MLC performance prognosis using a degradation model based on trajectory log data from a daily test

PURPOSE

This paper investigates the feasibility of implementing a predictive maintenance program for a multileaf collimator (MLC) based on data collected in trajectory logs (TLs) obtained by conducting a simple daily test, with the aim of minimizing unscheduled downtime.

METHODS

A dynamic field test was designed, and the TLs generated in the course of daily administration in a linear accelerator were collected to evaluate trajectory deviations of the MLC leaves as well as interlocks (COL 420219/20, COL 420207/08) reported by the machine. During this evaluation, we observed that the trajectory deviations of some leaves increased up to a threshold value beyond which certain interlocks began to appear in treatment fields in those leaves. An exponential degradation model was therefore developed to predict this drift and determine each leaf's remaining useful life (RUL). Once the applicability of the model was confirmed, we added a second accelerator equipped with an MLC with the same configuration to validate the model.

RESULTS

The model was able to predict certain COL 420219/20 interlocks resulting from primary readout/expected position discrepancies and to estimate each leaf's RUL. In total, 11 cases (8 interlocks + 3 potential interlocks avoided due to service interventions [27.3% of the total]) were detected over 7 days in advance, with no false positive results. Scheduling of service interventions several days prior to MLC failure would therefore be possible. When these types of interlocks were not predicted by the model, they were always generated by leaf motor failure. Consequently, intervention time could also be optimized by directly replacing the motor. During the study period, for these types of interlocks, our approach would have reduced downtime from 35.25 to 4.00 h (88.7%) and from 34.75 to 22.83 h (34.3%) for each accelerator, respectively. For COL 420207/08 interlocks, which are generated by primary/secondary readout discrepancies, no correlation with leaf trajectory deviation increases recorded in the TLs was found. Throughout the study period, these types of interlocks requiring service intervention, also mainly for motor replacement, represented a downtime of 9.50 h for the first accelerator (21.2% of total downtime) and by 4.33 h (11.1% of total downtime) for the second accelerator.

CONCLUSION

This study demonstrates that by applying a predictive MLC maintenance program based on information collected in TLs, it is possible to predict certain interlocks and therefore schedule preemptive interventions to avoid their occurrence. This could optimize health-care delivery performance and minimize the loss of treatment sessions.

Interlocking of Single-Walled Carbon Nanotubes with Metal-Tethered Tetragonal Nanobrackets to Enrich a Few Hundredths of a Nanometer Range in Their Diameters

We have separated carbon nanotubes through host-guest complexation using host molecules named "nanotweezers" and "nanocalipers". In this work, a host molecule named tetragonal "M-nanobrackets", consisting of a pair of dipyrrin nanocalipers corresponding to two brackets "[" and "]" tethered by two metals (M), is designed, synthesized, and employed to separate single-walled carbon nanotubes (SWNTs). A facile three-step process including one-pot Suzuki coupling is developed to synthesize M-nanobrackets in a 37% total yield (M = Cu). Upon extraction of SWNTs with a square nanobracket and Cu(II), in situ formed tetragonal M-nanobrackets are found to interlock SWNTs to disperse them in 2-propanol. The interlocking is confirmed by absorption and Raman spectroscopy as well as transmission electron and atomic force microscopy. Especially, Raman spectroscopy is utilized to prove the interlocking of SWNTs; Cu-nanobrackets are found to show inherent resonance Raman signals and affect the SWNT signals, or a radial breathing vibration, due to the rigid rectangular structure of Cu-nanobrackets. The interlocking is facilely and thoroughly released through demetalation to recover the pristine SWNTs as well as the square nanobracket. Such chemically controlled locking and unlocking for SWNTs are one of the characteristics of our separation process. This enables a precise evaluation by Raman, photoluminescence, and absorption spectroscopy of the diameter selectivity to SWNTs, revealing the diameter enrichment of only three kinds of SWNTs, (7,6), (9,4), and (8,5), in the 0.02 nm diameter range from 0.90 to 0.92 nm among ∼20 kinds of SWNTs from 0.76 to 1.17 nm in their diameter range.

Examining the role of trauma in alcohol interlock performance: A structural pathway analysis

OBJECTIVE

Self-medication using alcohol is a common coping response among individuals dealing with trauma as is driving under the influence of alcohol (DUI). A common intervention for drivers convicted of DUI, is an alcohol ignition interlock device (IID)-which requires breath samples before starting the car. If the sample is above a predetermined limit (.025), the car will not start, thus preventing impaired driving. IIDs are an effective intervention to reduce rates of drinking and driving among high risk populations; however, limited research has examined how traumatic experiences may impact performance on IIDs.

METHODS

This study is an archival analysis of the Managing Heavy Drinking (MHD) study of drivers in New York state. The MHD is a comprehensive study of drivers convicted of a DUI from 2015-2020. Participants (N = 121) completed questionnaires and provided consent to retrieve information from interlock providers. Outcome variable included high BAC lockout ratios (number of high BAC lockouts [BAC>.08]/number of clean blows [BAC ≤ .025]). Other variables included demographic variables, alcohol treatment history, trauma experiences, and prior DUI history. Variables were entered into a structural equation model.

RESULTS

In the final structural model, pathways that demonstrated a p-value of greater than .10 were dropped from the model. This produced acceptable overall model fit statistics (χ2 = 27.059(10), p=.003; CFI = .900; NFI = .898; RMSEA = .063). A significant pathway was found from the trauma measure to alcohol use (β = .132), and from alcohol use to interlock performance (β = .636). However, no significant relationship was found between trauma and interlock performance other than through alcohol use.

CONCLUSIONS

The current study provides a useful framework upon which to understand the role traumatic experiences have on alcohol IID performance. Traumatic experiences are in of themselves insufficient to impact IID performance directly, but it may indirectly impact IID performance through increasing alcohol use.

Microfluidic Assembly of Microblocks into Interlocked Structures for Enhanced Strength and Toughness

Compared with monolithic materials, topologically interlocked materials (TIMs) exhibit higher toughness based on their enhanced crack deflection and deformation tolerance. Importantly, by reducing the block size of TIMs, their structural strength can also be improved due to the reduced flexural span. However, the assembly of microscale blocks remains a huge challenge due to the inadequacy of nanoscale self-assembly or macroscale pick-and-place operations. In this work, octahedral microblocks are fabricated and constructed into interlocked structures with different patterns through microfluidic channels with variable cross sections. The pattern of the interlocked panel is demonstrated to affect its strength and toughness. The failure strength and energy absorption of assembled panels significantly exceed that of their monolithic counterpart by ∼33% and ∼19.1 folds, respectively. Generally, the presented microfluidic method provides a unique technique for the assembly of interlocked architecture, which facilitates the design and fabrication of TIMs with highly improved strength and toughness.

The impact of interlock installation on driving behavior and drinking behavior related to driving

OBJECTIVE

There is a substantial body of evidence that the recidivism of impaired-driving offenders is reduced while an ignition interlock device (IID) is on their vehicles. This study examines changes in driving behaviors and drinking behaviors used by DWI offenders to manage driving with the IID.

METHODS

A total of 166 IID participants who completed two surveys covering the period from arrest to IID installation (T1) and during IID use (T2) were examined. Four domains were covered: demographics, driving environments and transportation needs, reported driving activity, and reported drinking activities. Participants were on average 38 years old, 43% were female, 35% completed college, 34% had an income of more than $50,000, and 83% were employed. For those who provided it, the mean blood alcohol content (BAC) at arrest was .184 g/dL, with only 8 (5%) individuals below .08 g/dL, and 93 (56%) at over .18 g/dL. About 45% were repeat DWI offenders.

RESULTS

Between T1 and T2 there was a slight increase in acknowledging public transportation was available (p=.001), an increase in other individuals driving the interlock-equipped vehicle (p=.002), an increase in the number of vehicles in the household not registered to the DWI offender (p< .001), and an increase in the number of participants who reported that driving was important to their lifestyle (p=.008). Initial (T1) expectations about whether the interlock would be a problem were significantly different from actual experiences reported in T2 (p<.001). With respect to alcohol consumption, 14% reported abstinence at T2 compared to 2% at T1 (p=.001) and the number of drinks per drinking occasion decreased from a mean of 4.90 at T1 to 3.14 at T2 (p=.001), but the number of drinking occasions increased by a third (p=.003). The number of drinking locations (p=.001), the frequency of stopping after work for a drink (p=.001), and drinking at a bar all decreased (p<.001).

CONCLUSIONS

Interlock users make some adjustments in how they drink, the amount they drink, and where they drink. This finding suggests that there may be methods that can be used to extend the benefits of the IID beyond the sanction period.

[In-machine Fault Monitoring Mechanism and Maintainability Improvement of Varian Linear Accelerator]

Through repaired the RF driver momentary oscillation stop of Varian 2300CD linear accelerator, systematically and comprehensively expounds the three state machine mode of control system and the in-machine fault monitoring mechanism involved in maintainability of Varian high energy accelerator. It proposes an improved solution to bring RF driver output into interlock system, by doing so it can avoid the control computer breakdown and improve maintainability.

Stakeholders' opinions on a future in-vehicle alcohol detection system for prevention of drunk driving

INTRODUCTION

There is a common understanding that driving under the influence of alcohol is associated with higher risk of being involved in crashes with injuries and possible fatalities as the outcome. Various countermeasures have therefore from time to time been taken by the authorities to prevent drunk driving. One of them has been the alcohol interlock. Up to now, interlocks have mainly been used by previously convicted drunk drivers and in the commercial road transport sector, but not in private cars.

OBJECTIVE AND METHOD

New technology has today reached a level where broader implementation might be possible. To our knowledge, however, little is known about different stakeholders' opinions of a broader implementation of such systems. In order to increase that knowledge, we conducted a focus group study to collect in-depth thoughts from different stakeholders on this topic. Eight focus groups representing a broad societal span were recruited and conducted for the purpose.

RESULTS AND CONCLUSIONS

The results show that most stakeholders thought that an integrated system for alcohol detection in vehicles might be beneficial in lowering the number of drunk driving crashes. They said that the system would probably mainly prevent driving by people who unintentionally and unknowingly drive under the influence of alcohol. The groups did, however, not regard the system as a final solution to the drunk driving problem, and believed that certain groups, such as criminals and alcoholics, would most likely find a way around the system. Concerns were raised about the risk of increased sleepy driving and driving just under the legal blood alcohol concentration (BAC) limit. The results also indicate that stakeholders preferred a system that provides information on the BAC up to the legal limit, but not for levels above the limit; for those, the system should simply prevent the car from starting. Acceptance of the system depended on the reliability of the system, on its ability to perform fast sampling, and on the analytical process, as well as the system's more or less inconspicuous placement and user-friendliness. The stakeholders thought that drivers would probably not voluntarily demand the system. So if broad implementation was desired, it would have to be made compulsory by legislation. As an incentive to increase demand, lower taxes and insurance premiums were suggested.