Studies on Thickness Swelling Mechanism of Wood Particle-Polypropylene Fiber Composite by Scanning Electron Microscopy

ChanHoLee,차재경,엄영근 한국목재공학회 2002 목재공학 Vol.30 No.3

This study was carried out through scanning electron microscopy to elucidate the mechanism of thickness swelling in wood particle-polypropylene composite which is a typical way of using wood and plastic materials. For this purpose, control particleboards and nonwoven web composites from wood particle and polypropylene fiber formulations of 100:0, 70:30, 60:40, and 50:50 were manufactured at target density levels of 0.5, 0.6, 0.7, and 0.8 g/cm3. Their water absorption and thickness swelling were tested according to ASTMD 1037-93 (1995). To elucidate thickness swelling mechanism of composite through the observation of morphological change of internal structures, the specimens before and after thickness swelling test by 24-hour immersion in water were used in scanning electron microscopy.From the scanning electron microscopy, thickness swelling of composite was thought to be caused by the complicated factors of degree of built-up internal stresses by mat compression and/or amount of wood particles encapsulated with molten polypropylene fibers during hot pressing. In the composites with wood particle contents of 50 to 60% at target densities of 0.5 to 0.8 g/cm3 and with wood particle content of 70% at target densities of 0.5 to 0.7 g/cm3, thickness swellings seemed to be largely dependent upon the restricted water uptake by encapsulated wood particles with molten polypropylene fibers. Thickness swelling in the composite with wood particle content of 70% at target density of 0.8 g/cm3, however, was thought to be principally dependent upon the increased springback phenomenon by built-up internal stresses of compressed mat.

Investigation of Noise Characteristics of pn Diodes by Using a Device Simulator

HyunchulNah,Young-JunePark,HongShickMin,ChanhoLee,HyungsoonShin 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.6

The noise characteristics of pn diodes obtained using a partial dierential equation (PDE) based device simulator with the transfer impedance method and the diffusion and the generationrecombination processes as the fundamental noise sources are investigated. From this approach, the noise behaviors over the entire operating region from the reverse to the very high forward bias regions for both long- and short-base diodes are obtained, and the results demonstrate good agreement with the previously reported data, except for the high forward bias region. A noise equivalent circuit model is introduced to explain the noise behaviors for that region and is proven to be useful for long-base diodes.

A Study of the Characteristics of Heat Transfer for an Ammonia-Water Bubble Mode Absorber in Absorption Heat Pump Systems

Jae-CheolLee,이기봉,전병희,ChanHoLee,JongJooHa,김성현 한국화학공학회 2002 Korean Journal of Chemical Engineering Vol.19 No.4

absorber is a major component in absorption refrigeration systems and its performance greatly affectsthe overall system performance. In this study, experimental analyses of the characteristics of heat transfer for removal ofabsorption heat in an ammonia-water bubble mode absorber were performed. The heat transfer coeficient was es-timated as a function of the input gas flow rate, solution flow rate, temperature, concentration, absorber diameter andheight, and input flow direction. The increase of gas and solution flow rate affects positively in heat transfer. However,the increase of solution temperature and concentration affects negatively. Moreover, under the same Reynolds num-ber, countercurrent flow is superior to cocurrent flow in heat transfer performance. In adition, from these experimentaldata, empirical corelations that can explain easily the characteristics of heat transfer are derived.

Analysis of the Accuracy of the Local Thermal Noise Sources for the Impedance Field Method Using the Monte Carlo Method

Sung-JoonHong,HyunchulNah,YoungJunePark,HongShickMin,ChanhoLee,HyungsoonShin 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.1

We show that the local thermal noise sources for the impedance eld method (IFM) can be calculated accurately using the Monte Carlo method (MC). Using the results from MC method, we investigate the accuracy of the conventional thermal noise sources used to calculate the noise with the IFM. The results for a 0.1 m N+-N-N+ device show that the conventional local thermal noise sources can be wrong for submicron devices. We also present the method of terminal noise calculation using an impedance eld which is suitable for the Monte Carlo method. This method is compared with the conventional method which uses the autocorrelation function in Monte Carlo method. The results show that the method using the impedance eld is very stable and fast numerically.

Effects of Nano-sized Ag Particles on Heat Transfer of Nanofluids

Chan Ho Lee,김성현,Seung-Woo Kang 한국공업화학회 2005 Journal of Industrial and Engineering Chemistry Vol.11 No.1

Oscillator Strength of Normal-Incidence Intersubband Absorption in Conduction Bands of Si and Ge Quantum Wells Using Polarization

Chanho Lee 한국정보과학회 1998 Journal of Electrical Engineering and Information Vol.3 No.1

A theoretical calculation and an optical measurement method of normal-incidence absorption are proposed. By using a waveguide structure, optical interference and the problem of low level signal can be avoided in the measurement of normal-incidence absorption. The oscillator strength of intersubband absorption for a waveguide structure is calculated in Si(001), Si(110), and Ge(001) quantum wells. The polarization angle dependence of the measured and the calculated absorption strength can be obtained with the same waveguide structure, and be compared after normalization. The normal-incidence absorption in Si(110) and Ge(001) quantum wells is shown theoretically, and can be observed in the optical measurement using waveguide structures at the polarization angle of 900˚.

A Systematic Review of the Mechanical CPR and Manual CPR on Out-of-Hospital Cardiac Arrest Occurring in High-rise Building

ChanHo Lee,ByounGgil Yoon,HongBeom Ahn,YongSeok Kim 국제문화기술진흥원 2022 International Journal of Advanced Culture Technolo Vol.10 No.4

CPR in High-rise building is one of the challenging tasks to 119 paramedics, evacuating patient from the narrow and vertical area. This study was built to compare the method of mechanical CPR and manual CPR is to maximizing on-scene treatment time, and minimizing the hand-off time in cardiac arrest, transporting patient as fast as possible. The electronic data research (Science, Pubmed, Medline, Medline and 55 academic DB interworking) was conducted, and five articles were included by reviewing and excluding through the Covidence program and Review Manager version 5.4(Cochrane Collaboration). OHCA occurring on the higher floor indicates lower in survival. A total studies uniformly reported mechanical CPR is more effective during the high-rise building evacuation, than manual CPR in rate, depth, and hands-on time of chest compression. Use of mechanical CPR device is more suitable in case of High-rise building OHCA to improve the survival rate which is affected by high-quality CPR.

Design of eMMC Controller with Virtual Channels for Multiple Processors

Chanho Lee,Chulhoon Kim 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.2

Portable embedded systems includes several non-volatile memory devices for the external storage. Multiple processors and multiple processing are popular and reading and writing data in the storage limit the performance of the system. The conventional architectures combine the devices to a single channel or assign the devices to multiple channels one by one to increase the performance. However, performance improvement depends on the applications due to the various requirements of data transfer. In this paper, we propose architecture for non-volatile memory controller with virtual channels for systems with multiple processors. The proposed architecture has an AMBA AXI master interface for data transfer and an AMBA APB slave interface for writing instructors and reading status and responses to be connected to a host system. Device adapters are connected to the devices and form physical channels. It can respond to the requests of the multiple processors by configuring virtual channels which have a single or multiple physical channels and can be activated independently. The waiting times and the transfer times of memory requests can be traded-off dynamically for the better system performance. An eMMC controller is designed using Verilog-HDL according to the proposed architecture, and is implemented using an FPGA. The operation of the controller is verified by simulation and measurement.

Free Paper Presentation : OS-39 ; Association Between COPD and Educational Level in Korean Adult Population

( Chanho Lee ),( Young Sam Kim ) 대한결핵 및 호흡기학회 2014 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.118 No.-

Background: Chronic obstructive pulmonary disease(COPD) has been one of the major diseases and prevalence and mortality is still increasing worldwide. Methods: Korean National Health and Nutrition Examination Survey(KNHANES) is a nationwide cross-sectional survey of the Korean population and 50,405 subjects performed health and nutritional survey during fourth and fifth KNHANES. Among them, 25,812 subjects aged over 40 years old performed spirometry and a trained interviewer administered a questionnaire on respiratory diseases and various health-related information, including educational level, residential pattern, income, smoking, and other risk factors of COPD. The educational level was classified into four groups and household income was stratified into 4 quartiles. The statistical analyses were carried out using SAS 9.3 (SAS Institute Inc.). T-test, Chi-square test and logistic regression analysis were done. Results: Data from 15,971 adults who performed spirometry adequately were used for this analysis. Of all subjects, 6,871 (43.0%) were male and 9,100 (57.0%) were female. The mean age was 56.7 for men and 57.1 for women. Prevalence of COPD, defined as FEV₁/ FVC<0.7, was 13.6% (22.7% male; 6.7% female). COPD is more prevalent in older age group, male gender, heavy smoker and lower income and educational level population. Multivariate analysis showed that older age, male gender, smoking status, and lower educational level were significant independent risk factors for COPD. The prevalence of smoker is higher and duration of smoking is longer in lower educational level group and total amount of smoking expressed as pack-year is bigger. Conclusions: Low educational level may considered as an independent risk factor of COPD in Korean adult population and further study is needed.

A New Culling Scheme for Low Power 3D Graphic Processors

Chanho Lee,Kyeongeun Choi 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7

Recently, portable devices employ applications using 3D graphics such as 3D games and 3D navigations. The portable devices require small area and low power consumption. We propose an efficient culling scheme for low power 3D graphics processors. The proposed culling scheme consists of the selection and back-face culling in the geometry engine and the elimination of pixels outside in the rasterizer engine. The new scheme reduced both the hardware complexity and the number of operation cycles of culling operations. We design a 3D graphic pipeline using Verilog-HDL according to the proposed scheme, and verify it on an FPGA prototyping board. The latency of the proposed architecture is reduced by 15 cycles and the gate count of the synthesized result is reduced by 8%.