• Journal of Nutrition and Health
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• v.31 no.8
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• pp.1347-1354
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• 1998

The purposes of this study were to : (a) anlayze wating time, service rate, arrival rate, and coustomer expectations/satisfaction in cafeteria business foodservices and (b) identify the differences in those factors between foodservices by menu managmenet systems. The samples were two business foodservices operated by contract management in Seoul. The queue, laptime , service rate, and arrival rate were measured at each foodservice by stopwatch observation. The menu type, delivery system, number of meals served , servide time, and turnover rate of each foodservic was investigated. Questionnaires were developed to survey customer expectations and satisfaction. Satistical data analysis was completed using the SAS package programs for descriptive analysis and t-test. The mean waiting time of island type dafeteria system with separte set -menu was shorter than that of the other. In both foodservices, arrival rates were not significantly different from one another , but sevice rates were significnatly high in dafeteria menu systems. The peak time of the queue was found out at combination set menu line. The separate set menu line had a higher servide rate than the combination set menu line. The mean waiting time of the island type cafeteria line was shorter than that of the straifth type . At the straight type dafeterial line, both arrival rate and service rate were higher than those of island-type. The results of this study suggested that a separate set-menu would be more desirable than a combination set-menu in case of providing set menu with cafeteria menu.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1142-1144
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• 1999

A 4-beam cross type silicon elastic body was fabricated for the electromagnetic type vibration micro transducer. To improve energy transfer efficiency, the structure and size of vibration transducer were optimized by the FEA simulation package. Experimental results of the fabricated transducer shows $0.5{\sim}8$ dyne of vibration force at the condition of $1{\sim}4$ mA of current source $100{\sim}7000$ Hz of frequency band width. These results presented the useful applications for micro actuators and sensors.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.10
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• pp.59-65
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• 2008

We have proposed a UHF/HF multi-band RFID reader, and have implemented it into a system in a package(SiP). The proposed SiP RFID reader has been designed to support both for EPCgloabal Class1 Generation2 protocol of UHF band, and 13.56MHz RFID protocols of ISO14443 A/B type, and ISO15693 standards. The operating mode is controlled by embedded RISC core, and the mode can be selected by users. The area of implemented SiP is $40mm{\times}40mm$ with 4 metal layers. The implemented reader SiP operates at single supply voltage of 3.3V. The maximum current consumption is 210mA. The operating distances are 5cm for 13.56MHz modes, and 20cm for UHF mode.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.2
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• pp.96-101
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• 2016

The thermal management of high-power LED components in an assembly structure is crucial for the stable operation and proper luminous function. This study employs numerical tools to determine the optimum thermal design in LEDs with a heat sink consisting of a crevice-type vapor-chamber heat pipe. The effects of the MCPCB are investigated in terms of the substrate thicknesses on which the LEDs are mounted. Further, different placement configurations in a system module are considered. This study found that for a confined area, a power of 40 W/LED is applicable to a high-power package. Furthermore, the thermal conductivity of dielectric layer materials should ideally be greater than 0.9 W/m.K. The temperature conditions of the vapor chamber in a heat pipe greatly affect the thermal performance of the system. At an offset distance of 9.0 mm and a $2^{\circ}C$ increase in the temperature of the heat pipe, the resulting maximum temperature increase is approximately $1.9^{\circ}C$ for each heat dissipation temperature. Finally, at a thermal conductivity of 0.3 W/m.K, it was found that the total thermal resistance changes dramatically. Above 1.2 W/m.K, the resistance change reduces exponentially.

• Proceedings of the Korean Nuclear Society Conference
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• 2005.05a
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• pp.231-232
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• 2005

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.11a
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• pp.186-192
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• 2000

The heat generated in contact type braking system can cause an unacceptable braking performance. Thermal behavior of ventilated disk brake system is presented in this paper. The temperature and velocity fields of 3-D unsteady simulated model are obtained using a software package "FLUENT". The numerical results show that there exits a temperature nonuniformity between the disk faces contacting with pads. The conduction rate through the disk and pad is calculated and the effect of material conductivity is also investigated.estigated.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3156-3161
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• 2007

In the field of yarn dyeing, the most generally employed method is a type of package dyeing which uses a package of cheeses stacked on a spindle made of a perforated tube. In order to understand the process of level dyeing, it is essential to perform a study of the porous flow through the spindle for the cheese dyeing method. In this paper, the axisymmetric, incompressible, Navier-Stokes equations are solved for several spindle configurations using a fully implicit finite volume scheme. For investigating the flow patterns through the spindle, porous diameter and porosity is varied in the present study. The computational results show that the total pressure loss depends only on the velocity of inflow regardless of porous diameter and porosity and a large percentage of the mass flow rate through the spindle is discharged at the upside of the spindle. Therefore, it is required to design a new spindle to obtain the level dyeing.

• Journal of Sensor Science and Technology
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• v.32 no.4
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• pp.207-212
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• 2023

H₂S is a toxic and harmful gas, even at concentrations as low as hundreds of parts per million; thus, developing an H₂S sensor with excellent performance in terms of high response, good selectivity, and fast response time is important. In this study, an H₂S sensor with a high response and fast response time, consisting of a sensing material (SnO₂), an electrode, a temperature sensor, and a micro-heater, was developed using micro-electro-mechanical system technology. The developed H₂S sensor with a micro-heater (circular type) has excellent H₂S detection performance at low H₂S concentrations (0-10 ppm), with quick response time (<16 s) and recovery time (<65 s). Therefore, we expect that the developed H₂S sensor will be considered a promising candidate for protecting workers and the general population and for responding to tightened regulations.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.165-172
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• 2005

In MEMS (Micro-Electro-Mechanical System), packaging induced stress or stress induced structure deformation becomes increasing concerns since it directly affects the performance of the device. In the decoupled vibratory MEMS gyroscope, the main factor that determines the yield rate is the frequency difference between the sensing and driving modes. The gyroscope, packaged using the anodic bonding at the wafer level and EMC (epoxy molding compound) molding, has a deformation of MEMS structure caused by thermal expansion mismatch. This effect results in large distribution in the frequency difference, and thereby a lower yield rate. To improve the yield rate we propose a packaged SiOG (Silicon On Glass) process technology. It uses a silicon wafer and two glass wafers to minimize the wafer warpage. Thus the warpage of the wafer is greatly reduced and the frequency difference is more uniformly distributed. In addition. in order to increase robustness of the structure against deformation caused by EMC molding, a 'crab-leg' type spring is replaced with a semi-folded spring. The results show that the frequency shift is greatly reduced after applying the semi-folded spring. Therefore we can achieve a more robust vibratory MEMS gyroscope with a higher yield rate.

• Journal of the Korea Society for Simulation
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• v.19 no.1
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• pp.1-11
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• 2010

K company produces semiconductor package products under the make-to-order policy to supply for domestic and foreign semiconductor manufacturing companies. Its production process is a machine-paced assembly line type, which consists of die sawing, assembly, and test. This paper suggests three plans to increase process throughput based on the process analysis of K company and evaluates them via a simulation model using a real data collected. The three plans are line balancing by adding machines to the bottleneck process, product group scheduling, and reallocation of the operators in non-bottleneck processes. The evaluation result shows the highest daily throughput increase of 17.3% with an effect of 2.8% reduction of due date violation when the three plans are applied together. Payback period for the mixed application of the three plans is obtained as 1.37 years.