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Ratio Estimation of Indirect Cost Sector about Defense Companies by Statistic Technique
Hyeoncheol Lim(임현철),Suhwan Kim(김수환) 한국산업경영시스템학회 2017 한국산업경영시스템학회지 Vol.40 No.4
In the defense acquisition, a company’s goal is to maximize profits, and the government’s goal is to allocate budgets efficiently. Each year, the government estimates the ratio of indirect cost sector to defense companies, and estimates the ratio to be applied when calculating cost of the defense articles next year. The defense industry environment is changing rapidly, due to the increasing trend of defense acquisition budgets, the advancement of weapon systems, the effects of the 4th industrial revolution, and so on. As a result, the cost structure of defense companies is being diversifying. The purpose of this study is to find an alternative that can enhance the rationality of the current methodology for estimating the ratio of indirect cost sector of defense companies. To do this, we conducted data analysis using the R language on the cost data of defense companies over the past six years in the Defense Integrated Cost System. First, cluster analysis was conducted on the cost characteristics of defense companies. Then, we conducted a regression analysis of the relationship between direct and indirect costs for each cluster to see how much it reflects the cost structure of defense companies in direct labor cost-based indirect cost rate estimates. Lastly a new ratio prediction model based on regularized regression analysis was developed, applied to each cluster, and analyzed to compare performance with existing prediction models. According to the results of the study, it is necessary to estimate the indirect cost ratio based on the cost character group of defense companies, and the direct labor cost based indirect cost ratio estimation partially reflects the cost structure of defense companies. In addition, the current indirect cost ratio prediction method has a larger error than the new model.
중국 RLDA 데이터에 의한 Shock Absorber 내구 시험모드 개발
임현철(Hyeoncheol Lim),정인승(Inseung Chung),김대성(Daesung Kim),김기훈(Gihoon Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In order to guarantee the durability performance of vehicle suspension component, the criterion for design and evaluation based on service loading condition are necessary. In this study, it was established durability evaluation criterion under Chinese service condition for suspension system. The main parameters causing system failure were founded through the analysis of failure examples. The loading condition including the parameters was measured from the vehicle test on Chinese public road over 8,000㎞. The measured data was used to make the durability evaluation criterion by extrapolation method based on Chinese operating profile. The criterion was compared with others from Korean and European public road in oder to analyse the severity of Chinese road condition. The IO-step block program test signal was designed to evaluate the durability of Chinese type semi-active suspension system. To prove reliability of the rig test, the road durability test with taxi was performed and the results from road test and rig test were compared.
PZT 주파수 특성 분석 및 유연 1-3 복합 초음파 트랜스듀서 제작
임현철(Hyeoncheol Lim),김회준(Hoe Joon Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
This study reports a flexible piezoelectric transducer based on 1-3 mode PZT and PDMS composite structure. The thickness of PZT is about 0.3 mm which gives a resonant frequency of 2 MHz. For device design, we have performed a COMSOL study to predict the frequency response and relative acoustic pressure of the device with varying dimensions. To make rigig PZT into a flexible form, we diced the PZT film in 150 μm by 150 μm sized pixels and coated the PZT arrays with PDMS. Our simulation and measurement match well and the fabricated device bends without any damage under pressure. In later state, we will metallize the device and perform further device characterization. In addition, we will use the device as a source and a sensor for ultrasound measurements for bio-healthcare applications.
지속적인 중심혈압 측정을 위한 단일 유연 초음파 센서의 디자인, 제작, 및 특성분석
임현철(Hyeoncheol Lim),정순인(Soonin Jung),정동규(Dongku Jung),남상우(Sangwoo Nam),유재석(Jaesok Yu),김회준(Hoe Joon Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
This study reports a new simple design of a single flexible ultrasonic sensor with the flexible copper electrode to obtain conformal contact to the target with high penetration depth and broad – 6 dB fractional bandwidth for non-invasive continuous monitoring of the central blood pressure. The central blood pressure from carotid and aorta deeply embedded under the skin (~ 30mm) has stronger correlation to cardiovascular diseases than the blood pressure from peripheral vessels. The existing wearable ultrasonic sensors for continuous monitoring of the blood pressure either have insufficient penetration depth for measuring the central vessels or complicated array structures fabricated by complex processes resulting in low device yield. Here, we solve these problems with a simple design of the single flexible ultrasonic sensor using a flexible 1-3 piezoelectric composite. It shows a high effective electromechanical coupling factor (0.69), high penetration depth (40 mm), a resonant frequency of 1.96 MHz, and - 6 dB fractional bandwidth of 32% with the sensor size of 12 x 5 ㎟. In the near future, we will measure the central blood pressure. We believe this proposed sensor is suited for continuous monitoring of the central blood pressure.
지속적인 중심혈압 측정을 위한 단일 유연 초음파 센서의 디자인, 제작, 및 특성분석
임현철(Hyeoncheol Lim),정순인(Soonin Jung),정동규(Dongku Jung),남상우(Sangwoo Nam),유재석(Jaesok Yu),김회준(Hoe Joon Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11
This study reports a new simple design of a single flexible ultrasonic sensor with the flexible copper electrode to obtain conformal contact to the target with high penetration depth and broad – 6 dB fractional bandwidth for non-invasive continuous monitoring of the central blood pressure. The central blood pressure from carotid and aorta deeply embedded under the skin (~ 30mm) has stronger correlation to cardiovascular diseases than the blood pressure from peripheral vessels. The existing wearable ultrasonic sensors for continuous monitoring of the blood pressure either have insufficient penetration depth for measuring the central vessels or complicated array structures fabricated by complex processes resulting in low device yield. Here, we solve these problems with a simple design of the single flexible ultrasonic sensor using a flexible 1-3 piezoelectric composite. It shows a high effective electromechanical coupling factor (0.69), high penetration depth (40 mm), a resonant frequency of 1.96 MHz, and - 6 dB fractional bandwidth of 32% with the sensor size of 12 x 5 ㎟. In the near future, we will measure the central blood pressure. We believe this proposed sensor is suited for continuous monitoring of the central blood pressure.
자외선 경화가능한 나노복합소재의 중합두께 예측모델 개발
임현철(Hyeoncheol Lim),최영(Young Choi),박상헌(Sangheon Park),황반토(Hoang Van Tho),윤상희(Sang-Hee Yoon) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12
Ultraviolet (UV) curable nanocomposites (NCs) are emerging as viable alternatives to thermal curable NCs in a variety of advanced engineering applications due to their fast polymerization. Despite extensive efforts, little is known about how to model the polymerized thickness of UV curable NCs especially when non-spherical nanofillers are embedded therein. Here, we develop a theoretical model for predicting the polymerized thickness of UV curable NCs by modifying the Beer-Lambert law to reflect both inter-nanofiller distance and nanofiller UV screening. The accuracy of the model is accessed by comparing its prediction with experimental data for graphite nanoflake (GnF)-embedded SU-8 composites having different GnF concentrations of 1 to 25 wt%. The findings of this study will lead to successful and growing development of UV curable NCs.