Spatial Variability in Soils: High Resolution Assessment with Electrical Needle Probe

The global response of a soil is affected by spatial as well as temporal scales. An electrical needle-size probe is developed to effectively assess one-dimensional spatial variability. The probe is designed for laboratory specimens (needle diameter 1.2–2.2 mm), and it can be scaled for field applications. Design considerations include the tip shape, insertion disturbance, electrochemical effects, corrosion, operating frequency, and electrical resonance. Two calibration methods are presented to determine local soil permittivity and resistivity from the measured complex impedance; the simplified calibration procedure is based on resistance measurements only. The local electrical parameters permit one to infer the soil porosity and the electrolyte conductivity. The attainable spatial resolution depends on the needle diameter; submillimetric resolution is typically achieved in laboratory applications. Reconstituted sand specimens and undisturbed clayey specimens are tested to explore the resolution potential of this probe. The electrical needle probe clearly detects the spatial variability that results from different specimen preparation methods in sands and soil layering from natural formation histories such as those in varved clays.     

Risk Assessment Methodology for Underground Construction Projects

This paper presents a risk assessment methodology for underground construction projects. A formalized procedure and associated tools were developed to assess and manage the risks involved in underground construction. The suggested risk assessment procedure is composed of four steps of identifying, analyzing, evaluating, and managing the risks inherent in construction projects. The main tool of the proposed risk assessment methodology is the risk analysis software. The risk analysis software is built upon an uncertainty model based on fuzzy concept. The fuzzy-based uncertainty model is designed to consider the uncertainty range that represents the degree of uncertainties involved in both (1) probabilistic parameter estimates and (2) subjective judgments. Other tools developed in this study include the survey sheets for collecting risk-related information and the detail check sheets for risk identification and analysis. The paper finally discusses a detailed case study of the developed risk assessment methodology performed for a subway construction project in Korea.     

Higher order eigensensitivity analysis of damped systems with repeated eigenvalues

A simplified method for the computation of first-, second- and higher-order derivatives of eigenvalues and eigenvectors associated with repeated eigenvalues is presented. Adjacent eigenvectors and orthonormal conditions are used to compose an algebraic equation. The algebraic equation which is developed can be used to compute derivatives of eigenvalues and eigenvectors simultaneously. Since the coefficient matrix in the proposed algebraic equation is non-singular, symmetric and based on N-space, it is numerically stable and very efficient compared to previous methods. To verify the efficiency of the proposed method, the finite element model of the cantilever beam and a mechanical system in the case of a non-proportionally damped system are considered.     

A Personalized Defection Detection and Prevention Procedure based on the Self-Organizing Map and Association Rule Mining: Applied to Online Game Site

Customer retention is an increasinglypressing issue in today's competitiveenvironment. This paper proposes a personalizeddefection detection and prevention procedurebased on the observation that potentialdefectors have a tendency to take a couple ofmonths or weeks to gradually change theirbehaviour (i.e., trim-out their usage volume)before their eventual withdrawal. For thispurpose, we suggest a SOM (Self-Organizing Map)based procedure to determine the possiblestates of customer behaviour from pastbehaviour data. Based on this staterepresentation, potential defectors aredetected by comparing their monitoredtrajectories of behaviour states with frequentand confident trajectories of past defectors.Also, the proposed procedure is extended toprevent the defection of potential defectors byrecommending the desirable behaviour state forthe next period so as to lower the likelihoodof defection. For the evaluation of theproposed procedure, a case study has beenconducted for a Korean online game site. Theresult demonstrates that the proposed procedureis effective for defection prevention andefficiently detects potential defectors withoutdeterioration of prediction accuracy whencompared to that of the MLP (Multi-LayerPerceptron) neural networks.     

A new computer-assisted three-dimensional reconstruction method provides accurate measurement of glomerular mesangial volume

Many glomerulopathies are characterized by progressive mesangial (interstitial) expansion which can be quantitated by morphometric analysis. The purpose of this study was to analyze mesangial and glomerular volumes using a new computer-assisted reconstruction (CAR) method. CAR was compared to two standard planar methods, point-counting and linear integration, for accuracy and time efficiency. In Phase I of the study, a computer-based model of the mesangial space was created by placing spherical and ellipsoidal objects of known volume into an enclosing volume mimicking the glomerulus. The simulated mesangium occupied approximately 10 percent of the glomerular volume. The model glomerulus was sectioned serially into ten sections of equal thickness and the three morphometric methods applied to determine the mesangial/glomerular volume. The complexity of the mesangial model was varied by increasing the number of mesangial regions from one to ten to 100. The CAR method estimated the model mesangial volume more accurately (1–9 percent error) through each level of complexity compared to point-counting (3–17 percent error) and linear integration (3–18 percent error). The point-counting method consistently overestimated (P < 0.05) the fractional mesangial volume for the ten- and 100-region mesangium models. In Phase II of the study, a normal rat glomerulus was sectioned serially (215 sections) and a transmission electron micrograph (TEM) of every fifth section (n = 43) was obtained. Each TEM image (2% of glomerular surface) was digitized for analysis by CAR. Point-counting and linear integration were also performed on the whole glomerular TEMs (n = 10, randomly chosen). The estimated relative mesangial/glomerular volume was 6.6 ± 0.1 percent by CAR (x? ± SD), 9.7 ± 1.5 by linear integration, and 14.9 ± 3.4 by point-counting. The point-counting method was most efficient, requiring 40 ± 8 sec/section, followed by CAR at 85 ± 24 sec/section. Linear integration was least efficient (93 ± 23 sec/section). We conclude that CAR is the most accurate morphometric method of the three compared for estimating mesangial and glomerular methods, although it is more time consuming than the point-counting method and requires more complex instrumentation. CAR is the only method that will analyze the shape and three-dimensional complexity of glomerular structures using TEMs.     

Numerical analysis of welding residual stress using heat source models for the multi-pass weldment

Numerical prediction of welding-induced residual stresses using the finite element method has been a common practice in the development or refinement of welded product designs. Various researchers have studied several thermal models associated with the welding process. Among these thermal models, ramp heat input and double-ellipsoid moving source have been investigated. These heat-source models predict the temperature fields and history with or without accuracy. However, these models can predict the thermal characteristics of the welding process that influence the formation of the inherent plastic strains, which ultimately determines the final state of residual stresses in the weldment. The magnitude and distribution of residual stresses are compared. Although the two models predict similar magnitude of the longitudinal stress, the double-ellipsoid moving source model predicts wider tensile stress zones than the other one. And, both the ramp heating and moving source models predict the stress results in reasonable agreement with the experimental data.     

In Vitro hydrodynamic evaluation of prosthetic polymer heart valves in steady flow

Hydrodynamic comparison of two polymer valves with two mechanical valves is presented. The valves were perfused in a steady flow system, and comparisons between the valves were made on the transvalvular pressure distribution and drop, opening area, and leakage volume. Particular emphasis was placed on a slit-type bileaflet polymer valve which was newly designed and fabricated in our research group. The results showed that the functional characteristics of a slit-type bileaflet polymer valve compared favorably with that of mechanical valves. This valve may be a viable and inexpensive alternative, especially for short-term use in TAH or VAD systems.     

Ultra-precision lapping of machinable ceramic Si3N4-BN by in-process electrolytic dressing

The machinable ceramic Si₃N₄-BN is a material which is increasingly being employed for automobile bearings and machinable ceramics. This material is very hard and has high resistance against volatile temperature and wear. It's efficient quality and accurate surfaces have always been of high demand for many applications in the industrial field. Besides, this material is varied by the percentage of BN contained in it, and the characteristics of lapping also varies according to this percentage of BN. Hence, in-process electrolytic dressing for ultra-precision lapping was introduced and used to experiment with the differing BN percentages in machinable ceramic Si₃ N₄. Metal-bonded super-abrasive diamond lapping wheels have superior qualities such as high bond strength, high stability and high machinability. The major problems encountered are wheel loading and glazing, which impedes the effectiveness of the cast-iron bonded diamond lapping wheel and, therefore, dressing should be considered. In this respect, in-process electrolytic dressing (IED) is proposed as an effective method regarding continuous protruding abrasives on the surface of wheels, whereby loading and glazing phenomena can apparently disappear. In this paper, the machining characteristics of machinable ceramic Si₃N₄-BN have been studied by adapting the IED lapping process in terms of the percentage of h-BN material.     

Bio-information scanning technology using an optical pick-up head

We have developed a low cost and a highly compact bio-chip detection technology by modifying a commercially available optical pick-up head for CD/DVD. The highly parallel and miniaturized hybridization assays are addressed by the fluorescence emitted by the DNA-chip using the optical pick-up head. The gap between the objective lens and the bio-chip is regulated by the focus servo during the detection of the fluorescence signal. High-resolution and high-speed scanning is effectively realized by this simple scanning system instead of utilizing high-precision mechanism. Regardless of achievement of effective detection mechanism, the technique of fluorescence detection can prove to be disadvantageous because of the low stability of the dyes with low S/N ratio and an expensive setup such as a PMT detector is always required for fluorescence detection. We propose, for the first time, a novel scanning scheme based on metal nanoparticles in combination with a bio-chip substrate having a phase change recording layer. We found that the phase change process is highly affected by the existence of the densely condensed metal nanoparticles on the phase change layer during the writing process of the pick-up head.     

A cross-sectional analysis of composite beams based on asymptotic framework

This paper presents the accurate prediction of static behavior of composite beams with arbitrary cross-sections. The asymptotic recursive formulation is reviewed first, where the initial three-dimensional problems are split into the macroscopic 1D problems and the microscopic 2D problems. The finite element formulation for the microscopic 2D problems is then presented in order to find the crosssectional warping solutions. The warping solutions obtained contribute the cross-sectional properties to the macroscopic 1D problems. The end effect of the 1D beam problem is also considered via the kinematic correction for a displacement prescribed boundary. The approach presented is applied to the beams with relatively complicated material distributions and cross-sectional geometry. As numerical test-beds, a three-layered sandwich beam and a composite beam with the multi-cell cross-section are taken to analyze the local deformation. A parametric study is also carried out to investigate the significance of shear deformation due to the cross-sectional orthotropic characteristics. The cross-sectional deformation is predicted based on the asymptotic framework. The accuracy of the present approach is assessed by comparing the results obtained with the 3D FEM solutions obtained by ANSYS.