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다중 안테나 다중 사용자 환경에서 최대 성능에 근접하는 선형 precoding 기법
장승훈,김동구,양장훈,장규환 한국통신학회 2009 韓國通信學會論文誌 Vol.34 No.4
본 논문은 최적 전송률에 가까운 성능을 보이는 선형 precoding 기법을 제안한다. MMSE precoding은 ZF precoding 방식보다 우수한 평균 자승 오차 성능을 가진다. 반면 MMSE precoding 방식의 전송률은 낮은 SNR 범위에서는 ZF 방식에 비해 개선된 성능을 보여주지만 높은 SNR에서는 오히려 성능 열화현상을 보인다. 본 논문에서는 최적 전송률에 근접하는 선형 precoding 기법을 제안한다. 제안된 방식은 ZF precoding방식에서 사용되는 역행렬 연산을 전송율이 최대화될 수 있도록 정규화(regularization)하는 방식이고 이를 위한 간단한 수치 알고리즘이 제안된다. 또한 그 과정에서 낮은 복잡도를 가지는 간단한 전력 재할당에 의한 regularization 방식이 제안된다. 시뮬레이션과 성능분석을 통해 제안된 방식이 모든 SNR 범위에서 기존의 ZF precoding 방식과 MMSE precoding방식보다 높은 전송률을 가짐을 보인다. 또한 제안된 방식은 채널 추정 오차가 존재하는 경우에도 기존의 선형 precoding 방식과 비교하여 성능 이득을 유지하면서 채널 추정 오차에 강인함을 가진다.
장승훈,신승수,김혜영,임현우,김재우,박인규,김영환,이계영,이경수,이종목,황보빈,백상현,김진환,성낙진,이상현,황승식,김수영,김열,이원철,성숙환,박보영 대한의사협회 2015 대한의사협회지 Vol.58 No.4
Lung cancer is the leading cause of cancer death in many countries, including Korea. The majority of patients are inoperable at the time of diagnosis because symptoms are typically manifested at an advanced stage. A recent large clinical trial demonstrated significant reduction in lung cancer mortality by using low dose computed tomography (LDCT) screening. A Korean multisociety collaborative committee systematically reviewed the evidences regarding the benefits and harms of lung cancer screening, and developed an evidence-based clinical guideline. There is highlevel evidence that annual screening with LDCT can reduce lung cancer mortality and all-cause mortality of high-risk individuals. The benefits of LDCT screening are modestly higher than the harms. Annual LDCT screening should be recommended to current smokers and ex-smokers (if less than 15 years have elapsed after smoking cessation) who are aged 55 to 74 years with 30 pack-years or more of smoking-history. LDCT can discover non-calcified lung nodules in 20 to 53% of the screened population, depending on the nodule positivity criteria. Individuals may undergo regular LDCT follow-up or invasive diagnostic procedures that lead to complications. Radiation-associated malignancies associated with repetitive LDCT, as well as overdiagnosis, should be considered the harms of screening. LDCT should be performed in qualified hospitals and interpreted by expert radiologists. Education and actions to stop smoking must be offered to current smokers. Chest radiograph, sputum cytology at regular intervals, and serum tumor markers should not be used as screening methods. These guidelines may be amended based on several large ongoing clinical trial results.
마우스 각종 장기의 Xanthine Dehydrogenase-Xanthine Oxidase 활성도에 미치는 산소 농도의 영향
장승훈,한기정,권년수,이희성 중앙대학교 의과대학 의과학연구소 1993 中央醫大誌 Vol.18 No.2
Xanthine oxidase (XO) derved from xanthine dehydrogenase (XD) during ischemia plays important roles in tissue damage by generating superoxide radicals. In the present study, we examined in vivo regulations of XD-XO activities of various organs by environmental oxygen tension. Mice were exposed to 100% oxygen for 3, 10, or 30 h, or 7% oxygen (73% nitrogen) for 4h. XD-XO activities of liver, kidney, lung and brain were measured. The enzyme activities in both liver and kidney were markedly increased by the treatment with 100% oxygen. In the liver the enhanced activity was sustained until 30 h, while the elevated renal activity was found only in the mouse treated for 10 h. XD-XO activities were decreased in lung and brain by the treatment with 100% oxygen. When mice were exposed to 7% oxygen, XD-XO activity was markedly decreased in lung and brain, while the activites in liver and kidney were not significantly changed. These results indicate that XD-XO can be regulated by the environmental oxygen tension, and the regulation is organ-specific.
음곡에 시술한 석위약침이 Lipopolysaccharide로 유도된 흰쥐의 신장염에 미치는 영향
장승훈,김재홍,임윤경 대한침구의학회 2015 대한침구의학회지 Vol.32 No.3
Objectives : The purpose of this study is to investigate the effects of Pyrrosiae Herba herbal- acupuncture(PH-HA) at KI10(Umgok) on nephritis induced by lipopolysaccharide(LPS) in rats. Methods : Rats were assigned to four groups: normal, LPS, saline and PH-HA. Rats in the saline and PH-HA groups were treated with saline injection and PH-HA respectively at KI10, three times over the period of one week. All animals, except those in the normal group, were injected intra-peritoneally with LPS to induce nephritis. WBC, in blood, tumor necrosis factor alpha(TNF-α), cytokine-induced neutrophil chemoattractant 1(CINC-1), blood urea nitrogen(BUN), creatinine in serum, urinal volume, total protein creatinine in urine, and renal myeloperoxidase (MPO) were analyzed. Results : 1. PH-HA group showed significantly reduced levels of serum BUN, serum creatinine, TNF-α, and CINC-1 compared to the LPS group. Furthermore, a significant increase in urine output and more significant decreases in total protein in urine and MPO in renal tissue were observed in the PH-HA group when compared to the LPS group. 2. The PH-HA group showed significantly reduced levels of serum creatinine and renal MPO, and a more significant increase in urine output compared to the saline group. Conclusions : According to these results, it is postulated that PH-HA at KI10 has anti- inflammatory and renal-protective effects on LPS-induced nephritis in rats, and both acupoint KI10 and the herb Pyrrosiae Herba made contributions to these effects. Further studies on the interaction between acupoint KI10 and the herb Pyrrosiae Herba may be needed.