bluuebunny/crossref_metadata_2025 huggingface dataset:
ANALYTICAL REASONING SKILLS INVOLVED IN GRADUATE STUDY: PERCEPTIONS OF FACULTY IN SIX FIELDS
Authors: Powers Donald E. , Enright Mary K.
Published: September 2014

This study was intended to provide information on the role of analytical abilities in graduate study. Graduate faculty in six fields of study (chemistry, computer science, education, English, engineering, and psychology) were asked to judge:

the importance for academic success of a wide variety of analytical skills

the seriousness of various reasoning errors

the degree to which a variety of “critical incidents” had affected their estimations of students' analytical abilities.

Faculty members were generally able to discriminate among the various skills, errors, and incidents they were asked to consider, although the vast majority of skills, for example, were rated to be at least moderately important on average. Some skills were viewed as extremely important in all disciplines. More typically, however, disciplines varied quite markedly with respect to faculty perceptions of the importance, seriousness, and impact of these skills, errors, and incidents.

Several relatively interpretable dimensions were found to underlie particular clusters of reasoning skills. These dimensions or factors involved (a) the analysis and evaluation of arguments, (b) the drawing of inferences and the development of conclusions, (c) the definition and analysis of problems, (d) the ability to reason inductively, and (e) the generating of alternative explanations or hypotheses. These dimensions were judged to be differentially important for success in the six disciplines included in the study.

The study results would appear to have definite implications for developing future editions of the GRE analytical ability measure. For instance, some reasoning abilities that were perceived as very important are well represented in the current version of the analytical measure but others are not. That some abilities appear to be much more important in some fields than in others would imply the need to carefully balance the measurement of various reasoning skills to ensure fairness to test takers from different fields of study. Fairness should be aided by including for measurement those skills rated as consistently important across all disciplines. Finally, the several dimensions underlying various clusters of reasoning skills should be applicable to extending the test specifications for the current version of the analytical measure.
GENERALIZATION OF GRE GENERAL TEST VALIDITY ACROSS DEPARTMENTS
Authors: Boldt Robert F.
Published: September 2014

This study of the validity of the GRE General Test used data from predictive validity studies that were conducted by the GRE Validity Study Service (VSS) in 79 graduate departments. The performance criterion was first‐year grades in graduate school. Observed validities were computed, and for each graduate department validities were also estimated for groups at two other stages of selection–applicants for admission to the department, and all GRE takers.

Two validity generalization hypotheses were tested. One was that the General Test's validities were equal across studies; the other was that the General Test's validities had equal ratios across studies, that is, that the level of the validities might vary from institution to institution but the ratios would be constant. These hypotheses were applied for VSS groups, applicant groups, and all GRE takers, and implied validities (validities that would be observed if the hypotheses were true) were calculated. When the implied validities were compared to the observed validities, it was found that the assumption of equal validity did not account well for differences in the level of observed validity of the GRE General Test. The equal ratio hypothesis accounted for the observed validities rather well, possibly due to overcapitalization on chance, but departmental discipline was not significantly related to the degree of fit of observed to implied validities.

At all levels of selection, the study yielded applicant validities that were predominantly positive. This lends support to the presumption that the General Test's validity is transportable, i.e., institutions that do not use the General Test can, if they adopt it, expect it to prove valid. In view of the scarcity of very low or negative validities, studies revealing such validities should be questioned.
THEORY AND PRACTICE: THE RATIONALE FOR A CAREER GUIDANCE WORKBOOK
Authors: Katz Martin R.
Published: September 2014

Theoretical issues such as the structure of individual attributes and their linkage to occupational information are examined in the context of a new workbook.
WHICH COMES FIRST, CAUSE OR EFFECT?
Authors: Holland Paul W.
Published: September 2014

This is a short introduction to Rubin's model for the study of causal inference in experiments and observational studies. More details, proofs of mathematical assertions, and expanded discussions can be found in the references.
CONSTRUCT VALIDITY OF THE GRE ANALYTICAL TEST: A RESOURCE DOCUMENT
Authors: Duran Richard , Powers Donald , Swinton Spencer
Published: September 2014

The purpose of the study reported here was to plan further research aimed at understanding how the current version of the GRE analytical measure reflects cognitive skills that are important to success in graduate education. Several activities were completed, including selective literature reviews of (a) cognitive and psychometric research on reasoning and (b) more general educational research on the role of reasoning in higher education. The two analytical item types included in the current test were analyzed to determine more precisely the kinds of basic skills that underlie their solution. Based on these activities a summary was made of the major thinking and language skills that seem to be required for successful performance on the test. Two major conclusions that were reached are that (1) although there is a considerable body of research on reasoning, thinking, and problem solving, there are few well‐developed models or theories to guide the measurement of analytical ability and (2) although reasoning, critical thinking, and other such processes are assumed to be requirements of successful academic performance, there is little documentation of the specific involvement of these skills in graduate education. Based on these general conclusions and other more specific findings, further work has been planned and is proposed in a separate document.
A STUDY OF THE EFFECTS OF ITEM OPTION REARRANGEMENT ON THE LISTENING COMPREHENSION SECTION OF THE TEST OF ENGLISH AS A FOREIGN LANGUAGE
Authors: Golub‐Smith Marna L.
Published: September 2014

The study was conducted to provide information for the TOEFL program about the effects of option rearrangement as a means of increasing test security during administrations of the listening comprehension section of the TOEFL. Two forms, consisting of items whose options were systematically scrambled, were spiraled together with the base versions during the pretesting phase of test development. The results indicated that scrambling an item's options does produce differences in both the estimated item response functions and equating functions. Therefore, it was recommended that this procedure not be adopted for the operational program.
THE DUTCH IDENTITY: A NEW TOOL FOR THE STUDY OF ITEM RESPONSE THEORY MODELS
Authors: Holland Paul W.
Published: September 2014

The Dutch Identity is a useful way to reexpress the basic equations of item response theory (IRT) that relate the manifest probabilities to the item response functions (IRFs) and the latent trait distribution. The identity may be exploited in several ways. For example: (a) to show how IRT models behave for large numbers of items – they are submodels of second‐order log‐linear models for 2J tables; (b) to suggest new ways to assess the dimensionality of IRT models – factor analysis of matrices composed of second‐order interactions from log‐linear models; (c) to give insight into the structure of latent class models; and (d) to illuminate the problem of identifying the IRFs and the latent trait distribution from sample data.
SEARCH FOR PATTERNS OF SUCCESS ON GRE GENERAL TEST ITEMS
Authors: Boldt Robert F.
Published: September 2014

The impetus for the present study comes from the rather inconclusive results from “test bias” studies, which can be characterized as studies to determine whether ethnic, racial, or gender groups differ from the rest of the population taking the GRE General Test in terms of patterns of item difficulty. The results of such studies have been sufficiently weak as to suggest that test items are not strongly “biased” for any particular subgroups of test takers as defined by race, gender, or ethnicity. It is possible, however, that (a) there are subgroups of test takers whose patterns of item difficulty differ but whose members are demographically mixed, or (b) there are no groups for whom item difficulty differences exist (except for overall level of performance on the test. The potential groupings that underlie test performance are called latent groups because they are not defined beforehand, but are a product of the study. Latent groups are defined as groups that differ in the patterns of their item difficulties.

To clarify the results of bias studies, the present study sought to discover latent groups of examinees by utilizing only test performance data. Factor analyses were performed to determine lower bounds for the numbers of latent groups. Two types of coefficients were analyzed: the proportion of joint successes on pairs of items, and phi‐coefficients. Both types of coefficients were well accounted for by a single factor. This result implies the existence of no more than one group.

To be sure that the effects of group heterogeneity were not being masked, test takers who described themselves as White were sampled down so that the responses of other demographic groups could more strongly effect the results. However, using either of the coefficients analyzed, a single factor still accounted very well for the relationships among test items.

Clearly, if any latent group structure were to be detected, a more sensitive approach was required. Thus, the subsequent approach adopted examined the value of each residual after a given number of factors was extracted. This approach led to a three‐group solution for the verbal subtest, and a two‐group solution for the quantitative subtest. This pattern of item difficulties suggested that these groups were differentiated due to bends in the item characteristic curves, rather than through demographic effects. In addition, a large number of groups were identified for the analytic subtest, but the vector of item difficulties proved to be essentially proportional. Also, demographic and item content information proved uninterpretable. It was concluded that the tests were essentially unitary as intended.
EQUATING THE SCORES OF THE PRUEBA DE APTITUD ACADÉMICA™ AND THE SCHOLASTIC APTITUDE TEST®
Authors: Angoff William H. , Cook Linda L.
Published: September 2014

The present study is a replication, in certain important respects, of an earlier study conducted by Angoff and Modu (1973) to develop algorithms for converting scores expressed on the College Board Scholastic Aptitude Test (sat) scale to scores expressed on the College Board Prueba de Aptitud Académica (paa) scale, and vice versa. Because the purpose and the design of the studies, though not all of the psychometric procedures, were identical in the two studies, the language of this report often duplicates that of the earlier study. The differences in procedure, however, are worth noting, and it is hoped that this study will contribute in substance and method to the solution of this important problem.

The study described in this report was undertaken in an effort to establish score equivalences between two College Board tests—the Scholastic Aptitude Test (sat) and its Spanish‐language equivalent, the Prueba de Aptitud Académica (paa). The method involved two phases: (1) the selection of test items equally appropriate and useful for English‐ and Spanish‐speaking students for use as an anchor test in equating the two tests; and (2) the equating analysis itself. The first phase called for choosing a set of items in each of the two languages, translating each item into the other language, “back‐translating” independently into the original language, and comparing the twice‐translated versions with their originals. This process led to the adjustment of the translations in several instances and, in other instances, to the elimination of some items considered too difficult to be translated adequately. At this point both sets of “equivalent” items, each in its original language mode, were administered as pretests, chiefly to determine whether the two response functions for each item were sufficiently similar for the items to be considered equivalent.

On the basis of these analyses two sets of items—one verbal and the other mathematical—were selected for use as anchor items for equating. These were administered again (in the appropriate language) at regularly scheduled administrations of the sat and the paa. An item response theory (irt) model was used to equate the paa to the sat, with the anchor items serving as the link in the equating process.

The equating itself showed definite curvilinear relationships in both verbal and mathematical tests, indicating in this instance that both sections of the paa are easier than the corresponding sat sections. The results also showed good agreement between the current conversions and the 1973 Angoff‐Modu conversions for the mathematical tests, but not so close agreement for the verbal tests. The reasons for the difference are (speculatively) attributed to improved methodology in the present study, especially for the more difficult verbal equating, and to the possibility of scale drift in one or the other test (or both tests) over the intervening 12 to 15 years since the last study.
DIFFERENTIAL ITEM FUNCTIONING FOR MALES AND FEMALES ON SAT®‐VERBAL READING SUBSCORE ITEMS
Authors: Lawrence Ida M. , Curley W. Edward , McHale Frederick J.
Published: September 2014

The Reading Comprehension and Sentence Completion items from four forms of the SAT‐verbal sections were examined for differential item functioning (DIF) between male and female test‐takers. In general, minimal DIF was observed for the items analyzed in this investigation. However, among the relatively few items exhibiting substantial DIF, two trends related to science content were noted.

An important factor that appears to be connected to DIF on Reading Comprehension items is the distinction between technical and nontechnical reading passage material. Items associated with passages containing technical (as opposed to historical or philosophical) science material are generally more difficult for female examinees. This trend emerged for three of the four forms studied. Data from the fourth form suggested that there may be an interaction between the technical science factor and the passage location. Confirmation of this finding will require a follow‐up study.

The main factor that appears to be related to DIF on Sentence Completion items is the distinction between nonscience or surface science references and true science references. Items containing true science references tend to be more difficult for females.

Because the majority of items in the Reading subscore exhibited minimal DIF, the conclusions described in this report are based on limited data. Findings from this study also indicate the confounded nature of multiple factors thought to contribute to DIF. There is a need for experimental research in which item features and passage features can be controlled and counterbalanced in variable sections of the SAT.
A COMPARISON OF OBSERVED SCORE AND TRUE SCORE EQUATING METHODS FOR REPRESENTATIVE SAMPLES AND SAMPLES MATCHED ON AN ANCHOR TEST1
Authors: Lawrence Ida M. , Dorans Neil J.
Published: September 2014

This paper addresses the sample invariant properties of four equating methods (Tucker and Levine linear equating, Equipercentile equating through an anchor test, and three‐parameter item response theory equating). Equating results across two sampling conditions, “representative” sample and “matched” sample, were compared to determine which equating procedures produced the most consistent results. In the representative sample condition, equatings were based on old‐form and new‐form samples that differed in ability; in the matched sample condition, the old‐form sample was selected to match the anchor test score distribution of the new‐form sample.

Results for the item response theory equating method differed for representative and matched samples, as did the equating results for Levine and Equipercentile methods. Results based on the Tucker observed‐score equating method were found to be essentially the same across representative and matched sample conditions. Results for the four equating methods tended to converge under the matched sample condition. The last section of this paper offers tentative explanations for the findings.
NATIVE LANGUAGE, ENGLISH PROFICIENCY, AND THE STRUCTURE OF THE TEST OF ENGLISH AS A FOREIGN LANGUAGE
Authors: Oltman Philip K. , Stricker Lawrence J. , Barrows Thomas S.
Published: September 2014

Responses on the TOEFL© test may reflect both the influence of the examinees' native language and their level of English proficiency. The aim of this study was to appraise the effect of these examinee variables on the structure of the test. The interrelations among TOEFL items, using all of the information provided by the various responses to the items (the four alternatives, omitted, and not reached), were analyzed by three‐way multidimensional scaling for samples of examinees systematically varying in native language and level of English proficiency. Four dimensions were identified: three corresponded to the sections of the test, and the fourth was an end‐of‐test phenomenon. The dimensions were predominantly defined by easy items and were most salient for low‐scoring examinees. The salience of the dimensions did not differ for the various language groups, except for the end‐of‐test dimension. Major conclusions were that the TOEFL's construct validity is supported, the test's interpretation varies with the examinees' English proficiency, easy and difficult items differ in their potential for diagnosis and global screening, and the dimensionality of the TOEFL and of competence in English depend on the examinees' English proficiency.
MEANING AND VALUES IN TEST VALIDATION: THE SCIENCE AND ETHICS OF ASSESSMENT1
Authors: Messick Samuel
Published: September 2014

Since both score meaning and the value implications of scores as a basis for action are central issues in test validation, a unified view of validity is required that comprehends both the scientific and the ethical underpinnings of test interpretation and use. This unified concept of validity integrates considerations of content, criteria, and consequences into a construct framework for testing rational hypotheses about theoretically relevant relationships, including those of an applied as well as of a scientific nature. The essence of unified validity is that the appropriateness, meaningfulness, and usefulness of score‐based inferences are inseparable and that the unifying force behind this integration is the trustworthiness of empirically grounded score interpretation, that is, construct validity.
NONRESPONSE BIAS IN THE GRE BACKGROUND QUESTIONNAIRE
Authors: Grandy Jerilee
Published: September 2014

Results of some studies of the GRE database suggest that analyses relying upon information from the background questionnaire may lead to misleading or erroneous conclusions because of nonresponse bias. This study examined existing data from all examinees who took the General Examinations for the first time in 1984/85 to estimate the extent of non‐response bias and how seriously it may be affecting statistical summaries and interpretations.

Results indicate that nearly all examinees who answer the first item on the questionnaire generally complete the questionnaire or omit just one or two items. However, 16% never answer the first item.

Of those who indicate on the first item that they are taking the GRE for the first time, the response rate to all other items is generally better than 97%. The response rate is even higher for U.S. citizens and resident aliens.

The first five questionnaire items involve various branching instructions, and examinees make a number of errors in the course of branching. U.S. citizens and resident aliens are instructed to answer the questions on ethnicity and state of residence, while all others are to skip these two questions. Almost 98% of the U.S. citizens answer the ethnicity question, but 17% of the foreign examinees living abroad answer the ethnicity question when they have been instructed to skip it.

There is no correlation between GRE scores and the number of questionnaire items left blank. However, the differences in test score averages between examinees who omit a given question and examinees who answer it are often quite large. Furthermore, those who omit a question may have either higher or lower average test scores than those who answer it. Foreign examinees are generally more likely to omit a question than are U.S. citizens. Among U.S. citizens, those who answer a question often have higher GRE quantitative and analytical scores, but lower verbal scores, than those who omit the question.

Despite the sometimes large differences in test scores between those who omit an item and those who answer it, the numbers of omitters are small–generally on the order of 1 or 2%. The extent to which their test scores affect statistical summaries of the much larger group averages is negligible.

This study concludes that there appears to be some confusion regarding the branching instructions involving the first five items, with the result that some foreign examinees answer the ethnic question when they should not. Because most statistical summaries are broken down by citizenship and ethnicity, these questions are important. A recommendation is made to simplify these items future revisions of the questionnaire by removing branching instructions.
FINAL REPORT: EXPLOITING COLLATERAL INFORMATION IN THE ESTIMATION OF ITEM PARAMETERS
Authors: Mislevy Robert J.
Published: September 2014

When using item response theory (IRT) models in educational and psychological measurement, it is standard practice to estimate the operating characteristics of test items from examinees' item responses alone. This is the final report of a project that employed Bayesian and empirical Bayesian methods to exploit additional information that is often available about test items (e.g., format, content, or cognitive processing requirements) or about examinees (e.g., educational background or demographic status). Practical and theoretical results obtained in a series of research reports are summarized.
A STUDY OF THE COMPARABILITY OF SCORES OBTAINED ON THE ATP MATHEMATICS LEVEL I AND LEVEL II TESTS1
Authors: Cook Linda , Eignor Daniel , Mazzeo John
Published: September 2014

This report describes the results of two studies which were conducted to obtain information regarding the comparability of scores on the Admissions Testing Program Mathematics Level I and Mathematics Level II tests. It has been assumed that if the scaling and equating process used with the tests is functioning properly, those students with adequate preparation to take both tests should receive similar scaled scores regardless of the test they choose to take. Results of previous studies had raised some concern that the scaling and equating methods used to date have not resulted in the proper alignment of the scales of the two tests. In addition, concern has been raised that the inclusion of Plane Geometry items in the Mathematics Level I exam disadvantages examinees prepared to take the Level II exam in that they have, in general, taken their course in plane geometry some time prior to the test. In the first study, an experimental single‐group equating of scores from a form of the Mathematics Level II test to scores from a form of the Mathematics Level I test was conducted using data from a sample of examinees who elected to take both tests at the December 1983 administration. The resulting raw‐to‐scale conversion was compared to the operational conversion which was derived from a common‐item equating of the Mathematics Level II form to a previous form of the same test. In the second study, the relative performance of groups of students with comparable amounts of course preparation but different amounts of time since they last took a plane geometry course was examined. The results of the equating study, though not definitive, suggest that the scale of the Mathematics Level II test may be somewhat higher than the scale of the level I test. The results of the second study indicate that students prepared to take both tests are probably not disadvantaged by the inclusion of plane geometry items in the Mathematics Level I test.
TOWARD A PSYCHOMETRICS FOR TESTLETS§
Authors: Wainer Howard , Lewis Charles
Published: September 2014

In 1987 the testlet was introduced as one way of dealing with a variety of problems that might occur with the algorithmic construction of tests. In the short time since this introduction its range of plausible usages has been broadened considerably through the work of other researchers. In this paper we examine three different applications of the testlet concept and describe the psychometric models which seem most suitable for each application. In each case, the testlet concept gracefully solves a problem that would have been awkward with other, more traditional approaches.
ENHANCING THE INTERPRETATION OF A NORM‐REFERENCED SECOND‐LANGUAGE TEST THROUGH CRITERION‐REFERENCING: A RESEARCH ASSESSMENT OF EXPERIENCE IN THE TOEIC TESTING CONTEXT
Authors: Wilson Kenneth M.
Published: September 2014

This study was undertaken to develop guidelines for making interpretive inferences from scores on the Test of English for International Communication (TOEIC), a norm‐referenced test of English‐language listening comprehension (LC) and reading (R) skills, about level of ability to use English in face‐to‐face conversation, indexed by performance in the Language Proficiency Interview (LPI) situation. LPI performance, rated according to behaviorally defined levels on the LPI/ILR/FSI quasi‐absolute proficiency scale, was treated as a context‐independent criterion, using the familiar regression model in an apparently novel application (for such criterion‐referencing purposes) in the context of a large‐scale ESL‐testing program. The study employed TOEIC/LPI data‐sets generated during operational ESL assessments in representative TOEIC‐use settings (places of work or work‐related ESL training) in Japan, France, Mexico, and Saudia Arabia, involving samples of adult, educated ESL users/learners in or preparing for ESL‐essential positions with companies engaged in international commerce. The pattern of TOEIC/LPI concurrent correlations was consistent across samples and there was relatively close fit between sample LPI means and estimates from TOEIC scores, especially TOEIC‐LC, using combined‐sample regression equations. Theoretical and pragmatic implications of the findings are discussed. General guidelines are provided for making inferences about LPI‐assessed level of oral English proficiency from TOEIC scores. Directions are suggested for further research and development activities in the TOEIC testing context.
EMPIRICAL ESTIMATION ERRORS IN ITEM RESPONSE THEORY AS A FUNCTION OF TEST PROPERTIES*
Authors: Stocking Martha L.
Published: September 2014

The success of applications of Item Response Theory (IRT) depends upon the properties of the estimates of model parameters. Many theoretical properities of these estimates have been extensively studied. However, the properties of estimates obtained empirically from real data depend not only on the theoretical results, but also on the data and the estimation procedures used to obtain them. In this paper, the properites of estimates obtained from a commonly‐used implementation of the joint maximum likelihood approach (LOGIST) are examined extensively and shown to be, in part, functions of the properties of the test or item set being calibrated. A small study is also made of the properties of estimates obtained from a commonly‐used implementation of the marginal maximum likelihood approach (BILOG). Recommendations are made for the improvement of both procedures.
Stability analysis of rotary power flow controller
Authors: Tolue Khayami Mohammad , Shayanfar Heidarali , Kazemi Ahad
Published: September 2014

This paper deals with the stability analysis of a rotary power flow controller (RPFC). RPFC is a newly presented flexible alternating current transmission system device based on the rotary phase shifting transformer (RPST) configuration. This device comprises a shunt and a series transformer and two RPSTs. In this paper, a linear model is developed for RPFC in the dq‐reference frame. The model includes two RPSTs, shunt, and series transformers. Stability of the device is studied using eigenvalues of the state matrix. Effects of system parameters such as resistance, reactance, and phase difference of the shunt and series transformers and RPSTs on stability are investigated using eigenvalue sensitivity analysis. Simulation results using PSCAD/EMTDC software and analytical results based on eigenvalue analysis are presented to evaluate effects of different parameters on stability of RPFC. Copyright © 2014 John Wiley & Sons, Ltd.
Broadband circularly polarized beam‐steering antenna array for wireless applications
Authors: Aribi T. , Naser‐Moghadasi M. , Sadeghzadeh R. A.
Published: September 2014

This article describes the implementation of a broadband circularly polarized (CP) antenna array for switched beam applications. The antenna comprises of four identical CP slot elements in a 2 × 2 configuration that uses a 4 × 4 feeding network. Each CP slot element in the array is sequentially rotated with respect to each other to enhance the antenna's axial‐ratio (AR) bandwidth. Measured results confirm the array exhibits an impedance bandwidth of 2.25 GHz that extends over the frequency range 4.6–6.85 GHz (∼40%) for S11 ≤ −10 dB, and 3 dB AR bandwidth of 1.7 GHz that extends between 4.8–6.5 GHz (∼30%). The antenna's gain is in excess of 6.8 dBi between 5–6 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2813–2817, 2014
A low loss double‐pole double‐throw switch in 65 nm CMOS for wigig applications
Authors: Choi Sunkyu , Son Juho , Hong Seungpyo , Shin Gyong‐Seop , Kim Choul‐Young
Published: September 2014

This article presents a 60 GHz low insertion loss double‐pole double‐throw (DPDT) switch implemented in 65 nm standard CMOS process. To achieve the low insertion loss, various techniques are used such as the double‐well body‐floating, gate‐floating, high‐performance thin‐film microstrip line, resonating the capacitance of the off‐state transistor, and the transmission line based matching network. To achieve both high performance and small area, EM simulations are intensely performed to model passive components. The DPDT switch achieves insertion loss of less than 2.7 dB, and return loss of better than 10 dB over the 52–66 GHz band. The measured IIP3 is 18 dBm (simulated IP1dB is 11.4 dBm). The fabricated DPDT switch has an effective area of 0.073 mm2. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2864–2867, 2014
Compact metamaterial‐inspired band‐pass filter
Authors: Palandöken Merih , Uçar Mustafa H. B.
Published: September 2014

ABSTARCT

In this article, a compact, metamaterial‐inspired band‐pass filter is introduced for the passband frequencies between 3.9 and 4.54 GHz with the physical size of main filtering section as compact as λo/11 ×λo/14. The design and operation principles are verified with numerical and experimental results. The measured and simulated results show good agreement. The proposed filter is additionally modeled with lumped circuit elements as equivalent circuit model to confirm the operation and design principle. This compact filter in comparison to the conventional stepped impedance or coupled line filter designs does not require an external matching network, which reduces the filter physical size significantly. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2903–2907, 2014
Hundreds megawatt‐level pulse transmission waveguide vacuum port using series inductive post‐wall
Authors: Choi Jun‐Ho , Shin Jin‐Woo , So Joon‐Ho , Kim Yong‐Hoon
Published: September 2014

A simple waveguide vacuum port for hundreds MW pulse transmission at S‐band is proposed. It uses the series inductive post‐wall to improve the characteristics of the RF leakage attenuation and maximize the unit area of the vacuum port related with effective pumping speed. This type of vacuum port significantly increases RF leakage attenuation above −50 dB without RF electrical breakdown phenomena and provides simple structure to enhance the conductance
of the waveguide vacuum port found to be around
for above −50 dB RF leakage attenuation. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2894–2896, 2014
A multiband power amplifier using a switch‐based reconfigurable matching network for optimized power performance
Authors: Lee G. , Jung J. , Jang J. , Song J.
Published: September 2014

A multiband power amplifier (MBPA) with a switch‐based reconfigurable output matching network is presented for long‐term evolution handset applications. The MBPA is designed in a dual‐path configuration to improve efficiency in two different power levels for different frequency bands of the evolved UMTS terrestrial radio access (E‐UTRA). The dual‐path MBPA with the switch‐based reconfigurable output matching network delivered a collector efficiency of 31.8–38.5%, while satisfying the linearity specification (i.e., an adjacent channel leakage ratio less than −30 dBc) at an output power of 26.5 dBm across the five popular frequency bands of the E‐UTRA. In the low power mode, the MBPA delivered a collector efficiency of 21.8–35.4% with an adjacent channel leakage ratio smaller than −32.3 dBc at an average output power of 18 dBm. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2881–2884, 2014
A modeling method for dumbbell‐shaped DGS and its parameter extraction
Authors: Woo Duk‐Jae , Lee Taek‐Kyung , Nam Sangwook
Published: September 2014

This article presents an equivalent circuit model for a dumbbell‐shaped defected ground structure (DGS) in a microstrip line. The effects of equivalent circuit elements of a dumbbell‐shaped DGS and their magnetic coupling to the host transmission line are modeled as a simple lumped‐element circuit. By adding a virtual capacitor on the narrow etched gap, the values of inductance and capacitance of the dumbbell‐shaped DGS in the ground plane were extracted. Also, other main circuit parameters of the proposed circuit model were extracted using EM simulation result. This article provides one approach for understanding the operating principle of the DGS structures. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2910–2913, 2014
A novel approach for the design of a modified excitation signal using a narrow pulse generator for high‐resolution time‐domain reflectometry applications
Authors: Ojaroudi Mohammad , Mehrshahi Esafndiar , Fathy Aly. E.
Published: September 2014

In this article, a novel modified stimulus signal is used to improve the accuracy of localizing discontinuities for time‐domain reflectometry (TDR) measurements. This pulse shaping puts more energy at higher frequencies in contrast with conventional step or impulse TDR. Hence, a wider bandwidth is available to achieve higher accuracy for precise spatial localization. The proposed modified TDR is less expensive than a vector network analyzer, very practical as it is based on more realistic signals rather than assuming ideal impulses or steps. Simulated and measured results are presented to validate the accuracy of the proposed approach. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2987–2990, 2014
New types of associating monomers and polymers from α‐aminocaprolactam and 2‐isocyanatoethyl (meth)acrylate: properties in condensed phase and in solution
Authors: Mondrzyk Adam , Ritter Helmut
Published: September 2014

α‐Aminocaprolactam is reacted with the isocyanate function of 2‐isocyanatoethyl (meth)acrylate to yield monomers 2‐[3‐(2‐oxoazepin‐3‐yl)ureido]ethyl (meth)acrylate. These hydrogen bond‐forming monomers crystallize easily in macroscopic bunches of needles. Subsequently, homopolymers and copolymers of the monomers with N,N‐dimethylacrylamide are synthesized radically. The homopolymers have spherical structures and are semi‐crystalline showing large amorphous domains. Polymeric solutions of the homopolymers in water–ethanol have an upper critical solution temperature. In contrast, the solutions of the copolymers in water have a lower critical solution temperature. If copolymerized in concentrated solution, the copolymers show gelation after treatment with excess water. © 2014 Society of Chemical Industry
Area‐selective microwrinkle formation on poly(dimethylsiloxane) by treatment with strong acid
Authors: Watanabe Masashi , Hashimoto Ryoma
Published: September 2014

Microwrinkles were formed by treating poly(dimethylsiloxane) (PDMS) surfaces with a mixture of concentrated sulfuric acid and nitric acid at 80 °C followed by a water rinsing step. The acid treatment oxidized the treated area, which also swelled owing to absorption of water during the rinsing step. This absorption of water induced a compressive stress on the PDMS surface that caused the formation of wrinkles. The appearance of wrinkles was controlled by the time interval between the end of the acid treatment and the beginning of the water rinsing step. Wrinkles were formed when the time interval was shorter than 5 s, as water was absorbed by the hygroscopic acid molecules within the treated surface. For longer time intervals of 300 s, this phenomenon was not observed. Based on these findings, a procedure for forming wrinkles in specific areas was developed by hydrating the chosen areas with wet filter paper cut into specific shapes after the acid treatment. The formation of wrinkles was confined to the area under the piece of paper. The orientation and alignment of the wrinkles at the boundaries were also characterized. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 167–174
Flexural behaviour of recycled aggregate concrete graded slabs
Authors: Xiao Jianzhuang , Sun Chang , Jiang Xinghan
Published: September 2014

This paper proposes a new concept for “recycled aggregate concrete graded slabs”, which can be achieved through graded distribution for the mechanical properties of the recycled aggregate concrete (RAC). In this study, one four‐point bending test was used to investigate six RAC graded slabs and three homogeneous slabs with RAC. The major parameters considered were the layers with different recycled coarse aggregates (RCAs) replacement percentages (0, 50 and 100%), the grading pattern (different casting methods) and the reinforcement ratio. It has been concluded that RAC graded slabs have similar flexural behaviour to that of homogeneous slabs with RAC. The reinforcement ratio, the layers with different RCA replacement percentages and the grading pattern can influence the flexural behaviour of RAC graded slabs. Furthermore, the effects of the three factors on both the flexural capacity and the deflection of the RAC graded slabs were studied with finite element method (FEM) simulation using ABAQUS software. Both the experiments and the FEM analysis indicate that the flexural behaviour of RAC slabs can be improved by using this suitable grading method.
Diagnostic Approach to Retromolar Trigone Cancer by Multiplanar Computed Tomography Reconstructions
Authors: Mazziotti Silvio , Pandolfo Ignazio , D'Angelo Tommaso , Mileto Achille , Visalli Carmela , Racchiusa Santi , Blandino Alfredo , Ascenti Giorgio
Published: September 2014

Neoplasms of retromolar trigone have important peculiarities due to their spatial relationships with the surrounding structures. Tumours that involve this area can extend to nearby muscles; adipose spaces; and other anatomic structures, such as the soft palate, the tonsillar fossa, the parapharyngeal space, and the floor of the mouth. In spite of a relatively quick diagnosis, the real extent of these tumours is typically underestimated at clinical examination. Our purpose was to propose a systematic approach to the use of multiplanar computed tomography reconstructions to evaluate normal retromolar trigone anatomy and the main pathways of spread for tumours that arise in this area. To our knowledge, only few reports exist in literature about this topic and none are about the usefulness of multidetector computed tomography and multiplanar reconstructions.
Eigenvalue sensitivity, singular values and discrete frequency selection mechanism in noise amplifiers: the case of flow induced by radial wall injection
Authors: Cerqueira Stéphane , Sipp Denis
Published: September 2014

We have performed linearized direct numerical simulations (DNS) of flow induced by radial wall injection forced by white-noise Gaussian forcings. We have shown that the frequency spectrum of the flow exhibits low-frequency discrete peaks in the case of a spatial structure of the forcing that is large scale. On the other hand, we observed that the spectrum becomes smooth (with no discrete peaks) if the spatial structure of the forcing is of a smaller extent. We have then tried to analyse these results in the light of global stability analyses. We have first computed the eigenvalue spectrum of the Jacobian and shown that the computed eigenvalues in the frequency range of interest were strongly damped and extremely sensitive to numerical discretization choices if large domains in the axial direction were considered. If shorter domains are used, then the eigenvalues are more robust but still extremely sensitive to the location of the upstream and downstream boundaries. Analysis of the$\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}\epsilon $-pseudo-spectrum showed that eigenvalues located in a region displaying ‘background’ values of$ \epsilon $below$10^{-12}$were extremely sensitive and confirmed that all values in this region of the spectrum were actually quasi-eigenvalues. The eigenvalues are therefore ill-behaved and cannot be invoked to explain the observed discrete frequency selection mechanism. We have then performed a singular value decomposition of the global resolvent matrix to compute the leading optimal gains, optimal forcings and optimal responses, which are robust quantities, insensitive to numerical discretization details. We showed that the frequency response of the flow with the large-scale forcing can accurately be reproduced by an approximation based on the leading optimal gain/forcing/response. Analysis of this approximation showed that it is the projection coefficient of the forcing onto the leading optimal forcing that is responsible for the discrete frequency selection mechanism in the case of the large-scale forcing. From a more physical point of view, such a discrete behaviour stems from the streamwise oscillations of the leading optimal forcings, whose wavelengths vary with frequency, in combination with finite extent forcings (which start or end at locations where the leading optimal forcings are strong). Experimental results in the literature are finally discussed in light of these findings.
Practical approach to determine apparent digestibility of canine diets
Authors: Hagen-Plantinga Esther A. , Bosch Guido , Hendriks Wouter H.
Published: September 2014

A practical approach to determine apparent faecal digestibility using privately owned dogs may be a useful tool in evaluating differences in nutrient digestibility between dogs with various life stages. The aim was to develop a simple method that would suit such studies using the whitening agent titanium oxide (TiO2) as an indigestible marker. Forty privately owned, healthy male and female dogs of various breeds were included. Selection was based on an owner questionnaire. Means with their standard errors age and body weight (BW) of the dogs were 6·2 (0·6) years (range 1·0–13·0 years) and 22·3 (2·5) kg (range 5·0–43·2 kg), respectively. Owners were provided a commercial dry extruded diet supplemented with a commercially available TiO2 containing kibble (final dietary TiO2 content: 0·77 g/kg). Dogs were fed the diet for seven consecutive days at 480 kJ × BW0·75. On day 7, owners were asked to collect all faeces during 24 h and store faeces at −20°C. Faecal samples were analysed for DM, ash, N, crude fat (CF), crude fibre and Ti and gross energy (GE) and organic matter were calculated. Means with their standard errors apparent faecal digestibility of GE, DM, organic matter, N, CF and crude fibre was 83·7 (0·71), 77·4 (0·79), 83·0 (0·61), 77·7 (0·81), 94·3 (0·51) and 30·3 (4·85), respectively. No significant differences were observed in nutrient digestibility due to weight, age, sex or neuter status. The digestibility assay using a practical approach described here may be a promising tool to determine digestibility of dietary nutrients under free-living conditions. Owner compliance, however, is a potentially limiting factor.
Evolutionary Planning of Safe Ship Tracks in Restricted Visibility
Authors: Szlapczynski Rafal
Published: September 2014

The paper presents the continuation of the author's research on ship track planning by means of Evolutionary Algorithms (EA). The presented method uses EA to search for an optimal set of safe tracks for all ships involved in an encounter. Until now the method assumed good visibility – compliance with standard rules of the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS, 1972). However, in restricted visibility, when Rule 19 applies instead of Rules 11 to 18, the problem is a different one. Therefore this paper introduces the extended method, with a focus on compliance with Rule 19 and its implications. It includes descriptions of detecting, penalizing and eliminating violations of Rule 19. The method has been implemented and the paper contains sample results of computer simulation tests carried out for ship encounters in restricted visibility in both open and restricted waters. They confirm the effectiveness of the chosen approach and suggest that the method could be applied in on board decision support systems.