• Journal of Korean Society of Environmental Engineers
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• 제38권5호
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• pp.219-227
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• 2016

As the largest source of food waste is housing, and the food waste properties are good enough to recycle, the proactive approach to conventional food waste disposal is highly regarded. This research is to examine food waste management in the Seoul Metropolitan Area (SMA) and non-SMA and to analyze the public inclination to disseminate zero-food waste system (ZFWS) with fermentation and extinction technology in multifamily housing estates. The self-administered questionnaire survey was conducted and the collected data were statistically analyzed. The main findings are summarized as follows: food waste in multifamily housing estates were retrieved by refuse truck and largely recycled for compost and forage. Also, many local governments were in favor of ZFWS, and unwilling to invest in it due to financial constraint. It's found that logistics of ZFWS is likely to be influenced by important features such as a considerable amount of cost saving, effective energy recovery, and efficient operation/management.

• Journal of the Korean Recycled Construction Resources Institute
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• 제3권1호
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• pp.58-63
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• 2015

Several researches on cement zero concrete using alkali-activators have been conducted to investigate its fundamental material properties such as slump, strength and durability, however, research on the structural behavior of relevant members involving the elastic modulus, stress-strain relationship is essential for the application of this cement zero concrete to structural members. In this paper the shear behavior of reinforced concrete beams using 50 MPa-alkali activated slag concrete was experimentally evaluated. To achieve such a goal, six reinforced concrete beam specimens were fabricated and their shear behaviors were observed. The maximum difference between test results and analysis results in crack shear stress for beam specimens without stirrups is 31%, while that for beam specimens with stirrup is 15%. Furthermore, it is also found that the shear strength of alkali activated slag concrete is by 22~57% greater than the nominal shear strength calculated by design code, implying that shear design equations would provide conservative results on the safety side.

• The Transactions of the Korean Institute of Electrical Engineers A
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• 제48권5호
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• pp.586-592
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• 1999

We investigate the characteristic of 소데 responses of the Manabe standard form which is used recently for design of the controller. We obtain some theorems and these theorems have the properties of the relationship between the roots of the polynomial and the stability indices which are used for the Manabe standard form. The Manabe standard form has the following properties: The sum of the squal to zero, the sum of the reciprocal of the squared roots is greater than zero and the parameter $\tau$ is the negative value of the sum of the reciprocal of the roots. We compare the step responses of the Manabe standard form with those of the ITAE form, the dead beat response and Bessel forms. We choose the 6th order closed loop polynomial and keep the same settling time for the four forms. Under these conditions we find that the Manabe standard form have faster 90% rising time than the Bessel and dead beat response. We see that the ITAE, bessel and dead beat responses have some overshoot, whereas the Manabe standard form has none. We also compare the Manabe form with the other three forms for the controller design using the pole assignment technique. If the open loop transfer function is a type-1 system (transfer functions having one integrator), then, for the closed loop system associated with the open loop transfer function, the steady state error of the unit ramp input is obtained in terms of the parameter $\tau$ of the Manabe standard form.

• Journal of the Korean Society of Radiology
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• 제15권3호
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• pp.345-353
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• 2021

Digital radiography imaging systems can also help diagnose lesions in patients, but if x-rays that enter the human body cause scatter x-ray due to interaction with substances, they affect the signal and noise characteristics of digital x-ray images. To regard the human body as polymethyl methacrylate (PMMA) and observe the properties of scattered x-ray generated from PMMA on x-ray images, we analyze signal and noise in the spatial domain as well as noise-power spectrum (NPS), and detective quantum efficiency (DQE) at zero frequency. As PMMA thickness increased, signals decreased, the noise increased, and NPS degradation was identified in overall spatial frequencies. Based on these characteristics, zero-frequency performance was also shown to be degraded. Comparative analysis with Monte-carlo simulations will need to be made to analyze the zero-frequency performance by scattered x-ray of indirect conversion-type x-ray detectors more quantitatively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제14권2호
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• pp.163-168
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• 2001

This dissertation describes the development of a sensor for measuring microscopic displacement where we use CoFeSiB amorphous alloy magnetic ribbon having near zero magnetostrictive properties. For the development of the sensor, we first fabricate amorphous alloy magnetic ribbon, and then investigate its physical and magnetic properties. Finally, its possibility of practical application as a displacement sensor is discussed. The experimental samples were made of near zero magnetostrictive (Co$\_$0.94/Fe$\_$0.06/)$\_$9/Si$_2$B$\_$19/ alloy which were fabricated by a rapid liquid quenching method. As a results, we got amorphous alloy magnetic ribbons of 12㎛ in thickness, 10 mm in length, and 2.5 m in width. It was found that the crystallization temperature and the Curie temperature are around 451$\^{C}$ and around 441$\^{C}$ respectively. We couldn't observe any noticeable change of the impedance frequency of 10MHz, but observed the impedance change of 3.76 %/Oe at 100 MHz. The inductance was nearly stable over the frequency range of 1∼10 MHz, In addition, it was observed that the variation of the inductance and the impedance were linear within the displacement ranges of 20∼60㎛. As the results of the experiments, it is suggested that the displacement sensor which is fabricated by using amorphous alloy magnetic ribbon of (Co$\_$0.04/Fe$\_$0.06/)$\_$79/Si$_2$B$\_$19/ compound, can be used as a sensor to detect microscopic displacement.

• Proceedings of the KSME Conference
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• 대한기계학회 2008년도 추계학술대회A
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• pp.49-55
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• 2008

Strip bending test has been frequently utilized to measure the mechanical properties of freestanding thin films in substitute for the micro-tensile test. However, in spite of its simplicity and reliability, strip bending test has a few problems, for example, the measurement of strain and the calculation of stress at zero strain. In this study, these problems are precisely reviewed and proved. Upon this review, strip bending tester has been developed, which uses the confocal laser displacement meter to measure the deformed configuration of the specimen and the possibility and limitation of this testing system is carefully investigated including the estimation of uncertainty of the measurement of strain. Finally, to prevent errors and to improve the accuracy of this testing system, the shape of the specimen has been carefully studied and is proposed.

• Honam Mathematical Journal
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• 제44권2호
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• pp.259-270
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• 2022

This paper is devoted to the geometry of vector fields and timelike flows in terms of anholonomic coordinates in three dimensional Lorentzian space. We discuss eight parameters which are related by three partial differential equations. Then, it is seen that the curl of tangent vector field does not include any component in the direction of principal normal vector field. This implies the existence of a surface which contains both s - lines and b - lines. Moreover, we examine a normal congruence of timelike surfaces containing the s - lines and b - lines. Considering the compatibility conditions, we obtain the Gauss-Mainardi-Codazzi equations for this normal congruence of timelike surfaces in the case of the abnormality of normal vector field is zero. Intrinsic geometric properties of these normal congruence of timelike surfaces are obtained. We have dealt with important results on these geometric properties.

• Journal of the Mineralogical Society of Korea
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• 제30권4호
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• pp.173-178
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• 2017

In this study, the effect of sintering temperature and zero valent iron (ZVI) content on the physical properties of functional ceramic filter(alumina based materials) such as strength and porosity were investigated. The fabrication process of the functional ceramic filter were performed under various sintering temperature ($1150^{\circ}C$, $1250^{\circ}C$) and ZVI content (10, 20, 30, 50%) conditions. With increasing the sintering temperature and ZVI content, strength was increased but porosity was decreased. The physical properties for functional ceramic filter showed that the strength and porosity were obtained under ZVI content (50%) and sintering temperature ($1250^{\circ}C$) of 99.01 MPa and 34.5%, respectively.

• Journal of Mechanical Science and Technology
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• 제20권7호
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• pp.950-960
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• 2006

An output time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via a digital computer. A new method for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed in this paper. This method is applied to the sampled-data representation of a nonlinear system with a constant output time-delay. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. In addition, 'hybrid' discretization schemes resulting from a combination of the 'scaling and squaring' technique with the Taylor method are also proposed, especially under conditions of very low sampling rates. A performance of the proposed method is evaluated using two nonlinear systems with time-delay output.

• Polymer(Korea)
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• 제24권5호
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• pp.728-735
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• 2000

Fentanyl-loaded biodegradable poly(L-lactide-co-glycolide) (75 : 25 by mole ratio of lactide to glycolide, PLGA) microspheres (MSs) were prepared to study the possibility for long-acting local anesthesia. We developed the fentanyl base (FB, slightly water-soluble)-loaded PLGA MSs by means of conventional O/W solvent evaporation method. The size of MSs was in the range of 10~150 ${\mu}{\textrm}{m}$. The morphology of MSs was characterized by SEM, and the in vitro release amounts of FB were analyzed by HPLC. The lowest porous cross-sectional morphology and the highest encapsulation efficiency were obtained by using gelatin as an emulsifier. The influences of several preparation parameters, such as emulsifier types, molecular weights and concentrations of PLGA, and initial drug loading amount, etc., have been observed in the release patterns of FB. The release of FB in vitro was more prolonged over 25 days, with close to zero-order pattern by controlling the preparation parameters. We also investigated the physicochemical properties of FB-loaded PLGA MSs by X-ray diffraction and differential scanning calorimeter.