• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.1
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• pp.33-41
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• 1998

The response characteristics of the PZT transducers during glass capillary breakage were studied at the epicenter of the glass plate. The PZT transducers had been made by using EC-65 PZT ceramics(supplied by Edo co.) with a constant area and a various thickness. The theoretical displacement and velocity at the epicenter of glass plate with an air boundary condition were calculated by assuming the point load of 1N force strength and a rise time of 280 ns with a ramped functional dependence, and the 1st pulses of the PZT transducer may be considered as the vertical velocity incident on the electrode of the PZT ceramic. The responses of the PZT transducer may be depended on the thickness mode of the PZT ceramic below 0.33 in the ratio of the thickness to the diameter of PZT ceramic, but the reponse of the PZT transducer may be depended on the other modes of PZT transducer in the addition of the thickness mode of the PZT ceramic above 0.33. The full time of half maximum at the 1st pulse was nearly 280 ns without a variation of applied breakage load and the resonant frequency of the PZT transducer, and then may be considered as the rise time of a AE source. The maximum amplitude of the 1st pulse depended on the incident vertical velocity and capacitance of the PZT transducer. Therefore, the full time of half maximum and maximum amplitude of the 1st pulse may be considered as the rise time and strength of acoustic emission source respectively.

• Journal of Chest Surgery
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• v.29 no.11
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• pp.1232-1240
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• 1996

From January 1990 through June 1995, we operated on 121 patients who were suspected for pulmonary tuberculosis without definite final diagnosis. After operation the final pathologic diagnoses were as follows: 68 pulmonary tuberculosis in which 29 were tuberculoma, 23 lung cancer, 16 bronchiectasis, 6 aspergilloma, 2 lung abscess, 2 benign cyst and 4 others. In 121 cases, 81 were male and 40 were female and the peak age incidence was 4th decade in tuberculosis (39.7%) and 6th and 7th decade in lung cancer (69.6%). The diagnoses in 44 cases presented roentgenographically as pulmonary nodules were pulmonary tuberculosis(29 cases) and lung cancer(15 cases). Tuberculous nodules tended to be smaller in size with calcification and satellite lesions compared to carcinomas. Indications for operation were solitary nodules 44 cases (36.4%); destroyed lobe 31(25.6%); hemoptysis 25 (20.7%); cavitary lesion 11(9.1 %); bronchostenosis 3 (2.5%); destroyed lung 5(4.1 %) and destroyed lung with empyema 2(1.7%). We conclude that preoperatively suspected pulmonary tuberculosis should be distinguished from various pulmonary lesions such as carcinoma, bronchiectasis, aspergilloma, lung abscess and benign cyst. For the possibility of carcinoma, pulmonary nodules of size greater than 3cm, non-calcified, non satellite lesion, newly developed nodule even under the anti-tuberculous medication, negative PPD skin test with elevated CEA level are recommended for an early resectional surgery and follow-up and delayed surgery is recommended in cases such as pulmonary nodules less than 3 cm in size with calcification, satellite lesion, positive PPD skin reaction and elevated ESR, CRP, ALP levels.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.179.1-179
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• 2003

본 연구는 각종 영양성분과 기능성 물질을 함유한 식용마의 소비확대와 새로운 가공식품을 개발하고자, 당절임한 식용 마의 건조방법에 따른 물성 및 일반 성분의 변화를 조사하였다. 동결건조한 당절임 식용마의 명도는 높았고 적색도와 황색도는 열풍 및 진공 건조한 것에 비해 낮았으며, 수분함량과 재수화율은 동결건조한 것이 높게 나타났다. 수용성 단백질은 동결건조한 것이 6.43mg/100g으로 가장 낮았으며 총당과 환원당의 함량은 건조방법에 따라 뚜렷한 차이가 없었다. 주요 유기산은 malic, acetie, citric acid 이었고, acetic, citirc acid는 열풍 및 진공 건조한 것이 많았으나 malic acid는 동결 건조한 것이 월등히 높게 나타났다. 구성아미노산은 진공 건조한 것에 많았으며, 유리아미노산은 큰 차이가 없었다. 총 비타민 C함량도 별다른 차이가 없었으나 환원형 비타민 C는 동결이 산화형 비타민 C는 열풍 및 진공 건조한 것이 높게 나타났고, 무기질 함량은 K, Na, Mg의 함량이 많았다. 마 스낵의 관능검사에서는 열풍 및 진공건조에 비해 동결 건조한 것이 우수한 것으로 평가되었으며, 전자현미경적 관찰에서는 열풍 및 진공 건조한 것은 세포와 세포벽의 형태를 찾아 볼 수 없었으나 동결 건조 한것은 세포의 형태와 세포벽의 파괴가 일어나지 않았다. 본 연구는 당절임한 식용 마의 건조 방법에 따른 물성 및 성분의 변화를 조사한 결과, 동결건조한 것이 품질이 우수하였고, 영양성과 기능성을 함유한 마의 가공 식품의 개발의 가능성을 제시한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.2
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• pp.164-172
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• 2007

Surface cracks in concrete are common defects that can cause significant deterioration and failure of concrete structures. Therefore, the early detection, assessment, and repair of the cracks in concrete are very important for the structural health. Among studies for crack depth assessment, self-calibrating surface wave transmission method seems to be a promising nondestructive technique, though it is still difficult in determination of the crack depth due to the variation of the experimentally obtained transmission functions. In this paper, the spectral energy transmission method is proposed for the crack depth estimation in concrete structures. To verify this method, an experimental study was carried out on a concrete slab with various surface-opening crack depths. Finally, effectiveness of the proposed method is validated by comparing the conventional time-of-flight and cutting frequency based methods. The results show an excellent potential as a practical and reliable in-situ nondestructive method for the crack depth estimation in concrete structures.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.1
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• pp.32-38
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• 2001

Although the ultrasonic method has been developed and used widely in the fields, it has been used only for measuring the defect size and thickness loss. In this study, the relationship between surface wave attenuation through micro-crack growth and variation of velocity under repeated cyclic loading has been investigated. The specimens are adopted from 2.25Cr-1Mo steel, which is used for power plant and pipeline system, and have dimensions of $200{\times}40{\times}4mm$. The results of ultrasonic test with a 5MHz transducer show that surface wave velocity gradually decreases from the point of 60% of fatigue life and the crack length of 2mm with the increasing fatigue cycles. From the results of this study, it is found that the technique using the ultrasonic velocity change is one of very useful methods to evaluate the fatigue life nondestructively.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.3
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• pp.246-253
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• 2003

The initiation and growth of short fatigue cracks in the simulated aircraft structure with a series of rivet holes was detected by acoustic emission (AE). The location and the size of short tracks were determined by AE source location techniques and the measurement with traveling microscope. AE events increased intermittently with the initiation and growth of short cracks to form a stepwise increment curve of cumulative AE events. For the precise determination of AE source locations, a region-of-interest (ROI) was set around the rivet holes based on the plastic zone size in fracture mechanics. Since the signal-to-noise ratio (SNR) was very low at this early stage of fatigue cracks, the accuracy of source location was also enhanced by the wavelet transform do-noising. In practice, the majority of AE signals detected within the ROI appeared to be noise from various origins. The results showed that the effort of structural geometry and SNR should be closely taken into consideration for the accurate evaluation of fatigue damage in the structure.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.4
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• pp.320-324
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• 2001

According to the rapid growth of computer and internet recently, A hacking to steal infonnations and the computer vinls to destroy the data in computer are now prevailing in the whole world. A study of methods to protect the data of computer is in progress. One of the study is constmction of computer immune system using biological immune system tbat has ability of removal and protection from extemal invasion. In this paper, we make a change detection algorithm which is based on ability of distinction between self and nonself in T-cytotoxic cell that is one of biological immune cell. In algorithm, MHC receptors are composed of a part of self-file that is recognized as itself and those shall distinguish self-file from the changed file. As a result of applying this algorithm to the changed self-files, we prove the efficacy of detection of the self-files changed by computer virus and hacking.

• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.750-758
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• 2002

Concrete is deformed by load and subjected to micro damage under allowable deformation because of non-homogeneous property. When micro damage is accumulated, it is cracked and finally fractured. Characterization of AE can be demonstrated the micro damage which it is not discovered from visual observation, and it become known to an advantage that was clearly discriminated from the existing NDT method. This study was carried out the analysis and evaluation of concrete damage by acoustic emission technique. As a results of damage analysis, it was found out that the more concrete strength has increased, the more concrete has subjected to micro damage at lower stress ratio for chylinder specimen, and this is possible only AE method which could be described the brittle properties. Also it was revealed that the kaiser effect and felicity effect were existed in reinforced concrete bending specimens and it is found out that the onset of interface debonding between concrete and steel could be conformed in comparison with felicity ratio, AE activity and load history. From the results of this study, it was conformed that the deteriorative degree of reinforced concrete structure should be evaluated using felicity ratios.

• Tuberculosis and Respiratory Diseases
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• v.55 no.6
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• pp.551-559
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• 2003

Background : Emergency management in hemoptysis is bronchial artery angiography and embolization. This study was designed to investigate the accuracy of localization of bleeding site by simple roentgenogram, computed tomography(CT) and bronchoscopy prior to embolization and to evaluate the outcome of embolotherapy. Method : We retrospectively evaluated 50 patients performed bronchial artery embolization(BAE), admitted to tertiary university hospital due to hemoptysis. Results : The most common causes were pulmonary tuberculosis, old tuberculous related parenchymal damage, aspergilloma, and bronchiectasis. The success rate of BAE within one month was 90%; within 3 months was 88%; during follow up period of mean 11.6 months was 76%. The concordant rate of simple roentgenogram with angiographic outcome in terms of bleeding site is 70%; in chest CT 80%; in bronchoscopy 81%; in combined information of simple roentgenogram and CT 83%; in combined information of simple roentgenogram and bronchoscopy 78%. Conclusion : The diagnostic accuracy for the bleeding site was similar between chest CT and bronchoscopy, showing high diagnostic yield. The success rate of BAE was comparative to prior studies. Further study will be needed in a large scale in near future.

• The Journal of the Korean bone and joint tumor society
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• v.6 no.2
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• pp.61-68
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• 2000

Purpose : We examined the patients to evaluate the radiologic findings of solitary plasmacytoma of the bone. Materials and Methods : We retrospectively reviewed radiologic findings of 9 cases with solitary plasmacytoma of the bone (SPB) for recent 5 years, but 2 cases were not included this study due to an abnormal finding of bone marrow and another 2 cases were not included due to an abnormal manifestations of computed tomography (n=1) and MRI (n=1). Results : Among 5 cases, 4 cases had an osteolytic bone destruction and 1 case had an osteosclerotic bone destruction on the plain radiograph. Computed tomography and MRI showed more informations about trabeculated bone destruction and the soft-tissue extension of the lesion comparing to plain radiographs. The MRI finding of SPB in 4 cases showed a relatively high signal intensity on T1-weighted image and intermediate signal intensity on T2-weighted image, on which the signal intensity of the lesion is slightly higher than that of the muscle. One case had an extensive soft-tissue involvement and multiple necrosis, which presented iso to low signal intensity on T1-weighted image and high heterogeneous signal intensity on T2-weighted image. The Gadolinium-enhanced T1-weighted images of 5 cases showed diffusely strong enhancement of the lesion except on the necrosis areas. Conclusion : Computed tomography and MRI may present some characteristics of SPB and demonstrate another foci of plasma cell infiltrates, so these can be helpful for the diagnosis and treatment of SPB.