scholarly journals A Publicly Available Dataset of Out-of-Field Dose Profiles of a 6 MV Linear Accelerator

2021 ◽  
Author(s):  
Samuel Peet ◽  
Naasiha Cassim ◽  
Tanya Kairn ◽  
Jamie V Trapp ◽  
Scott B Crowe
Keyword(s):  
Linear Accelerator ◽  
Feature Matching ◽  
Field Measurements ◽  
Analytical Models ◽  
Water Tank ◽  
Large Dataset ◽  
Beam Incident ◽  
Recent Developments ◽  
Novel Method ◽  
Development And Validation

Abstract An increase in radiotherapy-induced secondary malignancies has led to recent developments in analytical modelling of out-of-field dose. These models must be validated against measurements, but currently available datasets are outdated or limited in scope. This study aimed to address these shortcomings by producing a large dataset of out-of-field dose profiles measured with modern equipment. A novel method was developed with the intention of allowing physicists in all clinics to perform these measurements themselves using commonly available dosimetry equipment. A standard 3D scanning water tank was used to collect 36 extended profiles. Each profile was measured in two sections, with the inner section measured with the beam directly incident on the tank, and the outer section with the beam incident on a water-equivalent phantom abutted next to the tank. The two sections were then stitched using a novel feature-matching approach. The profiles were compared against linac commissioning data and manually inspected for discontinuities in the overlap region. The dataset is presented as a publicly accessible comma separated variable file containing off-axis ratios at a range of off-axis distances. This dataset may be applied to the development and validation of analytical models of out-of-field dose. Additionally, it may be used to inform dose estimates to radiosensitive implants and anatomy. Physicists are encouraged to perform these out-of-field measurements in their own clinics and share their results with the community.

Organic Reactivity Control by Means of Neighboring Groups and Organometallics. A Personal Account

1994 ◽  
Vol 59 (1) ◽  
pp. 1-74 ◽  
Author(s):  
Pavel Kočovský
Keyword(s):  
Transition Metals ◽  
Cyclopropane Ring ◽  
Allylic Substitutions ◽  
Recent Developments ◽  
Cardioactive Drug ◽  
Novel Method ◽  
Metal Catalyzed ◽  
Electrophilic Additions ◽  
Near Future ◽  
First Time

This review summarizes the main topics of our research and covers the period of the last 15 years. The prime interest is focused on various ways of controlling the regio- and stereoselectivity of selected organic reactions, in particular electrophilic additions, cleavage of cyclopropane rings, and allylic substitutions by means of neighboring groups and/or transition and non-transition metals. In the first part, the factors governing the course of electrophilic additions are assessed, culminating in the formulation of selection rules for the reactivity of cyclohexene systems, and in a concise synthesis of the natural cardioactive drug, strophanthidin. These studies also contribute to a better understanding of the mechanisms of electrophilic additions. The second part describes recent developments in the stereo- and regiocontrolled cleavage of cyclopropane rings by non-transition metals (Tl and Hg), and the reactivity and transmetalation (with Pd) of the primary products. This methodology has resulted in novel routes to unique polycyclic structures, and will have synthetic applications in the near future. Evidence for the stereospecific "corner" cleavage of the cyclopropane ring has been provided for the first time for Tl and later for Hg. The third part deals with transition metal-catalyzed allylic substitution. Evidence for a new "syn" mechanism for the formation of the intermediate (π-allyl)palladium complex has been provided, which runs counter to the generally accepted "anti" mechanism. A novel method for a Pd-catalyzed allylic oxidation has been developed and employed in the synthesis of natural sesquiterpenes. The increasing importance of transition and non-transition metals for synthetic organic chemistry is demonstrated by their unique reactivity in a number of the papers included in this review.

scholarly journals Observing merger trees in a new light

2018 ◽  
Vol 35 ◽  
Author(s):  
Rhys J. J. Poulton ◽  
Aaron S. G. Robotham ◽  
Chris Power ◽  
Pascal J. Elahi
Keyword(s):  
Dark Matter ◽  
Galaxy Formation ◽  
Diagnostic Tool ◽  
Cosmic Time ◽  
Analytical Models ◽  
Dark Matter Halos ◽  
Assembly Simulation ◽  
Novel Method ◽  
Tree Building

AbstractMerger trees harvested from cosmologicalN-body simulations encode the assembly histories of dark matter halos over cosmic time and are a fundamental component of semi-analytical models of galaxy formation. The ability to compare the tools used to construct merger trees, namely halo finders and tree building algorithms, in an unbiased and systematic manner is critical to assess the quality of merger trees. In this paper, we present the dendrogram, a novel method to visualise merger trees, which provides a comprehensive characterisation of a halo’s assembly history—tracking subhalo orbits, halo merger events, and the general evolution of halo properties. We show the usefulness of thedendrogramas a diagnostic tool of merger trees by comparing halo assembly simulation analysed with three different halo finders—VELOCIraptor, AHF, and Rockstar—and their associated tree builders. Based on our analysis of the resulting dendrograms, we highlight how they have been used to motivate improvements to VELOCIraptor. Thedendrogramsoftware is publicly available online, at:https://github.com/rhyspoulton/MergerTree-Dendrograms.

scholarly journals Development of Airtightness of Estonian Wooden Buildings

2019 ◽  
Vol 24 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Jaanus Hallik ◽  
Targo Kalamees
Keyword(s):  
Field Measurements ◽  
Building Structure ◽  
Air Leakage ◽  
Large Dataset ◽  
Apartment Buildings ◽  
Timber Construction ◽  
Significant Difference ◽  
Minimum Requirements ◽  
Post Hoc

The field measurements of airtightness in Estonian detached and apartment buildings conducted between2003 – 2017 were combined into a large dataset for further analysis. The buildings were classified basedon building structure, number of storeys, year of construction, energy classification and compactnessfactors. A subset with all wooden buildings (313 in total) was statistically analysed to determine theaverage (median) air leakage rates at 50 Pa and tested (Kruskal-Wallis test with post-hoc Conovertest) for significant differences within the grouping factors. As expected, the median air leakage (q50)of older buildings between 10.7 and 13.9 m3/(hm2) has decreased to 1.1 m3/(hm2) after the minimumrequirements for energy efficiency have taken effect. A more detailed analysis on newer buildings showedthat quality of the workmanship combining systematic measurement routines as well as prefabrication,yields significantly lower median air leakages compared to on-site construction. The buildings with betterenergy classification targets also achieved lower median air leakages compared to buildings designedto meet minimum requirements. Further analysis showed significant differences between buildingswith lightweight timber construction and those with log construction. This can be due to fact that theairtightness has been predominantly measured in prefabricated buildings compared to on-site buildingtechnology. Surprisingly, the analysis showed no significant difference between buildings with a differentcompactness factor or a different number of storeys. For use in energy calculations, the base values ofair leakage rates for each group are calculated and presented accounting for variation of measurements.

Damping Mechanisms in Cable-Harnessed Structures for Space Applications: Analytical Modeling

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Pranav Agrawal ◽  
Armaghan Salehian
Keyword(s):  
Structural Parameters ◽  
Analytical Models ◽  
Space Structures ◽  
Real Time Control ◽  
Space Applications ◽  
Time Control ◽  
Starting Point ◽  
Recent Developments ◽  
Damping Effects ◽  
Distributed Transfer Function

Abstract Recent developments in the aerospace industry have driven focus toward accurately modeling the effects of the cables and electronic cords on space structures. In the past, researchers have modeled the mass and stiffness effects of these cables but primarily overlooked their damping effects through careful analytical model developments. The objective of the current work is to present analytical models for cable-harnessed structures that also include the damping effects in their vibration response. Obtaining simple, low-order and high-fidelity models are highly advantageous in designing robust vibration real-time control algorithms for structures. Additionally, the analytical models are useful tools in providing insight into and better understanding of the dynamics of space structures as they are often difficult to be tested prior to launch due to their large size and at best only a few components may be tested. Motivated by the space applications, this work considers beam structures wrapped with cables which are modeled using beam and string theory assumptions. Two different damping models namely Kelvin–Voigt and hysteretic damping are considered. The homogenization approach is used as a starting point for structures of periodic wrapping patterns. Using the variational principle, the governing partial differential equation for the transverse coordinate of vibrations is found for three cable patterns and the results are compared to those from the distributed transfer function method (DTFM). Finally, the effects of several structural parameters are studied on the overall system damping.

Full Scale Data Comparison for the Horn Mountain Spar Mooring Line Tensions During Hurricane Isidore

2005 ◽  
Author(s):  
Arcandra Tahar ◽  
Lyle Finn ◽  
Pierre Liagre ◽  
John Halkyard
Keyword(s):  
Excellent Agreement ◽  
Coulomb Friction ◽  
Field Measurements ◽  
Analytical Models ◽  
Mooring Line ◽  
Conservative Estimate ◽  
Dynamic Tension ◽  
Mooring Lines ◽  
Data Comparison ◽  
Scale Data

The Horn Mountain Production Spar was installed in 5,400 feet of water in June 2002. This was the deepest floating production unit at that time. A comprehensive instrumentation program was initiated to measure spar and riser responses (Edwards et al, DOT 2003), while motion comparisons were presented on previous publication (Halkyard et al, OMAE 2004). The present paper discusses the results of these measurements and compares with analytical predictions of spar mooring tension during hurricane Isidore in September 2002. Particular attention has been placed on the importance of Coulomb friction between wire chain and the fairlead bearing to the dynamic tension of mooring lines. Mooring tensions were measured at chain jack location (inboard tension), while analytical models computed those tensions at the fairlead location (outboard tension). Our conclusion is that there is excellent agreement between field measurements and computed tensions at the chain jacks when fairlead friction is included, and when the vessel motions are accurately predicted. Ignoring fairlead friction results in a slightly conservative estimate for the tension at the chain jack. This has been the standard practice in all spar designs to date.

scholarly journals Dual-Probe Near-Field Phaseless Antenna Measurement System on Board a UAV

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4663 ◽  
Author(s):  
María García Fernández ◽  
Yuri Álvarez López ◽  
Fernando Las-Heras
Keyword(s):  
Measurement System ◽  
Phase Retrieval ◽  
Near Field ◽  
Field Measurements ◽  
Dual Band ◽  
Antenna Measurement ◽  
Antenna Performance ◽  
Simultaneous Acquisition ◽  
Recent Developments ◽  
The One

On-site antenna measurement has been recently attracting an increasing interest in order to assess the antenna performance in real operational environments. The complexity and cost of these kind of measurements have been significantly cut down due to recent developments in unmanned aerial vehicles’ (UAVs) hardware and antenna measurement post-processing techniques. In particular, the introduction of positioning and geo-referring subsystems capable of providing centimeter-level accuracy together with the use of phase retrieval techniques and near-field to far-field transformation algorithms, have enabled near field measurements using UAVs. This contribution presents an improved UAV-based on-site antenna measurement system. On the one hand, the simultaneous acquisition on two measurement surfaces has been introduced and calibrated properly, thus reducing geo-referring uncertainties and flight time. On the other hand, the positioning and geo-referring subsystem has been enhanced by means of a dual-band real time kinematics (RTK) unit. The system capabilities were validated by measuring an offset reflector antenna, and the results were compared with the measurements at the spherical range in the anechoic chamber and with the measurements collected with a previous version of the implemented system.

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