• Advances in materials Research
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• v.7 no.1
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• pp.17-28
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• 2018

Niobium is a candidate base for new alloys devoted to applications at especially elevated temperatures. Elaborating and shaping niobium-based alloys by conventional foundry may lead to mechanically interesting microstructures. In this work a series of charges constituted of pure elements were subjected to high frequency induction melting in cold crucible to try obtaining cast highly refractory Nb-xCr and Nb-xCr-0.4 wt.%Calloys(x=27, 34 and 37 wt.%). Melting and solidification were successfully achieved. The as-cast microstructures of the obtained alloys were characterized by electron microscopy and X-ray diffraction and their hardness were specified by Vickers macro-indentation. The obtained as-cast microstructures are composed of a body centered cubic (bcc) niobium dendritic matrix and of an interdendritic eutectic compound involving the bcc Nb phase and a $NbCr_2$ Laves phase. The obtained alloys are hard to cut and particularly brittle at room temperature. Hardness is of a high level (higher than 600Hv) and is directly driven by the chromium content or the amount of {bcc Nb - $NbCr_2$} eutectic compound. Adding 0.4 wt.% of carbon did not lead to carbides but tends to increase hardness.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.201-218
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• 1989

The purpose of this study was to evaluate the influence of attachment technique on mechanical properties and microstructures of wrought wires. The wires tested in this study were precious metal wires: PGP (Platinum-Gold -Palladium), Elastic #12, Denture Clasp, Standard, Jelenko No. 2, Degulor-Klammerdraht, DM (Dong Myung) and base metal wire : Ticonium. Each wire was divided into three groups, and each group was heat treated as embedding, cast to, and soldering state. Heat treated sample was evaluated by tensile test, bending test, microhardness test, element analysis and microstructure test. The obtained results were as follows: 1. In tensile test, cast to and soldering procedures have an effect on wrought wire clasp as hardening heat treatment. 2. Maximum bending strength was significantly increased in Elastic #12, Denture Clasp, Standard, and DM in cast to procedure. 3. Ticonium showed the highest Victors hardness number, followed by PGP, and there was no significant difference in other wrought wires. In cast to and soldering procedure, Victors hardness number was significantly increased in precious wrought wires. 4. The precious wrought wire showed typical fibrous structure and this was disappeared in cast to and soldering procedure. But physical properties were not influenced by this phenomenon.

• Weed & Turfgrass Science
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• v.4 no.4
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• pp.368-375
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• 2015

Earthworm cast occurred in surface of turfgrass in golf courses which affect turfgrass maintenance and golf play. In this study several survey of seasonal fluctuation of earthworm cast in different golf courses (Anseong, Gapyeong, Gunpo and Yongin in Gyeonggi province, and Geumjeong in Busan) was done. A number of earthworm, soil temperature and moisture of detection site of earthworm cast in each golf course were also done. Cast occurred in different golf courses are found mostly from April to November on turf surface and the cast number varied in different month as well as in golf courses. In the same golf courses, a number of detected cast was difference from individual sites. A number of cast and earthworm was correlated. Also, in higher soil moisture showed the higher cast density in different golf courses. Soil temperature and moisture of detecting cast ranging from $2.1^{\circ}C$ to $33.1^{\circ}C$ and 4.9 to 44.1%, respectively. In case of cast, soil temperature level lies in between $10-15^{\circ}C$ where the highest soil moisture was 25%.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.4
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• pp.239-244
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• 2003

The common errors in preoperative treatment plan for the orthognathic surgery can be occurred during cast impression, cast mounting procedure with face-bow transfer, surgical stent fabrication, and so on. One of the most common errors exists during mounting process of the model on the articulator. Accurate mounting of dental casts to articulator should be achieved by transferring the 3-dimensional spatial relationship of the maxillary arch to an articulator. A face-bow is used for transfer this relationship to articulator, usually by relating the face-bow to a plane of reference of maxillary cast. The purpose of this study is evaluation of the accuracy of face-bow transferring of maxillary model to the articulator. The maxillary casts of thirty patients for orthognathic surgery were mounted on articulator with an face-bow instrument. The relationship of occlusal plane angle to Frankfort horizontal plane relations were compared the cephalogram with the cast-mounted articulator. As a result of this study, the significant difference between the maxillary occlusal planes angle in the cephalogram and articulator were found. The results were followed, 1. The mean occlusal plane angle in cast-mounted articulator was $13.5^{\circ}\;(SD{\pm}5.4)$. 2. The mean occlusal plane angle in cephalogram was $10.4^{\circ}\;(SD{\pm}4.3)$. 3. The mean difference of occlusal plane angle between cast-mounted articulator and cephalogram was $3.3^{\circ}\;(SD{\pm}4.6)$. According to the result, we should suggest that the occlusal plane angle to Frankfort plane in cast-mounted articulator is more steeper than that of cephalogram. And then, maxillofacial surgeon should try to get a more predictable result by suggesting the proper correction method and mounting the cast accurately.

• Journal of the Korean Data and Information Science Society
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• v.24 no.6
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• pp.1297-1307
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• 2013

Several multi-hop applications developed for vehicular ad hoc networks use broadcast as a means to either discover nearby neighbors or disseminate useful traffic information to othet vehicles located within a certain geographical area. However, the conventional broadcast mechanism may lead to the so-called broadcast storm problem, a scenario in which there is a high level of contention and collision at the link layer due to an excessive number of broadcast packets. To solve broadcast storm problem, we propose an RPB-MACn-based LV-CAST that is a vehicular broadcast algorithm for disseminating safety-related emergency message. The proposed LV-CAST identifies the last node within transmission range by computing the distance extending on 1 hop from the sending node of an emergency message to the next node of receiving node of the emergency message, and the last node only re-broadcasts the emergency message. The performance of LV-CAST is evaluated through simulation and compared with other message dissemination algorithms.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.209-216
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• 2004

Numerical analysis is carried out to identify the appropriateness of the design codes that is available for the tensile design of fastening system at Nuclear Power Plant (NPP) in this study. This study is intended for the cast-in-place anchor that is widely used for the fastening of equipment in Korean NPPs. The microplane model and the elastic-perfectly plastic model are employed for the quasi-brittle material like concrete and for the ductile material like anchor bolt as constitutive model for numerical analysis and smeared crack model is employed for the crack and damage phenomena. The developed numerical model is verified on a basis of the various test data of cast-in-place anchor. The appropriateness of both ACI 349 Code and CCD approach of CEB-FIP Code is evaluated for the tensile design of cast-in-place anchor and it is proved that both design codes give a conservative results compared with real tensile capacity of cast-in-place anchor.

• Corrosion Science and Technology
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• v.2 no.1
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• pp.30-35
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• 2003

In this study, sand cast AZ91E and zirconium grain refined MEZ are representative of two typical groups of magnesium alloys: those containing aluminium and those containing no aluminium but with zirconium as a grain refiner. The corrosion performance of these two alloys was evaluated and compared in 5%wt NaCI solution through measurements of weight loss and polarisation curves and examination of microstructure. Corrosion damage of AZ91E was deeper and more localised than that of MEZ, while MEZ had a lower rate of cathodic hydrogen evolution and a higher rate of anodic dissolution than AZ91E. These differences in behaviour can be related to the differences in microstructure and chemical composition between the two alloys.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1223-1236
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• 2014

With the extension of wireless technology, vehicular ad hoc networks provide important services for the dissemination of general data and emergency warnings. However, since, the vehicle topology frequently changes from a dense to a sparse network depending on the speed of the moving vehicles and the time of day, vehicular ad hoc networks require a protocol that can facilitate the efficient and reliable dissemination of emergency messages in a highly mobile environment under dense or intermittent vehicular connectivity. Therefore, this paper proposes a new vehicular broadcast protocol, called BL-CAST, that can operate effectively in both dense and sparse network scenarios. As a low overhead multi-hop broadcast protocol, BL-CAST does not rely on the periodic exchange of beacons for updating location information. Instead, the location information of a vehicle is included in a broadcast message to identify the last rebroadcasting vehicle in an intermittently connected network. Simulation results show that BL-CAST outperforms the DV-CAST protocol in terms of the end-to-end delay, message delivery ratio and network overhead.

• Journal of the Korean Society for Heat Treatment
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• v.16 no.2
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• pp.71-77
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• 2003

We investigate the phase formation in the compound layer of cast irons during the gaseous nitrocarburising of four different cast irons, that contain different types of graphites in the shape and size. We examine the change in the surface roughness with the nitrocarburising time. The observation of cross-sectional microstructure and X-ray diffraction analysis indicate that the compound layer consists of single ${\varepsilon}-Fe_{2-3}(N,C)$ phase and that its thickness increases in a parabolic manner with the treatment time. The surface roughness parameters, Rz and Ra increase with increasing treatment time. In other words, the roughness parameters increase as the thickness of compound layer increases. The parameters also depend on the shape and size of graphite in the individual cast irons.

• Journal of Korea Foundry Society
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• v.2 no.2
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• pp.10-17
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• 1982

This study has been carried out to determine the change of mechanical properties and microstructures by the heattreatment to relieve the residual stresses for gray cast irons. The results have been obtained from the experiment as follows; 1) The annealing above $600^{\circ}C$ for the stress relieving of gray cast iron decrease the tensile strength and hardness 2) The decrease reates of tensile strength and hardness of gray cast iron after annealing above $600^{\circ}C$ are increased with increasing the holding time. 3) The gray cast iron containing the elements of Mn, Cr has increased the heating temperature for the decrease of tensile strength and hardness. 4) The decrease of mechanical properties by annealing are assumed that the formation of ferrite takes placed from the decomposition of eutectoid cementite in the matrix.