Earticle

The structure of MMSE receiver front-ended by CMA(Constant Modulus Array) array working in CDMA forward link which is applicable to LEO spread spectrum satellite communication system is proposed. By using the despreaded pilot signal of forward link as a reference signal, the CMA array can capture multi-path signals securely even in severely faded LEO satellite channel. The remaining MAI (Multiple Access Interference) is cancelled by the cascaded MMSE receiver. Besides theoretical development, through relevant computer simulation, it is proved that the proposed system shows much better BER performance than any other possible candidate systems. As a spatio-temporal receiver mounted on a mobile vehicle, the proposed system also reduces implemental cost and complexity by adopting the simplest algorithm for its spatial and temporal domain processing.

Background: Coating a culture plate with molecules that aid in cell adhesion is a technique widely used to produce animal cell cultures. Extracellular matrix (ECM) is known for its efficiency in promoting adhesion, survival, and proliferation of adherent cells. Gelatin, a cost-effective type of ECM, is widely used in animal cell cultures including feeder-free embryonic stem (ES) cells. However, the optimal concentration of gelatin is a point of debate among researchers, with no studies having established the optimal gelatin concentration. Methods: In this study, we coated plastic plates with gelatin in a concentrationdependent manner and assessed Young’s modulus using atomic force microscopy (AFM) to investigate the microstructure of the surface of each plastic plate. The adhesion, proliferation, and differentiation of the ESCs were compared and analyzed revealing differences in surface microstructure dependent on coating concentration. Results: According to AFM analysis, there was a clear difference in the microstructure of the surface according to the presence or absence of the gelatin coating, and it was confirmed that there was no difference at a concentration of 0.5% or more. ES cell also confirmed the difference in cell adhesion, proliferation, and differentiation according to the presence or absence of gelatin coating, and also it showed no difference over the concentration of 0.5%. Conclusions: The optimum gelatin-coating for the maintenance and differentiation of ES cells is 0.5%, and the gelatin concentration-mediated microenvironment and ES cell signaling are closely correlated.

In this study, the pre-stress characteristics of magnetic rheological rubber, an intelligent material widely applied to mechanical systems, are measured. Intelligent materials are substances that change their properties in response to external inputs and are extensively used in mechanical systems. Magnetic rheological rubber is a representative intelligent material that can exhibit variable characteristics depending on the conditions. When measuring the physical properties of magnetic rheological rubber, it is placed in a magnetic field application device, where a magnetic field is applied, and the material is subjected to pre-stress. Similarly, when manufacturing intelligent mechanical systems using magnetic rheological rubber, pre-stress is induced by components used to apply the magnetic field. Generally, when a material is subjected to pre-stress, its properties change. Consequently, the performance of magnetic rheological rubber under pre-stress also varies. If the characteristics of the material under pre-stress change, the expected performance during design may deviate, leading to differences in the mechanical system's performance from the intended design. This variability makes it challenging to design mechanical systems based on intelligent materials, highlighting the importance of experimentally investigating their characteristics. Therefore, this study measures and identifies the pre-stress characteristics of magnetic rheological rubber under pre-stress. These findings can be applied to improve the measurement methods and design approaches for magnetic rheological rubber in pre-stressed conditions.

본 연구는 유방 팬텀을 이용하여 초음파 스캔 파라미터 변화가 전단파 탄성초음파(SWE) 정량값의 변동성 및 재현성에 미치는 영향을 평가하였다. 유방 팬텀 내 정상조직, 양성 및 악성 모사 타겟을 대상으로 탄성계수(kPa)와 전단파 전파속도(m/s)를 5회씩 반복 측정하였으며, 변동계수(CV%)와 측정 신뢰도 지수(RMI)를 산출하고 One-way ANOVA 분석을 통해 통계적 유의성을 검증하였다. 연구 결과, 모든 파라미터 조건에서 정상, 양성, 악성모사 타겟 순으로 경직도가 높게 나타났다. 파라미터별로 살펴보면, Gain 변화는 악성 모사 타겟에서만 유의한 변동성을 보였고(p=0.004), DR 변화에 따른 정량값 변동은 미미했으나 110 dB에서 악성 모사 타겟의 RMI가 0.804로 저하되었다. Frequency 변화는 양성 모사 타겟에 가장 큰 영향을 미쳤으며(p<0.001), 저주파에서 고주파로 전환 시 탄성계수가 8.81% 상승하였다. Harmonic On 조건에서는 악성 모사 타겟의 탄성계수가 유의하게 상승했으나(p=0.009), RMI는 0.76으로 크게 저하되었다. 결론적으로 유방 SWE 검사 시 정확하고 재현성 있는 정량값을 얻기 위해서는 Gain과 Frequency의 표준화가 필수적이며, 특히 악성 병변 평가 시에는 HI 기능을 Off로 설정할 것이 권장된다.

This study evaluated how ultrasound scanning parameter variations affect the variability and reproducibility of quantitative values in shear wave elastography(SWE) using a breast phantom. Elasticity modulus(kPa) and shear wave velocity(m/s) were measured five times each for normal tissue, benign-mimicking, and malignant-mimicking targets. The coefficient of variation(CV%) and reliability measurement index(RMI) were calculated, and statistical significance was verified by one-way ANOVA. Across all parameter conditions, stiffness increased in the order of normal, benign, and malignant targets. Gain produced significant variability only in malignant targets(p=0.004). Dynamic Range(DR) caused minimal changes, although the malignant RMI decreased to 0.804 at 110 dB. Frequency most affected benign targets (p<0.001), with elasticity rising 8.81% from low to high frequency. With Harmonic Imaging(HI) on, malignant elasticity increased significantly(p=0.009), but RMI dropped to 0.76. Standardizing Gain and Frequency is essential for accurate, reproducible breast SWE, and turning HI off is recommended when evaluating malignant lesions.

This study compares the shear behavior of anisotropic magnetorheological elastomers (MREs) using natural rubber (NR) and silicone rubber (Si) as matrices. The effects of magnetic flux density and compressive pre-stress on the shear modulus were experimentally investigated. Results showed that silicone-based MREs exhibited a 10–20% higher magnetorheological effect than NR-based ones due to stronger particle–matrix bonding and stable chain alignment under magnetic fields. In contrast, NR-based MREs showed greater stiffness variation under compressive stress, attributed to strain-hardening and volumetric constraint effects. These findings indicate that matrix selection significantly governs the magneto-mechanical response: silicone MREs are suitable for precision control and sensing, while NR MREs perform better in high-stress damping systems. This study provides fundamental insight for tailoring MREs according to design requirements.

Demolition waste generation has exceedingly increased in the world, including korea. It is estimated the approximately 115 thousand tons of waste concrete are occurred in 2009 in this country. And it is estimated that the waste concrete will be more generated more each year than those of today. Therefore, it is necessary to use waste concrete for aggregate of concrete. Many studies have been conducted to reuse of recycled aggregate for construction materials. To make use of recycled aggregate, the elastic modulus of recycled aggregate concrete must bo assured. The purpose of this study is to predict elastic modulus of recycled aggregate concrete using neural network which was applied to predict properties of engineering problems. New learning algorithms for the prediction on the elastic modulus of recycled aggregate concrete is proposed focusing on input layer components and a normalization method for input data and their validity is examined through elastic modulus data of recycled aggregate concrete. In artificial neural network algorithm, the main input data to be trained are the water content, fine and coarse aggregate ratios, curing temperature of recycled aggregate concrete, water/cement ratios and etc. Through this study, it was confirmed that artificial neural network successfully predict the elastic modulus of recycled aggregate concrete.

This study compares the shear behavior of anisotropic magnetorheological elastomers (MREs) using natural rubber (NR) and silicone rubber (Si) as matrices. The effects of magnetic flux density and compressive pre-stress on the shear modulus were experimentally investigated. Results showed that silicone-based MREs exhibited a 10–20% higher magnetorheological effect than NR-based ones due to stronger particle–matrix bonding and stable chain alignment under magnetic fields. In contrast, NR-based MREs showed greater stiffness variation under compressive stress, attributed to strain-hardening and volumetric constraint effects. These findings indicate that matrix selection significantly governs the magneto-mechanical response: silicone MREs are suitable for precision control and sensing, while NR MREs perform better in high-stress damping systems. This study provides fundamental insight for tailoring MREs according to design requirements.

Purpose: This study is to compare the flexural strength and modulus by inserting a mesh and stick type fiberglass reinforcement into resin specimens. Methods: Wax specimens (length 64 mm, width 39 mm, thickness 5 mm) are prepared according to ISO 20795-1:2013. Mesh type and stick type glass fiber reinforcements were prepared. The prepared wax specimens were used plaster and flask for investment. The flask was separated and the wax was removed. The heat curing resin was injected into the flask, and then a mesh type and stick type fiberglass reinforcement were inserted. The prepared resin specimen was cut into three equal parts (length 64 mm, width 10 mm, thickness 3.3 mm). The mesh type glass fiber reinforcement (MT group) and the stick type glass fiber reinforcement (ST group) were classified into two groups. The prepared specimen was measured using a universal testing machine (UTM). The data were analyzed by Mann-Whitney U test, and the significance level was set to 0.05. Results: In the flexural strength, the ST group was higher than the MT group, and there was a significant difference between the two groups (p<0.05). In the flexural modulus, the ST group was higher than the MT group, and there was a significant difference between the two groups (p<0.05). Conclusion: The stick-type glass fiber increased the flexural strength than the mesh-type glass fiber reinforcement.

The demand for high-stength concrete is increasing worldwide, and the elastic modulus plays a very important role as a material variable in structual calculation considering the safety and usability of buildings, The elastic modulus estimation equation is presented independently by each country and association, and thus estimated value also shows a big difference. In this study, five types of high-stength concrete were produced, and the error with the previously suggested estimation equation was evaluated using the measured values. The compressive strength ranged from about 72 to 128Mpa, and the elastic modulus was 41 to 50 GPa. As a result, the CEB-FIP estimation equation showed the smallest error from the measured value of this study, so it was foud that the reliability in prediction the elastic modulus was the highest. The elastic modulus estimation equation suggested by the domestic regulation KDS estimates the elastic modulus lower than the measured value, which is thought to lead to overdesign, and it is thought that improvement is needed to further match the measured value even in the high-strength area.

This study investigated the influence of alloying elements on the elastic modulus variation of titanium alloys and conducted theoretical density calculations, yielding the following conclusions. In Ti-M (M=Zr, Ag, Au, and Cu) alloys, the Md value ranges from 2.89325 to 11.1530, and the Bo value ranges from 2.30180 to 3.22978. Ti-Zr alloys are most suitable as optimal dental implant materials in terms of electronic structural stability and strength. Ti–Au and Ti–Ag primarily contribute to biocompatibility, corrosion resistance, and antibacterial performance, while offering less benefit for mechanical strengthening. Ti-Cu, while having low structural stability, exhibits excellent antibacterial functionality and is therefore worthy of consideration as a supplementary alloying element. The physical properties of ‑titanium–based Ti–M binary alloys have been examined, and future research will focus on extending the study to ternary and quaternary titanium alloy systems.

In contemporary society, vibration and noise in the road nearby buildings have become social problems as vehicles operation has increased. Especially, in the case of the building used to art performance, available suitability of the building is tested by the indoor noise class. Therefore, the purpose of this paper is the measurement of the structure-borne noise of Seoul Art Center nearby Umyeonsan tunnel and analyzing the effects of countermeasure to it. To measure the effects of countermeasure, not only structure-borne noise is measured, but also the vibration is measured, before and after the construction of pavement using pad and porous asphalt. Consequently, the sound pressure level in art center 1st floor is reduced after mat pavement method, structure-borne noise that was high in 25Hz wide-band before pavement decreased regardless of experimental vehicle's velocity. Using porous asphalt pavement the noise was reduced about 3 dB(A).

연구목적: 본 연구에서는 탄소성해석과 수치해석의 차이점 분석과 해석 결과치의 유사한 경향을 도출 하기 위한 설계지반정수 재산정 방법의 연구를 수행하였다. 연구방법: 얕은굴착과 깊은굴착에 따라 벽 체변위가 같아지는 시점에서의 지반반력계수와 지반변형계수의 관계식을 유도하였다. 연구결과: 계측 결과를 바탕으로 역해석을 진행하여 현장지반에 맞는 지반물성을 재산정하고 도출된 식과 문헌식을 이용하여 벽체변위에 대한 비교·검증한 결과 제안식이 가장 유사한 값을 나타내고 있었다. 결론: 제안 식을 이용하면 설계시 실제와 가장 비슷한 지반물성치를 유추할 수 있어 실무에 도움이 될 것이다.

Purpose: In this study, an analysis of the differences between the elastoplastic analysis and the numerical analysis and a study of the design ground constant recalculation method to derive similar trends in the analysis results were conducted. Method: The relational expression between the ground reaction force coefficient and the ground deformation coefficient at the time when the wall displacement becomes the same according to shallow excavation and deep excavation was derived. Result: Based on the measurement results, reverse analysis was performed to re-calculate the ground properties suitable for the site ground, and as a result of comparing and verifying the wall displacement using the derived formula and the literature formula, the proposed formula showed the most similar value. Conclusion: If the proposed formula is used, it will be helpful in practice because it is possible to infer the most similar ground properties to the actual at the time of design.v

연구목적: 본 연구에서는 서울 ․ 경기지역의 화강암을 대상으로 시추조사 시 채취된 암석 시료에서 측정된 물리적 특성 중 탄성파속도와 탄성계수로부터 암석의 일축압축강도와의 상관성을 분석하여 암석의 일축압축강도를 추정하는 것을 목 적으로 한다. 연구방법: 119개의 화강암 시추 코아 시료를 대상으로 탄성파 속도와 탄성계수 그리고 일축압축강도와의 상관관계를 도출하 기 위하여 실내 암석 실험을 실시하였다. 연구결과: 화강암에 대하여 탄성파속도와 일축압축강도 그리고 탄성계수와의 상호 관계를 단순회 귀와 다중회귀로 분석한 결과는 전반적으로 관계식에 나타난 것처럼 신뢰도가 낮음을 확인하였다. 이는 화강암의 구성 입자가 균질하지 못 하여 탄성파속도와 탄성계수를 이용한 압축강도 추정에 대한 활용성이 낮은 원인으로 사료된다. 결론: 본 연구에서 암석의 탄성파속도와 탄 성계수로부터 일축압축강도를 추정하기 위한 상관관계를 분석하기 위하여 단순회귀분석과 다중회귀분석 방법을 이용하였다. 단순회귀분 석은 결정계수(R2)가 0.61~0.67 이었으며 , 다중회귀분석은 0.71로 나타났다. 따라서 다중회귀분석을 이용하여 암석의 일축압축강도를 추 정할 때 다소 신뢰성이 높아질 수 있다. 또한, 향후 탄성파 속도와 탄성계수를 이용한 암석의 일축압축강도를 추정할 때 다양한 통계분석 기 법(회귀분석, 인공신경망, 빅데이터 분석 등)을 활용하면 보다 신뢰성이 높은 결과를 얻을 수 있을 것으로 본다.

Purpose: The purpose of this study is to attain the correlation analysis and thereby to deduce the uniaxial compressive strength of rock specimens through the elastic wave velocity and the elastic modulus among the physical characteristics measured from the rock specimens collected during drilling investigations in Seoul and Gyeonggi region. Method: Experiments were conducted in the laboratory with 119 granite specimens in order to derive the correlation between the compressive strength of the rocks and elastic wave velocity and elastic modulus. Results: In the case of granite, the results of the analysis of the interaction between the compressive strength of a rock and the elastic wave velocity and elastic modulus were found to be less reliable in the relation equation as a whole. And it is believed that the estimation of the compressive strength by the elastic wave velocity and elastic modulus is less used because of the composition of non-homogeneous particles of granite. Conclusion: In this study, the analysis of correlation between the compressive strength of a rock and the elastic wave velocity and elastic modulus was performed with simple regression analysis and multiple regression analysis. The coefficient determination (R2) of simple regression analysis was shown between 0.61 and 0.67. Multiple regression analysis was 0.71. Thus, using multiple regression analysis when estimating compressive strength can increase the reliability of the correlation. Also, in the future, a variety of statistical analysis techniques such as recovery analysis, and artificial neural network analysis, and big data analysis can lead to more reliable results when estimating the compressive sterength of a rock based on the elastic wave velocity and elastic modulus.

Nanoindentation test is a useful analytical technique that can analyze the local properties of polymer composite materials or the surface properties of polymer thin films that cannot be measured by traditional mechanical property measurement methods such as tensile testers or Vickers hardness tests. The measurement principle of the nanoindentation test is to apply a load to the surface of the material to be measured using an indenter of a certain geometric shape, and to continuously measure the load and indentation depth that appear during the removal process, and to interpret the indentation-load curve obtained to measure the mechanical properties of the material. We will use Helmut Fisher's nanoindentator, the most representative testing machine for nanoindentation testing, to analyze the mechanical properties of polymer thin films coated on wafer glass. In addition, we will measure the mechanical properties of samples made under three process conditions from the analysis results, compare the mechanical properties of the three process conditions, and derive the optimal process conditions by analyzing them.