• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.418-418
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• 2008

The electrochemical etching of silicon in HF-based solutions is known to form various types of porous structures. Porous structures are generally classified into three categories according to pore sizes: micropore (below 2 nm in size), mesopore (2 ~ 50 nm), and macropore (above 50 nm). Recently, the formation of macropores has attracted increasing interest because of their promising characteristics for an wide scope of applications such as microelectromechanical systems (MEMS), chemical sensors, biotechnology, photonic crystals, and photovoltaic application. One of the promising applications of macropores is in the field of MEMS. Anisotropic etching is essential step for fabrication of MEMS. Conventional wet etching has advantages such as low processing cost and high throughput, but it is unsuitable to fabricate high-aspect-ratio structures with vertical sidewalls due to its inherent etching characteristics along certain crystal orientations. Reactive ion dry etching is another technique of anisotropic etching. This has excellent ability to fabricate high-aspect-ratio structures with vertical sidewalls and high accuracy. However, its high processing cost is one of the bottlenecks for widely successful commercialization of MEMS. In contrast, by using electrochemical etching method together with pre-patterning by lithographic step, regular macropore arrays with very high-aspect-ratio up to 250 can be obtained. The formed macropores have very smooth surface and side, unlike deep reactive ion etching where surfaces are damaged and wavy. Especially, to make vertical microwire or nanowire arrays (aspect ratio = over 1:100) on silicon wafer with top-down photolithography, it is very difficult to fabricate them with conventional dry etching. The electrochemical etching is the most proper candidate to do it. The pillar structures are demonstrated for n-type silicon and the formation mechanism is well explained, while such a experimental results are few for p-type silicon. In this report, In order to understand the roles played by the kinds of etching solution and mask patterns in the formation of microwire arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, dimethyl sulfoxide (DMSO), iso-propanol, and mixtures of HF with water on the structure formation on monocrystalline p-type silicon with a resistivity with 10 ~ 20 $\Omega{\cdot}cm$. The different morphological results are presented according to mask patterns and etching solutions.

• Journal of the Korean Geotechnical Society
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• v.20 no.2
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• pp.87-96
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• 2004

Application of the soil nailing method is continuously extending in maintaining stable excavations and slopes. However, ground anchor support system occasionally may not be used because of space limitations in urban excavation sites nearby the existing structures. In this case, soil nailing system with relatively short length of nails could be efficiently adopted as an alternative method. The general soil nailing support system, however, may result in excessive deformations particularly in an excavation zone of the existing weak subsoils. Pretensioning the soil nails then could play important roles to reduce deformations mainly in an upper part of the nailed-soil excavation system as well as to improve local stability. In this study, a newly modified soil nailing technology named as the PSN (Pretension Soil Nailing) is developed to reduce both facing displacements and ground surface settlements in top-down excavation process as well as to increase the global stability. Up to now, the PSN system has been investigated mainly focusing on an establishment of the design procedure. In the present study, laboratory model tests are carried out to investigate the failure mechanism and behavior characteristics of the PSN system. Various results of model tests are also analyzed to provide a fundamental basis for the efficient design.

• KDI Journal of Economic Policy
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• v.31 no.1
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• pp.27-69
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• 2009

This paper studies the logic of fiscal constraints and fiscal autonomy in a political agency model with both moral hazard and adverse selection. The electoral process not only disciplines incumbents who may act against the public interest but also opts in politicians who are most likely to act along voters' interests. We characterize perfect Bayesian equilibria under shared tax system and fiscal autonomy with fiscal constraints for local public good provision. It is shown that the local voters' expected welfare under fiscal autonomy is higher than under shared tax system if the same fiscal constraints are applied. In order to examine the effects of party's candidate selection processes on the behavior of local politician and national politician, we extend the model to an environment where local politician can compete for the candidacy of national assembly with incumbent national politician. If local politician wins majority of votes against incumbent national politician, then he can move on to serve as a national politician. Otherwise, his political career will end as a local politician. It is the gist of this primary system portrayed by this setup that local politician and national politician compete to garner more votes. Therefore, primary system as a candidate selection mechanism enhances local residents' welfare compared to top-down candidate selection processes.

• Korean Security Journal
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• no.26
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• pp.121-144
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• 2011

The Framework Act on the Management of Disasters and Safety 2004(FAMDS) currently underpins Korean civil protection system, and under this FAMDS, Korean civil protection establishes a three-tiered government structure for dealing with crises and disasters: central government, provincial & metropolitan government, and local government tiers. In particular, the concept of Integrated Emergency Management(IEM) emphasizes that emergency response organizations should work and act together to respond to crises and disasters effectively, based on the coordination and cooperation model, not the command and control model. In tune with this trend, civil protection matters are, first, dealt with by local responders at the local level without direct involvement of central or federal government in the UK or USA. In other words, central government intervention is usually implemented in the UK and the USA, only when the scale or complexity of a civil protection issue is so vast, and thus requires a degree of central government coordination and support, resting on the severity and impact of the event. In contrast, it appears that civil protection mechanism in Korea has adopted a rigid centralized system within the command and control model, and for this reason, central government can easily interfere with regional or local command and control arrangements; there is a high level of central government decision-making remote from a local area. The principle of subsidiarity tends to be ignored. Under these circumstances, it is questionable whether such top-down arrangements of civil protection in Korea can manage uncertainty, unfamiliarity and unexpectedness in the age of Risk Society and Post-modern society, where interactive complexity is increasingly growing. In this context, the study argues that Korean civil protection system should move towards the decentralized model, based on coordination and cooperation between responding organizations, loosening the command and control structure, as with the UK or the USA emergency management arrangements. For this argument, the study basically explores mechanisms of civil protection arrangements in Korea under current legislation, and then finally attempts to make theoretical suggestions for the future of the Korean civil protection system.