Detector Radius Research Articles

METHOD OF NUMERICAL MODELING OF DETERMINING THE INDICATOR OF MISSILE FIRING EFFICIENCY AT VARIOUS AIR TARGETS WHEN PRACTICING TARGETING FROM A BATTERY COMMAND POST

A methodology for numerical modeling of determining the efficiency of missile firing in the form of conditional probability of hitting air targets is developed and presented. The firing of missiles at different windward targets during the development of targeting from a battery command post or regimental command post is considered. The modeling takes into account the design and technical characteristics of the stations and systems of the combat vehicle and missile. The flight altitudes of different airborne targets are 500 m, 1000 m, 5000 m, with the flight speed of a typical target being 230 m/s and 40 m/s for an unmanned aerial vehicle. The effect of active noise interference of different densities on the radar channels of the target tracking station and the missile fuze is shown. Interference from weak to feeder density (or their residues) of the same level was used, after appropriate compensation. The influence of possible maneuvering of airborne targets with overloads up to 10 g and different effective scattering surfaces of targets from 10-3 m2 to 102 m2 is calculated. The ranges of target acquisition for automatic tracking are determined when the target parameters are no more than 103 m and taking into account the range of the target from the antenna pattern of the combat vehicle target tracking station. The values of the inclined ranges to the far limit of the kill zone of an anti-aircraft missile system for different effective scattering surfaces, interference, and target velocities are presented. Values are given for the first kind of missile firing errors, namely the probability of a missile passing through a “tube” of the required radius. The values of the systematic components of missile guidance errors and their standard deviation are given, depending on the point of contact between the missile and the target. The largest missile miss (at which the fuse is triggered with a probability of 0,5) and the average miss and its standard deviation of errors are found. The values of the second kind of firing errors, i.e., the probability of triggering the missile's radio fuse, were calculated. The standard deviation of the missile's radar detector errors is calculated, taking into account the scalar diffraction field in the intermediate and near zones of its receiving antenna. The values of the mathematical expectation of the random value of the radius of the missile's radar detector, which corresponds to a certain target under the given conditions of the missile's meeting with the target, are found. To calculate the conditional probability of a missile's radar detector being triggered, the general case of the probability of a missile's radar detector being triggered at fixed values of different effective scattering surfaces, interference levels, and missile misses is used. The paper analyzes the values of conditional probabilities of hitting air targets when firing a single missile, which are limited by the values of the circular law of target destruction. The obtained values of the conditional probabilities of hitting air targets are strictly tied to the far limit of the complex's kill zone. The analytical expressions for the calculations, the results of the calculations, and the corresponding graphical material are presented.

A proposed numerical method for absolute efficiency calibration of α-spectrometers and its application for activity calculation

In this work, an absolute method to calibrate an α-spectrometer is proposed taking into account the Source-to-Detector, and lateral distances due to eccentric source distribution. An analytical formula to calibrate an α-spectrometer is derived and the Simpson's integration method was utilized to solve these equations in its integral form numerically using a written C computer code. The general Monte Carlo N-particle code, MCNP as well as experimental measurements for some standard α-emitters are used to benchmark the proposed method. An agreement was found between the efficiency results calculated by MC and the proposed method with a maximum relative difference of about 0.5%. While, experimental measurement of α-emitters activity employing the proposed method differs by about 1.65% from the certified values. Accounting for the man made error allows to accurately quantify the assayed sample. Therefore, the inaccuracy in the efficiency results due to non-accurate inputs pertained to the source, and detector radii, Source–Detector distances, and eccentric source distribution are investigated in the Source-to-Detector distance range of (4 to 44 mm). The results show that a difference of ±1% in the detector radius, and Source-to-Detector distance than the normal values yields a relative difference of about ±2%, while a difference of ±50% in the source radius or source lateral distance from detector symmetry axis could only yields inaccuracy of less than ±3% in the efficiency results.

Monte Carlo simulation of a simple and fast method to experimentally determine the partial sensitivity of a bare LR-115 detector using planar alpha sources

Partial sensitivity of the bare LR-115 detector (KB) to radon or thoron, or any of their airborne progeny, is an essential component in the detector's calibration factor. Its experimental determination is complex, requires expensive and sophisticated instruments and facilities, and is time consuming. Using the TRACK_TEST and SRIM programs, and Monte Carlo simulations, the possibility of a simple and fast method to determine KB experimentally was demonstrated. The method is based on calculations of the average value of detection efficiencies (i.e., the cumulative efficiency) for alpha particles emitted by a planar alpha source placed at different distances from detectors. Source radius can be estimated from the energy of emitted alpha particles, detector radius, and parameters dependent on etching conditions. Varying the emission energy of alpha particles, the source and detector radii, and the source-detector distance step length, an average value of 0.02 tracks. cm−2 per Bq.d.m−3 (0.22 cm) was obtained assuming standard etching conditions. In addition to alpha electrodeposited sources, sealed sources such as those built with anodized aluminium sheets proved to be suitable for this proposal. Experimentally, KB can be estimated from: track densities registered in detectors exposed at different distances from the source, range of distances that produce visible tracks, and source activity. The developed method is much simpler and faster than the conventional method that uses standard sources of radon and its progeny and large chamber with controlled conditions.

Metalens integrated receiver to reduce the effect of angle of arrival jitter in free space optical communication

In this paper, we propose a metalens integrated receiver for free space optical communication, which provides robust performance in the presence of angle of arrival fluctuations jitter. As a proof of concept, we show that our proposed receiver can tolerate up to a 2.5 mrad angle of arrival fluctuations with a detector radius of 20 µm before reaching a 3 dB power penalty. We design a meta unit cell to realize the optimized phase profile and present a quasi-3D full wave simulation of the proposed architecture. The system shows steady signal power and bit error rate in the presence of angle of arrival fluctuation.

A Modified Gray Wolf Optimizer-Based Negative Selection Algorithm for Network Anomaly Detection

Intrusion detection systems are crucial in fighting against various network attacks. By monitoring the network behavior in real time, possible attack attempts can be detected and acted upon. However, with the development of openness and flexibility of networks, artificial immunity-based network anomaly detection methods lack continuous adaptability and hence have poor detection performance. Thus, a novel framework for network anomaly detection with adaptive regulation is built in this paper. First, a heuristic dimensionality reduction algorithm based on unsupervised clustering is proposed. This algorithm uses the correlation between features to select the best subset. Then, a hybrid partitioning strategy is introduced in the negative selection algorithm (NSA), which divides the feature space into a grid based on the sample distribution density and generates specific candidate detectors in the boundary grid to effectively mitigate the holes caused by boundary diversity. Finally, the NSA is improved by self-set clustering and a novel gray wolf optimizer to achieve adaptive adjustment of the detector radius and position. The results show that the proposed NSA algorithm based on mixed hierarchical division and gray wolf optimization (MDGWO-NSA) achieves a higher detection rate, lower false alarm rate, and better generation quality than other network anomaly detection algorithms.

Cohering and decohering power of massive scalar fields under instantaneous interactions

Employing a non-perturbative approach based on an instantaneous interaction between a two-level Unruh-DeWitt detector and a massive scalar field, we investigate the ability of the field to generate or destroy coherence in the detector by deriving the cohering and decohering power of the induced quantum evolution channel. For a field in a coherent state a previously unnoticed effect is reported whereby the amount of coherence that the field generates displays a revival pattern with respect to the size of the detector. It is demonstrated that by including mass in a thermal field the set of maximally coherent states of the detector decoheres less compared to a zero mass. In both of the examples mentioned, by making a suitable choice of detector radius, field energy and coupling strength it is possible to infer the mass of the field by either measuring the coherence present in the detector in the case of an interaction with a coherent field or the corresponding decoherence of a maximally coherent state in the case of a thermal field. In view of recent advances in the study of Proca metamaterials, these results suggest the possibility of utilising the theory of massive electromagnetism for the construction of novel applications for use in quantum technologies.

Geometrical optimisation of a segmented HPGe detector for spectroscopic gamma emission tomography—A simulation study

Segmented coaxial HPGe (High Purity Germanium) detectors have recently been shown to be feasible for Gamma Emission Tomography (GET). This type of detector allows for a combination of high efficiency and high energy resolution in gamma spectrometry of irradiated nuclear fuel. The ultimate aim of developing segmented HPGe for GET measurements is to achieve a high spatial resolution to facilitate imaging of rod-internal features and interrogation of smaller irradiated fuel samples.In this work, we present the optimisation of a segmented HPGe detector through a simulation study using the Monte Carlo particle transport code MCNP. Constraints to each dimension of the detector were identified, from manufacturing limitations and requirements arising from the use of a finite-sized collimator slit. In particular, a relationship between the minimum inner radius of the coaxial detector and the segments azimuthal dimension was derived based on the identified constraints. Segment azimuthal and radial dimensions have been varied (based on the derived relationship between the azimuthal and radial dimension) and the full energy efficiency and misidentification rate were evaluated to obtain the optimal dimensions. The optimal ranges of the segment dimensions were determined.

A Comparison and Analysis of Domestic and Foreign Standards Related to Unwanted Fire Alarms

As unwanted fire alarms within the automatic fire detection system increase, fire-fighting power gets wasted. This is recognized as important because it causes a decrease in the evacuation reliability of the occupancy. Therefore, in order to develop measures to reduce unwanted fire alarms, foreign (United States and, United Kingdom) and domestic standards related to unwanted fire alarms were compared and analyzed in the present study. Through the analysis the problems with the standards were identified as uncertainty regarding the detecting space and radius of the smoke detector, the absence of a statistical database (DB) for unwanted fire alarms, the absence of a protocol for managing unwanted fire alarms, and the absence of testing standards for unwanted fire alarms based on scenarios. Consequently, it is proposed that to deal with the problems, it is necessary to ascertain the detecting space and radius of the smoke detector, to propose unwanted fire alarm protection codes for database (DB) system construction, to supplement the fire safety management log by developing related manuals, and to develop unwanted fire alarm testing standards of Korean type based on scenarios.

A Novel Fault Diagnosis Method Based on Improved Negative Selection Algorithm

In this article, an improved negative selection algorithm (NSA) is proposed and then applied to fault detection and fault isolation (also called as fault diagnosis). Coverage rate and overlap rate are the two important performance indexes on evaluating NSA. A higher coverage rate means a lower fault missing rate, and a lower overlap rate means a lower computation cost. However, the existing NSAs cannot keep a good balance between the coverage rate and the overlap rate. In our work, a new formula for overlap rate is first proposed, which is more accurate than the existing works. Then, the screening rule is introduced to decrease the overlap rate. More importantly, the detector radius can change automatically according to the overlap rate, and simultaneously, the detector movement is adopted to increase the coverage rate. Hence, the proposed improved NSA can not only increase the coverage rate but also decrease the overlap rate, which is then applied to fault detection and isolation. Finally, simulations on the data from the three-tank system are conducted to verify the effectiveness of the proposed scheme.

Fault Detection of Aircraft Control System Based on Negative Selection Algorithm

The aircraft control system controls the whole flight movement process. Its fault detection can assist the aircraft PHM system in making decisions and completing the targeted maintenance, which is of great significance to improve the safety and reliability of the aircraft. In this paper, by taking advantage of the strong leaning and intelligent recognition ability and the characteristic of less information required in the negative selection artificial immune system, a fault detection method is proposed for aircraft control system based on negative selection algorithm. Basically, after extracting the fault characteristics from the aircraft flight parameters, the negative selection module is utilized to generate fault detectors to monitor the aircraft control system. Afterward, the hypothesis test is introduced to evaluate the detector coverage more efficiently, and the detector cover area is optimized by applying geometric mathematics in the optimization of the detector center position and radius. The method is verified by simulation of a certain aircraft control system, and the results show that it has a good detection effect on the system faults.

Preliminary geometric parameters optimization of lobster-eye-type wide field of view soft x-ray imager

The lobster-eye optical system is widely used in the wide field of view (FOV) soft x-ray imaging device. The payload soft x-ray imager (SXI) onboard the solar wind magnetosphere ionosphere link explorer satellite will apply this technology to achieve panoramic imaging of the dayside magnetosphere. In order to optimize the imaging performance of SXI, we focus on geometric parameters optimization of a lobster-eye lens. The results show an appropriate microchannel ratio of length to width of lobster-eye optics with radius of curvature of 600 mm could be 30:1 (microchannel width of 40 μm and length of 1.2 mm). For a monochromatic parallel light source with energy of 1 keV, this combination of parameters can theoretically provide relatively large total effective area of about 15.52 cm2 and focusing efficiency of about 0.2887 along with spatial angular resolution of about 6 arc min at the center of FOV. Combined with the actual lobster-eye optics, the aberrations from deformation of the microchannel, the deviation of radius of curvature and planar detector are analyzed. For SXI with planar CCD detector, an optimum focal length could be 304.2 mm to ensure better resolution in full FOV.

Effects of thermal loads representations on the dynamics and characteristics of carbon nanotubes-based mass sensors

Uniform, linear, and nonlinear temperature gradients are considered to perform buckling and vibration analyses of carbon nanotube (CNT)-based mass sensors modeled as a clamped-clamped Euler–Bernoulli nanobeam with a deposited atomic-scale particle. Size dependent effects are taken into account using the Eringen’s nonlocal elasticity theory. Employing the Hamilton’s principle, the governing equations of motion considering the three types of temperature distribution are derived. To investigate the effects of various thermal loadings on the mass detection sensitivity of clamped CNT-mass detectors, four distinct noble gas atoms, namely Helium (He), Neon (Ne), Argon (Ar), and Krypton (Kr) with very low chemical reactivity are considered as attached atomic-scale masses. The influence of important parameters, such as the length and diameter of the CNT, the deposited mass and its location, the nonlocal parameter, the surface temperature difference, the temperature rise, and the type of temperature distribution on the errors in thermal buckling loads and frequency shifts are also studied. Assessing the impacts of the inaccuracies of uniform and linear temperature distributions on the critical thermal buckling load and the frequency shift of the CNT-based mechanical resonator is the primary contribution of the work. The numerical results indicate that in the pre-buckling region, the assumptions of uniform and linear temperature distributions through the thickness of the CNT estimate higher values of the natural frequency and the frequency shift compared to the nonlinear temperature gradient. On the contrary, the nonlinear thermal gradient across the radius of the CNT-based mass detector yields the largest values of the frequency shift and hence the highest mass detection sensitivities of the CNT-based mass sensor in the post-buckling configuration.

87. Lesion dosimetry in metastatic thyroid cancer treated with 131I: Method and preliminary results

Purpose 131I treatment of metastatic thyroid cancer should take into account doses to metastasis for an optimized approach as highlighted by EU 2013/59 Directive. A SPECT-TC dose calculation method is proposed and verified to standardize the operating protocol; patients’ preliminary results are shown. Methods SPECT-TC was calibrated with a phantom (spheres 11.5, 5.6, 1.1 ml, cylinder 130 ml) filled with liquid 131I (13 MBq/ml). Acquisition (64views, circular-orbit, 256 × 256, Iterative SCAC) on successive days allowed partial volume effects, dead-time and detector radius (25 ÷ 33 cm) corrections to calculate the dose, whose accuracy was verified. For 8 patients after the therapeutic administration and for 2 patients also in pre-therapy phase 4 SPECT-TC (4 ÷ 6, 24, 48, 96 ÷ 144 h) were performed to calculate the dose to 30 lesions (24 bone,7 lymph node,6 pulmonary) with the MIRD spheres model. Results Calibration factors (cylinder 1.4 kcts/MBq) confirmed partial volume effects (130 ml:100%, 11 ml:75%, 5.5 ml:58%, 1.1 ml:6%) and radius dependence ( ∼ 10%). Dead-time strongly influences counts in early acquisition (up to 17 %). Mean accuracy on activity −15% [−9% ÷ −24%] and dose −13 % [−9% ÷ −18%] for volumes larger than 2.5 cc validates the dosimetric method, according to literature (MIRD24). Dose to lesions per activity unit varies among patients (mean ± 1dev.st 26 ± 38, range 0.1 ÷ 189 Gy/GBq) and within the same patient (up to +583 %) and uptake seems to decrease in following treatments: individualized dosimetry is needed. CT-based method is recommended for VOIs segmentation (mean – 4.9% compared to the isocontour threshold one). In-therapy dose values show high differences (up to −126%) compared to pre-therapy results, whose efficacy must be further investigated with more patients also in terms of optimal activity to be administered to simulate the treatment. Conclusions Lesion dosimetry of metastatic thyroid cancer treated with radioiodine is accurate with SPECT-TC and provides to the physician a fundamental tool to optimize the treatment. Download : Download high-res image (119KB) Download : Download full-size image Download : Download high-res image (118KB) Download : Download full-size image

Artificial Immune System-Negative Selection Classification Algorithm (NSCA) for Four Class Electroencephalogram (EEG) Signals.

Artificial immune systems (AIS) are intelligent algorithms derived from the principles inspired by the human immune system. In this study, electroencephalography (EEG) signals for four distinct motor movements of human limbs are detected and classified using a negative selection classification algorithm (NSCA). For this study, a widely studied open source EEG signal database (BCI IV–Graz dataset 2a, comprising nine subjects) has been used. Mel frequency cepstral coefficients (MFCCs) are extracted as selected features from recorded EEG signals. Dimensionality reduction of data is carried out by applying two hidden layered stacked auto-encoder. Genetic algorithm (GA) optimized detectors (artificial lymphocytes) are trained using negative selection algorithm (NSA) for detection and classification of four motor movements. The trained detectors consist of four sets of detectors, each set is trained for detection and classification of one of the four movements from the other three movements. The optimized radius of detector is small enough not to mis-detect the sample. Euclidean distance of each detector with every training dataset sample is taken and compared with the optimized radius of the detector as a nonself detector. Our proposed approach achieved a mean classification accuracy of 86.39% for limb movements over nine subjects with a maximum individual subject classification accuracy of 97.5% for subject number eight.

A new method to detect and correct sample tilt in scanning transmission electron microscopy bright-field imaging

Important properties of functional materials, such as ferroelectric shifts and octahedral distortions, are associated with displacements of the positions of lighter atoms in the unit cell. Annular bright-field scanning transmission electron microscopy is a good experimental method for investigating such phenomena due to its ability to image light and heavy atoms simultaneously. To map atomic positions at the required accuracy precise angular alignment of the sample with the microscope optical axis is necessary, since misalignment (tilt) of the specimen contributes to errors in position measurements of lighter elements in annular bright-field imaging. In this paper it is shown that it is possible to detect tilt with the aid of images recorded using a central bright-field detector placed within the inner radius of the annular bright-field detector. For a probe focus near the middle of the specimen the central bright-field image becomes especially sensitive to tilt and we demonstrate experimentally that misalignment can be detected with a precision of less than a milliradian, as we also confirm in simulation. Coma in the probe, an aberration that can be misidentified as tilt of the specimen, is also investigated and it is shown how the effects of coma and tilt can be differentiated. The effects of tilt may be offset to a large extent by shifting the diffraction plane detector an amount equivalent to the specimen tilt and we provide an experimental proof of principle of this using a segmented detector system.

Calculation of the full-energy peak efficiency of NaI(Tl) detector using the efficiency transfer method for large radioactive cylindrical sources

A new theoretical approach is introduced in this article to calculate the full-energy peak efficiency of cylindrical NaI(Tl) γ-ray detectors. This new approach depends mainly on an analytical calculation of the photon average path lengths inside the source-to-detector system. The effective solid angle Ω join mathematically with the efficiency transfer method (ET) to obtain a simple formula for the detection efficiency. The self attenuation factor of the source (with a radius greater than the detector's radius) matrix is also considered. In addition, the attenuation factors of the source container, the detector housing and any absorbing materials during the measurement are also included. Results are compared with those obtained from ETNA program and those measured by two different cylindrical NaI(Tl) detectors with resolution (FWHM) at 662 keV equal to 7.5% and 8.5%, respectively. 152Eu aqueous radioactive cylindrical sources covering the energy range from 121 keV up to 1408 keV are used. The measured and the calculated with ETNA program efficiencies are compared with those calculated with this new approach. The results are found satisfactory with negligible discrepancies.

SU‐F‐T‐661: Dependence of Gold Nano Particles Cluster Morphology On Dose Enhancement of Photon Radiation Therapy Apply for Radiation Biology Effect

Purpose:Injected gold nano particles (GNPs) to a body for dose enhancement are known to form in the tumorcell cluster morphology. We investigated the dependence of dose enhancement on the morphology characteristic with an approximated morphology model by using Monte Carlo simulations.Methods:For MC simulation, TOPAS version 2.0P‐03 was used. GNP cluster morphology was approximated as a body center cubic(BCC) model by placing 8 GNPs at the corner and one at the center of cube with length from 2.59 µm to 0.25 µm located in a 4 µm length water filled cube phantom. 4 µm length square shaped beams of poly‐energetic 50, 260 kVp photons were irradiated to the water filled cube phantom with 100 nm diameter GNPs in it. Dose enhancement ratio(DER) was computed as a function of distance from the surface of the GNP at the cube center for 18 cubes geometries. For scoring particles, 10 nm width of concentric shell shaped detector was constructed up to 100 nm from the center. Total dose in a sphere of 100 nm radius of detector were normalized to 2.59 µm length cube morphology. To verified biological effect of BCC model applied to cell survival curve fitting.Results:DER increase as the distance of the GNPs reduces. DER was largest for 0.25 µm length cube. Dependence of GNP distance DER increment was 1.73, 1.60 for 50 kVp, 260 kVp photons, respectively. Also, Using BCC model applied to cell survival curve was well prediction.Conclusion:DER with GNPs was larger when they are closely packed in the phantom. Therefore, better therapeutic effects can be expected with close‐packed GNPs.This research was supported by the NRF funded by the Ministry of Science, ICT & Future Planning (2012M3A9B6055201 and 2012R1A1A2042414), Samsung Medical Center grant[GFO1130081]

ZICOS - New project for neutrinoless double beta decay experiment using zirconium complex in liquid scintillator

A liquid scintillator containing a tetrakis (isopropyl acetoacetato) zirconium has been developed for new project of neutrinoless double beta decay experiment (ZICOS experiment). We have synthesized a tetrakis (isopropyl acetoacetato) zirconium, which have high solubility (over 31.2 wt.%) in anisole. We measured the performance of liquid scintillator containing 10 wt.% concentration of a tetrakis (isopropyl acetoacetato) zirconium, and obtained 48.7 ± 7.1% of the light yield of BC505 and the energy resolution of 4.1 ± 0.6% at 3.35 MeV assuming 40% photo coverage of the photomultiplier, respectively. We also estimated that ZICOS experiment should be sensitive to (mν) < 0.1 eV assuming gA = 1.25, gpp = 1.11 and QRPA model, if a radius of the inner detector is 1.5 m and the detector is filled with this liquid scintillator with an enriched 96Zr nucleus and we can reduce 208 Tl backgrounds to be one tenth order of magnitude of KamLAND-Zen using Cherenkov lights.

Calculation of NaI(Tl) detector full-energy peak efficiency using the efficiency transfer method for small radioactive cylindrical sources

A direct analytical mathematical method is introduced to calculate the efficiency of gamma ray cylindrical detectors. The efficiency expression is deduced through a straightforward mathematical approach. The presented method is based on the accurate analytical calculation of the average path length covered by the photon within the detector's active volume, effective solid angle, and the efficiency transfer method in an integral form, so as to obtain a simple formula for the detection efficiency. In addition, the self-attenuation coefficient of the source matrix, the attenuation factors of the source container (with a radius smaller than the detector radius) and the detector housing materials are also treated by calculating the average path length within these materials. 152Eu aqueous radioactive sources covering the energy range from 121 keV to 1408 keV were used. Remarkable agreement between the measured and the calculated efficiencies was achieved, with discrepancies less than 6 %.

Use of Compton Back Scattering Technique for Detection of Corrosion in Pipes

The multiple Compton backscattering (MCBS) technique has been used to investigate the detection and imaging corrosion under the insulation pipe. An energy source with a mono – energy 0.662MeV of 137Cs has been used. Gamma ray photons have been allowed to be incident vertically on the insulator pipe whose outside diameter, wall and asbestos insulation thickness are (28, 1, 4) cm respectively. The steel pipe has a corrosion defect with a diameter 8 cm. The count rate of scattered γ – photons with scattering angle in the range (130 – 140) degrees has been collected by NaI(Tl) detector with different radius. Assuming the source and detector locations are in the same side from the pipe. Monte Carlo simulation has been written in FORTRAN95 language programming to follow the history of photons. This study provides the ability of this technique to detect and imaging the corrosion under the insulator pipes. The radius of detector which gives good results for corrosion detection and imaging is 6cm among five different selected radiuses.