• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.987-990
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• 2007

The accuracy of sound strength (G) measurement method in ISO 3382 has been questioned. One of the main reason is the difficulty in measuring a reference sound level in an anechoic chamber with the same set-up which was applied for the actual hall measurements. In the present paper, an in-situ measurement method for G was proposed by investigating the present G measurement method shown in ISO 3382. In addition, the sound radiation characteristics of typical omnidirectional loudspeakers were investigated and Phi (O) of auto correlation function (ACF) parameters was also calculated from an actual music excerpt to characterize the sound energy distribution in concert halls.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
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• pp.114-119
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• 1992

The main disadvantages of destructive testing methods are the delay in obtaining test results, the relatively high cost of testing, and the lack of reproducibility in the test results. As a result, nondestructive testing methods are generally used. There are three objectives in this paper. The first is to determine the equations of the compressive strength of concrete estimated by Schmidt hammer technique, ultrasonic pulse velocity method and combined method respectively in laboratory. The second is to determine the correction factors according to the concrete age which affects most in evaluating the compressive strength of in-situ concrete. The third is to examine the applicability of the equations to evaluation of the compressive strength of in-situ concrete structures.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 추계 학술논문 발표대회
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• pp.71-72
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• 2014

Green Frame is a building frame system to construct a column-beam structure using composite precast concrete members. To reduce the cost of producing precast concrete, in-situ production of members is required. However, when the structural members are produced on site, it needs a large space for production. So, "Just-In-Time" production method should be adopted. For Just-In-Time to be realized, the early strength of members should be ensured for them to be transported. Thus, steam curing to secure the early strength is applied in Green Frame. Yet, a large-scale steam curing system is not possible for in-situ production of precast concrete. A smaller steam curing system is needed. In this regard, the study is aimed to develop a new steam curing method applicable to the in-situ production of precast concrete.

• Membrane and Water Treatment
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• 제6권3호
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• pp.205-224
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• 2015

A novel hydrophilic poly (vinylidene fluoride)/poly (p-phenylene terephthalamide) (PVDF/PPTA) blend membrane was prepared by in situ polycondensation of p-phenylene diamine (PPD) and terephthaloyl chloride (TPC) in PVDF solution with subsequent nonsolvent induced phase separation (NIPS) process. For comparison, conventional solution blend membrane was prepared directly by adding PVDF powder into PPTA polycondensation solution. Blend membranes were characterized by means of viscometry, X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM). The effects of different blending methods on membrane performance including water contact angle (WCA), mechanical strength, anti-fouling and anti-compression properties were investigated and compared. Stronger interactions between PVDF and PPTA in in situ blend membranes were verified by viscosity and XPS analysis. The incorporation of PPTA accelerated the demixing rate and caused the formation of a more porous structure in blend membranes. In situ blend membranes exhibited better hydrophilicity and higher tensile strength. The optimal values of WCA and tensile strength were $65^{\circ}$ and 34.1 MPa, which were reduced by 26.1% and increased by 26.3% compared with pure PVDF membrane. Additionally, antifouling properties of in situ blend membranes were greatly improved than pure PVDF membrane with an increasing of flux recovery ratio by 25%. Excellent anti-compression properties were obtained in in situ blend membranes with a stable pore morphology. The correlations among membrane formation mechanism, structure and performance were also discussed.

• 대한금속재료학회지
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• 제48권7호
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• pp.683-689
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• 2010

In this study, FeAl based intermetallic matrix composites reinforced with in-situ synthesized TiC particles were fabricated by an in-situ liquid mixing process. The microstructures, mechanical properties and fracture behaviors of the in-situ liquid mixing processed composite were investigated and compared with the vacuum suction casting processed composite. The results showed that the in-situ formed TiC particles exhibited fine and uniform dispersion in the liquid mixing processed composite, while significant grain boundary clustering and coarsening of TiC particles were obtained by the vacuum suction process. It was also shown in both types of composites that the hardness and bending strength were increased with the increase of the TiC volume fractions. Through the study of fractography in the bending test, it was considered that the TiC particles prohibited brittle intergranular fracture of FeAl intermetallic matrix by crack deflections. Because of the uniformly distributed fine TiC particles, the bending strength of the liquid mixing processed composite was superior to that of the casting processed composite.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.3-14
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• 2000

Anisotropic consolidation, shear, a transportational component during or after deposition each may produce anisotropic fabrics, which result in the anisotropic properties of soils. Nevertheless, the isotropically consolidated compression triaxial tests are commonly used in practice to determine the strength of the anisotropically consolidated soils because of their practicality and simplicity. In this paper the effects of anisotropic consolidation on the strength properties of soils are discussed. For the sandy soils consolidated under a constant vertical consolidation pressure, the deformation modulus decreases with decreasing consolidation pressure ratio($\sigma$$\sub$3c/'/$\sigma$ sub 1c/'), but the liquefaction resistance increases. For the saturated cohesive soils, both the undrained shear strength and undrained creep strength decrese with decreasing the consolidation pressure ratio. When the in-situ strength properties of the anisotropically and normally consolidated soils are determined by the isotropically consolidated tests, the undrained shear strength and creep strength of saturated cohesive soils as well as the deformation modulus of sandy soils are measured to be higher than the rear in-situ values. This, therefore, could lead to a dangerous judgement in stability analysis

• 한국세라믹학회지
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• 제51권5호
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• pp.386-391
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• 2014

Silicon nitride ($Si_3N_4$) is regarded as one of the most promising materials for high temperature structural applications due to its excellent mechanical properties at both room and elevated temperatures. However, one high-temperature $Si_3N_4$ material intended for use in radomes has a relatively high dielectric constant of 7.9 - 8.2 at 8 - 10 GHz. In order to reduce the dielectric constant of the $Si_3N_4$, an in-situ reaction process was used to fabricate $Si_3N_4-SiO_2$-BN composites. In the present study, an in-situ reaction between $B_2O_3$ and $Si_3N_4$, with or without addition of BN in the starting powder mixture, was used to form the composite. The in-situ reaction process resulted in the uniform distribution of the constituents making up the composite ceramic, and resulted in good flexural strength and dielectric constant. The composite was produced by pressure-less sintering and hot-pressing at $1650^{\circ}C$ in a nitrogen atmosphere. Microstructure, flexural strength, and dielectric properties of the composites were evaluated with respect to their compositions and sintering processes. The highest flexural strength (193 MPa) and lowest dielectric constant (5.4) was obtained for the hot-pressed composites. The strength of these $Si_3N_4-SiO_2$-BN composites decreased with increasing BN content.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 연약지반처리위원회 학술세미나
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• pp.71-78
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• 2000

SHANSEP method involves the consolidation to stresses in excess of the preconsolidation pressure in order to overcome sample disturbance effect. The concept of SHANSEP is based on an approach to laboratory test which attempts to reproduce the in-situ conditions more closely than is possible in routine tests and evaluates normalized strength parameters for the soil as a function of OCR. But SHANSEP method can be applied only to fairly uniform clay deposits, and is unsuitable for a random deposit. In this study, CK/sub o/U triaxial compression test and incremental loading consolidation test were performed for the application of SHANSEP method on Yangsan clay. During the K/sub o/-consolidation, triaxial specimens were consolidated to stress equal to two times the in-situ vertical effective stress. And for overconsolidated condition, the specimens were swelled to a known vertical effective stress in order to have the desired OCR. With the results of CK/sub o/U triaxial compression test using the block samples, the relationship between c/sub u//σ/sub vc/' and OCR on Yangsan clay was established. For evaluating the undrained shear strength of Yangsan clay with depth, CK/sub o/U triaxial compression test was performed using the piston samples taken from Yangsan site. And also undrained shear strength was analyzed from the in-situ test such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that of CK/sub o/U triaxial compression test.

• Archives of Metallurgy and Materials
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• 제67권4호
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• pp.1497-1501
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• 2022

In-situ observation of the transformation behavior of acicular ferrite in high-strength low-alloy steel using confocal laser scanning microscopy was discussed in terms of nucleation and growth. It is found that acicular ferrite nucleated at dislocations and slip bands in deformed austenite grains introduced by hot deformation in the non-recrystallization austenite region, and then proceeded to grow into an austenite grain boundary. According to an ex-situ EBSD analysis, acicular ferrite had an irregular shape morphology, finer grains with sub-grain boundaries, and higher strain values than those of polygonal ferrite. The fraction of acicular ferrite was affected by the deformation condition and increased with increasing the amount of hot deformation in the non-recrystallization austenite region.

• Journal of Welding and Joining
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• 제33권6호
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• pp.21-26
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• 2015

Recently, application of UHSS(Ultra High Strength Steels) whose tensile strength is over 1000MPa to car body structure are growing due to great needs for light weighting and improved crash worthiness. However, their poor weldability is one of obstacles to expand selecting to car body. In this study, effect of Phosphorus contents on resistance spot weldability of high elongation DP980 steel whose Si content is over 1% was investigated. The cross tension strength (CTS) was decreased showing partial interface fracture as Phosphorus content increase because of solidification segregation of Phosphorus. In order to improve resistance spot weldability by modification of welding condition, in-situ post-weld heating pulse was introduced after main pulse. The optimum cooling time between main and post pulse and post-pulse current condtion were determined through FEM welding simulation and DOE tests. The CTS was increased about 1.5 time showing plug fracture. The decrease of Phosphorus segregation was found to be a major reason for weld ductility and CTS improvement.