• 한국정밀공학회지
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• 제16권4호통권97호
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• pp.148-154
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• 1999

This study was carried out to verify grinding performance of dental diamond bur and investigate the possibility of AE application in dentistry field. Workpieces were made of acryl and bovine respectively for the experiments in this study. Grinding test was conducted to get the data of grinding resistance and specific grinding energy of four different types of diamond bur by using tool dynamometer. AE signal was acquired to verify grinding process in the AE measuring system. Tool wear was observed to find parameters about grinding characteristics of diamond bur by means of SEM picture. It was found that the wear of dental diamond bur could be detected with polishing of grinding material, removal of adhesive parts, wear of particles neighboring cutting nose, loss of material and elevation of temperature. The wear of B, C, D type diamond bur is due to wear and fracture of grain size. Abnormal state can be found through the behavior of AE signal in the grinding working. As a result, it is expected that forecast of abnormal state is possible using AE equipments under real time process.

• Journal of Welding and Joining
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• 제25권3호
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• pp.78-84
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• 2007

Laser Material Processing has been replaced the conventional machining systems - cutting, drilling, welding and surface modification and so on. Especially, LTH(Laser Transformation Hardening) process is one branch of the laser surface modification process. Conventionally, some techniques like a gas carburizing and nitriding as well as induction and torch heating have been used to harden the carbon steels. But these methods not only request post-machining resulted from a deformation but also have complex processing procedures. Besides, LTH process has some merits as : 1. It is easy to control the case depth because of output(laser power) adjustability. 2. It is able to harden the localized and complicated a.ea and minimize a deformation due to a unique property of a localized heat source. 3. An additional cooling medium is not required due to self quenching. 4. A prominent hardening results can be obtained. This study is related to the surface hardening of the rod-shaped carbon steel applied to the lathe based complex processing mechanism, a basic behavior of surface hardening, hardness distribution and structural characteristics in the hardened zone.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권1호
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• pp.38-44
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• 2003

In this study, the balance beam control subsystem, new type of construction machinery using the mechanism of CMG (control moment gyro), for the attitude control of an unstructured object such as a beam carried by a tower crane, is designed and implemented. The balance beam controller consists of a wheel spinning at high speed and an outer gimbal for controlling the attitude of the wheel. Two motors, one for the wheel and the other for the gimbal, are used. Applying force to the spin axis of the wheel, as an input of the system, leads the torque about the axis because of the gyro effects. This torque is used to control the attitude of the unstructured object in this study. For the stabilizer function, in addition, holding the load at the current position, the attitude of the wheel is freed by cutting the power applied to the gimbal motor of the balance beam controller, which result in the braking force to stop the load by gyro effect. The works presented here include the mechanical system of the balance beam controller, the remote controller, the servo controller and the control software for the system. We also present experimental results to show that the system we proposed is useful as a new construction machinery which can control the attitude of the beam hanging from a tower crane.

• Steel and Composite Structures
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• 제18권3호
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• pp.739-756
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• 2015

This paper presents investigations on the hysteretic behavior of concrete-filled circular tubular (CFCT) T-joints subjected to axial cyclic loading at brace end. In the experimental study, four specimens are fabricated and tested. The chord members of the tested specimens are filled with concrete along their full length and the braces are hollow section. Failure modes and load-displacement hysteretic curves of all the specimens obtained from experimental tests are given and discussed. Some indicators, in terms of stiffness deterioration, strength deterioration, ductility and energy dissipation, are analyzed to assess the seismic performance of CFCT joints. Test results indicate that the failures are primarily caused by crack cutting through the chord wall, convex deformation on the chord surface near brace/chord intersection and crushing of the core concrete. Hysteretic curves of all the specimens are plump, and no obvious pinching phenomenon is found. The energy dissipation result shows that the inelastic deformation is the main energy dissipation mechanism. It is also found from experimental results that the CFCT joints show clear and steady stiffness deterioration with the increase of displacement after yielding. However, all the specimens do not perform significant strength deterioration before failure. The effect of joint geometric parameters ${\beta}$ and ${\gamma}$ of the four specimens on hysteretic performance is also discussed.

• Applied Microscopy
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• 제46권4호
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• pp.206-216
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• 2016

This communication is to elucidate the state-of-the-art of techniques necessary to gather information on a new class of nanoelectronic devices known as memristors and related resistive switching devices, respectively. Unlike classical microelectronic devices such as transistors, the chemical and structural variations occurring upon switching of memristive devices require cutting-edge electron microscopy techniques. Depending on the switching mechanism, some memristors call for the acquisition of atomically resolved structural data, while others rely on atomistic chemical phenomena requiring the application of advanced X-ray and electron spectroscopy to correlate the real structure with properties. Additionally, understanding resistive switching phenomena also necessitates the application not only of pre- and post-operation analysis, but also during the process of switching. This highly challenging in situ characterization also requires the aforementioned techniques while simultaneously applying an electrical bias. Through this review we aim to give an overview of the possibilities and challenges as well as an outlook onto future developments in the field of nanoscopic characterization of memristive devices.

• International Journal of Computer Science & Network Security
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• 제21권8호
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• pp.196-202
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• 2021

DNA sequencing provides fundamental data in genomics, bioinformatics, biology and many other research areas. With the emergent evolution in DNA sequencing technology, a massive amount of genomic data is produced every day, mainly DNA sequences, craving for more storage and bandwidth. Unfortunately, managing, analyzing and specifically storing these large amounts of data become a major scientific challenge for bioinformatics. Those large volumes of data also require a fast transmission, effective storage, superior functionality and provision of quick access to any record. Data storage costs have a considerable proportion of total cost in the formation and analysis of DNA sequences. In particular, there is a need of highly control of disk storage capacity of DNA sequences but the standard compression techniques unsuccessful to compress these sequences. Several specialized techniques were introduced for this purpose. Therefore, to overcome all these above challenges, lossless compression techniques have become necessary. In this paper, it is described a new DNA compression mechanism of pattern matching extended Compression algorithm that read the input sequence as segments and find the matching pattern and store it in a permanent or temporary table based on number of bases. The remaining unmatched sequence is been converted into the binary form and then it is been grouped into binary bits i.e. of seven bits and gain these bits are been converted into an ASCII form. Finally, the proposed algorithm dynamically calculates the compression ratio. Thus the results show that pattern matching extended Compression algorithm outperforms cutting-edge compressors and proves its efficiency in terms of compression ratio regardless of the file size of the data.

• 드라이브 ㆍ 컨트롤
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• 제18권2호
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• pp.20-31
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• 2021

An excavator is a construction machine that can perform various tasks such as trenching, piping, excavating, slope cutting, grading, and rock demolishing. In the 2010s, unmanned construction equipment using ICT technology was continuously developed. In this paper, the path design process was studied to implement the output data of the decision stage, and the path design algorithm was developed. For example, the output data of the decision stage were terrain data around the excavator, excavator mechanism information, excavator hydraulic information, the position and posture of the bucket at key points, the speed of the desired bucket path, and the required excavation volume. The result of the path design was the movement of the hydraulic cylinder, boom arm, bucket, and bucket edge. The core functions of the path design algorithm are the function of avoiding impact during the excavation process, the function to calculate the excavation depth that satisfies the required excavation volume, and the function that allows the bucket to pass through the main points of the excavation process while maintaining the speed of the desired path. In particular, in the process of developing the last function, the node tracking method expressed in the path design table was newly developed. The path design algorithm was verified as this path design satisfied the JCMAS H02 requirement.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.417-423
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• 2005

Contractor's opportunistic bidding behavior refers to contractor's deliberate low-bid, which cannot accord with the cost, and expectation for beyond-contractual reward (BCR), the compensation earned through cutting corners or claims after undertaking the construction project. This research applies System Dynamics to develop a model of contractor's pricing with consideration for dimensions of "cost", "market competition", and "BCR". Iterative computer simulations were performed to analyze the effects of contractor's pricing on the market price. The results were then examined by statistical analysis on data collected from 44 highway projects in Taiwan. It is found that the critical force driving the contractors to bid opportunistically is their excessive expectations in BCR under the current environment. Within the price competition mechanism, if the problem of BCR exists, even if the bidding system is further improved, contractors would still prefer opportunistic bidding behavior, and eventually make the whole construction industry operate ineffectively. Therefore, it is crucial to remedy the aforementioned BCR problem by more effective management policy.

• Earthquakes and Structures
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• 제25권2호
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• pp.113-123
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• 2023

A novel type of buckling restrained brace with built-up angle steel was developed. The core segment was formed by welding angle steel, and the middle section was reduced by cutting technology to solve the problem that the end of BRB was easy to buckle. The experimental program has been undertaken to study the performance of BRBs with different unbonded materials (silica gel, kraft paper) and different filler materials (ordinary concrete, full light-weight concrete). Four specimens were designed and fabricated for low cycle reciprocating load tests to simulate horizontal seismic action. The failure mode, hysteretic curves, tension-compression unbalance coefficient and other mechanical parameters were compared and analyzed. The finite element software ABAQUS was used to conduct numerical simulation, and the simulation results were compared with the experimental phenomena. The test results indicated that the hysteretic curve of each specimen was plump. Sustaining cumulative strains of each specimen was greater than the minimum value of 200 required by the code, which indicated the ductility of BRB was relatively good. The energy dissipation coefficient of the specimen with silica gel as unbonded material was about 13% higher than that with kraft paper. The experimental results were in good agreement with the simulation results.

• Steel and Composite Structures
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• 제21권5호
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• pp.1157-1182
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• 2016

A newly puzzle shape of crestbond rib shear connector is a type of ductile perfobond rib shear connector. This shear connector has some advantages, including relatively easy rebar installation and cutting, as well as the higher shear resistance strength. Thus, this study proposed a newly puzzle shape of crestbond rib with a "${\mho}$" shape, and its shear resistance behaviors and shear strengths were examined using push-out tests. Five main parameters were considered in the push-out specimens to evaluate the effects of shear resistance parameters such as the dimensions of the crestbond rib, transverse rebars in the crestbond dowel, concrete strength, rebar strength, and dowel action on the shear strength. The shear loading test results were used to compare the changes in the shear behaviors, failure modes, and shear strengths. It was found that the concrete strength and number of transverse rebars in the crestbond rib were significantly related to its shear resistance. After the initial bearing resistance behavior of the concrete dowel, a relative slip occurred in all the specimens. However, its rigid behavior to shear loading decreased the ductility of the shear connection. The cross-sectional area of the crestbond rib was also shown to have a minor effect on the shear resistance of the crestbond rib shear connector. The failure mechanism of the crestbond rib shear connector was complex, and included compression, shear, and tension. As a failure mode, a crack was initiated in the middle of the concrete slab in a vertical direction, and propagated with increasing shear load. Then, horizontal cracks occurred and propagated to the front and rear faces of the specimens. Based on the results of this study, a design shear strength equation was proposed and compared with previously suggested equations.