• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제33권6A호
• /
• pp.599-606
• /
• 2008

In this paper, the channel estimation performance of proposed TSC (TSC-S) is investigated in terms of the BER and BLER performances when HSR is considered for GERAN evolution system. The performance is evaluated by the link level simulation and is compared with the other TSC proposal (TSC-E). Numerical results show that the performance employing the TSC-S is almost same to that using the TSC-E. In the case of cochannel interferences, the similar tendency is shown, when joint least square is adopted for channel estimation.

• Journal of the Korean Solar Energy Society
• /
• 제37권6호
• /
• pp.1-12
• /
• 2017

The DC link of Grid-Connected 3-Phase 3-Level T-type Photovoltaic PCS (PV-PCS) consists of two series connected capacitors for using their neutral voltage. The mismatch between two capacitor characteristics and transient states happened in load change cause the imbalance of neutral voltage. As a result, PV-PCS performance is degraded and the system becomes unstable. In this paper, a mathematical model for analyzing the imbalance of neutral voltage is derived and a compensation method using offset voltage is proposed, where offset voltage adjusts the applying time of P-type and N-type small vectors. The validity of the proposed methods is verified by simulation and experiment.

• Proceedings of the KIEE Conference
• /
• 대한전기학회 2007년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.194-197
• /
• 2007

This paper proposes a linearization technique for the 3 level NPC type inverter, which increases the linear control range of inverter up to the 6-step inverter. The overmodulation range is divided into two modes depending on the modulation index(MI), In mode I, the reference angles are derived from the Fourier series expansion of the reference voltage corresponds to the MI. In mode II, the holding angles are also derived in the same way. Therefore, it is possible to obtain the linear control and the maximized utilization of PWM inverter output voltage.

• Biomolecules & Therapeutics
• /
• 제20권4호
• /
• pp.418-424
• /
• 2012

Repeated stress induces corticosterone release. However, it is not clear that stress results in further elevation of corticosterone levels, and the roles of released corticosterone to aggravate stress-related symptoms are also not clear. This study investigated whether neuronal modulation was induced in the amygdala after two kinds of stress, that is, such as electric shock and corticosterone injection. It was found that stress by electric shock decreased the expression of tyrosine hydoroxylase (TH) in the amygdala while the expression of pERK was increased. However, there is no difference in the expressions of TH and pERK in the frontal cortex compared with those of the control group. The level of corticosterone was significantly increased in the serum after stress. To determine the effect of corticosterone on the induction of anxiety and the expression of TH, the rats received corticosterone (20 mg or 40 mg/kg i.p.) for 1 day, 1 week, 2 weeks and 3 weeks, respectively. The spent time in open arms of the EPM (elevated plus maze) test was significantly decreased after 1 week, 2 weeks and 3 weeks. The time spent in open arms of the EPM test after repeated injections of corticosterone was significantly decreased in a dose-dependent manner. The expression of TH in the amygdala was reduced after following repeated corticosterone treatment for 2 weeks and 3 weeks. Collectively, this study suggests that corticosterone has a major role in the induction of anxiety and the modulation of TH expression, at least, in the amygdala.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• 제19권12호
• /
• pp.462-470
• /
• 2018

This descriptive survey was conducted to explore the effects of work engagement and its associated factors among general hospital nurses. Nurses working in general hospitals were recruited in D city and K region. Data were analyzed by descriptive statistics, t-test, one-way ANOVA, Pearson's correlations, and stepwise multiple regression using IBM SPSS 25. The mean score of work engagement of the subjects was 3.08. The mean scores of emotional modulation effects in profession, patient focused emotional suppression, and emotional pretense by norms which are subgroups of emotional labor by norms were 3.82, 3.28, and 3.22, respectively, while that of the nursing work environment was 2.59. Work engagement was significantly positively correlated with emotional modulation effects in profession (r=0.30, p=0.001), patient-focused emotional suppression (r=0.20, p=0.030), and nursing work environment (r=0.21, p=0.024). The results showed that the factors that affect the work engagement were age, current position, and emotional modulation effects in profession, which explained 20% of the variance in work engagement (F=10.37, p<0.001). Therefore, to establish strategies for improving the level of work engagement, it is necessary to consider age and current positions of nurses and to develop a nursing intervention program to strengthen emotional modulation effects among general hospital nurses.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• 제8권3호
• /
• pp.87-92
• /
• 2008

In this paper, certain scaling functions are generated using the dyadic subband tree structure and applied to a time-hopping, pulse position modulation, ultra-wideband (TH-PPM UWB) system. Scaling functions can be obtained by iterating a lowpass filter at each level using a critically sampled dyadic tree. The performance of the TH-PPM UWB system employing scaling functions as the mono-cycle waveform is evaluated through computer simulations in a Rayleigh fading environment.

• Proceedings of the KIEE Conference
• /
• 대한전기학회 1989년도 하계종합학술대회 논문집
• /
• pp.515-517
• /
• 1989

This PWM inverter are used bridge circuit of two pair complementary transistor at each phase. The operation signals are 3 level PWM wave of W type and M type modulation, Which were obtained from switching time data by switching position calculation of triangular and sine wave. The output voltage waveforms of this inverter have the 5 level phase voltage and the 9 level line voltage of PWM.

• The Journal of the Korean dental association
• /
• 제49권11호
• /
• pp.679-687
• /
• 2011

Low-level laser therapy (LLLT) is the application of light to pathology to promote tissue regeneration, reduce inflammation, and relieve pain. LLLT has a photochemical effect whereby the light is absorbed and exerts a chemical change. The clinical applications of LLLT include improvement in wound and bone healing processes, control of pain and tooth hypersensitivity, modulation of periodontal inflammation, the prevention and treatment of cancer therapy-induced oral mucositis, management of burning mouth syndrome, and improvement in temporomandibular disorder symptoms. Further research is needed to better elucidate the cellular mechanisms of LLLT and provide a solid scientific basis for the clinical application of LLLT in dentistry.

• The Transactions of the Korean Institute of Power Electronics
• /
• 제20권6호
• /
• pp.509-516
• /
• 2015

The overmodulation characteristics of a carrier-based medium vector pulse width modulation (CBMVPWM) are examined in this study. CBMVPWM can completely eliminate leakage currents in a three-phase, three-level inverter using only the switching states with the same common mode voltage even in an overmodulation operation. The analytic equations for the magnitude of the output voltage and the switching frequency are derived for overmodulation operation, and the effect of dead time on the leakage current is demonstrated. This study presents the operating principle of CBMVPWM, basic overmodulation features, and simulations and experiments for operating verification.

• Journal of Computing Science and Engineering
• /
• 제7권3호
• /
• pp.168-176
• /
• 2013

Long-term evolution (LTE) is emerging as a major candidate for 4G cellular networks to satisfy the increasing demands for mobile broadband services, particularly multimedia delivery. Multiple-input multiple-output (MIMO) technology combined with orthogonal frequency division multiple access and more efficient modulation/coding schemes (MCS) are key physical layer technologies in LTE networks. However, in order to fully utilize the benefits of the advances in physical layer technologies, the MIMO configuration and MCS need to be dynamically adjusted to derive the promised gains of 4G at the application level. This paper provides a performance evaluation of video traffic with variations in the physical layer transmission parameters to suit the varying channel conditions. A quantitative analysis is provided using the perceived video quality as a video quality measure (evaluated using no-reference blocking and blurring metrics), as well as transmission delay. Experiments are performed to measure the performance with changes in modulation and code rates in poor and good channel conditions. We discuss how an adaptive scheme can optimize the performance over a varying channel.