bluuebunny/crossref_metadata_2025 huggingface dataset:
The Little Engine
Authors: Abrams Michael
Published: July 2018

This article focuses on research and development works in the field of silicon-gas turbine engines to enable them produce power for portable devices. Alan Epstein, a professor of aeronautics and astronautics at the Massachusetts Institute of Technology, and his team are working on tiny silicon gas-turbine engines that could soon power laptops or cell phones. The group chose pressurized gas bearings, which can hold more weight relative to their size as they get smaller. Thrust bearings with spiral grooves and holes in their centers are self-pumping and keep the rotor in the right position. Epstein’s group considered magnetic bearings early on, but found that in addition to the manufacturing difficulties, the magnetic materials had too Iowa Curie point and would not stay magnetic at the temperatures at which the engine would operate: Instead, they chose pressurized gas bearings, which conveniently can hold more weight relative to their size as they get smaller. Thrust bearings with spiral grooves and holes in their centers are self-pumping and keep the rotor free and in the right position. While there is clearly plenty of room for improving efficiency, the microengine may very well end up as the only significant way to power, say, a laptop, an iPod, or a soldier's thermal weapon sight, to say nothing of a palm-size plane.
Remodeling the Gulf
Authors: Brown Alan S.
Published: July 2018

This article discusses how researchers are rethinking the weather of the Gulf to protect investments as well as lives. The National Hurricane Center tracked Opal since its inception. Its central pressure, the motor that sustained its 150-mph winds, was lower than any storm that had not reached Category 5 severity. Met-ocean theorists believe that hurricanes stir up cold water from deep under the Gulf, which cools and weakens them. If any hurricane crosses the Loop Current, however, the warm water induces it to intensify and grow larger. This may account for the central zone’s large hurricanes. Storms in zones on either side of it are less intense. In the western zone, warm eddies that break away from the Loop Current intensify hurricanes only modestly. The Gulf is one of the nation’s greatest resources, supplying 30 percent of its oil and 20 percent of its natural gas. Gasoline and heating oil prices spiked in the aftermath of Katrina and Rita. By improving the structural integrity of its offshore infrastructure, industry can perhaps avoid an upset like that again. Producers clearly want to protect strategic assets.
Licensing Renewed
Authors: Testa Bridget Mintz
Published: July 2018

This article reviews that for the first time in a generation, utilities are starting the regulatory process to build nuclear reactors. There has been a virtual moratorium on new nuclear power plants in the United States during the past generation, and it has many causes. But one significant factor in the industry's decline was the Nuclear Regulatory Commission’s licensing process. There are now dozens of applications being submitted and approved for 20-year license renewals for established nuclear power plants. But before the nuclear power industry truly can be said to be reborn, new reactors must be constructed. The new rules allow for an early site permit and for a separate combined construction and operating license. Although the commission invited the nuclear power industry to test the two new processes when they were first announced, no company volunteered. One of the thorniest technical issues faced by the early applicants so far involves a new way of calculating, for a specific plant site, the ground motion that would result from a seismic event. When older plants were designed and built, the best available technique for these calculations was deterministic.
Seeing Mechanical
Authors: McCormick David
Published: July 2018

This article reviews a case for advancing the role of sketching in the art of engineering. Engineers have adopted productivity tools that promise more predictable outcomes. Computer-aided design, for example, is one of those tools. The evolution of design documentation made a huge advance when engineers no longer defined their designs in the universal graphics language known as orthographic projection drawings. Engineers now create a 3D simulation of the solid design instead of creating 2D representations of views. The 3D CAD process is closer to sculpting the design than drawing it. Sketches are part of a successful design process acting as a channel between creative engineering thinking and critical engineering thinking. Visualizing a design prepares the way to more traditional analytical engineering activities. In this early phase, engineering decisions are being made with little if any data. Intuition is a guide to get the project to a point where data can be collected and analyzed.
Digital Product Development
Authors: Burgess Mark A.
Published: July 2018

This article discusses changes in the digital product development. Advances in computing power are multiplying the capabilities of design engineers. Information technology has advanced at a tremendous pace. Developers of design systems have exploited this capability with sophisticated mathematics, and today's systems are capable of producing very complex designs in much higher definition than ever before. Advances in geometric modeling have made it possible to represent 3-D solids in minute detail. Process modeling, which began with the study of a single manufacturing process, eventually gave way to complete factory flow simulations. The recent advances in IT enabled crossing the boundaries among technology, geometry, and process modeling with integrated computer-aided engineering, computer-aided design, and process planning. Current trends have now extended process modeling throughout the integrated supply chain and the extended enterprise.
Working Backward
Authors: Thilmany Jean
Published: July 2018

This paper discusses role of reverse engineering in biomedical and other bioscience applications. Reverse engineering is one of the most relevant examples of methods that have moved from engineering to find a role in biomedical and other bioscience applications. For an early introduction to the method's use in both biomedical and engineering fields, reverse engineering is commonly taught to biomedical undergraduates. Scientists in the biomedical hybrid fields of systems and synthetic biology call upon reverse engineering in ways that may look foreign to the practicing mechanical or electrical engineer—or even to the practicing biomedical engineer. The paper also highlights that synthetic biology, a new area of research, focuses solely on designing and building new biological systems. Synthetic biology often focuses on ways of taking parts of natural biological systems, characterizing and simplifying them, and using them as components of an engineered, biological system. According to critics, biological circuits can be integrated into organisms to change their interactions or products or, ultimately, to synthesize fundamentally new and possibly hazardous organisms. The new field of study—like all other fields encompassed by biomedical engineering—has seen fit to use reverse engineering as an everyday tool.
The Most Hazardous and Dangerous and Greatest Adventure on Which Man has Ever Embarked
Authors: Dicht Burton
Published: July 2018

This report highlights on run-up to success, the American space program that had absorbed a series of high-profile embarrassments as the Soviet Union, with which the United States was competing in a so-called Space Race, seemed to remain one step ahead. To declare so publicly the goal to land a man on the moon before the end of the decade was to risk another humbling loss. At the time, the public spotlight shined on the face of the space program, the astronauts who had already become national heroes. One of the biggest issues to settle was the mission architecture—the steps through which spacecraft would be launched, landed on the moon, and returned safely. The engineers who designed the remarkable pieces of space hardware were only a part of the overall Apollo team. Thousands of engineers were involved in launch processing and monitoring the flights. In an era when computer systems were primitive compared to what we have today, constant communication between the astronauts and an army of engineers back in Houston was critical to ensure the safety of the astronauts as well as the success of the mission.
Benefits and Challenges of Pressure-Gain Combustion Systems for Gas Turbines
Authors: Brophy Chris , Roy Gabriel
Published: July 2018

This article discusses benefits and challenges of Pressure-Gain Combustion Systems for Gas Turbines. The article also highlights that one approach to substantially improve gas turbine thermal efficiency is to replace the nearly constant pressure combustion process with some form of pressure-gain heat release such as either a constant volume or detonative mode of combustion. These systems commonly possess some form of rotating inlet valve design to control the filling process for an annular array of combustors and maintain the appropriate amount of inlet isolation. Although evaluation of turbine life and performance needs to continue, turbine efficiencies approaching values comparable to those of steady-state operation have been reported. The article concludes that the collaborative efforts, such as listed in the article, are ultimately required in times of reduced funding for continued technology development. Even with the risks and challenges associated with this technology, a high payoff potential exists with hybrid gas turbine architectures.
Leading the Dispersed Workforce
Authors: Reilly Richard R. , Lojeski Karen Sobel
Published: July 2018

This review explains the concept of virtual distance and its increasing usage in the research and development field. Virtual distance occurs when individuals work together and communicate primarily through electronic media. After five years of research, results show that virtual distance is not about geographic distance alone. Instead, it has three major components: physical distance involving differences in space, time, and environment; operational distance including the psychological gaps that arise from day-to-day problems in the workplace; and affinity distance embodying the emotional disconnects among virtual team members who have no relationship with one another. The review also discusses that Techno- dexterity, boundary breaking, globalization, and authenticity are four key competencies effective leaders use to manage virtual distance. It also illustrates the concept of coactivating leaders, which emphasize not only global experience but also the ability to bond with and understand diverse cultures. They also use both forward and reverse mentoring to both teach and learn from their employees.
Green Decisions
Authors: Thilmany Jean
Published: July 2018

This article discusses the introduction and implementation of environmental regulations in manufacturing industry. Manufacturers are responding to customer demand for environmentally friendly products. Several vendors such as PTC and Siemens PLM Software make products that track environmental performance of products, parts, materials, and suppliers. Many products are integrated with a company’s supply chain and product development systems. IBM offers Environmental Product Lifecycle Management, which includes software and consulting services, and assists clients in analyzing every phase their product passes through to ensure environmental compliance. A number of lifecycle assessment software packages have been released in recent years to help designers. Sustainable Minds develops software, for example, that is intended to give engineers pertinent supplier and material information, which allows them to weigh each design decision from an environmental standpoint. Engineers call upon lifecycle analysis software to ensure their products comply with environmental regulations. Meanwhile, the number of manufacturers who will need to meet those regulations represents a growing market for software makers.
Airborne, Autonomous & Collaborative
Authors: Basso Brandon , Love Joshua , Hedrick J. Karl
Published: July 2018

This article describes how collaboration of unmanned aerial vehicles (UAVs) can be done to achieve a common goal. With UAVs becoming both cheap and easy to build, the field's leading edge is now collaborating squadrons of two or five or ten aircrafts, to achieve a common goal. The ambition is to use teams of flying robots to develop vision-based maps of large areas, track moving objects, fuse information from multiple aircraft and multiple sensors, and perform high-level task planning. One form of collaboration consists of enabling teams of UAVs to work together on a task that would be impossible with only one UAV. The next extension of UAV collaboration is to enable the vehicles to work together on several tasks at the same time. It is possible to have a human user manually assign individual UAVs to specific tasks. Automated allocation can also be done through heuristic algorithms, such as the nearest-neighbor approach, which assigns the UAV closest to the task. The heuristics produce simple rules that behave predictably, but not necessarily optimally.
Engineering Taste
Authors: Fryer Peter , Bakalis Serafim
Published: July 2018

This article discusses a study focusing on developing a mathematical model for creating and modifying the structure of chocolates. In the experimental study at the University of Birmingham's Centre for Formulation Engineering, researchers cooled and heated chocolate through rapid programmed temperature changes and then studied what happened using differential scanning calorimetry. The data was fitted to six kinetic processes. To make the modeling easier, the system of six polymorphs and liquid chocolate was simplified to model only three materials: stable solids, unstable solids, and melt. Then equations were developed to describe the nucleation of crystals, growth of stable and unstable phases, and the melting of the stable and unstable solids. The model developed simplifies the number of crystal forms, but this simplification makes it possible to model differential scanning calorimetry data. Once fitted to differential scanning calorimetry data over a range of cooling rates, the model can then be used both to predict behavior and to explain what is happening in the process. The model can be used to show how ‘frozen cone’ methods work.
Stemming the Flood
Authors: Richardson John , Waterman Pamela
Published: July 2018

This article discusses measures being taken by the U.S. Army Corps of Engineers to protect New Orleans from future flood events. The U.S. Army Corps of Engineers is redesigning and upgrading the 350-mile network of linked levees, floodwalls, gates, and pumps in the New Orleans area. The Corps of Engineers’ plan for New Orleans flood control involves upgrading some existing structures such as levees and floodwalls and adding some new risk-reduction features, two of which are movable gates. The proposed Bayou Bienvenue Gate will sit near the junction of the Gulf Intracoastal Waterway and the Mississippi River Gulf Outlet to keep floodwater away from the southern end of the Industrial Canal. The Seabrook Gate will span the northern end of the Industrial Canal where it meets Lake Pontchartrain. By preventing storm surges from entering the Industrial Canal, these gates will protect a densely populated residential and commercial area. However, the presence of the new gates will change day-to-day current patterns in ways that could impact existing structures and use.
Property Values
Authors: Bookoff Leslie I. , Melwani Dinesh N.
Published: July 2018

This article focuses on the importance of intellectual property (IP) in startup companies to attract investment. Various examples of startup companies dealing with medical devices were also discussed. Much of a medical device startup’s assets, however, lie in ideas or concepts it hopes to develop into a commercial product. Patent protection often is considered a critical component of corporate transactions involving medical technologies because it can protect the significant upfront investments required for R'D and regulatory activities. Investors evaluating the IP of a target medical device company are attracted to a demonstrated awareness of IP and to a clean house as it relates to administrative issues potentially affecting the company’s intellectual property. A target company also may make investment more attractive by minimizing or eliminating contractual restrictions on the transfer of its IP. A startup company seeking its portion of investment dollars must pay attention to its IP: it must ensure that its technology is freely marketable without infringing third-party rights and that its IP portfolio is free of encumbrances and has the necessary protection.
Thinking Outside the CAD Box
Authors: Lipson Hod
Published: July 2018

This article reviews new 3D printing capabilities for computer-aided design (CAD) engineers. As additive manufacturing technologies such as 3D printing and rapid prototyping become increasingly capable, traditional barriers of resources and skill for manufacturing are all but vanishing. Three-dimensional printers are giving designers unprecedented control over the shape and composition of matter. High-end 3D printers today can combine multiple materials into arbitrary patterns at a resolution close to 10 mm, leading to the ability to create geometry with fidelity and complexity that rivals that of the natural world. The growing accessibility of personal manufacturing tools, such as 3D printers, is democratizing design and enabling new types of designers. The combination of new geometric representations, new design paradigms, and new interfaces leads to new challenges and opportunities in the CAD field as never before. Good design tools are often the hidden enabler of technological innovation; however, balancing the existing performance engine with a new paradigm shift is a difficult but not an impossible task.
Printed Life
Authors: Thilmany Jean
Published: July 2018

This article discusses the advancement in bioprinting technology that would enable three-dimensional printing of living organs for transplant. Today, artificial or replacement tissue is commonly grown on collagen scaffolds that contain biological starter cells. The goal here is the growing of a biocompatible piece of tissue to repair or replace a patient’s own damaged body part, such as bone, cartilage, blood vessels, or skin. In future, bioprinting technology will allow making living organs for transplant. The method is much the same as additive manufacturing, in which a printer deposits a material, layer by layer, until a three-dimensional object is made. For bioprinting, the material used is likely to be living cells taken directly from the patient’s body and infused into an ink or gel to keep them alive. After printing, the material is incubated in a cell culture that mimics human body conditions until it fuses or becomes otherwise usable for implant.
To a T
Authors: Meyler Nicholas J.
Published: July 2018

This article focuses on breadth and depth of skills needed by candidates for engineering jobs. Adaptability—that is, the ability to keep up with the rapid pace of change—and practical skills rank high with today’s employers. Recruiters are finding that breadth of knowledge and experience trumps depth in the form of overspecialization in engineering; in recruitment, this means finding the engineer who fits a job opening ‘to a T.’ The best jobs are won by candidates who demonstrate a breadth of knowledge and experience in their own discipline and the disciplines related to it. According to the experts, systems engineers are specialists in simplifying complexity, resolving ambiguity, and focusing the creativity of others—but they are not generalists. The present day’s engineering students learn to define system boundaries, goals, and functions. They also learn to anticipate failure modes, to plan for mitigation and recovery, and to define and manage interfaces. Engineers with multidisciplinary skills are much more adaptable, and more in demand; but in engineering, there still are more specialists than generalists. The demands of today’s competitive business environments tilt the balance toward breadth. As technologies mature, the balance will tilt back toward depth.
Professional Networking
Authors: Thilmany Jean
Published: July 2018

This article explores engineers’ diverse ways of using the explosive growth in social networks that has taken place during the past 5 years. Engineers Looking for Stuff (ELFS) is a group for engineers available on both the LinkedIn and Facebook social networking sites. Engineers are turning to sites like Facebook, LinkedIn, Meetup, Twitter, and a growing number of more specifically tailored sites to find jobs, get questions answered, and connect with people who share professional interests. The L.A. Robotics Club takes advantage of Meetup, which is intended to bring like-minded people together for live events. The club is home for anyone interested in robotics. Members work together on robotic cars and drones and on their own products. Inventor Matt Ferguson and his colleagues used Twitter to help market the Ankle Foot Maximizer (AFX), a device which strengthens foot and ankle tendons and muscles. The AFX is used in sports medicine and physical rehabilitation and in athletic training to enhance jumping and running.
A Free-Liquid-Piston Engine Compressor for Compact Robot Power
Authors: Barth Eric J. , Hofacker Mark E. , Kumar Nithin
Published: July 2018

This article focuses on the use of a free-liquid-piston engine compressor (FPEC) for compact robot power. The FPEC presented in the article combines the engine and the compressor into a single unit. FPEC, a high-power density form of actuation, can help operate human-scale robots. An energy source that provides pneumatic power presents an appealing alternative that alleviates many of the scalability problems of hydraulics while preserving a high actuation power density. The system also presents additional advantages such as power-on-demand with no idle. Taking advantage of the high inertance piston, high-pressure air and high vapor pressure fuel enable the engine to operate in an inject and fire cycle. Dynamically, the FPEC is similar to a bug converter circuit in that the flow is amplified and the high-inheritance piston plays the same energetic role as the inductor. The data suggests that pneumatic systems using the FPEC as a power source would exhibit system energy densities comparable to, if not better than, the best electrochemical systems.
Medical Starts with ME
Authors: Thilmany Jean
Published: July 2018

This article discusses the importance of mechanical engineers and their various roles in projects. Experts in the industry agree that mechanical engineers are integral to device design regardless of its complexity. The engineers work with a number of people from different backgrounds—physicians, marketers, and engineers of other disciplines—during the development process and come up with creative solutions that make many advances in medical treatment possible. Mechanical engineers are often creating the practical foundation on which a project rests to develop a medical device. Students studying to be mechanical engineers can expect the medical device business to offer plenty of opportunity in the years ahead, according to practitioners in the field. Engineers are not only involved in design, they also help drive development of the entire device these days. Experts believe that engineers will be stronger players if they can truly hear a doctor or patients’ problems and design for them; otherwise, a lot gets lost in translation.
An Imprint for the Latest Technolgy
Authors: Zhang Libo
Published: July 2018

This article discusses how Harbin Boiler Co. Ltd (HBC) has incorporated the ASME Boiler and Pressure Vessel Code to ensure that the research, manufacturing, and servicing behind its products are in line with the international standard. HBC got to know ASME Codes in the early 1980s. In 1987, HBC became the first manufacturer of utility boilers in China to obtain ASME Authorization Certificates and Code stamps S (power boilers), U (pressure vessels), and Ш (alternative rules for pressure vessels). HBC obtained the National Board Authorization Certificate and Code stamp R (repair and alteration of boilers) in 1996. In 2004, HBC completed manufacturing the first product project with the U stamp – 24 oil tanks and gas tanks for the Three Gorges Zuoan Power Plant. During the course of obtaining ASME certificates and Code stamps, HBC also enhanced its design capability and manufacturing level, promoted its technology and management levels, further improved its quality and management system, and greatly strengthened its comprehensive competitiveness in the market.
Making a Difference and a Profit
Authors: Van Bossuyt Douglas L.
Published: July 2018

This article examines different approaches that could be applied / used by engineers for lean design. Lean design can let companies make a profit while satisfying customers in the developing world.

In developing markets, difficulty in gathering the necessary data can lead to lengthy delays or broad assumptions in the product development cycle. The iterative approach of lean design stresses leveraging sales data, customer feedback, and distributor feedback to evaluate and refine the important metrics of value, growth, and impact of a particular product that could drive the design process and optimize the product. The experts also say that when designing products for the developing world, making money is not the only value proposition. Engineers must keep ethics in mind. Engineers must also understand the social and health consequences of introducing products into the marketplace and ensure that any product does not adversely impact the customer or community. Products must be designed that have broad enough appeal to drive a sustainable market for the company.
Analysis of Wellbore Temperature Distribution and Influencing Factors During Drilling Horizontal Wells
Authors: Zhang Zheng , Xiong Youming , Guo Fang
Published: July 2018

Horizontal well drilling technology is widely used in the exploitation of petroleum and natural gas, shale gas, and geothermal resources. The temperature distribution of wellbore and surrounding formation has a significant influence on safe and fast drilling. This study aims to investigate the temperature distribution of horizontal wellbores during circulation by using transient temperature model. The transient temperature prediction model was established by the energy conservation law and solved by the relaxation iterative method. The validity of the model has been verified by the field data from the Tarim Oilfield. The calculation results showed that the highest temperature of the drilling fluid inside the drill string was at the bottomhole and the highest temperature of annulus drilling fluid was at some depth away from the bottomhole. Sensitivity analysis of various factors that affect the temperature distribution of annulus drilling fluid were carried out, including the circulation time, the flow rate, the density of drilling fluid, the inlet temperature, the vertical depth, the horizontal section length, and the geothermal gradient. It can be found that the vertical depth and the geothermal gradient have a significant influence on the bottomhole temperature, and inlet temperature plays a decisive influence on the outlet temperature. These findings can supply theoretical bases for the horizontal wellbore temperature distribution during drilling.
Investigation of 127I(n,2n)126I and 23Na(n,2n)22Na Reactions Using 252Cf Neutron Source
Authors: Schulc Martin , Košťál Michal , Novák Evžen , Šimon Jan , Burianová Nicola
Published: July 2018

This work deals with 23Na(n,2n)22Na and 127I(n,2n)126I reactions in the 252Cf spontaneous fission neutron source. 252Cf neutron source with approximate emission of 6·× 108 n/s was employed for the irradiation of sodium iodide. The spectrum-averaged cross sections (SACS) were then inferred from experimentally determined reaction rates and compared with calculations in MCNP6 using various nuclear data libraries. The experimental reaction rates were derived from the net peak areas (NPAs) measured using the high purity germanium spectroscopy. The measured SACS for the 23Na(n,2n)22Na reaction in the 252Cf spectrum was determined as equal to (8.98±0.32)·× 10−6 b. The resulting SACS for the 127I(n,2n)126I reaction in the 252Cf spectrum was derived as (2.044±0.0072)·× 10−3 b. These experimental data can be used for nuclear data libraries validation and to specify high energy tail of the 252Cf neutron spectrum.
Development of a Durable Vapor Phase Deposited Superhydrophobic Coating for Steam Cycle Power Generation Condenser Tubes
Authors: Duron Christopher M. , Zhong Jie , David Allan E. , Ashurst William R. , Bhavnani Sushil H. , Morris Jacob R. , Bates Andrew C.
Published: July 2018

Condenser performance benefits afforded by dropwise condensation have long been unattainable in steam cycle power plant condensers due to the unavailability of durable and long-lasting hydrophobic surface treatments. However, recent work in superhydrophobic coating technology shows promise that durable coatings, appropriate for use on condenser tubes in steam cycle power generation systems, may soon become a reality. This work presents a nanoscale, vapor phase deposited superhydrophobic coating with improved durability comprised of several layers of rough alumina nanoparticles and catalyzed silica with a finishing layer of perfluorinated silane. This coating was applied to solid, hemicylindrical test surfaces fabricated from several common condenser tube materials used in power generation system condensers: Titanium, Admiralty brass, Cupronickel, and Sea Cure stainless steel as well as 304 stainless steel stock. The development evolution of the coating and its effect on condensation behavior on the above materials are presented. Results show that the performance enhancement, measured in rate of heat transfer spikes corresponding to condensate roll-off events, was best for the titanium surface, which produced 64% more events than the next most active material when coated using the most durable surface treatment tested in this work.
Control of Down-Hole Drilling Process Using a Computationally Efficient Dynamic Programming Method
Authors: Ke Chong , Song Xingyong
Published: July 2018

The unconventional down-hole resources such as shale oil and gas have gradually become a critical form of energy supply thanks to the recent petroleum technology advancement. Its economically viable and reliable production highly depends on the proper operation and control of the down-hole drilling system. The trend of deeper drilling in a complex environment requires a more effective and reliable control optimization scheme, either for predrilling planning or for online optimal control. Given the nonlinear nature of the drilling system, such an optimal control is not trivial. In this paper, we present a method based on dynamic programming (DP) that can lead to a computationally efficient drilling control optimization. A drilling dynamics model that can enable this method is first constructed, and the DP algorithm is customized so that much improved computational efficiency can be achieved compared with using standard DP. A higher-order dynamics model is then used to validate the effectiveness of the optimized control, and the control robustness is also evaluated by adding perturbations to the model. The results verify that the proposed approach is effective and efficient to solve the down-hole drilling control optimization problem.
Mechanical Properties of Cubic (U,Zr)O2
Authors: Kitagaki Toru , Hoshino Takanori , Yano Kimihiko , Okamura Nobuo , Ohara Hiroshi , Fukasawa Tetsuo , Koizumi Kenji
Published: July 2018

Evaluation of fuel debris properties in the Fukushima Daiichi nuclear power plant (1F) is required to develop fuel debris removal tools. In the removal of debris resulting from the Three Mile Island unit 2 (TMI-2) accident, a core-boring system played an important role. Considering the working principle of core boring, hardness, elastic modulus, and fracture toughness were found to be important fuel debris properties that profoundly influenced the performance of the boring machine. It is speculated that uranium and zirconium oxide solid solution (U,Zr)O2 is one of the major materials in the fuel debris from 1F. In addition, the Zr content of the fuel debris from 1F is expected to be higher than that of the debris from TMI-2 because the 1F reactors were boiling-water reactors. In this research, the mechanical properties of cubic (U,Zr)O2 samples containing 10%–65% ZrO2 are evaluated. The hardness, elastic modulus, and fracture toughness are measured by the Vickers test, ultrasonic pulse echo method, and indentation fracture method, respectively. In the case of (U,Zr)O2 samples containing less than 50% ZrO2, Vickers hardness and fracture toughness increased, and the elastic modulus decreased slightly with increasing ZrO2 content. Moreover, all of those values of the (U,Zr)O2 samples containing 65% ZrO2 increased slightly compared to (U,Zr)O2 samples containing 55% ZrO2. ZrO2 content affects fracture toughness significantly in the case of samples containing less than 10% ZrO2. Higher Zr content (exceeding 50%) has little effect on the mechanical properties.
Design and Control of a Fully-Actuated Hexrotor for Aerial Manipulation Applications
Authors: Lee Jameson Y. S. , Leang Kam K. , Yim Woosoon
Published: July 2018

This paper addresses the issue of controller complexity for multirotor aerial manipulator (AM) implementation by utilizing a special class of fully actuated hexrotor within the framework of a firmware, which allows standard multirotor actuation modes. Using this platform, manipulator and vehicle dynamics are decoupled, making the airframe inherently more robust than standard multirotor for trajectory tracking in AM applications. Furthermore, its unique design allows for the implementation of modular control strategies. The proposed rotor orientation model makes it possible to decouple the dynamics, allowing full analytical development of the optimal solution. A methodology for analysis, control allocation, and design of this special class of hexrotor is presented, and the implementation of a custom flight stack is demonstrated using a hexrotor prototype in closed-loop flight testing. The flight stack developed is compliant with the open-source ArduPilot Mega (APM) firmware, allowing it to take advantage of all generic multirotor control algorithms. Experimental results are presented to demonstrate feasibility of the system.
Discrete Fractional Derivative Based Computational Model to Describe Dynamics of Bed-Load Transport
Authors: Sun HongGuang , Li ZhiPeng , Zhang Yong , Liu XiaoTing
Published: July 2018

Bed-load transport in natural rivers exhibits nonlinear dynamics with strong temporal memory (i.e., retention due to burial) and/or spatial memory (i.e., fast displacement driven by turbulence). Nonlinear bed-load transport is discrete in nature due to the discontinuity in the sediment mass density and the intermittent motion of sediment along river beds. To describe the discrete bed-load dynamics, we propose a discrete spatiotemporal fractional advection-dispersion equation (D-FADE) without relying on the debatable assumption of a continuous sediment distribution. The new model is then applied to explore nonlinear dynamics of bed-load transport in flumes. Results show that, first, the D-FADE model can capture the temporal memory and spatial dependency characteristics of bed-load transport for sediment with different sizes. Second, fine sediment particles exhibit stronger super-diffusive features, while coarse particles exhibit significant subdiffusive properties, likely due to the size-selective memory impact. Third, sediment transport with an instantaneous source exhibits stronger history memory and weaker spatial nonlocality, compared to that with a continuous source (since a smaller number of particles might be blocked or buried relatively easier). Hence, the D-FADE provides a strict computational model to quantify discrete bed-load transport, whose nonlinear dynamics can be sensitive to particle sizes and source injection modes, both common in applications.
Cycle Calculations of a Small-Scale Heat Removal System With Supercritical CO2 as Working Fluid
Authors: Straetz Marcel , Starflinger Joerg , Mertz Rainer , Brillert Dieter
Published: July 2018

In the case of an accident in a nuclear power plant with combined initiating events (loss of ultimate heat sink and station blackout), an additional heat removal system could transfer the decay heat from the core to an ultimate heat sink (UHS). One specific additional heat removal system, based upon a Brayton cycle with supercritical carbon dioxide (CO2) as working fluid, is currently investigated within the European Union-funded project “sCO2-HeRo” (supercritical carbon dioxide heat removal system). It serves as a self-launching, self-propelling, and self-sustaining decay heat removal system used in severe accident scenarios. Since this Brayton cycle produces more electric power than it consumes, the excess electric power can be used inside the power plant, e.g., for recharging batteries. A small-scale demonstrator is attached to the pressurized water reactor (PWR) glass model at Gesellschaft für Simulatorschulung (GfS), Essen, Germany. In order to design and build this small-scale model, cycle calculations are performed to determine the design parameters from which a layout can be derived.
A Density Functional Theory Study on the Diffusion of Fission Gas Atoms in Uranium Dioxide
Authors: Zhao Qiang , Zhang Zheng , Ouyang Xiaoping
Published: July 2018

Uranium dioxide (UO2) is the typical fuel that is used in the current nuclear power plant; fission gas atoms are produced during and after the nuclear reactor operation; the fission gas atoms have a significant effect on the performance of UO2 fuel in the nuclear reactor. In this paper, we investigated the diffusion of the fission gas atoms in the UO2 fuel by using the first-principles calculation method based on the density functional theory (DFT). The results indicate that the volume of the UO2 cell increased when there is a fission gas atom enters in the UO2 supercell; the elastic properties of UO2 are in good agreement with other simulation results and experimental data and the fission gas atoms make the ductility of UO2 decreased; the fission gas atoms prefer to occupy the octahedral interstitial site (OIS) over the uranium vacancy site and the oxygen vacancy site, and the oxygen vacancy site is the most difficult occupied site due to the formation of an oxygen vacancy is more difficult than that of the uranium vacancy; the diffusion barrier of a He atom in the UO2 supercell is higher than that of an oxygen atom, that means that the diffusion of the He atom in UO2 fuel is weaker than that of the oxygen atom. Our works may shed some light on the formation mechanism of the bubbles caused by the fission gas atoms in the UO2 fuel.
Research on Thermal Characteristics of Spindle System With Tilting Pad Bearing
Authors: Jiang Shuyun , Shen Deyang
Published: July 2018

Spindles with tilting pad bearings have been widely applied in machine tools due to their high running precision. However, friction power loss will increase dramatically when the bearing runs at a higher speed. So far, little research on the thermal modeling of spindle systems with tilting pad bearings can be found in literature. In this paper, based on the Newtonian law of viscosity, formula that describes the friction power loss of the tilting pad bearing has been derived. The thermodynamic equilibrium equation for the spindle lubrication system has been established. Thermal boundary condition of the spindle system has been obtained using the heat transfer theory. Thermal model of the spindle system with tilting pad bearing has been built with the finite element method in order to calculate its temperature and thermal displacement distribution. Effects of the eccentricity ratio and the lubricant flow rate on thermodynamic behavior of the spindle system have been studied systematically. Finally, experiments have been conducted to verify the proposed thermal model for the spindle system with tilting pad bearing.
Investigations on Convective Heat Transfer Enhancement in Circular Tube Radiator Using Al2O3 and CuO Nanofluids
Authors: Alosious Sobin , Sarath S. R. , Nair Anjan R. , Krishnakumar K.
Published: July 2018

In this study, forced convective heat transfer inside a circular tube automobile radiator is experimentally and numerically investigated. The investigation is carried out using Al2O3 and CuO nanofluids with water as their base fluid. A single radiator circular tube with the same dimensions is numerically modeled. Numerical model is validated using the experimental study results. In the experimental study, Al2O3 and CuO nanofluids of 0.05% volume concentrations (ϕ) were recirculated through the radiator for the Reynolds number (Re) between 260 and 1560. The numerical investigation is conducted for the nanoparticle volume concentration from 0% to 6.0% and 260 < Re < 1560. The investigation shows an enhancement of convective heat transfer coefficient (h) with the increase in nanoparticle volume concentration and with the Reynolds number. A maximum enhancement of 38% and 33% were found for Al2O3 and CuO nanofluids of ϕ = 1% and Re = 1560. For the same cooling load of the radiator, the pumping power can be reduced by 8% and 10%, when Al2O3 and CuO nanofluids (ϕ = 0.8%) were used. Enhancement in convective heat transfer can be utilized to reduce the radiator surface area required. However, the addition of nanofluid results in an enhancement of density (ρ) and viscosity (μ) along with a reduction in specific heat capacity (Cp). Hence, the selection of nanoparticle volume concentration should consider its effect on the thermophysical properties mentioned earlier. It is found that the preferred concentration is between 0.4% and 0.8% for both Al2O3 and CuO nanofluids. In our investigations, it is observed that the convective heat transfer performance of Al2O3 nanofluid is better than the CuO nanofluid.
Design and Optimization of Thermoelectric Cooling System Under Natural Convection Condition
Authors: Ying Xiaoyuan , Ye Fangming , Liu Ruitao , Bao Hua
Published: July 2018

A design method for the thermoelectric cooling system is improved in this work based on a graphical approach. It is used to select an appropriate thermoelectric cooler (TEC) and determine the value of optimum input current. Theoretical analysis has been conducted to investigate the cooling performance of the system using the design method. Numerical simulation and experimental tests for the entire cooling system validate the calculation result, which indicates the high reliability of the theoretical design method. The temperature dependence of the heat sink resistance and the contact resistance are the major reasons for the small discrepancy. Research is then conducted based on the design method to investigate how a thermoelectric cooling system under natural convection performs, where the optimization of heat sinks at hot side of TEC is done by using the generalized correlations in the previous studies. Comparison is made between the thermoelectric cooling system and the bare-heat-sink system under natural convection. Results show that the thermal resistance of the heat sink attached to TEC is critical to the cooling performance of the whole system. Besides, TEC under natural convection can perform better than the passive cooling if the heat load is not very high (qc″≤20,000 W/m2). The design process and results can provide a useful guidance for other thermal engineers.
Controlling Out-of-Plane Elastic Shear Wave Propagation With Broadband Cloaking
Authors: Liu M. , Zhu W. D.
Published: July 2018

A major challenge in designing a perfect invisibility cloak for elastic waves is that the mass density and elasticity tensor need to be independent functions of its radius with a linear transformation medium. The traditional cloak for out-of-plane shear waves in elastic membranes exhibits material properties with inhomogeneous and anisotropic shear moduli and densities, which yields a poor or even negative cloaking efficiency. This paper presents the design of a cylindrical cloak for elastic shear waves based on a nonlinear transformation. This excellent broadband nonlinear cloak only requires variation of its shear modulus, while the density in the cloak region remains unchanged. A nonlinear ray trajectory equation for out-of-plane shear waves is derived and a parameter to adjust the efficiency of the cylindrical cloak is introduced. Qualities of the nonlinear invisibility cloak are discussed by comparison with those of a cloak with the linear transformation. Numerical examples show that the nonlinear cloak is more effective for shielding out-of-plane elastic shear waves from outside the cloak than the linear cloak and illustrate that the nonlinear cloak for shear waves remains highly efficient in a broad frequency range. The proposed nonlinear transformation in conjunction with the ray trajectory equation can also be used to design nonlinear cloaks for other elastic waves.
Effect of Inlet Distortion Features on Transonic Fan Rotor Stall
Authors: Page James H. , Hield Paul , Tucker Paul G.
Published: July 2018

The effect of inlet distortion from curved intake ducts on jet engine fan stability is an important consideration for next-generation passenger aircraft such as the boundary layer ingestion (BLI) “silent aircraft.” Highly complex inlet flows which occur can significantly affect fan stability. Future aircraft designs are likely to feature more severe inlet distortion, pressing the need to understand the important factors influencing design. This paper presents the findings from a large computational fluid dynamics (CFD) investigation into which aspects of inlet distortion cause the most significant reductions in stall margin and, therefore, which flow patterns should be targeted by mitigating technology. The study considers the following aspects of distortion commonly observed in intakes: steady vortical distortion due to secondary flow, unsteady vortical distortion due to vortex shedding and mixing, static pressure distortion due to curved streamlines, and low momentum endwall flow due to thickened boundary layers or separation. Unsteady CFD was used to determine the stall points of a multipassage transonic rotor geometry with each of the inlet distortion patterns applied. Interesting new evidence is provided, which suggests that low momentum flow in the tip region, rather than distortion in the main body of the flow, leads to damaging instability.
A Kinetic Assessment of Entrained Flow Gasification Modeling
Authors: Rakhshi A. , Wiltowski T.
Published: July 2018

A kinetics assessment of the quasi-global homogeneous and heterogeneous reaction mechanisms is carried out for entrained flow coal gasification modeling. Accurate closure of the chemical source term in gasification modeling necessitates a detailed study of turbulence-chemistry interaction. Toward this end, a time-scale analysis of the homogeneous reactions is discussed using eigenvalue analysis of the reaction rate Jacobian matrix. A singular value decomposition (SVD) of the stoichiometric reaction matrix is performed to assess the behavior of the homogeneous reactions in a reduced species vector space. The significant factors affecting the heterogeneous char reactions are assessed, and the relative importance of bulk diffusion and inherent char kinetics is analyzed in a gasifier. The overall study is carried out using numerical and experimental results of an actual pilot scale gasifier.