AFM‐Based Spin‐Exchange Microscopy Using Chiral Molecules

Local magnetic imaging at nanoscale resolution is desirable for basic studies of magnetic materials and for magnetic logic and memories. However, such local imaging is hard to achieve by means of standard magnetic force microscopy. Other techniques require low temperatures, high vacuum, or strict limitations on the sample conditions. A simple and robust method is presented for locally resolved magnetic imaging based on short‐range spin‐exchange interactions that can be scaled down to atomic resolution. The presented method requires a conventional AFM tip functionalized with a chiral molecule. In proximity to the measured magnetic sample, charge redistribution in the chiral molecule leads to a transient spin state, caused by the chiral‐induced spin‐selectivity effect, followed by the exchange interaction with the imaged sample. While magnetic force microscopy imaging strongly depends on a large working distance, an accurate image is achieved using the molecular tip in proximity to the sample. The chiral molecules' spin‐exchange interaction is found to be 150 meV. Using the tip with the adsorbed chiral molecules, two oppositely magnetized samples are characterized, and a magnetic imaging is performed. This method is simple to perform at room temperature and does not require high‐vacuum conditions.     

Improving the optical efficiency of a concentrated solar power field using a concatenated micro-tower configuration

The concatenated micro-tower (CMT) is a new configuration for concentrated solar power plants that consists of multiple mini-fields of heliostats. In each mini-field, the heliostats direct and focus sunlight onto designated points along an insulated tube, where thermal receivers are located. The heat transfer fluid, flowing through a multitude of discrete receivers, is combined and directed towards a single power block. The key advantages of CMT are its dual-axis tracking system and dynamic receiver allocation, i.e., the ability of each heliostat to direct sunrays towards receivers from adjacent mini-fields throughout the day according to their optical efficiency. Here we compare between the annual optical efficiencies of a conventional trough, large tower, and CMT configuration, all located at latitude 36 N. For each configuration, we calculated the annual optical efficiency based on the cosine factor and atmospheric transmittance. CMT’s dynamic receiver allocation provides more uniform electricity production during the day and throughout the year and improves the annual optical efficiency by 12-19% compared to conventional trough and large tower configurations.     

An Effective Load Balancing Policy for Geometric-Decaying Algorithms

Parallel algorithms are often first designed as a sequence of rounds, where each round includes any number of independent constant time operations. This so-called work–time presentation is then followed by a processor scheduling implementation on a more concrete computational model. Many parallel algorithms are geometric-decaying in the sense that the sequence of work loads is upper bounded by a decreasing geometric series. A standard scheduling implementation of such algorithms consists of a repeated application of load balancing. We present a more effective, yet as simple, policy for the utilization of load balancing in geometric-decaying algorithms. By making a more careful choice of when and how often load balancing should be employed, and by using a simple amortization argument, we show that the number of required applications of load balancing should be nearly constant. The policy is not restricted to any particular model of parallel computation, and, up to a constant factor, it is the best possible.     

Hash tables with finite buckets are less resistant to deletions

We show that when memory is bounded, i.e. memory buckets are finite, dynamic hash tables that allow insertions and deletions behave significantly worse than their static counterparts that only allow insertions. This behavior differs from previous results in which, when memory is unbounded, the two models behave similarly.We show the decrease in performance in dynamic hash tables using several hash-table schemes. We also provide tight upper and lower bounds on the achievable overflow fractions in these schemes. Finally, we propose an architecture with content-addressable memory (CAM), which mitigates this decrease in performance.     

A decision-making support system module for project manager selection according to past performance

This paper proposes a decision-making support system (DMSS) module for selecting project managers and demonstrates its implementation. The selection of a new project manager is based mainly on the past performance of potential managers, for example, on the relative performance evaluations they have received on projects managed by them in the past. Past projects are ranked in accordance with a ranking method. Project managers are ordered according to past project rank. The difference in quality between the past performance of the candidates is statistically examined using the Mann–Whitney–Wilcoxon U test. This enables the establishment of a subgroup of one or more preferred candidates, where the significance level of the statistical test has an impact on the subgroup size. The final candidate may be selected from this subgroup according to personal qualifications and suitability for the specific project. We demonstrated the use of such a DMSS module by an Israeli information technology company as part of their process to select a project manager. A ranking method within the Data Envelopment Analysis context (the Cross-Efficient method) was implemented with three inputs and four outputs selected for the project ranking.     

A new MILP approach for the facility process-layout design problem with rectangular and L/T shape departments

We propose a new approach for the facility process-layout design problem, and introduce new mixed-integer linear programming (MILP) formulations for solving the problem. In this approach, we consider simultaneously, in a process-layout setting, the shape and location of the departments within the facility as well as the internal arrangement of the machines within the departments. Two models are suggested, the first assumes a rectangular shape of the departments and the second allows non-rectangular departments defined by an L/T shape. For the latter model, new constraints are developed to assure a correct design of the L/T shapes and to avoid irregular department shapes, and cuts are added to shorten the solution time. Finally, we conduct an extensive numerical study, in which we show the capabilities of both formulations in solving problems of medium size, and the superiority of the L/T department shape solutions over the rectangular department solutions.     

On Horowitz's contributions to reset control

History shows that Prof. Isaac Horowitz was often ahead of the curve in his feedback control research, especially in developing quantitatively driven design procedures. In some topics, his work was so out of line with the main stream that it has received virtually no recognition from the control community until a few decades later. In this paper, we present recent research that was directly motivated by Horowitz's pioneering work on reset controllers in the 1970s. Reset controllers are linear controllers that reset some of their states to zero when their inputs reach a threshold. Horowitz motivated their use by showing that with qualitative design, they can exhibit better performance trade‐offs than those in linear, time‐invariant systems. This paper supports and advances his thinking by presenting recent theoretical and experimental results on reset control. Copyright © 2002 John Wiley & Sons, Ltd.     

Minimising throughput loss in assembly lines due to absenteeism and turnover via work-sharing

In this paper we analyse the loss of throughput rate of assembly line caused by slow pace of substitute workers (replacing absentees) having no prior experience in the required tasks. We proposed work-sharing mechanisms that improve the balance of the workload during the learning period. The proposed mechanisms add to the experienced neighbouring workers some of the workload of the inexperienced worker substituting an absentee. We call this workload ‘shared work’. After the performance of the substitute workers improves due to learning, the shared work is re-assigned to them (relieving their experienced neighbours). We provide analytic expressions for the line throughput rate, which is determined by sets of bottleneck workstations. These sets of consecutive workstations consist of the inexperienced workers replacing the absentees and the experienced workers assisting them during the learning periods. The decision variables of this model are: (1) the amount of shared work, and (2) the time in which the shared work is re-assigned to the substitute worker. Unique optimal values of these two variables are found via numerical study, for buffered and non-buffered lines. Experiments show that the proposed work-sharing mechanisms can significantly improve the line’s throughput, compared to the original system without work-sharing.     

Sensory Arrays of Covalently Functionalized Single‐Walled Carbon Nanotubes for Explosive Detection

Chemiresistive sensor arrays for cyclohexanone and nitromethane are fabricated using single‐walled carbon nanotubes (SWCNTs) that are covalently functionalized with urea, thiourea, and squaramide containing selector units. Based on initial sensing results and ¹H NMR binding studies, the most promising selectors are chosen and further optimized. These optimized selectors are attached to SWCNTs and simultaneously tested in a sensor array. The sensors show a very high level of reproducibility between measurements with the same sensor and across different sensors of the same type. Furthermore, the sensors show promising long‐term stability, which renders them suitable for practical applications.