• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.476-476
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• 2014

서론: 저 전력 소모를 필요로 하는 무선 센서 네트워크 관련 기술의 급격한 발달과 함께 자체 전력 수급을 위한 진동 에너지 수확 기술에 대한 연구가 활발히 이루어지고 있다. 다양한 구조와 소재를 압전 외팔보에 적용하여 제안하고 있다. 그 중에서도 진동 기반의 에너지 수확 소자는 주변 환경에서 쉽게 진동을 얻을 수 있고, 높은 에너지 밀도와 제작 방법이 간단하다는 장점을 가지고 있어 많은 분야에 응용 및 적용 가능하다. 기존 연구에서는 2차원적으로 진동 에너지 수확을 위한 휜 구조의 압전 외팔보를 제안 하였다. 휜 구조를 갖는 압전 외팔보는 각각의 짧은 두 개의 평평한 외팔보가 일렬로 연결된 것으로 볼 수 있다. 하나의 짧고 평평한 외팔보는 진동이 가해지면 접선 방향으로 응력이 생겨 최대 휨 모멘텀을 갖게 된다. 그러므로 휜 구조를 갖는 외팔보는 진동이 인가됨에 따라 길이 방향과 수직 방향으로 진동한다. 하지만, 이 구조는 수평 방향으로 가해지는 진동에 대한 에너지를 수확하기에는 한계점을 가진다. 즉, 3축 방향에서 임의의 방향에서 진동 에너지를 수확하기는 어렵다. 본 연구에서는 3축 방향에서 에너지를 효율적으로 수확할 수 있도록 헤어-셀 구조의 압전 외팔보 에너지 수확소자를 제안한다. 제안된 소자는 길이 방향과 수직 방향뿐만 아니라 수평 방향으로도 진동하여 임의의 방향에서 진동 에너지를 수확할 수 있다. 구성 및 공정: 제안하는 소자는 3축 방향에서 임의의 진동을 수확하기 위해서 길이를 길게 늘이고 길이 방향을 따라 휘어지는 구조의 헤어-셀 구조로 제작하였다. 외팔보의 구조는 외팔보의 폭 대비 길이의 비가 충분히 클 때, 추가적인 자유도를 얻을 수 있다. 그러므로 헤어-셀 구조의 에너지 수확 소자는 기본적인 길이 방향, 수직방향 그리고 수평방향에 더불어 추가적으로 뒤틀리는 방향을 통해서 3차원적으로 임의의 주변 진동 에너지를 수확하여 전기적인 에너지로 생성시킬 수 있다. 제작된 소자는 높은 종횡비를 갖는 무게 추($500{\times}15{\times}22{\mu}m3$)와 길이 방향으로 길게 휜 압전 외팔보($1000{\times}15{\times}1.7{\mu}m3$)로 구성되어있다. 공정 과정은 다음과 같다. 먼저, 실리콘 웨이퍼 위에 탄성층을 형성하기 위해 LPCVD SiNx를 $0.8{\mu}m$와 LTO $0.2{\mu}m$를 증착 후, 각각 $0.03{\mu}m$과 $0.12{\mu}m$의 두께를 갖는 Ti와 Pt을 하부 전극으로 스퍼터링한다. 그리고 Pb(Zr0.52Ti0.48)O3 박막을 $0.35{\mu}m$ 두께로 졸겔법을 이용하여 증착하고 상부 Pt층을 두께 $0.1{\mu}m$로 순차적으로 스퍼터링하여 형성한다. 상/하부 전극은 ICP(Inductively Coupled Plasma)를 이용해 건식 식각으로 패턴을 형성한다. PZT 층과 무게 추 사이의 보호막을 씌우기 위해 $0.2{\mu}m$의 Si3N4 박막이 PECVD 공정법으로 증착되고, RIE로 패턴을 형성된다. Ti/Au ($0.03/0.35{\mu}m$)이 E-beam으로 증착되고 lift-off를 통해서 패턴을 형성함으로써 전극 본딩을 위한 패드를 만든다. 초반에 형성한 실리콘 웨이퍼 위의 SiNx/LTO 층은 RIE로 외팔보 구조를 형성한다. 이후에 진행될 도금 공정을 위해서 희생층으로는 감광액이 사용되고, 씨드층으로는 Ti/Cu ($0.03/0.15{\mu}m$) 박막이 스퍼터링 된다. 도금 형성층을 위해 감광액을 패턴화하고, Ni0.8Fe0.2 ($22{\mu}m$)층으로 도금함으로써 외팔보 끝에 무게 추를 만든다. 마지막으로, 압전 외팔보 소자는 XeF2 식각법을 통해 제작된다. 제작된 소자는 소자의 여러 층 사이의 고유한 응력 차에 의해 휨 변형이 생긴다. 실험 방법 및 측정 결과: 제작된 소자의 성능을 확인하기 위하여 일정한 가속도 50 m/s2로 3축 방향에 따라 입력 주파수를 변화시키면서 출력 전압을 측정하였다. 먼저, 소자의 기본적인 공진 주파수를 얻기 위하여 수직 방향으로 진동을 인가하여 주파수를 변화시켰다. 그 때에 공진 주파수는 116 Hz를 가지며, 최대 출력 전압은 15 mV로 측정되었다. 3축 방향에서 진동 에너지 수확이 가능하다는 것을 확인하기 위하여 제작된 소자를 길이 방향과 수평 방향으로 가진기에 장착한 후, 기본 공진 주파수에서의 출력 전압을 측정하였다. 진동이 길이방향으로 가해졌을 때에는 33 mV, 수평방향으로 진동이 인가되는 경우에는 10 mV의 최대 출력 전압을 갖는다. 제안하는 소자가 수 mV의 적은 전압은 출력해내더라도 소자는 진동이 인가되는 각도에 영향 받지 않고, 3축 방향에서 진동 에너지를 수확하여 전기에너지로 얻을 수 있다. 결론: 제안된 소자는 3축 방향에서 진동 에너지를 수확할 수 있는 에너지 수확 소자를 제안하였다. 외팔보의 구조를 헤어-셀 구조로 길고 휘어지게 제작함으로써 기본적인 길이 방향, 수직방향 그리고 수평방향에 더불어 추가적으로 뒤틀리는 방향에서 출력 전압을 얻을 수 있다. 미소 전력원으로 실용적인 사용을 위해서 무게추가 더 무거워지고, PZT 박막이 더 두꺼워진다면 소자의 성능이 향상되어 높은 출력 전압을 얻을 수 있을 것이라 기대한다.

• Radiation Oncology Journal
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• v.11 no.1
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• pp.69-77
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• 1993

Treatment of cerebellar medulloblastoma has been much improved with modern surgical technique for gross total tumor removal and adequate radiation therapy for the whole craniospinal axis. Questions have been arosen about the optimal radiation dose for the preventive treatment of whole cranium and whole spinal axis. Recently, many authors have reported their treatment results as comparable to older data, using lower than conventional dose of 3,600 cGy-4,000 cGy. For 50 patients treated between 1981 and 1990 at the Department of Radiation Therapy of SNUH, retrospective analysis was done for the treatment result, especially the neuraxis control, by radiation dose for the presymptomatic area of the disease. Analysis only by total spinal dose did not give any significant difference. But further analysis by following patient group; 3,600 cGy/150 cGy (n=6), 3,000 cGy/150 cGy (n=10), 2,400 cGy/150 cGy (n=17) and 2,400 cGy/100-120 cGy (n=11) showed significant improvement of neuraxis control by decreasing order (p =0.003). There was no significant difference in overall survival between the groups. For the 19 patients who had been confirmed initially as having no neuraxis disease, TDF 30 was the cur-off value that could prevent neuraxis failure (p =0.004). We couldn't define any TDF value that give reasonable control for the patient group with positive CSF study at initial diagnosis.

• Radiation Oncology Journal
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• v.11 no.1
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• pp.35-42
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• 1993

The dose response of the number of micronuclei in cytokinesis-blocked (CB) lymphocytes after in vitro irradiation with $\gamma$-rays and neutrons in the 5 dose ranges was studied for a heterogeneous population of 4 donors. One thousand binucleated cells were systematically scored for micronuclei. Measurements performed after irradiation showed a dose-dependent increase in micronuclei (MN) frequency in each of the donors studied. The dose-response curves were analyzed by a linear-quadratic model, frequencies per 1000 CB cells were ($0.31{\pm}0.049$)D+($0.0022{\pm}0.0002)D^2+(13.19{\pm}1.854) (r^2=1.000,\;X^2=0.7074,\;p=0.95$) following $\gamma$ irradiation, and ($0.99{\pm}0.528$)\;D+(0.0093{\pm}0.0047)\;D^2+(13.31{\pm}7.309)\;(r^2=0.996,\;X^2=7.6834,\;p=0.11) following neutrons irradiation (D is irradiation dose in cGy). The relative biological effectiveness (RBE) of neutrons compared with $\gamma$-rays was estimated by best fitting linear-quadratic model. In the micronuclei frequency between 0.05 and 0.8 per cell, the RBE of neutrons was $2.37{\pm}0.17$. Since the MN assay is simple and rapid, it may be a good tool for evaluating the $\gamma$-ray and neutron response.

• Childhood Kidney Diseases
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• v.1 no.2
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• pp.155-160
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• 1997

Purpose : Tethered cord syndrome is characterized by progressive motor and sensory disturbances in lower extremities, foot deformities caused by a pathologic fixation of spinal cord resulting in excessive stretching of the spinal cord. It is also frequently associated with urological symptoms include urinary frequency, incontinence, enuresis, urgency and recurrent urinary tract infection. Because there is few report in the literature about urological manifestations of theterd cord syndrome, we conducted a retrospective study on the patients diagnosed as tethered cord syndrome to delineate the characteristics of urologic manifestations in tethered cord syndrome and to establish the policy to evaluate patients who is suspected of tethered cord syndrome. Method : A retrospective study was conducted by reviewing the medical records of nine patients who was diagnosed as tethered cord syndrome from November 1991 to July 1996 in Yeungnam University Hospital. Result : 1) The age distribution of nine patients was as follows; 5 patients were under 2 years, 1 case from 2 to 6 years and 3 cases from 6 to 10 years. 2) Of 9 patients 6 had voiding frequency, urinary incontinence, enuresis, urgency and loss of micturation sense. Radiologic urodynamic studies revealed neurogenic bladder in 5 patients, hydronephrosis and hydroureter in 3, vesicoureteral reflux in 3. 3) Of 6 patients with urological abnormal manifestations 4 underwent spinal cord surgery (detethering). In spite of surgical intervention, the urological manifestations improved in only one patient. Conclusion : Urological abnormalities were common in tethered cord syndrome. Abnormal laboratory findings including urodynamic study were found even before the onset of urological symptoms. We have to concern tethered cord syndrome as one of common causes of voiding frequency and enuresis and to evaluate urological abnormalities as thetered cord syndrome is diagnosed.

• The Korean Journal of Nuclear Medicine Technology
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• v.12 no.1
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• pp.39-43
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• 2008

Purpose: There are various methods to diagnose hemangioma, such as ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI) and nuclear medicine. However, by development of SPECT imaging, the blood-pool scan using $^{99m}Tc$-labeled red blood cell has been used, because it was non-invasive and the most economical method. Therefore, in this study, we proposed that the usefulness of $^{99m}Tc$-RBC scan and SPECT of the head and neck to diagnose unlocated hemangiomas. Materials and Methods: $^{99m}Tc$-RBC scan and SPECT was performed on 6 patients with doubtful hemangioma (4 person, head; 1 person, neck; 1 person, another). We labeled radiopharmaceutical using modified in vivo method and then, centrifuged it to remove plasma. After a bolus injection of tracer, dynamic perfusion flow images were acquired. Then, anterior, posterior, both lateral static blood-pool images were obtained as early and 4 hours delayed. SPECT was progressed 64 projections per 30 seconds. Each image was interpreted by physicians, Nuclear medicine specialist, and technologist blinded to patient's data. Results: In 5 patients of all the radioactivity of doubtful site didn't change in flow images, but, in blood-pool, delayed and SPECT images, it was increased. So, it was a typical hemangioma finding. The size of lesion was over 2 cm, and it could discriminate as comparing to the delayed and SPECT imaging. On the other hand, in 1 patient, the radioactivity was increased in blood-pool images, but, not in delayed and SPECT images, so, it was proved no hemangioma. Conclusion: Using $^{99m}Tc$-RBC Scan and SPECT, we could diagnose the hemangiomas in head and neck, as well as, liver, more non-invasive, economical, and easy. Therefore, it considered that $^{99m}Tc$-RBC scan and SPECT would offer more useful information for diagnosis of hemangioma, rather than otherimaging such as US, CT, MRI.

• Horticultural Science & Technology
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• v.32 no.6
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• pp.872-878
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• 2014

This study aimed to enhance storage and freshness of strawberry fruits and foliage vegetables by spray treatment with Chlorella vulgaris as a bio-fertilizer. The tested strain, C. vulgaris CHK0008, was isolated from an organically cultivated rice paddy and identified as C. vulgaris by its morphology and 18S rDNA and 23S rDNA sequence homology. We successfully cultured C. vulgaris CHK0008 in BG11 modified medium (BG11MM) and adjusted $2.15{\times}10^6cell/mL$ C. vulgaris CHK0008 to one OD value by measuring the optical density at 680 nm using a UV-vis spectrophotometer. The soluble solid content of 'Seolhyang' and 'Yukbo' strawberry fruits treated by spray application with C. vulgaris CHK0008 was enhanced by 22.2% and 11.5% respectively, compared to untreated controls. Additionally, the decay rates of treated 'Seolhyang' and 'Yukbo' strawberry fruits decreased 63.8% and 74.4% respectively, compared to untreated control. Surface color changes and chlorosis of leaves in leaf vegetables such as lettuce, kale, red ornamental kale, white ornamental kale and beet were observed in samples treated with water spray for 10 days after cold storage. However, the decay rate of leafy vegetables treated with foliar application of 25% C. vulgaris CHK0008 liquid culture was significantly decreased compared to that of the untreated control during storage at $4^{\circ}C$.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.401-410
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• 2003

This study investigates the biomechanical efficacies of various cement augmentation techniques with or without pressurization for varying degrees of osteoporotic femur. For this study, a biomechanical analysis using a finite element method (FEM) was undertaken to evaluate surgical procedures, Simulated models include the non-cemented(i.e., hip screw only, Type I), the cement-augmented(Type II), and the cemented augmented with pressurization(Type III) models. To simulate the fracture plane and other interfacial regions, 3-D contact elements were used with appropriate friction coefficients. Material properties of the cancellous bone were varied to accommodate varying degrees of osteoporosis(Singh indices, II∼V). For each model. the following items were analyzed to investigate the effect surgical procedures in relation to osteoporosis of varying degrees : (a) von Mises stress distribution within the femoral head in terms of volumetric percentages. (b) Peak von Mises stress(PVMS) within the femoral head and the surgical constructs. (c) Maximum von Mises strain(MVMS) within the femoral head, (d) micromotions at the fracture plane and at the interfacial region between surgical construct and surrounding bone. Type III showed the lowest PVMS and MVMS at the cancellous bone near the bone-construct interface regardless of bone densities. an indication of its least likelihood of construct loosening due to failure of the host bone. Particularly, its efficacy was more prominent when the bone density level was low. Micromotions at the interfacial surgical construct was lowest in Type III. followed by Type I and Type II. They were about 15-20% of other types. which suggested that pressurization was most effective in limiting the interfacial motion. Our results demonstrated the cement augmentation with hip screw could be more effective when used with pressurization technique for the treatment of intertrochanteric fractures. For patients with low bone density. its effectiveness can be more pronounced in limiting construct loosening and promoting bone union.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.198-208
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• 2006

This research was to apply a multi-metric approach, so called the Index of Biological Integrity (IBI) as a tool for biological evaluations of water environments, to a wadable stream. For the study, we surveyed 5 sampling locations in Kap Stream during August 2004 ${\sim}$ September 2005. We also compared the biological data with long-term water quality data, obtained from the Ministry of Environment, Korea and physical habitat conditions based on the Quantitative Habitat Evaluation Index (QHEI). We used ten metric systems for the IBI model to evaluate biological stream health. Overall IBI values in Kap Stream averaged 24 (range: 20${\sim}$30, n=5), indicating a "fair ${\sim}$ poor" conditions according to the modified criteria of Karr (1981) and US EPA(1993). Exclusive of 4th survey, average IBI values at the upstream reach (S1 ${\sim}$ S3)and downstream reach (S4 ${\sim}$ S5) were 20 and 24, respectively. However, in 4th survey the averages were 21 and 20 in the upstream and downstream reaches, respectively. This difference was larger in the upstream than in the downstream because of physical condition disturbed during summer monsoon. Values of the QHEI varied from 75(fair condition) to 148 (good condition) and values of QHEI in the S3 were significantly (P=0.001, n=5) lower than other sites. Biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were greater by 3 ${\sim}$ 8 fold in the downstream than in the upstream reach. We believe that present IBI approach applied in this study may be used as a key tool to set up specific goals for restoration of Kap Stream.

• Tuberculosis and Respiratory Diseases
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• v.46 no.4
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• pp.512-522
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• 1999

Background: Due to the paucity of suitable donor organs for lung allotransplantation, a number of techniques have been developed to improve the lung preservation. Ultrastructural studies of the morphologic changes of the flushing, preservation and reperfusion injury in donor lungs have rarely been reported. Methods: Adult dogs (n=46) were matched as donors and recipients for the single lung transplantation. The donor lungs were preserved after flushing with preservation solution and transplanted after 20-hours of preservation at $10^{\circ}C$. Ultrastructural features of the lung were examined after flushing, preservation and 2 hours after lung transplantation (reperfusion) respectively. Results: Electron microscopy after flushing showed focal alveolar collapse and mild swelling of type I epithelial cells. After preservation both type I epithelial cells and endothelial cells were swollen and destroyed focally. The endothelial cells showed protrusion of tactile-like structures into the lumina, blebs or vacuoles of the cytoplasm After reperfusion the lung tissue showed fibrin material in the alveoli, prominent type I epithelial cell swelling with fragmented cytoplasmic debris and marked endothelial cell swelling with vacuoles or tactile-like projections. The alveolar macrophages showed active phagocytosis. Scanning electron microscopic examination of the pulmonary parenchyma showed focally alveolar collapse and focal consolidation after the preservation and more prominent changes after the reperfusion procedure. The lungs preserved with low potassium dextran glucose solution, with additional prostaglandin $E_1(PGE_1)$ and verapamil(VP) showed relatively well preserved ultrastructures compared with those which were preserved with modified Euro-Collins or University of Wisconsin, and with additional $PGE_1$ and/or VP. Conclusion: The ultrastructural changes associated with flushing were mild in severity, the donor lungs were injured during the preservation, and further damage was occurred during the reperfusion. The reperfusion injury resulted in prominent pulmonary parenchymal alterations with a pattern of acute lung injury.

• KDI Journal of Economic Policy
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• v.31 no.1
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• pp.169-206
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• 2009

This study stems from a question, "How should we understand the pattern of the Korean economy after the 1990s?" Among various analytic methods applicable, this study chooses a Structural Vector Autoregression (SVAR) with long-run restrictions, identifies diverse impacts that gave rise to the current status of the Korean economy, and differentiates relative contributions of those impacts. To that end, SVAR is applied to four economic models; Blanchard and Quah (1989)'s 2-variable model, its 3-variable extensions, and the two other New Keynesian type linear models modified from Stock and Watson (2002). Especially, the latter two models are devised to reflect the recent transitions in the determination of foreign exchange rate (from a fixed rate regime to a flexible rate one) as well as the monetary policy rule (from aggregate targeting to inflation targeting). When organizing the assumed results in the form of impulse response and forecasting error variance decomposition, two common denominators are found as follows. First, changes in the rate of economic growth are mainly attributable to the impact on productivity, and such trend has grown strong since the 2000s, which indicates that Korea's economic growth since the 2000s has been closely associated with its potential growth rate. Second, the magnitude or consistency of impact responses tends to have subsided since the 2000s. Given Korea's high dependence on trade, it is possible that low interest rates, low inflation, steady growth, and the economic emergence of China as a world player have helped secure capital and demand for export and import, which therefore might reduced the impact of each sector on overall economic status. Despite the fact that a diverse mixture of models and impacts has been used for analysis, always two common findings are observed in the result. Therefore, it can be concluded that the decreased rate of economic growth of Korea since 2000 appears to be on the same track as the decrease in Korea's potential growth rate. The contents of this paper are constructed as follows: The second section observes the recent trend of the economic development of Korea and related Korean articles, which might help in clearly defining the scope and analytic methodology of this study. The third section provides an analysis model to be used in this study, which is Structural VAR as mentioned above. Variables used, estimation equations, and identification conditions of impacts are explained. The fourth section reports estimation results derived by the previously introduced model, and the fifth section concludes.