Improper Calibration Research Articles

Underestimation of sulfate concentration in PM2.5 using a semi-continuous particle instrument based on ion chromatography

Recently, a variety of ion-chromatography-based semi-continuous particle instruments such as the Dionex gas particle ion chromatograph (GP-IC), wet-annular denuder/steam-jet aerosol collector (WAD/SJAC), particle-into-liquid sampler with ion chromatograph (PILS-IC), gas and aerosol monitoring system (GAMS) have been introduced for measuring particle chemical components in the atmosphere. It has been reported that sulfate concentrations in PM2.5 measured by these semi-continuous particle instruments correlate well with those measured by other semi-continuous instruments such as the Aerodyne aerosol mass spectrometer (AMS), R&P 8400S and R&P 8400N analyzers, and Thermo model 5020 sulfate particle analyzer and at times exhibit a unity slope. However, the sulfate concentration measured by some of these semi-continuous instruments has been reported to be underestimated by 20-50%, as compared to that in PM2.5 filter samples. In this study, numerous potential causes for underestimation of the sulfate concentrations by the GP-IC were investigated. We found a 30-40% negative artifact arising from an improper calibration procedure inherent within the instrument design. An improved calibration procedure was developed and it substantially reduced the sulfate concentration difference between the GP-IC measurements and PM2.5 filter samples from 36% to 5%.

State-of-the-Art of Serum Testosterone Measurement by Isotope Dilution–Liquid Chromatography– Tandem Mass Spectrometry

The recent interest of clinical laboratories in developing serum testosterone assays based on isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) stems from the lack of accuracy of direct immunoassays. In this study, we assessed the accuracy and state of standardization (traceability) of 4 published ID-LC-MS/MS procedures in a method comparison with an ID-gas chromatography (GC)-MS reference measurement procedure listed in the database of the Joint Committee for Traceability in Laboratory Medicine. The study used 58 specimens from different patient categories. Each specimen was measured in triplicate (ID-LC-MS/MS) and quadruplicate (ID-GC-MS) in independent runs. The testosterone concentrations by ID-GC-MS were 0.2-4.4 nmol/L (women), 0.2-2.0 nmol/L (hypogonadal man), and 10.1-31.3 nmol/L (normogonadal men). For ID-GC-MS, the CV was nearly constant, with a median of 1.0%; for ID-LC-MS/MS, it was concentration-dependent, with a median of up to 8%. Weighted Deming regression gave mean slopes, intercepts, and correlation coefficients of 0.90-1.11, -0.055-0.013 nmol/L, and 0.993-0.997, respectively. The % difference plot showed between 7% and 26% of the results outside a total error limit of 14%, with median deviations from ID-GC-MS between -9.6 and 0.4%. This study demonstrated fairly good accuracy and standardization of the tested ID-LC-MS/MS procedures. Performance differences between procedures were evident in some instances, due to improper calibration and between-run calibration control. This emphasizes the need for thorough validation, including traceability, of new ID-LC-MS/MS procedures.

Effect of Weigh-in-Motion System Measurement Errors on Load-Pavement Impact Estimation

Weigh-in-motion (WIM) technology has found increasing application in the highway and transportation areas for traffic data collection for the purpose of highway capacity analysis, aiding enforcement and, most recently, pavement design. The measurement accuracy of a WIM scale is critical. There are numerous existing studies involving the measurement accuracy per se; however, the implications and effect of the accuracy in the context of pavement design have been rarely examined. To address this issue, two particular aspects are considered in this study. First, with traffic data obtained from WIM stations in Texas, axle load spectra are developed from both statistical data fit and load-pavement impact perspectives. Axle load spectra are shown to be captured best by mixed-lognormal distributions. Second, based on the first aspect, two scenarios are investigated by incorporating two types of errors into the load measurements: (1) A random error component due to the WIM scale intrinsic properties; and (2) a systematic error component due to the improper calibration of WIM system. The relationship between jointly varying measurement error levels and load-pavement impact estimation errors is established. It is demonstrated (and quantified) that both types of errors contribute to load-pavement impact estimation inaccuracy. The random error leads to overestimation of load-pavement impact. The results also show that WIM system calibration is of more importance because load-pavement impact estimation is more sensitive and significantly related to systematic error than random error. In addition, the estimated load-pavement impact is found to be more sensitive to overcalibration (positive bias) than undercalibration (negative bias) condition. In summary, the findings in this study provide an effective and efficient approach to evaluate WIM measurement errors in conjunction with load-pavement impact in pavement design and rehabilitation. The findings in this study could be further applied for the determination of adequate pavement design reliability standards. Results can also be useful to highway agencies in assessing and selecting WIM equipment.

Remote characterisation of shallow seafloor using airborne TEM

Helicopter-borne time-domain electromagnetic (EM) systems combine the advantages of portability with large transmitter moments. In order to demonstrate the potential of helicopter TEM for shallow bathymetric mapping, a HoistEM survey was conducted near the entrance of Port Jackson (Sydney Harbour) in March 2002. 1D inversion of rescaled HoistEM yielded accurate (± 1m) water depth predictions to depths of about 55m. The seawater depths inferred from HoistEM were in good agreement with the depths obtained from accurate single-beam and multi-beam sonar soundings. It was necessary to rescale the HoistEM data in order to account for improper calibration. Re-scaling was possible because a considerable amount of ``ground truth' was available. Synthetic TEM decays were computed for numerous models representing shallow water, sediment and basement at a number of locations within the survey area. Measured and calculated data were compared at each delay time, and were found to be linearly related. A rescaling factor was then applied to each decay time, irrespective of water depth. Given the successful bathymetric mapping demonstration, the potential of airborne EM for seafloor characterisation has been investigated. Accordingly, the sediment thickness inferred from 1D inversion of HoistEM has been compared with estimates based on marine seismic studies. Generally, the sediment thickness, and hence depth to resistive bedrock, inferred from HoistEM was in reasonable agreement with depths estimated from marine seismic data when the seawater was less than about 20 m deep and the sediment was less than about 40 m thick.

Physical modeling of degenerately doped compound semiconductors for high-performance HBT design

Numerous research groups are currently developing high-performance InP HBTs with fT and fMAX greater than 400GHz. However, the heavily degenerate doping concentrations used in these devices present new challenges to numerical device simulation. This work focuses on three physical phenomena in InP and In0.53Ga0.47As and their implementation in physics based device simulators. First, the use of the parabolic band approximation yields a constant DOS effective mass, but this results in an erroneously deep Fermi-level under heavily degenerate donor concentrations. An empirical model is presented and shown to have good agreement with previously published simulations and experimental data. Second, bandgap narrowing parameters and a table based model are used as a more generic model for compound semiconductors. Third, calculated parameters to address the Mott transition are used to obtain the proper free-carrier concentrations throughout the HBT. The improper calibration or neglect of these three physical phenomena is shown to alter HBT band profiles at thermal equilibrium by as much as 400meV; the turn-on voltage by approximately 50mV; and the fT dependence on JC by approximately 18%.

Failure Detection and Diagnosis in Microsimulation Traffic Models

Effective and feasible procedures for validating microscopic, stochastic traffic simulation models are in short supply. Exercising such microsimulators many times may lead to the occurrence of traffic gridlock (or simulation failures) on some or all replications. Whereas lack of failures does not ensure validity of the simulator for predicting performance, the occurrence of failures can provide clues for identifying deficiencies of the simulation model and invite strategies for model improvement. Failure is defined as a severe malfunction in one or more traffic links on the network where vehicles are unable to discharge for an unusually long period. Such malfunctions can be detected with link-based time traces of vehicle trips. Identifying locations where malfunctions arise requires further spatial analyses. A procedure for identifying whether, when, and where failures occur is described. The simulator CORSIM serves as the test-bed simulator for the proposed methodology, but the procedure is applicable to any comparable microscopic model; real-world traffic networks are simulated as case studies. Possible root causes of detected failures are ( a) flaws in the simulator behavioral algorithms, ( b) improper calibration of inputs, and ( c) capacity problems related to the specific network (for example, when heavy traffic demand projections are simulated). Strategies to identify why failures occur are used in the case studies. The results indicate that the proposed failure detection and diagnosis process is an effective (and essential) way to explore the validity of traffic simulators and find improvements where needed.

WE‐D‐I‐6B‐01: Soft Tissue Visualization Using a Highly Efficient Megavoltage Cone Beam CT Imaging System

Purpose: Recent developments in two‐dimensional x‐ray detector technology have made volumetric Cone Beam CT (CBCT) a feasible approach for integration with conventional medical linear accelerators. The requirements of a robust image guidance system for radiation therapy include the challenging combination of soft tissue sensitivity with clinically reasonable doses. Previously, low contrast objects have generally not been perceptible with MV energies due to relatively poor signal to noise ratio (SNR) performance. We have developed an improved imaging system that is optimized for MV CBCT and acquire CBCT images containing soft tissue contrast using a 6MV x‐ray beam. Method and Materials: Many factors, such as image noise, x‐ray scatter, improper calibration and acquisitions have a profound effect on the imaging performance of CBCT. In this study attempts were made to optimize these factors in order to maximize the SNR. A QC‐3V and contrast/resolution phantoms were used to determine the contrast to noise ratio (CNR) and f50 of a single 2‐D projection and the contrast and spatial resolution of the reconstructed images. Results: The computed f50 was 0.43 lp/mm and the CNR for a radiation dose of 0.02cGy was 43. Relative electron density as low as 1% can be resolved with clinically reasonable radiation doses. Clinical Megavoltage CBCT images acquired with this system demonstrate that anatomical structures such as the prostate and optic nerves are visible using radiation doses in range of 4 to 8cGy. Conclusion: We have developed an imaging system that is optimized for MV and acquire Megavoltage CBCT images containing soft tissue contrast using a 6MV x‐ray beam and irradiation doses in range of 4 to 8cGy. This system can also be used for routine portal imaging applications without risk of saturation for high dose/high energy treatment/verification imaging, or dosimetry applications. Conflict of Interest : Sponsored by Siemens.

Volume CT with a flat‐panel detector on a mobile, isocentric C‐arm: Pre‐clinical investigation in guidance of minimally invasive surgery

A mobile isocentric C-arm (Siemens PowerMobil) has been modified in our laboratory to include a large area flat-panel detector (in place of the x-ray image intensifier), providing multi-mode fluoroscopy and cone-beam computed tomography (CT) imaging capability. This platform represents a promising technology for minimally invasive, image-guided surgical procedures where precision in the placement of interventional tools with respect to bony and soft-tissue structures is critical. The image quality and performance in surgical guidance was investigated in pre-clinical evaluation in image-guided spinal surgery. The control, acquisition, and reconstruction system are described. The reproducibility of geometric calibration, essential to achieving high three-dimensional (3D) image quality, is tested over extended time scales (7 months) and across a broad range in C-arm angulation (up to 45 degrees), quantifying the effect of improper calibration on spatial resolution, soft-tissue visibility, and image artifacts. Phantom studies were performed to investigate the precision of 3D localization (viz., fiber optic probes within a vertebral body) and effect of lateral projection truncation (limited field of view) on soft-tissue detectability in image reconstructions. Pre-clinical investigation was undertaken in a specific spinal procedure (photodynamic therapy of spinal metastases) in five animal subjects (pigs). In each procedure, placement of fiber optic catheters in two vertebrae (L1 and L2) was guided by fluoroscopy and cone-beam CT. Experience across five procedures is reported, focusing on 3D image quality, the effects of respiratory motion, limited field of view, reconstruction filter, and imaging dose. Overall, the intraoperative cone-beam CT images were sufficient for guidance of needles and catheters with respect to bony anatomy and improved surgical performance and confidence through 3D visualization and verification of transpedicular trajectories and tool placement. Future investigation includes improvement in image quality, particularly regarding x-ray scatter, motion artifacts and field of view, and integration with optical tracking and navigation systems.

Inter-laboratory calibration of low-field magnetic and anhysteretic susceptibility measurements

Inter-laboratory and absolute calibrations of rock magnetic parameters are fundamental for grounding a rock magnetic database and for semi-quantitative estimates about the magnetic mineral assemblage of a natural sample. Even a dimensionless ratio, such as anhysteretic susceptibility normalized by magnetic susceptibility ( K a/ K) may be biased by improper calibration of one or both of the two instruments used to measure K a and K. In addition, the intensity of the anhysteretic remanent magnetization (ARM) of a given sample depends on the experimental process by which the remanence is imparted. We report an inter-laboratory calibration of these two key parameters, using two sets of artificial reference samples: a paramagnetic rare earth salt, Gd 2O 3 and a commercial “pozzolanico” cement containing oxidized magnetite with grain size of less than 0.1 μm according to hysteresis properties. Using Gd 2O 3 the 10 Kappabridges magnetic susceptibility meters (AGICO KLY-2 or KLY-3 models) tested prove to be cross-calibrated to within 1%. On the other hand, Kappabridges provide a low-field susceptibility value that is ca. 6% lower than the tabulated value for Gd 2O 3, while average high-field susceptibility values measured on a range of instruments are indistinguishable from the tabulated value. Therefore, we suggest that Kappabridge values should be multiplied by 1.06 to achieve absolute calibration. Bartington Instruments magnetic susceptibility meters with MS2B sensors produce values that are 2–13% lower than Kappabridge values, with a strong dependence on sample centering within the sensor. The K a/ K ratio of ca. 11, originally obtained on discrete cement samples with a 2G Enterprises superconducting rock magnetometer and a KLY-2, is consistent with reference parameters for magnetites of grain size <0.1 μm. On the other hand, K a values from a 2G Enterprises magnetometer and K values from a Bartington Instruments MS2C loop sensor for u-channel and discrete cement samples, will produce average K a/ K values that are unrealistically high if not properly corrected for the nominal volume detected by the sensors for these instruments. Inter-laboratory measurements of K and K a for standard paleomagnetic plastic cubes filled with cement indicate remarkable differences in the intensity of the newly produced ARMs (with a standard deviation of ca. 21%), that are significantly larger than the differences observed from the calibration of the different magnetometers employed in each laboratory. Differences in the alternating field decay rate are likely the major source of these variations, but cannot account for all the observed variability. With such large variations in experimental conditions, classical interpretation of a “King plot” of K a versus K would imply significant differences in the determination of grain size of magnetite particles on the same material.

Potato Yield Monitoring on Commercial Fields

An accurate yield map is imperative for successful precision farming. For 3 years (1998 to 2000) two to four potato (Solanum tuberosum) fields on a commercial farm in southeastern Washington were yield-monitored using commercial yield monitoring equipment without operator interaction. Multiple potato diggers were used to harvest the fields and diggers used were not necessarily the same at each harvest. In all years, yield monitoring data were missing due to equipment failure or lack of yield monitoring equipment on all diggers. Banding, due to dissimilar calibrations, different equipment used, or differential digger performance was observed in 1998 and 2000. Based on experience described here, some yield monitor data need minimal postprocessing or correction, other data need substantial postprocessing to make them usable, and other data may not be reliable due to equipment failure, improper calibration, or other causes. Even with preharvest calibration, it is still likely that the potato yield monitor data will need differential postprocessing, indicating that yield maps lack accuracy. In addition, comparison to yield data collected at multiple points within the field, this study found that the yield monitor over estimated potato yield. Thus, with some postprocessing, a useful yield map showing within field differences is possible. However, without significant postprocessing, the practice of using multiple diggers and yield monitors for potato harvest, both within and between fields, severely limits the ability to make consistent yield maps in commercial potato operations.

A Better Statutory Approach to Whistle-blowing

Abstract:Statutory approaches toward whistle-blowing currently appear to be based on the assumption that most observers of wrongdoing will report it unless deterred from doing so by fear of retaliation. Yet our review of research from studies of whistle-blowing behavior suggests that this assumption is unwarranted. We propose that an alternative legislative approach would prove more successful in encouraging valid whistle-blowing and describe a model for such legislation that would increase self-monitoring of ethical behavior by organizations, with obvious benefits to society at large.A defense contractor’s inspectors used improper calibration standards when inspecting missile parts and other military products, used noncertified inspectors when inspecting such products, and used employees without top-secret clearance to work on classified projects. This created potentially life-threatening products as well as potential compromises of military secrets.Quality-control officials on the Trans Alaska Pipeline were threatened with physical harm, demoted, and spied on in an effort to force them not to turn in negative reports or report problems. As a result, the likelihood of damaging oil spills due to improperly built and maintained equipment is heightened.A major corporation allegedly initiated an analysis of the cost savings that would result from circumventing or reducing compliance with health, safety and environmental standards. Two officers who objected to this noncompliance cost/benefit analysis were subsequently fired.

Troubleshooting industrial flotation columns

Since the early 1980s flotation columns have been progressively incorporated in milling operations all over the world. Improvements in final concentrate grade, using single cleaning stages, have been in most cases the reason for using this new technology. However, the main disadvantage with respect to conventional mechanical cells is the large spread of'results, mainly in terms of recovery, which is normally compensated by a high circulating load and high capacities (overdesign). Besides normal changes in feed grade and flowrate, and the need for periodic maintenance for gas spargers, the following common troubles in plant practice are discussed: . improper calibration and maintenance of instrumentation to measure froth depth and gas rate . bias definition and estimation . uneven wash water distribution . uneven froth depth in baffled columns . lack of robustness of control strategies Proper boundaries for superficial wash water rate (0.1–0.2 cm/s), froth depth (0.5–1.0 m) and superficial gas rate (I-2 cm/s), based on fundamental knowledge and experience in large size columns, are suggested for stable operation. Unfortunately, the lack of coordination between these variables is an important limitation for metallurgical improvements. The effect of altitude on gas rate and gas holdup in flotation columns operating at 1500–4500 m over the sea level is analysed.

Direct measurement of gas rate in a flotation machine

Gas rate measurement in a flotation cell and especially in a column has generally been a problem for the industry. Some of the reasons for this are: improper calibration and maintenance of the flowmeter, inadequate knowledge of the air pressure related to the measurement, and the correction for standard conditions (STP). A novel method was developed to allow direct measurement of the gas rate ina flotation machine. Tests were conducted in a laboratory flotation cell and in a 10-cm diameter laboratory column, with a water-air system and with three-phase systems having silica or sulfides as the solids. A 2.5-cm inside probe was located vertically above the flotation machine with its tip at a known depth in the pulp zone. Material was pumped from the pulp through a peristaltic pump. The slurry and air pumping rates, and the percentage of solids were measured. A correlation was developed that yields the gas rate in the cell from the slurry and air volumetric rates with a standard error of estimate of 0.05 cm/s. The correlation depends on the flotation machine geometry, and the amount of solids present. The method has been applied successfully in 3 plants, at 6 flotation columns.

Guidelines for experimental studies

Objectives. The purpose of this document is to present guidelines for the training of researchers and for the planning of experiments that ensure optimum interaction and communication among the investigators and statisticians of the research team. Methods. The protocol described in this document is designed to systematically guide a researcher through a sequence of planning steps and checkpoints to ensure proper experimental design, data management, statistical analyses, and interpretation. Results. The investigator and the statistician, as a collaborative team, will be able to determine the most effective and appropriate procedures and tools necessary for the successful completion of a research project. Significance. Planning an experimental study necessitates much thought. Lack of essential communication with a statistician in the initial stages of the experimental design can doom the experiment to failure. Flawed research studies may be associated with one or more of the following: failure of the established testable hypothesis, uncontrolled biases, insufficient sample size, lack of appropriate controls, variability in specimen preparation, improper calibration of instruments or standardization of measurements, incorrect data entries, inappropriate statistical analyses, errors in interpretation of statistical analyses, and erroneously drawn conclusions. Standard guidelines will eliminate many of these potential problems.

PC Software for Urban Transportation Planning

Abstract This article reviews nine PC-based urban transportation planning (UTP) software packages, all of which are relatively complex and require significant education, training, and experience to use properly. Inappropriate use of UTP modeling software can result from insufficient training or data, improper model calibration, inappropriate model application, or from the black box syndrome, which often plagues complex modeling efforts. Recent UTP modeling innovations include new developments in the areas of subarea focusing, site impact analysis, the evaluation of travel demand management strategies, the integration of UTP models with geographic information systems, and the integration of land use and activity modeling with the traditional four-step UTP process.

Remarks on the Calibration of Steric Exclusion Liquid Chromatography by Polymolecular Standards

Abstract The relation of polymer molecular characteristics versus chromatographic parameters in steric exlusion liquid chromatography (GPC) was considered as a typical black box problem. Practical problems were discussed for cases of the GPC black box calibration with polymolecular polystyrene standards and of using an improper calibration model. It was concluded that checking the reliability of the GPC black box calibration is of utmost importance especially when narrow calibration standards are not available.

Digital simulation of mechanical stereoplotters

Due to design considerations, production tolerances, wear and tear, improper calibration or maladjustment, aging, external influences, etc., the accuracy and performance state of analog stereo restitution instruments is often not at its optimum. The large number of spatial linkages and optical elements required for a technical reconstruction of the original bundles of rays, gives rise to the accumulation of small systematic errors that are difficult to describe. By making use of the principal flow of information in a stereoplotter, the kinematics of both the spatial linkage mechanisms from the model to the image and the geometric optics between measuring marks and image, however, can be formulated algebraically. The formulation itself can be extended to a computer algorithm which is used as the basis of a digital simulation of the metric state of the stereoplotter. The paper discusses the principle of the mathematical representation of rotations and translations of spatial linkages and the procedure used in determining the dependent pair variables of a typical stereoplotter mechanism. By a simple ray-tracing method applied to the essential optical elements, the process of photogrammetric static measurements can be simulated. Preliminary test results of the computer simulation program are presented, and its full potential is discussed by artificially introduced instrumental errors. The results are of interest to the efforts of sub-group 2 (Testing of Instruments) of I.S.P.'s Commission II.

Solubility of Benzene in Water.

F o r the determination of individual mass transfer coeff ic ients for the benzene-water system, the mutual solubility of the components is required. T h i s paper dea ls with the solubility of benzene in water. T h e interpretation by Seidell (23) of the then-available portion of the present (1, 3-5, 7-19, 21-23, 25, 26) data on the solubility of benzene in water indicated a relationship that continually increased with temperature in a manner similar t o h i s other interpretations on the solubility of hydrocarbons in water. T h e more recent data of Bohon and Claussen (4) were the first to indicate a minimurn in the solubility curve for benzene (and other aromatic compounds), although Hill (13) suspected one. Taken a s a whole, the avai lable data might have been considered discordant. As a precise analytical technique for the analysis of benzene in water was needed for mass transfer s tudies , it was decided t o demonstrate and prove the technique by a redetermination of the solubility relationship. Ultraviolet spectrophotometry was selected a s the analytical tool. Study and experience indicated that the analytical technique had to b e developed with great care to avoid errors due to excess ive volatility, such as found by Saylor, Stuckey, and Gross (22), to improper calibration, to temperature-induced hazes , and perhaps to wall adsorption effects.