• 열처리공학회지
• /
• 제10권3호
• /
• pp.165-171
• /
• 1997

Laser hardening for the piston ring groove of ductile cast iron was tried. Mechanical and microstructural investigation for the hardened area indicated that the laser heating technique could replace conventional induction hardening process completely and further showed that post grinding process would be eliminated by minimizing bulging of heat treated area. In laser hardening, the volume increase caused by martensitic phase transformation proved to be less than $10{\mu}m$, which insures no post machining on the hardened surface. As expected, the depth of hardening was inversely proportional to the beam scanning velocity and the highest surface hardness was obtained at the beam velocity of 0.75m/min. Heat treatment using phosphate coating demonstrated quite comparable result to the case of graphite suscepter.

• 대한전자공학회논문지
• /
• 제27권1호
• /
• pp.81-90
• /
• 1990

In this study, ion beam deposited tungsten thin film for gate material of GaAs SAGFET(Self Aligned Gate FET) was annealed from 800\ulcorner to 900\ulcorner using RTA and detailed investigations of structural and electrical characteristics of this film were carried out using four-point probe, XRD, SEM, AES and current-voltage measurement. Investigated results showed phase of as deposited tungsten film was fine grain \ulcornerphase and phase tdransformation of this film into \ulcornerphase occured at annealing condition of 900\ulcorner, 6sec. But regardless of phase transformation, electrical characteristics of tungsten film were very stable to 900\ulcorner and in case of 900\ulcorner, 4sec annealing condition Schottky barrier height obtained from 10 diodes measurements was 0.66 + 0.003 eV.

• Computers and Concrete
• /
• 제2권6호
• /
• pp.481-498
• /
• 2005

A wavelet based approach is proposed for structural damage detection in beams, plate and delamination of composite plates. Wavelet theory is applied here for crack identification of a beam element with a transverse on edge non-propagating open crack. Finite difference method was used for generating a general displacement equation for the cracked beam in the first example. In the second and third example, damage is detected from the deformed shape of a loaded simply supported plate applying the wavelet theory. Delamination in composite plate is identified using wavelet theory in the fourth example. The main concept used is the breaking down of the dynamic signal of a structural response into a series of local basis function called wavelets, so as to detect the special characteristics of the structure by scaling and transformation property of wavelets. In the light of the results obtained, limitations of the proposed method as well as suggestions for future work are presented. Results show great promise of wavelet approach for damage detection and structural health monitoring.

• 한국안전학회지
• /
• 제4권1호
• /
• pp.47-58
• /
• 1989

This paper treats the vibration analysis of a simply supported rectangular plate stiffened with viscoelastic beams. The effect of viscoelastic beams on the vibration of the plate is analyzed by using Dirac delta function and the equation of motion can be expressed only one equation. The frequency equation is obtained by applying Laplace transformation. The effect of volumes, numben and aspect ratios of beam on the frequency of the plate is analyzed.

• 제어로봇시스템학회논문지
• /
• 제17권11호
• /
• pp.1168-1172
• /
• 2011

Beam projector is popularly used for presentation. In order to pay attention to local area of the beam projector display, a laser pointer is used together with a pointing device(Mouse). Simple wireless presenter has limited functions of a pointing device such as "go to next slide" or "back to previous slide" in a specific application(Microsoft PowerPoint) through wireless channel; thus, there is inconvenience to do other tasks e.g., program execution, maximize/minimize window etc. provided by clicking mouse buttons. The main objective of this paper is to implement a multi-functional laser-pointer mouse that has the same functions of a computer mouse. In order to get position of laser spot in the projector display, an image processing to extract the laser spot in the camera image is required. In addition, we propose a transformation of the spot position into computer display coordinates to execute mouse functions on computer display.

• 한국태양에너지학회 논문집
• /
• 제36권3호
• /
• pp.9-16
• /
• 2016

This paper discusses a refined model for investigating the micro-mechanical behavior of beam-like structures, which are composed of various elastic moduli and complex geometries varying through the cross-section directions and are also periodically-repeated and heterogeneous along the axial direction. Following the previous work (Lee and Yu, 2011), the original three-dimensional static problem is first formulated in a unified and compact form using the concept of decomposition of the rotation tensor. Taking advantage of the smallness of the cross-sectional dimension-to-length parameter and the micro-to-macro heterogeneity, while also performing homogenization along the dimensional reduction simultaneously, the variational asymptotic method is rigorously used to construct a total energy function, which is asymptotically correct up to the second order. Furthermore, through the transformation procedure based on the pure kinematic relations and the linearized equilibrium equations, a generalized Timoshenko model is systematically established. For the purpose of dealing with realistic and complex geometries and constituent materials at the microscopic level, this present approach is incorporated into a commercial analysis package. A few examples available in literature are used to demonstrate the consistency and efficiency of this proposed model, especially for the structures, in which the effects of transverse shear deformations are significant.

• Journal of Electrical Engineering and Technology
• /
• 제9권4호
• /
• pp.1418-1425
• /
• 2014

In ultrasonic medical imaging, spatial compounding of images is a technique where ultrasonic beam is steered to examine patient tissues in multiple angles. In the conventional ultrasonic diagnostic imaging, the steering of the ultrasonic beam is achieved electronically using the phased array transducer elements. In this paper, a spatial compounding approach is presented where the ultrasonic probe element is rotated mechanically and the beam steering is achieved mechanically. In the spatial compounding, target position is computed using the value of the rotation axis and the transducer array angular position. However, in the process of the rotation mechanism construction and the control system there arises the inevitable uncertainties in these values. These geometric parameter errors result in the target position error, and the consequence is a blurry compounded image. In order to reduce these target position errors, we present a spatial compounding scheme where error correcting transformation matrices are computed and applied to the raw images before spatial compounding to reduce the blurriness in the compounded image. The proposed scheme is illustrated using phantom and live scan images of human knee, and it is shown that the blurriness is effectively reduced.

• Structural Engineering and Mechanics
• /
• 제12권6호
• /
• pp.657-668
• /
• 2001

Fiber reinforced cementitious composites are nowadays widely applied in civil engineering. The postcracking performance of this material depends on the interaction between a steel fiber, which is obliquely across a crack, and its surrounding matrix. While the partly debonded steel fiber is subjected to pulling out from the matrix and simultaneously subjected to transverse force, it may be modelled as a Bernoulli-Euler beam partly supported on an elastic foundation with non-linearly varying modulus. The fiber bridging the crack may be cut into two parts to simplify the problem (Leung and Li 1992). To obtain the transverse displacement at the cut end of the fiber (Fig. 1), it is convenient to directly solve the corresponding differential equation. At the first glance, it is a classical beam on foundation problem. However, the differential equation is not analytically solvable due to the non-linear distribution of the foundation stiffness. Moreover, since the second order deformation effect is included, the boundary conditions become complex and hence conventional numerical tools such as the spline or difference methods may not be sufficient. In this study, moment equilibrium is the basis for formulation of the fundamental differential equation for the beam (Timoshenko 1956). For the cantilever part of the beam, direct integration is performed. For the non-linearly supported part, a transformation is carried out to reduce the higher order differential equation into one order simultaneous equations. The Runge-Kutta technique is employed for the solution within the boundary domain. Finally, multi-dimensional optimization approaches are carefully tested and applied to find the boundary values that are of interest. The numerical solution procedure is demonstrated to be stable and convergent.

• 건축역사연구
• /
• 제29권3호
• /
• pp.79-90
• /
• 2020

In Korean traditional architecture, the Gong-po style is divided into the Jusimpo, Dapo and Ikgong. Jusimpo and Chulmok-Ikong, where only Gong-po is placed on the column, differ in form of Gong-po depending on the viewpoint. Since 'Chulmok-Ikgong' has been generally regarded as 'One Chulmok-Two Ikgong', the precedent researches have been conducted mainly on 'One Chulmok-Two Ikgong' in the Gong-po style classification. However, when it comes to 'One Chulmok', the style of Ikgong can be organized from the one to three steps and this study is particularly for examining the occurrence and transformation of 'One Chulmok-One Ikgong'. One of the case study sites, Bonghwa Cheongamjeong was originally built in the 16th century, and is believed to have been repaired from 'Non Chulmok-One Ikgong' to 'One Chulmok-One Ikgong'. Since the beam linked directly to the upper part of a capital, it does not connect the eave trave(architrave) in between. Also, Soro which supports Jangyeo(the architrave strip) has been placed and linked in comparatively lower position. It is confirmed by the signigicant difference in the hierarchy of Gong-po forms in one architecture. The Jeonju-Hyanggyo Daeseongjeon, which was built in the 17th century among the subjects, was similar with 'One Chulmok-One Ikgong', but it was found to be the type of Jusimpo form because the bottom of the beam and the top of the Ikong are apart. And Gongan is confirmed at Cheomcha. In the 17th century, it can be seen that Heot-Cheomcha disappeared and Ikgong was started to use as a constant figure. The end of the 18th century, it can be seen that it was changed into a ornament added on Haeng-gong, being seen in the case of Hwaseong Dongjangdae. In conclusion, it can be seen that 'One Chulmok-One Ikgong' were developed in both the Jusimpo and Ikong style. The transformation into 'One Chulmok-One Ikgong' was inevitable consequence related with an elevation difference between the eave trave and the column trave.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.1311-1320
• /
• 2000

In this study, shape memory alloy(SMA) wires and piezoceramic actuators(PZT's) are employed in order to generate higher modes on the beam deformations. Compressive force is generated and applied to the beam by the pre-strained SMA wires attached at both ends of the beam. PZT's apply concentrated moments to several locations on the beam. Combinations of the compressive force and concentrated moments are investigated in order to understand the higher-mode deformation of beams. The first desired mode shape is obtained by controlling the temperature of the SMA wires. The first and third mode shapes are performed experimentally by heating SMA wires up to phase transformation temperature. The adaptive wing is defined as a wing whose shape parameters such as the camber, wing twist and thickness can be varied in order to change the wing shape for various flight conditions. In this research, control of the camber has been studied. The wing model consists of three plates and many ribs. Two of the plates are placed parallel to each other and they are clamped at one edge. Third plate connects the other edges of the parallel plates together. Each rib is made of SMA wire and connected to the parallel plates. It generates concentrated force and applies to the plates in oblique directions. The PZT's are bonded onto the plates and exert concentrated moments upon the plate at several locations. The object of this research is to generate various shape of wing by combining the concentrated forces and moments.