Field Setup Research Articles

Using appropriate prior information to eliminate choice sets with a dominant alternative from D-efficient designs

Discrete choice experiments are frequently applied in transportation research to explore the value of travel time savings. Most profile attributes in these studies, such as the travel time or the travel cost of a mode or road choice, have a clear rank order in their attribute levels. Therefore one option in a choice set can dominate the other alternatives in the set. This research shows, for a specific setup in the transportation field, that a proper choice of prior information, adequately incorporating the dominance of preferred attribute levels, eliminates choice sets with a dominant alternative from Bayesian D-efficient designs.

Early drought stress detection in cereals: simplex volume maximisation for hyperspectral image analysis.

Early water stress recognition is of great relevance in precision plant breeding and production. Hyperspectral imaging sensors can be a valuable tool for early stress detection with high spatio-temporal resolution. They gather large, high dimensional data cubes posing a significant challenge to data analysis. Classical supervised learning algorithms often fail in applied plant sciences due to their need of labelled datasets, which are difficult to obtain. Therefore, new approaches for unsupervised learning of relevant patterns are needed. We apply for the first time a recent matrix factorisation technique, simplex volume maximisation (SiVM), to hyperspectral data. It is an unsupervised classification approach, optimised for fast computation of massive datasets. It allows calculation of how similar each spectrum is to observed typical spectra. This provides the means to express how likely it is that one plant is suffering from stress. The method was tested for drought stress, applied to potted barley plants in a controlled rain-out shelter experiment and to agricultural corn plots subjected to a two factorial field setup altering water and nutrient availability. Both experiments were conducted on the canopy level. SiVM was significantly better than using a combination of established vegetation indices. In the corn plots, SiVM clearly separated the different treatments, even though the effects on leaf and canopy traits were subtle.

Parabolic flight experiment "Convection in a Cylinder" – Convection patterns in varying buoyancy forces

Within the project "Convection in a Cylinder" (CiC) heat transfer enhancement is studied for the case of two concentric, vertically aligned cylinders. The cylindrical gap is filled with a dielectric liquid, which viscosity is just few times higher than that of water. The inner cylinder is heated and the outer one is cooled. This setup in a gravitational buoyancy field leads to a fluid movement in a single convective cell with hot fluid rising at the inner boundary and cold fluid sinking at the outer boundary. The top and bottom part of the system shows horizontal movement, again in boundary layers. The strengthening of temperature gradient induces instabilities of that convective motion. If we vary the buoyancy force by means of electro-hydrodynamic effects, the patterns of convection differ from those instabilities rising only from variation of the temperature gradient.

Potential of Two-Dimensional Electro-Fluid-Dynamic Devices for Continuous Purification of Multiple Components from Complex Samples

Two-dimensional electro-fluid-dynamic (EFD) devices, in which both electric field and hydrodynamic pressure are used to drive the analyte and fluid migration, enable two-dimensional channel networks to be used for chemical separation instead of one-dimensional column separation systems. Investigation of the theory of mass transfer in symmetrical Y-shaped EFD devices shows that the magnitude of pressure-induced velocity in lateral channels at critical boundary conditions between different steady state migration paths is independent of the channel cross-sectional area ratio. Therefore, the analyte has four possible mass transfer pathways according to the electric field and pressure setup in all symmetrical Y-shaped 2-D EFD devices, and such devices with any cross-sectional area ratio have the capacity to continuously purify two analytes from a mixture simultaneously. In addition, a new format of multiple-branched 2-D EFD devices is introduced to process multiple analytes. A "proof-reading" mechanism based on the infinite resolution conditions ensures the purity of the components collected. The separation processes are simulated by COMSOL Multiphysics, and the migration behavior of the analytes was monitored using fluorescent dyes to verify the flow behavior of different analytes in individual channels. These 2-D EFD devices offer the potential of continuous fractionation and purification of analytes from complex sample mixtures.

Reliability study of AlGaN/GaN HEMT under electromagnetic, RF and DC stress

In the context of studying the reliability of RF High Power Amplifiers (HPA) in their real environment, a study of the behavior of AlGaN/GaN HEMTs performances under electromagnetic stress is presented in this paper. The DUT has undergone several stress combinations (electromagnetic stress, electromagnetic and RF stress, electromagnetic and DC stress, …). The near field setup is used to disturb with electromagnetic field the device under test (DUT). Degradations in DC and power characteristics are observed for all stress types. This could be associated with electron trapping within the AlGaN barrier and AlGaN surface leading depletion of the 2-DEG.

SU-E-T-526: Is the Marker Matching Method Adequate for Daily Setup of Pelvic Fields in Prostate Irradiation?

Purpose: It is common practice to implant fiducial markers and to perform daily setups based on these markers in delivering radiation to prostate. When the pelvic nodes are also treated, the fields are significantly larger and extend superiorly. Will it still prove adequate to align these fields based on the marker matching method? Alternatively, if we choose to align the fields relative to bony anatomy, will the prostate PTV be adequately covered? The current study attempts to carefully examine these problems. Methods: We choose to use a 2D/2D match for the pelvic nodal irradiation and to use marker matching for the cone‐downs. Daily orthogonal setup KV images for 20 patients, over the course of pelvic nodal irradiation ranging from 25 to 28 treatment, are first matched to bony anatomy, then to contours of the markers, which are delineated during the planning process. The differences between these two methods were recorded and analyzed. This study assumes that a perfect alignment to the bony anatomy can be achieved. The images showing obvious pelvis tilt were excluded from this study and the misalignment of the patient in coronal direction is corrected by applying pedestal rotation. A total of 466 image pairs were studied. Results: Analysis showed that 121 out of 466 cases (26%) needed pedestal rotation ranging from 0.1° to 2.4°, which cannot be picked up using the marker matching method. Additionally we discovered that the percentage of cases that prostate shifted by more than 5mm, relative to bony anatomy, was 7.73%, 1.07% and 0.0% in the vertical, longitudinal and lateral directions respectively. Conclusions: Marker matching is inadequate for large pelvic field alignment. Pelvic fields should be aligned relative to bony anatomy and, then, if the mismatch between the markers and their corresponding contours exceeds a predetermined threshold, table shifts should be adjusted to compensate.

SU‐E‐T‐347: A Cost‐Effective Technique for Treating Penis Cancer with Delivery Accuracy Verified with In‐Vivo Measurement

Purpose: To report an in‐house cost‐effective, easily made and set up, yet accurate technique for treating penis cancer at a community freestanding cancer. Methods: Recently, a patient with penis cancer was under radiotherapy at our institution. The treated site was his penis only. The patient was simulated in supine position with his penis inserted in a custom supporting tool. This supporting tool is made of a regular candle that can be bought at any retail store. It measures about 10 cm in diameter and has a HU about −100. A hole slightly larger than the patientˈs penis was drilled in the middle with enough buildup wall left for a 6 MV beam used for the treatment plan. For the remaining space not occupied by the patientˈs penis, regular flour was filled in tightly, which has a HU about −200. The plan was done with an opposing lateral conformal field setup to get a uniform dose distribution across the treatment site. It makes essential no difference whether the heterogeneity is turned on or not in the dose calculation with Varianˈs Eclipse TPS. Four MOSFET dosimeters were placed on the surface of the penis for in‐vivo measurement for two consecutive fractions. The prescription was 180 cGy/fx. The mean dose for the skin (3 mm deep region from the surface contoured in Eclipse) was 182.9 cGy with a minimum of 179.3 cGy and a maximum of 185.8 cGy. Results: The in‐vivo measurement was 183.2 cGy +/− 1.4 cGy, including a port film with 2 MU. The measurement was in good agreement with the calculation. Conclusions: In‐vivo measurement proved the in‐house developed supporting tool to be cost‐effective, easily made, and easy to set up on a daily basis for accurately treating penis cancer.

Influence of paper insulation on the prebreakdown phenomena in mineral oil under lightning impulse

This paper presents the results of experimental studies about the prebreakdown phenomena in mineral oil under lightning impulse. Experiments were carried out in a non-uniform field setup with HV electrode covered by crepe paper. The results of the experiments were compared with the results of research performed for bare HV electrodes. The onset voltage, propagation velocity, time to initiation, shadowgraph photos of discharges and light emission were respectively measured or recorded during the experiments. Analysis of the research outcomes indicates that the fundamental role of paper insulation is to raise the onset voltage by shoving away the onset sites out of the region of high field stress. The insulation wrapping does not have an influence on the shape of discharge patterns and on the propagation velocity. Some of the results connected with the times to initiation that the mechanism of discharge initiation at the HV electrode surface does not depend on the fact it is insulated. The source of weak points of the paper-oil insulation system is the oil, not the surface of insulation wrapping or metal of electrode. Observation of the oscillograms of light emitted by discharge channels indicates the difference in the mechanism of discharge propagation. The surface and space charge carriers left in the interelectrode space after discharge flash play an important role. In the case of insulated electrodes, the surface charge remains longer on the surface of electrode, reducing the electric field stress which is responsible for reignition. Simultaneously, the space charge reduces the degree of channel ramification. Both the observations are clearly visible on the oscillograms of light as differences in the frequency of light impulses and their peak values.

SU‐E‐T‐806: IMRT Technique for CSI: Better Dose Distribution, Simplified Setup, No Need to Shift Junctions

Purpose: To report an IMRT technique for CSI, which reduces the dose to critical structures in cranial area, improves the dose coverage to PTVs and simplifies the setup. Methods: A supine setup was used for both patient comfort and anesthesia administration in pediatric patients. Patient is immobilized with indexed head rest and face mask, and also with indexed vaclock from the mid‐thigh down to feet. Four half beam (Y1=0) IMRT fields with ISO at the level of the chin to cover the cranial PTV. Cranial PTV is consisted with brain volume plus 5mm margin and portion of the C‐spine superior of the ISO with proper margin. From the first ISO the inferior portion has a PA field (PA1). 2nd PA field (PA2) is added in order to cover the spinal PTV. The spinal PTV is the volume of the spinal canal plus 2cm laterally. The inferior extension of this volume is determined by MRI to cover the thecal nerve. The optimization constrains are applied to maximize the dose coverage of both cranial PTV and spinal PTV, to minimize the dose to parotid glands and lens and to achieve better dose homogeneity. There should be several cm overlap between the two PA fields. During the optimization the leaf sequence forms step wedges in the overlap area and widens the penumbra of these two fields. This makes it more forgiving to the daily patient setup variations. Results: There is 32.8% reduction in mean parotid gland dose, 46.2% reduction for max lens dose without losing dose coverage to brain PTV, compared with the opposite lateral fields setup. The dose homogeneity for the spinal PTV is improved. And the setup is greatly simplified. Conclusions: We have developed a technique which reduces the dose to critical structures and improves the dose coverage and simplifies the setup in CSI.

The different roles of product originality and usefulness in generating word-of-mouth

This paper explores how the dimensions of new products, specifically, the originality and usefulness of the products, influence word-of-mouth (WOM). In four studies, using lab and field setups, we find that originality and usefulness have different effects on WOM. We show that consumers spread more WOM about original products, but the valence of what they say depends on the usefulness of the product. Therefore, originality enhances the effect of usefulness such that consumers spread relatively more and more positively valenced WOM about original and useful products compared to less original but equally useful products. Conversely, consumers spread more and more negatively valenced WOM about original products that are not useful compared to less original products with the same level of low usefulness. The results indicate that product originality should be managed carefully when developing and positioning new products. Although originality increases buzz, it might lead to negatively valenced WOM when the usefulness of the product is perceived to be low.

Optimization of electrical stimulation parameters for enhanced cell proliferation on biomaterial surfaces

From the point of view of biocompatibility of bone analog materials, cell-material interaction is of fundamental importance. In this article, we report the effect of pulse electric field stimulation on cell-material interaction by analyzing cellular functionality and viability. An in-house fabricated pulse electric field setup was used for the application of electric field during cell culture experiments. To optimize voltage/electric field, the first set of exploratory experiments was conducted with varying field strength at fixed frequency, and subsequently, the frequency of the electrical stimulation was varied to study its influence on the proliferation of L929 mouse fibroblast cells on gelatin-coated control disc. Subsequently, L929 cells were cultured on hydroxyapatite (HA) and HA-40 wt % BaTiO₃ composite. Cell-cultured samples were analyzed qualitatively as well as quantitatively using fluorescence microscope and scanning electron microscope. It has been demonstrated that due to the application of electric field during the cell culture experiment, the cell proliferation and the cell spreading on the surface of the biomaterials were enhanced within a narrow window of voltage/frequency of electrical stimulation. At lower field intensities, the energy density is quite low and increases parabolically with field strength. There is no significant increase in the temperature (ΔT ~10⁻⁵ K) of the medium due to the application of short duration pulse electric field. This led us to believe that electric field with appropriate strength and duration can enhance the cell-material interaction.

Effect of aligning magnetic field on the magnetic and calorimetric properties of ferrimagnetic bioactive glass ceramics for the hyperthermia treatment of cancer

The magnetic and heat generating properties of the ferrimagnetic zinc-ferrite containing bioactive glass ceramics have been enhanced by aligning magnetic field, without any compositional or micro-structural changes in the material. The glass ceramics were heated to 600 °C and cooled in an aligning magnetic field of 1 T. Magnetically aligned samples were compared with the non-aligned samples. VSM measurements taken at 500 Oe showed that coercive force, remanance magnetization and hysteresis area increased for the aligned samples. This occurred because the aligning magnetic field setup an easy axis for the magnetic domains. After cooling, the domains were trapped and became stable along the direction of aligning field. Now stronger magnetic field was required to turn the domains away from their aligned positions. Thus magnetic properties were enhanced by the aligning magnetic field and it led to enhance the heat generation under magnetic induction furnace operating at 500 Oe and 60 kHz for 2 min. Data showed that maximum specific power loss and temperature increase after 2 min were 4.4 W/g and 6.3 °C respectively for the aligned sample of maximum zinc-ferrite crystalline content having pseudo single domain crystalline structure. The glass ceramics were immersed in simulated body fluid over weeks. FTIR, SEM and EDX results indicated the growth of precipitated Hydroxyapatite suggesting the bioactivity of the materials.

The influence of the field setup on the dosimetry of abutted fields in single‐isocenter half‐beam techniques

To study the influence of the field setup on the dosimetry at the junction in single-isocenter half-beam techniques. The dosimetry at the junction for a two-field setup with the gantry at zero was first evaluated with radiochromic films. A three-field setup, with an anterior field and two opposed lateral fields, was also analyzed for two different relative positions of the fields involved. In all cases, the dose increase at the central axis, called the junction dose, was measured. Junction doses varied greatly with the setup. For the three-field setup, the junction dose differed from that obtained with the two-field setup, and it greatly depended on the relative position of the fields. When the anterior field was closer to the gantry than the lateral fields, a field gap occurred and the junction dose was negative. When the anterior field was farther from the gantry than the lateral fields, a field overlap was obtained and the junction dose was positive. The difference in the junction dose between the three-field setups was around 18% for the three accelerators evaluated. Having a uniform dose distribution for two fields at gantry 0 degrees does not guarantee a uniform distribution at other gantry angles. Junction doses are largely affected by the relative position of the radiation fields, which may have an impact in clinical practice. Therefore, any method aiming to assess or to optimize the dose homogeneity at the junction should take this effect into account.

Using Appropriate Prior Information to Eliminate Choice Sets with a Dominant Alternative from D-Efficient Designs

Most attributes in transportation studies, such as the travel time and the travel cost of a travel mode or road alternative, have a clear rank order in their attribute levels. Therefore one option in a choice set of an experimental design can dominate the other alternatives in the set. This research finds Bayesian D-efficient designs for a specific setup in the transportation field. It is shown that with a proper choice of prior information which adequately incorporates the dominance of lower attribute levels, no choice sets with a dominant alternative will be included in the efficient designs.

A Fiber Bragg Grating Sensor System for Train Axle Counting

Railway signaling facilitates two main functions, namely, train detection and train control, in order to maintain safe separations among the trains. Track circuits are the most commonly used train detection means with the simple open/close circuit principles; and subsequent adoption of axle counters further allows the detection of trains under adverse track conditions. However, with electrification and power electronics traction drive systems, aggravated by the electromagnetic interference in the vicinity of the signaling system, railway engineers often find unstable or even faulty operations of track circuits and axle counting systems, which inevitably jeopardizes the safe operation of trains. A new means of train detection, which is completely free from electromagnetic interference, is therefore required for the modern railway signaling system. This paper presents a novel optical fiber sensor signaling system. The sensor operation, field setup, axle detection solution set, and test results of an installation in a trial system on a busy suburban railway line are given.

Study on Thermal Field of Mass Concrete by Experiment and Numerical Simulation

An experimental study is conducted to simulate the thermal field in mass concrete. Accurate prediction of the thermal stress by analysis is quite difficult particularly at early ages, due to uncertain age-dependent properties of concrete. A series of tests was conducted in which the temperature was measured for a large number of observation points. The effect of aging and the amount of measuring points on thermal field development that can occur in realistic structures was evaluated. Numerical simulations of the thermal field setup were also performed using the finite element with ANSYS software to verify and extend the experimental interpretation and to determine the maximum temperature value which would occur under construction process. Mass concrete temperature field and stress field for specific projects were measured and analyzed. Numerical simulation of mass concrete temperature field for the actual project is compared with the measured results. The results show that the temperature field of numerical simulation results and measured curves result are of the same trend. And it is feasible that mass concrete temperature field is simulated based on ANSYS.

Plant-emitted semi-volatiles shape the infochemical environment and herbivore resistance of heterospecific neighbors

Plant-emitted volatiles have been reported to shape ecological interactions occurring among species within single or between multiple trophic levels. The ecological contribution of volatiles to plant-herbivore, plant-pathogen, plant-to-plant and multitrophic interactions can be mutualistic, or may either favour or disfavour the players involved in the infochemical network. Emitting, perceiving or being passively engaged with airborne volatiles can result in ecological costs and/or benefits, render competitive advantage and shape population dynamics. We recently demonstrated a cost-effective way for plants to take advantage of volatile-based defence: by adsorbing neighbor-emitted compounds to defend against herbivory. We found that specific semi-volatiles emitted by Rhododendron tomentosum Harmaja are adsorbed to neighboring birch (Betula sp.) foliage in a natural habitat, in a field set-up and in the laboratory. These semi-volatiles were found to deter certain birch herbivores, and may thus confer associational resistance to birch. Here we show the relative change in the volatile profile of birch that occurs when neighbored by R. tomentosum. We further discuss the potential wider role of biogenic semi-volatiles for ecological interactions in natural environments and suggest how they might be utilized for pest management in agricultural crop production.

On the Potential of Kinematic GPR Surveying Using a Self-Tracking Total Station: Evaluating System Crosstalk and Latency

In this paper, we present an efficient kinematic ground-penetrating radar (GPR) surveying setup using a self-tracking total station (TTS). This setup combines the ability of modern GPR systems to interface with Global Positioning System (GPS) and the capability of the employed TTS system to immediately make the positioning information available in a standardized GPS data format. Wireless communication between the GPR and the TTS system is established by using gain variable radio modems. Such a kinematic surveying setup faces two major potential limitations. First, possible crosstalk effects between the GPR and the positioning system have to be evaluated. Based on multiple walkaway experiments, we show that, for reasonable field setups, instrumental crosstalk has no significant impact on GPR data quality. Second, we investigate systematic latency (i.e., the time delay between the actual position measurement by TTS and its fusion with the GPR data) and its impact on the positional precision of kinematically acquired 2-D and 3-D GPR data. To quantify latency for our kinematic survey setup, we acquired forward-reverse profile pairs across a well-known subsurface target. Comparing the forward and reverse GPR images using three fidelity measures allows determining the optimum latency value and correcting for it. Accounting for both of these potential limitations allows us to kinematically acquire high-quality and high-precision GPR data using off-the-shelf instrumentation without further hardware modifications. Until now, these issues have not been investigated in detail, and thus, we believe that our findings have significant implications also for other geophysical surveying approaches.

Interference from long-tailed finches constrains reproduction in the endangered Gouldian finch

1. Interspecific interference competition for nest-sites among cavity-nesting birds can have important effects on reproductive fitness and the distribution of competing species. 2. We observed interference at nest-sites in free-living populations of the endangered Gouldian finch (Erythrura gouldiae) and sympatric long-tailed finch (Poephila acuticauda), and also experimentally tested the relative strength and effect of interference at nest-sites in captive populations. 3. Levels of competitive interference at nest-sites in the wild were high for Gouldian, but not long-tailed finches, and interference frequency was inversely related to Gouldian finch reproductive success. High levels of interference conferred reduced fledging success but did not affect offspring condition. 4. Captive experiments corroborated the field data, also demonstrating fitness costs of interspecific competition, and that long-tailed finches dominated resources under standardized conditions. 5. Such asymmetrical competition dynamics are likely to constrain reproduction in Gouldian finch populations, potentially affecting recruitment and hindering the recovery of remaining populations of this endangered species.

A RapidArc planning strategy for prostate with simultaneous integrated boost

Since the clinical implementation of novel rotational forms of intensity‐modulated radiotherapy, a variety of planning studies have been published that reinforce the major selling points of the technique. Namely, comparable or even improved dose distributions with a reduction in both monitor units and treatment times, when compared with static gantry intensity‐modulated radiotherapy. Although the data are promising, a rigorous approach to produce these plans has yet to be established. As a result, this study outlines a robust and streamlined planning strategy with a concentration on RapidArc class solutions for prostate with a simultaneous integrated boost. This planning strategy outlines the field setup, recommended starting objectives, required user interactions to be made throughout optimization and post‐optimization adjustments. A comparative planning study, with static gantry IMRT, is then presented as justification for the planning strategy itself. A variety of parameters are evaluated relating to both the planning itself (optimization and calculation time) and the plans that result. Results of this comparative study are in line with previously published data, and the planning process is streamlined to a point where the RapidArc optimization time takes 15±1.3 minutes. Application of this planning strategy reduces the dependence of the produced plan on the experience of the planner, and has the potential to streamline the planning process within radiotherapy departments.PACS numbers: 87.55.x, 87.55.D, 87.55.de, 87.55.dk