CIGS Photovoltaics: Reviewing a Evolving Paradigm

Copper indium selenide chalcopyrite-structure alloys with gallium (CIGS) are unique among the highest performing photovoltaic (PV) semiconductor technologies. They are structurally disordered, nonstoichiometric materials that have been engineered to achieve remarkably low bulk nonradiative recombination levels. Nevertheless, their performance can be further improved. This review adopts a fundamental thermodynamic perspective to comparatively assess the root causes of present limitations on CIGS PV performance. The topics of selectivity and passivation of contacts to CIGS and its multinary alloys are covered, highlighting pathways to maximizing the electrochemical potential between those contacts under illumination. An overview of absorber growth methods and resulting properties is also provided. We recommend that CIGS researchers consider strategies that have been successfully implemented in the more mature wafer-based GaAs and Si PV device technologies, based on the paradigm of an idealized PV device design using an isotropic absorber with minimal nonradiative recombination, maximal light trapping, and both electron-selective and hole-selective passivated contacts. We foresee that CIGS technology will reach the 25% efficiency level within the next few years through enhanced collection and reduced recombination. To significantly impact power-generation applications, cost-effective, manufacturable solutions are also essential.

Consumable electrode – additional filler wire arc interaction control under surfacing (DE-GMAW)

Introduction. Arc surfacing through feeding an additional filler wire heated by an additional arc burning between the filler wire and the electrode wire is considered. Under the conditions of such surfacing, the minimization of the input of the remelted substrate metal into the weld metal is studied. The research objectives are to examine the conditions providing self-regulation of this advanced arc surfacing process, and to evaluate control capabilities of the heat impact power on the metal and on the weld metal flow.Materials and Methods. In solving a wide range of welding and surfacing tasks, it is advisable to use engineering analysis methods based on physicomathematical modeling of processes and phenomena. These include:self-regulation of the arc process under joint melting of the electrode and the filler wires;assessment of the possibilities to control the heat impact power on the metal and on the weld metal flow during the formation of the weld The features of the arc surfacing of anticorrosive chromium-nickel steels on low-alloy steel are considered in the paper.Results. New mathematical dependences are proposed that describe physical phenomena under surfacing with an arc interaction between the electrode and filler wire. A physicomathematical model of the joint melting of the electrode and filler wire is developed. It provides determining the values of the control parameters. In addition, you can find out how much heat affects the substrate from:heat release in the main arc,droplet flows of the weld electrode and filler metal,arc plasmaDiscussion and Conclusions. It is established how the current and the lengths of the main and additional arcs are affected by the supply voltages. The feed rate of the electrode and filler wire with a diameter of 1.6 mm and 1.2 mm made of Inconel 625 alloy is determined. It is shown what thermal effect the substrate undergoes in this case. It is noted that due to the larger value of the main arc current, the diameter of the electrode wire should be larger than that of the filler wire. The heat flow in the substrate is created mainly by the flow of the weld metal droplets.

Rising Power of Today's Brands

Today, businesses use communication channels, which is usually done to create brand value on consumers and to support the sale of the brand. However, it is controversial whether these efforts find the expected response in consumers. On the consumer side, there are word-of-mouth communication channels, which have become an electronic WOM (eWOM) concept after the spread of internet and social networking sites. Consumers are seeking information about products/brands and taking into account the impact and approval of certain reference groups such as market mavens. Market mavens have become much more effective in the digital environment and has reached an impact power that both affects and directs consumers via eWOM. As confidence and commitment to market mavens developed, interest in the products/brands they offered increased. Today's brands that realize the importance of market mavens will be able to survive and stand out in a competitive environment. Such brands can benefit from this marketing advantage by generating messages and content that can be viral for market mavens through eWOM.

Concussion and the severity of head impacts in mixed martial arts

Concern about the consequences of head impacts in US football has motivated researchers to investigate and develop instrumentation to measure the severity of these impacts. However, the severity of head impacts in unhelmeted sports is largely unknown as miniaturised sensor technology has only recently made it possible to measure these impacts in vivo. The objective of this study was to measure the linear and angular head accelerations in impacts in mixed martial arts, and correlate these with concussive injuries. Thirteen mixed martial arts fighters were fitted with the Stanford instrumented mouthguard (MiG2.0) participated in this study. The mouthguard recorded linear acceleration and angular velocity in 6 degrees of freedom. Angular acceleration was calculated by differentiation. All events were video recorded, time stamped and reported impacts confirmed. A total of 451 verified head impacts above 10g were recorded during 19 sparring events (n = 298) and 11 competitive events (n = 153). The average resultant linear acceleration was 38.0624.3g while the average resultant angular acceleration was 256761739 rad/s2. The competitive bouts resulted in five concussions being diagnosed by a medical doctor. The average resultant acceleration (of the impact with the highest angular acceleration) in these bouts was 86.7618.7g and 756163438 rad/s2. The average maximum Head Impact Power was 20.6kW in the case of concussion and 7.15kW for the uninjured athletes. In conclusion, the study recorded novel data for sub-concussive and concussive impacts. Events that resulted in a concussion had an average maximum angular acceleration that was 24.7% higher and an average maximum Head Impact Power that was 189% higher than events where there was no injury. The findings are significant in understanding the human tolerance to short-duration, high linear and angular accelerations.

Theoretical and Experimental Study of the Effects of Impact Drilling Parameters on the Properties of Surrounding Rock Damage

Using a self-designed hydraulic impact drilling test-bed and rock core drill, six groups of cylindrical granite specimens (93 mm dia. × 200 mm) containing central axial holes formed either by impact or nonimpact drilling methods were tested in uniaxial compression to failure on an Instron 1346 universal testing machine to investigate their mechanics and damage properties. The longitudinal acoustic wave velocities were measured before testing. The rock specimens were grouped according to the method of drilling the central hole (impact load exerted by different impact power and different frequencies for an approximately identical impact power, or nonimpact drilling). In this study, a statistical constitutive damage model based on Weibull distribution was used to calculate the degree of rock damage after drilling center holes. The experimental curves were measured to analyze the damage evolution process and the radius of rock damage. These indicate that rock damage increased with the increase of impact power and decreased with increasing impact frequency at constant impact power. This was also verified by the measured longitudinal wave velocity in all rock specimens. These results have significance for guiding the design of composite rock drilling tools that are dedicated to improving rock-breaking efficiency.

EVALUATION OF PARAMETERS OF HYDRAULIC IMPACT DEVICES OF ACTIVE BUCKET WITH DIRECT CONNECTION TO THE HYDRAULIC SYSTEM OF II GRADE EXCAVATOR

The impact power of hydraulic percussion system of active bucket of Belarus EO-2628 excavator with a capacity of 0.25 m required for the effective mining of rocks with ultimate compressive strength of 60-80 MPa and frozen soils of V-VIII category is determined. The diagram of direct connection of hydraulic impact devices to excavator hydraulic system is presented. Using the HPS software, the parameters and characteristics of impact devices are selected.

Mengoptimalkan Window Ligthing untuk Foto Potret dengan Menggunakan Kamera DSLR 1000D dan 60D

Photography is a visual language that prioritizes the role of light. In photography there are several shooting formats, one of which is portrait or shooting vertically. Portrait photos are photos of a person's face that can reveal the character of the person, therefore the shooting exposure must be precise. In fact, the current portrait photos are not optimal because they do not consider the aspects of light and the correct shooting technique. Portrait photos can easily be done using window lighting techniques. This research was carried out on portrait photos with window lighting techniques produced from two different types of DSLR cameras. In the world of photography especially beginner photographers assume that the higher the level or class of the camera can produce better images. However, in the world of photography the results of good images are not solely produced by professional-class cameras, but by considering the exact exposure when shooting. Through this window lighting technique, researchers hope to find the essence and formula of making portrait photos that are of good quality and can be done by DSLR camera users. A good portrait photo, besides revealing a person's character also has a strong impact power.