• International Journal of Naval Architecture and Ocean Engineering
• /
• v.12 no.1
• /
• pp.691-698
• /
• 2020

In this study, the effects of hydrodynamic interceptors on a high-speed vessel were investigated to identify the operating principle based on experiments. Model tests were performed using a high-speed towing carriage. The resistance, trim and rise of Center of Gravity (CG) of the high-speed vessel were measured for various ship speeds and interceptor heights. As the interceptor height increased, the trim and rise of CG were reduced. In order to quantitatively analyze these phenomena, the pressure at the stern bottom was measured using tactile sensors. The reliability of the measured results from the tactile sensors was verified through repeat tests. The pressure on the stern bottom increased in proportion to the interceptor height, as the interceptor partially blocked the flow there. Then, the trim was reduced. However, as the ship speed increases, the pressure at the location close to the interceptor decreases when the interceptor height is small, leading to increased trim. Therefore, the interceptor height for running attitude control should be carefully determined considering multiple factors in the operating condition of the high-speed planing hull.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.9 no.4 s.44
• /
• pp.55-66
• /
• 2005

The effectiveness of fuzzy supervisory control technique for the control of seismic responses of smart base isolation system is investigated in this study. To this end, first generation base isolated building benchmark problem is employed for the numerical simulation. The benchmark structure under consideration is an eight-story base isolated building having irregular plan and is equipped with low-damping elastometric bearings and magnetorheological (MR) dampers for seismic protection. Lower level fuzzy logic controllers (FLC) for far-fault or near-fault earthquakes are developed in order to effectively control base isolated building using multi-objective genetic algorithm. Four objectives, i.e. reduction of peak structural acceleration, peak base drift, RMS structural acceleration and RMS base drift, are used in multi-objective optimization process. When earthquakes are applied to benchmark building, each of low level FLCs provides different command voltage and supervisory fuzzy controller combines two command voltages io one based on fuzzy inference system in real time. Results from the numerical simulations demonstrate that base drift as well as superstructure responses can be effectively reduced using the proposed supervisory fuzzy control technique.

• Journal of Korean Society for Atmospheric Environment
• /
• v.27 no.6
• /
• pp.772-790
• /
• 2011

In this paper, we use the HDDM (High-order Decoupled Direct Method)-driven ozone sensitivity to predict change in ozone concentrations in response to domain-wide $NO_x$(Oxides of Nitrogen) and VOC (Volatile Organic Compound) emission controls over the Seoul Metropolitan Area during June 11~19, 2007. In order to validate the applicability of HDDM to $NO_x$ and VOC control scenarios, the HDDM results are compared to Brute Force Method (BFM). For VOC controls, NME (Normalized Mean Error) between BFM and HDDM remains less than 2% until the domain-wide VOC emissions are reduced by 80%. The NME for a 40% reduction in the domain-wide $NO_x$ emissions is less than 5% but increases abruptly after further reductions in the $NO_x$ emissions (i.e., 80% reduction). The results indicates that it may be inaccurate to use ozone sensitivity coefficients estimated at a given base emission condition in predicting ozone after $NO_x$ reductions larger than ~50% of the domain total in the SMA. Therefore, HDDM application on piecewise emissions is desirable to predict ozone response to emission controls with accuracy (i.e., truck emissions rather than the domain total). For computational efficiency, HDDM shows approximately 30% faster than the BFM sensitivity approach.

• Asian-Australasian Journal of Animal Sciences
• /
• v.28 no.3
• /
• pp.343-350
• /
• 2015

Cocoa pod is among the by-products of cocoa (Theobroma cacao) plantations. The aim of this study was to apply a number of treatments in order to improve nutritional quality of cocoa pod for feeding of ruminants. Cocoa pod was subjected to different treatments, i.e. C (cocoa pod without any treatment or control), CAm (cocoa pod+1.5% urea), CMo (cocoa pod+3% molasses), CRu (cocoa pod+3% rumen content) and CPh (cocoa pod+3% molasses+Phanerochaete chrysosporium inoculum). Analysis of proximate and Van Soest's fiber fraction were performed on the respective treatments. The pods were then subjected to an in vitro digestibility evaluation by incubation in rumen fluid-buffer medium, employing a randomized complete block design (n = 3 replicates). Further, an in vivo evaluation of the pods (35% inclusion level in total mixed ration) was conducted by feeding to young Holstein steers (average body weight of $145{\pm}3.6kg$) with a $5{\times}5$ latin square design arrangement (n = 5 replicates). Each experimental period lasted for 30 d; the first 20 d was for feed adaptation, the next 3 d was for sampling of rumen liquid, and the last 7 d was for measurements of digestibility and N balance. Results revealed that lignin content was reduced significantly when cocoa pod was treated with urea, molasses, rumen content or P. chrysosporium (p<0.01) with the following order of effectiveness: CPh>CAm>CRu>CMo. Among all treatments, CAm and CPh treatments significantly improved the in vitro dry matter and organic matter digestibility (p<0.05) of cocoa pod. Average daily gain of steers receiving CAm or CPh treatment was significantly higher than that of control (p<0.01) with an increase of 105% and 92%, respectively. Such higher daily gain was concomitant with higher N retention and proportion of N retention to N intake in CAm and CPh treatments than those of control (p<0.05). It can be concluded from this study that treatment with either urea or P. chrysosporium is effective in improving the nutritive value of cocoa pod.

• Korean Journal of Agricultural Science
• /
• v.49 no.4
• /
• pp.973-981
• /
• 2022

'Shine Muscat' (Vitis labruscana Bailey x Vitis vinifera L.) grapes recently have been greatly favored in Korea, and as of 2022, account for 38.6% of the total grape market in Korea. However, there is a lack of research on post-harvest quality control appropriate to the unique characteristics of 'Shine Muscat'. In order to continuously increase domestic demand and exports in the future, it is essential to establish proper postharvest techniques. Essential oils have remarkable potential as biologically active and environmentally friendly antiseptics for the fruit industry. The objective of this study is to evaluate the effects of essential oils and aroma constituent treatment on fruit quality attributes of 'Shine Muscat' grapes in order to extend fruit quality during a simulated export period. A cluster of 'Shine Muscat' grapes was placed in a newly developed paper box container, and treated with rosemary essential oil, thyme essential oil, and linalool, along with an untreated control. The results showed no significant effect on fruit quality indices, such as cluster weight loss, berry firmness, soluble solids content, titratable acidity, sugar acid ratio, and color change, but showed a positive effect on the alleviation of berry shatter compared to the untreated control. In addition, rosemary oil treatment reduced the proportion of unhealthy berries. Therefore, the results indicated that the newly developed packaging container along with certain essential oil treatment could be applied as a promising packaging material for table grape export.

• Physical Therapy Korea
• /
• v.27 no.2
• /
• pp.126-132
• /
• 2020

Background: Augmented somatosensory feedback stimulates the mechanoreceptor to deliver information on bodily position, improving the postural control. The various types of such feedback include ankle-foot orthoses (AFOs) and vibration. The optimal feedback to mitigate postural sway remains unclear, as does the effect of augmented somatosensory feedback on muscle co-contraction. Objects: We compared postural sway and ankle muscle co-contraction without feedback (control) and with either of two forms of somatosensory feedback (AFOs and vibration). Methods: We recruited 15 healthy subjects and tested them under three feedback conditions (control, AFOs, vibration) with two sensory conditions (eyes open, or eyes closed and the head tilted back), in random order. Postural sway was measured using a force platform; the mean sway area of the 95% confidence ellipse (AREA) and the mean velocity of the center-of-pressure displacement (VEL) were assessed. Co-contraction of the tibialis anterior and gastrocnemius muscles was measured using electromyography and converted into a co-contraction index (CI). Results: We found significant main effects of the three feedback states on postural sway (AREA, VEL) and the CI. The two sensory conditions exerted significant main effects on postural sway (AREA and VEL). AFOs reduced postural sway to a level significantly lower than that of the control (p = 0.014, p < 0.001) or that afforded by vibration (p = 0.024, p < 0.001). In terms of CI amelioration, the AFOs condition was significantly better than the control (p = 0.004). Vibration did not significantly improve either postural sway or the CI compared to the control condition. There was no significant interaction effect between the three feedback conditions and the two sensory conditions. Conclusion: Lower-extremity devices such as AFOs enhance somatosensory perception, improving postural control and decreasing the CI during static standing.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.12
• /
• pp.1184-1191
• /
• 2009

In order to reduce the download around the Smart UAV(SUAV) at Transition mode, flow control using synthetic jet has been performed. Many of the complex tilt rotor flow features are captured including the leading and trailing edge separation, and the large region of separated flow beneath the wing. Based on the results of part 1 of the present work, synthetic jet is located at 0.01c, $0.95c_{flap}$ and it is operated with the non-dimensional frequency of 0.5, 5 to control the leading edge and trailing edge separation. Consequently, download is substantially reduced compared to with no control case at transition mode using leading edge jet only. The present results show that the overall flight performance and stability of the SUAV can be remarkably improved by applying the active flow control strategy based on synthetic jet.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.4
• /
• pp.339-346
• /
• 2012

In this paper, equivalent models for active control devices are proposed so that building structures with such devices are analyzed using commercial structural analysis programs for the assessment of the structural members under active vibration control. Equivalent link models represent active control device with a virtual linear spring and dashpot, and equivalent force models are control force history acting at the installation point in structural models. Active controllers are designed based on the reduced-order models for a vertical cantilever model and a high-rise building model and corresponding equivalent models are determined from control gain matrices. Based on acceleration, displacement and member force responses, the effectiveness of the equivalent models is verified. As a result, proposed equivalent models, of which equivalent link model showed better performance, appear to enable detailed investigation of structural behavior to the extent of member force level.

• Journal of Digital Convergence
• /
• v.17 no.10
• /
• pp.223-232
• /
• 2019

With the development of the information communication industry, the size of the communication device has been reduced to a system that generates a large amount of heat. Therefore, since the amount of heat generated by the wireless equipment is large in the wireless base station, the energy consumption is continuously consumed and the failure of the wireless base station may occur. Therefore, in this study, The study was analyzed. As a research method, we performed base station with a lot of calorific value and electric charge. We selected 25 base stations and obtained data for two weeks. To ensure reliability, the room temperature was kept constant at $27^{\circ}C$, and the control system was installed and equiped for two weeks to obtain the date analysis. In order to calculate the test results in the study method, the instrument was used with a computer, a digital thermometer, and dust measurement. For the date analysis, we conducted a research study on 25 wireless basestations before and after the installation of Control Sysetm.

• Journal of Power Electronics
• /
• v.14 no.1
• /
• pp.61-73
• /
• 2014

Multiphase machines are characterized by high power density, enhanced fault-tolerant capacity, and low torque pulsation. For a voltage source inverter supplied multiphase machine, the probability of load imbalances becomes greater and unwanted low-order stator voltage harmonics occur. This paper deals with the PWM control of multiphase inverters under unbalanced load conditions and it proposes a novel near-five-vector SVPWM algorithm based on the five-phase six-leg inverter. The proposed algorithm can output symmetrical phase voltages under unbalanced load conditions, which is not possible for the conventional SVPWM algorithms based on the five-phase five-leg inverters. The cause of extra harmonics in the phase voltages is analyzed, and an xy coordinate system orthogonal to the ${\alpha}{\beta}z$ coordinate system is introduced to eliminate low-order harmonics in the output phase voltages. Moreover, the digital implementation of the near-five-vector SVPWM algorithm is discussed, and the optimal approach with reduced complexity and low execution time is elaborated. A comparison of the proposed algorithm and other existing PWM algorithms is provided, and the pros and cons of the proposed algorithm are concluded. Simulation and experimental results are also given. It is shown that the proposed algorithm works well under unbalanced load conditions. However, its maximum modulation index is reduced by 5.15% in the linear modulation region, and its algorithm complexity and memory requirement increase. The basic principle in this paper can be easily extended to other inverters with different phase numbers.