• Food Science of Animal Resources
• /
• v.30 no.1
• /
• pp.49-54
• /
• 2010

The aim of this research was to estimate the effect of temperature and develop predictive models for the growth of total viable cells (TVC) and Escherichia coli (EC) on chicken breast under aerobic and various temperature conditions. The primary models were determined by Baranyi model. The secondary models for the specific growth rate (SGR) and lag time (LT), as a function of storage temperature, were developed by the polynomial model. The initial contamination level of chicken breasts was around 4.3 Log CFU/g of TVC and 1.0 Log CFU/g of E. coli. During 216 h of storage, SGR of TVC showed 0.05, 0.15, and 0.54 Log CFU/g/h at 5, 15, and $25^{\circ}C$. Also, the growth tendency of EC was similar to those of TVC. As storage temperature increased, the values of SGR of microorganisms increased dramatically and the values of LT decreased inversely. The predicted growth models with experimental data were evaluated by $B_f$, $A_f$, RMSE, and $R^2$. These values indicated that these developed models were reliable to express the growth of TVC and EC on chicken breasts. The temperature changes of distribution and showcase in markets might affect the growth of microorganisms and spoilage of chicken breast mainly.

• Journal of the Korea Society for Simulation
• /
• v.15 no.3
• /
• pp.103-114
• /
• 2006

Now distribution centers include an ASRS (Automated Storage and Retrieving System) and automated transfer systems such as conveyors and AGV (Automated Guided Vehicle). These automated distribution centers have lots of parameters to be considered fur operating performance. The general basic parameters in the distribution centers are specifications of storage equipment, system operating rules, configuration of storage area and unit load features. In this paper, an approach using simulation and metamodeling with response Surface method to optimize the design parameters of an automated distribution center model is presented. The simulation based metamodel will constitute an efficient approximation of the system function, and the approximate function will be used to design rapid optimal parameters of the distribution center model. This paper provides a comprehensive framework for economical material flow system design using the simulation and metamodeling.

• Journal of Environmental Science International
• /
• v.26 no.11
• /
• pp.1247-1253
• /
• 2017

The Fuji variety of apple, introduced in Japan, has excellent storage quality and good taste, such that it is the most commonly cultivated apple variety in Gunwi County, North Gyeongsang Province, Korean Peninsula. Accurate prediction of harvest maturity allows farmers to more efficiently manage their farm in important aspects such as working time, fruit storage, market shipment, and labor distribution. Temperature is one of the most important factors that determine plant growth, development, and yield. This paper reports on the beta distribution (function) model that can be used to simulate the the phenological response of plants to temperature. The beta function, commonly used as a skewed probability density in statistics, was introduced to estimate apple harvest maturity as a function of temperature in this study. The model parameters were daily maximum temperature, daily optimum temperature, and maximum growth rate. They were estimated from the input data of daily maximum and minimum temperature and apple harvest maturity. The difference in observed and predicted maturity day from 2009 to 2012, with optimal parameters, was from two days earlier to one day later.

• Journal of Korea Water Resources Association
• /
• v.30 no.5
• /
• pp.449-457
• /
• 1997

This study attempts to develop a stochastic-dynamic real-time flow forecasting model for an event-orient watershed storage function model (SFM), which has been used as an official flood computation model in Korea, and to evaluate its performance for real-time flow forecast. The study area is the 747.5$\textrm{km}^2$ Hwecheon basin with outlet at Gaejin and the 8 single flow events during 1983-1986 are selected for comparison and verification of model parameter and model performance. The used model parameters in this study are the same values on field work. It is shown that results from the existing model highly depend on the events, but those from the developed model are stable and well predict the flows for the selected flood events. The coefficient of model efficiency between observed and predicted flows for the events was above 0.90. It is concluded that the developed model that can consider model and observation uncertainties during a flood event is feasible and produces reliable real-time flow forecasts on the area.

• Water for future
• /
• v.29 no.4
• /
• pp.209-221
• /
• 1996

It may be difficult to make exact estimates of peak discharge or runoff depth of a flood and to establish the proper measurement for the flood protection since water stages or discharges have been rarely measured at small river basins in Korea. Three small catchments in the Su-Young river basin in Pusan were selected for the study areas. Various runoff parameters for the study areas were determined, and runoff analyses were performed using three different runoff models available in literatures; the storage function method, the discrete, linear, input-output model, and the linear reservoir model. The hydrographs calculated by three different methods showed good agreement with the observed flood hydrographs, indicating that the models selected are all capable of sucessfully modeling the flood events for small watersheds. The storage function method gave the best results in spite of its weakness that it could not be applicable to small floods, while the linear reservoir model was found to provide relatively good results with less parameters. The capabilities of simulating flood hydrographs were also evaluated based on the effective rainfall from the storage function parameters, the $\Phi$-index method, and the constant percentage method. For the On-Cheon stream watershed, the storage function parameters provided better estimates of effective rainfall for regenerating flood hydrographs than any others considered in the study. The $\Phi$-index method, however, resulted in better estimates of effective rainfall for the other two study areas.

• Food Science and Biotechnology
• /
• v.17 no.6
• /
• pp.1316-1321
• /
• 2008

This study was conducted to develop a model to describe the effect of antimicrobials [potassium sorbate (PS), potassium lactate (PL), and combined PL and sodium diacetate (SDA, PLSDA)] on the growth parameters of Listeria monocytogenes such as specific growth rate (SGR) and lag phase periods (LT) in air-dried raw sausages as a function of storage temperature (4, 10, 16, and $25^{\circ}C$). Results showed that the SGR of L monocytogenes was dependent on the storage temperature and level of antimicrobials used. The most effective treatment was the 4% PLSDA, followed by the 2% PLSDA and 4% PL and 0.2% PS exhibited the least antimicrobial effect. Increased growth rates were observed with increasing storage temperatures from 4 to $25^{\circ}C$. The growth data were fitted with a Gompertz equation to determine the SGR and LT of the L. monocytogenes. Six polynomial models were developed for the SGR and LT to evaluate the effect of PS (0.1, 0.2%) and PL (2,4%) alone and PLSDA (2, 4%) on the growth kinetics of L. monocytogenes from 4 to $25^{\circ}C$.

• Journal of Power Electronics
• /
• v.15 no.4
• /
• pp.1006-1017
• /
• 2015

This paper presents a finite control set model predictive control (FCS-MPC) strategy for the AC/DC matrix converter used in grid-connected battery energy storage system (BESS). First, to control the grid current properly, the DC current is also included in the cost function because of input and output direct coupling. The DC current reference is generated based on the dynamic relationship of the two currents, so the grid current gains improved transient state performance. Furthermore, the steady state error is reduced by adding a closed-loop. Second, a Luenberger observer is adopted to detect the AC input voltage instead of sensors, so the cost is reduced and the reliability can be enhanced. Third, a switching state pre-selection method that only needs to evaluate half of the active switching states is presented, with the advantages of shorter calculation time, no high dv/dt at the DC terminal, and less switching loss. The robustness under grid voltage distortion and parameter sensibility are discussed as well. Simulation and experimental results confirm the good performance of the proposed scheme for battery charging and discharging control.

• Tribology and Lubricants
• /
• v.27 no.3
• /
• pp.167-173
• /
• 2011

In this paper, an actuator model of the thrust magnetic bearing for the flywheel energy storage is derived using magnetic circuit theory. And we compared this result with finite element magnetic field analysis result. Based on the actuator model, we made a simulation model of the thrust magnetic bearing system. We showed the closed loop transfer function and sensitivity function of the thrust magnetic bearing system using both the simulation model and the experiment. The experimental result at rotation velocity 18,000rpm of thrust magnetic bearing system is included.

• Water for future
• /
• v.19 no.3
• /
• pp.267-276
• /
• 1986

This study aims at the development of flood runoff model by comparing and analyzing nonlinear models with linear models in rier basins. The models which are used at the analysis are Nash model and Runoff function method as linear models, and Tank model and Storage function method as nonlinear models. The results, which are obtained from the analysis of these models by using hydrologic data of a representative basin in Nakdong river, Wi-chun basin, show that the peak time, peak flow and flood hydrogrphs by nonlinear models are better than those by linear models in comparison with observed ones, and that nonlinear models are suittable as flood runoff model.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.34 no.8
• /
• pp.308-316
• /
• 1985

This paper proposes an analytic tool for long-term generation expansion planning based on the maximum principle. Many research works have been performed in the field of generation expansion planning. But few works can be found with the maxinmum principle. A recently published one worked by professor Young Moon Park et al. shows remarkable improvements in modeling and computation. But this modeling allows only thermal units. This paper has extended Professor Park's model so that the optimal pumped-storage operation is taken into account. So the ability for practical application is enhanced. In addition, the analytic supply-shortage cost function is included. The maximum principle is solved by gradient search due to its simplicity. Every iteration is treated as if mathematical programming such that all controls from the initial to the terminal time are manipulated within the same plane. Proposed methodology is tested in a real scale power system and the simulation results are compared with other available package. Capability of proposed method is fully demonstrated. It is expected that the proposed method can be served as a powerful analytic tool for long-term generation expansion planning.