Sharif Digital Repository

The COVID-19 pandemic cast doubts on governments' traditional crisis responses and sparked a surge in citizen-led, participatory, bottom-up responses. Iran's experience is worth investigating because it relied significantly on citizen groups to manage the crisis despite long-term sanctions and extremely restricted resources. The authors undertook an exploratory case study using the grounded theory (GT) method and an online survey to explore Iran's confrontation. The central notion discovered was referred to as 'faith-driven civic engagement.’ The response was characterized by adaptability, promptness, and comprehensiveness. The causes and strategic orientations included intrinsic motives,... 

Boost converter operating in critical conduction mode is widely used in low-power power factor corrector because of its simplicity and low switching losses. The switching loss due to parasitic capacitor discharge at the on-time instant can also be reduced by a valley switching technique. In this paper, we introduce a new driver topology for the high-side switch in a synchronous boost converter operating in the critical conduction mode to obtain full zero-voltage switching. Using the proposed high-side driver topology, the conventional control circuit is sufficient to control the low-side switch, and no additional control circuit is required to adjust the timing of the switches. Finally, the... 

In this study, Dunstan's infant cry data set is pre-processed with the feature vector approach, including MFCC (19 features) and energy (one feature). By using extracted features and Support Vector Machine (SVM), Multilayer Perceptron (MLP), and Convolutional Neural Network (CNN) classifiers, five classes of infant cry (“Neh” = hungry; “Eh” = need to burp; “Owh” = tired; “Eairh” = stomach cramp; “Heh” = physical discomfort) are distinguished. The proposed MLP and CNN structures are analyzed according to the loss and the accuracy based on the epoch; moreover, to evaluate the performance of classifiers AUC-ROC, Confusion matrix, accuracy, f1_score, recall, and precision have been used. All... 

In this study isolated perfused rat muscle was used to examine the direct effect of temperature changes on the eccentric contraction-induced force and desmin loss. The left medial gastrocnemius muscle was separated and the entire lower limb was transferred into a prewarmed (35°C) organ bath. Temperature was adjusted to 31 or 39°C before and during eccentric contractions. Maximal isometric force and desmin loss were measured after 15 isometric or eccentric contractions. According to our data, organ bath temperature changes before or during eccentric contractions had no significant effect on force loss. However, a strong correlation between desmin loss and temperature changes before (r = 0.93,... 

Background: The typical features of eccentric exercise-induced muscle damage are delayed-onset muscle soreness (DOMS) and prolonged loss of muscle strength. It has been shown that passive warmth is effective in reducing muscle injury. Due to the interaction of different systems in vivo, we used isolated perfused medial gastrocnemius skeletal muscle to study the direct effect of temperature on the eccentric contraction-induced force loss. Methods: After femoral artery cannulation of a rat, the left medial gastrocnemius muscle was separated and then the entire lower limb was transferred into a prewarmed (35oC) chamber. With the chamber temperature at 31, 35 and 39oC before and during eccentric... 

Self-oscillating converters operating in the critical conduction mode are popular in low power applications because of their simplicity and low cost. However, these converters are not suited for Power Factor Correction (PFC) because the peak switch current is controlled to regulate the output voltage and does not follow the shape of the line voltage waveform. A new control circuit implementation is proposed for a self-oscillating boost converter to achieve power factor correction. A full featured design example is provided which can be simplified for use in various cost sensitive applications such as electronic lighting, etc. This wide input voltage range self-oscillating PFC prototype... 

Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar  

SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity  

In this paper, we consider an integrated sensing and communication (ISAC) system with wireless power transfer (WPT) where an unmanned aerial vehicle (UAV)-based radar serves a group of energy-limited communication users in addition to its sensing functionality. In this architecture, the radar senses the environment in phase 1 (namely sensing phase) and mean-while, the communications users (nodes) harvest and store the energy from the radar transmit signal. The stored energy is then used for information transmission from the nodes to UAV in phase 2, i.e., uplink phase. Performance of the radar system depends on the transmit signal as well as the receive filter; the energy of the transmit... 

One of the important obstacles in MIMO (Multiple Input Multiple Output) radars is the issue of designing proper transmit signals. Indeed, the capability of signal design is a significant advantage in MIMO radars, through which, the system can achieve much better performance. Many different aspects of this performance improvement have been considered yet, and the transmit signals have been designed to attain such goal, e.g., getting higher SNR or better detector's performance at the receiver. However, an important tool for evaluating the radar's performance is its ambiguity function. In this paper, we consider the problem of transmit signal design, in order to optimize the ambiguity function... 

Two gains play key roles in recently developed MIMO wireless communication systems: "spatial diversity" gain and "spatial multiplexing" gain. The diversity gain refers to the capability to decrease the error rate of the MIMO channel, while the multiplexing gain implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the diversity gain) and increasing data rate (via an increase in the multiplexing gain). On the other hand, recently, MIMO radars have attracted much attention for their superior ability to enhance... 

It is a well known fact that using multiple antennas at transmit and receive sides improves the detection performance. However, in such multiple-input multiple-output (MIMO) configuration, proper positioning of transmitters and receivers is a big challenge that can have significant influence on the performance of the overall system. In addition, determining the power of each transmitter under a total power constraint is a problem that should be solved in order to enhance the performance and coverage of such a system. In this paper, we design the Neyman-Pearson detector under the Rayleigh scatter model and use it to introduce a criterion for the antenna placement at both transmit and receive... 

There has been much interest, recently, towards exploiting the Multiple-Input Multiple-Output (MIMO) technique in radar. It is shown that using multiple antennas at transmit and receive sides can improve the performance of the system. However, in order to analyze the system's performance, its ambiguity function, i.e. the ambiguity function of a MIMO radar, is needed to be defined. In this paper, beginning from the information theoretic definitions, we derive such function, specifically for a MIMO radar with widely separated antennas  

By combining the two ideas of MIMO (Multiple Input Multiple Output) and PCL (Passive Coherent Location) in radar, one can achieve the advantages of both recently developed techniques simultaneously. While using multiple antennas at the receive side provides a spatial diversity of the object to be detected, using multiple illuminators of opportunity, most importantly, makes the radar covert to the interceptors. One obstacle in such MIMO configuration is choosing the positions of the receive antennas. In this paper, after analyzing the Neyman-Pearson detector for the DVB-T based PCL, we introduce the probability of missed detection as a criterion to place the receive antenna. Here, we only... 

One of the most important obstacles in passive radar applications is removing the direct signal from the target channel. Otherwise, week echoes from the targets in the target channel would be ignored due to the limited dynamic range of the system. One of the most effective techniques in this field is using adaptive filters. In this paper various adaptive filters are introduced and their performances are shown and compared  

It has been shown that using multiple antennas in a radar system improves the performance considerably, since multiple target echoes are received from different aspect angles of the target. In this way, the target detection is improved. However, when using multiple antennas, some problems, such as designing the transmit signals, synchronization, etc. emerge that should be solved. One of such problems is the receiver placement. Receiver placement deals with choosing a proper position for the receive antenna in order to optimize the whole system's performance. In this paper, a receiver placement procedure based on improving the radar ambiguity function is proposed for the case of a multisite...