Board Applications Research Articles

Stiffness and thermal expansion predictions for hybrid short fiber composites

AbstractA model is developed to predict thermal expansion coefficients and elastic moduli of multi‐component (hybrid) composites. The model includes the influences of fiber aspect ratio; isotropic and anisotropic fiber materials; planar, three‐dimensional or arbitrary fiber orientation; hollow and solid spherical reinforcements; and voids. The first step in the procedure is to predict the properties of an aligned‐fiber single‐reinforcement composite for each reinforcement type. Various micro‐mechanics approaches are used, depending on the type of reinforcement. A simplified version of Lee and Westmann's theory is found to work well for hollow spherical reinforcements. Performing an orientation average accounts for the spatial orientation of each reinforcement, then an aggregate averaging procedure combines the single‐reinforcement properties to model the hybrid. Predictions of the model compare favorably to experimental elastic and thermal properties of short fiber/hollow sphere composites designed for very high speed integrated circuit (VHSIC) board applications.

Reflections from bends in a printed conductor

An electrical model which is known to characterize a reactive discontinuity on a lossless transmission line is used to determine the maximum signal reflection from a bend in a printed microstrip transmission line. For printed wiring board applications using the usual FR4 dielectric, the maximum signal reflection from a simple 90 degrees bend is shown to be approximately 4.5% at an 80% signal risetime of 0.123 ns. Scaling laws for other risetimes and dielectrics are developed. A 180 degrees bend and a mitered 45 degrees bend are also treated. The electrical model yields signal reflections which agree well with corresponding experimental results. for bit rates as high as a few gigabits per second and suitable dielectrics, simple 90 degrees bends are still adequate. For much higher bit rates and more gradual bends, other parasitics also become important and limit the performance of electrical interconnections. >

The performance of the AT&T single mode ST® connector and its latest enhanced features

Abstract The AT&T single mode ST® connector is a low-loss, low-reflection connector suitable for high-speed, wideband digital transmission. This new connector offers enhanced hardware for easier use and more stable connections. In addition, a new backplane-compatible version is introduced for circuit board applications. The insertion loss of AT&T's single mode ST connector averages 0.34 dB with a standard deviation of 0.28. The reflection of an AT&T ST connection (product against product) averages -42.8 dB with a worst case of -34.1 dB. The environmental performance of the connector is characterized by low variations in loss and refection. The AT&T single mode ST connector and its backplane version were subjected to a battery of tests whose results are discussed in this article.

Characterization of a bis-maleimide triazine resin for multilayer printed circuit boards

The thermosetting resin investigated in this study was a mixture of bis-maleimide and bis-cyanate, frequently referred to as BT (bis-maleimide triazine). For printed circuit board applications, a brominated epoxy resin was blended with BT to impart flame resistance. Resin curing was extensively investigated using a combination of thermoanalytical techniques (thermal analysis, heated-cell infrared spectroscopy, dynamic mechanical analysis, and microdielectrometry). Differential scanning calorimetry indicated a minimum of two separate reactions. Fourier-transform infrared spectroscopy provided more detailed information on the cross-linking reactions during the curing. The onset of cyclotrimerization was found to appear at 150°C, correlating with one of the peaks observed in the differential scanning calorimetry measurements. Dynamic mechanical methods were used to investigate the viscosity profile during simulated lamination temperature profiles. Microdielectrometry performed simultaneously with parallel-plate rheometry provided further insight into the physical changes that occur during lamination.

GaAs ICs for high-speed signal processing

A complete family of small-scale integration (SSI) and middle-scale integration (MSI) analog and digital GaAs ICs for real-time signal processing is reported. These circuits have been used on several microstrip PC board applications with clock frequencies ranging from 500 MHz to 1 GHz. Detailed circuit performances and future trends are presented and discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Medical Licensing Requirements

While there are differences among the licensing jurisdictions in regard to the details of licensing, in general boards require applicants to have graduated from an acceptable school, to have completed a period of residency training in the United States or Canada, and to pass an acceptable licensing examination. Applicants for licensure should seek information about the detailed requirements for licensure from the licensing board where they want to be licensed. Medical graduates who are being licensed through FLEX should keep in mind that later applications for licensure by endorsement will depend on fulfilling acceptable licensing requirements in connection with initial licensure. Thus, graduates should be informed in general of licensing requirements at the time of initial licensure. The annual AMA licensing publication, cited previously, is a good source of information of this kind. Boards are increasing the length of graduate medical education required for licensure at present; they are also adding to the requirements for endorsement of licenses, for instance, setting limits to the number of years a licensing examination will be accepted for licensure endorsement. The AMA will continue its efforts to provide information about licensing requirements and to adopt policy positions in regard to licensing that will serve the interests of the medical profession while protecting the health and welfare of the American public.

Thermal characterization of a bis‐maleimide/bis‐cyanate/epoxy thermosetting resin for composites

AbstractThe thermosetting resin investigated here was a mixture of bis‐maleimide and bis‐cyanate, frequently referred to as BT (bis‐maleimide triazine). Triazine is the reaction product of the cyclotrimerization of bis‐cyanate during curing. For circuit board applications, a brominated epoxy resin was blended with BT to impact flame resistance. Resin cure was extensively investigated using a combination of thermoanalytical techniques (thermal analysis, heated cell infrared spectroscopy, and dynamic mechanical analysis). The ultimate glass transition temperature was found to be 240°C, which could only be obtained using cure temperatures above 225°C. At lower temperatures, the reaction does not reach full conversion, since the glass transition temperature of the curing network equals or slightly exceeds the cure temperature. Differential scanning calorimetry (DSC) indicates a minimum of two separate reactions. Fourier transform infrared spectroscopy provided more detailed information on the crosslinking reactions during cure. The onset of cyclotrimerization was found to start at 150°C, correlating with one of the peaks in the DSC. At higher temperatures, the epoxide reacts with the cyanate functionality forming oxazoline ring structures. It was not possible to unambiguously assign the origins of the high temperature peaks in the DSC. These high temperature peaks may be attributed to several reactions, including epoxy homopolymerization and polymerization of bis‐maleimide. The high temperature reaction mechanisms warrant further investigation.

Base, Substrate Materials for the Construction of Electronic Assemblies; Special Application of Surface Mount Technology Printed Circuit Boards

The general section of the paper discusses in detail the demands of SMD‐Technology on Printed Circuit Boards, namely dimensional, thermal, electrical and chemical requirements on both substrates and finished PCBs, besides characteristic features of the production process and the overall performance of the assembly. The second part is concerned with a survey of materials and methods suitable for the needs of SMT printed circuitry. Emphasis is laid on appropriate substrates, thermal management of assemblies and PCBs for high speed/high frequency applications

Non‐conventional Substrates

This paper describes recent printed board applications in circuit manufacturing on novel non‐laminate substrates. It specifically discusses properties pertinent to metal core, thermal plastics, and new processing conditions for circuitising the new substrates. Techniques explored are intended to provide rigidity, flatness, dimensional stability and improved thermal management.

New development in high speed copper plating for printed wiring board applications

SummaryThe driving force for high speed acid copper systems is improved productivity. Using electrochemical engineering principles, processes have been developed which address this need. Model cost analysis demonstrates a 40 per cent savings from these systems. Production data has confirmed both the technical and economic benefits. This paper summarises the development of high speed acid copper processes with emphasis on process chemistry, theoretical electrochemical engineering, system development and field data.

Eine bisher unbekannte Abhandlung über das Rechenbrett aus dem beginnenden 14. Jahrhundert

This article considers a previously unnoticed mathematical treatise on the counting board, presumably written about 1310 in Bordeaux by an otherwise unknown master Johannes de Elsa. The treatise is contained in manuscript lat. qu. 526, in the Staatsbibliothek Preussischer Kulturbesitz, Berlin. The author of the treatise explains the application of a counting board made from lead for three purposes: for sexagesimal fractions, for the Indian-Arabic calculations with whole numbers and for displaying the coins of shopkeepers and businessmen. His counting board is unusual for the period around 1300; it is similar to line and coin boards preserved from the end of the 15th century and later. This article contains an interpretation and an edition of the Latin text.

Current Control Modulators: General Theory on Specific Designs

High power distribution in continuous or pulsed mode on board application satellites has drastically complicated the design of power conditioning regulators by requiring the reliable operation with brilliant dynamic behavior of complex modular structures to satisfy their powerful loads. Current control modulators satisfy these requirements by the energy control capability. The 50-percent duty ratio instability is analyzed for each power cell configuration and canonical small signal models are given and verified in the case of an MC 2 buck regulator. The model validation is verified by application of the least square measurement technique which allows the accurate determination of any transmittance of the closed loop system.

USING "ANGELS AND DEVILS"

The incidence of perceptual deprivation and social isolation effects, possible correlates of such effects, and the potential for remediation of effects was studied for 32 nursing home residents through playing a discussion-stimulating board game called "Angels and Devils." Results indicate a high incidence of sensory deprivation and social isolation effects in the population, as meausred by resident response to questionnaire items. These do not correlate with length of institutionalization, amount of social contact, or degree of medical restriction and may be reduced by stimulating resident-staff discussion. Findings are interpreted as indicating the need for more research in application of board games to ameliorate negative effects emerging in institutional environments.

The role of hybrids in LSI systems: C. T. Goddard IEEE Trans. Components, Hybrids Mfg Technology. Chmt-2(4), 367 (December 1979)

N THE PURSUIT of very large scale integration (VLSI), the physical nature of the single chip may assume many forms. Several of these are displayed in Fig. 1. The beam lead and appliqued beam versions usually have I/O pins on lo- and 20-mil centers. JEDEC standard chip carriers provide external connections on 40- or 50-mil centers and standard hermetic and plastic DIP’s provide leads on lOO-mil centers with 2 rows of leads spaced 300 mils or more. In all of the devices shown here, the physical extension from the chip edges is essentially a mechanical transformer which provides a simple fan-out of leads to provide a match with the grid associated with the technology of the interconnection medium. The larger packages are best suited to multilayer board (MLB) application and the unpackaged varieties are particularly compatible with the hybrid technologies. The chip carrier is intermediate, of course. The nature of simple thin and thick film multichip hybrids combining SSI silicon chips and film resistors is shown in Fig. 2. The distinction between thick and thin film is beginning to smear a little as evidenced by the thick film crossovers used in the thin film circuit. A feature of particular interest here is the reduction in package pin-outs for the hybrid compared to the number of pins which would require interconnection on MLB if each of the nine silicon chips had been separately packaged. For a system requiring the interconnection of several times the nine silicon chips (in single chip packages), either a markedly larger board would be required or board complexity measured in interconnections per square inch would increase. Both of these may have an adverse effect on system economics and both of these assume greater importance as the scale of integration in silicon is increased.

Factors determining the waveform of cardiokymography.

The mechanism of detecting the cardiac wall motion by Cardiokymography (CKG) using a sensing coil was studied by the following experiments. 1) The precordial maps of CKG were recorded on 3 subjects. When the surface movement of the chest was eliminated by a piece of acrylic board in each subject, the amplitude of CKG was reduced to average of 22.7±2.5% of the initial amplitude (p<0.01). 2) As the content of salt was increased in water and blood above the probe, the oscillation frequency dropped slightly at first, then it went up beyond the initial value. 3) When an artificial pneumothorax was made in a dog, the amplitude was reduced. Then, by the application of an acrylic board, the wave form became flat. 4) CKG could not detect the movement of the resected canine heart containing blood in a normal saline solution. These data indicate that the capacitance was the main determinant of oscillation frequency in man and that the most significant factor of the wave form was the surface movement of the chest.

Using Angels and Devils: a board game developed for play in nursing homes.

The incidence of perceptual deprivation and social isolation effects, possible correlates of such effects, and the potential for remediation of effects was studied for thirty-two nursing home residents through playing a discussion-stimulating board game called Angels and Devils. Results indicate a high incidence of sensory deprivation and social isolation effects in the population, as measured by resident response to questionnaire items. These do not correlate with length of institutionalization, amount of social contact, or degree of medical restriction, and may be reduced by stimulating resident-staff discussion. Findings are interpreted as indicating the need for more research in application of board games to ameliorate negative effects emerging in institutional environments.

External quality control in haematological morphology: a method to assess the performance of an individual laboratory and changes in it.

A method is described to assess the performance of individual laboratories in estimating blood cell morphology by microscopy. The method was designed for the Finnish interlaboratory proficiency testing programme in haematological morphology. The method is based on the following principles: (1) on application of a detailed result form to collect the results from the participants in a standardized manner and (2) on application of a reference board to establish the morphological 'truth'. A consensus of greater than or equal to 80% of the reference board of haematology experts is the prerequisite for acceptance of a morphological detail as a 'target finding' for the participants. For each proficiency testing survey a score 'mean percentual performance' (MPP) was calculated for each participating laboratory. The MPP score indicates the percentual amount of correct identifications of the 'target findings' of the survey specimens and is an overall measure of performance of an individual laboratory. A running MPP graph was plotted to evaluate the changes in the performance over a course of time. Different types of 'performance profiles' among the participants were detected with this method. The merits of the MPP scoring method are discussed with special reference to the goals of external quality control in haematological morphology.

Some Additional Applications of the Population Sampling Board

Research Article| March 01 1975 Some Additional Applications of the Population Sampling Board Ronald F. Barnes Ronald F. Barnes Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1975) 37 (3): 180–181. https://doi.org/10.2307/4445140 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Ronald F. Barnes; Some Additional Applications of the Population Sampling Board. The American Biology Teacher 1 March 1975; 37 (3): 180–181. doi: https://doi.org/10.2307/4445140 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright 1975 National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

The application of basalt paper and board as filtration materials for the purification and sterilization of air

Papers have appeared in recent years on the application of special types of paper and board for the sterilization of air by filtration [1-3]. The properties of these materials depend on many factors: the type of fibers used, methods of physicochemical treatment, the presence of sizing agents, etc. The structure of a sheet for air purification is that of a fairly porous interweaving of fibers of various lengths The most dependable method of preparing filter paper and board of uniform structure is the multilayer pouring method [4], since on superimposing thin leaves one upon the other, possible defects in individual layers are covered. Sterile air is used in the process of manufacturing antibiotics and is obtained by filtration through a layer of fibrous filtration material. Sterile air, which is supplied for aeration in the fermentation process, must have a defined temperature and moisture content. In the event of a drop in air temperature below the dew point, moisture separation occurs which wets the filtration material and leads to a reduction in its mechanical strength. Moreover, as a result of the swelling of cellulose fibers the pore size and consequently the air penetrability is reduced [4, 5]. To prevent the phenomenon mentioned and to impart hydrophobicity and ~-et strength to the paper and board, various polymeric binders are introduced into the fibrous mass which after special treatment confer stiffness on the paper fibers. The filtration materials obtained in this way are sufficiently tough, stable to the action of moisture, and retain their previous values of specimen porosity thus guaranteeing a high moisture penetrability. At the present time basalt superfine fiber (BSFF) (fiber diameter 1 p) is used as a filtration material in filters for the fine purification of air [6]. This material answers the requirements set for a material for sterilization by the filtration method, viz. a high effectiveness in retaining particles of contaminants (99.999 % of 0.3 p particles), sufficient vapor and thermal stability, and an extended service life. The comparatively small mechanical strength is a shortcoming of the material. This shortcoming also caused a search for a filtration material based on BSFF and more sturdy and convenient in operation. Specimens of materials in form of paper and board based on BSFF have been developed in the Ukrainian Paper Research Institute [7]. Pulverized cellulose fibers and latex were added to increase the durability of materials in manufacture. An investigation has been carried out in the All-Union Scientific-Resea rch Institute of Antibioties on specimens of basalt paper and board with the aim of possibly using them for the sterilization of process air in antibiotic manufacture. It is known that materials for air purification are evaluated according to the drop in pressure and the size retention of particles entering with the air [8]. An increase in the drop in pressure is energetically unprofitable; however, simultaneously with the growth of this parameter the efficiency of retaining particles is raised, and consequently it is necessary to find the size of the optimal ratio of the values mentioned. An investigation to find the optimum has been carried out with the aim of elucidating the interrelationshi p of the properties of the paper and the sizes of the characteristics mentioned. Tests on specimens of paper and board were carried out at afiltration rate ofl cm/sectaldng the highly effective materials for testing [9] The effectiveness of a material was verified on a test bed with an oil spray [I0]. Averaged results of several measurements are presented in Tables 1 and 2. In column 2 of Tables 1 and 2 the labelling of the basaltic materials submitted by the manufacturer is given. For example,

Efficiency of Channel Electron Multipliers for Electrons of 1–50 keV

The calibration of the University of California, San Diego (UCSD) plasma detector on board Applications Technology Satellite 5 (ATS-5) has been used to determine the shape of the efficiency vs energy curve for channel electron multipliers. Results are compared with other workers with reasonable agreement. The measured efficiencies are well expressed in the range 1–50 keV by ε=1−{2/[3+6.5/(E−0.5)+30/(E−0.5)3]}.