Block Geometry Research Articles

Design and characterization of a low-vibration laboratory with cylindrical inertia block geometry.

Many modern nanofabrication and imaging techniques require an ultra-quiet environment to reach optimal resolution. Isolation from ambient vibrations is often achieved by placing the sensitive instrument atop a massive block that floats on air springs and is surrounded by acoustic barriers. Because typical building noise drops off above 120Hz, it is advantageous to raise the flexural resonance frequencies of the inertia block and instrument far above 120Hz. However, it can be challenging to obtain a high fundamental frequency of the floating block using a simple rectangular design. Here, we design, construct, and characterize a vibration isolation system with a cylindrical inertia block, whose lowest resonance frequency of 249Hz shows good agreement between finite element analysis simulation and directly measured modes. Our simulations show that a cylindrical design can achieve a higher fundamental resonance frequency than a rectangular design of the same mass.

Metal-organic frameworks from pre-synthesized heterometallic (d-f) complexes: Synthesis, structure and luminescent properties

The use of heterometallic pivalate complexes [M2Ln(piv)7(H2O)2] (M = Zn2+, Cd2+; Ln = Eu3+, Tb3+; piv– = pivalate anion) as sources of heterometallic sites in the reaction with 1,4-naphthalenedicarboxylic acid (H2ndc) makes it possible to fully preserve the geometry of the building block in the structure of the obtained metal–organic organic frameworks (MOFs). Solvothermal synthesis in dimethylformamide (DMF) results in a series of isostructural layered MOFs (Me2NH2)[M2Ln(dmf)2(ndc)4]·DMF. The structure of the MOF (Me2NH2)[Cd2Tb(dmf)2(ndc)4]·DMF was determined by the means of single crystal X-ray diffraction analysis. Compounds based on europium cations show characteristic luminescence in the red region, while compounds based on terbium cations do not exhibit characteristic green luminescent properties and have ligand-centered emission. The reactions of [Cd2Eu(piv)7(H2O)2] under similar conditions with 2,5-furandicarboxylic acid (H2fdc) are complicated, with complete destruction of the heterometallic fragment. The composition and structure of the homometallic MOF (Me2NH2)2[Cd(fdc)2]·DMF·H2O obtained in such conditions were determined by single crystal X-ray diffraction performed using synchrotron radiation.

Modelling of the Micro Lubricating Gap Geometry Between Valve Plate and Cylinder Block in an Axial Piston Pump

The paper focuses on the effect of force and torque balance (FTB) of cylinder block, coaxiality error (CE) between main shaft and cylinder block, and other factors, especially eccentric wear (OTEW) of valve plate on wedge angle of the micro lubricating gap between valve plate and cylinder block, and a novel trigonometric function model of the gap geometry and mechanical balance equations of cylinder block are proposed. The three eddy current displacement sensors are used to measure the gap thickness. The results show that, the theoretical wedge angle due to FTB is nearly 1.2E-4, the test wedge angle owing to CE 1.65E-4~4.3E-4, the wedge angle by OTEW about 1.35E-3, therefore, CE and OTEW have a larger impact on the wedge angle. The test results demonstrate the total wedge angle obviously increases with the enlargement of swash plate angle but slightly rises with the increasing working pressure.

Useful island block geometries of a passive intensity modulator used for intensity-modulated bolus electron conformal therapy.

PurposeThis project determined the range of island block geometric configurations useful for the clinical utilization of intensity‐modulated bolus electron conformal therapy (IM‐BECT).MethodsMultiple half‐beam island block geometries were studied for seven electron energies 7‐20 MeV at 100 and 103 cm source‐to‐surface distance (SSD). We studied relative fluence distributions at 0.5 cm and 2.0 cm depths in water, resulting in 28 unique beam conditions. For each beam condition, we studied intensity reduction factor (IRF) values of 0.70, 0.75, 0.80, 0.85, 0.90, and 0.95, and hexagonal packing separations for the island blocks of 0.50, 0.75, 1.00, 1.25, and 1.50 cm, that is, 30 unique IM configurations and 840 unique beam‐IM combinations. A combination was deemed acceptable if the average intensity downstream of the intensity modulator agreed within 2% of that intended and the variation in fluence was less than ±2%.ResultsFor 100 cm SSD, and for 0.5 cm depth, results showed that beam energies above 13 MeV did not exhibit sufficient scatter to produce clinically acceptable fluence (intensity) distributions for all IRF values (0.70–0.95). In particular, 20 MeV fluence distributions were unacceptable for any values, and acceptable 16 MeV fluence distributions were limited to a minimum IRF of 0.85. For the 2.0 cm depth, beam energies up to and including 20 MeV had acceptable fluence distributions. For 103 cm SSD and for 0.5 cm and 2.0 cm depths, results showed that all beam energies (7–20 MeV) had clinically acceptable fluence distributions for all IRF values (0.70–0.95). In general, the more clinically likely 103 cm SSD had acceptable fluence distributions with larger separations (r), which allow larger block diameters.ConclusionThe geometric operating range of island block separations and IRF values (block diameters) producing clinically appropriate IM electron beams has been determined.

Double‐Layered Supramolecular Prisms Self‐Assembled by Geometrically Non‐equivalent Tetratopic Subunits

AbstractSupramolecular cages/vesicles in biology display sophisticated structures and functions by utilizing a few types of protein subunit quasi‐equivalently at distinct geometrical locations. However, synthetic supramolecular cages still lack comparable complexity to reach the high levels of functionality found in natural systems. Herein we report the self‐assembly of giant pentagonal supramolecular prisms (molecular weight >50 kDa) with tetratopic pyridinyl subunits serving different geometrical roles within the structures, and their packing into a novel superstructure with unexpected three‐fold rotational symmetry in a single two‐dimensional layer of crystalline state. The formation of these complicated structures is controlled by both the predetermined angles of the ligands and the mismatched structural tensions created from the multi‐layered geometry of the building blocks. Such a self‐assembly strategy is extensively used by viruses to increase the volume and complexity of capsids and would provide a new approach to construct highly sophisticated supramolecular architectures.

A New Thermal Conductivity Model and Two-Phase Mixed Convection of CuO-Water Nanofluids in a Novel I-Shaped Porous Cavity Heated by Oriented Triangular Hot Block.

This paper investigates the cooling performance of nanofluid (NF) mixed convection in a porous I-shaped electronic chip with an internal triangular hot block using Buongiorno’s two-phase model. This type of cavity and hot block geometry has not been studied formerly. The NF was assumed to be a mixture of water and CuO nanoparticles (NP) up to 4% of volume concentration. As most published mathematical models for the thermal conductivity of NF give inaccurate predictions, a new predictive correlation for effective thermal conductivity was also developed with a high accuracy compared to the experimental data. The results showed that any increase in the NP volume concentration enhances the average Nusselt number () and the normalized entropy generation, and reduces the thermal performance of the cavity in all orientations of the hot block. The maximum enhancement in cooling performance was 17.75% and occurred in the right-oriented hot block in the sand-based porous cavity. Furthermore, adding the NP to the base fluid leads to a more capable cooling system and enhances the irreversibility of the process.

NATURAL CONVECTION IN A MICROPOLAR NANOFLUID FILLED OPEN RECTANGULAR ENCLOSURE EMBEDDED WITH A HEATED OBJECT OF DIFFERENT GEOMETRIES

A numerical investigation has been performed to analyze heat convection through a micropolar nanofluid in an open rectangular enclosure. It embedded the inner heated object of different geometries and finite heat source length on the bottom wall with uniform heat flux. The remaining portion of the wall containing heat source and all the remaining walls are assumed as adiabatic except the top wall. Successive over-relaxation (SOR) method coupled with Gauss-Seidel iteration technique are employed in order to numerically tackled the nonlinear model momentum and energy equations. The effect of the calibrated parameters such as Rayleigh number, length of the wall heat source, the geometry of the inner block, vortex viscosity parameter, the type of nanoparticles, and the concentration of nanoparticles on the flow and thermal performance is studied. The computed results show that increasing in the Rayleigh number and the concentration of nanoparticles have a positive effect on Nusselt number whereas increasing in wall heat source length and vortex viscosity attenuates the Nusselt number. Also, the geometry of the inner block has effect in the flow pattern and the temperature distribution.

Geomorphology and triggering mechanism of a river-damming block slide: February 2018 Mangapoike landslide, New Zealand

Landslide dams can be very dangerous, with inundation occurring via rising waters upstream, and flooding downstream via dam breaching. Here, we report on a landslide that dammed the Mangapoike River in eastern North Island, New Zealand. The landslide is a low-angle wedge failure in the Miocene weak rock sandstones and mudstones of the Tolaga Group, forming a landslide dam (volume c. 8 million m3) and a lake 50 m deep with a surface area of 0.35 km2, before explosives were used to form a dam spillway to decrease lake level. The landslide formed along an escarpment in northwest-dipping sandstones, and is characterised by a linear lateral scarp, a headscarp, and a bedding-plane rupture surface, which controlled the landslide block geometry. The headscarp and lateral scarp have developed along propagating vertical fractures. The slide surface is a smoothed, northwest-dipping bedding plane, and intersects the vertical fractures in the lateral scarp, forming a wedge. While the principal failure mechanism was sliding involving a single large wedge-shaped block, the rapid movement led to disintegration of most of the block. Part of the detached slide block remained intact, but most of the displaced mass forming the landslide dam is disaggregated blocks in a sandy-silty matrix. Rainfall and meteoric groundwater probably did not initiate failure. Instead, river incision of the dip slope toe, and overpressurisation of fluids that are known to accumulate in sandstones overlain by impermeable mudstones in the region, probably decreased the effective stress along the existing bedding plane, initiating failure.

Agricultural land partitioning model based on irrigation efficiency using a multi‐objective artificial bee colony algorithm

AbstractIn the process of agricultural land consolidation, the land parcels are optimally redesigned and rearranged in such a way that the dimensions of the resulting parcels are proportional to agricultural criteria such as irrigation discharge, soil texture, and cropping pattern. Besides these criteria, spatial factors like slope, road accessibility, volume of earthwork, and geometrical factors such as size and shape of parcels are also included in the design process of agricultural land partitioning. In this study, a land partitioning model was proposed using a multi‐objective artificial bee colony algorithm (MOABC‐LP) taking into consideration the mentioned factors. Initially, a feasible dimension range of parcels in a block was calculated based on irrigation efficiency. Two partitioning layouts were defined according to the topography and geometry of blocks. The proposed method was applied to a real study area and the results suggest that the land partitioning plan obtained by the MOABC‐LP model, in comparison with a designer's plan, not only makes the shape and size of parcels more compatible with the topographical and agricultural conditions of each block, but also reduces their cut‐and‐fill ratio.

HIGH-PRECISION OBJECT DELINEATION WITH UAV – DEMONSTRATED ON A TRACK SYSTEM

Abstract. The proper function of rail-based transport networks relies on the accurate positioning of the tracks. Regular control and maintenance intervals are in place to guarantee safe and reliable operation. This also holds for the crane rails of the storage cranes in the container terminal in the Hamburg harbour. Especially in the terminal “Altenwerder” the geomorphological conditions of the soil lead to a permanent subsidence of the tracks and thus ask for intensive surveying and maintenance activities. The allowed tolerances are in the range of 10mm in the XY-plane on a stretch of 300m. In the daily practice, the measurements are done using traditional tachymetric survey, in combination with a rail car carrying a reflector. This method is reliable but comes with the disadvantage that the operation of cranes needs to be interrupted. In this paper we present an alternative, automatic approach which employs state-of-the-art UAV-based photogrammetry to measure the actual location of the rail. The mid-format camera system combined with a 150mm tele-lens results in a GSD of 0.9mm at 35m flying height. Challenges addressed concern the proper setup and installation of the ground control network, the flight planning and bundle adjustment. Furthermore, an automated rail delineation in the derived surface model was developed. First experiments show that an automatic workflow is possible, including the delineation task. Remaining obstacles concern, for instance, the compliance with the requirements regarding absolute positional accuracy, since the inner block geometry is theoretically much more accurate than the realised control point network.

Influence of the orientation of cohesive blocks upon the structural grain of fold-and-thrust belts: An appraisal by means of analogue modeling

Analogue sand-box experiments have been set up to illustrate and analyze the control exerted by lithological heterogeneities on the evolution of a model fold-and-thrust belt (FTB). The structural architecture within many FTBs is highly sensitive to pretectonic obstacles (e.g., basement highs or intrusive bodies). To address FTB evolution with emphasis on the latter, we perform a series of experiments that include tabular cohesive blocks surrounded by a layered sandpack of negligible cohesion. Two degrees of cohesion are tested (low vs high cohesion) as well as different geometrical boundary conditions (longer axis parallel vs oblique relative to the main far-field stress). Modeling results show a tendency of sequential faults to avoid rigid obstacles, enhancing frontal accretion and propagation of the deformation front. Structural traces have arcuate patterns in map-view, strongly consistent with the geometry of the underlying block/obstacle. High-cohesion models show major deviations on the structural pattern with respect to models with low-cohesion blocks. We find that the rheological contrasts between rock types have an important effect on the structure of the upper crust, controlled by the degree of the contrast and the geometry (orientation) of the discordant block. An interesting aspect of our results is that orientation of the block plays a considerable role on whether new thrusts cut the block or stresses propagate towards the foreland through the cohesive body. Block obliquity also influences the generation of back-thrusts. These features are compared to natural cases as well as to other physical models of FTBs. We suggest that irregular structural patterns in FTBs may shed light on the presence of buried rock bodies (intrusive bodies, metamorphic complexes or crystalline basement highs) within the components of the deformed rock sequence.

DESIGN OF DRILLING AND EXPLOSION WORKS IN UNDERGROUND MINING USING IN MICROMINE GGIS

In the modern world, an increasing number of enterprises involved in geological exploration and exploration use special software and information systems in their work. The use of such systems can significantly accelerate the processing and analysis of information. They make it possible to automate the processing and interpretation of geological exploration data, as well as use them to model deposits and design underground drilling and blasting operations. GGIS Micromine will automate the design of drilling and blasting operations while ensuring well placement taking into account the block geometry and rock properties, and a rational distribution of borehole charges for the most efficient crushing of rock mass. In conditions of high intensity of mining operations at the MGIS quarries, Micromine ensures the efficiency and multivariance of design decisions when performing blasting.

Characterization of a High-Aspect Ratio Detector With Lateral Sides Readout for Compton PET

Although positron emission tomography is probably the most specific molecular imaging modality, it still lacks a high detection sensitivity. One way of improving this is by implementing larger axial scanners and, therefore, increasing the solid angle coverage. Alternatively, it is possible to increase the sensitivity gain by improving the timing capabilities of the detectors. However, from the most fundamental nature of particle interactions with matter, the 511-keV gamma rays suffer, in most of the cases, from scatter collisions either in the patient or within the detector block, before a photoelectric event eventually occurs. Recovering all scattered (Compton) events would improve scanner sensitivity. In this work, we show the performance of a detector block geometry suitable for the development of PET scanners based on several detector layers. A geometry using multiple layers favor the process of scattered events, at the time that allows one for their proper identification. The detector block consists of a LYSO crystal with $51.5\times 51.5$ mm2 surface and 3 mm thickness, resulting in a very high aspect ratio above 17. Four custom-made SiPM arrays of $1\times 16$ elements with $3\times 3$ mm2 area each are coupled to the lateral sides of the crystal. Four different methods to estimate the gamma-ray interaction position using the information collected by the four SiPM arrays have been implemented and compared in order to assess the most suitable one for this detector configuration and aspect ratio. A novel calibration method based on Voronoi diagrams has been successfully implemented, allowing us to recover data for the entire detector block. We have reached an intrinsic spatial resolution for the whole block of less than 1.6 mm FWHM, combined with an energy resolution of 12.1%. We have also compared the performance results with detector blocks using the same crystal but employing the standard backreading approach. Similar results were obtained but making use of four times less SiPM active area in the case of the lateral reading compared to the backreading method, and with the possibility to minimize the undesirable scatter in the photosensor layers.

THE MAGNETIC FIELD ABOUT A THREE-DIMENSIONAL BLOCK NEODYMIUM MAGNET

AbstractNeodymium magnets were independently discovered in 1984 by General Motors and Sumitomo. Today, they are the strongest type of permanent magnets commercially available. They are the most widely used industrial magnets with many applications, including in hard disk drives, cordless tools and magnetic fasteners. We use a vector potential approach, rather than the more usual magnetic potential approach, to derive the three-dimensional (3D) magnetic field for a neodymium magnet, assuming an idealized block geometry and uniform magnetization. For each field or observation point, the 3D solution involves 24 nondimensional quantities, arising from the eight vertex positions of the magnet and the three components of the magnetic field. The only unknown in the model is the value of magnetization, with all other model quantities defined in terms of field position and magnet location. The longitudinal magnetic field component in the direction of magnetization is bounded everywhere, but discontinuous across the magnet faces parallel to the magnetization direction. The transverse magnetic fields are logarithmically unbounded on approaching a vertex of the magnet.

Evaluation of quantitative, efficient image reconstruction for VersaPET, a compact PET system.

Previously we developed a high-resolution positron emission tomography(PET) system-VersaPET-characterized by a block geometry with relatively large axial and transaxial interblock gaps and a compact geometry susceptible to parallax blurring effects. In this work, we report the qualitative and quantitative evaluation of a graphic processing unit (GPU)-accelerated maximum-likelihood by expectation-maximization (MLEM) image reconstruction framework for VersaPET which features accurate system geometry and projection space point-spread-function (PSF) modeling. We combined the ray-tracing module from software for tomographic image reconstruction (STIR),an open-source PET image reconstruction package, with VersaPET's exact block geometry for the geometric system matrix. Point-spread-function modeling of crystal penetration and scattering was achieved by a custom Monte-Carlo simulation for projection space blurring in all dimensions. We also parallelized the reconstruction in GPU taking advantage of the system's symmetry for PSF computation. To investigate the effects of PSF width, we generated and studied multiple kernels between one that reflects the true LYSO density in the MC simulation and another that reflects geometry only (no PSF). GATE simulations of hot and cold-sphere phantoms with spheres of different sizes, real microDerenzo phantom, and human blood vessel data were used to characterize the quantitative and qualitative performances of the reconstruction. Reconstruction with an accurate system geometry effectively improved image quality compared to STIR (version 3.0) which assumes an idealized system geometry. Reconstructions of GATE-simulated hot-sphere phantom data showed that all PSF kernels achieved superior performance in contrast recovery and bias reduction compared to using no PSF, but may introduce edge artifact and lumped background noise pattern depending on the width of PSF kernels. Cold-sphere phantom simulation results also indicated improvement in contrast recovery and quantification with PSF modeling (compared to no PSF) for 5 and 10mm cold spheres. Real microDerenzo phantom images with the PSF kernel that reflects the true LYSO density showed degraded resolving power of small sectors that could be resolved more clearly by underestimated PSF kernels, which is consistent with recent literature despite differences in scanner geometries and in approaches to system model estimation. The human vessel results resemble those of the hot-sphere phantom simulation with the PSF kernel that reflects the true LYSO density achieving the highest peak in the time activity curve (TAC) and similar lumped noise pattern. We fully evaluated a practical MLEM reconstruction framework that we developed for VersaPET in terms of qualitative and quantitative performance. Different PSF kernels may be adopted for improving the results of specific imaging tasks but the underlying reasons for the variation in optimal kernel for the real and simulation studies requires further study.

The ratio of shear to elastic modulus of in-plane loaded masonry

When designing unreinforced masonry buildings, the wall stiffness and, consequently, the masonry elastic and shear modulus E and G are essential parameters. Current codes provide empirical estimates of the masonry elastic modulus and a ratio between the shear and elastic modulus, G/E. This ratio, commonly taken as 0.4, is not based on scientific evidence and there appears to be no consensus concerning its value and influencing parameters, meaning that current code standards might not accurately portray the shear deformations of masonry elements. To give the choice of the G/E ratio a theoretical foundation, this paper presents closed-form expressions for the G/E ratio of running-bond masonry that capture the effects of finite joint thickness, finite wall thickness and orthotropic block properties. Based on the geometry of blocks and joints as well as their elastic parameters, a validation of the developed expression using 3D finite element analyses shows good performance. For modern masonry typologies with hollow clay bricks, a G/E ratio of 0.20–0.25 is obtained. For historical masonry typologies, such as dry stacked or mortared stone masonry, as well as solid clay brick masonry, ratios between 0.30 and 0.40 are computed.

Analysis of block random rocking on nonlinear flexible foundation

In this paper the rocking response of a rigid block randomly excited at its foundation is examined. A nonlinear flexible foundation model is considered accounting for the possibility of uplifting in the case of strong excitation. Specifically, based on an appropriate nonlinear impact force model, the foundation is treated as a bed of continuously distributed springs in parallel with nonlinear dampers. The statistics of the rocking response is examined by an analytical procedure which involves a combination of static condensation and stochastic linearization methods. In this manner, repeated numerical integration of the highly nonlinear differential equations of motion is circumvented, and a computationally efficient semi-analytical solution is obtained. Comparisons with pertinent Monte Carlo simulations demonstrate the efficiency and reliability of the proposed approach. Finally, the survival probability related to toppling of the blocks subject to filtered white noise excitation is investigated, for different kinds of block geometries, foundation materials, and filter parameters.

A Path Planning Optimization Framework for Concrete Based Additive Manufacturing Processes

Concrete based Additive Manufacturing (AM) is an emerging technological sector including numerous potential application fields, varying from buildings to facades and furniture. Path planning optimization of Concrete based AM is considered as a milestone, towards further automation and utilization of the technology. The current study presents a modular framework for the holistic multi-level optimization of path planning for concrete AM. Steps are described in detail and include strategies for the selection of a near optimum path and selection of acceptable process parameters, along with controlling actions of a cable robot based concrete AM process head. Also, following outcomes derived from the path strategy, an appropriate building block geometry is generated through design successive approximations. These building blocks fulfil (mechanical and thermal) functional requirements as well as they meet buildability criteria, with emphasis on minimizing idle times. Finally, a software platform supporting the aforementioned activities has been implemented and is presented herein. It provides an interface based on Web-Services, achieving portability of data and functionalities.

Investigating the Effects of the Block Geometries and Sidewall Divergences on the Local Scour Downstream of Baffled Chute Spillways

Due to the lack of any specific study about the sidewalls and other blocks’ changes in the case of hydraulic and scour downstream, the present study was conducted to investigate this issue. For this purpose, drainage projects and spillway chutes, as well as many baffle block chutes, were designed and constructed with the parallel sidewalls and trapezoidal shape using the U.S. Bureau of Reclamation (USBR) instructions. Three divergence ratios of ((b1/b2) = 1.45, 1.75, and 2.45), a parallel sidewall of (b1/b2 = 1), and also three geometry blocks including trapezoidal USBR, trihedral, and semicircle blocks were applied and tested in the hydraulic laboratory using a baffle chute with the slope of (2 : 1), (H : V). The material used in this study was sediment sand with a uniform grain size of d50 = 1.2 mm, 15 cm of thickness, and 2 m of length. The experiment was conducted with seven different discharges in lasting condition, and the flow characteristic and scour hole dimensions were measured. The results revealed that in comparison with the USBR blocks, changes in the baffle sidewall and block shape made an approximate 50% reduction in the maximum depth of the scour hole. Thus, increasing the divergence ratio from 1 to 2.45 had a significant effect on reducing the maximum depth and the topographic shape of the scour hole. According to the range mentioned in the literature for the Weber number, the scale effect was negligible for the chute with baffle blocks. Generally, it can be concluded that the sidewall changes also can make a reduction in the number of overbaffle blocks, causing a reduction in the construction cost.

Análise numérico-experimental de paredes de alvenaria de bloco cerâmico com diferentes espessuras em altas temperaturas

O estudo discute sobre a resistência ao fogo de sistemas de vedação vertical compostos por blocos cerâmicos com furos verticais em altas temperaturas. O sistema construtivo de vedação em alvenaria é amplamente utilizado no mercado da construção civil no Brasil por tratar-se de um sistema de baixo custo e alta produtividade em comparação aos elementos convencionais. Os resultados foram obtidos com modelos computacionais de elementos finitos, através do software Ansys Mechanical, calibrados por ensaio experimental em escala real, determinando-se o tempo de resistência ao fogo (TRF) para diferentes geometrias de blocos. As análises computacionais levaram a resultados que apontam um limite para eficiência do aumento de espessura de uma parede para se atingir TRF elevados em relação ao isolamento térmico.