• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.157-158
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• 2023

Doors that are opened and closed when entering or exiting a general building are connected to the door frame and open and close. They are equipped with door locking devices of various structures, and are either locked to the door frame for the closing operation or released from the door frame for the opening and closing operation. Here, a single-stage door binding device having a door latch that is independently disposed at the center of one axis of the door is commonly used. On the other hand, if the size of the door is over a certain size or if the door is medium to large, the opening and closing operation may not be performed smoothly with only a single stage binder, or the closing state may not be achieved stably during the closing operation. In particular, in the case of the single-stage binding device provided in medium to large fire doors, the door is fixed to the door frame unstable, causing fatal errors in the fire prevention function of the fire door. Accordingly, in order to fundamentally solve these problems, we researched and developed a three-stage door binding machine that combines a top and bottom fastening structure with a single-stage fastening structure. This 3-stage door binder not only has the fire resistance performance of a fire door, but also has a T-shaped terminal in its fastening method, so if you eliminate the upper and lower fastening, it is a 1-stage binder like a regular product, but if you remove the door latch of the 1st-stage binder, it functions as an upper and lower 2-stage binder and forms a single mold. We researched and developed a three-stage door binder that can manufacture and produce three products at the same time, satisfying both product performance and price.

• Environmental Engineering Research
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• v.25 no.1
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• pp.1-17
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• 2020

With benefits to the human health, environment, economy, and energy, anaerobic digestion (AD) systems have attracted remarkable attention within the scientific community. Anaerobic digestion system is created from (bio)reactors to perform a series of bi-metabolism steps including hydrolysis/acidogenesis, acetogenesis, and methanogenesis. By considering the physical separation of the digestion steps above, AD systems can be classified into single-stage (all digestion steps in one reactor) and multi-stage (digestion steps in various reactors). Operation of the AD systems does not only depend on the type of digestion system but also relies on the interaction among growth factors (temperature, pH, and nutrients), the type of reactor, and operating parameters (retention time, organic loading rate). However, these interactions were often reviewed inadequately for the single-stage digestion systems. Therefore, this paper aims to provide a comprehensive review of both single-stage and multi-stage systems as well as the influence of the growth factors, operating conditions, and the type of reactor on them. From those points, the advantages, disadvantages, and application range of each system are well understood.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.143-149
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• 2016

The two-stage converter is widely used in traditional DC/AC inverter. It has several disadvantages such as complex topology, large volume and high loss. In order to overcome these shortcomings, a novel half load-cycle worked dual SEPIC single-stage inverter, which is based on the analysis of the relationship between input and output voltages of SEPIC converters operating in the discontinuous conduction mode (DCM), is presented in this paper. The traditional single-stage inverter has remarkable advantages in small and medium power applications, but it can’t realize boost DC/AC output directly. Besides one pre-boost DC/DC converter is needed between the DC source and the traditional single-stage inverter. A novel DC/AC inverter without pre-boost DC/DC converter, which is comprised of two SEPIC converters, is studied. The output of dual SEPIC converters is connected with anti-parallel and half load-cycle control is used to realize boost and buck DC/AC output directly and work properly, whatever the DC input voltage is higher or lower than the AC output voltage. The working principle, parameter selection and the control strategy of the inverters are analyzed in this paper. Simulation and experiment results verify the feasibility of the new inverter.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1432-1434
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• 2005

Single-stage converters are simpler and less expensive than convention two-stage converters. It can be a challenge, however, to design single-stage converters to satisfy certain key criteria such as input power factor, primary-side do bus voltage, and output voltage ripple. This is especially true for higher power single-stage AC/DC TTFC(Two-Transistor Forward Converter).

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.252-257
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• 1998

Two-stage power factor correction (PFC) converter with a single PWM controller for universal input voltage (90-264V) is proposed. It consists of a power factor pre-regulator cascaded by a DC/DC converter as in a conventional two-stage approach. However, a single PWM controller is used as in a single-stage, single-switch PFC approach. The switch in the PFC part is synchronized with the switch in the DC/DC converter with a fixed switching frequency. Employing an adaptive delay scheme the switch in the PFC part is controlled to limit the energy storage capacitor voltage within a designed range for the optimum efficiency, and to reduce input current harmonic distortion. The experimental results obtained on a 200W (5V/40A) prototype PFC converter are given to verify the effectiveness of the proposed control method.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.4
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• pp.372-380
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• 2004

This paper proposes a single-power-stage high frequency resonant AC-DC converter with high power factor using ZVS(Zero Voltage Switching), and integrates a conventional converter with two stage into single stage converter. Input power factor is possible to be improved as a high power factor because inductor for power factor correction(PFC) is connected in input and converter is operated in discontinued current mode(DCM) with constant duty cycle and variable switching frequency. The conventional converter with two stage need to add a switch in order to control a power factor, but single stage converter have a advantage that system is simple and cost is down, confidence is improved, etc. This paper described a operation principle and characteristic analysis for single stage AC-DC converter with high power factor and have evaluated characteristic values by using normalized parameter. We make a experimental equipment using MOSFET as a switching device on the basis of characteristic values obtained from characteristic evaluations and we conform a rightfulness of theoretical analysis by comparing theoretical waveforms and experimental waveforms.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.361-370
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• 2006

A single-stage single-switch flyback converter with synchronous rectifier is proposed. The proposed single-stage single-switch technique meets the IEC 61000-3-2 harmonic requirements. The proposed SR is the voltage driven synchronous rectifier (VDSR) which operates depending on the voltage drop across the drain and source of the MOSFET. Experimental results for the 85W (12V /7.1A) proposed converter are shown.

• Journal of Korean Society on Water Environment
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• v.20 no.4
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• pp.307-312
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• 2004

This study was focused on experiment for the separation and concentration process of Cu(II), Zn(II) solution with the variation of applied pressure and concentration using reverse osmosis plate and frame modules. Rejection coefficient and degree of concentration for Cu(II) component using single and multi-stage reverse osmosis process were showed 96.3~97.8%, 0.044~0.191(in single-stage), 96.3~98.4%, 0.400~2.264(in multi-stage) within the range of experimental condition, respectively. Those of Zn(II) were 93.3~97.1%, 0.019~0.395(in single-stage), 96.3~98.2%, 0.365~1.454(in multi-stage), respectively. Degree of concentration of multi-stage were higher than those of single-stage. Heavy metal[Cu(II), Zn(II)] separation was very efficient in using reverse osmosis plate and frame type modules. Separation efficiency for a mixed solution Cu(II) and Zn(II) was higher than those of each one of Cu(II) and Zn(II).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1030-1039
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• 2006

A high power and high gain Doherty amplifier is designed by using embedded driver amplifiers in the final stage. The operational characteristics of a two-stage Doherty amplifier are analyzed, as a function of the two-stage peaking amplifier gate biases. The driver stages and final output stages are implemented using two single-ended MRF21045s and a single push-pull packaged MRF5P21180, respectively. This two-stage Doherty amplifier demonstrated 27 dB gain with a PAE of 23 % at 15 W average output power.

• Journal of Korean Society for Quality Management
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• v.13 no.2
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• pp.29-36
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• 1985

The problem of selecting the gamma population with the largest mean out of k gamma populations, each of which has the same shape parameter is considered. An elimination type two-stage procedure is proposed which guarantees the same probability requirement using the indifference-zone approach as does the single-stage procedure of Gibbons, Olkin and Sobel (1977). The two-stage procedure has the highly desirable property that the expected total number of observations required by the procedure is always less than that of the corresponding single-stage procedure regardless of the configuration of the population parameters.