• Korean Journal of Remote Sensing
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• v.25 no.6
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• pp.531-546
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• 2009

The main objective of this study is to analyse the polarimetric characteristics of the various terrain targets by ground-based polarimetric SAR system and to confirm the compatible and effective polarimetric analysis method to reveal the polarization properties of different terrain targets by the GB-SAR. The fully polarimetric GB-SAR data with HH, HV, VH, and VV components were focused using the Deramp-FFT (DF) algorithm. The focused GB-SAR images were processed by the H/A/$\alpha$ polarimetric decomposition and the combined H/$\alpha$ or H/A/$\alpha$ and Wishart classification method. The segmented image and distribution graphs in H/$\alpha$ plane using Cloude and Pottier's method showed a reliable result that this quad-polarization GB-SAR data could be useful to classified corresponding scattering mechanism. The H/$\alpha$-Wishart and H/A/$\alpha$-Wishart classification results showed that a natural media and an artificial target were discriminated by the combined classification, in particular, after applying multi-looking and the Lee refined speckle filter.

• Structural Engineering and Mechanics
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• v.35 no.5
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• pp.571-592
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• 2010

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial, bending and shear fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In the first part of this study, energy expressions that construct the constitutive law are equated in the form of total strain energy and the distortion energy dissipated in a fatigue cycle. The resulting equation is further evaluated to acquire the equivalent stress per cycle using energy based methodologies. The equivalent stress expressions are developed both for biaxial and multiaxial fatigue loads and are used to predict the number of cycles to failure based on previously developed prediction criterion. The equivalent stress expressions developed in this study are further used in a new finite element procedure to predict the fatigue life for two and three dimensional structures. In the second part of this study, a new Quadrilateral fatigue finite element is developed through integration of constitutive law into minimum potential energy formulation. This new QUAD-4 element is capable of simulating biaxial fatigue problems. The final output of this finite element analysis both using equivalent stress approach and using the new QUAD-4 fatigue element, is in the form of number of cycles to failure for each element on a scale in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure at each location in gas turbine engine structural components. In order to obtain experimental data for comparison, an Al6061-T6 plate is tested using a previously developed vibration based testing framework. The finite element analysis is performed for Al6061-T6 aluminum and the results are compared with experimental results.

• Physical Therapy Korea
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• v.19 no.2
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• pp.20-28
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• 2012

The lumbar multifidus muscle, which can be separated into deep fascicles (DM) and superficial fascicles (SM), is important for lumbar segmental stability. However, no previous studies have investigated the effect of lumbar stabilization exercises on the thickness of DM and SM. Thus, the purpose of this study was to assess DM thickness after three different lumbar segmental stabilization exercises. In total, 30 healthy male participants were recruited and randomly assigned to one of three exercise groups: hollowing in the quadruped position (H-Quad), contralateral arm and leg lift (CALL), and bilateral arm and leg lift (BALL). Each lumbar segmental stabilization exercise was conducted over 4 weeks. Ultrasonography was used to compare the DM and SM thickness before and after the 4 weeks of exercise. A mixed-model analysis of variance using Scheffe's post-hoc test was used for statistical analysis. The results showed a significant effect for the measurement time (before vs. after 4 weeks of exercise) in the DM (F=31.26, p<.05) and SM (F=4.56, p<.05). At the end of the 4 weeks, the DM thickness had increased significantly in the H-Quad exercise group, and the SM thickness had increased significantly in the CALL and BALL exercise groups. Also in the BALL exercise group, the SM thickness was greater compared with that in the H-Quad exercise group. These findings suggest that the thickness of the DM and SM were increased by different types of lumbar segmental stability exercise after 4 weeks.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.251-255
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• 2007

In this paper, propagation analysis method in using 3D Ray Tracing propagation model in wireless cell planning is proposed. Through 3D Ray Tracing model, we can predict the distribution of propagation loss of the received signal. For correct and a low complex analysis, Quad Tree and Pre-Ordering and Hash Function algorithms are included in 3D Ray Tracing algorithm. And 3D Ray Tracing model is embodied in CellTREK that is developed by KT and used to plan Wibro system analysis. In CellTREK, propagation analysis is performed and that result is represented in 3D viewer. In numerical results, it is showed that the proposed scheme outperforms Modified HATA model when comparing with measurement data.

• The korean journal of orthodontics
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• v.43 no.4
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• pp.186-192
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• 2013

Objective: To analyze the fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro. Methods: Roots of human mandibular central incisors were covered with silicone, mimicking the periodontal ligament, and embedded in polymethylmethacrylate. The specimens (N = 50), with two teeth each, were randomly divided into five groups (n = 10/group) according to the retainer materials: (1) Interlig (E-glass), (2) everStick Ortho (E-glass), (3) DentaPreg Splint (S2-glass), (4) Ribbond (polyethylene), and (5) Quad Cat wire (stainless steel). After the recommended adhesive procedures, the retainers were bonded to the teeth by using flowable composite resin (Tetric Flow). The teeth were subjected to 10,00,000 cyclic loads (8 Hz, 3 - 100 N, $45^{\circ}$ angle, under $37{\pm}3^{\circ}C$ water) at their incisoproximal contact, and debonding forces were measured with a universal testing machine (1 mm/min crosshead speed). Failure sites were examined under a stereomicroscope (${\times}40$ magnification). Data were analyzed by one-way analysis of variance. Results: All the specimens survived the cyclic loading. Their mean debonding forces were not significantly different (p > 0.05). The DentaPreg Splint group (80%) showed the highest incidence of complete adhesive debonding, followed by the Interlig group (60%). The everStick Ortho group (80%) presented predominantly partial adhesive debonding. The Quad Cat wire group (50%) presented overlying composite detachment. Conclusions: Cyclic loading did not cause debonding. The retainers presented similar debonding forces but different failure types. Braided stainless steel wire retainers presented the most repairable failure type.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.12
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• pp.2933-2942
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• 2015

This paper proposes a new method which traces significant element of 2-dimensional natural images and encrypts them by using Fresnelet transform (FRNLT). After analyzing property of the subbands obtained by the FRNLT, we estimated the information for ciphering 2D images. Considering FRNLT levels, energy of subbands, and visual effect, we estimated the optimized point for encryption. By selecting various levels and encrypting region, we can encrypt 2D image with various robustness. Encryption effectiveness was showed by analyzing numerical result, executing time for encryption, area of encrypted region, and visual observation. Therefore encryption for various application can be applied by using the suggested parameters without additional analysis. Identifying the experimental result, in the case of $L_{TH}=4$ and $L_{TH}=4$, an image was not recognized through encrypting only 0.42% among the entire data.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.5
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• pp.312-320
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• 2003

This work describes an 8b 200 MHz 0.18 urn CMOS analog-to-digital converter (ADC) based on a pipelined architecture for flat panel display applications. The proposed ABC employs an improved bootstrapping technique to obtain wider input bandwidth than the sampling tate of 200 MHz. The bootstrapuing technique improves the accuracy of the input sample-and-hold amplifier (SHA) and the fast fourier transform (FFT) analysis of the SHA outputs shows the 7.2 effective number of bits with an input sinusoidal wave frequency of 500 MHz and the sampling clock of 200 MHz at a 1.7 V supply voltage. Merged-capacitor switching (MCS) technique increases the sampling rate of the ADC by reducing the number of capacitors required in conventional ADC's by 50 % and minimizes chip area simultaneously. The simulated ADC in a 0.18 um n-well single-poly quad-metal CMOS technology shows an 8b resolution and a 73 mW power dissipation at a 200 MHz sampling clock and a 1.7 V supply voltage.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.33-39
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• 2021

In this study, there are regional limitations for the fine dust data provided by public data to represent the wide area air quality. It is about a method that can provide detailed data in a specific area beyond location restrictions. The goal of this implementation is to mount the IoT-based fine dust sensor on a quadcopter that can fly autonomously beyond the positional limitations of the current measuring station, which is fixed, and quickly move the fire-generating area and the area of rapid fine dust to make detailed measurements. Through this, the system is designed and implemented to enable the fundamental analysis of the occurrence. We designed a QDMS system and proposed a method to measure detailed changes in fine dust at a specific location through manufacturing and experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.12
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• pp.819-828
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• 2022

Sensitivity of aircraft sizing depending on battery performance was studied for a generic quad tilt rotor type electric vertical takeoff and landing vehicle. The mission requirements proposed by Uber Elevate and NASA were used for initial sizing, and the calculated gross weight is ranged between 5,000lb and 11,000lb for battery specific energy range of 200-400Wh/kg in pack level and continuous discharge rate range of 4-5C. For the assumed gross weight of 7,000lb, the required battery performance was calculated with two different criteria: available power and energy, and the effects of battery specific energy and discharge rate are analyzed. The maximum discharge rate is also recommended considering failure cases such as one battery pack inoperative and one prop rotor inoperative.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.739-746
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• 2007

Recently, models in STL files are widely used in reverse engineering processes, CAD systems and analysis systems. However the models have poor geometric quality and include only triangles, so the models are not suitable for the finite element analysis. This paper presents a general method that generates finite element mesh from STL file models. Given triangular meshes, the method estimates triangles and makes clusters which consist of triangles. The clusters are merged by some geometric indices. After merging clusters, the method applies plane meshing algorithm, based on domain decomposition method, to each cluster and then the result plane mesh is projected into the original triangular set. Because the algorithm uses general methods to generate plane mesh, we can obtain both tri and quad meshes unlike previous researches. Some mechanical part models are used to show the validity of the proposed method.