• 대한전자공학회논문지SP
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• 제48권3호
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• pp.119-124
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• 2011

보간 필터는 통신과 멀티미디어 응용프로그램에 널리 사용된다. 다항식 보간은 보간된 값을 얻기 위해서 입력정보에 따른 다항식의 계수를 계산한다. 최근에 다항식 보간방법의 성능을 향상시키기 위하여 보조필터를 이용한 FIR 보간방법이 제안되었다. 본 논문에서는 최대값 또는, 최소값 계산 등 특정 순간의 보간 값만 필요한 응용에서 보간필터의 성능을 더욱 향상시킬 수 있는 보조필터를 이용한 가중치 적용 보간방법을 제안한다. 제안한 방법을 X-선 형광분석장치에서 사용되는 정규분포곡선에 대한 보간에 적용하여 기존 보간방법에 비해 더욱 우수한 보간 성능이 제공됨을 보인다.

• 한국주거학회논문집
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• 제16권5호
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• pp.91-98
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• 2005

The purpose of this study is to analysis of propagation characteristics for floor impact noise in attendance upon investigating standard of insulation performance, measurement and evaluation, understanding characteristics of a measuring factor for floor impact noise in apartment houses. Four cases which was before occupied apartment in Daegu was selected for experiment. Floor impact noise of measurement and evaluation method which are specified in the Korea Standard 2810-1, 2810-2, 2863-1 and 2863-2 was selected for this study. As the result of this study, 1) Especially, there is not a difference for apartment size, but the apartment of 40py type is lower than 30py's about $1\~2\;dB$ for light-weighted and heavy weighted impact sound. 2) The floor impact sound insulation performance is similar about measurement location of the same floor structure. 3) The floor impact sound insulation performance is not a difference about the slab area.

• 대한전자공학회논문지
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• 제26권4호
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• pp.98-105
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• 1989

선택적인 주파수 특성을 가지고 있는 인간의 시각 시스템(HVS)을 왈쉬함수로 표현되는 아다마르변환 영역에서 적용하였다. 아다마르 기본함수의 주파수 성분을 구하여 시각 시스템을 모델링하였으며 이때 오차측정의 기준으로서 저 전송율 변환 부호화기에서 중요한 요소인 블록 경계상의 오차와 평균자승 오차를 사용한 결과 인간이 가장 높은 감도를 갖는 공간 주파수는 이산 여현 변환의 경우보다 높게 나타났다. 부호화기에서 HVS 모델을 적용하여 시각적 감도가 높거나 중요한 정보만을 전송하고 북호화기에서는 역하중이 없는 방법을 제시하였다. 블록과 블록이 교차하는 영역에서 특히 크게 나타나는 오차를 감소시키기위해 시각적 하중 방법을 사용하였으며 0.8 bpp이하의 전송율에서 인간의 시각 특성에 만족되는 변환부호화를 시험하였다.

• 대한산업공학회지
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• 제39권4호
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• pp.247-252
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• 2013

Korea gas corporation (KOGAS) is responsible for the whole sale of natural gas in the domestic market. It is important to forecast the daily demand of city gas for supply and demand control, and delivery management. Since there is the autoregressive characteristic in the daily gas demand, we introduce a modified autoregressive model as the first step. The daily gas demand also has a close connection with the outdoor temperature. Accordingly, our second proposed model is a temperature-based model. Those two models, however, do not meet the requirement for forecasting performances. To produce acceptable forecasting performances, we develop a weighted average model which compounds the autoregressive model and the temperature model. To examine our proposed methods, the forecasting results are provided. We confirm that our method can forecast the daily city gas demand accurately with reasonable performances.

• 한국측량학회지
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• 제37권5호
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• pp.293-302
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• 2019

In mountain accident events, it is important for the search team commander to determine the search area in order to secure the Golden Time. Within this period, assistance and treatment to the concerned individual will most likely prevent further injuries and harm. This paper proposes a method to determine the search priority area based on missing persons behavior and missing persons incidents statistics. GIS (Geographic Information System) and MCDM (Multi Criteria Decision Making) are integrated by applying WLC (Weighted Linear Combination) techniques. Missing persons were classified into five types, and their behavioral characteristics were analyzed to extract seven geographic analysis factors. Next, index values were set up for each missing person and element according to the behavioral characteristics, and the raster data generated by multiplying the weight of each element are superimposed to define models to select search priority areas, where each weight is calculated from the AHP (Analytical Hierarchy Process) through a pairwise comparison method obtained from search operation experts. Finally, the model generated in this study was applied to a missing person case through a virtual missing scenario, the priority area was selected, and the behavioral characteristics and topographical characteristics of the missing persons were compared with the selected area. The resulting analysis results were verified by mountain rescue experts as 'appropriate' in terms of the behavior analysis, analysis factor extraction, experimental process, and results for the missing persons.

• Korean Journal of Radiology
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• 제25권7호
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• pp.623-633
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• 2024

This study systematically reviewed the role of diffusion-weighted imaging (DWI) in the assessment of molecular prognostic biomarkers in breast cancer, focusing on the correlation of apparent diffusion coefficient (ADC) with hormone receptor status and prognostic biomarkers. Our meta-analysis includes data from 52 studies examining ADC values in relation to estrogen receptor (ER), progesterone receptor (PgR), human epidermal growth factor receptor 2 (HER2), and Ki-67 status. The results indicated significant differences in ADC values among different receptor statuses, with ER-positive, PgR-positive, HER2-negative, and Ki-67-positive tumors having lower ADC values compared to their negative counterparts. This study also highlights the potential of advanced DWI techniques such as intravoxel incoherent motion and non-Gaussian DWI to provide additional insights beyond ADC. Despite these promising findings, the high heterogeneity among the studies underscores the need for standardized DWI protocols to improve their clinical utility in breast cancer management.

• Clinical and Experimental Pediatrics
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• 제53권7호
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• pp.759-765
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• 2010

Purpose: This study evaluated the clinical manifestations of and risk factors for pituitary insufficiency in children and adolescents with Rathke's cleft cysts. Methods: Forty-four patients with Rathke's cleft cysts younger than 19 years who visited Seoul National University Children's Hospital between January 1995 and September 2009 were enrolled. Rathke's cleft cysts were confirmed histologically through an operation in 15 patients and by brain magnetic resonance imaging (MRI) in 29 patients. The clinical, hormonal, and imaging features were reviewed retrospectively. Results: The clinical presentation of symptomatic patients was as follows: headache (65%), endocrinopathy (61%), and visual disturbance (19%). Endocrinopathy included central precocious puberty (18%), diabetes insipidus (14%), general weakness (11%), and decreased growth velocity (7%). After surgery, hyperprolactinemia resolved in all patients, but growth hormone insufficiency, hypothyroidism, and diabetes insipidus did not improve. Pituitary insufficiency except gonadotropin abnormality correlated significantly with severe headache, visual disturbance, general weakness, and cystic size. Suprasellar extension of cysts and high signals in the T2-weighted image on brain MRI were related to hypothyroidism, hypocortisolism, and diabetes insipidus. Multivariable linear regression analysis showed that only general weakness was a risk factor for pituitary insufficiency ($R^2$=0.549). Conclusion: General weakness is a risk factor for pituitary insufficiency in patients with Rathke's cleft cysts. When a patient with a Rathke's cleft cyst complains of general weakness, the clinician should evaluate pituitary function and consider surgical treatment.

• 한국국방경영분석학회지
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• 제33권1호
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• pp.1-18
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• 2007

본 연구의 목적은 비교항목들의 척도가 서로 상이하고 측정치를 산정하기 곤란한 대안들의 의사결정시 대안 비교를 과학적으로 할 수 있는 지식기반 대안분석모델(KAAM)을 제안하는 것이다. KAAM은 기존의 방법인 Saaty, Delphi/Shang, Consensus, SAW 기법을 근간으로 하는 하이브리드 방식으로 구성되고 엑셀기반으로 구현하였다. 또한, 무기체계 획득사업의 사전분석 단계에서 최적 획득방안을 선정하는 실증적 사례를 적용함으로서 KAAM의 유용성을 확인하였다.

• ETRI Journal
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• 제45권2호
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• pp.213-225
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• 2023

Physical layer security (PLS) can improve the security of both terrestrial and nonterrestrial wireless communication networks. This study proposes a simplified framework for nonterrestrial cyclic prefixed orthogonal variable spreading factor (OVSF)-encoded multiple-input and multiple-output nonorthogonal multiple access (NOMA) systems to ensure complete network security. Various useful methods are implemented, where both improved sine map and multiple parameter-weighted-type fractional Fourier transform encryption schemes are combined to investigate the effects of hybrid PLS. In addition, OVSF coding with power domain NOMA for multi-user interference reduction and peak-toaverage power ratio (PAPR) reduction is introduced. The performance of $\frac{1}{2}$-rated convolutional, turbo, and repeat and accumulate channel coding with regularized zero-forcing signal detection for forward error correction and improved bit error rate (BER) are also investigated. Simulation results ratify the pertinence of the proposed system in terms of PLS and BER performance improvement with reasonable PAPR.

• 유통과학연구
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• 제13권9호
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• pp.37-45
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• 2015

Purpose - This paper's aim is to investigate whether or not gross profitability explains the cross-sectional variation of the stock returns in the Korean stock market. Gross profitability is an alternative profitability measure proposed by Novy-Marx in 2013 to predict cross-sectional variation of stock returns in the US. He shows that the gross profitability adds explanatory power to the Fama-French 3 factor model. Interestingly, gross profitability is negatively correlated with the book-to-market ratio. By confirming the gross profitability premium in the Korean stock market, we may provide some implications regarding the well-known value premium. In addition, our empirical results may provide opportunities for the fund distribution industry to promote brand new styles of funds. Research design, data, and methodology - For our empirical analysis, we collect monthly market prices of all the companies listed on the Korea Composite Stock Price Index (KOSPI) of the Korea Exchanges (KRX). Our sample period covers July1994 to December2014. The data from the company financial statementsare provided by the financial information company WISEfn. First, using Fama-Macbeth cross-sectional regression, we investigate the relation between gross profitability and stock return performance. For robustness in analyzing the performance of the gross profitability strategy, we consider value weighted portfolio returns as well as equally weighted portfolio returns. Next, using Fama-French 3 factor models, we examine whether or not the gross profitability strategy generates excess returns when firmsize and the book-to-market ratio are controlled. Finally, we analyze the effect of firm size and the book-to-market ratio on the gross profitability strategy. Results - First, through the Fama-MacBeth cross-sectional regression, we show that gross profitability has almost the same explanatory power as the book-to-market ratio in explaining the cross-sectional variation of the Korean stock market. Second, we find evidence that gross profitability is a statistically significant variable for explaining cross-sectional stock returns when the size and the value effect are controlled. Third, we show that gross profitability, which is positively correlated with stock returns and firm size, is negatively correlated with the book-to-market ratio. From the perspective of portfolio management, our results imply that since the gross profitability strategy is a distinctive growth strategy, value strategies can be improved by hedging with the gross profitability strategy. Conclusions - Our empirical results confirm the existence of a gross profitability premium in the Korean stock market. From the perspective of the fund distribution industry, the gross profitability portfolio is worthy of attention. Since the value strategy portfolio returns are negatively correlated with the gross profitability strategy portfolio returns, by mixing both portfolios, investors could be better off without additional risk. However, the profitable firms are dissimilar from the value firms (high book-to-market ratio firms); therefore, an alternative factor model including gross profitability may help us understand the economic implications of the well-known anomalies such as value premium, momentum, and low volatility. We reserve these topics for future research.