• Proceedings of the KIEE Conference
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.997-998
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• 2011

본 논문에서는 영구자석 동기전동기의 영구자석 평균온도를 다이나모 시험을 통해 얻어진 토크 데이터로부터 간접적으로 계산하는 방법이 제시된다. 특히 영구자석의 온도에 따른 잔류자속밀도 변화에 자기 포화 효과를 고려하여 다양한 운전점에서의 온도추이를 간단하고 정확히 계산할 수 있다.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제21권3호
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• pp.369-377
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• 1997

The torque converter, a major part of automatic transmissions, has many difficulties in analysis due to the factors such as power transmission through fluid flow, complex internal geometry, and various operating conditions. Because of such difficulties, the dynamic analysis and design of a torque converter are generally carried out by using equivalent performance model which is based on the concept of mean flow path. Since the design procedures of a torque converter are essential technology of automotive industry, the details of the procedures are rarely published. In this study, the basic design procedures of a torque converter are systemized and coded based on the equivalent performance model. The mathematical methods to deal with mean flow path determination and the core-shape are developed. And by using this model, the method of determination of performance parameters satisfying the requested performance is proposed. Finally, to embody the three-dimensional shape, the intermediate blade angles which maximize the tractive performance are determined and laid out.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제24권2호
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• pp.506-517
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• 2000

One dimensional performance model has been used for the design of torque converter. The model is based on the concept of constant mean flow path and constant flow angle. These constant-assumed para meters make the design procedure to be simple. In practice, some parameters are usually replaced with geometric raw data and, the constant experiential correction factors have been used to minimize the design error. These factors have no definite physical meaning and so they cannot be applied confidently to the other design condition. In this study, the detail dynamic model of torque converter is presented to establish the theoretical background of correction factors. To verify the validity of theoretical model, steady state performance test was carried out on the several input speed. The oil temperature effect on the performance is analysed and adjusted. The constant equivalent flow angles are determined at a part of performance region by comparing the theoretical model and the test data. The sensitivity of correction factors to the input speeds are studied and the change of torus flow is presented.

• Transactions of the Korean Society of Automotive Engineers
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• 제10권1호
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• pp.244-254
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• 2002

To enhance the acceleration performance and fuel consumption rate of a vehicle, the torque converter is modified or newly-developed with reliable analysis model. Up to recently, the one dimensional performance model has been used for the analysis and design of torque converter. The model is described with constant parameters based on the concept of mean flow path. When it is used in practice, some experiential correction factors are needed to minimize tole estimated error. These factors have poor physical meaning and cannot be applied confidently to the other specification of torque converter. In this study, the detail dynamic model of torque converter is presented to establish the physical meaning of correction factors. To verify the validity of model, performance test was carried out with various input speed and oil temperature. The effect of oil temperature on the performance is analysed, and it is applied to the dynamic model. And, to obtain the internal flow pattern of torque converter, CFD(Computational Fluid Dyanmics) analysis is carried out on three-dimensional turbulent flow. Correction factors are determined from the internal flow pattern, and their variation is presented with the speed ratio of torque converter. Finally, the sensitivity of correction factors to the speed ratio is studied for the case of changing capacity factor with maintaining torque ratio.

• Proceedings of the KIEE Conference
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 A
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• pp.31-34
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• 2003

There are several types of switching table for selection voltage vector in direct torque control of induction motor. In general, two-quadrant and four-quadrant operation switching table are used mostly. Two-quadrant operation has an advantage that reduced the torque ripples in comparison with four-quadrant operation, but it has the defect that is not constant average torque. Because the torque increasing slope size by non-zero voltage vector is different from the torque decreasing slope size by zero voltage vector as speed region. The main objective of this study is to maintain constant average torque using two-quadrant operation switching table. In proposed method, the torque increasing slope or decreasing slope are calculated before selected voltage vector is applied. Then, it is applied to zero voltage vector or non-zero voltage vector until the torque increasing slope and decreasing slope are equal. In total magnitude. Therefore it becomes to maintain average torque at whole operation speed. The validity of the proposed method is proven by simulated and experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제16권8호
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• pp.5082-5088
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• 2015

In this paper, durability test of 1000cc level gasoline engine has been carried out. Durability test set total 300 hours and WOT condition. Engine torque, power, fuel consumption, blow-by gas flow rate, and oil pressure are measured to analyse performance variation by time. As a result, engine performance of high rpm range gradually reduced by time but for relatively low rpm range shows stable performance. Blow-by gas flow rate shows 0.4% of averaged induction air flow rate, which is excellent rate for 1000cc level gasoline engine. Engine torque and fuel consumption data show the break-in upto 100 hours and aging trend after that. After 300 hours, engine is disassembled and each part is checked for the damage or crack.

• Proceedings of the KIEE Conference
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 전기설비
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• pp.47-48
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• 2006

본 논문에서는 LabVIEW를 이용한 휴대용 3상 유도전동기 회전자 바 고장 진단 시스템을 개발하였다. LabVIEW는 NI사에서 개발한 그래픽컬 프로그래밍 언어로서 VI(Virtual Instrument)기술을 이용하여 계측, 분석, 표현 프로그램에 최적화된 언어이다. 유도전동기의 입력단에 Current Probe를 연결하여 전류를 측정하였고, NI사의 USB-DAQ보드를 이용하여 데이터를 수집한 후 노트북 컴퓨터에서 실행되는 LabVIEW 프로그램에 의해 고장을 진단할 수 있는 실시간 휴대용 진단 시스템을 개발하였다. 회전자 바에 고장이 일어나면 선 전류의 불균형, 손실 증가, 토크맥동과 평균 토크의 감소를 가져올 수 있다. 고장 진단 방법으로는 회전자 바 고장의 특징 주파수를 찾아 진단하는 방법이 있다. 회전자 바 고장에 대하여 1개와 2개 바를 절단한 회전자를 사용하여 각각 실험하였으며, FFT 분석에 의하여 실시간으로 유도전동기 회전자 바 고장을 진단 할 수 있음을 보였다.

• The Korean Journal of Food And Nutrition
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• 제11권2호
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• pp.192-199
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• 1998

1. 조사 대상자들의 평균 키와 체중은 각각 161.00$\pm$4.15cm, 50.45$\pm$8.15kg이었으며 BMI는 19.81$\pm$3.98, 체지방율은 26.12$\pm$4.12, skinfold thickness는 40.40$\pm$12.56mm로 나타났다. 2. 조사 대상자들의 혈액성상은 적혈구 수, 헤모글로빈, 헤마토크리트치, albumin, globulin, 총 콜레스테롤, LDL-콜레스테롤, HDL-콜레스테롤, 총 중성지방을 측정하였으며 헤마토크리트치를 제외한 나머지 성상들은 모두 정상 범위에 속하였다. 헤마토크리트치는 정상범주에 미달되는 것으로 나타나 이로 말미암아 철분 결핍성 빈형에 노출될 확률이 아주 많음을 보였다. 3. 용돈별로 체지방율을 분류하여 분석한 결과 한달 용돈이 평균 20~30만원을 쓰는 group의 체지방율이 22.00%로서 정상 수준 이었으며, 30만원 이상 사용하는 group은 비만으로 나타났다.(p<0.05) 한편, 그 외의 group들은 체내 체지방율 수준도 정상 수준인 20~25%를 넘어 체중으로 나타났다. 또한 30만원 이상 사용하는 group은 다른 group보다 RBC(million/㎣), Hb(g/이), Hct(%) 모두가 낮게 나타났으며, 빈혈로 판정될 수 있는 수준이었다. 4. 다이어트 빈도별 각 요인들간의 상관관계를 살펴보면 다이어트 시도를 자주 한다고 답변한 group이 거의 실시하지 않는다., 실시해 본 적이 없다라고 대답한 group보다 체중과 BMI가 유의적으로 낮았다.(p<0.05) 그러나 skinfold thickness(mm)와 체지방율은 유의차가 나타나지 않았다. 따라서 비록 다이어트 실시를 자주할 경우 절대적인 체중감량은 감소되지만 체내 지방량이 감소되는 것은 아니라고 판단된다. 5. 다이어트 실시기간에 따라 혈액 성상을 분석한 결과, 4개월 미만 다이어트를 실시하였으나, 1개월 전부터 현재(설문지에 응답한 시점)까지 기간 중에는 다이어트를 실시한 적이 없다고 대답한 group의 Alb(g/dl)과 Glo(g/dl)의 수치가 다이어트를 실시한 적이 없다고 대답한 group에 비해 유의적으로 높게 나타났다.(p<0.05) 6. 체중은 BMI와 양의 상관관계를 나타내었으며, BMI는 견갑골과도 높은 양의 상관관계를 가졌다. 상완부는 견갑골, skinfold thickness(mm), 체지방율과 높은 양의 상관관계를 보였으며, 반면 Hb(g/dl), Hct(%)와는 음의 상관관계를 나타내었다. 견갑골은 BMI 뿐 아니라 skinfold thickness(mm), 체지방율과 양의 상관관계를 나타내었으며, skinfold thickness(mm)는 체지방율과 유의적인 양의 상관관계가 있음이 나타났다. 7. RBC(million/㎣)는 Hb(g/dl) 및 Hct(%)와 유의적인 양의 상관관계를 나타내었으며, Hb(g/dl)도 Hct(%)와 유의적인 양의 상관관계를 나타내었다. Alb(g/dl)은 Glo(g/dl) 및 TCH(mg/dl), HDL(mg/dl)과도 양의 상관관계를 가졌다. Glo(g/dl)은 TCH(mg/dl)과 양의 상관관계를 보였으며, TCH(mg/dl)은 Alb(g/dl), Glo(g/dl)이에도 TTG(mg/dl), LDL-cho(mg/dl) HDL-cho과도 양의 상관관계를 나타내었다. TTG(mg/dl)은 LDL-cho(mg/dl)과는 양의 상관관계를 HDL-cho(mg/dl)과는 음의 상관관계를 나타내었다.

• Journal of Biomedical Engineering Research
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• 제23권1호
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• pp.9-16
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• 2002

Localized muscle fatigue can be identified by a downward shift of the EMG frequency typically represented by a fall in the median frequency The Present experimental study was Performed to investigate the time change of the median frequency and the muscle torque during maximal isometric back extension exercises at different exercise angles (0$^{\circ}$, 12$^{\circ}$, 36$^{\circ}$and 72$^{\circ}$) Twenty heath subjects (mean age : 24.35 $\pm$ 2.70) were Participated in this study Median frequency was extracted from EMG signals by employing the fast Fourier transform. Initial median frequency and the slope of median frequency was not significantly correlated with the muscle torque. Pearson's Product moment correlation was used to quantify the relationship between slopes of median frequency and torque. The results may suggest that the exorcise angle during maximal isometric back extension exercises does not affect the slopes of the median frequency and torque, and y-intercept of the median frequency among exercise angles There was no significant correlation between slopes of median frequency and torque. But there was a moderate correlation between median frequency and torque at each exercise angle. In conclusion, the exercise angle during maximal isometric back extension exercise is not a direct effect on slopes of median frequency and torque. But results showed that the shift of median frequency and torque shift were highly correlated in all subjects.

• The Journal of Korean Academy of Prosthodontics
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• 제49권2호
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• pp.168-176
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• 2011

Purpose: This study aims at investigating the influence of various insertion torques on thermal changes of bone. A proper insertion torque is derived based on the thermal analysis with two different implant designs. Materials and methods: For implant materials, bovine scapula bone of 15 - 20 mm thickness was cut into 35 mm by 40 - 50 mm pieces. Of these, the pieces having 2 - 3 mm thickness cortical bone were used as samples. Then, the half of the sample was immersed in a bath of $36.5^{\circ}C$ and the other half was exposed to ambient temperature of $25^{\circ}C$, so that the inner and surface temperatures reached $36.5^{\circ}C$ and $28^{\circ}C$, respectively. Two types of implants ($4.5{\times}10\;mm$ Br${\aa}$nemark type, $4.8{\times}10\;mm$ Microthread type) were inserted into bovine scapula bone and the temperature was measured by a thermocouple at 0.2 mm from the measuring point. Finite element method (FEM) was used to analyze the thermal changes at contacting surface assuming that the sample is a cube of $4\;cm{\times}4\;cm{\times}2\;cm$ and a layer up to 2 mm from the top is cortical bone and below is a cancellous bone. Boundary conditions were set on the basis of the shape of cavity after implants. SolidWorks was used as a CAD program with the help of Abaqus 6.9-1. Results: In the in-vitro experiment, the Microhead type implant gives a higher maximum temperature than that of the Br${\aa}$nemark type, which is attributed to high frictional heat that is associated with the implant shape. In both types, an Eriksson threshold was observed at torques of 50 Ncm (Br${\aa}$nemark) and 35 Ncm (Microthread type), respectively. Based on these findings, the Microthread type implant is more affected by insertion torques. Conclusion: This study demonstrate that a proper choice of insertion torque is important when using a specific type of implant. In particular, for the Microthread type implant, possible bone damage may be expected as a result of frictional heat, which compensates for initial high success rate of fixation. Therefore, the insertion torque should be adjusted for each implant design. Furthermore, the operation skills should be carefully chosen for each implant type and insertion torque.