• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.1
• /
• pp.11-23
• /
• 2015

In this study the laboratory test for hydraulic conductivity and the seepage analysis with finite element method on measurement section of sea dike embankment were performed for the purpose of estimating the relative density of embankment from the measured pore water pressures, and both results of the test and the analysis were coupled with the method of estimating seepage blocking state with the hydraulic head loss rate in sea dike embankment. The relationship of void ratio vs hydraulic head loss rate was obtained by setting hydraulic conductivity as common ordinate on the relationships between the void ratio and the hydraulic conductivity and between the hydraulic conductivity and the hydraulic head loss rate. The void ratio on the segment between measuring points was calculated from the coupled relationship of the void ratio vs the hydraulic conductivity. The allowable upper and lower limits of hydraulic head loss rate and those of void ratio on the safety were generated from the coupled relationship between the laboratory compaction test and the sedimentation test. Current hydraulic head loss rate and void ratio were evaluated in the allowable range between upper and lower limits.

• Journal of Welding and Joining
• /
• v.7 no.3
• /
• pp.44-54
• /
• 1989

This study was undertaken to evaluate the allowable welding heat input range for high strength steels manufactured by various processes and to compare the weldability of TMCP steel for high heat input welding with that of conventional Ti-added normalized steel. The allowable welding heat input ranges for conventional 50kg/$mm^2$ steel to guarantee D or E grade of ship structural steel were below 150 and 80kJ/cm respectively. Such a limit in welding heat input was closely related with the formation of undesirable microstructures, such as grain boundary ferrite and ferrite side plate in the coarse grain HAZ. In case of 60 and 80kg/$mm^2$ quenched and tempered steels, for securing toughness in weldments over toughness requirements for base metal, each welding heat input had to be restricted below 60 and 40kJ/cm, that was mainly due to coarsened polygonal ferrite in weld metal and lower temperature transformation products in coarse grain HAZ. The TMCP steel could be appropriate as a grade E ship hull steel up to 200kJ/cm, but the Ti-added normalized steel could be applied only below 130kJ/cm under the same rule. This difference was partly owing to whether uniform and fine intragranular ferrite microstructure was well developed in HAZ or not.

• Journal of Advanced Navigation Technology
• /
• v.19 no.2
• /
• pp.147-152
• /
• 2015

The compensation characteristics of WDM channels depending on residual dispersion per spans (RDPS) deviation in optical links with the randomly distributed RDPS for the adaptive configuration are investigated in this paper. Also, the link design rule related with RDPS deviations is proposed, from the viewpoint of the allowable net residual dispersion (NRD). It is confirmed that the effect of compensation for the distorted WDM channels is more increased as RDPS deviation is smaller. Also, it is confirmed that the decrease of the allowable NRD range for the exact eye opening penalty (EOP) is proportional to RDPS deviation. Therefore, the results of this research is expected to be the design reference for the flexible link configuration of long-haul optical transmission links.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.18 no.1
• /
• pp.116-121
• /
• 2019

The LVDT (Linear Variable Displacement Transducer) type sensor used for the existing ship's steering gear is simple on / off that does not perform proportional control operation to the control & unloading device. When the main spool is located at both extremes, It is reflected in the price by using an expensive sensor for import. In this paper, the Hall Effect Sensor is applied to Hydraulic Locking Alarm to analyze classification rules, structure, characteristics and operation principle of valves, and research on localization development in terms of cost reduction. The comparative analysis of the existing prototypes and the cause analysis of the problems were carried out, and the structural analysis showed satisfactory results within the allowable stress range. In addition, it was verified through experiments that the actual operation is realized by applying the actual developed product, and it was confirmed that the load on the maximum value exceeds the allowable maximum load even in the case of the universal tensile test in preparation for the departure of the rod casing.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.48 no.2
• /
• pp.233-253
• /
• 2024

This study analyzed differences between three-dimensional (3D) body scanning and manual measurements, aiming to assess whether 3D scanning can replace traditional anthropometric tools, such as tape measures and calipers. Data from 4,478 participants in the 8th Size Korea Project were analyzed, covering 43 measurement items. Since Given that the 3D and manual measurements were performed on the same subjects in the 8th Size Korea Project, it was possible to determine the correlation more accurately between the two measurement methods more accurately. Using Applying ISO 20685-1(2018) standards, 15 out of the 43 items fell within allowable error limits. When classified into six types, "small circumferences" and "segment lengths" showed averages of 3.35 mm and 3.10 mm, respectively, within acceptable range. "Body heights" and "body depths" slightly exceeded the limit, with averages of 5.28 mm and 6.58 mm. "Body widths" and "large circumferences" surpassed the limit, with means of 16.77 mm and 16.18 mm. The study offers an objective basis to for validate validating 3D measurements' measurements' reliability and accuracy, addressing various industries' needs for information on the human body's dimensions information.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.11
• /
• pp.1023-1029
• /
• 2013

The integration between a gas turbine and an air separation unit (ASU) is important in IGCC plants. The portion of ASU air extracted from the gas turbine and the degree of nitrogen supply from the ASU to the gas turbine side are important operating parameters. Their effect on the gas turbine performance and operability should be considered in a wide ambient temperature range. In this study, appropriate nitrogen dilution rate and turbine inlet temperature that satisfy the two limitations of turbine blade temperature and maximum allowable power output were predicted. The air integration was set at zero. The simulation showed that the power output increases and turbine blade temperature decreases as the nitrogen dilution increases. The maximum allowable power output can be obtained under medium and low ambient temperature ranges. Under a high ambient temperature range, the achievable power is less than the maximum power.

• Journal of the Korean Society of Safety
• /
• v.37 no.1
• /
• pp.12-19
• /
• 2022

Circuit breakers are a crucial factor in ensuring the safety of a Direct Current (DC) grid. One type of DC circuit breaker, the Z-source DC circuit breaker (ZCB), uses a thyristor, which is a type of semiconductor switch. In the event of a fault in the circuit, the ZCB isolates the fault by generating a zero crossing current in the thyristor. The thyristor quickly and actively isolates the fault while generating a zero crossing current, but thyristor switch cannot control turn-off and the allowable current is lower than the current of the mechanical switch. Therefore, it is best to use a mechanical switch with a high allowable current capacity that is capable of on/off control. Due to the slow reaction time of mechanical switches, they may not isolate the fault during the zero crossing current time interval created by the existing circuit. In this case, the zero crossing current time can be increased by using the property that hinders the rapid change in the current of the inductor. This paper will explore whether adding system inductance to increase the zero crossing current time interval is a solution to this problem. The simulation of changing inductor and capacitor (LC) of the circuit is repeated to find an optimal change in the zero crossing current time according to the LC change and provides an inductor and capacitor range optimized for a specific load. The inductor and capacitor range are expected to provide optimization information in the form LC values for future applications of ZCB's using a mechanical switch.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.5
• /
• pp.689-697
• /
• 2012

This paper proposes a new coordinated voltage control scheme between STATCOM (Static Synchronous Compensator) and reactive power compensation devices, such as shunt elements(shunt capacitor and shunt reactor) and ULTC(Under-Load Tap Changer) transformer in a local substation. If STATCOM and reactive power compensators are cooperatively used with well designed control algorithm, the target of the voltage control can be achieved in a suddenly changed power system. Also, keeping reactive power reserve in a STATCOM during steady-state operation is always needed to provide reactive power requirements during emergencies. This paper describes the coordinative voltage control method to keep or control the voltage of power system in an allowable range of steady-state and securing method of momentary reactive power reserve using PSS/E with Python. In the proposed method of this paper, the voltage reference of STATCOM is adjusted to keep the voltage of the most sensitive bus to the change of loads and other reactive power compensators also are settled to supply the reactive power shortage in out range of STATCOM to cope with the change of loads. As the result of simulation, it is possible to keep the load bus voltage in limited range and secure the momentary reactive power reserve in spite of broad load range condition.

• Journal of Power Electronics
• /
• v.10 no.5
• /
• pp.477-484
• /
• 2010

A pulse width modulation-voltage source inverter (PWM-VSI) is used for variable speed permanent magnet synchronous motor (PMSM) drives. The PWM-VSI fed PMSM has two major disadvantages. Firstly, the PWM-VSI DC-link voltage limits the magnitude of the PMSM terminal voltage. As a result, the motor speed is restricted. Secondly, in a low speed range, the PWM-VSI modulation index declines. This is caused by a high DC-link voltage and a low terminal voltage ratio. As a result, the distortion of the voltage command and the stator current are increased. This paper proposes an optimal pulse amplitude modulation (PAM) control which can adjust the inverter DC-link voltage by using a buck-boost DC-DC converter. At a low speed range, the proposed system can reduce the distortion of the voltage command, which improves the stator current waveform. Also, the allowable speed range is extended. In order to verify the proposed method, experimental results are provided to confirm the simulation results.

• Korean Journal of Agricultural Science
• /
• v.50 no.3
• /
• pp.469-484
• /
• 2023

In this study, three types of structures-stepped gabion retaining walls, vertical gabion retaining walls, and parapets-were installed on the dam floor crest to prevent the overflow of deteriorative homogeneous reservoirs. The acceleration response, displacement behavior, and pore water pressure ratio behavior were compared and evaluated using shaking-table model tests. The experimental conditions were set to 0.154 g in consideration of the domestic standard and the seismic acceleration range according to the magnitude of the earthquake, and the input waveform was applied with Pohang, Gongen, and artificial earthquake waves. The acceleration response according to the design ground acceleration increased as the height of the embankment increased, and the observed value were larger in the range of 1.1 to 2.1 times the input acceleration for all structures. The horizontal and vertical displacements exhibited maximum values on the upstream slope, and the embankment was evaluated as stable and included within the allowable range for all waveforms. The settlement ratio considering the similarity law exhibited the least change in the case of the parapet structure. The amplification ratio was 1.1 to 1.5 times in all structures, with the largest observed in the dam crest. The maximum excess pore water pressure ratio was in the range of 0.010 - 0.021, and the liquefaction evaluation standard was within 1.0, which was considered very stable.