• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.109-115
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• 2000

This study was designed to investigate the quality of the simplified water supplies by regional groups in Uijoungbu. For this objective physicochemistric and microbiological experiment were performed. Simplified water in Uijoungbu(Howondong Darakwon, Singokdong Chudong, Songsandong Mangadae, Songsandong Gacbawe, Songsandong Gusungmal, Songsandong Baebul, Ganeung3dong) tested by this study physicochemistric elements suited the test. However, Songsandong Mangadae exceeded the minimum level suggested as $NO_3-N(10mg/{\ell})$. The population of general bacteria were exceeded the minimum level suggested as drinkable water(less than $100CFU/m{\ell}$). Some simplified water in Uijoungbu were proven to be contaminated.

• Tribology and Lubricants
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• v.38 no.6
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• pp.287-290
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• 2022

Compressed-water-type launching devices convert the force from compressed water into force-launching underwater structures, such as torpedos and autonomous underwater vehicles. In particular, the overpressure wave in the launching tube is a critical design factor for the launching device. This paper presents a simplified formula for simulating overpressure waves in the launching tube of a compressed-water-type launching device. Scaled model experiments were performed to obtain actual measurement data of overpressure waves in a launching tube with varying piston speeds to examine the practical applicability of the simplified formula. The main factor of the simplified formula was estimated using an optimization technique. The time history of the overpressure waves was satisfactorily simulated using the estimated factor values and showed consistency with the measurement data. In addition, the trend of change by the piston speed of the estimated factors was reviewed, and the practical applicability was demonstrated. A systematic study of the factors influencing the overpressure waves in launching tubes will be possible using experimental data for more various conditions and the proposed simplified formula.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.1
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• pp.115-127
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• 2015

The aim of this study is to develop a simplified formula for added mass coefficients of a two-dimensional floating body moving vertically in a finite water depth. Floating bodies with various sectional areas may represent simplified structure sections transformed by Lewis form, and can be used for floating body motion analysis using strip theory or another relevant method. Since the added mass of a floating body varies with wave frequency and water depth, a correction factor is developed to take these effects into account. Using a developed two-dimensional numerical wave tank technique, the reference added masses are calculated for various water depths at high frequency, and used them as basis values to formulate the correction factors. To verify the effectiveness of the developed formulas, the predicted heave added mass coefficients for various wetted body sections and wave frequencies are compared with numerical results from the Numerical Wave Tank (NWT) technique.

• Journal of Periodontal and Implant Science
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• v.53 no.1
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• pp.85-95
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• 2023

Purpose: In recent years, guided implant surgery has been widely used for the convenience of patients and surgeons. Further streamlining the surgical procedure would make implant surgery more convenient. Low-speed water-free conditions are often used in guided implant surgery. Therefore, in this study, we attempted to confirm once again whether drilling was safe at a low speed without water. The main purpose of this study was to evaluate whether a simplified drilling protocol that omits some intermediate steps in the drilling process was safe from the viewpoint of heat generation. Methods: D1 density artificial bone blocks were drilled under 50 rpm, 10 N·cm water-free conditions, and the surface temperature was measured using a digital infrared camera. First, drilling was performed with the sequential drilling method, which is the most widely used technique. Second, for each drill diameter, the temperature change was measured while performing simplified drilling with omission of the previous 1, 2, or 3 steps. Results: In sequential drilling, the heat generated during drilling at all diameters was less than the critical temperature of osteonecrosis (47℃) except for the ⌀2 drill. Statistical significance was observed in all groups when comparing sequential and simplified drilling in the ⌀3.2, ⌀3.8, and ⌀4.3 drills (P<0.001). However, in the simplified drilling procedures, the temperature was below the osteonecrosis threshold temperature (47℃) except for the ⌀4.3 drill with the omission of the previous 3 steps (⌀3.0, ⌀3.2, and ⌀3.8). Conclusions: In general, drilling under low-speed, water-free conditions has shown stable results in terms of heat generation. Simplified drilling showed statistically significantly greater heat generation than sequential drilling. However, most of the diameters and omitted steps seem to be clinically acceptable, so it will be useful if an appropriate selection is made according to the patient's clinical condition.

• Journal of Ocean Engineering and Technology
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• v.27 no.1
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• pp.80-84
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• 2013

This study is to develop the simplified formulae for added mass coefficient of a 2-D floating body with a semi-circle section in a finite water depth. The semi-circle floating body may represent a simplified midship section transformed by Lewis form, which can be used for the ship motion analysis by strip theory. Since the added mass coefficient varies with motion frequencies and sea bottom effect, the correction factor representing the effect of water depth and frequencies is developed for accurate prediction of added mass. Using a two-dimensional numerical wave tank (NWT) technique based on the boundary element method (BEM) including sea bottom boundary the reference values of added mass are calculated to develop the correction factor. For verification and effectiveness of the formulae, the predicted added mass coefficients for various frequencies and water depth ratios are compared with the calculated values from NWT technique.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.3-14
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• 2008

ASM No. 2(Activated sludge model No. 2) is very useful model to analyze the wastewater treatment which removes nitrogen and phosphorus. But, it is difficult to apply ASM No. 2 to control of wastewater treatment since it has 17 material divisions and 46 parameters. So the purpose of this study was the simplification of ASM No. 2 and the provement of simplification model. Firstly ASM No. 2 was simplified with 5 material division and three phases(Anaerobic, aerobic, anoxic phases). The simplified model was proved by R-square using track study data. As a result of provement, the values of R-square in ${NH_4}^+$ were 0.9815 in ASM No. 2 and 0.9250 in simplified model and in ${NO_3}^-$ were 0.8679 in ASM No. 2 and 0.7914 in simplified model and in ${PO_4}^{3-}$ are 0.9745 in ASM No. 2 and 0.9187 in the simplified model when the ability to express the material variation was compared by R-square. So, the simplified model has enough ability to express the variation of ${NH_4}^+$, ${NO_3}^-$ and ${PO_4}^{3-}$.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.1
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• pp.27-37
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• 2022

This study established a water supply network based on the operation case of Mandae Reservoir in Yanggu-gun, Gangwon-do, to analyze the efficient distribution and management of agricultural water supplied from the reservoir to irrigation areas using the hydraulic analysis model SWMM. In order to construct a model to analyze the water canal network, network conditions needs to be simplified, and in particular, excessive detail or simplification of the irrigation area can lead to errors in the analysis results. Therefore, the effect of the water canal network model was analyzed by simulating the appropriate simplification process step by step. The results of simplifying the actual block shape of the analysis target area using SWMM showed that there was no significant difference in the results even if 7 lots were simplified to 2. Also, it was found that the construction and analysis of a simplified network model were reliable when the excess quantity was 2% or more compared to the required quantity for each case of analysis of the paddy field.

• Water for future
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• v.21 no.2
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• pp.193-201
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• 1988

A simplified model for higher order scanning curves in the soil water characteristic function is suggested. The conceptual hysteresis models developed by $Mualem_{8,9}$ are simplied for higher order scanning curves. Higher order drying curves are regarded as primary drying curves and the last wetting reversal point is assumed to be on the main wetting curve by moving that point vertically downward. For the higher order wetting curves, it is assumed that these curves can be regarded as primary curves and the last wetting reversal point sits on the imaginary main drying curve which passes through the last wetting reversal point. The water content computed from the simplified model are compared with those obtained from Mualem's original model for second order scanning curves. It is found that absolute differences between the two methods aree relatively small and the simplified model always underestimates for higher order drying curves while it overestimates for higher order wetting curves. Hence, those two tend to compensate each other for repeated drying-wetting processes. The simplified model approximates higher order scanning curves well and reduces computation considerably.

• Wind and Structures
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• v.21 no.3
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• pp.289-309
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• 2015

Vertical profiles of mean and fluctuating wind velocities over water waves were studied, by performing Large-Eddy Simulations (LES) on a fully developed turbulent boundary layer over simplified water waves. The water waves were simplified to two-dimensional, periodic and non-evolving. Different wave steepness defined by $a/{\lambda}$ (a : wave amplitude; ${\lambda}$ : wavelength) and wave age defined by $c/U_b$ (c: phase velocity of the wave; $U_b$ : bulk velocity of the air) were considered, in order to elaborate the characteristics of mean and fluctuating wind profiles. Results shows that, compared to a static wave, a moving wave plays a lesser aerodynamic role as roughness as it moves downstream slower or a little faster than air, and plays more aerodynamic roles when it moves downstream much faster than air or moves in the opposite direction to air. The changes of gradient height, power law index, roughness length and friction velocity with wave age and wave amplitude are presented, which shed light on the wind characteristics over real sea surfaces for wind engineering applications.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.122-130
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• 1998

A simplified heat transfer model for the cooling capability of the AP 600 PCCS is proposed I this paper. As the PCCS domain is covered with very thin and long water film, it is phenomenologically divided into 3 regions; water entrance effect region, asymptotic region, and air entrance effect region. As the length of the asymptotic region is estimated to be over 90% of the whole domain, the phenomena in the asymptotic region is focused. Using the analogy between heat and mass transfer phenomena in a turbulent situation, a new dependent variable combining temperature and vapor mass fraction was defined. The similarity between the PCCs phenomena in the asymptotic region and the buoyant air flow phenomena on a vertical heated plate is derived. Using the similarity, the simplified heat transfer correlations for the interfacial heat fluxes and the ratios of latent heat transfer to sensible heat transfer were established. To verify the accuracy of the correlation, the results of this study were compared with those of other numerical analyses performed for the same configuration and they are well within the range of 15% difference.