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  • Title/Summary/Keyword: Pulse-on duration

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A Study on the Computational Analysis of 355nm UV Laser Multiple-Pulsed Micro Machining Considering the Strain Rate Effect (변형률 속도 효과를 고려한 355nm UV 레이저 다중 펄스 미세가공의 전산해석에 관한 연구)

  • Lee, Jung-Han;Oh, Jae-Yong;Park, Sang-Hu;Nam, Gi-Jung;Ryu, Gwang-Hyun;Shin, Suk-Hun;Shin, Bo-Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.10
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    • pp.29-33
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    • 2010
  • UV laser micromachining of metallic materials has been used in microelectronic and other industries. This paper shows on experimental investigation of micromachining of copper using a 355nm UV laser with 50ns pulse duration. A finite element model with high strain rate effect is especially suggested to investigate the phenomena which are only dominated by mechanically pressure impact in disregard of thermally heat transfer. In order to consider the strain rate effect, Cowper-Symonds model was used. To analyze the dynamic deformation during a very short processing time, which is nearly about several tens nanoseconds, a commercial Finite Element Analysis (FEA) code, LS-DYNA 3D, was employed for the computational simulation of the UV laser micro machining behavior for thin copper material. From these computational results, depth of the dent (from one to six pulsed) were observed and compared with previous experimental results. This will help us to understand interaction between UV laser beam and material.

Relationship between roar sound and regional groups of Steller sea lion, Eumetopias jubatus (큰바다사자의 명음과 지역적 그룹과의 관계)

  • Park, Tae-Geon;Iida, Kohji;Kim, Wook-Sung;Kim, Sung-Ki;Kim, Seok-Jae;Ryu, Kyong-Jin;Lee, Yoo-Won
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.51 no.2
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    • pp.195-202
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    • 2015
  • Hundreds of Steller sea lions, Eumetopias jubatus, migrate from Sakhalin and the northern Kuril Islands to Hokkaido in Japan every winter. During this migration, they may use their roaring sounds to navigate and to maintain their groups. We recorded the roars of wild Steller sea lions that had landed on reefs on the west coast of Hokkaido, and those of captive sea lions, while making video recordings. The fundamental frequency (F0), Formant frequency (F1), pulse repetition rate (PRR), and duration of syllables (T) were analyzed using a sonagraph. F0, F1, and PRR of the roars emitted by captive sea lions increased in the order male, female. By contrast, the F1 of wild males was lower than that of females, while the F0 and PRR of wild males and females did not differ statistically. These results suggest regional differences between the five groups showed that.

Relationship between roar sound characteristics and body size of Steller sea lion

  • Park, Tae-Geon;Iida, Kohji;Mukai, Tohru
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.46 no.4
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    • pp.458-465
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    • 2010
  • Hundreds of Steller sea lions, Eumetopias jubatus, migrate from Sakhalin and the northern Kuril Islands to Hokkaido every winter. During this migration, they may use their roaring sounds to navigate and to maintain their groups. We recorded the roars of wild Steller sea lions that had landed on reefs on the west coast of Hokkaido, and those of captive sea lions, while making video recordings. A total of 300 roars of wild sea lions and 870 roars of captive sea lions were sampled. The fundamental frequency (F0), formant frequency (F1), pulse repetition rate (PRR), and duration of syllables (T) were analyzed using a sonagraph. F0, F1, and PRR of the roars emitted by captive sea lions increased in the order male, female, and juvenile. By contrast, the F1 of wild males was lower than that of females, while the F0 and PRR of wild males and females did not differ statistically. Moreover, the F0 and F1 frequencies for captive sea lions were higher than those of wild sea lions, while PRR in captive sea lions was lower than in wild sea lions. Since there was a linear relationship between body length and the F0 and F1 frequencies in captive sea lions, the body length distribution of wild sea lions could be estimated from the F0 and F1 frequency distribution using a regression equation. These results roughly agree with the body length distribution derived from photographic geometry. As the volume of the oral cavity and the length of the vocal cords are generally proportional to body length, sampled roars can provide useful information about a population, such as the body length distribution and sex ratio.

A Study of Antinociception of Electroacupuncture to SI6 on the Acute Ankle Sprained Rats (흰쥐의 족과 염좌(捻挫) 통증(痛症)에 대한 양노(養老)(SI6) 전침(電鍼)의 진통(鎭痛) 기전에 대한 연구(硏究))

  • Yang, Bum-Sik;Kim, Jae-Hyo;Jang, Jae-Hun;Ahn, Sung-Hun;Kim, Kyoung-Sik;Sohn, In-Chul
    • Korean Journal of Acupuncture
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    • v.25 no.3
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    • pp.81-96
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    • 2008
  • Objectives : The purpose of the present study is to determine the effective analgesic parameters of manual acupuncture (MA) and/or electroacupuncture (EA), thus how MA & EA of specific acupoint works after acute ankle sprain in rats. Thus, one series of experiments was designed to analyze the analgesic effects of acupuncture in either the normal or sprained rat, by comparing the behavioral features before and after MA or EA at several acupoints. Methods : Ankle sprain was induced manually by hyper-extension of ligaments of the right ankle in rat. Either MA or EA was applied to the LI4, TE17, 足三里 and SI-6 acupoints at an intensity of 2 mA (1 ms pulse duration) with a frequency of 10 Hz for 30 minutes. Results : Behaviorally, manual acupuncture or electroacupuncture produced potent analgesic effects on acute ankle sprained animals as measured by weight bearing capacity of the affected limb. Furthermore, antinociceptive effect of EA was suppressed by alpha adrenoceptor antagonist phentolamine (5 mg/kg, i.p.) but not by opioid antagonist naltrexone (10 mg/kg, i.p.). Conclusions : It is suggested that acupuncture-induced antinociception may involve the descending inhibition of α2-adrenoceptor.

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Predictive model of fatigue crack detection in thick bridge steel structures with piezoelectric wafer active sensors

  • Gresil, M.;Yu, L.;Shen, Y.;Giurgiutiu, V.
    • Smart Structures and Systems
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    • v.12 no.2
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    • pp.97-119
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    • 2013
  • This paper presents numerical and experimental results on the use of guided waves for structural health monitoring (SHM) of crack growth during a fatigue test in a thick steel plate used for civil engineering application. Numerical simulation, analytical modeling, and experimental tests are used to prove that piezoelectric wafer active sensor (PWAS) can perform active SHM using guided wave pitch-catch method and passive SHM using acoustic emission (AE). AE simulation was performed with the multi-physic FEM (MP-FEM) approach. The MP-FEM approach permits that the output variables to be expressed directly in electric terms while the two-ways electromechanical conversion is done internally in the MP-FEM formulation. The AE event was simulated as a pulse of defined duration and amplitude. The electrical signal measured at a PWAS receiver was simulated. Experimental tests were performed with PWAS transducers acting as passive receivers of AE signals. An AE source was simulated using 0.5-mm pencil lead breaks. The PWAS transducers were able to pick up AE signal with good strength. Subsequently, PWAS transducers and traditional AE transducer were applied to a 12.7-mm CT specimen subjected to accelerated fatigue testing. Active sensing in pitch catch mode on the CT specimen was applied between the PWAS transducers pairs. Damage indexes were calculated and correlated with actual crack growth. The paper finishes with conclusions and suggestions for further work.

Experiment of Drifting Mobilities of Holes and Electrons in Stabilized a-Se Film

  • Kang, Sang-Sik;Park, Ji-Koon;Park, Jang-Yong;Kim, Jae-Hyung;Nam, Sang-Hee
    • Transactions on Electrical and Electronic Materials
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    • v.4 no.6
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    • pp.9-12
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    • 2003
  • The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 μm. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73μs and 229.17μs, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/μm. Above 4V/μm, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 cm2 V\^-1/s\^-1/ sand 0.00174 cm2V\^-1/s\^-1/ at 10 V/μm.

Suppression of stray electrons in the negative ion accelerator of CRAFT NNBI test facility

  • Yuwen Yang ;Jianglong Wei ;Junwei Xie ;Yuming Gu;Yahong Xie ;Chundong Hu
    • Nuclear Engineering and Technology
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    • v.55 no.3
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    • pp.939-946
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    • 2023
  • Comprehensive Research Facility for Fusion Technology (CRAFT) is an integration of different demonstrating or testing facilities, which aim to develop the critical technology or composition system towards the fusion reactor. Due to the importance and challenge of the negative ion based neutral beam injection (NNBI), a NNBI test facility is included in the framework of CRAFT. The initial object of CRAFT NNBI test facility is to obtain a H0 beam power of 2 MW at the energy of 200-400 keV for the pulse duration of 100 s. Inside the negative ion accelerator of NNBI system, the interactions of the negative ions with the background gas and electrodes can generate abundant stray electrons. The stray electrons can be further accelerated and dumped on the electrodes or eject from the accelerator. The stray electrons, including the ejecting electrons, cause the unwanted particle and heat flux onto the electrodes and the inner components of beamline (especially the temperature sensitive cryopump). The suppression of the stray electrons from the CRAFT accelerator is carried out via a series of design and simulation works. The paper focuses the influence of different magnetic field configurations on the stray electrons and the character of the ejecting electrons.

EFFECTS OF THE ER,CR:YSGG LASER ON BONE BED PREPARATION WITH VARIOUS LASER TIPS

  • Kim, Seong-Kyun;Heo, Seong-Joo;Koak, Jai-Young;Hong, Seong-Doo;Lee, Shin-Jae;Lee, Joo-Hee
    • The Journal of Korean Academy of Prosthodontics
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    • v.46 no.3
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    • pp.255-260
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    • 2008
  • STATEMENT OF PROBLEM: Preparation of implant beds with lasers is considered a safe and reliable method, but the accuracy of this technique has not been examined. PURPOSE: The purpose of this study was to evaluate the accuracy and effectiveness of implant bed preparation using an Er,Cr:YSGG laser. MATERIAL AND METHODS: An Er,Cr:YSGG laser was applied to pig rib bone. The laser was employed at a 5.75 W power setting, 30 Hz/sec pulse repetition, and 70 μs pulse duration with 50 % water and 60% air spray. According to laser tips the groups were divided as follows; Group 1: paralleled - shaped sapphire tip (0.6 mmΦ), Group 2: paralleled - shaped zirconia tip (0.6 mmΦ), Group 3: tapered sapphire tip (0.4 mmΦ). The Er,Cr:YSGG laser tip was separated by 1 mm from the bone and applied for 15 seconds in a non-contact mode. After the application, the bone was sectioned for specimens. Histologic measurements were determined by computerized morphometry. The length of the prepared bone surface was measured and the width of the entrance was measured. The results were analyzed with one-way ANOVA (P<0.05). RESULTS: The prepared length of group 3 was longer than that of group 2. The prepared bone width was larger than the width of the laser tip in every group. Additional bone removal was observed adjacent to the prepared area and displayed an irregular surface. CONCLUSION & DISCUSSION: Different cutting effects were observed according to the laser tip, emphasizing the importance of proper tip selection in the clinical setting. This preliminary study supported the existence of hydrokinetic effects.

Postnatal Development of Echolocation Vocalizations in the Serotine Bat, Eptesicus serotinus (Chiroptera: Vespertilionidae) (문둥이박쥐(Eptesicus serotinus)의 생후 반향정위 발성 발달에 관한 연구)

  • Chung, Chul-Un;Han, Sang-Hoon;Kim, Sung-Chul;Lim, Chun-Woo;Cha, Jin-Yeol
    • Korean Journal of Environment and Ecology
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    • v.29 no.6
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    • pp.858-864
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    • 2015
  • Developmental changes in the vocal signals of serotine bats (Eptesicus serotinus) during their infancy were examined in this study. The analysis was conducted on 4 infant serotine bats from 1 to 40 days after their birth. Pulse duration (PD), pulse interval (PI), peak frequency (PF), maximum frequency (FMAX), minimum frequency (FMIN), and bandwidth (BW) were measured. As the bats grew, their vocalizations became increasingly consistent and similar to those of adults. For infant bats, PD and PI decreased as they grew older, whereas PF, FMAX, FMIN, and BW increased. The greatest change in vocalizations was observed between the 10th and 20th days after birth. Also, PF, FMAX, FMIN and BW, which describe sound frequency, increased dramatically during the period between the 10th and the 20th days. In contrast, the greatest change in PD occurred between the 30th and 40th days after birth. The results collected in this study suggest that frequency increased as the contraction ability of the muscles developed by around 20 days of age. Muscle relaxation ability, which is related to PD, was found to develop significantly at 30 to 40 days of age. According to the results of this study, although 40 day-old infant bats are not yet able to fly, their vocal signals were similar to those of adults. This indicates that vocal development and flying activity develop separately in young bats.

Electromagnetic Retarder's Power Recovery Device and Voltage Control (전자기형 리타더의 전력회수장치 및 전압제어)

  • Jung, Sung-Chul;Yoon, In-Sik;Ko, Jong-Sun
    • The Transactions of the Korean Institute of Power Electronics
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    • v.21 no.5
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    • pp.396-403
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    • 2016
  • Usually, large-sized buses and trucks have a very high load. In addition, frequent braking during downhill or long-distance driving, causes the conventional method using the brake friction to have a problem in safety because of brake fade and brake burst phenomenon. Auxiliary brakes dividing the braking load is essential. Hence, environment-friendly auxiliary brakes, such as contactless brake rather than the engine auxiliary brake system are needed. A study aimed at improving the energy efficiency by recharging electric energy with changing mechanical to electrical energy that occurs when braking is actively in progress. In this paper, the voltage control method is utilized to recover the electric energy generated in the electromagnetic retarder instead of the eddy current. To regenerate the braking energy into the electrical energy, the resonant L-C circuit is configured in the retarder. The voltage generated in the retarder is simply modeled as a transformer. However, retarder voltage control in this paper is simulated by modeling the induction generator because this induction generator modeling is more practical than transformer modeling. The changes in the voltage of the resonance circuit, which depends on the switch pulse duration of the control device, were analyzed. A PI controller algorithm to control this voltage is proposed. The feasibility of modeling retarder and voltage controller are shown by using MATLAB Simulink in this paper.