Data perturbation for fewer triangles in marching tetrahedra

A simple efficient method is proposed to reduce the total number of triangles in an isosurface extraction method based on tetrahedral decomposition. We slightly perturb the input volumetric data so that useless small and thin triangles are removed. The perturbed volumetric data contain the exact isovalues from which a mesh is extracted. Since the proposed method is a pre-process of an isosurface extraction, it is not necessary to modify the mesh structure unlike the other similar methods.     

Au–Sn flip-chip solder bump for microelectronic and optoelectronic applications

As an alternative to the time-consuming solder pre-forms and pastes currently used, a co-electroplating method of eutectic Au–Sn alloy was used in this study. Using a co-electroplating process, it was possible to plate the Au–Sn solder directly onto a wafer at or near the eutectic composition from a single solution. Two distinct phases, Au₅Sn (ζ-phase) and AuSn (δ-phase), were deposited at a composition of 30 at.%Sn. The Au–Sn flip-chip joints were formed at 300 and 400°C without using any flux. In the case where the samples were reflowed at 300°C, only an (Au,Ni)₃Sn₂ IMC layer formed at the interface between the Au–Sn solder and Ni UBM. On the other hand, two IMC layers, (Au,Ni)₃Sn₂ and (Au,Ni)₃Sn, were found at the interfaces of the samples reflowed at 400°C. As the reflow time increased, the thickness of the (Au,Ni)₃Sn₂ and (Au,Ni)₃Sn IMC layers formed at the interface increased and the eutectic lamellae in the bulk solder coarsened.     

Effect of displacement rate on ball shear properties for Sn–37Pb and Sn–3.5Ag BGA solder joints during isothermal aging

The interfacial reactions and ball shear properties of ball grid array (BGA) solder joints aged at 170 °C for up to 21 days were investigated with different displacement rates. Two different kinds of solders, Sn–37Pb and Sn–3.5Ag (all wt.%), and an electroplated Ni/Au BGA substrate were employed in this work. A continuous Ni₃Sn₄ intermetallic compound (IMC) layer was formed at the interfaces between both the Sn–37Pb and Sn–3.5Ag solders and the substrate during reflow. After aging, two different reaction layers, consisting of (Au_xNi_1−x)Sn₄ IMC and Pb-rich phase, were additionally observed between the Sn–37Pb solder and the Ni₃Sn₄ IMC layer. The thicknesses of these interfacial reaction layers increased with increasing aging time. After reflow, all the fractures occurred inside the bulk solder. The fracture location of the Sn–37Pb solder joints was shifted toward the solder/Ni interface with increasing aging time and displacement rate, whereas the fracture of the Sn–3.5Ag solder joints mainly occurred inside the bulk solder, irrespective of the aging time and displacement rate. Consequently, the shear properties of the Sn–37Pb solder joints significantly decreased with increasing aging time, whereas those of the Sn–3.5Ag solder joints slightly decreased. The tendency toward brittle fracture of the Sn–37Pb solder joints was intensified with increasing displacement rate. The shear properties of the ductile solder joints increased with increasing displacement rate, while the displacement until fracture, deformation energy and displacement rate sensitivity of the brittle solder joints significantly decreased with increasing displacement rate.     

Frequency-Domain Measurement Method for the Analysis of ESD Generators and Coupling

A method for analyzing electrostatic discharge (ESD) generators and coupling to equipment under test in the frequency domain is proposed. In ESD generators, the pulses are excited by the voltage collapse across relay contacts. The voltage collapse is replaced by one port of a vector network analyer (VNA). All the discrete and structural elements that form the ESD current pulse and the transient fields are excited by the VNA as if they were excited by the voltage collapse. In such a way, the method allows analyzing the current and field-driven linear coupling without having to discharge an ESD generator, eliminating the risk to the circuit and allowing the use of the wider dynamic range of a network analyzer relative to a real-time oscilloscope. The method is applicable to other voltage-collapse-driven tests, such as electrical fast transient, ultrawideband susceptibility testing but requires a linear coupling path.     

Fabrication of a 3-dimensional microstructure by sequential anodic oxidation (SAO)

Scanning probe lithography (SPL) has considerable potential for producing small features (<100 nm) with a high spatial precision, and would be useful for fabricating 2-dimensional (2D) structures. However, it has not been used successfully in the fabrication of 3-dimensional (3D) structures due to the low aspect ratio of the resulting feature. Herein, we describe a simple 3D pattering method with repeated SPL, in which precise layer-by-layer alignment is not needed. Results and processes of the pattern can be readily observed in real-time. Using the proposed method, we successfully fabricated a 3D pyramidal structure. Additional growth for repeated oxidation was observed due to the superposition of energy absorbed on the pre-oxidized species.     

In Planta Response of Arabidopsis to Photothermal Impact Mediated by Gold Nanoparticles

Biological responses to photothermal effects of gold nanoparticles (GNPs) have been demonstrated and employed for various applications in diverse systems except for one important class – plants. Here, the uptake of GNPs through Arabidopsis thaliana roots and translocation to leaves are reported. Successful plasmonic nanobubble generation and acoustic signal detection in planta is demonstrated. Furthermore, Arabidopsis leaves harboring GNPs and exposed to continuous laser or noncoherent light show elevated temperatures across the leaf surface and induced expression of heat‐shock regulated genes. Overall, these results demonstrate that Arabidopsis can readily take up GNPs through the roots and translocate the particles to leaf tissues. Once within leaves, GNPs can act as photothermal agents for on‐demand remote activation of localized biological processes in plants.     

Removing escrow from ciphertext policy attribute-based encryption

Attribute-based encryption (ABE) is a promising cryptographic primitive for fine-grained access control of distributed data. In ciphertext policy attribute-based encryption (CP-ABE), each user is associated with a set of attributes and data are encrypted with access policies on attributes. A user is able to decrypt a ciphertext if and only if his attributes satisfy the access policy embedded in the ciphertext. However, key escrow is inherent in ABE systems. A curious key generation center in that construction has the power to decrypt every ciphertext. We found that most of the existing ABE schemes depending on a single key authority suffer from the key escrow problem. In this study, we propose a novel CP-ABE key issuing architecture that solves the key escrow problem. The proposed scheme separates the power of issuing user keys into two parties: the key generation center and the attribute authority. In the proposed construction, the key generation center and the attribute authority issue different parts of secret key components to users through a secure two-party computation protocol such that none of them can determine the whole set of keys of users individually. We demonstrate how the proposed key issuing protocol can be applied in the existing CP-ABE scheme and resolve the key escrow problem.     

Development of Wall Climbing Robot System by Using Impeller Type Adhesion Mechanism

In this paper, we present a wall climbing robot system, called “LARVA”, developed for visual inspection of structures with flat surfaces. The robot has two differential driving wheels with a suspension and an adhesion mechanism. The adhesion mechanism is composed of an impeller and two–layered suction seals. It is designed to provide sufficient adhesion force and be controlled so that the robot can move freely on various wall surfaces. The static and aerodynamic modeling of the adhesion mechanism is given and the analysis of the adhesion mechanism, air leakage, and inner flow are carried out to be useful for the design as well as the control. Finally, the performances of the robot are experimentally verified on several kinds of walls and its feasibility is validated.     

A self-alignment crowned pulley design for high speed paper media transport systems

Misalignment of mechanical rolling elements such as belt and pulley causes catastrophic malfunctions of high speed paper feeding systems like automated teller machines (ATMs), printers, and copy machines. A combination of a crown pulley and a belt can be an effective self-alignment mechanism for the systems. In this paper, an equation of motion of the belt and pulley system is driven, verification tests are carried out, and a design improvement strategy is suggested for high speed paper media transport systems.     

Seismic response prediction for cabinets of nuclear power plants by using impact hammer test

An effective method to predict the seismic response of electrical cabinets of nuclear power plants is developed. This method consists of three steps: (1) identification of the earthquake-equivalent force based on the idealized lumped-mass system of the cabinet, (2) identification of the state-space equation (SSE) model of the system using input-output measurements from impact hammer tests, and (3) seismic response prediction by calculating the output of the identified SSE model under the identified earthquake-equivalent force. A three-dimensional plate model of cabinet structures is presented for the numerical verification of the proposed method. Experimental validation of the proposed method is carried out on a three-story frame which represents the structure of a cabinet. The SSE model of the frame is accurately identified by impact hammer tests with high fitness values over 85% of the actual frame characteristics. Shaking table tests are performed using El Centro, Kobe, and Northridge earthquakes as input motions and the acceleration responses are measured. The responses of the model under the three earthquakes are predicted and then compared with the measured responses. The predicted and measured responses agree well with each other with fitness values of 65-75%. The proposed method is more advantageous over other methods that are based on finite element (FE) model updating since it is free from FE modeling errors. It will be especially effective for cabinet structures in nuclear power plants where conducting shaking table tests may not be feasible. Limitations of the proposed method are also discussed.