• Journal of Mechanical Science and Technology
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• v.18 no.5
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• pp.770-779
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• 2004

This paper describes the micro cutting of wear resistant tungsten carbides using PCD (Poly-Crystalline Diamond) cutting tools in performance with SEM (Scanning Electron Microscope) direct observation method. Turning experiments were also carried out on this alloy (V50) using a PCD cutting tool. One of the purposes of this study is to describe clearly the cutting mechanism of tungsten carbides and the behavior of WC particles in the deformation zone in orthogonal micro cutting. Other purposes are to achieve a systematic understanding of machining characteristics and the effects of machining parameters on cutting force, machined surface and tool wear rates by the outer turning of this alloy carried out using the PCD cutting tool during these various cutting conditions. A summary of the results are as follows: (1) From the SEM direct observation in cutting the tungsten carbide, WC particles are broken and come into contact with the tool edge directly. This causes tool wear in which portions scrape the tool in a strong manner. (2) There are two chip formation types. One is where the shear angle is comparatively small and the crack of the shear plane becomes wide. The other is a type where the shear angle is above 45 degrees and the crack of the shear plane does not widen. These differences are caused by the stress condition which gives rise to the friction at the shear plane. (3) The thrust cutting forces tend to increase more rapidly than the principal forces, as the depth of cut and the cutting speed are increased preferably in the orthogonal micro cutting. (4) The tool wear on the flank face was larger than that on the rake face in the orthogonal micro cutting. (5) Three components of cutting force in the conventional turning experiments were different in balance from ordinary cutting such as the cutting of steel or cast iron. Those expressed a large value of thrust force, principal force, and feed force. (6) From the viewpoint of high efficient cutting found within this research, a proper cutting speed was 15 m/min and a proper feed rate was 0.1 mm/rev. In this case, it was found that the tool life of a PCD tool was limited to a distance of approximately 230 m. (7) When the depth of cut was 0.1 mm, there was no influence of the feed rate on the feed force. The feed force tended to decrease, as the cutting distance was long, because the tool was worn and the tool edge retreated. (8) The main tool wear of a PCD tool in this research was due to the flank wear within the maximum value of $V_{max}$ being about 260 $\mu\textrm{m}$.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.2
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• pp.68-76
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• 2018

In this paper, we describe the correlation processing method of multi-polarization observation data of the Daejeon Correlator. VLBI observations include single or multiple polarized observations depending on the type of object. Polarization observations are performed to observe the characteristics of the object. During the observations of the celestial object, polarization measurements are also performed to determine the delay values and causes of changes in the object. Correlation processing of polarization observation data of the Daejeon correlator is proposed by OCTAVIA of a synchronous reproduction processing apparatus that outputs data input to each antenna unit by using an output bit selection function to convert bits and the order of the data streams is changed, And the input of the Daejeon correlator is configured to perform the polarization correlation processing by conducting correlation processing by setting the existing stream number to be the same. Correlation processing is conducted on the test data observed for the polarization correlation processing and it is verified through experiments that the polarization correlation processing method of the proposed Daejeon correlator is effective.

• Journal of muscle and joint health
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• v.6 no.2
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• pp.226-241
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• 1999

This study was undertaken to find out the causal perception of rheumatoid arthritis patients, and to understand the typology. The Q-population consisted of 236 statements of causal perception were collected. Thirty eight Q-samples of causal perception were selected. The P-sample for this study were made up of 28 first visiting female rheumatoid arthritis patients from a rheumatoid arthritis specialty hospital. Each respondent responded Q-set of causal perception according to 9-point scale. The result of Q-sorting were coded and analyzed using QUANL PC program. 1) Typological Observation on Causal Perception (1) Physical Fatigue Type : Type 1 perceived that the illness occurred due to excessive work requiring physical labor or strain that had occurred from not resting after excessive physical labor, therefore, thinking the origin of the illness was from physical strain. (2) Physical origin Type : Type 2 perceived that the major cause for the illness is not only excessive physical labour but also fecundity and old age. (3) Causality to Environment Type : Type 3 perceived that rheumatoid arthritis occurred from injury to the joints or bad and humid weather. (4) Conscience of Guilty Type : Type 4 consisted of people with guilty conscience for lack of religious commitment. They perceived that the illness was a punishment from God for not praying or because of bad luck. (5) Rationally Perceiving Type : People who belong in type 5 perceived the cause of illness in light of scientific facts such as genetics, unbalanced diet or lack of exercise. (6) Psychological Stress Type : People who belong in type 6 believed that excessive stress was the cause of the illness. 2) Emotions of Rheumatoid arthritis patients Rheumatoid arthritis patients' positive emotions included determination, courage, coping, acceptance, hope, and adoption ; and their negative emotions were prostration, worry, stupor, conflicts, grievance, giving-up, resignation, depression, loss, solitariness, fear, anxiety, avoidance, anger and loneliness. Rheumatoid arthritis patients experience different level of emotions from their suffering experience from the severe pains. Rheumatoid arthritis patients also experience negative emotions when they could not perform self-care and lose their self-esteem from painful suffering ; however, they regain positive emotions when they recover from pain with the use of drugs, physical therapy or exercise. Their emotional states are closely connected to level of and presence of pain.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.3
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• pp.306-318
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• 2008

Anodic spark deposition method(ASD) surface treated titanium implant possesses a considerable osteoconductive potential that promoting a high level of implant osseointegration in normal bone. The purpose of this study was to observe the ASD implant's osseointegration in the osteoporosis-induced animal model. Twenty four rats, 10 weeks of age, were ovarectomized and 5 weeks later divided into two groups : ASD implant group and control implant group. Titanium screw implants (diameter; 2.0 mm, length, 3.5 mm; pitch-height, 0.4 mm) were designed for this study. Experimental implants were ASD treated and no treatment on control implants. ASD implants and control implants were placed in to left tibiae of rats. The rats were sacrificed at different time interval(1, 2, 4 and 8 weeks after implantation) for histopathologic observation and immunohisto-chemistrical observation, with collagen type Ⅰ, fibronectin, integrin ${\alpha}_2{\beta}_1$ and integrin ${\alpha}_5{\beta}_1$ antibodies. The results obtained from this study were as follow: 1. Histopathologic findings, overall tissue response and the pattern of bone formation in both groups were similar. In ASD group, more newly formed bone was seen at 1 week and 2weeks than control group. 2. The levels of type Ⅰ collagen and fibronectin expression were the most abundant at 2weeks and decreased gradually in both groups. Fibronectin and type Ⅰ collagen expression in ASD group were stronger than control group but no significance. 3. The levels of integrin ${\alpha}_2{\beta}_1$ and Integrin ${\alpha}_5{\beta}_1$ expression were most abundant at 2 weeks and decreased gradually in both groups. No significant difference was observed in both groups. From this results, anodic oxidized titanium implants were more advantages in early stage of bone formation than control group, but have no significance in tissue responses and late bone formations. It could be stated that although anodic oxidized titanium implant possesses considerable osteoconductive potential but in osteoporotic bone condition dental implant procedure should performed after improving or treating the osteoporotic bone condition.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.44.1-44.1
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• 2016

The Sagittarius-Carina spiral arm in the Galaxy contains several massive young open clusters. We present a deep optical photometric study on the massive young open clusters in the Sagittarius-Carina arm, Westerlund 2 and the young open clusters in the ${\eta}$ Carina nebula. Westerlund 2 is a less studied starburst-type cluster in the Galaxy. An abnormal reddening law for the intracluster medium of the young starburst-type cluster Westerlund 2 is determined to be $R_{V,cl}=4.14{\pm}0.08$. The distance modulus is determined from zero-age main-sequence fitting to the reddening-corrected color-magnitude diagrams of the early-type members to be $V_0-M_V=13.9{\pm}0.14mag$. The pre-main sequence (PMS) members of Westerlund 2 are selected by identifying the optical counterparts of X-ray emission sources from the Chandra X-ray observation and mid-infrared emission sources from the Spitzer/IRAC (the Infrared Array Camera) observation. The initial mass function (IMF) shows a slightly flat slope of ${\Gamma}=-1.1{\pm}0.1$ down to $5M_{\odot}$. The age of Westerlund 2 is estimated to be. 1.5 Myr from the main-sequence turn-on luminosity and the age distribution of PMS stars. The ${\eta}$ Carina nebula is the best laboratory for the investigation of the Galactic massive stars and low-mass star formation under the influence of numerous massive stars. We have performed deep wide-field CCD photometry of stars in the ${\eta}$ Carina nebula to determine the reddening law, distance, and the IMF of the clusters in the nebula. We present VRI and $H{\alpha}$ photometry of 130,571 stars from the images obtained with the 4m telescope at Cerro Tololo Inter-American Observatory (CTIO). RV,cl in the η Carina nebula gradually decreases from the southern part (~4.5, around Trumpler 14 and Trumpler 16) to the northern part around Trumpler 15 (~3.5). Distance to the young open clusters in the ${\eta}$ Carina nebula is partly revised based on the zero-age main-sequence fitting to the reddening-corrected color-magnitude diagrams (CMDs) and the (semi-) reddening-independent CMDs. We select the PMS members and candidates by identifying the optical counterparts of X-ray sources from the Chandra Carina Complex Survey and mid-infrared excess emission stars from the Spitzer Vela-Carina survey. From the evolutionary stage of massive stars and PMS stars, we obtain that the northern young open cluster Trumpler 15 is distinctively older than the southern young open clusters, Trumpler 14 (${\leq}2.5 Myr$) and Trumpler 16 (2.5-3.5 Myr). The slopes of the IMF of Trumpler 14, Trumpler 15, and Trumpler 16 are determined to be $-1.2{\pm}0.1$, $-1.5{\pm}0.3$, and $-1.1{\pm}0.1$, respectively. Based on the RV,cl of several young open clusters determined in this work and the previous studies of our group, We suggest that higher RV,cl values are commonly found for very young open clusters with the age of < 4 Myr. We also confirm the correlation between the slope of the IMF and the surface mass density of massive stars.

• Journal of the Korean GEO-environmental Society
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• v.16 no.10
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• pp.33-38
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• 2015

This study conducted experimental observations of the settling velocity of a coarse particle in water varying material type and particle size and compared the results with preexisting empirical equations. Three types of materials, which are polyacetal, glass and steel, were used in this study and the diameter of particle ranged from 1 mm to 20 mm. Experiment results showed that the settling velocity of coarse particle had a significant difference from Stokes equation which is known applicable for a fine particle smaller than $50{\mu}m$. In addition, the observed particle velocity showed a significant difference when compared with other empirical equations, which was proposed for estimating the settling velocity of a particle regardless of particle size, depending on the material type and particle size. The results from experimental observations indicated that the settling velocity of a coarse particle was relatively in smaller difference to other empirical equations for the particle size smaller than 3 mm, but as the size increased the difference in the settling velocity also increased. This study clearly showed that the settling velocity of a coarse particle velocity can be significantly different depending on particle size and density and the empirical equations may not reliably estimate the settling velocity of a coarse particle so that they should not be used as it is and a verification of them is necessarily before any use. The study results would provide a useful information for a better understanding of settling velocity of a particle in water.

• The korean journal of orthodontics
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• v.50 no.5
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• pp.336-345
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• 2020

Objective: To investigate the treatment modalities (Tx-Mods) for patients with unilateral hemifacial microsomia (UHFM) according to Pruzansky-Kaban types and growth stages. Methods: The samples consisted of 82 Korean UHFM patients. Tx-Mods were defined as follows: Tx-Mod-1, growth observation due to mild facial asymmetry; Tx-Mod-2, unilateral functional appliance; Tx-Mod-3, fixed orthodontic treatment; Tx-Mod-4, growth observation due to a definite need for surgical intervention; Tx-Mod-5, unilateral mandibular or bimaxillary distraction osteogenesis (DO); Tx-Mod-6, maxillary fixation using LeFort I osteotomy and mandibular DO/sagittal split ramus osteotomy; Tx-Mod-7, orthognathic surgery; and Tx-Mod-8, costochondral grafting. The type and frequency of Tx-Mod, the number of patients who underwent surgical procedures, and the number of surgeries that each patient underwent, were investigated. Results: The degree of invasiveness and complexity of Tx-Mod increased, with an increase in treatment stage and Pruzansky-Kaban type (initial < final; [I, IIa] < [IIb, III], all p < 0.001). The percentage of patients who underwent surgical procedures increased up to 4.2 times, with an increase in the Pruzansky-Kaban type (I, 24.1%; IIa, 47.1%; IIb, 84.4%; III, 100%; p < 0.001). However, the mean number of surgical procedures that each patient underwent showed a tendency of increase according to the Pruzansky-Kaban types (I, n = 1.1; IIa, n = 1.5; IIb, n = 1.6; III, n = 2.3; p > 0.05). Conclusions: These findings might be used as basic guidelines for successful treatment planning and prognosis prediction in UHFM patients.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.771-780
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• 2014

We installed HF Radar of Array type in Site A and Site B, observing the real-time wave and current in the central East coast of Korea. WERA(WavE RAdar) in this research uses HF Radar of Array Type with frequency range of 24.525 MHz, developed by Helzel, Germany. Each site is a 8-Channel system consisting of four transmitters and eight receivers, generating wave and current data, being observed every thirty minutes at the present time. HF Radar has grid resolution of an interval of 1.5 km using bandwidth of 150 kHz; The wave data covers an observation range of about 25 km, and the current data covers the maximum observation range of about 50 km. The Wave data observed by HF Radar was compared and verified with the AWAC data observed in the research sites. MIT also compared the Current data observed by HF Radar with Monthly the East sea average surface current and current flow pattern provided by KOHA(Korea Hydrographic and oceanographic Administration). The regression line and deviation of the comparison data of Wave was calculated by Principal Component Analysis, which showed correlation coefficient 0.86 and RMSD 0.186. Besides, data analysis of long-term changes of the current in the East coast showed that, during August and September, the North Korean Cold Current flow into the southward direction and the East Korean Warm Current flow into the northward direction in the coast.

• Atmosphere
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• v.25 no.4
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• pp.611-622
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• 2015

Heavy rainfall ($>30mm\;hr^{-1}$) over the Korean Peninsula is examined in order to understand thermo-dynamic characteristics of the atmosphere, using radiosonde observational data from seven upper-air observation stations during the last 17 years (1997~2013). A total of 82 heavy rainfall cases during the summer season (June-August) were selected for this study. The average values of thermo-dynamic indices of heavy rainfall events are Total Precipitable Water (TPW) = 60 mm, Convective Available Potential Energy (CAPE) = $850J\;kg^{-1}$, Convective Inhibition (CIN) = $15J\;kg^{-1}$, Storm Relative Helicity (SRH) = $160m^2s^{-2}$, and 0~3 km bulk wind shear = $5s^{-1}$. About 34% of the cases were associated with a Changma front; this pattern is more significant than other synoptic pressure patterns such as troughs (22%), migratory cyclones (15%), edges of high-pressure (12%), typhoons (11%), and low-pressure originating from Changma fronts (6%). The spatial distribution of thermo-dynamic conditions (CAPE and SRH) is similar to the range of thunderstorms over the United States, but extreme conditions (supercell thunderstorms and tornadoes) did not appear in the Korean Peninsula. Synoptic conditions, vertical buoyancy (CAPE, CIN), and wind parameters (SRH, shear) are shown to discriminate among the environments of the three types. The first type occurred with high CAPE and low wind shear by the edge of the high pressure pattern, but Second type is related to Changma front and typhoon, exhibiting low CAPE and high wind shear. The last type exhibited characteristics intermediate between the first and second types, such as moderate CAPE and wind shear near the migratory cyclone and trough.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.79.2-79.2
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• 2012

SN 2011fe (also known as PTF 11kly) is a Type-1a supernova that appeared in M101, 2011 August. Being only 6.4 Mpc away, this supernova has been intensively observed by various facilities in the world. We monitored this supernova in UBVRI, grizY, and ZYJHK-bands using SNUO, LOAO, SOAO, CQUEAN/McDonald, UKIRT telescopes, and small telescopes in Korea and Mongolia. The monitoring observation is still ongoing, and the light curve has been accumulated over a year. We present the results of the long-term monitoring observation, together with a light-curve fitting result. We will also discuss our findings in terms of the usefulness of Type-Ia supernovae as a distance indicator.