Electroweak Baryogenesis and Dark Matter via a Pseudoscalar vs. Scalar

We study the electroweak baryogenesis in a fermionic dark matter scenario with a (pseudo)scalar being the mediator in the Higgs portal. It is discussed that the electroweak phase transition turns to be first-order after taking into account the role of the (pseudo)scalar in the thermal effective potential in our extended standard model. Imposing the relic density constraint from the WMAP/Planck and the bounds from the direct detection experiments XENON100/LUX, we show that the dark matter scenario with a scalar mediator is hardly capable of explaining the baryogenesis while the same model with a pseudoscalar mediator is able to explain the baryon asymmetry. For the latter, we constrain more the model with {\it Fermi}-LAT upper limit on dark matter annihilation into $b\bar b$ and $\tau^+\tau^-$. The allowed dark matter mass that leads to correct relic abundance, renders the electroweak phase transition strongly first-order, and respects the {\it Fermi}-LAT limit, will be in the range $110-320$ GeV. The exotic and invisible Higgs decay bounds and the mono-jet search limit at the LHC do not affect the viable space of parameters.Comment: 15 pages, 4 figures. Fermi-LAT constraint on DM DM to b\bar, tau^+ tau^- in the model was imposed. The range of the mediator mass was shown in a figure. Published in JHE

DAMPE Electron-Positron Excess in Leptophilic Z′Z' model

Recently the DArk Matter Particle Explorer (DAMPE) has reported an excess in the electron-positron flux of the cosmic rays which is interpreted as a dark matter particle with the mass about $1.5$ TeV. We come up with a leptophilic $Z'$ scenario including a Dirac fermion dark matter candidate which beside explaining the observed DAMPE excess, is able to pass various experimental/observational constraints including the relic density value from the WMAP/Planck, the invisible Higgs decay bound at the LHC, the LEP bounds in electron-positron scattering, the muon anomalous magnetic moment constraint, Fermi-LAT data, and finally the direct detection experiment limits from the XENON1t/LUX. By computing the electron-positron flux produced from a dark matter with the mass about $1.5$ TeV we show that the model predicts the peak observed by the DAMPE.Comment: 18 pages, 7 figures, matches with the published versio

A Stochastic Process Study of Two-Echelon Supply Chain with Bulky Demand Process Incorporating cost Sharing Coordination Strategies

This research considers a single-item two-echelon supply chain facing a sequence of stochastic bulky customer demand with random order inter-arrival time and random demand size. The demand process is a general renewal process and the cost functions for both parties involve the renewal function and its integral. The complexity of the general renewal function causes the computational intractability in deciding the optimal order quantities, so approximations for the renewal function and its integral are introduced to address the computational complexity. Asymptotic expansions are commonly used in the literature to approximate the renewal function and its integral when the optimal decisions are relatively large compared to the mean of the inter-renewal time. However, the optimal policies do not necessarily fall in the asymptotic region. So the use of asymptotic expansions to approximate the renewal function and its integral in the cost functions may cause significant errors in decision making. To overcome the inaccuracy of the asymptotic approximation, this research proposes a modified approximation. The proposed approximation provides closed form functions for the renewal function and its integral which could be applied to various optimization problems such as inventory planning, supply chain management, reliability and maintenance. The proposed approximations are tested with commonly used distributions and applied to an application in the literature, yielding good performance. By applying the proposed approximation method to the supply chain cost functions, this research obtains the optimal policies for the decentralized and the centralized cases. The numerical results provide insights into the cost savings realized by the centralization of the supply chain compared to the decentralized case. Furthermore, this research investigates coordination schemes for the decentralized case to improve the utilities of parties. A cost sharing mechanism in which the vendor offers the retailer a contract as a compensation of implementing vendordesired inventory policy is investigated. The sharing could be realized by bearing part of the retailer’s inventory holding cost or fixed cost. The contract is designed to minimize the vendors cost while satisfying the individual rationality of the retailer. Other forms of coordination mechanisms, such as the side payment and delayed payment, are also discussed

Enhancing thermal performance in shell-and-tube latent heat thermal energy storage units: An experimental and numerical study of shell geometry effects

This study investigates the influence of shell geometry on the thermal performance of latent heat storage (LHS) units. Three transparent shell-and-tube LHS units, featuring circular, horizontal, and vertical obround shell geometries, each possessing a similar shell volume, were fabricated and filled with paraffin as the phase change material (PCM). Employing a combination of visualization experiments and numerical simulations, the thermal performance of LHS units with horizontally and vertically oriented obround shell geometries was comprehensively analyzed and compared with conventional circular shell-and-tube heat exchangers (HX), commonly utilized in the industry. Data derived from image processing of photographs, coupled with recorded temperatures, were used to calculate liquid fractions, analyze heat transfer characteristics, and ascertain the dominant heat transfer mechanisms during the melting process. The results reveal that the utilization of a horizontal obround shell enhances the heat transfer rate, thereby expediting the melting process. A comparative analysis of melting photographs demonstrates that the horizontal obround shell reduces the melting time by 32% compared to the circular shell, while the vertical obround shell extends the total melting time by 13%. In contrast to the circular shell, the horizontal obround shell exhibits a substantial improvement of 41% in the time-averaged heat transfer rate, whereas the vertical obround shell shows a decrease of 12%.</p

A situational analysis of human resources in Iranian hospitals affiliated with ministry of health in 2008.

زمینه و هدف: بیمارستان به عنوان یکی از سازمان های اصلی ارایه خدمات بهداشتی درمانی، یکی از عمده ترین عوامل رشد هزینه ها است. این مطالعه به منظور بررسی و شناخت وضعیت نیروی انسانی شاغل در بیمارستان های کشور انجام گرفت. هدف ما بدست آوردن اطلاعاتی بود که مبنای سیاستگذاری و تصمیم گیری و تخصیص منابع مبتنی بر شواهد قرار گیرند و آنها را تا حدودی به واقعیت نزدیک نمایند. روش بررسی: این پژوهش از نوع مطالعه تجزیه و تحلیل سیاستگذاری سلامت بود که در سال 1387 در 139بیمارستان کشور انجام شد. از نظر تعداد تخت، بیمارستان ها به 4 دسته تقسیم شدند (الف – بیمارستان های زیر 50 تخت، ب– بیمارستان های 51 تا 150 تخت، ج – بیمارستان های 151 تا 300 تخت، د – بیمارستان های بالای 300 تخت). برای جمع آوری داده ها از جداول جامع گردآوری اطلاعات بیمارستان که به صورت تحت وب، طراحی شده بود استفاده گردید. یافته ها: بیمارستان های مورد پژوهش دارای 23674 تخت فعال و 48238 نفر پرسنل بودند. سرانه نفر به تخت 04/2 بود که این نسبت در بیمارستان های آموزشی (09/2) بیشتر از بیمارستان های درمانی (9/1) بود و در مناطق محروم (17/2) اندکی بیشتر از مناطق برخوردار (02/2) بود. از نظر تحصیلات 4/48 فوق دیپلم و کمتر، 40 لیسانس و بقیه بالاتر از لیسانس بودند. گروه پرستاری و مامایی با 1/48 بیشترین گروه پرسنلی را تشکیل می داد. ولی تراکم کارکنان حوزه پشتیبانی از سایر بخش ها بالاتر بود (1/29). نسبت کادر درمانی به کل کارکنـــان در بیمارستـــان های آموزشی (1/71) بیشتر از بیمارستان های درمانی (4/70) و در بیمارستان های مناطق برخوردار (2/71) بیشتر از بیمارستان های مناطق محروم (7/68) بود. میانگین ضریب اشغال تخت کل بیمارستان ها 8/57 بود که کمترین میزان مربوط به بیمارستان های زیر 50 تخت (4/31) بود. نتیجه گیری: تراکم بالای پرسنل در واحد پشتیبانی بیمارستان ها مؤید تاثیر منفی این حجم نیرو بر تولید خدمت در این بیمارستان ها می باشد. با وجود افزایش نسبت کادر درمانی به کل کارکنان، نسبت گروه پزشکی با افزایش تخت های بیمارستانی کاهش می یابد که مطلوب نیست. بیمارستان های بزرگ از نظر اشغال تخت وضعیت بهتری دارند