• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.7
• /
• pp.1262-1269
• /
• 2002

It is inevitable to evaluate the life of turbine rotor because the operating periods of power plants need to be extended. For the test, seven kinds of specimens with different degradation levels were prepared by the isothermal heat treatment at $630^{\circ}C$. Magnetic methods utilizing Barkhausen noise coercive force($BN_c$) were applied to detect the degradation caused by thermal aging. Magnetic property of material is related with domain dynamics and that is affected by the microstructure of material. Therefore $BN_c$ is very sensitive to the microstructure change of the material. With the increase of degradation, $BN_c$ was decreased and this phenomenon is considered due to precipitations and grain size. The result was compared with Vickers hardness($H_v$) and coercive force($H_c$) to detect the relative variation, and was related with $H_v$ and YS to estimate the change of the mechanical properties with the degradation.

• Journal of the Korean Ceramic Society
• /
• v.54 no.2
• /
• pp.150-157
• /
• 2017

Three types of piezoelectric single crystals [PMN-PT (Generation I $[Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3]$), PMN-PZT (Generation II $[Pb(Mg_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3]$), PMN-PZT-Mn (Generation III)] were grown by the solid-state single crystal growth (SSCG) method, and their dielectric and piezoelectric properties were measured and compared. Compared to (001) PMN-PT and PMN-PZT single crystals, the (001) PMN-PZT-Mn single crystals exhibited a higher transition temperature between the rhombohedral and tetragonal phases ($T_{RT}=144^{\circ}C$), as well as a higher coercive electric field ($E_C=6.3kV/cm$) and internal bias field ($E_I=1.6kV/cm$). The (011) PMN-PZT-Mn single crystals showed the highest coercive electric field ($E_C=7.0kV/cm$), and the highest stability of $E_C$ and $E_I$ during 60 cycles of polarization measurement. These results demonstrate that both Mn doping (for higher electromechanical quality factor ($Q_m$)) and a (011) crystallographic orientation (for higher coercive electric field and stability) are necessary for high power transducer applications of these piezoelectric single crystals. Specifically, the (011) PMN-PZT-Mn single crystal (Gen. III) had the highest potential for application in the fields of SONAR transducers, high intensity focused ultrasound (HIFU), ultrasonic motors, and others.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1989.10a
• /
• pp.88-88
• /
• 1989

• Journal of Surface Science and Engineering
• /
• v.35 no.3
• /
• pp.127-132
• /
• 2002

High speed performance of ferroelectric Pb(Zr,Ti)$O_3$ (PZT) based capacitors is reported. La substitution up to 10% was performed to systematically lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a ($Ti_{0.9}$ /$Al_{0.1}$ )N/Pt conducting barrier composite. Ferroelectric capacitors substituted with 10% La show significantly lower coercive voltage compared to capacitors with 0% and 3% La. This is attributed to a systematic decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. Furthermore, the samples doped with 10% La showed dramatically better retention and pulse width dependent polarization compared to the capacitors with 0% and 3% La. These capacitors show promise as storage elements in low power high density memory architectures.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.12 no.3
• /
• pp.157-160
• /
• 2002

The ferroelectric domain variation and electrical performance of $Pb(Zr,Ti)O_{3}$ (PZT) based capacitors through La additions were systematically studied. La substitution up to 10 % was performed to lower the coercive and saturation voltages of epitaxial ferroelectric capacitors grown on Si using a (Ti_{0.9}Al_{0.1})N/Pt$ conducting barrier composite. Ferroelectric capacitors substituted with 10 % La show significantly lower coercive voltage compared to capacitors with 0 % and 3 % La. This is attributed to a systematic microstructure change into $180^{\circ}C$ domain and decrease in the tetragonality (i.e., c/a ratio) of the ferroelectric phase. These capacitors show promise as storage elements in low power memory architectures.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.02a
• /
• pp.228-229
• /
• 2003

The quasi-phase matching (QPM) technique has dramatically changed the guidelines in developing nonlinear optical materials, which doesn't require birefringence and off-diagonal components for efficient wavelength conversion. Minimum requirement for QPM is the modulation of nonlinearity and ferroelectric materials with low coercive field has become fascinating in periodical poling. Stoichiometric lithium tantalate (SLT) has attractive advantages of low coercive field (∼l .5 KV/mm), high nonlinearity, high optical damage resistance and low thermo-optic coefficients, leading to a large aperture QPM devices for high power operation. (omitted)

• Journal of Korean Academy of Nursing
• /
• v.27 no.1
• /
• pp.169-177
• /
• 1997

This study aims at empirically clarifying the relationship between power and the interpersonal conflict, including nurses' understanding of their relative power, the causes of interpersonal conflicts with the nurses, and strategies to resolve conflicts, in order to understand how nurses' relative power affect their conflicts. For the empirical survey, the population was defined as all the nurses working at a medical organization in Seoul, Korea. 1083 nurses were selected as the sample for the questionnaire survey and statistical analyses. For the sampling, 32 medical organizations were selected by a stratified random method and sub-samples were arbitrarily drawn from each organization to obtain the final sample of 1083 nurses who responded to the questionnaire designed by the reseacher. According to the result of the study, most nurses experience conflict more than once a month, and 70.4% of the respondents answered that interpersonal conflicts were directly or indirectly caused by power relations. which indicates that they perceive power relations as the main cause of interpersonal conflicts. Nurses experienced the most conflicts with interns and residents(29.7%), then patients and their families(24.3%), higher-positioned nurses(12.3%), nurse colleagues(7.7%), lower-positioned nurses(6.5%), and staff doctors(5.1%). If we classify these into three groups. the frequency of the conflicts, from most frequent to least. is in the order of doctors. nurses, and patients. In terms of relative power, nurses perceive that they have greater power than patients and their families, lower-positioned nurses, and nurse colleagues. In contrast, nurses perceive that they have less power than interns and residents, higher-positioned nurses. and staff doctors. Among these groups. nurses perceive that they have the most power over patients and the least over staff doctors. These results indicate that nurses tend to experience more conflicts with members of groups that are stronger than themselves in terms of relative power, Nurses use positive strategies such as the compromise strategy(32.3%) or the collaboration strategy (20.3%) to manage conflicts, more than other strategies. However, they use avoidance or competition strategy more at the earlier stage, compromise strategy more in the mid stage, and collaboration strategy more at the later stage of the interpersonal conflict. In relation to power, nurses use the collaboration strategy or the compromise strategy more when their perceived power is greater than or equal to their counterpart's, and they use the avoidance strategy or the accommodation strategy if their power is less. In terms of source of power, nurses' perceived relative power is greater in the order of referent power. expert power, reward power, legitimate power. and coercive power. where referent power is perceived as having the greatest power and coercive power is least. Most nurses(69.3%) used their power to resolve a conflict. with positive outcomes. Expert power was used most frequently. Overall. this study strongly indicates that the enhancement of power of nurses to have equal power relations with doctors would heighten the success of conflict resolution, since power is the main cause of conflicts. Specifcally. nurses experience most conflicts with doctors against whom they perceive the greatest gap in power. and the choice of a conflict management strategy depend upon their power relations.

• Fashion & Textile Research Journal
• /
• v.15 no.1
• /
• pp.22-34
• /
• 2013

This study investigates the perception of conflict and satisfaction factors by salesperson of department store middle management system. This study was performed through a qualitative research method. An in-depth interview was given to 14 fashion shop managers and salespeople who have three or more years of department store work experience. The results show two categories of factors(factors according to power sources and factors according to job environment) that influence the perception of department store middle management system by fashion product salesperson. The factors(according to power sources) were classified into coercive power, reward power, expert/informational power, and referent power. The factors(according to job environment) were classified into physical environment, work conditions, and regulations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.997-1000
• /
• 2001

Pb(Zr$\sub$0.52/Ti$\sub$0.48/)O$_3$(PZT) thin films have been prepared by rf-magnetron sputtering methods and investigated the structural and electrical properties. In order to investigate the effects of sputtering conditions, input power was controlled during deposition. Crystallization process and microstructure of PZT thin films were largely affected by input power. Highly crystallized PZT films with the perovskite structure were successfully obtained on Pt/Ti bottom electrode. The dielectric constants and polarization of PZT thin films were increased with increasing input power, and the coercive electric field was decreased with increasing input power . The dielectric constant of PZT thin films with input power 150 W was 966 at 1 kHz. we, authors, proposed that preferred orientation of PZT thin films were controlled by input power in sputtering methods.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.9
• /
• pp.418-423
• /
• 2003

This paper describes an electronic compass using micromachined X- and Y-axis micro fluxgate sensors which were perpendicularly aligned each other to measure X- and Y-axis magnetic fields respectively. The fluxgate sensor was composed of rectangular-ring shaped magnetic core and solenoid excitation(49 turns) and pick-up(46 turns) coils. Excitation and pick-up coil patterns which were formed opposite to each other wound the magnetic core alternatively to improve the sensitivity and to excite the magnetic core in an optimal condition with reduced excitation current. The magnetic core has DC effective permeability of ~1000 and coercive field of ~0.1 Oe. The magnetic core is easily saturated due to the low coercive field and closed magnetic path for the excitation field. To decrease the difference of induced second harmonic voltages from X- and Y-axis, excitation condition of 2.8 $V_{P-P}$ and 1.2 MHz square wave was selected. Excellent linear response over the range of -100 $\mu$T to +100 $\mu$T was obtained with 210 V/T sensitivity. The size of each micro fluxgate sensor excluding pad region was about 2.6${\times}$1.7 $mm^2$ and the power consumption was estimated to be 14 mW.W.