Biography:

In the past N.J. Kim has collaborated on articles with H.W. Lee and C.-J. Kim. One of their most recent publications is Effects of the constituents on the mechanical behavior of low carbon steels. Which was published in journal Scripta Metallurgica.

More information about N.J. Kim research including statistics on their citations can be found on their Copernicus Academic profile page.

N.J. Kim's Articles: (8)

Role of the brane curvature scalar in the brane world cosmology

AbstractWe include the brane curvature scalar to study its cosmological implication in the brane world cosmology. This term is usually introduced to obtain the well-defined stress-energy tensor on the boundary of anti-de-Sitter–Schwarzschild space. Here we treat this as the perturbed term for cosmological purpose. We find corrections to the well-known equation of the brane cosmology. It contains new interesting terms which may play the important role in the brane cosmology.

Probing the BTZ black hole with test fields

AbstractWe introduce a set of scalar fields as test fields to study the dynamical behaviors of the BTZ (Banados-Teitelboim-Zanelli) black hole. These include minimally coupled scalar, conformally coupled scalar, dilaton, and tachyon. To calculate the decay rate of the BTZ black hole, we consider both the Dirichlet boundary condition at spatial infinity and the stability condition. It turns out that the tachyon may be a relevant field to get information of the BTZ black hole.

Original articleInfectious diseasesWhich tissues are best for microbiological diagnosis in patients with pyogenic vertebral osteomyelitis undergoing needle biopsy?

AbstractIdentification of the causative microorganism is important in the management of pyogenic vertebral osteomyelitis (PVO). The aim of this study was to investigate whether culture positive rates differ between needle biopsy sites in patients with PVO, and which tissues are best for microbiological diagnosis. Between January 2005 and December 2013, we conducted a retrospective cohort study of PVO patients who had soft-tissue abscesses (paraspinal or psoas abscesses) and who received needle biopsy for microbiological diagnosis. Needle biopsy sites were classified into two anatomical categories: vertebral bodies, or soft tissues (intervertebral discs, paraspinal abscesses, or psoas abscesses). A generalized estimating equation model was developed to identify factors associated with tissue-culture positivity. During the study period a total of 136 tissues were obtained by needle biopsy from 128 PVO patients with soft-tissue abscesses. The culture positive rates of vertebral bodies and soft tissues were 39.7% (29/73), and 63.5% (40/63), respectively (p < 0.05). In a multivariate analysis, male gender (adjusted odds ratio (aOR) 2.24, 95% CI 1.00–5.02), higher C-reactive protein (aOR 1.07, 95% CI 1.01–1.15), positive blood culture (aOR 2.57, 95% CI 1.01–6.59), and soft tissues as biopsy site compared with vertebral bodies (aOR 2.28, 95% CI 1.08–4.78) were independent factors associated with tissue culture positivity. Soft tissues were the best sites for microbiological diagnosis in PVO patients undergoing needle biopsy.

Full length articleThe microstructure of as-quenched 12Mn steel

AbstractFe-12Mn steel has the unique and interesting property that, when quenched to α′ martensite from the austenite phase, it forms an ultrafine grained microstructure that has exceptional resistance to cleavage fracture at cryogenic temperatures. The present research was undertaken to complete the characterization of this microstructure and understand why it forms and why it has such exceptional crack resistance. A combination of EBSD and TEM analysis shows that the microstructure is a dislocated lath martensite in which the laths have the Kurdjumov-Sachs relation to the parent austenite. As in other dislocated lath martensites, the prior austenite grains are divided into packets, each of which contains the 6 (of 24) KS variants that mate with the same {111}γ plane. Uniquely, however, the packets are stacks of thin plates that contain all 6 KS variants. The variants within the plate are organized into 3 pair of twinned KS variants that are elongated along their {112}α twin planes, rotated 120° from one another, and interwoven to form the 6-variant plate. The ultrafine grains are the laths themselves; twin boundaries between KS variants are known to provide strong barriers to cleavage crack propagation. This unusual microstructure is apparently due to the transformation path; austenite transforms to the hexagonal ε martensite phase before its ultimate transformation to α′, and the 6-variant plate is the preferred element to minimize elastic energy in a microstructure created by a dominant γ→ε→α′ transformation path.

The effect of yttrium addition on the oxidation resistance of EPM TiAl-based intermetallics

AbstractThe effect of yttrium on the oxidation resistance of elemental powder metallurgy (EPM) processed TiAl-based alloys was studied. Y-addition improved the oxidation resistance of the experimental alloys exposed at 800 °C for 350 h. The improved oxidation resistance was attributed to a fine-grained (Y, Al)O-type oxides and the segregation of Y in the grain boundaries and at the interfaces of Al2O3 in the Y-rich layer.

Deformation behavior of a twin-roll-cast Mg–6Zn–0.5Mn–0.3Cu–0.02Zr alloy at intermediate temperatures

The mechanical properties of a twin-roll-cast Mg–6Zn–0.5Mn–0.3Cu–0.02Zr were measured at temperatures from 423 to 523 K. Constant strain rate, strain-rate-change and temperature change tests were employed to characterize the plastic flow behavior of the alloy. It was observed that a in low-strain-rate and high-temperature regime the alloy follows a power-law behavior; however, the power law breaks down at high strain rates and low temperatures. Transient experiments were also conducted to identify the deformation mechanism.

Microstructures and tensile properties of a twin roll cast and heat-treated Mg–2.4Zn–0.1Ag–0.1Ca–0.1Zr alloy

An Mg–2.4Zn–0.1Ag–0.1Ca–0.1Zr alloy sheet, with a tensile yield strength of 316 MPa, an ultimate tensile strength of 342 MPa and an elongation of 17%, has been processed by twin roll casting (TRC), hot rolling and heat treatment. The high yield strength has been attributed to a uniform distribution of fine rod-like precipitates of MgZn2 phase. The TRC and hot-rolled sheet also showed an exceptionally high stretch formability with a limiting dome height much larger than those of other Mg alloys.

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