• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.44-53
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• 2008

In this paper, we present the design of delta-sigma modulation-based class-D amplifier for driving headphones in portable audio applications. The presented class-D amplifier generates PWM(pulse width modulation) signals using a single-bit fourth-order high-performance delta-sigma modulator. To achieve a high SNR(signal-to-noise ratio) and ensure system stability, the locations of the modulator loop filter poles and zeros are optimized and thoroughly simulated. The test chip is fabricated using a standard $0.18{\mu}m$ CMOS process. The active area of the chip is $1.6mm^2$. It operates for the signal bandwidth from 20Hz to 20kHz. The measured THD+N(total harmonic distortion plus noise) at the $32{\Omega}$ load terminal is less than 0.03% from a 3V power supply.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.5
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• pp.694-699
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• 2012

This paper proposes a new sensorless speed control scheme of permanent magnet DC motor using a numerical model and hysteresis controller, which requires neither shaft encoder, speed estimator nor PI controllers. By supplying the identical instantaneous voltage to both model and motor in the direction of reducing torque difference, the rotor speed approaches to the model speed, namely setting value and the system can control motor speed precisely. As the numerical model whose electric parameters are the same as those of the actual motor is adopted, the armature rotating speed can be converged to the setting value by controlling torque on both sides to be equalized. And the hysteresis controller controls torque by restricting the torque errors within respective hysteresis bands, and motor torque are controlled by the armature voltage. The experiment results indicate good speed and load responses from the low speed range to the high, show accurate speed changing performance.

• Journal of Ginseng Research
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• v.20 no.3
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• pp.241-247
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• 1996

The effects of ginseng total saponin, ginsenoside-Rb, and -Rb, on the reduction of chmlesterol level and the myNA expression rates of HMG CoA reductase and LDL receptor in Hep G2 were investigated and compared with that of lovastatin, a competitive HMG CoA reductase Inhibitor. The amounts of cholesterol in Hep G2 decreased in total saponin-and ginsenoside-treated groups as compared with that of control group, while there was no significant reduction in lovastatin-treated group. The mRNA expression rates of HMG CoA reductase increased in total saponin and gin- senoside groups except for ginsenoside-Rb, (10-3%) group and decreased in lovastatin group com- pared with that of control group. The mRNA expression rates of LDL receptor generally increased In all of the test groups except for total saponin (10-5%) group compared with that of control group. Because the ginseng components tested were more effective in the reduction of cholesterol level in Hep G2 than lovastatin and induced the gene expression of LDL receptor, we suggest the possibility that they could be used as a replacement agent for lovastatin which can not be prescribed especially to patients with hepatic diseases.

• Archives of Pharmacal Research
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• v.28 no.3
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• pp.343-350
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• 2005

Gamma radiation causes suppression of the immune function, and immune properties are related to cytokine production. In the present study, the polysaccharide, Ginsan, purified from an ethanol-insoluble fraction of Ginseng (Panax ginseng C.A. Meyer, Araliaceae) water extract was studied to assess its effects on the immunosuppressive activities of gamma radiation. Gin­san was found to stimulate murine normal splenocytes by inducing the mRNA expressions of Th1 and Th2 type cytokines, and also restore the mRNA expression of IFN-$/gamma$, Th1 cytokine, after its inhibition by whole-body gamma irradiation. Therefore, Ginsan was found to restore the T lymphocytes function that had been suppressed by gamma irradiation in allogenic MLR (mixed lymphocyte reactions). However, Ginsan exhibited no excessive stimulatory effects on the control group. The above results indicated that Ginsan may constitute a new noble agent for the improvement of gamma radiation-induced immunosuppression.

• Proceedings of the Ginseng society Conference
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• 1998.06a
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• pp.253-262
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• 1998

Ochratoxin A (OA) is a potent mycotoxin causing considerable health hazard and economic loss- e,i. OA is of concern as it is hepato-nephrotoxic, mutagenic, and carcinogenic to a great variety of animals. LDso of crude OA was 8.5 mgf kg.b.w., i.p. The clinical symptoms, mortalities and necropsy were recorded in rats injected with OA (LD5o, i.p.) during 10 days of daily treatment. Ginseng treatments (20 mg 1 kg. b.w., i.p.) : before, mixed with, or after OA dose, completely prevented the mortality in rats. OA-treated animals showed microcytic normochromic anaemia, lucocytosis, hypoproteinaemia and elevation of serum ALT, AST, AP, urea, and creatinine values. These findings were declined near the normal levels when ginseng injected with OA. OA (115 LDso) induced chromosomal aberrations (65.66%) compared to the control. When ginseng given 10 min before OA injection, chromosomal aberrations were reduced to be 31.66% compared to OA-treated animals. In conclusion: ginseng has a protective effect against ochratoxicosis, it has anti-genotoxic activity and it can repair the chromosomal damage induced by ochratoxin A. Key words Ochratoxicosis, Chromosomal aberrations, Mycotoxins, Ochratoxin A, Korean gin sting, Protective effect of Panax ginseng, Rat

• The Korean Journal of Pain
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• v.6 no.2
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• pp.220-223
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• 1993

Administration of local anesthetics or morphine through epidural space has the effect of curbing postoperative increases in endocrine hormone. Other benefits include improving metabolic reaction and eliminating postoperative pain. However, repeated administration of local anesthetics through epidural space causes tachyphylaxis, and the unstable blockade of sensory nerve resulting in insufficient analgesia. Morphine has excellent postoperative analgesic effect, but complications including: itching, nausea, vomiting, urinary retention and respiratory depression may be associated with its administration. Sixty patients that fall into the category of ASA class I and II were randomly selected for the purpose of the experiment. Thirty patients were give 4 mg of morphine and the rest, 4 mg of morphine plus 80 ml of 0.25% bupivacaine administered through epidural space with the Baxter infuser. Analgesic effect was satisfactory in both groups. On the day of operation, the effect was stronger in group I (P<0.05) and on postoperative second day, group II showed better analgesic effect (P < 0.05). Group II had more patients who complained of itching (P < 0.05). Other complications were statistically insignificant. The findings indicate that administration of morphine through epidural space for postoperative pain management is an effective procedure. Baxter infuser was found to be very instrumental in pain control while reducing the chance of complications.

• Journal of Periodontal and Implant Science
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• v.30 no.1
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• pp.11-27
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• 2000

The purpose of this study was to evaluate the clinical effects of Dipotassium glycyrrhizinate, Allantoin, Hinokitiol, Cetylpyridinium chloride containing gel($Dentheth^{(R)}$) on periodontitis. 41 patients with sites having pocket depth of 4-6mm were selected for the study. We classified 2 groups which consisted of 21 patients in the test group(exp.) and 20 patients in the control(placebo) respectively. Following a baseline examination, plaque and calculus were removed and then the experimental gel were handed out to the patients and topical application regimens were initiated. During the 4-week experimental period, pocket depth, bleeding on probing, gingival index, plaque index as a clinical parameters were measured in the baseline, 2 weeks, 4 weeks respectively. A questionnaire was delivered to each patients in 2 weeks, 4 weeks respectively. The results were as follows : 1. Probing pocket depth showed a significant difference in the Exp. group compared with the control group in the changes from baseline to 2 weeks(p<0.05), but there was no significant difference between the groups in the changes from baseline to 4 weeks, from 2 weeks to 4 weeks(p<0.05). 2. The Exp. group showed a significant difference compared with the control group in the changes from baseline to 2 weeks, from baseline to 4 weeks, from 2 weeks to 4 weeks in bleeding on probing(p<0.05). 3. The gingival index showed a significant difference compared with the control group in the changes from baseline to 2 weeks, from baseline to 4 weeks, from 2 weeks to 4 weeks after 4 weeks use of a gel(p<0.05). 4. The plaque index showed a significant difference in the Exp. group compared with the control group in the changes from baseline to 2 weeks(p<0.05), but there was no significant difference between the groups in the changes from baseline to 4 weeks, from 2 weeks to 4 weeks(p<0.05). 5. A questionnaire was consisted of 5 kinds as to bleeding, pus discharge, pain, burning sensation, patient's satisfaction and all of the questions showed a significant difference compared with the control group in the changes from 2 weeks to 4 weeks(p<0.05). 6. During the 4-week experimental period, important side-effects were not finded out, but each groups had one patient appealed nausea or discomfort respectively. These results indicate that application of periodontitis medical gel was useful as an additional aid of mechanical treatment.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.916-922
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• 2014

Diode rectifiers have been widely used for an AC to DC converter. But a big problem is that they include large harmonics components in the input currents. A 12-pulse configuration with phase shifting transformer is useful for reducing them. however, it still includes the ($12{\pm}1$)th (m; integer) harmonics in the input currents. In this paper, we propose a single-phase square wave auxiliary voltage supply which is inserted in the middle DC bus. It reduces harmonics especially the 11th and 13th and the harmonic characteristic becomes almost equivalent to a 24-pulse rectifier. Theoretical analysis of the combined 12-pulse diode rectifier with the auxiliary supply is presented and a control method of the auxiliary supply is proposed. The reduction in the input current harmonics is verified by simulation using software PSIM.

• Journal of Fashion Business
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• v.24 no.4
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• pp.63-84
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• 2020

It is essential to consider the heavy industrial working environment factors which are regarded as harmful to workers' health and safety and suitable work motion factors for the workers' motion while developing the work clothes for painting workers in the machinery and shipbuilding industries. This study suggests the use of 3D virtual clothing simulations as a solution to protect the human body from hazardous working conditions accompanying the development of painting work clothes and assessing the work motion performance associated with the comfort while workers wear them during the work clothes. The initial aim of the study is to examine a male avatar to run work motions simultaneously within a 3D virtual clothing simulator, secondly, to present the simulation images of coverall type men's painting work clothes with the application of two experimental painting work motions and one control motion to the avatar, and finally, to present the distance analysis images of the painting work clothes and the avatar body and air gap rates through the analysis of cross-sections of the avatar body while wearing the coverall work clothes according to the work motions. The results showed that the distance degree of painting work clothes to the avatar body for each part of the human body when performing painting work motions. Moreover, 3D virtual clothing simulations enabled the creation of a male model avatar to run painting work motions together and the painting work clothes developed were found to be suitable for the painting work motions.

• Annals of Clinical Neurophysiology
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• v.14 no.2
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• pp.64-71
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• 2012

Background: It is generally accepted that upper motor neuron (UMN) lesion can alter lower motor neuron (LMN) function by the plasticity of neural circuit. However there have been only few researches regarding the axonal excitability of LMN after UMN injury especially during the acute stage. The aim of this study was to investigate the nerve excitability properties of the LMNs following an acute to subacute supratentorial corticospinal tract lesion. Methods: An automated nerve excitability test (NET) using the threshold tracking technique was utilized to measure multiple excitability indices in median motor axons of 15 stroke patients and 20 controls. Testing of both paretic and non-paretic side was repeated twice, during the acute stage and subacute stage. The protocols calculated the strength-duration time constant from the duration-charge curve, parameters of threshold electrotonus (TE), the current-threshold relationship from sequential sub-threshold current, and the recovery cycle from sequential supra-threshold stimulation. Results: On the paretic side, compared with the control group, significant decline of superexcitablity and increase in the relative refractory period were observed during the subacute stage of stroke. Additionally, despite the absence of statistical significance, a mildly collapsing in ('fanning in') of the TE was found. Conclusions: Our results suggest that supratentorial brain lesions can affect peripheral axonal excitability even during the early stage. The NET pattern probably suggests background membrane depolarization of LMNs. These features could be associated with trans-synaptic regulation of UMNs to LMNs as one of the "neural plasticity" mechanisms in acute brain injury.