• Journal of Power Electronics
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• v.16 no.3
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• pp.1025-1035
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• 2016

Luenberger observer (LO)-based sensorless multi-loop control of a converter requires an iterative trial-and-error design process, considering that many parameters should be determined, and loop gains are indirectly related to the closed-loop characteristics. Robust H∞ control adopts a compact sensorless controller. The algebraic Riccati equation (ARE)-based and linear matrix inequality (LMI)-based H∞ approaches need an exhaustive procedure, particularly for a low-order controller. Therefore, in this study, a novel robust H∞ synthesis approach is proposed to design a low-order sensorless controller for boost converters, which need not solve any ARE or LMI, and to parameterize the controller by an adjustable parameter behaving like a "knob" on the closed-loop characteristics. Simulation results show the straightforward closed-loop characteristics evaluation and better dynamic performance by the proposed H∞ approach, compared with the LO-based sensorless multi-loop control. Practical experiments on a digital processor confirmed the simulation results.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.1
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• pp.70-82
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• 2014

A nano-power CMOS voltage reference is proposed in this paper. Through a combination of switched-capacitor technology with the body effect in MOSFETs, the output voltage is defined as the difference between two gate-source voltages using only a single PMOS transistor operated in the subthreshold region, which has low sensitivity to the temperature and supply voltage. A low output, which breaks the threshold restriction, is produced without any subdivision of the components, and flexible trimming capability can be achieved with a composite transistor, such that the chip area is saved. The chip is implemented in $0.18{\mu}m$ standard CMOS technology. Measurements show that the output voltage is approximately 123.3 mV, the temperature coefficient is $17.6ppm/^{\circ}C$, and the line sensitivity is 0.15 %/V. When the supply voltage is 1 V, the supply current is less than 90 nA at room temperature. The area occupation is approximately $0.03mm^2$.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.415-423
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• 2021

For a battery module where single cells are connected in series, the single cells should each have a similar state of charge (SOC) to prevent them from being exposed to an overcharge or over-discharge during charge-discharge cycling. To detect the existence of unbalanced SOC cells in a battery module, we propose a simple measurement method using a single-frequency response of electrochemical impedance spectroscopy (EIS). For a commercially available graphite/nickel-cobalt-aluminum-oxide lithium-ion cell, the cell impedance increases significantly below SOC20%, while the impedance in the medium SOC region (SOC20%-SOC80%) remains low with only minor changes. This impedance behavior is mostly due to the elementary processes of cathode reactions in the cell. Among the impedance values (Z, Z', Z"), the imaginary component of Z" regarding cathode reactions changes heavily as a function of SOC, in particular, when the EIS measurement is performed around 0.1 Hz. Thanks to the significant difference in the time constant of cathode reactions between ≤SOC10% and ≥SOC20%, a single-frequency EIS measurement enlarges the difference in impedance between balanced and unbalanced cells in the module and facilitates an ~80% improvement in the detection signal compared to results with conventional EIS measurements.

• Journal of Preventive Medicine and Public Health
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• v.44 no.4
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• pp.149-156
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• 2011

Objective: The purpose of the present study was to examine the relationship between the use of senior center and health-related quality of life in Korean older adults. Methods: A questionnaire survey was conducted to two types of older adults who lived in Busan, Korea: 154 older adults who used a senior center and 137 older adults who did not use a senior center. The Korean version of short-form 36-item health survey was administered to assess the health-related quality of life. Demographic variables were obtained from a questionnaire. These were gender, age, family status, marital status, education, monthly income, present illness, body mass index and physical activity. Results: The 8-domain scales of physical function and role-physical were significantly higher in the users of the senior center compared with the non-users (F=4.87, p=0.027 and F=7.02, p=0.009, respectively). The 8-domain scales of vitality was also significantly higher in the users of the senior center compared with the non-users (F=7.48, p=0.007). Conclusions: The present study showed that the users of the senior center have higher physical function, role-physical and vitality compared with the non-users. These findings suggest that although the results are unable to specify causal relationships using the senior center may lead to some improvement in health-related quality of life.

• Industrial Engineering and Management Systems
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• v.14 no.4
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• pp.335-346
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• 2015

The electronic commerce site (EC site) has become an important marketing channel where consumers can purchase many kinds of products; their access logs, including purchase records and browsing histories, are saved in the EC sites' databases. These log data can be utilized for the purpose of web marketing. The customers who purchase many product items are good customers, whereas the other customers, who do not purchase many items, must not be good customers even if they browse many items. If the attributes of good customers and those of other customers are clarified, such information is valuable as input for making a new marketing strategy. Regarding the product items, the characteristics of good items that are bought by many users are valuable information. It is necessary to construct a method to efficiently analyze such characteristics. This paper proposes a new latent class model to analyze both purchasing and browsing histories to make latent item and user clusters. By applying the proposal, an example of data analysis on an EC site is demonstrated. Through the clusters obtained by the proposed latent class model and the classification rule by the decision tree model, new findings are extracted from the data of purchasing and browsing histories.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.230-236
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• 2009

Double-front construction machinery, which was designed for complicated tasks, requires intelligent systems that can provide the quantitative work analysis needed to determine effective work procedures and that can provide operational and cognitive support for operators. Construction work environments are extremely complicated, however, and this makes state identification difficult. We therefore defined primitive static states (PSS) that are determined using on-off data for the lever inputs and manipulator loads for each part of the grapple and front and that are completely independent of the various environmental conditions and operator skill levels. To confirm the usefulness of PSS, we performed experiments with a demolition task by using our virtual reality simulator. We confirmed that PSS could robustly and accurately identify the work states and that untrained skills could be easily inferred from the PSS-based work analysis. We also confirmed in skill-training experiments that advice information using PSS-based skill analysis greatly improved work performance. We thus confirmed that PSS can adequately identify work states and are useful for work analysis and skill improvement.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1113-1116
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• 2002

For contents delivery systems, the service is considered in which the utility depends on each priority class. This paper deals with the multiple priority class of the contents delivery system from the viewpoint of the utility. The willingness to pay (WTP) is introduced as a measure of utility, and the optimum condition is analyzed to maximize the total user's utility. For the system with multiple priority classes, the optimum condition is given in terms of the traffic load, wating time for service for each priority class. Systems with the priority classes, 1, 2 and 3 are analyzed, and the effect of the number of priority classes is examined.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.130-132
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• 1997

In this paper, we propose a new type of tubular linear induction motor(TLIM) with two-dimensional motion. The proposed motor consists of four short primary LIMs arranged on a same circumference and a common secondary. By adopting independently energized ring-windings to the primary, we can expect the reduction of coil-end region and the freedom of alternating current supply. The secondary conductor is capable of producing anyone of rotary, linear, and helical motions by controlling the phase of supply currents in each primary winding. From the 3-D finite element analysis and the experiment, we derive the feeding conditions to increase the subsidiary rotary-force and an optimal arrangement of primary currents to reduce the number of slot.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.133-135
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• 1997

In this paper, we propose a new type of rotor construction in the permanent magnet synchronous motor. By using plural permanent magnets for one-role of the rotor, it is possible not only to reduce space harmonics of air-gap fields but also to provide spacs for damper windings in the inter-pole space. The dimensions of the plural permanent magnets are derived by Fourier analysis. Based on the investigation by numerical analyses. we propose an optimal rotor construction in view of both the reduction of space harmonics and the damping effect.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1736-1739
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• 2002

The advanced in semiconductor, hardware, and software technologies enables the integration of more com- plex systems and the increasing design complexity. As system design complexity becomes more complicated, System-level design based on the If block and processor model is more needed in most of the RTL level or low level. In this paper, we present a novel approach fur the system-level design, which satisfies the various required constraints and an optimization method of image encoder based on codesign of function, algorithm, and architecture. In addition, we show an MPEG-4 encoder as a design case study. The best tradeoffs between algorithm and architecture are necessary to deliver the design with satisfying performance and area constraints. The evaluations provide the effective optimization of motion estimation, which is in charge of an amount of performance in the MPEG-4 encoder module.