bluuebunny/crossref_metadata_2025 huggingface dataset:
Crisis Leadership of the Bush Presidency: Advisory Capacity and Presidential Performance in the Acute Stages of the 9/11 and Katrina Crises
Authors: ‘T HART PAUL , TINDALL KAREN , BROWN CHRISTER
Published: July 2009

This paper examines the operation of the presidential advisory system during the 9/11 and Hurricane Katrina crises in order to explain the marked differences in presidential crisis leadership performance during the acute phase of both crises. It first presents a conceptual framework for the systematic study of “crisis advisory configurations” around presidents, based on an integrated review of the advisory systems and crisis management literatures. Second, the framework is applied to George W. Bush's performance in three crucial crisis leadership task domains—sense making, decision making, and meaning making. The article concludes by identifying key challenges of building crisis management capacity around heads of government such as the U.S. president.
Reluctant Liberator: Theodore Roosevelt's Philosophy of Self‐Government and Preparation for Philippine Independence
Authors: WERTHEIM STEPHEN
Published: July 2009

Theodore Roosevelt is well known as an imperialist. The common understanding is both too weak and too strong. Too weak, because Roosevelt idealized an imperialism that could last forever in civilizing savages. Too strong, because Roosevelt prepared the American‐occupied Philippines for independence within a generation. This article analyzes Roosevelt's philosophy of self‐government and reinterprets his Philippines policy in light of the philosophy. Roosevelt emerges as a reluctant anti‐imperialist—an imperialist by desire but an anti‐imperialist in governance. His imperialist ambitions were thwarted by America's ideals of self‐government and its democratic political system, channeled through the powers of Congress and the process of regular elections. At a crest of imperial opportunity, America eschewed empire. Imperial occupation remained a great aberration in American foreign relations.
The White House Office of Public Liaison
Authors: PIKA JOSEPH A.
Published: July 2009

The Office of Public Liaison has been a specialized unit of the White House staff since the Gerald Ford administration, though the basic features of the staff assignment can be traced to Franklin D. Roosevelt. The OPL has helped presidents achieve their goals in multiple ways: to mobilize public support for presidential initiatives in order to sell programs to Congress; to factor groups' views into White House policy making; and to serve as an adjunct to the reelection campaign. The unit also has provided symbolic representation for groups in the White House, helping them with “casework” and interpreting their policy positions and internal group politics to administration decision makers. Within the White House, the OPL staff has operated within different systems of reporting and coordination, but the generic roles played by the staff members tend to be similar across administrations, as are the strategic design choices that administrations must make.
The Contemporary Presidency: The Obama Presidential Transition: An Early Assessment
Authors: BURKE JOHN P.
Published: July 2009

Transitions to the presidency bear wide‐ranging consequences for the successes—and failures—of the administrations that follow. Barack Obama's effort in 2008 and early 2009 is no exception. In many ways, it was a successful transition to office. Despite severe economic constraints, the transition paved the way for an ambitious post‐inaugural agenda and the first steps toward fleshing out Obama's campaign themes of “hope” and “change.” But all was not perfect. It was a transition that also offers cautionary lessons about how early mistakes, errors, and omissions potentially can hinder that success.
Polls and Elections: Opinion Formation, Polarization, and Presidential Reelection
Authors: BURDEN BARRY C. , HILLYGUS D. SUNSHINE
Published: July 2009

The authors examine the dynamics of public opinion formation and change around a sitting president and their implications for reelection contests. Because of the biases inherent in information processing and the information environment, two distinct, but simultaneous, effects of citizen learning during a presidential term are expected. For those with prior opinions of the president, learning contributes to more polarized evaluations of the president. For those initially uncertain about the president, learning contributes to opinion formation about the president. Because the gap in uncertainty generally favors the incumbent over a lesser‐known challenger, races with an incumbent presidential candidate are typically marked, perhaps paradoxically, by both a polarization of public opinion and an incumbency advantage.
(Re)implementing the Agreement on Trade‐Related Aspects of Intellectual Property Rights to Foster Innovation
Authors: Gervais Daniel J.
Published: July 2009

This article considers the impact of the Agreement on Trade‐Related Aspects of Intellectual Property Rights (TRIPS) in developing countries. After an initial phase of “paper compliance” with TRIPS, followed by efforts to manage the welfare costs of its implementation, a number of developing countries are looking at ways to optimize the implementation or reimplementation of the agreement to foster domestic competitiveness and innovation. One part of the equation involves attracting technology‐intensive foreign direct investment. Another involves enhancing local innovation potential. Surfing the wave of outsourcing, which increasingly targets higher knowledge functions, a number of developing countries are becoming globally competitive innovators and displacing the geographical centres of innovation, with substantial political and economic impacts.
Adaptive evolution of baker's yeast in a dough‐like environment enhances freeze and salinity tolerance
Authors: Aguilera Jaime , Andreu Pasqual , Randez‐Gil Francisca , Prieto Jose Antonio
Published: July 2009

We used adaptive evolution to improve freeze tolerance of industrial baker's yeast. Our hypothesis was that adaptation to low temperature is accompanied by enhanced resistance of yeast to freezing. Based on this hypothesis, yeast was propagated in a flour‐free liquid dough model system, which contained sorbitol and NaCl, by successive batch refreshments maintained constantly at 12°C over at least 200 generations. Relative to the parental population, the maximal growth rate (µmax) under the restrictive conditions, increased gradually over the time course of the experiment. This increase was accompanied by enhanced freeze tolerance. However, these changes were not the consequence of genetic adaptation to low temperature, a fact that was confirmed by prolonged selection of yeast cells in YPD at 12°C. Instead, the experimental populations showed a progressive increase in NaCl tolerance. This phenotype was likely achieved at the expense of others traits, since evolved cells showed a ploidy reduction, a defect in the glucose derepression mechanism and a loss in their ability to utilize gluconeogenic carbon sources. We discuss the genetic flexibility of S. cerevisiae in terms of adaptation to the multiple constraints of the experimental design applied to drive adaptive evolution and the technologically advantageous phenotype of the evolved population.
A rare tumour in the mandible of a young man: a case report and literature review of mesenchymal chondrosarcoma of the mandible
Authors: Myers R.P. , Jiang S. , Girotto J.A.
Published: July 2009

Mesenchymal chondrosarcoma (MCS) is a rare malignancy that was first described by Lichtenstein and Bernstein in 1959. This paper reports the latest case of mandibular MCS and provides a review of cases of mandibular MCS from 1971 to the present. The literature was searched using the PubMed and Ovid engines; bibliographies were cross referenced. A meta‐analysis of the reported cases was performed and Kaplan–Meier curves generated for all treatment options. In the paediatric population, MCS is a rare and aggressive tumour. Since 1971, only 15 cases of MCS have been reported in the mandible of patients less than 20 years old. Surgical treatment positively impacts survival and is not improved with radiation or chemotherapy. Local recurrence was frequent, aggressive and dramatically affects survival. This meta‐analysis shows that primary intervention with surgery remains the standard of care for MCS. The role for chemotherapy and radiation therapy in the treatment of MCS remains unclear.
Infrequent clinicopathologic features of keratocystic odontogenic tumour: a 29‐year multi‐institutional retrospective review
Authors: Ide F. , Horie N. , Shimoyama T. , Saito I. , Tanaka A. , Kusama K.
Published: July 2009

Aim:  Keratocystic odontogenic tumour (KCOT), formerly known as odontogenic keratocyst, is an interesting and challenging entity. This study addresses the spectrum of clinicopathologic features of KCOT other than those classically described.

Materials and methods:  Three hundred forty‐seven cases of KCOT from the records of three institutions over a period of 29 years were retrospectively reviewed to analyse their clinical presentation, radiographic features, histopathology and biological behaviour.

Results:  Six cases of KCOT with infrequent findings were retrieved, none of which was associated with the nevoid basal cell carcinoma syndrome. Two lesions gave an erroneous radiographic impression of radicular cyst and nasopalatine duct cyst, respectively; the former periapical KCOT showed recurrence. An additional small KCOT adjacent to the initially presenting lesion was incidentally discovered, and both periradicular KCOT recurred twice. In interradicular KCOT, the growth rate of 2.4 mm per year was successfully estimated on radiographs. One paediatric KCOT showed a deceptive feature of eruption cyst and recurrence was not evident, despite of the fenestration. Microscopic rarities included mural cartilaginous metaplasia in a recurrent periradicular KCOT.

Conclusions:  This series of cases substantiates the preceding observations that KCOT has a reputation for clinically confusing jaw lesions, often resulting in a potential endodontic or periodontal misdiagnosis. Believed to exhibit occasional recurrent behaviour, missing a diagnosis of KCOT has serious implications for the patient. Both in principle and in practice, the differential diagnosis of KCOT deserves consideration in non‐healing radiolucencies associated with the roots of teeth.
Mandibular reconstruction after resection of benign tumours using non‐vascularised methods in a series of patients that did not undergo radiotherapy
Authors: Mehrotra D. , Kumar S. , Pradhan R.
Published: July 2009

Aim:  A case series analysis of 52 consequent subjects of immediate mandibular reconstruction after tumour resection using non‐vascularised methods, undertaken at U.P. King George's University of Dental Sciences and King George's Medical University, is being reported. To assess the success of reconstruction on subjective and objective evaluation based upon Mandibular Reconstruction Assessment Scale (MRAS) questionnaire.

Methods:  Patients with benign mandibular tumours irrespective of age, sex, site and socio‐economic status were included. Primary reconstruction was carried out after resection in two surgical units on surgeon's choice using stainless steel wire (6/52; 12%), stainless steel reconstruction plate (10/52; 19%) or titanium reconstruction plate (36/52; 69%) without bone graft (23/52; 44%) or with bone graft (29/52; 56%). Bone grafts were harvested from iliac crest (21/52; 40%), rib (2/52; 4%) and an additional pectoralis major myocutaneous flap with iliac crest bone graft (6/52; 12%) to provide cover to the reconstruction plate was also used.

Results:  The primary outcome measurements were wound healing, mouth opening, chewing efficiency, jaw movements, cosmetic achievement and speech on a five‐point scale, all of which improved significantly after surgery. The overall complication rate was 17%. Three patients (6%) had loosening of the screw, two (4%) showed dehiscence of the plate, two (4%) showed tumour recurrence and one (2%) had infection of the graft that was subsequently removed.

Conclusion:  Titanium reconstruction plates with iliac crest graft provided good result in the absence of microvascular reconstruction because of unavailable long operating time and lack of expertise. Long‐term satisfactory rehabilitation can be achieved using removable dentures or prosthesis on dental implants on the contraption provided by the non‐vascularised tissue despite non‐calcified bone visible on the skiagram.
Actinomycosis of the infratemporal fossa: an unusual cause of trismus
Authors: Sethi A. , Bansal R. , Sareen D. , Jain S.
Published: July 2009

We report the case of a 43‐year‐old female who presented to us with trismus. She was found to have unilateral tonsillar enlargement on examination. A computerised tomography scan revealed an enhancing mass lesion involving the infratemporal fossa and the parapharyngeal space. A fine needle aspiration cytology of the enlarged tonsil revealed actinomycosis. The patient responded well to tonsillectomy followed by medical management and is asymptomatic 6 months following the completion of treatment.
Angiography for multiple dental extractions in Sturge–Weber Syndrome: report of a case
Authors: Siddiqi A. , Morkel J.A. , Zafar S.
Published: July 2009

Sturge–Weber Syndrome is a rare neurocutaneous syndrome. This case involves a possible complication of excessive intra‐operative bleeding. Surgical management of such patients may be challenging due to the risk of haemorrhage. The purpose of this case report is to discuss the importance of pre‐operative angiography in such patients for oral surgical procedures.
The Politics of Social Harmony: Ruling Strategy and Health Care Policy in Hu's China
Authors: Yu Bin
Published: July 2009

This study seeks to explain the causes of social welfare policy change in a single‐party authoritarian system. Using the evolution of Chinese health care policy as an example, it discerns why the Hu Jintao administration opted for a compensation‐oriented welfare policy paradigm in the absence of adequate interest articulation and apparent electoral accountability, despite the virtual collapse of the Chinese social welfare system during the 1990s. I explore the hypothesis that a high level of political pressure, coupled with a high degree of economic openness, drove the Chinese Communist Party to alter its ruling strategy, a political paradigm that best ensures its monopoly on political power and consequently produces distinct implications for public policy outputs. This study suggests that authoritarian regimes can and do compensate the citizenry under certain circumstances. Further, it also reveals a self‐adaptation process initiated by a single‐party authoritarian system.
A Country of No Significance? InterpretingThe Japan Times's Inattentive Approach to Chinese Affairs in 1997
Authors: Shih Chih‐yu , Yang Victoria
Published: July 2009

This article seeks to explain whyThe Japan Timestakes a backseat approach to events in China. Specifically, the Japanese English‐language newspaper demonstrated a lack of sensitivity when dealing with events that took place in China during 1997.The Japan Times's attitude is tantamount to actualizing a familiar identity strategy of withdrawal. For modern Japanese thinkers, such as Nishida Kitaro, Takeuchi Yoshimi, and Mizoguchi Yuzo, the withdrawal is a common strategy when dealing with the issue of universality. This is a surprising observation, given these scholars' vast differences when narrating Japanese identities. Accordingly, China has defined the condition from which withdrawal seems imperative for Japan to fulfill modernity.The Japan Times's apparent inattention to China may serve as the contemporary example of “withdrawing for universality” and poses different narrators against one another to show the indecisive conditionThe Japan Timeshas created for all of them.
Anatomy of Autonomy: Assessing the Organizational Capacity and External Environment of the Autonomous Region in Muslim Mindanao
Authors: Jimenez Benedict S.
Published: July 2009

Decentralization and autonomy can potentially increase public sector efficiency, effectiveness, and accountability, as well as fulfill a conflict‐mitigating role. There is no guarantee, however, that decentralization, once implemented, would automatically produce the expected benefits. Using the case of the Autonomous Region in Muslim Mindanao (ARMM) in the Philippines, this article explores the importance of organizational capacity and the cultural, political, and social conditions in the region to explain the performance of the autonomous government. The article concludes that for autonomy to work, the administrative and institutional capacity of the regional government should be revitalized and the current politico‐administrative structure redesigned to accommodate local customs and practices and facilitate a consultative and collegial local governance arrangement.
Voter Turnout in Thai Elections: An Analysis of the 2005 Thai National Election
Authors: Owen David A.
Published: July 2009

This article tested two contending theories of political participation, the resource theory and the theory of clientelism, utilizing provincial data from all 76 provinces in Thailand for the 2005 national election, collected from government sources that have remained unexamined until now. According to the resource theory, one would expect turnout to be higher in wealthy provinces where education and income levels are higher. However, where there are high levels of clientelism, one would expect lower turnout in provinces with higher levels of education and/or income. I used a linear regression model to test several hypotheses derived from these contending theories and found that there is support for the theory of clientelism. The results have important implications for the state of the Thai democracy before the September 2006 coup and the country's prospects for a return to democracy.
Exercise‐induced neuronal plasticity in central autonomic networks: role in cardiovascular control
Authors: Michelini Lisete C. , Stern Javier E.
Published: July 2009

It is now well established that brain plasticity is an inherent property not only of the developing but also of the adult brain. Numerous beneficial effects of exercise, including improved memory, cognitive function and neuroprotection, have been shown to involve an important neuroplastic component. However, whether major adaptive cardiovascular adjustments during exercise, needed to ensure proper blood perfusion of peripheral tissues, also require brain neuroplasticity, is presently unknown. This review will critically evaluate current knowledge on proposed mechanisms that are likely to underlie the continuous resetting of baroreflex control of heart rate during/after exercise and following exercise training. Accumulating evidence indicates that not only somatosensory afferents (conveyed by skeletal muscle receptors, baroreceptors and/or cardiopulmonary receptors) but also projections arising from central command neurons (in particular, peptidergic hypothalamic pre‐autonomic neurons) converge into the nucleus tractus solitarii (NTS) in the dorsal brainstem, to co‐ordinate complex cardiovascular adaptations during dynamic exercise. This review focuses in particular on a reciprocally interconnected network between the NTS and the hypothalamic paraventricular nucleus (PVN), which is proposed to act as a pivotal anatomical and functional substrate underlying integrative feedforward and feedback cardiovascular adjustments during exercise. Recent findings supporting neuroplastic adaptive changes within the NTS–PVN reciprocal network (e.g. remodelling of afferent inputs, structural and functional neuronal plasticity and changes in neurotransmitter content) will be discussed within the context of their role as important underlying cellular mechanisms supporting the tonic activation and improved efficacy of these central pathways in response to circulatory demand at rest and during exercise, both in sedentary and in trained individuals. We hope this review will stimulate more comprehensive studies aimed at understanding cellular and molecular mechanisms within CNS neuronal networks that contribute to exercise‐induced neuroplasticity and cardiovascular adjustments.
Replacement of connexin 43 by connexin 32 in a knock‐in mice model attenuates aortic endothelium‐derived hyperpolarizing factor‐mediated relaxation
Authors: López Diego , Rodríguez‐Sinovas Antonio , Agulló Esperanza , García Ángeles , Sánchez Jose A. , García‐Dorado David
Published: July 2009

Previous studies demonstrated that intercellular communication through endothelial, smooth muscle or myoendothelial connexin channels contributes to the control of vascular tone. At least four connexin types are present in the arterial wall. The aim of the present work was to assess the role played by connexin 43 (Cx43)‐formed gap junctions on vessel function. Aortic reactivity to noradrenaline, acetylcholine and sodium nitroprusside, and endothelium‐derived hyperpolarizing factor (EDHF)‐mediated relaxations, were analysed in a Cx43KI32 mouse model in which the coding region of Cx43 was replaced by that of connexin 32 (Cx32). Aortic rings were placed in organ baths containing a Krebs solution oxygenated at 37°C (pH 7.4). Confocal images of aortic rings confirmed connexin substitution in mutant mice. In control conditions, replacement of Cx43 by Cx32 in homozygous mutant mice did not modify endothelium‐independent contractile responses to noradrenaline, or relaxations in response to sodium nitroprusside (endothelium independent) or acetylcholine (endothelium dependent). However, residual endothelium‐dependent relaxations in response to acetylcholine after nitric oxide synthase and cyclooxygenase inhibition (EDHF type) were significantly reduced in homozygous Cx43KI32 mice (maximal effect values: 4.86 ± 0.37% of noradrenaline precontractionversus7.06 ± 0.31% in wild‐type,n= 8,P< 0.05). This attenuation was mimicked by treatment of rings from wild‐type animals with the connexin‐mimetic peptide37,43Gap27 (5 × 10−6m). In conclusion, replacement of Cx43 by Cx32 attenuates EDHF‐mediated relaxations in mice aortic rings, suggesting that they are, at least in part, dependent on Cx43‐formed gap junctions. In contrast, aortic responses to tested endothelium‐independent agonists were not modified in knock‐in animals.
Efficient Procedures for Form-Closure Grasp Planning and Fixture Layout Design
Authors: Zheng Yu , Chew Chee-Meng
Published: July 2009

This paper presents an algorithm for optimal grasp planning and fixture synthesis. The object surface is depicted by a number of discrete points, which are used as the candidate contact points. This algorithm consists of two procedures. The first procedure selects a minimal subset of contacts from the candidates so as to construct a form-closure grasp or fixture, which is to determine a minimal subset of contact wrenches such that their convex hull forms a simplex containing the origin of the wrench space as an interior point. The second procedure adjusts the contact positions or alters the selected contact wrenches to maximize the minimum distance from the origin to the facets of the simplex, which enhances the capability of the grasp or fixture to immobilize and balance the object. As this algorithm does not employ any general optimization techniques and utilizes recursive formulas for most computations, it runs very fast. Its effectiveness and efficiency are demonstrated with illustrative examples.
Tolerance Analysis Considering Weld Distortion by Use of Pregenerated Database
Authors: Lee Dongyul , Kwon Ki Eak , Lee Jaeyeol , Jee Haeseong , Yim Hyunjune , Cho Seong Wook , Shin Jong-Gye , Lee Gyubong
Published: July 2009

A general and efficient methodology has been developed to analyze dimensional variations of a welded assembly, taking into account of weld distortion. Weld distortion is generally probabilistic because of the random nature of welding parameters such as the welding speed, maximum welding temperature, ambient temperature, etc. The methodology is illustrated by a very simple example of two perpendicular plates fillet-welded to each other. Two steps comprise the methodology: establishment of a weld distortion database and tolerance analysis using the database. To establish the database, thermo-elastoplastic finite element analyses are conducted to compute the weld distortion for all combinations of discrete values of major welding parameters. In the second step of tolerance analysis, the weld distortion retrieved from the database is taken into account in addition to the dimensional tolerances of the parts. As a result of such an analysis, sensitivities of the assembly’s dimensional variations to the part tolerances and weld distortion are obtained, which could provide a guideline for improving dimensional quality of the assembly.
Spatially Resolved Characterization of Geometrically Necessary Dislocation Dependent Deformation in Microscale Laser Shock Peening
Authors: Wang Youneng , Kysar Jeffrey W. , Vukelic Sinisa , Yao Y. Lawrence
Published: July 2009

As the laser spot size in microscale laser shock peening is in the order of magnitude of several microns, the anisotropic response of grains will have a dominant influence on its mechanical behavior of the target material. Furthermore, conventional plasticity theory employed in previous studies needs to be re-examined due to the length scale effect. In the present work, the length scale effects in microscale laser shock peening have been investigated. The crystal lattice rotation underneath the shocked surface was determined via electron backscatter diffraction. From these measurements, the geometrically necessary dislocation (GND) density that the material contains has been estimated. The yield strength increment was then calculated from the GND distribution by using the Taylor model and integrated into each material point of the finite element method (FEM) simulation. Finite element simulations, based on single crystal plasticity, were performed for the process both with and without considering the GND hardening, and the comparison has been conducted.
3D Finite Element Modeling of an Assembly Process With Thread Forming Screw
Authors: Mathurin Florestan , Guillot Jean , Stéphan Pierre , Daidié Alain
Published: July 2009

This paper presents a 3D finite element (FE) model of a thread forming screw assembly process based on the ABAQUS 6.5.4 Explicit software program. The model consists of two principal elements: an M10×12 thread forming screw and a lower 4 mm plate into which the screw taps its threads. The aim was to develop a robust industrial dimensioning tool; the model can be extended to establish the preload and investigate other types of assemblies. A 45 deg sector, which represents 1/8 of the joint, was modeled to maintain a good compromise between calculation time and an accurate representation of the thread forming process. The intent of the study was to analyze the material flow throughout the thread forming process; a parametrical study was also conducted to identify the most influential process parameters. To validate the model, FE numerical simulation results are compared with published experimental results. The study shows that the lead hole diameter has an important influence on the screwing torque.
Mathematical Foundations for Form Inspection and Adaptive Sampling
Authors: Gilbert Robin C. , Raman Shivakumar , Trafalis Theodore B. , Obeidat Suleiman M. , Aguirre-Cruz Juan A.
Published: July 2009

Nonlinear forms such as the cone, sphere, cylinder, and torus present significant problems in representation and verification. In this paper we examine linear and nonlinear forms using a heavily modified support vector machine (SVM) technique. The SVM approach applied to regression problems is used to derive quadratic programming problems that allow for generalized symbolic solutions to nonlinear regression. We have tested our approach to several geometries and achieved excellent results even with small data sets, making this method robust and efficient. More importantly, we identify process or inspection tendencies that could help in better designing the processes. Adaptive feature verification can be achieved through effective identification of the manufacturing pattern.
Theoretical and FE Analysis of Ultrasonic Welding of Aluminum Alloy 3003
Authors: Siddiq A. , Ghassemieh E.
Published: July 2009

Ultrasonic welding (consolidation) process is a rapid manufacturing process that is used to join thin layers of metal at low temperature and low energy consumption. Experimental results have shown that ultrasonic welding is a combination of both surface (friction) and volume (plasticity) softening effects. In the presented work, an attempt has been made to simulate the ultrasonic welding of metals by taking into account these effects (surface and volume). A phenomenological material model has been proposed, which incorporates these two effects (i.e., surface and volume). The thermal softening due to friction and ultrasonic (acoustic) softening has been included in the proposed material model. For surface effects, a friction law with variable coefficient of friction that is dependent on contact pressure, slip, temperature, and number of cycles has been derived from experimental friction tests. The results of the thermomechanical analyses of ultrasonic welding of aluminum alloy have been presented. The goal of this work is to study the effects of ultrasonic welding process parameters, such as applied load, amplitude of ultrasonic oscillation, and velocity of welding sonotrode on the friction work at the weld interface. The change in the friction work at the weld interface has been explained on the basis of softening (thermal and acoustic) of the specimen during the ultrasonic welding process. In the end, a comparison between experimental and simulated results has been presented, showing a good agreement.
Fabricating Lensed Fiber Using a Novel Polishing Method
Authors: Tseng Yih-Tun , Huang Jhong-Bin , Su Wei-Jyun
Published: July 2009

In optical communication systems, 980 nm high-power laser modules are applied for long-distance communication amplifiers. Since the mode field of the 980 nm laser diodes is different from single-mode fibers, coupling losses may occur. In order to improve this problem, lensed fibers have been used widely recently, such as lensed fiber employing quadrangular-pyramid-shaped fiber endface (QPSFE). The QPSFE can easily yield any elliptical microlens aspect ratio to match the far field of the high-power laser diode but the fiber endface must be polished and then spliced during present manufacturing process. It is a time-consuming task and the melting depth of the fiber endface is controlled with difficulty. This study develops a novel fiber endface polishing method for manufacturing the lensed fiber employing QPSFE. Using this new method, the coupling efficiency exceeds 70%.
Analytical Expression of the Swept Surface of a Rotary Cutter Using the Envelope Theory of Sphere Congruence
Authors: Zhu LiMin , Zhang XiaoMing , Zheng Gang , Ding Han
Published: July 2009

Based on the observation that many surfaces of revolution can be treated as a canal surface, i.e., the envelope surface of a one-parameter family of spheres, the analytical expressions of the envelopes of the swept volumes generated by the commonly used rotary cutters undergoing general spatial motions are derived by using the envelope theory of sphere congruence. For the toroidal cutter, two methods for determining the effective patch of the envelope surface are proposed. With the present model, it is shown that the swept surfaces of a torus and a cylinder can be easily constructed without complicated calculations, and that the minimum distance (between the swept surface and a simple surface) and the signed distance (between the swept surface and a point in space) can be easily computed without constructing the swept surface itself. An example of global tool path optimization for flank milling of ruled surface with a conical tool, which requires to approximate the tool envelope surface to the point cloud on the design surface, is given to confirm the validity of the proposed approach.
Online detection system of microtarget assembly
Authors: Qiu Zurong , Wang Ting , Wang Jinjiang , Li Xinghua , Zhong Ying
Published: July 2009

This article describes an online detection system for measuring the geometrical parameters of the microtarget in inertial confinement fusion (ICF). The measurement can be done during the microtarget’s assembly process and then the message, according to the online detection results, can be sent to the assembly robots as the adjustment order. This detection system consists of three parts: a laser confocal system, a machine-vision system, and a motion-control system. During the real-time monitoring in the assembly process, the machine-vision system detects the position information of each part and the laser confocal system detects the reference points which have higher-precision requirements. The laser confocal system and the machine-vision system can be operated by the motion-control system so as to achieve the best measurement effect. The test data got by the two systems are then unified in the calibrated coordinate system. Using various fitting algorithms, the authors can find the parameter status, make the error analysis, or evaluate the tested beeline, round, sphere, and so on. With the error analysis of the motion-control system and the experiments, the measurement results is less than 3μm, which can meet the requirement of the assembly system. So this online detection system is feasible.
Feature filling modeling for step and flash imprint lithography
Authors: Chauhan Siddharth , Palmieri Frank , Bonnecaze Roger T. , Willson C. Grant
Published: July 2009

The authors analyze the feature filling phenomena for step and flash imprint lithography (SFIL) via diffusion of a gas, entrapped in the features, through liquid imprint resist. The model and simulation for the dynamics of feature filling including gas dissolution during the SFIL imprint step is presented. Several factors including the gas concentration profile across the liquid resist drop, the filling progression, and the total filling time for different pattern configurations are investigated to quantify feature filling. Simulation results show that initial filling is pressure controlled and very rapid [∼O(1ms)]. The rest of the feature filling is diffusion controlled, but fast enough [∼O(1s)] to conclude that diffusion of entrapped gas is not a cause for nonfilling of features. Also, the result that the smaller size features fill faster than the larger ones (with the same depth) makes SFIL the prime contender for high resolution and high throughput next generation lithography.
Energetic deposition of B10 on high aspect ratio trenches for neutron detectors
Authors: Klepper C. C. , Monteiro O. R. , Carlson E. P. , Keitz M. D.
Published: July 2009

Filtered cathodic arc deposition of fully ionized boron (B) was used to fill ∼2 μm wide trenches in silicon, having a depth:width ratio of up to 3:1. Optimal, void-free, infill is achieved with proper balance between deposition and self-sputtering, as controlled by the substrate bias. Previously, this technique was used to fill similar trenches with copper [O. R. Monteiro, J. Vac. Sci. Technol. B 17, 1094 (1999)]. In this work, successful extension of this process to B was found to require up to ten times higher bias voltage (up to 1000 V) for the sputtering phase and to benefit from a stronger angular dependence of self-sputtering yield for this lighter element.
Method for measuring solvent permeation through polymer film on porous dielectric films
Authors: Geil Robert D. , Senkevich Jay J. , Rogers Bridget R.
Published: July 2009

An analytical technique for measuring the permeation rate of chlorine-tagged organic solvents through thin polymer films on low-k porous dielectrics was developed. All samples consisted of a silicon substrate with 450nm thick porous silicon oxicarbide overlayer. The porous layers of some samples were sealed by a 17nm thick chemical vapor deposited polymer (parylene X) film. Samples were exposed to liquid 3-chloro-1-propanol at room temperature and pressure. The chlorine atom on the propanol molecule was used as a marker, enabling Rutherford backscattering spectrometry analysis to determine the total amount of chemical penetration into the porous layer as a function of the exposure time. Solvent penetration into the sealed porous material increased linearly for exposure times of less than 30min. Exposures over 30min saturated the sealed samples with 10.5μgofsolvent∕cm2. The permeation rate of 3-chloro-1-propanol through the 17nm parylene X layer was approximately 6.5×10−3μg∕cm2s.
Well-aligned TiO2 nanofibers grown by near-field-electrospinning
Authors: Rinaldi M. , Ruggieri F. , Lozzi L. , Santucci S.
Published: July 2009

Well-aligned TiO2 nanofibers were grown using the near-field electrospinning technique onto a silicon dioxide substrate. These nanofibers were several millimeters long with a diameter of about 200–400nm. The scanning electron microscopy showed the presence of microcystallites, whose crystalline structure was evaluated by x-ray diffraction measurements after a thermal process was performed to remove the solvent used in the solution. The chemical composition was investigated by x-ray photoemission spectroscopy showing the presence of TiO2.
Electrical properties of nanoscale Au contacts on 4H-SiC
Authors: Han Sang Youn , Lee Jong-Lam , Pearton S. J.
Published: July 2009

Electrical properties of the contacts consisting of nanoscale junctions separated within the Debye length (multinanocontact) were characterized both experimentally and numerically. The reduction in contact size from micrometer into the nanometer scale led to a decrease in effective Schottky barrier height from 1.69 to 1.09 eV and a much higher reverse leakage current density. This originated from a narrower barrier height beneath the contact, resulting in the increase in the tunneling current. In a multinanoscale contact separated within Debye length, the current density was expected to be higher than that of individual nanocontact (single nanocontact). This was attributed by the facts that in the multinanocontacts, the peripheral area of the depletion region would be thicker than that of the single nanocontact due to the extension of each depletion width. Thus this causes the decrease in the tunneling probability through the edge of depletion region, leading to the decreased current density in the multinanoscale contact.
Proximity effect in ion-beam-induced deposition of nanopillars
Authors: Chen Ping , Salemink Huub W. M. , Alkemade Paul F. A.
Published: July 2009

Ion-beam-induced deposition (IBID) is a powerful technique for prototyping three-dimensional nanostructures. To study its capability for this purpose, the authors investigate the proximity effect in IBID of nanopillars. In particular, the changes in shape and dimension of pillars are studied when a second pillar is grown near an existing pillar. On a semiconducting bulk Si and on an insulating Si3N4 membrane the first pillar gets broader, whereas on Si it starts to bend. They attribute the broadening and bending to the additional deposition induced by the particles scattered from the growing second pillar. On Si the second pillar is taller than the first one, while on Si3N4 it is shorter and rougher. This difference points to an important role of the substrate conductivity in the proximity effect. In a conductive environment the changes in the second pillar are mainly caused by a precursor coverage enhancement in the pillar surface. This enhancement is caused by precursor molecules, which are reflected or desorbed from the first pillar. In the case of an insulating environment, the changes in the second pillar are mainly caused by the reduction in the substrate surface charging due to the presence of the first pillar.
Scanning tunneling microscope–cathodoluminescence measurement of the GaAs/AlGaAs heterostructure
Authors: Watanabe Kentaro , Nakamura Yoshiaki , Ichikawa Masakazu , Kuboya Shigeyuki , Katayama Ryuji , Onabe Kentaro
Published: July 2009

The authors studied local optical properties of GaAs/AlGaAs heterostructure by scanning tunneling microscope–cathodoluminescence (STM-CL) spectroscopy, where low-energy (∼100 eV) electrons field emitted from STM tips were used as bright excitation sources. The STM-CL measurements were performed at the (110) cross-sectional surface of the GaAs/AlGaAs multilayer structure. By evaluating contributions to the spatial resolution from the thermalization and the diffusion of minority carriers (electrons), they found that the field emission electron beam (FEEB) diameter provides the dominant contribution to this spatial resolution of the STM-CL spectroscopy. They also clarified that the difference between the STM-CL measurement position and the STM tip position was caused by the angular deviation of the FEEB from the surface normal.
Lift-off process using bilayer ultraviolet nanoimprint lithography and methacryloxypropyl-terminated-polydimethylsiloxane-based imprint resin
Authors: Jung Ho Yong , Hwang Seon Yong , Bae Byeong Ju , Lee Heon
Published: July 2009

A high-fidelity lift-off process using bilayer ultraviolet nanoimprint lithography (UV-NIL) to fabricate nanosized metal pattern was demonstrated. High O2 reactive ion etching (RIE) selectivity of the imprinted resist pattern to the underlayer is necessary to create the undercut pattern profile that is essential for the stable lift-off process. A methacryloxypropyl-terminated polydimethylsiloxane (M-PDMS)-based UV-curable liquid-phase imprint resin and a polyvinyl alcohol (PVA) underlayer were applied to bilayer UV-NIL for the high-fidelity lift-off process. The M-PDMS-based imprinted resist pattern showed high etch resistance to O2 plasma and the undercut pattern profile of the PVA underlayer for the lift-off process was formed by the O2 RIE process. The size and shape of the imprinted resist patterns were hardly changed during PVA underlayer etching by O2 RIE. As a result, high-fidelity and high-aspect-ratio metal patterns without rabbit-ear-shaped defects were fabricated by the lift-off process using bilayer UV-NIL with the M-PDMS-based imprint resin, which has high etch resistance to O2 RIE, and the PVA underlayer.
Violet light-emitting diodes grown on crack-free AlGaN templates
Authors: Wang Tong-Wen , Chen Nie-Chuan , Lien Wei-Chieh , Wu Meng-Chyi , Shih Chuan-Feng
Published: July 2009

This study investigates the violet light-emitting diodes (LEDs) grown on crack-free AlGaN templates, which were prepared on GaN and AlN nucleation layers (NLs) over sapphire substrates by metal-organic chemical-vapor deposition using a two-step growth method. Symmetric and asymmetric x-ray diffraction patterns show that the LED structure grown on the AlGaN template with a GaN NL exhibits a better crystalline quality as compared to that with an AlN NL. When observed from the analyses of secondary-ion-mass spectroscopy and transmission-electron microscopy, it is found that the thickness and the indium composition in the InGaN wells of InGaN∕GaN multiquantum wells are slightly different at the growth temperatures of 720 and 750°C. In addition, the LEDs with GaN NL exhibit a narrower full width at half maximum of the excitonic peaks than those with AlN NL.
Fabrication of Si-based two-dimensional photonic quasicrystals by using multiple-exposure holographic lithography
Authors: Yeo Jong-Bin , Yun Sang-Don , Kim Nam-Hoon , Lee Hyun-Yong
Published: July 2009

Two-dimensional (2D) photonic quasicrystal (PQC) template patterns have been fabricated by using multiple-exposure holographic lithography (MHL). The MHL technique is based on Lloyd’s mirror setup using interference of two equivalent beams, which is an excellent method for fabricating periodic structures of a large area. The 2D PQC array shows various sizes and shapes with a change in the incident angle (θ) and rotation angle (γ) of the multiple-exposure beams. In addition, the filling factor (η), which is a very important factor for optical characteristic of 2D PQCs, was controlled by the exposure time (τ). The fabricated PQCs showed eight-, ten-, and 12-fold patterns with high-order rotational symmetries. Diffraction patterns using 632.8 nm HeNe laser were also observed with n-rotation symmetry for the corresponding n-fold PQCs. After fabricating the PQCs, reactive-ion etching of the silicon wafer was performed with 50-nm-thick chromium (Cr) as a mask in CF4/O2 plasma to a 1.3 μm depth. The authors confirmed that fabrication of n-fold 2D PQCs in a large area with suitable optical characteristics could be controlled by some parameters of MHL.
Characterization of 5MeV proton-irradiated gallium nitride nanowires
Authors: Kim H.-Y. , Ahn J. , Mastro M. A. , Eddy C. R. , Han J. , Yang T. , Kim J.
Published: July 2009

GaN nanowires were irradiated using a cyclotron at 5MeV energy with a fluency of up to 3.38×1015∕cm2 protons. The resistance of the GaN was increased by 95% at a dose of 1.69×1015∕cm2 protons and then 116% at a dose of 3.38×1015∕cm2 protons because of the damage induced by the high energy protons. Cathodoluminescence of the GaN nanowires found a slight broadening of near band-edge emission and a dramatic decrease in the intensity of midgap transitions. These GaN-based nanomaterials have a potential in space technology because of their strong bonding energy compared to other material systems such as silicon and GaAs. Furthermore, the relatively small decrease in resistivity confirms the predicted robustness to proton irradiation of GaN nanowires compared to a GaN thin film.
p
-type behavior of nitrogen doped, lithium doped, and nitrogen-lithium codoped Zn0.11Mg0.89O thin films
Authors: Qiu M. X. , Gu X. Q. , Ye Z. Z. , Lu J. G. , He H. P. , Zhang Y. Z. , Zhao B. H.
Published: July 2009

N-doped, Li-doped, and Li–N doped Zn0.89Mg0.11O thin films have been prepared by pulsed laser deposition. Hall-effect measurements indicate that the doping technique plays an important role in the p-type behavior of ZnMgO. Li doping produces high-resistivity p-type ZnMgO films, whereas N doping produces ZnMgO films with indeterminate carrier type. In contrast, Li–N codoping results in low resistivity and stable p-type ZnMgO films. The enhancement by Li and N coincorporation is investigated by secondary ion mass spectroscopy and is possibly responsible for the good p-type conduction in Li–N dual-acceptor doped Zn0.89Mg0.11O.
Dependence of local structural and electrical properties of nitride doped zinc oxide films on growth temperature
Authors: Chen Sy-Hann , Yu Chang-Feng , Liu Yen-Ju , Lin Tzu-Jen , Li Ya-Chi
Published: July 2009

Conducting atomic force microscopy was utilized to study the nanoscale surface electrical properties of N-doped zinc oxide films that had been prepared by pulsed laser deposition at different substrate temperatures. Current-voltage measurements were made while the conducting tip was fixed at different contact current points after scanning for normal imaging. Experimental results indicated that changes in the substrate temperature caused the redistribution of n-type carrier (Ohmic contact) and p-type carrier (Schottky contact) regions on the surface. Such a microscopic measurement method can be adopted to observe precisely the variances in the local carriers on the surface of films, benefiting future studies of nanoscale p-n homojunctions.
Light enhancement of Al nanoclusters embedded in Al-doped ZnO films of GaN-based light-emitting diodes
Authors: Lee Ching-Ting , Chou Ying-Hung , Yan Jheng-Tai , Lee Hsin-Ying
Published: July 2009

The aluminum (Al)-doped ZnO (AZO) films embedded with Al nanoclusters were employed to enhance the light output power of III-nitride-based light-emitting diodes (LEDs). The ZnO and Al targets were sputtered using a magnetron cosputtering system. Al nanoclusters embedded in AZO films were found in the AZO films deposited with Al dc power of 10W and ZnO rf power of 100W using high resolution transmission electron microscopy. An increase of 20% in the light output power of the GaN-based LEDs with AZO films embedded with Al nanoclusters can be obtained compared to the conventional LEDs operated at 500mA.