• Bulletin of the Korean Chemical Society
• /
• v.26 no.5
• /
• pp.755-762
• /
• 2005

A series of catalysts, NiO/$CeO_2-ZrO_2/WO_3$, for ethylene dimerization was prepared by the precipitation and impregnation methods. For NiO/$CeO_2-ZrO_2/WO_3$ sample, no diffraction line of nickel oxide was observed up to 40 wt%, indicating good dispersion of nickel oxide on the surface of catalyst. The hexagonal and monoclinic phases of $WO_3$ up to the calcination temperature of 500 ${^{\circ}C}$ were observed, whereas the hexagonal phase of WO3 completely was transformed into monoclinic phase of $WO_3$ at 600 ${^{\circ}C}$ and above. The role of $CeO_2$ in the catalysts was to form a thermally stable solid solution with zirconia and consequently to give high surface area and acidity. The catalytic activities for ethylene dimerization were correlated with the acidity of catalysts measured by the ammonia chemisorption method. 25-NiO/5-$CeO_2-ZrO_2/15-WO_3$ containing 25 wt% NiO, 15 wt% $WO_3$ and 5 mol% $CeO_2$, and calcined at 400 ${^{\circ}C}$ exhibited a maximum catalytic activity due to the effects of $WO_3$ modifying and $CeO_2$ doping.

• Archives of Plastic Surgery
• /
• v.35 no.5
• /
• pp.615-618
• /
• 2008

Purpose: Pyoderma gangrenosum is a rare cutaneous ulcerative disease. First described in 1930, the condition is characterized by progressive ulceration with deeply undermined purple-red edge. The lower extremities are most commonly affected but other parts of the skin and mucous membranes may also be involved. Although medical treatments with topical wound therapy are commonly used, surgical intervention is still controversial. In this paper, we report an atypical case of pyoderma gangrenosum which was characterized by extensive soft tissue breakdown. Methods: A 27-year-old male patient was referred to our institution with a $7{\times}8cm$ sized deeply undermined ulceration with pus-like discharge and fever. Incision and drainage was performed at another clinic 3 days prior to admission to our institution. After a thorough physical examination and the MRI review, a diagnosis of necrotizing faciitis was made. Accordingly, fasciotomy and debridement was performed. However, the wound enlarged progressively and the patient remained highly febrile for 9 days after the treatment. Septic screening did not reveal any occult infection. After a secondary review of the case, the initial diagnosis of necrotizing fasciitis was rejected and changed to pyoderma gangrenosum. With the use of dexamethasone intravenously, the wound improved dramatically and the fever was eliminated. Steroid mediation was tapered with duration of 1 month. The wound was stabilized and subsequently covered with split-thickness skin graft. Results: Split-thickness skin grafting with 1 : 1.5 mesh was successfully taken. Conclusion: Initial clinical features of pyoderma gangrenosum are very similar to that of necrotizing fasciitis. High fever and progressive ulceration with severe pain could invite earlier surgical approach. The advancing wound margins (the well defined violaceous, undermined border and necrotic ulcer base) and lack of isolation of pathogenic organism was used to make the correct diagnosis of pyoderma gangrenosum. We achieved a good result with proper medication and split-thickness skin graft.

• The Journal of the Korea Contents Association
• /
• v.18 no.3
• /
• pp.148-159
• /
• 2018

This study empirically examined the influence of ownership structure(public/private) and revenue structure (high dependency on advertisement/low dependency on advertisement) of broadcasting companies upon journalists' perceptions regarding the degree of freedom in news reporting, the factors that limit freedom of press, satisfaction with the work autunomy and satisfaction with company's policies of news reporting and editing in light of resource dependency theory. The result showed that both the ownership structure and revenue structure of broadcasting companies influenced the journalists' perception regarding the degree of freedom in news gathering and reporting. It was also confirmed that only the revenue structure affected the level of satisfaction with work autonomy while the degree of satisfaction with the company's policies on editing and programing was influenced by the ownership structure. The perception of the factors that limit the freedom of press was found to be influenced only by the ownership structure, as did the satisfaction with policies on editing and programing. These results are very significant as they show that the level of dependence on advertising revenue affects journalists' news reporting, and that journalists of public broadcasting companies are influenced by the dependence on government or other political powers as well as on advertising revenue.

• Journal of Wetlands Research
• /
• v.10 no.3
• /
• pp.79-86
• /
• 2008

To improve water quality for agricultural use, it is needed to introduce the natural and low-cost self-purification system. It is also necessary to develop the water purification facilities for more efficient and convenient design, construction, operation and management. This study aims to develop the practical facilities to improve water quality for agricultural use. The practical detention pond system, which uses artificial floating island and shield skirts with bio-media, enhanced removal efficiencies of SS, TN and TP more particularly than the detention pond using an auxiliary dam. The removal efficiencies SS, TN and TP for the practical detention pond were 55.7%, 61.0% and 55.9%, respectively. The facilities of the practical detention pond has a lot of disadvantages such as the low-cost and high efficiency as well as uncountable impacts regarding ecology and landscape. However, an auxiliary dam is recommended to be installed in shallow depth due to low efficiency.

• Journal of electromagnetic engineering and science
• /
• v.9 no.4
• /
• pp.218-222
• /
• 2009

In this paper, we present a CPW-based 77 GHz 3-stage power amplifier MMIC for automotive radar systems. The power amplifier MMIC has been realized using a 130 nm $In_{0.88}$GaP/$In_{0.4}$AlAs/$In_{0.4}$GaAs metamorphic high-electron mobility transistors(mHEMTs) technology and an output stage with a cascode configuration. This produced a good output power and gain performance at 77 GHz. The fabricated power amplifier MMIC exhibited a small-signal gain of 18 dB, an output power of 17 dBm and 9 % power added efficiency(PAE) at 77 GHz with a total gate width of 800 ${\mu}m$ in the output stage. These performances could be useful to low-cost and small-sized components for 77 GHz automotive radar systems.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.9
• /
• pp.54-58
• /
• 2011

In this paper a dual-band Class-E power amplifier using Composite Right-/Left-Handed transmission lines and PIN diode is proposed. Dual-band operation is achieved by the frequency offset and nonlinear phase slope of CRLH TL for the matching network of power amplifiers. The proposed power amplifier has been realized by using in the input and the output matching network for high power added efficiency. PIN diode has been used to obtain the dual-band of power amplifier. The measured results show that output powers of 42.17 dBm and 41.43 dBm were obtained at 800 MHz and 1900 MHz, respectively. At this frequency, we have obtained the power-added efficiency(PAE) of 67.84 % and 65.31 % in two operation frequencies, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.2
• /
• pp.88-92
• /
• 2020

Thermal effects in bulk and SOI FinFETs are briefly reviewed herein. Different techniques to measure these thermal effects are studied in detail. Self-heating effects show a strong dependency on geometrical parameters of the device, thereby affecting the reliability and performance of FinFETs. Mobility degradation leads to 7% higher current in bulk FinFETs than in SOI FinFETs. The lower thermal conductivity of SiO₂ and higher current densities due to a reduction in device dimensions are the potential reasons behind this degradation. A comparison of both bulk and SOI FinFETs shows that the thermal effects are more dominant in bulk FinFETs as they dissipate more heat because of their lower lattice temperature. However, these thermal effects can be minimized by integrating 2D materials along with high thermal conductive dielectrics into the FinFET device structure.

• Journal of the Korea Society of Computer and Information
• /
• v.15 no.3
• /
• pp.81-89
• /
• 2010

The research on peer-to-peer streaming schemes has largely focused on tree-push and mesh-pull structures. However, the tree-push structure has a defect that the tree restructuring time is long, and the mesh-pull structure has long startup delay and lag time from source servers. In this paper, we propose a new peer-to-peer live streaming scheme based on a push-mesh structure that takes advantages of tree-push and mesh-pull structure simultaneously. This structure basically provides the mesh-pull mechanism for data transmission and utilizes peers with high network upload capacity. It also supports the push mechanism along with paths from a source server, super peers, and selected general peers. By NS-2 simulation experiments, we finally show that our proposed scheme can achieve shorter startup delay than the mesh-pull structure, similar lag time to tree-push structure and best playback continuity among the three schemes.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.48 no.1
• /
• pp.51-60
• /
• 2006

This study was conducted to investigate experimentally the drying shrinkage and the strength properties of redispersible SBR and PAE powder-modified mortars. Polymer-cement ratio, content of shrinkage-reducing agent and antifoamer content were manipulated as the experimental variables. The peculiarity of this study is to obtain a high early-age strength by using the portland cement and alumina cement with the ratio of 8 : 2. Until 7 days of age, the drying shrinkage remarkably increased up to $1\~2\times10^{-4}$, while it tended to decrease as the ratio of polymer to cement ratio and the content of shrinkage-reducing agent increased. Polymer-cement ratio was effective in improving the flexural, tensile and adhesive strengths: As the ratio increased, the strengths correspondingly increased. The flexural strength was in the range of $7\~11$ MPa, the tensile strength was $3.5\~5$ MPa and the adhesive strength was $1.2\~3.9$ MPa. On the other hand, the compressive strength tended to decrease as the polymer-cement ratio increased, and it was in the range of $23\~39$ MPa. All strengths, flexural, tensile, adhesive and compressive strengths, decreased as the content of powder shrinkage-reducing agent increased. It turned out that the polymer-cement ratio influenced more on the behavior of drying shrinkage and the properties of strength than the powder shrinkage-reducing agent did.

• Bulletin of the Korean Chemical Society
• /
• v.27 no.12
• /
• pp.1989-1996
• /
• 2006

The $NiSO_4/CeO_2-ZrO_2 $catalysts containing different nickel sulfate and $CeO_2$ contents were prepared by the impregnation method, where support, $CeO_2-ZrO_2$was prepared by the coprecipitation method using a mixed aqueous solution of zirconium oxychloride and cerium nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt %, indicating good dispersion of nickel sulfate on the surface of $CeO_2-ZrO_2$. The addition of nickel sulfate (or $CeO_2$) to $ZrO_2$ shifted the phase transition of $ZrO_2$ from amorphous to tetragonal to higher temperatures because of the interaction between nickel sulfate (or $CeO_2$) and $ZrO_2$. A catalyst (10-$NiSO_4/1-CeO_2-ZrO_2$) containing 10 wt % $NiSO_4$ and 1 mole % $CeO_2$, and calcined at $600{^{\circ}C}$ exhibited a maximum catalytic activity for ethylene dimerization. The catalytic activities were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The role of $CeO_2$was to form a thermally stable solid solution with zirconia and consequently to give high surface area, thermal stability and acidity of the sample.