Continuations and Aspects to Tame Callback Hell on the Web

JavaScript is one of the main programming languages to develop highly rich responsive and interactive Web applications. In these kinds of applications, the use of asynchronous operations that execute callbacks is crucial. However, the dependency among nested callbacks, known as callback hell, can make it difficult to understand and maintain them, which will eventually mix concerns. Unfortunately, current solutions for JavaScript do not fully address the aforementioned issue. This paper presents Sync/cc, a JavaScript package that works on modern browsers. This package is a proof-of-concept that uses continuations and aspects that allow developers to write event handlers that need nested callbacks in a synchronous style, preventing callback hell. Unlike current solutions, Sync/cc is modular, succinct, and customizable because it does not require ad-hoc and scattered constructs, code refactoring, or adding ad-hoc implementations such as state machines. In practice, our proposal uses a) continuations to only suspend the current handler execution until the asynchronous operation is resolved, and b) aspects to apply continuations in a non-intrusive way. We test Sync/cc with a management information system that administers courses at a university in Chile.

Recommendations for Running a Tandem of Adsorption Chillers Connected in Series and Powered by Low-Temperature Heat from District Heating Network

In this paper, we investigate implications of running a cooling system of two silicagel/water adsorption chillers powered by a district heating network. The devices are connected in series, i.e., the heating water output from the primary chiller is directed to the secondary one. In consequence, the secondary device must deal with an even lower driving temperature and with temperature fluctuations caused by the primary device. We have evaluated three factors that influence the operation of those coupled devices: synchronization of their operating cycles, selection of their cycle time allocations (CTAs), and changing the heating water mass flow rate. Numerical analyses indicate that the performance of the secondary chiller drops significantly if the coupled devices that use the same CTA run asynchronously. The decrease is largest if the shift between the operating cycles is x=0.375 and x=0.875. We found that it is possible to reduce the negative influence of the asynchronous operation by implementing different CTA in each chiller. The best performance is achieved if the primary chiller uses an adsorption time to desorption time ratio f=1.0 and the secondary chiller uses f = 0.6–0.7.

IMPLANT TREATMENT IN PATIENTS WITH SEVERE TOOTH WEAR ON THE OCCLUSAL SURFACE

Examination along with implant treatment was carried out in 21 patients with severe tooth wear on the occlusal surface. This disorder features a variety of clinical symptoms including changes in the facial features and the lower jaw movement amplitude, disturbed canine and incisor guidance, supercontacts, asynchronous operation of the masticatory muscles, etc. We have proposed a treatment algorithm aimed at eliminating these issues. The temporary non-removable dentures allowed creating occlusal marks (Stage 1) followed with their transfer onto permanent orthopedic structure (Stage 2) using implants. The complexity of the approach to treating this disease, as well as the effectiveness of our method has been confirmed by clinical data and the outcomes obtained through an instrumental study involving electromyography and electronic axiography. The extra additional research methods employed, such as electromyography and electronic axiography, allowed to assess the activity of masticatory muscles and the lower jaw articulation, thus to ensure occlusal-articulation interaction when restoring the lower facial height.

Specifics of Emergency Operation in Distribution Grid and their Effect on Integration and Functioning of Distributed Generation Facilities

This paper focuses on the characteristic features of distribution grids, which have the greatest impact on the stability of generators and motor loads. It shows that severe accidents in distribution and transmission grids differ in nature, starting with an overload leading to line disconnections and further evolving into a voltage collapse. It appears that where generator capacity is commensurate with the total power of motors in a grid, the motor load has a significant impact on transients. The paper discusses how asynchronous operation is triggered, progresses, and can be addressed in a grid with distributed generation (DG) facilities. It further analyzes the consequences of deep grid sectionalization and proves why grid structure needs to be optimized for further development. The paper also shows how to take into account the specifics of emergency processes (i.e., accident-associated processes) in distribution grids when integrating and operating DG facilities.

On Two Methods to Computate the Trapezoidal Characteristic of Automatics for Elimination of Asynchronous Operation Based on Equal-Step Data

The paper presents two methods to compute the trapezoidal characteristic of automatics for elimination of asynchronous operation (AEAO). The source data are hodographs of asynchronous operations (AO hodographs). Every AO hodograph is an array of active and reactive resistances values, which have been received or calculated with equal time step. The first method is based on the phase increase of characteristic size without proportions sacrificing of sensitive and coarse elements of the characteristic (trapeze). Trapeze bases are stretched as long as we have unfixed AO hodographs for AEAO. The second method is based on narrowing the coarse characteristic element without sacrificing the initial size of the sensitive element. Both methods are iterative homogenous operations algorithms. These homogenous operations are necessary to compute the cha­racteristic with minimal size and keep constraints for AEAO. The main emphasis of the characteristic computation is on keeping the sensitivity constraints and fixing the AO hodographs. These methods are used to build up a software. The paper also describes a computational experiment based on actual data. The experiment showed these methods are effective when calculating the AEAO sets. Experts on electrical modes can use these methods to adjust the AEAO with trapezoidal characteristic.

Protection against the Effects of the Asynchronous Operation of Synchronous Motors Based on the Principle of Comparison of the Machine Power Factor

<span style="font-family: 'Times New Roman',serif; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-US">This paper deals with the possibility of using the principle of comparison of the operational power factor for evaluation of the asynchronous operation of synchronous motors. This way of definition of the asynchronous operation is possible to use for motors protection and other protective systems of drives with synchronous motors.</span>

Sun tracker sensor for attitude control of space navigation systems

We report a sun tracker sensor for attitude control of space navigation systems. The sensor exploits the concept of asynchronous operation previously devised by the authors for those devices. Asynchronous luminance sensors optimize sun trackers operation because only illuminated pixels are readout and can transmit data. This approach outperforms classic frame-based sun trackers in terms of bandwidth consumption, latency, and power consumption. The new sensor under study has been optimized for operation and interaction with other attitude control systems when it is embarked. The sensor power consumption is quite reduced. To save power, its pixels enter automatically in standby mode after gauging illumination levels. The device operates with only 0.45V. The pixel matrix has been devised to optionally be directly powered by energy harvesting systems based on photovoltaic diodes connected to a storage capacitor without a DC-DC converter.