• Journal of the Korean Vacuum Society
• /
• v.12 no.4
• /
• pp.239-250
• /
• 2003

The reliability degradation phenomena in the SiGe hetero-junction bipolar transistor (HBT) are investigated in this review. In the case of the SiGe HBT the decrease of the current gain, the degradation of the AC characteristics, and the offset voltage are frequently observed, which are attributed to the emitter-base reverse bias voltage stress, the transient enhanced diffusion, and the deterioration of the base-collector junction due to the fluctuation in fabrication process, respectively. The reverse-bias stress on the emitter-base junction causes the recombination current to rise, increasing the base current and degrading the current gain, because hot carriers formed by the high electric field at the junction periphery generate charged traps at the silicon-oxide interface and within the oxide region. Because of the enhanced diffusion of the dopants in the intrinsic base induced by the extrinsic base implantation, the shorter distance between the emitter-base junction and the extrinsic base than a critical measure leads to the reduction of the cut-off frequency ($f_t$) of the device. If the energy of the extrinsic base implantation is insufficient, the turn-on voltage of the collector-base junction becomes low, in the result, the offset voltage appears on the current-voltage curve.

• Journal of Trauma and Injury
• /
• v.21 no.1
• /
• pp.36-45
• /
• 2008

Purpose: We conducted this retrospective epidemiological study to assess the incidence and severity of lower extremity injuries in Korea Methods: For this study, we retrospectively reviewed nationwide lower-extremity injury data compiled from 2001 to 2003 based on the National Injury Database, what included National Health Insurance Corporation (NHIC), Car Insurance, and Industry Insurance data. Data were standardized in terms of demographic characteristics, region, and socioeconomic status by using NHIC data. To assess the degree of the injuries, we used the Modified Abbreviated Injury Scale (MoAIS), what has been changed from the International Classification of Disease-10 (ICD-10) code. By using the Excess Mortality Ratio-adjusted Injury Severity Score (EMR-ISS), we classified the degree of severity into four categories: mild, moderate, severe and critical. Results: From 2001 to 2003, lower extremity injuries increased slightly, with a yearly average of 2,437,335. Insurance data should that lower-extremity injuries were the most common, followed by upper-extremity injuries. Significant difference were seen in the numbers of lower extremity injuries based on gender and age. As for provinces, Seoul and Gyeongi provinces had the highest numbers of cases. Junlabukdo had the highest rate of 55,282 cases per 1 million people for standardized gender and population. The annual incidence of the insured patients with lower extrimity injuries was higher than the employer's medical insurance contributions to the medical insurance program. Daily cases occur most often in May and June, with the lowest occurrences being in January and February. Conclusion: The result of this study shows that lower extremity injuries comprised common cause of all injuries. In addition, differences associated with gender, location and socioeconomic status were observed. Further studies are needed to find reasons and then this knowledge will allow strategies to prevent the lower extremity injuries.

• Information Systems Review
• /
• v.5 no.2
• /
• pp.241-256
• /
• 2003

This empirical study is to explain critical success factors for building effective regional IT cluster from the literature reviews which have some limitations, and is to suggest new key factors from the views of Regional Innovation System and Sectoral Systems of Innovation. For building successful cluster, the new key factors not only stress on regional networks, the spill-over of tacit knowledge through learning by interacting, institutions which contain regional custom, norms, established practices, culture, and characteristics from the Regional Innovation System, but also emphasize on heterogeneous agents who are interacting by each others from Sectoral Systems of Innovation. From these factors we suggest some strategies for building effective "Daegu IT Cluster" as following; making characterized IT brands which are selected and concentrated based on regional and IT sectoral characteristics, strengthening learning competence of tacit knowledge built in multiple heterogeneous agents network, establishing strong agent networks which are composed of universities, companies, institutes and government, and sharing the institution of mind-opening culture in order to correspond with environmental changes and link to other industrial clusters. By putting above strategies in force, the compatabilities of Daegu region are reinforced. Tacit knowledges spill over and the regional innovation competence are accumulated. Also IT cluster plays core role of employment in Daegu for long term. Especially, "Daegu IT Cluster" changes city's image from medium and small manufacturing city to new industrial city based on high technologies.

• Journal of Korea Water Resources Association
• /
• v.44 no.12
• /
• pp.1015-1029
• /
• 2011

Conventional MCDA techniques have been used in the field of water resources in the past. A GIS can offer an effective spatial data-handling tool that can enhance water resources modeling through interfaces with sophisticated models. However, GIS systems have a limited capability as far as the analysis of the value structure is concerned. The MCDA techniques provide the tools for aggregating the geographical data and the decision maker's preferences into a one-dimensional value for analyzing alternative decisions. In other words, the MCDA allows multiple criteria to be used in deciding upon the best alternatives. The combination of GIS and MCDA capabilities is of critical importance in spatial multi-criteria analysis. The advantage of having spatial data is that it allows the consideration of the unique characteristics at every point. The purpose of this study is to identify, review, and evaluate the performance of a number of conventional MCDA techniques for integration with GIS. Even though there are a number of techniques which have been applied in many fields, this study will only consider the techniques that have been applied in floodplain decision-making problems. Two different methods for multi-criteria evaluation were selected to be integrated with GIS. These two algorithms are Compromise Programming (CP), Spatial Compromise Programming (SCP). The target region for a demonstration application of the methodology was the Suyoung River Basin in Korea.

• Korean Journal of Remote Sensing
• /
• v.14 no.4
• /
• pp.325-342
• /
• 1998

Two RADARSAT SAR images with different modes acquired by Canadian Space Agency to test the effectiveness of geological lineament extraction and spring water detection over the Cheju Island. Geological lineaments are poorly developed this basalt dominant volcanic island, but more linear features can be extracted when SAR and TM images are simultaneously analyzed than when TM image alone is used. This results mainly owe to the facts that RADARSAT SAR systems are able to provide data with different frequencies, azimuth, and incidence angles. Distribution of spring water along coast is poorly correlated with geological lineaments or drainage pattern, but those in middle range of mountain region are developed along geological lineaments. Detection of spring water using remotely sensed images are turned out to be very difficult to achieve. Radial shaped sea surface temperature anomaly derived from TM thermal band should be the best candidate for spring water, but the resolution is not high enough. We also investigate the normalized radar cross section (or sigma naught) converted from RADARSAT and ERS-1 SAR data but to discriminate the spring water effectively except where relatively large water mass is observed on land side. Speckle noise and irregularity in physical sea surface condition are the serious obstacles for this application. ERS-1 SAR image acquired in low incidence angle was more useful for geological lineament estimation and water body study than RADARSAT SAR images with high incidence angles. Therefore the selection of incidence angle is critical in geological and spring water applications of SAR images, and low incidence angles less than about 30$^{\circ}$ are recommended to monitor the Cheju volcanic island.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2016.05a
• /
• pp.1-1
• /
• 2016

Many of the world's large ecosystems are severely stressed due to population growth, water quality and quantity problems, vulnerability to flood and drought, and the loss of native species and cultural resources. Consequences of climate change further increase uncertainties about the future. These major societal challenges must be addressed through innovations in governance, policy, and ways of implementing management strategies. Science and engineering play a critical role in helping define possible alternative futures that could be achieved and the possible consequences to economic development, quality of life, and sustainability of ecosystem services. Science has advanced rapidly during the past decade with the emergence of science communities coalescing around 'Grand Challenges' and the maturation of how these communities function has resulted in large interdisciplinary research networks. An example is the River Experiment Center of KICT that engages researchers from throughout Korea and the world. This trend has been complemented by major advances in sensor technologies and data synthesis to accelerate knowledge discovery. These factors combine to allow scientific debate to occur in a more open and transparent manner. The availability of information and improved communication of scientific and engineering issues is raising the level of dialogue at the science-policy interface. However, severe challenges persist since scientific discovery does not occur on the same timeframe as management actions, policy decisions or at the pace sometimes expected by elected officials. Common challenges include the need to make decisions in the face of considerable uncertainty, ensuring research results are actionable and preventing science being used by special interests to delay or obsfucate decisions. These challenges are explored in the context of examples from the United States, including the California Bay-Delta system. California transfers water from the wetter northern part of the state to the drier southern part of the state through the Central Valley Project since 1940 and this was supplemented by the State Water Project in 1973. The scale of these activities is remarkable: approximately two thirds of the population of Californians rely on water from the Delta, these waters also irrigate up to 45% of the fruits & vegetables produced in the US, and about 80% of California's commercial fishery species live in or migrate through the Bay-Delta. This Delta region is a global hotspot for biodiversity that provides habitat for over 700 species, but is also a hotspot for the loss of biodiversity with more than 25 species currently listed by the Endangered Species Act. Understanding the decline of the fragile ecosystem of the Bay-Delta system and the potential consequences to economic growth if water transfers are reduced for the environment, the California State Legislature passed landmark legislation in 2009 (CA Water Code SS 85054) that established "Coequal goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem". The legislation also stated that "The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." The challenges of integrating policy, management and scientific research will be described through this and other international examples.

• Nuclear Engineering and Technology
• /
• v.53 no.10
• /
• pp.3217-3228
• /
• 2021

Flow blockage of the fuel assembly in the lead-based fast reactor (LFR) may produce critical local spots, which will result in cladding failure and threaten reactor safety. In this study, the flow blockage characteristics were analyzed with the sub-channel analysis method, and the circumferentially-varied method was employed for considering the non-uniform distribution of circumferential temperature. The developed sub-channel analysis code SACOS-PB was validated by a heat transfer experiment in a blocked 19-rod bundle cooled by lead-bismuth eutectic. The deviations between the predicted coolant temperature and experimental values are within ±5%, including small and large flow blockage scenarios. And the temperature distributions of the fuel rod could be better simulated by the circumferentially-varied method for the small blockage scenario. Based on the validated code, the analysis of blockage characteristics was conducted. It could be seen from the temperature and flow distributions that a large blockage accident is more destructive compared with a small one. The sensitivity analysis shows that the closer the blockage location is to the exit, the more dangerous the accident is. Similarly, a larger blockage length will lead to a more serious case. And a higher exit temperature will be generated resulting from a higher peak coolant temperature of the blocked region. This work could provide a reference for the future design and development of the LFR.

• Journal of Life Science
• /
• v.29 no.4
• /
• pp.499-508
• /
• 2019

Cancer stem cells (CSCs), which are primarily responsible for metastasis and recurrence, have self-renewal, differentiation, therapeutic resistance, and tumor formation abilities. Numerous studies have demonstrated the signaling pathways essential for the acquisition and maintenance of CSC characteristics, such as WNT/${\beta}$-catenin, Hedgehog, Notch, B lymphoma Mo-MLV insertion region 1 homolog (BMI1), Bone morphogenetic protein (BMP), and TGF-${\beta}$ signals. However, few therapeutic strategies have been developed that can selectively eliminate CSCs. Recently, neutralizing antibodies against Cytotoxic T-lymphocyte associated protein 4 (CTLA-4) and Programmed cell death protein 1 (PD-1)/Programmed death-ligand 1 (PD-L1), immune checkpoint inhibitors (ICIs), have shown promising outcomes in clinical trials of melanoma, lung cancer, and pancreatic cancer, as well as in hematologic malignancies. ICIs are considered to outperform conventional anticancer drugs by maintaining long-lasting anti-cancer effects, with less severe side effects. Several studies reported that ICIs successfully blocked CSC properties in head and neck squamous carcinomas, melanomas, and breast cancer. Together, these findings suggest that novel and effective anticancer therapeutic modalities using ICIs for selective elimination of CSCs may be developed in the near future. In this review, we highlight the origin and characteristics of CSCs, together with critical signaling pathways. We also describe progress in ICI-mediated anticancer treatment to date and present perspectives on the development of CSC-targeting ICIs.

• Korean Journal of Heritage: History & Science
• /
• v.46 no.3
• /
• pp.32-47
• /
• 2013

The concepts of authenticity and integrity are very important standards to be satisfied in the conservation and utilization of Scenic Site (名勝), literally meaning the places of scenic beauty, as a public heritage. These concepts, which are frequently used in the conservation and utilization of the World Heritage inscribed by UNESCO, can be applied to all kinds of heritages. Recently, it has been widely recognized that the concepts of authenticity and integrity are not separable but interconnected. Accordingly, the maintenance of authenticity in Scenic Site should include not only the physical preservation but also the succession of historical tradition of enjoyment. The integrity in Scenic Site refers to the physical and social conditions under which authenticity can be satisfactorily protected. The aim of this study is to reconstruct the traditional ways of enjoying historical and cultural Scenic Site with emphasis on the Yeongnam Region and make a critical examination of cultural property protection areas that have been designated. Then, this study aims to find the ways to utilize Scenic Site to secure the standards of authenticity and integrity. As a result it was discovered that cultural property protection areas are not designated well enough to satisfy the standards of authenticity and integrity. Considering the fact that cultural property protection areas are the minimal institutional systems to maintain the original value of Scenic Site, it is necessary to pay more careful attention to the ways of securing the authenticity and integrity in Scenic Site.

• Journal of the Korean Society of Radiology
• /
• v.13 no.4
• /
• pp.645-652
• /
• 2019

Phosphor with phosphorus doped with rare earth ions was investigated by searching Sr and Eu phosphors suitable for substitution of Eu ions with similar ionic radius to polyphosphate host. The $NaSr(PO_3)_3$ phosphor was synthesized by the solid state method and the $NaSr(PO_3)_3:Eu^{2+}$ phosphor was prepared by the carbon thermal reduction method. Both of the phosphors were identified by X - ray diffraction. The excitation and emission spectra of $NaSr(PO_3)_3:Eu^{3+}$ increased fluorescence intensity and intensity quenching with increasing $Eu^{3+}$ concentration. The higher the $Eu^{3+}$ concentration in the emission spectrum, the higher the local symmetry of $Eu^{3+}$ environment. The mechanism of concentration quenching, in which fluorescence decreases due to the energy transfer between $Eu^{2+}$ ions with the closest critical distance between $Eu^{2+}$ ions with increasing $Eu^{2+}$ ion concentration, was confirmed in the emission spectrum of $NaSr(PO_3)_3:Eu^{2+}$ concentration. It is possible to change the fluorescent region through the post-processing of single rare earth ion added phosphors, and it is possible to change the fluorescence by applying the energy transfer and concentration quenching mechanism according to the local symmetry of $Eu^{3+}$ will be used for high phosphor development.