Journal of the Korean Physical Society最新文献

Small gantries and long, thin scintillation pixels are used in preclinical positron emission tomography, resulting in parallax errors outside the system’s field of view. To solve this problem, a detector for measuring the depth of interaction (DOI) was developed. In addition, conduct of research on methods for DOI measurement through deep learning is underway. In this study, we designed a detector for measurement of DOI, consisting of two layers of scintillation pixel arrays and developed a method for specifying 3-dimensional (3D) position through deep learning. DETECT2000 simulation was performed to assess the 3D-positioning accuracy of the designed detector. Data acquired through DETECT2000 simulation wereused for learning a deep learning model, and assessment of location specification accuracy was performed using data generated at a new location and the deep learning model. According to the result, the 3D-position measurement accuracy was calculated as 94.48% on average.

We investigate a novel covariant matrix adaption-evolution strategy (CMA-ES)-based method proposed for extracting channel phase information by measuring a two-dimensional (2D) target intensity image (2D-TII) of a coherent beam combining (CBC) system both numerically and experimentally for the first time to the best of our knowledge. The proposed method was first investigated on 1,000 samples of 2D-TIIs numerically generated by a virtual 3-channel CBC system. For all samples, the channel phase information was extracted almost perfectly, with the inter-image correlation coefficient reaching or exceeding 0.99 and the overall root-mean-square phase error of 0.0735 rad within 17 iterations of the algorithm, for example. Next, the investigation was extended onto another 1,000 samples of 2D-TIIs experimentally measured with a real-world 3-channel CBC setup via a charge-coupled device (CCD) camera at a rate of 16 fps with an exposure time of 10 ms. The channel phase information was extracted with the inter-image correlation coefficient reaching or exceeding 0.9 for 972 or 979 samples within 15 or 45 iterations of the algorithm, respectively, with the latter case of which its overall average was estimated at 0.947. The relatively low performance of the proposed method within 21 out of 1,000 samples, where the overall average of the inter-image correlation coefficient remained at 0.880 regardless of further increases in the number of iterations, was attributed to the lowered image contrasts of the measured 2D-TIIs caused by the uncontrolled intrusion of external noise components that could not be rectified by the CCD camera due to its limited exposure time. We expect the proposed method to be useful for research and analysis on a variety of real-world CBC systems as well as other related applications where phase information needs to be extracted.

It is difficult to calculate monitor units in the proton treatment planning system due to the complexity of using this system in the double scattering mode of proton therapy. Moreover, the range and spread-out Bragg peak (SOBP) values using the conversion algorithm (CONVALGO) provided by IBA (({C}_{{text{range}}}), ({C}_{{text{SOBP}}})) are different from the actual measured range (({M}_{{text{range}}})) and SOBP (({M}_{{text{SOBP}}})) values. In this regard, the CONVALGO (FC) value (({FC}_{{text{range}}}), ({FC}_{{text{SOBP}}})) should be measured according to the quality assurance (QA) of patient treatment, which requires physical effort and time. This study, therefore, aimed to reduce the time and effort spent on QA. The predictive model was trained using six parameters. Main option, sub-option, ({M}_{{text{range}}}) and ({M}_{{text{SOBP}}}) were used as input values, and ({FC}_{{text{range}}}) and ({FC}_{{text{SOBP}}}) were used as label. The trained model predicted the CONVALGO (PC) values of ({PC}_{{text{range}}}) and ({PC}_{{text{SOBP}}}). The test dataset has 261 patient data that were not used for training. Difference, mean absolute error (MAE), and root mean square error (RMSE) values were used for comparison. Compared to the FC value, the maximum difference was − 2.2 mm for ({PC}_{{text{range}}}) and − 3.4 mm for ({C}_{{text{range}}}). The acceptable standard of patient QA in our institute is within 1 mm and the number of data points that met the acceptable standard was 196 for ({PC}_{{text{range}}}) and 191 for ({C}_{{text{range}}}). For the MAE of ({PC}_{{text{SOBP}}}), options 1, 2, and 3 showed values within 1 mm. In the MAE of ({C}_{{text{SOBP}}}), the values were > 1 mm for all options.

Shock and solitary waves are very important nonlinear structure in the channel of field-effect transistors (FET). In this paper, the propagation of shock and solitary waves with quantum effects in the channel of FET is investigated. Using reductive perturbation expansion, the quantum hydrodynamic equations are reduced to KdV–Burgers and KdV equations describing the characteristic of shock and solitary waves with quantum effects in the channel of FET. The analytical and numerical results show that there are two different types of shock waves and solitary waves in this system; the monotone shock waves, the oscillatory waves and the solitary waves can transform each other under certain condition; the quantum effects strengthened shock waves oscillation and change the width of the solitary waves. This finding provides a new idea for finding efficient THz radiation sources and opens up a new mechanism for the development of THz technology.

This study explores the performance and channel-scalability of the covariance matrix adaptation evolution strategy (CMA-ES)-based coherent optical phase control algorithm for coherent beam combining (CBC) systems. Leveraging the probabilistic nature of its optimization process, the CMA-ES algorithm emerges as a promising candidate for a next-generation phase control algorithm for CBC systems. To assess its functionality and channel-scalability, we conduct numerical investigations into the CMA-ES-based phase control algorithm applied to both 37- and 61-channel CBC systems with varying its algorithmic parameters. For the 37-channel configuration, consistent results demonstrate an average beam combining efficiency (BCE) exceeding 0.9, with a constrained standard deviation of 0.1 with phase sample numbers surpassing 30. The analysis of the time complexity reveals that the CMA-ES-based algorithm efficiently converges to a BCE value of 0.9 within a 10 MHz bandwidth within a 5 μs atmospheric time scale. In the case of the 61-channel configuration, a majority of phase samples exhibit an average BCE exceeding 0.95, with a small number of trials slightly falling below 0.85 yet still achieving a BCE of approximately 0.8. Similar to the 37-channel case, with the bandwidth < 12 MHz, the CMA-ES-based algorithm can give rise to the BCE level of 0.9 within a 5 μs atmospheric time duration.

The article reports about the variation of an ion sheath thickness in discharge and diffusion plasma. Two ion sheaths are formed at two negatively biased plates placed in discharge and diffusion region of a double plasma device. Plasma is only produced in one section of the device by hot filament discharge and there is no filament in the other section. When energy of primary electrons is increased, ion sheath in discharge region expands and it contracts in the diffusion region. For an increase in population of primary electrons, an ion sheath in both discharge and diffusion region contracts. Again, for drainage of electrons or ions from discharge region, the sheath structure in discharge region is highly influenced by the plasma potential whereas in diffusion region; sheath structure is mainly influenced by local plasma density.

The effect of boundaries on the bulk properties of quantum many-body systems is an intriguing subject of study. One can define a boundary effect function, which quantifies the change in the ground state as a function of the distance from the boundary. This function serves as an upper bound for the correlation functions and the entanglement entropies in the thermodynamic limit. Here, we perform numerical analyses of the boundary effect function for one-dimensional free-fermion models. We find that the upper bound established by the boundary effect function is tight for the examined systems, providing a deep insight into how correlations and entanglement are developed in the ground state as the system size grows. As a by-product, we derive a general fidelity formula for fermionic Gaussian states in a self-contained manner, rendering the formula easier to apprehend.

In the recent study of proton therapy, the expectation of the normal tissue-sparing effect of the proton minibeam radiation therapy (pMBRT) using a multi-slit collimator (MSC) is increasing. We designed and conducted animal experiments to verify the sparing effect on normal tissues. Proton beam irradiation was carried out on two groups of mice except a control group (0 Gy). One group was irradiated with a conventional broad beam, and the other with a minibeam. A dose of 8.5 Gy was delivered to both femurs of mice in every group. In the pMBRT group, the survival rate of bone marrow cells was significantly improved as compared to the conventional broad beam group. The survival rate in the minibeam group was 2.5 times higher. In conclusion, the pMBRT has been strongly proven to have a superior tissue-sparing effect than the conventional broad beam.

In this present study, our objective is to investigate the formation of dust ion-acoustic solitary and periodic waves in a superthermal magnetised plasma featuring both positive and negative charged ions, energetic trapped electrons, and oppositely charged dust particles. We have used the reductive perturbation technique (RPT) to get the Schamel–Korteweg-de Vries (Schamel–KdV) equation, which describes the behaviour of dust ion-acoustic solitary waves (DIASWs). Based on the theory of planar dynamical systems, the possible existing solution of the Schamel–KdV equation is shown in the phase portrait diagram. Sagdeev’s pseudopotential equation is also derived and the features of DIASWs are analysed in combination with the soliton solution. Through the graphical presentation, we have analysed the role of the physical parameters on the characteristics of solitonic and periodic waves, along with the electric field. This investigation has the potential to elucidate the formation of nonlinear waves in diverse astrophysical settings (e.g., ionosphere, solar wind, mesosphere, auroral zone, magnetosphere, etc.) and also laboratory devices that contain opposite-polarity dust-charged particles, superthermally trapped electrons, and both positive and negative ion species.

Metal slot antennas exhibit high transmission characteristics at resonant frequencies when electromagnetic waves with polarization in the width direction of the rectangular hole structure enter, having wavelengths approximately twice the length of the rectangular hole. In this study, we utilize COMSOL multiphysics simulation to examine the transmission behaviors of such resonators operating in terahertz frequency range, with a specific emphasis on their performance when incorporating micron-sized conductive embedding within the central region of the rectangular slot. We observe that as the conductivity of the embedding material increases, the resonant frequency undergoes a shift towards higher values through non-resonant behaviors in the intermediate conductivity range, eventually reaching nearly twice the fundamental resonant mode. The additional analytic microscopic calculation reveals that the interference effect of the electromagnetic field inside the slot antenna can be responsible for the transmittance modifications and provides a reference for investigating unknown embedded targets. These findings provide valuable insights into the versatile applications of metal slot antennas, particularly in areas such as sensing and detection of subwavelength materials.