• Journal of Ocean Engineering and Technology
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• v.6 no.1
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• pp.19-28
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• 1992

The motion of a cylindrical object resting on shallow seabed due to wave forces and soil friction is studied. Given environmental conditions such as wave characteristics and seabed soil properties, the equations of motion are derived and the corresponding reponses of the cylinder in two dimensional plane, i.e., translational and rotational displacements, accelerations, are calculated. The motion is substantially restrained by the penetration of a cylinder into seabed and the parametric study focuses on finding out a minimum penetration depth which makes the cylinder motionless.

• Structural Engineering and Mechanics
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• v.9 no.2
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• pp.169-180
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• 2000

An optimization procedure has been prescribed for the minimum weight design of symmetrical parabolic arches subjected to arbitrary loading. The cross section is assumed to be a symmetrical box section with variable depth and flange areas. The webs are unstiffened and have constant thickness. The proposed sequential, iterative search technique determines the optimum geometrical configuration of the parabolic arch which includes the optimum depth profile and the optimum lengths and areas of the required flange plates corresponding to the prescribed number of curtailments. The study shows that the optimum value of rise to span ratio (h/L) of a parabolic arch is maximum at 0.41 for uniformly distributed loading over the entire span. For any other loading, the optimum value of h/L is less than 0.41.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1923-1929
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• 2009

The design of SPMSM(surface mounted permanent magnet synchronous motor) has been performed to reduce cogging torque and torque ripples. In general, cogging torque and torque ripples are affected by the shapes of teeth width, yoke depth, magnet pole arc, etc. Particularly, the minimum design point of cogging torque and torque ripples are different so that the design of SPMSM should be done to compromise both of them for precision application. In this paper, the design of PMSM for EPS(electric power steering) system is performed to verify the validity, and the design characteristics versus teeth width, yoke depth, and magnet pole arc are investigated in order to find out the minimum point of cogging torque and torque ripples. In addition, skew of PM is applied for cogging torque reduction.

• Computers and Concrete
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• v.14 no.3
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• pp.211-231
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• 2014

Prestressed hollow-core slabs (HCS) are widely used for modern lightweight precast floor structures because they are cost-efficient by reducing materials, and have excellent flexural strength and stiffness by using prestressing tendons, compared to reinforced concrete (RC) floor system. According to the recently revised ACI318-08, the web-shear capacity of HCS members exceeding 315 mm in depth without the minimum shear reinforcement should be reduced by half. It is, however, difficult to provide shear reinforcement in HCS members produced by the extrusion method due to their unique concrete casting methods, and thus, their shear design is significantly affected by the minimum shear reinforcement provision in ACI318-08. In this study, a large number of shear test data on HCS members has been collected and analyzed to examine their web-shear capacity with consideration on the minimum shear reinforcement requirement in ACI318-08. The analysis results indicates that the minimum shear reinforcement requirement for deep HCS members are too severe, and that the web-shear strength equation in ACI318-08 does not provide good estimation of shear strengths for HCS members. Thus, in this paper, a rational web-shear strength equation for HCS members was derived in a simple manner, which provides a consistent margin of safety on shear strength for the HCS members up to 500 mm deep. More shear test data would be required to apply the proposed shear strength equation for the HCS members over 500 mm in depth though.

• Journal of Environmental Science International
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• v.6 no.6
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• pp.595-604
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• 1997

To investigate characteristics of biogeochemical environment of the Korea Deep Ocean Study(KODOSI area in the northeast Pacific Ocean, we preferentially measured Inorganic nutrients and fluorescent organic matters. Typically. the permanent thermocline was well developed at the depth of 200~1000m In the study area. Nitrate. phosphate and silicate were low In the surface mixed layer and Increased with depth. N/P and N/Si showed 15 and 0.2 respectively In the deeper layer. Two fluorophores, biomacromolecule(protein-like) and geomacromolecule (humid-like) , were observed by three dimensional fluorescence excltatlon/ emission spectra matrix. Biomacromolecule(maximum fluorescence at $Ex_{280m}/Em_{330nm}$) ranged from 41.9 to 147.0 TU with its maximum In the surface mixed layer and minimum in deeper water, This is a same trend that has been reported for DOC in the equatorial Pacific. This suggests that biomacromolecule might be labile and converted to refractory humic substance after bacterial degradation In the deeper layer. On the contrary, geomacromolecule(maximum fluorescence at $Ex_{330m}/Em_{430m}$), ranged from 7.6 to 46.5 QSU, showed minimum in the surface nixed layer(euphotic zone) Implying photodegradation and then increased with depth at all stations. In the characteristics of vertical profiles, the relationship between biomacromolecule and geomacromolecule showed negative correlation. Such trend can be attributed to biochemical regeneration or formation of fluorescent materials accompanying oxidation and rennnerallzation of settling organic matter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.976-981
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• 2009

MEMS capacitive gap sensor is developed for measuring abrasion depth of gun barrel rifling. Measuring abrasion depth of gun barrel rifling is very important because it is related with exactness of firing and life of arms. The method using a gap sensor is not to hurt rifling. And it can measure abrasion depth through minimum shooting, because the developed gap sensor can measure from $1{\mu}m{\sim}12{\mu}m$ using Polydimethylsiloxane(PDMS) material and making a stretchable electrode on PDMS. And it's resolution is 1 ${\mu}m$ using capacitive method and MEMS technology.

• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.1
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• pp.1-9
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• 2006

Regardless of the recent observed warmer winters in Korea, more freeze injuries and associated economic losses are reported in fruit industry than ever before. Existing freeze-frost forecasting systems employ only daily minimum temperature for judging the potential damage on dormant flowering buds but cannot accommodate potential biological responses such as short-term acclimation of plants to severe weather episodes as well as annual variation in climate. We introduce 'dormancy depth', in addition to daily minimum temperature, as a complementary criterion for judging the potential damage of freezing temperatures on dormant flowering buds of grape vines. Dormancy depth can be estimated by a phonology model driven by daily maximum and minimum temperature and is expected to make a reasonable proxy for physiological tolerance of buds to low temperature. Dormancy depth at a selected site was estimated for a climatological normal year by this model, and we found a close similarity in time course change pattern between the estimated dormancy depth and the known cold tolerance of fruit trees. Inter-annual and spatial variation in dormancy depth were identified by this method, showing the feasibility of using dormancy depth as a proxy indicator for tolerance to low temperature during the winter season. The model was applied to 10 vineyards which were recently damaged by a cold spell, and a temperature-dormancy depth-freeze injury relationship was formulated into an exponential-saturation model which can be used for judging freeze risk under a given set of temperature and dormancy depth. Based on this model and the expected lowest temperature with a 10-year recurrence interval, a freeze risk probability map was produced for Hwaseong County, Korea. The results seemed to explain why the vineyards in the warmer part of Hwaseong County have been hit by more freeBe damage than those in the cooler part of the county. A dormancy depth-minimum temperature dual engine freeze warning system was designed for vineyards in major production counties in Korea by combining the site-specific dormancy depth and minimum temperature forecasts with the freeze risk model. In this system, daily accumulation of thermal time since last fall leads to the dormancy state (depth) for today. The regional minimum temperature forecast for tomorrow by the Korea Meteorological Administration is converted to the site specific forecast at a 30m resolution. These data are input to the freeze risk model and the percent damage probability is calculated for each grid cell and mapped for the entire county. Similar approaches may be used to develop freeze warning systems for other deciduous fruit trees.

• Journal of Biosystems Engineering
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• v.7 no.1
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• pp.42-52
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• 1982

This study was intended to develop a cost function for the natural air in-bin drying: system which could lead to an optimization of the drying system cost. Based on the cost function developed, a series of simulated drying tests were conducted with 10-year weather data (1970~1979) for 7 different regions by applying an appropriate levels of system factors. System performance factors treated in this study were initial moisture content, airflow rate, bin diameter and grain depth. An optimization procedure to find the least cost system was developed as follows: First, the worst year of the past decade was determined in consideration of the dryiang time and maximum dry matter loss. Second, the minimum airflow rate for a fixed bin diameter and grain depth was determined. Third, the optimum grain depth was found for the minimum airflow rate with different initial moisture contents and bin diameters. The results obtained in this study are summarized as follows: 1. The optimization procedure developed in this study was able to reduce the time and efforts significantly. 2. Optimum values of drying parameters including airflow rate, grain depth, and fan size were determined for different initial moisture contents and bin diameters in each region. The results are shown in Tables 3 to 9. 3. Optimum grain depths decreased as the initial moisture content and airflow rate increased. 4. Drying time for the least cost system should be reduced with higher initial moisture content and lower drying potential to prevent grain spoilage. 5. The fixed cost was 65 to 75 percent of the total system cost and the variable cost was 25 to 35 percent. To reduce the fixed cost it is desirable to use a drying bin 2 or 3 times a year.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.6
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• pp.113-126
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• 1992

Recently the multi-kind, small-amount manufacturing system has been replacing the mass manufacturing system, and domestic machining inustry also is eager to absorb the new technology because of its high productivity and cost reduction. The optimization of the cutting condition has been a vital problem in the machining industry, which would help increase the productivity and raise the international competitiveness. It is intended in this study to investigate the machining costs per unit time which is essential to the analysis of the optimal cutting condition, to computer the cutting speed that lead to the minimum machining costs and the maximum production to suggest the cutting speed range that enables efficient speed cutting, and to review the machining economy in relation to cutting depth and feed. Also considered are the optimal cutting speed and prodution rated in rrelation with feed. It is found that the minimum-cost cutting speed increases and the efficient cutting speed range is reduced as machining cost per unit time increases since the cutting speed for maximum production remains almost constant. The machining cost is also lowered and the production rate increases as the feed increases, and the feed should be selected to satisfy the required surface roughness. The machining cost and production rate are hardly affected by the cutting depth if the cutting speed stays below 100m/min, however, they are subject to change at larger cutting depth and the high-efficient speed range also is restricted. It can be established an adaptive optimal cutting conditions can be established in workshop by the auto-selection progam for optimal operation. It is expected that this method for choosing the optimal cutting conditions might contribute to the improvement of the productivity and reduced the cost. It is highly recommended to prepare the optimal cutting conditionthus obtained for future use in the programing of G-function of CNC machines. If proper programs that automatically select the optimal cutting conditions should be developed, it would be helpful to the works being done in the machine shops and would result in noticeable production raise and cost reduction.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.848-851
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• 1996

Based on the minimum cutting time criteria, the tool path generation algorithm of a pocket machining is developed as a form of a built-in cycle for the WOP(workshop oriented programming) of a CNC controller. Based on the given CAD database and tool information, an optimal cutting depth and geometric properties can be generated, then six different tool paths will be generated internally and automatically. Finally, the G code which commands tool movements is generated for CNC machining.