Circular Block Research Articles

Monomer conversion of composite dental resins photoactivated by a halogen lamp and a LED: a FT-Raman spectroscopy study

Eighteen circular blocks of resins cured either by a LED or a halogen lamp (20, 40 and 60 s), had their top (T) and bottom (B) surfaces studied using a FT-Raman spectrometer. Systematic changes in the intensity of the methacrylate C=C stretching mode at 1638 cm-1 as a function of exposure duration were observed. The calculated degree of conversion (DC) ranged from 45.0% (B) to 52.0% (T) and from 49.0% (B) to 55.0% (T) for the LED and halogen lamp, respectively. LED and halogen light produced similar DC values with 40 and 60 s of irradiation.

Pressure drop and heat transfer of arrays of in-line circular blocks on the wall of parallel channel

Pressure drop and heat transfer of arrays of in-line circular blocks on the wall of a parallel channel are measured. Diameter and height of the blocks are 40 and 18 mm, respectively, while pitches of the blocks are varied. The effects of the number of lines and rows and other factors on pressure drop and heat transfer are investigated. The pressure loss coefficient ζ is the sum of the pressure drop across three regions, the inlet, intermediate and outlet regions, and is formulated as an empirical equation that agrees with experimental data to within ±10%. Average heat transfer coefficient of the first row of blocks is 10% lower than that of the second row. Coefficients of the first 5 rows Nu m i , are approximated to within ±10% by Nu m i =0.118( Re/ β) 0.75, where β is the opening ratio. The average Nusselt number of the second to fifth rows is also correlated to fan power, P w, to within 5% by Nu ave=190 P w 0.25, where P w=Δ PU m A 0,Δ P is the pressure difference, U m is the mean velocity and A 0 is the cross-sectional area of the duct. Finally, the Nusselt number is represented by a non-dimensional expression as Nu ave=0.134( ζ 1/3 Re) 0.75.

Degree of conversion of composite resin: a Raman study.

Near infrared Raman spectroscopy (RS) was used to monitor, in vitro, the degree of conversion (DC) of composite resins (Z100, 3M), photoactivated by both the halogen lamp and the argon laser beam. Several methods were used to study the alterations of composite resins. Vibration methods such as RS allow a precise assessment of the depth of polymerization and the degree of conversion of composite resins. Sixty circular blocks of resin (7 mm x 2.5 mm) were cured using a halogen light source (n=30, lambda=400-500 nm, power density=478 mW/cm2) or an argon laser beam (n=30, lambda=488 nm, power density=625 mW/cm2) using the same irradiation time (5, 10, 20, 30, 40, and 60 sec). The directly irradiated (top) and the non-irradiated (bottom) surfaces were analyzed immediately after curing by Raman spectroscopy. The Raman results show systematic changes of the relative intensities between the peaks at 1610 (aromatic C=C stretching mode) and the 1640 cm(-1) (methacrylate C=C stretching mode), as a function of irradiation time. After 60 sec of irradiation time, the maximum degree of conversion reached for the samples cured either by the argon laser or halogen lamp was 66.4% and 62.2%, respectively. The argon laser was more effective and showed better biocompatibility, with less residual monomer in the bottom (2.5 mm). These results show that RS can be used as an effective method to study the degree of conversion of composite resins.

Dosimetric evaluation and clinical application of virtual mini-multileaf collimator.

One of the major concerns with multileaf collimators (MLC) is the jagged field edge that produces a larger penumbra compared with that produced by a Cerrobend block. The dosimetric undulation of the MLC can be minimized by replacing an existing MLC with a mini-MLC, an expensive replacement, or by software implementation, which essentially converts a regular MLC into a virtual mini-MLC. In this study, the dosimetry in the penumbra region of a virtual mini-MLC replacing the Cerrobend block is investigated for clinical applications. HD270, a software program implemented by Siemens (Concord, CA), combines the use of an MLC and a table translation perpendicular to the leaf plane to produce a smooth field edge, thus reducing isodose undulation. Three different step resolutions are available: 5 mm, 3 mm, and 2 mm. Using film dosimetry, the penumbra regions are studied at two different depths for clinical blocks and corresponding MLC setup, as well as HD270 with different resolutions for both 6-MV and 15-MV x-ray beams. The dose delivery time for HD270 on auto-sequencing mode is compared with the use of Cerrobend blocks. The clinical applications of HD270 in head-and-neck (head and neck) and prostate treatments are investigated. For single-field irradiation, the 80-20% penumbra widths for both the 45 degrees block and the circular block are reduced with HD270 compared with MLC for both 6 and 15 MV at different depths. At 2-mm resolution, the scalloping isodose lines (IDLs) with MLC completely disappear, although the penumbra is still larger than the Cerrobend block. On the other hand, the difference in dose undulations between 2-mm and 3-mm resolution is small. In the head and neck irradiation, the 80-20% widths with HD270 are 1 to 2 mm less than MLC, but they are still 2 mm wider than with a Cerrobend block. The 50% IDL is reduced by 2 mm with HD270 compared with MLC, which provides safety near spinal cord. Dose-volume histogram (DVH) calculations for the different shielding techniques indicate that the HD270 improves the spinal cord dose distribution significantly compared with MLC. A similar improvement in dose undulation is observed for the prostate case. In the dose region, >60% of the prescribed dose, there is approximately 10% less irradiated volume for the rectum when HD270 (3 mm resolution) is employed compared with MLC. The treatment time was compared with that from the Cerrobend block, and it was found that even at 3-mm resolution, there is a 20% reduction in treatment time in a head and neck treatment; with a 2-mm resolution, there is a 15% increase in time. The isodose undulation due to MLC can be significantly reduced with the HD270. Clinical application with HD270 for head and neck and prostate irradiation provides a smaller penumbra region compared with MLC, although it still gives a larger one compared with the Cerrobend block. In the clinical cases presented in this study, the 3-mm resolution is the most effective in improving the penumbra and delivery time. The HD270 implementation is a versatile and cost-effective solution for reducing MLC undulation.

Round-dance neighbour designs from terraces

In a round-dance neighbour design, an odd number v of objects is arranged successively in ( v−1)/2 rings (circular blocks) such that any two of the objects are adjacent to one another in exactly one ring. A round-dance neighbour design is also a Hamiltonian decomposition of the complete graph on v vertices. We show how such designs can be constructed from terraces, which are building blocks for row-complete Latin squares. A round-dance neighbour design is equivalent to a Tuscan square in which the reverse of each row is also a row. Terraces for the cyclic group of order n are used to construct elegantly patterned round-dance neighbour designs for n2 m +1 objects for any positive integer m.

A study on a generalized parametric interpolator with real-time jerk-limited acceleration

The impossibility of exact arc length computation for ‘standard’ parametric curves such as Bézier/B-spline curves makes it difficult to generate a feedrate profile with desired accelerations in real-time. This paper presents a new recursive trajectory generation method that estimates an admissible path increment and determines the initiation of the final deceleration stage according to the distance left to travel estimated at every sampling time, resulting in exact feedrate trajectory generation through jerk-limited acceleration profiles for the parametric curves. The proposed approach allows the feedrate profile to be dynamically adjusted according to geometrical path constraints for the curved path. The simulation result has been also provided to illustrate the generation of smooth feedrate profile encompassing a sequence of mixed NC blocks including traditional linear and circular blocks.

Matrix Controller Design and Deadlock Analysis of Automated Manufacturing Systems. Part 1. Designing the Matrix-Based Controller

A system theory approach is used to design rule-based discreteevent controllers for the sequencing of jobs in manufacturing systems. The controller is described in terms of matrix equations that are easy to implement on a personal computer. Industrial engineering (IE) techniques and the concepts of Petri nets (PN) are included. A standard bill of materials (BOM) is used in the first design step to make a task sequencing matrix. Then a resource requirement matrix is constructed to add non-shared resources and shared resources (e.g. pallets, transport robots, and material handling machines). Non-shared resources are controlled using inner decision loops. However, shared resources require outer decision loops for dispatching and routeing that resolve conflicts, taking into account the specified performance measures to be optimised (e.g. percentage of idle time, throughput, etc.). Failures are simply represented as disturbance inputs, allowing design for failure recovery. The rule-based controller design algorithm is a step-by-step procedure with repeatability and guaranteed conflict/deadlock resolution. It shows that the closed-loop system, once designed, is equivalent to a Petri net (PN); this gives, as a by-product, an algorithm for PN design. Furthermore, the matrix formulation allows a rigorous analysis of deadlocks in terms of circular wait and blocking, and the resources available.

ESTIMATES OF STANDARD DEVIATION OF SPEARMAN'S RANK CORRELATION COEFFICIENTS WITH DEPENDENT OBSERVATIONS

We consider the problem of estimating the standard deviation of the Fisher-transformed Spearman's rank correlation coefficient between two random variables X and Y when both or either of them is serially correlated. When X or Y is not i.i.d., Efron's bootstrap (EB) and the jackknife fail to capture the autocorrelation structure in the data. The circular block bootstrap (CBB) and the stationary bootstrap (SB) can be applied as alternative nonparametric resampling schemes for stationary time series. When we can assume a time series regression model, we can apply the parametric bootstrap (PB) and the bootstrap of residuals from the model (RB) to estimate the standard deviation. We compare these six methods—EB, the jackknife, CBB, SB, PB, and RB—of estimating the standard deviation, using the simulated data which have a highly correlated first order autoregression model. As we expect, the conventional bootstrap and the jackknife perform most poorly, and the PB and RB taking into account the time series model structure are the best in bias and mean squared errors. When estimating the standard deviation of the untransformed Spearman's rank correlation, we observe a very similar result.

Wireless multicarrier communications

Relying on basic tools such as eigensignals of linear time-invariant systems, linear and circular block convolution, and fast Fourier transforms (FFTs), this article develops a systematic discrete-time framework and designs novel systems for single- and multiuser wireless multicarrier communications-a field rich in signal processing challenges that holds great potential in various applications including audio/video broadcasting, cable television, modem design, multimedia services, mobile local area networks, and future-generation wideband cellular systems. Wireless multicarrier (MC) communication systems utilize multiple complex exponentials as information-bearing carriers. MC transmissions thus retain their shape and orthogonality when propagating through linear time-dispersive media, precisely as eigensignals do when they pass through linear time-invariant (LTI) systems.

Comparison of interpolated vs. calculated micro-multileaf settings in dynamic conformal arc treatment

Stereotactic radiosurgery has developed into a technique where patient positioning and treatment delivery can be performed with submillimeter precision. Achievement of this level of precision has allowed margins to be significantly reduced, and in some cases, removed altogether. Joined with these reductions in treatment margin has come a desire to shape the radiation beam, further limiting dose to normal tissues. Initial applications of shaped radiosurgery fields utilized circular blocking apertures in an attempt to shape the beam to these small volumes. The resultant dose distributions conformed well to spherical treatment volumes but were inadequate for situations where the volume of interest was irregular in shape. Other techniques, such as applying these circular apertures through multiple isocenter positions to a single volume, have been investigated as possible ways to better conform dose distributions to these irregularly-shaped volumes. Recent technological advances allow the use of micromultileaf collimators which dynamically shape the beam by adjustment of individual leaves as the gantry rotates through the arc. With margins potentially so tight, accurate evaluation of these dynamically adjusting treatment parameters becomes critical. Our current treatment planning software evaluates adjustments of the leaf positions in increments of 10° and then does a linear interpolation between increments. Treatment delivery, however, is performed with adjustment in leaf position more consistent with a 1° increment. This paper compares the individual position of each leaf as determined for the 10° interpolation to required changes in leaf position when the calculation is performed at increments of less than 10°. Our data suggest that there are instances where improvements can be seen when corrections in leaf positions are made at these smaller increments.

Pressure Drop and Heat Transfer of Arrays of In-Line Circular Blocks on the Wall of Parallel Channel.

Pressure drop and heat transfer of arrays of in-line circular blocks on the wall of parallel channel were measured. The diameter and height of the block were 40 mm and 18 mm, respectively. The effects of the pitches of the blocks, the number of line and row and the other factors on the pressure drop, △p, and heat transfer were clarified. The pressure drop coefficient, ζ, is given by the sum of the pressure drop of three regimes : the inlet, intermediate and outlet part. And the coefficient ζ can be formulated and the recommended equation agrees with the experimental data within ±10%. The average Nusselt number of the block of 1st row is 10% lower than that of 2nd row. Those of 1st to 5th rows, Numican be approximately expressed within ±10% by the following equation : Numi=0.118(Re/β)0.75where β is the opening ratio. The average Nusselt number of 2nd to 5th rows was also correlated by using the pumping power, Pw, within 5% as follows : Nu^^-=190P0.25w, where Pw=△pUmAo, Um is the mean velocity and Ao is the cross-sectional area in a duct. Finally, the Nusselt number is represented by the non-dimensional expression as follows : Nu^^-=0.134(ζ1/3Re)0.75.

Algorithm and Design of an Intelligent Digital Integrated Circuit for a Watermelon Harvesting Robot

We propose an algorithm and design of an intelligent digital integrated circuit for recognition of circular patterns in a binary image based on template matching using a modified matching degree. The proposed system consists of a preprocessor #1 (noise reduction, coarsening, and edge detection), a preprocessor #2 (noise filtering and location parameter detection), and a circular pattern recognition block. The proposed system is implementable onto field programmable gate arrays (FPGAs) and forming part of the vision system for a watermelon harvesting robot. Functional verification, logic synthesis, and implementation are detailed for the FPGA circular pattern recognition block.

Analysis of Deadlock and Circular Waits Using a Matrix Model for Flexible Manufacturing Systems

The problem of deadlock in a large class of reentrant flowline systems is analysed based on a Petri net model. The relation between deadlock and circular waits is established by rigorously defining the situation of circular blocking. Deadlock analysis is then performed in terms of circular waits and their associated structures, the so-called critical siphons and critical subsystems. A dynamical system representation obtained by coupling the Petri net marking transition equation with the matrix rule-based controller equations is adopted. The task of computing the Petri net structures of deadlock analysis is largely simplified (operations involved are of polynomial complexity) by using the matrices of this system description. An on-line maximally permissive control policy for deadlock avoidance (MAXWIP) is then devised. This can be efficiently implemented by incorporating the “outer-loop” control decisions via certain dispatching control inputs. The result is a dispatching control with deadlock avoidance, which is a generalized kanban scheme.

An approximate analytical solution for the initial transient process of close-contact melting on an isothermal surface

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.

Bootstrapping the sample means for stationary mixing sequences

We propose a circular block resampling procedure to modify Künsch's moving block bootstrap. Our procedure has the special feature that the resampled data are like drawing from the empirical distribution function of dependent observations. No information is lost concerning the nature of dependency of the original observations coming from a general stationary sequence. We prove two general theorems on bootstrapping sample means for stationary sequences. Applications to stationary α-mixing, ρ-mixing and φ-mixing sequences are also discussed.

Block rotation in western Turkey and elsewhere: 2. Theoretical models

Rotation of domains within the upper crustal brittle layer around vertical axes has been documented in many actively deforming regions. Some domains in western Turkey and elsewhere comprise sets of blocks that are bounded by subparallel faults, are elongated and angular in plan view, coupled to the underlying plastic deformation, and rotate in the same sense at a uniform rate that may equal approximately half the vertical vorticity in the underlying plastic deformation. However, other domains in western Turkey that appear approximately circular in plan view and comprise a single block with little internal deformation appear to rotate in the opposite sense to the regional counterclockwise vertical vorticity, and are thus apparently decoupled from the underlying plastic deformation. Rotational behavior of any block in the brittle layer may be affected by torques acting both on its base and on its margins. The torque acting on the base of a circular block with radius R caused by viscous coupling with the underlying plastic deformation is likely to be proportional to R4, as well as proportional to the difference between the angular velocity of the block and that expected given the vertical vorticity in the underlying plastic deformation. The frictional torque acting on the margins of such a circular block is likely to be proportional to R2. Thus, provided a circular block has sufficiently small radius, the frictional torque acting its margins will exceed the viscous torque acting on its base. Frictional torques generated in this manner may cause circular blocks to rotate in the opposite sense to the regional vertical vorticity beneath the brittle layer. The circular domains identified in western Turkey comprise single blocks, are within the size range for frictional torques to dominate viscous torques, and their geometrical relationship to adjacent domains and to the regional deformation pattern allows them to rotate in the opposite sense to their surroundings. This suggests that frictional torques may cause their observed clockwise rotations.

Bending of Composite Plates-I

The problems of bending of aelotropic incompressible composite circular blocks into elliposidal shell have been studied following the method of Seth, et al. and a particular case has been obtained.

Finite Bending of Blocks

The problem of bending of a circular block with concentric hole into ellipsoidal shell is considered, and the earlier results have been obtained as particular cases.

Theoretical head variograms for steady flow in statistically homogeneous aquifers

Flow through two‐dimensional porous formations is modeled as a random process using an approximate formulation of flow physics in order to obtain an expression for the head variogram. (The variogram is related to the variance of the head difference between two points separated by a vector h and has leapt into prominence owing to its central role in kriging.) The model domain investigated here is unbounded, composed of arbitrarily placed circular blocks of random, statistically homogeneous dimension and transmissivity, these two properties being independently distributed. The model medium can represent only transmissivity autocorrelation functions which decline monotonically from 1 to 0. Steady, uniform average flow is investigated. Flow physics are simplified by ignoring any differences among blocks of the same size and transmissivity and then using their random setting to ease spatial integrations involved in head statistics. The head variogram proves significantly anisotropic, with heads differing more widely on average for a fixed lag parallel to the head gradient than perpendicular to it. Field practice presently ignores anisotropy; the implications are examined for a hypothetical case and indicate that kriged standard deviation is overestimated perpendicular to the mean flow and underestimated parallel to it. For lag magnitude greater than the largest block diameter the variogram is logarithmic in the lag magnitude and proportional to the head gradient squared. This leads to a technique to reduce data scatter in empirically fitted variograms. Once an empirical head variogram is selected, the inverse problem may be solved for a particularly simple medium structure.

Neighbor designs

A neighbor design is an arrangement of r copies of each of v varieties into b circular blocks of size k > 1 such that neighboring objects in each block are distinct and every pair of distinct varieties appears as neighbors in the set of circular blocks exactly λ times. Necessary conditions for the existence of a neighbor design with these parameters v, k, λ, r, b are that r = λ(v − 1) 2 , and b = λv(v − 1) 2k be integers for k > 2 and v > 2; and for k = 2 or v = 2, it is also necessary that λ be even or k be even, respectively. In this paper we show that these necessary conditions are also sufficient by giving a method to construct a neighbor design for all values of the parameters satisfying the necessary conditions.