Carbon diffusion behavior and mechanical properties of carbon-doped TiZrN coatings by laser carburization (레이저 침탄된 TiZrN 코팅에서 탄소확산거동과 기계적 특성)
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- Journal of the Korean Crystal Growth and Crystal Technology
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- v.31 no.1
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- pp.32-36
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- 2021
This study was investigated in carbon diffusion behavior of laser-carburized TiZrN coating layer and the changes of mechanical properties. The carbon paste was deposited on TiZrN coatings, and the laser was irradiated to carburize into the coatings. The XRD peak corresponding to the (111) plane shifted to a lower angle after the carburization, showing the lattice expansion by doped carbon. The decreased grain size implied the compression by the grain boundary diffusion of carbon. The XPS spectra for the bonding states of carbon was analyzed that carbon was substitute to nitrogen atoms in TiZrN, as carbide, through the thermal energy of laser. In addition, the combination of sp2 and sp3 hybridized bonds represented the formation of an amorphous carbon. The cross-sectional TEM image and the inverse FFT of the TiZrN coating after carburizing were observed as the wavy shape, confirming the amorphous phase located in grain boundaries. After the carburization, the hardness increased from 34.57 GPa to 38.24 GPa, and the friction coefficient decreased by 83 %. In particular, the ratio of hardness and elastic modulus (H/E) which is used as an index of the elastic recovery, increased from 0.11 to 0.15 and the wear rate improved by 65 %.
This paper, a sequel to Yoo and Lee (1990), attempts to investigate the interindustry determinants of technical efficiency in Korea's manufacturing industries, and also to conduct an exploratory analysis on the stability of technical efficiency over time. The hypotheses set forth in this paper are most found in the existing literature on technical efficiency. They are, however, revised and shed a new light upon, whenever possible, to accommodate any Korea-specific conditions. The set of regressors used in the cross-sectional analysis are chosen and the hypotheses are posed in such a way that our result can be made comparable to those of similar studies conducted for the U.S. and Japan by Caves and Barton (1990) and Uekusa and Torii (1987), respectively. It is interesting to observe a certain degree of similarity as well as differentiation between the cross-section evidence on Korea's manufacturing industries and that on the U.S. and Japanese industries. As for the similarities, we can find positive and significant effects on technical efficiency of relative size of production and the extent of specialization in production, and negative and significant effect of the variations in capital-labor ratio within industries. The curvature influence of concentration ratio on technical efficiency is also confirmed in the Korean case. There are differences, too. We cannot find any significant effects of capital vintage, R&D and foreign competition on technical efficiency, all of which were shown to be robust determinants of technical efficiency in the U.S. case. We note, however, that the variables measuring capital vintage effect, R&D and the degree of foreign competition in Korean markets are suspected to suffer from serious measurement errors incurred in data collection and/or conversion of industrial classification system into the KSIC (Korea Standard Industrial Classification) system. Thus, we are reluctant to accept the findings on the effects of these variables as definitive conclusions on Korea's industrial organization. Another finding that interests us is that the cross-industry evidence becomes consistently strong when we use the efficiency estimates based on gross output instead of value added, which provides us with an ex post empirical criterion to choose an output measure between the two in estimating the production frontier. We also conduct exploratory analyses on the stability of the estimates of technical efficiency in Korea's manufacturing industries. Though the method of testing stability employed in this paper is never a complete one, we cannot find strong evidence that our efficiency estimates are stable over time. The outcome is both surprising and disappointing. We can also show that the instability of technical efficiency over time is partly explained by the way we constructed our measures of technical efficiency. To the extent that our efficiency estimates depend on the shape of the empirical distribution of plants in the input-output space, any movements of the production frontier over time are not reflected in the estimates, and possibilities exist of associating a higher level of technical efficiency with a downward movement of the production frontier over time, and so on. Thus, we find that efficiency measures that take into account not only the distributional changes, but also the shifts of the production frontier over time, increase the extent of stability, and are more appropriate for use in a dynamic context. The remaining portion of the instability of technical efficiency over time is not explained satisfactorily in this paper, and future research should address this question.
A post-processing technique for the measurement signal of a solenoid-type sensor is introduced. The solenoid-type sensor nondestructively evaluates an external tendon of prestressed concrete using the total flux leakage (TFL) method. The TFL solenoid sensor consists of primary and secondary coils. AC electricity, with the shape of a sinusoidal function, is input in the primary coil. The signal proportional to the differential of the input is induced in the secondary coil. Because the amplitude of the induced signal is proportional to the cross-sectional area of the tendon, sectional loss of the tendon caused by ruptures or corrosion can be identified by the induced signal. Therefore, it is important to extract amplitude information from the measurement signal of the TFL sensor. Previously, the amplitude was extracted using local maxima, which is the simplest way to obtain amplitude information. However, because the sampling rate is dramatically decreased by amplitude extraction using the local maxima, the previous method places many restrictions on the direction of TFL sensor development, such as applying additional signal processing and/or artificial intelligence. Meanwhile, the proposed method uses amplitude demodulation to obtain the signal amplitude from the TFL sensor, and the sampling rate of the amplitude information is same to the raw TFL sensor data. The proposed method using amplitude demodulation provides ample freedom for development by eliminating restrictions on the first coil input frequency of the TFL sensor and the speed of applying the sensor to external tension. It also maintains a high measurement sampling rate, providing advantages for utilizing additional signal processing or artificial intelligence. The proposed method was validated through experiments, and the advantages were verified through comparison with the previous method. For example, in this study the amplitudes extracted by amplitude demodulation provided a sampling rate 100 times greater than those of the previous method. There may be differences depending on the given situation and specific equipment settings; however, in most cases, extracting amplitude information using amplitude demodulation yields more satisfactory results than previous methods.
The objective of this study was to evaluate the freezing and thawing resistance of the existing drainage system for leakage treatment of underground concrete structures operating in cold regions. The freezing and thawing test was conducted on 4 types of drainage system specimens to evaluate the freezing and thawing resistance of the drainage system. The freezing and thawing resistance was evaluated on 4 types of Hotty-gel, as a waterproofing material, connection methods and on two methods to fix the drainage board with Hotty-gel on the surface of cement concrete specimen. One cycle of the freeze-thaw testing was 48 hours (24 hours of freezing and 24 hours of thawing), and the temperatures of freezing and thawing were at
This is a cross-sectional descriptive correlation study that aimed to understand the relationship between the level of sexual contacts during the dates and psycho-social factors in teenage girls who have or had boyfriends. The purpose of this study was to describe the relationship between sexual contacts and self-esteem and self- assertiveness. The subjects of the study were 6,130 teenage girls who have or had boyfriends. They were selected convienently 12,733 teenage girls from 254 secondary schools located in 7 large cities and 9 provinces in Korea. A structured questionaire was used it included items one general characteristics, the levels of sexual contacts, self-esteem and self-assertiveness. Seven levels of sexual contacts were rated they were holding a hand, putting arms around each other's shoulders, kiss, french kiss, touching breast, petting genitalia, and sexual intercourse during the dates. Self-esteem and self-assertiveness were measured by the "Self-esteem scale" of Rogenberg (1971) and the questionaires developed by S. B. Chang et al(2000), respectively. The self-reported questionaires were collected from October 2, to October 28, 2000 and analyzed by using SPSS 10.0 Program. The data were analyzed by descriptive statistics, reliability, One-way ANOVA with Duncan method & Scheffe method. The results of the analysis were as follows. 1.An average Percentage of the respondents who have (46.1%) or had (53.9%) boyfriends was 48.1% (n=6,130) and the most common sexual contact during the dates was french kiss (26.7%, n=1,634). While 7.5%(458) of respondents had a sexual intercourse, 13.7%(842) of respondents didn't have any sexual contact during the dates. 2. Distribution of starting point of the first sexual contact demonstrates that 1,950 respondents (31.8%) held partner's hand at the first date and 1,367 respondents (22.3%) put arms around each other's shoulders at the 2nd or 3rd date. Sexual contacts such as kiss, french kiss, touching breast, petting genitalia, or sexual intercourse were experienced mostly at the later than the 10th date. However, surprisingly large number(1.7%) of respondents had genital contact and sexual intercourses at the first date. 3. The means of self-esteem and self-assertiveness socres of the respondents who have or had boyfriends are 27.43
The growth of the high-quality GaN epilayers is of significant technological importance because of their commercializedoptoelectronic applications as high-brightness light-emitting diodes (LEDs) and laser diodes (LDs) in the visible and ultraviolet spectral range. The GaN-based heterostructural epilayers have the polar c-axis of the hexagonal structure perpendicular to the interfaces of the active layers. The Ga and N atoms in the c-GaN are alternatively stacked along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs, the stress applied along the same axis contributes topiezoelectric polarization, and thus the total polarization is determined as the sum of spontaneous and piezoelectric polarizations. The total polarization in the c-GaN heterolayers, which can generate internal fields and spatial separation of the electron and hole wave functions and consequently a decrease of efficiency and peak shift. One of the possible solutions to eliminate these undesirable effects is to grow GaN-based epilayers in nonpolar orientations. The polarization effects in the GaN are eliminated by growing the films along the nonpolar [
The purpose of this study is to acquire essential data to reduce the amount of woody debris resulted from the debris flow. This research examined topographic characteristics of the channelbed affecting generation, movement and storage of woody debris and woody characteristics related to number, sizes, shapes, decay, storage direction to mountainous stream. 1. The number of woody debris had a tendency to increase in proportion to stream width, but it was hardly affected by longitudinal gradient of stream. Especially, the greater amount of woody debris was stored at wide section of the stream with compound channel, and it was found in deposits of channelbed rather than in the present channel. 2. Total woody debris over 10cm in diameter and over 2m in length was 402 units and storage number was 35.3 units per 100m of stream. Average diameter of breast height and length were 14cm and 4m, respectively. The woody debris appeared shorter in length and greater in diameter at down-stream than up-stream. 3. Since woody debris met sediments and bed-materials of great roughness in moving, the greater amount of woody debris without root was found in up-stream and down-stream, but deformed woody debris was discovered in upper stream. Decay of woody debris was more severe in down-stream and woody debris on rotting process was found down-stream. 4. Storage direction of woody debris was mainly parallel to center line of stream, and rate of parallel and perpendicularity was 276 and 126 units, respectively. But, as woody debris storing to the perpendicular direction was unstable, the traveling debris could easily be stored. Therefore, some counterplan was required to prevent the traveling woody debris. 5. Tree species of woody debris was mainly larch, which occupied about two third of total woody debris(256 units). The woody debris of larch is easy to move due to hitting of channelbed materials or lower channelbed fluctuation because the lower part of larch is weaker than its upper part. Therefore, the section of the tree species planting in the riparian vegetation needs much more carefulness.
The purpose of this study is to analyze morphological characteristics of maxillary primary molar's root and root canal. 268 children aged 3 - 7 years (175 boys, 93 girls) who had CBCT (152 children) and 3D CT (116 children) taken in Seoul National University Dental Hospital from January 2006 to April 2020 were included. The number of roots and root canals were analyzed in 1002 teeth without any root resorption or periapical pathologies. Curvature, angulation, length of root and root canal, as well as cross-sectional shapes of the root canal were analyzed in 218 teeth. By using Mimics and 3-Matics software, volume, surface area, and volume ratio of root canal was analyzed in 48 teeth. More than half of maxillary primary molars have 3 roots and 3 root canals. The degree of symmetry of root canal type was about 0.63 (Cohen's kappa coefficient). The most frequent shape of roots and canals was linear in 1st primary molars and curved in 2nd primary molars. Angulation, length of root and root canals was the largest on palatal roots. Most teeth showed ovoid or round shapes at apex. The largest root canal volume, surface area, volume ratio was found in the palatal roots.
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70