• Journal of Biosystems Engineering
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• v.26 no.1
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• pp.29-38
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• 2001

A navigation system was developed for autonomous guidance of a combine. It consisted of a DGPS, a machine vision system, a gyro sensor and an ultrasonic sensor. For an autonomous operation of the combine, target points were determined at first. Secondly, heading angle and offset were calculated by comparing current positions obtained from the DGPS with the target points. Thirdly, the fuzzy controller decided steering angle by the fuzzy inference that took 3 inputs of heading angle, offset and distance to the bank around the rice field. Finally, the hydraulic system was actuated for the combine steering. In the case of the misbehavior of the DGPS, the machine vision system found the desired travel path. In this way, the combine traveled straight paths to the traget point and then turned to the next target point. The gyro sensor was used to check the turning angle. The autonomous combine traveled within 31.11cm deviation(RMS) on the straight paths and harvested up to 96% of the whole rice field. The field experiments proved a possibility of autonomous harvesting. Improvement of the DGPS accuracy should be studied further by compensation variations of combines attitude due to unevenness of the rice field.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11C
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• pp.917-924
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• 2008

Motion estimation and compensation in the spatial domain check the searching area of specified size in the previous frame and search block to minimize the difference with current block. When we check the searching area, it consumes the most encoding times due to increasing the complexity. We can solve this fault by means of motion estimation using shifting matrix in the transform domain instead of the spatial domain. We derive so the existed shifting matrix to a new recursion equation that we decrease more computations. We modify simply vertical shifting matrix and horizontal shifting matrix in the transform domain for motion estimation of half-pixel accuracy. So, we solve increasing computation due to bilinear interpolation in the spatial domain. Simulation results prove that motion estimation by the proposed algorithm in DCT-based transform domain provides higher PSNR using fewer bits than results in the spatial domain.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2024-2034
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• 2016

This paper presents a DC-DC buck converter with a Phase-Locked Loop (PLL) that can compensates for power efficiency degradation over a wide input range. Its switching frequency is kept at 2 MHz and the delay difference between the High side driver and the Low side driver can be minimized with respect to Process, Voltage and Temperature (PVT) variations by adopting the PLL. The operation mode of the proposed DC-DC buck converter is automatically changed to Pulse Width Modulation (PWM) or PWM frequency modes according to the load condition (heavy load or light load) while supporting a maximum load current of up to 1.2 A. The PWM frequency mode is used to extend the CCM region under the light load condition for the PWM operation. As a result, high efficiency can be achieved under the light load condition by the PWM frequency mode and the delay compensation with the PLL. The proposed DC-DC buck converter is fabricated with a $0.18{\mu}m$ BCD process, and the die area is $3.96mm^2$. It is implemented to have over a 90 % efficiency at an output voltage of 5 V when the input range is between 8 V and 20 V. As a result, the variation in the power efficiency is less than 1 % and the maximum efficiency of the proposed DC-DC buck converter with the PLL is 95.4 %.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.4
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• pp.957-970
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• 2016

This study diagnosed the status of marine environmental impact assessment(MEIA) for project near the habitat of marine protected seagrass species such as Zostera caespitosa, Zostera asiatica, Phyllospadix iwatensis. For the preparation of a marine environmental impact statement, different monitoring parameters are used without any specific guideline for the assessment of current status. And also, both tools and techniques for MEIA are needed to improve for implementing. The monitoring plans and parameters are not considered well with the accuracy of the environmental predictions and effectiveness of any applicable mitigation measures. This study suggested the reasonable standard of the MEIA for the conservation of the marine protected seagrass species which have the habitat located near affected area. The inshore seagrasses need to be monitored including shoot count based on the "No Net Loss of Seagrass" as part of the monitoring parameters to assess the status of marine environment of environmental impact statement. In a process of effect prediction, we suggested a concentration of 10 mg/L suspended solids which added by the new developmental project near seagrasses habitat, referring to study of overseas case. But a further study for an appropriate standard is necessary effectively. In a mitigating process, priority needs to be considered in order of avoidance, minimization, reduction, compensation. In a post-monitoring process, it is necessary to monitor the seagrass species abundance to identify the variation of b/a (before and after) project. And in a case of implementing transplantation, survival rate need to be included to determine a success of project.

• ETRI Journal
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• v.31 no.6
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• pp.660-666
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• 2009

We investigate the effects of interfacial dielectric layers (IDLs) on the electrical properties of top-gate In-Ga-Zn-oxide (IGZO) thin film transistors (TFTs) fabricated at low temperatures below $200^{\circ}C$, using a target composition of In:Ga:Zn = 2:1:2 (atomic ratio). Using four types of TFT structures combined with such dielectric materials as $Si_3N_4$ and $Al_2O_3$, the electrical properties are analyzed. After post-annealing at $200^{\circ}C$ for 1 hour in an $O_2$ ambient, the sub-threshold swing is improved in all TFT types, which indicates a reduction of the interfacial trap sites. During negative-bias stress tests on TFTs with a $Si_3N_4$ IDL, the degradation sources are closely related to unstable bond states, such as Si-based broken bonds and hydrogen-based bonds. From constant-current stress tests of $I_d$ = 3 ${\mu}A$, an IGZO-TFT with heat-treated $Si_3N_4$ IDL shows a good stability performance, which is attributed to the compensation effect of the original charge-injection and electron-trapping behavior.

• Journal of IKEEE
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• v.24 no.1
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• pp.319-325
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• 2020

In this paper, a discontinuous-conduction mode (DCM) DC-DC buck converter is presented for mobile device applications. The buck converter consists of compensator for stable operations, pulse-width modulation (PWM) logic, and power switches. In order to achieve small hardware form-factor, the number of off-chip components should be kept to be minimum, which can be realized with simple and efficient frequency compensation and digital soft start-up circuits. Burst-mode operation is included for preventing the efficiency from degrading under very light load condition. The DCM DC-DC buck converter is fabricated with 0.18-um BCDMOS process. Programmable output with external resistors is typically set to be 1.8V for the input voltage between 2.8 and 5.0V. With a switching frequency of 1MHz, measured maximum efficiency is 92.6% for a load current of 100mA.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.826-832
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• 1998

In this study the thin films with the structure of Si+SiO$_2$+TiN are made by RF supttering method. TiN, which has small diffusion coefficient and low resistivity, is evaporated between SiO$_2$ and Al layers. It investigates the V-R characteristics depending on the thickness of SiO$_2$ which is used as insulation layer and researches its effects on voltage stability of thin film and varistor. These films show very small resistance valus in negative(-) voltage and large and large value in positive voltage band, and with the increase of voltage, resistance value is rapidly reduced and the satisfactory characteristic of varistor is shown at +1[V]. It is found that resistance value of TiN thin film is small and also TiN thin film has more current than the thin film which is not evaporated by TiN thin film. When Al electrode is evaporated of SiO$_2$ thin film, spiking occurs, but the spiking can be prevented with evaporation of TiN between SiO$_2$ and Al layers and this thin films in made easily because of its good attachment. With the increase of voltage, the resistance is changed into non-linear pattern and the bidirectional varistor characteristic is shown and then its theory can be verified by this experiment. Accordingly, when TiN is evaporated of Si Wafer(n-100), it obtains better voltage-resistance than thin film which is not evaporated and also when varistor character is used electrically to automatic control element such as elimination of flame, power distribution arrestor and constant voltage compensation, satisfactory reproducibilities are expected.

• Journal of the Korea Institute of Building Construction
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• v.10 no.1
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• pp.175-180
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• 2010

Despite continuous efforts by the construction industry to achieve better quality, it doesn't seem that much has been improved. This is mainly because current specifications do not satisfy a change in the market environment, which is that a higher level of quality is now demanded by users. Quality improvement efforts have been satisfied merely to meet specifications. On the other hand, advanced countries have been experienced great success in their construction techniques and have reduced costs by introducing apay adjustment system to the construction industry, in which compensation is based on performance. Following their example, Koreashould introduce such a pay adjustment system in order to motivate the members of our construction industry to achieve better quality and a higher level of construction techniques. However, there has been a lack of a rational approach to the development of a system for cost coordination, as well as performance and quality inspection. Thus, in this study a legal and logical plan was developed that can be used to adjust the construction cost, along with the performance inspection of quality results, in order to introduce a pay adjustment system that is appropriate for domestic regulations.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.2
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• pp.73-78
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• 2011

A frequency synthesizer for DAB applications is designed using $0.18{\mu}m$ CMOS process with 1.8V supply. NP-core type is chosen for VCO core to improve low power characteristic and symmetric characteristic of output waveform. VCO range is 1302.34 MHz - 1949.51 MHz using switchable capacitor bank and varactor bank. Varactor biases that improve varactor capacitance characteristics were minimized as two, $K_{vco}$(VCO gain) is maintained using technique of varactor bank switching. Intervals of $K_{vco}$ are maintained adding VCO frequency compensation logic. Each block of VCO and frequency synthesizer designed $0.18{\mu}m$ CMOS process with 1.8V supply is verified by Cadence Spectre, measured VCO consumes 9mA current, and is 39.8% tuning range, total power consumption of the frequency synthesizer is 18mW.

• Safety and Health at Work
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• v.1 no.2
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• pp.149-157
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• 2010

Objectives: To quantify disability level in salespeople with concurrent low back pain (LBP) and to determine the relative associations between demographic, occupational, psychosocial and clinical factors and back disability. LBP is the most common cause of work-related disability in people under 45 years of age and the most expensive cause of work-related disability, in terms of workers' compensation and medical expenses. Evidence suggests high prevalence of LBP in salespeople. Methods: A cross-sectional survey was conducted in which 184 saleswomen with a current episode of self-reported LBP working in a large up-scale department store filled out a battery of 6 self-administered questionnaires and received a standardised physical examination. Results: Saleswomen with concurrent LBP had low disability levels. Factors significantly associated with disability were pain intensity, measured by a visual analogue scale, in the past week (p < 0.001), physical and mental health status (p < 0.001, p = 0.003, respectively), fear avoidance scores for both work and physical activities (p = 0.031, p = 0.014, respectively), past history of LBP (p = 0.019), and self-reported frequency of pushing or pulling objects placed in high positions during work (p = 0.047). A significant level (45%) of the variance in disability status was explained by these variables. Conclusion: In clinical management of LBP workers who required prolonged standing, such as salespeople, clinicians should look for modifiable risk factors associated with disability. Specific measures need to be taken to prevent disability due to LBP among salespeople.