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In this study, optimization of the external load resistance of a piezoelectric bistable energy harvester was performed for primary harmonic (period-1T) and subharmonic (period-3T) interwell motions. The analytical expression of the optimal load resistance was derived, based on the spectral analyses of the interwell motions, and evaluated. The analytical results are in excellent agreement with the numerical ones. A parametric study shows that the optimal load resistance depended on the forcing frequency, but not the intensity of the ambient vibration. Additionally, it was found that the optimal resistance for the period-3T interwell motion tended to be approximately three times larger than that for the period-1T interwell motion, which means that the optimal resistance was directly affected by the oscillation frequency (or oscillation period) of the motion rather than the forcing frequency. For broadband energy harvesting applications, the subharmonic interwell motion is also useful, in addition to the primary harmonic interwell motion. In designing such piezoelectric bistable energy harvesters, the frequency dependency of the optimal load resistance should be considered properly depending on ambient vibrations.
Sungryong Bae; Pilkee Kim. Load Resistance Optimization of a Broadband Bistable Piezoelectric Energy Harvester for Primary Harmonic and Subharmonic Behaviors. Sustainability 2021, 13, 2865 .
AMA StyleSungryong Bae, Pilkee Kim. Load Resistance Optimization of a Broadband Bistable Piezoelectric Energy Harvester for Primary Harmonic and Subharmonic Behaviors. Sustainability. 2021; 13 (5):2865.
Chicago/Turabian StyleSungryong Bae; Pilkee Kim. 2021. "Load Resistance Optimization of a Broadband Bistable Piezoelectric Energy Harvester for Primary Harmonic and Subharmonic Behaviors." Sustainability 13, no. 5: 2865.
In this study, a semi-analytic approach to optimizing the external load resistance of a bi-stable electromagnetic energy harvester is presented based on the harmonic balance method. The harmonic balance analyses for the primary harmonic (period-1T) and two subharmonic (period-3T and 5T) interwell motions of the energy harvester are performed with the Fourier series solutions of the individual motions determined by spectral analyses. For each motion, an optimization problem for maximizing the output power of the energy harvester is formulated based on the harmonic balance solutions and then solved to estimate the optimal external load resistance. The results of a parametric study show that the optimal load resistance significantly depends on the inductive reactance and internal resistance of a solenoid coil––the higher the oscillation frequency of an interwell motion (or the larger the inductance of the coil) is, the larger the optimal load resistance. In particular, when the frequency of the ambient vibration source is relatively high, the non-linear dynamic characteristics of an interwell motion should be considered in the optimization process of the electromagnetic energy harvester. Compared with conventional resistance-matching techniques, the proposed semi-analytic approach could provide a more accurate estimation of the external load resistance.
Sungryong Bae; Pilkee Kim. Load Resistance Optimization of Bi-Stable Electromagnetic Energy Harvester Based on Harmonic Balance. Sensors 2021, 21, 1505 .
AMA StyleSungryong Bae, Pilkee Kim. Load Resistance Optimization of Bi-Stable Electromagnetic Energy Harvester Based on Harmonic Balance. Sensors. 2021; 21 (4):1505.
Chicago/Turabian StyleSungryong Bae; Pilkee Kim. 2021. "Load Resistance Optimization of Bi-Stable Electromagnetic Energy Harvester Based on Harmonic Balance." Sensors 21, no. 4: 1505.
Recent technical developments brought negative side effects such as air pollution and large-scale fires, increasingly exposing people to diesel engine exhaust particles (DEP). Testing how DEP inhalation triggers pathophysiology in animal models could be useful in determining how it affects humans. To this end, the aim of this study was to investigate the effects of pulmonary exposure to DEP for seven consecutive days in experimental male C5BL6/N mice. Twenty-four C5BL6/N mice were treated with one of the three test materials: distilled water for control, a low DEP exposure (5 mg/kg), or a high DEP exposure (15 mg/kg). Exposure to DEP induced decreased body weight; however, it gradually increased pulmonary weight in a DEP-dose-dependent manner. DEP exposure significantly elevated soot accumulation in the lungs, with the alteration of pulmonary homeostasis. It also elevated infiltrated immune cells, thus significantly increasing inflammatory cytokine mRNA and protein production in the lungs and broncho-alveolar lavage fluid, respectively. Pulmonary DEP exposure also altered behavioral responses in the open field test (OFT). Low exposure elevated moving distance and speed, while significantly decreasing the number of trials to enter the central zone. Different concentrations of DEP resulted in different behavioral changes; however, while anxiety levels increased, their degree was independent of DEP concentrations. Results suggest that DEP exposure may possess pro-inflammatory responses in the lungs and trigger anxiety.
Sunyoung Jeong; Jong-Hwa Lee; Jung-Heun Ha; Jinhee Kim; Inyong Kim; Sungryong Bae. An Exploratory Study of the Relationships between Diesel Engine Exhaust Particle Inhalation, Pulmonary Inflammation and Anxious Behavior. International Journal of Environmental Research and Public Health 2021, 18, 1166 .
AMA StyleSunyoung Jeong, Jong-Hwa Lee, Jung-Heun Ha, Jinhee Kim, Inyong Kim, Sungryong Bae. An Exploratory Study of the Relationships between Diesel Engine Exhaust Particle Inhalation, Pulmonary Inflammation and Anxious Behavior. International Journal of Environmental Research and Public Health. 2021; 18 (3):1166.
Chicago/Turabian StyleSunyoung Jeong; Jong-Hwa Lee; Jung-Heun Ha; Jinhee Kim; Inyong Kim; Sungryong Bae. 2021. "An Exploratory Study of the Relationships between Diesel Engine Exhaust Particle Inhalation, Pulmonary Inflammation and Anxious Behavior." International Journal of Environmental Research and Public Health 18, no. 3: 1166.
The most used fire effect models on evacuees are only focused on the physical capacity of the evacuees. However, some of the evacuees in a fire situation continuously move through the familiar route, although the familiar route is smoke-filled and they know that they are moving towards the fire source. Thus, the additional evacuation models are required for considering the behavioral changes due to the psychological pressure when the evacuees are moving through the smoke or towards the fire source. In this study, the inner smoke region force is modified to improve the accuracy and practicality of the BR-smoke model by varying the walking speed according to the smoke density. Additionally, the BR-smoke model is applied to FDS+Evac to compare the simulation results of the modified BR-smoke model with those of existing models. Based on the results, the evacuation characteristics inside the smoke region can be improved by using the modified BR-smoke model because the evacuees are continuously influenced by the modified inner smoke force inside the smoke region. However, additional studies for determining more reliable evacuee psychological factors are required to improve the reality of the modified BR-smoke model.
Sungryong Bae; Jun-Ho Choi; Hong Sun Ryou. Modification of Interaction Forces between Smoke and Evacuees. Energies 2020, 13, 4177 .
AMA StyleSungryong Bae, Jun-Ho Choi, Hong Sun Ryou. Modification of Interaction Forces between Smoke and Evacuees. Energies. 2020; 13 (16):4177.
Chicago/Turabian StyleSungryong Bae; Jun-Ho Choi; Hong Sun Ryou. 2020. "Modification of Interaction Forces between Smoke and Evacuees." Energies 13, no. 16: 4177.