• Journal of Applied Reliability
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• v.18 no.1
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• pp.56-65
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• 2018

Purpose: The purpose of this study is to estimate shelf life of fuze MTSQ (Mechanical Time & Super Quick) KM577A1 from Ammunition Stockpile Reliability Program (ASRP) data. Methods: For many years, ammunition test data had been gathered from ASRP. In this study, lot selection criteria and reliability score of functioning time for fuze are proposed. Reliability score of functioning time and failure data are used to estimate shelf life. Results: The results of this study are as follows; The failure modes of fuze MTSQ KM577A1 are dud, inverse function and mechanical time functioning failure (not operating in intended time). Dud and inverse function are major failure modes. Fuze MTSQ KM577A1's shelf life ($B_5$) is estimated 18.2 years conservatively. Conclusion: Degradation of chemical components in fuze MTSQ KM577A1 is major factor for its reliability. And shelf life ($B_5$) of fuze MTSQ KM577A1 is estimated 18.2 years conservatively.

• Membrane Journal
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• v.25 no.4
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• pp.367-372
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• 2015

In pressure-retarded osmosis (PRO) and forward osmosis (FO) processes, solvent (permeate) flux depends on which surface the draw solution faces. There are two operation modes. PRO mode indicates that the active layer faces the draw solution, and FO mode means that the porous substrate fronts the draw stream. It is often observed that the PRO mode produces higher flux than that of FO under the same operating conditions. The current work uses the method of proof by contradiction, and mathematically proves the intrinsic flux inequality between the two modes.

• Journal of IKEEE
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• v.20 no.4
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• pp.435-438
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• 2016

HEVC CABAC binary arithmetic decoder operates in three decoding modes i.e. regular, bypass, and termination modes, where their decoding operations and time differ a lot. Furthermore, when renormalization occurs, its internal feedback loop induces large delay. In this paper, a binary arithmetic decoder was designed to solve this problem. In advance, it checks all range values with possible renormalization. When renormalization occurs, it immediately updates range value and finishes all calculation in a cycle. When implemented in 0.18 um process technology, its maximum operating frequency and gate counts are 215 MHz and 5,423 gates, respectively.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.63-72
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• 2006

The purpose of this raper is to address the negative impedance instability in DC/DC converters. We present the negative impedance instability of PWM DC/DC converters loaded by constant power loads (CPLs). An approach to design digital controllers for DC/DC converters Is presented. The proposed method, called Power Alignment control technique, is applied to DC/DC step-down choppers operating in continuous conduction or discontinuous conduction modes with CPLs. This approach uses two predefined state variables instead of conventional pulse width modulation (PWM) to regulate the output voltage. A comparator compares actual output voltage with the reference and then switches between the appropriate states. It needs few logic gates and comparators to be implemented thus, making it extremely simple and easy to develop using a low-cost application specific integrated circuit (ASIC) for converters with CPLs. Furthermore, stability of the proposed controllers using the small signal analysis as well as the second theorem of Lyapunov is verified. Finally, simulation and analytical results are presented to describe and verify the proposed technique.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.170-177
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• 1998

The purpose of superconducting magnetic bearing flywheel energy storage system(SMB-FESS) is to store unused nighttime electricity as kinetic energy and convert it to electricity during daytime. The SMB-FESS is proposed as an efficient energy storage system because there is no mechanical problems, such as friction and wear The flywheel over SMB is rotated at a high speed, 50,000rpm. The major source of energy loss in the SMB-FESS is vibration of flywheel. Therefore, the vibration characteristics of SMB-FESS should be identified. In this study, the axial/radial stiffness and damping coefficient of SMB are measured by a vibration test. Natural frequencies and natural modes of flywheel and magnet are analyzed by a finite element method. The modal analysis of system is performed using the modal parameters of each component and the measured stiffness/damping coefficient. So, natural at frequencies and mode shapes of the joined system can be obtained. According to critical speed analysis, the system has two rigid conical modes in the low speed range. Nevertheless, the system has not been affected by the critical speed in the main operating range.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.12
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• pp.43-49
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• 2009

We present an efficient estimation method of the battery lifetime considering various power consumption profiles in wireless sensor nodes. The power profiles in single and periodic modes and the current dissipations in different operating modes are taken into account to find the total current consumption. Also, the self-discharge rate of a battery is taken into account to estimate the battery lifetime of a given sensor node. Finally we present a governing equation for finding the battery lifetime. We believe the proposed estimation method of the battery lifetime can be an efficient and effective method for low power design of sensor nodes.

• Nuclear Engineering and Technology
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• v.49 no.2
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• pp.360-372
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• 2017

Many advanced reactor designs rely on passive systems to fulfill safety functions during accident sequences. These systems depend heavily on boundary conditions to induce a motive force, meaning the system can fail to operate as intended because of deviations in boundary conditions, rather than as the result of physical failures. Furthermore, passive systems may operate in intermediate or degraded modes. These factors make passive system operation difficult to characterize within a traditional probabilistic framework that only recognizes discrete operating modes and does not allow for the explicit consideration of time-dependent boundary conditions. Argonne National Laboratory has been examining various methodologies for assessing passive system reliability within a probabilistic risk assessment for a station blackout event at an advanced small modular reactor. This paper provides an overview of a passive system reliability demonstration analysis for an external event. Considering an earthquake with the possibility of site flooding, the analysis focuses on the behavior of the passive Reactor Cavity Cooling System following potential physical damage and system flooding. The assessment approach seeks to combine mechanistic and simulation-based methods to leverage the benefits of the simulation-based approach without the need to substantially deviate from conventional probabilistic risk assessment techniques. Although this study is presented as only an example analysis, the results appear to demonstrate a high level of reliability of the Reactor Cavity Cooling System (and the reactor system in general) for the postulated transient event.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.201-209
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• 1984

In order to examine the effect of initial spray condition on the spray combustion mode and flame characteristics, theoretical analysis was carried out to predict combustion mode and flame structure for various initial distribution of droplets in spray. A system of conservation equations of spray flame in two dimensional axisymmetric for two phase flow was solved by a discrete element method for n-Butylbenzen (C$_{10}$ $H_{14}$). As a results of present study, there are two principal group combustion modes that may occur independently for various initial group combustion numbers in a spray burner. These group combustion modes are termed as an external and internal group combustion mode. The critical group combustion number between the internal and external group combustion mode and the flame characteristics of those flame are also predicted. These results may be used as a basic data in the designing of new combustors as well as proper operating conditions for spray burners.s.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1813-1820
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• 2016

Dual-mode photovoltaic power system should be capable of operating in grid-connected (GC) and stand-alone (SA) modes for distributed generation. Under different working modes, the optimal parameters of inverter output filters vary. Inverters commonly operate in GC mode, and thus, a small capacitance is beneficial to the GC topology for achieving a reasonable compromise. A predictive current control scheme is proposed to control the grid current in GC mode and thereby obtain high-performance power. As filter are not optimal under SA mode, a compound control strategy consisting of predictive current control, instantaneous voltage control, and repetitive control is proposed to achieve low total harmonic distortion and improve the output voltage spectrum. The seamless transfer between GC mode and SA mode is illustrated in detail. Finally, the simulation and experimental results of a 4 kVA prototype demonstrate the effectiveness of the proposed control strategy.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1821-1832
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• 2016

This study presents a strategy using the synchronized output regulation method (SOR) for controlling inverters operating in stand-alone and grid-connected modes. From the view point of networked dynamic systems, SOR involves nodes with outputs that are synchronized but also display a desirable wave shape. Under the SOR strategy, the inverter and grid are treated as two nodes that comprise a simple network. These two nodes work independently under the stand-alone mode. An intermediate mode, here is named the synchronization mode, is emphasized because the transition from the stand-alone mode to the grid-connected mode can be dealt as a standard SOR problem. In the grid-connected mode, the inverter operates in an independent way, in which the voltage reference changes for generalized synchronization where its output current satisfies the required power injection. Such a relatively independent design leads to a seamless transfer between operation modes. The closed-loop system is analyzed in the state space on the basis of the output regulation theory, which improves the robustness of the design. Simulations and experiments are performed to verify the proposed control strategy.