep data. The experimental creep and shrinkage data of various films have been modeled to obtain viscoelastic parameters. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 78–88, 2004     

Phosphoproteomics Unravel HBV Triggered Rewiring of Host Phosphosignaling Events

Hepatitis B virus (HBV) infection persists as a major global health problem despite the availability of HBV vaccines for disease prevention. However, vaccination rates remains low in some regions of the world, driving the need for novel strategies to minimise infections and prevent disease progression. Thus, understanding of perturbed molecular signaling events during early phases of HBV infection is required. Phosphosignaling is known to be involved in the HBV infection processes, yet systems-level changes in phosphosignaling pathways in the host during infection remain unclear. To this end, we performed phosphoproteome profiling on HBV-infected HepG2-NTCP cells. Our results showed that HBV infection drastically altered the host phosphoproteome and its associated proteins, including kinases. Computational analysis of this phosphoproteome revealed dysregulation of the pathways involved in immune responses, cell cycle processes, and RNA processing during HBV infection. Kinase Substrate Enrichment Analysis (KSEA) identified the dysregulated activities of important kinases, including those from CMGC (CDK, MAPK, GSK, and CLK), AGC (protein kinase A, G, and C), and TK (Tyrosine Kinase) families. Of note, the inhibition of CLKs significantly reduced HBV infection in HepG2-NTCP cells. In all, our study unravelled the aberrated phosphosignaling pathways and the associated kinases, presenting potential entry points for developing novel therapeutic strategies for HBV treatment.     

Characterization of corrosion morphologies from deteriorated underground cast iron water pipes

Following the completion of the Advanced Condition Assessment and Pipe Failure Prediction project in Australia, it has emerged that cast iron pipes normally experience corrosion damages extending over the large spatial area that resemble a patch, and structural failures are commonly associated with these patches. In this study, we defined a corrosion patch as a cluster of individual defects within or less than the one‐wall‐thickness distance of each other and conducted a morphometric study on patches from several deteriorated cast iron pipes. It was found that the size parameters, viz., the patch length, width, area, and volume potentially attain steady‐state progression over long‐term deterioration and are consistent with current understanding in underground corrosion. The rectangularity, convex deficiency, and solidity shape parameters were found to be related to each other and could be described by power‐law functions. Moreover, the analysis of two‐dimensional (D_2D) and three dimensional (D_3D) fractal dimension parameters revealed that they serve as useful proxies for different patch properties. In particular, the D_3D revealed linear trends with the patch aspect ratio and an ability to delineate between failed and in‐service pipes. It is expected that the results from this study will serve as important baseline information for future works aiming to generate and implement realistic corrosion patches for pipe structural integrity analysis.     

Extraction and processing of real time strain of embedded FBG sensors using a fixed filter FBG circuit and an artificial neural network

Fibre Bragg Grating (FBG) sensors have been used in the development of structural health monitoring (SHM) and damage detection systems for advanced composite structures over several decades. Unfortunately, to date only a handful of appropriate configurations and algorithm sare available for using in SHM systems have been developed. This paper reveals a novel configuration of FBG sensors to acquire strain reading and an integrated statistical approach to analyse data in real time. The proposed configuration has proven its capability to overcome practical constraints and the engineering challenges associated with FBG-based SHM systems. A fixed filter decoding system and an integrated artificial neural network algorithm for extracting strain from embedded FBG sensor were proposed and experimentally proved. Furthermore, the laboratory level experimental data was used to verify the accuracy of the system and it was found that the error levels were less than 0.3% in predictions. The developed SMH system using this technology has been submitted to US patent office and will be available for use of aerospace applications in due course.     

Floor Space per Person and Housing Development: An Urban Growth Approach to Estimate Housing Supply in Hong Kong

This article estimates an empirical model of new housing supply in Hong Kong based on the urban growth approach. The article introduces a new factor, space usage per person (SPP), to this model reflecting the quality of housing, the demand and supply aspects of the housing market, along with prices and other standard variables. SPP may also be used as a human settlement development indicator. Empirical results provide strong evidence that the introduced new factor exerts a strong positive influence on new housing supply, and that even a marginal change in the space usage pattern would have a great impact on housing supply. This suggests that non-price measures too should receive priority when estimating future housing development needs. Empirical estimates also suggest that a 10 per cent rise in real house prices leads to a 0.6 per cent increase in new housing starts and twofold rise in real house prices would increase the entire housing stock by 6 per cent.

     

Effects of static–fatigue (tension) on the tension–tension fatigue life of glass fibre reinforced plastic composites

The effects of static–fatigue interaction on tension–tension fatigue life of glass fibre reinforced plastic (GFRP) composites were investigated. This paper proposed a new static–fatigue model, which is capable of predicting residual strength after a period of static loading. Also an algorithm is proposed to calculate fatigue lives with the inclusion of static–fatigue interaction. Predictions from the proposed static–fatigue model show a good agreement with the experimental results. Static–fatigue interaction has shown a considerable effect on fatigue lives of GFRP composites at intermediate and lower applied stress levels possibly due to a longer exposure to applied loads. At higher load levels approximately greater than 65% of ultimate stress, and higher stress ratios range like 0.5 < R < 0.9, fatigue lives shown to be closer to material’s static–fatigue limits which is shorter than the expected lifetime by cyclic fatigue.