• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.89-97
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• 2011

We analyze the performance of various techniques to overcome degradation of performance of STAP caused by nonhomogeneous clutter. The performance of NHD that used to eliminate outliers from nonhomogeneous clutter is improved by using the projection statistics(PS) that is robust to multiple outliers. The method of clutter covariance matrix estimation using a median value and the conventional method are also investigated and then compared. From the simulation results of STAP, the method of clutter covariance matrix estimation using a median value shows better performance than the conventional method for the calculation of the SINR loss, and MSMI for the single target and the multiple targets regardless of the NHD methods.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.4
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• pp.120-128
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• 2012

In this paper, we propose a modified iterative pre-whitening projection statistics (MIPPS) scheme for improving multi-target detection performance in non-homogeneous clutter environments. As a non-homogeneity detection (NHD) technique of space-time adaptive processing algorithm for airborne radar, the MIPPS scheme improves the average detection probability of weak target when multiple targets with different reflection signal intensities are located in close range. Numerical results show that the conventional NHD schemes suffers from the masking effect by strong targets and clutters and the proposed MIPPS scheme outperforms the conventional schemes with respect to the average detection probability of the weak target at low signal-to-clutter ratio.

• Koreanishche Zeitschrift fur Deutsche Sprachwissenschaft
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• v.9
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• pp.23-44
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• 2004

Das Forschungsziel dieser Untersuchung ist es, den linguistischen Begriff der Analogie zu definieren, und die auftretenden analogischen Ausgleichsprozesse vom Mittelhochdeutschen zum Neuhochdeutschen und auch im Neuhochdeutschen selbst insbesondere im System der starken Verben vorzuzeigen und zu $erkl\"{a}ren$. Und diese Forschungsergebnisse sind wie folgt. $Au{\ss}er$ dem Phonemwandel, der immer das Phonemsystem tangiert, gibt es M$Lautver\"{a}nderungen$, die auf assoziativer Ubertragung von Lautungen aus konkurrierenden sprachlichen Formen beruhen, die sog. Analogiebildungen. $N\"{a}mlich$ in der sprachlichen Entwicklung vom Mittelhochdeutschen zum Neuhochdeutschen zeigt sich eine sehr starke innere Tendenz der Sprache, diese durch $gesetzm\"{a}{\ss}igen$ Lautwandel entstandene Formenvielfalt innerhalb eines Paradigmas zu vereinheitlichen. Das $hei{\ss}t$; Analogischer Ausgleich ist als universaller sprachlicher Simplifizierungsprozess zu werten. Diese sprachlichen Ausgleichsprozesse werden als analogischer Ausgleich bzw. paradigmatischer Ausgleich bezeichnet. $Gem\"{a}{\ss}$ der Klassifikation von Frey teile ich auch analogischen Ausgleich Bereichen ein: a) im Stammsilbenvokalismus b) im Stammsilbenkonsonantismus c) in den Konjugationsendungen. (equation omitted) (c) Analogischer AusgIeich der Konjugationsendungen: Die Endung der 1. Pers. P1. $Pr\"{a}s$. Ind. im Althochdeutschen, -ames wird durch die Endung der 1. Pers. P1. $Pr\"{a}s$. Konj., -em ersetzt. $fr\"{h}ahd$. wir nem-ames > ahd. wir nem-em > mhd. wir nem-en > nhd. wir nehm-en Die Endung der 3. Pers. P1. $Pr\"{a}s$. Ind. im Mittelhochdeutschen, -ent wird durch die Endung der 1. Pers. P1. $Pr\"{a}s$. Ind., -en ersetzt. ahd. sie nem-ant > fruhmhd. sie nem-ent > mhd. sie nem-en > nhd. sie nehm-en Als Markierung der 2. Pers. Sg. war -st urprunglich nur in der 2. Pers. Sg. $Pr\"{a}s$. Ind. vorhanden: ahd. nim-ist > mhd. nim-est > nhd. nimm-st Von hier aus breitet es sich aus in die 2. Pers. Sg. Pras. Konj. ahd. nem-es > mhd. nem-est > nhd. nehm-est Vom $Pr\"{a}s$. Ind/Konj. breitet sich -st in das $Pr\"{a}t$. Ind. aus; ahd. nam-i > fruhmhd. naem-e > mhd. naem-est > nhd nahm-st Und $schlie{\ss}lich$ greift es vom $Pr\"{a}t$. Ind. auch auf den Konj. $\"{u}ber$. ahd. nam-is > mhd. nem-est > nhd. $n\"{a}hm-st$

• Journal of the Institute of Convergence Signal Processing
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• v.10 no.1
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• pp.72-79
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• 2009

This paper describes the performance evaluation of NHD(nonhomogeneity detector) for STAP(space-time adaptive processing) airborne radar according to various normalization methods in the nonhomogeneous clutter environment. In practice, the clutter can be characterized as random variation signals, because it sometimes includes signals with very large magnitude like impulsive signal due to the system environment. The received interference signals are composed of homogeneous and nonhomogeneous data. In this situation, NHB is needed to maintain the STAP performance. The normalization using the NHD result is an effective method for removing the nonhomogeneous data. The optimum normalization can be performed by a representative value considered with a characteristic of the given data, so we propose the K-means clustering algorithm. The characteristic of random variation data due to nonhomogeneous clutters can be considered by the number of clusters, and then the representative value for selecting the homogeneous data is determined in the clustering result. In order to reflect a characteristic of the nonstationary interference data, we also investigate the algorithm for a calculation of the proper number of clusters. Through our simulations, we verified that the K-means clustering algorithm has very superior normalization and target detection performances compared with the previous introduced normalization methods.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.1
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• pp.20-27
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• 2010

In this paper, we presented a signal model of STAP and actual environment of clutter. The novel estimation method of clutter covariance matrix using median value is proposed to overcome serious performance degradation after NHD in nonhomogeneous clutter. Eigen value characteristic is improved through diagonal loading. Target detection ability and SINR loss of the proposed method though MSMI statistic is also compared with conventional method using average value. The simulation results, confirm the proposed method has better performance than others.

• Journal of the Korean earth science society
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• v.36 no.5
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• pp.437-446
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• 2015

Many edge detection methods, based on horizontal and vertical derivatives, have been introduced to provide us with intuitive information about the horizontal distribution of a subsurface anomalous body. Understanding the characteristics of each edge detection method is important for selecting an optimized method. In order to compare the characteristics of the individual methods, this study applied each method to synthetic magnetic data created using homogeneous prisms with different sizes, the numbers of bodies, and spacings between them. Seven edge detection methods were comprehensively and quantitatively analyzed: the total horizontal derivative (HD), the vertical derivative (VD), the 3D analytic signal (AS), the title derivative (TD), the theta map (TM), the horizontal derivative of tilt angle (HTD), and the normalized total horizontal derivative (NHD). HD and VD showed average good performance for a single-body model, but failed to detect multiple bodies. AS traced the edge for a single-body model comparatively well, but it was unable to detect an angulated corner and multiple bodies at the same time. TD and TM performed well in delineating the edges of shallower and larger bodies, but they showed relatively poor performance for deeper and smaller bodies. In contrast, they had a significant advantage in detecting the edges of multiple bodies. HTD showed poor performance in tracing close bodies since it was sensitive to an interference effect. NHD showed great performance under an appropriate window.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.480-480
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• 2013

태양에너지는 신재생 에너지 중에서 무한한 에너지원으로서 태양에너지에 대한 활발한 연구가 이루어지고 있다. 그 중에서도 결정형 실리콘 태양전지에 대해 다양한 연구가 진행 중이다. 이러한 실리콘 태양전의 제작은 실리콘 식각 용액을 이용하여 기판의 절삭 손상된 부분을 식각한 후 텍스쳐링(texturing) 공정을 통해 표면의 흡수율을 높이고, 반면에 반사율을 감소시킨다. 텍스쳐링 공정이 끝난 후 도핑 공정을 통해 에미터(emitter)를 형성, 반사방지막을 증착, 기판의 전면과 후면에 페이스트를 바르고 스크린인쇄법으로 전극을 형성한 후 마지막으로 형성된 전극을 소성 공정을 통해 전극이 에미터와 접촉하면 태양전지가 완성된다. 하지만 텍스쳐링 공정을 통해 만들어진 피라미드 구조는 도핑공정을 하게 되면, 꼭짓점 부분의 균일한 도핑이 이루어지지 않는다. 이러한 균일하지 않은 공정으로 인해 전극 소성 공정에서 일부의 에미터층을 뚫어버리게 되므로 누설전류가 증가하게 된다. 그래서 본 논문에서는, 변환 효율을 개선시키기 위해 표면 구조와 반사방지막의 열처리 공정에 대한 연구를 하였다. 우선 피라미드 구조를 균일하게 만들었으며, 반사방지막 형성 후 열처리를 하여 소수 캐리어 수명을 증가시켰으며, 누설전류를 감소하였다. 균일한 도핑 및 전극 형성을 용이하게 하는 부드러운 피라미드 구조를 형성하기 위해 HND (HF：HNO3 : D.I wafer=5 : 100 : 100) 용액을 사용하여 식각하였다. 그 결과 직렬저항은 NHD용액을 사용하여 300초 동안 식각하였을 때 $1.284{\Omega}$ 낮아지는 결과를 얻을 수 있었으며, 도핑을 균일화하여 누설전류를 감소시킬 수 있었다.