This study investigates the optimization of online compressor washing frequency for enhanced performance and profitability of industrial gas turbines. Two representative engines: an aero-derivative LM2500 and a heavy-duty V94.3A (also designated SGT5-4000F) were simulated in GasTurb software under varying washing intervals of one day and ten days. Experimental data were applied to model reductions in compressor isentropic efficiency and mass-flow capacity due to fouling. The results indicate that extending the washing interval from daily to every ten days for one year causes significant performance deterioration. For the LM2500, power output decreased from 7 % to 16 %, thermal efficiency from 2.6 % to 6 %, and heat rate rose from 2.7 % to 6.6 %. Corresponding changes for the V94.3A were smaller, confirming that the aero-derivative turbine is more sensitive to fouling than the heavy-duty unit. Economic evaluation showed that while more frequent washing increased wash fluid consumption and operational costs, it provides substantial financial benefits. Daily washing produced additional annual net profits of approximately £11.69 million for the V94.3A and £4.6 million for the LM2500 compared with ten-day intervals. Overall, the findings demonstrate that optimizing compressor washing frequency is essential to sustain turbine performance, improve fuel efficiency, and maximize profitability. Frequent online washing mitigates the adverse effects of fouling and ensures cost-effective, reliable, and energy-efficient gas-turbine operation.
Abstract Lubiak, SM, Proppe, CE, Rivera, PM, Howard, MA, Prajapati, AJ, Shah, NM, Patel, NN, Hammer, SM, Trevino, MA, Dinyer-McNeely, TK, Richardson, LD, Roth, BL, Zak, RB, and Hill, EC. Acute effects of running and blood flow restriction on gas exchange and perceptual responses. J Strength Cond Res 39(3): e436–e443, 2025—The purpose of this investigation was to examine gas exchange and perceptual responses during discrete running bouts performed at different peak running speeds with and without blood flow restriction (BFR). Twelve college-aged male subjects randomly performed four, 3-minute running bouts at 70%BFR, 80%BFR, and 90%BFR of their running speed at peak V̇o2 with BFR (applied bilaterally and most proximally on each leg) at 40% of total arterial occlusion pressure and 100%NOBFR of their running speed at peak V̇o2 without BFR. Separate 2-way, 4 (Speed [70%BFR, 80%BFR, 90%BFR, and 100%NOBFR]) × 3 (Time [120, 150, and 180 seconds]), Bayesian repeated-measure models were performed to examine differences in oxygen consumption (V̇o2), carbon dioxide production (V̇co2), and minute ventilation (V̇E) as well as ratings of perceived exertion (RPE) and pain. V̇o2, V̇co2, and V̇E increased across running speeds and was similar between the 90%BFR and 100%NOBFR speeds for V̇o2 (Meandiff = −1.49 ± 0.003 ml·kg−1·min−1; 95% HDI: −4.8 to 1.8) and V̇E (Meandiff = −6.97 ± 0.65 L·min−1; 95% HDI: −16.5 to 2.52). Ratings of perceived exertion was highest during the 90%BFR and 100%NOBFR speeds (90%BFR and 100%NOBFR > 80%BFR > 70%BFR), whereas pain was greater during the 90%BFR speed relative to the 70%BFR (Meandiff = −1.31 ± −0.20 au; 95% HDI: −2.63 to −0.0165) and 100%NOBFR (Meandiff = 1.3 ± 0.26 au; 95% HDI: 0.01–2.56) speeds. Applying BFR during 90%BFR of peak running speed induced comparable V̇o2 and V̇E responses as 100%NOBFR but was not associated with lower RPE and provoked more pain. Collectively, BFR exhibits a small, potentially negligible effect on gas exchange, which were largely speed dependent. Coaches and practitioners may consider treadmill running with BFR when reductions in exercise intensity are warranted.
The article examines the key aspects of resolving international commercial disputes in the absence of an arbitration clause in the contract. The author analyzes potential strategies available to the claimant, start ing with a detailed examination of the contract terms and cond, the applicable law, and international regula tions that may govern the dispute resolution procedure. The significance of pre-trial settlement is emphasized, including negotiations and mediation, which allow the parties to avoid lengthy litigation. Particular attention is paid to the procedure for concluding a supplementary arbitration agreement, its legal validity, and the es sential terms and conditions the parties must consider. In the event arbitration proves impossible, alternative options are explored, such as recourse to national courts, the determination of their jurisdiction, and the chal lenges of enforcing judgments in the international legal context. The author concludes by highlighting the im portance of including arbitration mechanisms in contracts at the outset to minimize risks and ensure efficient dispute resolution
ABSTRACT As, H and Ozkaya, O. Evaluation of acute metabolic and physiologic responses obtained from sprint interval trainings performed by low cadence/high resistance and high cadence/low resistance. J Strength Cond Res XX(X): 000-000, 2025-This study aimed to compare the acute metabolic and physiologic responses obtained from different sprint interval training (SIT) protocols performed by low cadence/high resistance and high cadence/low resistance. Ten moderately trained men completed two 6 × 30-second all-out SIT protocols with 4 minutes recovery periods as follows: (a) traditional fixed-load protocol, that is, using 7.5% of body mass (BM), (traditional SIT [SITTRAD]) and (b) adjusted-load protocol, that is, using an initial load of 5% of BM and then adjusting load for subsequent bouts based on the criterion of ≥120 rpm mean cadence for the last 5 seconds of each 30-second bout, (modified SIT [SITMOD]). Gas exchange variables and blood lactate concentration ([La]) were measured before, during, and after both protocols. Total net O2 consumption and 3-hour postexercise recovery fat oxidation values were similar between SITTRAD and SITMOD (p > 0.05). However, SITMOD demonstrated a greater anaerobic contribution than SITTRAD (p < 0.001), despite similar aerobic contributions (p = 0.32). The mean cadence was significantly higher in SITMOD (139 ± 3) than that in SITTRAD (98 ± 5 rpm; p < 0.001). SITMOD elicited both the highest peak delta [La] (∆[La]) at the end of the session (19.6 ± 1.4 vs. 17.8 ± 1.8 mmol·L-1, respectively; p = 0.003) and higher ∆[La] values at the 30th, 60th, 90th, and 120th minute of recovery compared with SITTRAD (11.1 ± 1.4 vs. 8.3 ± 2.2, 4.5 ± 0.6 vs. 3.1 ± 1.1, 3.2 ± 0.8 vs. 1.9 ± 0.8, and 2.1 ± 0.9 vs. 0.7 ± 0.6 mmol·L-1, respectively; p < 0.05). In conclusion, the high-cadence/low-resistance protocol (i.e., SITMOD) resulted in a greater anaerobic contribution than the traditional fixed-load protocol that leaded low cadence/high resistance (i.e., SITTRAD).
Danielle A. Sterner, Jeffrey R. Stout, Brandi B. Antonio
et al.
Abstract Sterner, DA, Stout, JR, Antonio, BB, Anderson, AW, Hill, EC, and Fukuda, DH. Physical working capacity at pain intensity threshold in females. J Strength Cond Res 39(5): e628–e633, 2025—This study aimed to establish a new threshold parameter in women called the physical working capacity at pain intensity threshold (PWCPIT) similar to that in males. The objectives were to (a) assess if the PIT scale can be used to estimate PWCPIT in females and (b) evaluate relationships between PWCPIT and other established thresholds: PWC at maximal oxygen consumption (PWCV˙O2), PWC at heart rate threshold (PWCHRT), and gas exchange threshold (GET). Eleven female volunteers (age: 21.1 ± 2.7 years, height: 165.3 ± 6.8 cm, body mass: 66.1 ± 13.4 kg, V˙ o2 peak: 27.38 ± 5.2 ml·kg−1·min−2) participated in the study. Subjects completed a graded exercise test to exhaustion, followed by four 8-minute randomly ordered work bouts on separate days at 70–100% peak power output (56–200 W) to establish their PWCPIT, PWCHRT, and PWCV˙O2. One-way repeated-measures analysis of variance with Bonferroni post hoc tests and a zero-order correlation matrix were used to analyze these thresholds. No significant differences were found among the estimated power outputs for GET (69 ± 20 W), PWCPIT (80 ± 36 W), PWCHRT (84 ± 24 W), and PWCV˙O2 (88 ± 30 W). Physical working capacity at PIT significantly correlated with PWCHRT (r = 0.905, p < 0.001) and PWCV˙O2 (r = 0.947, p < 0.001), but not with GET (r = 0.539, p = 0.087). The significant correlations between PWCPIT and other established thresholds (PWCHRT and PWCV˙O2) in females suggest that PWCPIT may provide valuable insights into endurance performance. Further research examining how PWCPIT aligns with, differs from, or complements existing PWC threshold measures may provide a more comprehensive understanding of the factors governing endurance performance in females.
Eftixia Chatzikamagianni, Athanasios Poulios, Alexandra Avloniti
et al.
ABSTRACT Chatzikamagianni, E, Poulios, A, Avloniti, A, Rosvoglou, A, Liakou, C, Papanikolaou, K, Stampoulis, T, Tsimeas, P, Batrakoulis, A, Chatzinikolaou, A, Draganidis, D, Jamurtas, AZ, and Fatouros, IG. Evaluation of the physiological responses and energy expenditure induced by suspension training exercises. J Strength Cond Res XX(X): 000-000, 2025-This study determined the energy expenditure and physiological responses of 6 beneficial suspension training (ST) exercises (overheads [OS], single-leg squat [SLS], torso rotations [TR], back row [BR], chest press [CP], and plank). Ten healthy young adults randomly completed both of 2 trials of ST exercises, for 30 (T30) or 45 (T45) seconds. The training load was monitored using a mobile gas analyzer, heart rate monitors, and blood lactate measurements. The total energy expenditure (TEE) (classified as the sum of oxidative [OES], glycolytic [GC], and excess postexercise energy cost [EPOC]) was estimated using the V̇o2 consumption (at rest, during exercise, and postexercise) and blood lactate (La) concentration (at rest and postexercise). The level of significance was set at p ≤ 0.05. All exercises were associated with a low-to-moderate physiological strain (rate of perceived exertion: 7.3-12.3; % of maximal heart rate: 52.3-61.7%; METs: 2.6-3.7; La: 2.2-3.9 mM; EPOC duration: 5.7-7.8 minutes), with the OS and the SLS associated with the greatest physiological/metabolic load in both trials. T45 induced a greater heart rate (53.7-61.7 %HRmax), with SLS and OS inducing the highest values. Minimal differences were noted between T30 and T45 for TEE, MET, and La values for most. EPOC had a greater contribution to TEE compared with OES and GC. Low-to moderate physiological effort during ST results in a TEE of 16.6-24.7 and 20.1-30 kcal·min-1 when performed for 30 and 45 seconds, respectively. There is a variation in TEE and physiological overload among ST exercises. Weight management exercise programs and dietary regimens need to take these finding into account.
This review explores the possibility of enhancing the efficiency and accuracy of Industrial Gas turbine Performance testing by critically assessing the traditional methods, their limitations, and how modern technologies can be used to complement the existing traditional testing approaches, optimize data acquisition, and predict operational failures. A systematic and comprehensive search strategy was employed to identify relevant academic and industry literature. Studies on traditional testing practices were reviewed to highlight their constraints, while researches involving the application of emerging technologies for performance diagnostics were also reviewed to illustrate their benefits. Findings show that measured data such as turbine inlet temperature, compressor pressure ratio, exhaust temperature, fuel flow, shaft speed, and vibration remain essential for both traditional and AI-enhanced methods. These parameters, typically obtained through standardized testing procedures, provide the foundational input for AI models such as machine learning algorithms and digital twins. The study revealed that AI technologies thrive in data-rich, repeatable environments by enhancing processes like instrumentation, data logging, and normalization. The study also revealed that machine learning, deep learning, artificial neural networks, and digital twins can be used for more effective planning, reduce redundant testing, and mitigate delays caused by variable factors like weather or load conditions.
Cool astrophysical objects, such as (exo)planets, brown dwarfs, or asymptotic giant branch stars, can be strongly affected by condensation. Condensation does not only directly affect the chemical composition of the gas phase by removing elements but the condensed material also influences other chemical and physical processes in these objects. This includes, for example, the formation of clouds in planetary atmospheres and brown dwarfs or the dust-driven winds of evolved stars. In this study we introduce FastChem Cond, a new version of the FastChem equilibrium chemistry code that adds a treatment of equilibrium condensation. Determining the equilibrium composition under the impact of condensation is complicated by the fact that the number of condensates that can exist in equilibrium with the gas phase is limited by a phase rule. However, this phase rule does not directly provide information on which condensates are stable. As a major advantage of FastChem Cond is able to automatically select the set stable condensates satisfying the phase rule. Besides the normal equilibrium condensation, FastChem Cond can also be used with the rainout approximation that is commonly employed in atmospheres of brown dwarfs or (exo)planets. FastChem Cond is available as open-source code, released under the GPLv3 licence. In addition to the C++ code, FastChem Cond also offers a Python interface. Together with the code update we also add about 290 liquid and solid condensate species to FastChem.
In response to the competing factors governing the operation of oil and gas facilities, i.e., the stringent safety and environmental regulations, and the challenging business environment that entails minimizing the running cost, a risk-based inspection (RBI) program became a vital part of all Asset Integrity Management (AIM) frameworks. The objective is to ensure asset mechanical integrity while optimizing the maintenance and inspection resources and minimizing production downtime. There are different risk models being used to manage operational risk for equipment. The decision-maker should be attentive to the subjectivity and reliability of the risk results to establish an adequate risk target that can achieve the ultimate goal of RBI by determining the cost-effective inspection and maintenance plan without compromising plant safety, integrity or reliability. This paper presents evaluations of the most quantitative RBI models through a case study from an offshore gas producing platform. A case study was implemented for topside equipment on an offshore platform. The study analyzed the impact of contributing factors to the probability of failure (PoF) model through a sensitivity analysis to quantify the reliability and subjectivity in the failure probabilities. A sensitivity analysis and comparison between both API consequence modelling methodologies (i.e., CoF level 1 and 2) were performed to manifest the reliability of risk results. The sensitivity analysis revealed the variance in the calculated risk and demonstrated that a risk target/threshold should be established based on the deployed risk model. Using the same risk target for different risk models cannot effectively define all equipment items that actually need more resources to mitigate the risk. And can result in omitting critical equipment which can jeopardize asset integrity and lead to major losses, or spend resources on unnecessary equipment.
An early study of saturated 4He film flow instability is revisited in view of recent theoretical work by Hiromitsu Takeuchi et al. (arXiv:0909.2144v1 [cond-mat.quant-gas] Sept. 2009). I show additional data that suggests a qualitative agreement with this theory and discuss the experimental details.
Spin photocurrents generated by homogeneous optical excitation with circularly polarized radiation in quantum wells (QWs) are reviewed. The absorption of circularly polarized light results in optical spin orientation due to the transfer of the angular momentum of photons to electrons of a two-dimensional electron gas (2DEG). It is shown that in quantum wells belonging to one of the gyrotropic crystal classes a non-equilibrium spin polarization of uniformly distributed electrons causes a directed motion of electron in the plane of the QW. A characteristic feature of this electric current, which occurs in unbiased samples, is that it reverses its direction upon changing the radiation helicity from left-handed to right-handed and vice versa. Two microscopic mechanisms are responsible for the occurrence of an electric current linked to a uniform spin polarization in a QW: the spin polarization induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asymmetric distribution of spin polarized carriers in k-space of systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. Spin photocurrents provide methods to investigate spin relaxation and to conclude on the in-plane symmetry of QWs. The effect can also be utilized to develop fast detectors to determine the degree of circular polarization of a radiation beam. Furthermore spin photocurrents at infrared excitation were used to demonstrate and investigate monopolar spin orientation of free carriers.
Spin photocurrents generated by homogeneous optical excitation with circularly polarized radiation in quantum wells (QWs) are reviewed. The absorption of circularly polarized light results in optical spin orientation due to the transfer of the angular momentum of photons to electrons of a two-dimensional electron gas (2DEG). It is shown that in quantum wells belonging to one of the gyrotropic crystal classes a non-equilibrium spin polarization of uniformly distributed electrons causes a directed motion of electron in the plane of the QW. A characteristic feature of this electric current, which occurs in unbiased samples, is that it reverses its direction upon changing the radiation helicity from left-handed to right-handed and vice versa. Two microscopic mechanisms are responsible for the occurrence of an electric current linked to a uniform spin polarization in a QW: the spin polarization induced circular photogalvanic effect and the spin-galvanic effect. In both effects the current flow is driven by an asymmetric distribution of spin polarized carriers in k-space of systems with lifted spin degeneracy due to k-linear terms in the Hamiltonian. Spin photocurrents provide methods to investigate spin relaxation and to conclude on the in-plane symmetry of QWs. The effect can also be utilized to develop fast detectors to determine the degree of circular polarization of a radiation beam. Furthermore spin photocurrents at infrared excitation were used to demonstrate and investigate monopolar spin orientation of free carriers.