High Limit Values Research Articles

Self Organizing Maps (Kohonen) untuk Cluster Bidang Karya Ilmiah (Skripsi) Mahasiswa Berdasarkan Nilai-Nilai Matakuliah Pendukung Machine Learning

The time for the preparation of scientific papers is considered too fast and not suitable for students due to several things in the scope of its preparation. One of the reasons is that the student is unable to complete and the supporting aspects of the field of scientific work being done, many students whose topics of scientific work are in machine learning or the like, but these students are unable to complete their scientific work because they do not understand the theoretical supporting knowledge of the machine learning field. So that it can make the student depressed or even harder to repeat his scientific work the next semester. The scope of machine learning courses are statistics and probability, matrix and linear algebra, algorithms and programming, and data structures. This research was conducted to overcome the problems faced by students, namely knowing the suitability group for the field of student scientific work they will be working on. So that in its preparation students can be responsible in their trial and are of higher quality. The clustering test with the self organizing maps (SOM) algorithm is more stable because the input according to the data owned is not random, only the weighting is done randomly but based on the uniform low (mins) and high (max) limit values. The desired number of clusters is two namely cluster 0 is able to do scientific work based on machine learning and cluster 1 vice versa. The SOM process for 40 student data with a target of two clusters and the results are cluster 0 = 14 students, cluster 1 = 26 students. The result is obtained by increasing the radius = 1, which previously this achievement was not successful if radius = 0.

The Predictability Limit of Ocean Mesoscale Eddy Tracks in the Kuroshio Extension Region

In this study, the nonlinear local Lyapunov exponent and nonlinear error growth dynamics are employed to estimate the predictability limit of oceanic mesoscale eddy (OME) tracks quantitatively using three datasets. The results show that the mean predictability limit of OME tracks is about 53 days for cyclonic eddy (CE) and 52 days for anticyclonic eddy (AE) in the Kuroshio Extension (KE). The predictability limit varies spatially. The predictability limit of OME tracks is higher for the eastern region (about 62.5 days) than that for the western part (about 46 days). The CEs (AEs) predictability limit is relatively high in the southern (northern) region. Additionally, the lifetime, amplitude, and radius of OME are closely related to the predictability limit. The long-lived, large-amplitude, and large-sized OMEs tend to be more predictable. The eastern region often generates long-lived and large-size OMEs, thereby obtaining a higher predictability limit of OME tracks. Furthermore, the relationship between the predictability limit and the smoothness of the OME tracks was investigated using a metric to describe the track’s complexation. Usually, OMEs with high predictability limit values often show extender and smoother trajectories. The effects of the surface ocean circulations and the surface winds are also investigated. The strong and energetic currents lead to a short limitation in the west region.

Model and Material Analysis of Gokart Chassis

The present study of this paper is to select the best material for manufacturing the Go-Kart. To meet this designing of go-kart chassis done by using CAD software CATIA tool and simulate with ANSYS work-bench. To select the best material, strength to weight ratio plays major role on it. Steel is considering to existing material another two materials Aluminum-6061, Kevlar selected. The main reason behind choosing Aluminum-6061, Kevlar materials is two materials are having less density and high yield limit values, and this factor can increase the strength/weight ratio compare to existing material steel. In this project material selection is one of the main design decisions that greatly increase the safety, reliability and performance. The material selection is choosen after my extensive research with various parameters like strength, weight and cost. We are comparing Aluminum-6061and Kevlar materials with mild steel. In this process boundary conditions applied on each material and calculated results like deformation, stress, strain, safety factor, natural frequency values, by knowing all these results, concluded with optimum material.

Effect of mineralogical composition related to profile depth on index and strength properties of regolith soil

While chemical weathering is the most significant geochemical process that affects the engineering behavior of rocks, the fact that authigenic soils present different values of their physical and mechanical properties depending on the depth is also directly related to weathering. Although it is known that such variation is applicable for regolith soils with thickness reaching tens of meters, significant differences can be observed through the depth of residual soils with the thickness of only a few meters. Ignoring such aspects especially in sites with a high risk of landslide leads to many engineering problems. Therefore, Trabzon Province, which has the highest potential of landslide in Turkey, has been selected as the pilot area within the scope of this study. The variations in engineering properties of regolith soils, which have a depth of up to 15 m and are weathered products of volcanic rocks, have been researched as a function of geochemical properties. For this purpose, the data collected from borehole applications, geophysical surveys, in situ cone penetration tests (CPT), and standard penetration test (SPT) as well as laboratory experiments have been evaluated; and it is observed that physico-mechanical properties are directly based on geochemical variations. While the zones with low SiO2 and high Al2O3 and Fe2O3 values are characterized with high content of clay and cohesion, depths with low S wave velocity correspond to areas with the highest chemical alteration index values and the highest degree of weathering. And high liquid limit (LL) values correspond to areas with high illite content as well as high Al2O3 and Fe2O3 values. At these depths, high friction ratio values are observed in CPT results. Obtained data indicate that physico-mechanical properties vary as a function of the depth based on geochemical properties, and this suggests that the soil in projects with regolith soils needs to be separated into different layers and analyzed.

Disposal of waste-based fuels and raw materials in cement plants in Germany and Switzerland – What can be learned for global co-incineration practice and policy?

Abstract The limit value for emissions of total organic carbon (TOC) for incinerators in the European Union (EU) is 10 mg/m3. However, clinker burning is a material conversion process during which TOC emissions from the fuels occur concurrently with the thermal decomposition of organic material from the raw material mixture (limestone, marl, shale, etc.) in the preheater, which alone can emit more than 10 mg/m3. Therefore, the German legislature has created an exemption that allows authorities to set higher limit values for cement kilns if the cause of the higher emissions is the natural raw material mixture and not the co-incinerated waste. Separating the effects requires a test to determine the baseline emission of the natural raw material or waste raw material. Up until now, these tests were only used internally by companies. By applying such tests, the emissions from the fuels, particularly from waste-based fuels, can be determined, restricted and controlled. TOC emissions from natural materials cannot be avoided. In Switzerland and Germany these emissions are on average around 20–35 mg/m3. Switzerland has recently set a high TOC limit value of 80 mg/m3 for cement kilns, independent of the source of organic emissions, and even allows the use of polychlorinated biphenyl (PCB) contaminated soils as raw material (up to 10 mg/kg). This limit is too high and can result in unnecessary emissions of carcinogenic benzene, PCBs and other pollutants. Both the natural raw materials and waste raw materials emit organic carbon. However, there is one major difference. The natural raw materials emit mostly aliphatic compounds at temperatures up to about 600 °C, whereas the organic compounds originating from waste-based raw material components can include hazardous pollutants like polychlorinated biphenyls (PCBs) and other persistent organic pollutants (POPs), which desorb in the preheater and are released into the environment. Therefore, waste raw materials such as soils contaminated with POPs or other semivolatile toxic chemicals cannot be introduced via the raw mill -(leading to desorption in the preheater) but need to be fed in the kiln inlet. Cement kilns treating POPs or raw materials with problematic semivolatile organics need strict control and possibly continuous monitoring for dioxins and other POPs.

Canal structure subsidence investigation using ground penetrating radar and geotechnical techniques

Channel structure settlement along a canal in Lagos, southwestern Nigeria, was investigated using the ground penetrating radar (GPR) and geotechnical techniques with a view to establishing the cause(s) of the structure failure. GPR probing was carried out along eight parallel traverses in the E–W direction using the GSSI SIR-3000 200 MHz monostatic antenna. Geotechnical investigations involving sieve analysis, Atterberg limits, moisture content, organic content and consolidation test were carried out for soil classification and competence test. X-ray diffraction (XRD) studies were conducted to determine clay mineralogy of the peaty soil. The GPR data were processed using Radpro software. Four lithological layers consisting the topsoil (sand), peat, clay and sandy clay were delineated from the processed GPR data. Peat occurred at shallow depth to depths deeper than the foundation depth of the engineering structure investigated. The geotechnical results revealed that the peat has 125–167 % moisture content, high liquid limit and plastic index values of 109–174 % and 60–100 % respectively and organic content of 5.12 %. The sieve analysis showed that the peaty soil is fine grained having up to 98 % passing at 0.004 mm sieve opening exhibiting high compressibility and low consolidation coefficients. This peat was classified as organic clay with peat using the unified soil classification system. The XRD analyses showed the dominance of kaolinite, illite and quartz minerals in the peaty soil. This study revealed that the peaty soil underlying the investigated area has geologic and engineering properties not suitable to sustain the canal construction.

Cardiopatías estructurales y funcionales en pacientes adultos con inmunodeficiencia comun variable

Antecedentes: la inmunodeficiencia común variable es la inmunodeficiencia primaria con mayor cantidad de comorbilidades en la vida adulta. Se ha asociado con bronquiectasias en 17 a 76%, y éstas, con complicaciones cardiovasculares, como hipertensión arterial pulmonar e insuficiencia cardiaca. Los nuevos métodos diagnósticos de imagen permiten evaluar la conformación estructural y funcional cardiovascular de los pacientes adultos con bronquiectasias y, de esta manera, establecer diagnósticos más eficientes y oportunos.Objetivo: determinar las cardiopatías estructurales y funcionales en pacientes con inmunodeficiencia común variable mediante ecocardiografía transtorácica.Material y método: estudio transversal, descriptivo, efectuado en una cohorte de 26 pacientes adultos con diagnóstico de inmunodeficiencia común variable y tratamiento sustitutivo con inmunoglobulina intravenosa (IgIV), pertenecientes a la Clínica de Inmunodeficiencias. A todos los pacientes se les realizó ecocardiografía transtorácica con ecocardiograma doppler y tisular; los resultados fueron evaluados por un médico cardiólogo ecocardiografista.Resultados: evaluamos a 26 pacientes; de ellos, 10 fueron del género masculino, con media de edad de 35.7 ± 13.7 años. Los resultados de la ecocargiografia torácica en las cavidades cardiacas izquierdas reportaron las siguientes alteraciones funcionales: 17 de 26 pacientes tuvieron insuficiencia mitral y sólo 2 tuvieron insuficiencia aórtica; ninguno de ellos con síntomas. Respecto de las alteraciones estructurales de las cavidades derechas: 8 pacientes adultos con inmunodeficiencia común variable tuvieron crecimiento de las cavidades derechas y en 5 pacientes se encontró tabique interauricular delgado e hipermóvil; respecto de las alteraciones funcionales, 24 pacientes tuvieron insuficiencia tricuspídea, en 21 de ellos fue leve y sólo en 3 fue moderada. Además, 12 pacientes tuvieron insuficiencia de la válvula pulmonar y 6 pacientes tuvieron hipertensión arterial pulmonar; de ellos, en 2 sujetos fue leve y en 2, moderada y 4 pacientes tuvieron presión sistólica de la arteria pulmonar con valores límites altos.Conclusiones: los pacientes con inmunodeficiencia común variable, a pesar de tener alta incidencia de bronquiectasias, tienen baja incidencia de hipertensión arterial pulmonar; pero un número importante de pacientes tiene presión sistólica de la arteria pulmonar con valor límite alto, por lo que estos pacientes deben tener un seguimiento anual, debido a que probablemente evolucionarán a hipertensión arterial pulmonar. Además, tienen alta incidencia de insuficiencias valvulares leves debido a cambios degenerativos con esclerosis valvular, por lo que también requieren vigilancia periódica.

Laboratory Evaluation of the Geotechnical Characteristics of Wastewater Biosolids in Road Embankments

An extensive suite of geotechnical laboratory tests were undertaken on wastewater biosolids to evaluate their sustainable usage as a fill material in road embankments. Geotechnical tests undertaken include particle size distribution, specific gravity, Atterberg limits, compaction, consolidation, hydraulic conductivity, California bearing ratio (CBR), field vane shear, direct shear, and triaxial shear. The geotechnical tests indicated that biosolids are equivalent to organic fine-grained soils of medium to high plasticity with high moisture content and liquid limit values. Consolidation tests indicate that biosolids have similar consolidation characteristics to that of organic soils. Shear strength tests on compacted biosolids samples indicated relatively high internal friction angles, comparable to that of inorganic silts. Compacted biosolids samples exhibit a modest cohesion comparable to organic clays. CBR tests results indicate high deformation potential of biosolids. Chemical and environmental assessment tests indicated that heavy metals, dichloro diphenyl trichloroethane (DDT) and organochlorine pesticides concentration along with pathogens (bacteria, viruses, or parasites) results were within acceptable limits for usage in geotechnical applications. With regards to contaminants containing nitrogen, phosphorus, and total organic carbon, the biosolids were found to require special protection in the event there is potential leaching/flow to adjoining water bodies. The geotechnical testing results indicate that untreated biosolids have insufficient bearing capacity to enable its usage as a fill material. The biosolids will have to be stabilized with an additive or blended with a high-quality material to enhance its geotechnical properties to enable it to be considered as an engineering fill material.

Experimental and numerical study of the role of crystallographic texture on the formability of an electro-galvanized steel sheet

In this work, the influence of plastic anisotropy on forming-limit strains for a drawing-quality steel sheet was investigated. For this purpose, hourglass-type samples, taken at 0°, 45° and 90° with respect to the sheet rolling direction were tested with a typical punch and die fixturing. Numerical simulations were carried out in order to validate two viscoplastic (VP) polycrystalline models, self-consistent (SC) and full-constraint Taylor-type (FC), in conjunction with the Marciniak and Kuczynski (MK) localization approach. The observed shift to the right in the minimum of the forming limit diagram (FLD), inherent to Nakazima test, was taken into account in the simulations. Keeping the set of adjustable parameters to a minimum in the calibration of the viscoplastic polycrystal model, only the material's initial texture and a power law fit to the tensile data needed to be measured. Without other adjustments to either model, MK-VPSC gives realistic predictions over the entire FLD, while the MK-FC predictions only follow the measured limit curve on the tensile side of plane strain. In the positive biaxial quadrant of the FLD, MK-FC predicts unrealistic high limit values. It was found that, despite these extremely high limit values, the similarity in the measured limit strains for the three sample orientations is captured by both models. However, a consistency in the MK-VPSC predictions indicates that this model seems to be a more suitable tool for describing the role of crystallographic texture on the sheet metal forming processes.

Recycled Aggregate Performance Experiment Study on Basis of Saturated Surface Dried Crush Value Index

Crush value index is a key parameter for measurement of coarse aggregate strength performance. In this paper the eight group of crush value index are tested for the recycled aggregate used of waste concrete which is gathered from three different remove construction plants. The experiment analysis result is shown that the crush value of recycled aggregate is greater 2.5 times than natural aggregate. Meanwhile, compared with air dried condition, the crush value index of saturated face dried condition is from 7.22% to18.2%. Furthermore the recycled aggregate can be suitable to make concrete requirement which compression strength grade is C35 and lower than C35 in China. In the experiment, comparative analysis is found that the RA-10 aggregate compressive strength is slightly from 2.06% to 8.7%. Those which are higher limit value of standard for test method of mechanical properties on ordinary concrete and the divergence are less than 10%. Consequently the recycled aggregate can be used for concrete, and its compressive strength is also fundamentally satisfied for requirement of concrete compressive strength.

Predicting optimum hollowness of normally loaded cylindrical rollers using finite element analysis

Fatigue life investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages between 20 and 80% have been tested to find the optimum percentage hollowness that gives the longest fatigue life. Two main models were built for this purpose: model 1 with two identically sized rollers and model 2 with two non-identically sized rollers. In each model, two cases have been studied: when both rollers are hollow and when one roller is hollow while the other one is solid. The Ioannides–Harris (IH) theory was used to calculate the relative fatigue life of the hollow rollers with respect to solid rollers under the same loading. Investigations have been made for five different materials: CVD 52100, carburised steel, VIMVAR M50, M50NiL and induction hardened steel. The finite element package ABAQUS has been used to study the stress and deformations in the loaded rollers. In general, the optimum hollowness percentage with the longest fatigue life ranges between 60 and 70% based on the kind of the material, whether the rollers are of the same or different size and whether one or both rollers are hollow. Using the IH theory for fatigue life calculation resulted in having infinite fatigue life for those rollers made of induction hardened steel that relatively has high fatigue limit value. Rollers in the optimum range are flexible enough to get the best redistribution of stress in the contact zone. For models of a hollow cylindrical roller in contact with a solid roller, the optimum hollowness is around 70%. When both cylindrical rollers are hollow, the optimum hollowness decreases between 60 and 65%. At the optimum hollowness, small differences in the fatigue life have been found between models of one hollow roller and models of two hollow rollers, even though having both hollow rollers means less weight, thus saving more material and more stability for the system.

Cauchy relation in relaxing liquids

The Cauchy-like relation M(infinity) = A + BG(infinity) has recently been found to hold for the high frequency limit values of the longitudinal modulus M(infinity) and transverse modulus G(infinity) of viscoelastic liquids, with B approximately 3 in all the investigated systems. The Brillouin scattering results here reported for curing epoxy systems and thermal glass formers give evidence for the validity of a Cauchy-like relation M(') = A + BG(') for the real part of the elastic moduli measured at finite frequencies. Our results suggest as well the validity of a pure Cauchy relation DeltaM = 3 DeltaG for the relaxation strengths of longitudinal and shear moduli in relaxing liquids.

Fatigue strength of metals and alloys modified by ion beams

The objective of the present research is the critical analysis of test results, dedicated to the effect of ion-beam irradiation conditions upon the fatigue strength of metallic materials. The shaped specimens, simulating the gas turbine engine blade operation and directly the blades, produced of titanium and nickel alloys as well as refractory steels by machining method are used as the study objects. The arc-pulsed ion implantation and irradiation of targets by the high-power pulsed ion beam were realised by means of Raduga-2, Temp-M and MUK accelerators. The irradiation conditions were varied within the following ranges: La, B, Sm and Hf ion implantation— E=30–80 keV (ion energy), j=1–5 mA/cm 2 (ion current density), f=30 Hz (pulse frequency), D=10 16–5×10 17 ion/cm 2 (irradiation dose); high-power pulsed ion beam irradiation—ions of carbon (60–70%) and protons, E=120–300 keV, j=30–200 A/cm 2, τ=50–100 ns (pulse duration), n=3–20 pulses (number of pulses). After irradiation, some targets were subjected to vacuum annealing for 2 h at their service temperature. Fatigue tests of initial and irradiated samples and blades were performed in air at the operating temperatures (450–650 °C) on the magneto-strictional vibrobanches with the loading frequency to 5000 Hz and low-frequency vibrobenches (50–80 Hz). The target surface state prior to and after tests was studied by electron Auger spectroscopy, scanning electron microscopy and X-ray structural analysis. The fracture surface was studied by optical and electron fractography. The test results showed that the endurance limit of samples and blades, subjected to the ion-beam irradiation with the post-process vacuum annealing at the optimum conditions, could be increased by 30–180% depending on an alloy type. Using the electron fractography, it was stated that the fatigue strength increase was associated both with the crack nucleation mechanism change and its growth rate deceleration. The extremely high endurance limit values were observed for patterns and VT8M titanium alloy blades with sharp edges after the high-power ion beam irradiation (pulse number: 15–20 at not high current density, j=60±10 A/cm 2) and vacuum annealing at 500 °C for 2 h.

Frequency and temperature dependence of the ferromagnetic resonance linewidth in single crystal platelets and pulsed laser deposited films of barium ferrite

The half power ferromagnetic resonance (FMR) linewidth ΔH has been measured from 8 to 300 K for a nominal frequency of 61 GHz and from 50 to 75 GHz at room temperature for normally magnetized single crystal platelets and pulsed laser deposited (PLD) films of barium ferrite. The platelet linewidth versus temperature data show a peak value of 27 Oe at 25–30 K, a dip to 21 Oe at 75 K, structure related to line merging at 130–160 K, and a region of slow increase at 240–295 K. The 240 –300 K data extrapolate to a 0 K linewidth of about 8 Oe. The corresponding film data show a peak value of 240 Oe at 20 K and a gradual decrease at higher temperatures. Both the platelet and film linewidths show a weak frequency dependence at about 0.3 Oe/GHz at room temperature (RT). The film data also show several linewidth spikes due to interference effects between the FMR response and dielectric resonances in the substrate. The RT linewidth zero frequency intercepts for the platelet and the film were 9 and 30 Oe, respectively. The frequency dependence of the platelet linewidth was also examined at 230–295 K. The frequency responses and intercepts for these data were affected by the line merging at lower temperatures and showed high temperature limit values of 0.35 Oe/GHz and 9.5 Oe, respectively. The linewidth frequency response in both cases is attributed to conductivity. The linewidth versus temperature peaks are attributed to impurities. The linewidth dip at 75 K for the platelet results from the drop in ΔH on the tail of the temperature peak and an increase associated with iron ion hopping motion.

Effect of soil properties on pavement failures along the F209 highway at Ado-Ekiti, south-western Nigeria

A case of of long-term and frequent highway pavement failure induced by poor soil properties, at a locality along the F209 highway at Ado-Ekiti was investigated. Visual observation revealed an extensive pavement failure right down to the subgrade level. Laboratory test results of the disturbed soil samples, collected from the failed sections of the road showed that the natural soil moisture ranged from 2.5% to 8.3%, the liquid limit from 43% to 60.50%, the linear shrinkage from 1 to 10.10 and the specific gravity values from 2.57 to 2.67. X-Ray diffraction analysis confirmed the presence of abundant kaolinite and illite in the soil sample. A CBR value of 20% indicated a strong reduction in the strength of the soil materials used in the construction of the road. Excess fines and very high liquid limit values combined with a very low CBR value to instigate the failure of the pavement at this locality. The geotechnical properties indicated substandard paving properties for Nigerian roads. Therefore, some method of soil improvement, such as soil stabilisation is required to improve the strength of the soil and prolong the useful life and durability of the road.

Influence of Solid State Environment Effects on Measured Elastic Scattering Cross Sections in the X-ray Regime and the Associated Anomalous Dispersion

Experimental elastic scattering cross sections in the atomic region 21 ≤ Z ≤ 82 are measured at an angle of 90° using monoenergetic unpolarised Mo Kα radiation. The measurements are based on a new method developed to estimate the degree of monochromaticity, the efficiency of the detecting system solid angle correction and some considerations which are necessary in experiments using secondary targets as excitation sources. Unpolarised monoenergetic radiation is produced using an X-ray tube and a secondary target. To reflect the data on the current knowledge, the results are compared with theoretical estimates based on form factor formalisms including the anomalous scattering factors and with the recent S-matrix values. Based on the experimental evidence, the present results indicate the influence of solid state environmental effects, the importance of anomalous corrections near thresholds, superiority of S-matrix values over form factor values, correctness of high energy limit values on measured elastic scattering cross sections. However, the comparison of the experimental results with theoretical estimates indicates the importance of numerical calculations based on the multipole expansion of the S-matrix approach and high energy limit values.

Theoretical study of alkoxyl radical decomposition reactions: structure–activity relationships

Simple expressions for predicting independently the kinetic and thermodynamic parameters for the decomposition reactions of alkoxyl radicals are proposed. These relationships have been parametrized, using quantum chemistry ab initio BAC-MP4 and density functional theory calculated activation energies and reaction enthalpies on a set of linear and branched C1 to C5 alkoxyl radical decomposition processes. Once parametrized, and validated against experimental data, the proposed relationships can be extrapolated to larger alkoxyl radical decomposition reactions relevant to atmospheric modelling. They only involve the ionisation potential of the departing alkyl group of the alkoxyl radicals and the parameter nH, defining whether the radical is primary, secondary or tertiary. One of the main interests of these findings is to predict with a reasonable accuracy the activation energies without knowing a priori the enthalpies of the reactions. In addition, RRKM calculations have shown that rate constant corrections for fall-off behavior are less than a factor of 2, at room temperature and atmospheric pressure, which is within experimental uncertainties. Nevertheless, Arrhenius pre-exponential factors can be very low at that pressure, compared with their high pressure limit value. The relationships proposed in this work provide kinetic parameters that are in reasonable agreement with available experimental data.

A new method to estimate elastic scattering cross sections in the X-ray region and the associated anomalous dispersion

Using nearly monoenergetic unpolarised Kα radiation, we have measured the elastic scattering cross sections for Pt, Au and Pb in the energy region 5.41 ≤ E ≤ 9.23 keV. The experimental results for Pt, Au and Pb are new. A new X-ray scattering system was assembled using an X-ray tube and secondary targets. In order to improve the peak-to-background ratio and the efficiency of the detection system, particularly in the low-energy region, excitation source, sample and detector assembly were placed in a vacuum chamber at a pressure of 10 −2 mbar. The present system helped considerably in reducing the scattering and background effects, and in removing the interference of Ar K X-rays which fall in the investigated regions. A new method was developed to estimate the degree of monochromaticity, geometrical effects of the measuring system, solid angle correction and some considerations which are necessary in experiments using X-ray tube with secondary target arrangement. Experimental elastic scattering cross sections are compared with theoretical estimates, a combination of relativistic modified form factors with angle independent anomalous scattering factors (RMF + ASFs) and recent theoretical estimates based on the multipole expansion of the second order S-matrix approach. Deviations are observed around the edges (high energy side) indicating the importance of the dispersion correction terms. The present experimental results are useful taking into account that the available calculated values describe the free atom and deviations for a solid have to be expected. This is due to the difference of the electronic structure of the solid in comparison to the free atom as a base for theoretical estimations. However, the comparison of experimental results with theoretical estimates indicates the importance of numerical calculations based on the multipole expansion of the second order S-matrix approach and high energy limit values (RMF + ASFs).

Problems in experimental measurements of dust explosions

The experimental method employed for measuring the parameters of dust explosions was critically examined using methane/air as a model system. Because of the rapid rate that air enters the test vessel (in order to disperse the dust), the system is not at thermodynamic equilibrium which causes the actual concentration of air to be about 15% less than indicated by the measured pressure at the time of ignition, thus creating a significant error in the determination of explosion pressures. For measuring the lower explosible limit, the ignitor must be of optimum strength, otherwise too high or low limit values are obtained. Pyrotechnic ignitors, which are usually used for igniting dusts, produce a significant pressure by themselves; a method for accurately taking this effect into account is given. Some unusual problems encountered with particular dusts are discussed.

Determining Reference Ranges by Linear Analysis: Serum Electrolyte Concentrations

We determined reference ranges for serum sodium, potassium, and chloride concentrations by collecting results from 200 consecutive hospitalized patients. For each electrolyte, the value at each whole percentile was determined, and the value-vs-percentile plot was constructed. The central linear portion of each value-vs-percentile plot was determined as follows: First, the least-squares straight line with 95% confidence limits was calculated through all values. Second, the highest values above the high confidence limit and lowest values below the low confidence limit were excluded. Third, the least-squares straight line with 95% confidence limits was recalculated through all unexcluded values. Fourth, extreme values again were excluded as described above, and the process was repeated until highest and lowest values were within the 95% confidence limits. The line connecting these extreme values was extended to the Oth and 100th percentiles, and the values at these percentiles were defined as the reference limits.