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Direct laser melting(DLM) is an additive manufacturing process that can produce parts by solidification of molten metallic powder layer by layer. The properties of the fabricated parts strongly depend on characteristics of the metallic powder. Atomized powders having spherical morphology have commonly been used for DLM. Mechanical ball-milling is a powder processing technique that can provide non-spherical solid powders without melting. The aim of the current study was to investigate the effect of powder morphologies on the deposition quality in DLM. To characterize the morphological effect, the performances of spherical and non-spherical powders were compared using both single- and multi-track DLM experiments. DLM experiments were performed with various laser process parameters such as laser power and scan rate, and the deposition quality was evaluated. The surface roughness, cross-section bead shape and process defects such as balling or non-filled area were compared and discussed in this study.

In maritime logistics, the technology for transmitting status information has been greatly developed, but it has not been available in general logistics environment or it is impossible to support two-way communication as it simply receives and transfers a container's information. In particular, to support two-way communication in all sections of the global maritime logistics, the address value, which can identify the tag, should be managed. In this context, to improve the 433 MHz-based RFID, the project called "DASH 7" has been conducted in recent years. However, it has stopped proceeding because of its slow progress, including the standardization and development of references. In this paper, we introduced an active IP-RFID system configuration for real-time communication in global maritime logistics using a two-way communication-which is characteristic of an IP-applying virtual address values in the RFID tag, and proposing its process and function. When you apply the IP-RFID system proposed in this paper, not only real-time status tracking in the maritime logistics area is possible, but it is also applicable for controlling the tag.

Hydroforming of a non-axisymmetric thin-walled tubular component with variable cross sections was analyzed. In order to solve the sealing problem which occurred due to the thin and non-axisymmetric shape, the use of a lead patch on the punch, which had been successful in hydroforming of thin tubes, was evaluated. A lead patch was attached to the punch to solve the sealing problem, which was caused by the stress gradient in the non-axisymmetric shape. FEM and experiments were also performed to analyze these sealing problems associated with the punch shape and non-axisymmetric shape. Finally, the lead patch was attached at tube surface where intensive local strain concentration would occur to enhance the hydroformability. These methods were successfully used to fabricate non-axisymmetric thin-walled tubular component with variable cross sections that had previously failed during traditional hydroforming. Key Words : Hydroforming, Thin-wall Tube, Non-axisymmetric Shape, Variable Cross Sections, Sealing Problem, Lead Patch

During roll forming a sheet metal is continuously and progressively formed into a product of the required cross-section and longitudinal shape. An example product is a circular tube with a required diameter, wall-thickness and straightness. Roll forming occurs by passing the sheet through a series of forming rolls that are arranged in tandem. Each pair of forming rolls in the roll forming line plays a particular role in obtaining the required cross-section and longitudinal shape in the product. In recent years, that process is often applied to car body parts by automotive industries. In the current study, an optimal model design and proper roll-pass sequences as well as the number of forming rolls and bending angles were used to produce a sill side. The effects of the process parameters on the final shape formed by roll forming defects were evaluated.

Functionally graded properties are characterized by the gradual variation in composition and structure through the volume of the material, resulting in corresponding gradation in properties of the material. Direct laser melting (DLM) is a prototyping process whereby a 3-D part is built layer-wise by melting metal powder with laser scanning. Studies have been performed on the functionally graded properties induced by direct laser melting of compositionally selected metallic powders. For the current study, quadrangle structures were fabricated by DLM using Fe-Ni-Cr powders having variable compositions. Hardness and EDX analysis were conducted on cross-sections of the fabricated structure to characterize the properties. From the analysis, it is shown that functionally graded properties can be successfully obtained by DLM of selected metallic powders with varying compositions.

Bursting during tube hydroforming is preceded by localized necking. The retardation of the initiation of necking is a means to enhance hydroformability. Since high strain gradients occur at the necking sites, a decrease in local strain gradients is an effective way to retard the initiation of necking. In the current study, the expansion at potential necking sites was intentionally restricted in order to reduce the strain gradient at potential necking sites. From the strain distribution obtained from FEM, it is possible to determine strain concentrated zones, which are the potential necking sites. Prior to the hydroforming of a trailing arm, an incompressible material(such as lead) is attached to the tube where the strain-concentrated zone would contact the die. Due to the incompressibility of lead, the tube expansion is locally restricted, and the resultant strain extends to adjacent regions of the tube during hydroforming. After the first stage of hydroforming, the lead is removed from the tube, and the hydroforming continues to the final targeted shape without any local restriction. This method was successfully used to fabricate a complex shaped automotive trailing arm that had previously failed during traditional hydroforming fabrication.

The use of roll-formed products increases every year due to its advantages, such as high production rates, reduced tooling cost and improved quality. However, till now, it is limited to part profiles with constant cross section. In recent years, the flexible roll forming process, which allows variable cross sections of profiles by adaptive roll stands, was developed. In this study, an attempt to optimize profile design for the flexible roll forming process was performed. An equation that predicts the longitudinal strain for part geometries with variable cross-sections was proposed. The relationship between geometrical parameters and the longitudinal strain was analyzed and investigations on the optimal profile design were performed. Experiments were conducted with a lab-scale roll forming machine to validate the proposed equation. The results show that the profile design method proposed in this study is feasible and parts with variable cross sections can be successfully fabricated with the flexible roll forming process.

Direct Laser Melting is a prototyping process whereby a 3-D part is built layer wise by melting the metal powder with laser scanning. This process is strongly influenced by the shielding gas and the laser operating parameters such as laser power, scan rate, layering thickness, and rescanning. The shielding gas is especially important in affecting the microstructure and mechanical properties. In the current study, fabrication experiments were conducted in order to analyze the effect of shielding gas on the forming characteristics of direct laser melting. Cylindrical parts were produced from a Fe-Ni-Cr powder with a 200W fiber laser. Surface quality, porosity and hardness as a function of the layering thickness and shield gas were evaluated. By decreasing the layering thickness, the surface quality improved and porosity decreased. The selection of which shield gas, Ar or , to obtain better surface quality, lower porosity, and higher hardness was examined. The formability and mechanical properties with a atmosphere are better than those parts formed under an Ar atmosphere.

Tube hydroforming is a technology that utilizes hydraulic pressure to form a tube into desired shapes inside die cavities. Due to its advantages, such as weight reduction, increased strength, improved quality, and reduced tooling cost, single-layered tube hydroforming is widely used in industry. However in some special applications, it is necessary to produce multi-layered tubular components which have corrosion resistance, thermal resistance, conductivity, and abrasion resistance. In this study, a hollow forming process to fabricate a part from multi-layered tubes for structural purposes is proposed. To accomplish a successful hydroforming process, an analytical model that predicts optimal load path for various parameters such as tube material properties, thickness of tubes, diameter of holes and the number of holes was developed. Tubular hydroforming experiments to fabricate a hollow part were performed and the optimal loading path developed by the analytical model was successfully verified. The results show that the proposed hydroforming process can effectively produce hollow parts with multi-layered tube without defects such as wrinkling or fracture.

The most important parameters in success of tube hydroforming process are internal pressure and axial force loading paths. Theoretical calculations and finite element trial-and-error simulations to find the optimum loading paths are so time-consuming and costly. In this paper, pressure and force loading paths in tube hydroforming process are investigated and optimized using Simulated Annealing optimization method. The final aim is to obtain the optimal loading paths for tube hydroforming of axisymmetric geometries under a failure criterion based on the maximum allowable thinning and von-Mises stress. Simulated Annealing algorithm is directly incorporated into the non-linear structural finite element code ANSYS/LS-DYNA to analyze the forming parameters. This novel approach is validated by experiments on ASTM C11000 copper tubes. The results are also compared and verified with another literature, in which a good correlation is obtained. Less thinning and better shape conformation is attained using the optimized parameters.

Hydroforming has attracted the attention of manufacturing industries for vehicles and transportation systems. A wide range of products such as subframes, camshafts, radiator frames, axles and crankshafts are made by the hydroforming process. Hydroformed parts often need to be structurally joined to other components during assembly. Therefore it is useful if the hydroformed automotive parts can be attached with a localized flange. In this study, a hydroforming process to produce a rectangular shape flange is proposed. FE analysis to form the flanged rectangular shape was performed by Dynaform 5.5. The hydroforming characteristics at various die aspect ratios and feeding conditions were analyzed and optimal process conditions which can avoid defects are suggested. For validation purposes, hydroforming experiments to form the flange were conducted with the optimized conditions. The results show that the flanged parts can be successfully formed with a hydroforming process without additional processing steps.

Direct laser melting(DLM) is promising as a joining method for producing parts for automobiles, aerospace, marine and medical applications. An advantageous characteristic of DLM is that it affects the parent metal very little. The mechanical properties of parts made by DLM are strongly affected by the porosity and surface roughness of the laser melted beads. This is a systematic study of the effects of the porosity and surface roughness of laser melted beads using various processing parameters, such as laser power, scan rate and overlapping ratio of the fill spacing. The specimens were fabricated with 316L and 304L austenitic stainless steel powder. Dense parts with low porosity were obtained at low laser scan speed, as it increased the aspect ratio of the parental material and the depth of penetration. The variations of surface roughness were examined at various processing parameters such as overlapping ratio and laser power.

The combination of tailor welded blank (TWB) and hot stamping often offers improved crash-worthiness and reduced mass of stamped parts in the automobile body. To investigate the formability of laser TWB and the reliability of weld line, the present study used 22MnB5 boron steel sheet of the same thickness and used the Erichsen cupping test at elevated temperatures. The effects of laser direction, die temperature, weld line positions and forming speed on formability(the limiting dome height) were studied and the results were compared with the formability of the base material.

CSD is IEEE Stan없rd 802.15.4b based Container Security Device which is proposed by the U.S Department of Home Security. It is mounted inside the container to sense opening of the container door. ConTracer is the CSD which is developed in this research whose major features are sensing door opening status as well as history inquiring on internal environment and shock to the container by mounting the temperature/humidity/shock sensors. Moreover, its RFID frequency bandwidth uses 2.4GHz 10 correspond actively to the radio regulations used by different countries. This. paper introduces the development trend of CSD, compares the ConTracer which is developed thru this research and other company`s CSD, and introduces CSD System which is designed and established using ConTracer. Finally, the implemented CSD System is verified by applying the demonstration service to container distribution between Korea and Japan.

Manufacturing of the bipolar plate of a direct methanol fuel cell (DMFC) by direct laser melting technology (DLM) was attempted. The DLM technology is highly influenced by process parameters such as laser power, scan rate and layering height. Therefore, an analysis of the DLM technology was performed under various conditions. The bipolar plates were fabricated using the DLM process with 316L stainless steel (STS 316L) plates and powder. Powder melting trials at various energy density were performed in order to select a feasible melting range for a given laser power. The melting line height increases and eventually saturates when the energy density increases, but decreases when the laser power increases at a given energy density. For the estimation of the potential performance of the bipolar plate, the surface roughness and contact resistance of the DLM layer were also analyzed. The changes of line height and thickness are useful information to report when manufacturing bipolar plate of fuel cell through the DLM process.

Selective laser melting (SLM) is emerged as a new manufacturing technique to directly fabricate precise parts using metallic materials. The final characteristics of a component fabricated through the SLM process are strongly dependent upon various parameters such as laser power, scan rate and pulse duration, etc. This paper, therefore, focuses on the dimensional characteristics of melted 20㎛ Fe-Cr-Ni powder by fiber laser for the selective laser melting process. With energy density decrease, the height and depth were decreased. Although the conditions are of the same energy density, the shape is different by laser power and scan rate. The shapes at various laser parameters were divided into 3 groups based on depth over height. The smooth regular shape is obtained under the conditions of 50㎛ of powder height and 15-20㎲ of pulse duration. And the laser power influenced the variation of shape more significantly than the scan rate. Key Words : Selective Laser Melting(SLM), Fiber Laser, 20㎛ Fe-Cr-Ni Powder, Processing Parameters, Melted Shape

Double layered tube that has been used for transportation and oil piping system is occasionally exposed to elevated temperature. The change in stress state at elevated temperature is important for the safe design of double layered tube. In this study, the variation of stress state for hydroformed double layered tube of which inner tube is stainless steel and outer tube is mild steel has been analytically analyzed. To characterize the thermal stress at elevated temperature, analytical model to provide thermal stresses between outer tube and inner tube was developed by using theories of elasticity and Lame equation. The feasibility of analytical model is verified by finite element analysis using ANSYS CLASSIC TM , commercially available code. The variation of thermal stress at various thickness combination of inner and outer tube has also been investigated by proposed analytical model. Key Words : Double Layered Tube, Tube Hydroforming, Thermal Stress, Coefficient of Linear Expansion

Hydroforming is the technology that utilizes hydraulic pressure to form tube or sheet materials into desired shapes inside die cavities. Tube hydroforming provides a number of advantages over the conventional stamping process, including fewer secondary operations, weight reduction, assembly simplification, adaptability to forming of complex structural components and improved structural strength. In many case, hydroformed parts have to be structurally joined at some point. Therefore it is useful if the hydroformed automotive parts can be given a localized attachment flange. In this study for the numerical process design FE analysis was performed with DYNAFORM 5.5. Die parting angle and circumferential expansion ratio was optimized. With optimized condition, bulge and hydroforming experiments to form flange were performed. Forming characteristic at various pressure conditions was analyzed and optimized internal pressure condition was evaluated. The results show that flanged parts can be successfully produced by tube hydroforming process.

Hydroforming has attracted a great deal of attention in the manufacturing industries for vehicles and transportation systems. Hydroforming technology contributes to weight reduction, increased strength, improved quality and reduced tooling cost. Hydroformed automotive parts used as structure components in vehichle body frame often have to be structurally joined at some point. Therefore it is useful if the hydroformed automotive parts can be given a localized attachment flange. For a given flange shape, a parting plane for the dies is established relative to which the various surfaces of the flange shape, in cross section, have no significant reverse curvature. In this study, hydroforming process for flange forming was proposed. FE analysis to form flanged circular shape and flanged rectangular shape was preformed with Dynaform 5.5. To accomplish successful hydroforming process design, thorough investigation on proper combination of process parameters such as tool geometry and hydraulic pressure has been performed and optimized. The results show that flanged automotive parts can be successfully produced with tube hydroforming.

Thermal energy control is a important factor to control properties of large sized product in ingot-forging. Good control of thermal energy helps to increase characteristics and eliminate defects of large cast-forged part, such as large sized forged shell. We have studied about not only large size ring forging process and after heat treatment process by FEM simulation. Changes of temperature and microstructure for forged shell were predicted according to different heat treatment conditions. Therefore, we can choose the proper heat treatment condition by FEA. The sectional properties confirmed by practical experiment and evaluation have presented possibilities of process design by computational analysis.

Strain hardening behavior during hydroforming has been experimentally investigated. The variation of flow stress was used as an index of strain hardening during respective processes and the flow stress was estimated from the correlationship between flow stress and effective strain. The local hardness after hydroformig was also predicted by effective strain. By using the inter-relationships between hardness-flow stress-effective strain at variable pre-strains, the strain hardening behavior during hydroforming has been successfully analyzed. The comparison of predicted hardness with measured hardness confirmed that the methodology used in this study was feasible and the strain hardening behavior can be quantitatively estimated.

It is well known that flavanones, sophoraflavanone G 1 , kurarinone 2 , and kurarinol 3 , from the root of Sophora flavescens, have extremely strong tyrosinase inhibitory activity. This study delineates the principal pharmacological features of kurarinol 3 that lead to inhibition of the oxidation of l -tyrosine to melanin by mushroom tyrosinase (IC 50 of 100 nM). The inhibition kinetics analyses unveil that compounds 1 and 2 are noncompetitive inhibitors. However similar analysis shows kurarinol 3 to be a competitive inhibitor. Compounds 1 and 2 exhibited potent antibacterial activity with 10 μg/disk against Gram-positive bacteria, whereas kurarinol 3 did not ostend any antibacterial activity. Interestingly, kurarinol 3 inhibits production of melanin in S. bikiniensis without affecting the growth of microorganism. It is thus distinctly different from the other tyrosinase inhibitors 1 and 2 . In addition, kurarinol 3 manifests relatively low cytotoxic activity (EC 50 >30 μM) compared to 1 and 2 . To account for these observations, we conducted molecular modeling studies. These suggested that the lavandulyl group within 3 is instrumental in the interaction with the enzyme. More specifically, the terminal hydroxy function within the lavandulyl group is most important for optimal binding.

Sidewall curl is the curvature that results from non-uniform through-thickness strain present in the sheet stamping process which involves material flow over a die radius. In order to understand and control curl for tight fit-up tolerances, an analytical model that can provide a reliable measure for the amount of curl would be very helpful. In this study, a model is developed based on the moment-curvature relationship during bending-under-tension operations. For the verification of analytical model, sidewall curl is experimentally measured after deformation of a strip using a bending-under-tension test system. The results show a consistent relationship between the theoretically predicted value and the experimentally obtained one, especially in regions of high curl.

Hydroformability and fracture criteria of FE analysis based on ductile fracture were investigated in warm hydroforming of A16061 tube. To evaluate the hydroformability, uni-axial tensile test and bulge test were performed at room temperature and . The measured flow stresses were used as input parameters for FE analysis. The damage values were calculated by FE analysis based on ductile fracture criteria at maximum radius of free bulged tubes. Damage values were compared of hexagonal shaped hydroformed parts. As a result, the formability by critical damage value for extruded tube is lower than that of full annealed tube up to 0.5.

Sidewall curl is the curvature that results from non-uniform through-thickness strain present in the sheet stamping process which involves material flow over a die radius. In order to understand and control sidewall curl for tight fit-up tolerances, an analytical model that can provide a reliable measure for the amount of curl would be very helpful. In this study, a model is developed based on the moment-curvature relationship during bending-under-tension operations. The analytical model includes the variables of applied tensile force, the yield strength, the elastic modulus, the bending radius, and the sheet thickness, which are the primary factors affecting sidewall curl during sheet stamping operations. For the accuracy of analytical model, six possible deformation patterns are proposed on the basis of material properties and bending geometries.

The effects of yeast (Saccharomyces cerevisiae) culture (SC), fungal (Aspergillus oryzae) fermentation extract (AO) and non-ionic surfactant (NIS) as feed additives on dry matter intake (DMI) and milk production of dairy cow were investigated. Forty Holstein dairy cows were equally assigned to four treatments including the control in randomized block design, and fed the total mixed rations supplemented 20 g, 100 g and 50 mL day−1 head−1 for SC, AO and NIS during prepartum period, and 30 g, 150 g and 50 mL day−1 head−1 for SC, AO and NIS during postpartum period, respectively. Cows fed the diets supplemented SC or AO had greater (P

Cultures of the rumen anaerobic fungus, Piromyces communis strain 22 culture (AFC), filtered AFC and autoclaved AFC were evaluated for their ability to influence cumulative gas production, cellulose digestion, microbial population and enzyme activities by mixed ruminal microorganisms in vitro. The addition of AFC, filtered AFC and autoclaved AFC caused a marked increase in gas production, especially showing the significant ( P P

The non-ionic surfactant (NIS) was evaluated for its ability to influence rumen fermentation characteristics, microbial growth, enzyme activity and digestibility in the rumen of Korean native cows. The administration of NIS solution to the rumen significantly ( P 3 -N in rumen fluids, and the growth rate of rumen anaerobic microorganisms. In situ dry matter degradation rate of rice straw was significantly ( P 9 cfu per ml of rumen fluids) by NIS administration, compared to control ( P These results indicated that the addition of NIS could greatly stimulate the release of certain enzymes without decreasing cell growth rate in contrast to trends reported with aerobic microorganism. Our results showed that NIS might be of use as an alternative feed additive to stimulate multiple enzyme activity and microbial growth in the rumen.

Speeded up robust features (SURF) is one of the most popular feature extraction algorithms used for detecting, recognising, and tracking objects in various applications. However, it is not suitable for real-time implementation because its operating speed does not satisfy real-time constraints. In this Letter, operating speed is highly dependent on the amount of computations required for the Haar wavelet response (HWR) step, and present a fast descriptor extraction method that eliminates repeated operations in the HWR step is shown. Experimental results show that the proposed method (PM) can achieve operation time-savings of approximately 27% without using additional resources, while the descriptor extraction performance of the PM is exactly identical to that of the original reference software.

This paper presents an improved parallel processing uninterruptible power supply (UPS) for a strong grid using a bi-directional voltage-controlled voltage source inverter (VCVSI). To maintain the load voltage at the desired value and to control the active power flow between the VCVSI and grid, the amplitude and phase angle of the inverter output voltage (power angle) must be controlled. Selecting the power angle operating range is an important factor which has a direct effect on various parameters, such as the size of a decoupling inductor, grid power factor and the power ratings of VCVSI components. It is shown how the optimum power angles can be chosen and by restricting the operation of this, the power factor can be maintained above 0.9 at different loads and operating conditions. The paper examines the steady state modeling and analysis of a single phase parallel processing UPS while maintaining a high system power factor under different conditions. Experimental and simulation results of a prototyped 1 KVA VCVSI confirms the validity of the proposed method.

Radio frequency identification (RFID) technology is an automatic identification method using radio frequencies between RFID readers and tags. In RFID systems, tag collection is very important issue to collect data from all the tags in reader communication range using anticollision algorithm. There are several researches to develop the efficient anticollision algorithm, but they almost focus on passive RFID systems and show the simulation results. This paper focuses on tag collection in active RFID systems complying with ISO/IEC 18000-7 standard. We propose the modified tag collection algorithm based on the standard and develop an active RFID reader and tags which comply with ISO/IEC 18000-7 and utilize the modified algorithm. As the experiments are achieved with a reader and 30 tags in the real-world environment, the modified algorithm shows better performance of tag collection than the standard algorithm in our active RFID system.

Several practical intelligent setting schemes that consider the effect of df/dt are suggested and simulated for a power system operating in an underfrequency situation. Considerations for df/dt relay setting are discussed. These intelligent setting schemes have made a positive improvement in the underfrequency condition. As an extension of these new intelligent control schemes, a microcontroller based intelligent under/over frequency relay is introduced. With its advanced hardware and intelligent software, this microcontroller has the advantages of high flexibility, less cost, and high communication ability. >

This paper presents the Hessenberg method, a new sparsity-based small signal stability analysis program for large interconnected power systems. The Hessenberg method as well as the Arnoldi method computes the partial eigen-solution of large systems. However, the Hessenberg method with pivoting is numerically very stable comparable to the Householder method and thus re-orthogonalization of the Krylov vectors is not required. The fractional transformation with a complex shift is used to compute the modes around the shift point. The program has been successfully tested on the New England 10-machine 39-bus system and Korea Electric Power Co. (KEPCO) system in the year of 2000, which is comprised of 791-bus, 1575-branch, and 215-machines. The method is so efficient that CPU time for computing five eigenvalues of the KEPCO system is 3.6 sec by a PC with 400 MHz Pentium II processor.

A new efficient, robust and unified strategy is presented to compute the saddle node bifurcation (SNB) by the combined use of the continuation power flow (CPF), point of collapse (PoC) method and the method of a pair of multiple load flow solutions (PMLFS) with Lagrange interpolation utilizing only their advantages. The approximate nose curves and critical loading is determined fast by interpolating two stable and two unstable solutions using the PMLFS and robust CPF, and the exact SNB is computed using the quadratically converging PoC method. The proposed method is so efficient that computation time for determining the SNB in Korea Electric Power Co. (KEPCO) 791-bus system is about 24 sec in PC with Pro-Pentium processor, 166 MHz. Presented is also an improved direct method for calculating the closest SNB (CSNB) where the structure and size of the nonlinear systems equations is the same as those of the PoC method. It is shown with Klos-Kerner 11-bus system that voltage stability may be improved significantly by shifting generations in the direction of the left eigenvector at the CSNB.

Direct stability analysis using an energy function has recently been widely used for angular and voltage stability analysis in electric power systems. Considerable efforts have concentrated on seeking energy functions for lossy power systems, accomplished only for the simple two-bus system. A new approach is presented to derive an energy function by using the complex integral of bus current equations with respect to bus voltages. Under an assumption that all transmission lines have a uniform R/X ratio, it is shown that the energy function can be developed for multimachine power systems with losses. The proposed energy function is tested on sample systems by comparing the time simulation method, which shows the validity of the proposed method.