Search

Introduction: The transmission pathways of coronavirus disease 2019 (COVID-19) remain not completely clear. In this case study the test for the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in pharyngeal swab and anal swab were compared. Case presentation: A 3-month-old girl was admitted to our hospital with COVID-19. Her parents had both been diagnosed with COVID-19. The results of pharyngeal swab and anal swab of the little girl were recorded and compared during the course of the disease. The oropharyngeal specimen showed negative result for SARS-CoV-2 on the 14th day after onset of the illness. However, the anal swab was still positive for SARS-CoV-2 on the 28th day after the onset of the illness. Conclusion: The possibility of fecal-oral transmission of COVID-19 should be assessed. Personal hygiene during home quarantine merits considerable attention. Key words: COVID-19; Anal swab; SARS-CoV-2; Fecal-oral transmission

Intestinal lipomas are rare nonepithelial tumors that are typically small in size and detected incidentally. Colonic intussusception is an uncommon complication of colonic lipoma. A 56 y old woman visited our emergency room with sudden onset of intermittent abdominal cramps. A CT scan showed a 5.0 cm, nodular, homogenous, hypodense structure in the hepatic flexure of the colon as the lead point of an intussusception. The hypodense structure was suggestive of a colonic lipoma, and the tumor was suspected to be the cause of the intestinal intussusception. Laparoscopic exploration was performed, and the pathology demonstrated a mature submucosal colonic lipoma. In addition to the case report, we discuss the role of imaging modalities in diagnosing neoplasms and for assessing the clinical behavior of lipomas when symptomatic.

Employee recruitment and retention are keys to the overall success of academic libraries, library administrators, and search committees face challenges when filling new and vacant faculty positions. This article presents and discusses the findings of a survey on hiring in an academic setting, including subjects such as staffing, criteria for hiring, how search committees evaluate candidates, and length of the hiring process. This research study reveals answers from 242 survey respondents who shared their experiences and opinions regarding the hiring process in academic libraries. The aim of this study to unlock the mystery involving faculty searches by examining key factors affecting the odds of obtaining an interview and the outcome of an application. The findings help people on both sides of the job search equation form a better understanding of the hiring process. This information should be taken into consideration by those applying for a position to learn how to best present themselves and by search c...

PurposeThis paper seeks to examine attitudes toward the use of clickers, as well as practicalities and pedagogical considerations that inform them. Drawing on interviews from a variety of viewpoints at one institution of higher education, this paper aims to situate a librarian perspective among those of teaching faculty, administration, and students.Design/methodology/approachThis paper is a case study of a single institution of higher education in which the experiences of teaching faculty, an administrator, and a library faculty member are gathered using semi‐structured interviews. Student opinions are obtained through the use of a focus‐group interview.FindingsThis paper provides attitudes and experiences of nursing teaching faculty who use clickers in their instruction, an administrator who purchased clickers for his department, and a library faculty member who uses clickers in bibliographic instruction, as well as those of nursing students who used the technology in class.Research limitations/implicationsBecause of the nature of the research method employed, reported results may not be universally generalizable.Practical implicationsThis paper may help inform the choices of those deciding to use clickers in their instruction.Originality/valueThis paper fulfills an identified need to analyze reactions to clicker use in instruction among students, instructors, and other program participants, including librarians.

An online survey was sent to academic libraries and consortia with an integrated library system (ILS) migration project, based on review of press releases from major U.S. ILS vendors. This study takes a systematic approach to provide a snapshot of the academic ILS market and key factors affecting the outcome of an ILS migration project. It reveals the challenges and opportunities facing academic libraries and ILS vendors in an environment with rapidly changing technology and increasingly sophisticated academic users.

PurposePotential and benefits of classification schemes and thesauri in building organizational taxonomies cannot be fully utilized by organizations. Empirical data of building an organizational taxonomy by the top‐down approach of using classification schemes and thesauri appear to be lacking. The paper seeks to make a contribution in this regard.Design/methodology/approachA case study of building an organizational taxonomy was conducted in the information studies domain for the Division of Information Studies at Nanyang Technology University, Singapore. The taxonomy was built by using the Dewey Decimal Classification, the Information Science Taxonomy, two information systems taxonomies, and three thesauri (ASIS&T, LISA, and ERIC).FindingsClassification schemes and thesauri were found to be helpful in creating the structure and categories related to the subject facet of the taxonomy, but organizational community sources had to be consulted and several methods had to be employed. The organizational activities and stakeholders' needs had to be identified to determine the objectives, facets, and the subject coverage of the taxonomy. Main categories were determined by identifying the stakeholders' interests and consulting organizational community sources and domain taxonomies. Category terms were selected from terminologies of classification schemes, domain taxonomies, and thesauri against the stakeholders' interests. Hierarchical structures of the main categories were constructed in line with the stakeholders' perspectives and the navigational role taking advantage of structures/term relationships from classification schemes and thesauri. Categories were determined in line with the concepts and the hierarchical levels. Format of categories were uniformed according to a commonly used standard. The consistency principle was employed to make the taxonomy structure and categories neater. Validation of the draft taxonomy through consultations with the stakeholders further refined the taxonomy.Originality/valueNo similar study could be traced in the literature. The steps and methods used in the taxonomy development, and the information studies taxonomy itself, will be helpful for library and information schools and other similar organizations in their effort to develop taxonomies for organizing content and aiding navigation on organizational sites.

PurposeThe purpose of the paper is to describe the Long Island University Brooklyn Campus Library's experience with a Smart Space Project. This paper recounts how the library creates new instructional spaces, through the use of smart technologies. This study illustrates challenges facing the library, recounts collaboration with other campus units, and describes support service provided by Library Information Technology. This account contributes to the sharing and discussion of experiences among modern academic libraries regarding needs assessment, space planning, and utilization of technology to support library services.Design/methodology/approachThe literature review includes space planning, building renovation and construction, and instructional technology. Various aspects of the Smart Space Project are described and analyzed. Studies and experiences from other academic libraries are also discussed.FindingsSpace renovation projects may be complex, requiring a systematic approach encompassing vision, needs assessment, funding, planning, technological considerations, and collaboration with other campus units. Creativity, flexibility, open‐mindedness, and attention to details are keys to the success of renovation projects.Research limitations/implicationsIn the areas of library space, student learning behaviour, utilization of technology, and smart technology's impacts on online/distance library instruction, more research needs to be conducted.Practical implicationsThis account provides useful information and first‐hand experience for library administrators and faculty planning instructional space projects.Originality/valueThis article provides a snapshot of the efforts of a mid‐sized urban library to address issues of limited space, budgetary constraints, growing collections, and increasing user needs. It provides practical lessons and suggestions for other library administrators and faculty seeking to make building and instructional technology improvements. It also offers valuable information for library information technology units implementing smart instructional projects.

Deoxynivalenol (DON) is a group B trichothecene and a common contaminant of crops worldwide. This toxin is known to cause a spectrum of diseases in animals and humans such as vomiting and gastroenteritis. Importantly, DON could inhibit the synthesis of protein and nucleonic acid and induce cell apoptosis in eukaryote cells. The transduction of signaling pathways is involved in the underlying mechanism of the cytotoxicity of DON. Mitogen-activated protein kinase and Janus kinase/signal transducer and activator of transcription seem to be two important signaling pathways and induce the inflammatory response by modulating the binding activates of specific transcription factors. This review mainly discussed the toxic mechanism of DON from the vantage point of signaling pathways and also assessed the profiles of DON and its metabolites in humans. Importantly, we conducted a human exposure risk assessment of DON from cereals, cereal-based foods, vegetables, water, and animal-derived foods in different countries. Some regular patterns of DON occurrence in these countries are suggested based on an analysis of global contamination with DON. This review should provide further insight for the toxic mechanism study of DON and human exposure risk assessment, thereby facilitating mycotoxin control strategies.

A fuzzy logic rule-based damping controller for STATCOM has been proposed in this paper. The proposed controller has two control loops. One is voltage control, with traditional PI control; the other is damping control, with the proposed rule-based controller. The input signal to the voltage control loop is the terminal voltage, and the input signal to the damping control loop is the generator speed, which can calculated from local variables. The effectiveness of the proposed controller was demonstrated in a single machine infinite bus system with Siemens NETOMAC. Further study will focus on the control strategy of STATCOM on multi-machine system.

Fast valving has long been regarded as an effective and economical method of performing transient control in a power generation plant. Due to the inherent nonlinearities that exist in this operation, fast valving controllers designed in a conventional way cannot deliver satisfactory control. This paper introduces a new approach to construct a fast valving controller by applying an adaptive fuzzy technique. A rule-generation and adaptation scheme is formulated in a fuzzy-system framework. Then the implementation issue is discussed in detail. From the outcome of on-line testing, it is shown that the controller constructed in this way not only maintains global stability, but also appears to be robust in different fault situations.

Based on the zero-sequence component of the reference voltages, this paper comprehensively analyzes the neutral-point variation and balancing control for three-level neutral-point-clamped inverter. An analytical method is proposed to accurately calculate the injected zero-sequence voltage for NP balancing. Based on the analytical analysis, the limitation of NP balancing control is revealed and the NP-fully-controllable region is presented. A real-time NP balancing algorithm is proposed as well. The feasibility of the proposed method is verified using simulation results for a 6 kV/1800 kVA medium voltage drive.

Power quality disturbances (PQD) are normally monitored by dedicated PQ devices. The devices capture disturbances' waveform in real-time. Magnitude is accepted as a significant index for detection, general classification and later assessment analysis. To choose a suitable way of magnitude characterization is a fundamental work of PQD measuring and monitoring. This study presents three different ways, RMS voltage, peak voltage and fundamental voltage component, to determine magnitude. The algorithms of the three approaches implemented in Matlab are introduced. The algorithms are FFT-based and wavelet transformation (WT) based. A voltage sag benchmark in a radial test system is used to verify and validate the study. The depth-duration characterization of voltage sags is illustrated. The most appropriate approach is suggested at the end of the paper according to the practical monitoring or measuring requirements. The research result is applied to a new PQ monitor with DSP infrastructure being developed by us. The proper window length selection and technique to avoid oscillation is also discussed in the rest of the paper. The information obtained from the magnitude characterization can be furthered to extract features for PQD detection and classification.

Power systems are undergoing improvements and development in computing technology and assessment tools. For a multi-machine power system, transient stability simulation has been believed as an indispensable tool for planning, design, operation and research. The model of a synchronous generator is considered the most important factor which influence the simulation result. In this paper, two types of synchronous generator model are discussed according to their complexity. Digital simulation of an actual system of North China Power System is fulfilled to study the different characteristics of the two models and a comparison is also made.

Static VAr compensators (SVCs) are the fastest and most widely applied FACTS devices at present. However, the SVC's high speed control can only be applied effectively if the type and size of the power components as well as the control and protection schemes are well matched to the specific network configuration and operation requirements. The combination of intensive computer and advanced real-time simulation is of great benefit for the design verification of new FACTS application. This paper presents the use of an RTDS simulator for the real-time testing of an SVC controller. It is a pure digital simulator for the SVC project and special measures have been taken to improve the precision of firing angle for TCRs. Some results of a SVC project study are presented.

The thyristor controlled series compensator (TCSC), composed of a capacitor in parallel with a thyristor controlled reactor (TCR), is a variant topology circuit. For such circuits there is no universal method to build the analytical mathematical model. The paper focuses on building an analytical model by the method of "topology" to describe the dynamic behavior of TCSC. Based on the model, the steady-state model is derived and the dynamic characteristics are discussed. The model is verified by digital simulation and the method can be extended to similar devices and be used for optimizing the control systems.

A /spl plusmn/20 MVAr STATCOM (static synchronous compensator) using GTO technology was commissioned in China in 1998. The STATCOM is designed to supply fast voltage control and to enhance the damping of inter-area electromechanical oscillations of the system. In this paper, by investigating the added synchronizing and damping torque induced by STATCOM, the conflicts between these control objectives are analyzed and the limitations or even invalidity of the fixed-parameters damping controller for certain system parameters and load conditions is discussed. A rule-based controller, which employs bang-bang, fuzzy logic or fixed-parameter PI control strategy according to the operation state of the system, is designed. The advantages of the proposed controller over the fixed-parameter PI controller are demonstrated by nonlinear digital simulations.

The first thyristor controlled series compensation (TCSC) project in China is expected to be applied to the Yimin-Fengtun 500 kV transmission line in the Year 2000 to improve its transmission capability. As a part of the project's feasibility study, this paper focuses on the steady-state and dynamic characteristics of TCSC based on digital simulations and physical experiments. It is necessary to comprehend the characteristics of TCSC devices for modeling TCSC correctly and proposing an effective transient control strategy. The paper studies the following several characteristics of TCSC: the steady-state characteristics in four typical operation modes; the operation symmetry under various control modes; the differences between closed-loop and open-loop impedance control; and the influences of different synchronizing signals on dynamic characteristics of impedance variations.

Thyristor controlled series compensation (TCSC) is expected to provide various benefits to power systems, including transient stability improvement, subsynchronous resonance (SSR) mitigation, power swings damping, fault current reduction, etc. Grasping the characteristics of TCSC installations and ending effective firing control strategies are essential to implement these advantages. This paper studies two important aspects of TCSC characteristics, the time constant of TCSC dynamic response and impacts of reference signals for thyristor firing angles on TCSC dynamic response. Closed-loop impedance control is proposed to speed the dynamic response of TCSC. A "two-stage" firing control method is presented to accomplish smooth switching between the capacitive region and inductive region. Both digital simulations with EMTDC/PSCAD software and physical experiments are employed in the study.

A desirable transient stability control scheme should be able to ensure the first-swing stability as well as provide effective damping. This paper presents a T-S model based fuzzy control scheme for thyristor controlled series compensation (TCSC) in power system transients. The nonlinear power system containing a TCSC is modelled as a fuzzy "blending" of a set of locally linearized models. A linear optimal control is designed for each local linear model. Different control requirements at different stages during power system transients can be considered in deriving the linear control rules. The resulting fuzzy controller is then a fuzzy "blending" of these linear controllers. Furthermore, a gradient descent algorithm is put forward to modify the rule truth factors for optimization. For convenient industrial realization of the fuzzy control scheme, a practical approach requiring only local signals is also described. Simulation with NETOMAC software has verified the effectiveness of the fuzzy control scheme.

The Takagi-Sugeno model (T-S model) based fuzzy control scheme for nonlinear systems is presented in this paper. In the T-S fuzzy model, a nonlinear system is represented with a set of fuzzy rules which describe the local linear dynamics. Then the parallel distributed compensation (PDC) design is employed in the fuzzy controller design. Linear optimal control is used in the derivation of each control rule. The overall fuzzy controller is a fuzzy blending of each individual linear controller. Quadratic stability of the overall nonlinear control system can be checked and ensured with H/sup /spl infin// control theory. The fuzzy control scheme is applied to thyristor-controlled series compensator control in power system transients. Digital simulations with NOTOMAC software have demonstrated that the fuzzy control scheme is superior to other conventional control methods. The fuzzy controller effectively improves power systems transient stability and very quickly damp power swings.

The operational performance of static synchronous compensators (STATCOMs) under unbalanced and distorted system voltage is a great concern of designers and operation engineers. Based on a novel per-unit STATCOM mathematical model, this paper makes a theoretical analysis of STATCOM performance under distorted system voltage. Algebraic expressions as well as the 3-D curves are given to reveal the relationship between STATCOM harmonics and the main circuit parameters. The theoretical analysis was verified by digital simulation results of PSCAD/EMTDC and tests on a 10 kVAr prototype experimental device. The good agreement between the analytical results and the experimental results show that the approach proposed in this paper can be used to select the passive elements and assess the operation performance of STATCOM under unbalanced or distorted system voltage.

This paper presents the results of physical experiments on a /spl plusmn/10 kVAr STATCOM model developed by Tsinghua University of China, which is the prototype of a /spl plusmn/20 MVAr STATCOM to be commissioned in the Henan province of China. A series of physical experiments, including open/closed loop step response, pulse-blocking under severe disturbances, voltage regulation improvement, voltage stabilization under surge loads, power system stability limits enhancement and damping improvement of power swings, were performed on the model to simulate the performance of the STATCOM in a real power system. The conclusions derived in the laboratory are expected to be helpful to the operation of the /spl plusmn/20 MVAr STATCOM in the near future.

This paper is a summary of our research work for seven years in applying the theory of optimal control to the excitation system of a generator (Optimal Excitation Controller, OEC). It analyzes problems of OEC by means of digital simulating and physical modelling. It also points out the merits of OEC and what research works should be done in the future.