• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2003.11a
• /
• pp.249-271
• /
• 2003

The purpose of the present study is to identify the drying cylinder model in paper plants and to analyze characteristics of process responses for changes in input variables. The model developed in this work is based on actual plant operation data and the steam pressure applied to the cylinder behaves as one the main variables. It is found that heat transfer coefficients from the condensate to the canvas could be represented as empirical relations based on heat conductivities and operation date. The effectiveness of the cylinder model is demonstrated by the measured moisture contents and web temperature. Using transfer functions derived from the cylinder model stability of the drying process is analyzed.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.4
• /
• pp.289-298
• /
• 2011

This paper provides procedures to effectively determine arrangement of hydraulic type top-bracings, which are popular for the main engine of the mid and large sized commercial vessels. Analyzing the operation mechanism of hydraulic top-bracing, ideal unified nonlinear stiffness curve is presented for linear frequency response analysis and nonlinear transient response analysis. Nonlinear stiffnesses of the curve are determined based on the regression analysis of test results. It is noted from linear frequency response analysis, initial setting pressure is most important among the setting values of the other stiffness intervals. From transient response analyses for two top-bracing arrangement scenarios, it is recognized that, as far as initial setting pressure is well controlled for the concerning vessels, only two top-bracings are enough to suppress H-mode excitation forces from main engine.

• Korean Chemical Engineering Research
• /
• v.45 no.1
• /
• pp.17-24
• /
• 2007

The purpose of the present study is to identify the drying cylinder model in paper plants and to analyze characteristics of process responses for changes in input variables. The model developed in this work is based on actual plant operation data where the steam pressure applied to the cylinder behaves as the major variable. It is found that heat transfer coefficients from the condensate to the canvas could be represented as empirical relations based on heat conductivities and operation data. The effectiveness of the cylinder model is demonstrated by the measured moisture contents and web temperature. Stability of the drying process is analyzed based on the transfer functions derived from the cylinder model.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.5
• /
• pp.287-296
• /
• 2020

The wave-impact load on offshore structures can be divided into green-water and wave-slamming impact loads. These wave impact loads are known to have strong nonlinear characteristics. Although the wave impact loads are dealt with in the current classification rules in the shipping industry, their strong nonlinear characteristics are not considered in detail. Therefore, to investigate these characteristics, wave-impact loads induced by a breaking wave on a circular cylinder were analyzed. A model test was carried out to measure the wave-impact loads due to breaking waves in a two-dimensional (2D) wave tank. To generate a breaking wave, the focusing wave method was applied. A series of 2D tank tests under a horizontal wave impact was carried out to investigate the structural responses of the cylindrical structure, which were obtained from the measured model test data. According to the results, we proposed a structural damage-estimation procedure of an offshore tubular member due to a wave impact load. Furthermore, a recommended wave-impact load is suggested that considers the minimum required thickness of each member. From the experimental results, we found that the required minimum thickness is dependent on the impact pressure located in a three-dimensional space on the surface of a tubular member.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2017.04a
• /
• pp.71-71
• /
• 2017

농용트랙터의 운전자는 작업, 주행으로 인한 유해한 저주파 진동에 장시간 노출된다. 이에 따라 운전자에게 전달되는 노면 진동을 감소시켜주기 위한 전방차축 현가장치의 역할이 커지고 있다. 트랙터의 전방차축 현가장치는 주로 유압식으로 설계되어 있으며 이를 구성하는 유압요소 선정이 현가장치의 성능에 중요한 영향을 미친다. 하지만, 실제와 유사한 조건에서 트랙터 차체 무게만큼 큰 부하를 제공하여 유압회로의 성능을 실험하는 것은 비용과 시간 측면에서 비효율적이다. 본 연구에서는 이를 대체하기 위하여 개별 유압요소의 성능을 테스트 할 수 있는 현가장치 유압회로 요인 시험기를 설계제작 하였다. 이를 이용하여 개별 부품의 성능곡선을 센서를 이용 측정하였고 얻은 특성값을, 구성한 유압 시뮬레이션 모델에 반영하여 실제조건의 유압특성을 얻을 수 있는 유효한 시뮬레이션 모델 개발에 활용하였다. 또한, 실험실 환경에서 유압식 현가장치를 간소화 시킨 형태로 유압회로의 성능을 예비시험해 볼 수 있도록 다양한 센서를 장착 데이터를 취득할 수 있도록 하였다. 개발한 요인 시험기는 하부에 설치된 가진 실린더를 이용하여 상부에 설치된 현가장치 실린더의 스트로크 변위와 속도에 따른 힘을 측정할 수 있도록 구성하였다. 이를 위해 현가장치 실린더의 헤드부와 로드부에 각각 압력센서를 설치하였으며 헤드부, 로드부의 압력 차이와 로드셀을 이용해 측정한 가진 실린더의 힘의 관계를 확인하였다. 상부의 현가 실린더 장치는 복동 형태로 제작되어 헤드부, 로드부 양쪽 방향으로 유량이 흐를 수 있도록 설계되었다. 이를 이용해 헤드부와 로드부 사이에 어큐뮬레이터, 가변 오리피스, 릴리프 밸브 등으로 유압회로를 구성하였으며 어큐뮬레이터 용량에 따른 힘의 변화, 가변 오리피스의 개도량에 따라서 전달되는 힘의 크기 등을 측정하였다. 하부의 가진 실린더는 사인파, 삼각파, 계단 입력, DC 레벨 등의 신호를 발생시킬 수 있도록 제작되었다. 신호의 주파수는 0~4Hz, 범위에서 사용자가 조절할 수 있도록 설정되었으며 계단응답 성능 측정 시험을 평가한 결과 정상상태오차는 0.470mm~0.536mm, 입상시간은 0.194초~0.202초, 정착시간은 0.230초~0.421초로 나타났다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.10
• /
• pp.1307-1313
• /
• 2011

The mechanical limited slip differential (LSD) in vehicles is being replaced by the electromagnetic LSD because of its fast response and better active control characteristics. The coil housing made of STS 304 is one of the most important parts in the solenoid assembly of the electromagnetic LSD. High geometrical accuracy is a prerequisite for the manufacture of such coil housings, but precision machining is difficult because of the use of STS 304 thin plate and the variance in machining variables. The aim of this study is to optimize the mean and variance of the shape accuracy in the coil housing by finding a robust solution for the machining process conditions. The mean and standard deviation of the jaw contact pressure, cutting speed, and feed rate are considered to be the major parameters for minimizing the geometrical mean and variance. The response surface model based on the second-order Taylor series is combined together to minimize the mean and variance of the shape accuracy of the coil housing.

• Journal of Sensor Science and Technology
• /
• v.9 no.5
• /
• pp.334-340
• /
• 2000

This paper presents the fabrication of a micro electromagnetic flow sensor for the liquid flow rate measurement. The micro electromagnetic flow sensor has some advantages such as a simple structure, no heat generation, a rapid response and no pressure loss. The principle of the micro electromagnetic flow sensor is based on Faraday's law. If conductive fluid passes through a magnetic field, the electromotive force is generated and detected by two electrodes on the wall of the flow channel. The flow sensor consists of two permanent magnets and a silicon flow channel with two electrodes. The dimension of the flow sensor is $9\;mm\;{\times}\;9\;mm\;{\times}\;1\;mm$. The micro flow channel is mainly fabricated by anisotropic etching of two silicon wafers, and the detection electrodes are fabricated by metal evaporation process. The characteristic of the fabricated flow sensor is obtained experimentally. When the flow rates of water with the conductance of $100-200\;{\mu}S/cm$ are 9.1 ml/min and 62 ml/min, the generated electromotive forces are $261\;{\mu}V$ and 7.3 mV, respectively.

• Journal of the Korean GEO-environmental Society
• /
• v.19 no.8
• /
• pp.5-10
• /
• 2018

This study provides a method to assess the compressive strength of granitic gneiss using total sound signal energy, which is calculated from the signal of sound pressure measured when an object impacts on rock surface, and its results. For this purpose, many test specimens of granitic gneiss were prepared. Each specimen was impacted using a devised device (impacting a specimen by an initial rotating free falling and following repetitive rebound actions) and all sound pressures were measured as a signal over time. The sound signal was accumulated over time (called total sound signal energy) for each specimen of granitic gneiss and it was compared with the directly measured compressive strength of the specimen. The comparison showed that the total sound signal energy was directly proportional to the measured compressive strength, and with this result the compressive strength of granitic gneiss can be reliably assessed by an estimation equation of total sound signal energy. Furthermore, from the study results it is clearly believed that the compressive strength of other rocks and concrete can be assessed nondestructively using the total sound signal energy.

• Journal of the Korean Society for Advanced Composite Structures
• /
• v.2 no.3
• /
• pp.1-11
• /
• 2011

The typical truss-lattice material successively packed by repeated cubic symmetric unit cells consists of sub-elements (SE) proposed in this study. The representative continuum model for this truss-lattice material such as the effective strain and stress relationship can be formulated by the homogenization procedure based on the notation of averaged mechanical properties. The volume fractions of micro-scale struts have a significant influence on the effective strength as well as the relative density in the lattice plate with replicable unit cell structures. Most of the strength contribution in the lattice material is induced by axial stiffness under uniform stretching or compression responses. Therefore, continuum based constitutive models composed of homogenized member stiffness include these mechanical characteristics with respect to strength, internal stress state, material density based on the volume fraction and even failure modes. It can be also recognized that the stress state of micro-scale struts is directly associated with the continuum constitutive model. The plastic flow at the micro-scale stress can extend the envelope of the analytical stress function on the surface of macro-scale stress derived from homogenized constitutive equations. The main focus of this study is to investigate the basic topology of unit cell structures with the cubic symmetric system and to formulate the plastic models to predict pressure dependent macro-scale stress surface functions.