Low Power Test Research Articles

Parameters of Performance: A Deep Dive into Liquid-to-Air CDU Assessment

The rapid growth in data center workloads and the increasing complexity of modern applications have led to significant contradictions between computational performance and thermal management. Traditional air-cooling systems, while widely adopted, are reaching their limits in handling the rising thermal footprints and higher rack power densities of next-generation servers, often resulting in thermal throttling and decreased efficiency, emphasizing the need for more efficient cooling solutions. Direct-to-chip liquid cooling with cold plates has emerged as a promising solution, providing efficient heat dissipation for high-performance servers. However, challenges remain, such as ensuring system stability under varying thermal loads and optimizing integration with existing infrastructure. This comprehensive study digs into the area of data center liquid cooling, providing a novel, comprehensive experimental investigation of the critical steps and tests necessary for commissioning coolant distribution units (CDUs) in direct-to-chip liquid-cooled data centers. It carefully investigates the hydraulic, thermal, and energy aspects, establishing the groundwork for Liquid-to-Air (L2A) CDU data centers. A CDU’s performance was evaluated under different conditions. First, the CDU’s maximum cooling capacity was evaluated and found to be as high as 89.9 kW at an approach temperature difference (ATD) of 18.3 °C with a 0.83 heat exchanger effectiveness. Then, to assess the cooling performance and stability of the CDU, a low-power test and a transient thermohydraulic test were conducted. The results showed instability in the supply fluid temperature (SFT) caused by the oscillation in fan speed at low thermal loads. Despite this, heat removal rates remained constant across varying supply air temperatures (SATs), and a partial power usage effectiveness (PPUE) of 1.042 was achieved at 100% heat load (86 kW) under different SATs. This research sets a foundation for improving L2A CDU performance and offers practical insights for overcoming current cooling limitations in data centers.

Development of a new tuning method for an radio frequency quadrupole accelerator

Tuning is a critical step in the low-power test of the radio frequency quadrupole (RFQ) accelerator. A 163 MHz RFQ for boron neutron capture therapy (BNCT) at Lanzhou University has been fully assembled. Its designed output energy is 2.6 MeV, and the designed output current in continuous wave mode is 30 mA. Before the feeding of high power, a low-power tuning was performed. First, based on the analysis of the tuning algorithm, a new tuning code capable of tuning the RFQ longitudinal field distribution to any desired target field distribution has been developed using Matlab. The tuning code mainly consisted of two parts: the data processing module and the tuning module, including sub-functions such as smoothing processing function and Fourier expansion function. Among them, the smoothing function based on the Gaussian distribution can effectively eliminate random errors in the measured voltage distribution, thereby optimizing the tuning procedure. Then, a new bead-pull system which can directly track the cavity phase shift was built. The bead-pull system was mainly composed of a vector network analyzer, a stepper motor, etc. Finally, the field unflatness of the RFQ was controlled below 1% after 4 times of tuning. The experiment also measured the radio-frequency performance of the RFQ cavity after installing the fixed copper tuners. The results showed that the RFQ operation frequency was 162.937 MHz, the unflatness of the quadrupole voltage was ±0.74%, and the asymmetry of the dipole voltage was ±1.19%, all of which met the requirements of beam dynamics.

The Implicit Association Test and its difficulty(ies): Introducing the test difficulty concept to increase the true-score variance and, consequently, the predictive power of implicit association tests.

We introduce the test difficulty concept from classical test theory to tackle the issue of low predictive power of implicit association tests (IATs). Following classical test theory, we argue that IATs of moderate difficulty (defined as mean IAT scores of zero) have more predictive power than IATs of extreme difficulties (defined as mean IAT scores deviating strongly from zero). Furthermore, we assume this relationship to be mediated by the true-score variance in IAT scores, with moderate difficulty resulting in more true-score variance. To test our hypotheses, we used nonexperimental (Studies 1 and 2) and experimental designs (Study 3). In Studies 1 and 2, we compared IATs of different test difficulties with regard to their ability to predict direct attitude measures, drawing on the Attitudes, Identities, and Individual Differences study. In Study 1, a subset of 95 attitude IATs (n = 127,259) was analyzed using multilevel structural equation models. As expected, IAT test difficulty strongly moderated the predictive power of IATs, and this effect was mediated by IAT true-score variance. In Study 2, we replicated the results with the same analyses but a different subset of 95 identity IATs (n = 43,745). In Study 3, we experimentally manipulated the IAT test difficulty. In total, three IATs (n = 480) were analyzed using multigroup structural equation models. Again, the IAT closer to moderate difficulty had more true-score variance and predictive power than the IATs of extreme difficulty. Accordingly, for correlational research, we recommend developing moderately difficult IATs to maximize IAT true-score variance and provide suggestions on how to achieve that. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Development of a novel Internal Radio-frequency Ion Source for Cyclotrons (IRISC)

IRISC (Internal Radio-frequency Ion Source for Cyclotrons) is an innovative design of an internal ion source, primarily for producing H− ions, in which 2.45 GHz radio-frequency power is supplied to its electrodes for achieving electron emission. Theoretical work indicates that lower electrode sputtering and higher extraction efficiency of H− may be achieved as compared to its standard cold-cathode direct current (DC) Penning Ionization Gauge (PIG) counterparts. If achieved, IRISC would arise as a ground-breaking ion source with significant importance for compact cyclotrons. IRISC dimensions have been matched to CIEMAT’s AMIT cold-cathode DC PIG ion source so that, in the future, side-by-side testing can be carried out and, eventually, both types can be used in AMIT cyclotrons. This contribution presents IRISC key design aspects, outcome from simulations, its dedicated test bench and first low-power test results from a prototype.

Investigations on the multiple-sector hard-copper X-band accelerating structures

The development of advanced, high gradient accelerating structures is one of the leading activity of the particle accelerator community. In the technological research of new construction methods for these devices, high-power testing is a critical step for the verification of their viability.Recent experiments showed that accelerating cavities made out of hard copper, fabricated without high-temperature processes, can achieve better performance as compared with soft copper ones. Recently, we have built cavities using Tungsten Inert Gas welding and the high-power experiments confirmed that this joining process is a robust and low-cost alternative to brazing or diffusion bonding. This is a good solution for high-gradient operation, with a gradient of about 150 MV/m in X-band, at a breakdown rate of 10−3/pulse/meter using a shaped RF pulse with a 150 ns flat part.We continue the design, construction and high power tests of three-cells standing-wave X-band accelerating cavities fabricated with a split-open geometry, made of hard copper and vacuum-sealed by welding. Our aim is the fabrication of accelerating structures made out of hard copper alloys by using innovative cost-effective technologies. Moreover, our method of multiple-sector structures opens the way to new technological approaches and design methods, for example providing the possibility of placing dampers of the parasitic higher-order modes. Such structures with dampers allow for acceleration of multi-bunch beams, both in standing and in travelling-wave accelerating modality.This paper describes the design of two cavities made of multiple sectors that were fabricated at the Italian Institute for Nuclear Physics in Frascati, Italy (INFN-LNF), assembled by means of clamping and then joined with the Tungsten Inert Gas welding in order to preserve the hardness of the metal. These are three-cell standing-wave X-band accelerating cavities, to be operated in the π-mode. We report the low-power RF tests of the first one, made of two halves, and the RF design of the second one, made of four quadrants. Both structures were built for high-gradient tests at SLAC National Accelerator Laboratory.

Fast and thermal neutron spectrum dosimetry measurements in the Advanced Test Reactor large-B and small-l positions following the sixth core internals change-out

The Advanced Test Reactor (ATR) has a wide variety of irradiation positions that have had experiments that were developed by users from around the world. Most experiment irradiations rely on thoroughly benchmarked numerical models. However, some irradiation positions in ATR are not as well- characterized and are complicated by spectral perturbations from control cylinder orientation. The “small I” and “large-B” irradiation positions are located nearby control cylinders and suffer from these flux perturbations from control cylinder orientations that change during an irradiation cycle to maintain the desired core power distribution. Models predicted that these types of position would exhibit both spectral shifts and amplitude changes in neutron flux, but few measurements have been conducted to benchmark these predictions. Recently, requalification testing was performed to confirm the operational readiness of the ATR following the completion of the Core Internals Change-out (CIC). These tests provided a unique opportunity to validate the analytical methods used to simulate the ATR because nearly all components in the reactor were in a clean as-built state, significantly reducing modelling uncertainties. One subset of the testing included characterization of the fast and thermal neutron flux in the “small-I” and “large-B” positions using silver, cobalt, and nickel neutron dosimetry. In contrast to typical irradiation cycles, the control cylinders were held in position during the post-CIC nuclear testing. The specific activity of these dosimeter wires was measured following two low-power tests with different control cylinder positions.

Radio Frequency System, Power Converters and Cryomodule installation and tests as a Polish in-kind contribution to the European Spallation Source (ESS)

The European Spallation Source (ESS) project currently enters the final stage of installation. Since 2017, a group of engineers and technicians from The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Science (IFJ PAN) are involved in the project. The contribution to the project can be divided into three main tasks: Radio Frequency Distribution System (RFDS), RF (Radio Frequency) Power Stations and Cryomodules.The RFDS in ESS project is one of the largest installations of this type consisting of 155 RF high power systems. Engineers and technicians from IFJ PAN were responsible for preparation, installation and RF measurements of the above-mentioned system. The team is also involved in preparation and conducting low and high power tests of the RF stations.The IFJ PAN team is also responsible for the preparation as well as vacuum and cryogenic tests for 9 Medium and 21 High Beta Cryomodules, before they are installed in the tunnel.The advanced quality control and quality assurance were mandatory for this work because the costs of failures, as well as potential delays, would have a huge impact in the project realisation. Therefore dedicated methods and approaches have been adapted to this work using experience gained by the IFJ PAN team on previous projects like LHC, XFEL and W7X.

In-situ Low Power Tests of the ASDEX Upgrade ECRH Transmission Lines

An Electron Cyclotron Resonance Heating (ECRH) system employing 8 gyrotrons is in routine operation at the ASDEX Upgrade tokamak at IPP Garching. The gyrotrons are of two-frequency type operating at 105 and 140 GHz with a maximum output power of up to 1 MW and 10 s pulse length. The gyrotron output beams are coupled to 8 waveguide transmission lines via quasi-optical Matching Optics Units (MOUs). The oversized corrugated HE11 waveguides with a diameter of 87 mm are operated at atmospheric pressure with overall lengths between 65 and 103 meters. The number of quasi-optical miter bends per line is between 6 and 8. High mode purity in the transmission lines is critical with respect to both, losses and atmospheric breakdowns in the waveguides. Beam measurements at low power have been performed along the transmission lines and are compared to high power measurements. Near-field calculations and measurements of mm-wave beams radiated from open-ended HE11 waveguides show, that varying intensity patterns determine the distribution of Ohmic loading in compact mm-wave beam launching antennas, where the first mirror is located in the reactive near-field or close to the Fresnel maximum.

Design, fabrication, and characterization of a drift tube linac type double gap re-buncher cavity.

The Low Energy High Intensity Proton Accelerator (LEHIPA) at Bhabha Atomic Research Centre, India, has recently been commissioned to the target energy of 20MeV by beam acceleration through a 352MHz radio frequency quadrupole (RFQ) and drift tube linac (DTL). The medium energy beam transport (MEBT) line of LEHIPA matches the 3MeV beam from RFQ to the DTL using four electromagnetic quadrupoles and a re-buncher cavity. In the beam transport lines of high frequency linacs, TM010 mode single gap buncher cavities are conventionally used, while a double gap re-buncher cavity was chosen for the short length LEHIPA MEBT based on beam dynamics simulations. The 352MHz double gap re-buncher cavity has been designed in a DTL type geometry with a cell length of βλ. This double gap cavity is found to be more power efficient with a higher shunt impedance and transit time factor than the conventional single gap buncher cavity. Electromagnetic design simulations, fabrication details, low power and high-power RF test results, and beam test results of the re-buncher cavity are presented in this paper.

Test Compression for Launch-on-Capture Transition Fault Testing

A new low-power test compression scheme, called Dcompress , is proposed for launch-on-capture transition fault testing by using a new seed encoding scheme, a new design for testability architecture, and a new low-power test application procedure. The new seed encoding scheme generates seeds for all tests by selecting a primitive polynomial that encodes all tests of a compact test set. A software-defined linear feedback shift register architecture, called SLFSR , is proposed to make the new method conform to the current flow of design and test. Experimental results on benchmark circuits show that test data volume can be compressed up to 6300X with the well-compacted baseline test set for a design with 11.8M gates and more than 1.1M scan flip-flops.

A new non-parametric hypothesis testing with reliability analysis applications to model some real data

Due to the essential necessities of current technology and contemporary sciences, a methodical approach to investigating every occurrence or action occurring in the world was required. As a result, it makes sense that such an approach would be required in the investigation of the reliability of technological systems and products. In actuality, there are instances when system parts gradually deteriorate over time t, at which point the system needs to be updated by replacing the spare parts. Although renewal tries to improve system usability, it is unable to restore the system to its prior state. We discovered that an entirely novel domain of reliability known as classes of life distributions has emerged as a result of the growth of criteria for determining the success or failure of dependability over the previous few decades. Moreover, the other nonparametric tests of life distribution lack test efficiency and have low test power. On the other hand, based on that approach, the non-parametric statistical test utilized in this study evaluates different types of treatment by examining failure behavior in the survival data that was collected. As a result, in this ivestigation, we have developed a novel test of life distribution in this study that considers the power and effectiveness of the test. In order to compare data belonging to the harmonic new better than used in expectation (HNBUE) class with data that follow an exponential distribution, this article suggests nonparametric tests for both censored and uncensored data. The higher percentile points of the test statistics are collected, and the suggested test's normality is verified. The Pitman asymptotic relative efficiency (PARE) and powers of proposed test are calculated a few well-known alternative asymmetric models. Three asymmetric real-world data sets are examined to demonstrate the paper's findings.

Data-adaptive and pathway-based tests for association studies between somatic mutations and germline variations in human cancers.

Cancer is a disease driven by a combination of inherited genetic variants and somatic mutations. Recently available large-scale sequencing data of cancer genomes have provided an unprecedented opportunity to study the interactions between them. However, previous studies on this topic have been limited by simple, low statistical power tests such as Fisher's exact test. In this paper, we design data-adaptive and pathway-based tests based on the score statistic for association studies between somatic mutations and germline variations. Previous research has shown that two single-nucleotide polymorphism(SNP)-set-based association tests, adaptive sum of powered score (aSPU) and data-adaptive pathway-based(aSPUpath) tests, increase the power in genome-wide association studies (GWASs) with a single disease trait in a case-control study. We extend aSPU and aSPUpath to multi-traits, that is, somatic mutations of multiple genes in a cohort study, allowing extensive information aggregation at both SNP and gene levels. -values from different parameters assuming varying genetic architecture are combined to yield data-adaptive tests for somatic mutations and germline variations. Extensive simulations show that, in comparison with some commonly used methods, our data-adaptive somatic mutations/germline variations tests can be applied to multiple germline SNPs/genes/pathways, and generally have much higher statistical powers while maintaining the appropriate type I error. The proposed tests are applied to a large-scale real-world International Cancer Genome Consortiumwhole genome sequencing data set of 2583 subjects, detecting more significant and biologically relevant associations compared with the other existing methods on both gene and pathway levels. Our study has systematically identified the associations between various germline variations and somatic mutations across different cancer types, which potentially provides valuable utility for cancer risk prediction, prognosis, and therapeutics.

Reconstructing echoes completely submerged in background noise by a stacked denoising autoencoder method for low-power EMAT testing

Low-power electromagnetic-acoustic transducer (EMAT) is crucially important for safety-critical equipment in industry, especially for potential explosives and inflammable petrochemical equipment and facilities. When the excitation power is very low, the corresponding echoes are overwhelmed in noise and related measurement would be inaccurate. To solve this problem, this paper presents a new echo reconstruction method based on a deep stacked denoising autoencoder (DSDAE) for nondestructive evaluation. First, the uses of reference signals and new data structure are to improve the training efficiency. A hybrid method based on variational mode decomposition and wavelet transform is used to obtain clean reference signals as inputs of the deep network. Then, the modified network structure and loss function aim to improve the ability of feature extraction and reconstruct clean echoes from low-power EMAT signals. To validate the effectiveness of the proposed method, the experiments of self-excitation and receiving A-scan inspections of stepped specimens with different thicknesses are conducted at some excitation voltages, as low as 25 V. The results indicate that the proposed DSDAE shows better and more stable denoising performance than some popular processing methods for different specimens and excitation voltages. It greatly improves the signal-to-noise ratio of the reconstructed signal to 20 dB. When applying to thickness measurement of specimens, its relative error is lower than 0.3%, which provides a practical and accurate tool for low-power EMAT testing.

Work-life balance policies and organizational financial performance: a scoping review

PurposeWork-life balance (WLB) policies have become a popular topic in both academic literature and organizations. However, previous studies in this area have provided mixed results, and the impact of WLB policies on various indicators of organizational financial performance remains unclear. There has been no comprehensive review that synthesizes the current state of knowledge and indicates future research directions. This review addresses this gap and provides a systematic review of published papers investigating the relationship between WLB policies and organizational financial performance.Design/methodology/approachThe review follows the PRISMA-ScR guidelines for scoping reviews. An analysis of 421 relevant records in Web of Science and Scopus databases identified 22 original empirical studies that focused on the relationship between WLB policies and financial performance at the level of the organization.FindingsMost reviewed studies indicated a weak positive relationship between WLB policies and financial performance. There was the strongest support for the effectiveness of flexible working hours and job sharing, while there was mixed support for the policy of working from home. There were a higher proportion of positive results in studies conducted in Western countries compared to Asian countries, which indicates a potential moderating effect of culture. This review also describes the primary limitations of previous studies, namely, low test power and insufficient evidence about causality.Originality/valueThis review summarizes the growing body of quantitative research on the relationship between WLB policies and organizational financial performance. It presents a model that includes moderators and mediators of this relationship and indicates potentially fruitful areas for future research.

High-directivity and compact microstrip coupler for RF power applications.

A microstrip coupler was designed, fabricated, and tested to monitor the power of the 500MHz kW-level amplifier modules currently installed in an 80-kW solid-state transmitter. The proposed coupler consists of multi-section coupled lines and employs a reverse-coupling scheme, achieving a very compact structure. The dual-side configuration with good termination enables the coupler to have high directivity and wide bandwidth without using any lump components for better temperature stability. Under a low-power test, the measured coupling is 37.69 dB with high directivity from 82 to 700MHz. The coupling is almost independent of the power at 499.65MHz, while the directivity slightly decreases to 33.85 dB at the input power of 1 kW. The maximal insertion loss of 0.08 dB was observed at 1-kW input power. The proposed directional coupler suits many high-power applications, especially in low-frequency regimes.

Terminal Explosion Power Test Flight Platform of Warhead

Aiming at the shortcomings of high risk, high cost, low landing speed and low attitude accuracy of warhead terminal dynamic performance test, a low cost, recyclable and modular warhead terminal explosion power test flight platform is proposed. The overall scheme of two-stage flight is constructed, and the aerodynamic load of the flight process is analysed. In addition, the flight trajectory is designed. The numerical simulation results show that the flight platform can send the warhead to the specified test window, accurately control the drop velocity and attitude of the warhead in the test window, simulate the real flight environment of the warhead and the motion law of the terminal point. Therefore, the flight platform can realize the terminal explosion power test and test of the subsonic and supersonic warheads, providing technical support for the development of the warhead.

Evaluation of Five Host Inflammatory Biomarkers in Early Diagnosis of Ventilator-Associated Pneumonia in Critically Ill Children: A Prospective Single Center Cohort Study.

Background: Early diagnosis of ventilator-associated pneumonia (VAP) remains a challenge due to subjective clinical criteria and the low discriminative power of diagnostic tests. We assessed whether rapid molecular diagnostics in combination with Clinically Pulmonary Index Score (CPIS) scoring, microbiological surveillance and biomarker measurements of PTX-3, SP-D, s-TREM, PTX-3, IL-1β and IL-8 in the blood or lung could improve the accuracy of VAP diagnosis and follow-up in critically ill children. Methods: A prospective pragmatic study in a Pediatric Intensive Care Unit (PICU) was conducted on ventilated critically ill children divided into two groups: high and low suspicion of VAP according to modified Clinically Pulmonary Index Score (mCPIS). Blood and bronchial samples were collected on days 1, 3, 6 and 12 after event onset. Rapid diagnostics were used for pathogen identification and ELISA for PTX-3, SP-D, s-TREM, IL-1β and IL-8 measurements. Results: Among 20 enrolled patients, 12 had a high suspicion (mCPIS > 6), and 8 had a low suspicion of VAP (mCPIS < 6); 65% were male; and 35% had chronic disease. IL-1β levels at day 1 correlated significantly with the number of mechanical ventilation days (rs = 0.67, p < 0.001) and the PICU stay (r = 0.66; p < 0.002). No significant differences were found in the levels of the other biomarkers between the two groups. Mortality was recorded in two patients with high VAP suspicion. Conclusions: PTX-3, SP-D, s-TREM, IL-1β and IL-8 biomarkers could not discriminate patients with a high or low suspicion of VAP diagnosis.

The Concept of a Nuclear Power Unit on the Basis of a Low-Power Multipurpose Test Research Reactor with Supercritical Light-Water Coolant

The Concept of a Nuclear Power Unit on the Basis of a Low-Power Multipurpose Test Research Reactor with Supercritical Light-Water Coolant

Reporting and interpreting non-significant results in animal cognition research.

How statistically non-significant results are reported and interpreted following null hypothesis significance testing is often criticized. This issue is important for animal cognition research because studies in the field are often underpowered to detect theoretically meaningful effect sizes, i.e., often produce non-significant p-values even when the null hypothesis is incorrect. Thus, we manually extracted and classified how researchers report and interpret non-significant p-values and examined the p-value distribution of these non-significant results across published articles in animal cognition and related fields. We found a large amount of heterogeneity in how researchers report statistically non-significant p-values in the result sections of articles, and how they interpret them in the titles and abstracts. Reporting of the non-significant results as "No Effect" was common in the titles (84%), abstracts (64%), and results sections (41%) of papers, whereas reporting of the results as "Non-Significant" was less common in the titles (0%) and abstracts (26%), but was present in the results (52%). Discussions of effect sizes were rare (<5% of articles). A p-value distribution analysis was consistent with research being performed with low power of statistical tests to detect effect sizes of interest. These findings suggest that researchers in animal cognition should pay close attention to the evidence used to support claims of absence of effects in the literature, and-in their own work-report statistically non-significant results clearly and formally correct, as well as use more formal methods of assessing evidence against theoretical predictions.

8.56-GHz quasi-optical launcher system with incident-mode selectivity on the QUEST spherical tokamak

An 8.56-GHz quasi-optical launcher system with incident-mode selectivity was developed for non-inductive electron cyclotron (EC) plasma ramp-up and long-pulse sustainment, and effective bulk-electron heating on the Q-shu University experiment with steady-state spherical tokamak (QUEST). A novel polarization-selective system was proposed to conduct fundamental and second harmonic EC heating and current drive experiments with ordinary and extra-ordinary mode waves, respectively. Selectivity of the incident modes or polarizations was confirmed using the whole developed system at a low power level. A large-sized mirror launcher was developed to inject the beam whose size was as small as possible near the QUEST major radius. The designed mirror performance was checked using a three-dimensional electromagnetic-wave simulator and a low-power test. Ultimately, 0.15-m sized beams for both the two polarizations were successfully attained near the QUEST major radius, even in low-frequency applications with long propagation.