Geometry Factors Research Articles

Determination of radial electric field from Pfirsch–Schlüter flows in the HSX stellarator

Inboard/outboard asymmetry in the impurity ion parallel flow is observed in the HSX stellarator using charge exchange recombination spectroscopy (CHERS). This observation shows the presence of counter-streaming Pfirsch–Schlüter flow predicted by neoclassical theory. The asymmetry of the flow is used to calculate the magnitude and direction of the radial electric field (Er), as well as the mean flow, using computed magnetic geometry factors. This method enables calculation of Er near the core of the HSX plasma where the Er obtained from the radial force balance equation has large uncertainties due to the relatively large width of the diagnostic neutral beam with respect to the plasma minor radius.

Spatial Hadamard encoding of J-edited spectroscopy using slice-selective editing pulses.

A new approach for simultaneous dual-voxel J-difference spectral editing is described, which uses spatially selective spectral-editing pulses and Hadamard encoding. A theoretical framework for spatial Hadamard editing and reconstruction for parallel acquisition (SHERPA) was developed, applying gradient pulses during the frequency-selective editing pulses. Spectral simulations were performed for either one (gamma-aminobutyric acid, GABA) or two molecules (glutathione and lactate) simultaneously detected in two voxels. The method was tested in a two-compartment GABA phantom, and finally applied to the left and right hemispheres of 10 normal control subjects, scanned at 3T. SHERPA was successfully implemented at 3T and gave results in close agreement with conventional MEGA-PRESS scans in both the phantom and in vivo experiments. Simulations for GABA editing for (3cm)3 voxels in the left and right hemispheres suggest that both editing efficiency losses and contamination between voxels are about 2%. Compared with conventional single-voxel single-metabolite J-difference editing, two- or fourfold acceleration is possible without significant loss of SNR using the SHERPA method. Unlike some other dual-voxel methods, the method can be used with single-channel receiver coils, and there is no SNR loss due to unfavorable receive-coil geometry factors.

High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out

Developing wide-area cryogenic light detectors with baseline resolution better than 20 eV is one of the priorities of next generation bolometric experiments searching for rare interactions, as the simultaneous read-out of the light and heat signals enables background suppression through particle identification. Among the proposed technological approaches for the phonon sensor, the naturally multiplexed Kinetic Inductance Detectors (KIDs) stand out for their excellent intrinsic energy resolution and reproducibility. The potential of this technique was proved by the CALDER project that reached a baseline resolution of 154 ± 7 eV RMS by sampling a 2 × 2 cm2 Silicon substrate with 4 Aluminum KIDs. In this paper, we present a prototype of Aluminum KID with improved geometry and quality factor. The design improvement, as well as the combined analysis of amplitude and phase signals, allowed to reach a baseline resolution of 82 ± 4 eV by sampling the same substrate with a single Aluminum KID.

エルボ管におけるFAC減肉速度と物質移行係数の評価について

Flow accelerated corrosion (FAC) is one of the causes for wall thinning mechanisms in carbon steel pipes. Prediction of geometry factor is the key elements for estimation of FAC. Geometry factor is defined as the ratio of wall mass transfer coefficient in the piping systems such as elbow to that in a straight pipe. In order to simulate the mass transfer coefficient, we adopt the analogy between mass transfer and heat transfer. In this study, geometry factor of the elbow pipe is computed by using large eddy simulation (LES) for various Prandtl number and Reynolds number. When Prandtl number is close to unity, geometry factor changes depending on Prandtl number. However, as Prandtl number increases sufficiently, geometry factor becomes independent of Prandtl number. As the Reynolds number increases, geometry factor of the INSS elbow decreases, with reduction of the area in which large geometry factor is observed.

A Simplified Multipath Component Modeling Approach for High-Speed Train Channel Based on Ray Tracing

High-speed train (HST) communications at millimeter-wave (mmWave) band have received a lot of attention due to their numerous high-data-rate applications enabling smart rail mobility. Accurate and effective channel models are always critical to the HST system design, assessment, and optimization. A distinctive feature of the mmWave HST channel is that it is rapidly time-varying. To depict this feature, a geometry-based multipath model is established for the dominant multipath behavior in delay and Doppler domains. Because of insufficient mmWave HST channel measurement with high mobility, the model is developed by a measurement-validated ray tracing (RT) simulator. Different from conventional models, the temporal evolution of dominant multipath behavior is characterized by its geometry factor that represents the geometrical relationship of the dominant multipath component (MPC) to HST environment. Actually, during each dominant multipath lifetime, its geometry factor is fixed. To statistically model the geometry factor and its lifetime, the dominant MPCs are extracted within each local wide-sense stationary (WSS) region and are tracked over different WSS regions to identify its “birth” and “death” regions. Then, complex attenuation of dominant MPC is jointly modeled by its delay and Doppler shift both which are derived from its geometry factor. Finally, the model implementation is verified by comparison between RT simulated and modeled delay and Doppler spreads.

A Cross Scale Analysis of the Relationship between Energy Efficiency and Urban Morphology in the Greek City Context

Urban form is a decisive factor for the energy efficiency of the city. The compact city has been suggested as the most sustainable urban form, but it has been questioned as well by many researchers. Urban morphology is not a simple aggregation of geometry factors, but also the interaction among a set of parameters, that include constructional, functional and building regulation constraints concerning a range of different scales as well. This paper examines in which way the interaction of such parameters affects the energy efficiency of the urban tissue focusing in the Greek city context. A set of building block typologies are analyzed with regard to their geometry factors such as S/V ratios, plot ratio and building ratio. Thermal loads are calculated in order to draw conclusions about the relation between geometry factors and energy efficiency. The results of the research indicate that there is a strong relationship between urban morphology factors and energy efficiency. The theory of compactness of the urban form is generally confirmed by the results of the study which are valuable, since they indicate the energy profile of each typology and can be used for predicting the performance of potential energy demand of urban blocks with similar geometry.

Enhanced System Acquisition for NB-IoT

Machine-type communication (MTC) is the key technology to support data transfer among devices (sensors and actuators) in Internet of Things (IoT). Although cellular communication technologies are developed mainly for “human-type”communications, enabling MTC with cellular networks not only improves the connectivity, accessibility, and availability of an MTC network but also has the potential to further drive down the operation cost. However, cellular MTC, especially when applied to low-power massive IoT (mIoT), poses some unique challenges due to the low-cost and low-power nature of an mIoT device. One of the most challenging issues is providing a robust way for an mIoT device to acquire the network under a large frequency offset due to the use of low-cost crystal oscillators and under extended coverage. Although differentiation is a well-known technique for removing impairments caused by frequency offset, its “noise amplification”effect limits its applications in cellular communications due to the fact that cellular communication is typically interference limited. Matched-filter-based detection is, therefore, almost unexceptionally used. We show that the differential technique can actually benefit system acquisition in mIoT, where the use of low-cost crystals is a default. Although the existing system acquisition design in a cellular mIoT system, i.e., NB-IoT, facilitates both techniques, there still remain issues that need to be solved in order to take full advantage of the design. We provide a comprehensive analysis on the performance of two most common techniques when applied in a typical NB-IoT environment based on two factors, the geometry factor and the frequency offset factor. Finally, we derive the operating regions for matched-filter-based detection and differentiation using these two factors, in which the system acquisition performance of the two types of techniques is maximized for NB-IoT.

Study of Signal to Noise Ratio of Coded Source Neutron Imaging with Analysis Method and Numerical Simulation

Coded source imaging (CSI) technique could increase the utilization rate of neutron when high L/D required in neutron imaging. The images need to be reconstructed from the raw projections. The reconstruction would amplify the noise of the raw projection, which will affect the quality of reconstructed images. Study of Signal to Noise Ratio (SNR) in CSI shows image quality depends on geometry structure and neutron beam parameters. With analysis method based on correlation reconstruction arithmetic, SNR was detailed to assess the effects from different geometry factors. Numerical simulation as a further supplement proves the rationality of analysis method. The comparison of SNR between CSI and traditional neutron radiography (NR) shows that the SNR of CSI could be better than NR in some conditions.

Anatomical study of petrous and cavernous parts of internal carotid artery.

The petrous and cavernous parts of internal carotid artery (ICA) are obscure and are not readily accessible to observation/imaging. These parts have broad biological and medical interest because of their peculiar shape. Given the their clinical importance and the scarce data available based mostly on imaging, the present study was aimed at studying these parts of ICA by dissection. The study was carried out on 56 ICAs obtained from embalmed adult cadavers and 10 ICAs from five fetuses. The foetal ICAs were studied in situ. The morphometric analysis of the adult ICA was done after its removal from cranial cavity to gain an insight into the geometry of the vessel, i.e., length, various bends, and diameters at various locations. ICAs in fetuses ran a relatively straighter course taking gentle curves at three positions (two intrapetrous, one cavernous). Adult ICAs were more tortuous and exhibited greater variability in length and angulations. The length of respective portions of the ICA correlate negatively with the measure of angles. The angles in the petrous and cavernous parts were positively correlated to each other. The carotid siphon was positively, highly significantly correlated to other angles. Longer vessels are more tortuous with acute bends. An acute carotid siphon is an indication of more tortuous ICA. The findings of the present study have created a reference data of unsuspected adult population and has potential implications for studying cause/effect relationship of vessel geometry and hemodynamic factors.

Analysis of Geomechanical Factors Affecting Rock Bursts in Sedimentary Rock Formations

Rock bursts are defined as sudden, violent failures of rock mass that are of such a magnitude that they expel large amounts of coal and rock into the face area during longwall or pillar extraction in sedimentary rocks. In an attempt to develop tools for assessing stress bump potential, the first author initiated a comprehensive study using site specific information from 25 case studies undertaken in U.S. mines. This effort builds on an initial study while expanding the data base and including additional variables and analyses. Multiple linear regression and numerical modeling analyses of geological and mining conditions were used to identify the most significant factors contributing to stress bumps in coal mines. Twenty-five factors were considered initially (mechanical properties of strata, stress fields, face and pillar factors of safety, joint spacings, mining methods, and stress gradients, among others). Allowances were made for favorable local yielding characteristics of mine roof and floor in reducing damage severity. Pillar and face factors of safety were calculated using displacement-discontinuity methods for specific geometries in case studies having experienced both violent and nonviolent failures. This work identified the most important variables contributing to coal bumps and violent failure of near seam strata. These are [1] mechanical properties of strata, including local yield characteristics of a mine roof and floor, [2] gateroad geometry and/or gate pillar factors of safety, [3] stress gradients associated with the approach of mining to areas of higher stress concentrations such as abutment stresses from multiple seam mining, and [4] roof beam thickness, joint spacing, and stiffness characteristics, which influence cave conditions and dynamic loading. The latter variables, combined together to form a new variable called “strata rigidity-cavability”, reflect some of the most important aspects of violent failure, i.e. having massive and stiff near-seam stratigraphic units capable of absorbing high strain energy, forming high stress on mine structures and poor cave conditions, and thus the potential for dynamic loads.

形状係数測定における壁面伝達境界条件が及ぼす影響に関する研究

形状係数測定における壁面伝達境界条件が及ぼす影響に関する研究

Influence of Geometry on Rotordynamic Coefficients of Brush Seal

AbstractIt has been observed that the geometry of a brush seal has a significant effect on the sealing performance. However, the relationship between rotordynamic coefficients and geometry factors of the brush seal itself are rarely considered. In this article, the rotordynamic coefficients of a typical single-stage brush seal for different geometries and operating conditions were numerically analyzed using CFD RANS solutions coupled with a non-Darcian porous medium model. The reaction force which plays an essential role in rotordynamic coefficients was obtained by integrating the dynamic pressure distribution. The influence of the bristle pack thickness, fence height, clearance size and other working condition parameters on aerodynamic force, stiffness coefficients, and damping coefficients of brush seal were presented and compared. In addition, the effects of various geometric configurations on pressure and flow features were also discussed.

片側切欠きばりの4点曲げ試験（4SENB試験）による木材および中密度繊維板の<i>K</i><sub>Ic</sub>値の測定

Mode I critical stress intensity factor KIc obtained by four-point single-edge-notched bending (4SENB) tests of wood and medium-density fiberboard (MDF) was experimentally and numerically analyzed. To determine the critical load for crack propagation, the relationship between the load and loading-line deflection (LLD) and that between the load and crack opening displacement (COD) were measured, and the results obtained were compared with each other. Additionally, a double cantilever beam (DCB) test was conducted and the results were compared with those of 4SENB tests. Similar to the results obtained in several previous studies, the value of KIc was obtained by introducing an additional crack length into appropriate equations as the crack geometry factor used for analyzing the 4SENB test. Additionally, the load-COD relationship was more sensitive in detecting the crack propagation than the load-LLD relationship, so the measurement of COD is recommended for determining the KIc value in the 4SENB test accurately.

Displacement front behavior of near miscible CO2 flooding in decane saturated synthetic sandstone cores revealed by magnetic resonance imaging

It is of great importance to study the CO2-oil two-phase flow characteristic and displacement front behavior in porous media, for understanding the mechanisms of CO2 enhanced oil recovery. In this work, we carried out near miscible CO2 flooding experiments in decane saturated synthetic sandstone cores to investigate the displacement front characteristic by using magnetic resonance imaging technique. Experiments were done in three consolidated sandstone cores with the permeabilities ranging from 80 to 450mD. The oil saturation maps and the overall oil saturation during CO2 injections were obtained from the intensity of magnetic resonance imaging. Finally the parameters of the piston-like displacement fronts, including the front velocity and the front geometry factor (the length to width ratio) were analyzed. Experimental results showed that the near miscible vertical upward displacement is instable above the minimum miscible pressure in the synthetic sandstone cores. However, low permeability can restrain the instability to some extent.

Global Satellite Navigation Systems at High Latitudes, Visibility and Geometry

Abstract Since few years the significance of the navigation at high latitudes (60° and more), increases incessantly, e.g. northern passages between Atlantic and Pacific Waters. In these regions the user’s position can be obtained mainly from global satellite navigation systems (SNS). Nowadays (September 2016) two systems, American GPS and Russian GLONASS, are fully operational, two next, Galileo in Europe and BeiDou in China, are under construction. As the error of user’s position obtained from these systems depends on geometry factor DOP (Dilution Of Precision) among other things the knowledge of the number of satellites visible by this user above given masking elevation angle Hmin and the distributions of DOP coefficient values, GDOP in particular, is very important. The lowest and the greatest number of satellites visible in open area by the user at high latitudes for different Hmin, the percentage of satellites visible above angle H, distributions of satellites azimuths and GDOP coefficient values for different Hmin for all these four SNSs at different user’s latitudes (beginning from 60°) and other distributions are presented in the paper. All calculations were made for constellation of BeiDou 27 MEO satellites, Galileo 24 satellites, GLONASS 24 and GPS 31 satellites.

Digesting the safety effectiveness of cable barrier systems by numbers

This paper presents median cable barrier safety effectiveness by numbers as experienced on Tennessee highways. Apart from descriptive statistics and parametric tests, before and after statistical evaluation utilizing Empirical Bayes (EB) was used to estimate the cable barriers Safety Effectiveness. The findings from the descriptive statistics, paired t-test and EB evaluation were very similar which reinforces the positive safety effectiveness performances of the cable barriers in Tennessee. The study found that the statewide cable barriers Safety Effectiveness (statistical percentage change in crash frequency across all statewide cable barrier segments) for fatal crashes is 94%, incapacitating injury crashes is 92% and fatal and incapacitating injury crashes combined is also 92%. The safety effectiveness for fatal and all injury crashes combined was found to be 85%. In a direct comparison through descriptive statistics, statewide fatal crashes were reduced by 82% after the cable barriers installation while the incapacitating injury crashes were reduced by 76%. In addition, head-on crashes went down by 96% and crashes involving two or more vehicles went down by 92%. Fatalities due to median crossover crashes were reduced by 83% while number of people injured went down by 71% as a result of cable barriers. Through modeling, wider cable offsets and inside shoulders were found to help reduce number of median related crashes while high differential elevations and high posted speed limit segments significantly had higher number of crashes compared to the opposite features. The findings can be used by state transportation agencies as a decision tool when considering installation of median cable barriers as well in determination geometry and traffic factors that play role in enhancing or worsening performance of the median cable barriers.

Analysis on Wood Quality, Geometry Factor, and Their Effects on Lathe Check of Samama (Anthocephalus macrophyllus) Veneer

Relatively little information is available regarding the correlation between wood and veneer quality, especially for Samama wood, an endemic wood species in eastern Indonesia. This study addresses the quality of 8 years old Samama wood and its effect on the veneer quality. Samama wood quality was determined by evaluating its specific gravity, moisture content, fiber dimensions, and microfibril angle from pith toward bark. Meanwhile, veneer quality was assessed by examining veneer thickness and lathe check characteristics. Geometry factor model was constructed to elaborate the quantities of lathe check from pith toward bark. Results show that fair variations of veneer thickness, ranging from 1.5 mm to 3.0 mm, could be obtained from Samama wood. The quantity, depth, and length of lathe check were noticeably decreasing toward bark. Further, in the same manufacturing process, geometry factor was determined as the dominant factor over other wood properties in affecting the frequency of lathe checks from pith towards bark. These facts should be put into consideration in producing veneer from Samama wood. Moreover, these results enlighten the potential of Samama wood as plywood and other excellent veneer-based products.

Implementation of ICRP 116 Dose Conversion Coefficients for Reconstructing Organ Dose in a Radiation Compensation Program.

Since 2000, National Institute for Occupational Safety and Health (NIOSH) has used dose conversion coefficients published by the International Commission on Radiation Protection in report 74 (ICRP 74) to determine organ dose from external radiation sources. In 2010, the ICRP issued publication 116 using more realistic phantoms than ICRP 74. NIOSH has developed a Monte Carlo method to sample the energy-organ-specific distribution of the ICRP 116 conversion coefficients to determine the organ dose and the associated uncertainty. Using Monte Carlo methods, irradiation geometry factors (IGFs) were developed to convert the measured dosemeter dose on the front of the body to values that are compatible with ICRP 116 organ dose conversion coefficients. Specific IGFs were developed for (1) both neutrons and photon exposures, (2) to male and female workers and (3) for rotational and isotropic exposure geometries. The computed mean organ dose and the associated uncertainty are used in the probability of causation calculation for compensation.

Biomechanical Indices for Rupture Risk Estimation in Abdominal Aortic Aneurysms

Purpose: To review the use of biomechanical indices for the estimation of abdominal aortic aneurysm (AAA) rupture risk, emphasizing their potential use in a clinical setting. Methods: A search of the PubMed, Embase, Scopus, and Compendex databases was made up to June 2015 to identify articles involving biomechanical analysis of AAA rupture risk. Outcome variables [aneurysm diameter, peak wall stress (PWS), peak wall shear stress (PWSS), wall strain, peak wall rupture index (PWRI), and wall stiffness] were compared for asymptomatic intact AAAs vs symptomatic or ruptured AAAs. For quantitative analysis of the pooled data, a random effects model was used to calculate the standard mean differences (SMDs) with the 95% confidence interval (CI) for the biomechanical indices. Results: The initial database searches yielded 1894 independent articles of which 19 were included in the analysis. The PWS was significantly higher in the symptomatic/ruptured group, with a SMD of 1.11 (95% CI 0.93 to 1.26, p<0.001). Likewise, the PWRI was significantly higher in the ruptured or symptomatic group, with a SMD of 1.15 (95% CI 0.30 to 2.01, p=0.008). After adjustment for the aneurysm diameter, the PWS remained higher in the ruptured or symptomatic group, with a SMD of 0.85 (95% CI 0.46 to 1.23, p<0.001). Less is known of the wall shear stress and wall strain indices, as too few studies were available for analysis. Conclusion: Biomechanical indices are a promising tool in the assessment of AAA rupture risk as they incorporate several factors, including geometry, tissue properties, and patient-specific risk factors. However, clinical implementation of biomechanical AAA assessment remains a challenge owing to a lack of standardization.

Performance Analysis of the Automotive TEG with Respect to the Geometry of the Modules

Recently there has been increasing interest in applying thermoelectric technology to recover waste heat in automotive exhaust gas. Due to the limited space in the vehicle, it’s meaningful to improve the TEG (thermoelectric generator) performance by optimizing the module geometry. This paper analyzes the performance of bismuth telluride modules for two criteria (power density and power output per area), and researches the relationship between the performance and the geometry of the modules. A geometry factor is defined for the thermoelectric element to describe the module geometry, and a mathematical model is set up to study the effects of the module geometry on its performance. It has been found out that the optimal geometry factors for maximum output power, power density and power output per unit area are different, and the value of the optimal geometry factors will be affected by the volume of the thermoelectric material and the thermal input. The results can be referred to as the basis for optimizing the performance of the thermoelectric modules.