• Wind and Structures
• /
• 제16권2호
• /
• pp.157-178
• /
• 2013

Output-only modal parameter identification is based on the assumption that external forces on a linear structure are white noise. However, harmonic excitations are also often present in real structural vibrations. In particular, it has been realized that the use of forced acceleration responses without knowledge of external forces can pose a problem in the modal parameter identification, because an external force is imparted to its impulse acceleration response function. This paper provides a three-stage identification procedure as a solution to the problem of harmonic and white noise excitations in the acceleration responses of a linear dynamic system. This procedure combines the uses of the mode indicator function, the complex mode indication function, the enhanced frequency response function, an iterative rational fraction polynomial method and mode shape inspection for the correlation-related functions of the force-embedded acceleration responses. The procedure is verified via numerical simulation of a five-floor shear building and a two-dimensional frame and also applied to ambient vibration data of a large-span roof structure. Results show that the modal parameters of these dynamic systems can be satisfactorily identified under the requirement of wide separation between vibration modes and harmonic excitations.

• Journal of Chest Surgery
• /
• 제16권3호
• /
• pp.356-361
• /
• 1983

Pulmonary tuberculosis is still one of unsolved problems in Korea due to increased number of far-advanced and drug-resistant patients, who have poor pulmonary function. We have analyzed 1332 operated Gases during the period of 1958-1981. Annual incidence of the disease decreased from 110 [1960] to 21 [1980]. The ratio between male and female was 7:3 and the age of peak incidence was in the 3rd and 4th decades. Recently, patients below the age of 20 years were slightly decreased, but above 50 years were slightly increased. The patients consisted of far-advanced case in 60% and moderately-advanced in 39% in 1980, as compared with 40% and 59% correspondingly in 1965. Preoperative sputum positively decreased from 91% [1958-1963] to 43.8% [ 1974-1981 ]. Medically treated patients for more than 3 years increased from 16% [1958-1963] to 51% [1974-1981]. From the view of surgical indication, totally destroyed hung increased from 27% [1958-1963] to 4396 [1974-1981 ]. Therefore, pneumonectomy occupied 53.8% of total surgical management recently. Mode of surgical treatment showed that thoracoplasty [33%], resection [57%] in 1958-1963 and thoracoplasty [2%], resection [98%] in 1974-1981. As Semb`s thoracoplasty was the first choice of treatment until 1960, thereafter resection became the choice. Postoperative mortality increased from 1.6-2.096 to 396 recently as well as morbidity. It was mainly due to increased number of poor pulmonary function and postoperative spread of disease. On the basis of our experience, far-advanced and drug-resistant patients increased in number recently, whose pulmonary function was poor. So postoperative mortality and morbidity increased. Proper surgical intervention should be considered before the appearance of resistance for all chemotherapeutic drugs.

• Journal of Chest Surgery
• /
• 제25권1호
• /
• pp.79-85
• /
• 1992

We have analyzed 1559 operated cases during the 32 year period, from October, 1958 to December, 1990. Annual incidence of the surgical treatment decreased from 101[1960] to 25[1990]. The ratio between male and female was 2.1: 1 and the age of peak incidence was in the 3rd and 4th decades. Recently, patients below the age of 20 years were decreased, but above 50 years were much increased. The patients were consisted of far-advanced case in 71.8% and moderately-advanced case in 22.0% in 1990, as compared with 44% and 54% correspondingly in 1960. Preoperative sputum positivity decreased from 91%[1958~1963] to 38%[1982~1990]. Preoperative antituberculous chemotherapy for more than 3 years increased from 16% [1958~1963] to 56.5% [1982~1990]. From the view of surgical indication, totally destroyed lung and destroyed lobe or segment has been main indication. Recently empyema with parenchymal lesion was increased, and so more extensive surgical resection such as pleuropneumonectomy was performed more frequently. The trends in the mode of surgical treatment revealed that thoracoplasty has virtually disappeared and operations required for residuals of pleural disease have increased. Postoperative mortality increased from 1.6-2.0% to 3.6% recently as well as morbidity. On the basis of our study, far-advanced and drug-resistant patients increased in number recently, whose pulmonary function was poor. So postoperative mortality and morbidity was increased despite improved anesthetic and surgical techniques. Proper surgical intervention should be considered before the appearance of resistance for all chemotherapeutic drugs.

• Bulletin of the Korean Chemical Society
• /
• 제20권3호
• /
• pp.285-290
• /
• 1999

In the present paper, we report a molecular dynamics (MD) simulation study for the structure and dynamics of H+ ions in non-rigid dehydrated H12-A zeolite framework at 298.15 K, using the same method we used in our previous studies of rigid and non-rigid zeolite-A frameworks. It is found that two different structures appear, depending on the choice of the Lennard-Jones parameter (σ) for the H+ ion, as is also observed in the study of rigid dehydrated H12-A zeolite framework, but the ranges of σ are different for the two structures. It is also found that some of the H+ ions exchanged their sites without changing the number of H+ ions at each site. The agreement between experimental and calculated structural parameters for non-rigid dehydrated H12-A zeolite is generally quite good. The calculated IR spectrum by Fourier transform of the total dipole moment auto-correlation function shows two major peaks, one around 2700 cm-1 and the other around 7000 cm-1. The former appears in the calculated IR spectra of non-rigid zeolite-A framework only system and the latter remains unexplained except, perhaps, as an indication of a new formation of a vibrational mode of the framework due to the adsorption of the H+ ions.

• 한국안광학회지
• /
• 제14권2호
• /
• pp.9-14
• /
• 2009

목적: 본 연구는 근거리 작업자의 주시선 각도 변화에 따른 조절효율과 순목횟수, 조절래그에 대한 상관관계를 조사하여 독서, 컴퓨터나 TV등을 오랜 시간동안 주시할 때 두통을 동반하거나 눈의 피로를 호소하는 원인 및 안정피로를 완화시키는 적합한 주시각도를 알아보고자 실시하였다. 방법: 컴퓨터 등의 근거리 작업을 많이 하는 20세에서 36세까지의 대학생 남자 12명과 여자 15명 총 27명을 대상으로 근거리 작업자의 주시선의 각도 변화에 따른 조절효율과 눈 깜빡임 횟수, 조절래그량의 크기를 조사하였다. 굴절이상을 완전교정한 후 포롭터를 근거리 모드로 전환하여 40 cm에 근거리 시표를 위치시키고 수평면을 기준으로 $40^{\circ}$ 아래방향, $20^{\circ}$ 아래방향, 수평방향, $20^{\circ}$ 윗 방향을 주시하였을 때 각각의 주시방향에서 1분 동안의 조절효율성, 눈의 깜빡임 횟수를 측정하였고 검영기를 이용하여 동적검영법으로 조절래그를 측정하였다. 결과: 주시선이 $40^{\circ}$ 하방보다 윗 방향쪽으로 이동할수록 조절효율은 감소하였고, 눈 깜빡임 횟수와 조절래그량은 증가하여 근거리 작업 시 눈이 건조해지고 조절반응량이 감소하는 것으로 조사되었다. 결론: 근거리 작업 시 책이나 컴퓨터 화면의 위치를 수평방향보다 $40^{\circ}$ 하방에 위치시키면 눈의 피로도를 최소화할 수 있다.