• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.422-428
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• 2018

Increase in use of lightweight structures, coupled with the increased acoustic loads resulting from larger and longer range guided missiles, has made missile more susceptible to failures caused by acoustic loads. Thus, accurate prediction of acoustic environment and the response is becoming ever more important for mission success. In this paper, the acoustic response of a sandwich composite skin structure to diffuse acoustic excitation is predicted over a broad frequency range. For the low frequency acoustic analysis, coupled FE-BEM method is used where the structure is modeled using FEM and the interior and exterior fluid is modeled using BEM. For the high frequency region, statistical energy analysis is applied. The predicted acoustic level inside the structure is compared with the result from acoustic test conducted in reverberation chamber, which shows very good agreement.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.716-723
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• 2019

It is crucial to understand the characteristics of cloud occurrence frequency for development of high precision guided missile using infrared imaging sensor. In this paper, we investigated the vertical structure of cloud for altitude using upper-air observation data. We find that cloud occurrence frequency is high at altitudes of 1.3 km and 9.5 km. Theses features have seasonal and temporal dependency. In the summer, cloud often occur more than average regardless of altitude. In the winter, low clouds occur frequently, and high clouds do not occur well. In temporal characteristics, clouds occur more frequently in daytime than in nighttime regardless of altitude. Many of clouds exist in single layer or double layers in the air. We also find that the 40 % of cloud occurrence frequency at high altitude when low clouds under altitude of 2 km cover entire sky.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.501-511
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• 1995

The purpose of this study was to evaluate the position and shape of mental foramen in periapical radiographs. For this study, periapical radiographs of premolar areas were obtained from the 200 adults. Accordingly, the positional and shape changes of mental foramen were evaluated. The authors obtained radiographs according to changes in radiation beam direction in periapical radiographs of premolar areas, and then evaluated the positional and shape changes of mental foramen. The following results were obtained: 1. Shapes of mental foramen were observed elliptical(34.3％), round or oval(28.0％), unidentified(25.5％) and diffuse(12.2％) type in descending order of frequency. 2. Horizontal positions of mental foramen were most frequently observed at the 2nd premolar area(55.3％), the area between the 1st premolar and 2nd premolar(39.6％), the area between the 2nd premolar and 1st molar(3.4％), the 1st premolar area(1.0％), the area between the canine and 1st premolar(0.7％) in descending order of frequency. 3. Vertical positions of mental foramen were most frequently observed at the inferior to apex(67.1％), and at apex(24.8％), overlap with apex(6.4％), superior to apex(1.7％) in descending order of frequency. 4. Shapes of mental foramen were more obviously observed at the upward 10° positioned periapical radiographs. And according to the changes of horizontal and vertical position, they were observed similar to normally positioned periapical radiographs.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.1
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• pp.88-93
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• 2004

In general, a fundamental structural design consideration for an automobile is the overall dynamic behavior in bending and torsion. Dynamic behavior of the automobile are mainly influenced by the structural stiffness of B.I.W.(body-in-white) and the physical property of trim components. In this paper, the modeling techniques for various trim components of middle-sized bus are presented, and the dynamic effects of the trim components on the vibration characteristics of the bus are investigated. The $1^{st}$ torsional frequency is decreased by attaching windshield and backlite to the B.I.W., but the $1^{st}$ vertical bending frequency and the $1^{st}$ lateral bending frequency are increased. The natural frequencies of the bus are decreased by attaching doors and windows. And also, the natural frequencies of the bus are large decreased by attaching seats, instrument panel etc. The study shows that the dynamic characteristics of the bus can be effectively predicted in the initial design stage.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.10
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• pp.99-106
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• 2008

5kWh FESS(Flywheel Energy Storage System) using AMB(Active Magnetic Bearing) has been under development and 1st trial system has been finished and run the operating test. Unfortunately, the test result was not satisfactory because FESS could increase the rotational speed up to 9,000 rpm only although the target rotational speed is 18,000rpm. It's because 1st bending mode frequency of flywheel shaft was too low and imbalance response was too big. To achieve the target speed, 1st bending mode and imbalance response must be improved and the whole FESS needed to be designed again. This paper presents the newly designed FESS and what has been changed from the 1st trial FESS to improve 1st bending mode and imbalance response. The experimental results to see how much 1st bending mode frequency was improved are presented, too.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.4
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• pp.148-156
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• 2001

Brake judder, one of low Sequency vibrations in brake system is determined by the excitation of Brake Torque Variation (BTV). The largest contributor to BTV is disc thickness variation. In this study, the static loads of brake torque at Suspension Mounting Points (SW) are obtained by the quasi-static analysis using DADS. The dynamic loads with frequency of BTV at SW are derived from correlation between forced vibration analysis with static loads and brake test results. And the accelerations at steering wheel were analyzed by forced vibration analysis with dynamic loads using commercial finite element program MSC/NASTRAN so that vibration characteristics of vehicle due to brake judder were investigated. Reliability of analysis results was verified through comparing the brake test results. Also, a parametric study with natural frequencies of frame, such as the 1st torsional mode and 1st bending mode, was conducted to reduce vibration amplitudes. As a result we could detect frame natural frequency conditions to improve vibration characteristics and obtained the frame model to reduce vibration amplitude.

• Journal of Acupuncture Research
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• v.24 no.2
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• pp.187-201
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• 2007

Objectives: This study was to investigate the effect of high frequency electro-acupuncture (EA) at $ST_{36}$ acupoint on the Freund's Complete Adjuvant (FCA)-induced arthritis in rats. Methods : Arthritis was induced by intradermal injection of FCA into base of tail. Experimental groups were divided into 4 groups; Normal, Control, $ST_{36}$ and Non-Acupoint (NA). $ST_{36}$ group was treated by 120Hz EA at $ST_{36}$ acupoint. Body weight, paw edema volume and ankle joint thickness were measured after treatment. And we investigated the effects of 120Hz EA via WBC count, segmen neurophil, lymphocyte, PGE2 assay and NADPH-d histochemistry. Results and Conclusions : The mean of body weight and ankle joint thickness of $ST_{36}$ group was increased compared with control group. The mean of paw edema volume, WBC count, segment neutrophil and lymphocyte of were not decreased with control group. The mean of PGE2 concentration ($1,851.00{\pm}160.11$) and NADPH-d positive neurons ($13.12{\pm}1.23$) were changed significantly (p

• Journal of Advanced Navigation Technology
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• v.10 no.4
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• pp.348-355
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• 2006

In this paper, frequency multipliers used S-band transponder of the KOMPSAT 3 are designed and fabricated. In the transponder, 108 times multiplier which generate 1st LO signal(2008.8MHz) is comprised of the X9 frequency multiplier, 1st X2 multiplier, 2nd X2 multiplier and the last stage of the X3 frequency multiplier. As results, output power of 8.17 dBm at 2008.8MHz, the harmonic suppression of -56.67dBc, the bandwidth of 14MHz were measured.

• Journal of Veterinary Clinics
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• v.36 no.3
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• pp.150-154
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• 2019

The purpose of this study was to investigate the etiological distribution, therapeutic outcome, and survival time in canine epilepsy. The medical records of 57 epileptic dogs were reviewed for the evaluation of etiological distribution. Among them, 27 dogs (47%) and 30 dogs (52%) had idiopathic epilepsy (IdE) and structural epilepsy (StE), respectively. Twenty-nine dogs (IdE: 16 dogs, StE: 13 dogs) were evaluated for therapeutic outcome and survival time. The incidence of generalized epileptic seizure (IdE, 56% vs. StE, 44%; P = 0.043) and the median seizure frequency at the time of first presentation (IdE, 2.0/month vs. StE, 13.3/month; P < 0.01) were significantly different between the two groups. Although pre-treatment seizure frequency and duration were not different, the median duration of seizure in the IdE group (0.5 min) was significantly shorter than that in the StE group (3 min) after treatment (P < 0.01). In addition, the median frequency of seizure was relatively lower in the IdE group (0.25/month) compared to the StE group (2.00/month) following antiepileptic therapy (P = 0.053). The median survival time of the IdE group (1.5 years [95% CI, 1.0-2.3 years]) was significantly longer than that of the StE group (0.4 year [95% CI, 0.2-1.3 years]) (P < 0.01). The information on etiological data and intracranial lesions may be useful for predicting treatment response and prognosis in epileptic dogs.

• Journal of Acupuncture Research
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• v.25 no.4
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• pp.1-9
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• 2008

Objectives : This study was to investigate the effect of low frequency electroacupuncture according to acupoints combination on NOS positive neurons in the PAG and Hippocampus of Rat with adjuvant induced Rheumatoid arthritis. Methods : Arthritis was induced by intradermal injection of FCA into base of tail. Experimental group were divided into 6 group ; Normal, Control, $ST_{36}$, $SP_9$, $ST_{36}+SP_9$, and NA. Normal group was injected with normal saline and not treated electroacupuncture. Control group was injected with FCA and not treated electroacupuncture. ST36 group was injected with FCA and treated by 2 Hz electroacupuncture at $ST_{36}$. $SP_9$ group was injected with FCA and treated by 2 Hz electroacupuncture at $SP_9$. $ST_{36}+SP_9$ group was injected with FCA and treated by 2 Hz electroacupuncture at $ST_{36}+SP_9$. NA group was injected with FCA and treated by 2 Hz electroacupuncture at non acupoint. Each groups were evaluated by the number of NOS-positive neurons in PAG and hippocampus by using an image analyzer and a microscope. Results : 1. The number of NOS-positive neurons of the NA group were significantly decreased in the CA2-3. 2. The number of NOS-positive neurons of the ST36 group were significantly decreased in the PAG and CA2-3. 3. The number of NOS-positive neurons of the SP9 group were significantly decreased in the PAG and DG 4. The number of NOS-positive neurons of the ST36+SP9 group were significantly decreased in the PAG, CA1 and DG. Conclusions : It is expected that low frequency electroacupuncture can be used a treatment of rheumatoid arthritic pain and that treatment of electroacupuncture at combined acupoints is more efficient than treatment of low frequency electroacupuncture at one acupoint.