• The Journal of Fisheries Business Administration
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• v.41 no.3
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• pp.129-151
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• 2010

This study is to analyze the efficiency of Korean fishing ports using DEA. First, the study calculated the efficiency scores based on a CCR-BCC framework and hence technical, pure technical, and scale efficiency scores are seperated for the 38 fishing ports under study. The Average of technical, pure technical, and scale efficiency are turned out to be 0.6834, 0.8582, and 0.7774 respectively. The 15 fishing ports are fully efficient under the constant returns to scale while 21 fishing ports under the variable returns to scale. Second, the super efficiency scores are also calculated under the radial model without the consideration of slacks. The highest score is turned out to be 4.4984 for the P16 fishing port with the average score of 0.9652 for the entire fishing ports. Nevertheless, P16 fishing port has showed up only once as a reference set. On the other hand, P34 fishing port has showed up 11 times as a reference set, which scored the second highest score of 2.9815. Finally the super efficiency scores are calculated under the non-radial model with the explicit consideration of slacks. Now the P34 fishing port scored the highest score of 2.3424 with even 15 times referred to a bench-mark. Therefore the importance of P34 fishing port is emphasized once again on the field of bench-marking for the efficiency of fishing ports. When the targets for the input factors to improve the efficiency of each DMU are calculated the area of fishing port needs the most adjustment to be reduced for 40.36% on the average, while the cosignment sales area does the least adjustment for 13.70%.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.5
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• pp.27-35
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• 2000

This paper deals with a control strategy for constant output power of SSRT(Soft Switching Resonant Type) FB(Full Bridge) DC-DC converter by an improved phase shift controller. When the FB DC-DC converter for the high density and the high effect control is operated in high speed switching, the switching loss and switching stress of the switching devices are increased. So, the soft switching method, which has the phase shift control with the digital I-PD controller, must be use in order to reduce its. And the output voltage that controlled by the digital I-PD controller tracks a reference without steady state error in variable input voltage. The validity of control strategy that proposed is verified from simulation results and experimental results by the DSP(TMS320C32).

• Journal of Korea Society of Waste Management
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• v.35 no.8
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• pp.721-730
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• 2018

We investigated the effects of heavy metals in cement in the last 3 years and the amount of waste in the cement manufacturing process. The result shows that the average $Cr^{6+}$ content in cement products is controlled at 10 mg/kg. Cu and Pb have lower detection tendency in white cement than in ordinary portland cement. In addition, heavy metals such as Cd show a certain level of detection regardless of the input wastes. Copper slag and phosphate gypsum are the main influencing factors on the heavy metals in cement products. In auxiliary fuels, plastics waste and wood waste are considered to affect heavy metals in cement products. Alternative raw materials are considered to be affected by the alternative raw materials managed as byproducts. In the case of supplementary fuels, auxiliary fuels managed as waste instead of auxiliary fuels managed as byproducts affect the heavy metals in cement. This study examined the input amount without considering the heavy metals in each waste. Therefore, the result may vary in different situations, and further research must be conducted to supplement the findings. However, if the heavy-metal contents in the waste are constant, it can be used as a reference material for the control of heavy metals in cement products.

• Journal of Technology Innovation
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• v.24 no.4
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• pp.27-53
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• 2016

This case analyzed the efficiency of 79 R&D projects performed within one private research center in machine tools industry. DEA was used for efficiency analysis. Input variables were R&D investment expense and man-month. Output variables were achievement rate on target development period and expected net sales within 5-years. Samples are divided into product development, Prior technology development, and control technology development. The key result is that Prior technology showed the lowest efficiency because of high uncertainty. It was so difficult to determine its goals and to make its specific plans. With respect to scale, the proportions of CRS(constant returns to scale) were 34.6%, 14.3% and 38.9% for product development, prior technology, control technology respectively. As for IRS(increase returns to scale), they were 53.8%, 85.7% and 38.9% for product development, prior technology, control technology respectively. As for DRS(decrease returns to scale) they were 11.5%, 0% and 22.2% for product development, prior technology, control technology respectively. On the whole, in this case, insufficient input was more problematic than excessive input, which means the lack of investment in R&D. Prior technology can be the source of the future competitiveness of companies. To operate inefficient DMU efficiently, the optimal input should be managed and it is derived from comparison with the reference group.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.2
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• pp.247-258
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• 2003

In this paper, we present a pen-shaped input device equipped with accelerometers and gyroscopes that measure inertial movements when a user writes on 2 or 3 dimensional space with the pen. The measurements from gyroscope are integrated once to find the attitude of the system and are used to compensate gravitational effect in the accelerations. Further, the compensated accelerations are integrated twice to yield the position of the system, whose basic concept stems from the field of inertial navigation. However, the accuracy of the position measurement significantly deteriorates with time due to the integrations involved in recovering the handwriting trajectory This problem is common in the inertial navigation system and is usually solved by the periodic or aperiodic calibration of the system with external reference sources or other information in the filed of inertial navigation. In the presented paper, the calibration of the position or velocity is performed on-line and off-line. In the on-line calibration stage, the complementary filter technique is used, where a Kalman filter plays an important role. In the off-line calibration stage, the constant component of the resultant navigational error of the system is removed using the velocity information and motion detection algorithm. The effectiveness and feasibility of the presented system is shown through the experimental results.

• Journal of IKEEE
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• v.14 no.2
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• pp.51-57
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• 2010

A CMOS rail-to-rail high voltage buffer amplifier is proposed to drive the gamma correction reference voltage of large TFT LCD panels. It is operating by a single supply and only shows current consumption of 0.5mA at 18V power supply voltage. The circuit is designed to drive the gamma correction voltage of 8-bit or 10-bit high resolution TFT LCD panels. The buffer has high slew rate, 0.5mA static current and 1k$\Omega$ resistive and capacitive load driving capability. Also, it offers wide supply range, offset voltages below 50mV at 5mA constant output current, and below 2.5mV input referred offset voltage. To achieve wide-swing input and output dynamic range, current mirrored n-channel differential amplifier, p-channel differential amplifier, a class-AB push-pull output stage and a input level detector using hysteresis comparator are applied. The proposed circuit is realized in a high voltage 0.18um 18V CMOS process technology for display driver IC. The circuit operates at supply voltages from 8V to 18V.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1152-1162
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• 2011

In this paper, a single-phase DC-AC inverter using two embedded Z-source converters is proposed. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The output AC voltage of the inverter is obtained by the difference of output capacitor voltages of each converter. The output voltage of each converter take shape of the asymmetrical AC waveform centering zero voltage. Therefore, the proposed inverter can generate the same output voltage despite low VA rating L-C elements, compared to the conventional inverter using high DC voltage with AC ripple. To verify the validity of the proposed system, the PSIM simulation was achieved under the condition of rapid increase of DC source (110[V]${\rightarrow}$150[V]) and R-load (50[${\Omega}$]${\rightarrow}$300[${\Omega}$]). For controlling the voltage of the inverter system, the one-cycle controller was adopted. As results, the proposed inverter output the constant AC voltage (220[V]rms/60[Hz]) for all conditions. Also, the R-L load and nonlinear diode load were adopted for the proposed inverter loads, and we could know that the its output voltage characteristics were as good as the pure R-load. Finally, the RMS and THD of output AC voltage were examined for the different loads, input DC voltages and reference voltage signals.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.304-308
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• 2010

This paper presents a methodology for identifying track irregularity using a wavelet transfer function. An equivalent wavelet SISO (single-input single-output) transfer function is defined by the measured track geometry and the acceleration data measured at a bogie of a train. All the measured data with various sampling frequencies were rearranged according to the constant 25cm reference recording distance of the track recording vehicle used in the field. Before applying the wavelet transform, measured data were regressed by eliminating those out of the range. The inverse wavelet transfer function is also formulated to estimate track geometry. The closeness of the estimated track geometry to the actual one is evaluated by the coherence function and also by FRF (frequency response function). A track irregularity index is defined by comparing the variance of the estimation error from the intact condition and that from the current condition. A simulation study has been carried out to examine the proposed algorithm.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.3
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• pp.422-429
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• 2022

In this paper, the intermediate frequency transmission signal level between the network system-based baseband and RF unit consisting of multi-channel airborne relay devices and a lot of mission devices, which are currently undergoing technology development tasks, is kept constant at the reference signal level. Considering the other party's receiving input range, despite changes in the short-range long-range wireless communication environment, it presents a multi-link protection and MLP-A algorithm that allows signals to be transmitted stably and reliably through signal detection automatic gain control, and experiments and analysis considering short-distance and long-distance wireless environments were performed by designing, manufacturing, and implementing RF units to which MLP-A algorithms were applied, and applying distance calculation equations to the configuration of multiple air movements and verification networks. Through this, it was confirmed that a stable and reliable RF communication system can be operated.

• Journal of Distribution Science
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• v.12 no.8
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• pp.5-15
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• 2014

Purpose - The method of TV home shopping is a kind of retail method that provides the viewer with information about products and, further, sells the products to consumers through the media of television. The domestic home-shopping industry has been expanding since 1995, and there are six companies in this arena as of 2012. In this study, we evaluate the management efficiency of TV home-shopping companies and provide suggestions for improving efficiency, using the DEA (data envelopment analysis) model. Hence, we expect to contribute to the progress of the companies' efficiency and the development of the TV home-shopping industry, where deepening competition is inevitable because it is experiencing the maturing market stage in its life cycle. Research design, data, and methodology - Efficiency is the ratio of the quantity of input to the quantity of output of a product or service. It is necessary to estimate aggregate inputs and aggregate outputs, which are calculated by applying a weighting to a number of input and output factors, to measure the efficiency. The DEA model is divided into the CCR model and the BCC model. The CCR model is a basic model that assumed constant returns to scale (CRS), and the BCC model extends the CCR model to accommodate technologies exhibiting variable returns to scale (VRS), and concerns only the technical efficiency without considering the efficiency of returns to scale. In this study, we consider six companies each year from 2008 to 2012 as a DMU (Decision Making Unit) and analyze the differences in efficiency for each company in each year. Furthermore, we evaluate the operating characteristics of TV home-shopping companies, using three models, in accordance with the overall performance, profitability, and marketability of the business. Results - The result of the analysis, using DEA models, shows that Hyundai Home Shopping (2009, 2010, 2011), GS Home Shopping (2011), NS Home Shopping (2011) and CJ O Shopping (2012) possess MPSS (most productive scale size), with a score 1.0 in CCR, BCC, and scale efficiency. Particularly, Hyundai Home Shopping is shown to be the most efficient in terms of overall business performance, marketability, and profitability. The overall efficiency of the home shopping industry has displayed an increasing trend since 2008, even though it decreased marginally in 2012; further, we can observe that home shopping companies operate with increasing efficiency with the passage of time. Conclusions - Home shopping companies have focused on market expansion rather than profits, as they displayed better efficiency in marketability than increase in profitability during the period 2008-2012. In addition, the main reason for the increased efficiency in the home shopping industry is the market expansion through the revenue increase of each home shopping company. This study can be used as a reference when home shopping companies attempt to devise future strategies, as it suggests efficiency benchmarks and development levels for each home shopping company.