• Clinical and Experimental Pediatrics
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• v.55 no.9
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• pp.344-349
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• 2012

Purpose: Short sleep duration is associated with obesity. Urinary 6-sulfatoxymelatonin (6-OHMS), the principal metabolite of melatonin, is closely related with sleep. We evaluated the difference in urinary 6-OHMS levels between obese girls and normal weight girls, and the relationship of urinary 6-OHMS with other hormones regulating body weight and metabolism. Methods: A total of 79 girls (6.3 to 12.4 years) were included in this study, of whom 34 were obese; 15, overweight; and 30, normal-weight. We examined their pubertal status and bone age. Fasting serum levels of total ghrelin, leptin, insulin, and first morning urinary 6-OHMS were measured. Homeostatic model assessment-insulin resistance (HOMA-IR) was calculated from the fasting insulin and glucose levels. Results: There was no significant difference in the creatinine adjusted 6-OHMS levels between the obese girls and the control group. Urinary 6-OHMS did not show any correlations with body mass index (BMI), BMI percentile, total ghrelin, leptin, and HOMA-IR. Negative correlations were found between urinary 6-OHMS levels and chronological and bone ages. Conclusion: Our results suggest that melatonin production is not reduced consistently in obese girls.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.1
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• pp.67-73
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• 2009

The stress-strain behavior and its effects on the crack initiation and growth of ITO film on PET substrate with a sheet resistance of 45 ohms/sq were investigated. Electrical resistance increased gradually at the strain of 0.7% in the elastic to plastic transition region of the stress strain curves. Numerous cracks were observed after 1% strain and the increase of the resistance can be linked to the cracking of ITO thin films. The onset strain for the increase of resistance increased with increasing strain rate, suggesting the crack initiation is dependent on the strain rate. Upon loading, the initial cracks perpendicular to the tensile axis were observed and propagated the whole sample width with increasing strain. The spacing between horizontal cracks is thought to be determined by the fracture strength and the interfacial strength between ITO and PET. The crack density increased with increasing strain. The spacing between horizontal cracks (perpendicular to the stress axis) increased with decreasing strain rate, The increase of crack density with decreasing strain rate can be attributed to the higher fraction of the plastic strain to the total strain at a given total strain. As the strain increased over 5% strain, cracks parallel to the stress axis were developed and increased in number with strain, accompanied by drastic increases of resistance.

• Journal of Korea Multimedia Society
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• v.20 no.9
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• pp.1551-1558
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• 2017

Audio power amplifiers have been designed based on the premise that the impedance of loudspeakers is fixed at nominal 4 ohms or 8 ohms. However, it is known that the impedance varies with frequency and takes on the nominal value at some limited frequencies. The principle of the loudspeaker operation reveals that the sound pressure produced by the loudspeaker is proportional to the current flowing in the voice coil, not the voltage between the two terminals. We take the characteristics of the loudspeaker into account and compare the frequency responses of the loudspeaker in voltage-drive mode and current-drive mode via computer simulations, to conclude that the audio amplifier drive mode should be re-considered in an effort to improve the sound quality.

• Progress in Superconductivity
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• v.4 no.1
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• pp.80-85
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• 2002

In order to disseminate the IEC international standard of RRR measurement of Cu／Nb／-Ti composite superconductors, a measuring system was developed at KRISS. The system consisted of helium reservoir, base plate, thermometer, voltmeter and current source. The helium reservoir and base plate provided a stable temperature of a range from 4.2 K to 300 K and the voltmeter measured several order of $mutextrm{V}$ on specimen for obtaining RRR of the Cu／Nb-Ti composite superconductor. Three specimens of the Cu／Nb-Ti composite superconductors were measured using this system for characterizing their RRR. The resistance-temperature curves ortho specimens showed 10／sup -6／ to 10／sup -5／ Ohms near transition temperature and 10／sup -4／ to 10／sup -3／ Ohms at 293 K. The RRR values of the specimens were 145, 71 and 140, respectively.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.5
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• pp.545-551
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• 2022

We proposed a design method for constant current pyro squib circuit. The current method using N MOSFET for the stability problem has a weakness of the current change, requiring a new design. This paper identified the problem with conventional squib circuit where the current is reduced by 25 % when maximum resistance is 3 ohms. Thus, we proposed a stable constant current driving circuit using P MOSFET and PNP BJT. We confirmed stable constant circuit operation through simulations and measurements of the proposed circuit design where the current did not change until the resistance reached 3 ohms.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.681-686
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• 2010

Two different MFC designs were evaluated in batch mode: single compartment combined membrane-electrodes (SCME) design and twin-compartment brush-type anode electrodes (TBE) design (single chamber with two air cathodes and brush anodes at each side of the reactor). In SCME MFC, carbon anode and cathode electrodes were assembled with a proton exchange membrane (PEM). TBE MFC was consisted of brush-type anode and carbon cloth cathode electrodes without the PEM. A brush-type anode was fabricated with carbon fibers and was placed close to the cathode electrode to reduce the internal resistance. Substrates used in this study were glucose, leachate from cattle manure, or sucrose at different concentrations with phosphate buffer solution (PBS) of 200 mM to increase the conductivity thereby reduce the internal resistance. Hydrogen generating bacteria (HGB) were only inoculated in TBE MFC. The peak power densities ($P_{peak}$) produced from the SCME systems fed with glucose and leachate were 18.8 and $28.7mW/m^2$ at external loads of 1000 ohms, respectively. And the $P_{peak}$ produced from TBE MFC were 40.1 and $18.3mW/m^2$ at sucrose concentration of 5 g/L and external loads of 470 ohms, with a mediator (2-hydroxy-1, 4-naphthoquinone) and without the mediator, respectively. The maximum power density ($P_{max}$) produced from mediator present TBE MFC was $115.3mW/m^2$ at 47 ohms of an external resistor.

• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.5
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• pp.1-8
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• 1976

Microwave GaAs Metal Semiconductor Field effect Transistors (MESFET) with the gate-length of two micrometers are investigated. The scattering parameters of the transistors have been measured from 1GHz to 2GHz by Hp8545 Automatic network analyzer. From the measured data, an equivalent circuit is established which consists of an ntrinsic and. extrinsic transistor elements. In this paper, GaAb MESFET Amplifier is used in conjunction with conventional microstrip techniques to match into a 50 ohms high input/output impedances system. We found that Power gain is less than 8dB and VSWR is less than 1.5 in L-Band.

• Journal of Advanced Navigation Technology
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• v.11 no.2
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• pp.196-202
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• 2007

In this paper, The TE(transverse electric) scattering problems by a resistive strip grating over a grounded dielectric plane with edge boundary condition are analyzed by applying the FGMM(Fourier-Galerkin Moment Method) known as a numerical procedure. For a TE scattering problem, the induced surface current density is expected to the zero value at both edges of the resistive strip, then the induced surface current density on the resistive strip is expanded in a series of the multiplication of Gegenbauer(Ultraspherical) polynomials with the first order and functions of appropriate edge boundary condition. To verify the validity of the proposed method, the numerical results of normalized reflected power for the uniform resistivity R = 100 ohms/square and R = 0 as a conductive strip case show in good agreement with those in the existing papers.

• Journal of the Korean Society of Clothing and Textiles
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• v.45 no.1
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• pp.168-179
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• 2021

This study presents and develops a textile type touch sensor structural design that is easy to implement. First, the design of the touch sensor circuit finds the size of the switch with the easiest finger contact and selects a structure with a long circuit with the lowest resistance value. An experiment is performed on a change in an electrostatic capacitance value that accompanies the distance on the electrode and the magnitude of the electrode area of the structure; however, the structure having the distance on the electrode and the large electrode area shows the best resistance change. The laundry assessment was conducted three times at a time and ten times at a time with an average standard deviation less than one ohm, with little change in resistance. Consequently, there were no problems with durability and performance for laundry. Finally, in the bending evaluation, the difference in resistance can be seen between 1-2 ohms and was developed as a smart wearable in the future; in addition, there was no problem as a difference in resistance can be seen between 1 and 2 ohms.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.761-769
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• 1999

In this paper the effect of aging heat treatment to the Corrosion behavior for the Nimonic 80A superalloy was studied by AC Impedance methods. Tested solution was 3.5% with tempera-ture $25^{\circ}C$ Electro-chemical corrosion test were carried out for the Nimonic 80A super-alloy which solution heat treated at $1080^{\circ}C$ for 8 hours followed by aging heat treated at $650^{\circ}C,\;700^{\circ}C,\;750^{\circ}C\;800^{\circ}C$ and $850^{\circ}C$ with 16hours under vacuum environment. The obtained results were as follows; 1. Base metal and solution-treated materials were exhibited similar corrosion tendency as Ran-dle equivalent cell. The value of passive film resistance was 579 ohms for the base metal and 124,770 ohms for the solutionized metal such a difference was arose by the ${{\gamma}_^'}$ precipitate on the metal surface during heat treatment. 2. The measure value of $R_p$ for heat-treated at $650^{\circ}C,\;700^{\circ}C,\;800^{\circ}C$and $850^{\circ}C$ were 97,943, 93, 111, 26,961, 15,798 and 11,780ohm respectively. Which indicated that the passive film resistance Rp was reduced as aging temperature increased due to the growth of grain size and sensitization at the grain boundary. 3. The similar tendency was exhibited for corrosion behavior of the electro-chemical corrosion polarization method and AC impedance method and confirmed that AC impedance method was useful tool for corrosion research.