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排序方式: 共有317条查询结果,搜索用时 15 毫秒
1.
H Uchino 《Canadian Metallurgical Quarterly》1997,44(7):499-508
For better understanding of the sexual behaviours that are high-risk in terms of HIV infection, a random sample of 200 people aged above 20 and below 60 years, from a population of 23,700, was selected in the provincial city of Nagano and surveyed by visitation. The responses of 156 people (a rate of response of 78%) were collected and the results were statistically analyzed. The methods employed in conducting a survey on sexual behaviour were also evaluated. The number of sexual partners is an indicator of high-risk sexual behaviour for HIV infection. The data reveals that 65.3% of the men and 37% of the women had two or more partners in the past, with 37.5% of the men and 12.5% of the women having two or more partners in the last 5 years, and 19.1% of the men and 4.2% of the women having two or more partners in the last year, revealing that a higher percentage of men than women have multiple partners. Comparison by age group reveals that young men and women in their 20s have the highest percentage of multiple partners. For both men and women first sexual intercourse before the age of 18, for men self-employment, being a craftsmen or in agriculture, and for women, higher education, were all factors in having greater numbers of partners. In conducting a survey on sexual behaviour the following should be kept in mind. 1) The psychological background of the respondent; Sex counseling skills are required on the part of the interviewer when taking a survey on sex since it is a very private and personal topic for people. Respondents have a tendency to be those who are open-minded about sex and are active in life, and these factors can exaggerate the survey results. 2) Conduct of a survey on sexual behaviour; The survey should be taken only after the purpose of the survey has been fully explained to the respondents and trust has been established. In principle, therefore, mailing of a letter of request and the actual questions should not be the method utilized prior to the collection of responses. 相似文献
2.
Masahide Hojo Yasunori Mitani Toshifumi Ise Kiichiro Tsuji 《Electrical Engineering in Japan》2002,138(3):43-51
The advancement of power electronics technologies has significantly developed the power system stabilizing controllers. Quantitative as well as qualitative evaluation of their effectiveness in power systems is a matter of great importance for the feasibility investigation of these apparatus. In this paper, the possible control region of FACTS controllers with series and/or shunt configuration in a single machine to infinite bus system is formulated in the powerangle curve with a set of algebraic equations. The effectiveness of TCPST (Thyristor‐Controlled Phase Shifting Transformer), SSSC (Static Synchronous Series Compensator), and TCSC (Thyristor‐Controlled Series Compensator) for the improvement of the transient stability is evaluated quantitatively as a numerical example. The correctness of the proposed method has been confirmed by analysis based on the electromagnetic transients simulation with a detailed system model. © 2001 Scripta Technica, Electr Eng Jpn, 138(3): 43–51, 2002 相似文献
3.
Heat Generation in Multilayer Piezoelectric Actuators 总被引:1,自引:0,他引:1
Jiehui Zheng Sadayuki Takahashi Shoko Yoshikawa Kenji Uchino J. W. C. de Vries 《Journal of the American Ceramic Society》1996,79(12):3193-3198
Multilayer piezoelectric actuators when driven under high frequency, generate significant heat, which influences the reliability and other piezoelectric properties. In this paper, heat generation in various types of multilayer PZT-based actuators was studied. Experimental results showed that heat generation is mainly caused by ferroelectric hysteresis loss in the stress-free state. A simplified analytic method was established to evaluate the temperature rise, which is useful for the design of multilayer and other high-power actuators. 相似文献
4.
S Ikeda Y Sera H Ohshiro T Izaki S Uchino M Akizuki H Goto 《Canadian Metallurgical Quarterly》1998,14(1-2):140-141
In infants and children requiring prolonged, multiple central venous (CV) catheterizations, the superior (SVC) and inferior vena cava may become thrombosed or stenotic, making CV access a difficult problem. Use of the iliac vein may be an acceptable alternative. We report a patient with thrombosis of the SVC in whom the external iliac vein was accessed through a retroperitoneal approach for placement of an implantable port. This technique is easy to perform, and there are no special materials or patient positioning required. 相似文献
5.
Dielectric and piezoelectric properties of 0.02Pb(Y2/3 W1/3 )O3 0.98Pb(Zr0.52Ti0.48)O3 ceramics doped with additives (Nb2 O5 , La2 O3 , MnO2 , and Fe2 O3 ) were investigated. The grain sizes of these ceramics decreased with increasing amounts of additives. For additions of MnO2 and Fe2 O3 , dielectric losses decreased, while for Nb2 O5 and La2 O3 , these values increased. The maximum values of the mechanical quality factor Qm were found to be 956 and 975 for additions of 0.9 wt% Fe2 O3 and 0.7 wt% MnO2 , respectively, but donor dopants (Nb2 O5 and La2 O3 ) did not change the values of Qm . On the other hand, the piezoelectric constant d33 and the electromechanical coupling factor kp decreased with additions of MnO2 and Fe2 O3 , but improved with additions of Nb2 O5 and La2 O3 . 相似文献
6.
Loss mechanisms and high power piezoelectrics 总被引:1,自引:0,他引:1
K. Uchino J. H. Zheng Y. H. Chen X. H. Du J. Ryu Y. Gao S. Ural S. Priya S. Hirose 《Journal of Materials Science》2006,41(1):217-228
Heat generation is one of the significant problems in piezoelectrics for high power density applications. In this paper, we
review the loss mechanisms in piezoelectrics first, followed by the heat generation processes for various drive conditions.
Heat generation at off-resonance is caused mainly by dielectric loss tan δ′ (i.e., P-E hysteresis loss), not by mechanical
loss, while the heat generation at resonance is mainly attributed to mechanical loss tan φ′. Then, practical high power materials
developed at Penn State is introduced, which exhibit the vibration velocity more than 1 m/s, leading to the power density
capability 10 times of the commercially available “hard” PZTs. We propose a internal bias field model to explain the low loss
and high power origin of these materials. Finally, using a low temperature sinterable “hard” PZT, we demonstrated a high power
multilayer piezoelectric transformers. 相似文献
7.
This paper compares two converter configurations for a multi-10 MVA gate-turn-off (GTO) reactive power compensator (STATCOM) from the viewpoints of converter connection and switching frequency. One is a single-bridge system consisting of a three-phase bridge converter unit and a transformer. Its pulsewidth modulation (PWM) frequency varies from 450 to 1800 Hz, and its line frequency is 50 Hz. The other is a multiconnected converter system consisting of plural, single-, or three-phase converter units and transformers. Its switching frequencies are chosen to be the lowest possible. The evaluated items are harmonic distortion, power loss, GTO utilization factor, and control response. Our simulation study shows that the multiconnected converter system with the lowest switching frequency is superior to the single-bridge system with the higher switching frequency in every case, even when there are severe line faults requiring very quick response. A new control strategy is adopted for obtaining quick response 相似文献
8.
The environment surrounding the iron and steel industry has changed greatly. This paper describes the technology adopted by the Japanese iron and steel industry to cope with changes in global demand, changes in the availability of coal and iron ore resources, correspondence to the extension of plant life, and energy conservation. In addition, efforts to reduce the amount of exhausted CO2 due to environmental concerns are discussed. 相似文献
9.
A. Ngamjarurojana S. Ural S.H. Park S. Ananta R. Yimnirun K. Uchino 《Ceramics International》2008,34(4):705-708
In this study, in order to develop low-temperature sintering ceramics for a multilayer piezoelectric transformer application, we explored CuO and Bi2O3 as sintering aids at low temperature (900 °C) sintering condition for Sb, Li and Mn-substituted 0.8Pb(Zr0.48Ti0.52)O3–0.16Pb(Zn1/3Nb2/3)O3–0.04Pb(Ni1/3Nb2/3)O3 ceramics. These substituted ceramics have excellent piezoelectric and dielectric properties such as d33 347 pC/N, kp 0.57 and Qm 1469 when sintered at 1200 °C. The addition of CuO decreased the sintering temperature through the formation of a liquid phase. However, the piezoelectric properties of the CuO-added ceramics sintered below 900 °C were lower than the desired values. The additional Bi2O3 resulted in a significant improvement in the piezoelectric properties. The composition Sb, Li and Mn-substituted 0.8Pb(Zr0.48Ti0.52)O3–0.16Pb(Zn1/3Nb2/3)O3–0.04Pb(Ni1/3Nb2/3)O3 + 0.5 wt% CuO + 0.5 wt% Bi2O3 showed the value of kp = 0.56, Qm = 1042 (planar mode), d33 = 350 pC/N, when it was sintered at 900 °C for 2 h. These values indicated that the newly developed composition might be suitable for multilayer piezoelectric transformer application. 相似文献
10.
Novel method for driving the ultrasonic motor 总被引:4,自引:0,他引:4
Kim Hw Dong S Laoratanakul P Uchino K Park Tg 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2002,49(10):1356-1362
This paper reports a novel driving method for an annular plate-type ultrasonic motor. Instead of the direct current/alternating current (DC/AC) converter type driver using a conventional electromagnetic transformer, a compact disc-type piezoelectric transformer is used to obtain a high voltage output for driving the ultrasonic motor. The piezoelectric transformer is operated in the radial vibration mode at resonance frequency close to the resonance frequency of the ultrasonic motor. Later, it was found that the piezoelectric transformer could drive the ultrasonic motor, even if their resonance frequencies are not exactly the same by incorporating a matching network in the circuit. The maximum speed of the ultrasonic motor obtained by using this driving method is over 300 rpm. It is believed that the results of this study will have impact on the integration and miniaturization of the ultrasonic motor and its driving circuit. 相似文献