• Journal of the FoodService Safety
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• v.4 no.1
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• pp.7-20
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• 2023

This study was conducted to investigate the impact of refrigerator type and temperature fluctuations on the quality changes of refrigerated foods. Phycochemical and sensory quality, as well as microbial growth, were measured for various foods stored in open- or door-type refrigerators set at 5℃ during storage. The average temperatures recorded were 11.50±1.14℃ in an open refrigerator, and 6.34±0.97℃ in a closed refrigerator. The average surface temperatures of the food items were 9.60±1.20 and 6.00±0.80℃ for open and closed refrigerators, respectively. Significant changes in color and appearance quality were observed in lettuce, mackerel, ground beef, and cut pineapples when stored in open refrigerators. Ready-to-Eat foods such as gimbap and sandwiches exhibited higher levels of microbiological proliferation when stored in open refrigerators compared to closed refrigerators. Processed foods, such as sterilized milk and packaged tofu, did not show significant differences in quality among various types of refrigerators. The installation of refrigerator doors can effectively minimize temperature fluctuations caused by external factors, thereby reducing variations in food quality. These findings provide essential insights into the quality changes associated with the implementation of refrigerator doors, serving as fundamental data for ensuring optimal food preservation.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.308-310
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• 1995

Most of the elevator door controllers have been controlled by DC Motors as an actuator. Recently, The control system using AC induction motor and general purpose inverter has been applied to control of elevator door. But there are some difficulties in making use of this system, such as adjustment of door speed pattern, door open-close time, and security of passenger safety. In order to solve these problems, a special inverter has, been developed with an encoder feedback. From the result of field-test, we proved that a special inverter with encoder feedback device has come to considerable effect. Until now about 1,200 sets of these inverters are operated in Korea and about 100 sets are operated in South-east Asia.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.539-544
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• 2020

The research is on progressing to operate digital door lock with the method to guarantee the security and safety in the meantime to use digital door lock conveniently using Internet of Things (IoT) standardizing various service providing technology using IoT in home network currently. In this study, compose home network interconnecting Raspberry-PI and web server reflection this trend and composed the system to control the door lock after connect Arduino substituting converter function. Making Raspberry-PI using dynamic IP address using existing open source easily maintain DNS information and possible to connect internet network in home network ethernet and finally, making the smartphone can control door lock remotely entering designated address after connect the internet. The connection between home network and Arduino is executed by Raspberry-PI and bluetooth pairing as 1:1 and make random user's access to be impossible. Especially, to make open/close the door lock with smartphone not by using password on the keypad or using RFID card is judged as the method increasing the security make random user's access to be impossible and also increased the usefulness making remote control to be possible.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.89-96
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• 2020

In this study, we developed a finite element model for the built-in bottom-freezer type refrigerator and then used the structural analysis method to analyze and evaluate the deflection of the doors. We tested the validity of the developed analytical model by measuring the deflection of the hinge when loads were applied to the upper and lower hinges of the refrigerating compartment and compared these with the analysis results. The comparison of the vertical displacement of the measured result and the analysis result showed an error ratio of up to 12.8%, which indicates that the analytical model is consistent. Using the analytical model composed of the cabinet, hinges and doors, we performed analyses for two cases: both doors closed, and the refrigerating door open. Since the maximum vertical displacement of the refrigerating compartment door (R-door) with the food load is smaller than the gap between the lower surface of the R-door and the upper surface of the freezer compartment door (F-door), it is judged that the R-door and the F-door do not contact when the doors are opened or closed. In addition, the analysis result showed that the difference between the vertical displacement at the hinge on the opposite side and the hinge side of the R-door is favorably smaller than the management criterion of the refrigerator manufacturer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.721-727
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• 2015

The mechanical components for wind turbines are mainly manufactured using open-die forging. This research introduces an advanced forging method to produce the door frame of the tubular wind turbine tower. The advantages of this new forging method are an increase in the raw material utilization ratio and a reduction in energy cost. In the conventional method, the door frame is hot forged with a hydraulic press and amounts of material are machined out because of the shape difference between the forged and final machine products. The proposed forging method is composed of hot forging and ring rolling processes to increase the material utilization ratio. The effectiveness of this new forging method is deeply related to the ring rolled blank dimension before the final forging. To get the optimal ring rolled blank, forged shape prediction using the finite element analysis method was applied. The forged dimensions produced by the new forging method were verified through the first article production.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.6
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• pp.556-564
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• 2013

This paper proposes an initial rotor position detecting algorithm of a PM synchronous motor using an incremental encoder. The proposed algorithm estimates the phase offset between the rotor magnetic flux and the Z-pulse of the incremental encoder by applying six aligning mode current control. The absolute rotor position for driving a PM synchronous motor is calculated by using the phase offset of the Z pulse and A, B pulse signals of the encoder. The PMSM drives based on the estimated rotor position is applied to the elevator door system. The door length is measured on line at first setup of the elevator. The speed control for open, close, and reopen of the elevator door is also presented and the proposed algorithm for the elevator door system is verified by experiment.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.27 no.4
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• pp.361-370
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• 2017

Objectives: This study evaluated the diesel engine exhaust (DEE) exposure levels of door-to-door deliverers in Daegu from July to September. Methods: We measured exposure levels of DEE surrogates for the same door-to-door deliverers who joined the particulate matter 2.5 exposure study previously published in this journal. Black carbon(BC) concentrations were measured using real-time BC monitoring devices with 1 minute interval. $NO_2$ concentrations were monitored using passive badges. DEE exposure data were analyzed using the same characteristics and GPS information as the first study. Results: A total of 40 measurements of BC concentrations and $NO_2$ concentrations were collected during delivery of parcels. The average exposure levels to BC, and $NO_2$ were $2.23{\mu}g/m^3$ ($0.001-350.85{\mu}g/m^3$) and 21.26 ppb(3.3-61.37 ppb), respectively. Exposure levels to BC according to the day of a week and coverage areas were not significantly different(p>0.05). Delivery trucks manufactured before 2006 caused significantly higher exposure to BC than the trucks manufactured after 2006(p<0.05). Exposure levels of BC integrated for each time in residential area and roadsides were $1.96{\mu}g/m^3$ and $3.46{\mu}g/m^3$, respectively, and the difference was statistically significant(p<0.001). The Pearson correlation coefficients between the ambient $PM_{2.5}$ and BC was significant, r=0.26(p<0.01); however, the correlations between $PM_{2.5}$ and ambient $PM_{2.5}$, and between BC of DEE and $PM_{2.5}$ of DEE did not show a significant correlation Conclusions: BC and $NO_2$ exposure levels were significantly lower when door-to-door deliverers drove newer trucks. BC exposure levels of deliverers were higher in roadsides than in residential area. DEE from nearby vehicles through open windows might be the main source of BC exposure.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2E
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• pp.60-68
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• 1996

In this paper, we implement the door lock system based on pattern matching technique for speaker recognition using DTW. In this study, major features of our system are summarized as follows:(1) Make the average reference pattern using DTW. This method keeps the high recognition rate compared with the other systems whose performances degrade rapidly as time goes on. (2) Use F-ratio values of the cepstral coefficients. We find that the weighted cepstral reveals an effect on intensifying the difference between th customer and the imposter. The system hardware is composed of two parts : the door lock part and the speaker recognition processing part. We use an 8051 microprocessor in the door lock park for serial communication with host processor to open or close the lock. Using our system, we obtain speaker recognition rate of about 99.5%.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.59-60
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• 2013

In this paper, we implemented a digital doorlock using microprocessor Atemega128 made in Atmel. We added RFID reader to identify different existing Doorlock. To operate the system, first, if RFID reader recognize card, LCD is used to operate password input message. Second, if password is correct, door is opened. But if password is incorrect, door will not be open. To extend security intensity for opening door key, we used RFID module and can operate it easily.

• Fire Science and Engineering
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• v.26 no.4
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• pp.24-30
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• 2012

The purpose of this study is to analyze the problem in measuring the differential pressure between the fire area and the neighboring smoke control zone as well as the opening force of a fire door and to present the actual values measured by an objective method. NFSC 501A specifies that the force necessary to open an access door when operating a smoke control system shall be less than 110 N. When the smoke control system does not operate in the space where it is installed, the door opening force can be measured by the test method in KS F 2805. However, when the smoke control system operates, additional opening force is required to overcome the force generated by the differential pressure between the fire area and smoke control room. Therefore, it can be seen that the method proposed by the standard has insufficient reliability. The analog measuring device and digital measuring device showed that the opening forces, $F_a$ and $F_d$, of the fully closed door before the smoke control system were 27.8 N and 27.4 N, respectively. When the door remained open by $5^{\circ}$, the opening forces, $F_a$ and $F_d$, were 33 N and 33.6 N, respectively. When the smoke control system operated and the door was fully closed, the door opening forces, $F_a$ and $F_d$, were 77.6 N and 76.0 N, respectively. Therefore, since the door opening forces are different from the criteria presented by KS F 2805, it is required to review the criteria appropriately.