Pub Date : 2014-10-29DOI: 10.17764/JIET.57.1.K0UW6777L1073HX7
J. Niehues
Industry standard practices lead to discrepancies in the severity of flight and test environments. Steps in common processes defined in guidance documents are based upon assumptions and simplifications not always evident. Not acknowledging these assumptions leads to non-flight like environments in test and analysis. Documents such as MIL-STD-1540, NASA-HDBK-7005, and MIL-STD-810 all provided valuable guidance but should not be applied without consideration of underlying assumptions and simplifications. Hypothetical examples, based on real experiences, will be reviewed to illustrate the importance of understanding, modifying, or eliminating the assumptions and simplifications. The examples provided are primarily random vibration environments but the messages also apply to other dynamic environments including shock and acoustics. This paper is separated into two parts. The first addresses environment specification. The second addresses qualification and acceptance test requirements.
{"title":"Discrepancies Caused by Common Industry Standard Practices Part 1: Environment Specification","authors":"J. Niehues","doi":"10.17764/JIET.57.1.K0UW6777L1073HX7","DOIUrl":"https://doi.org/10.17764/JIET.57.1.K0UW6777L1073HX7","url":null,"abstract":"Industry standard practices lead to discrepancies in the severity of flight and test environments. Steps in common processes defined in guidance documents are based upon assumptions and simplifications not always evident. Not acknowledging these assumptions leads to non-flight like environments in test and analysis. Documents such as MIL-STD-1540, NASA-HDBK-7005, and MIL-STD-810 all provided valuable guidance but should not be applied without consideration of underlying assumptions and simplifications. Hypothetical examples, based on real experiences, will be reviewed to illustrate the importance of understanding, modifying, or eliminating the assumptions and simplifications. The examples provided are primarily random vibration environments but the messages also apply to other dynamic environments including shock and acoustics. This paper is separated into two parts. The first addresses environment specification. The second addresses qualification and acceptance test requirements.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67808782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-29DOI: 10.17764/JIET.57.1.LJ5X82412J018246
R. Dittler, J. Kishore, C. Geisert, F. Shadman
A combination of experimental investigation and process simulation was used to analyze the effect of various operational parameters on impurity back diffusion into ultra-high-purity (UHP) gas distribution systems. The process model developed in this work was validated by comparing its predictions with data from the experimental test bed. Surface diffusion as well as convection and dispersion in the bulk fluid played a strong role in the transport of moisture from vents and lateral branches into the main line. Parametric studies on the effect of key operational and design parameters were performed experimentally and with the application of a process simulator. In this analysis, a dimensionless number (Peclet Number) was derived and applied as the key indicator of the relative significance of various transport mechanisms in moisture back diffusion. Guidelines and critical values of Peclet Number were identified for assuring the operating conditions meet the purity requirements at the point of use while mini...
{"title":"Contamination of Ultra-High-Purity (UHP) Gas Distribution Systems by Back Diffusion of Impurities","authors":"R. Dittler, J. Kishore, C. Geisert, F. Shadman","doi":"10.17764/JIET.57.1.LJ5X82412J018246","DOIUrl":"https://doi.org/10.17764/JIET.57.1.LJ5X82412J018246","url":null,"abstract":"A combination of experimental investigation and process simulation was used to analyze the effect of various operational parameters on impurity back diffusion into ultra-high-purity (UHP) gas distribution systems. The process model developed in this work was validated by comparing its predictions with data from the experimental test bed. Surface diffusion as well as convection and dispersion in the bulk fluid played a strong role in the transport of moisture from vents and lateral branches into the main line. Parametric studies on the effect of key operational and design parameters were performed experimentally and with the application of a process simulator. In this analysis, a dimensionless number (Peclet Number) was derived and applied as the key indicator of the relative significance of various transport mechanisms in moisture back diffusion. Guidelines and critical values of Peclet Number were identified for assuring the operating conditions meet the purity requirements at the point of use while mini...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67809058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-10-28DOI: 10.17764/JIET.56.2.C1J085562L837155
M. Hale, W. Barber
The generation of Gaussian noise with a specific auto spectral density (ASD) is a well-documented process employed in drive signal generation in vibration control applications. In recent years, vibration control system vendors have introduced the ability to modify the probability density function (PDF) characteristics associated with the reference ASD, yielding a non-Gaussian drive. The specific parameter defining this process is kurtosis. This paper will discuss concerns with this practice in terms of synthesizing a time history with dissimilar PDF characteristics to that of the measured data upon which the original ASD and kurtosis characteristics were based. An example is discussed from both statistical and fatigue perspectives.
{"title":"Evaluation of Vibration References with Equivalent Kurtosis and Dissimilar Amplitude Probability Densities","authors":"M. Hale, W. Barber","doi":"10.17764/JIET.56.2.C1J085562L837155","DOIUrl":"https://doi.org/10.17764/JIET.56.2.C1J085562L837155","url":null,"abstract":"The generation of Gaussian noise with a specific auto spectral density (ASD) is a well-documented process employed in drive signal generation in vibration control applications. In recent years, vibration control system vendors have introduced the ability to modify the probability density function (PDF) characteristics associated with the reference ASD, yielding a non-Gaussian drive. The specific parameter defining this process is kurtosis. This paper will discuss concerns with this practice in terms of synthesizing a time history with dissimilar PDF characteristics to that of the measured data upon which the original ASD and kurtosis characteristics were based. An example is discussed from both statistical and fatigue perspectives.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67807849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-10-28DOI: 10.17764/JIET.56.2.5600210764M14370
Deling Liu
Sampling representative aerosol particles in fast-moving air is a challenging task. Aerosols are significantly more massive than gas molecules, thus they might not follow air streamlines well and could be more easily subjected to sampling errors. This work examines the physical factors that govern the aspiration efficiency of an aerosol sampling probe in unidirectional moving air, and explores the plausible sampling deviations under various high air velocity scenarios. The particle sizes of 0.5 and 5 μm are of particular interest due to their use in defining air cleanliness levels in ISO 14644-1[1] and FED-STD-209.[2]* Our analytical results indicate that significant sampling errors could occur for 5-μm particles when a thick-walled sampling probe is used, or when the air velocity at the sampling probe inlet does not match the velocity of the incoming air (i.e., anisokinetic sampling). The aspiration efficiency of 0.5-μm particles, on the other hand, is nearly 100% due to sufficiently small inertia of the...
{"title":"Evaluating Aerosol Aspiration Efficiency in Fast-moving Air","authors":"Deling Liu","doi":"10.17764/JIET.56.2.5600210764M14370","DOIUrl":"https://doi.org/10.17764/JIET.56.2.5600210764M14370","url":null,"abstract":"Sampling representative aerosol particles in fast-moving air is a challenging task. Aerosols are significantly more massive than gas molecules, thus they might not follow air streamlines well and could be more easily subjected to sampling errors. This work examines the physical factors that govern the aspiration efficiency of an aerosol sampling probe in unidirectional moving air, and explores the plausible sampling deviations under various high air velocity scenarios. The particle sizes of 0.5 and 5 μm are of particular interest due to their use in defining air cleanliness levels in ISO 14644-1[1] and FED-STD-209.[2]* Our analytical results indicate that significant sampling errors could occur for 5-μm particles when a thick-walled sampling probe is used, or when the air velocity at the sampling probe inlet does not match the velocity of the incoming air (i.e., anisokinetic sampling). The aspiration efficiency of 0.5-μm particles, on the other hand, is nearly 100% due to sufficiently small inertia of the...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67807730","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-10-28DOI: 10.17764/JIET.56.2.41344333010617Q6
D. Smallwood
Specification of the cross spectra for a multiple-input/multiple-output (MIMO) vibration test is challenging. This paper presents a method for tests where the specifications of the output (the control points) autospectra are available. The autospectra of the outputs are specified and cross spectra between the outputs are derived that will minimize the trace of the autospectra of the inputs (the drive signals) with the constraint that the input spectral density matrix is positive definite. The hypothesis is that nature likes a minimum energy solution.
{"title":"Minimum Input Trace for Multiple Input Multiple Output Linear Systems","authors":"D. Smallwood","doi":"10.17764/JIET.56.2.41344333010617Q6","DOIUrl":"https://doi.org/10.17764/JIET.56.2.41344333010617Q6","url":null,"abstract":"Specification of the cross spectra for a multiple-input/multiple-output (MIMO) vibration test is challenging. This paper presents a method for tests where the specifications of the output (the control points) autospectra are available. The autospectra of the outputs are specified and cross spectra between the outputs are derived that will minimize the trace of the autospectra of the inputs (the drive signals) with the constraint that the input spectral density matrix is positive definite. The hypothesis is that nature likes a minimum energy solution.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67807985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-10-28DOI: 10.17764/JIET.56.2.5561RJ6668887H43
Deling Liu
This work examines the physical factors that contribute to sampling errors in an aerosol sampling system consisting of a sampling probe and a sampling line. Aerosol particles are more massive than gas molecules and therefore tend to deviate from air streamlines in response to sudden directional change, which potentially leads to sampling errors during sample transfer processes. Based on well-established studies involving particle transport and deposition, an analysis was performed to determine the sampling line transmission efficiency for 0.5- and 5-μm particles as these particle sizes are used in defining air cleanliness level in ISO 14644-1[1] and FED-STD-209E.[2]* Our analytical results indicate that significant particle losses for 5-μm particles can occur if bends exist in the sampling lines. In addition, particle losses typically can be reduced by lowering the air velocity in the sampling line, and this can be achieved by using a sampling line with a larger inner diameter (I.D.). The example calculat...
{"title":"Evaluating Aerosol Transmission Efficiency in a Sampling System","authors":"Deling Liu","doi":"10.17764/JIET.56.2.5561RJ6668887H43","DOIUrl":"https://doi.org/10.17764/JIET.56.2.5561RJ6668887H43","url":null,"abstract":"This work examines the physical factors that contribute to sampling errors in an aerosol sampling system consisting of a sampling probe and a sampling line. Aerosol particles are more massive than gas molecules and therefore tend to deviate from air streamlines in response to sudden directional change, which potentially leads to sampling errors during sample transfer processes. Based on well-established studies involving particle transport and deposition, an analysis was performed to determine the sampling line transmission efficiency for 0.5- and 5-μm particles as these particle sizes are used in defining air cleanliness level in ISO 14644-1[1] and FED-STD-209E.[2]* Our analytical results indicate that significant particle losses for 5-μm particles can occur if bends exist in the sampling lines. In addition, particle losses typically can be reduced by lowering the air velocity in the sampling line, and this can be achieved by using a sampling line with a larger inner diameter (I.D.). The example calculat...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67807688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-10-28DOI: 10.17764/JIET.56.2.46512M9447T62X13
J. Weaver
Objectively evaluating laboratory staff is a very difficult task. Variations in supported equipment, student performance, and process sensitivity prevent the use of direct, objective criteria in employee performance measurement. These factors are multiplied in research facilities, where equipment uptime and process performance measurements are not easily determined. Supervisors, therefore, must apply more subjective techniques in staff evaluation, which often results in the perception of inequity. This paper presents a rigorous evaluation process that utilizes significant employee participation to address this issue of perceived inequity.The process utilizes five areas of evaluation: Goals and Accountability; Job Performance; Individual Characteristics; Aspirations and Assistance; and Employee Feedback. These areas, applied through an employee self-evaluation followed by direct interaction between employee and supervisor, serve as discussion points as well as a means of performance documentation. While st...
{"title":"Laboratory Staff Evaluation Process","authors":"J. Weaver","doi":"10.17764/JIET.56.2.46512M9447T62X13","DOIUrl":"https://doi.org/10.17764/JIET.56.2.46512M9447T62X13","url":null,"abstract":"Objectively evaluating laboratory staff is a very difficult task. Variations in supported equipment, student performance, and process sensitivity prevent the use of direct, objective criteria in employee performance measurement. These factors are multiplied in research facilities, where equipment uptime and process performance measurements are not easily determined. Supervisors, therefore, must apply more subjective techniques in staff evaluation, which often results in the perception of inequity. This paper presents a rigorous evaluation process that utilizes significant employee participation to address this issue of perceived inequity.The process utilizes five areas of evaluation: Goals and Accountability; Job Performance; Individual Characteristics; Aspirations and Assistance; and Employee Feedback. These areas, applied through an employee self-evaluation followed by direct interaction between employee and supervisor, serve as discussion points as well as a means of performance documentation. While st...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67808053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-10-01DOI: 10.17764/jiet.56.2.43g5n424308r4016
B. Kosinski, D. Cronin
Highly Accelerated Life Testing (HALT) is used in the commercial electronics industry to improve product robustness prior to starting production. The basic theory is that testing well beyond expected, intended-use environments may uncover design flaws that could become field failures after a product is in production. By fixing issues prior to starting production, costly recalls can be avoided. HALT has proven to be effective, as evidenced by its wide incorporation in the commercial electronics industry. Could HALT also be worth the time and expense of performing on commercial satellite hardware, which is designed to rigorous standards and tested over military-grade environmental test specifications? This paper summarizes Space Systems/Loral's (SS/L) initial experience with HALT, experience over time, and refinement of the traditional HALT process with emphasis on finding the operating limit margins before purposely searching for any failure limits. The methodology used by SS/L has proven to be effective w...
{"title":"Highly Accelerated Life Test (HALT) Program at Space Systems Loral","authors":"B. Kosinski, D. Cronin","doi":"10.17764/jiet.56.2.43g5n424308r4016","DOIUrl":"https://doi.org/10.17764/jiet.56.2.43g5n424308r4016","url":null,"abstract":"Highly Accelerated Life Testing (HALT) is used in the commercial electronics industry to improve product robustness prior to starting production. The basic theory is that testing well beyond expected, intended-use environments may uncover design flaws that could become field failures after a product is in production. By fixing issues prior to starting production, costly recalls can be avoided. HALT has proven to be effective, as evidenced by its wide incorporation in the commercial electronics industry. Could HALT also be worth the time and expense of performing on commercial satellite hardware, which is designed to rigorous standards and tested over military-grade environmental test specifications? This paper summarizes Space Systems/Loral's (SS/L) initial experience with HALT, experience over time, and refinement of the traditional HALT process with emphasis on finding the operating limit margins before purposely searching for any failure limits. The methodology used by SS/L has proven to be effective w...","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67807939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-03-05DOI: 10.17764/JIET.56.1.T210J78522820327
J. Weaver
{"title":"IEST and UGIM Working Together","authors":"J. Weaver","doi":"10.17764/JIET.56.1.T210J78522820327","DOIUrl":"https://doi.org/10.17764/JIET.56.1.T210J78522820327","url":null,"abstract":"","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67807971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-03-05DOI: 10.17764/JIET.56.1.T2607368N1K89R04
D. Grimard, L. Jones
Efficiently running a major nanofabrication research user facility within the framework of a university is a daunting task. Operational costs, staffing, training, safety, and the diversity of the research, faculty, and users are but a few of the challenges facing the management team. This article reports on a subset of metrics used to characterize such user facilities, based on an extensive survey of 12 major university laboratories. Data relating to such factors as laboratory staffing, operating costs, subsidies, cost recovery, tuition, comparative tool rates, hours of use, and populations are summarized and reported on in the context of determining a reasonable measure of an efficient laboratory operation.
{"title":"Financial and Operational Survey of 12 Major University Nanofabrication Facilities: A Benchmarking Study","authors":"D. Grimard, L. Jones","doi":"10.17764/JIET.56.1.T2607368N1K89R04","DOIUrl":"https://doi.org/10.17764/JIET.56.1.T2607368N1K89R04","url":null,"abstract":"Efficiently running a major nanofabrication research user facility within the framework of a university is a daunting task. Operational costs, staffing, training, safety, and the diversity of the research, faculty, and users are but a few of the challenges facing the management team. This article reports on a subset of metrics used to characterize such user facilities, based on an extensive survey of 12 major university laboratories. Data relating to such factors as laboratory staffing, operating costs, subsidies, cost recovery, tuition, comparative tool rates, hours of use, and populations are summarized and reported on in the context of determining a reasonable measure of an efficient laboratory operation.","PeriodicalId":35935,"journal":{"name":"Journal of the IEST","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2013-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67807976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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