MODIFIED CRACK CLOSURE INTEGRAL (MCCI) FOR 3-d PROBLEMS USING 20-NODED BRICK ELEMENTS

Abstract— The Modified Crack Closure Integral (MCCI) technique based on Irwin's crack closure integral concept is very effective for estimation of strain energy release rates G in individual as well as mixed-mode configurations in linear elastic fracture mechanics problems. In a finite element approach, MCCI can be evaluated in the post-processing stage in terms of nodal forces and displacements near the crack tip. The MCCI expressions are however, element dependent and require a systematic derivation using stress and displacement distributions in the crack tip elements.
Earlier a general procedure was proposed by the present authors for the derivation of MCCI expressions for 3-dimensional (3-d) crack problems modelled with 8-noded brick elements. A concept of sub-area integration was proposed to estimate strain energy release rates at a large number of points along the crack front. In the present paper a similar procedure is adopted for the derivation of MCCI expressions for 3-d cracks modelled with 20-noded brick elements. Numerical results are presented for center crack tension and edge crack shear specimens in thick slabs, showing a comparison between present results and those available in the literature.     

Thermal behaviour of hollow-cored concrete slabs

This paper presents a detailed theoretical analysis of the thermal performance of hollow-cored concrete slabs. The governing equations are solved using appropriate boundary conditions and the results show that the heat flux entering the room through the roof is independent of the location of the air cavity within the depth of the slab.     

Computer-mediated group support, anonymity, and the software inspection process: an empirical investigation

In software inspection, a key principle endorsed by Fagan (1986) is openness. However, scholars have recently questioned the efficacy of openness. For example, some argue that ego-involvement and personality conflicts that become more transparent due to openness might impede inspection. Still others point out that familiarity and (preexisting) relationships among inspection team members negatively affect the comprehensiveness in detection of defects. This brings up concerns if the openness as originally envisioned by Fagan may in fact lead to suboptimal outcomes. As the trend towards computer-based inspection continues, we believe that anonymity could play a positive role in overcoming some of the drawbacks noted in team-based inspection. Drawing upon the literature on software inspection and group support systems, this research proposes possible influences of group member anonymity on the outcome of computer-mediated software inspection and empirically examines the validity of the posited relationships in a set of controlled laboratory experiments. Two different inspection tasks with varying levels of software code complexity are employed. While both the control groups (i.e., teams without anonymity) and treatment groups (i.e., teams with support for anonymity) consume more or less the same time in performing the inspection tasks, the treatment groups are more effective in identifying the seeded errors in the more complex task. Treatment groups also express a more positive attitude toward both code inspection tasks. The findings of the study suggest a number of directions for future research.     

A thermal system model for a radiant-tube continuous reheating furnace

A thermal system mathematical model developed for a gas-fired radiant-tube continuous reheating furnace is discussed. The mathematical model of the furnace integrates submodels for combustion and heat transfer within the radiant tube with models for the furnace enclosure. The transport processes occurring in the radiant tube are treated using a one-dimensional scheme, and the radiation exchange between the load, the radiant-tube surfaces, and the furnace refractories are analyzed using the radiosity method. The continuous furnace operation is simulated under steady-state conditions. Model simulations of load surface temperature variation compare well with measurements in an industrial galvannealing furnace. The scope and flexibility of the model are assessed by performing extensive parametric studies using furnace geometry, material properties, and operating conditions as input parameters in the model and predicting the thermal performance of the furnace. The various parameters studied include the effects of load and refractory emissivities, load velocities, properties of the stock material, and variations in the radiant-tube designs.     

Analysis of a cracked lug loaded by an interference fit pin

In the present study, a lug joint fitted with an interference fit (oversized) pin is considered with radial through cracks situated at diametrically opposite points perpendicular to the loading direction. A finite element contact stress algorithm is developed with linear elastic assumptions to deal with varying partial contact/separation at the pin-plate interface using a marching solution. Stress Intensity Factor (SIF) at the crack tips is evaluated using the Modified Crack Closure Integral (MCCI) method. The effect of change in crack length and edge distance on the load-contact relation, SIFs and stress distributions are studied. A rigorous plane stress elasticity solution of the pin-plate interface at the crack mouth confirmed the existence of the stress concentration leading to a local peak in the radial stress at the crack mouth and provided a method of estimating it quantitatively.     

Electrochemical assay of proteinase inhibitors using polycation-sensitive membrane electrode detection

OBJECTIVE: Past research has shown response biases to influence the accuracy of results from self-report measures. In pain assessment, where a percentage of patients have financial and other reasons to minimize or exaggerate psychological disturbance, it becomes especially important to identify the influence of response bias in self-report of adjustment. This study investigated the susceptibility of three commonly used self-report pain assessment measures to response bias. DESIGN: This study used a within-subjects (asymptomatic subjects) design with two experimental conditions and nonequivalent control group (chronic pain patients). SUBJECTS: Experimental group: 40 students enrolled in an occupational therapy program at a major southeastern United States university. Control group: 200 subjects referred to a multidisciplinary pain clinic at a major teaching hospital. MEASURES: Coping Strategies Questionnaire, Multidimensional Pain Inventory, and Pain Beliefs and Perceptions Inventory. RESULTS: With few exceptions, asymptomatic subjects scored significantly differently on these measures while portraying themselves as either coping well or coping poorly. In addition, when using the "coping poorly" response set, asymptomatic subjects reproduced scores similar to those of symptomatic chronic pain patients. CONCLUSION: The susceptibility to manipulation appeared constant across the three measures, a finding that highlighted the difficulties clinicians and researchers encounter in accurate interpretation of results from these measures in the absence of validity indicators. This study also emphasizes the ease with which subjects with sufficient motivation can present themselves in an untruthful and manipulative manner and can generate scores that are, on their own, difficult to distinguish from those of a group of typical chronic pain patients.     

Anisotropic strength and deformational behavior of Himalayan schists

Anisotropy, which is characteristic of metamorphic rocks such as schists, is due to a process of metamorphic differentiation. Preferred orientation of minerals like mica and chlorite in response to tectonic stresses makes schistose rocks foliated. As a result their engineering properties vary with the direction of loading.The influence of transverse anisotropy on strength and deformational responses of four schistose rocks obtained from the foundation of two underground powerhouse sites in the Himalayas has been critically examined. Specimens at different orientation (β) of the foliations varying from 0° to 90° with respect to the axial stress (σ₁) in the unconfined state and also in the confined states up to 100 MPa of confining pressure were tested to evaluate the applicability of the non-linear strength criterion for the prediction of triaxial compressive strength and modulus. Based on the analysis of large experimental results it has been possible to predict strength and modulus with minimum pre-evaluation experimental data, i.e. only with three uniaxial compressive strength tests at 0°, 30° and 90° and two triaxial compression tests conducted at convenient confining pressures at β=90°orientation. Predicted non-linear stress–strain curves, using predicted values of strength and modulus have been found to match well with the experimental stress–strain curves even at higher confining pressures.     

An adaptive symbol-spaced equalizer to compensate analog imperfections

This paper presents an adaptive symbol-spaced equalizer solution to compensate for analog imperfections in a single carrier communication systems operating at very high symbol rates up to 500 Msym/s. Pass-band variations in the analog domain are typical at these high data rates, where the required bandwidth is approximately 1 GHz. Non-ideal analog filter responses and phase distortion produce Inter Symbol Interference (ISI) which increases modem implementation loss. This paper presents modeling of the modem?s analog imperfections, an overview of the equalizer algorithm and FPGA architecture, plus analysis and simulation of the expected performance gain. Pre and post equalization results from the real time tests, including BER performance with different modulation schemes such as BPSK, QPSK and 8PSK are also shown.     

Small Cell Planning: Resource Management and Interference Mitigation Mechanisms in LTE HetNets

In an attempt to address the huge data demand of indoor mobile users and poor signal strength from outdoor base stations to indoor environments, opertaors have started deploying variety of small cells likes Femtos, picos and micro cells. In this work, we used Femtos as small cells. Femto cells are low-cost, low-power consuming cellular base stations which operate only in licensed spectrum and are designed for both outdoor and indoor communication. Although small cells can be used for enhancing network capacity and coverage, arbitrary deployment of large number of small cells can lead to increase in operators expenditure and may create severe interference issues for cell edge users. In this paper, we look into optimal placement of small cell solutions to improve data rates of users in LTE HetNets using Femtos. Besides, these solutions address the main concerns of interference and resource management by proposing mechanisms for optimal placement of Femtos (OptFP, MinNF), dynamic power control and bandwidth allocation in Femtos (SOPC) and dynamic offloading. We provide a comparison of placement solutions and the applicability of each proposal keeping the operators’ revenue in mind.