Window Plane Research Articles

SSRMP Recommendations No 9: Reference dosimetry in low and medium energy x-ray beams

The SSRMP recommendations on reference dosimetry in kilovolt beams as used in radiation therapy were revised to establish current practice in Switzerland.The recommendations specify the dosimetry formalism, reference class dosimeter systems and conditions used for the calibration of low and medium energy x-ray beams. Practical guidance is provided on the determination of the beam quality specifier and all corrections required for converting instrument readings to absorbed dose to water. Guidance is also provided on the determination of relative dose under non-reference conditions and on the cross calibration of instruments.The effect of lack of electron equilibrium and influence of contaminant electrons when using thin window plane parallel chambers at x-ray tube potentials higher than 50kV is elaborated in an appendix. In Switzerland the calibration of the reference system used for dosimetry is regulated by law. METAS and IRA are the authorities providing this calibration service to the radiotherapy departments. The last appendix of these recommendations summarise this calibration chain.

Quasi-optical mode converter for a high power TE8,3-mode gyrotron

We successfully developed a Gyrotron HS-III (28-GHz/400-kW/5-s) for electron cyclotron resonance heating in a spherical tokamak EXL-50, which operated in the TE8,3 mode. An internal quasi-optical-mode converter was designed to separate the spent electron beam from the outgoing power and convert the operating mode to a fundamental Gaussian wave beam. The particle swarm optimization algorithm was used to reduce diffraction loss from the launcher in such a low-frequency band. This enabled us to optimize the perturbation distribution of the launcher and beam waist of the target function to obtain the largest possible scalar correlation coefficient. The launcher was followed by three mirrors: one quasi-parabolic mirror and two phase-correcting mirrors. These were also optimized based on the scalar diffraction theory and Katsenelenbaum–Semenov algorithm to allow us to change the beam direction and increase the purity of the Gaussian output beam. Simulation results revealed a transmission efficiency of 96% and vector Gaussian mode purity of 99.8% at the window plane.

Smart window with grating optical filter: Comparison with smart windows fully coated with chromogenic layer

A comparative analysis is presented of a smart window with grating filter and a conventional smart window fully covered with switchable layer using the same chromogenic material in its colored and bleached states. The filter, formed by two thin-film gratings with alternating transmissive and chromogenic strips, has an angular-selective transmission of direct sunlight. Both gratings are sloped on the window plane at an angle to the horizontal, calculated taking into account the window azimuth to adapt to the solar trajectory relative to this window. The previously obtained calculation methods are modified and expanded, on the basis of which the temporal characteristics of light and solar transmittance, as well as direct and diffuse illuminance and irradiance indoors, of windows with two different southeast azimuths for June 15, September and December are calculated. The results show two main advantages of a grating smart window over a conventional one. Firstly, in active (colored) mode, due to angular selectivity of transmission it has self-adjusting light and solar transmittance throughout the day and year without using the daylight shading/redirecting devices, and in the bleached state, it has a higher transmittance. Secondly, by adjusting the transmission of direct sunlight, the filter transmits more than twice as much diffuse light in both colored and bleached states, thereby increasing indoor comfort in any season.

An Assessment of Orientation on Effective Natural Ventilation for Thermal Comfort in Primary School Classrooms in Enugu City, Nigeria

The current harsh climatic and high thermal conditions observed across the globe due to climate change is a challenge for indoor thermal comfort in buildings. In most developing nation, educational buildings where formal teaching and learning is conducted are designed to function without mechanical ventilation in an attempt to save energy costs hence relying solely on Natural ventilation. However, the effects of orientation on effective natural ventilation in educational buildings in the hot-humid tropical environments have not been adequately explored. The aim of this study was to investigate the effect of orientation of the classroom buildings with respect to cardinal and wind directions on effective natural ventilation desired for thermal comfort in buildings of public primary schools in the city of Enugu, Nigeria. It adopted a combination of experimental and descriptive survey research design. Instruments for data collection were two thermo-anemometer data logging device (AZ 9871) for determining both indoor and outdoor temperatures, wind velocities and relative humidity of classrooms of selected 60 public primary school building in the metropolis based on stratified sampling technique. Data analysis was done using linear regression analysis, the global coefficient of ventilation and building orientation standards. The research results showed that there was a correlation between classroom building orientations and effective natural ventilation coefficient and that the mean natural ventilation efficiency of 80% above the 60% global ventilation efficiency standard was achieved. In addition, orientation of classroom buildings in terms of inlet window planes to the dominant wind direction had positive significant effect on natural ventilation efficiency, invariably influencing the thermal comfort conditions of the investigated classrooms. The research concludes that adequate attention should be given to the orientation in classroom buildings especially in the hot humid tropical environments by architects and building designers to ensure thermal comfort is achieved for effective teaching and learning.
 Keywords: Building orientation, Natural ventilation, Tropical environment, Classroom buildings, Thermal comfort

Chiral Absorber-Based Frequency Selective Rasorber With Identical Filtering Characteristics for Distinct Polarizations

In this article, we propose a new paradigm to design frequency-selective rasorber (FSR) with two-sided efficient absorptions and broadband transmission in a chiral structure. The proposed FSR is implemented via combining two chiral absorber layers with a bandpass frequency-selective surface (FSS). An absorptive split-ring resonator (ASRR) inserted with a resistive film is designed to provide efficient spin-sensitive absorption. Then, four ASRRs are arranged to form a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{4}$ </tex-math></inline-formula> symmetric split-ring absorber (SRA) with identical absorption for distinct polarized incident waves. The physical mechanisms of spin-selective absorption and polarization-insensitive absorption are discussed theoretically. The broadband bandpass FSS is introduced to provide a transparent window and ground plane for the absorbers. A prototype is fabricated and measured to verify the feasibility of the method. The simulation and experimental results manifest over 90% absorptive bands of 1.5–3.6 and 15.2–21.6 GHz and a transmission band of 8–12 GHz with insertion loss less than 2 dB. Compared with previous FSRs, the proposed FSR has a broadband transmission, efficient absorptions with high-frequency selectivity, and easy geometric structure.

Analysis of tympanic sinus shape for purposes of intraoperative hearing monitoring: a microCT study

PurposeSinus tympani is the space in the retrotympanum, with variable morphology. Computed tomography is a common tool to investigate sinus tympani anatomy. During cochlear implantation or tympanoplasty, electrocochleography can be used for hearing monitoring. In such a surgical strategy the electrode is placed in the round window’s region throughout posterior tympanotomy. Common accessible needle-shaped electrodes using is difficult in achieving intraoperative stabilization. The aim of the study is to assess the dimensions and shape of sinus tympani, basing on the micro computed tomography scans for purposes of establishing the possible new electrocochleography electrode shape.Materials and methodsSixteen fresh frozen cadaveric temporal bones were dissected. MicroCT measurements included the depth and the width of sinus tympani, width of facial canal with stapedius muscle chamber. Obtained data were analyzed statistically with the use of RStudio 1.3.959 software.ResultsThe highest average width of sinus tympani amounted for 2.68 mm, depth measured at the round window plane for 3.19 mm. Width of facial canal with stapedius muscle chamber highest average values at the round window plane- 3.32 mm. The lowest average minimum and maximum values were calculated at the 1 mm above the round window plane. The highest average posterior tympanotomy width was 2.91 mm.ConclusionsThe shape of the tympanic sinus is like a trough with the narrowest and deepest dimensions in the middle part. The ST shape and dimensions should be taken into account in constructing the ECochG electrode, designed for optimal placement through posterior tympanotomy approach.

Sensor minimization method for integrated daylighting control by a mathematical approach

We proposed a simplified integrated daylight control (SIDC) system, which is a mathematical daylight control approach for multiple personal offices that use a couple of sensors installed in the outside of buildings. After the window plane illuminance that could reflect the external obstruction and the solar position was predicted, the correlation between the window and the work plane illuminance was analyzed through the pre-calculation phase. We allowed this correlation to reflect the roller-shade position. The roller-shade control approaches were proposed using two methods: one is a method of control via the position of the sun, and the other is a method of control via effective window plane illuminance based on the discomfort illuminance level of the work plane. After simple equations to predict the work plane illuminance according to the roller-shade positions in the pre-calculation phase were derived, the SIDC system was controlled with one of two roller-shade control methods. We used climate-based simulations for verification. As a result, roller-shade control using effective window plane illuminance was more efficient than control using solar position. 90.21% of all office hours were met with satisfactory visual comfort conditions. Energy usage was reduced by 86.96% compared to that of on/off control.

Evaluation of a daylight-responsive, iterative, closed-loop light control scheme

In this paper an iterative, closed-loop light control scheme is proposed and evaluated by a white light emitting diode-based, daylight-responsive luminaire to follow the time-varying pattern of correlated colour temperature and illuminance of a daylight scene. The proposed control scheme functions primarily with the response signals of two RGB colour sensors, viz., a daylight sensor to monitor the daylight scene at the window plane and an internal light sensor to monitor the light scene created by the test white light emitting diode luminaire. The control scheme controls the lumen delivery of individual light emitting diode arrays of the test luminaire by adjusting the duty cycles to follow the instantaneous correlated colour temperature of daylight and at the same time to respond to the variation of window plane illuminance in the reverse pattern. Evaluation is conducted by laboratory testing and in situ testing. The maximum deviations in correlated colour temperature, illuminance and chromaticity from the required values under laboratory testing and in situ testing are found to be [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text], [Formula: see text] respectively, which establish the acceptable performance of the proposed iterative light control scheme.

Benefits of Unidirectional Design Based on Decoupled Transmitters and Receivers in Tackling Traffic Asymmetry for Elastic Optical Networks

We consider a unidirectional design approach to tackle the traffic asymmetry in an elastic optical network (EON). We decouple a bidirectional transponder into a pair of separate unidirectional transmitters and unidirectional receivers, and consider different multi-flow transmitters that use either an array of laser diodes or a broadband laser source with filters to generate multiple sub-carriers. To evaluate the benefit of this unidirectional design, we have considered the routing and spectrum allocation optimization problem for the EON. An integer linear programming model and an efficient heuristic algorithm based on spectrum window planes have been developed. Simulation results show that the proposed unidirectional design approach can significantly improve capacity utilization and minimize network cost compared to one based on bidirectional symmetric traffic flows. It is also efficient for network scenarios with spatial traffic asymmetry and where multi-period network planning is required.

Output System of A 220-/247.5-/275-GHz, 1.0-MW, Triple-Frequency Regime Gyrotron

In this paper, the design studies of an output system [comprising a nonlinear taper, a quasi-optical launcher (QOL), and an RF window] for 220-/247.5-/275-GHz, triple-frequency gyrotron are presented. The precisely chosen mode-triplet is TE39,14/TE43,16/TE47,18 to support adequate power transfer at their corresponding frequencies of operation. The nonlinear uptaper is optimized using our in-house code Gyrotron Design Suite version 4.0 (GDSv4.0 2016) [7] in order to reduce the mode conversion for all the frequencies. A common dimpled wall QOL is designed and simulated using commercially available launcher optimization tool. A chemical vapor-deposited-diamond RF window is recommended with a decent transmission bandwidth for all the operating frequencies. The knowledge of correct phase of the Gaussian-like beam coming out of the RF window of any high-power gyrotron is most important for scheming a correct matching optic unit. Hence, the theoretical phase of the beams at a window plane is retrieved using an iterative phase retrieval algorithm.

SDN Enabled Restoration With Triggered Precomputation in Elastic Optical Inter-Datacenter Networks

Flexi-grid elastic optical networks (EONs) provide a promising infrastructure for meeting the high-bandwidth and low-latency requirements of interconnecting datacenters. Since failures of high-capacity fiber links prevent users from accessing cloud services and lead to large amounts of data loss, much recent research has focused on inter-datacenter network failure recovery. In this paper, we build upon software-defined networking (SDN) technology and develop a fast restoration strategy with triggered precomputation (FR-TP) that achieves fast failure recovery with minimal resource overhead. Our work makes several contributions. We extend the controller functionality and OpenFlow protocol for software-defined elastic optical inter-datacenter network architectures, so as to obtain the global network state information quickly and accurately. We then present the FR-TP strategy and an associated trigger mechanism to compute backup paths before a link failure occurs. Furthermore, to improve the efficiency of path computation and bandwidth resource assignment, we construct a layered auxiliary graph of spectrum window planes (SWP-LAG) using a residual capacity matrix to change dynamically the width of the spectrum window planes (SWPs) to satisfy different service requests. Simulation results demonstrate that, compared with existing restoration strategies, the proposed FR-TP strategy combined with SWP-LAG reduces the recovery time by up to 30.4% in the network topologies studied without increasing the blocking probability.

Elastic Versus WDM Networks With Dedicated Multicast Protection

We consider the routing and spectrum allocation (RSA) problem of protecting all-optical multicast sessions against a single link failure in elastic optical networks (EONs). A tree is derived to support a multicast session and can be considered as a set of paths originating from a common source. We use a scheme to protect each of the paths by an arc-disjoint backup path in the case of any link failure. For this problem, we provide a node-arc integer linear programming (ILP) formulation and propose a heuristic algorithm for this protection scheme. We evaluate the improvement achieved by the flexible grids adopted in EONs over the fixed-grid wavelength-division multiplexing (WDM) networks. The evaluation is done by considering static modeling based on ILP and heuristics as well as dynamic simulations. We consider two approaches for heuristic algorithms: one is a two-step (TS) approach that computes the routing trees then allocates spectrum. The other uses the spectrum window plane (SWP) and constructs auxiliary graphs for the relevant range of spectrum to jointly solve the RSA problem. We evaluate the performances of the proposed algorithms under static and dynamic traffic models. Based on the studied scenarios, we observe consistent improvement in efficiency of flexible grid EONs over fixed-grid WDM networks. Moreover, we demonstrate that the network size (likely because of the availability of more alternative routes) can significantly affect the benefit in efficiency achieved by the SWP-based approaches over the TS approaches.

Investigation of photoconductivity of individual InAs/GaAs(001) quantum dots by Scanning Near-field Optical Microscopy

The spatial distribution of the photocurrent in the input window plane of a GaAs-based p–i–n photodiode with embedded self-assembled InAs quantum dots (QDs) has been studied with the photoexcitation through a Scanning Near-field Optical Microscope (SNOM) probe at the emission wavelength greater than the intrinsic absorption edge of the host material (GaAs). The inhomogeneities related to the interband absorption in the individual InAs/GaAs(001) QDs have been observed in the photocurrent SNOM images. Thus, the possibility of imaging the individual InAs/GaAs(001) QDs in the photocurrent SNOM images with the lateral spatial resolution ∼ 100 nm (of the same order of magnitude as the SNOM probe aperture size) has been demonstrated.

Effect of force and location of bottleneck for particle moving through window under encapsulation

One of the central assumptions to explain appearance of an anomalous diffusion regime in microporous materials is the cancellation of forces experienced by a moving particle at the bottleneck. In this work, we examine this issue of force cancellation inside a microporous material exploring the diffusion path and cross-checking bottleneck associated with diffusion. Conventional wisdom is that window of a microporous material is the bottleneck for diffusion. Our study reveals that bottleneck for diffusion is not at the window, it is always 2.6 A to 3.0 A away from the window plane and depending on guest size, it lies in different parts of the inner surface of $$\alpha $$ -cage. Window has significant effect in diffusion process only when diffusing particle size is comparable or larger than the window free diameter. Window does not play any role if particle size is smaller than window free diameter. We show that in the anomalous diffusion regime there is no signature of force cancellation at the window. Activation energy and total force along the diffusion path are responsible for the existence of anomalous diffusion regime in microporous materials. Correlation between diffusivity (D) and activation energy ( $$E_a$$ ) in faujasite zeolite is shown. Force cancellation at the window of microporous material does not play any role in the diffusion process unless diffusing particle size is larger than the window free diameter. The location of bottleneck for diffusion is not at the window, it is always 2.6 A to 3.0 A away from the window plane.

Migration From Fixed to Flexible Grid Optical Networks With Sub-Band Virtual Concatenation

A novel strategy is presented to operate a mixed fixed/flexible grid optical network which may be used to gradually migrate from a fixed to a flexible mode of operation. Routing and spectrum allocation (RSA) in an optical network where fixed and flexible grids co-exist using a multi-path sub-band virtual concatenation (VCAT) or split spectrum (SS) technique is considered. Mixed integer linear programming models and an efficient heuristic algorithm based on spectrum window planes are proposed for the RSA optimization. The results obtained for the static traffic demand indicate that it is operationally more convenient to use the multi-path VCAT only by itself in a mixed grid optical network to guarantee performance comparable to that of the joint multi-path and single-path VCAT case. Network performance is also evaluated in terms of bandwidth blocking probability (BBP) under a dynamic traffic demand. Simulation results show that the multi-path VCAT scheme can efficiently utilize the overall spectrum resources with low blocking. The results of studies with both static and dynamic traffic demands also confirm that migration from a pure fixed grid optical network to a pure flexible grid will be desirable for better network capacity utilization.

Routing and Spectrum Assignment for Dual Failure Path Protected Elastic Optical Networks

We present the design of a dual failure protected elastic optical network (EON) for different sharing capabilities of protection lightpaths. Routing and spectrum assignment (RSA) is considered for such a network so as to minimize the maximum number of frequency slots (FSs) used. The key principles for protection resource sharing among the first and the second protection lightpaths are identified for dedicated 1:1:1, mixed 1:1:1, 1+1:1, and 1+1+1 protection. Both integer linear programming (ILP) models and spectrum window plane (SWP)-based heuristic algorithms are proposed for RSA in dual failure protected EONs. Simulation results indicate that, apart from being efficient, the proposed SWP-based heuristic algorithm not only performs close to the ILP model but also does much better than a benchmark adaptive routing algorithm. We find that 1:1:1 protection technique performs better in terms of the maximum number of FSs used and the spare capacity redundancy than both the 1+1:1 and 1+1+1 techniques. In addition, the mixed 1:1:1 case outperforms the dedicated 1:1:1 case both in minimizing the maximum number of link FSs used and its spare capacity redundancy.

Benefit of adaptive FEC in shared backup path protected elastic optical network.

We apply an adaptive forward error correction (FEC) allocation strategy to an Elastic Optical Network (EON) operated with shared backup path protection (SBPP). To maximize the protected network capacity that can be carried, an Integer Linear Programing (ILP) model and a spectrum window plane (SWP)-based heuristic algorithm are developed. Simulation results show that the FEC coding overhead required by the adaptive FEC scheme is significantly lower than that needed by a fixed FEC allocation strategy resulting in higher network capacity for the adaptive strategy. The adaptive FEC allocation strategy can also significantly outperform the fixed FEC allocation strategy both in terms of the spare capacity redundancy and the average FEC coding overhead needed per optical channel. The proposed heuristic algorithm is efficient and not only performs closer to the ILP model but also does much better than the shortest-path algorithm.

Cooperative Reformable Channel System with Unique Recognition of Gas Molecules in a Zeolitic Imidazolate Framework with Multilevel Flexible Ligands

We report a cooperative reformable channel system in a ZIF-L crystal arising from coexistence of three types of local flexible ligands. The reformable channel is able to regulate permeation of a nonspherical guest molecule, such as N2 or CO2, based on its longer molecular dimension, which is in a striking contrast to conventional molecular sieves that regulate the shorter cross-sectional dimension of the guest molecules. Our density functional theory (DFT) calculations reveal that the guest molecule induces dynamic motion of the flexible ligands, leading to the channel reformation, and then the guest molecule reorientates itself to fit in the reformed channel. Such a unique “induced fit-in” mechanism causes the gas molecule to pass through six-membered-ring windows in the c- crystal direction of ZIF-L with its longer axis parallel to the window plane. Our experimental permeance of N2 through the ZIF-L membranes is about three times greater than that of CO2, supporting the DFT simulation predictions.

Induced fluid rotation and bistable fluidic turn-down valves (a survey)

Paper surveys engineering applications of an unusual fluidic principle — momentum transfer through a relatively small communicating window into a vortex chamber, where the initially stationary fluid is put into rotation. The transfer is often by shear stress acting in the window plane, but may be enhanced and perhaps even dominated by fluid flow crossing the boundary. The case of zero-time-mean fluid transport through the window has found use in experimental fluid mechanics: non-invasive measurement of wall shear stress on objects by evaluating the induced rotation in the vortex chamber. The case with the non-zero flow through the interface became the starting point in development of fluidic valves combining two otherwise mutually incompatible properties: bistability and flow turning down.

Distance Adaptive Dynamic Routing and Spectrum Allocation in Elastic Optical Networks with Shared Backup Path Protection

This paper considers distance adaptive dynamic routing and spectrum assignment (RSA) for elastic optical networks with shared backup path protection (SBPP). Efficient heuristic algorithms based on spectrum window planes are proposed for implementing distance and modulation format adaptive RSA so as to maximize spare capacity sharing among multiple protection lightpaths. A differentiated sharable frequency slot cost was also defined for the first time to more efficiently share protection resource. Network performance is evaluated in terms of bandwidth blocking probability (BBP) through simulations. The proposed SBPP technique is effective in reducing BBP and improving spectral efficiency compared to conventional SBPP schemes and 1+1 path protection. The impact of transponder tunability on bandwidth blocking performance is also evaluated to show that a limited tuning range is sufficient to achieve a BBP performance close to that with full tunability.