Experimental Studies of a High-Gradient X-band Welded Hard-Copper Split Accelerating Structure

Recent research on high-gradient radio frequency (RF) accelerating structures indicates that the use of hard copper alloys provides improvement in high gradient performance over annealed copper. Such structures are made by bonding individually manufactured parts. However, there are no well-established bonding techniques that preserve the hardness, surface finish and cleanliness required for high gradient operation. To preserve the copper hardness, RadiaBeam has developed a joining technique based on electron beam welding. This technique provides efficient bonding with strong, clean welds and minimal thermal loading, while maintaining a clean inner RF environment. Our RF design and fabrication methodology limits the small heat affected zone to the outer cavity envelop, with virtually no distortions or thermal loading of critical RF surfaces. It also incorporates provisions to precisely control the gap despite conventional issues with weld joint shrinkage. To date we have manufactured and validated an RF accelerating structure joined by electron-beam welding that incorporates a novel open split design to significantly reduce the assembly complexity and cost. In this paper, we will present the electromagnetic design of this structure, discuss bonding, and present the results of high-power tests, where the accelerating gradients of 140 MV/m with surface peak fields of 400 MV/m were achieved for flat-top pulse length of 600 ns with an RF breakdown rate of 10-4 1/(pulse∙m).

Analysis of Corrosion Breakdown Rate in Low Carbon Steel with Aluminum Coating

This study aims to analyze the corrosion penetration rate of low carbon steel with aluminium coating. The method used is the potentiodynamic method to determine the value of the corrosion rate. The corrosion medium used was HCl. The aluminium used is aluminium frame waste powder. The coating process is by dipping low carbon steel pipes into aluminium frame waste that had been liquefied in the Hot Dip Galvanizing (HDG) method of 700oC and immersion time of 45 seconds. The results of this study show that low carbon steel which has been coated with aluminum frame waste powder has a high corrosion rate which is proven to have a corrosion rate of 18,1808 mm/year. So that the corrosion rate is at an unacceptable level.

Tunable Boc Modification of Lignin and Its Impact on Microbial Degradation Rate

<p>A new type of modified lignin, lignin-p-Boc, was obtained through reaction with di-<i>tert</i>-butyl dicarbonate (Boc₂O) in aqueous media catalyzed by 4-dimethylaminopyridine (DMAP). Boc modification occurred regardless of type of lignin, was tunable, and proceeded well in recovering lignin at high purity from sodium lignosulfonate (a common byproduct from pulping industry; lignin content: 60%). Lignin-p-BOC was demonstrated as a potential reactive filler in green plastic and as a potential crosslinker in design of bioresorbable composite polymeric implants. Furthermore, the effects of the modification on the breakdown rate of alkali lignin by microbes was investigated, and the results showed that the modification substantially decreases the breakdown rate. The tunable Boc modification process was designed via a system thinking, including availability of raw lignin, economical/green modification, potentiality of drop-in-change to current thermoplastic processing, modification impact on microbial degradability/disposed environment at the end of use life; hence the holistic consideration makes this alternative method for upgrade of technical lignins very practical for future industrial application. Via forming “easily breakable covalent bonds” with thermopolymers, Lignin-p-BOCs are also promising to play an important role as both excellent binders via “random match” and reductants in transforming linear plastic waste into circular plastics.</p><br>

Effects of high-altitude reservoirs on the structure and function of lotic ecosystems: a case study in Italy

Alpine and pre-alpine lotic ecosystems are often remote and not affected by humans, which makes them some of the world’s most pristine ecosystems. However, their status is often altered by the presence of reservoirs that are built to fulfill agricultural needs and hydroelectric demands. These reservoirs also disrupt stream continuity and alter the magnitude, timing, and frequency of natural flows. The present work assessed how high-altitude reservoirs affect the riverine ecosystems focusing on the following: (i) the macroinvertebrate communities, (ii) the breakdown of organic matter, and (iii) the thermal regime. Stretches altered by high-altitude reservoirs had the best conditions for most macroinvertebrate families due to a more stable flow conditions. The breakdown rate of coarse particulate organic matter was not affected by high-altitude reservoirs but its availability was higher in altered compared to pristine stretches. The presence of hydroelectric power plants modified the stream thermal regime. Reservoirs mitigate the atmospheric influence on stream water temperature while run of the river plants strengthen it in the diverted stretches. Where both these alterations were present, the thermal regime of the stream was more similar to the natural ones compared to stretches subjected to only one kind of alteration. This research showed how river impoundment alters the structure of macroinvertebrate communities and the function of the downstream lotic ecosystems and can provide the basis to correctly guide management strategies for lotic ecosystems affected by hydrological alterations.

Analisis Penerapan Total Productive Maintenance (TPM) dengan Metode Overall Equipment Effectiveness (OEE) pada Mesin Kneader (Studi Kasus PT. XYZ)

ABSTRACT PT. XYZ has implemented Total Productive Maintenance (TPM) to improve the efficiency and effectiveness of manufacturing companies as a whole. However, the implementation is still not optimal and seen from not achieving the production target. This study aims to measure the value of the effectiveness of equipment, find the root causes of problems and provide suggestions for improvement. The study was conducted on a kneader machine that had the highest breakdown rate. This research begins by measuring the overall equipment effectiveness (OEE) achievement value, then identifying the six big losses that occur. The results showed that the average OEE value on the kneader machine was 81.62%, the effectiveness value was classified as very low because the standard OEE value for world-class companies was ideally 85%. The biggest factor influencing the low OEE value is the performance rate with a factor of six big losses in reducing spees losses of 42.66% and idling and minor stoppages of 31.27% of all time losses. What causes the magnitude of losses consists of human, machine, material, method, and environmental factors. Human and machine factors are the most dominant factors. To reduce these losses, companies should provide skills and knowledge training to operators about the signs of damage to the equipment. In addition, operators are given additional work in the form of equipment maintenance that is often used in work so that maintenance work can be more focused. Then the company must pay more attention to the comfort of the operator at work so that fatigue can be reduced and operator productivity is increased and increase operator awareness of the tools they use. Keywords: Overall Equipment Effectiveness (OEE), Six Big Losses, Idling and Minor Stoppages ABSTRAK XYZ telah menerapkan Total Productive Maintenance (TPM) guna meningkatkan efisiensi dan efektivitas perusahaan manufaktur secara menyeluruh. Namun dalam pelaksanaannya masih belum optimal dan dilihat dari tidak tercapainya target produksi. Penelitian ini bertujuan untuk mengukur nilai efektivitas peralatan, mencari akar penyebab masalah dan memberikan usulan perbaikan. Penelitian dilakukan pada mesin kneader yang selama ini memiliki tingkat breakdown yang tertinggi. Penelitian ini dimulai dengan mengukur pencapaian nilai overall equipment effectiveness (OEE), kemudian mengidentifikasi six big losses yang terjadi. Hasil penelitian menunjukan bahwa rata-rata nilai OEE pada mesin kneader sebesar 81,62%, nilai efektivitas ini tergolong sangat rendah karena standar nilai OEE untuk perusahaan kelas dunia idealnya adalah 85%. Faktor terbesar yang mempengaruhi rendahnya nilai OEE adalah performance rate dengan faktor persentase six big losses pada reduce spees losses 42,66% dan idling and minor stoppages sebesar 31,27% dari seluruh time losses. Yang menyebabkan besarnya losses terdiri dari faktor manusia, mesin, material, metode, dan lingkungan. Faktor manusia dan mesin merupakan faktor yang paling dominan. Untuk mengurangi kerugian tersebut, perusahaan sebaiknya memberikan pelatihan skill dan pengetahuan kepada operator tentang tanda-tanda kerusakan alat tersebut. Selain itu operator diberikan tambahan pekerjaan berupa perawatan peralatan yang sering digunakannya dalam bekerja sehingga pekerjaan bagian maintenance bisa lebih berfokus. Kemudian perusahaan harus lebih memperhatikan kenyamanan operator dalam bekerja sehingga kelelahan bisa dikurangi dan produktivitas operator lebih meningkat serta meningkatkan kepedulian operator terhadap alat yang digunakannya.

Preventive Maintenance Interval Optimization for Continuous Multistate Systems

Preventive maintenance (PM), which is performed periodically on the system to lessen its failing probability, can effectively decrease the loss caused by the system breakdown or the performance degradation. The optimal PM interval has been well studied for both binary-state systems (BSSs) and discrete multistate systems (MSSs). However, in reality, the performance of many systems can change continuously, ranging from complete failure to perfect functioning. Considering such characteristics of systems, two types of performance-based measures, performance availability and probabilistic resilience, are addressed to quantify the system’s behaviour for continuous MSS. A Monte Carlo-based method is given to analyse the performance change process of the system, and an optimization framework is proposed to find the optimal PM interval with the considerations of per-unit-time cost, system breakdown rate, performance availability, and probabilistic resilience. A computer cluster is used as an example to illustrate the effectiveness of our proposed method.

Simulation study of direct current vacuum breakdown and its application to high-gradient accelerating structures

It is well known that radio frequency breakdown is one of the main limitations in high frequency accelerators. Similarities have been detected between breakdowns in direct current vacuum gaps and those in superconducting radio frequency cavities. Therefore, cavity break- downs due to electric field phenomena can be understood by studying direct current vacuum breakdowns. Significant irregularity of a surface and a variety of involved processes objectively stipulate a number of factors which may lead to a breakdown. In this paper, the effects of surface conditions, accelerator gradient, pulse length, and operating frequency on the breakdown have been studied by using COMSOL simulation package. It was found that the dependence of breakdown rate on accelerating gradient and pulse length follows scaling laws. Based on the time evolutions of electron density and the potential in cone-cylinder electrode configuration at the pressure of 0.1 Pa, the time scale of a vacuum breakdown has been established. It was also confirmed that the emission from an electrode surface can be regarded as a major factor leading to electrical breakdown in vacuum. The obtained results could be very useful in high-gradient accelerating structures.

The effects of resource subsidy duration on detritus-based stream ecosystem: a stream mesocosm experiment

SummaryMost of the resource subsidies are temporally variable, and studies have revealed that ecological processes can be mediated by the temporal attributes of subsidies, such as timing and frequency. Less studies have, however, examined the effects of the subsidy duration, an another major temporal attribute, on consumer populations, communities and ecosystem functions. Using an outdoor mesocosm experiment, we demonstrated that, even with the same total amounts, the prolonged subsidy let large-stage fish effectively monopolize the subsidy over small-stage fish, while the pulsed subsidy allowed small-stage fish to increase the ingestion rate of the subsidy. This effect resulted in causing weaker indirect positive effects on in-situ benthic prey and a leaf breakdown rate with the prolonged subsidy than with the pulsed-subsidy although it depended on dominant benthic prey species having different edibility. Increasing evidences have shown that global warming would not only advance, but also prolong the growing seasons, which may, in turn, make subsidies more prolonged. The ecological significance of the subsidy duration might be common in nature, and should be incorporated to better understand ecological processes in spatially and temporally coupled ecosystems.

The importance of shredding caddis larvae (Trichoptera: Limnephilidae) in leaf litter breakdown

In field and laboratory experiments, we assessed the role of caddisfly larvae in leaf decomposition occurring in headwaters with a focus on the breakdown of alien Quercus rubra leaves. A field experiment was conducted at two sites: in Wolbórka Spring and 150 m downstream. Eight 0.5 x 0.5 m “mats” were constructed. 1m2 of one type of fallen leaves: Quercus robur, Acer pseudoplatanus, Quercus rubra and Alnus glutinosa was placed in each mat. The caddisfly assemblages on the leaf mats consisted of 550 shredder larvae and 394 predatory larvae of Plectrocnemia conspersa. Among the 4 shredder species in both years, the larvae of P. nigricornis dominated on all leaf species at both sites. In the laboratory experiment, ten Vth instar larvae of Potamophylax nigricornis were placed in to each of four square (30 x 30 cm) boxes containing 500 cm2 of Q. robur, A. pseudoplatanus, Q. rubra and A. glutinosa leaves. The length of time of leaf decomposition was measured in the laboratory. The fastest loss of leaf surface was noted with respect to A. glutinosa (in the field as well as in the laboratory). Shredders collected from Q. rubra mats were numerous and the breakdown rate of leaf litter in the field as well as in the laboratory experiments was similar to Q. robur and A. pseudoplatanus. The number of caddis corresponded with the time of decomposition, which in 2014 was 20 days shorter than in 2013.