The Crab nebula is widely used as a polarization angle calibrator for single-dish radio observations because of its brightness, high degree of linear polarization, and well-known polarization angle over a wide frequency range. However, the Crab nebula cannot be directly used as a polarization angle calibrator for single-dish observations with the Korean VLBI Network (KVN), because the beam size of the telescopes is smaller than the size of the nebula. To determine the polarization angle of the Crab nebula as seen by KVN, we use 3C 286, a compact polarized extragalactic radio source whose polarization angle is well-known, as a reference target. We observed both the Crab nebula and 3C 286 with the KVN from 2017 to 2021 and find that the polarization angles at the total intensity peak of the Crab nebula (equatorial coordinates (J2000) R.A. = 05h34m32.3804s and Dec = 22◦00′44.0982′′) are 154.2◦ ±0.3◦, 151.0◦ ±0.2◦, 150.0◦ ±1.0◦, and 151.3◦ ±1.1◦ at 22, 43, 86, and 94 GHz, respectively. We also find that the polarization angles at the pulsar position (RA = 05h34m31.971s and Dec = 22◦00′52.06′′) are 154.4◦ ±0.4◦, 150.7◦ ±0.4◦, and 149.0◦ ± 1.0◦ for the KVN at 22, 43, and 86 GHz. At 129 GHz, we suggest to use the values 149.0◦ ± 1.6◦ at the total intensity peak and 150.2◦ ± 2.0◦ at the pulsar position obtained with the Institute for Radio Astronomy in the Millimeter Range (IRAM) 30-meter Telescope. Based on our study, both positions within the Crab nebula can be used as polarization angle calibrators for the KVN single-dish observations.

목적 : 본 연구는 안경원의 운영관리 요소가 고객만족도 및 가맹본사만족도, 그리고 경영성과에 미치는 영향을 체계적으로 분석하였다. 방법 : 설문조사 자료는 2021년 5월 12일~28일까지 전국의 안경원 원장들을 대상으로 수집한 총 258개를 활 용 분석하였다. 결과 : 안경원 유형(대형브랜드, 중소형브랜드, 일반안경원)에 관계없이 모든 안경원은 공통적으로 고객관리를 중요한 성공요소로 인식하고 있는 것으로 나타났다. 유형별 안경원의 경영성과 요소는 전체적으로 ‘고객만족도’가 높게 나타난 반면, ‘매출성과’는 낮게 나타났다. 통계적으로는 ‘가맹본사만족도’, ‘매출성과’, ‘고객 수’에서 p<0.010 수준에서 집단 간에 유의한 차이가 있는 것으로 나타났다. 마지막으로 안경 프랜차이즈 브랜드별로 운영관리 성공 요인을 분석한 결과, 브랜드별로 안경원의 성공요인에 차이가 있다는 것을 확인하였다. 특히, 대형 A브랜드는 가 맹본사 교육 및 가맹본사 지원관리에서 훨씬 우월한 것으로 나타났다. 결론 : 본 연구의 결과로 대형브랜드 안경원이 브랜드 이미지를 강조하며 안경사 전문성과 접근성이 좋은 우량 한 점포위치를 선호하는 반면, 중소형브랜드는 마케팅역량을 가장 중요한 성공 요소로 인식하고 있는 것으로 생각 된다.

Many manufacturers applying third party logistics (3PLs) have some challenges to increase their logistics efficiency. This study introduces an effort to estimate the weight of the delivery trucks provided by 3PL providers, which allows the manufacturer to package and load products in trailers in advance to reduce delivery time. The accuracy of the weigh estimation is more important due to the total weight regulation. This study uses not only the data from the company but also many general prediction variables such as weather, oil prices and population of destinations. In addition, operational statistics variables are developed to indicate the availabilities of the trucks in a specific weight category for each 3PL provider. The prediction model using XGBoost regressor and permutation feature importance method provides highly acceptable performance with MAPE of 2.785% and shows the effectiveness of the developed operational statistics variables.

Organic scintillator is easy to manufacture a large size and the fluorescence decay time is short. However, it is not suitable for gamma measurement because it is composed of a low atomic number material. Organic scintillation detectors are widely used to check the presence or absence of radiation. The fluorescence of organic scintillators is produced by transitions between the energy levels of single molecules. In this study, an organic scintillator development study was conducted for use in gamma measurement, alternative materials for secondary solute used in basic organic scintillators were investigated, and the availability of alternative materials, detection characteristics, and neutron/gamma identification tests were performed. In other words, a secondary solute showing an improved energy transfer rate than the existing material was reported, and the performance was evaluated. 7-Diethylamino -4-methylcoumarin (DMC), selected as an alternative material, is a benzopyrone derivative in the form of colorless crystals, has high fluorescence and high quantum yield in the visible region, and has excellent light stability. In addition, it has a large Stokes shift characteristic, and solubility in solvent is good. Through this study, it was analyzed that the absorption wavelength range of DMC coincided with the emission wavelength range of PPO, which is the primary solute. Through this study, it was confirmed that the optimal concentration of DMC was 0.04wt%. As a result of performing gamma and neutron measurement tests using a DMC-based liquid scintillator, it showed good performance (FOM=1.42) compared to a commercial liquid scintillator. Therefore, the possibility of use as a secondary solute was demonstrated. Based on this, if studies on changes in the composition of secondary solute or the use of nanoparticles are conducted, it will be possible to manufacture and utilize a scintillator with improved efficiency compared to the existing scintillator.

The safe, efficient and cost-effective decommissioning and dismantling of radioactive facilities requires the accurate characterization of the radionuclide activities and dose rate environment. And it is critical across many nuclear industries to identify and locate sources of radiation accurately and quickly. One of the more challenging aspects of dealing with radiation is that you cannot see it directly, which can result in potential exposure when working in those environments. Generally, semiconductor detectors have better energy resolution than scintillation detectors, but the maximum achievable count rates are limited by long pulse signals. Whereas some high pure germanium detectors have been developed to operate at high count rates, and these HPGe detectors could obtain gamma-ray spectra at high count rates exceeding 1 Mcps. However, HPGe detectors require cooling devices to reduce the leak currents, which becomes disadvantageous when developing portable radiation detectors. Furthermore, chemicalcompound semiconductor detectors made of cadmium telluride and cadmium zinc telluride are popular, because they have good energy resolution and are available at room temperature. However, CdTe and CZT detectors develop irradiation-induced defects under intense gamma-ray fields. In this Review, we start with the fundamentals of gamma rays detection and review the recent developments in scintillators gamma-ray detectors. The key factors affecting the detector performance are summarized. We also give an outlook on the field, with emphasis on the challenges to be overcome.