Yooj yim Installation Stabilized Av Mixing Cog | Tuam Tshoj Chaw tsim tshuaj paus

Ib Yooj Yim Txhim Kho Cov Av Nruab Nrab Sib Txawv Cog yog ib qho khoom siv ua ntej, cov khoom siv ua ntej sib dhos tsim los tsim cov khoom siv cement-stabilized rau txoj kev thiab kev tsim kho vaj tse. Los ntawm kev siv cov txheej txheem ntim cov qauv thiab cov tshuab hluav taws xob ntsaws thiab ua si, cov nroj tsuag no txo ​​cov sij hawm sib dhos ntawm qhov chaw los ntawm lub lis piam mus rau hnub. Qhov kev tsim qauv no txo cov kev xav tau ntawm pej xeem engineering, txo cov nqi zog, thiab tso cai rau kev hloov pauv sai ntawm cov chaw ua haujlwm, ua rau nws yog qhov kev xaiv zoo tshaj plaws rau cov neeg cog lus nrhiav kev ua haujlwm zoo thiab kev txav mus los hauv 2026.

Ib qho yooj yim Installation Stabilized Av Mixing Cog yog dab tsi?

Ib qho chaw ruaj khov av sib xyaw, tseem hu ua cement-stabilized av sib xyaw chaw nres tsheb, yog qhov tseem ceeb rau kev tsim cov txheej txheem zoo rau txoj kev loj, tshav dav hlau, thiab txoj kev hauv nroog. Qhov "yooj yim installation" variant yog hais txog ib qho kev hloov pauv ntawm cov tshuab no. Tsis zoo li cov nroj tsuag nyob ruaj ruaj uas yuav tsum tau ua haujlwm ntau hauv lub hauv paus, vuam, thiab kev sib koom ua ke ntawm qhov chaw, yooj yim-installation qauv feature a modular tsim.

Txhua chav ua haujlwm-xws li cov txheej txheem sib sau ua ke, cov cement silo, cov khoom siv dej, thiab cov tswv tsev sib xyaw - tau muab tso rau hauv cov thawv ntim khoom lossis cov thawv hlau. Cov modules no yog pre-wired thiab pre-piped ntawm lub Hoobkas. Thaum tuaj txog ntawm qhov chaw tsim kho, lawv tsuas yog xav tau kev sib tw, kev sib txuas yooj yim, thiab lub zog sib txuas. Txoj hauv kev no hloov pauv txoj haujlwm engineering nyuaj rau hauv txoj haujlwm sib dhos ncaj nraim, ua raws cov kev xav tau niaj hnub rau kev nrawm thiab yooj yim hauv kev tsim kho vaj tse.

Core Cheebtsam ntawm Modular Design

Lub efficiency ntawm ib qho yooj yim installation cog stems los ntawm nws cov integrated Cheebtsam. Kev nkag siab txog cov khoom no pab cov neeg yuav khoom ntsuas qhov zoo thiab kev ua haujlwm:

  • Modular Batching System: Cov khoom sib xyaw ua ke feem ntau yog folded los yog stacked nyob rau hauv lub thawv thav ntawv. Lawv nthuav dav hydraulically lossis los ntawm kev sib txuas tus pin yooj yooj yim, tshem tawm qhov xav tau ntawm cov pob zeb loj loj.
  • Integrated Mixing Host: Twin-shaft tov khoom yog mounted ntawm ib tug robust steel thav duab uas ua hauj lwm raws li ob qho tag nrho cov kev txhawb nqa qauv thiab lub thauj unit. Qhov no txo ​​cov hneev taw thiab ua kom yooj yim nqa cov haujlwm.
  • Pre-assembled Control Room: Lub kaw lus tswj tau nyob hauv lub thawv huab cua-pov thawj uas nruab nrog cua txias thiab rwb thaiv tsev. Tag nrho cov sensors thiab PLCs raug kuaj ua ntej xa khoom xa tuaj, kom ntseeg tau tias kev npaj ua haujlwm tam sim ntawd.
  • Cement Module: Ntsia hlau conveyors thiab cement silos yog tsim los rau kev sib txuas ceev. Qee cov qauv siv lub hnab ntim tau hloov pauv thiab cov tshuab pneumatic uas txuas ntawm cov qauv flanges, txo cov plua plav tawm thaum teeb tsa.

Vim li cas thiaj xaiv Ib qho yooj yim Installation dua li cov nroj tsuag?

Hauv kev sib tw toj roob hauv pes ntawm kev tsim kho, lub sijhawm yog nyiaj. Tsob ntoo nyob ruaj ruaj muaj peev xwm tab sis raug kev txom nyem los ntawm kev xa mus ntev. Ib qho yooj yim installation cov nroj tsuag txuas qhov sib txawv ntawm kev txav mus los thiab muaj peev xwm ntau lawm. Nov yog vim li cas ntau tus neeg cog lus hauv 2026 tab tom hloov mus rau qhov thev naus laus zis no:

1. Kev txo qis hauv lub sijhawm teeb tsa

Cov nroj tsuag tsoos tuaj yeem siv sijhawm 4-8 lub lis piam los txhim kho, suav nrog kev kho lub hauv paus, kev sib dhos steel qauv, thiab kev xa hluav taws xob. Ib qho yooj yim installation stabilized av sib xyaw cog tuaj yeem ua haujlwm hauv 7 mus rau 15 hnub. Feem ntau ntawm kev ua haujlwm yog ua nyob rau hauv lub hoobkas, qhov kev tswj kom zoo yog nruj dua. Nyob rau ntawm qhov chaw, cov txheej txheem tsuas yog tso rau qhov chaw nyob thiab txuas cov khoom siv sab nraud.

2. Tus nqi qis dua Civil Engineering

Vim hais tias cov modules yog kev txhawb nqa tus kheej, qhov yuav tsum tau ua rau cov pob zeb loj loj raug tshem tawm. Ib qho yooj yim hardened av nto los yog me me sawb foundations yog txaus. Qhov no txo ​​qis kev siv peev txheej pib (CAPEX) ntau heev, tshwj xeeb tshaj yog nyob rau thaj chaw deb uas thauj pob zeb kim.

3. Txhim Kho Mobility thiab Reusability

Txoj kev tsim kho tej yaam num feem ntau yog linear thiab ib ntus. Thaum ib ntu ntawm txoj kev ua tiav, cov nroj tsuag yuav tsum txav mus rau ntu tom ntej. Modular nroj tsuag tuaj yeem disassembled thiab thauj mus rau cov tsheb thauj khoom sai. Qhov kev rov siv tau dua no txuas ntxiv lub cuab tam lub neej voj voog thiab txhim kho kev rov qab los ntawm kev nqis peev (ROI) rau cov neeg cog lus tswj hwm ntau qhov chaw.

4. Kev ua tau zoo raws li lub Hoobkas Precision

On-site welding thiab sib dhos yog ua rau tib neeg yuam kev thiab ib puag ncig kev hloov pauv. Los ntawm kev sib sau cov ntsiab lus tseem ceeb hauv ib puag ncig ntawm lub Hoobkas, cov tuam txhab ua kom muaj kev sib tw siab dua hauv kev sib tw thiab kev sib txuas hluav taws xob. Qhov no ua rau muaj kev sib xyaw ua haujlwm ruaj khov thiab muaj kev tawg tsawg dua thaum lub sijhawm pib ua haujlwm.

Technical Advantages ntawm Zibo Jixiang's Manufacturing Approach

Thaum xaiv ib lub chaw tsim khoom rau cov cuab yeej tshwj xeeb, tus tsim khoom muaj peev xwm thiab cov cuab yeej cuab tam yog qhov tseem ceeb. Zibo Jixiang sawv tawm raws li qhov kev xaiv tseem ceeb hauv cov haujlwm no. Nrog rau cov peev txheej sau npe ntawm 234 lab yuan, 670 tus neeg ua haujlwm, thiab qhov chaw tsim khoom loj 280-acre, Zibo Jixiang tsis yog tus xa khoom nkaus xwb tab sis yog tus thawj coj thev naus laus zis. Raws li thawj lub pob txha pob txha loj tshaj plaws los tsim cov pob zeb sib xyaw thiab xa cov tshuab hauv Suav teb, lub tuam txhab tau teeb tsa cov qauv kev lag luam rau kev ntseeg siab thiab kev tsim kho tshiab.

Lub tuam txhab kev cog lus rau kev ua tau zoo yog tshwm sim hauv nws ntau qhov kev qhuas. Zibo Jixiang tau lees paub tias yog Shandong High-tech Enterprise thiab Machinery Industry Modernization Management Enterprise. Nws lub koob npe nrov rau cov khoom siv tiv thaiv ib puag ncig ntsuab tau ua rau nws lub npe nrov tshaj plaws ntawm cov neeg siv hauv kev lag luam pob zeb. Tsis tas li ntawd, nws cov xwm txheej raws li qhov zoo tshaj plaws kev lag luam ua qauv qhia kev lag luam hauv Tuam Tshoj txoj kev siv tshuab ua vaj tse underscores nws txoj cai.

Cov khoom lag luam tshwj xeeb ua tiav qhia txog qhov kev txawj ntse no. JLB3000 qauv asphalt mixing cog tau txais Suav Tuam Txhab Machinery Khoom TOP50 khoom plig, thaum lub hydraulic pob zeb tov khoom JS9000 yeej lub Platinum Award rau Cov Khoom Pom Zoo. Cov khoom plig no tsis yog tsuas yog kho kom zoo nkauj xwb; lawv qhia txog kev sim nruj thiab cov qauv kev tsim vaj tsev zoo tshaj plaws uas tau siv ncaj qha rau lawv cov av sib xyaw cov nroj tsuag. Lub "Star Product Award" los ntawm CMIIC2019 Tuam Tshoj Kev Tsim Kho Machinery Kev Lag Luam Hauv Is Taws Nem Kev Sib Tham ntxiv tau lees paub lawv cov peev txheej digital thiab kev sib koom ua ke.

Engineering Excellence hauv Modular Design

Zibo Jixiang siv nws cov kev paub dhau los hauv cov tshuab ua vaj tse rau kev tsim cov nroj tsuag hauv av ruaj khov. Qhov yooj yim-installation nta tsis yog tom qab tab sis cov qauv tsim qauv. Cov qauv kev ncaj ncees ntawm cov modules yog optimized rau ob qho tib si thauj kev ntxhov siab thiab kev ua haujlwm vibration. Cov tshuab hluav taws xob siv cov khoom siv qib qib uas tiv taus plua plav thiab ya raws, tseem ceeb heev rau kev tsim kho hnyav. Qhov kev nthuav dav no ua kom ntseeg tau tias "kev teeb tsa yooj yim" cov lus cog tseg tsis cuam tshuam txog kev ua haujlwm ntev lossis kev ua haujlwm.

Step-by-Step Installation Guide

Txhawm rau kom tau txais txiaj ntsig zoo tshaj plaws ntawm kev teeb tsa yooj yim stabilized av sib xyaw cog, ua raws li txheej txheem kev teeb tsa yog qhov tseem ceeb. Txawm hais tias yooj yim dua li cov txheej txheem ib txwm muaj, qhov tseeb tseem yuav tsum tau ua kom pom kev sib xyaw kom raug thiab cov cuab yeej siv tau ntev.

Theem 1: Kev Npaj Qhov Chaw

Ua ntej cov cuab yeej tuaj txog, qhov chaw yuav tsum tau npaj. Txawm hais tias lub hauv paus hnyav tsis xav tau, hauv av yuav tsum yog theem thiab compacted.

  • Leveling: Siv cov cuab yeej laser theem kom ntseeg tau tias qhov sib txawv hauv av yog nyob rau hauv ± 5mm hla tag nrho cov nroj tsuag hneev taw. Cov av tsis sib xws tuaj yeem ua rau muaj kev ntxhov siab ntawm cov qauv.
  • Hardening: Compact cov av thiab nteg ib txheej ntawm gravel los yog pob zeb slab los tiv thaiv sinking nyob rau hauv lub luj ntawm aggregates thiab cement.
  • Utility Access: Xyuas kom meej tias cov kab hluav taws xob thiab cov dej hauv qhov chaw nyob ze rau cov ntsiab lus sib txuas kom txo tau qhov ntev ntawm cable thiab hose.

Theem 2: Module Positioning

Siv cranes, nqa txhua qhov module rau hauv nws txoj haujlwm. Daim duab layout muab los ntawm cov chaw tsim khoom yuav tsum ua raws li nruj me ntsis.

  • Ib ntus: Feem ntau, pib nrog tus tswv tsev sib xyaw thiab tswj chav, tom qab ntawd muab cov txheej txheem sib xyaw ua ke, thiab thaum kawg cov cement silo thiab dej tank.
  • Kev sib tw: Xyuas kom meej tias cov chutes tawm thiab conveyor siv tau zoo kawg nkaus ntawm cov modules. Misalignment tuaj yeem ua rau cov khoom nchuav thiab txhaws.
  • Kev ruaj ntseg: Bolt lub modules rau hauv av anchors los yog rau ib leeg raws li tau teev tseg. Tsis txhob overtighten bolts thawj zaug; tso cai rau kev hloov me me ua ntej qhov kawg torqueing.

Theem 3: Kev sib txuas ntawm cov tshuab thiab hluav taws xob

Qhov no theem leverages pre-assembled xwm ntawm cov nroj tsuag.

  • Plug-and-Play Wiring: Txuas lub ntsiab fais fab cable rau chav tswj. Txuas lub inter-module kev sib txuas lus cables siv cov khoom siv dej tsis sib haum. Feem ntau cov tshuab siv cov xim-coded plugs los tiv thaiv kev ua yuam kev.
  • Piping: Txuas cov kav dej thiab cov cement ntsia hlau conveyors. Siv daim kab xev los yog gaskets los xyuas kom muaj kev sib txuas ntawm airtight, tiv thaiv cov plua plav to thiab dej poob.
  • Calibration: Ua ntej ua haujlwm puv, ntsuas qhov ntsuas qhov hnyav rau cov khoom sib xyaw, cement, thiab dej. Cov kauj ruam no yog qhov tseem ceeb heev rau kev sib ntsib sib xyaw tsim qauv specifications.

Kev sib piv: Ib qho yooj yim Installation vs. Tsob Ntoo Nroj Tsuag

Kev nkag siab txog qhov sib txawv yuav pab txiav txim siab txog kev yuav khoom. Cov lus hauv qab no qhia txog qhov sib txawv tseem ceeb raws li kev ua haujlwm tsis zoo hauv 2026.

Yam zoo Ib qho yooj yim installation cog Tsob Ntoo Tsob Ntoo Tsob Ntoo
Lub Sijhawm Txhim Kho 7-15 hnub 4-8 lub lis piam
Kev xav tau Foundation Yam tsawg kawg nkaus (hardened av) Cov pob zeb dav dav
Kev mus ncig High (modular thauj) Tsawg (yuav tsum tau dismantling)
Tus nqi pib Cov nqi ua haujlwm qis dua Cov nqi ua haujlwm siab dua
Kev sib dhos yooj yim Tsawg (plug-thiab-play) High (welding thiab kev cai haum)
Zoo tshaj rau Ntau qhov chaw, cov haujlwm luv luv Qhov chaw ruaj khov mus ntev

Cov Ntawv Thov thiab Siv Cov Ntaub Ntawv

Ib qho yooj yim installation stabilized av mixing nroj tsuag yog ntau yam thiab haum rau ntau yam infrastructure tej yaam num. Lawv kev txav mus los thiab teeb tsa ceev ua rau lawv zoo tagnrho rau cov xwm txheej uas lub sijhawm thiab qhov chaw hloov pauv yog qhov tseem ceeb.

Kev loj thiab kev nthuav dav kev tsim kho

Txoj kev loj feem ntau hla ntau pua mais. Cov neeg cog lus yuav tsum tsim cov khoom hauv paus ntawm ntau lub ntsiab lus raws txoj kev kom txo cov tsheb thauj mus los tsawg. Ib qho yooj yim-installation cog tuaj yeem txav tau txhua 50-100 mais, ua kom cov khoom siv tshiab thiab txo cov nqi thauj khoom.

Txoj Kev Txhim Kho Hauv Nroog

Hauv nroog ib puag ncig, qhov chaw tsis muaj kev txwv, thiab cov kev cai suab nrov / plua plav yog nruj. Kev cog lus hneev taw thiab kaw tsim ntawm cov nroj tsuag modular pab ua raws li cov qauv ib puag ncig. Kev teeb tsa ceev kuj tseem txo qis kev cuam tshuam kev tsheb thaum lub sijhawm teeb tsa.

Tshav dav hlau Runway Base Layers

Tshav dav hlau tej yaam num yuav tsum tau high-precision sib tov rau ruaj khov txheej txheej. Lub Hoobkas-calibrated systems ntawm ib qho yooj yim-installation nroj tsuag kom zoo ib yam mix ratios, uas yog ib qho tseem ceeb rau cov hnyav-load bearing yuav tsum tau ntawm runways.

Rural Infrastructure Development

Hauv cov cheeb tsam nyob deb nroog, kev nkag mus rau cov neeg ua haujlwm txawj thiab cov peev txheej tsim nyog yuav raug txwv. Qhov yooj yim ntawm kev txhim kho thiab ua haujlwm ntawm cov nroj tsuag no tso cai rau cov pab pawg hauv zos los tswj kev tsim khoom nrog tsawg kawg kev txhawb nqa sab nraud.

FAQ: Cov lus nug nquag nug

Yuav ua li cas sib xyaw qhov tseeb ntawm cov nroj tsuag yooj yim-installation piv rau cov tsoos?

Qhov sib xyaw ua ke yog qhov sib piv, yog tias tsis zoo dua, vim tias qhov ntsuas qhov hnyav thiab cov tshuab tswj tau raug ntsuas ua ntej hauv lub hoobkas. Cov nroj tsuag ib txwm cia siab rau ntawm qhov chaw calibration, uas tuaj yeem cuam tshuam los ntawm ib puag ncig yam thiab kev txawj ua haujlwm. Zibo Jixiang cov nroj tsuag siv high-precision load hlwb thiab cov teeb liab ua tiav los xyuas kom meej qhov sib piv ntawm cov cement, dej, thiab aggregates.

Dab tsi yog qhov yuav tsum tau saib xyuas rau cov nroj tsuag modular?

Kev kho yog yooj yim vim yog siv tau los ntawm kev tsim cov modules. Kev kuaj xyuas tsis tu ncua muaj xws li lubricating mixer bearings, tshuaj xyuas txoj siv conveyor rau hnav, thiab ntxuav cov cement lim. Cov qauv modular tso cai yooj yim rau kev nkag mus rau cov khoom siv sab hauv piv rau cov qauv nruj nruj. Zibo Jixiang muab cov phau ntawv saib xyuas kev nyab xeeb thiab kev txhawb nqa chaw taws teeb los pab cov neeg ua haujlwm.

Cov nroj tsuag no puas tuaj yeem daws cov qauv sib txawv?

Yog lawm, niaj hnub yooj yim-installation nroj tsuag yog nruab nrog advanced PLC tswj tshuab uas tuaj yeem khaws ntau cov qauv sib xyaw. Cov neeg khiav dej num tuaj yeem hloov pauv ntawm cov zaub mov txawv ntawm cov av ruaj khov (piv txwv li, cov ntsiab lus sib txawv ntawm cov cement los yog sib sau ua ke) nrog ob peb nias. Qhov kev hloov pauv no yog qhov tseem ceeb rau cov haujlwm uas xav tau cov txheej txheem sib txawv rau ntau ntu ntawm txoj kev.

Puas muaj kev txhawb nqa thaum lub sijhawm teeb tsa?

Cov tuam txhab muaj koob npe zoo li Zibo Jixiang muab cov kev taw qhia rau cov chaw taws teeb thiab, yog tias tsim nyog, kev txhawb nqa ntawm tus kws ua haujlwm hauv tsev thaum pib teeb tsa. Muab lub tuam txhab cov xwm txheej raws li kaum Suav pob zeb sib xyaw cog cov neeg siv khoom lag luam, lawv cov kev pabcuam txhawb nqa muaj zog, kom ntseeg tau tias txhua qhov teeb meem raug daws sai sai kom txo qis sijhawm.

Kev Qhia Txog Kev Xaiv: Yuav Ua Li Cas Xaiv Cov Chaw Tsim Khoom Zoo

Xaiv tus khub zoo rau koj cov av ruaj khov sib xyaw cog yog qhov tseem ceeb xws li xaiv cov cuab yeej siv nws tus kheej. Xyoo 2026, kev ua lag luam tau sau nrog cov kev xaiv, tab sis tsis yog txhua tus neeg tsim khoom xa tawm ntawm cov lus cog tseg ntawm "kev txhim kho yooj yim" thiab kev ntseeg tau.

Ntsuam Xyuas Kev Lag Luam Loj thiab Keeb Kwm

Nrhiav cov tuam ntxhab nrog cov ntaub ntawv pov thawj. Zibo Jixiang, nrog nws qhov chaw 280-acre thiab 670 tus neeg ua haujlwm, ua kom pom lub peev xwm los tswj cov kev txiav txim loj thiab cov teeb meem engineering nyuaj. Ib lub tuam txhab keeb kwm, xws li yog thawj lub hauv paus loj hauv kev lag luam hauv Suav teb rau cov tshuab no, qhia txog kev ruaj ntseg thiab kev paub txog kev lag luam tob.

Tshawb nrhiav khoom plig thiab ntawv pov thawj

Cov khoom plig zoo li Shandong High-tech Enterprise tsim thiab CMIIC Star Product Award yog qhov qhia txog kev tsim kho tshiab thiab zoo. Cov kev lees paub no qhia tias cov chaw tsim khoom tau nqis peev hauv R & D thiab ua raws li cov qauv siab. Platinum Award rau JS9000 tov khoom, piv txwv li, qhia txog qhov zoo ntawm cov khoom siv hauv lawv cov nroj tsuag.

Ntsuas Kev Pabcuam Tomqab Muag

Ib qho yooj yim installation tsis txhais hais tias xoom txij nkawm. Xyuas kom cov chaw tsim khoom muaj cov kev pab cuam tom qab muag tag nrho, suav nrog cov khoom seem muaj, kev cob qhia, thiab kev kuaj xyuas tej thaj chaw deb. Zibo Jixiang lub koob npe nrov tshaj plaws ntsuab ib puag ncig tiv thaiv cov khoom lag luam qhia txog kev muaj zog rau cov neeg siv khoom.

Xav txog Environmental Compliance

Nrog nce thoob ntiaj teb tsom rau kev ruaj khov, xaiv cov chaw tsim khoom lag luam uas tseem ceeb rau kev siv tshuab ntsuab. Zibo Jixiang qhov kev lees paub tias yog lub hom lag luam ntsuab ua kom ntseeg tau tias lawv cov nroj tsuag ua tau raws li cov qauv tsim tawm thiab suab nrov, pab koj ua raws li cov cai hauv zos.

Tag

Ib Yooj Yim Txhim Kho Cov Av Nruab Nrab Sib Txawv Cog sawv cev rau lub tswv yim zoo rau cov kev tsim kho niaj hnub no. Los ntawm kev txo lub sijhawm teeb tsa, txo cov nqi hluav taws xob hauv vaj tse, thiab txhim kho kev txav mus los, nws tso cai rau cov neeg cog lus teb sai sai rau qhov kev xav tau yam tsis muaj kev cuam tshuam rau qhov zoo. Cov qauv tsim qauv, txhawb nqa los ntawm lub Hoobkas precision, ua kom ntseeg tau kev ua tau zoo thiab sib xyaw ua ke zoo.

Rau cov lag luam tab tom nrhiav kev nqis peev hauv cov thev naus laus zis no, kev koom tes nrog cov chaw tsim khoom tsim thiab tso cai yog qhov tseem ceeb. Zibo Jixiang, nrog nws cov kev paub dhau los, cov khoom tau txais txiaj ntsig zoo, thiab kev cog lus rau kev tsim kho tshiab, muaj cov kev daws teeb meem txhim khu kev qha. Lawv cov nroj tsuag tsis yog tshuab xwb; lawv yog engineered tshuab tsim los optimize koj workflow thiab profitability. Txawm hais tias kev tsim kho txoj kev loj, kev txhim kho hauv nroog, lossis kev txhim kho nyob deb nroog, lawv cov chaw tsim khoom yooj yim muab cov txiaj ntsig thiab kev ntseeg siab xav tau hauv kev lag luam niaj hnub no.

Txhawm rau kawm paub ntau ntxiv txog cov qauv tshwj xeeb, cov kev qhia tshwj xeeb, lossis thov kom muaj cov lus qhia tshwj xeeb rau koj qhov project, tshawb xyuas peb cov khoom lag luam kom ntxaws. Ua qhov kev xaiv ntse rau koj qhov project infrastructure tom ntej.

Saib cov khoom lag luam thiab cov kev daws teeb meem


Post lub sij hawm: 2026-10-29

Thov tso peb cov lus