The thermal management issue in OLED (organic light emitting diode) devices has a significant impact on the efficiency, reliability, and life time of the device. In particular, in OLED systems with multipolar or double cathode electrodes, it is important to accurately interpret the effect of heat generated by current flow between electrodes on the emitting layer. In this study, the governing equation was established based on the heat conduction equation to mathematically model and analyze this heat distribution, and the heat distribution analysis was performed using the COMSOL program. It was confirmed that the temperature generated in the OLED with the double cathode structure reached a maximum of 343.157 K centered on the emitting layer. The heat distribution generated in the proposed OLED structure with the double cathode electrodes was confirmed to be highly distributed in the center toward the double cathode electrodes, which is believed to be because the arrangement of the double cathode electrodes improves the symmetrical distribution of temperature while reducing power consumption.

In the era of the Fourth Industrial Revolution, electronic devices are becoming increasingly miniaturized and lightweight to overcome spatial limitations, necessitating lower power consumption. Triboelectric nanogenerators (TENGs), which convert mechanical energy into electrical energy, offer an ideal solution as small-scale power generators for these compact devices. Recent research has focused on various materials and structural designs to maximize the output of triboelectric energy harvesters, highlighting the growing importance of theoretical structure analysis software for precise evaluation. COMSOL Multiphysics software provides an accurate method for simulating the electrical characteristics of TENGs. This Tutorial Status Report introduces the process of modeling TENGs and analyzing their electrical output using COMSOL Multiphysics

The key to determining the lifetime of OLED device is how much brightness can be maintained. It can be said that there are internal and external causes for the degradation of OLED devices. The most important cause of internal degradation is bonding and degradation in the excited state due to the electrochemical instability of organic materials. The structure of OLED modeled in this paper consists of a cathode layer, electron injection layer (EIL), electron transport layer (ETL), light emission layer, hole transport layer (HTL), hole injection layer (HIL), and anode layer on a glass substrate from top to bottom. It was confirmed that the temperature generated in OLED was distributed around the maximum of 343.15 K centered on the emission layer. It can be seen that the heat distribution generated in the presented OLED structure has an asymmetrically high temperature distribution toward the cathode, which is believed to be because the sizes of the cathode and positive electrode are asymmetric. Therefore, when designing OLED, it is believed that designing the structures of the cathode and anode electrodes as symmetrically as possible can ensure uniform heat distribution, maintain uniform luminance of OLED, and extend the lifetime. The thermal distribution of OLED was analyzed using the finite element method according to Comsol 5.2.

Recently, as power and electronic devices have increased in frequency and capacity, it has become a major concern to protect electronic circuits and electronic components used in these devices from abnormal voltages such as various surges and pulse noise. To respond to variously rated voltages applied to power electronic devices, the rated voltages of various varistors can be obtained by controlling the size of internal particles of the varistor or controlling the number of layers of the varistor. During bonding, the problem of unbalanced thermal runaway occurring between the electrode and the varistor interface causes degradation of the varistor and shortens its life of the varistor. In this study, to solve the problem of unbalanced heat distribution of stacked varistors to adjust the operating voltage, the contents of the ZnO-based varistor composition were 96 wt% ZnO, 1 mol% Sb₂O₃, 1 mol% Bi₂O₃, 0.5 mol% CoO, 0.5 mol% MnO, and 1 mol% TiO₂. A multi-layered ZnO varistor was modeled by bonding a single varistor with a composition in three layers according to the operating voltage. The thermal distribution of the triple-layered ZnO varistor was analyzed for the thermal runaway phenomenon that occurred during varistor operation using the finite element method according to Comsol 5.2.

Since the ZnO varistor is a semiconductor device, the internal thermal distribution during the varistor operation is recognized as an important factor in the performance and deterioration of the varistor. For an optimal varistor structure design, the thermal runaway phenomenon during the varistor operation was interpreted using the Comsol 5.2 analysis program by a finite element analysis. The maximum temperature of the center measured in the cross section of the ZnO varistor was confirmed to increase as the temperature moved from the lower electrode to the center towards the upper electrode up to 572.6 K. The electrodes are thinned so that the influence of the Schottky barrier is not great. The heat gradient balance is determined to be improved when the electrode of the hybrid form is introduced. The thickness, density, pore distribution, impurity uniformity, and particle size of the ZnO varistor are required, and it is determined that the pyrolysis gradient will be improved regardless of the electrode thickness. When these results are applied to design the ZnO varistor, the optimal structure of the ZnO varistor can be obtained.

In the 4^th industrial age, electronic devices are becoming smaller and lighter with a low power consumption to overcome spatial limitation. The piezoelectric energy harvesters can convert mechanical kinetic energy into electric energy; thus, enabling the operation of small electronic devices. Recently, various piezoelectric harvesters have been reported and the electric output from these harvesters could be anticipated by theoretical analysis methods. For example, COMSOL Multiphysics software provides a theoretical simulation of piezoelectric effect with a combination of mechanical and electrical phenomena in the piezoelectric materials. This article introduces a brief modeling of piezoelectric harvester to investigate mechanical stress and electrical output of harvesting devices by the COMSOL Multiphysics software.

The 22.9 kV vacuum interrupter (VI) built-in load bus switcher (LBS), which is most often used as a load switch for distribution, extinguishes the arc that occurs during normal load opening and closing and fault current interruption within the VI housing to quickly switch circuits. As a protective device for contact separation, the rated current is supplied in a normal state. When a fault current flows due to a fault or an accident in the power system, the contact is disconnected in a vacuum state to block the fault current. In this study, in order to design the optimal VI, the heat dissipation characteristics of VI according to the center electrode distance 0/1/2/3 cm were analyzed by applying the finite element method, and the results were reflected to improve the structure of the VI.

Atmospheric environmental problems have a major impact on human health and lifestyle. In humans, inhalation of nitrogen oxides causes respiratory diseases, such as bronchitis. In this paper, thermal analysis of a gas sensor was carried out to design and fabricate a wearable nylon-yarn gas sensor for the detection of NO_x gas. In the thermal analysis method, the thermal diffusion process was analyzed while operating the sensors at 40 and 60℃ to secure a temperature range that does not cause thermal runaway due to temperature in the operating environment. Thermal diffusion analysis was performed using the COMSOL software. The thermal analysis results could be useful for analyzing gas adsorption and desorption, as well as the design of gas sensors. The thermal energy diffusion rate increased slightly from 10.05 to 10.1 K/mm as the sensor temperature increased from 40 to 60℃. It was concluded that the sensor could be operated in this temperature range without thermal breakdown.