본 연구에서는 중국 북동지역에서 발생하는 산불에 의한 생체연소 배출물이 장거리 수송으로 한국의 미세먼지 질량농도에 미치는 영향을 WRF-Chem 모델을 활용하여 분석하였다. 2020년 4월 4-7일에 한국은 중국 북동지역의 생체 연소 배출물과 더불어 중국 동부지역의 인위적 배출과 중국 북부와 몽골에서 발생한 황사의 영향을 함께 받고 있었다. 인위적 배출과 황사가 혼재된 대기오염 상황에서 zero-out 방법을 활용하여 생체연소 배출물을 분류하고 미세먼지 장거 리 수송 기여도를 분석하였다. 또한, 광역적인 생체연소 배출물의 분포에 따라 한반도 주변의 육지와 해양에 대한 복사 에너지 수지를 분석하였다. 2020년 4월 5-6일에는 한국의 하루평균 미세먼지 질량농도에 대한 생체연소 배출물의 장거리 수송 기여도가 60%로 산출되었다. 더불어 한반도 주변에 광역적으로 분포하는 생체연소 배출물의 영향으로 육지와 해양의 순 복사 플럭스는 음의 값을 나타내었다. 그러나 2020년 4월 7-8일에는 중국 동부지역에서 발생한 인위적 오염 물질이 생체연소 배출물에 더해지면서 한국의 미세먼지 질량농도는 4월 5-6일보다 증가하였으나 생체연소 배출물의 기 여도는 45% 이하로 감소하였다. 또한, 생체연소 배출물의 영향이 줄어들면서 순 복사 플럭스는 양의 값을 나타내었다.

범밀도이론함수(Density Functional Theory, DFT) 기반의 제일원리전산모사는 기저상태의 DFT 에너지를 구하는데 많은 시간소요 및 전산자원을 소모하였다. 이러한 막대한 전산자원의 소모는 DFT 계산에서 고려할 원자수를 수 백개 이 하로 제한되게 되었으며, 이를 해결하기 위해서는 전자구조 계산이 아닌 원자의 환경 내에 원자간 상호작용을 정의 (Force Field, 힘장)하고 이를 통해 주어진 조성 혹은 구조에 따른 에너지를 빠르게 예측 할 수 있어야 한다. 본 논문에서 는 Behler-Parrinello가 제시한 인공신경망 모델을 활용해 인공지능 다원계 힘장을 개발하고 코발트-구리 산화물의 조성에 따른 에너지를 예측하고 안정한 구조를 탐색하는 연구를 수행하였다. 인공신경망 기술로 부터 구리-코발트 산화물에 대 해 15.7 meV/atom의 에너지 오차와 단위거리당 힘 103.6 meV/Å의 정확도를 가지는 인공신경망 포텐셜을 개발하였다. 이 방법으로 빠르고 정확하게 CuCoO 표면구조의 산소 결함률에 따른 생성에너지를 계산할 수 있었고, 에너지 컨벡스 홀을 도시 조성에 따른 안정한 구조를 예측하였다.

In this study, the frequency response analysis of a bistable electromagnetic vibration energy harvester is performed, based on an electromagnetic oscillator model, to investigate its nonlinear dynamic behaviors. The displacement and current responses are obtained, by the direct integration of the model, with the variations of mechanical and electromagnetic parameters. It is shown that the operating frequency band of the system can be broadened by the increase in mechanical parameters(inertial mass and Q-factor), but it does not depend significantly on any electromagnetic parameters(an external load resistance and the internal resistance of a coil). On the other hand, the output current of the energy harvester is affected only by the electromagnetic parameters (specifically, the sum of two resistances). Thus, the mechanical and electromagnetic parameters of the electromagnetic energy harvester must be designed properly, respectively, for broader and more efficient performance.

In this study, the power consumption and illuminance were analyzed by replacing the fluorescent and incandescent lamps used as light sources for the engine room lighting of the training ship with LED light sources. By replacing 40W and 20W fluorescent lamps with 17W and 11W LED lamps, 40W fluorescent lamps reduced power consumption by 57.5% and 20W fluorescent lamps reduced power consumption by 45% and improved illumination by 56.8%. In particular, as a result of replacing 60W incandescent lamps with LEDs, power consumption was reduced by 85%. By installing an auxiliary cooling seawater pump that supplies cooling seawater to the engine control room air conditioner and boiler drain cooler in parallel, there is an energy saving effect of 88.1%. was confirmed.

Background: Low back and neck pain are two of the most common medical problems in the adult population. It is estimated that between 70% and 80% adults experience an episode of low back pain at least once during their lifetime. Objects: This study aimed to compare the effects of various stretching exercises and muscle energy techniques used for treatment of iliopsoas, quadratus lumborum, and hamstrings of patients with low back pain. Methods: A total of 52 subjects were randomly assigned to the control group (n = 17), the muscle energy technology group (METG, n = 19), and the stretching exercise group (SEG, n = 16). Interventions were performed twice a week for 4 weeks. Outcomes were measured before and after 4 weeks of treatment in the three groups, using the Korean version of the Oswestry Disability Index, the Visual Analogue Scale (VAS), the Fear Avoidance Belief Questionnaire (FABQ), the Finger to Floor test (FTF), the Modified-Modified Schober Test (MMS), and the Trunk Flexion Range of Motion test. Results: This study showed significant reduction in the pre-test and post-test KODI, VAS, and FABQ scores in all the three groups (p < 0.05). The KODI, VAS, FABQ and FTF assessed in this study showed interactions between the groups and the measurement time point (p < 0.01). After intervention, the KODI, VAS, FABQ and FTF in the SEG and METG were significantly higher (p < 0.05), and there was no difference between the METG and SEG. MMS and HFROM test showed no difference between the three groups (p > 0.05). Conclusion: KODI, VAS, FABQ and FTF showed significant improvement after basic physical therapy, muscle energy technique, and stretching exercise intervention. And there was no significant difference in the intervention effect between the muscle energy group and the stretching exercise group.

Background: Lower back pain (LBP) is a major cause of disability and a common musculoskeletal disorder encountered at some point in life. Dysfunction of the lumbar vertebrae has been associated with decreased flexibility of the hamstrings, which exhibited a strong positive correlation with LBP. Hamstring tension affects lumbar pelvic rhythm. We aimed to activate pelvic stability with compression by Active Therapeutic Movement (ATM), muscle energy technique (MET) was applied to increase the flexibility of the hamstring. Objects: In this study, we aimed to investigate the effects of MET with ATM and general MET were applied to the hamstring of adults, who were in their twenties with nor without LBP, on their pelvic inclination and the length of their hamstring. Methods: A total of 32 subjects were briefed about the purpose of this study and agreed to participate voluntarily. Before the experiment, all subjects were pre-examined, and they were divided into an LBP group and a no lower back pain group accordingly. Thereafter, all subjects participated in both in a crossover manner. After at least one week, they switched to another group and participated in the same experiment. Results: The study results revealed that both groups demonstrated significant results in the modified active knee extension test (p < 0.01) and the sit and reach test (p < 0.01) performed to assess the hamstring flexibility; an interaction (p < 0.05) was noted. Moreover, a more significant difference was observed between the MET with ATM and the general MET. Although significant results were obtained for the pelvic inclination (p < 0.01), interaction was not noted. Conclusion: Conclusively, in this study, when the MET with ATM was applied to the two groups, there was a significant difference compared to the general MET for hamstring flexibility, but it was confirmed that there was no significant difference for the pelvic inclination.

Recently, high-entropy carbides have attracted considerable attention owing to their excellent physical and chemical properties such as high hardness, fracture toughness, and conductivity. However, as an emerging class of novel materials, the synthesis methods, performance, and applications of high-entropy carbides have ample scope for further development. In this study, equiatomic (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide powders have been prepared by an ultrahigh- energy ball-milling (UHEBM) process with different milling times (1, 5, 15, 30, and 60 min). Further, their refinement behavior and high-entropy synthesis potential have been investigated. With an increase in the milling time, the particle size rapidly reduces (under sub-micrometer size) and homogeneous mixing of the prepared powder is observed. The distortions in the crystal lattice, which occur as a result of the refinement process and the multicomponent effect, are found to improve the sintering, thereby notably enhancing the formation of a single-phase solid solution (high-entropy). Herein, we present a procedure for the bulk synthesis of highly pure, dense, and uniform FCC single-phase (Fm3m crystal structure) (Hf-Ti-Ta-Zr-Nb)C high-entropy carbide using a milling time of 60 min and a sintering temperature of 1,600oC.

The Calorifier is a device that supplies hot water to the crew for showering and cooking. In particular, problems such as hot water not coming out when a trainee and a crew member take a shower at the same time may occur due to a malfunction of the temperature control valve that controls the temperature. In particular, when the hot water usage time is almost constant, such as a training ship, a high calorific value is required. When there is no dissatisfaction with the use of hot water, satisfaction with the educational environment is improved. Therefore, in this study, a solenoid temperature control valve is applied to increase satisfaction with hot water use, and a mechanical time switch is applied to the hot water circulating water pump to save energy.

In this study, we have prepared a Ti-6Al-4V/V/17-4 PH composite structure via a direct energy deposition process, and analyzed the interfaces using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The joint interfaces comprise two zones, one being a mixed zone in which V and 17-4PH are partially mixed and another being a fusion zone in the 17-4PH region which consists of Fe+FeV. It is observed that the power of the laser used in the deposition process affects the thickness of the mixed zone. When a 210 W laser is used, the thickness of the mixed zone is wider than that obtained using a 150 W laser, and the interface resembles a serrated shape. Moreover, irrespective of the laser power used, the expected  phase is found to be absent in the V/17-4 PH stainless steel joint; however, many VN precipitates are observed.

선박으로부터 발생하는 온실가스 배출을 저감하기 위한 규제가 점차 강화되고 있다. 현존선에서도 EEXI(Energy Efficiency Existing Index)가 도입되었으며 이와 같은 온실가스 배출 감축목표를 달성하기 위해 다양한 연구가 진행되고 있다. 본 연구에서는 국제항 해에 종사하는 현존선 중 자동차운반선에 태양광 발전시스템을 적용하여 연료유 사용량을 줄임으로써 온실가스 배출이 저감될 수 있는 시스템을 제안하였다. 제안된 태양광 발전시스템은 태양광 모듈, 에너지저장시스템, 전력변환장치 등으로 구성되었으며, 본 시스템의 적 용 가능성을 확인하기 위해 전력전자프로그램을 통해 시스템을 모델링하였으며, 시뮬레이션을 실시하였다. 또한, 실제 선박에 적용하기 위한 타당성 검증을 위해 경제성 분석을 실시하였으며, 약 11년 이후 경제성 부분에서도 유의미한 결과가 도출됨을 확인할 수 있었다.

Recently, due to high theoretical capacitance and excellent ion diffusion rate caused by the 2D layered crystal structure, transition metal hydroxides (TMHs) have generated considerable attention as active materials in supercapacitors (or electrochemical capacitors). However, TMHs should be designed using morphological or structural modification if they are to be used as active materials in supercapacitors, because they have insulation properties that induce low charge transfer rate. This study aims to modify the morphological structure for high cycling stability and fast charge storage kinetics of TMHs through the use of nickel cobalt hydroxide [NiCo(OH)2] decorated on nickel foam. Among the samples used, needle-like NiCo(OH)2 decorated on nickel foam offers a high specific capacitance (1110.9 F/g at current density of 0.5 A/g) with good rate capability (1110.9 - 746.7 F/g at current densities of 0.5 - 10.0 A/g). Moreover, at a high current density (10.0 A/g), a remarkable capacitance (713.8 F/g) and capacitance retention of 95.6% after 5000 cycles are noted. These results are attributed to high charge storage sites of needle-like NiCo(OH)2 and uniformly grown NiCo(OH)2 on nickel foam surface.

The process optimization of directed energy deposition (DED) has become imperative in the manufacture of reliable products. However, an energy-density-based approach without a sufficient powder feed rate hinders the attainment of an appropriate processing window for DED-processed materials. Optimizing the processing of DEDprocessed Ti-6Al- 4V alloys using energy per unit area (Eeff) and powder deposition density (PDDeff) as parameters helps overcome this problem in the present work. The experimental results show a lack of fusion, complete melting, and overmelting regions, which can be differentiated using energy per unit mass as a measure. Moreover, the optimized processing window (Eeff = 44~47 J/mm2 and PDDeff = 0.002~0.0025 g/mm2) is located within the complete melting region. This result shows that the Eeff and PDDeff-based processing optimization methodology is effective for estimating the properties of DED-processed materials.

In order to explore the job crafting experience of millennial safety workers, this study conducted a qualitative case research with five safety workers of S Energy from March 26 to September 27, 2021 . As a result of the analysis, task crafting showed ‘matching one’s strong suit with a given task’, ‘expanding work knowledge using social network service (SNS)’, and ‘making changes in job performance methods for preemptive safety management activities’. Also, Cognitive crafting showed ‘recognition of social vocation as a safety job’, ‘recognition of a role to grow as a safety management expert’, and ‘cognitive changes from means of organizational adaptation to enjoyment and energy of life’. At the same time, in relation crafting, ‘establishment of amicable relationships through SNS in non-face-to-face and rapid communicating situations’, ‘safety management made through with mutual cooperations between business people’, and ‘reborn as a mutual safety net in business relationships’ appeared. These can be used as basic data to accumulate the theoretical basis for job crafting research of millennial safety workers and to improve their job satisfaction. A follow-up study was proposed for safety workers with occupations of various kinds.