• Journal of Agricultural Extension & Community Development
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• v.16 no.1
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• pp.69-98
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• 2009

This study empirically studies the effects of Agricultural Technology Service Center's educational program for farmers on their incomes. The educational program for farmers has widely been managed in discourse and policy in Korea. In 2008, Agricultural Technology Service Center managed 88 educational program for farmers, where 6,409 farmers received a certificate. While there are important studies, most of them have concentrated on qualitative analysis and noneconomic effects to an educational program for farmers. This study tried to analyze whether or not there is an economic effect of an educational program for farmers, focusing on the relationship between the educational program for farmers and their income status. Multilevel models (or hierarchical linear models) were applied to this study. Multilevel model is a quantitative model of parameters that vary at more than one level and show hierarchical structures between levels. This study particularly accentuates that an educational program for farmers is more meaningful when it can raise farmers' incomes by region and by educational program for farmers.

• Toxicological Research
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• v.24 no.4
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• pp.235-243
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• 2008

While in some instances, loss of diversity results from acute toxicity (e.g. major pollution incidents), in most cases it results from long-term sub-lethal effects that alter the relative competitive ability and fitness of certain organisms. In such cases the sub-lethal effects will cause a physiological response in the organism that ultimately leads to community level changes. Very sensitive tools are now available to study sub-lethal responses at the molecular level. However, relating such laboratory measurements to ecological effects represents a substantial challenge that can only be met by investigation at all scales (molecular, individual organism and community level) with an appropriate group of organisms. Among the various in vertebrates which can be used as model organisms in such a way, the soil nematode, Caenorhabditis elegans appear to be a promising biological model to diagnose environmental quality. This paper reviews the current status of multilevel biomarkers in environmental toxicology, and C. elegans as promising organisms for this approach.

• Journal of Power Electronics
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• v.5 no.1
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• pp.76-82
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• 2005

A novel variant of full multi-modulation applications to diode-clamped and cascade multilevel inverter-termed single carrier multi-modulation is presented. The proposed PWM-technique is advantageous for its simple implementation. The correlation between multi-carrier and single-carrier multi-modulations is deduced. For the PWM methods, a mathematical model of voltage source inverter and general algorithm for the multi-modulating modulator are proposed. The theory is demonstrated by simulation results

• Environmental and Resource Economics Review
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• v.16 no.4
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• pp.803-832
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• 2007

Electricity and heat load profiles by use types on an hourly basis at the least are essential for assessing economic viability of new cogeneration and CES projects and for optimally operating existing cogeneration and CES facilities. We adopt a multilevel model to specify heat load profiles so as to utilize in a flexible manner the panel nature of our data on weather and heating/cooling use. Converting the multilevel model to the linear mixed-effects model, we estimate the model by panel FGLS. The estimated load profile model for each distinct use type accounts for the effects of temperature, humidity, each hour over the year, each day of the week, each type of legal holidays, and heating/cooling area on energy use. To save space, we feature in detail the heating profile of the household.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.261-270
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• 2015

In this paper, the Optimal Harmonic Stepped Waveform (OHSW) method is proposed in order to eliminate the selective harmonic orders available at the output of cascaded multilevel inverter (CMLI) fed by solar photovoltaic (SPV). This technique is used to solve the harmonic elimination equations based on stepped waveform analysis in order to obtain the optimal switching angles which in turn reduce the Total Harmonic Distortion (THD). The OHSW method considers the output voltage waveform as four equal symmetries in each half cycle. In the proposed method, a solar fed fifteen level cascaded multilevel is considered where the magnitude of six numbers of harmonic orders is reduced. A programmable pulse generator is developed to carry the switching angles directly to the semiconductor switches obtained as a result of OHSW analysis. Simulations are carried out in MATLAB/Simulink in which a separate model is developed for solar photovoltaic which serves as the input for cascaded multilevel inverter. A 3kWp solar plant with multilevel inverter system is implemented in hardware to show the effectiveness of the proposed system. Based on the observation the OHSW method provides the reduced THD thereby improving power quality in renewable energy applications.

• Journal of Power Electronics
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• v.13 no.3
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• pp.419-428
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• 2013

The modular multilevel cascade converter (MMCC) is a new family of multilevel power converters with modular realization and a cascaded pattern for submodules. The MMCC family can be classified by basic configurations and submodule types. One member of this family, the Hexverter, is configured as Double-Delta Full-Bridge (DDFB). It is a novel multilevel AC/AC converter with direct power conversion and comparatively fewer required components. It is appropriate for connecting two three-phase systems with different frequencies and driving an AC motor directly from a utility grid. This paper presents the dq model of a Hexverter with both of its AC systems by state-space representation, which then simplifies the continuous time-varying model into a periodic discrete time-invariant one. Then a generalized multivariable optimal control strategy for regulating the Hexverter's independent currents is developed. The resulting control structure can be adapted to other MMCCs and is flexible enough to include other control criterion while guaranteeing the original controller performance. The modeling method and control design are verified by simulation results.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1217-1220
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• 1996

For the purpose of the good tracking to variable load demands of the thermal power plant, a decentralized multilevel control(DMC) scheme is presented. It is applied to the drum type boiler-turbine system which is simplified from Boryung T/P #1,2 model[4]. A linearized model is decomposed into three subsystems by means of linear transformation. Then the DMC based on such subsystem is designed. Simulation using Matlab-Simulink shows that the proposed algorithm works very well to the large step change of power demand.

• Analyses & Alternatives
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• v.4 no.2
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• pp.5-38
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• 2020

This paper investigates how public opinion has affected the United States Senate's votes on arms control treaties. Applying multilevel modeling with post-stratification to national polls, this paper produces estimates of state-level opinion on both the New Strategic Arms Reduction Treaty of 2010 and the Comprehensive Test Ban Treaty of 1999. Using these estimate, this paper examines the relationship between public opinion and the Senate's votes on the treaties. This paper finds that the influence of public opinion was mostly significant but indirect. These findings indicate that some version of the delegate model of representation is more applicable to foreign policy making in Congress.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.52 no.4
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• pp.172-178
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• 2003

This paper examines the application of high voltage static var compensator(SVC) with cascade multilevel inverter which employs H-bridge inverter(HBI). This method has the primary advantage that the number of voltage levels can be increased for a given number of semiconductor devices when compared to the conventional control methods. The SVC system is modeled using the d-q transform which calculates the instantaneous reactive power. This model is used to design a controller and analyze the SVC system. From the mathematical model of the system, the design procedures of the circuit parameters L and C are presented in this thesis. To meet the specific total harmonic distortion(THD) and ripple factor of the capacitor voltage, the circuit parameters L and C are designed. Simulated and experimental results are also presented and discussed to validate the proposed schemes.

• Asia Marketing Journal
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• v.24 no.3
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• pp.109-120
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• 2022

The COVID-19 lockdown has had an unprecedented impact on people in various ways. This study evaluates the effect of lockdown repeal from both marketing and public-policy perspectives. Combining the Bayesian multilevel model with the difference-in-differences design, we find that a lockdown repeal has had a negative impact on socialization. Furthermore, the results show that those who have a low level of risk perception are less affected by lockdown repeal. Also, the negative effect of lockdown repeal varies depending on past socialization behaviors; that is, the lockdown-repeal effect is attenuated for those who socialized more than others in the past. Our findings contribute to the intersection of public policy and marketing literature and provide both academic and practical implications.