• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.104-109
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• 2019

An analytical threshold voltage model is proposed to analyze the threshold voltage roll-off and drain-induced barrier lowering (DIBL) for a junction-based double-gate (JBDG) MOSFET and a junction-less double-gate (JLDG) MOSFET. We used the series-type potential distribution function derived from the Poisson equation, and observed that it is sufficient to use n=1 due to the drastic decrease in eigenvalues when increasing the n of the series-type potential function. The threshold voltage derived from this threshold voltage model was in good agreement with the result of TCAD simulation. The threshold voltage roll-off of the JBDG MOSFET was about 57% better than that of the JLDG MOSFET for a channel length of 25 nm, channel thickness of 10 nm, and oxide thickness of 2 nm. The DIBL of the JBDG MOSFET was about 12% better than that of the JLDG MOSFET, at a gate metal work-function of 5 eV. It was also found that decreasing the work-function of the gate metal significantly reduces the DIBL.

• Journal of the Korea Safety Management & Science
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• v.15 no.3
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• pp.133-141
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• 2013

As a work analysis technique, Work Domain Analysis (WDA) aims to identify the design knowledge structure of a work domain that human operators interact with through human-system interfaces. Abstraction hierarchy (AH) is a multi-level, hierarchical knowledge representation framework for modeling the functional structure of any kinds of systems. Thus, WDA based on AH aims to identify the functional knowledge structure of a work domain. AH has been used in a range of work domains and problems to model their functional knowledge structure and has proven its generality and usefulness. However, many of researchers and system designers have reported that it is never easy to understand the concepts underlying AH and use it effectively for WDA. This would be because WDA is a form of work analysis that is different from other types of work analysis techniques such as task analysis and AH has several unique characteristics that are differentiated from other types of function analysis techniques used in systems engineering. With this issue in mind, this paper introduces the concepts of WDA based on AH and offers a comprehensive list of references. Next, this paper proposes a set of principles for effectively applying AH for work domain analysis, which are developed based on the author's experiences, consultation with experts, and literature reviews.

• Korean Management Science Review
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• v.20 no.2
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• pp.33-43
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• 2003

In this paper we applied dynamic programming to determining work schedule type. In dynamic programming formulation, each day during a planning horizon represents a stage for which a decision is made. The alternatives are given by work schedule types that combine regular time, overtime, additional shift, and so on. In this case, their associated return function is labor cost. The state is defined as the amount of work time allocated to stage 1, stage 2,…, and current stage. A case study for a real manufacturing company was performed to apply dynamic programming to scheduling daily work hours during a week. The case study showed that total cost of our solution derived from dynamic programming decreased by about 6％ as compared with the solution obtained from the previous method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.477-481
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• 2007

The purpose of this study is to provide the ideal forecasting model of cadastral survey work load through the Economeatric Analysis of Time Series, Granger Causality and VAR Model Analysis, it suggested the forecasting reference materials for the total amount of cadastral survey general work load. The main result is that the derive of the environment variables which affect cadastral survey general work load and the outcome of VAR(vector auto regression) analysis materials(impulse response function and forecast error variance decomposition analysis materials), which explain the change of general work load depending on altering the environment variables. And also, For confirming the stability of time series data, we took a unit root test, ADF(Augmented Dickey-Fuller) analysis and the time series model analysis derives the best cadastral forecasting model regarding on general cadastral survey work load. And also, it showed up the various standards that are applied the statistical method of econometric analysis so it enhanced the prior aggregate system of cadastral survey work load forecasting.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.74.1-74
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• 2001

In this paper, we deal with an allocation model of vertical type container yard for minimizing the total ATC work time and the equivalence of ATC work´s load in each block on automated container terminal. Firstly, a layout of automated container terminal yard is shown. The characteristic of equipment which is operated in the terminal and basic assumption are given. Next, an allocation model which concerns with minimizing the total work time and the equivalence of work´s load is proposed for the effectiveness of ATC work in automated container terminal. Also, a weight values on critical function are suggested to adjust the critical values by evaluating the obtained allocation plan. To find the solution of allocation model in given terminal yard situation, a GA is applied, where the real information of container is used ...

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.90-96
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• 2005

The existing safety-management manual is confined to list data based on regulations, and only provide ways to prevent accidents/incidents for particular work which accidents occur frequently. As it is difficult to understand the complete process involved the work, we can not expect the manual to function as a guide to prevent unfortunate events. When establishing WBS(work breakdown structure) of railway line engineering, consideration of the characteristics of train operation will enable many benefits. Therefore in this research it is conducted to materialize it in the manual. Main contents in this research are to review the way that change complete work performance process and person in charge of different tasks into WBS(work breakdown structure), and trough the newly developed WBS , the ways to improve roles and functions of the manual which Korean Railroad made are recommended.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.4
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• pp.525-533
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• 2015

Objectives: Alongside smoking, occupational exposure is an important risk factor for chronic obstructive pulmonary disease. The purpose of this study was to evaluate factors associated with occupational pulmonary function decline that can be used to create guidelines for the health management of shipyard workers Materials: This study analyzed spirometry from 10,597 male shipbuilding workers. Functional decline in spirometry was defined as FEV1/FVC <70% and logistic regression for work duration and occupational hazard exposure was performed Results: Among the subjects, 4.2% showed an obstructive pattern in pulmonary function. The odds ratios for hazard exposure were 1.67(indirect) and 3.54(direct), and for work duration 1.97(10-18 years), 2.29(19-27), and 5.02(28+). After adjusting for smoking and work-related factors, the odds ratios for work durations of over 10 years were 1.73(10-18 years), 1.99(19-27), and 4.09(28+), but for hazards exposure was 1.71(direct) alone after adjustment. Conclusions: Occupational COPD is insidious and chronic, and thus long-term hazard exposed(especially over 10 years) shipyard workers with functional decline in spirometry need to prevent and manage COPD. This study is important for establishing guidelines to manage hazard exposure among shipyard workers and prevent COPD.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.111.2-111.2
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• 2015

Typical electrodes (metal or indium tin oxide (ITO)), which were used in conventional organic light emitting devices (OLEDs) structure, have transparency and conductivity, but, it is not suitable as the electrode of the flexible OLEDs (f-OLEDs) due to its brittle property. Although Graphene is the most well-known alternative material for conventional electrode because of present electrode properties as well as flexibility, its carrier injection barrier is comparatively high to use as electrode. In this work, we performed plasma treatment on the graphene surface and alkali metal doping in the organic materials to study for its possibility as anode and cathode, respectively. By using Ultraviolet Photoemission Spectroscopy (UPS), we investigated the interfaces of modified graphene. The plasma treatment is generated by various gas types such as O2 and Ar, to increase the work function of the graphene film. Also, for co-deposition of organic film to do alkali metal doping, we used three different organic materials which are BMPYPB (1,3-Bis(3,5-di-pyrid-3-yl-phenyl)benzene), TMPYPB (1,3,5-Tri[(3-pyridyl)-phen-3-yl]benzene), and 3TPYMB (Tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane)). They are well known for ETL materials in OLEDs. From these results, we found that graphene work function can be tuned to overcome the weakness of graphene induced carrier injection barrier, when the interface was treated with plasma (alkali metal) through the value of hole (electron) injection barrier is reduced about 1 eV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.32-32
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• 2009

Silicon carbide (SiC) is a wide-bandgap semiconductor that has materials properties necessary for the high-power, high-frequency, high-temperature, and radiation-hard condition applications, where silicon devices cannot perform. SiC is also the only compound semiconductor material. on which a silicon oxide layer can be thermally grown, and therefore may fabrication processes used in Si-based technology can be adapted to SiC. So far, atomic force microscopy (AFM) has been extensively used to study the surface charges, dielectric constants and electrical potential distribution as well as topography in silicon-based device structures, whereas it has rarely been applied to SiC-based structures. In this work, we investigated that the local oxide growth on SiC under various conditions and demonstrated that an increased (up to ~100 nN) tip loading force (LF) on highly-doped SiC can lead a direct oxide growth (up to few tens of nm) on 4H-SiC. In addition, the surface potential and topography distributions of nano-scale patterned structures on SiC were measured at a nanometer-scale resolution using a scanning kelvin probe force microscopy (SKPM) with a non-contact mode AFM. The measured results were calibrated using a Pt-coated tip. It is assumed that the atomically resolved surface potential difference does not originate from the intrinsic work function of the materials but reflects the local electron density on the surface. It was found that the work function of the nano-scale patterned on SiC was higher than that of original SiC surface. The results confirm the concept of the work function and the barrier heights of oxide structures/SiC structures.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.432.2-432.2
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• 2014

Recently, colloidal core/shell type quantum dots lighting-emitting diodes (QDLEDs) have been extensively studied and developed for the future of optoelectronic applications. In the work, we fabricate an inverted CdSe/ZnS quantum dot (QD) based light-emitting diodes (QDLED)[1]. In order to reduce work function of indium tin oxide (ITO) electrode for inverted structure, a very thin (<10 nm) polyethylenimine ethoxylated (PEIE) is used as surface modifier[2] instead of conventional metal oxide electron injection layer. The PEIE layer substantially reduces the work function of ITO electrodes which is estimated to be 3.08 eV by ultraviolet photoemission spectroscopy (UPS). From transmission electron microscopy (TEM) study, CdSe/ZnS QDs are uniformly distributed and formed by a monolayer on PEIE layer. In this inverted QD LED, two kinds of hybrid organic materials, [poly (9,9-di-n-octyl-fluorene-alt-benzothiadiazolo)(F8BT) + poly(N,N'-bis (4-butylphenyl)-N,N'-bis(phenyl)benzidine (poly-TPD)] and [4,4'-N,N'-dicarbazole-biphenyl (CBP) + poly-TPD], were adopted as hole transport layer having high highest occupied molecular orbital (HOMO) level for improving hole transport ability. At a low-operating voltage of 8 V, the device emits orange and red spectral radiation with high brightness up to 2450 and 1420 cd/m2, and luminance efficacy of 1.4 cd/A and 0.89 cd/A, respectively, at 7 V applied bias. Also, the carrier transport mechanisms for the QD LEDs are described by using several models to fit the experimental I-V data.