• Journal of Advanced Information Technology and Convergence
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• v.10 no.1
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• pp.1-14
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• 2020

Antenna selection is a method to enhance the performance of spatial multiplexing multiple-input multiple-output (MIMO) systems, which can achieve the diversity order of the full MIMO systems. Although various selection criteria have been studied in the literature, they should be adjusted to the detection operation implemented at the receiver. In this paper, antenna selection methods that optimize the post-processing signal-to-noise ratio (SNR) and eigenvalue are considered for the lattice reduction (LR)-based receiver. To develop a complexity-efficient antenna selection algorithm, the incremental selection strategy is adopted. Moreover, for improvement of performance, an additional iterative selection method is presented in combination with an incremental strategy.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.4
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• pp.429-438
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• 1986

In this paper we have designed and implemented a real-time, full-duplex SBC (sub-band coding) codec at 16kbps using a high speed digital signal processor, NEC 7720. The SBC codec employs a QMF(quadrature mirror filter) filter bank based on the tree structures of two-band analysis-synthesis pairs to partition speech signal into 4 octabe bands. Computer simulation has been done to investigate the effect of fixed-point computation of the NEC 7720. Three different performance measures, the conventional signal-to-noise ratio, the informal listening test, and an LPC(linear predictive coding)distance measure, have been used in this simulation. The necessary parameters have been optimized through the simulation. The developed hardware and software have been tested in real-time operation using a hardware emulator.

• Korean Journal of Materials Research
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• v.34 no.7
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• pp.363-369
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• 2024

In this study, the magnetocaloric effect and transition temperature of bulk metallic glass, an amorphous material, were predicted through machine learning based on the composition features. From the Python module 'Matminer', 174 compositional features were obtained, and prediction performance was compared while reducing the composition features to prevent overfitting. After optimization using RandomForest, an ensemble model, changes in prediction performance were analyzed according to the number of compositional features. The R2 score was used as a performance metric in the regression prediction, and the best prediction performance was found using only 90 features predicting transition temperature, and 20 features predicting magnetocaloric effects. The most important feature when predicting magnetocaloric effects was the 'Fe' compositional ratio. The feature importance method provided by 'scikit-learn' was applied to sort compositional features. The feature importance method was found to be appropriate by comparing the prediction performance of the Fe-contained dataset with the full dataset.

• Journal of Chest Surgery
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• v.25 no.11
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• pp.1169-1179
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• 1992

To determine the period and degree of full recovery of postoperative pulmonary function, the author performed seiral pulmonry function test with spirometry at preoperative period and 1st, 2nd, 3rd, 4th, 6th and 8th postoperative week in 64 patients who underwent chest surgery form 1990. 1. to 1990. 8. at Dep. of Thoracic & Cardiovascular surgery, Pusan National University Hospitcal, Pusan, Korea 28 patients underwent lung resection[Group A], 14 patients mediastinal and other thoracic surgery[Group B], and 22 patients heart surgery with cardiopulmonary bypass[Group C]. Al of them recovered normally and discharged without any complications. Their serial changes of pulmonary function test were compaired and its results was as follows; l. Over all mean recovery time of restrictive ventilatory function tests[ie, VC, ERV, IC, FEF1, FVC, FEF200-1200, MVV] were 4th & 6th postoperative week, and that of obstructive ventilatory function tests[ie., EFE25-75%, Vmax50] were 2nd postoperative week. 2. In patient who underwent lung resection surgery[Group A], FEF1 recovered in 4th~6th postoperative week and its ratio to preoperative value was 70% in pneumonectomy, and 75% in lobectomy. FVC recovered in 4th~6th postoperative week and its ratio to preoperative value was 65% in pneumonectomy, and 80% in lobectomy. MVV was recovered in 4th~8th postoperative week and recovery ratio was 80%, FEF200-1200 was recovered at 4th~6th postoperative week and its recovery ratio was 70%, FEF25-75% and Vmax50 was recovered in 2nd~4th postoperative week and recovered nearly to preoperative level. 3. In patient who underwent mediastinal and other thoracic surgery[Group B], FEV1 and FVC and recovered in 4th~6th postoperative week and the recovery ratio of FVC in blebectomy was 90%. MVV reached preoperative level in 4th~8th postoperative week. FEF200-1200, FEF25-75% and Vmax50 were recovered in 2nd~4th postoperative week and the recovery of FEF25-75% and Vmax50 in blebectomy was prominant. 4. In patient who underwent heart surgery[Group C], FEV1 and FVC were recovered in 4th~6th postoperative week. The recover ratio of FEF25-75% and Vmax50 was delaied to 6th~8th postoperative week From the above results we concluded that the recovery time of posoperative restrictive ventilatory disorder was 4th postoperative week and pulmonary complication would possibly occure during that period. So more intensive observations will be needed.

• Transactions of Materials Processing
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• v.22 no.5
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• pp.264-268
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• 2013

Aluminum clad sheets for brazing materials in the automotive heat exchangers are required to exhibit both high strength and excellent erosion resistance. In this study, the effects of microstructural changes on the property of clad sheets due to thermomechanical treatment were investigated. The clad sheets were fabricated by roll bonding of twin-roll-cast AA3527 and AA4343 alloys followed by cold rolling down to a thickness of 0.22mm. Partial or full annealing was conducted at the final thickness in order to improved the erosion resistance while keeping the proper strength. Since full annealing was achieved for a temperature of $400^{\circ}C$, annealing treatments were performed at 360, 380, and $400^{\circ}C$, respectively. The tensile strength of 3527/4343 clad material was found to be inversely proportional to the annealing temperature before the brazing heat treatment. After this latter treatment, however, the tensile strength of the clad material was about 195~200MPa regardless of the annealing temperature. The erosion depth ratio of the clad annealed at $400^{\circ}C$ was 8.8% (the lowest), while that of the clad annealed at $380^{\circ}C$ was 17% (the highest). The effect of annealing temperature on the tensile and erosion properties of 3527/4343 aluminum clad sheets was elucidated by means of microstructural analyses.

• Magazine of the Korea Concrete Institute
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• v.7 no.2
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• pp.165-174
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• 1995

It is well known that the behavior of R /C members under static cyclic loading is somewhat different from that under dynamic cyclic loading, such as earthquake loading, because static loading rate is substantially lower than that corresponding to the Frequencies of seismic excitation. The purpose of this research is to estabilish the reliance for modeling techniques of small-scale specirr~ens subjected to dynamic cyclic loading. This research focused on the similitude requirements for reinforced concrete frame structures subjeced to dynamic cyclic loading. Length scale ratio of specimens were 1 : 2 : 4, and eleven specimens were tested at the frequencies of 0.0025Hz-2.OHz. It was confirmed that rnode1ir.g techniques based on the similitude requirements were useful methods to evaluate the behavior of full-size R /C structures subjected to earthquake type loading.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.96-103
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• 2006

To establish of standard technique of nano-length measurement in 2D plane, new AFM system has been designed. In the long range (about several tens of ${\mu}m$), measurement uncertainty is dominantly affected by the Abbe error of XY scanning stage. No linear stage is perfectly straight; in other words, every scanning stage is subject to tilting, pitch and yaw motion. In this paper, an AFM system with minimum offset of XY sensing is designed. And XY scanning stage is designed to minimize rotation angle because Abbe errors occur through the multiply of offset and rotation angle. To minimize the rotation angle optimal design has performed by maximizing the stiffness ratio of motion direction to the parasitic motion direction of each stage. This paper describes the design scheme of full AFM system, especially about XY stage. Full range of fabricated XY scanner is $100{\mu}m\times100{\mu}m$. And tilting, pitch and yaw motion are measured by autocollimator to evaluate the performance of XY stage. As a result, XY scanner can have good performance. Using this AFM system, 3um pitch specimen was measured. The uncertainty of total system has been evaluated. X and Y direction performance is different. X-direction measuring performance is better. So to evaluate only ID pitch length, X-direction scanning is preferable. Its expanded uncertainty(k=2) is $\sqrt{(3.96)^2+(4.10\times10^{-5}{\times}p)^2}$ measured length in nm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.596-599
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• 2004

The robotic $CO_2$ welding is a manufacturing process to produce high quality joints for metal and it could provide a capability of full automation to enhance productivity. Despite the widespread use in the various manufacturing industries, the full automation of the robotic $CO_2$ welding has not yet been achieved partly because the mathematical model for the process parameters of a given welding task is not fully understood and quantified. Several mathematical models to control welding quality, productivity, microstructure and weld properties in arc welding processes have been studied. However, it is not an easy task to apply them to the various practical situations because the relationship between the process parameters and the bead geometry is non-linear and also they are usually dependent on the specific experimental results. Practically, it is difficult, but important to know how to establish a mathematical model that can predict the result of the actual welding process and how to select the optimum welding condition under a certain constraint. In this research, an attempt has been made to develop an intelligent algorithm to predict the weld geometry (top-bead width, top-bead height, back-bead width and back-bead height) as a function of key process parameters in the robotic $CO_2$welding. To achieve this above objective, Taguchi method was employed using five different process parameters (tip gap, gas flow rate, welding speed, arc current, welding voltage) as a guide for optimization of process parameters.

• The Journal of Internal Korean Medicine
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• v.18 no.1
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• pp.156-174
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• 1997

This study is investigation of clinical statistics toward to old patients of 164 persons over full 65 years old to go to hospital in 5 internal medicine department of the Dongguk University Oriental Medicine Hospital for full one year from 1995. 8 to 1996. 7. The results are followings ; 1. The ratio of male and female was 1:1.6, and in offspring figures five persons or more(60.3%) was most. A couple(32.3%) was extremely much in residing forms, but in accordance to sexual distinction in male a couple(51.7%), in female solitude(31.0%) and an eldest son couple(30.0%) was far much. 2. An attack time, first cure was most in western hospital(59.2%), 81.1% of them desired western-oriental medicine cooperation, in a medical fee charging, themselves(50.7%) were far much, and most were affirmative(76.8%) against aging prevention of restorative. 3. Main diseases were cerebral nerve(41.5%) and circulatory system(25.6%), hypertention (23.8%, 9.8%) was most in complication and the past. In defecation constipation(31.7%), in urination frequence(46.7%) was far much. 4. In preventive measures of diseases invigorant(25.6%) and nothing(24.3%) was far much and in a person tending the sick a mate in male(16.7%), a son in female(13.0%) was extremely much. 5. In sexual life most of(91.5%) didn't act, a mate death was 53.1% and female was far much. And paralysis attack was extremely much in 65-74 years old(76.5%).

• Earthquakes and Structures
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• v.10 no.5
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• pp.1125-1141
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• 2016

The direct displacement based design (DDBD) approach is spreading in the field of seismic design for many types of structures. This paper is carried out to present a robust approach for the DDBD procedure for single degree of freedom (SDOF) concentrically braced frames (CBFs). Special attention is paid to the choice of an equivalent viscous damping (EVD) model that represents the behaviour of a series of full scale shake table tests. The performance of the DDBD methodology of the CBFs is verified by two ways. Firstly, by comparing the DDBD results with a series of full-scale shake table tests. Secondly, by comparing the DDBD results with a quantified nonlinear time history analysis (NLTHA). It is found that the DDBD works relatively well and could predict the base shear forces ($F_b$) and the required brace cross sectional sizes of the actual values obtained from shake table tests and NLTHA. In other words, when comparing the ratio of $F_b$ estimated from the DDBD to the measured values in shake table tests, the mean and coefficient of variation ($C_V$) are found to be 1.09 and 0.12, respectively. Moreover, the mean and $C_V$ of the ratios of $F_b$ estimated from the DDBD to the values obtained from NLTHA are found to be 1.03 and 0.12, respectively. Thus, the DDBD methodology presented in this paper has been shown to give accurate and reliable results.