• ETRI Journal
• /
• v.33 no.1
• /
• pp.32-38
• /
• 2011

We investigated the light-emitting performances of blue phosphorescent organic light-emitting diodes, known as PHOLEDs, by incorporating an N,N'-dicarbazolyl-3,5-benzen interlayer between the hole transporting layer and emitting layer (EML). We found that the effects of the introduced interlayer for triplet exciton confinement and hole/electron balance in the EML were exceptionally dependent on the host materials: 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, 9-(4-tert-butylphenyl)-3,6-ditrityl-9H-carbazole, and 4,4'-bis-triphenylsilanyl-biphenyl. When an appropriate interlayer and host material were combined, the peak external quantum efficiency was greatly enhanced by over 21 times from 0.79% to 17.1%. Studies on the recombination zone using a series of host materials were also conducted.

• Structural Engineering and Mechanics
• /
• v.46 no.1
• /
• pp.111-135
• /
• 2013

An experimental study has been carried out on square plain concrete (PC) and reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. A total of 78 specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. Slenderness of the columns, number of wrap layers and concrete strength were the test parameters. Compressive stress, axial and hoop strains were recorded to evaluate the stress-strain relationship, ultimate strength and ductility of the specimens. Results clearly demonstrate that composite wrapping can enhance the structural performance of square columns in terms of both maximum strength and ductility. On the basis of the effective lateral confining pressure of composite jacket and the effective FRP strain coefficient, new peak stress equations were proposed to predict the axial strength and corresponding strain of FRP-confined square concrete columns. This model incorporates the effect of the effective circumferential FRP failure strain and the effect of the effective lateral confining pressure. The results show that the predictions of the model agree well with the test data.

• Journal of Information Display
• /
• v.10 no.3
• /
• pp.107-110
• /
• 2009

Efficient deep-blue organic light-emitting diodes were demonstrated using 4,4'-bis(9-ethyl-3-carbazovinylene)-1,1'-biphenyl doped in double-emission layers (D-EMLs). The D-EML system, which consists of 2-methyl-9,10-di(2-naphthyl)anthracene and 1,4-(dinaphthalen-2-yl)-naphthalene as blue hosts, was employed to broaden the recombination zone and to ensure the good confinement of the holes and electrons. The optimized device showed a peak current efficiency of 4.47 cd/A, a peak external quantum efficiency of 4.09%, and Commission Internationale de L'Eclairage coordinates of (0.16, 0.10).

• Steel and Composite Structures
• /
• v.1 no.3
• /
• pp.355-376
• /
• 2001

An experimental research program on end-plate beam-to-column composite joints under cyclic loading is presented. The major focus relates to the identification of the contribution of the concrete confinement in composite columns to the behaviour of the joint, on internal nodes and external nodes, together with an assessment of degradation of strength and stiffness in successive loading cycles. From the experimental results it was possible to identify the various failure modes and to fit the corresponding hysteretic curves to the Richard-Abbott and Mazzolani models. These curve-fitting exercises highlighted the need to adapt both models, either for improved ease of application, or to deal with some aspects previously not covered by those models.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.67 no.3
• /
• pp.149-154
• /
• 2018

We consider the system is subject to the linearly polarized oscillatory external field. We study the optical quantum transition Line shapes(QTLS) which show the absorption power and the quantum transition line widths(QTLW) of electron-piezoelectric phonon interacting system. We analyze the magnetic field dependence of the QTLS and the QTLW in various cases. In order to analysis the quantum transition, we compare the magnetic field dependence of the QTLW and the QTLS of two transition process, the intra-Landau level transition process and the inter-Landau level transition process.

• Journal of Magnetics
• /
• v.8 no.3
• /
• pp.103-107
• /
• 2003

Relaxation of magnon in a very thin ferromagnetic film through spontaneous emission of photon shows an enhancement of the decay rate due to the phase coherence between the magnon and the planar component of wave vector of photon. The coupling between magnon and photon under a strong external magnetic field is considered only at the lowest order one-magnon one-photon process, which we believe the most dominant channel for the radiation from the system. Theoretical understanding related to the geometric confinement is pursued; the phase coherence due to the crystal symmetry in the film plane gives rise to superradiative emission on one hand, but the symmetry breaking along the direction perpendicular to the film renders the possibility of emission itself, providing the increased degrees of freedom for the photon.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.9
• /
• pp.724-729
• /
• 2010

We have proposed a new configuration on the cathode structure to improve a neutron yield without the application of external ion sources in an inertial electrostatic confinement (IEC) device. A neutron yield in the IEC device is closely related to the potential well structure generated inside the cathode and is proportional to the ion current. Therefore, the application of a double grid cathode structure to the IEC device is expected to produce a higher ion current and neutron yield than at a single grid cathode due to a high electric field strength generated around the cathode. These possibilities were verified as compared with the ion current calculated from both shape of the single and double grid cathode. Additionally from the results of ion's lives and trajectories examined at various outer cathode voltages and grid cathode configurations by using particle simulations, the validity of the double grid cathode was confirmed.

• Steel and Composite Structures
• /
• v.30 no.5
• /
• pp.405-416
• /
• 2019

Profiled composite slab has been widely used in civil engineering due to its structural merits. The extension of this concept to the bearing wall forms the profiled composite wall, which consists of two external profiled steel plates and infill concrete. This paper investigates the structural behavior of this type of wall under axial compression. A series of compression tests on profiled composite walls consisting of varied types of profiled steel plate and edge confinement have been carried out. The test results are evaluated in terms of failure modes, load-axial displacement curves, strength index, ductility ratio, and load-strain response. It is found that the type of profiled steel plate has influence on the axial capacity and strength index, while edge confinement affects the failure mode and ductility. The test data are compared with the predictions by modern codes such as AISC 360, BS EN 1994-1-1, and CECS 159. It shows that BS EN 1994-1-1 and CECS 159 significantly overestimate the actual compressive capacity of profiled composite walls, while AISC 360 offers reasonable predictions. A method is then proposed, which takes into account the local buckling of profiled steel plates and the reduction in the concrete resistance due to profiling. The predictions show good correlation with the test results.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.31A no.10
• /
• pp.79-86
• /
• 1994

Gain-guided broad-area single quantum well separate confinement heterostructure diode lasers have been fabricated from structures grown by metal organic vapor phase epitaxy. The active layer of the epi-structure is InGaAs emitting 962-965nm and the guiding layer GaAs. The channel width is fixed to 150${\mu}$m and the cavity length varys within the range of 300~800${\mu}$m. For uncoated LD's, the output power of 0.7W has been obtaained at a pulsed current level of 2A, which results about 60% external quantum efficiency. The threshold current density is 200A/cm$^{2}$ for the cavity lengths of 800.mu.m LD's. The stain effect upon the transparent current density has been observed. The internal quantum efficiency is expected to be 88% and the internal loss to be 18$cm^{-1}$. The beam divergence has been measured to be 7$^{\circ}$to lateral and 40$^{\circ}$to transverse direction. finally, 1.2W continuous-wave output power has been obtained at a current level of 2A for AR/HR coated LD's die-bonded on Cu heat-sink and cooled by TEC.

• The Research Journal of the Costume Culture
• /
• v.22 no.5
• /
• pp.688-701
• /
• 2014

This study examined the expression characteristics in pop art works of Jean-Charles de Castelbajac. The study here aimed at possibility to find a design development in building up the unique art world of creativity based on popularity, artistry, and originality without confinement to the trend only. For the research method, review of literature and analysis about Castelbajac's works reflecting the pop art feature in the collections from 2000S/S to 2012F/W were performed. The results of research are as follows. The external expression form of Castelbajac's works based on pop art was grouped roughly into use of mass culture image, appropriation of pop art expression technique, and parody of art works. First, his work appeared as application of the mass culture image such as symbolic thing in the modern consumer society, object in an ordinary life, character of well-known animation, national flag and famous star. Second, such appropriated pop art techniques showed as pop color in strong primary color and silk screen, photomontage, collage, assemblage, graffiti, and lettering. Third, a variety of images featured earlier in art works were shown in parody. These works are valuable in that they are expressed aesthetically through regeneration of popular culture's various images in view of fashion, they are described in the non-traditional value with frolic resistance and deviation out of existing fashion norm, and they are given the dynamic creativity integrated with art and fashion.