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result(s) for
"Jung, Sang Wook"
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Design studies of the Ku-band, wide-band Gyro-TWT amplifier
by
Lee, Han Seul
,
Jang, Kwong Ho
,
So, Jun Ho
in
Magnetic fields
,
Traveling wave tubes
,
Traveling waves
2014
This paper reports a Ku-band, wide band Gyrotron-Traveling-wave-tube(Gyro-TWT) that is currently being developed at Kwangwoon University. The Gyro-TWT has a two stage linear tapered interaction circuit to obtain a wide operating bandwidth. The linearly-tapered interaction circuit and nonlinearly-tapered magnetic field gives the Gyro-TWT a wide operating bandwidth. The Gyro-TWT bandwidth is 23%. The 2d-Particle-in-cell(PIC) and MAGIC2d code simulation results are 17.3 dB and 24.34 kW, respectively for the maximum saturated output power. A double anode MIG was simulated with E-Gun code. The results were 0.7 for the transvers to the axial beam velocity ratio (=alpha) and a 2.3% axial velocity spread at 50 kV and 4 A. A magnetic field profile simulation was performed by using the Poisson code to obtain the grazing magnetic field of the entire interaction circuit with Poisson code.
Journal Article
Cilostazol in Acute Ischemic Stroke Treatment (CAIST Trial): A Randomized Double-Blind Non-Inferiority Trial
by
Hong, Keun-Sik
,
Kim, Jong S.
,
Lee, Byung-Chul
in
Aged
,
Aspirin - adverse effects
,
Aspirin - therapeutic use
2011
Background: Aspirin is a proven antiplatelet agent in acute ischemic stroke, and there are no current guidelines for other antiplatelet treatments. We aimed to compare the efficacy and safety of cilostazol with aspirin in acute stroke. Methods: Patients with measurable neurological deficits (NIHSS score ≤15) within 48 h of onset were randomly assigned to cilostazol (200 mg/day) or aspirin (300 mg/day) for 90 days. The primary endpoint was a modified Rankin Scale (mRS) score of 0–2 at 90 days. Cardiovascular events, bleeding complications, and other functional outcomes were also assessed. Statistical analysis was carried out by intention-to-treat and per-protocol bases. This trial is registered with ClinicalTrials.gov (NCT00272454). Results: In total, 458 patients were enrolled (mean age of 63 years, median NIHSS of 3), and mRS at 90 days was obtained in 447 patients. The primary endpoint was achieved in 76% (173/228) of those randomized to cilostazol and in 75% (165/219) assigned to aspirin, which supported the pre-specified non-inferiority of cilostazol to aspirin (95% CI of proportion difference: –6.15 to 7.22%, p = 0.0004). These results were also supported by per-protocol analysis (p = 0.045). Cardiovascular events occurred in 6 patients (3%) treated with cilostazol, and in 9 patients (4%) treated with aspirin (p = 0.41). Adverse events were more common in cilostazol-treated patients during the trial (91 vs. 85%, p = 0.055), while the frequencies of bleeding complications (cilostazol 11%, aspirin 13%, p = 0.43) or drug discontinuation (cilostazol 10%, aspirin 7%, p = 0.32) were not different. Conclusion: Cilostazol is feasible in acute ischemic stroke, and comparable to aspirin in its efficacy and safety.
Journal Article
Experiments on a Ku-band gyrotron traveling-wave-tube amplifier with a tapered waveguide
by
Lee, Han Seul
,
Choi, Jin Joo
,
Jang, Kwang Ho
in
Bandwidths
,
Cyclotron resonance devices
,
Electron beams
2015
A Ku-band gyrotron traveling-wave-tube (gyro-TWT) amplifier was investigated. To obtain a wide operating bandwidth, we used a two-stage tapered rectangular waveguide interaction circuit. An electron beam of 27 keV and 3.56 A was produced from a double-anode magnetron-injection-gun (MIG). The measured frequency bandwidth over 10 dB gain in the linear operation region was found to be 18%. The gyro-TWT’s saturated output power was 14.9 kW at 14.4 GHz, corresponding to a saturated output power gain of 27.4 dB and an efficiency of 15.5%. The measured experimental results were in agreement with those of non-linear numerical simulations.
Journal Article
Bandwidth broadening effect in a traveling-wave-tube amplifier by using impulse electron beam
2012
This paper reports on a wideband amplification mechanism involving an impulse electron beam. To prove broadband amplification with the impulse beam, we perform 3-dimensional particle-incell (3D PIC) code simulation. An impulse electron beam with a pulse width of 1 ns with electric potential 17.2 kV is injected into an interaction circuit of a coupled-cavity traveling-wave-tube (CCTWT) driven by a continuous-wave (CW) signal of 29.1 GHz. The resulting output bandwidth was 2.96%, and the peak output power of 713 W was the same as that obtained with CW operation at a single frequency. The simulation yielded very similar results with ultra short impulse signal from the simulation.
Journal Article
Quantitative comparison of similarity measure and entropy for fuzzy sets
2011
Comparison and data analysis with the similarity measures and entropy for fuzzy sets were carried out. The distance proportional value between the fuzzy set and the corresponding crisp set was considered by the fuzzy entropy. The relation between the similarity measure and the entropy for fuzzy set was also analyzed. The fuzzy entropy was reformulated as the dissimilarity measure. Furthermore, crisp set having the minimum uncertainty with respect to the corresponding fuzzy set was also proposed. Finally, derivation of a similarity measure from entropy with the help of total information property was derived. A simple example shows the relation between similarity measure and fuzzy entropy, in which the summation of similarity measure and fuzzy entropy represents a constant value.
Journal Article
Tailoring of Mechanical Properties of Indirect Hot Stamping Steel Tubes by Laser Assisted Local Rapid Heating
by
Mahmudun Nabi CHOWDHURY Ju-ri KIM Sung-tae HONG Jin-wook JUNG Heung-nam HAN Sang-woo SO
in
Applied and Technical Physics
,
Crush tests
,
Engineering
2016
The effect of laser assisted local heating on the mechanical properties of a hot stamping steel tube was in vestigated. A heated region with a spiral shape was generated on the surface of the tube by combining the linear movement of the laser and the rotation of the tube. The results of axial crush tests show that the laser assisted local heating can be effectively used to modify the mechanical performance of the tube. A microstructural analysis confirms that the laser locally induces a martensitic phase transformation in the heated region and results in inhomogeneous microstructures alon- the length of the tube.
Journal Article
Patient-reported ejaculatory function and satisfaction in men with lower urinary tract symptoms/benign prostatic hyperplasia
by
Min Chul Cho;Jung Kwon Kim;Sang Hoon Song;Sung Yong Cho;Sang Wook Lee;Soo Woong Kim;Jae-Seung Paick
in
Aged
,
Androgens
,
Bladder
2018
This study aimed to investigate perceived ejaculatory function/satisfaction before treatment for lower urinary tract symptoms (LUTS)/benign prostatic hyperplasia (BPH) and to identify associations between specific categories of ejaculatory dysfunctions (EjDs) and LUTS. A total of 1574 treatment-naive men with LUTS/BPH were included in this study. All patients underwent routine evaluation for LUTS/BPH including the International Index of Erectile Function and a 5-item questionnaire developed to assess ejaculatory volume/force/pain/satisfaction/latency time. Patients who had sexual intercourse over the past 4 weeks were classified as sexually active group. A total of 783 patients were categorized as sexually active group. Decreased ejaculatory volume and force were reported by 53.4% and 55.7% of 783 sexually active men, respectively, There was a strong correlation between ejaculatory volume and force. Ejaculatory pain/discomfort, premature ejaculation (PE), and delayed ejaculation (DE) were reported in 41,0%, 16.3%, and 41.4% of the patients, respectively. Over 40.0% of men without decreased ejaculation volume/force were satisfied with ejaculatory function, whereas approximately 6.0% of men with decreased volume/force were satisfied with ejaculatory function. About 30.0% of men with decreased volume/force had orgasmic dysfunction, while approximately 10.0% of men without decreased volume/force did. Decreased ejaculatory volume or force was associated with LUTS severity after adjusting for other influential factors including testosterone level, erectile function, and prostate size on ultrasonography, but PE or DE or ejaculatory pain/discomfort was not. In conclusion, a considerable portion of men with LUTS/BPH appear to have a variety of EjDs. Ejaculatory volume/force and satisfaction/orgasm do not always appear to be concordant. Ejaculatory volume or force is independently associated with LUTS severity, whereas PE or DE or ejaculatory pain/discomfort is not.
Journal Article
Similarity measure design and similarity computation for discrete fuzzy data
2011
The similarity computations for fuzzy membership function pairs were carried out. Fuzzy number related knowledge was introduced, and conventional similarity was compared with distance based similarity measure. The usefulness of the proposed similarity measure was verified. The results show that the proposed similarity measure could be applied to ordinary fuzzy membership functions, though it was not easy to design. Through conventional results on the calculation of similarity for fuzzy membership pair, fuzzy membership-crisp pair and crisp-crisp pair were carried out. The proposed distance based similarity measure represented rational performance with the heuristic point of view. Furthermore, troublesome in fuzzy number based similarity measure for abnormal universe of discourse case was discussed. Finally, the similarity measure computation for various membership function pairs was discussed with other conventional results.
Journal Article
Younger patients have poorer biochemical outcome after radical prostatectomy in high-risk prostate cancer
by
Sung Kyu Hong Jung Soo Nam Woong Na Jong Jin Oh Cheol Yong Yoon Chang Wook Jeong Hyun June Kim Seok-Soo Byun Sang Eun Lee
in
Aged
,
Humans
,
Male
2011
The aim of this study was to investigate the prognostic significance of patient age with respect to tumour aggressiveness in men who underwent radical prostatectomy (RP) for prostate cancer. In this study, we reviewed the records of 743 patients who received RP without neoadjuvant or adjuvant therapy at our institution and were followed up for 〉2 years postoperatively. For our analyses, the patients were divided into two groups according to age: younger (〈60 years) and older (≥ 60 years). Through uni- and multivariate analyses, associations of various clinicopathological parameters, including biochemical recurrence-free survival, with patient age, were evaluated among all patients, and the patients were stratified according to their D'Amico risk classification. Among all subjects, younger (n= 126) and older (n=617) patients showed no significant differences regarding pathological parameters and biochemical recurrence-free survival (P=0.288). For the high-risk group (n= 206), younger patients had a lower rate of biochemical recurrence-free survival following surgery than older patients (P=0.017), despite the fact that no significant differences were observed regarding various known prognostic parameters between the two age groups. In addition, multivariate analysis revealed that age was an independent predictor of biochemical recurrence-free survival among the high-risk group (P=O.O03). Our results showed that relatively younger patients have a comparable biochemical outcome compared with their older counterparts following RP performed for prostate cancer. However, among patients with high-risk disease, younger patients have a worse biochemical outcome following RP compared with older patients.
Journal Article