• Journal of Korean Institute of Industrial Engineers
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• v.33 no.2
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• pp.282-289
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• 2007

While demands for express couriers service are rapidly increasing due to recent progress of electronic commerce, express courier service companies are struggling to take a larger market share through ongoing improvement in their service processes. Cut-off time is the time limit that all orders delivered before the limit are guaranteed for the delivery within the very next day. Extending cut-off time for express service centers can provide the express company with increase of total sales, but it may also cause increasing the possibility not to satisfy customer needs due to work delay in the consolidation terminal. We develop a design model for express courier service network based on a recursive optimization/simulation procedure. With the optimization model, we seek key design parameters such as the cut-off time for express service centers and the capacity of the consolidation terminal maximizing total sales profit while satisfying the desired level of performances. With the simulation model, we consider the dynamic nature of the network and obtain relationships between the design parameters and the performance measures with the multiple linear regression. The validity of the model is examined with an example.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.200-200
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• 2011

Although the cut-off probe, a precise measurement method for the electron density, is widely used in the industry, the physics on the wave spectrum of the cut-off is not understood yet, only cut-off point frequency containing the information of electron density has been analyzed well. This paper analyzes the microwave frequency spectrum of the cut-off probe to see the physics behind using both microwave field simulation (CST Microwave Studio) and simplified circuit simulation. The result shows that the circuit model well reproduces the cut-off wave spectrum especially in the low frequency regime where the wavelength of the driving frequency is larger than the characteristic length and reveals the physics of transmission characteristics with frequency as resonances between vacuum, plasma and sheath. Furthermore, by controlling the time domain in solver of the microwave simulator, the cut-off like transmission peaks above the cut-off frequency which has been believed as cavity effect is verified as chamber geometry effect. The result of this paper can be used as the basis for the improvement of cut-off probe.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.845-852
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• 2010

Collecting statistics from client requests, the broadcast server partitions data items into hot and cold-item sets with the optimal cut-off point. Hot items are broadcast periodically with periods based on their access probabilities. In a time slot with no hot items scheduled, the server broadcasts a proper cold item considering the waiting time and the number of outstanding requests. We analyze the optimal the cut-off point by calculating average response time as a function of the cut-off point. Simulation results show that our proposed algorithm outperforms existing methods in various circumstances.

• IE interfaces
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• v.16 no.spc
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• pp.99-104
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• 2003

While demands for express service are rapidly increasing according to recent progress of electronic commerce, express service companies are struggling to take a larger delivery service market share through ongoing improvement in their service processes. Extension of cut-off time for express service centers can provide the express company with increase of total sales, but it may also cause to increase the possibility not to satisfy customer needs due to work delay in the consolidation terminal. Therefore, compromised decision for cut-off time of each service center should be made by taking operation characteristics of the consolidation terminal into account. This study suggests an approach for determining the cut-off time for express service centers according to operational characteristics of the consolidation terminal with the objective of maximizing expected incremental sales. The problem defined in this study can be represented as two successive models; one is an integer programing model in which the best cut-off time for each sales center are determined, and the other is a single machine scheduling model in which a working schedule in the consolidation terminal is obtained. A genetic algorithm is developed to solve the two models simultaneously. Finally, an example problem is carried out to verify applicability and performance of the algorithm with the data set collected from an express company.

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1157-1166
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• 2021

In this study, a numerical sensitivity analysis was performed to determine the fire suppression time for a large number of water mist nozzles in a large fire compartment. Fire simulations were performed using FDS (Fire dynamics simulator) 6.5.2 under the same condition as the test scenario 5 of the International Maritime Organization (IMO) 1165 test protocol. The sensitivities of input parameters including cell size, extinguishing coefficient (EC), droplets per second (DPS), and peak heat release rate (HRR) of fuel were investigated in terms of the normalized HRR and temperature distribution in the compartment. A new method of determining the fire suppression time using FDS simulation was developed, based on the concept of the cut-off time by cut-off value (COV) of the heat release rate per unit volume (HRRPUV) and the cooling time by the HRR cooling time criteria value (CTCV). In addition, a method was developed to determine the average EC value for the simulation input, using the cooling time and cut-off time.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.84-87
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• 1996

This paper presents a energy function to reflect the control effect of speed governor which has a cut-off property which means position and rate limit The proposed energy function satisfies the semi-negativeness of its time derivative and well reflects the parameters of speed governor to the energy function. The transient stability analysis by the direct method for the single machine infinite bus system has been conducted with the use of the proposed energy function, which shows that the results by the direct method well agree with that by the conventional time simulation method. This thesis shows a possibility of more accurate stability analysis by taking into account the cut-off property of speed governor's output.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.1
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• pp.147-155
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• 2000

Five reinforced concrete rigid frame and masonry infilled wall and cut off type masonry infilled wall were tesed during vertical and cyclic loads simultaneously. Experimental programs were accomplished to improve and evaluate the structural performance of test specimens, such as the hysteretic behavior, the maximum horizontal strength, crack propagation, and ductility etc. Test variables are hoop reinforcement ratio, with or without masonry infilled wall, and masonry method. All the specimens were constructed in one-third scale size. Based on the test results, the following conclusions can be made. For masonry infilled wall(IFB-1), maximum horizontal capacity was increased by 1.45 time in comparision with that of rigid frame(FB-0). For cut off masonry infilled wall (IFBC-1~3), maximum horizontal capacity was increased by 1.73~1.98 time in comparision with that of rigid frame(FB-0). For cut off masonry infilled wall(IFBG-1~3), ductility was increased by 1.48~2.08 time in comparision with that of masonry infilled wall (IFB-1).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.109-114
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• 1992

This paper describes an effect of operating condition on surface roughness in wire-cut FDM. The experimental values of surface roughness were measured by the test pieces under the condition of changing. On time, Off time, and Feed rate after fixing other conditions. The material of the test pieces is the alloy tool steel(STD 11) and was used after heat treatment. The results are as follows: 1. The surface roughness became rapidly worse according to the increase of On time and Feed rate. 2. The surface roughness became slowly better according to the increase of Off time.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.19-29
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• 1996

In this paper, it is presumed that the stress time history was generated by simulation method and investigated compatibility in regard to the reappearance of stress time history. In this procedure, the identified frequency distribution of stress range of the steel railroad bridge varies with the rational values of cut off point and bar width. Thus, we show variable aspect of the equivalent stress range results from change of cut off point and bar width. In addition, we analyze the variable of RMC and RMS model due to the cut off point and bar width of the measured stress history which influencs the prediction of fatigue life in the steel railroad bridge. The simulated stress time history is carried out by the superposition method incorporating the vertical load with rotation moment obtained from the Hermition interpolation function, and compared with developing stress results from measured maxi mum stress. Through this study, we can estimate the remaining fatigue life from a safety point of view and comparative accuracy.

• Journal of Korean Critical Care Nursing
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• v.16 no.3
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• pp.24-33
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• 2023

Purpose : This study aims to establish an optimal cut-off score on the Braden scale for the assessment of pressure injury to detect pressure injury risks among inpatients in a South Korean tertiary hospital. Methods : This retrospective study used electronic medical records, from January to December 2022. A total of 654 patients were included in the study. Of these, 218 inpatients with pressure injuries and 436 without pressure injuries were classified and analyzed using 1:2 Propensity Score Matching (PSM), and the generalized estimating equation was performed using SPSS Version 26 and the R Machlt package program. Results : The cut-off value on the Braden scale for distinguishing pressure injury was 17 points, and the AUC (area under the ROC curve) was 0.531 (0.484-0.579). The sensitivity was 56.6% (45.5-67.7%) and the specificity was 69.7% (66.0-73.4%). With 17 points, the Braden scale cut-off distinguished those who had pressure injuries from those who did not at the time of admission (p < .03). In the pressure injury group, the Braden score on the day of the pressure injury was 14, with significant results in all subcategories except the moisture category. Conclusion : Our findings revealed that a cut-off value of 17 was optimal for predicting the risk of pressure injuries among tertiary hospital inpatients. Future studies should evaluate the optimal cut-off values in different clinical environments. Additionally, it is necessary to conduct multicenter large sample studies to verify the effectiveness of a 17 value in PI risk assessments.