• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.113-118
• /
• 2000

Experimental results describing the effects of blowing ratio on film cooling from two rows of holes with opposite orientation angles are presented. The inclination angle was fixed at $35^{\circ}$ and the orientation angles were set to be $45^{\circ}$ for downstream row. and $-45^{\circ}$ for upsream row. The studied blowing ratios were 0.5, 1.0 and 2.0. The boundary layer temperature distributions were measured using thermocouple at two downstream loundary layer temperature distributions were measured using thermocouple at two downstream locations. Detailed adiabatic film cooling effectiveness and heat transfer coefficient distributions were measured with TLC(Thermochromic Liquid Crystal). The adiabatic film cooling effectiveness and heat transfer coefficient distributions are discussed in connection with the injectant behaviors inferred from the boundary layer temperature distributions. Film cooling performance, represented by heat flux was calculated with the adiabatic film cooling effectiveness and heat transfer coefficient data.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.5
• /
• pp.2468-2483
• /
• 2017

The construction of completely random sensing matrices of Compressive Sensing requires a large number of random numbers while that of deterministic sensing operators often needs complex mathematical operations. Thus both of them have difficulty in acquiring large signals efficiently. This paper focuses on the enhancement of the practicability of the structurally random matrices and proposes a semi-deterministic sensing matrix called Partial Kronecker product of Identity and Hadamard (PKIH) matrix. The proposed matrix can be viewed as a sub matrix of a well-structured, sparse, and orthogonal matrix. Only the row index is selected at random and the positions of the entries of each row are determined by a deterministic sequence. Therefore, the PKIH significantly decreases the requirement of random numbers, which has a complex generating algorithm, in matrix construction and further reduces the complexity of sampling. Besides, in order to process large signals, the corresponding fast sampling algorithm is developed, which can be easily parallelized and realized in hardware. Simulation results illustrate that the proposed sensing matrix maintains almost the same performance but with at least 50% less random numbers comparing with the popular sampling matrices. Meanwhile, it saved roughly 15%-35% processing time in comparison to that of the SRM matrices.

• Geotechnical Engineering
• /
• v.10 no.2
• /
• pp.57-68
• /
• 1994

To find out the most efficient arrangement of root piles reinforcing sandy soil under a strip footing, a series of model tests for the patten A of by R.H. Bassett and N.C. Last are carried out. In the model test, the variables adopted are a pile length, longitudinal spacing, and the number of rows of piles. According to the results, the most efficient longitudinal spacing of piles is six times of a pile diameter. When the pile length exceeds five times of footing width, no further increase of reinforcing effect is observed. In the pattern A, piles of second row exhibit the largest reinforcing effect and the fifth row show no significant reinforcing effect on the soil.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.56-59
• /
• 2009

Roll forming process is one of important metal processing technology because the process is simple and economical. These days, roll forming process is tried to be employed in manufacturing the circuit board, barrier ribs and solar cell plate for productivity. However, it is difficult to apply to the forming of micro scale or sub-micro scale pattern. In this study, the roll forming processing for the micro scale is designed and analyzed. In this study, the forming of micro pattern for solar cell plate by incremental roll forming process is analyzed. The solar cell plate may have thousands of patterns, and the analysis of forming considering all the patterns is impossible due to the computational costs. In this study, analyses are carried out for various numbers of patterns and the results are compared. It is shown that the analyses results with four row patterns and twelve row patterns are same. So, it is considered that the analysis can be carried out for only four rows of pattern for the design of incremental roll forming process.

• Journal of Korean Society for Geospatial Information Science
• /
• v.24 no.2
• /
• pp.25-35
• /
• 2016

Since a sophisticated location determination technology (LDT) is necessary for accurate positioning in urban area environments, numerous studies related to the LDT using the RFID (Radio Frequency IDentification) technology have been implemented for real-time positioning and data transferring. However, there are still lots of unsolved questions especially regarding what to use as base stations and what are corresponding results under the intrinsic complexity of alignment and configuration of components used for the RFID positioning. This study proposes the street light fixtures as base stations where the RFID receivers will be embedded for the mobile tracking scheme. As street light fixtures are usually installed at a certain distance interval, they can be used as base stations for the RFID receiver installation. Using the principle of the single row triangle network, the RFID receiver organization is determined based on the experiments such as recognition distance measurement and tag position accuracy estimation at inside and outside of the single row triangle network. The results verify that the mobile tracking scheme which uses RFID-embedded street light fixtures, suggested and configured in this study, is effective for the real-time outdoor positioning.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.1016-1020
• /
• 2017

This study was conducted to develop a test facility that simulates the combustion instability that occurs in a real-scale liquid rocket combustor. A separate engine head with 3 injectors arranged in a row was designed/manufactured and verified through preliminary tests. The flow rate and spray pattern of the head were confirmed by the cold flow test. Next, propellant spray test and combustion test were carried out. A preliminary combustion test was carried out at 10 bar and the combustion chamber pressure was measured to be significantly lower than the target pressure. This is because it was a low pressure test, and it is expected to be resolved in the high pressure test in the future.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.11 no.4
• /
• pp.251-258
• /
• 1986

There is much redundancy in image data such as TV signals and many techniques to redice it have been studied. In this paper, Hadamard transform is studied through computer simulation and experimental model. Each element of hadamard matrix is either +1 or -1, and the row vectors are orthogonal to another. Its hardware implementation is the simplest of the usual orthogonal transforms because addition and sulbraction are necessary to calculate transformed signals, while not only addition but multiplication are necessary in digital Fourier transform, etc. Linclon data (64$ imes$64) are simulated using 8th-order and 16th-order Hadamard transform, and 8th-order is implemented to hardware. Theoretical calculation and experimental result of 8th-order show that 2.0 bits/sample are required for good quality.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.23 no.3
• /
• pp.88-95
• /
• 1981

This study was carried out to investigate the relation between seepage losses and flow section area in earth canals. Totally 77 seepage measurement was gained by ponded method and the tested canals belong to the irrigation area of Farmland Improvement Association in each province, Korea. The results obtained from this study may be used as a reasonable criteria for the estimation of canal seepage losses in the design of irrigation systems. Obtained results are summarized as follows: 1. Average seepage rates in each Soils is 14cm/day in ML, 6. 3cm/day in CL and 24.9 cm/day in SM. 2. Water depth and water surface width in eath canals have little influenced on the seepage rate, while the seepage losses was increased in proportion as the water surface width lengthens. 3. A formula of S=C.An defining a relationship between seepage losses and flow section was derieved as follows. ML:S=O. 35 VA 1.20 (m$^3$/day/m) CL:S=O. 13 VA 0.84 SM:s=O.67VA-1.56 4. The average seepage loss rates per 1km of canal are as followings. Measured Time ML CL SM 0-4 hrs 2.2% 0.6% 4.5% 4-2 4hrs 1.0% 0.15% 2.0% In above table we may obtain the following results. The first row is suitable for the canal having short delivery time of irrigation, while the second row for the canal having long delivery time.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.5
• /
• pp.1023-1031
• /
• 1989

An experimental study is conducted to investigate the turbulent wake flow around tubes in vertical single row tube banks. All measurements are performed at Reynolds number(Re$_{max}$) 4.2*10$_{3}$ - 2.5*10$_{4}$ with varying tube spacings from the wide pitch ratio(H/D=3.07) to the very narrow one(H/D=1.23). Flow patterns are visualized using the smoke-wire method. Mean static pressures, velocity components, and various statistical quantities of turbulence are obtained by the computer on-line technique. In the case of wide tube spacings, the near wakes of tube show similar trends to those of a single tube, and their flow indicats an anisotropic turbulence. However, as the pitch ratio decreases, wide and narrow wakes appear alternately behind adjacent tubes due to the deflected flow. Also, in the case of H/D .leq. 1.54, Karman vortex is not formed at the side of relatively wide wake.e.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.185-191
• /
• 2008

The aerodynamic losses so attributed to the endwall - usually termed secondary flow losses or secondary losses - can be as high as 30$\sim$50% of the total aerodynamic losses in a blade or stator row. Inlet guide vanes, with lower total turning and higher convergence ratios, will have smaller secondary losses, amounting to as much as 20% of total loss for an inlet stator row. These are important part for improving a turbine efficiency. The present study deals with a leading edge chamfer groove on a wing-body to investigate the vortex generation and characteristics of a horseshoe vortex with the installed height, and depth of the groove. The current study is investigated with $FLUENT^{TM}$.