• Journal of Aerospace System Engineering
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• v.18 no.5
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• pp.90-96
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• 2024

Previous researches on helicopter noise have often focused on hovering conditions or non-lifting conditions to facilitate testing and clearly identify noise sources. While these studies are beneficial for understanding noise sources and validating analysis tools, they may not align well with noise certification flight tests. To predict and analyze results from noise certification flight tests, it is necessary to study the characteristics of helicopter rotor noise depending on microphone and aircraft positions during flight tests. Results from noise flight tests indicate that high-speed impulsive (HSI) noise dominates during forward flight, with an increase in noise observed with an increase in forward Mach number. Broadband noise is predominant after the helicopter passes the microphone compared to blade noise. Noise during landing approaches exhibits complex and irregular characteristics due to interference between blades and tip vortex.

• Wind and Structures
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• v.39 no.4
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• pp.271-285
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• 2024

The multiple-fan wind tunnel is an important facility for reproducing target wind field. Existing control methods for the multiple-fan wind tunnel can generate wind speeds that satisfy the target statistical characteristics of a wind field (e.g., power spectrum). However, the frequency-domain features cannot well represent the nonstationary winds of extreme storms (e.g., downburst). Therefore, this study proposes a multiple-fan wind tunnel control scheme based on Deep Reinforcement Learning (DRL), which will completely transform into a data-driven closed-loop control problem, to reproduce the target wind field in the time domain. Specifically, the control scheme adopts the Deep Deterministic Policy Gradient (DDPG) paradigm in which the strong fitting ability of Deep Neural Networks (DNN) is utilized. It can establish the complex relationship between the target wind speed time series and the current control strategy in the DRL-agent. To address the fluid memory effect of the wind field, this study innovatively designs the system state and control reward to improve the reproduction performance based on historical data. To validate the performance of the model, we established a simplified flow field based on Navier Stokes equations to simulate a two-dimensional numerical multiple-fan wind tunnel environment. Using the strategy of DRL decision maker, we generated a wind speed time series with minor error from the target under low Reynolds number conditions. This is the first time that the AI methods have been used to generate target wind speed time series in a multiple-fan wind tunnel environment. The hyperparameters in the DDPG paradigm are analyzed to identify a set of optimal parameters. With these efforts, the trained DRL-agent can simultaneously reproduce the wind speed time series in multiple positions.

• Progress in Medical Physics
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• v.35 no.2
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• pp.36-44
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• 2024

Purpose: This study assessed and compared the dosimetric performance of HyperArc and RapidArc in stereotactic radiosurgery (SRS) for a single brain metastasis. Methods: Twenty patients with intracranial brain metastases, each presenting a distinct target volume, were retrospectively selected. Subsequently, volumetric modulated arc therapy (VMAT) plans were designed using RapidArc (VMAT_RA) and HyperArc (VMAT_HA) for each patient. For planning comparisons, dose-volumetric histogram (DVH) parameters for planning target volumes (PTVs) and normal brain regions were computed across all VMAT plans. Subsequently, their total monitor units (MUs), total beam-on times, and modulation complexity scores for the VMAT (MCS_v) were compared. A statistical test was used to evaluate the dosimetric disparities in the DVH parameters, total MUs, total beam-on times, and MCS_v between the VMAT_HA and VMAT_RA plans. Results: For the PTVs, VMAT_HA presented a higher homogeneity index (HI) than VMAT_RA. Moreover, VMAT_HA presented significantly smaller gradient index (GI) values (P<0.001) than VMAT_RA. Thus, VMAT_HA demonstrated better performance in the DVH parameters for the PTV than VMAT_RA. For normal brain tissues, VMAT_HA presented lower volume receiving 50% of the prescription dose and V_2Gy to the normal brain tissues than VMAT_RA (P<0.0001). While the total MUs required for VMAT_HA was significantly higher than those for VMAT_RA, the total beam-on time for VMAT_HA was superior to that for VMAT_RA. Conclusions: Thus, VMAT_HA exhibited superior performance in achieving rapid dose fall-offs (as indicated by the GI) and a higher HI at the PTV compared to VMAT_RA in brain SRS. This advancement positions HyperArc as a significant development in the field of radiation therapy, offering optimized treatment outcomes for brain SRS.

• The Journal of Korean Academy of Prosthodontics
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• v.62 no.4
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• pp.328-338
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• 2024

Advancements in CAD-CAM technology have allowed for a variety of options in implant-supported fixed prosthesis restorations for completely edentulous patients. For patients with severe alveolar bone resorption, zirconia prosthetic restorations that include the gingival portion, such as implant-supported hybrid dentures, are possible, as well as monolithic zirconia prosthetic restorations in the form of crowns. The integration of digital technology in fixed prosthetic restoration using implants enables predictable treatment through diagnosis and virtual surgery by integrating the patient's clinical and radiological information. In this case, the utilization of digital software allowed for the establishment of implants in appropriate positions, considering both the remaining alveolar bone and the final prosthesis. By designing both the maxillary removable prosthesis and the mandibular fixed prosthesis simultaneously in CAD software, bilateral balanced occlusion could be easily achieved. Furthermore, maintaining the initial interocclusal relationship from provisional restorations to final prostheses allowed for convenient transition while ensuring functional and aesthetic satisfaction.

• Journal of Korean Society of Archives and Records Management
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• v.4 no.2
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• pp.41-75
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• 2004

This research discusses how to improve the current environment for record management in relation to the Revision of the Law of Record Management in South Korea. Three major issues are: 1) Legal status of the National Archives & Records Service of Korea as the government institution in charge of managing centrally records, 2) System for the education and training of professionals who specialize in record management, and 3) Foundation of the national museum and archives of records. Findings are as follows: First, the existing 'National Office of Records' as the government institution in charge of managing records, should be promoted to the 'National Archives & Records Service of Korea' in order to be administered by the class of a vice-minister in the Ministry of Government Administration and Home Affairs. Second, the qualification criteria which currently requires the Master's degree of Record Management, should be modified to include the Bachelor's degree in the field in order to expand the pool of professional human resources. Also, to hire the public officials for record management, either the positions of 'researcher/record manager group' should be created, or the existing positions of librarian, archivist, and record manager should be integrated into the new position of 'record culture group'. Third, the most significant task for the office of record management of local governments is to inherit and further develop the traditional culture and documentary legacy which are unique to those local communities and governments at various levels, and a priority should be given to those tasks. Therefore, when the Law of Record Management will be later revised, the establishment of the office of record management for local governments at every level should be required, and the museum and archives of records should be also established as a significant part of the institution. Unique local culture and history of particular communities should be collected and preserved in systematically specialized and differentiated ways in those institutions of record management, and the names should be uniquely given to the institutions according to the characteristics of local governments.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.3
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• pp.251-258
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• 2020

Single crystal of fully dehydrated and partially Ca²⁺-exchanged zeolites A (|Ca₄Na₄|[Si₁₂Al₁₂O₄₈]-LTA) was brought into contact with Se in fine pyrex capillary at 523 K for 5 days. Crystal structure of Se-sorbed |Ca₄Na₄|[Si₁₂Al₁₂O₄₈]-LTA has been determined by single-crystal X-ray diffraction techniques at 294 K in the cubic space group $Pm{\bar{3}}m$ (a = 12.2787(13) Å). The crystal structure of yellow |Ca₄Na₄Se₄|[Si₁₂Al₁₂O₄₈]-LTA has been refined to the final error indices of R₁/wR₂ = 0.0960/0.3483 with 327 reflections for which F_o > 4s(F_o). In this structure, 4 Na⁺ and 4 Ca²⁺ ions fill every 6-ring site: These ions are all found at three crystallographic positions, on 3-fold axes equipoints of opposite 6-rings. Selenium atoms are found at three crystallographically distinct positions: 2 Se atoms per unit cell at Se(1) are located opposite 6-rings in the sodalite cavity (Se(1)-Na(1) = 2.53(5) Å) and 1 at Se(2) opposite 4-rings (Se(2)-O(1) = 2.76(10) Å) and 1 at Se(3) opposite 6-rings in the large cavity (Se(3)-Na(1) = 2.48(5) Å). Two molecular of Se₂ (Se(1)-Se(1) = 2.37(7) or 2.90(8) Å and Se(2)-Se(3) = 2.91(5) ) Å) are found in all sodalite cavity and large cavity. Other clusters such as Se₄ and Se₈ could be existed in large cavity. The inter-selenium distances turned out to be longer that of gases Se₂ molecule.

• Journal of Animal Science and Technology
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• v.44 no.2
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• pp.181-190
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• 2002

This study was performed to determine sequences of the mt DNA D-loop region, including $tRNA^{Pro}$ and $tRNA^{Pre}$ and to analysis sequence variation polymorphism in Korean cattle. The resulting sequencies were compared with previously published sequences for other cattle breeds(GenBank J01394). The PCR was used to amplify an 1142bp between nucleotides 15061 and 404 within the D-loop region of mt DNA using specific primers. Korean cattle showed 24 polymorphic sites by nucleotide substitutions and insertions of single base pairs. About 50% of polymorphic sites were found in positions 16042 to 16122 with the most variable region. Among these polymorphic sites, variations at 16055, 16230 and 16260 bp were detected as new sequence variants in Korean cattle. These specific polymorphic sites have not been reported in the Japanese black cattle and European cattle. Therefore, mt DNA variants in the D-loop region may be used as genetic markers for specifying Korean cattle. The frequencies of positions 169, 16302, 16093, 16042, 16119 with a high level of sequence polymorphism were 0.81, 0.56, 0.56, 0.50 and 0.43, respectively. In comparison of genetic distances, Korean cattle showed the more closely to European cattle as Bos taurus than Bos indicus such as African and India breeds. In conclusion, these mt DNA sequence polymorphisms in the D-loop region for Korean cattle may be useful for the analysis of cytoplasmic genetic variation and associations with economic important traits and genetic analysis of maternal lineage.

• Progress in Medical Physics
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• v.21 no.3
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• pp.291-297
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• 2010

This study examined the dosimetric influence of implanted gold markers in proton therapy and the effects of their positions in the spread-out Bragg peak (SOBP) proton beam. The implanted cylindrical gold markers were 3 mm long and 1.2 mm in diameter. The dosimetric influence of the gold markers was determined with markers at various locations in a proton-beam field. Spatial dose distributions were measured using a three-dimensional moving water phantom and a stereotactic diode detector with an effective diameter of 0.5 mm. Also, a film dosimetry was performed using Gafchromic External Beam Treatment (EBT) film. The GEANT4 simulation toolkit was used for Monte-Carlo simulations to confirm the measurements and to construct the dose-volume histogram with implanting markers. Motion data were obtained from the portal images of 10 patients to investigate the effect of organ motions on the dosimetric influence of markers in the presence of a rectal balloon. The underdosed volume due to a single gold marker, in which the dose was less than 95% of a prescribed amount, was 0.15 cc. The underdosed volume due to the presence of a gold marker is much smaller than the target volume. However, the underdosed volume is inside the gross tumor volume and is not smeared out due to translational prostate motions. The positions of gold markers and the conditions of the proton-beam field give different impacts on the dose distribution of a target with implanted gold markers, and should be considered in all clinical proton-based therapies.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.3
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• pp.39-48
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• 2007

The stimulus of accommodation A, the stimulus of convergence C and the prism diopter ${\Delta}$ are reviewed and redefined more obviously. How the A and C are managed in the practice are reviewed and summarized. As a result, the common practical process of the binocular vision findings is most suitable in the case of the $l_c=26.67mm$, where the near distance is measured from the test lens to the near target and its value is 40 cm and the average of the P.D equal to 64 mm. The $l_c$ is the distance between the test lens and the center of rotation. Those values were used at calculating the various values in this paper. The error of the stimulus of accommodation values which are evaluated by the practically used formula (5) are calculated. Where the distance between lens and the principle point of eye is 15.07 mm ($=l_H$). The incremental stimulus of convergence values P' caused by the addition prism $P_m$ are evaluated by the recursion computation method. The P' are varied with the $P_m$, the distance $p_c$ between the prism and the center of rotation, the initial convergence value (or inverse target distance) $C_o$ and the refractive index n of the prism material. The recursion computation method and the other formulas are described in detail. In this paper n=1.7 is used. The two factors by which the P' is increased are exist. The one which is major is the property by which the values of convergence whose unit is ${\Delta}$ are not added in the generally way. The other is the that the actual power of the prism is varied with the angle of incidence light. And the P' is decreased remarkably by an increase in the $p_c$ and $C_o$. The $P^{\prime}/P_m$ are calculated and graphed which are varied with the $p_c$ and $C_o$, where the $P_m=20{\Delta}$, P.D=64 mm and n=1.7. The index n dependence of the $P^{\prime}/P_m$ is negligible (refer to fig. 6). The $p_c$ are evaluated at which the P' equal to the $P_m$ for various $P_m$ (refer to table 1). The actual values of the stimulus of convergence and accommodation which are manipulated simply in the practice are calculated. Two graphical forms are suggested. The one is like as the commonly used one. But the stimulus of convergence and of accommodation values in the practice are positioned at the exact positions when the graphic is made (refer to fig. 9). The other is the form that the incremental stimulus of convergence values caused by the addition prisms are represented at actual positions (refer to fig. 11).

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.42-49
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• 2011

We deposited $SiN_x$ thin films by using PECVD technique at $200^{\circ}C$ with various flow ratios of the $SiH_4/N_2$ gases. The photoluminescence measurements revealed that the maximum emission wavelength shifted to long wavelength as the ratio increased, however, positions of the several peak wavelengths, such as 1.9, 2.2, 2.4, and 3.1 eV, were independent on the ratio. Changes of the photoluminescence spectra were measured in the $N_{2}-$, $H_{2}-$, and $O_2$-annealed films. The luminescence intensities increased after the annealing process. In particular, the maximum emission wavelength shifted to short wavelength after $H_{2}-$ or $O_2$-annealing. But there were still several peaks on the spectra of all annealed films, several peak positions remained to be unchanged after the annealing. As for the light emission mechanism, we have considered the defect states of the Si- and N- dangling bonds in the $SiN_x$ energy gap, so that the energy transitions from/to the conduction/valence bands and the defect states in the gap were attributed to the light emission in the $SiN_x$ films. The experimental results point to the possibility of a Si-based light emission materials for flexible Si-based electro-optic devices.