Showing papers by "Boise State University published in 2008"

Near-Surface Wetland Sediments as a Source of Arsenic Release to Ground Water in Asia

Abstract: Tens of millions of people in south and southeast Asia routinely consume ground water that has unsafe arsenic levels. Arsenic is naturally derived from eroded Himalayan sediments, and is believed to enter solution following reductive release from solid phases under anaerobic conditions. However, the processes governing aqueous concentrations and locations of arsenic release to pore water remain unresolved, limiting our ability to predict arsenic concentrations spatially (between wells) and temporally (future concentrations) and to assess the impact of human activities on the arsenic problem. This uncertainty is partly attributed to a poor understanding of groundwater flow paths altered by extensive irrigation pumping in the Ganges-Brahmaputra delta, where most research has focused. Here, using hydrologic and (bio)geochemical measurements, we show that on the minimally disturbed Mekong delta of Cambodia, arsenic is released from near-surface, river-derived sediments and transported, on a centennial timescale, through the underlying aquifer back to the river. Owing to similarities in geologic deposition, aquifer source rock and regional hydrologic gradients, our results represent a model for understanding pre-disturbance conditions for other major deltas in Asia. Furthermore, the observation of strong hydrologic influence on arsenic behaviour indicates that release and transport of arsenic are sensitive to continuing and impending anthropogenic disturbances. In particular, groundwater pumping for irrigation, changes in agricultural practices, sediment excavation, levee construction and upstream dam installations will alter the hydraulic regime and/or arsenic source material and, by extension, influence groundwater arsenic concentrations and the future of this health problem.

Preferential killing of cancer cells and activated human T cells using ZnO nanoparticles

Abstract: Here we disclose the response of normal human cells to ZnO nanoparticles under different signaling environments and compare it to the response of cancerous cells. ZnO nanoparticles exhibit a strong preferential ability to kill cancerous T cells (˜28-35X) compared to normal cells. Interestingly, the activation state of the cell contributes toward nanoparticle toxicity as resting T cells display a relative resistance while cells stimulated through the T cell receptor and CD28 costimulatory pathway show greater toxicity in direct relation to the level of activation. The novel findings of cell selective toxicity towards potential disease causing cells indicate a potential utility of ZnO nanoparticle in the treatment of cancer and/or autoimmunity.

Advancing process‐based watershed hydrological research using near‐surface geophysics: A vision for, and review of, electrical and magnetic geophysical methods

Abstract: We want to develop a dialogue between geophysicists and hydrologists interested in synergistically advancing process based watershed research. We identify recent advances in geophysical instrumentation, and provide a vision for the use of electrical and magnetic geophysical instrumentation in watershed scale hydrology. The focus of the paper is to identify instrumentation that could significantly advance this vision for geophysics and hydrology during the next 3–5 years. We acknowledge that this is one of a number of possible ways forward and seek only to offer a relatively narrow and achievable vision. The vision focuses on the measurement of geological structure and identification of flow paths using electrical and magnetic methods. The paper identifies instruments, provides examples of their use, and describes how synergy between measurement and modelling could be achieved. Of specific interest are the airborne systems that can cover large areas and are appropriate for watershed studies. Although airborne geophysics has been around for some time, only in the last few years have systems designed exclusively for hydrological applications begun to emerge. These systems, such as airborne electromagnetic (EM) and transient electromagnetic (TEM), could revolutionize hydrogeological interpretations. Our vision centers on developing nested and cross scale electrical and magnetic measurements that can be used to construct a three-dimensional (3D) electrical or magnetic model of the subsurface in watersheds. The methodological framework assumes a ‘top down’ approach using airborne methods to identify the large scale, dominant architecture of the subsurface. We recognize that the integration of geophysical measurement methods, and data, into watershed process characterization and modelling can only be achieved through dialogue. Especially, through the development of partnerships between geophysicists and hydrologists, partnerships that explore how the application of geophysics can answer critical hydrological science questions, and conversely provide an understanding of the limitations of geophysical measurements and interpretation. Copyright © 2008 John Wiley & Sons, Ltd.

Buyer–supplier relationships: derived value over two decades

Abstract: This paper reviews studies of buyer–supplier relationships published in four prominent U.S.-based academic journals between 1986 and 2005. Our review revealed that the focus of academic researchers on types of value being extracted from buyer–supplier relationships changed between 1986 and 2005, as did their interest in the buyer mechanisms implemented to create value in these relationships. Although emphasis has changed over time, we found that scholars have primarily investigated four types of value derived from buyer–suppler relationships: operational performance improvements, integration-based improvements, supplier capability-based improvements and financial performance outcomes. The review also noted that researchers considered more buyer–supplier mutual efforts since 1996 than the earlier decade, but the number of studies investigating buyer practices has declined as a percentage of total publications. We conclude with a discussion of the review's implications for future research and practice.

Defense of trust management vulnerabilities in distributed networks

Abstract: Establishing trust among distributed network entities has been recognized as a powerful tool to secure distributed networks such as MANETs and sensor networks. Similar to most security schemes, trust establishment methods themselves can be vulnerable to attacks. In this article we investigate the benefits of introducing trust into distributed networks, the vulnerabilities in trust establishment methods, and the defense mechanisms. Five attacks against trust establishment methods are identified, and defense techniques are developed. Effectiveness of the attacks and the defense is demonstrated in the scenarios of securing routing protocols and detecting malicious nodes in MANETs.

P-T-t data from central Nepal support critical taper and repudiate large-scale channel flow of the Greater Himalayan Sequence

Abstract: A new synthesis of pressure-temperature conditions and pressure-temperature-time (P-T-t) paths is presented for high-grade metamorphic thrust sheets associated with the Main Central Thrust, in the Langtang and Darondi regions, central Nepal. From structurally low to structurally high, major structures include the Lesser Himalayan Duplex, Munsiari Thrust, Main Central Thrust (thrust contact between the Greater and Lesser Himalayan Sequences), and Langtang Thrust. Key P-T-t results include the following: in a transect from Lesser Himalayan Duplex to Langtang Thrust rocks, peak metamorphic P-T conditions are uniformly ∼550 °C and 8 kbar in the Lesser Himalayan Duplex, and show a strong gradient to ∼725 °C and 10–12 kbar over a structural distance of less than 2 km associated with the Munsiari Thrust and Main Central Thrust; T9s then increase and P9s decrease gradually upsection, reaching ∼825 °C and 8 kbar in the Langtang Thrust. Juxtaposition of thrust sheets occurred at moderate pressure (8–12 kbar) on thrust surfaces roughly coincident with the modern Main Himalayan Thrust. Published monazite ages demonstrate synmetamorphic thrusting, with peak metamorphic ages decreasing progressively downward: 21 ± 2 Ma (Langtang Thrust), 16 ± 1 Ma (Main Central Thrust), 10.5 ± 0.5 Ma (Munsiari Thrust), and 3.5 ± 0.5 Ma (Lesser Himalayan Duplex). Together with published thermochronologic results, these data constrain initial cooling ages and rates: 15–20 Ma and ∼40 °C/m.y. for the Langtang Thrust and Main Central Thrust, and 3–10 Ma and ≥100 °C/m.y. for the Munsiari Thrust and Lesser Himalayan Duplex. Overall, metamorphic and chronologic patterns are matched well by expectations of critical taper models, including (1) uniformly high pressures of metamorphism (8–12 kbar) for all structural levels and thrust movement along the paleo–Main Himalayan Thrust, (2) isobaric cooling from the peak of metamorphism for Greater Himalayan rocks (deep juxtaposition of thrust sheets), (3) “hairpin” P-T paths for Lesser Himalayan rocks, and (4) relatively slow cooling rates for Greater Himalayan rocks. However, observations contrast significantly with published channel flow models, which predict (1) peak P-T conditions within the sillimanite stability field for Lesser and lower Greater Himalayan rocks (versus observations of P-T conditions in the kyanite stability field), (2) peak metamorphic pressures that decrease structurally downward—7–13, 6, 5, and 5 kbar for rocks achieving temperatures recorded by Langtang Thrust, Main Central Thrust, Munsiari Thrust, and Lesser Himalayan Duplex rocks (versus observations of 8, 10–12, 10, and 8 kbar), (3) retrograde isothermal exhumation P-T trajectories for Greater Himalayan rocks (versus isobaric cooling of the Main Central Thrust and Langtang Thrust), (4) cooling of migmatitic Greater Himalayan rocks after 10 Ma (versus observations of 15–20 Ma), and (5) isobaric heating of the Lesser Himalayan rocks (versus observations of simultaneous increases in P and T for some Lesser Himalayan rocks). Neither model matches “clockwise” P-T paths observed in structurally high Lesser Himalayan rocks, or the extraordinary cooling rate of the Lesser Himalayan Duplex, which points to complications in their evolution in the context of end-member models. Most generally, although channel flow may have initiated since ca. 10 Ma due to focused erosion above the Lesser Himalayan Duplex, it does not appear responsible for past transport and exhumation of the migmatitic core of the Himalaya.

Factors that influence informal learning in the workplace

Abstract: Purpose – The purpose of this research is to investigate factors that influence informal learning in the workplace and the types of informal learning activities people engage in at work. More specifically, the research examined: the relationship between informal learning engagement and the presence of learning organization characteristics; and perceived factors that affect informal learning engagement.Design/methodology/approach – Workplace learning and performance improvement professionals were invited to respond to an anonymous online survey, and 125 professionals volunteered to participate in the study.Findings – This study did not find a significant correlation between informal learning engagement and the presence of learning organization characteristics. While age and education level did not impact informal learning engagement, it was found that older workers tended to engage in more informal learning. There were also certain types of informal learning activities in which they were most likely to eng...

Preserving accuracy in GenBank

Abstract: GenBank, the public repository for nucleotide and protein sequences, is a critical resource for molecular biology, evolutionary biology, and ecology. While some attention has been drawn to sequence errors ([1][1]), common annotation errors also reduce the value of this database. In fact, for

Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Alaska: Potential impacts on headwater stream ecosystems

Abstract: [1] Permafrost is a defining characteristic of the Arctic environment. However, climate warming is thawing permafrost in many areas leading to failures in soil structure called thermokarst. An extensive survey of a 600 km2 area in and around the Toolik Lake Natural Research Area (TLNRA) revealed at least 34 thermokarst features, two thirds of which were new since ∼1980 when a high resolution aerial survey of the area was done. Most of these thermokarst features were associated with headwater streams or lakes. We have measured significantly increased sediment and nutrient loading from thermokarst features to streams in two well-studied locations near the TLNRA. One small thermokarst gully that formed in 2003 on the Toolik River in a 0.9 km2 subcatchment delivered more sediment to the river than is normally delivered in 18 years from 132 km2 in the adjacent upper Kuparuk River basin (a long-term monitoring reference site). Ammonium, nitrate, and phosphate concentrations downstream from a thermokarst feature on Imnavait Creek increased significantly compared to upstream reference concentrations and the increased concentrations persisted over the period of sampling (1999–2005). The downstream concentrations were similar to those we have used in a long-term experimental manipulation of the Kuparuk River and that have significantly altered the structure and function of that river. A subsampling of other thermokarst features from the extensive regional survey showed that concentrations of ammonium, nitrate, and phosphate were always higher downstream of the thermokarst features. Our previous research has shown that even minor increases in nutrient loading stimulate primary and secondary production. However, increased sediment loading could interfere with benthic communities and change the responses to increased nutrient delivery. Although the terrestrial area impacted by thermokarsts is limited, the aquatic habitat altered by these failures can be extensive. If warming in the Arctic foothills accelerates thermokarst formation, there may be substantial and wide-spread impacts on arctic stream ecosystems that are currently poorly understood.

Application of time-lapse ERT imaging to watershed characterization

Abstract: Time-lapse electrical resistivity tomography ERT has many practical applications to the study of subsurface properties and processes. When inverting time-lapse ERT data, it is useful to proceed beyond straightforward inversion of data differences andtakeadvantageofthetime-lapsenatureofthedata.Weassess various approaches for inverting and interpreting time-lapse ERTdataanddeterminethattwoapproachesworkwell.Thefirst approachismodelsubtractionafterseparateinversionofthedata from two time periods, and the second approach is to use the inverted model from a base data set as the reference model or prior information for subsequent time periods. We prefer this second approach. Data inversion methodology should be considered when designing data acquisition; i.e., to utilize the second approach, it is important to collect one or more data sets for which the bulk of the subsurface is in a background or relatively unperturbed state.Athird and commonly used approach to time-lapse inversion,invertingthedifferencebetweentwodatasets,localizes the regions of the model in which change has occurred; however, varying noise levels between the two data sets can be problematic. To further assess the various time-lapse inversion approaches,weacquiredfielddatafromacatchmentwithintheDry Creek Experimental Watershed near Boise, Idaho, U.S.A. We combined the complimentary information from individual static ERTinversions,time-lapseERTimages,andavailablehydrologicdatainarobustinterpretationschemetoaidinquantifyingseasonalvariationsinsubsurfacemoisturecontent.

Individual differences, rereading, and self-explanation: concurrent processing and cue validity as constraints on metacomprehension accuracy.

Abstract: The typical finding of metacomprehension studies is that accuracy in monitoring one’s own level of understanding is quite poor. In the present experiments, monitoring accuracy was constrained by individual differences in both reading comprehension ability and working memory capacity (WMC), but rereading particularly benefited low-ability and low-WMC readers, effectively eliminating the relationship between monitoring accuracy and these reader characteristics. In addition, introducing a self-explanation reading strategy improved the accuracy of all the readers above mere rereading. The observed interaction between individual differences and rereading is interpreted in terms of concurrent-processing constraints involved in monitoring while text is processed, whereas the more general self-explanation effect is interpreted in terms of accessibility of valid, performance-predicting cues.

Preserving accuracy in GenBank

Abstract: GenBank, the public repository for nucleotide and protein sequences, is a critical resource for molecular biology, evolutionary biology, and ecology. While some attention has been drawn to sequence errors ([1][1]), common annotation errors also reduce the value of this database. In fact, for

Adult Attachment as a Risk Factor for Intimate Partner Violence The “Mispairing” of Partners' Attachment Styles

Abstract: This study examined the relationship between intimate partner violence and adult attachment in a sample of 70 couples. The attachment style of each partner and the interaction of the partners' attachment styles were examined as predictors of intimate partner violence. Additional analyses were conducted to examine violence reciprocity and to explore differences in the relationship between attachment and violence using continuous and dichotomous violence measures. Results of hierarchical regression analyses indicated the "mispairing" of an avoidant male partner with an anxious female partner was associated with both male and female violence. When controlling for partner violence, the relationship between attachment and violence was significant for males only. In addition, analyses using a dichotomized violence variable produced different results from analyses using a continuous violence measure. Clinical implications include focusing on the discrepancy between partners' needs for intimacy and distance within the couple as a strategy for treating intimate partner violence.

Computer-mediated instruction: a comparison of online and face-to-face collaboration

Abstract: This study investigated the effects of collaboration mode and group composition during a computer-mediated collaborative (CMC) program. Six intact sections of a computer literacy course were assigned to either a face-to-face or a virtual, online collaboration treatment condition. Groups consisted of homogeneous lower-ability, homogeneous higher-ability, or heterogeneous-ability pairs. The study examined the effects of collaboration mode and group composition on individual posttest performance, group project performance, collaborative interaction behavior, and attitudes towards the instruction. Results indicated that virtual dyads exhibited significantly more questioning behaviors and significantly better project performance than those who collaborated face-to-face. By comparison, students in the face-to-face condition performed significantly better on the individual posttest than those in the virtual online condition. Findings suggest that both virtual and face-to-face collaboration can be effective in achieving learning goals. However, consideration should be given to the collaborative structure of the lesson and the type of task in the design of CMC environments.

Faculty and Student Assessment of and Experience with Incivility in Nursing Education

Abstract: Academic incivility is a significant problem and reports of discord on college campuses underscore the need for addressing uncivil behaviors in a forthright manner. In this study, 504 respondents from 41 states--194 nursing faculty, 306 nursing students, and 4 who did not specify their status--completed the Incivility in Nursing Education survey. The most frequently cited uncivil student behaviors included holding distracting conversations, using computers unrelated to class, and demanding make-up examinations and grade changes. The uncivil student behaviors occurring most frequently were arriving late for class, holding distracting conversations, and being unprepared. The uncivil faculty behaviors most frequently cited included making condescending remarks, making rude gestures or comments, and exerting superiority over others. The uncivil faculty behaviors occurring most frequently included ineffective teaching methods, arriving late for scheduled activities, and deviating from the syllabus and changing class assignments. Student and faculty uncivil behaviors were viewed similarly by both groups.

Lack of Pathology in a Triple Transgenic Mouse Model of Alzheimer's Disease after Overexpression of the Anti-Apoptotic Protein Bcl-2

Abstract: Alzheimer9s disease (AD) is characterized by the accumulation of plaques containing β-amyloid (Aβ) and neurofibrillary tangles (NFTs) consisting of modified tau. Although Aβ deposition is thought to precede the formation of NFTs in AD, the molecular steps connecting these two pathologies is not known. Previous studies have suggested that caspase activation plays an important role in promoting the pathology associated with AD. To further understand the contribution of caspases in disease progression, a triple transgenic Alzheimer9s mouse model overexpressing the anti-apoptotic protein Bcl-2 was generated. Here we show that overexpression of Bcl-2 limited caspase-9 activation and reduced the caspase cleavage of tau. Moreover, overexpression of Bcl-2 attenuated the processing of APP (amyloid precursor protein) and tau and reduced the number of NFTs and extracellular deposits of Aβ associated with these animals. In addition, overexpression of Bcl-2 in 3xTg-AD mice improved place recognition memory. These findings suggest that the activation of apoptotic pathways may be an early event in AD and contributes to the pathological processes that promote the disease mechanisms underlying AD.

The dance of incivility in nursing education as described by nursing faculty and students.

Abstract: Uncivil and disruptive behaviors in nursing education are serious problems requiring ongoing attention and research. Academic incivility jeopardizes the welfare of faculty, students, and the campus community. This article describes a qualitative study involving 289 nursing faculty members and students from 41 states who responded to 4 open-ended questions included in the Incivility in Nursing Education survey. A conceptual model is introduced to illustrate the study findings. The model depicts how stress, attitude, and a lack of effective communication and intentional engagement may contribute to the "dance" of incivility in nursing education.

Revealing Online Learning Behaviors and Activity Patterns and Making Predictions with Data Mining Techniques in Online Teaching

Abstract: This study was conducted with data mining (DM) techniques to analyze various patterns of online learning behaviors, and to make predictions on learning outcomes. Statistical models and machine learning DM techniques were conducted to analyze 17,934 server logs to investigate 98 undergraduate students’ learning behaviors in an online business course in Taiwan. The study scientifically identified students’ behavioral patterns and preferences in the online learning processes, differentiated active and passive learners, and found important parameters for performance prediction. The results also demonstrated how data mining techniques might be utilized to help improve online teaching and learning with suggestions for online instructors, instructional designers and courseware developers.

Deamidation destabilizes and triggers aggregation of a lens protein, βA3‐crystallin

Abstract: Protein aggregation is a hallmark of several neurodegenerative diseases and also of cataracts. The major proteins in the lens of the eye are crystallins, which accumulate throughout life and are extensively modified. Deamidation is the major modification in the lens during aging and cataracts. Among the crystallins, the βA3-subunit has been found to have multiple sites of deamidation associated with the insoluble proteins in vivo. Several sites were predicted to be exposed on the surface of βA3 and were investigated in this study. Deamidation was mimicked by site-directed mutagenesis at Q42 and N54 on the N-terminal domain, N133 and N155 on the C-terminal domain, and N120 in the peptide connecting the domains. Deamidation altered the tertiary structure without disrupting the secondary structure or the dimer formation of βA3. Deamidations in the C-terminal domain and in the connecting peptide decreased stability to a greater extent than deamidations in the N-terminal domain. Deamidation at N54 and N155 also disrupted the association with the βB1-subunit. Sedimentation velocity experiments integrated with high-resolution analysis detected soluble aggregates at 15%–20% in all deamidated proteins, but not in wild-type βA3. These aggregates had elevated frictional ratios, suggesting that they were elongated. The detection of aggregates in vitro strongly suggests that deamidation may contribute to protein aggregation in the lens. A potential mechanism may include decreased stability and/or altered interactions with other β-subunits. Understanding the role of deamidation in the long-lived crystallins has important implications in other aggregation diseases.

Explaining Long-Term Exercise Adherence in Women Who Complete a Structured Exercise Program

Abstract: The purpose of this study was to qualitatively examine factors related to physical activity adherence to understand why women continue to participate in long-term exercise after completing a structured exercise program. Data were collected from focus groups, interviews, and e-mails, and analysis used grounded theory. The central category related to physical activity adherence was self-worth. Motivation, activity enjoyment, priorities, body image, ability to access support, and self-regulation skills had an impact on the self-worth of nonadherers and adherers. Women must value themselves enough to continue to participate in physical activity once they start. Exercise and fitness professionals are encouraged to use strategies to increase self-worth and long-term adherence to physical activity. Some recommended strategies include (a) increasing motivation and enjoyment relative to activity, (b) making activity a high priority in a woman's life, (c) improving or deemphasizing body image, (d) increasing a woman's ability to access support, and (e) facilitating the use of self-regulation strategies. This study is the first to examine qualitative perspectives of exercise adherence among women who completed a structured exercise program. Several concepts related to adherence presented in the quantitative literature are confirmed and enhanced in this study.

On the Reasons We Want Teachers of Good Disposition and Moral Character

Abstract: The point of this article is to make a case for teachers of moral disposition without regard for the moral development of students. The article concludes that there are multiple reasons for wanting teachers of good disposition and moral character; that teachers' dispositions are best conceived as modifiers to the methods that they employ; and that the crux of the dispositions debate is ultimately grounded in avoiding poor moral character. Implications of the article point teacher educators toward a conception of teacher education that focuses on preparing teachers of good disposition and moral character simply for the sake of teaching that accords with what is good, right, and virtuous. The analysis suggests that the scope of a teacher's dispositions should be broadened to include all matters of classroom life and teacher effectiveness.

Cancellation of spurious arrivals in Green's function extraction and the generalized optical theorem

Abstract: The extraction of the Green's function by cross correlation of waves recorded at two receivers nowadays finds much application. We show that for an arbitrary small scatterer, the cross terms of scattered waves give an unphysical wave with an arrival time that is independent of the source position. This constitutes an apparent inconsistency because theory predicts that such spurious arrivals do not arise, after integration over a complete source aperture. This puzzling inconsistency can be resolved for an arbitrary scatterer by integrating the contribution of all sources in the stationary phase approximation to show that the stationary phase contributions to the source integral cancel the spurious arrival by virtue of the generalized optical theorem. This work constitutes an alternative derivation of this theorem. When the source aperture is incomplete, the spurious arrival is not canceled and could be misinterpreted to be part of the Green's function. We give an example of how spurious arrivals provide information about the medium complementary to that given by the direct and scattered waves; the spurious waves can thus potentially be used to better constrain the medium.

Dielectrophoretic trapping of DNA origami

Abstract: In this thesis three-dimensional tube-shaped DNA-origamis were dielectrophoretically trapped within lithographically fabricated nanoelectrodes. The origamis had been premade while the electrodes were fabricated specifically for these experiments with two different gapsizes, 150 nm and 400 nm. The aim of the work was to capture individual nanotubes in the gap between the electrodes by utilizing the dielectrophoretic forces present in the structure when a solution containing the origamis was put onto the electrodes and a voltage was applied. It was observed during the experiments that the success of the dielectrophoretic trapping depended strongly on the trapping conditions. This caused the trapping to be somewhat challenging and it was also noticed that the electrode structure with the 400 nm gap particularly required patience in order to produce good results, since the origamis to be trapped were of the same size as the gap between the electrodes making the successful trapping problematic. Despite this, a sufficient amount of trapped single nanotubes were produced.

The Expatriate Glass Ceiling: The Second Layer of Glass.

Abstract: The corporate glass ceiling continues to be a challenge for many organizations. However, women executives may be facing a second pane of obstruction – an expatriate glass ceiling – that prevents them from receiving the foreign management assignments and experience that is becoming increasing critical for promotion to upper management. The responsibility to break the expatriate glass ceiling lies with both female managers and the multinational corporations that utilize expatriates. In this paper, we propose pre-assignment, on-assignment, and post-assignment strategies for breaking the expatriate glass ceiling.

Reduced Switching-Frequency Active Harmonic Elimination for Multilevel Converters

Abstract: This paper presents a reduced switching-frequency active-harmonic-elimination method (RAHEM) to eliminate any number of specific order harmonics of multilevel converters. First, resultant theory is applied to transcendental equations to eliminate low-order harmonics and to determine switching angles for a fundamental frequency-switching scheme. Next, based on the number of harmonics to be eliminated, Newton climbing method is applied to transcendental equations to eliminate high-order harmonics and to determine switching angles for the fundamental frequency-switching scheme. Third, the magnitudes and phases of the residual lower order harmonics are computed, generated, and subtracted from the original voltage waveform to eliminate these low-order harmonics. Compared to the active-harmonic-elimination method (AHEM), which generates square waves to cancel high-order harmonics, RAHEM has lower switching frequency. The simulation results show that the method can effectively eliminate all the specific harmonics, and a low total harmonic distortion (THD) near sine wave is produced. An experimental 11-level H-bridge multilevel converter with a field-programmable gate-array controller is employed to experimentally validate the method. The experimental results show that RAHEM does effectively eliminate any number of specific harmonics, and the output voltage waveform has low switching frequency and low THD.

How instructional design experts use knowledge and experience to solve ill‐structured problems

Abstract: This study examined how instructional design (ID) experts used their prior knowledge and previous experiences to solve an ill-structured instructional design problem. Seven experienced designers used a think-aloud procedure to articulate their problem-solving processes while reading a case narrative. Results, presented in the form of four assertions, showed that experts (1) narrowed the problem space by identifying key design challenges, (2) used an amalgam of knowledge and experience to interpret the problem situation, (3) incorporated a mental model of the ID process in their problem analyses, and (4) came to similar conclusions about how to respond to the situation, despite differences in their initial conceptualizations. Implications for educating novice instructional designers are discussed.