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ABSTRACT: The arginine-degrading and ornithine-producing enzymes arginase has been used to treat arginine-dependent cancers. This study was carried out to obtain the microbial arginase from Bacillus subtilis, one of major microorganisms found in fermented foods such as Cheonggukjang. The gene encoding arginase was isolated from B. subtilis 168 and cloned into E. coli expression plasmid pET32a. The enzyme activity was detected in the supernatant of the transformed and IPTG induced cell-extract. Arginase was purified for homogeneity from the supernatant by affinity chromatography. The specific activity of the purified arginase was 150 U/mg protein. SDS-PAGE analysis revealed the molecular size to be 49 kDa (Trix·Tag, 6×His·Tag added size). The optimum pH and temperature of the purified enzyme with arginine as the substrate were pH 8.4 and 45°C, respectively. The Km and Vmax values of arginine for the enzyme were 4.6 mM and 133.0 mM/min/mg protein respectively. These findings can contribute in the development of functional fermented foods such as Cheonggukjang with an enhanced level of ornithine and pharmaceutical products by providing the key enzyme in arginine-degradation and ornithine-production.
The Journal of Microbiology 04/2013; 51(2):222-8. · 1.10 Impact Factor
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ABSTRACT: Till now, various types of current-fed converters have been developed, and they exhibit good performance in isolated step-up applications. However, they have a common limitation in that the duty cycle must be larger than 0.5 for a proper operation, which guarantees a conducting path for the boost-inductor current. The limited duty cycle causes an inrush current at start-up and it makes it difficult to regulate the output voltage in a light-load condition. Although various auxiliary circuits have been developed that can be solutions for a duty cycle below 0.5, they increase the size and complexity of the total circuit. To relieve these problems, a new two-transformer current-fed (TTCF) converter, which can be operated along a wide duty cycle range with a simple structure, is proposed in this paper. In the TTCF converter, a magnetizing inductor of the transformer acts as a boost inductor, thus no additional boost inductor is needed. Moreover, only one auxiliary diode is employed for operation with a duty cycle below 0.5. Therefore, the proposed converter can be promising for isolated step-up applications with a simple structure.
IEEE Transactions on Power Electronics 08/2011; · 4.65 Impact Factor
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ABSTRACT: A transformer magnetizing current offset for a phase-shift full-bridge (PSFB) converter is dealt in this paper. A model of this current offset is derived and it is presented as a first order system having a pole at a low frequency when the effects from the parasitic components and the switching transition are considered. A digital offset compensator eliminating this current offset is proposed and designed considering the interference in an output voltage regulation. The performances of the proposed compensator are verified by experiments with a 1.2kW PSFB converter. The saturation of the transformer is prevented by this compensator.
Power Electronics and ECCE Asia (ICPE & ECCE), 2011 IEEE 8th International Conference on; 07/2011
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ABSTRACT: This study was performed to find the optimal volume of local anesthetics needed for a successful ultrasound-guided stellate ganglion block (SGB) to treat head and neck pathology.
Fifteen female and fourteen male sensory-neural hearing loss patients received 4 times SGBs with 0.2% ropivacaine in volumes of 6, 4, 3 and 2 ml at 1 to 3 day intervals. Using the transverse short-axis view of the neck that showed Chassaignac's tubercle at the C6 level, a 25-gauge, and 4 cm needle was inserted via the lateral paracarotid approach with out-of-plane targeting between the prevertebral fascia and the ventral surface of longus colli muscle (subfascial injection). A successful block was confirmed with the onset of ptosis (Horner's syndrome).
There were no significant statistical differences between the presence of Horner's syndrome and the volume of local anesthetics given. However, Horner's syndrome was present in all trials for the 4 ml and 6 ml groups. Six (20.7%) and three out (10.4%) of twenty-nine trials in the 2 ml and 3 ml groups, respectively, failed to elicit Horner's syndrome. The duration of action was significantly different in the 2 ml group compared to that of the 6 ml group, but there was no significant difference between the other groups, including the 4 ml vs. 6 ml groups. The side effects were not different between the groups.
This data suggests that the optimal volume of 0.2% ropivacaine for ultrasound-guided SGB to treat the head and neck pathology in daily practice is 4 ml.
Korean journal of anesthesiology 03/2011; 60(3):179-84.
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ABSTRACT: To obtain a high step-up gain with high efficiency in nonisolated applications, a high step-up technique based on isolated-type converters is introduced in this paper. By stacking the secondary side of an isolated converter in addition to its primary side, a high step-up conversion ratio and a distributed voltage stress can be achieved. Moreover, a careful choice of an isolated converter can provide zero-voltage switching, continuous input current, and reduced reverse recovery on diodes. Based on a conventional voltage-doubler-rectifier boost-integrated half-bridge converter, the derived converter satisfies all these features, which make it suitable for high step-up applications. The operational principle and characteristics of the proposed converter are presented, and verified experimentally with a 135-W, 24-V input, 250-V output prototype converter for a LED driver.
IEEE Transactions on Power Electronics 03/2011; · 4.65 Impact Factor
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ABSTRACT: A zero-voltage switching (ZVS) flyback-boost (FB) converter with a voltage-doubler rectifier (VDR) has been proposed. By combining the common part between a flyback converter and a boost converter as a parallel-input/series-output (PISO) configuration, this proposed circuit can increase a step-up ratio and clamp the surge voltage of switches. The secondary VDR provides a further extended step-up ratio as well as its voltage stress to be clamped. An auxiliary switch instead of a boost diode enables all switches to be turned on under ZVS conditions. The zero-current turn-off of the secondary VDR alleviates its reverse-recovery losses. The operation principles, the theoretical analysis, and the design consideration are investigated. The experimental results from a 250W and 42V-to-400V prototype are shown to verify the proposed scheme.
Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
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ABSTRACT: The voltage-doubler provides an additional step-up gain on top of that of the boost converter, while distributing voltage stresses on devices as well. The interface between the boost converter and the voltage-doubler is accomplished by a transformer and a balancing capacitor, which also constitute a resonant tank. Since this resonant operation shapes the current sinusoidal, a switch turn-off loss and a reverse recovery on diode can be reduced. Therefore, the proposed converter is promising for high step-up applications with high efficiency.
Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
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ABSTRACT: For a nonisolated high step-up converter, the combination of a boost converter with a series output module is investigated in this paper. As a solution to supplement the insufficient step-up ratio and distribute a voltage stress of a classical boost converter, a sepic-integrated boost (SIB) converter, which provides an additional step-up gain with the help of an isolated sepic converter, is proposed. Since the boost converter and the sepic converter share a boost inductor and a switch, its structure is simple. Moreover, the SIB converter needs no current snubber for the diodes, since the transformer leakage inductor alleviates the reverse recovery. The operational principle and characteristics of SIB converter are presented, and verified experimentally with a 200 W, 42 V input, 400 V output prototype converter.
IEEE Transactions on Power Electronics 10/2010; · 4.65 Impact Factor
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ABSTRACT: The output voltage of an adapter for a laptop computer should vary according to the load current in order to supply power to the computer. To satisfy this requirement, an LLC resonant converter with an adaptive link-voltage-variation (ALVV) scheme is proposed in this letter. The proposed ALVV scheme helps the LLC resonant converter to operate at a nearly constant resonant frequency and also allows for the optimal design of the converter. High power density and high efficiency can therefore be obtained. The proposed LLC resonant converter with the ALVV scheme is analyzed theoretically and verified experimentally.
IEEE Transactions on Power Electronics 10/2010; · 4.65 Impact Factor
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ABSTRACT: Glossopharyneal neuralgia (GPN) is generally considered to be a pain disease. However, it can be also be a life-threatening cardiac cause of syncope. Neuralgia in the throat and neck can trigger severe bradycardia up to the point of asystole, which can progress to cardiac syncope with or without seizures. A 65 year-old male patient diagnosed with glossopharyngeal neuralgia complained of severe paroxysmal pain in his right chin and ear followed by bradycardia, aystole and syncope. We report a case successfully treated with a permanent pacemaker and carbamazepine in a patient with GPN who had syncopal attacks preceded by paroxysms of pain.
The Korean journal of pain 09/2010; 23(3):215-8.
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ABSTRACT: Fabry disease is an X-linked lysosomal disease caused by deficiency of α-galactosidase, in which early diagnosis may be missed due to the wide variety of clinical symptoms presenting during disease progression. A 13 year-old boy visited our pain clinic complaining of pricking and burning pain in the toe tips of both feet. Continuous epidural infusion for pain management was performed because of oral analgesics ineffectiveness. The patient underwent α-galactosidase A (GLA) enzyme analysis based on the clinical impression of Fabry disease from pain with a peripheral neuropathic component and history of anhidrosis. He was diagnosed with Fabry disease after confirming mutation of the GLA gene through a screening test of GLA activity. Enzyme replacement therapy was initiated and pain was tolerated with oral analgesics.
The Korean journal of pain 09/2010; 23(3):207-10.
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ABSTRACT: In low-to-medium power applications, an active-clamp forward (ACF) converter is popular for its simple structure and zero-voltage switching (ZVS) capability. However, the high voltage stress on switches can be a burden in high-input-voltage applications. To relieve this, a three-switch ACF (TS-ACF) converter, which employs two main switches for a forward converter and one auxiliary switch for an active-clamp circuit (ACC), is proposed in this paper. With a repositioned ACC, all the switches of TS-ACF converter have relatively low voltage stress compared to the conventional one. In addition, one of the main switches always ensures ZVS during the transformer reset. Consequently, the TS-ACF converter can be promising for high-input-voltage applications with high efficiency.
IEEE Transactions on Power Electronics 05/2010; · 4.65 Impact Factor
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International Journal of Circuit Theory and Applications 04/2010; 39(7):733 - 749. · 1.63 Impact Factor
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ABSTRACT: A classical boost converter has a limited voltage step-up ratio because of its parasitic resistances, which does not make it suitable for high step-up applications. Therefore, to obtain a high step-up capability with high efficiency, non-isolated high step-up technique based on isolated type converters is introduced in this paper. By stacking the secondary sides in addition to the primary side, high step-up conversion ratio can be achieved. Moreover, a careful choice isolated converter provides zero-voltage-switching (ZVS), low voltage stress on devices, and continuous input current. The operational principle and characteristics of proposed converter are presented, and verified experimentally with a 140-W, 24-V<sub>dc</sub> input, 150~250-V<sub>dc</sub> output prototype converter for a LED driver.
Telecommunications Energy Conference, 2009. INTELEC 2009. 31st International; 11/2009
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ABSTRACT: Although LLC series resonant converter has advantages of wide operation range and high efficiency, hold up time requirement makes it difficult to optimal design at normal operating condition, results in increasing transformer size and low efficiency. In this paper, LLC series resonant converter with auxiliary circuit is proposed. Compare with conventional LLC series resonant converter, higher gain at the same frequency can be achieved because the proposed converter has a current boost up capability. Therefore, even if ac line is turned off, switching frequency range of LLC series resonant converter can be reduced. With the auxiliary circuit, LLC series resonant converter can achieve high power density and high efficiency at normal operation condition.
Telecommunications Energy Conference, 2009. INTELEC 2009. 31st International; 11/2009
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ABSTRACT: This paper presents zero-voltage switching (ZVS) dual inductor-fed DC-DC converter integrating a conventional dual inductor-fed boost converter (DIFBC) and a parallel bidirectional boost converter. Most of current-fed type boost topologies including dual inductor schemes have crucial defects such as a high voltage spike on the switches when it comes to turning off, an unattainable soft start-up due to the limited range of duty ratio, and considerable switching losses due to the hard switching. By adding two auxiliary switches and an output capacitor on the conventional DIFBC, the proposed circuit can solve mentioned problems and improve the efficiency with a simple method. The operational principle, theoretical analysis, and comparative features of the proposed converter have been included. Experimental results based on a 42 V input, 400 V/1 A output, and 50 kHz prototype are shown to verify the proposed scheme.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: Generally additional leakage inductance and two clamp diodes are adopted into the conventional phase shift full bridge (PSFB) converter for reducing the voltage stress of secondary rectifier diodes and extending the range of zero voltage switching (ZVS) operation. However, the core and copper loss caused by additional leakage inductor can be high enough to decrease the whole efficiency of DC/DC converter. Therefore, a new ZVS PSFB converter with separated primary winding (SPW) is proposed. The proposed converter makes both the transformer and additional leakage inductor with same ferrite core by separating the primary winding method. Using this method, leakage inductance is controlled by the winding ratio of SPW. Moreover, by using this integrated magnetic component with single core, size and core loss can be greatly reduced and it results in the improvement of efficiency and power density of DC/DC converter. The operational principle and analysis of proposed converter are presented and verified by the 1.2 kW prototype.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: Recently, the LLC series resonant converter (LLC-SRC) is widely used for many applications because it has many advantages over other power converters. However, it is difficult to apply this topology to high current applications because the current ripple stress on the output capacitor becomes severely high. Nevertheless, it is possible to reduce the output current ripple drastically as employing the interleaved technique. However, to ensure output current sharing, multiphase interleaved LLC-SRC causes design difficulty of resonant tanks, which consists of magnetizing inductance (LM), resonant inductance (LR), and resonant capacitance (CR). In this paper, design consideration to ensure output current sharing of multiphase interleaved LLC-SRC is proposed. In order to verify proposed design consideration, the laboratory experiments are executed and discussed with a 480 W prototype.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: The LLC resonant converter employing the center-tap rectifier can suffer from high voltage oscillation across the secondary diodes owing to the transformer secondary leakage inductance. The amplitude of the voltage oscillation is varied according to the operation region, i.e., below resonant region and above resonant region. To reduce the diode voltage stress without snubbers, this paper analyzes the voltage oscillation mechanism and presents the design guideline for small voltage oscillation.
Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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ABSTRACT: The charge equalizer design for a series-connected battery string is very challenging because it needs to satisfy many requirements, such as implementation possibility, equalization speed, equalization efficiency, controller simplicity, size and cost issues, voltage and current stress, and so on. Numerous algorithms and circuits were developed to meet the foregoing demands, and some interesting results have been obtained. However, for a large number of cells, for example, 80 or more batteries, the previous approaches might not easily satisfy the foregoing requirement. To overcome these difficulties, we propose a charge equalizer design method based on a battery modularization technique. In this method, a very long battery string is divided into several modules, and then, an intramodule equalizer and an outer-module equalizer are designed. This battery modularization scheme effectively reduces the number of cells that we consider in an equalizer design procedure; thus, the design of a charge equalizer becomes easier. Furthermore, by applying the previously verified charge equalizers to the intramodule and the outer module, we can make the equalizer design more flexible. Several examples and experimental results are presented to demonstrate the usefulness of the charge equalizer design method.
IEEE Transactions on Vehicular Technology 10/2009; · 1.92 Impact Factor
