Boundary‐Value Problems of Linear‐Transport Theory—Green's Function Approach

Case's technique utilizing Green's functions for dealing with boundary‐value problems of the neutron linear‐transport theory is exploited. We show that the Fourier coefficients of the Green's function over the Case spectrum are precisely the normal modes. In particular, if we assume that the scattering kernel is rotationally invariant (which indeed we do assume) and approximate it by a degenerate kernel consisting of spherical harmonics, the set of modes is deficient for problems lacking azimuthal symmetry. We also show that the expansion of the scattering kernel, in terms of spherical harmonics (or any set of orthogonal functions for that matter), permits the linear factorization of the Fourier coefficients of the Green's function in terms of the lowest element, with the proportionality functions consisting of complete orthogonal polynomials. As a consequence of this attribute of Fourier coefficients, the eigenfunctions (continuum and discrete) also factorize, which then permits decoupling of the appropriate singular integral equations. To illustrate our idea, we solve half‐space and slab problems. However, the basic procedure is kept sufficiently general so that the extension to problems involving other geometrics remains straightforward.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71085/2/JMAPAQ-11-10-3042-1.pd

Volt-ampere characteristics of cylindrical and spherical Langmuir probes for various potential models Scientific report

Volt-ampere characteristics of cylindrical and spherical Langmuir probes for various potential model

Performance of optimum detector structures for noisy intersymbol interference channels

The errors which arise in transmitting digital information by radio or wireline systems because of additive noise from successively transmitted signals interfering with one another are described. The probability of error and the performance of optimum detector structures are examined. A comparative study of the performance of certain detector structures and approximations to them, and the performance of a transversal equalizer are included

MEASUREMENT OF PLANTAR PRESSURE DURING HIGH IMPACT-SHORT CONTACT TIME SPORTS ACTIVITIES

INTRODUCTION Force Measurement is an important part of biomechanical research. Until now the measurement of plantar force during the more dynamic sports events have been primarily limited to the laboratory because the available systems capable of accurately measuring 'high impact-short contact-time' forces are not very portable. The purpose of this study was to evaluate the use of soft Parotec pressure sensors inside the shoe as a means of portable and reliable force measurement during jumping sport movements. METHODS The subjects (n =14) performed a series of 'depth jump' exercises simulated by a falling pendulum. Force curves were generated with the use of 4 soft Parotec force sensors (data collection rate 1000 Hz) which were held to the underside of the right fore-foot (Hallux, Metatarsals 1, 3, and 5) using tape and gymnastic shoes. Force curves were simultaneously generated using Kistler force sensors (data collection rate 1000Hz) which were used as control in evaluating the accuracy of the Parotec sensors. The following temporal aspects of the force curves were compared: total contact time (CT), time to first peak (TI), and time to second peak (T2). Further parameters were force at first peak(Fl), force at the saddle (FS) between the first and second peaks, and maximum force (F2). The times between initial contact and T1 and T2 were consistently (approx 70%) identical (+I- Oms) for both systems, although a variance of lms in either direction was seen in approximately 30% of the trials for both values. Although the time of initial contact was consistantly recorded the same by both systems the comparison of the exact total contact time was not usually possible because indistinct 'take-off' times were often measured by Parotec due to residual pressure in the shoe. As expected the force measured by the Parotec sensors recorded considerably less of the total force than the Kistler system. The Parotec sensors recorded force most accurately for the FS and F1 values where they captured up to 48% and 47% respectively of the force measured by the Kistler sensors. For the F2 force values they captured up to 32% of the force measured by Kistler. Greater discrepancies in force values were seen at higher total force values. CONCLUSIONS The comparison of the force curves in this study indicate that Parotec sensors, as used in the above described configuration for high impact-short contact time movements, are accurate in measuring important force parameters. This accuracy was best for the various time measurements. More experimentation is required in the of number of sensors and sensor placement to better measure the force for these type of movements

A sobering assessment of small-molecule force field methods for low energy conformer predictions

We have carried out a large scale computational investigation to assess the utility of common small-molecule force fields for computational screening of low energy conformers of typical organic molecules. Using statistical analyses on the energies and relative rankings of up to 250 diverse conformers of 700 different molecular structures, we find that energies from widely used classical force fields (MMFF94, UFF, and GAFF) show unconditionally poor energy and rank correlation with semiempirical (PM7) and Kohn–Sham density functional theory (DFT) energies calculated at PM7 and DFT optimized geometries. In contrast, semiempirical PM7 calculations show significantly better correlation with DFT calculations and generally better geometries. With these results, we make recommendations to more reliably carry out conformer screening

Quality care and safety know no borders

The public, governmental agencies, and payers expect medical professional organisations to develop practice guidelines and technical standards. The American College of Radiology proactively addresses these topics as well as other quality and safety interests including appropriateness criteria and accreditation. The College is also actively involved in development of a national radiology data base to collect data regarding quality and safety metrics in multiple areas. In addition, the College has developed RADPEER™, a simple, cost-effective process that allows peer review to be performed during the routine interpretation of current images. This paper discusses the efforts of the ACR in all of these areas