Entrance Plane Research Articles

Aerodynamic Control of an Inlet Flow in Crosswind Using Peripheral Bleed Actuation

The flow within the inlet of an engine nacelle model in the absence of a fan and the presence of crosswind is investigated in wind-tunnel experiments, with specific emphasis on the effects of separation over the inlet’s inner windward surface on the flow distortion and pressure recovery. The inlet’s entrance plane is tilted forward, and its cross section is asymmetric about the horizontal centerline. The flow topology within the inlet is characterized over a range of Mach numbers and crosswind speeds up to M=0.72 and Uo=18 m/s, respectively. It is shown that in the presence of sufficiently high crosswind to the inlet speed ratio, a three-dimensional horseshoe-like separation domain is formed over the inlet’s inner windward surface. Owing to the cross-sectional asymmetry of the entrance plane, the separation domain migrates azimuthally downward and expands azimuthally with increased crosswind to the inlet speed ratio. The present investigations demonstrate the utility of flow control for mitigating the adverse effects of the separation. The actuation is based on controllable distributed aerodynamic air bleed that is driven by the pressure differences across the nacelle’s inner and outer surfaces and reattaches the separated base flow up to crosswind speeds of 15.4 m/s, resulting in a gain of up to 38% in total pressure recovery and a decrease of up to 55% in total pressure distortion. The efficacy of the bleed actuation can be further improved by tailoring the bleed distribution to the topology of the separated flow domain.

Sum-frequency generation at interfaces: A Fresnel story. I. Designing high contrast in two interface systems.

When a homogeneous film of finite thickness is optically probed, interference due to multiple reflections modulates in amplitude the electric field of light. For optical processes located only at the interfaces between two media, as is common for Sum-Frequency Generation (SFG), interference also modulates the contrast between signals generated at the entrance and exit planes of the film. We introduce a universal formalism for Fresnel factors, which bear all the information about interference, valid at any point in a three-layer system and for the three beams involved in the SFG process. Their analysis provides general rules for obtaining a high contrast. In particular, we define four configurations leading to the cancellation of the SFG response from the entrance side of the film when its thickness or the angles of incidence are tuned. Cancellation conditions depend on the polarization of light and follow simple analytical rules, leading to a straightforward experimental implementation. Such a selective cancellation makes it possible to independently measure single components of the nonlinear susceptibility, for example, in a ppp experiment and to separate surface from bulk response by combining a few measurements.

Rule for Mode Coupling Efficiency in Optical Waveguide Crossing

Crossing an optical waveguide requires a beam coupling from free space to waveguide at the entrance plane and another beam coupling from waveguide to free space at the exit plane of the waveguide. The aim of this paper is to provide a simple rule expressing the relationship between the involved numbers of free and guided modes that efficiently rebuild the field at each end of the waveguide. Using a numerical program built on Maple software, the rule was determined to be effective independently of the ratio between the beam spot size and the waveguide radius.

A patient with femoral osteitis fibrosa cystica mimicking bone neoplasm: a case report

BackgroundOsteitis fibrosa cystica is a rare, benign and osteolytic lesion attributed to hyperparathyroidism. The high level of parathyroid hormone cause rapid bone loss.Case presentationThe patient is a 50-year-old male complaining of severe and persistent pain in the right knee joint. Imaging studies were suspicious for a benign tumor in the right distal femur. Biopsy under CT guidance showed numerous osteoclast aggregation and hemosiderin deposition around the bone trabeculae. Blood tests disclosed significantly elevated parathyroid hormone, serum calcium, serum alkaline phosphatase. Parathyroid ultrasonography and CT scan showed a solid mass in front of the trachea at the thoracic entrance plane. After resection of the mass, the clinical symptoms were relieved and the radiological results were significantly improved, which further confirmed the diagnosis.ConclusionsMetabolic diseases-associated bone lesions require a comprehensive diagnosis of multiple inspection items. An interprofessional team approach to the diagnosis and treatment of osteitis fibrosa cystica will provide the best outcome.

Development of the MICADO Flat-field and Wavelength Calibration Unit: From Design to Prototyping

We describe the evolution and the analysis of the design that led to the development of the Flat-field and wavelength Calibration Unit (FCU) for the Multi-AO Imaging CAmera for Deep Observations (MICADO) instrument. MICADO will be one of the first light instruments of the Extremely Large Telescope. The FCU challenge in terms of calibration is related to the large size of the MICADO entrance and final focal plane, ∼200 mm × 200 mm. Such a focal plane scale and its segmentation in 3 × 3 detectors, require significant design modifications with respect to the calibration units of the current and past generation of instruments. The design analysis and ray tracing calculations are complemented with the test and verification of lab prototypes to assess the reliability of the FCU architecture in terms of flat-field illumination uniformity and signal to noise, spectral calibration line coverage and radial velocity stability of the wavelength solution provided to the instrument.

Numerical reconstruction of turbid slab optical properties using global optimization algorithms.

The detection and reconstruction of the optical properties within turbid slabs/plate parallel mediums have been widely investigated for its applications in medical diagnosis, atmosphere detection, etc., where the scattering of light would be expected. Although the scattering signal can be utilized for diagnostics purposes, the multiple scattering in the intermediate scattering regime (with an optical depth ~ 2-9) has posed a remarkable challenge. Existing optical tomography methods usually only reconstruct the reduced scattering coefficient to investigate the properties of the scattering target, while reconstruction efforts in analyzing the exact scattering phase function are rare. Solving such issues can provide much more information for proper interpretation of the characteristics of the turbid slab. This work demonstrates an inversion method based on optimization algorithms and the angular distribution of the transmitted light at the entrance plane and the exit plane of the sought medium. Candidate phase functions were pre-calculated and the optimization algorithm is able to reconstruct the phase function spatial distribution of the turbid slab with a satisfactory computational cost. Parametric studies were also performed to analyze the performance of each optimization algorithm used and the sensitivity of this Markov reconstruction scheme to noise.

The last entrance plane method for contact indeterminacy between convex polyhedral blocks

This study proposes the last entrance plane (LEP) principle to identify the physical contact plane, which is applicable to resolve contact indeterminacy between convex polyhedral blocks. Based on contact theory, the LEP principle reveals that the physical contact point lies on the last entrance plane. The LEP method is developed to identify the physical contact plane before penetration considering the geometrical and kinematical information. It offers a unified solution to contact indeterminacy between 2D convex polygonal and 3D convex polyhedral blocks. Using discontinuous deformation analysis, several numerical tests are evaluated to validate the accuracy and robustness of the LEP method.

Dynamics of shape-invariant rotating beams in linear media with harmonic potentials

We introduce a type of shape-invariant rotating beam in linear media with harmonic potentials. This type of beam is constructed by superposing a series of properly selected Laguerre-Gaussian beams of different orders. During propagation, the beam is shape invariant, but the pattern rotates and its size varies periodically. The transverse position of the beam at the exit plane of a medium can be steered by tuning the input parameters, even if the transverse position at the entrance plane is fixed.

Analytical features of extended Airy beams

The presence of widely used features, in particular, the autofocusing feature, of classical Airy beams leads to a thought of a benefit of their modification. There are several generalizations of Airy function both on base of the differential equation modification and variations in the integral notion. In the paper one more type of extended Airy functions is investigated theoretically and numerically. The type is constructed by generalization of the integral notion in a wide range of non-integer values of power. A principal attention in the paper is devoted to obtaining of approximate analytical expressions for extended Airy functions under an arbitrary exponent. On base of introduced functions the new type of autofocusing beams is formed. Extended Airy beams are formed if a diffractive optical element called the generalized lens is placed in an entrance plane of the optical scheme. The numerical examination of beams features is implemented by usage of the fractional Fourier transformation.

Passive control of global instability in low-density jets

Many studies have shown that low-density jets exhibit self-excited varicose oscillations. We use direct numerical simulation of the low Mach number Navier–Stokes equations to perform a linear global stability analysis of a helium jet at the threshold of onset of these oscillations. We calculate the direct and adjoint global modes and overlap these to obtain the structural sensitivity. We find that the structural sensitivity has high magnitudes in the shear layer downstream of the entrance plane, where the flow is absolutely unstable. We use the direct and adjoint global modes to calculate the effect of a control force on the growth rate and frequency of the unstable mode. We produce maps of the regions of the flow that are most sensitive to localized open loop steady forcing in the form of a body force and a heat source. We find that the most sensitive location for open loop steady forcing is the area around the shear layer, around 2 jet diameters downstream of the exit plane, and that the influence of steady forcing and heat injection is advected by the flow outside the jet. We use these maps to calculate the influence of a ring placed in the flow. When the ring is at the same temperature as the flow, it influences the flow through its drag. The ring has most influence when placed in the inner edge of the shear layer. When the ring is heated, it also influences the flow through the density reduction caused by heat input. In this case, the ring has most influence when placed in the outer edge of the shear layer. It is also influential when placed outside the jet because the expanded gas is advected towards the jet. In both these cases, the influence of the steady change to the base flow is significantly greater than the influence of an unsteady feedback force caused by the ring.

Distortion reconstruction in S-ducts from wall static pressure measurements

PurposeThis paper aims to report the attempts for predicting “on-the-fly” flow distortion in the engine entrance plane of a highly curved S-duct from wall static pressure measurements. Such a technology would be indispensable to trigger active flow control devices to mitigate the intense flow separations which occur in specific flight conditions.Design/methodology/approachEvaluation of different reconstruction algorithms is performed on the basis of data extracted from a Zonal Detached Eddy Simulation (ZDES) of a well-documented S-Duct (Garnier et al., AIAA J., 2015). Contrary to RANS methods, such a hybrid approach makes unsteady distortions available, which are necessary information for reconstruction algorithm assessment.FindingsThe best reconstruction accuracy is obtained with the artificial neural network (ANN) but the improvement compared to the classical linear stochastic estimation (LSE) is minor. The different inlet distortion coefficients are not reconstructed with the same accuracy. KA2 coefficient is finally identified as the more suited for activation of the control device.Originality/valueLSE and its second-order variant (quadratic stochastic estimation [QSE]) are applied for reconstructing instantaneous stagnation pressure in the flow field. The potential improvement of an algorithm based on an ANN is also evaluated. The statistical link between the wall sensors and 40-Kulite rake sensors are carefully discussed and the accuracy of the reconstruction of the most used distortion coefficients (DC60, RDI, CDI and KA2) is quantified for each estimation technique.

Comparison of the safety of the application of painless gastroscopy and ordinary gastroscopy in chronic hypertension patients combined with early gastric cancer.

The aim of the present study was to compare the safety of the application of painless gastroscopy and ordinary gastroscopy for chronic hypertension patients combined with early gastric cancer. A total of 123 patients with early gastric cancer were selected at the Dongying People's Hospital from June, 2014 to August, 2016. The patients were randomly divided into the painless (n=63) and ordinary (n=60) gastroscopy groups. Proper pretreatment was performed according to whether anesthesia was performed or not. Arterial pressure, heart rate, and blood oxygen saturation were detected and compared before anesthesia, when gastroscope passed through the esophageal entrance plane, and after recovery from anesthesia. The incidence of nausea and vomiting, cough, dysphoria, throat discomfort and other adverse reactions during and after surgery were recorded and compared. Compared with the levels before anesthesia, the mean arterial pressure, heart rate and blood oxygen saturation were significantly reduced in painless gastroscopy when the gastroscope passed through the esophageal entrance plane (P<0.05). In the ordinary gastroscopy group, the mean arterial pressure, heart rate and blood oxygen saturation were significantly increased when the gastroscope passed through the esophageal entrance plane compared with the levels before anesthesia (P<0.05). Blood pressure decreased in the painless gastroscopy group whereas it increased in the ordinary gastroscopy group after anesthesia. The decrease in the painless gastroscopy group was lower than in the ordinary group. The incidence of intraoperative and postoperative adverse reactions including nausea, vomiting, cough, dysphoria, pharyngeal discomfort and other adverse reactions was significantly decreased in the painless gastroscopy group than in the ordinary gastroscopy group (P<0.05). The results suggest that the application of painless gastroscopy in chronic hypertension patients can significantly reduce the incidence of intraoperative and postoperative adverse reactions compared with that of the Gastric cancer ordinary gastroscopy. Thus, painless gastroscopy is safer than ordinary gastroscopy.

Dosimetric feasibility of using tungsten-based functional paper for flexible chest wall protectors in intraoperative electron radiotherapy for breast cancer

Intraoperative electron radiotherapy (IOERT), which is an accelerated partial breast irradiation method, has been used for early-stage breast cancer treatment. In IOERT, a protective disk is inserted behind the target volume to minimize the dose received by normal tissues. However, to use such a disk, the surgical incision must be larger than the field size because the disk is manufactured from stiff and unyielding materials. In this study, the applicability of newly developed tungsten-based functional paper (TFP) was assessed as an alternative to the existing protective disk. The radiation-shielding performance of the TFP was verified through experimental measurements and Monte Carlo simulations. Percentage depth dose curves and lateral dose profiles with and without TFPs were measured and simulated on a dedicated IOERT accelerator. The number of piled-up TFPs was changed from 1 to 40. In the experimental measurements, the relative doses at the exit plane of the TFPs for 9 MeV were 42.7%, 9.2%, 0.2%, and 0.1% with 10, 20, 30, and 40 TFPs, respectively, whereas those for 12 MeV were 63.6%, 27.1%, 8.6%, and 0.2% with 10, 20, 30, and 40 TFPs, respectively. Slight dose enhancements caused by backscatter radiation from the TFPs were observed at the entrance plane of the TFPs at both beam energies. The results of the Monte Carlo simulation indicated the same tendency as the experimental measurements. Based on the experimental and simulated results, the radiation-shielding performances of 30 TFPs for 9 MeV and 40 TFPs for 12 MeV were confirmed to be acceptable and close to those of the existing protective disk. The findings of this study suggest the feasibility of using TFPs as flexible chest wall protectors in IOERT for breast cancer treatment.

Influence of capillary die geometry on wall slip of highly filled powder injection molding compounds

Uneven distribution of solid particles contained in the feedstocks used in the process of powder injection molding (PIM) is observed in the close vicinity of the walls. A particle-free thin layer adjacent to the walls is formed by the binder only and is characterized by so-called wall slip. Wall slip is a key to successful modeling of injection molding step of PIM. For its determination we used capillary rheometers equipped with the dies of different entrance angles applied to four PIM feedstocks. The entrance angle has been found to be a crucial parameter to intercept wall slip. Conical dies are more suitable to obtain reliable slip velocity values of highly filled compounds than capillaries having plane entrance, which are used in the majority of studies.

Investigating the effect of cold expansion on frictional force evolution during fretting fatigue tests of AL2024-T3 plates

In this paper, fretting fatigue experiments are conducted on cold expanded holed plates using fretting test configuration which is designed to simulate fretting fatigue condition around the holes. Two values of normal contact force and longitudinal cyclic load are applied on the specimens, and the evolution of friction force is measured during the tests. Finite element simulation is performed for better understanding of the cold expansion process and its effect on the contact configuration. The obtained results show that a high degree of cold expansion does not increase fretting fatigue life. Moreover, the value of frictional force is low at the early cycles of tests and increases to reach a stabilized value. The stabilized value of frictional force on the entrance and exit planes of low degree cold expanded specimens is almost the same, while it is lower on the exit plane of high degree cold expanded specimens in comparison to the entrance plane of the same specimen. It is revealed that the geometrical change that occurs on the plate during the high degree cold expansion process is the main cause of this phenomenon, while the increased hardness around the hole is the subsidiary factor.

Numerical and experimental study of ratcheting in cold expanded plate ofAl‐alloy 2024‐T3 in double shear lap joints

AbstractIn this paper strain ratcheting in cold expanded flat plate of Al‐alloy 2024‐T3 in double shear lap joints was studied both experimentally and numerically. In the experimental part, two types of symmetric strain‐controlled and asymmetric stress‐controlled cyclic tests were performed. Also, the cold expanded double shear lap joints subjected to cyclic stress‐controlled tests. The required parameters for simulating the cyclic plastic behaviour of Al‐alloy 2024‐T3 were obtained on the basis of the experimental responses. In the numerical part, a combination of nonlinear isotropic and nonlinear kinematic hardening model (Chaboche) was implemented in the commercial finite element code of ABAQUS, using the subroutine UMAT written in FORTRAN. The results of simulations give an accurate prediction of ratcheting for all types of loading. The obtained results show that increasing the mean stress increases the strain ratcheting. It is clearly shown that the cold expansion process decreases the magnitude of strain ratcheting remarkably compared with “as drilled” specimens and the decrease is bigger for larger cold expansion sizes. Also, it is shown that the middle plane has the highest amount of ratcheting compared to the pin entrance plane and exit plane of the plate hole.

Theoretical study for aerial image intensity in resist in high numerical aperture projection optics and experimental verification with one-dimensional patterns

In optical lithography, high-performance exposure tools are indispensable to obtain not only fine patterns but also preciseness in pattern width. Since an accurate theoretical method is necessary to predict these values, some pioneer and valuable studies have been proposed. However, there might be some ambiguity or lack of consensus regarding the treatment of diffraction by object, incoming inclination factor onto image plane in scalar imaging theory, and paradoxical phenomenon of the inclined entrance plane wave onto image in vector imaging theory. We have reconsidered imaging theory in detail and also phenomenologically resolved the paradox. By comparing theoretical aerial image intensity with experimental pattern width for one-dimensional pattern, we have validated our theoretical consideration.

Interaction trajectory of solitons in nonlinear media with an arbitrary degree of nonlocality

The interaction trajectory of solitons in nonlocal nonlinear media is investigated. A simple differential equation describing the interaction trajectories is derived based on the light ray equation. Numerical calculations are carried out to illustrate the interaction trajectories with different parameters. The results show that the degree of nonlocality greatly affects the interaction of solitons. For a strongly nonlocal case, the interaction trajectory can be described by a cosine function. Analytical expressions describing the trajectory and the oscillation period are obtained. For generally and weakly nonlocal cases, the interaction trajectories still oscillate periodically, however it is no longer sinusoidal and the oscillation period increases with the nonlocal degree decreasing. In addition, the trajectory of two solitons launched with a relative angle at the entrance plane is investigated. It is found that there exists a critical angle. When the initial relative angle is larger than the critical angle, the two solitons do not collide on propagation. The influence of the degree of nonlocality on the critical angle is also discussed.

Dosimetric impact of dental metallic crown on intensity-modulated radiotherapy and volumetric-modulated arc therapy for head and neck cancer.

Metal dental restoration materials cause dose enhancement upstream and dose disturbance downstream of the high‐density inhomogeneous regions in which these materials are used. In this study, we evaluated the impact of a dental metallic crown (DMC) on intensity‐modulated radiotherapy (IMRT) and volumetric‐modulated arc therapy (VMAT) for head and neck cancer. Additionally, the possibility of sparing the oral mucosa from dose enhancement using an individual intraoral mouthpiece was evaluated. An experimental oral phantom was designed to verify the dosimetric impact of a DMC. We evaluated the effect on single beam, parallel opposing beam, arc beam, IMRT, and VMAT treatment plans. To evaluate the utility of a 3‐mm‐thick intraoral mouthpiece, the doses across the mouthpiece were measured. For single beam irradiation, the measured doses at the entrance and exit planes of the DMC were 51% higher and 21% lower than the calculated dose by the treatment planning system, respectively. The maximum dose enhancements were 22% and 46% for parallel opposing beams and the 90° arc rotation beam, respectively. For IMRT and VMAT, the measured doses adjacent to the DMC were 12.2%±6.3% (mean±1.96 SD) and 12.7%±2.5% higher than the calculated doses, respectively. With regard to the performance of the intraoral mouthpiece for the IMRT and VMAT cases, the disagreement between measured and calculated doses at the outermost surface of the mouthpieces were −2.0%, and 2.0%, respectively. Dose enhancements caused by DMC‐mediated radiation scattering occurred during IMRT and VMAT. Because it is difficult to accurately estimate the dose perturbations, careful consideration is necessary when planning head and neck cancer treatments in patients with DMCs. To spare the oral mucosa from dose enhancement, the use of an individual intraoral mouthpiece should be considered.PACS numbers: 87.55.km, 87.55.N‐, 87.55.Qr

Optical design of a Fresnel concentrating solar system for direct transmission of radiation through an optical fibre bundle

A challenge in high-temperature solar thermal applications is efficiently transferring the concentrated solar energy to the load. The use of a solar concentrator in conjunction with bundled optical fibres has advantages in terms of transmission efficiency compared to a conventional heat transfer system employing heat exchangers and a heat transfer fluid. In this paper, the transmission from a solar concentrator into and through an optical fibre bundle over distances of up to 100m is estimated using simulations and experiments. A point focus Fresnel lens is employed to produce a concentrated beam with a smaller incident angle than the acceptance angle of the individual optical fibres in a bundle. Since the sunlight has a broad band spectrum and a very limited spatial coherence, interference effects can be neglected. Hence a ray tracing model covering absorption within the fibres and losses due to non-ideal internal reflections is employed. The intensity of the radiation across the exit plane of the fibre is found by integrating across all directions and wavelengths at each point. For a 15mm diameter bundle comprising some 27,000 individual low OH fibres, the average transmission per metre length of fibre is found to be 52% with the Fresnel lens. Around two thirds of the loss occurred at the entrance plane to the bundle, due to absorption in the packing material between the individual fibres.