Search

This study presents chemical vapor deposition (CVD) growth of high-quality monolayer graphene on 100 nm-thick Pt thin films deposited on TiO2-coated silicon wafers. Conventional graphene growth on ...

This article presents the fabrication and characterization of on-diaphragm Pt thermistors for temperature-compensated calibration of piezoelectric pressure sensors. The micromachined pressure-sensitive diaphragms are 700 $\mu \text{m}$ in diameter and employ AlN as the piezoelectric material. The thermistors reside on top of the diaphragms and are patterned into a 100-nm-thick sputtered Pt electrode layer. Experimental characterization up to 600 °C demonstrates the importance of annealing to realize hysteresis-free resistance vs. temperature characteristics. Dynamic frequency response measurements of the pressure-sensitive diaphragms vs. temperature demonstrate a marked shift in compliance with temperature, and therefore demonstrates the importance of temperature-compensated pressure calibration in high-temperature measurement environments.

A microelectromechanical-system piezoelectric pressure sensor targeting hypersonic flow applications is presented. The sensing diaphragms have 500- $\mu \text{m}$ diameter and are comprised of a composite stack of Si, SiO2, and AlN. This paper presents the fabrication and packaging details of the sensor and then presents test results from a Mach-6 hypersonic-flow facility, in which the prototype sensor data are compared against data from a mature commercial sensor present in the same tests. Salient hypersonic-flow features are observed in signals captured by the prototype. The package is comprised of an on-chip two-element array with 650- $\mu \text{m}$ pitch, and signals from the elements captured during hypersonic-flow tests are highly correlated. [2018-0196]

The armed forces of major nations have utilized modeling and simulation technologies to develop weapon systems corresponding to changing modern battlefields and reducing the development cycle. However, model design is complex owing to the characteristics of current weapons, which require multiple functions. Therefore, this study proposes a method to support the automated design of weapon system models for simulation. We apply module-based modeling and an intelligent modeling process to our devised method. The former formalizes constituents and constraints regarding an element combination to design the required model, while the latter applies case-based reasoning (CBR) to intelligentize the modeling process based on the results of the former. Using a case study, our proposed method demonstrates that models that respond to operational circumstances can be designed based on simulation results. Consequently, when weapon systems can be represented in formalized structures and constituents, the weapon models can be reusable based on the addition, modification, and replacement of modules in the common structure. The CBR process can provide the models that satisfy the requirements by retrieving similar models and modifying the models. The proposed method is applicable to the process of weapon system design or improvement for changing battlefields.

This paper presents a microelectromechanical-system (MEMS) piezoelectric pressure sensor for measurements in hypersonic flows at extreme temperatures (>1000 °C). 700-µm diameter diaphragms are surface- and bulk-micromachined and employ aluminum nitride as the sensing material due to its potential for high-temperature operation. Novelty claims include the following: (1) First demonstration of MEMS piezoelectric pressure sensor to capture hypersonic-flow-specific features in field measurements, including shock waves and second-mode instabilities associated with laminar-to-turbulent transition, (2) Successful audio capture while the sensor is immersed in a butane flame, demonstrating operation at extreme temperatures, and (3) First dynamic pressure sensor to include on-diaphragm thin-film platinum temperature sensors for high-temperature readout.

Nesting is a common problem in industries such as shipbuilding, auto-maker, clothing, shoe-making, and furniture, in which various parts are cut off from a stock or stocks while minimizing the wastes or maximizing the utilization of the stock. Berth allocation at seaside is also considered one form of two dimensional nesting problems, in which a ship is assigned a location for service during a certain time slot. This paper presents an expert system using a heuristic search method for nesting problems. The parts and stocks are represented by pixels with which utility function is used to evaluate current state in search tree. The system is developed in CLIPS, an expert system shell and applied to various example problems with different constraints and to a berth allocation example to illustrate its applicability under different conditions.

An undulator-based superradiant oscillator as a source of intense terahertz pulses is investigated in an open resonating cavity. A confocal configuration for the optical cavity is found to be favorable for electron-radiation coupling. Constructive accumulation of superradiance over successive bunches of electrons is achieved if the bunch period is an even multiple of the round-trip time of the radiation pulse. Numerical simulations show that the bunch slippage relative to the radiation pulse determines the pulse width and the corresponding bandwidth. Automatic bunch-pulse positioning with which energy extraction is optimized is also observed, as was first observed in a closed-cavity environment.

Recently in the field of defense Modeling and Simulation (M&S), Component-Based Development technology is widely applying to save the cost and increase the reusability of weapon system development. Related with this, researches for rapid reconfiguration and simulation of the component-standardized weapon system is actively carrying out. To rapidly reconfigure the new weapon system, complex and various functions of component information has to be effectively searched. So, it requires differentiated search technique unlike existing Keyword-based Search method. Semantic Search System provides semantically related information among the extensive information. In this research, metadata of weapon system components and their representative functional words are built as an ontology. And it provides an ontology-based semantic search system.Key words : Ontology, Metadata, Weapon system, Component, Semantic search요 약최근 국방 분야의 모델링 및 시뮬레이션 (M&S)에서는 무기체계의 개발비용을 절감하고 재사용성을 높이기 위해 컴포넌트 기반 개발(Component Based Development) 기술을 사용한다. 이와 관련해서 무기체계를 컴포넌트로 표준화하여 신속히 재구성 및 시뮬레이션하기 위한 연구가 수행되고 있다 . 복잡하고 다양한 기능의 컴포넌트 정보를 검색하여 신 무기체계로 신속히 재구성하기 위해서는 기존의 키워드 검색방식과는 차별화된 검색 기법이 요구된다 . 이를 보완하기 위해 방대한 정보 사이에서 의미적으로 연관된 정보를 제공하는 시맨틱 검색 시스템 (Semantic Search System) 구축이 필요하다. 본 연구에서는 무기체계 컴포넌트 메타데이터와 이들의 대표적인 기능속성을 표현하는 용어들을 온톨로지 (Ontology) 로 구축하고 이를 활용한 시맨틱 검색 시스템을 제안한다 .주요어 : 온톨로지, 메타데이터, 무기체계, 컴포넌트, 시맨틱 검색

Ship block assembly planning is very complex due to the various activities and characteristics of ship production. Therefore, competitiveness in the shipbuilding industry depends on how well a company operates its ship block assembly plan. Many shipbuilders are implementing various studies to improve their competitiveness in ship block assembly planning, specifically regarding technology usage, such as modeling and simulation (M&amp, S) and Cyber-Physical Systems (CPS). Although these technologies are successfully applied in some production planning systems, it is difficult to tailor ship production planning systems with flexibility due to unexpected situations. Providing a flexible plan for these production planning systems requires a way to describe and review the organic relationships of ship production processes. In this research, a process-based modeling (PBM) method proposes a novel approach to describing the production process of ship block assembly planning by redefining production information based on changing instructions. The proposed method consists of four modeling steps. The first creates a unit model, which includes the products, processes, and resource information for the block. The second designs an integrated network process for linking unit models according to the bill of materials (BOM). The third creates a process-based model that describes the production processes by combining unit models. The fourth generates a simulation model by applying a Petri-net to the process-based model, which analyzes the productivity of the ship&rsquo, s block assembly processes. PBM identifies the assembly process&rsquo, interrelationship and shows that productivity can be reviewed to uncover ship production problems.

Three-dimensional (3D) thermal drawing at nanoscale as a novel rapid prototyping method was demonstrated to create multidirectional polymer nanoprobes for single cell analysis. This 3D drawing enables simple and rapid fabrication of polymeric nanostructures with high aspect ratio. The effect of thermal drawing parameters, such as drawing speeds, dipping depths, and contact duration on the final geometry of polymer nanostructures was investigated. Vertically aligned and L-shaped nanoprobes were fabricated and their insertion into living single cells such as algal cells and human neural stem cells was demonstrated. This technique can be extended to create more complex 3D structures by controlling drawing steps and directions on any surface.

A theoretical maximum achievable signal to noise ratio (SNR) for piezoelectric microphones is identified as a function of only microphone volume irrespective of architecture and construction details. For a given piezoelectric material, microphone SNR can be reduced to an expression containing only a dimensionless coupling coefficient and microphone volume. For a given material, the coupling coefficient has a theoretical upper bound defined by the most favorable deformation geometry. The ability to identify a theoretical maximum SNR as a function of only microphone size is surprising considering the numerous design variables and infinite design freedom afforded in the microphone design stage.

Micromachined, piezoresistive-sensed diaph- ragms are designed and fabricated specifically for infrasound sensing applications. Relatively large diaphragms, up to 6 mm $\times6$ mm, are fabricated to meet the high sensitivity requirements of infrasonic monitoring. A double-stack SOI wafer process is used, resulting in a streamlined two-mask process without the need for doping or ion-implantation. Pressure-sensitivities of diaphragms are studied using a custom static calibration set-up. The piezoresistance of longitudinal and transverse resistors are studied over a large pressure range of ±5,500 Pa so that the linear and nonlinear response regions of diaphragms are observed. Measurements are compared against a nonlinear finite element simulation—shown to accurately predict the sensor’s behavior over a large response range.

The Test and Evaluation (TE United States. This area of study requires new way of developing strategies in the T&E system of Korea. This study is to design the Operational T&E system for weapon systems based on modeling of processes. And we modeled the processes of operational performance evaluation through utilizing resources and performance modules of weapon systems and combined it with the simulation engine for 3D visualization. Through this, we propose the Operational T&E system for weapon systems based on modeling of processes that represent operational performances visually.

The undulator superradiance of periodic electron bunches in an optical cavity excites many cavity modes over an ultra-wide band. The interaction dynamics involves a coherent potential well constructed by many tiny ponderomotive potentials provided by individual modes. Decoherence between these tiny potentials is caused mainly by the slippage between the bunch and the radiation pulse. The overall influence of the ultra-wide band, however, does not alter the scaling law for the energy-conversion efficiency established in the single-mode interaction.

Machines and automated guided vehicles (AGVs) scheduling problems are two essential issues that need to be addressed for the efficiency of the overall production system. The purpose of this paper is to study the simultaneous scheduling problem of machines and AGVs in a flexible manufacturing system (FMS) since the global optimum cannot be reached by considering each of them individually. In this paper, a mixed integer linear programming (MILP) model is developed with the objective of makespan minimisation. The MILP model consists of the following two constraint sets: machines and AGVs scheduling sub-problems. As both sub-problems are known to be NP-hard, a heuristic algorithm based on tabu search (TS) is proposed to get optimal or near to optimal solution for large-size problems within reasonable computation time. The proposed algorithm includes a novel two-dimensional solution representation and the generation of two neighbour solutions, which are alternately and iteratively applied to improve solutions....