• Journal of Korean Neurosurgical Society
• /
• 제40권4호
• /
• pp.304-308
• /
• 2006

Statistical analyses used in clinical articles published on the Journal of Korean Neurosurgical Society were identified and appropriateness of statistical aspects in reporting results was assessed. Forty seven clinical articles were selected in this study, which were published from February, 2005 to February, 2006 on the journal. The frequency of statistical analysis was as follows : descriptive statistics only 24 [51.1%]. one type of statistical method 10 [21.3%], two or more methods 13 [27.6%]. An assessment of statistical aspects was performed in 24 clinical articles reporting inferential statistics. Ten articles [41.7%] did not adequately describe or reference all statistical methods used. There were six articles [25.0%] not reporting the confidence level used as the critical criteria of the statistical significance. In thirteen articles [54.2%] it seems more appropriate to implement multivariate analyses in addition to univariate analyses. We recommend that the journal readers should concentrate on improving their knowledge of basic statistics and statistical review for manuscripts submitted should be sought from professionals in the fields of biostatistics and epidemiology.

• Journal of Power Electronics
• /
• 제14권6호
• /
• pp.1217-1223
• /
• 2014

A novel half load-cycle worked dual input single output (DISO) DC/AC inverter is presented. The basic circuit consists of a dual buck regulator, which works in continuous current mode. The working principle of DISO DC/AC inverter has been used. The control method applied for half load-cycle worked DISO DC/AC inverter has been studied. The control effects of the open-loop proportional control and closed-loop proportional-integral control are compared by using PSIM software. The parameters are adopted in the realistic simulation and experiment test. Moreover, the waveforms, such as voltage of modulation reference signal and output voltage, were given. The simulation and experiment results proved that the half load-cycle worked DISO DC/AC inverter could achieve good performance, gain a line frequency of 50 Hz, and verify the correctness of theoretical analysis.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1998년도 하계종합학술대회논문집
• /
• pp.958-961
• /
• 1998

In this paper, a three phase boost converter that operates with unity power factor and sinusodial input currents is presented. The current control of the converter is based on the space vector strategy with fixed switching frequency and the input current tracks the reference current within one sampling time interval. Space vector strategy for current control was materialized as a digital control method by using DSP. By using this control strategy low ripples in the output voltage, low harmonics in the input current and fast dynamic responses are achieved with a small capacitance in the dc link.

• Journal of Positioning, Navigation, and Timing
• /
• 제6권1호
• /
• pp.35-41
• /
• 2017

Precise Point Positioning (PPP) method is based on dual-frequency data of Global Navigation Satellite Systems (GNSS). The recent multi-constellations GNSS (multi-GNSS) enable us to bring great opportunities for enhanced precise positioning, navigation, and timing. In the paper, the multi-GNSS PPP with a combination of four systems (GPS, GLONASS, Galileo, and BeiDou) is analyzed to evaluate the improvement on positioning accuracy and convergence time. GNSS observations obtained from DAEJ reference station in South Korea are processed with both the multi-GNSS PPP and the GPS-only PPP. The performance of multi-GNSS PPP is not dramatically improved when compared to that of GPS only PPP. Its performance could be affected by the orbit errors of BeiDou geostationary satellites. However, multi-GNSS PPP can significantly improve the convergence speed of GPS-only PPP in terms of position accuracy.

• Journal of Positioning, Navigation, and Timing
• /
• 제7권3호
• /
• pp.175-181
• /
• 2018

The use of dual-frequency measurements from the Global Navigation Satellite System (GNSS) enables us to observe precise ionospheric total electron content (TEC). Currently, many GNSS reference stations in South Korea provide both GPS and GLONASS data. In the present study, we estimated the grid-based TEC values and relative receiver differential code biases (DCB) from a GNSS network operated by the Korea Astronomy and Space Science Institute. In addition, we compared the diurnal variations in a TEC time series from solutions of the GPS only, the GLONASS only, and combined GPS/GLONASS processing. A significant difference between the GPS only TEC and combined GPS/GLONASS TEC at a specific grid point over South Korea appeared near the solar terminator. It is noted that GLONASS measurements can contribute to observing a variation in ionospheric TEC over high latitude regions.

• 소음진동
• /
• 제9권3호
• /
• pp.472-476
• /
• 1999

The effect of static preload on the dynamic properties of rubber materials is rather important, especially when good isolation characteristics are required at high frequencies. However, there are still few papers for dynamic characteristics of compressed rubber components. It was demonstrated in reference (4) that for bonded rubber material of a cylindrical shape, a simplified theory equation between linear dynamic and nonlinear static behavior of rubber material was useful to predict their combined effects. This paper presents the second part of the study. It is confirmed that for the compressed rubber material, the stress can be factored into a function of frequency and a function of strain(stretch). The finite element methodis applied to analyze non-linear large deformation of rubber material and its results are compared with those of a simplified theory equation. The predicted dynamic material properties based on non-linear static finite element analyses have a good agreement of experimental results and those based on simplified theory equation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 제39회 하계학술대회
• /
• pp.1541-1542
• /
• 2008

In this paper, we introduce a live wire power transmission line fault detection system using time-frequency domain reflectometry(TFDR). The TFDR is known that is more precise method than the other conventional ones. However, the TFDR is generally adopted only in fault detection for communication cable, and dead line power transmission line. Therefore, this paper suggests a TFDR system with coupler which separates 220V, 60Hz signal and TFDR reference signal for implementation the live wire fault detection system. This approach is verified by circuit simulation.

• 여성건강간호학회지
• /
• 제13권3호
• /
• pp.184-191
• /
• 2007

Purpose: This study was to determine the effects of foot reflexomassage on constipated college women for the treatment of constipation. Method: The researcher sampled nursing students attending a college of nursing science in Gyeonggi-Do, and checked if they were affected by constipation in reference to the Rome II criteria & CAS. They were randomly divided into an experimental group(15 subjects) and a control group(15 subjects). Foot reflexomassage was applied to the experimental group 10 times in 2 weeks: each time lasted 40 minutes. The frequency of defecation and severity of constipation by CAS were measured. The collected data was analyzed using the SPSS 11.5 program. Result: The CAS score of the experimental group was significantly lower after foot reflexomassage than those of the control group(p=.000). Conclusion: Foot reflexomassage can be considered an effective alternative treatment for constipated young women.

• 성인간호학회지
• /
• 제17권5호
• /
• pp.802-812
• /
• 2005

Purpose: to determine the effects of hand acupuncture on IBS-affected college women's bowel symptoms and psychologic health by applying the therapy to them. Method: The researcher sampled the nursing student attending a college of nursing science in Seoul and checked if they were affected by IBS in reference to the Rome II Criteria. Students were classified into a experimental group(21 subjects) and a control group(19 subjects). Hand acupuncture was applied to the experimental group 8 rounds for 4 weeks; each round lasted 30 minutes. Data were collected for 8 weeks from October 11 to December 1, 2004. The collected data were analyzed using the SPSS 12.0 program. Result: After the therapy, frequency(p=.005), distress(p=.001) and disability (p=.000) associated IBS bowel symptom and anxiety were significantly lowered in the experimental group(p=.026). Conclusions: It was confirmed through this study that the hand acupuncture would be effective in relieving IBS bowel symptoms and anxiety.

• Journal of Power Electronics
• /
• 제12권3호
• /
• pp.477-486
• /
• 2012

This paper proposes a novel current control scheme for vector-controlled induction machine (IM) drives in the overmodulation (OVM) range, with which the voltage utilization of the voltage-source inverter (VSI) can be maximized. In the OVM region, the original voltage reference is modified by changing its magnitude and angle, which causes the motor current to be distorted, resulting in a deterioration of the current control performance. To meet with this situation, the harmonic components in the feedback currents should be eliminated before being input to the PI current controllers. For this, a composite observer is applied to extract the fundamental and harmonic components from the distorted currents, which gives a good performance without a delay and the effect of a fundamental frequency variation. In addition, through a detailed analysis of the response of the PI current controllers in the OVM range, the effectiveness of using the composite observer is demonstrated. Simulation and experimental results for a 3-kW induction motor drive are shown to verify the validity of the proposed method.