• Journal of the Korean Society for Heat Treatment
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• v.13 no.2
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• pp.71-84
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• 2000

A study on adhesion and wear resistance of VC(vanadium carbide) coating on die steels, STD11 and STD61, has been carried out. The VC coating on the die steels was made by immersing them in molten borax bath, a kind of TRD(thermo-reactive deposition and diffusion). Adhesion strength and wear resistance were investigated using scratch test, indentation test and plate-disc test(Ogoshi type) respectively. The influence of sliding distance on the amount of wear has been determined and dominant wear mechanisms has been characterized using optical microscopy, scanning electron microscopy and EDS spectroscopy. The critical adhesion strength($L_c$) between VC coating layer and substrate(STD11) was increased to 60N($L_c$) in the scratch test. In the case of STD61, the strength increased to 24N. The wear resistance of VC coated die steels was excellent because the diffusion layer formed just below the coating layer. The dominant wear mechanism was identified as adhesive wear for VC coating die steels which were worn by combination of cracking and plucking of VC fragments and disc.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.1
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• pp.107-117
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• 2016

STD method using a mean and standard deviation is widely used in various inspection systems. The result of detection using the STD method is very dependent on the threshold value. This paper proposes an adaptive defect detection algorithm to with a precise detection of an ultimate defect. The proposed method is determined threshold value adaptively using a skewness that indicates a similarity of intensity and normal distribution of image. In the experiment, we used a various TFT-LCD images for a quantitative evaluation of defect detection performance evaluation result to prove the performance of the proposed algorithm.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.13-22
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• 2012

Forged and flat-bar rolled STD11 tool steel shows anisotropic dimensional change during heat treatment. The dimensional change in the rolling direction is larger than that in the transverse direction. The cause of the anisotropic dimensional change is that the steel is anisotropic in composition, microstructure and other properties. The decrease of anisotropic distortion in tool steel is important for making better precision cold working dies. In this study, the effect of ingot weight and hot rolling reduction ratio on the anisotropic dimensional change of STD11 during heat treatment has been studied. Dimensional change was evaluated by simulating a real heat treatment process, including gas quenching and tempering. Experimental results showed that all the rolled flat-bar products had anisotropic distortion to some degree, but the anisotropic distortion was reduced as hot rolling ratio increased. Ingot weight had a little effect on anisotropic distortion. Microstructural observation showed that the anisotropic dimensional change of STD11 tool steel was closely related to the amount, shape and distribution of coarse carbides.

• Journal of the Korean Magnetic Resonance Society
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• v.6 no.2
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• pp.94-102
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• 2002

An interesting recent application of intermolecular NOE experiment is the saturation transfer difference NMR(STD-NMR) method that is useful in screening compound libraries to identify bio-active ligands. This technique also identifies the group epitopes of the bound ligand in a reversibly forming protein-ligand complex. We present here a complete relaxation and conformational exchange matrix (CORCEMA) theory (Moseley et al., J. Magn. Reson. B, 108, 243-261 (1995)) applicable for the STD-NMR experiment. Using some ideal model systems we have analyzed the factors that influence the STD intensity changes in the ligand proton NMR spectrum when the resonances from some protons on the receptor protein are saturated. These factors will be discussed and some examples of its application in some model systems will be presented. This CORCEMA theory for STD-NMR and the associated algorithm are useful in a quantitative interpretation of the STD-NMR effects, and are likely to be useful in structure-based drug design efforts. They are also useful in a quantitative characterization of protein-protein (or protein-nucleic acid) contact surfaces from an intermolecular cross-saturation NMR experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.2
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• pp.139-150
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• 2014

This paper suggests an algorithm to improve QoS by using DTR bit employed in the MIL-STD-188-220 protocol, when there is a multi-path between source and destination in the environment of KVMF tactical network supporting NCW. The MIL-STD-188-220 protocol can evaluate the link quality relatively but it cannot support optimal path selection for QoS. In order to solve this problem, we design an algorithm for selecting path using topology table which reflects measured DTR of path after the completion of transmission. The performance of the proposed algorithm has been evaluated by OPNET simulator. As a result of the simulation, it is found that QoS of proposed algorithm is enhanced higher than that of the MIL-STD-188-220 in the aggravated communication environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.10
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• pp.977-985
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• 2012

Recently, many countries have been developing new protocols to improve the performance of tactical ad hoc networks for implementing NCW (Network Centric Warfare). Combat net radio (CNR) networks are the most important communication infra for the ground forces such as infantry of Army. U.S. Army had developed MIL-STD-188-220D that is the Interoperability Standard for DMTDs (Digital Messages Transfer Device Subsystems) for voice and data communication in CNR. MIL-STD-188-220D is a candidate for MAC protocol of TMMR which is next radio and has a few constraints to used in TMMR. NAD (Network Access Delay) defined in MIL-STD-188-220D needs time synchronization to avoid collision. However, it is difficult for time synchronization to fit in multi-hop environment. We suggest the enhanced DAP (Deterministic Adaptable Priority)-NAD to prevent conflicts and decrease delays in multi-hop CNR. Simulation results show that the proposed scheme improves the performance in multi-hop CNR networks.

• Journal of Advanced Navigation Technology
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• v.22 no.2
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• pp.57-63
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• 2018

In the case of aircraft-launched guided weapons, various interface tests such as MIL-STD-1760 based power source, discrete signal, MUX communication as well as BIT of missile can verify system safety and reliability. The purpose of this case study is to develop a test bench based on MIL-STD-1760E for interoperability testing between aircraft and weapons. We proposed a testing method of the launch sequence based on the defined TIME LINE in the development phase of the missile system from the application of the power of the missile to the targeting, the transfer order, and the missile separation process. Furthermore, it will be a reference model that can maximize the verification scope in the development phase of the air to surface missile system by simulating abnormal situation to the inert missile using the error insertion function.

• Journal of Life Science
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• v.22 no.6
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• pp.760-771
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• 2012

Marine triterpene glycosides are physiologically active natural compounds isolated from sea cucumbers(holothurians). It was demonstrated that they have a wide range of biological activities, including antifungal, cytotoxic, and antitumor effects. A previous study showed that stichoposide C (STC) isolated from Thelenota anax induces apoptosis through generation of ceramide by activation of acid sphingomyelinase (SMase) and neutral SMase in human leukemia cells. In this study, we investigated whether STD, a structural analog of STC, can induce apoptosis and examined the molecular mechanisms for its activity. It was found that STC and STD induce apoptosis in a dose- and time-dependent manner and lead to the activation of caspase-8, mitochondrial damage, activation of caspase-9, and activation of caspase-3 in K562 and HL-60 cells. STC activates acid SMase and neutral SMase, which results in the generation of ceramide. Specific inhibition of acid SMase or neutral SMase partially blocked STC-induced apoptosis, but not STD-induced apoptosis. In contrast, STD generates ceramide through the activation of ceramide synthase. Specific inhibition of ceramide synthase partially blocked STD-induced apoptosis, but not STC-induced apoptosis. Moreover, STC and STD markedly reduced tumor growth of HL-60 xenograft tumors and increased ceramide generation in vivo. These results indicate that STC and STD can induce apoptosis and have antitumor activity through the different molecular mechanisms, because they have a different sugar residue attached to aglycones. Thus, these results suggest that their actions are affected by a sugar residue attached to aglycones and they can be used as anticancer agents in the treatment of leukemia.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.20-24
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• 2012

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.857-862
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• 2014

The research on a thermal stress control layer (TSCL) begins to undertake to reduce residual stress and strain in the vicinity of the joined region between the hardfacing layer and the base part. The goal of this paper is to estimate the material combination and the thickness of TSCL for the Stellite21 hardfaced STD61 hot working tool steel via three-dimensional finite element analysis (FEA). TSCL is created by the combination of Stellite21 and STD61. The thickness of TSCL ranges from 0.5 mm to 1.5 mm. The influence of the material combination and the thickness of TSCL on temperature, thermal stress and thermal strain distributions of the hardfaced part have been investigated. The results of the investigation have been revealed that a proper material combination of TSCL is Stellite21 of 50 % and STD61 of 50 %, and its appropriate thickness is 1.0 mm.