Mirror Image Method Research Articles

A REFINED NUMERICAL SOLUTION TO THE INCLUSION PROBLEM

A refined numerical method for the inclusion problem involving known, but otherwise arbitrary shaped multiple regions with eigenstrains is advanced in this paper. The newly advanced algorithm, employing the mirror image method, derives its effectiveness from implementation of a hybrid multi-dimensional algorithm, based on convolution and correlation theorems. A good validation for various regularly shaped inclusions containing uniform eigenstrains is found. The method is subsequently applied to predict a critical interaction distance between two neighboring spherical inclusions, containing uniform or non-uniform dilatational eigenstrains.DOI: http://dx.doi.org/10.5755/j01.mech.19.3.4657

Annual risk of tuberculous infection among schoolchildren in Bhutan

School-based survey in the mountainous nation of Bhutan. To estimate the annual risk of tuberculous infection (ARTI) among children aged 6-8 years. A national-level tuberculin survey was carried out among children attending 64 schools selected by two-stage cluster sampling. The study population was comprised of children without and with bacille Calmette-Guérin (BCG) scar. Tuberculin testing was performed using 2 tuberculin units of purified protein derivative RT23. The maximum transverse diameter of induration was measured at 48-72 h. Of 6087 satisfactorily test-read children, 82% had a BCG scar. The frequency distribution of tuberculin reaction sizes in all children (with and without BCG scar) did not reveal the mode for tuberculous reactions. The mode seen at 17 mm among children without BCG scar was applied to estimate the prevalence of infection among all children using the mirror-image method. Estimation was also undertaken by shifting the mode by 1 mm on either side. The ARTI computed from the prevalence thus estimated varied between 0.2% and 0.7%. There was no difference in the prevalence of infection by BCG scar status, implying that the estimated ARTI was not influenced by BCG-induced tuberculin sensitivity. The ARTI has declined in Bhutan compared to the 1991 survey estimate of 1.9%.

SCHEMES OF ELECTRIC MACHINES REPLACEMENT

The article contains the equivalent circuits for direct current generators and motors, and also for synchronous machines. At a stage of initial knowledge and the analysis of electrical machines behavior they are so effective and useful, as well as equivalent circuits of transformers and asynchronous electrical machines. It is reached on the basis of the appendix of positions EET (multi-terminal networks, the Thevenin’s theorem, a method of mirror images, etc.) to the theory of electrical machines. Thereby the link providing research of all types of electrical machines by a uniform technique on the basis of principles of system and continuity is created that is important at construction of educational process.

A Productivity Evaluation Model and Its Application for an Infill Horizontal Well in Different Types of Reservoirs

Productivity evaluation for infill horizontal well should take into account the interference of other oil or water wells in the flooding pattern. On the basis of the mirror-image method and source-sink theory, a semianalytical model of productivity evaluation for infill horizontal well in different types of reservoirs was built, in which the effect of boundary, the interference of other wells, the randomicity of flooding pattern, and the pressure drop along the horizontal lateral were taken into account. Application of the novel semianalytical model has demonstrated its reliability and usefulness. It is an effective method for the productivity evaluation for infill horizontal well in different types of reservoirs.

Banking of fresh-frozen prostate tissue using the alternate mirror image protocol: methods, validation, and impact on the pathological prognostic parameters in radical prostatectomy

We evaluated the value of the 'alternative slices mirror image method' used in prostate tissue banking in terms of predicting the sampling of cancerous tissue while preserving the pathological prognostic information. The concordance of diagnosis between banked sections and their mirror image paraffin- sections was studied using 50 cases corresponding to 400 H&E sections taken from 400 banked frozen blocks (two presumed benign and two presumed cancer for each case). The mean number of paraffin blocks in each case was 21. On average 29% of the prostate gland was banked and banked tissue contained cancer in 47 cases (94%). There was no difference between the concordant and discordant groups in terms of the final Gleason score, pathological stage, prostate size, number of banked blocks and the percentage of the prostate submitted for banking. However, concordant cases had larger foci of cancer in the mirror image paraffin block (P=0.0088). In addition, the surgical margins sections which are not banked using this method provided important information about the pathological stage, surgical margins status and the final Gleason score in 2.6, 2.6, and 1.3% of cases, respectively. The 'alternative slices mirror image method' is a straightforward method that is highly efficient in banking prostatic cancerous tissue. Overall, tumor volume and especially size of tumor foci in the image paraffin block are the most important factors in dictating the success rate of banking frozen cancerous tissue. Including 'surgical margins' sections for histology provides additional important prognostic information in a minority of cases.

Dynamic Antiplane Behavior for a Quarter Infinite Piezoelectric Medium with a Subsurface Circular Inclusion

Dynamic antiplane behaviors are investigated theoretically in this paper for a quarter infinite piezoelectric medium with a subsurface circular inclusion. Based on complex variable and mirror image method, the expressions are obtained on dynamic stress concentration factor (DSCF) and electric field intensity concentration factor (EFICF) at the inclusion’s edge caused by the interaction between the inclusion and the right angle edge under time-harmonic anti-plane shearing. While some calculating cases are plotted, so as to show how the frequencies of incident wave, the piezoelectric material’s parameters and the structure’s geometry influence on DSCF and EFICF. The calculating results indicate that dynamic analyses are important to a quarter-infinite piezoelectric medium with defects at the surface vicinity.

The Integral Equation of the Micro-Fracture's Electrical Logging Response

On the condition that integral surfaces lie in instrument surface, well wall and fracture surface, we have deducted the integral equation for computing the logging response of micro-fracture. From the theoretical result we know that the integral value of the micro-fracture item is direct proportion to micro-fracture opening. To proof-test the deducted equation, we take the geological model as the infinite layered micro-fractured formation, and then compare the result computed by this method and one got by mirror image method, which is regarded as the precise value. The computation result show that with the decrease of the fracture opening h, the computation precision of the micro-fractured integral equation is improved, and when the micro-fracture opening less then 100um, the computation result owns higher precision, so the logging result computed by this method listed would meet with the computing requirement of practical project.

Active Noise Control Using Acoustic Wave Reflection of a Parametric Loudspeaker

This paper deals with active noise control (ANC) using an acoustic wave reflection of a parametric array loudspeaker (PAL). Making use of the strong directivity of a sound radiation a PAL has, it is possible to avoid spillover phenomenon leading to the augmentation of sound pressure in other region of the targeted control point. The strong directivity, however, may be double-edged for ANC. If an obstacle exists between a PAL and a target control point, it may no longer achieve ANC as a sound diffraction cannot be expected. To overcome this problem, this paper presents a control strategy based upon the use of a sound reflection, and hence the sound beam of a PAL may detour the obstacle, arriving at the control point. First, fundamental properties of a sound beam reflection are investigated, thereby assuring the possibility of a sound reflection for ANC. Furthermore, mathematical description of a sound beam is performed using a mirror image method, control effect of ANC being clarified. Finally, an experiment is conducted, demonstrating the validity of the proposed method.

Experiments on the generation of internal wavesby a hemispheroid in a linearly stratified fluid

Experiments are conducted to examine the characteristics of internal waves generated by a towing hemispheroid model alongside the side wall of stratified fluid flume with a linear density distribution. By the measured results with multi-channel conductivity arrays, the wave patterns, the vertical displacement and the correlation velocity for such internal waves are analyzed. Two distinct types of internal waves are obtained in experiments. One is the body-generated internal wave by the steady source with respect to the hemispheroid model, and the other is the wake-generated internal wave by the unsteady source. The transition between these two types of internal waves occurs at a critical Froude number of FrS=1.6. The corresponding comparison with towing spheroid model experiments is carried out. It follows that the number FrS is about 2/3 that of the spheroid and that the transition is more rapid and its borderline is more clear-cut than those of the spheroid modes. The body-generated internal waves of both experimental models have identical characteristics, but the draining-water volume is about 2/3 that of the spheroid model. Their wake-generated internal waves possess similar variation tendencyies, but their wave speed is about 2/3 that of the spheroid model . It also proves that this mirror-image experimental method in the flume can increase the effective range of spatio-temporal evolvement of body-generated internal waves.

Analysis on background magnetic field to generate eddy current by pulsed gradient of permanent-magnet MRI

In this paper the analytical expressions for the magnetic field H and induction B in iron-pole plates generated by MRI gradient coil are given using line-current and the multilayer dielectric plate model with the mirror-image method. Eddy current emanates from the magnetic flux in the iron-pole plates. In order to fully suppress the eddy current, this magnetic flux should be fully eliminated. The research results indicate the magnetic permeability of the resist-eddy plate must be bigger than that of magnetic pole material, i.e. pure iron, and that the resist-eddy plate should be thick enough to be far away from its magnetic saturation.

Design of Wideband Balanced Folded-Arms Dipole Antenna for Mobile Handsets

Investigations of a wideband balanced antenna for mobile handsets covering three bands—GSM1800, GSM1900, and UMTS—are presented. Balanced antennas have advantages in handset applications as they are less affected by juxtaposition with human tissue than unbalanced types. The antenna is a slotted planar dipole with its arms folded and not connected at their ends. The antenna is fed by a balanced voltage source. The antenna impedance was investigated using two different methods, including an S-parameter method and a mirror image method. For the purpose of antenna stability evaluation and power gain measurement, a wide bandwidth planar balun was adopted and modified to feed the antenna from an unbalanced source. For validation, prototypes of the antenna were fabricated and tested. The calculated and measured results in terms of return loss show good agreement and the results also show good wideband characteristics.

ANALYTICAL AND NUMERICAL ANALYSIS OF FORCE AND STIFFNESS IN A DIAMAGNETIC BEARING

In this letter, a bearing consisting of a disk-shaped NdFeB permanent magnet levitated by a ferrite magnet with a diamagnetic stabilizer made of two bismuth blocks has been statically analyzed. The analysis, including levitation force and stiffness characteristics of this diamagnetic bearing, has been incorporated with the diamagnetic mirror image method based on the finite element and dipole approximation methods. Force equations of the levitated magnet are derived from the potential of the system in terms of magnetic, diamagnetic and gravitational interactions. The dipole approximation and finite element method were compared with each other. It is observed that while the dipole approximation (an analytical method) is successful in predicting the force and stiffness of the bearing, the finite element method, on the other hand, only estimates the levitation force. It is shown that the dipole approach has advantages over the finite element method for various perspectives such as calculation time and precision.

Features of the transition radiation field

The method of mirror images is used to calculate transition radiation (TR) at the plane interface between a vacuum and an ideally conducting medium. The total field is considered (that is, the TR field plus the fields of the uniformly moving charge and its mirror image) and its evolution in space and time is traced, considering fields as functions of space coordinates and time rather than represented by spectral components. Conditions are analyzed under which the separation and measurement of a TR field are possible.

Colloid-wall interaction in a nematic liquid crystal: The mirror-image method of colloidal nematostatics

The new area of nematic colloidal systems (or nematic emulsions) has been greatly guided by the fruitful analogy between the colloidal nematostatics and electrostatics. The elastic charge density representation of the colloidal nematostatics [V. M. Pergamenshchik and V. O. Uzunova, Eur. Phys. J. E 23, 161 (2007); Phys. Rev. E 76, 011707 (2007)] develops this analogy at the level of charge density and Coulomb interaction. It shows, however, that the colloidal nematostatics in three dimensions substantially differs from the electrostatics both in its mathematical structure and physical implications: the elastic charge and multipoles are dyads; similar charges attract while opposite charges repel each other, and so on. In this paper we consider the interaction between an elastic charge and elastic dipole with a nematic surface (wall) at which the director alignment is fixed. Using the mirror image method of electrostatics as a guiding idea, we develop the mirror image method in the nematostatics for arbitrary director tilt at the wall. A wall is shown to induce a repulsive 1R{4} force on the elastic dipole which, in general, is accompanied by its reorientation. External torque on the colloid induces an elastic charge therein and triggers switching to the 1R{2} repulsion. The dyadic nature of an elastic dipole is shown to be essential: a particle-wall interaction potential cannot be obtained in phenomenological theories with a single component dipole. In the introductory sections we discuss connection between the director-mediated interaction in two and three dimensions and the electrostatic interaction and consider different symmetries of elastic dipoles. Conservation of the torque components exerted upon colloids is shown to play the role of Gauss' theorem and determines the elastic charge dyad.

Effect of the electron drift in a transverse electric field on the width of spark channels in a multichannel sliding discharge

The effect of electron drift on the transverse size of the spark channels in a multichannel sliding discharge on a dielectric surface is considered in a semianalytic approximation. The strength of an electric field transverse to the channel axis is estimated by the mirror image method. The estimate obtained is used to analyze the differential equation for the density of electrons with allowance for their drift from the channel into the surrounding layers. It is shown that the channel expands to a certain steady-state radius at which an increase in the local electron density due to the ionization of atoms is balanced by its decrease due to the electron drift from the surface channel layer into the surrounding layers. Numerical estimates are carried out for the conditions of earlier experiments with discharges in He, Ne, Ar, and Xe. The analysis applies to the initial nanosecond stage of the spark development, when the hydrodynamic expansion of the channels is still insignificant.

Vehicle wheel aerodynamic testing, using the double-symmetry technique

Within the scope of wheel drag investigation, a mirror image method for simulating relative motions of wheels and moving ground for road vehicle aerodynamics was developed using a double-symmetry technique. An initial study using no-wheeled bluff body demonstrated feasibility. The current paper further extends this technique to a wheeled model vehicle. The concept, measuring approach and EFD and CFD evaluations are described. The double-symmetry approach enabled simulated on-road vehicle drag tests. With the ability to replicate deformations at tyre contact patch, the approach presents evaluation of rotating wheel effects on accessories and their actual contribution to the vehicle road load.

Study on the concentration distribution in a trapezoidal open-channel flow with a side discharge

The number and distribution of pollutant concentration in a trapezoidal open channel flow with a side discharge is calculated and effects of the bank gradient are investigated in this paper. A sigma-coordinate water quality numerical model is used to simulate the process of both water and pollutant transportation in the trapezoidal channel open flow. The diffusion coefficient used in the prediction is determined by two methods including constant coefficient and the depth-averaged k-epsilon turbulence closure model. The change of the concentration with the bank gradient is acquired based on the simulation of cases with different bank gradients. An analytical formula is derived by using the mirror image method and related diffusion theories, ignoring the discharge momentum and the influence of the opposite bank. The formula can predict the number and distribution of pollutant concentration with some acceptable errors. The results demonstrate that the bank gradient has great influence on the concentration distribution which will decrease with the increase of the bank gradient approximately following a hyperbolic law.

Vertical Distribution of the Mirror Image Returns Observed by TRMM PR and Estimated for a 35-GHz Radar

Abstract The vertical distribution of Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR)-observed precipitation reflectivity and their mirror image (MI) reflectivity are outlined in this paper. The purpose of this study is to investigate the possibility and the limitation of the MI method, which can be used to estimate rain attenuation. Because the MI returns are attenuated much more greatly than the direct image returns, and also because the MI return is affected by the surface reflection and surface scattering, the MI returns are much smaller and more complex than the direct image (DI) returns. However, because the MI returns might be contaminated by the surface or contributed by bistatic scattering near the surface, there are many strong mirror returns between the surface and below surface at 1 km. The ratio of detectable MI return pixels to detected DI return pixels depends on rain rate, target height, and storm height. In addition, differences also exist between the convective and stratiform rain. The reason for this might be because the difference of the surface cross section and the difference of the storm height between the two types of rainfall. Furthermore, the direct and the mirror returns for a 35-GHz radar are also estimated. The virtue of the MI method of the Ka-band radar may reside in expanding the dynamic range of the MI method from 4–30 to 0.6–30 mm h−1.

Alpha-recoil track densities in mica and radiometric age determination

Recoiling daughters of α -decaying U and Th impurities in mica and other minerals produce localised lattice damage: alpha-recoil tracks. The age of a sample can be calculated from the number of tracks per unit volume ( N ART ) . To this end, the mica is etched and the etch pits at the sites of recoil-tracks are counted under the optical microscope. Because the measured track densities increase with etching time, N ART is calculated from the fitted regression line. A number of problems inherent in this approach are overcome by the etch–anneal–etch and the mirror-image methods. The track densities determined with these methods are independent of etching time. Although both methods need improvement, they hold the potential of a precise determination of N ART from a single measurement in future recoil-track dating.

Conservative methods for reducing lateral translation postures of the head: A nonrandomized clinical control trial

Fifty-one retrospective, consecutive patients were compared to twenty-six prospective volunteer controls in a nonrandomized clinical control trial. Both groups had chronic neck pain and lateral head translation posture. For treatment subjects, beginning and follow-up pain scales and anteroposterior (AP) cervical radiographs were obtained after 12.8 weeks of care (average of 37 visits), while the duration was a mean of 12 months for control subjects. Digitized radiographs were analyzed for Risser-Ferguson angles and a horizontal translation distance of C2 from a vertical line through T3. For treatment, patients received the Harrison mirror-image postural methods, which include mechanically assisted manipulation, opposite head posture exercise, and opposite head translation posture traction. While no significant differences were found in the control group subjects' pain scores and AP radiographic measurements, statistically significant improvements were observed in the treatment group subjects' pain scores and lateral translation displacements of C2 compared to T3 (pretrial score: 13.7 mm, posttrial score: 6.8 mm) and in angle measurements.