• KIEAE Journal
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• 제9권4호
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• pp.23-28
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• 2009

Standard sound source currently used in heavy-weight floor impact sounds that cause many social problems has excessive low-frequency energy within a range from 63 Hz to 125 Hz, and is difficult to evaluate and measure. To solve these problems, studies are widely performed using a new impact source, the impact ball. In this study, the sound fields in a receiving room were compared and analyzed according to the current impact source, the bang machine, and the impact ball. And deviation of sound pressure level according to the impact source positions were compared. In case of impact ball, the sound pressure level was lower at 63 Hz and below and higher at 125 Hz and above. The same trend was observed at the low-frequency range on the horizontal and vertical planes, regardless of the type of the impact source, which showed the influence of the room mode. There was a problem with the variations in the sound pressure level according to the size or shape of the receiving room. And it also shows that change of source positions may effect the single number rating scheme.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.75-79
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• 1993

The Thermally Stimulated Current(TSC) method has been allied to study the influence of the structural change and interface on the electrical properties of epoxy composites. Three DGBA- MeTHPA matrix model samples mixed different ratios arts silica(SiO$_2$) filled sample and silaln treating-filled sample have been studied. Above room temperature, the relaxation mode ${\alpha}$ peak associated with T$\_$g/ has been located at 110$^{\circ}C$. Below glass transition temperature(T$\_$g/), three relaxation modes are observed in all samples : a ${\beta}$ mode situated at 10$^{\circ}C$, a ${\gamma}$ mode located at -40$^{\circ}C$ and a $\delta$mode appeared in -120$^{\circ}C$, which may be due to segmental motion, side chains, substitution and terminal groups. The analysis of its fine structure indicates that constitution of elementary processes is characterized by the activation energy and relaxation time. Also the change of the molecular structure and their thermal motion are compared with the relaxation mode and conduction mechanism in TSC spectra through the dielectric properties and FTIR measurements.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.136-141
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• 1997

Rotary compressor is one of the most useful mechanism that is widely applied in refrigeration and air-conditioning systems. That is due to character of rotary compressor -compact, simple etc.While there is a lot of strong points, there is room for improvement because it is composed of many parts which have wear problem, friction losses and leakage. In this paper, theoretical investigation about vane and slot parts at which we observe severe wear is carried out. Through the study of lubrication, the behavior of vane during one cycle can be predicted and the cause of wear at slot will be discovered. To solve the equations, fletcher-powell method is applied. The result of analysis show that vane bevell to the slot part with discharge port before rotation of shaft is 180 degree and bevell to the slot part with suction port after 180 degree. The motion of vane is divided 3 mode that depends on behavior of vane. This paper define the first mode when vane tilt to the compression chamber, the second mode when vane tilt to the suction chamber, and the third mode when vane move straightway.

• 소성∙가공
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• 제17권7호
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• pp.473-480
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• 2008

Sheet metal forming of Mg alloy is usually performed at elevated temperature because of the low formability at room temperature. Therefore, strain rates affected with the forming temperature and speed must be considered as important factor about formability. Effects of process parameters such as various temperatures and forming speeds were investigated in circular cup deep drawing. From the experimental results, it is known that LDR (Limit Drawing Ratio) increase as the strain rate increase. On the contrary, the FLD (Forming Limit Diagram) shows lower value as faster strain rate. Therefore, anisotropy values are investigated according to the temperature and strain rates at each forming temperature. R-values also represent higher value as faster strain rate. It is known that the formability can be different with the deformation mode on warm forming of AZ31 alloy sheet.

• 수산해양기술연구
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• 제26권4호
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• pp.372-379
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• 1990

The effect of primary solidification phase on the solidification cracking sensitivity, corrosion resistance and toughness at cryogenic temperature was investigated for the austenitic stainless steel welds. The conclusions were summarized as follows; 1. Soldification crack sensitivity of austenitic stainless steel welds depends on the primary solidification mode. 2. Austenitic stainless steels were very susceptible to solidification cracking in case of solidification as primary ${\gamma}$ and immune when solidified as primary $\delta$. 3. When the ratio of Creq/Nieq is in the range of 1.46 to 1.55, the most resistance against solidification cracking was obtained. These results agreed well with the relationship between primary solidification mode, corrosion resistance and toughness at cryogenic temperature. 4. Optimum toughness, corrosion and solidification cracking resistance can be obtained when alloys having chemical compositions described above and solidifies as primary $\delta$ containing no ferrite at room temperature.

• 한국정보전자통신기술학회논문지
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• 제1권1호
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• pp.21-27
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• 2008

본 논문에서는 개인용 컴퓨터를 기반으로 한 실시간 마이크로폰 어레이 시스템을 제안한다. 제안한 시스템은 Generalized Sidelobe Canceller (GSC) 를 기반으로 하며, 새로운 적응 모드 제어기 (adaptation mode controller) 를 이용함을 특징으로 한다. 제안한 마이크로폰 어레이 시스템의 성능 평가를 위해, 일반 가정의 거실을 모델링한 실험 환경을 구축하여 실험을 수행하였다. 실험을 통해 제안된 시스템이 안정적으로 GSC의 적응 모드를 제어하고, 목적 신호의 왜곡을 최소화하면서도 간섭 신호 제거 성능이 뛰어남을 확인하였다.

• 한국주조공학회지
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• 제10권6호
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• pp.503-508
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• 1990

The effect of interlamellar spacing on tensile behavior and fracture mode at high temperatures has been studied for unidirectionally solidified $Al-CuAl_2$ eutectic composite. The tensile properties at room temperature in $Al-CuAl_2$ eutectic composite improved as the interlamellar spacing decreased due to the constraint effects of closely spaced lamellae, while the opposite behavior was observed at high temperatures due to the annihilation of the constraint effects by phase boundary sliding. The $Al-CuAl_2$ eutectic composite exhibited brittle fracture mode below the temperature at which the reinforcing phase softened but ductile fracture mode above the temperature.

• 한국광학회:학술대회논문집
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• 한국광학회 1991년도 제6회 파동 및 레이저 학술발표회 Prodeedings of 6th Conference on Waves and Lasers
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• pp.139-143
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• 1991

GRIN-SCH quantum well structured Laser Diode were fabricated using MOCVD and operated as CW at room temperature. The threshold current density of the LD with 670${\mu}{\textrm}{m}$ cavity length was 530 A/$\textrm{cm}^2$. For the ridge waveguide type index guiding structured LD with 6${\mu}{\textrm}{m}$ stripe width and 240${\mu}{\textrm}{m}$ cavity length, the threshold current was 50㎃. The maximum differential quantum efficiency was 0.95W/A when the optical output was 60mW. The lasing wavelength of QW LD was 865nm. In the L-I measurement. TE mode was superior to TM mode. From the near field pattern, single lateral mode operation was observed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.206-211
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• 2000

Fatigue test was conducted on a S45C steel using hour-glass shaped smooth tubular specimen under biaxial loading in order to investigate the crack formation and growth at room temperature. Three types of loading system, i.e fully reserved cyclic torsion without a superimposed static tension or compression, fully reserved cyclic torsion with a superimposed static tension and fully reserved cyclic torsion with a superimposed static compression were employed. The test results show that a superimposed static tensile mean stress reduced fatigue lifetime. however a superimposed static compressive mean stress increased fatigue lifetime. Experimental results indicated that cracks were initiated on planes of maximum shear strain with either a superimposed mean stresses or not. A biaxial mean stress had an effect on the direction which cracks nucleated and propagated at stage I (mode II).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.159-160
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• 2014

The floor impact noise arising between upper and lower households in residential houses has been known as one of major causes worsening residential environment and still led to serious social troubles in a residential community. It is known that the heavy weight floor impact noise is induced by flexural vibration modes in the relatively lower frequency ranges. In this study, a procedure is examined to evaluate the relations between the vibration modes and the corresponding noise of the slab. In the process, for simplicity of the numerical analysis, it is assumed that the slab is simply supported plate-like structure and the acoustic mode formed in the lower room by acoustic boundary conditions is ignored.