Microalgae are efficient fatty acid producers owing to their high photosynthetic activities. They can act as sources of biofuel, feed, and various bioactive compounds. This study aimed to determine optimal culture conditions, including culture medium, temperature, and light intensity, to enhance the biomass and fatty acid content of the indigenous freshwater microalga, Tetradesmus obliquus. Evaluation using a high-throughput photobioreactor revealed that the optimal culture temperature and light intensity were 25°C and 300 μmol m-2 s-1, respectively. Additionally, we optimized components (N, P, and Mg) of the BG-11 medium to enhance the microalgal biomass. Modified BG-11 medium increased the T. obliquus biomass by 37% compared to the standard BG-11 medium. Subsequently, the culture medium was replaced with N- and P-depleted media to determine the abiotic stress factor that could increase the cellular fatty acid content. Notably, fatty acid content was significantly increased from 8.5% up to 14.6% on day 7 of culture in N-deficient (N-P+ and N-P-) media. Sequential optimization effectively increased the biomass by 83% and fatty acid content by >76% in T. obliquus. Our optimization method can be used to enhance the biomass and fatty acid contents of various other microalgae.

In this study, the initial operation characteristics of a multi-type cooling system with three indoor units using an inverter compressor were investigated experimentally using a calorimeter. The operating characteristics of the cooling system were confirmed under the full load condition of simultaneous operation of three rooms and the partial load condition of individual operation of two or one room under the standard cooling conditions. The capacities of A, B and C are 50, 20, and 30% of the total capacity, respectively. The 3 room combination has 100% capacity, the 2 room combination has 50, 70 and 80% capacity, and the 1 room has 20, 30, and 50% capacity. The compressor condensing and evaporating pressures, the electronic expansion valve openings of indoor units A, B, and C, and the compressor operating frequencies were measured for 10 minutes after the cooling system was started. During the initial operation, the changes in the operating time and opening of the electronic expansion valve varied depending on the indoor unit combination and the operating load, and the relationship between the compressor pressure and the operating frequency was found.

For experimental studies on the production of MR fluid for MR dampers, MR fluid with a viscosity of 506 cP and a density of 2.6 g/cc was produced. In order for MR fluid to have suitable performance for MR dampers, it is important to select surfactants, magnetic particles, base oil, and characteristic additives to obtain high damping force and maintain physical and chemical properties. In order to investigate the redispersibility of MR fluid, viscosity, density, saturation magnetic flux density, dispersibility, and temperature effects were evaluated. A particle size distribution meter and a vibrating magnetometer were used, and a yield stress and redispersion device were developed to obtain the yield stress of the MR fluid. The recovery rate of MR fluid was approximately 97% at 0.2% succinic acid coating and 8% anti-settling agent. And when current is applied, the viscosity increases by more than 90% due to magnetic properties.

In order to design a seismic safety of a cabinet affected by an earthquake, vibration analysis was performed using a model cabinet. In order to analyze the vibration characteristics of the cabinet under earthquake conditions, 3D finite element analysis was performed using ANSYS Workbench and SolidWorks. The modal analysis of the cabinet showed nine natural modes and natural frequencies, and showed the deformation and vibration of the cabinet panel for each mode. The frequencies of the 1st and 2nd modes, which are low modes, were 10% of the natural frequency value of the 9th mode, so it was easy to predict the possibility of resonance occurrence. The response spectrum due to the earthquake showed that the displacement, acceleration, and stress distribution of the cabinet had different behaviors in the x, y, and z directions, and especially showed very large values in the z direction. Although the vibration characteristics of the structure were evaluated using the modal characteristics and response spectrum for the cabinet, research on the application of a tuned mass damper is necessary for the dynamic characteristics process of the cabinet due to an earthquake and resonance reduction.

In order to understand the MR fluid flow in the MR damper core, the annular orifice path was simplified into a square channel and the electromagnetic flow was analyzed. For this purpose, the CFD-ACE+ program was used. The temperature and magnetic field of the MR fluid were based on room temperature and orifice wall data, and 2-D steady incompressible laminar flow was assumed. The inlet and outlet of the orifice channel are at atmospheric pressure, and the inflow velocity of the MR fluid is 0.1 m/s. After analyzing the magnetic field of the core, which is a simple model of the 1 stage MR damper, the electromagnetic flow analysis of the MR fluid flowing through the orifice channel was performed. From this, the magnetic field of the orifice channel and the electromagnetic flow of the MR fluid were observed. As the magnetic flux density increased, the flow distribution and velocity of the MR fluid in the channel core changed significantly.

불확실한 대내외 환경에서 기업들이 살아남기 위한 효율적인 경영의 중요성이 대두되고 있다. 기업은 미래를 위한 투자를 아끼지 않으면서, 반대로 경기침체의 상황에서 생존하기 위한 비용 절감도 필요한 상충적인 상황에 놓여있다. 그에 따라 미래를 위한 투자의 일환으로 우수한 인적자원을 확보하고, 현재 보유하고 있는 인적자원의 역량을 높여 생산성을 높이고, 비용을 절감하기 위해 기업 특유의 기술에 대한 구성원들의 교육 중요성이 더욱 부각되고 있다. 특히, 기업 특유의 기술에 대한 역량을 향상시키기 위해서 는 형식교육과 더불어 무형식학습에 의한 교육이 중요하며, 이러한 경향에 따라 무형식학습에 대한 연구 가 활발히 진행되고 있다. 무형식학습을 통해 기업 특유의 기술에 대한 역량이 높아진 구성원은 직무수행 과정에서 느끼는 어려움과 스트레스가 감소하고, 자기효능감이 증가하여 직무에 대한 만족이 향상될 수 있다. 그리고 이러한 관계는 구성원의 인재우대 인식으로 더 강하게 나타날 수 있다. 구성원이 조직의 인 재우대를 높게 인식하고 있다면, 제도의 수용성이 높아지고 이는 무형식학습의 효과성을 높여 직무만족 이 높아지는 결과를 가져올 수 있다. 그러므로 본 연구에서는 무형식학습 참여가 직무만족에 미치는 영향 을 살펴보고, 이 관계가 인재우대 인식에 따라 조절되는 관계를 살펴보고자 한다. 본 연구의 목적은 첫째, 무형식학습과 무형식학습 효과성 인식과의 관계를 살펴보고, 둘째, 무형식학습 참여와 직무만족간의 관계에서 무형식학습 효과성 인식의 매개효과를 살펴본다. 셋째, 무형식학습 참여와 무형식학습 효과성 인식의 관계에서 인재우대 인식의 조절효과를 살펴본다. 마지막으로 무형식학습 참여 와 직무만족 간의 관계에서 무형식학습 효과성 인식의 매개효과가 인재우대 인식에 의해 조절되는지 살 펴보도록 한다. 연구가설을 검증하기 위해 한국직업능력연구원의 인적자본기업패널 2020년 근로자 데이터를 활용하였다. 연구자료분석 결과 첫째, 무형식학습 참여는 무형식학습 효과성 인식에 정적인 영향을 미쳤고, 둘째, 무형 식학습 참여는 무형식학습 효과성 인식을 매개로 직무만족에 정적인 영향을 미쳤다. 셋째, 무형식학습 참 여와 무형식학습 효과성 인식의 관계는 인재우대 인식이 높을수록 정적인 관계가 더 강하게 나타나는 것을 확인할 수 있었다. 마지막으로 무형식학습 참여가 무형식학습 효과성 인식을 매개하여 직무만족에 미치는 영향이 인재우대 인식이 높을수록 더 강하게 나타나는 조절된 매개효과를 확인할 수 있었다. 이러 한 연구결과를 통해 무형식학습의 실행과 효과에 대해 고민하는 실무자들을 위한 시사점을 제시하였다.

In this study, the calorimeter was used to experimentally investigate the heating characteristics of the variable A/C system according to changes in loading time and outdoor dry bulb temperature. The heating capacity, COP and compressor discharge temperature were measured while changing the loading time of the compressor. To develop the correlation for compressor discharge temperature, loading time, indoor dry bulb temperature and outdoor dry bulb temperatures were considered as operating variables. As the outdoor temperature and loading time increased, the heating capacity and COP increased. However, the change in COP showed different trends depending on the outdoor temperature. The evaporation temperature according to the loading time is a good estimate of the outdoor temperature. However, as the temperature difference between indoor and outdoor rooms decreases and the loading time increases, the condensation pressure increases significantly, so the condensation temperature increases. The maximum deviation between the correlation and the experimental value for compressor discharge temperature was within approximately 2℃.

In this study, the calorimeter was used to experimentally investigate the cooling characteristics of the variable A/C system according to changes in loading time and outdoor dry bulb temperature. The cooling capacity, COP and compressor discharge temperature were measured while changing the loading time of the compressor. To develop the correlation for compressor discharge temperature, loading time, indoor and outdoor dry bulb temperatures, evaporation and condensation temperatures were considered as operating variables. As the loading time increased, the cooling capacity and COP increased. The cooling capacity increased linearly with the loading time. The COP increased more at low loading times than at high loading times. The change in condensing temperature according to the loading time had a small temperature fluctuation range, and the evaporation temperature decreased linearly. The compressor discharge temperature increased linearly with the loading time and outdoor temperature, and the maximum deviation between the experimental value and the correlation was within about 2℃.

In the present study, the inertial electromagnetic actuator (IEA) and the FxLMS (filtered-x least mean square) method were applied to study vibration control using the active mount. IEA was designed and manufactured for the experiment, and FxLMS algorithm was developed to evaluate control performance and mount dynamic characteristics. For the vibration control experiment, active mounts were installed at the top and bottom, and the lower active mount controls the force transmitted to the structure by the excitation signal from the upper active mount. The experiment was performed by simultaneously exciting three frequencies in three axes. From the experimental results, it was confirmed that the force measured at the lower active mount when the actuator is off is greatly reduced when the actuator is on, and that vibration reduction in the vertical z-axis is more effective than vibration reduction in the x-y plane.